Note from the Editorial Board Dear Reader, In the Discovery Channel’s hit TV series, MythBusters, Adam Savage and Jamie Hyneman elegantly demonstrate some of the most amazing, mindblowing, and ridiculous questions about the world of science. While their daring experimentations often end with a bang—literally—they spark an interest in science in children and adults alike. This issue of the DUJS tackles many questions, myths, and other topics in popular science. Rest assured, it will not spontaneously combust, despite the MythBusters theme we have chosen for this issue. Rather, DUJS writers discuss some of the following myths: Myth #1: The world is struggling to find a potential source of alternative energy. Myth #2: Global warming will cause the world to end soon. Myth #3: Extinction for some species is far too near. Myth #4: Philosophy has no place in biology. Myth #5: Vaccines might do more harm than good. Myth #6: Dieting actually works. Myth #7: Caffeine is essential to the college student’s mind. Myth #8: Lowering your cholesterol to prevent heart disease is easy. Myth #9: We could never outrun a cheetah no matter how hard we tried. Gareth Roberg-Clark ’14 tries his hand at Myth #1 by explaining how nuclear fission may change the human race as we know it, Kristen Flint ’14 tackles Myth #2 in her description of the “Hottest Debate of the Decade,” and Kali Pruss ’14 compares the extinction potential of killer whales and blue whales. Yoo Jung Kim ’14 attempts a double-header—busting two myths in one issue—with an article on the long-standing connections between Philosophy and Biology and an article on the anti-vaccine controversy and movement that has broken out recently. Derek Racine ’14 discusses the growing popularity of dieting and its various forms, Diana Pechter ’12 explains how the late-night coffee from Novack helps keep you awake, Amir Khan ’14 explores the AIM-HIGH clinical trial, and Sara Remsen ’12 shows that humans are the optimal species for endurance running. In addition to our own myth busting, we feature three research articles by Dartmouth undergraduates. Jennifer Jaco ‘13 provides background on hearing loss and partial-restoration via technology, setting up a proposal for a hearing device that allows the blind to use echolocation to “see” their surroundings. Marielle Battistoni ‘11, Rohan Chaudhary ‘12, Zachary ClareSalzler ‘12, Ian Engler ‘12, and Suzanne Kelson ’12 report their findings on capuchin behavior from the Biology FSP last year. Last but not least, Riley Ennis ’15 shares his development of a cancer vaccine, which causes an antitumor immune response. We hope this issue sheds new light on your love and interest of science, as well as inspires you to go out and bust some of your own myths! Sincerely, The DUJS Editorial Board FALL 2011
The Dartmouth Undergraduate Journal of Science aims to increase scientific awareness within the Dartmouth community by providing an interdisciplinary forum for sharing undergraduate research and enriching scientific knowledge. EDITORIAL BOARD President: (Alice) Shu Pang ’12 Editor-in-Chief: Andrew Zureick ’13 Managing Editors: Kyle Heppenstall ’13, Aravind Viswanathan ’12, Derek Racine ’14 Assistant Managing Editors: Amir Khan ’14, Thomas Hauch ’13 Layout Editor: Shaun Akhtar ’12 Design Editor: Chen Huang ’12 Online Content Editor: Kristen Flint ’14 Public Relations Officer: Diana Pechter ’12 Secretary: Yoo Jung Kim ’14 DESIGN STAFF Connie Gong ’15 Derek Racine ’14 Sara Remsen ’12 Danny Wong ’14 STAFF WRITERS Allison Brouckman ’15 Pranam Chatterjee ’15 Riley Ennis ’15 Kristen Flint ’14 Andrew Foley ’15 Scott Gladstone ’15 Thomas Hauch ’13 Kyle Heppenstall ’13 Hunter Kappel ’14 Amir Khan ’14 John Kim ’13 Yoo Jung Kim ’14 Aaron Koenig ’14 Daniel Lee ’13 Una Lee ’15 Joyce Njoroge ’11 Kali Pruss ’14 Derek Racine ’14 Sara Remsen ’12 Gareth Roberg-Clark ’14 Elisabeth Seyferth ’14 Kevin Wang ’13 Robin Wang ’14 Danny Wong ’14 Viktor Zlatanic ’14 Andrew Zureick ’13 Faculty Advisors Alex Barnett - Mathematics William Lotko - Engineering Marcelo Gleiser - Physics/Astronomy Gordon Gribble - Chemistry Carey Heckman - Philosophy Richard Kremer - History Roger Sloboda - Biology Leslie Sonder - Earth Sciences David Kotz - Computer Science Special Thanks Dean of Faculty Associate Dean of Sciences Thayer School of Engineering Provost’s Office R.C. Brayshaw & Company Private Donations The Hewlett Presidential Venture Fund Women in Science Project DUJS@Dartmouth.EDU Dartmouth College Hinman Box 6225 Hanover, NH 03755 (603) 646-9894 http://dujs.dartmouth.edu Copyright © 2011 The Trustees of Dartmouth College
The Dartmouth Undergraduate Journal of Science aims to increase scientific by providing an interdisciplinary forum for sharing undergraduate research an
In this Issue... DUJS Science News (Alice) Shu Pang ‘12 4 Nuclear Fusion: The Power of the Future Gareth Roberg-Clark ‘14 6 Interview with Thalia Wheatley, Dartmouth Assistant Professor of Psychological and Brain Sciences Derek Racine ‘14
9
Busting the Anti-Vaccine Epidemic Yoo Jung Kim ‘14
12
Global Warming: The Hottest Debate of the Decade Kristen Flint ‘14 15 A New View of Species Extinction: Comparing Two Marine Mammal Species Kali Pruss ‘14 18 The Deal on Dieting Derek Racine ‘14
21
Acceptable Addiction? Health Benefits and Risks of Caffeine Diana Pechter ‘12 23
Visit us online at dujs.dartmouth.edu
Dartmouth Undergraduate Journal of Science
fic awareness within the Dartmouth community h and enriching scientific knowledge.
Myth: Philosophy Has No Place in Biology Yoo Jung Kim ‘14
25
The AIM-HIGH Study: How it Impacted Our Understanding of HDL Cholesterol in Cardiovascular Health Amir Khan ‘14 28 Elegance in Running: How Humans Can Beat Cheetahs Sara Remsen ‘12 31 Differences in Capuchin Locomotion between Sexes in Response to Predation Marielle Battistoni ‘11, Rohan Chaudhary ‘12, Zachary Clare-Salzler ‘12, Ian Engler ‘12, and Suzanne Kelson ‘12 34 Improving Hearing Loss: Humans Adapting Echolocation Jennifer Jaco ‘13
36
Nanoparticle-Based Intracellular Delivery System of Immunomodulatory Agents for Initiation of an Anti-Tumor Immune Response Riley Ennis ‘15 40
FALL 2011
DUJS
News
DUJS Science News
See dujs.dartmouth.edu for more information
Compiled by (Alice) Shu Pang ‘12
i BIOLOGY A New Quorum-Sensing Pathway for Pseudomonas Infection in Cystic Fibrosis
People with cystic fibrosis are at a heightened risk of developing chronic bacterial infections in their lungs. Pseudomonas can form biofilms and exhibit swarming motility, both of which make them particularly adept at inhabiting niches in the diseased lung. Understanding bacterial group behavior is essential to combating their virulence. Researchers at Dartmouth Medical School and the University of Cambridge recently published a study on cystic fibrosis patients in the Journal of Bacteriology. Ha et al. were surprised to isolate a mutant strain of Pseudomonas capable of restoring swarming motility. Further analysis localized the class of mutants to an operon that encodes a series of related biomolecules known to be involved in quorum sensing, Pseudomonas quinolone signal (PQS) and an intermediate in its production, 4-hydroxy-2-heptylquinoline (HHQ). Both molecules are secreted by cells.
Image courtesy of CDC.
Pseudomonas bacteria are among the most prevalent causes of infection in hospitals. 4
The gene regulation pathway of HHQ was traced to a group of genes responsible for the synthesis of phenazines, to which HHQ acts as a positive regulator. Analysis of phenazine mutants implicated phenazine in maintaining biofilms. Understanding the biochemical and gene regulatory processes that are disrupted in mutants leads to models of normal phenotype generation. High PQS levels detected in cystic fibrosis lungs suggest that HHQ is also present in high concentrations, indicating that the mutants isolated in the Ha et al. experiment may have a large contribution to the ability of normal Pseudomonas bacteria to form biofilms in their cystic fibrosis hosts.
i PSYCHOLOGY The Organization of Object Knowledge in the Brain
Alfonso Caramazza, professor of psychology at Harvard, recently spoke at the Dartmouth psychology department colloquium. Caramazza presented his model for the organization of object knowledge in the brain, which is based on modality independent representations. Thereby, Caramazza rejected the sensory-motor theory of concept recognition that has recently become popular among neuroscientists. Caramazza acknowledged a major divide in the way that scientists currently theorize about the organizational structures of the brain. Allport’s sensory-motor theory suggests that all information, including conceptual or abstract knowledge, is broken down and stored according to sensory-motor representations in the brain. The alternative, which forms the basis for Caramazza’s proposed structure, asserts that the brain is capable of abstract representations of conceptual knowledge that are modality independent. Caramazza explains that the concept of “domain” is at the base of this
hierarchy. Rather than sorting through information by relating it to functionality or sensory perceptions, each piece of information is sorted into a class or group. For example, one’s concept of a hammer would be connected with other information about tools, not simply the motor function of swinging a hammer. Caramazza’s study asked subjects to identify a series of items as “kitchen tools” or “garage tools” as well as to identify whether a pressing or a twisting motion was required to operate the tools. Neuroimaging results showed the areas of the subject’s brain that were most heavily involved in making each distinction. Caramazza observed “little if any conceptual information in visual form processing areas,” implicating abstract processing as important for object knowledge. Caramazza’s results illustrate instances where the sensory-motor theory cannot completely describe the organizational structure of the brain. Although evidence for a domainbased system of organization has remained elusive, it is clear that there is an important role for the processing of abstract and conceptual knowledge.
i PHYSICS X–Ray Emissions from Thunderstorms and Lightning
No consensus has yet been reached on how thunderstorms produce electricity, or how lightning gets started inside storm clouds. Joseph Dwyer addressed this issue recently at one of Dartmouth’s weekly physics and astronomy seminars. Dwyer’s research at the Florida Institute of Technology has led him to abandon the cosmic ray model of lightning initiation in favor of a model based on the production of x–rays and gamma rays in lightning. One theory for lightning initiation that has gained support is based on the cosmic ray model. The driving force for
Dartmouth Undergraduate Journal of Science
derstanding of a field that has developed relatively slowly since Benjamin Franklin’s “kite and key” revelation.
i CHEMISTRY Artificial Synthesis Utilized to Develop Natural Therapeutics
Image courtesy of Pete Hunt.
Dwyer’s research has shown that lightning is fueled by energy from x-rays.
lightning initiation in this model comes from cosmic rays, which are released into space from the collapse of a star and eventually enter Earth’s atmosphere. Rays that come into contact with storm clouds carry enough energy to carve a conductive channel that would allow for the transmission of electricity without reaching the 3,000,000 V/m threshold. However, Dwyer conducted studies that suggested that lightning initiation relies on energy from x–rays to make air more conductive. During lightning storms, he fired off rockets attached to spools of copper wire on the ground. The copper wire was strung out into storm clouds, which provided a regular path to guide lightning from the clouds to the ground. He then placed x–ray sensors next to the grounded copper wire, and recorded the x-rays. In addition to helping initiate lightning, x-rays also allowed Dwyer and other scientists to study thunderstorms and lightning remotely. X-ray imaging is also now poised to provide information that could resolve some of the other questions surrounding lightning. The observed distribution of xrays within lightning bolts has already shown support for the idea that lightning propagates through a “stepping” pattern. Dwyer hopes that new discoveries will continue to advance our unFALL 2011
Jeffrey Johnston, chemistry professor at Vanderbilt University, recently gave a presentation on his research investigating the development of new reactions and reagents used in molecular synthesis and therapeutics production. The focus of his study is the use of organic reactions to efficiently and economically synthesize molecular catalysts and improve high value reactions. “Small molecules and biologics will take us forward in the treatment of disease,” said Johnston. “[We have] the ability to propel studies forward with the power of chemical synthesis.” Johnston worked with Nutlin-3, a compound that inhibits cancer development by interfering with the p53-MDM2 apoptotic pathway. While Nutlin-3 is known for its tumor suppressing abilities, its investigatory use is limited by its high costs of up to $60 per milligram, meaning that a single in vivo study could cost upwards of $30,000. Through the use of aza-Henry reactions and chiroprotic acid catalysis, Johnston’s research team has been able to produce Nutlin-3 on a relatively large scale. Further, Johnston’s team was also able to successfully optimize the organic synthesis of VNI on a large scale. VNI is a therapeutic used in the treatment of Chagas disease, a parasitic infection affecting 10-12 million people worldwide. Johnston’s team
was able to develop a 10-step reaction with an 8.8% yield, which is significantly more efficient than the industryproduced drug Pensaconzole used to treat Chagas, which uses an expensive 24-step reaction with a 0.6% yield. Ultimately, Johnston and his team hope to develop cost-reducing reactions and reagents, which, through the use of artificial and chemical synthesis, allow for the creation of natural products that can be used to treat diseases.
i ENGINEERING Lab on a Chip
Cancer is the second major cause of death worldwide and can be ascribed to the difficulty to detect the early onset of the disease in order to begin treatment before the cancer spreads. The problem is that there are very few macroscopic indicators of cancer. Axel Scherer from the California Institute of Technology, who partnered with Dartmouth’s Thayer School of Engineering, presented a variety of projects in the nanotechnology arena at a recent Jones Seminar. The lab has developed a cancer blood-testing device that uses nanochannels on a silicon chip to recognize cancer markers. The technology promotes high specificity and can react to very low levels of protein, which makes it a pharmaceutically relevant system to screen for cancer. Further, with a grant from the Bill and Melinda Gates Foundation, the lab has developed a $200 battery powered polymerase chain reaction (PCR) machine that is mobile and penny-sized. His machine will allow for genetic screening for a variety of disorders in third world countries that lack proper medical technologies. Taken together, the lab has shown that nanolithography and microfluidics can play a huge role in changing the way we diagnose diseases and monitor body levels. Nanotechnology also offers a cheaper and more efficient mode of developing both new medical devices and electronics. Scherer calls his work “translational” because he has taken the concept of a “chip in a lab to a lab on a chip.”
The Nutlin-3 compound. 5
Physics
Nuclear Fusion The Power of the Future Gareth Roberg-Clark ‘14
H
ow will human civilization power itself as time goes on? This question has pervaded scientific debate and research for years as humanity has continued to consume massive quantities of fossil fuels. One alternative to fossil fuels, nuclear fusion, was viewed in the 1950’s as a means of completely replacing fossil fuel usage without generating any greenhouse gas emissions. Though research into fusion reactors began in earnest in the following decades, scientists began to realize the enormous obstacles they faced in getting fusion reactions, which normally occur in the intense heat and pressure of stars, to successfully occur in confined spaces on earth (1). A fusion reactor capable of powering humanity to this day has not been developed despite numerous and expensive attempts at creating controlled fusion. David Montgomery, the Eleanor and A. Kelvin Smith Professor of Physics at Dartmouth College, believes that fusion research could have had much greater success by now had the underlying nature of matter at extremely high temperatures and pressures been more thoroughly investigated before delving into these projects (2). However, he also believes that, if properly executed, fusion would be an amazing asset to humanity. Fusion has fantastic long-term benefits. Its fuel is abundant, it generates very little waste, and the chance and potency of its disasters are minimal. Fusion has plentiful fuel, it is sustainable, and it is very safe. For these reasons, nuclear fusion could be the answer to humanity’s energy problems thousands of years into the future. Nuclear reactions are reactions between atomic nuclei. Fusion is one type of nuclear reaction in which two nuclei collide with each other, fusing into a larger mass. The other type, fission, is the splitting apart of a nucleus into smaller nuclei. If a nuclear reaction is to be used as a power source, it has to release more energy than was put into its reactants. Energy is re6
Image by C.R. Nave retrieved from: http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/ nucbin.html.
Fig. 1: Binding energy, mass number, and the divide at Iron (3).
leased when light elements (smaller mass number than iron, Fe) fuse or when heavy elements (higher mass number than iron) split apart. Mass number refers to the sum of an element’s protons and neutrons, which make up atomic nuclei. Another quantity called binding energy refers to the potential energy used to keep an atom’s mass compacted into a nucleus (3). Fig. 1, which compares binding energy (BE) and mass number (A), shows the divide at iron between fusion and fission. One promising fusion reaction is the D-T reaction between deuterium (a hydrogen atom with a neutron in its nucleus, A=2) and tritium (a hydrogen atom with two neutrons in its nucleus, A=3). Both are nuclear iso-
topes of elemental hydrogen, which typically has no neutrons. The reaction products are Helium-4 (also called an alpha particle) and a fast-moving neutron (4). Fig. 2 depicts this reaction. The reaction’s output energy is granted to the product neutron, which in a fusion reactor collides with a blanket material covering its walls. The atoms in the blanket material vibrate, heating up and boiling water that surrounds the chamber. When converted to steam, the water vapor will turn a turbine and generate electricity. The D-T reaction, however, has a downside. It requires tritium, a radioactive isotope that has a half-life of 12.6 years. This means that in 12.6 years, half of a tritium sample’s atoms will send out potentially damaging particles and photons. The process continues until the radiation tapers off. Though 12.6 years is a relatively small half life, tritium is still radiotoxic, meaning its radiation could damage exposed living tissues over time (5). Tritium is also exceedingly rare in nature and has to be bred in a reaction with lithium metal. This lithium will most likely reside in the blanket material of the reactor, allowing neutron collisions to constantly create fuel for fusion reactions to occur. Fig. 3 describes the breeding process. Breeding complicates the process
Image by Chen Huang ‘12, DUJS Staff.
Fig. 2: Tritium reacting with Deuterium. Dartmouth Undergraduate Journal of Science
Image by Chen Huang ‘12, DUJS Staff.
Fig. 3: Generating lithium via breeding reactions.
of sustaining fusion fuel supplies considerably because the blanket material has to constantly flush out newly made tritium. Since tritium’s radioactive and rare nature is problematic, it would be better to eliminate it from the reaction altogether. In fact, two deuterium nuclei can fuse in a D-D reaction. There are three sets of products this reaction can create depending on how the deuterium fuses: tritium and a proton, Helium-3 and a neutron, or Helium-4 and a high-energy gamma ray (6). The only radioactive product is tritium, which could immediately fuse with deuterium to produce more energy. At the moment, however, fusion reactors are incapable of sustaining the temperatures required for the D-D reaction to occur (7). Designing a fusion reactor that could facilitate FALL 2011
the D-D reaction (or other reactions that utilize different elements) will take time and considerable research. Fusion occurs constantly in the sun. The sun’s environment has the ideal conditions that allow nuclei to fuse and radiate energy. On earth, a sustained environment has to be created to allow nuclei to interact in this manner. Often the environment is a plasma, a fluid composed of negatively and positively charged ions. The fusion fuel is heated to temperatures on the order of millions of degrees Celsius, forcing the electrons and nuclei of each atom apart and creating the plasma. The atomic nuclei, now isolated from negatively charged electrons, have enough energy at high temperatures to overcome the electrostatic repulsion between positively charged protons (7). Once nuclei are close enough, the attractive weak nuclear force can attract the two nuclei and force them to fuse. Unfortunately, plasmas are exceedingly difficult to contain. The constituent ions of the plasma tend to spread outward rapidly, dissipating heat by knocking into nearby neutral particles and eventually recombining into atoms (8). A few methods of confining plasmas have been devised. One is magnetic confinement, in which applied magnetic fields corral the ionized plasma, making sure that it does not knock into the reactor walls. Magnetic confinement is used in tokamak devices, an example of of which is ITER, an international project based in the south of France and run by Russia, the U.S., India, China, Japan, and the European Union. ITER’s goal is to reach ignition – a state in which the fusion fuel burns without additional supplied energy – by the year 2026. ITER’s ignition will last at most for 400 seconds (7). Stellarators, which also use magnetic confinement, may be able to harness the power of fusion reactions over sustained periods of time. This is the goal of Wendelstein 7-X, a project at the Max Planck Institute for Plasma Physics in Germany that is to be finished by 2015 (7). Wendelstein 7-X’s reactor will use a complicated “twisted torus” shape to confine its plasmas (9). Inertial confinement, another method, is under development at the National Ignition Facility in the United States. In inertial confinement, vast arrays of lasers are aimed at pellets of fu-
sion fuel, causing the samples to blow up rapidly. Inertial confinement seems more promising as a means of weapons development as opposed to power generation (8). No current project incorporates all of the elements of a successful fusion reactor, and this is why fusion power, if successful at all, can only be a viable energy source decades into the future. Once the power generation hurdle is overcome, however, humanity could continue to reap the benefits of this plentiful energy source. One reason nuclear fusion could remain a viable energy source long into the future is the widespread and consistent availability of its fuel, regardless of which reaction is carried out. Deuterium (in the form of D2O molecules) can be extracted from seawater on a continual basis. Tritium is not present in nature and will be obtained from breeding reactions with lithium metal or from reactions in nuclear fission plants. Lithium metal, though present in small concentrations in seawater, will likely be extracted from the earth’s crust (7). Without taking into account the lithium present in seawater, a report by four researchers of the European Fusion Development Agreement (EFDA) asserts that there is enough lithium to last a fusion power economy for 1000 years (10). This leaves ample time for researchers to develop reactors that utilize the D-D reaction. Once that technology is mastered, seawater could be harvested to provide fusion power indefinitely. An issue present in any energy source is the production of harmful waste, be it radioactive, polluting, or greenhouse-gas-effect-enhancing. Since the D-T reaction produces nonradioactive Helium-4 and a neutron, fusion will produce no direct radioactive waste and will not create greenhouse gas emissions. The same goes for the D-D reaction, which will not produce radioactive waste regardless of which specific reaction takes place, provided any tritium produced is absorbed as fuel and rapidly consumed to make Helium-4 (6). Tokamaks such as ITER, however, will produce two indirect sources of radioactive waste: tritiated dust and activated materials. Tritiated dust results from interactions between hot plasmas and their containing walls in tokamaks. A study 7
done by H. Maubert of the ITER organization and L. Di Pace of ENEA FUS/ TEC in Rome analyzed the output and possible impact of this radioactive dust on reactor workers and nearby civilians. They concluded that the minimal amount of dust created (0.25 grams each year) would even in a worstcase scenario have a negligible impact on these two groups of people (11). The other source of radioactive waste, activation, occurs as the walls of a fusion the reactor are continually bombarded with high-energy neutrons. The blanket material progressively degrades until it has become brittle and radioactive (7). According to Cook et al., the quantity of degraded material produced is comparable to that of a fission reactor (10). However, the material produced by fusion and fission are inherently different: activated fusion materials have a “maximum decay heat intensity nearly a hundred times lower and a lower long-term radiotoxicity than fission materials” (10). This means that, compared to fission-activated waste, fusion-activated waste requires less maintenance and energy to store and poses a smaller potential health risk to factory workers and civilians in the surrounding area. The EFDA suggests that with adequate research and incentive the majority of stored activated material could be recycled, reused, or at worst be placed in a repository, allowing its radiotoxicity to taper off over the course of a few hundred years after an initial storage period of fifty years (10). If proper research into appropriate recycling methods is done, fusion technology could produce very little lasting radioactive waste whose threat to humanity and the environment virtually disappears over short time scales. In essence, fusion would be a sustainable energy source. Fusion would also be a safe power source. The danger of nuclear-powerrelated emergency situations, all too clear after the recent disaster at the Fukushima Daiichi nuclear plant in Japan, would be diminished greatly if fusion power replaced fission power in the future. Radioactive meltdown would be a non-issue in fusion reactors for two reasons. Sustained fusion reactions require a continual supply of fuel, much like wood fires. “Runaway” reactions are not possible because fuel 8
supplies would be cut immediately if any malfunction in the reaction chamber occurred. Similarly, in the event of an in-plant accident, power to the reaction chamber would be cut off (7). Emergency scenarios for fusion plants still need to be considered, however. If an in-plant emergency occurred in which tritium fuel inventories leaked outside the plant to the public, civilians would be exposed to an amount of radiation roughly equal to that of natural radiation sources (10). In an even worse scenario in which an earthquake, the likes of which has never been recorded by humanity, struck a finished ITER plant, about 1 kg of radioactive tritium could be released to the public, exposing civilians to about 0.4 sievert of radiation. To give some comparison, the Fukushima Daiichi compound released 0.4 sievert per hour after a massive earthquake struck the plant (12). Therefore, a destroyed fusion plant similar to ITER could release a fraction of the total radioactive material that a top-tier nuclear fission disaster would. Thus, fusion reactors could release fast-spreading and potentially harmful tritium into the environment. However, the probability of such disasters occurring is low, especially considering that even more sophisticated defense mechanisms and containment methods could be developed as time goes on. As such, fusion power’s potential to drastically cut the severity and likelihood of future emergencies makes it an even more appealing long-term alternative energy source. With the right investment of resources and time, nuclear fusion could become an ideal power source long into humanity’s future. Fusion excels in terms of fuel availability, waste production, and safety, though developing fusion as a power source will no doubt cost colossal amounts of money, as the steep cost of the ITER project (€10 billion and rising) attests (13). One must bear in mind that any alternative energy source that effectively cuts greenhouse gas emissions will have an undesirable and weighty price tag. However, if researchers and governments take the initiative to fully understand the behavior of plasmas and harness the best reactions available, nuclear fusion could supply much needed power for the rest of humanity’s existence.
References 1. R. B. White, Theory of tokamak plasmas (North-Holland, Amsterdam, 1989). 2. D. Montgomery, Personal Interview, 21 May 2011. 3. R. Nave, Nuclear Binding Energy (n.d.). Available at http://hyperphysics.phy-astr.gsu. edu/hbase/nucene/nucbin.html (20 May 2011). 4. M. Moyer, Sci. Am. 302, 50-57 (2010). Available at http://www.nature.com/ scientificamerican/journal /v302/n3/full/ scientificamerican0310-50.html (22 May 2011). 5. Radiotoxicity (n.d.). Available at http:// www.euronuclear.org/info/encyclopedia/r/ radiotoxicity.htm (02 June 2011). 6. S. Atzeni, J. Vehn, The Physics of Inertial Fusion: Beam Plasma Interaction, Hydrodynamics, Hot Dense Matter (Clarendon Press, Oxford, 2004). 7. Nuclear Power - a Sustainable Energy Resource (n.d.). Available at http://www.worldnuclear.org/info/inf66.html (22 May 2011). 8. B. Rogers, Personal Interview, 19 May 2011. 9. D. Fisher, Personal Interview, 19 May 2011. 10. I. Cook et al., Safety and Environmental Impact of Fusion (2001). Available at http:// www.efda.org/eu_fusion_programme/ downloads/scientific_and_technical_ publications/SEIF_report_25Apr01.pdf (22 May 2011). 11. H. Maubert, L. Di Pace, Radioprotection 43, 13-22 (2008). Available at http://www. radioprotection.org/index.php?option=com_ article&access =standard&Itemid=129&url=/ articles/radiopro/pdf/2008/01/rad200720.pdf (22 May 2011). 12. R. Buerk, Japan earthquake: Radiation levels fall at Fukushima (2011). Available at http://www.bbc.co.uk/news/world-asiapacific-12749444 (22 May 2011). 13. I. Sample, Flagship Iter fusion reactor could cost twice as much as budgeted (2009). Available at http://www.guardian.co.uk/ science/2009/jan/29/nuclear-fusion-power-iterfunding (22 May 2011).
Dartmouth Undergraduate Journal of Science
Interview
Thalia Wheatley
Dartmouth Assistant Professor of Psychological and Brain Sciences Derek Racine ‘14
it is to someone asleep. Recently, there have been studies using fMRI that have shown actual brain processes going on during hypnosis that are interesting, different, and definitely worth studying.
Is everyone equally susceptible to being hypnotized?
Image courtesy of Thalia Wheatley.
Thalia Wheatley, Dartmouth assistant professor of psychological and brain sciences.
T
he DUJS talked to Thalia Wheatley, Dartmouth assistant professor of psychological and brain sciences, to gain insight into her research techniques, including hypnosis, how they are applied in a laboratory setting, and the ways that students can get involved. She currently teaches Psychology 23, Social Psychology.
What has been the focus of your personal research?
I have done a lot of different things. I have worked in morality, free will, animacy, emotion, and synchrony, and now I’m getting into abstract thought. But the center of my research is really on how people understand others or how the brain makes sense of other people and understands their emotions, social motives, and other things like that. This field is called “social neuroscience” because it merges social psychology with methods of cognitive neuroscience. We are social beings all the way down. Everything we do relates to our social networks and our social hierarchies. For other animals, it is all about peckFALL 2011
ing order. And then we think, well, we must be more sophisticated and civilized, but it really comes down to this.
What is hypnosis? How does it work?
What we know about hypnosis is that it seems to be an altered state of consciousness, but it is only recently that there has really been a big push to study hypnosis scientifically. Before, it was just seen a bit like the third rail in science. If you studied hypnosis, you were the hypnosis person. There is a weird taint with hypnosis—it has been the domain of gypsies, black magic, and stage shows for so long that it just does not seem possible that it could be a scientific topic of inquiry. However, that is not correct. Hypnosis is, very simply, an altered state of consciousness. It is not the same thing as sleep; people are not asleep when they’re under hypnosis and people have known this for a long time. If you put electrodes on people’s scalps while they’re under hypnosis, the activity that you see is actually more akin to someone awake and alert than
While hypnosis is a real thing, not everybody can be hypnotized. How do you figure out who can be hypnotized and who cannot be? There is simply no easy way to do so; you really have to just hypnotize people and see. You have to be open to it as a real thing because you kind of have to let yourself let go, and let yourself get into it as a state of mind. If you are skeptical or you do not think it is real, or you are not open to trying to experience it, then it will just not work. [Hypnosis] is like any kind of meditation; if people do not believe that meditation is real, how are they going to get into a state of meditation? You have to feel like it is possible in order to experience it.
How has the technique of hypnosis been applied to your research?
When I hypnotize people, they can do whatever I ask of them. For example, I could have a conversation with them, I could ask them to do certain things with their body or make certain decisions. They perform these things, but they do not necessarily perform them willfully. It is an altered state of consciousness that takes out their sense of agency; so, I can make people experience things that they themselves are creating, but they do not have a sense that they are themselves creating them. A hypnotist would say something like, “Clasp your fingers together, interlock your fingers together.” He would follow this with, “Your fingers are so tightly locked together. They are so tightly in9
terlocked that you can’t take them apart. You would like to take them apart but you cannot because they’re just locked in place.” You will see people actively struggling and squirming, with strain on their faces trying to take their hands apart to no avail. The hypnotist creates this state of mind, but the volunteer cannot recognize the situation. It is an interesting state where people can do all sorts of things, but not necessarily feel agency for what they’re doing.
Regarding your work on animacy, could you describe what the mirror system is and how it contributes to our social understanding of movement?
There are regions of the brain where people suggest there might be these things called mirror neurons, but we are not completely certain. Mirror neurons are typically found in monkeys, but there are regions of the human brain that respond the same way to how you behave as to how I behave. They have mirror properties in the sense that they respond to action in general and help us understand action. I have done a little bit of work with them in terms of how people move to express emotion, as well as the way we express emotion in music,
or any kind of dynamic stimulus that might express some social information.
How do you assess how people react while undergoing these different social interactions, or do you use monkeys as a model?
The way we tend to assess that at Dartmouth is with functional magnetic resonance imaging (fMRI). As to your other question though, there’s a difference between humans and monkeys, so some of the really high-level social understanding and social interactions cannot be assessed using monkeys. Humans are the right species to study sophisticated social intelligence.
With respect to your study of consciousness, how do you think the development of this experience might have contributed to our survival as a species?
Do you think other animals also experience consciousness?
As far as I know, we are the only species that can really contemplate our own mortality and have a “50,000-foot view” of our lives and plan for the future in that kind of sense. Because we can see our lives stretch out ahead of us and see our death looming in the future, I think it is necessary to develop this sense of self and will to kind of cope with these things. I think other animals have experience but we seem to have this other ability, a “meta-consciousness,” to think about our thoughts. We consider not just our experiences, but also what’s happening to us in the present, and, as a result, we plan in different ways.
Concerning your research on morality, do you believe that all humans are innately moral by some standard?
I think the belief that you are a free conscious agent making your own choices is critical. The belief of “What’s the point of life if I am just sort an observer of my actions and I’m not deciding anything,” would make things seem hopeless.
There is evidence that people find others’ distress aversive, and this causes brain activity associated with aversion to victim distress. I think that is just true of all healthy human brains. These things are just biologically innate to us; we experience strong dislikes of certain things that are bad, even if they are bad just for others. Certainly, within our communities, it would have been evolutionarily advantageous to support each other. A more recent example is in the trench warfare of World War I, between the English and the Germans, where they had to keep moving the troops along the front lines because they would set up these cooperations across; a German solider would fire over the heads of the English soldiers on the other side just to say, “Look! I could kill you if I wanted to, but I don’t want to, so I’m going to shoot over you.” They would keep doing this to each other, using up the artillery without actually killing any soldiers on the other side. These spontaneous cooperative alliances formed; thus, the generals would have to keep moving the troops in an effort to try and break this spontaneous cooperation.
Image retrieved from http://upload.wikimedia.org/wikipedia/commons/5/5c/Varian4T.jpg (Accessed 29 October 2011).
Functional magnetic resonance imaging is a recently developed way to measure neural activity. 10
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What did your career path consist of and how did you arrive at Dartmouth?
First, I will say that I love my job and I cannot imagine doing anything else. I think it is an embarrassment of riches to be able to come in and think, “Oh, wouldn’t it be interesting if people do this?” or “I wonder why people do that?” From that, I design some studies, go downstairs, and put some people in a scanner to see what happens to their brains when they interact with each other. It is just fantastic. That said, getting here from college took a really long time and a lot of dedication. It is difficult. When I was an undergraduate, I was actually a political science major. I took an introduction to social psychology course as an elective because it sounded easy. I planned to take this course and get my degree in three years, but I loved social psychology and realized that I wanted to do it for the rest of my life. I started working in a research lab, applied to graduate school in social psychology, entered a social psychology Ph.D. program, and spent the next seven years there. It was kind of a crazy time, but I loved it so much. Most people take five years, which is still a long time. In today’s FALL 2011
world of psychology or neuroscience, after the five years necessary to get a Ph.D., you have to have a post-doctoral experience if you want to do research. This involves going somewhere else for two to five years for further training in imaging, behavioral methods, etc. Then, you go on the job market, hopefully with an assistant professorship, followed by six or seven years on tenure track; eventually you come up for tenure, and that is when people decide whether or not you get to actually stay in your job or not. I am forty and about to come up for tenure. It has been a long, tough road, but it is my life and I love it.
What would be your advice to someone interested in scientific research in the psychological and brain sciences?
hours a week, and they run studies. We brainstorm at lab meetings. They do all sorts of different things. Oftentimes, I will get them in as freshmen and they will end up staying all four years, and they will even do honors theses in their senior year. It is the best sort of experience you can have for what graduate school would really be like. Then, when it comes time for you to write your application for graduate school, [admissions committees] look at potential graduate students [to see] if they really know what life is like as a researcher— have they been in a lab, do they have letters of recommendation from people who say “this person has been in my lab for a year or two, they are excellent, this is what they have done, they are committed…” and so forth. So, that’s my best advice: get into a lab.
If students are interested in psychology as undergraduates and they think they might want to go to graduate school, then get into a lab. That is my best advice—get into a lab and get into a lab as soon as you can. Even if you are a senior and you are just figuring it out, try to get into a lab. I have research assistants in my lab that work about ten 11
MEDICINE
Busting the Anti-Vaccine Epidemic Yoo Jung Kim ‘14
I
n February 2010, The Lancet, a preeminent British medical journal, retracted a 1998 article that established a possible link between Measles, Mumps and Rubella (MMR) Vaccines and the development of bowel disease and autism spectrum disorders in young children (1). An investigative report published by the English newspaper, The Sunday Times, revealed that Andrew Wakefield—the article’s lead author—manipulated patient data, broke several codes of medical research ethics, and received funding from solicitors seeking evidence to file a litigation against vaccine manufacturers (2, 3). In 2010, the British General Medical Council ruled that Wakefield held a “fatal conflict” of interest during the course of his research; they found him guilty of multiple counts of serious medical misconduct; and stripped Wakefield of his license to practice medicine (4). Since then, subsequent papers in respected journals, such as BMJ, have debunked the connection between MMR vaccines and autism. Despite Wakefield’s fall from grace, however, he has continued to assert the validity of his findings through public lectures and appearances, and his discredited research has further inflamed long-standing oppositions to vaccinations, with possible repercussions for the future of public health.
History of the Vaccine and the Anti-Vaccine Movement The history of vaccine oppositions spans as far back as vaccination itself. The British Vaccination Act of 1840 was the first case of state-mandated public inoculation, following the experiments of Edward Anthony Jenner. Based on the folk observation that milkmaids were generally spared from smallpox, Jenner, an English general practitioner, postulated milkmaids’ direct exposure to cowpox lymph through sores on their hands protected them from the 12
related and more virulent smallpox. He demonstrated that by inserting cowpox lymph into an incision made onto the skin, patients could gain immunity to smallpox. Jenner’s idea, novel for its time, immediately met with public criticism. Protesters objected to the idea of infecting seemingly healthy individuals. Members of the clergy claimed that vaccination was ceremoniously unclean, because the body fluid used to confer immunity was derived from animals. Others objected to vaccination because they believed that subsequent government efforts to increase vaccination undermined individuals’ rights to control their bodies and those of their children, a tension that escalated with the introduction of mandatory vaccination policies in England (4).
Vaccines and the Modern Anti-Vaccine Movement Vaccination technology has advanced greatly since the crude and direct infections of Jenner’s time. Liveattenuated vaccines use lab-weakened microbes that elicit a strong antibody response, which often confers lifelong immunity to the patient. Inactivated vaccines utilize microbes killed by chemicals, heat, or radiation in order to confer immunity, and, although the vaccine is more stable and portable than the live-attenuated counterpart, the effects are generally not as longlasting. Unlike both live-attenuated and inactivated vaccines, subunit vaccines use only the essential antigens used by the immune system to identity the disease microbe, thereby lowering the chances of adverse side effects (5). Current developments in vaccine technology promise increased safety and efficacy. Still in its experimental stages, the DNA vaccine, modeled after the genes of the microbe, would evoke a strong antibody response to the freefloating antigen secreted by cells infected by the microbe and stimulate
Image retrieved from http://upload.wikimedia.org/wikipedia/commons/3/32/Eduard_ Jenner.jpg (Accessed 29 October 2011).
Edward Jenner’s research led to the creation of the smallpox vaccine.
a strong cellular response against the microbial antigens displayed on infected cell surfaces. The recombinant vaccine, also in its developmental stages, would use an attenuated virus or bacterium to introduce microbial DNA to cells of the body that closely mimics a natural infection and effectively stimulates the immune system (5). While vaccine technology has evolved tremendously in recent years, the anti-vaccine movement itself has changed little from the anti-vaccine leagues of the nineteenth century. Its members encompass a vast range of individuals, from conspiracy theorists to educated consumers whose reasons against vaccines stem from a variety of popular reasoning such as “mixture of world views held about the environment, healing, holism . . . and a critical reading of the scientific and alternative literature” (7). Many vaccine refusers continue to be wary of the growing encroachment of the state over individual health. By the 1980s, all fifty states had passed immunization requirements for public schools, and the vaccination requirements have since grown (12). Whereas many of today’s parents received fewer than a dozen shots in their childhood, they are now advised to give their own children 30 shots before the age
Dartmouth Undergraduate Journal of Science
of six. The increasing requirements have piqued concerns regarding vaccine safety as more parents are taking advantage of state’s immunization provisions for vaccination exemptions. As of March 2008, all states permitted medical exemptions from school immunization requirements, 48 states allowed religious exemptions, and 21 states allowed exemptions based on philosophical or personal beliefs (12). Other major reasons for vaccine refusal in the United States can be attributed to increasing concern of vaccine safety and a decreasing concern regarding the risk of many vaccine-preventable diseases (12). Compared with parents of vaccinated children, parents who exempt their children from vaccination generally have a lower opinion of the severity and their children’s susceptibility to vaccine-preventable diseases (11). In a sense, vaccination has become a victim of its own phenomenal success. As more people are vaccinated, the virulence of disease fades away from public memory, and the population’s tolerance for side effects—even imagined ones—drops even further. The activities and theories of the vaccine refusers have been amplified to the general public through the Internet and mass media; a litany of celebrity activists and sensationalist media coverage have overshadowed scientific data. Opinions and speculations have triumphed over scientific consensus that there is no rational reason to fear immunization. Despite the lack of scientific proof, the vaccine refusers are gaining traction. An increasing number of American parents have refused or delayed vaccines for their children, creating a potential health risk for future generations and prompting a reemergence of long-dormant diseases.
mostly to patients with compromised or underdeveloped immune systems, such as infants, the elderly, chemotherapy patients, and HIV-positive patients (6). The risks posed by the extreme rarity of side effects are outweighed by the risk posed by non-vaccination, such as the resurgence of diseases long considered eradicated. For example, between 2001 and 2008, a median of 56 measles cases were reported to CDC annually, yet during the first 19 weeks of 2011, 118 cases of measles were reported—the highest recorded figure since 1996—among which 105 patients were unvaccinated (8). Children with exemptions from school immunization requirements are at increased risk for contracting measles and pertussis (whooping cough), and may pose a risk to others who are too young to be vaccinated, those who cannot be vaccinated, or those who were vaccinated but are unable to muster a sufficient immunologic response (11). Because sufficiently high immunization rates must be maintained throughout a given population to prevent future outbreaks, unvaccinated children pose a potential risk to public health.
How to Face the AntiVaccination Movement The real power of the anti-vaccine movement lies not in objective scientific validity but in the subjective and emotional stories of thousands of parents who believe that their children were negatively affected by immunization (12). Frustrated by the lack of an-
swers, concerned parents may mistake correlation as causation and create a state of misinformed fear that could convince other parents to refuse or delay vaccination for their own children. Laws concerning immunization are state-based; as such, the most efficient method to raise vaccination would be for state legislatures to make vaccination exemptions more difficult to obtain—for example, by requiring counseling on the hazards of non-vaccination for parents seeking exemption (12). Yet, the government must tread carefully; a heavy-handed approach may threaten individual liberty and further inflame the vaccine refusers, whereas a passive approach could potentially undermine public health (9). As such, in order to maintain high vaccination rates while preserving patient choice, the scientific community and local health providers must place an emphasis on educating the public to enable them to make informed decisions in consideration of the risks posed by vaccination exemption. Medical providers have an important role in affecting their patient’s choices of health consumption. A high proportion of those providing care for children whose parents have refused vaccination and those providing care for appropriately vaccinated children were both found to have favorable opinions of vaccines. However, health care practitioners providing care for unvaccinated children were less likely to have confidence in vaccine safety and less likely to perceive vaccines as benefitting individuals and communi-
Risk vs. Risk Concerns regarding vaccines are not unfounded. As a biological product, vaccines do carry real—but very rare— risks, ranging from rashes or tenderness at the site of injection to fever-associated seizures called febrile convulsions and dangerous infections (5). For instance, oral polio vaccine (OPV), a liveattenuated vaccine, is known to cause roughly one case of the disease per 2.4 million doses—a miniscule risk posed FALL 2011
Image courtesy of James Gathany/CDC.
In 1979, the World Health Organization declared that smallpox was eradicated due to the vaccine. 13
ties, suggesting a correlation between practitioner and patient opinion (12). Secondly, the scientific community must do a better job of disseminating its results to the wider public. Scores of data and professional opinion have gone unheeded, routed by baseless fears and rumors. The sidelining of scientific knowledge by uninformed clamor demonstrates the inability of the scientific community to effectively communicate with the masses, which may set a dangerous precedent for future fears. If the enormous benefits from vaccinations to society are to be maintained, increased efforts will be needed to educate the public about those benefits and to increase public confidence in the systems we use to monitor and ensure vaccine safety. Furthermore, the scientific community must become more effective in transmitting its message to the wider public, lest its lessons be swept away by the tide of misinformation. References 1. F. Godlee, Brit. Med. J. 342: 64-66 (2011) 2. B. Deer, Revealed: MMR Research Scandal (2004). Available at http://www.timesonline. co.uk/tol/news/uk/health/article1027603.ece (June 2011). 3. B. Deer, MMR doctor Andrew Wakefield fixed data on Autism (2009). Available at http://www. timesonline.co.uk/tol/life_and_style/health/ article5683671.ece (June 2011). 4. History of Anti-Vaccination Movements (2011). Available at http://www. historyofvaccines.org/content/articles/historyanti-vaccination-movements#Source (2 June 2011). 5. Vaccine Exemptions. Johns Hopkins Bloomberg School of Public Health — Institute for Vaccine Safety (2008). Available at http:// www.vaccinesafet y.edu/ccexem.htm (June 2011). 6. R. Kwok, Nature 473, 436-438 (2011). 7. A. Rogers, D. Pilgrim, Health Care Anal. 3: 99107 (1995). 8. Centers for Disease Control and Prevention, Morbidity and Mortality Report (2011). Available at http://www.cdc.gov/mmwr/ preview/mmwrhtml/mm6020a7.htm?s_ cid=mm6020a7_w (June 2011). 9. R. Wolf. Brit. Med. J. 325: 430-432 (2002). 10. N. Shapiro, The Anti-Vaccine Epidemic (2011). Available at http://www.seattleweekly. com/2011-06-15/news/the-anti-vaccineepidemic/ (June 2011). 11. S. Omer, New. Engl. J. Med. 360, 1981-1988 (2009). 12. D. Salmon, W. Pan, S. Omer et al., Hum. Vaccines 4, 286-289 (2008). 13. Johns Hopkins Bloomberg School of Public Health — Institute for Vaccine Safety, Vaccine Exemptions (2008). Available at http://www. vaccinesafet y.edu/ccexem.htm (June 2011).
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Dartmouth Undergraduate Journal of Science
WORLD
Global Warming
The Hottest Debate of the Decade Kristen Flint ‘14
G
lobal warming has been a point of contention in our society for years, and the extreme views from both sides of the argument have transformed the subject of global warming from a factual theory into a mythical idea. At one extreme, those who consider themselves “green” bemoan the tragedy that man is causing our planet’s climate to heat up while the other side of the debate refuses to believe any part of the global warming theory. Behind both opinions, there is often confusion, misunderstanding, and a general lack of knowledge. The theory that global warming has anthropogenic causes has existed for over a century, and scientists have collected evidence on global warming for over fifty years. In spite of the evidence, the public generally lives in the dark, constantly wondering if global warming is fact or fiction. Global warming is the increase in the Earth’s temperature caused by increased emission of greenhouse gases into the atmosphere (1). The greenhouse
gases, including CO2, form a blanket in the Earth’s atmosphere that traps heat and causes global temperatures to increase (1). This theory of global warming was first offered by a Swedish chemist named Svante Arrhenius in 1896 (2). Arrhenius estimated that “doubling the level of carbon dioxide in the atmosphere would raise the mean global temperature by several degrees” (2). Even then, his audience was skeptical as many other factors could also affect global temperature. Since Arrhenius’ paper, the global warming discussion has grown convoluted as both scientists and the media have addressed the subject. Scientists track climate change and publish their evidence, but then the media hypes it up in its articles to the public. To add to the confusion, the public tends to avoid thinking much about the topic unless extreme weather occurs unexpectedly. However, despite overwhelming opinions, there are facts to support both sides of the debate.
Media vs. Science The greatest source of confusion about global warming comes from the media. During periods of natural disaster—earthquakes, floods, hurricanes— the media reports more heavily about the existence of global warming. At other times, and in certain regions, the media stops discussing global warming completely. When global warming first came to the forefront of science, politics, and our culture, scientists were the main sources of information for the media (3). More recently, the sources have changed to interest groups and politicians rather than those directly researching the topic (3). For example, in 2006, Al Gore created the well-known documentary “An Inconvenient Truth” to relay certain facts and predictions about global warming. His documentary made over $49 million, reaching millions of people and starting more conversations about global warming (4). Its success outweighs the success of most
Image courtesy of Robert Simmon/NASA.
During the decade between 2000 and 2009, average surface temperatures increased by as much as two degrees Celsius in certain locations over benchmarks recorded between 1951 and 1980. FALL 2011
15
papers published in scientific magazines because it reached such a vast audience (4). The politician replaced the scientists as the informer of the public. This mixing of sources from scientists and politicians has caused the media to convey a greater sense of uncertainty about global warming. PhD student Jessica Durfee and associate professor Julia Corbett from the University of Utah department of communication studied the public’s response to articles about global warming that used conflicting sources (3). Durfee and Corbett made up four versions of a news story based on a scientific article that suggested some uncertainty about global warming (3). Several people read each version, which differed in the amount of controversy and context they included, and then took a survey about their certainty of global warming (3). Durfee and Corbett found that scientific context led to the greatest certainty about global warming, and controversy caused greater uncertainty about the issue (3). Furthermore, added controversy between the differing scientific and political opinions diminished the perceived importance of global warming (3). The Internet provides another source of confusion about global warming. Scientific articles, news articles, and blog entries found on the Internet all provide accounts of global warming but have dramatically different levels of credibility (1). However, the average Internet user does not take the credibility of his or her sources into account. To further complicate matters, the Internet has so many articles on the subject that the information a reader receives depends on factors such as the Web design of the article and the sites to which the article is linked rather than the credibility and truth of the article (1). Thus, the Internet does not always provide clear, high-quality facts and evidence for global warming.
Scientific Evidence
The global warming controversy also exists within the scientific community. Scientists agree that the theory makes sense: increased concentrations of greenhouse gases within the atmosphere should cause temperatures to rise (1). However, 16
they disagree about whether and how global warming has occurred. Scientists have a wide array of evidence to support the theory that man has caused global warming. Firstly, evidence from meteorological stations that record the global mean temperature supports the claim that global temperature has steadily risen since 1980 (5). Scientists have also studied ice cores to measure the amount of carbon dioxide present in the atmosphere during a given year (5). By plotting the temperature information with the measurements of carbon dioxide, scientists have found that the two have a positive correlation (5). Both temperature and the amount of carbon dioxide in the atmosphere have steadily increased since 1980, causing many scientists to agree that greater carbon dioxide emissions cause the temperature to increase. In 2007, Nature published a recap of changes that had occurred since 2005. Within those two years, the rate of polar ice melting increased, Antarctica weather balloons steadily warmed, and the sea level rose (6). Earth scientists also point to evidence from the natural climate change cycles of the Earth. The Earth has gone through many natural phases of climate change. Until approximately 2.75 million years ago, the climate changed every 23,000 years or so (7). After that, the intervals between the climate changes increased to today’s interval of 100,000 years. Again, the science world has reached a consensus that with this evidence, the Earth does appear to be warming. However, the skeptics still assert that man has not acted as the sole or primary factor causing global warming. Skeptical scientists point to evidence to back their claim that man is not the cause of global warming. These skeptics believe that global warming is a purely natural process. Skeptics discount much of the evidence that pro-global warming scientists have put forth. They claim that some research units that provide the global mean temperature series are “hiding data and falsifying scientific evidence on global warming” (8). More substantively, the skeptics also point out that the temperature data does not cover much of the world’s geography, and the temperature data is negatively affected by urban expansion in what is
known as the “heat island effect” (8). Skeptics also accuse climatologists who predict future global warming of leaving out the impact of natural processes, which are not easy to predict (8). Another factor that affects both groups’ opinions is the groups’ different sources of funding. The skeptics tend to be backed by industries that work with fossil fuels (1). Fossil fuel industries do not care so much about the debate as creating confusion amongst the public about the topic of global warming (1). Thus, while scientists generally agree that the Earth is warming, they disagree about the cause of global warming. More research will be needed to assign a definite cause to global warming.
Global Warming as a Boon and a Bane
With all the confusion surrounding the global warming debate, much of the public only takes from the media that global warming will harm our world. However, global warming has potential benefits as well as drawbacks. First of all, as the temperature increases, the Earth will have a longer growing season in many areas (9). In general, there will be less freezing weather, and the increased temperatures and carbon dioxide levels will allow more plant growth (9). With more plant growth and a longer growing season, there will be more food for people and livestock. The warmer weather will also positively affect transportation. Airplanes, trains, buses, and cars will stop having cold weatherrelated delays for ice and snow (9). Thus, contrary to popular belief, global warming can have some benefits. Of course, global warming also has many negative effects on the Earth. Global warming is and will continue to have dramatic effects on aquatic life and biodiversity (9). To compound the natural detrimental effects to ecosystems, humans may further disturb the ecosystems (9). For example, by trying to combat the effects of rising sea levels, man may work to maintain the coastline. In our attempts to protect the coastline habitat, other species may disappear. Increased temperatures will also negatively affect the food supply in many places, nullifying the
Dartmouth Undergraduate Journal of Science
benefits of a longer growing season. The temperature increases will bring hotter temperatures in the summer, which may cause plants to die. It could also cause weather patterns, such as more intense floods and storms (9). In the future, global warming could prove to be a boon and a bane to the world, but it is impossible to estimate just how much of either it could be.
Water Vapor as a Greenhouse Gas Carbon dioxide is not the only greenhouse gas contributing to global warming; at high altitudes, water vapor also acts as a greenhouse gas, trapping heat on the Earth’s surface (10). Water vapor acts as positive feedback to the greenhouse gas phenomenon because it prevents heat from leaving the Earth’s atmosphere, just like carbon dioxide. Carbon dioxide causes the greenhouse effect, but water vapor is a more serious problem because as the temperature rises from the greenhouse effect, more water is able to stay in its gaseous form higher in the atmosphere
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(10). Scientists have used computer models to find that the water vapor intensifies the warming effects of carbon dioxide by at least a factor of two (11). On the other hand, water vapor also contributes the global cooling process as it condenses and falls as rain when too much of it exists lower in the atmosphere. It also blocks some of the sun’s heat from reaching the Earth (11). Overall, water vapor currently has a net effect of keeping the Earth cooler even though it acts as a greenhouse gas (11).
Conclusion When trying to determine if global warming is fact or fiction, we must take into account evidence from all sides. Plenty of evidence exists within the science community, including skeptical opinions against global warming. While the evidence points to the existence of global warming, the cause is still widely disputed. Additionally, the media reports on other sources of evidence for global warming from different political groups. Ultimately, the world still lacks a consensus on the
topic of global warming: its causes, its presence, and its effects. However, armed with the proper knowledge, we can each decide for ourselves where we stand in the global warming debate. References: 1. P. Moriarty, D. Kennedy. Cybernet. Syst. 35, 723-725 (2004). 2. S. Weart, B. Atom. Sci. 67, 41-50 (2011). 3. J. Durfee, J. Corbett. Nieman Reports 59, 88-89 (2005). 4. S. Quiring, GeoJournal 70, 1-3 (2007). 5. G. A. Florides, P. Christodoulides. Environ. Int. 35, 390-401 (2009). 6. P. Pockley, Australasian Science 28, 28-31 (2007). 7. J. Rose, P. Geologist. Assoc. 121, 334-341 (2010). 8. S. Wang, Chinese Sci. Bull. 55, 1961-1962 (2010). 9. T. Moore, EMBO Reports 9, S41-S45 (2008). 10. S. Sherwood, Australasian Science 30, 25-27 (2009). 11. R. Spencer, Social Science and Public Policy 44, 45-50 (2007).
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ECOLOGY
A New View of Species Extinction Comparing the Value of Two Marine Mammal Species Kali Pruss ‘14
W
e all hear about climate change, species extinction, and impending environmental collapse. We see commercials, books, and films dedicated to inspiring action to save endangered species. However, species preservation is not as simple as human goodwill – investing in saving a species is an economic investment as well. With the number of endangered species climbing each year, it is not economically plausible to pour money into saving every single endangered species (1). Many intelligent mammal species receive more attention than declining plant or insect species. For example, whales have a “unique place in conservation lore” – they have become a symbol of humanity’s capacity for greedy overharvest (2). People also simply find them fascinating; whales have become the subject of successful commercial movies, such as Free Willy, and literature, such as Moby Dick. We speak of “saving the whales”, but is it
reasonable to attempt to do so? Given two marine mammal species, would one be more valuable to save? Based on ecologic, economic, and intrinsic value and the potential for reestablishment, would killer whales or blue whales be more worthwhile to sustain? We may ask, “What difference will it make if sharks or whales disappear?” It is estimated that the ocean holds ten million species–what’s the big deal with losing one or two (3)? Some scientists believe that “many species, perhaps most, do not seem to have any conventional value at all, even hidden conventional value” (4). Others think that biological diversity, the number, variety and variability of living organisms in a given assemblage is the key to life as we know it and “holds the world steady” (3, 5). Whales are some of the most voracious consumers in the oceans due to their great abundance and their large metabolic demands; thus, they have the potential to play an
ecologically significant role in marine ecosystems as important consumers in food webs. Additionally, their carcasses can support more than 350 species for 80 years (2). However, in his book The Future of Life, Wilson argues that every time humanity entered a virgin environment, most of the megafauna soon vanished (6). Humans routinely eat their way down the food chain: Native Americans quickly hunted North America’s largest mammals, such as the Wooly Mammoth and the Giant Sloth, to extinction. If megafauna vanish often, would the disappearance of whales, or one species of whale, matter? What are the ecological impacts of killer whales and blue whales independently? Killer whales have a large impact on their ecosystems. Bioenergetic analyses have been used to assess the caloric needs of average-sized whales. A 2,800-kilogram female requires 193,000 kilocalories per day; a 4,733-kilogram male requires 287,000
Image courtesy of Peter Nijenhuis.
Orcas, also known as killer whales, play an important in eco-tourism and the entertainment industry as the symbol of SeaWorld’s “Shamu” business. 18
Dartmouth Undergraduate Journal of Science
Fig. 1: A simplified version of the Antarctic food chain. Krill provides the basic resource for many large mammals (10).
kilocalories per day (2). Because orcas are top predators in the food chain, a cascade of effects may reverberate through their ecosystem, often negatively impacting the species below them. One example of this is from hunting of whales in Western Alaska, which led to orcas switching their primary prey to sea otters. Increased predation by killer whales led to decline in sea otter populations (2). Sea otters feed on sea urchins, so the urchin population exploded with increased killer whale predation. The increased sea urchin populations have deforested many kelp beds. The otter’s key role in the ecosystem was essentially eliminated by killer whale predation (7). Kelp forests are one of the most diverse and productive ecosystems in the world, and deforestation has profound and lasting impacts on many species (7, 8). Whale hunting led to killer whales having a negative impact on their ecosystems. Blue whales, on the other hand, have a less dramatic impact on their ecosystems. The largest animal on the planet, blue whales also have high metabolic demands. Blue whales require between four and eight tons of food per day (9). However, blue whales feed almost exclusively on krill, a small shrimp-like invertebrate. Krill abundance is crucial to blue whale populations. However, many other whale species also feed on krill as their main food resource (10). As other whale populations increase, krill population levels decrease, and as krill abundance decreases, blue whales may suffer. Commercial fleets also harvest krill and may also compete with blue whales for the resource (10). However, because FALL 2011
krill is widely abundant and has a relatively stable population, a decrease or increase in blue whale population will have relatively little effect on krill populations and the ecosystem as a whole. Krill have more predators than just blue whales, as shown in Fig. 1. The size of blue whale populations affects krill population sizes less than vice versa. Similar to the debated importance of biodiversity in terms of the health of ecosystems, the economic value of biodiversity is controversial. Many argue that a true value cannot be placed on the worth of biodiversity. Other economists calculate the total value of a species as the components that arise from current use and expected future use (4). “Use” may be commercial or noncommercial, such as the need for raw materials, aesthetic satisfaction or personal experiences. Determining the economic value of a species is anthropocentric because humans assign the values of what is “worthwhile” and utilitarian because different characteristics of a species count to the extent that people want them to (4). Whales may be economically valuable in many ways. Tourist activities, such as whale watching, yield high revenue in many countries. Countries around the world that have invested in whale watching currently host 13 million whale-watchers per year (11). Starting whale-watching industries in countries that do not yet have them could generate an additional 413 million dollars and 5,700 jobs. Doing so would increase total benefits from whale-watching to over 2.5 billion dollars per year at 19,000 jobs globally (11). Killer whales are important in eco-tourism and the entertainment
industry. Every year, thousands of people travel to the Pacific North Coast Integrated Management Area (PNCIMA) for opportunities to see orcas in the wild. The overall economic value of killer whales to the whale watching industry is millions of dollars per year (12). Expenditures per person per day on eco-tourism for killer whales were 472 dollars in 1986 and 530 dollars in 1989 (13). SeaWorld has turned the killer whale image into a multi-million dollar brand. “Shamu” is SeaWorld’s largest business and the company owns more killer whales than anyone else in the world (14). Blue whales yield less annual revenue than killer whales. Expenditures per person per day on eco-tourism for blue whales in 1986 and 1989 were only between 62.50 and 70.40 dollars (13). Blue whales are not used in the entertainment industry and are the subject of fewer whale-watching expeditions due to their lower densities than orcas. In his 1973 paper “Profit Maximization and the Extinction of Animal Species,” Colin Clark argues in favor of the economic value of the total extermination of blue whales (16). In historical human exploitations of various populations, Clark points out that a characteristic pattern occurs. As harvests expand, exploitation increases, fears are expressed for the survival of the population and associated industry, and conservation measures are considered, and sometimes implemented. However, it is a reasonable possibility that the owner of a resource would want to maximize the present value of harvest (and discount the future revenues by doing so). According to Clark, it is economically preferable to kill every blue whale in the ocean and to reinvest the profits in growing industries rather than wait for the long-lived species to recover to the point of sustainable annual harvest. It is impossible to assign a true value to the intrinsic worth of a species but still important to consider when determining a species’ worth. According to Earle, most people feel immense goodwill toward dolphins, whales, and other marine mammals (3). The high revenue that comes from killer whale eco-tourism is a result of the powerful aesthetic and intrinsic value humans hold for killer whales (12). Humans value orcas’ social behavior, intelligence, 19
and strength (12). Killer whales are highly protective of their young, and other adolescent females in a pod often assist mothers with infant care (9). Killer whales are the largest of the dolphins and are one of the world’s most powerful predators. Our fascination with these creatures is evident in our portrayal of them in literature throughout history: killer whales have been the subject of ancient mythological stories and current popular films as vicious monsters or as man’s best friend. Humans value blue whales for different reasons than they value orcas. Blue whales are the largest animals to ever inhabit the earth. They are as long as approximately three school buses (70 to 90 feet) and weigh between 200 and 300 thousand pounds. The blue whale has a heart the size of a small car and a tongue that weighs as much as an elephant (9, 15). These creatures leave us in awe. However, we know relatively little about blue whales. Unlike killer whales, they usually travel alone or in pairs and can hear each other from up to 1,000 miles away (9). Their relatively low densities make it difficult for researchers to learn about their migration patterns and life histories. Blue whales not only represent a marvel as the world’s largest animal, but also present a potentially interesting or important opportunity to learn more about ocean organisms and ecosystems. Killer whales have never been hunted extensively by humans and as of yet are not considered “endangered”, but “threatened” (9). Second to humans, they are the most widely distributed species in the world (17). They are not restricted to specific regions, a frequent characteristic of endangered species. Minimum worldwide abundance estimates of killer whales are around 50,000 individuals (2). Blue whales, on the other hand, are a highly endangered species. Their numbers have dropped significantly due primarily to whaling in the 20th century. Of the 5,000 blue whales which inhabited the North Pacific, only 1,200 are left; only a few hundred reside in the North Atlantic, and of the 20,000 blue whales in the Southern Hemisphere, only 9,000 remain, half of which are pygmy blue whales (18). Because of their “preciously low numbers”, blue whales are especially vulnerable to habitat degradation and 20
reduction of their main food source, krill. According to the Save the Whales foundation, due to the amount of time it takes for blue whales to grow and reproduce, it may be too late for their recovery despite all efforts to save them (18). Moreover, many blue whales have trouble finding mates due to their low densities. Mori and Butterworth claim that after their protection in Antarctica, the blue whale population there experienced an 8 percent per year increase (10). However, Save the Whales asserts that even though a few populations are increasing slightly, overall, their numbers are too small for recovery (19). While blue whales are a biological marvel and present possible research opportunities, killer whales have a greater economic benefit and will be easier to sustain. The loss of blue whales is likely to have relatively low ecological impact, and they may be beyond saving already. The already low economic revenue from blue whales would decrease greatly from the amount of resources that would be invested in the conservation of this species, as they may already be beyond saving. Although killer whales currently have many negative impacts on their ecosystems, humans could potentially change killer whales’ primary prey again by trophic manipulation to benefit the ecosystem. For example, since we know killer whales’ predation on otters caused the elimination of many kelp forests, introducing a new source of prey for killer whales could allow kelp forests to recover. Of course, we do not truly face an ultimatum between these two species, and Many would never advocate allowing the extinction of blue whales. However, this type of model can reveal a way of thinking about conservation that more traditional approaches would overlook. Most conservationists only consider each species’ intrinsic value and seek to restore every species to a sustainable abundance. While considering intrinsic value is important, this approach may not be practical. Taking a more holistic view by considering the benefit a species has to its ecosystem, to humans, and the amount of human resources which would be required for the species’ recovery may present a method which is difficult to accept but most pragmatic.
References 1. J. Shogren et al., Conserv. Biol. 13, 1257-1261 (1999). 2. J. Estes et al., Whales, Whaling and Ocean Ecosystems (Berkeley: University of California Press, Berkeley, CA, 2006). 3. S. Earle, The World is Blue: How Our Fate and the Ocean’s are One (National Geographic, Washington D.C., 2009). 4. E. Wilson, Ed., Biodiversity (National Academy Press, Washington D.C., 1988). 5. D. Pearce, D. Moran, The Economic Value of Biodiversity (Routeledge, London, UK, 1994). 6. E. Wilson, The Future of Life (Random House, Inc., New York, NY, 2002). 7. J. Estes, M. Tinker, T. Williams, D. Doak, Science 282, 473-476 (1998). 8. R. Steneck et al., Environ. Conserv. 29, 436-459 (2002). 9. National Geographic, Animals (2011). Available at http://animals.nationalgeographic. com/animals (May 2011). 10. M. Mori, D. Butterworth, Af. J. Mar. Sci. 26, 245-259 (2004). 11. A. Cisnero-Montemayor, U. Sumaila, K. Kaschner, and D. Pauly, Mar. Policy [in press], 1-6 (2010). 12. David Suzuki Foundation, Killer Whales (2011). Available at http://www.davidsuzuki.org/ issues/oceans/science/marine-planning-and conservation/killer-whales (May 2011). 13. L. Pendleton, J. Rooke, Understanding the Potential Economic Impact of Marie Wildlife Viewing and Whale Watching in California: Executive Summary (2006). Available at http:// www.dfg.ca.gov/mlpa/pdfs/binder3dii.pdf (May 2011). 14. Associated Press, SeaWorld’s Shamu shows resume today (2010). Available at http:// www.nhregister.com/articles/2010/02/27/news/ c6seaworld.txt (May 2011). 15. The Marine Mammal Center, Blue Whale (2011). Available at http://www. marinemammalcenter.org/education/marinemammal-information/cetaceans/blue-whale.html (May 2011). 16. C. Clark, J. Polit. Econ. 81, 950-961 (1973). 17. Sea World, Animals: Killer Whales (2011). Available at http://www.seaworld.org/animalinfo/info-books/killer-whale/index.htm (May 2011). 18. Save the Whales, Blue Whale Info (2008). Available at http://www.blue-whale.info/Save_ the_Whales.html (May 2011). 19. Save the Whales, Blue Whale: Balaenoptera musculus (2011). Available at http://www.savethewhales.org/blue.html (May 2011).
Dartmouth Undergraduate Journal of Science
health
The Deal on Dieting Derek Racine ‘14
W
hether you are on the new SmartChoice20 meal plan or the SmartChoice5 meal plan, eating at an all-you-can-eat buffet several times a week can start to weigh down on you. Somehow, countless, free Pavilion cookies manage to fill your plate. When you step on a scale, the freshman 15 might come as a surprise, and you might consider starting to diet. You take the next logical step and type “diets” into Google. Upon performing the search, you are bombarded by countless diets: the Atkins diet, Weight Watchers, the Diet to Go, SlimFast, Protein Power, the DASH diet, and countless others. What is the deal with all these diets? Do they even work?
The Body Before delving into how different diets work, an important understanding of digestion and metabolism is essential. Metabolism is set of chemical reactions used to break down organic molecules to release of energy, as well as the anabolic reactions that construct molecules from simpler components. When the body expends more energy than takes in through the diet, the body relies on internal stores of energy. One of these stores is glycogen, a complex carbohydrate stored in skeletal muscles and liver tissue. After this store is de-
Image retrieved from http://www.beginnerbaby.com/tag/weight-gain-during-pregnancy (Accessed 4 November 2011).
Many people choose to diet because of their dissatisfaction with their body weight or image. FALL 2011
pleted, the body turns to fat, which is stored in the specialized cells making up adipose tissue, and protein. This process of catabolizing, or breaking down, fat is called lipolysis. In this process, fats are broken down into glycerol and fatty acid components, which go on to produce a high-energy compound commonly known as ATP, or adenosine triphosphate. Macroscopically, this burning of fat is observed as weight loss.
has become a national pastime in the United States, “this preoccupation has done little to stem the tide of the obesity epidemic. In the past two decades, the prevalence of obesity in this country has doubled” (3). Ironically, some studies point to the increased stress of dieting as the main reason people ultimately fail to control weight (10).
Weight Loss
While many people diet to lose weight, others diet simply to maintain their current weight. Whatever the reason, dieting can have serious consequences. In fact, recent studies have found that dieting not only increases stress, but also causes a person to be more prone to eating more high-fat foods once they come off of their diet. Some authors have reasoned, “Dietinduced activation of the stress system might have downstream effects on brain feeding pathways that could drive the increased consumption of high-fat food” (1). Additionally, dieting is often a response to a “cultural pressure to be thinner than is required for good health,” and can cause a person to “try to achieve this goal through poor, and sometimes dangerous, nutritional choices” (7). This mentality may even lead to the development of eating disorders like anorexia and bulimia. In fact, “reviews of dieting studies have documented [many] negative emotional consequences of dieting, such as depression, anxiety, decreased self-esteem, nervousness, and irritability” (10).
To lose weight, many people choose to diet. Dieting is the practice of restricting the food people eat to encourage the body to break down stored fat. People often exercise in conjunction with dieting to further enhance their energy usage, specifically the amount of fat the body burns to sustain its metabolic processes. According to Laurie Wadsworth, an associate professor of human nutrition at St. Francis Xavier University, “eating high-calorie foods and then exercising to burn them off is not the way to go. While working out is good for you, don’t expect exercise alone to burn off hundreds of extra calories” (2). As a practice, dieting has been around for nearly a thousand years. William I, the King of England in 1087, attempted a diet of only alcohol to try and reduce his waistline. Evidently, rather than shedding weight, the corpulent King ended up in an accident, no doubt connected to his ambitious meal plan, with his horse that led to his death. Despite this dubious beginning, however, dieting has become enormously popular over the past century. Since Sylvester Graham assembled the first diet program, not surprisingly coined the “Graham diet,” the number of plans detailing the different foods to eat and those to stay away from has grown tremendously. Accordingly, “nearly a third of Americans have gone on 20 or more diets in their lives, trying an average of five different dieting strategies” (4). Nevertheless, while dieting
Dieting
Diets Most diets are one of the following types: low-fat diets, low-carbohydrate diets, low-calorie diets, and detox diets. While what constitutes good dietary habits continues to be debated, especially in the context of the low-fat versus low-carbohydrate diet controversy, “weight loss can be achieved by several highly divergent strategies” (6). As 21
a hormone released with stress, which could be responsible in part for the frequent failure of many of these diets.
Detox Diets
Detox diets are not aimed at weight loss. Rather, they claim to cleanse the body by eliminating deposits of food that have become stuck in the intestines and allowing the body to recover from the toxins that are regularly ingested through everyday foods. References
Image courtesy of Stu Spivack.
Many studies have examined the effects of the overconsumption and dependence of caffeine.
such, the specific diet plan is less important than the other factors that contribute to its success, namely the duration of the diet and how well a person conforms to its prescriptions. Additionally, while new diets seem to appear almost monthly—claiming to be more successful than their predecessors—the British Nutrition Foundation agrees that “despite the hype, key advice on healthy eating has changed very little over the past few decades” (6). Therefore, it is really a healthy lifestyle that should be encouraged, meaning, “following the time-honored advice of eating [a variety of] wholesome foods, eating in moderation, and exercising regularly” (3).
Low-Fat Diets
Low-fat diets consist of reducing saturated fat and cholesterol intake. In addition to its weight loss benefits, a diet low in fat is associated with a lower risk of coronary heart disease. While there are many factors that influence one’s risk of heart disease, “diets that are high in fat, especially saturated fat, can [greatly] increase your risk” (5). However, this diet also has several negative consequences. While too much fat can certainly be unhealthy, not enough fat can be even worse for a person. Dietary fat not only supplies energy to the body, but it also provides the basic building blocks of lipid macromolecules including essential fat-soluble vitamins like vitamin A, 22
D, E, and K, as well as fatty acids that are used in membrane biosynthesis.
Low-Carbohydrate Diets
Low-carbohydrate diets, including the Atkins diet and “Protein Power,” emphasize a reduction in carbohydrates by instead consuming a relatively high amount of protein. In this diet, foods like bread and pasta are limited and replaced with foods higher in fat and protein like meat, eggs, cheese, and nuts. Fruits and vegetables, which are low in carbohydrates, are also encouraged. Recently, researchers at the University of Illinois found, “A diet higher in protein and lower in carbohydrates than currently recommended may help people maintain desirable body weight and overall health” (9). Nevertheless, these diets also have problems associated with their long-term adherence. In fact, according to Tyler Cymet, an assistant professor at Johns Hopkins University, “the Atkins protocol has been shown to harm kidney function over time” (8).
1. E. Hutchinson, Nat. Rev. Neurosci. 12, 65 (2011). 2. A. Wood, Chatelaine 78, 130 (2005). 3.R. Kirby, Am. Fam. Physician 73, 1900 (2006). 4.Research Alerts 28.16 (2010). 5.Diet, Health Show - CBC Television (1997). Available on CBCA Complete (04 November 2011). 6.S. Schenker, Nutr. B. 26, 117-119 (2001). 7.S. Findlay, Paediatr Child Healt. 9, 7 (2004). 8.Anonymous, Baltimore Jewish Times 298, 35 (2007). 9.M. Mitka, JAMA- J. Am. Med. Assoc. 306, 1851-1852 (2011). 10.J. Tomiyama et al., Psychosom. Med. 72, 357-364 (2010).
Low-Calorie Diets
Low-calorie diets like the DASH diet, Diet-to-go, and Weight Watchers promote weight loss by simply restricting the number of calories ingested, regardless of origin. Even following this basic plan, there are several drawbacks to this type of diet. In fact, a recent study found that “restricting calories increased the total output of cortisol,” Dartmouth Undergraduate Journal of Science
health
Acceptable Addiction?
Health Benefits and Risks of Caffeine Consumption Diana pechter ‘12
I
t gets us out of bed in the morning, it makes us functional in the afternoon, it keeps us awake on the drive home from work, and it is one of the most consumed dietary ingredients throughout the world. What is this wonder drug that erupted in popularity in the second half of the 20th century? The answer: 1,3,7-trimethylxanthine, known more commonly as caffeine. A widely used central nervous system stimulant, caffeine provides many benefits to human health and performance. In the past decade, researchers have been hard-pressed to find a source of mass panic regarding caffeine consumption, nor have any deadly diseases been strongly enough caffeinelinked to elicit social aversion—as evidenced by the frequently long lines at Starbucks every morning. It seems that findings suggest the contrary, that caffeine can be a reducing risk factor in type2 diabetes mellitus (DM) and obesity and a symptom-reducer in variety of diseases. The risks of caffeine consumption, however, such as intoxication, withdrawal, and dependence, should not be ignored. In order to make informed dietary decisions, it is necessary to examine the benefits and risks of caffeine intake so that the positive qualities of caffeine use can be profited from without suffering adverse affects that accompany addiction.
tionally, caffeine may play a preventative role in sunlight-induced skin cancer, due to the function of caffeine in protecting DNA from damage (3). The link between coffee consumption and the risk for developing type 2 diabetes mellitus has been investigated in several studies. While one study did not recommend increasing coffee consumption to prevent type 2 DM until more research becomes available, it asserted that routine coffee consumption was associated with lower risk of type 2 DM (4). A recent study by Michel Lucas indicates reduced risk of depression in women with increased caffeine consumption (5). Many studies have associated caffeine with weight reduction and management. Research has demonstrated the role of caffeine in increasing metabolic rate, energy expenditure, lipid oxidation, and lipolytic and thermogenic activities, which are all favorable components of weight management and possible weight loss in humans (6). These results, however, should be taken with caution, since this study involved the caffeine intake from green tea (not coffee); green tea exerts the greatest effect on individuals who originally consume low amounts of caffeine (1). As one of the most-researched
substances in food, caffeine has a long history of safe use, and there is overwhelming scientific evidence that, when consumed in moderation, caffeine has no adverse health effects (7).
How much is too much caffeine? According to the diagnostic criteria from DSM-IV TR, the consumption of caffeine in excess of 250 mg, more than 2-3 cups of brewed coffee for comparison, can cause caffeine intoxication, which is defined as a set of symptoms that develop during or shortly after caffeine use (8). Developing five or more of the following symptoms shortly after caffeine consumption would be enough for a diagnosis of caffeine intoxication: restlessness, nervousness, excitement, insomnia, flushed face, dieresis, gastrointestinal disturbance, muscle twitching, rambling flow of thought and speech, tachycardia or cardiac arrhythmia, periods of inexhaustibility, or psychomotor agitation (9). A small amount of caffeine has the potential to induce these symptoms. Extreme side effects in humans can be observed at caffeine intakes of 15 mg/kg body weight (10). Individual differences to
Caffeine Consumption and Health The effects of caffeine have been widely studied with respect to human performance and health. Findings have shown that caffeine has the ability to enhance mood and alertness, to improve exercise performance, to increase the speed at which information is processed, awareness, attention, and reaction time (1). Caffeine has been implicated in reducing symptoms in Parkinson’s disease, such as deterioration of motor skills and tremors (2). AddiFALL 2011
Image by Andrew Zureick ‘13, DUJS Staff.
Approximate caffeine comparison of popular beverages. 23
take into account include body weight and sensitivity to caffeine. For people who are highly sensitive to caffeine, it is recommended to consume no more than 400 mg/day to avoid adverse effects, such as headache drowsiness, anxiety, and nausea (1). It is also important to consider that the amount of caffeine in any given cup of coffee fluctuates based on the variety of the coffee and the brewing equipment used.
Consequences of Withdrawal Caffeine withdrawal causes changes in cerebral blood flow, including vasodilation in high caffeine users, is thought to be associated with a throbbing, vascular-type headache (10). Double-blind studies of caffeine withdrawal have shown that a headache generally occurs 12-24 hours after the last dose of caffeine and usually resolves within 2-4 days, although some subjects continue to report sporadic headaches for as long as 11 days after cessation of caffeine use (11). About 50% of individuals in these studies report moderate to severe headaches, which may be worsened with physical exercise (9) . There has been some debate as to whether caffeine enhances cognitive performance or simply represents a reversal of deteriorated performance following caffeine withdrawal (12). If one builds up tolerance to caffeine from frequent exposure, resulting in a decrease in responsiveness, then addiction becomes much more likely.
Consequences of Dependence Caffeine dependence is associated with unsuccessful, persistent desires to cut down or control substance use. For many individuals, substance use is continued despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by the substance (9). When asked about caffeine use, 21% of individuals in a study by Svikis et al. (2005) indicated that they had previously been told by a health care professional that they should cut back or quit caffeine because of a medical condition including, fibrocystic breast disease, headaches, pregnancy, insomnia, and stomach problems (13). A number of comorbid conditions have been associated with caffeine dependence, the most common being alcohol abuse or dependence. In a study by Strain et al., 69% of subjects had other psychiatric disorders in remission, including substance use disorders, mood disorders, anxiety disorders, and eating disorders (9, 14).
Reducing from Heavy to Moderate Consumption Several studies with heavy caffeine consumers demonstrated efficacy of a structured caffeine reduction treatment program in achieving substantial reductions in caffeine consumption (12). This process of caffeine tapering or “fading” can be a useful method to treat
Image courtesy of Jennifer K. Warren.
caffeine withdrawal and dependence, which involves a tapering dose schedule rather than abrupt discontinuation. A combination of self-monitoring one’s daily caffeine use and reinforcement for decreased use have also been effective. Better education in stress management techniques and sleep strategies would be an essential step toward decreasing the negative impact of caffeine use, so that individuals resort to healthier ways of conquering fatigue. Taking a quick 20 to 30-minute nap, for example, has been shown to increase afternoon alertness more effectively than coffee (15). Coffee consumption has been demonstrated to have many positive effects on human health and performance. Though it may be one of the most socially acceptable addictions, there remain unfavorable consequences of frequent consumption. This reflects a need to improve general education regarding the multitude of effects of caffeine, including the constructive outcomes and the risks of addiction, so that individuals can make informed, healthy dietary choices. References 1. M. Heckman, J. Weil et al., J. Food Sci. 75, 77-88 (2010). 2. J. Trevitt, K. Kawa, A. Jalali, C. Larsen, Pharmacol. Biochem. Behav. 94, 24-29 (2009). 3. E. Abel et al., Eur. J. Cancer Prev. 16, 446-452. (2007). 4. R. Van Dam, Eur. J. Epidemiol. 18, 1115-1126 (2003). 5. M. Lucas et al., Arch. Intern. Med. 171, 1571-1578 (2011). 6. K. Acheson et al., Am. J. Clin. Nutr. 79, 40-46 (2004). 7. N. Clark, Physic. Sports Med. 25, 109-110 (1997). 8. American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders (APA, Washington, D.C., ed. 4, 2000) [fourth edition]. 9. R. Griffiths, Substance Abuse: Caffeine Use Disorders (McGraw-Hill Medical Publishing Division, Chichester, 2008). 10. Institute of Medicine, Caffeine for the sustainment of mental task performance: Formulations for military operations. (National Academy Press, Washington, D.C., 2001). 11. L. Juliano, R. Griffiths, Psychopharmacology 176, 1-29 (2004). 12. J. James, Neuropsychobiology. 38, 32-41. (1998). 13. D. Svikis et al., Am. J. Psychiat. 162, 2344-2351 (2005). 14. E. Strain et al., JAMA- J. Am. Med. Assoc. 272, 1043-1048 (1994). 15. J. Horne, C. Anderson, C. Platten, J. Sleep Res. 17, 432-436 (2008).
Many studies have examined the effects of the overconsumption and dependence of caffeine. 24
Dartmouth Undergraduate Journal of Science
biology
Myth: Philosophy Has No Place in Biology Answer: False
Yoo Jung Kim ‘14
I
nterest in the philosophy of Biology as an academic discipline has grown in the past three decades, in parallel to the rising prominence of the biological sciences (1). Some of the more recent questions currently debated within philosophy of biology address real problems within the fields such as evolutionary biology, systematic biology, developmental biology, and ecological biology. The relationship between scientific biology and the philosophy of biology is far from one-sided. In fact, philosophy of biology shares a complex relationship with its scientific counterpart that can be generalized into two categories: paternal and fraternal. Even within this categorization, the precise relationship between philosophy and the applied science remains difficult to scrutinize due to the varying opinions that biologists have in regards to applying philosophy within their science. Yet philosophy of biology has a place in biology because interdisciplinary scholarship between philosophy of biology and biology can benefit both fields and help solve current biological problems.
Introduction Although philosophy of biology focuses on the “critical examination that governs of our convictions [and] prejudices,” both biologists and philosophers of biology seek to observe and construct knowledge from the ontological reality to which the field of biology speaks (1). According to Andrew S. Yang, an associate professor of Biology in the School of Art Institute of Chicago, “the relationship between philosophy of science and research science appears similar to that of family members: intimately connected, mutually influential, and more than occasionally in a quarrel” (2). Although philosophy’s influence on biological practices and perceptions is evident, the exact nature of this influence—as well as the reciprocal sway of biology over philosophy—eludes a FALL 2011
simple explanation. Instead, Yang suggests that we can generalize interdisciplinary interactions into two categories: the fraternal and the paternal (2).
Image courtesy of LSE Library.
Sir Karl Popper argued that Darwinism was not a testable scientific theory.
Paternal Mode and Biology
The “paternal” mode of philosophy of science assumes authority over how science should be practiced and whether certain knowledge is scientifically meaningful (2). In 1974, Sir Karl Popper, considered one of the greatest philosophers of science in the twentieth century, attempted to rebut the classical inductivist form of the scientific method through his Principle of Demarcation and Falsifiability. Popper’s principle concluded that a theory should be considered scientific if and only if it is falsifiable, and as a demonstration of his principle, Popper suggested that Darwinism was not a testable scientific theory. His hypothesis quickly drew criticism from other contemporary philosophers of biology, such as the Darwinian philosopher Michael Ruse, and later, Popper ultimately retracted his theory. Despite the rejection of demarcation criteria by most of the philosophers
of science, Popper’s theory was revived eight years later, but this time, before the wider public. In 1981-82, during the Arkansas trial over the legitimacy of teaching “creation science,” both opponents and proponents of evolution invoked Popper’s theory in order to both denounce and to uphold, respectively, the legitimacy of evolution as a science. The testimony invoking the theory of demarcation as a criterion for validating the scientific legitimacy of evolution came from Ruse—the same Ruse who had denounced Popper’s theory almost a decade before. Ruse’s testimony prompted the presiding judge to declare in his ruling that Popper’s principle of demarcation and falsifiability was one of the “five essential characteristics” of what defines science (2). While Popper had originally used his theory to challenge the legitimacy of evolutionary biology, evolutionary biologists used Popper’s philosophy to entrench the authority of the field while popularizing Popper’s ideas in academic debates and in the public sphere. This case alone demonstrates the intricate complexities of the relation between biology and philosophy of biology, which, depending on the situational context may seem mutually supportive, conciliatory, and/or conflicting.
Fraternal Mode and Biology
The “fraternal” mode of philosophy of biology seeks to aid its scientific counterpart by addressing the necessity of new methods, tools, and concepts to address growing epistemological problems stemming from the breakneck progress of biological research (2). For instance, philosophy of biology has explored issues concerning causation, explanation, and methodology by utilizing evidence generated from research biology. By doing so, philosophy of biology has demonstrated the capacity to assist in the science of biology by better defining its questions and understanding its answers. Many of the different 25
schools of thought in the contemporary debates in philosophy of biology commonly utilize biological research to build up their arguments, which often boil down to subtle differences in definitions based on the nuanced interpretations of scientific findings.
Bridging the Two Fields Together To address the ontological nature of biology, philosophers utilize history and epistemology of representations while researchers utilize questions, measurements, and descriptive/prescriptive models. Despite differences in approach, both philosophy of biology and biology seek to address the same reality, and the product of each academic discipline can prove beneficial to the other. Philosophy of biology can critique the epistemological framework of biology while biology can provide philosophy of biology with data and evidence to fuel debates. Further interdisciplinary reciprocation of information will reveal that that there is no clear demarcation between the two, with “philosophy of biology [differing] from biology itself not in its knowledge base, but only in the questions it asks” (1). Members of the general biological community, however, commonly disregard philosophy’s importance, arguing that philosophy is “not applicable, and at worst, runs the risk of clouding the clear-eyed empiricism of basic research” (2). This type of assertion underscores the presumption that biology is a “natural, empirical science,” rather than a subjective approach of systematizing reality that may be swayed by assumptions of cultural, ideological, gender, and scientific normativity (3). Philosophy of biology has already assisted its scientific counterpart “in advancing ideas, putting issues to rest, and overthrowing faulty paradigms, as well as furthering technological comforts, establishing moral codes and alleviating pain and disease,” and it may be able to address its current problems—such as rapidly expanding fields and the threat of over-specialization—by providing a framework for critical analysis to redefine and reorganize our understanding of biology (3). For instance, less than six de26
cades after Watson and Crick cracked the molecular structure of the DNA, subsequent biological discoveries have allowed human beings to clone mammals, to genetically modify produce, to decode the human genome, and to give rise to a new set of biological subdisciplines, such as proteomics (coined in 1994) and genomics (coined in 1984) (4, 5). However, the influx of biological knowledge may lead toward academic overspecialization, impeding cooperation between subdisciplines and causing a rift between the public and academia. Fortunately, philosophy of biology can alleviate both problems by reconciling conceptual disparities between biological subfields and serving as an advocate for biological research in the public sector.
Biological Overspecialization and Ambiguity In the current state of biological academia, scientists face the daunting tasks of dealing with an ever-growing volume of biological knowledge and an increasing competition for limited funding and research positions, which have forced researchers to specialize in a small area of biology (6). Due to the current trend of overspecialization, biologists turn into “technical specialists” who often have little more than a “cursory” understanding of neighboring branches and may form specific concepts that fail to address related ideas in other subdisciplines (2). Without a framework for epistemological critique, specialized biologists may fall victim to a “subdisciplinary myopia” and lose sight of the field as a single, interconnected whole. Philosophy of biology, with its emphasis on rhetorical deconstruction and synthesis, can account for such conceptual disparities by forming more comprehensive concepts that can subsume existing definitions into models that better embody the connections between various branches of biology. Another problem of overspecialization lies in ambiguities stemming from a multiplicity of definitions. For example, botanist Wilhelm Johannsen first coined the term “gene” in 1909 and used it to describe the “Mendelian
units of heredity” (7). After a century of new discoveries, this definition has fallen obsolete, but even now, the denotation of a “gene” remains surprisingly inconsistent. According to the general definition found in Encyclopedia Britannica, a gene is a “unit of hereditary information that occupies a fixed position (locus) on a chromosome” (8). This definition fails to account for the existence of “jumping genes,” which can be transposed onto various locations on the genome. The National Human Genomic Research Institute defines the gene as a “basic physical unit of inheritance […] passed from parents to offspring [that] contains the information needed to specify traits” (7). This definition excludes genes that can be incorporated into the chromosomes through external means, such as retroviruses. Other commonly recognized terms such as “evolution” and “speciation” also experience this type of ambiguity as different subspecialties use different criteria and definitions suited for their respective fields. Furthermore, the continuous incorporation of new biological understanding causes these definitions to fluctuate constantly. Philosophers of biology help resolve these differences by providing more comprehensive models/criteria and by allowing for these differences by establishing a rationale for conceptual pluralism (commonly found in the debates of philosophy of biology) by recognizing the validity of multiple concepts based on their “relative significance to their respective fields” (9).
Connecting Biological Research with the Public Sphere Overspecialization of biology also harms relations with the public sphere. As concepts and fields become more specialized and cluttered with jargon, biology begins to elude the grasp of the general public. There arises a vast information gap between the average citizen and basic science. The cooperation of philosophy and the science of biology may help this disparity. For instance, those who hold the rare distinction of being respected figures in both biology and
Dartmouth Undergraduate Journal of Science
Image retrieved from http://en.wikipedia.org/wiki/File:Stephen_Jay_Gould_by_Kathy_ Chapman.png (Accessed 29 October 2011).
Evolutionary biologist Stephen Jay Gould who was wildly influential in 20th-century popular science.
the philosophy of biology have made remarkable strides in the education of the public. In his obituary, The New York Times lauded Stephen Jay Gould as a scientist who was “almost universally adored by those familiar with his work” outside of academia (10). Other inter-disciplinary scholars — such as Ernst Mayr, John Maynard Smith, and Richard Dawkins — formed the vanguard of biologists who incorporated philosophical concepts in their scientific work and popularized their respective fields in the public sphere Philosophers of biology, with their dual expertise over science and rhetoric, can serve as biology’s emissary to the public by informing them of current scientific advancements and possible implications for mainstream society. The rapid influx of biological knowledge has also unsettled certain members of the public, who have come to challenge biological researchers on the basis of morality and ethics over controversial biological topics. Philosophers can also intercede on behalf of biology by taking part in policy debates over current controversies in the discipline. In the debate over human embryonic stem cell research (hESC), the rationale of dissenters of hESC research cannot be pinned down merely on scientific ignorance. Rather, the problem lies in the incompatibility of beliefs (11). According to Alan Leshner, a former Chief Executive Officer of the American Association for the FALL 2011
Advancement of Science, to many, “the notion of destroying an embryo, no matter how noble the cause, conflicts with their core religious beliefs about when life begins, and its sanctity” (11). In these cases, educating dissenters about the process and the potential benefits of hESC research will not be enough. Instead, philosophers of biology can capitalize on their dual expertise over philosophical and biological knowledge by engaging in an ethical dialogue with members of the public, listening to their qualms and the moral dilemmas they perceive within the current trend of biological research. Reconciliation through philosophical engagement with dissenters may allow biologists and philosophers to move science forward while addressing legitimate public concerns stemming from the breakneck pace of biology. Philosophy of biology can address problems that originate from specialization and the rapid influx of biological knowledge. For instance, philosophers of biology can reconcile disparities and ambiguities that exist in the classification and concepts in biology. Furthermore, philosophers of biology can educate and engage the public in shaping the intellectual, moral, and ethical landscape of biological perception and research.
Philosopher-Scientists Taking these factors into consideration, steps to facilitate the inter-disciplinary interaction between biology and philosophy of biology have best been initiated by individuals. Yet biologists who demonstrate proficiency in philosophy are rare; despite the Latin roots of “Ph.D.” (philosophiae doctor), researchers often hold no professional obligations to engage in philosophical thinking. As such, for an inter-disciplinary relationship to take root, philosophers must win the cooperation of current biologists by engaging in more a fraternal vein of research that seeks to complement biology to do “better science” and by educating the incoming generation of scientists in the importance of philosophical modes of inquiry. Philosophers of biology must communicate the nature of their work to the broader scientific community so that the latter may recognize the
significance of philosophical thinking in biological research. The success of such collaboration may provide a model for other inter-multidisciplinary scholarship, which may demonstrate the unity of knowledge—not through reductionism or consilience—but as a product of creative human expression. References 1. P. Griffiths, “Philosophy of Biology,” The Stanford Encyclopedia of Philosophy (2011). Available at http://plato.stanford.edu/archives/ sum2011/entries/biology-philosophy/ (23 August 2011). 2. A. Yang, Int. Stud. Philos. Sci. 22, 212-225 (2008). 3. F. Ayala, “Introduction,” Contemporary Debates in Philosophy of Biology (WileyBlackwell, West Sussex, 2010). [first edition] 4. Definition of Proteomics (2003). Available at http://www.medterms.com/script/main/art. asp?articlekey=16299 (22 August 2011). 5. A. von Eenennaam, Animal Biotechnology Genomics (2010). Available at http:// animalscience.ucdavis.edu/animalbiotech/ Genomics/index.htm (22 August 2011). 6. L. Garwin, Nature. 376, 547 (1995). 7. Gene (2011) Available at http://www.genome. gov/Glossary/index.cfm?id=70 (August 2011) 8. Gene (2011). Available at http://www. britannica.com/EBchecked/topic/228226/gene (August 2011) 9. M. Dietrich, “Microevolution and Macroevolution are Governed by the Same Processes in Chemistry and/or Physics,” Contemporary Debates in Philosophy of Biology (Wiley-Blackwell, West Sussex, 2010). [first edition] 10. C. Yoon, Stephen Jay Gould, 60, Is Dead (2002). Available at http://www.nytimes. com/2002/05/21/us/stephen-jay-gould-60-isdead-enlivened-evolutionary-theory.html (22 August 2011). 11. A. Leshner, Science and Public Engagement (2006). Available at http://chronicle.com/article/ SciencePublic-Engagement/25084/ (22 August 2011).
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MEDICINE
The AIM-HIGH Study
How it Impacted Our Understanding of HDL Cholesterol in Cardiovascular Health Amir Khan ‘14
C
holesterol is an essential compound that contributes to a variety of physiological functions integral to human life. Obtained from dietary sources and synthesized within organs such as the liver, cholesterol serves as a precursor to both fat-soluble vitamins and steroid hormones. In addition, cholesterol is needed for the proper functioning of every cell within our body—it ensures that cell membranes are built with appropriate fluidity, and it is involved in intracellular transport and signaling. Interestingly, despite all of its functions within the body, high levels of cholesterol can lead to pathology. The most well known pathology, atherosclerosis, involves an accumulation of cholesterol as fatty deposits in arteries. Eventually, the thickening of arterial walls and the aggregation of plaque cause the narrowing of arteries. Atherosclerosis becomes a dangerous condition with the rupture of atherosclerotic plaque & activated platelets that lead to thrombosis and heart attacks, as shown in Fig. 1. It is important for both doctors and patients to better understand cholesterol, especially because it is a contributing factor to these deadly events (1). Cholesterol has been classified into different categories based on the lipoprotein that carries it through the blood. The three primary types of cholesterol are low-density lipoprotein (LDL), very-low density lipoprotein (VLDL), and high-density lipoprotein (HDL). LDL cholesterol, commonly referred to as “bad cholesterol,” carries cholesterol throughout the body; as Fig. 2 shows, the LDL cholesterol can
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dangerously accumulate into plaque if LDL levels are too high. VLDL cholesterol is mostly comprised of triglycerides and can actually strengthen LDL aggregates, which makes it another risky form of cholesterol if levels are not within a normal physiological range. On the other hand, HDL or “good” cholesterol removes excess cholesterol from the blood and transports it back to the liver. This reverse cholesterol transport process helps keep blood cholesterol levels under control (1). With such functionally different types of cholesterol, various medications have been developed to manipulate levels of each type as needed in order to decrease the risk of pathology. Because of the strong scientific support and evidence of the dangers of high levels of LDL cholesterol, LDL is a primary target of many forms of medication. The most potent of these medications are statins, which impede the production of cholesterol by the liver and help with the reabsorption of cholesterol into the liver. These two means of reducing blood levels of LDL
cholesterol directly stabilize plaque progression. As shown by trials such as the Heart Protection Study (HPS) and the ASCOT trials, statins have been found to have a huge impact on atherosclerotic development by lowering LDL levels up to 60 percent, and also mildly increasing HDL levels (1-3). While lowering LDL cholesterol levels is indeed a crucial aspect of fighting atherosclerosis, physicians also seek to raise HDL cholesterol in an effort to further control atherosclerotic progression. The scientific community has accepted the benefit of high HDL levels in reducing cardiovascular events particularly due to the Framingham Study of the 1980s. Comprised of 2815 elderly men and women, the Framingham Study demonstrated that HDL cholesterol had a significant “inverse association with the incidence of coronary heart disease (p < 0.001) in either men or women” (4). As shown in Fig. 3, the study concluded that “low HDL-cholesterol levels are associated with a higher risk of coronary heart disease irrespective of the level of LDL-cholesterol” (5).
Image retrieved from http://www.emirateshospital.ae/english/Cholesterol.asp (Accessed 29 October 2011).
Fig. 1: Myocardial infarction, or heart attack. Dartmouth Undergraduate Journal of Science
Image retrieved from http://drpinna.com/wp-content/uploads/2010/07/reduce-cholesterol.jpg (Accessed 29 October 2011).
Fig. 2: HDL and LDL cholesterol.
With the strong evidence provided by the Framingham Study, medications were developed to raise HDL cholesterol levels in patients with low HDL levels, who comprise “up to 29% of patients with [coronary heart disease]” (6). The two most potent medications that raise HDL levels are fibrates and niacin, also known as vitamin B3 and nicotinic acid. Both have raised HDL levels significantly, with niacin raising HDL levels “by up to 30%” (6). However, fibrates have the additional benefit of lowering triglyceride levels greatly, while niacin primarily focuses on raising HDL levels with some effects on triglycerides (5). Niacin, produced by Abbott Pharmaceuticals in the form of the extended-release drug Niaspan, is a main drug that focuses on raising HDL levels for cardiovascular benefit. It has been widely prescribed, and Abbott made $1 billion off the drug in 2010 alone (7). Such wide usage has been encouraged under the pretense that raising HDL levels will benefit patient health and combat the incidence of cardiovascular events, as demonstrated by the Framingham Study. However, this long-held belief has now been called under question by the Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/ High Triglycerides: Impact on Global Health outcomes (AIM-HIGH) trial. The AIM-HIGH trial surprised the medical and scientific community by demonstrating that Niaspan provides no benefit in combating the incidence of cardiovascular events, despite raisFALL 2011
ing HDL levels. A look into past trials and the AIM-HIGH trial can provide insight into how the public should interpret the implications of such shocking changes to the scientific understanding of Niaspan and HDL cholesterol in terms of cardiovascular health.
Before AIM-HIGH Before the AIM-HIGH trial, the medical community believed that high HDL levels were associated with a decreased rate of cardiovascular events in high-risk patients. In 1999, The HDL Atherosclerosis Treatment Study (HATS) analyzed 160 patients with coronary heart disease and low HDL cholesterol levels. The study assessed the effects of Niaspan + statin on patients compared to placebo groups with no Niaspan + statin treatment. The HATS trial demonstrated that “combining nicotinic acid with a statin improved HDL-cholesterol and LDL-cholesterol, inhibited the progression of atherosclerosis, and reduced cardiovascular event rates in a high-risk population with established coronary heart disease” (5). With these findings, HATS demonstrated the strong superiority of dual Niaspan and statin treatment to patients at risk of atherosclerosis and heart disease. However, statins have been accepted as an effective treatment for people at such risk, at all costs. Thus, there was a blatant need for trials comparing statin treatment to statin + Niaspan treatment, showing the specific benefits of Niaspan alone.
In 2004, the Arterial Biology for the Investigation of the Treatment Effects of Reducing Cholesterol (ARBITER-2) trial studied 167 high-risk patients with low HDL levels and normal LDL levels. The researchers compared the effects of Niaspan + statin to statin alone on carotid artery intima-media thickness (CIMT), a measurement representative of atherosclerotic levels. The results showed that Niaspan + statin significantly increased HDL levels and significantly reduced triglyceride levels compared to the statin group alone, with insignificant changes in LDL in both groups. There was a significant increase in CIMT in the statin group, whereas the Niaspan + statin group showed no change in CIMT, indicating Niaspan’s role in combating atherosclerotic development. ARBITER-2, however, was not monitoring the magnitude of cardiovascular events as an endpoint, since researchers used CIMT as an indicator of event occurrence to reach the conclusion that Niaspan + statin decreases cardiovascular event occurrence. Therefore, a trial was needed specifically to observe the effect of Niaspan + statin on cardiovascular event rates; this need was finally fulfilled with the AIM-HIGH trial (5).
The AIM-HIGH Trial The AIM-HIGH trial enrolled 3,414 participants, all of whom were at risk for cardiovascular events, had controlled LDL levels, and had a history of low HDL, high triglycerides, and heart disease. The trial was funded by the National Institutes of Health (NIH), as well as by Abbott Pharmaceuticals, who covered around $25 million of the costs. The trial was also monitored by an independent group of physicians and scientists to ensureproper oversight. The patients were divided into groups of statin + placebo and statin + Niaspan for analysis of the rate of cardiovascular events. Physicians and patients eagerly awaited the trial’s outcome to influence their decisions regarding treatment combating heart disease and atherosclerosis (7). Unexpectedly, the trial had to be stopped 18 months early due to the lack of clear benefit from Niaspan treatment. While data showed that Niaspan increased HDL levels and reduced 29
Conclusion
Image retrieved from http://eurheartjsupp.oxfordjournals.org/content/8/suppl_F/F74/F1.expansion.html (Accessed 29 October 2011).
Fig. 3: Coronary heart disease risk in Framingham Study based off of HDL and LDL levels.
triglyceride levels significantly, there was no significant reduction in “fatal or non-fatal heart attacks, strokes, hospitalizations for acute coronary syndrome, or revascularization procedures to improve blood flow in the arteries of the heart and brain” (8). In fact, the trial actually found more strokes in the Niaspan group than the control; however, due to analysis of past trials, these strokes have been deemed as anomalies due to chance rather than as any significant danger. Nevertheless, the researchers concluded that “adding high dose, extended-release niacin to statin treatment in people with heart and vascular disease, did not reduce the risk of cardiovascular events, including heart attacks and stroke” (8). Such a conclusion has raised a number of concerns considering the changes these findings might make on the longestablished approach to reducing heart risk; furthermore, simply the number of individuals currently prescribing for Niaspan warrants a thorough investigation into the validity of these claims.
Implications The AIM-HIGH trial has directly challenged a widely accepted medical consensus: raising HDL cholesterol with medications such as Niaspan can save lives. The results of the Framingham Study have clearly shown that high HDL levels can prevent cardiovas30
cular events. However, the AIM-HIGH study has negated the conclusion that raising HDL levels by medication benefits cardiovascular health. AIM-HIGH has shown that there is a distinct difference between high HDL levels due to genetics or cardiovascular exercise and high HDL levels due to medication. The results of AIM-HIGH contradict the conclusions of the ARBITER-2 study, which asserted that Niaspan+statin treatment reduced incidence of cardiovascular events based off CIMT measurements. Physicians and scientists are now pushing for more trials to further investigate Niaspan and raising HDL cholesterol levels. Perhaps the use of different kinds of statins other than the simvastatin used in AIM-HIGH will be enlightening in a future trial. Furthermore, differences in cholesterol particle size among HDL cholesterol may also be an area of interest for future studies. The results of AIM-HIGH have already led to sharp declines in the prescription of Niaspan for at-risk patients. Despite the fact that the NIH has explicitly stated that patients already on the drug should remain on it until further studies are conducted, those with unwanted side effects associated with Niaspan can safely consider dropping the drug. Nonetheless, the need for more insight into why raising HDL levels with medication fails to prevent life-threatening cardiovascular events remains an issue.
The AIM-HIGH trial has made a huge impact on the medical community, as well as on the lives of those at risk of cardiovascular disease. Not only has it helped advance the world’s understanding of cholesterol and heart disease, but it has also served as an example of how clinical trials should be conducted. Abbott’s role in funding a study that has shaken their profits shows a degree of integrity that serves as a model for all pharmaceutical companies. Furthermore, the direct comparison of two realistic treatment choices such as statin with or without Niaspan was very helpful for physicians and patients and should be incorporated more in trials for other drugs. Thus, while the world may not fully understand the mysteries of cholesterol yet, the AIM-HIGH trial has taken us a step closer to the truth, and, for such a deadly disease such as heart disease, that is truly a remarkable step. References 1. High Cholesterol Prevention (2011). Available at http://www.mayoclinic.com/health/high-bloodcholesterol/DS00178/DSECTION=prevention (October 2011). 2. Heart Protection Study Collaborative Group, Lancet 360, 7-22 (2002). 3. P. Sever et al., Lancet 361, 1140-1158 (2003). 4. T. Gordon et al., Am. J. Med. 62, 707-714 (1977). 5. A. Taylor, Eur. Heart J. Suppl. 8, F74-F80 (2006). 6. A. Wierzbicki, Curr. Med. Res. Opin. 18, 36-44 (2002). 7. H. Krumholz, Five Lessons From Niaspan’s Disappointing Study (2011). Available at http://www.forbes.com/sites/ harlankrumholz/2011/05/31/five-lessons-fromniaspans-disappointing-study/ (October 2011). 8. NIH stops clinical trial on combination cholesterol treatment (2011). Available at http:// www.nih.gov/news/health/may2011/nhlbi-26. htm (October 2011). 9. The AIM-HIGH Investigators, Am. Heart J. 161, 471-477 (2011). 10. J. Shepherd, Eur. Heart J. Suppl. 7, F15-F22 (2005).
AIM-HIGH logo retrieved from http://aimhigh-heart.com/ (Accessed 4 November 2011).
Dartmouth Undergraduate Journal of Science
PHYSIOLOGY
Elegance in Running
How Humans can Beat Cheetahs sara remsen ‘12
H
umans do not make the world’s top 20 fastest runners. We lose our spot to animals like cheetahs and pronghorn antelope. But, do not discount yourself as a top performer; we are actually capable of outrunning cheetahs—as long as the race is longer than 600 yards. Humans are so specialized for running that we can win in an endurance race against almost any animal, including those animals that we consider unbeatable. As one tribe of Bushmen in Africa has demonstrated, winning against the world’s fastest animals is only a matter of finding the right distance. Throughout millions of years of evolution, terrestrial animals developed many forms of getting around, such as walking, hopping, slithering, trotting, and running. Some terrestrial animals are born to run; these “cursorial mammals” possess adaptations that make running easy and efficient. Running is a survival advantage; these animals can travel further and more quickly to find food, escape from swift predators, and catch agile prey.
Specialized Runners Cheetahs and pronghorn antelope are two of the most specialized and successful runners—and the two fastest animals in the world. Cheetahs reach the global record at a top speed of 70 miles per hour (mph), with pronghorn antelope keeping pace at 50 mph. Cheetahs have been sprinting after antelope on the African Savannah
Image courtesy of Anup Shah/Nature Picture Library.
Fig. 1: A cheetah breaking into a run. FALL 2011
Image courtesy of Steve Garvie.
Fig. 2: A giraffe in a jarring galloping gait.
for the last 5 million years and are well adapted to the demands of their environment (see Fig. 1). Unlike lions, which depend on the other lions in the pride to hunt, cheetahs hunt independently, using their raw speed to catch an antelope. Their evolutionary success has been driven in part by the cheetah’s successful adaptations for the two components that drive speed: stride length and stride rate. A cheetah’s full stride, from the contact of its left front foot to the next contact of the same foot, can reach up to 25 feet in length (1). Both horses and cheetahs gather their legs underneath themselves during a gallop, with no feet touching the ground. Horses have a single airborne moment during each stride, documented by Eadweard Muybridge in 1978 with a series of photographs called “The Horse in Motion.” In comparison, cheetahs gain a second airborne suspension in a single stride when they extend both their front and hind legs (1). Like other cursorial mammals, cheetahs’ long legs help them lengthen their stride. Long legs are good for long strides, but they limit the number of strides per second (stride rate). For example, giraffes spend their day walking, but can gallop when necessary. Giraffes’ movements are deliberate and somewhat
awkward because their long, stiff legs prevent them from achieving the rapid stride rate of lions or cheetahs (see Fig. 2). The cheetah’s solution to this restriction is a flexible spine; it can coil its long legs so compactly that its front and hind feet never get tangled, which allows it to flex and extend its legs 2.5 times per second (1). In addition to a long stride and fast stride rate, a cheetah‘s tail acts like a stabilizer, and its semi-retractable claws can grip the savannah ground like track cleats (2, 3). The cheetah’s adaptations for the speed record have compromised its long-distance stamina. Its highly-specialized sprinting gallop is extremely fast, but also energetically exhausting; a cheetah can only run a distance of 1,300-2,000 ft before it tires (1). Nevertheless, those 600 yards are just long enough to chase down a swift gazelle and score a meal, leaving the lions to search for a new lunch.
Adaptations for Endurance The second fastest land animal is a little-known New World runner: the pronghorn antelope. The pronghorn 31
antelope ranges from western to central North America, and is about the size and shape of an African gazelle with long, spindly legs and two pronged horns (Fig. 3). Like the cheetah, the pronghorn is a champion sprinter, but it also possesses additional adaptations for sustaining high speeds. A pronghorn antelope’s top speed is 60 mph, but it can run for several hours at 35 mph (4). At that pace, it can outrun a biking Lance Armstrong over a 3-hour section of the Tour de France (5). The pronghorn’s efficient adaptations allow it to run for hours across the American plains, perhaps, as researchers suggested in a paper published in Nature, to escape from the now-extinct prehistoric American cheetah. Unlike the modern cheetah’s flexible spine, the pronghorn’s spine is less flexible but similar to the spine of a horse. A semiflexible spine stabilizes the pronghorn’s vertical motion so that it spends less energy lifting its body into the air in each stride (1). Like horses and gazelles, pronghorn antelope have lost extraneous digits and walk on their toes, giving them more speed by reducing unnecessary bone and muscle weight at the end of their legs. Pronghorn antelope also take in and use oxygen more efficiently than most other animals. The more oxygen that pronghorn antelope breathe in, the more oxygen that reaches their muscles; hence, the faster and longer their muscles can contract to allow them to run. Their maximum oxygen uptake relative to their body size is three times the uptake of any other running or flying animal (4). Pronghorn antelope have intricate lung surfaces to absorb the most oxygen possible to make the most out of each breath. They can also skip the warm-up jog because they are perpetually “warmed up”; they keep their muscles at a higher resting temperature than other mammals of their size so they are ready to run immediately.
Who is still going after 100 miles? There is a point at which horses and dogs can no longer sustain their running pace and must stop—and then we catch up. While the cheetah maximizes stride length and rate for intense bursts of speed and the pronghorn optimized its oxygen intake for flexible types of speed, humans specialize in long-distance marathons. Humans are the only primates that can run for extended periods of time; chimpanzees and gorillas are incapable of running upright for more than a few minutes. Dennis Bramble from the University of Utah and Daniel Lieberman from Harvard University believe that our ancestors’ development of running 2 million years ago may have influenced the evolution of human body. Humans evolved three ingenious adaptations that are remarkably well-suited to endurance running, allowing us to compete with the other cursorial mammals: our unique physical form, our ability to breathe, and our ability to sweat. The human physical form is unique among animal runners. The arch of the human foot is the biological engineer’s suspension bridge and one of the most simple, yet sophisticated adaptations for running. With each step we take, the lattice of tendons and ligaments in our foot stretches to absorb shock like an earthquake-proof bridge. Our
legs also absorb shock by compressing under our body, while our springy tendons and ligaments store and release energy over time. We can run for a long time because our bodies are built to conserve energy at every opportunity. Our second unique adaptation is our ability to regulate our breathing independently of our limb movement. Because all other cursorial mammals are quadrupeds, the expansion of their ribcage—and therefore the expansion of their lungs—is limited by each stride. As a cheetah gathers its legs midstride, its momentum slams the air out of its lungs; as it extends its legs, its internal weight pulls away from its chest and allows it to expand its lungs. The cheetah cannot breathe more than once per stride. Because humans stand upright, the movement of our legs as we walk and run does not affect the expansion of our lungs. Humans have only two gaits, walking and running. Unlike cheetahs, we can breath faster than we can move our legs, getting the maximum amount of oxygen to our muscles. The regulation of our breathing allows us to run for extended distances because we constantly remain in an energy-efficient gait. Humans compete against other mammals with a third ingenious and unique adaptation: the ability to cool our body temperatures by sweating. Most animals cool themselves by seeking
The Human Physique At a first glance, we are quick to dismiss humans as wimps in the running race. Horses and dogs—not to mention cheetahs and pronghorns—can beat us effortlessly down to the end of a football field. However, what happens when one football field becomes 100 football fields or 10,000 football fields? 32
Image courtesy of Rick Berg.
Fig. 3: A pronghorn antelope in Wyoming. Dartmouth Undergraduate Journal of Science
Image courtesy of Erik van Leeuwen.
Fig. 4: Usain Bolt (second from right), the world’s fastest human. At the Boston Marathon on April 18, 2011, Kenyan native Geoffrey Mutai ran the fastest marathon in the world. His time for 26.2 miles was 2:03:02, 55 seconds faster than the world record.
the shade or by panting to release hot, moist air through their mouths. However, animals cannot cool themselves and run simultaneously. Harvard scientists once measured the body temperature of a cheetah on a treadmill; as soon as its temperature reached 105º F, the cheetah halted and refused to run. Sweating allows us to regulate our internal body temperatures while running, without having to stop for shade or to pant. The combination of the foot’s arch, sweating, and breathing provides humans with unparalleled energy efficiency during an endurance run. As the distance and time of an extended run increase, we become better competitors against cursorial mammals such as horses or gazelles. Finally, at just the right distance, we can overtake them.
The Longest Race One isolated tribe on the Kalahari plains of Africa still performs persistence hunting, pursuing a gazelle to the point of exhaustion over the course of an entire day. When a gazelle sprints away from a pursuing hunter, it breaks from a trot of 15 mph into a gallop of 30 mph until it stops 500 yards away. In the switch from a trot to a gallop, it engages in a much more exhausting form of movement than a trot. The gazelle can only gallop away for a certain distance before it is limited by its FALL 2011
breathing rate and oxygen consumption, and slows down. However, the human hunter does not have to switch gaits to follow it and he continues to run efficiently as he speeds up from 5 mph to 12 mph. When he catches up to the gazelle, it gallops away again, and then stops. As the distance accumulates over the course of the day, the gazelle begins to tire from relentless sprinting. After an entire day of chase, the hunter finally catches up to the gazelle. It has collapsed from heat exhaustion, and cannot get enough oxygen to its muscles to keep its legs moving. By breathing and sweating, the human has run the gazelle to its death. The human has won the evolutionary challenge, perhaps not by chasing their prey with spears, but by running them to exhaustion (6, 7). In 1973, a man named Gordy Ainsleigh demonstrated humans’ modern endurance running ability. In June, he entered a horse race in California called the 100-mile Western States Trail Ride. At mile 29, his new horse went lame and he had to drop out of the race. When the race came around one year later, Ainsleigh decided to enter the race without his horse and compete on foot to his friends’ and family’s incredulity. He finished the race—while he did not win, he did unexpectedly finish within the 24-hour cutoff time. In 1977, so many runners decided to
compete on foot that the horserace split into the equestrian Tevis Cup and the world’s first 100-mile ultramarathon, the Western States 100 (7). While humans cannot beat dogs, horses, or cheetahs to the end of a football field, we are well adapted for races of 1,000 football fields. Although we have yet to compete directly against a pronghorn in an ultramarathon, persistence hunting shows that we are capable of running down a gazelle. Cheetahs and pronghorn antelope possess well-refined adaptations to survive and compete in their environment, whether by sprinting or sustaining high speeds, just as we possess our own unique and sophisticated specializations for endurance running (see Fig. 4). Our evolutionary success may even be attributed to our prowess as one of the world’s most persistent endurance runners. The human body form, our ability to regulate breathing, and our ability to cool by sweating are some of the most efficient and effective designs possessed by cursorial mammals. Each adaptation is independently ingenious, but it is the human combination that creates evolutionary elegance—and lets us catch cheetahs. References 1. M. Hildebrand, J. Mammal. 40, 481-495 (1959). 2. Fact Sheet (2011). Available at http://www. cheetah.org/?nd=cheetah_facts (24 April 2011). 3. K. Kardong, Vertebrates: Comparative Anatomy, Function, Evolution (McGraw-Hill Companies, Inc., New York, NY, 1998) [2nd Ed]. 4. S. Lindstedt et al., Nature 353, 748-750 (1991). 5. S. Ruibal, Lance Armstrong wins 7th consecutive Tour de France (2005). Available at http://www.usatoday.com/sports/cycling/ tourdefrance/2005-07-24-stage-21_x.htm (22 April 2011). 6. D. Bramble, D. Lieberman, Nature 432, 345-352 (2004). 7. C. McDougall, Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen (Alfred A. Knopf, New York, NY, 2009).
33
Ecology
Differences in Capuchin Locomotion Between Sexes in Response to Predation Marielle Battistoni ‘11, Rohan Chaudhary ‘12, Zachary Clare-Salzler ‘12, Ian Engler ‘12, and Suzanne Kelson ‘12
G
roup living in primates, as well as other vertebrates, is thought to have evolved to reduce individual predation risk. Primates may have developed differential roles between the sexes to protect the group from predation. The well-studied Old World primates display distinct roles between the sexes. However, sexually distinct behavior is not as well understood in the white-faced capuchin (Cebus capucinus), a New World monkey. We hypothesized that in response to predation, males would actively defend the group in return for status within the troop and reproductive success, while females would be more passive. We observed the movement of capuchin monkeys with and without a simulated threat using audio playback experiments. In general, males remained closer to the ground than females. In response to a capuchin alarm call, males jumped more, while females moved to higher levels of the canopy. Despite similar general behaviors between the sexes, males served the protective role in the troop.
Introduction Many animal species have adapted defense mechanisms to predation. In some species, males and females have evolved different responses to predators, often based on sexual dimorphism in size, behavior, activity level, or role in offspring protection (1). Alarm calls are one response that animals have evolved to alert others to the presence of a predator. White-faced capuchin (Cebus capucinus) alarm calls fall into two distinct categories—one to alert others to the presence of aerial predators and other monkeys, and one for terrestrial predators and snakes (2). Wheeler found that alarm calls in response to visual models of predators are motivated by parental care and kin protection with the intention of recruiting individuals to mob the predator (3). Treves found that sound playback experiments using predator vocalizations were effective at inducing a response from arboreal primates (4). Male capuchins are about 1.5 times larger than females, but, like other New World monkeys, they display few other sexually dimorphic traits (5,6). Gebo found only very slight differences in general posture and locomotion between male and female capuchins (5). Van Schaik and van Noordjwik observed that male capuchins display higher rates of vigilance in the presence of predators (7). They are also more active than females in detecting, approaching, and mobbing real and model predators. We examine sex-specific responses to predation by male and female white-faced capuchins, a species in which males exhibit dominance and display more aggressive behavior than females (8). We hypothesized that male capuchins, as the dominant members of the group, would actively defend the troop in the presence of threats simulated by audio recordings of ca34
puchin alarm calls and of predators. We predicted male defensive behavior would include more active movement, such as jumping and remaining closer to the ground to scan for predators. Females, by contrast, would act more cautiously by moving higher in the more protected canopy. We also predicted that in response to the sound of a terrestrial predator or an alarm call to a terrestrial threat, both sexes would spend more time higher in the trees to avoid predation.
Methods We followed two troops of 15-20 white-faced capuchins on January 13-14, 2011 in Palo Verde National Park, Costa Rica. We recorded baseline observational data on January 13 and conducted experimental trials on January 14 . We haphazardly selected a focal individual and observed it for 300 seconds (n = 132), noting sex, age (juvenile or adult), horizontal travel (number of trees traveled through per trial), and total number of jumps. Every 30 seconds, we also recorded approximate height above the ground (ground level = 0, 1-5m = 1, 5-10m = 2, 10-15m = 3). We used an iPod Nano and Tweakers portable speakers (YC Cable, SPKR-R1-BK-D01) to play three distinct recordings (9). We controlled for a sound response with a recording of a guayaquil squirrel (Sciurus stramineus), which is not a predator. We simulated a predator call with a jaguar (Panther onca) recording (10). We simulated a threat to the troop with a capuchin alarm call. We conducted one-sided two-sample t-tests by sex, comparing total number of jumps and rate of horizontal movement per five minutes for the observational group. For the experimental group, we compared height in canopy, total number of jumps, rate of horizontal movement against sex for each treatment: guayaquil squirrel, jaguar, and a capuchin alarm call. We used JMP 8.0 to perform ANCOVA (Analysis of Covariance) and t-tests.
Image courtesy of M. Battistoni & Co.
Fig. 1: Overall mean height in canopy by sex for C. capucinus. Mean height in canopy was based on an ordinal scale: 0 = scale level, 1= 1-5m above ground, 2=6-10m, 3=11-15m. Dartmouth Undergraduate Journal of Science
Image courtesy of M. Battistoni & Co.
Fig. 2: Response to audio cues in total jumps per trial by sex for C. capucinus.
Image courtesy of M. Battistoni & Co.
Fig. 3: Responses to audio cues in height in canopy by sex of C. capucinus.
Results Females were significantly higher in the canopy than males (t677 = -4.92, p < 0.01; Fig. 1). Overall, males did not jump significantly more than females (t677 = 0.90, p = 0.81), but males jumped more than females in response to a capuchin alarm call (ANCOVA, Treatment x Sex: F3,56 = 5.58, p < 0.01; Sex: F1,56 = 0.99, p = 0.33; Treatment: F3,56 = 3.52, p = 0.04; Fig. 2). Both males and females moved higher into the canopy in response to capuchin alarm calls and jaguar calls (Sex: F1,1 = 10.26, p < 0.01; Treatment: F2,2 = 20.45, p < 0.01; Fig. 3). Males remained significantly lower than females in response to the capuchin call (t115.17 = -3.97, p < 0.01).
Discussion Our data support the hypothesis that male capuchins exhibited more locomotive and postural behavior consistent with troop defense than females. Males spent significantly more time lower to the ground than females (Fig. 1), as Fragaszy observed (11). Two primary predators of capuchins, jaguars and large snakes, live on the ground. Being close to the ground is dangerous for capuchins, yet they must be close enough to discern predators. Because males spend more time lower to the ground than females, they are more likely to be looking for predators and protecting the troop. Being high in the canopy, by contrast, provides more protection from terrestrial predators (12). Thus, females may be able to stay in a safer area higher in the canopy because they are protected by the more vigilant males. FALL 2011
Our data also support the hypothesis that males defend the troop more actively against predation, while females take a more passive approach to defense. In response to a capuchin alarm call, male monkeys jumped more often (Fig. 2), whereas females moved even higher in the canopy (Fig. 3). A capuchin alarm call signifies a predator or other threat, and our data suggest that male monkeys must respond by evaluating this threat. Jumping, while energetically costly, allows males to move around quickly. This enables them to be more aware of the environment, predators, and potential threats. Several males also issued a loud call in response to the capuchin alarm call, which did not occur in response to the squirrel or jaguar calls. One potential source of error is the recordings used in our experiment. Our portable speakers had limited volume, so only monkeys nearby could hear the sounds. Also, we did not know precisely which capuchin alarm call we used. Defending the troop is dangerous for the males, as they are closer to the ground and more vulnerable to predators. Males may choose to accept that danger if protecting the troop gives them more social status and attracts potential mates. Many of the data we collected were not significantly different between males and females, suggesting that the two sexes exhibit similar behavior overall. Fedigan concluded that there are minimal sexually distinct behaviors in capuchins, yet our findings show a clear divergence in protective behavior between males and females, revealing a more nuanced view of the social structure of capuchins (6). Future studies could compare simulated predation with combinations of audio cues and visual cues, to determine which aspects of predation evoke a response from capuchins. Degree and type of threat from different predators, such as aerial versus terrestrial, could also elicit distinct responses for males and females. Examining other protective behaviors, such as scanning and issuing alarm calls, would give further insight into how protecting the troop is partitioned between the sexes.
Acknowledgements We would like to thank El Jardinero of La Hacienda near Palo Verde for effortlessly showing us the way to the monkeys. We would also like to thank Gillian Moritz for her tremendously generous help in the design of this study and in the field. References 1. R. Shine et al., Behav. Ecol. 11, 239-245 (2000). 2. C. Fichtel, S. Perry, J. Gros-Louis, Anim. Behav. 70, 165-176 (2005). 3. B. Wheeler, Anim. Behav. 76, 1465-1475 (2008). 4. A. Treves, Int. J. Primatol. 20, 35-67 (1999). 5. D. Gebo, Am. J. Primatol. 97, 49-76 (1992). 6. L. Fedigan, M. Baxter, Primates 25, 279-94 (1984). 7. C. Van Schaik, M. van Noordjwik, Behav. Ecol. Sociobiol. 24, 265-276 (1989). 8. F. Reid, A Field Guide to the Mammals of Central America and Southeast Mexico (Oxford University Press, New York, NY, 1997). 9. L. Emmons, B. Whitney, D. Ross Jr., Sounds of Neotropical Rainforest Mammals: An Audio Field Guide (University of Chicago Press, Chicago, IL, 1997). 10. S. Digweed, L. Fedigan, D. Rendall, Behaviour 142, 997-1021 (2005). 11. D. Fragaszy, Behav. Ecol. 1, 81-94 (1990). 12. P. Wright, Behaviour 135, 483-512 (1998). 35
ENGINEERING
Improving Hearing Loss Humans Adapting Echolocation Jennifer Jaco ‘13
A
n estimated 245 million people world-wide are visually impaired, and 39 million more are completely blind. Sixty-five percent of these people are over the age of fifty (1). Fifty is becoming the new thirty in many countries, as people are starting to live much longer. Despite advances in technology, after blindness has set in, there is nothing that can be done to reverse the damage. At this time, particularly in the fifty and older group, people often begin to feel helpless and separated from society. They no longer feel “normal” without their innate ability to see. This problem can theoretically be solved by echolocation, defined as the ability to “hear the locations and properties of silent objects by noticing how sound reflects off them” (2). Bats, dolphins, and toothed whales all use echolocation to “see” objects around them while they are in motion by using extremely high frequency sound waves outside of the human hearing range. With a device that allowed the human ear to use the principals of echolocation, people who were visually impaired would no longer need to use a cane to detect objects around them, thus preventing injuries and hassle. More advanced ear technology that incorporates echolocation would help improve the lives of millions of people worldwide. Rapidly changing technology allows us the ability to improve lives around the world—why not push it even further to revolutionize the way we perceive our world?
Anatomy and Physiology of the Ear The ear is divided into three portions that focus and process sound: the external ear, the middle ear, and the inner ear (3). Sound funnels through the cartilege-covered external ear into the external auditory canal, a short tube that ends at the tympanic membrane, commonly known as the ear drum (4). Encyclopedia Britannica explains that the middle ear is “a narrow, air-filled space that resembles a rectangular room with four walls, a floor, and a ceiling, and is made up of three bones [called the ossicles]: the malleus, incus, and stapes. The lateral wall of the middle-ear space is formed by the tympanic membrane, the inferior wall is a thin bone separating the cavity from the jugular vein and carotid artery below, the anterior wall is the opening of the Eustachian tube, which equalizes pressure between the external and middle ear, and the medial wall is a part of the bony otic capsule of the inner ear” (5). The medial wall has two openings: the oval window, closed by the stapes, and the round window, which is covered by a thin membrane (5). When sound travels through the external auditory canal, it vibrates the tympanic membrane. “It is the pressure from sound waves that makes the eardrum vibrate” (6). A vibration travels from the tympanic membrane through the malleus, is transferred through to the incus and stapes, and finally the oval window (6). By 36
transmitting sound waves from the tympanic membrane to the oval window, the middle ear functions as an acoustic transformer, amplifying the sound waves before they move into the inner ear. “The pressure of the sound waves on the oval window is about twenty times greater than that on the eardrum. This pressure increases due to the difference in size between the relatively large surface of the eardrum and the smaller surface of the oval window” (6). From the oval window, sounds are then transmitted to the inner ear, which contains the cochlea (7). The cochlea is coiled two and a half times around a hollow central pillar, which contains the cochlear artery, vein, and nerve. Inside the spirals of the cochlea is the Organ of Corti, which contains a fluid, called perilymph, as well as tiny hair cells that respond to sound vibrations. There are about 24,000 of these hairs embedded in the cochlea, arranged in four long rows. The movements in the perilymph cause different hair cells to be put into motion. When the hair cells move, they send electrical signals to the auditory nerve, which is connected to the temporal lobe of the brain. In the brain, the electrical impulses are translated into sounds that we can comprehend (8). As such, these hair cells are essential to hearing ability. Damage to the hair cells limits the capacity of the human ear to detect sound. Higher frequencies are harder to hear as age increases as a result of an age-related deterioration process called presbycusis (9). Most human ears can hear frequencies between 20 Hz and 20 kHz (10). The highest frequencies that a middle aged human can hear are around 12 kHz to 14 kHz, a threshold which only decreases with age. Other limitations of the human ear include deafness or severe hearing impairment (11). There are four main categories of hearing impairment: conductive hearing loss, sensorineural hearing loss, mixed hearing loss, and central hearing loss. Conductive hearing loss is usually caused by
Image retrieved from http://www.britannica.com/EBchecked/topic/175622/human-ear (Accessed 2 November 2011).
Fig. 1: Structure of the ear. Dartmouth Undergraduate Journal of Science
either a disease such as measles or an obstruction of the external ear. In this case, hearing can either be repaired surgically or it can be successfully compensated with a hearing aid. Sensorineural hearing loss, by comparison, is more profound than conductive hearing loss; it is caused by damage to the hair cells or nerves in the inner ear. Generally, only the loss of certain frequencies occurs, meaning a person can still hear some sounds. Mixed hearing loss is a combination of conductive hearing loss and sensorineural hearing loss. This means a person suffers from problems in both the external and middle ear, as well as the inner ear (12). Lastly, in central hearing loss, nerves leading to the central nervous system are damaged. Of the four, sensorineural hearing loss is the most common form of permanent hearing loss. This setback can be caused by head trauma, illnesses, or malformation of the inner ear, as well as more common events, such as repeated exposure to blaringly loud music at concerts or consistently listening to an iPods with the earbuds on full blast (13). Another shortcoming of the human ear is the lack of sound localization. If a sound arrives a few microseconds earlier in one ear than the other, the sound is recognized to be coming from the side that hears it first. In general, this principle works better for lower frequency sounds (14). Sound localization works best when both ears are working optimally. With only one functioning ear, it is difficult to determine the source of a sound. Human ears also have a problem determining how far away a sound source is. The only tool the human ear can depend on is loudness and relative estimation. Low-frequency tones propagate farther than high fre-
quency tones, so the latter can be assumed to be nearby (15).
Echolocation in the Animal Kingdom In the animal kingdom, several animals use echolocation to compensate for their poor vision. While some animals’ visions may be inferior to that of humans, they have managed to overcome the sound localization and frequency ranges inadequacies that humans possess. By using sonar and echolocation, the animal kingdom has found a solution to blindness before the medical world has. Bats have the ability to hear much higher frequencies than the human ear can hear. Compared to the human’s range of 20 Hz to 20 kHz, a bat can hear anywhere between 1 kHz to 150 kHz, a range nearly eight times as wide (16). While bats can detect lower frequencies, they generally ignore them, as the lower frequency sounds are of no use to echolocation (17). In order for echolocation to work, bats emit a high-pitched, rhythmic sound from their larynx, which reflects off objects and returns to the bat’s ears. When the sound wave returns, the bat can determine where the object is. A bat’s brain combines normal auditory functions, a stopwatch to determine how quickly the sound returns— which indicates how far away the object is—and a calculator to quickly compute these figures (18). Humans are able to locate which side sounds are on based on which ear the sound waves hit first; this is similar to how bats can determine the location of an object. If an echo hits the bat’s right ear before the left ear, the object must be on the right. However, bats have special folds in their ears that allow them to determine an object’s vertical position. Echoes that reach a bat’s ear from below will hit the fold differently than if the echoes come from above, producing a different sound (18). A bat’s ear can also determine the size of an object by the intensity of the echo—a smaller object reflects a smaller sound wave. Also, like humans, bats can sense how close an object is by the echo’s pitch; a closer object’s echo will have a higher pitch than an object moving further away (18). Like bats, dolphins and toothed whales use echolocation to locate objects when vision is obscured, such as when they are swimming in deep or murky waters. These animals have a frequency range from about 50 kHz to 200 kHz, a maximum even greater than that of bats. The velocity of sound is greater in water than in air, so at a given frequency, the wavelengths of sound waves are longer (v = f λ). As a result, aquatic animals have to use frequencies five times greater than those of bats (17). "The echoes from these sounds provide information about the seafloor, the shorelines, underwater obstacles, water depth, and the presence of other animals underwater… giving these animals a three-dimensional view of the world." (19). However, unlike bats and humans, dolphins and toothed whales receive these echoing waves in the oil filled channels of their lower jaws as opposed to directly in their ear drums (19). We would not be able to process such high frequencies without bursting our eardrums, so it is safe to say that hearing in the animal kingdom has surpassed human hearing capabilities, though we do have the ability to hear frequencies lower than some animals.
Image retrieved from http://www.britannica.com/EBchecked/topic/175622/human-ear (Accessed 2 November 2011).
Fig. 2: Structure of the middle ear. FALL 2011
37
Analysis of Technological Alternatives Currently, the greatest advances in improving hearing in humans have been hearing aids and cochlear implants. A hearing aid is an object that can be worn in the ear (ITE) or behind the ear (BTE). Hearing aids amplify certain sounds so that the person wearing the aid can “listen, communicate, and participate in daily activities” (20). A hearing aid has three basic parts: a microphone, an amplifier, and a speaker, which convert sound waves to electrical signals, increase the power of the signal, and transmit the signal to the ear, respectively (20). Undamaged hair cells can detect the larger vibrations and convert them into neural signals that are passed along to the brain. However, with increased hair cell damage comes more severe hearing loss; this requires greater amplification to compensate (20). If the damage is too severe, the signaling may not work, causing the hearing aid to be ineffective. Instead, a cochlear implant would be much more effective. According to the National Institute on Deafness and other Communication Disorders (NIDCD), the cochlear implant “goes around the dead hair cells that can no longer transmit sound, and directly stimulates the auditory nerve, which takes the sound signals to the brain” (21). Cochlear implants have internal and external components; externally, they are composed of a microphone, a speech processor, and a transmitter (22). Like the hearing aid, the microphone picks up sounds, while the speech processor analyzes sounds and sends them to the transmitter. Internally, a cochlear implant has a receiver and electrodes, both of which are implanted surgically. “The receiver takes the coded electrical signals from the transmitter and delivers them to the array of electrodes that have been surgically inserted in the cochlea. The electrodes stimulate the fibers of the auditory nerve, and sound sensations are perceived”
(22). Cochlear implants work best in those who have tried hearing aids with no success, those who lost hearing after developing speech, and those with severe hearing loss (22). While this device does not make sounds similar to the way normal ear would hear them, it still has beneficial results.
Proposal for Improved Design Blind individuals would greatly benefit from echolocation. In order to advance human hearing beyond its normal range of 20 Hz to 20 kHz, some type of implant will be necessary. This device, potentially called a “frequency amplification device,” is a cross between a hearing aid and a cochlear implant. Cochlear implants are beneficial because they are embedded deep into the ear, thus promoting better hearing than a hearing aid. Cochlear implants are more advanced than hearing aids because they have one or more microphones that can pick up the sound in the environment, a speech processor that organizes and processes speech, a transmitter that transmits to an inner device, and a receiver on the inside of the body. On the other hand, hearing aids, particularly ITE aids, are easier to conceal, are often invisible to others, and can be removed. Hearing aids amplify sound for the hard of hearing. This frequency amplification device will have the microphone, processor, and transmitter from the cochlear implant combined with the ease of ITE hearing aids. Inside the ear, there would be a device that is similar to the receiver of the cochlear implant. The curled up tip would be surgically implanted into the cochlea of the patient. On the outside, the ITE hearing aid would come into play. It would have microphones that are able to pick up frequencies above 20 kHz–normally unheard by the human ear—as well as normal speech without making sounds louder. Sounds would not be amplified, but rather the device would simply expand
Image retrieved from http://www.britannica.com/EBchecked/topic/175622/human-ear (Accessed 2 November 2011).
Fig. 3: Analysis of sound frequencies in the cochlea. 38
Dartmouth Undergraduate Journal of Science
Image retrieved from http://commons.wikimedia.org/wiki/File:Chiroptera_ echolocation.svg (Accessed 6 November 2011).
Bats emit sound waves to locate their prey (E = emitted wave, R = reflected wave).
our normal range of frequencies we can perceive. The device would also have processors to cancel out any interference. This type of processor is similar to a cellular phone, which has background noise cancelling technology. The outer ear device would also have a transmitter that would connect to the receiver on the inner ear by a magnet. The ITE device, which would be battery operated, can be taken out and charged, allowing its user to shower and sleep without any problems. Bats, dolphins, and toothed whales emit high frequency sounds that the human ear cannot detect. These sound waves bounce off objects and back to the animal, which determines where the objects are located based on the sound waves. In order for this high frequency device to work, there needs to be something that emits a high frequency for the frequency amplification device to pick up. A small device, which has the sole purpose of emitting a high frequency sound that is undetected by normal human ears, would be small enough that it would be put in a pocket or purse, or even carried around on the belt like a pager. This can be charged like the ITE portion of the frequency amplification device. After implantation, the patient could receive assistance and training to learn to use their device. There are many advantages and benefits to this frequency amplification device. First, it would allow the blind to learn to “see” objects by hearing them rather than feelin them. Not only would this make moving around much more effortless, but it would also help the person blend into public much easier. The blind could then become more active participants of society. With this technology, there would be many fewer obstacles for the blind. However, with every invention always comes several disadvantages. First, there could be surgical complications, such as infections. Also, because this device would work by emitting high frequencies, animals such as dogs and cats could hear the sounds, which might make living in an area with a large animal population difficult. Until echolocation is a very acquired skill, a person walking would have to pay very close attention to the echoes around them; walking with another person and holding a conversation would be very hard to do. Nonetheless, the frequency amplification device holds a plethora of benefits for the blind community. This device could help advance the lives of millions of people worldwide. FALL 2011
References: 1. World Health Organization: Deafness and Hearing Impairment (2010). Available at http://www.who.int/mediacentre/factsheets/fs300/en/index. html (20 April 2011). 2. E. Schwitzgebel, Human Echolocation (2007). Available at http:// schwitzsplinters.blogspot.com/2007/01/human-echolocation.html (20 April 2011). 3. Children’s Hospital of Pitssburgh, Anatomy and Physiology of the Ear (2008). Available at http://www.chp.edu/CHP/P02025 (20 April 2011). 4. The Ear (Human Anatomy): Picture, Function, Definition, Conditions, and More (2009). Available at http://www.webmd.com/brain/picture-of-theear (20 April 2011). 5. Encyclopedia Britannica Online, Human Ear: Cochlea (2011). Available at http://www.britannica.com/EBchecked/topic/175622/human-ear/65040/ Cochlea?anchor=ref531841 (20 April 2011). 6. The Middle Ear (2011). Available at http://www.hear-it.org/The-middleear-1 (25 October 2011). 7. The Ear - A Magnificent Organ (2011). Available at http://www.hear-it. org/index.dsp?page=4753 (20 April 2011). 8. The Inner Ear (2011). Available at http://www.hear-it.org/The-innerear-1 (25 October 2011). 9. Presbycusis (1997). Available at http://www.nidcd.nih.gov/health/ hearing/presbycusis.htm (20 April 2011). 10. Sensitivity of Human Ear (nd). Available at http://hyperphysics.phyastr.gsu.edu/hbase/sound/earsens.html (20 April 2011). 11. G. Elert, Frequency Range of Human Hearing (2004). Available at http://hypertextbook.com/facts/2003/ChrisDAmbrose.shtml (20 April 2011). 12. Hearing Loss Overview (2011). Available at http://www.deafaccess. org/hearing-loss-overview.htm (20 April 2011). 13. Sensorineural Hearing Loss (2011). Available at http://www.asha.org/ public/hearing/Sensorineural-Hearing-Loss (20 April 2011). 14. Encyclopedia Britannica Online, Human Ear Anatomy (2011). Available at http://www.britannica.com/EBchecked/topic/175622/humanear/65058/Analysis-of-sound-by-the-auditory-nervous-system (20 April 2011). 15. J. Kalat, Introduction to Psychology, (Wadsworth Publishing, Florence, KY, ed. 8, 2007) [eighth edition]. 16. Bat Ears (2007). Available at http://www.thefreelibrary.com/ Bat+ears.-a0169824710 (20 April 2011). 17. Encyclopedia Britannica Online, Sound Reception: Echolocation in Bats (2011). Available at http://www.britannica.com/EBchecked/ topic/555378/sound-reception/64827/Echolocation-in-bats (20 April 2011). 18. How Bats Work: Bats and Echolocation (2011). Available at http:// animals.howstuffworks.com/mammals/bat2.htm (20 April 2011). 19. Whales, Dolphins and Sound (2010). Available at http://www. environment.gov.au/coasts/species/cetaceans/sound.html (21 April 2011). 20. Hearing Aids (2007). Available at http://www.nidcd.nih.gov/health/ hearing/pages/hearingaid.aspx (20 April 2011). 21. More About Cochlear Implants (2010). Available at http://www.nidcd. nih.gov/health/hearing/coch_moreon.html (20 April 2011). 22. Cochlear Implants (2011). Available at http://www.asha.org/public/ hearing/Cochlear-Implant/ (20 April 2011). 39
medicine
Nanoparticle-Based Intracellular Delivery System of Immunomodulatory Agents for Initiation of an Anti-Tumor Immune Response Riley Ennis ‘15
Fraught with chronic side effects, the current paradigm of cancer therapy includes chemotherapy and radiation. Advancements in nanomedical techniques have led to the emergence of a new field of research, cancer immunotherapy, which is the study of stimulating the human immune system to elicit an anti-tumor response through the proliferation of cytotoxic T lymphocytes (CTL) and, the more recently discovered killer dendritic cells. The present research proposes an innovative vaccine delivery system of tumor associated antigens and immunomodulatory agents such as CpG oligodeoxyribonucleotide (CpG ODN) conjugated to poly(lactic-co-glycolic-acid) nanoparticles, all encapsulated within a pharmaceutically novel humanderived protein surfactant (MacroVax). As a whole, this vaccine complex promotes CTL clonal expansion through the innate immunological pathways of antigen-presenting cells (APCs) in order to breach the immunological barrier posed by tumor cells. Experimental studies on the vaccine showed that the vaccine targets APCs, activates intracellular APC pathways, induces T lymphocyte proliferation, and initiates the proper anti-tumor immune response.
Introduction Cancer is a polygenic disease that globally kills eight million people per year, a rate that has remained stagnant for five decades (1). The current paradigm for cancer treatment involves non-specific therapies including chemotherapy and radiation that lack the ability to differentiate between cancerous and healthy tissues. Scientists in the expanding field of cancer immunotherapy are applying bionanomedical techniques to design cancer vaccines with the ability to harness the patient’s own immune system to treat cancer. Scientists have found certain immunomodulatory agents called pathogen-associated molecular patterns (PAMPs) with the innate ability to initiate an anti-tumor immune response by blocking many of the tumor immunosuppressive barriers such as myeloid-derived suppressor cells (2, 3). The present study investigates the efficacy of the PAMP CpG oligodeoxyribonucleotide (CpG ODN) as the major immunostimulatory agent of an innovative vaccine complex that bridges the innate and adaptive immune functions to initiate an anti-tumor immune response by delivering antigens to designated immune cells after a patient has been diagnosed with cancer. During primary tumor development, a patient’s innate immune function is active; however, tumors have developed a multitude of “immunol” inhibitors, which subsequently suppress a patient’s immune system and promote complete tumor development. The proposed vaccine complex should breach the immunological barrier posed by primary tumors through the activation of macrophages and dendritic cells (DCs) in order to teach a patient’s immune system to rec40
ognize cell surface antigens and markers that distinguish tumors from healthy tissue. This complex process of “immunol education” stems from the adaptive immune function, which exploits the molecular properties of cytotoxic T lymphocytes (CTLs), specifically the intrinsic ability to recognize tumor-associated antigens and destroy the tumor cells through induced apoptosis (4). The proposed pathway is elicited through a three-prong immunol vaccine complex that applies a novel intracellular delivery system using nanoparticles and complex molecular interactions. Ultimately, this vaccine will activate DCs and CTLs, thus overcoming the immunological inhibition of tumor cells, and initiating molecular pathways of apoptosis to destroy tumor cells. The CpG ODN vaccine complex includes an outer coat of a pharmaceutically novel protein derived directly from the serum of the patient, an agonist of TLR9 CpG ODN, cytokine granulocyte macrophage-colony stimulating factor (GM-CSF), and poly(lactic-co-glycolic-acid) (PLGA) biodegradable fluorescent nanoparticles. The outer protein layer of the vaccine was selected for its ability to bind to certain pathogens and act as a chemical tag for APC phagocytosis and downstream stimulation, by binding to extracellular receptors on the extracellular matrix of APCs (4). The humanderived protein is abundant in the serum of patients with cancer, which allows for direct extraction for the synthesis of this organic and biologically specific vaccine. Within this protein coat are PLGA nanoparticles conjugated and internalized with two immunostimulatory agents, CpG ODN and GM-CSF. These two immune mediators coupled with the binding protein help activate CTL proliferation and the cytotoxic properties of DCs or killer dendritic cells (KDCs) (5). The vaccine complex forms through carboxyl group residue interaction in the process of self-assembly. The purpose of this vaccine complex is to draw in APCs around the tumor, using the protein coat (innate immune function) and the CTLs (adaptive immune function)
Image courtesy of Riley Ennis.
Fig. 1a: Epifluorescent image of untreated (control) and vaccine treated immature dendritic cells. Actin (Red Rhodamine Phalloidin), Nuclei (Blue-DAPI), Conjugated Nanoparticles (Green-GFP). 1200X magnification, scale bar = 50 µm. Treated cells underwent complete maturation, with increased cytoplasmic branching. The vaccine can be visualized in the cytoplasm of the treated cells. Dartmouth Undergraduate Journal of Science
Image courtesy of Riley Ennis.
Fig. 1b: Confocal image of treated immature dendritic cells. Actin (RedRhodamine Phalloidin), Nuclei (Blue-DAPI), Conjugated Nanoparticles (GreenGFP). Merge depicts two-dimensional plane of dendritic cells, and the definite phagocytosis of the vaccine complex.
to induce the recognition of tumor-associated antigens. The nanoparticle-based intracellular delivery system will aid in a prolonged and highly specific immune response that will enter into the endosomes or intracellular compartments of the APCs and begin immunol stimulation. The vaccine complex is also cost effective and biologically specific because the main vaccine component of the humanderived protein can be taken directly from the patient. This vaccine platform encapsulates new technologies in order to improve immunol stimulation and elicit a strong and specific anti-tumor immune response against cancer.
Materials and Methods Phagocytic and Morphogenic Study of VaccineTreated APCs
Phagocytosis and APC morphogenesis were studied in negatively enriched monocytes extracted from a human host first cultured in RPMI 1640 media on eight-chambered microscope culture slide. In addition, monocytes were extracted from Balb/c mouse bone marrow. All cells were then treated with the cytokines interleukin-4 (IL-4) and GM-CSF. These two growth factors promote monocyte differentiation into immature DCs and culture monocytes. The cells were allowed to differentiate for five days and then treated with 3 μl of CpG ODN vaccine complex for six hours. The media were aspirated from the microscope culture slides and washed with PBS. The cells were then fixed with 1% paraformaldehyde in PBS and immunostained with rhodamine phalloidin (Rh-ph) for F-actin and DAPI for the nucleus before applying a cover slip. The slides were then imaged using Olympus 300V Confocal Microscope and Nikon 800E Epifluorescent Microscope. Flow cytometry was also used on the fixed cells in order to study the morphologic change of the APCs post vaccine treatment. APC marker CD11b and APC activation marker CD86 were probed. A competition-binding assay was also performed. APC membrane blocker peptides were used to prevent vaccine phagocytosis before vaccine treatment. Next, the APCs were treated with the vaccine and probed for intracellular levels of nanoparticles tagged with GFP indicative of phagocytosis.
Intracellular Activation of Vaccine-Treated APCs
Interleukin-12 (IL-12) is the principal activator of both
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innate and adaptive immunity against infectious agents, as well as the key to the proliferation of tumor antigen specific CTLs (6). At the molecular level, IL-12 leads to the expression of interferon-gamma (IFN-g) and the inhibition of interleukin-10 (IL-10), a CTL inhibitor. RT-PCR quantification of IL-10, IL-12, and IFN-g mRNA expression and enzymelinked immunosorbent assay (ELISA) quantification of relative cytokine secretion levels should show that the vaccine complex increases expression profiles of IL-12 and IFN-g and decreases the expression of IL-10, proving that the vaccine has targeted its designated pathways inside the APCs. The experiments were carried out in immature monocytes in a two well-chambered culture dish. After complete differentiation of monocytes into immature DCs, one well was treated with 18 μl of complete CpG ODN vaccine complex and the other well with unconjugated nanoparticles (negative control). The cells were then rinsed with ice-cold PBS (pH 7.4) and then scraped with 0.5 ml of PBS. The cells were lysed by adding 0.5 ml of trizol to the cell pellet and then passed through a 25G needle 20 times. After 0.1 ml chloroform treatment, the cell lysates were microcentrifuged at 13,000 rpm for 10 minutes, and the RNA precipitated out with the addition of 0.25 ml of isopropanol and microcentrifuged at 13,000 rpm for 30 minutes. The pellet was washed with 1 ml of 80% ethanol and re-spun twice at 13,000 rpm for five minutes. The RNA pellet was reconstituted in RNase free water and incubated for five minutes at 55º C. The extracted RNA was subject to first strand cDNA synthesis. For cDNA synthesis, a cocktail of 8 μl 5x iScript reaction mix, 2 μl iScript RT, 20 μl H2O, and RNA template was run in a thermal cycler for five minutes at 25º C, 30 minutes at 42º C, and five minutes, at 85º C. To determine the mRNA profiles, the cDNA was added to the real-time PCR cocktail of 25 μl of SYBR green mix, 21 μl of H2O, 2 μl of the IL-12, IL-10, and IFN-g primers, and was subjected to 45 cycles of RT-PCR. The data was collected (n=3) and a Student’s T-test was performed to determine the statistical significance of the RT-PCR output.
Proliferations of Tumor-Specific CTLs
Once the vaccine has activated the APCs, the next step in the mechanism of action is the subsequent development and proliferation of T lymphocytes that can recognize and discriminate tumor-specific antigens. Mice were vaccinated two times with the vaccine complex over the course of the threeweek immunize and boost experiment, and their T lymphocytes were collected for analysis. The amount of proliferated T lymphocytes was analyzed for proliferation when they were re-exposed to tumor antigens via a proliferation assay and their activation profiles via IFN-g secretion detected by ELISA.
Results APCs Phagocytose and Respond to Vaccine Internalization
This study focused on the physical changes of the DCs when treated with the CpG ODN vaccine complex in vitro, as well as the phagocytosis of the vaccine conjugated nanoparticles. Within six hours, the CpG ODN delivery system 41
Image courtesy of Riley Ennis.
Fig. 2: Flow cytometry results for macrophages treated with either PLGA particles or the vaccine complex for three hours. The two markers of interest used were CD11b (X axis: macrophage marker) and CD86 (Y axis: activation marker). The first quadrant (circled in red) indicates the number of cells that express both CD11b and CD86. Untreated cells have approximately 4% of these activated cells and the vaccine-treated have approximately 90% of these activated cells.
initiated complete DC maturation. Both an epifluorescent microscope (Fig. 1a) and confocal microscope (Fig. 1b) were used to visualize cell morphogenesis. Immature inactive DCs have a spherical shape and are much smaller than mature DCs, which are physically recognizable by their cytoplasmic projections. The data suggest the complete morphogenesis of 85% of the treated cells and a 92% phagocytic efficiency. In addition, flow cytometry was used to monitor changes in surface markers on macrophages treated with the vaccine complex. Approximately 89.7% of the macrophages treated by the vaccine expressed both the CD11b macrophage marker and the CD86 activation marker, while only 3.82% of non-vaccine-treated macrophage populations carried the activation marker CD86 (Fig. 2). A competition assay was designed to prove the direct phagocytosis of the vaccine particle and its interaction with surface proteins on the plasma membrane of APCs. Mouse macrophages treated with the vaccine complex were preincubated with a membrane blocker antibody, which prevents the vaccine from entering the cell via its extracellular receptor interaction. If the vaccine was phagocytosed, the GFP signal attached to the nanoparticles could be detected. The concentration of intracellular GFP decreased as the concentration of blocker peptide increased (Fig. 3).
Image courtesy of Riley Ennis.
Fig. 3: Mouse macrophages were treated with a Membrane Blocker Antibody (Genetex) and then treated with GFP-tagged vaccine to study dose-response of the vaccine with respect to phagocytosis. Using a GFP Quantification Assay (BioVision), intracellular GFP was calculated. 42
Image courtesy of Riley Ennis.
Fig. 4: Using the critical threshold (Ct) value, the change in mRNA expression was calculated: 4-fold decrease in IL-10, 4-fold increase in IL-12, and 16-fold increase in IFN-Îł, normalized for GAPDH (n = 3). *= p < 0.001, ** = p < 0.01.
Vaccine Treatment Activated Intracellular Pathways Within APCs
Expression analysis was confirmed using qRT-PCR. IL-12 and IFN-g were highly expressed in cells treated with the vaccine complex, and inhibitory IL-10 was down regulated. IL-10 had a four-fold decrease in mRNA expression, while IL-12 and IFN-g exhibited a four-fold and 16-fold increase in mRNA expression, respectively, between the treated and untreated groups. Studentâ&#x20AC;&#x2122;s T-test found the RT-PCR results for IL-10 and IL-12 to have p < 0.01, and IFN-g to have a p < 0.001, deeming the output as statistically significant (Fig. 4). For macrophages, IL-10 is an immunological suppressor, while tumor necrosis factor a (TNF-a) is an immunological activator of the immune system. Using an ELISA assay, IL-10 and TNF-a levels were quantified between various treatment groups. IL-10 was secreted at higher levels in the control groups than in the vaccine treated groups, while TNF-a levels were secreted at lower levels in the control groups than in the vaccine treated groups.
Vaccine Induces Proliferation of TumorSpecific CTLs
CTLs are specialized T lymphocytes that recognize tumor surface antigens and destroy tumors. The goal of the proliferation assay was to uncover whether the lymphocytes of mice treated with the vaccine would proliferate and activate in the presence of tumor antigens in vitro. Mice were treated with the vaccine and boosted over a three-week period. Their spleens were collected, and lymphocytes were both isolated and cultured. When these lymphocytes were re-exposed to tumor antigens, the lymphocytes from the control-treated mice did not proliferate, while the lymphocytes from the vaccine-treated mice proliferated in a period of eight hours after exposure (Fig. 5). IFN-g secretion, indicative of T lymphocyte activation, was measured in another test. Vaccinetreated mouse lymphocytes, when exposed to tumor antigens in vitro, responded with significantly higher levels of IFN-g than in the control groups (Fig. 6). Dartmouth Undergraduate Journal of Science
Discussion Vaccine Complex Activation of APCs Upon Phagocytosis
Morphogenesis is the key process in APC maturation and activation. In vitro, the ‘12 CpG ODN delivery system was Kelly aho ‘11 and Elin beck shown to gain direct entry into APCs. The vaccine properly released its immunostimulatory agents, as indicated by DC cell morphogenesis (i.e. cytoplasmic streaming). Phagocytosis was confirmed using laser scanning confocal microscopy, proving the actual internalization of the vaccine complex. This type of microscopy not only allows the visualization of fluorophores within a biological system in the XY plane, but also allows the confirmation of the intracellular distribution of the fluorophore by imaging through the ZY or ZX axes, proving the actual internalization of the vaccine complex. Some cells were observed to remain unstimulated even in the presence of the vaccine complex or morphogenetically changed without a visible intracellular immune complex. For the DC experiment, some cells did not seem to uptake the vaccine complex, which refers to the inability of the host to elicit an immune response. This can be ascribed to the possible degradation of vaccine complex in the Petri dish prior to cellular uptake or anergy. On the other hand, the absence of a visible fluorescent signal within the confines of morphogenetically mature cells may be due the completed degradation of the vaccine complex, or at least the fluorescent tag, by the proteasome and lysosome complexes that abound in the juxtanuclear area. Another test looked at the presence of surface markers on macrophages treated with the vaccine complex. CD86 is present on activated macrophages and the data show that the vaccine causes the macrophages to evolve into an active form expressing many of the activation markers proved by flow cytometry. The cell sorting process indicated that the vaccine could be quickly processed by the cells to begin immunological activation. Finally, a dose response of inhibitory peptides was used to block entrance of the vaccine into the APCs, proving the direct phagocytosis of the vaccine via extracellular receptor-induced phagocytic pathways. The results show that as blocking peptide increased, less vaccine was present in the cell as plotted by a relatively loga-
Image courtesy of Riley Ennis.
Fig. 5: Mouse T lymphocytes collected from PLGA/lysate-treated mice (left) and MacroVax-treated mice (right) spleens (3 weeks of treatment) were exposed to tumor specific antigens and analyzed for clonal expansion via a cell proliferation assay. FALL 2011
Image courtesy of Riley Ennis.
Fig. 6: Mouse T lymphocytes collected from PLGA/lysate-treated, CpG/PLGA/ Lysate-treated, and MacroVax-treated mouse spleens (3 weeks of treatment) were exposed to tumor specific antigens and analyzed for activation via ELISA for IFN-γ.
rithmic function, which may allow the extrapolation of a dose response for in vitro experiments in order to maximize pharmaceutical potency while minimizing cost. In summary, the CpG ODN delivery system is readily taken up by the APCs and directly stimulates rapid maturation through morphological changes by cytoplasmic streaming; the activation of APCs will conceivably allow for its innate cytotoxic properties to function while initiating the down stream anti-tumor response.
Complex Immune Response Completion with ELISA and mRNA Analysis
The identity of the signaling cascades involved in the APC immune response to the vaccine can be gleaned from evaluating the mRNA expression of several cytokines. The CpG ODN vaccine complex significantly increases cytokine expression of IL-12 and IFN-g, and decreases the inhibitory IL-10. In addition, the marked (16-fold) increase in IFNg level indicates that downstream expression of IL-12 does not initiate negative feedback mechanisms because the inhibitor IL-10 continues to be down regulated post-vaccine treatment. Both IL-12 and IFN-g have been shown to be directly linked with the proper antigen specific CD8 and CD4 T cell immune responses, and the large secretion of these cytokines as indicated by the increase in their mRNA levels, proves the concept of immunol activating by the vaccine complex. The large discharge of these pro-immunol cytokines will proliferate the necessary T cells to bind to tumor surface antigens and begin tumor cell death. This process is completely organic, and applies two already studied processes in the immune system to breach the immunol suppression barrier of the tumor and uses immune cells to lyse the cancer. In parallel to this data are the results collected from the ELISA experiment of vaccine-treated macrophages, which echo the point that the vaccine has the ability to depress anti-inflammatory cytokines that may block immunological activities, and continues to raise the stimulatory cytokine levels. Together the data show that the vaccine activates the designated intracellular pathways and begins the process of cytokine secretion for CTL proliferation. 43
Vaccine Induces Proliferation of CTLs with the Capability to Tarnish Tumor Integrity
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The final piece of the vaccine lifespan is proliferation of tumor-specific CTLs that recognize and destroy tumor cells. Mice treated with the vaccine showed that their extracted lymphocytes had high affinity and proliferation potential when exposed to the tumor antigens ex vivo. The body produces CTLs as antigens that are presented on the surface of APCs to the lymphocytes. The lymphocytes, via a variety of genetic rearranging mechanisms, can function to recognize tumor surface antigens and destroy them. Immunized mice were given tumor cells in order to study tumor establishment in vivo but due to data sensitivity issues this information cannot be released.
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Conclusion The chronic side effects and shortcomings of current cancer therapies drive the new field of cancer immunotherapeutic research. The proposed nanomedical delivery system of CpG ODNs, and GM-CSF coupled with tumorassociated antigens, all encapsulated within a signaling protein coat improves the delivery of these immunomodulatory agents to specific APC pathways. The goal of this vaccine is to elicit an anti-tumor response and generate tumor antigen-specific CTLs while harnessing the understudied cytotoxic capabilities of DCs. This novel paradigm of a PLGA biodegradable nanoparticle vaccine complex encapsulated within a human-derived protein coat provides increased specificity and duration of DC activation. Future experiments include the creation of balb/c-4T1 tumor models and testing the efficacy of the vaccine on tumor establishment in vivo. APC-based cancer vaccines are the future of cancer therapeutics, and advancements in intracellular delivery mechanism technology will increase vaccine specificity and immune stimulation, thus promising to generate the most effective cancer therapy in the next few years.
Acknowledgements I would like to thank Georgetown University’s Department of Biochemistry, the Lombardi Cancer Center’s Shared Resources Department, and the Sheikh Zayed Institute for Pediatric Surgical Innovation at Children’s National Medical Center in Washington D.C.
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References 1. S. Cao et al., J. Immunol. 169, 5715-5725 (2002). 2. S. Miles, A. Sandler, Adv. Drug Deliver. Rev. 61, 275-282 (2009). 3. B. Weigel, D. Rodeberg, A. Krieg, B. Blazar, Clin. Cancer Res. 9, 3105–3114 (2003). 4. R. Seeley, Anatomy & Physiology (McGraw-Hill, Dubuque, IA, 2007). 5. E. Ullrich, N. Chaput, L. Zitvogel, Horm. Metab. Res. 40, 75–81 (2008). 6. J. Chace et al., Clin. Immunol. Immunopathol. 84, 185–193 (1997). 7. V. Brockton et al., J. Cell Sci. 121, 339-348 (2008). 8. B. Wu, Covalent Coupling Protocol for Phosphorex. Phosphorex Laboratories (12 September 2009). Web.
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