Scientia - Spring 2016

Scientia

A Journal by The Triple Helix at The University of Chicago

Spring 2016

Front Cover Photo: Distribution of the principal elements (Ca, Mg, Si, Al, K) in a limestone sample, based on XRD mapping performed

by SEM/EDS. Attribution: P. Kozlovcev and R. Prikryl. Materiales de Construcciรณn.

65, 319. July 2015.

Scientia 3 86

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Inquiries: Unraveling the Genetics of Cancer: An Interview with Dr. Funmi Olopade, M.D. Zainab Aziz

The Science Writer: An Interview with Steve Koppes Erin Fuller

In Depth: Chronic Arsenic Exposure Leads to Metabolic Dysfunction

Wakanene Kamau

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Exploring the Plausibility of Group Selection with Respect to Cancer Phenomena

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Scanning Electron Microscopy of Phosphorus Phases in Marine Sediments

Adil Menon

Leonard Shaw

Produced by The Triple Helix at the University of Chicago Layout and Design by Helena Zhang, Production Director Cover Letter written by Jake Russell, Co-Editor in Chief Scientia Board: Jake Russell, Luizetta Navrazhnykh, Michael Cervia, Amanuel Kibrom, Erin Fuller

Spring 2016

About Scientia Dear Reader, Our cover image for this issue of Scientia depicts the distribution of elements in an undersea mineral sample, analyzed by x-ray diffraction and scanning electron microscopy. These are but two of the myriad of techniques developed to investigate materials at the molecular level, and can provide details about topics ranging from the formation of Earth to the structure of a protein. Check out our article on marine sediments, by Leonard Shaw, to learn more.

This quarter has seen an expansion of Scientia into what we believe is an underappreciated but extremely relevant field: science writing. We held our first Science Writing Workshop, for which the President of the Chicago Science Writers Association, Justin Breaux, came to speak and answer questions about his career path. Afterwards, TTH writers and editors had a chance to work with him individually on their own articles.

We also present an Inquiry with the UChicago Associate Director for News, Steve Koppes.

Scientia is always looking to expand our scope to lesser known areas of research on campus. If you're finishing up a project and want to see it in print, or if there's a professor doing some incredible work you think everyone should know about, consider writing for us! We encourage all interested to get in touch with a member of our team, listed in back.

Meanwhile, please enjoy this issue of Scientia, by The Triple Helix.

Sincerely, Jake Russell Co-Editor-in-Chief, Scientia

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Scientia

Inquiries Unraveling the Genetics of Cancer: An Interview with Dr. Funmi Olopade, M.D. Zainab Aziz

Doctor Funmi Olopade became a medical doctor because her mother told her to – and she thanks her mother for her wise advice every day.

Dr. Olopade’s father was a minister whose greatest wish it was to see all his children enter the field of science. He was interested, she says, in the potential for science to explain the many unanswerable questions and phenomena of the world around them. Her mother urged her to enter medicine as opposed to theoretical physics (Dr. Olopade’s first choice) because her mother believed that she would excel in the pursuit of helping and serving others.

Dr. Olopade completed medical school at the University of Ibadan in Nigeria in 1980, and came to Cook County Hospital, before beginning a fellowship at the University of Chicago Medicine. One of the leading oncologists at the university at the time was Doctor Janet Rowley, a pioneer in cancer genetics. Dr. Rowley was studying abnormalities in chromosomes that led to leukemia. In her words, Dr. Olopade “found this work extremely compelling,” and began her own research with Dr. Rowley.

Together they studied a region of chromosome 9 that was frequently deleted in many cancers. The goal, Dr. Olopade says, was to understand why this specific region in question was deleted. If there were some tumor suppressor genes encoded in this region, their deletion would lead to increased

chances of developing cancer. Her suspicions were correct, and Dr. Olopade found that the commonly removed region of chromosome 9 did in fact contain important tumor suppressor genes.

Moreover, this sequence of genes was responsible for familial disposition to melanoma, or skin cancer.

This second discovery was the more important one for Dr. Olopade’s career, as it sparked her interest in studying other inherited cancers, and led her to ask why some people may have higher risk for developing cancers than others.

Dr. Olopade officially joined the university’s faculty in 1991, and began looking for families that had histories of melanoma to isolate the region of chromosome 9 that could lead to melanoma. She also studied families missing a region of chromosome 17 that similarly, when deleted, increased the chances of developing breast cancer. Incidentally, more families with breast cancer participated in her studies and volunteered their blood samples, allowing her to isolate and identify the gene of interest on chromosome 17. Since then, Dr. Olopade has studied families with history of inherited breast cancer, and has established the Center for Clinical Cancer Genetics to track these studies.

The Center for Clinical Cancer Genetics has two main branches. The first is a wet lab in the Knapp Center for Biological Discovery where Dr. Olopade

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Spring 2016 and her colleagues run tests on breast tissue, and attempt to describe the genomic landscape of breast tumors through dissections, DNA analysis, and RNA expression studies. These tests are meant to help Dr. Olopade’s team determine the mechanisms that drive tumor genesis, and, furthermore, determine what alterations have been made in these cells to make them cancerous. The Cancer Genetics Center’s other arm is the clinical, dry lab. The dry lab is where Dr. Olopade and genetic counselors draw up pedigrees and track cancer within families to explain to patients what exactly their cancer risk is, and what specifically can be done to prevent or cure the disease.

Genetics, Dr. Olopade says, used to solely focus on somatic, non-inherited mutations. She stresses how important it is to consider both inherited and non-inherited aspects of cancer.

“If you follow women with cancer, and look at their ancestry, some people have inherited the same mutations and never get cancer. But some people get cancer at 30,” says Dr. Olopade. She wants to know the modifiers that some people have that prevent them from developing cancer when their family members are developing the disease. Furthermore, she wants to figure out how to mark the genomic landscape of people who do or will develop the cancer, and map genetic and epigenetic changes before there are too many somatic mutations.

As a physician scientist, she is given the opportunity to work directly with the subjects of her experiments in the wet lab. What excites her the most is the opportunity to have everyone know their risk for cancer, then prevent it, or diagnose it early and treat it. For solid tumors like breast cancer, which she is researching, “we tell everyone to get mammograms,” Dr. Olopade says, “but this is ultimately unnecessary because not everyone will actually get cancer.” By personalizing risk assessment, doctors will also be able to personalize the best methods for treatment and cancer prevention. In the field of breast cancer risk assessment, Angelina Jolie is the example that everyone gives (Jolie had a double mastectomy in 2013 due to her high risk of developing breast cancer), but to Dr. Olopade, Jolie’s story is not the ideal example. Not everyone who has this risk will have the inclination or resources to have their breasts or ovaries removed prematurely. What is more practical for the general populace, according

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to Dr. Olopade, is having doctors who are going to help manage risk in a more reasonable way. To her this is a sure way to move the field of cancer prevention and treatment forward. **************** Dr. Olopade grew up and went to medical school in Nigeria. After comparing her experiences there to what she saw in America, she concluded that there can be many variants of a specific cancer. She had been taught that breast cancer, for example, is “one disease.” She realized that cancer can grow at different rates – sometimes prevention techniques such as mammograms are not enough to identify fast-growing tumors in time. In Nigeria, she says, cancers were big, and there was an abundance of young women with the disease. At the time, these observations were chalked up to the fact that many women in Nigeria were poor, without access to proper insurance and medical care. Dr. Olopade saw similar cases in immigrant women in both Cook County Hospital and UChicago Medicine, and she realized that there was a bigger reason behind the large, early onset tumors in women of African descent. These women had access to insurance and prevention techniques such as mammograms, but these resources were not enough to identify fast-growing tumors. Dr. Olopade hypothesized that there must be some genetic contribution to early onset cancer, and wanted to track who was developing these cancers. At the urging of her colleagues in Nigeria, Dr. Olopade opened a branch of her Cancer Genetics center in Nigeria in 1998.

Her goal was to see if there was a connection between the patterns she saw in women of African descent in America, and the women she had seen in Nigeria so many years before. Her suspicions were correct. Population genetics, she says, have definitely contributed to the excess triple negative early onset breast cancer seen in certain communities of women in America and in Western Africa. Dr. Olopade hopes to extend this research to other parts of the world, and make her mission to understand cancer genetics a truly global one. One of her mentees is interested in inheritance in North African and Arab women, whereas a colleague in her lab is studying tissue samples from Brazil. She is currently also sharing data with labs in India. She and the scientists in Nigeria learned so much from each

Scientia other, says Dr. Olopade, and she hopes that from this global initiative she will be able to understand so much more.

To Dr. Olopade, her greatest achievement thus far has been getting people to understand the importance of genetics. Understanding our genetics allows us to better stratify risk, and once we know our risk we can make an educated plan to ensure prevention. In her opinion, people focus too much on treatment, and she is proud to have contributed to a global dialogue on prevention. Too often, there is a misconception that cancer is a kind of witchcraft that arises with no explanation. Her goal is to provide this explanation – a mission she finds empowering. The most rewarding part of her work is when she sees that she’s moved the needle, she says. What makes her the most proud is when there is a family with cancer for many generations, and all of a sudden she sees people surviving, and passing on this health to the next generation.

Dr. Olopade credits much of her success to her outstanding mentor, Dr. Rowley, who both challenged and inspired her. Trying to follow in Dr. Rowley’s footsteps, and aspiring to be as prolific a researcher as her, was one of the factors that pushed Dr. Olopade to achieve all that she has. Dr. Olopade has made it one of her goals to provide similar guidance for young scientists today. She takes time out her busy days to listen to her mentees present their research, discuss project proposals, make summer research plans, and interview for student organizations such as the Triple Helix.

She has unwavering faith in the importance of role models in helping to build a successful and fulfilling career. To Dr. Olopade, it is necessary to see people at work and imagine yourself in their shoes before you can develop a deep and abiding passion for an occupation. Her parting words of advice to aspiring researchers and doctors – “There are many important milestones in life, and you should take advantage of every opportunity. One day you may be in class and something might just click – be flexible and go out of your comfort zone, and you’ll be fine.”

About the Author Zainab Aziz is a first year prospective Chemistry major.

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Spring 2016

The Science Writer: An Interview with Steve Koppes Erin Fuller

Steve Koppes didn’t know he was going to be a science writer in high school. He thought he was going to be an anthropologist.

“I’ve been interested in science for longer than I’ve been able to read,” he tells me in our interview.

“When I was four or five years old I’d look at pictures of dinosaurs and deep-sea creatures in my family’s set of encyclopedias. I’d watch ants build their anthills in my backyard. I’d later watch TV specials on undersea explorer Jacques Cousteau and paleontologist Louis Leakey. I’d go fossil-hunting with my father or with friends. I read books in the Time-Life Library of Science, some of which I still have in my personal library.”

As an undergraduate at the University of Kansas, he obtained his bachelor’s degree in anthropology, even though in his last semester, he decided that he didn’t want to pursue anthropology. He had always enjoyed writing throughout high school and college, and thought: “Hey, if I become a science writer, which I had always been interested in, I could write about something every week or two.”

After graduating from Kansas University with a masters degree in journalism, Koppes worked at a small daily newspaper in Kansas, and then opened a Fuddrucker’s knock-off restaurant with his brothers.

When the restaurant failed, in his words he recalleally sucked." he bounced from Arizona State University, to Georgia State University, finally the University of Chicago where he remains today.

Koppes is the associate director for news in the University of Chicago’s News Office and covers science and engineering news on campus. He is the

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author of Killer Rocks from Outer Space (2005), a book for young adults about comets, asteroids, and catastrophic meteorite impacts, and is the director of the Homewood-Flossmoor Science Pub, a monthly lecture series.

Koppes interviews professors and graduate students working in labs at the university about their work and condenses and clarifies their work for the general university audience. . . similar to the way The Triple Helix’s Inquiry articles are written.

“I’m not sure I’m a very good interviewer,” he admits. “I just try to have a conversation.”

He believes that a good science writer needs a high tolerance for technical language. This tolerance is especially important to his current project: creating a multimedia package about the involvement of the university’s high-energy physics group in the ATLAS experiment of the Large Hadron Collider (LHC).

The LHC verified the existence of the Higgs boson nearly four years ago. Now, new experiments seek to confirm if there is more than one type of Higgs particle and whether it has anything to do with dark matter and other exotic physics phenomena such as supersymmetry.

If you’ve recognized some of those things, you’ll recognize that Koppes may as well be considered a translator of the ultra technical. But why can’t researchers talk to us themselves?

Researchers often conceal themselves in the controlled, measurable world of the lab. They produce dangerous substances, bad smells, or loud noises-- that’s just the researcher, say nothing on the lab. It becomes difficult to tell whether the mold in

Scientia the lab refrigerator is an experiment or a forgotten lunch. Ultimately, they must shuffle out of their labs and tell us what they are doing. Sometimes they have spent so much time in the lab that dust sifts from their lab coats, they are hunchbacked from bending over the lab bench, and they squint at the sun.

When they speak, they speak in different languages: zygomatic arch, mandibular fossa, lacrimomaxillary suture. Anyone who was excited to hear them speak is now confused. What the hell are they saying?

Many researchers have a difficult time removing themselves from their work and explaining to others who are not in science, or in a different field, what it is they’re doing. After all, they study bacteria, bones, and black holes, not communication. This phenomenon is called the Curse of Knowledge.

Koppes says: “I believe my job exists because it’s important for scientists, universities, national laboratories and the like to share their research findings with the public in lay-accessible language. Much of the research is supported by tax dollars, so there’s a societal obligation to tell people what they’re getting for their money. A truly functioning democracy needs a well-informed, scientifically literate citizenry. And sometimes, as a bonus, young people will read about scientific research and become inspired to become scientists themselves.”

You are reading the Triple Helix because you are interested in science. You know about science through the Triple Helix, NOVA, Cosmos, Scientific American, or any number of publications or television programs designed to conduit complex ideas. These publications present ideas spoken in the original lab language and are translated by hardworking writers and editors to interested audiences through science writing. Good science writers know that understanding tough topics begins with good explanations.

When Koppes wants to explain a tough topic, he starts with the dominant idea.

“I understand this idea, and I know I need to put it in the announcement or the release or the story. I love it when I know what the lead is going to be during the interview. It doesn’t happen often enough but sometimes, someone will say something and I’ll think, ‘That’s how the story is going to start.’

I love that because then it just kind of flows.”

The worst ones, he explains, are the ones where you put together each bone of the skeleton. Each bone is an idea tied to the researcher’s work. Each idea is laid out separately, and his task is to put them together coherently so the reader can see the skeleton.

For example, take the physicists group working on the ATLAS Project. He gave me an example of the kind of the phrases they used: “The Higgs was discovered at the beginning in two decay modes: Higgs to two photons, called Higgs to gamma gamma or two photons; a Higgs to two zed bosons, and that decaying to two charged particles.”

What do these words mean? What is a decay mode? What is a boson? There is more than one kind? Did you know that?

Don’t panic.

“You don’t necessarily need to understand it all,” he said, “but you can’t let it intimidate you.”

A boson is a particle which carries force. An example of a boson is a photon, which carries electromagnetic force. The force of gravity is carried by the Higgs boson.

The Higgs boson falls apart--or decays-whenever it is produced. The Higgs tends to decay in different ways, known as decay modes. The products of the decay modes are other particles: gamma gamma, zed bosons, or other particles such as quarks (which also have different types).

Koppes says, “What I found striking is that theory predicts that the Higgs would decay more than half the time into two bottom quarks, but that actually hasn’t been observed yet. That’s because free quarks are invisible and even bottom quark jets are difficult to detect. But one of our physicists specializes in the detection of quark jets, so I’ve spent a fair amount text focusing on that aspect.”

The researchers he interviewed had overlapping interests and comparable material. Thus, much of the information he acquired was redundant. He emphasizes that he tries to get the redundancy out and uses the best explanations. He also tries not to explain everything, but only what is of the most interest to UChicago’s faculty. The University of Chicago’s physicists have been playing major and ongoing roles in the LHC’s research and in upgrading the experiment’s capabilities. Soon, the LHC will

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Spring 2016 begin another data-collection run, and will need his help in conveying their ideas to the community.

As long as there is science, there will be science writers. For those thinking about being a science writer, Koppes advises that they should seek out existing science publications, universities, national laboratories, and federal agencies. The University of Chicago News does take student freelancers from time to time, and encourages students to reach out to them for opportunities.

However, he says, “We’re not likely to ever recover the science writing opportunities that we’ve lost from the declining newspaper industry. The decline in magazines is perhaps less severe, but not exactly robust, at least to my perception.”

What may replace or supplement traditional media are blogs. Anyone can publish a blog, of course, but the best ones are likely to be those associated with an existing science publication of some kind, such as the Scientific American Blog Network, which can provide some measure of editorial quality control. Additionally, there’s been some talk as well about the potential of a non-profit model. Climate Central is a successful example of a science news non-profit.

No matter what news medium they use, every good science writer shares is powerful curiosity about the world and pleasure from writing.

“My central philosophy of science writing is rather selfish,” Koppes ended. “I write to please myself. That means, to the extent that I can, selecting the topics that appeal to me the most, then writing them up in a way that I find personally gratifying.”

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References [1]

Pinker, S. (2014). The Sense of Style: The Thinking Person’s Guide to Writing in the 21st Century . New York, NY: Penguin.

About the Author Erin Fuller is a 4th year English major and Environmental Studies minor, currently working for the University of Chicago Alumni Development and Relations Department and as a freelance writer for the UChicago News.

Scientia

In Depth Chronic Arsenic Exposure Leads to Metabolic Dysfunction Wakanene Kamau Sargic Laboratory Exposure to the metalloid arsenic (As) in drinking water poses a significant environmental health threat, affecting 150 million people globally. In particular, epidemiological literature has shown links between chronic arsenic exposure and insulin resistance, as well as type 2 diabetes mellitus (T2DM). To test this notion, we studied the effect of inorganic arsenite (iAs3+) on glucocorticoid receptor (GR) mediated metabolic gene expression ex vivo using primary murine adipose tissue. Following exposure, gene expression was analyzed using quantitative real-time PCR (qRT-PCR). We found that arsenic co-exposure alongside physiological concentration of the endogenous GR ligand corticosterone resulted in decreased GR-dependent gene expression. In order to model acute arsenic exposure in our system in vivo, eight-week old mice were exposed to inorganic arsenite (iAs3+) in their drinking water at a concentration of 50 ppm for 8 weeks. Body weight as well as water and food consumption were measured twice weekly. Glucose homeostasis was assessed by intraperitoneal glucose tolerance tests (IP-GTTs) and insulin tolerance tests (IP-ITTs). Pancreatic and adipose tissue mass was measured at sacrifice. Pancreatic endocrine cell area was assessed via immunofluorescence microscopy.

iAs3+ exposure did not alter body weight gain across the study; however, exposure markedly impaired glucose tolerance. Insulin sensitivity measured during IP-ITTs was not appreciably different in exposed mice, but was inappropriately normal given the hyperglycemia. Total pancreatic mass was reduced, but total islet cell, β-cell, and α-cell area were not altered by arsenic exposure. In sum, these data suggest that arsenic impairs normal glucose homeostasis via reduced insulin production. A clearer understanding of arsenic’s mechanisms of action will make for a more confident assessment of its role in the burgeoning metabolic disease epidemic and better inform treatment decisions and intervention strategies to address this significant threat to global metabolic health.

Introduction Arsenic (As) has long been acknowledged to have an adverse effect on human health. Found naturally in the Earth’s crust, the World Health Organization (WHO) estimates that over 200 million people worldwide are exposed to elevated levels of arsenic in drinking water. The WHO and US Environmental Protection Agency set a safety

standard of 10 ug/L of arsenic, yet in large portions of developing countries like Bangladesh, Vietnam, and Chile, As concentrations regularly exceed the safety standard. In the United States, the US Geological Survey (USGS) considers Maine, along with much of New England to be part of “the Arsenic Belt.” In a 2010 study conducted by the USGS of 174 towns with 20 or more sampled wells in Maine, more than 25 percent of the sampled wells in 44 towns exceeded

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Spring 2016 affected by intense, acute, arsenic exposure (i.e. a poisoning event) are subject to nausea, vomiting, abdominal pain, severe diarrhea, and possibly death, while chronic exposure (i.e. drinking water contamination) is linked to multisystem disease, including cardiovascular disease and cancers of the bladder, kidney, lungs, and skin. Additionally, a growing body of epidemiological literature has implicated arsenic exposure with diabetes, and animal models have suggested that arsenic can disrupt glucose homeostasis. Environmental pollutants, like As that operate as endocrine disrupting chemicals (EDCs), have recently been implicated as key players in the burgeoning obesity and type 2 diabetes mellitus (T2DM) epidemic.

Correlations between chronic arsenic exposure and insulin resistance, hyperglycemia, and T2DM have been previously reported, but this data has failed to establish conclusive causality. We believe that establishing a robust, mechanistic understanding of the obesogenic and diabetogenic effects of As is necessarily for the development of novel interventions.

Figure 1: Arsenic Contamination in Maine Arsenic concentration in private wells surveyed by the U.S. Geological Survey. The EPA ‘Maximum Contaminant Level’ for Arsenic is set at 10 ppm. The above graph only represents towns with more than 20 sampled wells, areas in grey either did not meet this threshold or were not surveyed. Reproduced from Nielsen, M.G., Lombard, P.J., and Schalk, L.F., 2010, Assessment of arsenic concentrations in domestic well water, by town, in Maine, 2005–09: U.S. Geological Survey Scientific Investigations Report 2010–5199, 68 p.

10 µg/L. In 19 towns, more than 10 percent of the sampled wells had arsenic concentration over 50 µg/L (see Figure 1). Prior studies estimated that nearly 10 percent of domestic wells in Maine contained arsenic. However, the presence of “hot spot” regions of wells, with more than five times the MCL for arsenic in the US, had not been well characterized. The prevalence of arsenic in private wells is of particular concern as federal legislation only produces mandates for monitoring public water systems. Similarly, rural regions in Cambodia have reported average groundwater arsenic concentrations of 217 ug/L with the highest single reading being 1610 ug/L. The worldwide exposure to this environmental contaminant creates a thorough understanding of its health effects critical for making necessary changes to curtail its impact on human health.

The adverse health effects of arsenic occur from both acute short term and chronic exposure. Those

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Results A. Gene Expression The role of arsenic on GR activation was investigated by assessing the expression of the glucocorticoid-induced leucine zipper (GILZ) gene as a physiological marker. GILZ has been recently reported to play a critical role in mediating glucocorticoid activity. In fact, multiple glucocorticoid response elements (GREs) are present in the promoter region of the GILZ gene, resulting in GILZ being positively regulated by the GR; thus, GILZ expression is a readout of endogenous GR

Figure 2: Gene Expression Primary murine adipose tissue was collected and used for mRNA gene expression analysis. (Left) Glucocorticoid-induced leucine zipper (GILZ) gene serves as a physiological marker for GR activity. Arsenic reduced GILZ expression at both 100 nM and 1uM concentrations. (Right) Insulin receptor substrate 1 (IRS-1) gene serves as a physiological marker for adipocyte function and insulin responsiveness. Arsenic reduced IRS-1 expression at both experimental concentrations, and the reduction gained significance at the 1uM concentration. p-value<0.001, Student’s T-Test

Scientia signaling. In an ex vivo assay, perigonadal fat pads from wild-type male C57BL/6J mice were removed, minced, and cultured with the vehicle (ethanol).

After which, the primary fat was supplemented with the endogenous glucocorticoid corticosterone (Cort) at a concentration of 10 nM and with iAs3+ at a concentration of either 100 nM or 1 uM for 4 hours.

Preliminary data showed that either concentration of iAs3+ produced robust effects in primary adipose tissue without evidence of cytotoxicity. After the 4-hour incubation time, the tissue was collected for RNA extraction, followed by gene expression analysis via qRT-PCR. iAs3+ was shown to reduce corticosterone-induced GILZ expression at 100 nM and 1 uM; however, the reduction did not quite achieve statistical significance. (see Figure 3, Left) To assess adipocyte function and insulin responsiveness, we investigated the effect of arsenic on the expression of the insulin receptor substrate 1 (IRS-1) gene. EDCs have been previously shown to modulate insulin signal transduction through alterations in IRS-1, a key intermediate in the insulin signal transduction cascade. In a manner similar to the GILZ mRNA expression assay, perigonadal fat pads from C57BL/6 mice were sterilely removed, minced, and incubated for 48 hr in media supplemented with Cort at 10 nM and iAs3+ at a concentration of either 100 nM or 1 uM for 4 hours. After incubation, RNA was extracted, and mRNA expression was assessed via qRT-PCR. iAs3+ was able to reduce IRS-1 gene expression at both exposure concentrations and significantly reduced IRS-1 gene expression at the 1 uM concentration (see Figure 3, Right). Because of the role of IRS-1 in insulin signal transduction, reductions in this expression of this molecule are predicted to promote cellular insulin resistance.

B. Glucose Homeostasis To determine if iAs3+ promoted global changes in glucose homeostasis and insulin sensitivity,

Figure 3: Experimental Schematic Male C57BL/6J mice were obtained from Jackson Laboratory at 2-3 weeks of age after weaning. Arsenite exposure began on week 8.

Serial metabolic measures (IP-GTT, IP-ITT) began on week 4 of arsenite exposure. Mice were sacrificed on week 16.

both glucose and insulin tolerance tests were performed (see Figure 3). After 8 weeks of iAs3+ exposure via drinking water, an IP-GTT test was performed after a 6-hour fast. iAs3+ exposed mice exhibited significantly impaired glucose tolerance, as evidenced by a higher area under the curve of glucose x time in the IP-GTTs. Additionally, blood glucose measurements taken at 10, 20, 30, 40, 60, 90 and 120 minutes following injection were significantly higher in iAs3+ exposed mice at each individual timepoint independently, indicative of

Figure 4: Glucose Homeostasis Top: (Right) Intraperitoneal glucose tolerance test (IP-GTT) was performed on mice exposed to control or 50 ppm sodium arsenite in drinking water for 8 weeks. n= 24-26 mice per group. *p-value <0.05 for each individual time point, calculated using Studentâ&#x20AC;&#x2122;s T-test.(Left) Area under the curve analysis performed using GraphPad Prism version 6. **p-value<0.01, Studentâ&#x20AC;&#x2122;s T-test Middle: At four time points (0, 15, 30, 60 mins.) across the IP-GTT, tail blood was collected, and plasma was used to measure insulin levels via ELISA. There were no statistically significant differences between the experimental animal groups. n= 24-26 mice per group.

Bottom: Intraperitoneal insulin tolerance test (IP-ITT) was performed on mice exposed to control or 50 ppm sodium arsenite in drinking water for 8 weeks. There were no statistically significant differences between the experimental animal groups. n= 8-11 mice per group.

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Spring 2016 totalistic impaired glucose handling (see Figure 4, Top). Glucose intolerance can arise from impaired insulin secretion or impaired insulin action. To assess whether iAs3+ altered global insulin sensitivity, an IP-ITT was performed after a 3-hour fast at 8 weeks of exposure. No significant difference between the groups was identified, suggesting that arsenic-induced glucose intolerance did not arise from insulin resistance (see Figure 4, Bottom).

Interestingly, insulin levels during the IP-GTT revealed no significant difference between iAs3+ -exposed and iAs3+ -naive mice (see Figure 4, Middle). This suggests that arsenic-treated mice did not adequately secrete insulin to limit the rise in blood sugar after the glucose load.

C. Immunohistochemistry While the pancreas has notable exocrine function used for digestive purposes, the pancreas also plays a critical role in the synthesis and secretion of many metabolically relevant endocrine hormones. Of note, the beta-cells of the endocrine pancreas are responsible for insulin production and release. To assess the role iAs3+ plays in modulating the endocrine function of the pancreas, the pancreas of each mouse was carefully dissected, weighed, and fixed in 4% paraformaldehyde solution, after 8 weeks of in vivo exposure. The pancreas was fixed for 24 hours before paraffin embedding and subsequent immunohistochemical processing.

Pancreata were stained and imaged, from which islet cell area was calculated (see Figure 5, BottomRight). No statistically significant difference was identified in beta-cell area between iAs3+ and control mice, suggesting that iAs3+ was not overtly toxic to the endocrine pancreas. Interestingly, pancreatic mass was significantly reduced in the iAs3+-exposed mice (see Figure 5, Top-Left). The reduction in mass in the pancreas is surprising given the lack of appreciable differences in the final body weight of the mice (see Figure 5, Top-Right). This phenotype is hypothesized to result from impaired insulin secretion as insulin functions as a pancreatic growth factor. In this manner, impaired insulin secretion could lead to stunted pancreatic growth.

Discussion Adipose tissue, now appreciated as an essential endocrine organ, is an important regulator of global energy metabolism. We have shown that inorganic

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Figure 5: Immunohistochemistry Top: (Right) Final body weight calculated upon sacrifice at 8 weeks of iAs3+ exposure. There were no statistically significant differences between the experimental animal groups. (Left) Pancreatic mass calculated upon sacrifice at 8 weeks of exposure. *** p-value<0.001, Studentâ&#x20AC;&#x2122;s T-test Bottom: (Right) Islet cell area calculated by automated contouring post immunofluorescence staining. (Left) Representative image of pancreatic islet. Green = insulin; Red = glucagon, White = somatostatin, Blue = DAPI

arsenite (iAs3+) can modulate glucocorticoid receptor-mediated gene expression in primary murine adipocytes ex vivo. By using GILZ expression as a readout of glucocorticoid activity, we report that iAs3+ reduced corticosterone-induced GR signaling.

To assess insulin responsiveness in adipocytes, we investigated the effect of iAs3+ on the expression of insulin receptor substrate 1 (IRS-1) gene. Previous work in our lab defined the importance of IRS-1 as an insulin signaling intermediate that can be specifically modulated by EDCs11. We show that iAs3+ was able to reduce ex vivo IRS-1 gene expression at both experimental conditions, with significance achieved at the 1 uM concentration. These results suggest that arsenic promotes changes in gene expression predicted to promote insulin resistance, a key metabolic disruption that leads to the development of diabetes.

We also report that iAs3+ promoted global changes in glucose homeostasis in vivo. Serial blood glucose measurements taken after a glucose challenge were significantly higher in iAs3+ exposed mice. This result is indicative of impaired glucose tolerance, an intermediate phenotype on the pathway to diabetes. Glucose intolerance is observed in vivo in cases of impaired insulin secretion or action and in cases of insulin resistance. Interestingly, despite

Scientia our ex vivo studies suggesting an increase in insulin resistance in adipose tissue, in vivo insulin sensitivity showed no significant difference between control and experimental groups. These results suggest that our observed iAs3+-induced glucose intolerance did not arise from insulin resistance. Furthermore, plasma insulin levels taken during glucose challenge showed no significant difference between control and experimental groups. This result suggests that mice exposed to iAs3+ did not adequately secrete insulin in response to a glucose challenge. In sum, the results from glucose and insulin tolerance tests support the hypothesis that in vivo iAs3+ exposure disrupts glucose homeostasis through an impairment in insulin production. This hypothesis is further corroborated by the observed reduction in pancreatic mass in iAs3+ -exposed mice since insulin serves as a pancreatic growth factor, and impaired insulin production, as in type 1 and latent autoimmune diabetes of adulthood, has been shown to result in reduced pancreatic mass.

Given arsenic’s widespread contamination of drinking water supplies, further mechanistic understanding of arsenic’s metabolic effects is critical for treating those at risk for arsenicaccelerated diabetes. The burgeoning epidemic of diabetes is projected to afflict 642 million individuals globally by 2040. As the field of environmental metabolic disruption expands, it is hoped that these studies will provide further insights into the effects and mechanisms by which environmental contaminants contribute to the burgeoning metabolic disease epidemic in order to develop interventions to mitigate the deleterious impact of toxicant exposures on human health.

Perspectives (Online) 121.7 (2013): 774.

[6] Thayer, Kristina A et al. “Role of environmental chemicals in diabetes and obesity: a National Toxicology Program workshop review.”

Environmental health perspectives 120.6 (2012): 779.

[7] Kuo, Chin-Chi et al. “Arsenic exposure, arsenic metabolism, and incident diabetes in the strong heart study.” Diabetes Care 38.4 (2015): 620-627.

[8] Ayroldi, Emira, and Carlo Riccardi. “Glucocorticoid-induced leucine zipper (GILZ): a new important mediator of glucocorticoid action.”

The FASEB Journal 23.11 (2009): 3649-3658.

[9]] Neel, Brian A, Matthew J Brady, and Robert M Sargis. “The endocrine disrupting chemical tolylfluanid alters adipocyte metabolism via glucocorticoid receptor activation.” Molecular endocrinology 27.3 (2013): 394-406.

[10] Maury, Eleonore, Kathryn Moynihan Ramsey, and Joseph Bass.

“Circadian rhythms and metabolic syndrome from experimental genetics to human disease.” Circulation research 106.3 (2010): 447-462.

[11] “IDF Diabetes Atlas Seventh Edition | International Diabetes Federation.” 2015. 5 May. 2016 <http://www.idf.org/ idf-diabetes-atlas-seventh-edition>

About the Author Wakanene Kamau is a 4th year in the College majoring in Biological Chemistry. This project was conducted in the lab of Prof. Robert Sargis.

References [1]

Naujokas, Marisa F et al. “The broad scope of health effects from chronic arsenic exposure: update on a worldwide public health problem.” Environmental Health Perspectives (Online) 121.3 (2013): 295.

[2] Nielsen, M.G., Lombard, P.J., and Schalk, L.F., 2010, Assessment of arsenic concentrations in domestic well water, by town, in Maine, 2005–09: U.S. Geological Survey Scientific Investigations Report 2010–5199, 68 p. (Also available at http://pubs.usgs.gov/ sir/2010/5199.)

[3] Kirkley, Andrew G, and Robert M Sargis. “Environmental endocrine disruption of energy metabolism and cardiovascular risk.” Current diabetes reports 14.6 (2014): 1-15.

[4] Ratnaike, Ranjit Nihal. “Acute and chronic arsenic toxicity.” Postgraduate medical journal 79.933 (2003): 391-396.

[5] Taylor, Kyla W et al. “Evaluation of the association between persistent organic pollutants (POPs) and diabetes in epidemiological studies: a national toxicology program workshop review.” Environmental Health

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Spring 2016

Exploring the Plausibility of Group Selection with Respect to Cancer Phenomena Adil Menon Group selection is a proposed mechanism of evolution in which natural selection operates at the level of the group, instead of the individual level as posited by most traditional theories. The majority of evolutionary biologists reject the plausibility of group selection. This rejection on the macroscopic scale has been expanded to encompass unicellular organisms as well. In light of recent studies, however, reexploring the plausibility of higher level selection on the microscopic scale is warranted. Based on the similarity of cancer cells and unicellular organisms, this paper seeks to evaluate the plausibility of group selection as an explanatory mechanism for a number of oncological phenomena.

Group Selection on the Macroscale The theory of group selection states that selective forces can act on competing groups of individuals, not just competing individuals (Thompson, 2000.

Critical to this theory is the emergence of behaviors which contribute to the persistence of a group over time despite there being a fitness cost to the individual manifesting them. Historically, many biologists, including Darwin himself, recognized this as a central conundrum within the theory of natural selection. Individuals who do not suffer the negative fitness effects of altruism should eventually outcompete an individual who decides to “act for the good of the group” (Price 2016). Altruistic traits should therefore never fix in a population; if they do, this population would be easily overtaken by invaders with selfish traits. Despite this intuitive logic the evolution of many unusual, less-than-selfish

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behaviors in nature such as kin selection is undeniable. While the evolutionary origins of these phenomena have not been fully elucidated after several decades of debate, the evolutionary biology community rejected the concept of group selection as a solution to this enigma in the 1960’s.

Steven Pinker outlines a number of the strongest indictments of the group selection theory. He first asserts that natural selection could legitimately apply to groups only under certain conditions.

The groups must reproduce asexually by budding or fission. In addition descendant groups must faithfully reproduce traits of the parent group, except for mutations, and must compete with one another in a meta-population (Pinker 2015). Pinker asserts this is not what happens in macroscopic “group selection.” The traits most often examined to defend “group selection” on the macroscale do not arise from some gene whose effects propagate

Scientia upward to affect the group as a whole, such as an ability of individuals to withstand stressful environments. Instead, they are often taught or in the case of human are cultural. In addition, while the reproductive success of organisms undoubtedly depends in part on the fate of their groups, if an individual has innate traits that encourage them to contribute to the group’s welfare and as a result contribute to its own welfare, group selection is unnecessary. Individual selection in the context of group living is adequate (Pinker 2015). Group selection only truly occurs when individuals display traits that are disadvantageous to themselves while benefiting their group. This brings us back to the central problem, which led most evolutionary biologists to reject the idea of group selection.

“Except in the theoretically possible but empirically unlikely circumstance in which groups bud off new groups faster than their members have babies, any genetic tendency to risk life and limb that results in a net decrease in individual inclusive fitness will be relentlessly selected against” (Pinker 2015). A new mutation with this effect would not come to predominate in the population, and even if it did, it would be driven out by any immigrant or mutant that did not subordinate its interests to those of the group.

Group Selection on the Cellular Scale While most evolutionary biologists have come to reject group selection on the macroscale, there exists a class of organisms that meet Pinker’s criteria of genetically faithful asexual selection; bacteria and other unicellular organisms. A German research team consisting of Anna Melbinger, Jonas Cremer, and Erwin Frey has demonstrated that under the appropriate conditions the presence of even a single cooperator in a free-riding population can lead to collaboration in bacterial colonies.

The researchers also verified that cooperative regimes arise over a broad set of parameters even when the worst-case scenarios for collaboration were utilized in the model (Melbinger 2015). The probability for colonies with cooperative mutants to succeed is only minimally dependent on the size of the initial cell population and cellular growth rate (Melbinger 2015). Given their success even under conditions adverse to cooperation, inter-bacterial collaboration can be theorized to be applicable

not just in the laboratory, but also in more realistic evolutionary scenarios where reassortment is not completely random and public goods are not equally distributed between all individuals (Julou 2013).

The literature also examined the group “fitness” impact of collaborators. Comparing p (the benefit of the public good) and c (the metabolic costs owing to the production of a public good) it was found that even for comparably small values of p the positive impact of a public good on the population size notably supports cooperation and thereby increases the survival probability (Melbinger 2015). While increasing cost of producing public goods negatively impacts survival chances to a degree, the benefits of cooperation are strong enough to compensate for selection disadvantages of up to 20% (Melbinger 2015). Once cooperation is established in a population, more advanced mechanisms which rely on cooperators already present in population, like kin discrimination in which close genetic relatives are selectively favored or other active forms of positive assortment, may evolve to further stabilize cooperative behavior (Hamilton 1964).

The theoretical results presented above are mirrored in the increased virulence of microbial populations with cooperative members that produce metabolically costly public goods (Kreft 2005).

One such organism is Pseudomonas aeruginosa.

When iron is lacking in the environment individual Pseudomonas bacteria produce iron-scavenging molecules called siderophores at a fitness cost to themselves (Diggle 2007). When they are released into the environment, these molecules can efficiently bind a single iron molecule, and the resulting complex can then be taken up by surrounding bacteria. Strains with cooperative Pseudomonas mutants regularly outperform wild type colonies killing infected model organisms 15% faster (Meyer 1996). This appears, at least on its surface, to represent a textbook case of group selection.

Furthermore, programmed cell death in unicellular organisms provides further evidence for the possibility of higher level selection. For a long time unicellular lineages were considered “immortal,” in the sense that they are only subject to accidental and predator-related death. Recent research has elucidated programmed cell death modes in both prokaryotic and eukaryotic unicellular lineages (Franklin et al. 2006). The presence of a trait with such a negative impact on the fitness of those

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Spring 2016 cells manifesting it is inconsistent with traditional individual level selection. Programmed cell death in unicellular lineages is broadly understood as an adaptation that benefits others (kin, population or even species) and that evolved and is maintained by either kin or group selection (Franklin et al. 2006).

The concept that unicellular programmed cell death is an altruistic adaptation has given rise to many speculations on the nature of the benefits and the evolutionary role of this trait. Most explanations for active death in unicellular lineages invoke direct or indirect benefits to kin, group, population, or species. Among the most frequently proposed advantages is the sparing of nutrients, and the release of nutrients from dying cells. In the absence of a specific mechanism directing these benefits to related individuals, these resources are made available both to close relatives and to non-kin, especially in unstructured populations (Bidle and Falkowski 2004). This is has not been addressed either theoretically or experimentally, however.

Despite the fact that research must still be done on how these seemingly altruistic mechanisms develop they nonetheless point to the possibility of higher level selection on the microscopic scale.

Possibility of Group Selection in Cancer Cancer is often portrayed as an example of radical autonomy, in which cells break free from the communal pressures of the body as a whole. At their most fundamental level, however, tumors are little more than amalgams of closely related cells.

Taking this view along with the increasing body of evidence for higher level selective pressures in unicellular organisms, it is possible to theorize that group selection plays a role in a number of enigmatic phenomena associated with tumor progression.

One common tumorigenic mechanism theorized to be associated with group selection is angiogenesis, the formation of new blood vessels by the tumor.

This process relies heavily on cooperation between various cell types. Mysteriously despite this reliance on collaboration many cells do not benefit from the newly formed vasculature. Multiple tumor cells release a broad range of proangiogenic factors as a means of altering the microenvironment, prompting changes in multiple cell types. Perivascular cells detach from the mature blood vessels, compromising their integrity, permitting their remodeling and

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promoting an activated phenotype. Platelets are recruited to sites of exposed basement membrane, where they become activated and release their stores of stimulatory factors into the tumor microenvironment. At the same time endothelial progenitor cells (EPCs) and myeloid cells from the bone marrow move to the perceived wound, where they release even more soluble factors locally (Chatterjee 2012). A central mystery of angiogenesis is why this wide range of cells sacrifice resources to promote vasculogenesis when so few derive any direct benefits. The tumor microenvironment is characterized by pockets of hypoxia, extremely low oxygen levels, amid the leaky and tortuous blood vessels leaving many cells in these hypoxic regions impaired (Weis 2011). Little evidence exists on how these hypoxic cancer cells are capable of securing sufficient levels of Adenosine Triphosphate (ATP) to maintain growth and proliferation. One possible explanation is intercellular collaboration. High ATPproducing normoxic cancer cells, the beneficiaries of angiogenesis, may release ATP while low ATPproducing cancer cells take up the released ATP from the intratumoral space to supplement their intracellular pool. As a result, the intracellular ATP concentrations of hypoxic cancer cells are elevated to such levels that they are capable of performing all the biological functions required for survival, growth, proliferation, and even the cell movement required for invasion and metastasis (Liberti 2015). This mitigation of the costs of angiogenesis could explain why tumor cells continue to recruit vasculature they themselves do not derive benefit from.

Another oncological phenomenon that may be associated with group selection is the Warburg effect. The Warburg effect refers to a metabolic process in which cancer cells rely on aerobic glycolysis, rather than the far more efficient oxidative phosphorylation. Aerobic glycolysis is an inefficient way to generate ATP. The advantage this reduced metabolic capacity confers to cancer cells continues to be unclear (Heiden 2009). However, evidence exists for the argument that the Warburg effect serves as a defense mechanism against reactive oxygen species (ROS). ROS act as a doubleedged sword with respect to cancer cells. They play a key role in facilitating tumor angiogenesis and, ligand-independent activation of receptor tyrosine kinase. They also promote invasion and metastasis

Scientia of cancer cells (Liberti 2016). At the same time, however, ROS are also a major contributor to oxidative damage. Thus, the cellular level of ROS must be vigorously maintained within certain ranges so that they will promote cancer cell growth and proliferation without causing severe oxidative damage and cell death. The Warburg effect, which leads to the production of NADPH- a vital molecule for energy production- and restores proper redox status, is perhaps an important survival mechanism for cancer cells (Liberti 2016). Perhaps individual cell’s metabolic potential is subordinated for the good of the tumor.

The Warburg Effect may also present a group level advantage for cell growth by modifying the tumor microenvironment. Elevated glucose metabolism decreases the pH in the microenvironment due to lactate secretion. The benefits of an acidic environment to cancer cells are well established. The acid-mediated invasion hypothesis suggests that H+ ions secreted from cancer cells diffuse into the surrounding environment and allow for enhanced invasiveness.

Tumor-derived lactate is also a contributor to tissue-associated macrophage (TAM) polarization facilitating extravasation. The high rate of glycolysis restricts the availability of glucose to tumor infiltrating lymphocytes as well. These immune cells require sufficient glucose to perform their functions. Restricting the supply of glucose therefore protects the community of tumor cells from immune system attack. The Warburg Effect provides an overall benefit that supports a tumor microenvironment conducive to cancer cell proliferation (Liberti 2016).

Moving beyond specific mechanisms to take a more general view of the phenomena necessary for successful carcinogenesis, the advantages of higher level cooperation between tumor cells becomes increasingly apparent. Cooperation may even account, in part, for the frequency of cancer.

The hypothesis of cooperation among tumor cells predicts that a tumor with a full deck of mutations will evolve from a normal cell much faster with the possibility of intercellular collaboration. This is because cooperation makes it possible that the population of cells can be malignant (i.e., can have a full deck of cancer hallmarks), at least transiently during the life of the tumor, even if none of its individual cells are malignant (Axelrod 2006). In that

period of time, the whole population of cooperating cells can accomplish more than any of its subclones can accomplish on its own. This means that cells that are missing a sharable resource necessary for oncogenesis are capable of proliferating rapidly, rather than proliferating little or dying. Malignancy in this theory exists as an emergent property of the population of partially transformed cells together with normal cells, and the microenvironment (Axelrod 2006).

If the sharable resources are non-excludable and non-rivalrous, higher level selection is all the more plausible. A resource is said to be non-excludable if one cell cannot prevent another from using the resource. The term non-rivalrous means that when one cell uses a resource, it does not limit the amount available to others. The most straightforward example of this phenomenon is the production and sharing of two different growth factors (GFs).

In this scenario, the production of a GF A by cell A stimulates itself in an autocrine manner while also assisting the growth of other cells nearby that have the receptor for GF A but are not producing it. Cell A therefore produces GF A at no additional cost to itself, and helps the other cells in its immediate neighborhood. Cooperation through by-product mutualism is easy to establish and to maintain. In fact, where by-product mutualism is possible, both cells continue without regard to what the other is doing.

Unlike cases of cooperation based on reciprocity where each produces a factor required by the other, a “player” engaged in by-product mutualism does not have to make its behavior contingent on the behavior of the another cell line. Additionally it does not suffer from the “free-rider” problem in which only one individual benefits at the cost to another, because what helps others is a costless by-product of what helps oneself. Therefore, by-product mutualism is the easiest form of cooperation to be sustained (Axelrod 2006).

Tumor cell collaboration with respect to resources and capabilities also helps provide an explanation of several observations that have been made about solid tumors including the non-uniform abundance of proteins observed in different regions of tumor tissue: the heterogeneity of genotypes and phenotypes and heterogeneity of response to cytotoxic drugs: the inefficiency of metastasis: inefficiencies of cell culture, as demonstrated by the difficulty of establishing cell lines from tumors:

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Spring 2016 the necessity to pass some tumor-derived cell lines at high concentrations (requirement for continued cooperation in vitro), and the relative low plating efficiency of single cells derived from such lines (accomplishable only by cells with a full deck of hallmarks, or the cancer “stem cell”) (Axelrod 2006).

Discussion After a review of the literature the presence of higher level selection in tumors seems viable.

Research findings indicating the positive impact and relative ease with which intercellular collaboration emerges in unicellular organisms provides ample evidence to warrant re-exploring the mechanism on the microscopic scale. Additionally unicellular organisms meet Pinker’s criteria and closely approximate tumor cells in their reproductive strategies and environmental pressures (space, nutrients, etc.). Cooperation based views of tumor cell interaction offers potential explains for a number of cancer related enigmas including the purpose of the Warburg effect, the recruitment of tumor vasculature by cells that do not directly benefit and a number of other oncological phenomena as well.

Despite the strong evidence for higher level selection presented my ultimate assessment after analyzing the literature is that it cannot be conclusively argued that it is group selection at work rather than inclusive fitness or kin selection.

While the concepts may seem similar the latter fits more neatly into traditional natural selection paradigms as one is protecting genetic relatives.

Elucidating this distinction is especially complicated with respect to cancer as both the host tissue and that of the tumor are extremely genetically similar.

Consequently in cancers the boundaries between group selection and kin selection are incredibly difficult to demarcate. Additionally in reconsidering our evidence from studies in unicellular organisms, the results are readily applicable to both theories.

Returning to the Pseudomonas aeruginosa for example it should be noted that despite the readily accessible nature of the iron molecules these bacteria recruit, the ultimate beneficiaries are other Pseudomonas aeruginosa. Similarly with altruistic programmed cell death, advocates of kin selection make it very clear that close kin are beneficiaries of the action even if more distant bacteria are granted increased access to resources.

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Perhaps the best evidence for favoring kin selection over group selection as an explanatory model with respect to cancer comes from an analysis of biofilms composed of different bacterial subpopulations. One of the strongest arguments used to argue that biofilms represent group selection on the unicellular scale are cooperative interactions between cell types. Close analysis reveals however that these interactions between cells in biofilms are primarily neighbor-structured, rather than occurring within well-defined and non-overlapping groups of cells (Okasha 2006; Godfrey-Smith 2006, 2012). In other words, the cells in a biofilm may each have unique interaction networks so that there can be no non-arbitrary division of the population into groups.

Without group structure there can be no group selection. Given that much of the basis of our theory of group selection in cancer is based on its similarity to amalgamations of unicellular organisms it is likely that kin selective rather than group selective methodologies better explains cooperation in cancer just as it does for bacteria.

Conclusion This review explores the hypothesis that oncological phenomena may be explained by the concept of group selection. While our exploration of the literature revealed that ample evidence for higher level selection exists both in unicellular organisms and in cancer cells ultimately this proved insufficient to conclusively determine group selection as a driver of tumor cell evolution. Alternative mechanisms such as inclusive fitness or kin selection remain equally viable options for explaining the findings presented in this analysis of the literature. Despite this fact I feel as though my efforts with regard to this exploration were nonetheless novel and contributed if only modestly to our understanding of oncological phenomena.

References [1]

Axelrod, R., Axelrod, D. E., & Pienta, K. J. (2006). Evolution of cooperation among tumor cells. Proceedings of the National Academy of Sciences, 103(36), 13474-13479.

[2]

Bidle K, Falkowski P (2004) Cell death in planktonic, photosynthetic microorganisms. Nat Rev Microbiol 2: 643–655 doi:10.1038/ nrmicro956.

[3]

Brockhurst, M. A. (2007). Population Bottlenecks Promote Cooperation in Bacterial Biofilms. PLoS ONE, 2(7).

[4]

Chatterjee, M. (2012). Angiogenesis and Gastric Cancer: Molecular Pathways & Therapeutic Targets. Angiogenesis &amp; Therapeutic

Scientia Targets In Cancer, 135-146.

[5]

Clarke, E. (2016). Levels of selection in biofilms: Multispecies biofilms are not evolutionary individuals. Biology &amp; Philosophy Biol Philos, 31(2), 191-212.

[6]

Diggle, S. P., Griffin, A. S., Campbell, G. S., & West, S. A. (2007).

Cooperation and conflict in quorum-sensing bacterial populations.

Nature, 450(7168), 411-414.

[7]

Franklin, D. J., Brussaard, C. P., & Berges, J. A. (2006). What is the role and nature of programmed cell death in phytoplankton ecology?

European Journal of Phycology, 41(1), 1-14.

[8]

Godfrey-Smith P (2006) Local interaction, multilevel selection, and evolutionary transitions. Biol Theory 1(4):372–380

[9] Godfrey-Smith P (2012) Varieties of population structure and the levels of selection. Br J Philos Sci 59(1):25–50.

[10] Hamilton, W. (1964). The genetic evolution of social behaviour. I. Journal of Theoretical Biology, 7(1), 1-16.

[11] Hazan, R., Sat, B., & Engelberg-Kulka, H. (2004). Escherichia coli mazEF-Mediated Cell Death Is Triggered by Various Stressful Conditions. Journal of Bacteriology, 186(11), 3663-3669.

About the Author Adil Menon graduated from the University of Chicago in June 2016. His major was the History, Philosophy, and Social Science of Science and Medicine (HIPS) with a concentration in medical history and bioethics.

Adil’s earlier academic credentials include authorship of Joseph Goldberger: Epidemiology’s Unsung Hero and Is there a United Hippocratic School? in the medical humanities journal Hektoen International, acknowledgements in the journal Future Oncology and an American Heart Association award for undergraduate research. He will be attending Harvard University to earn a Master’s in Bioethics starting this fall.

[12] Heiden, M. G., Cantley, L. C., & Thompson, C. B. (2009). Understanding the Warburg Effect: The Metabolic Requirements of Cell Proliferation.

Science, 324(5930), 1029-1033.

[13] Julou, T., Mora, T., Guillon, L., Croquette, V., Schalk, I. J., Bensimon, D., & Desprat, N. (2013). Cell-cell contacts confine public goods diffusion inside Pseudomonas aeruginosa clonal microcolonies. Proceedings of the National Academy of Sciences, 110(31), 12577-12582.

[14] Kreft, J. (2005). The evolution of groups of cooperating bacteria and the growth rate versus yield trade-off. Microbiology, 151(3), 637-641.

[15] Liberti, M. V., & Locasale, J. W. (2016). The Warburg Effect: How Does it Benefit Cancer Cells? Trends in Biochemical Sciences, 41(3), 211-218.

[16] Melbinger, A., Cremer, J., & Frey, E. (2015). The emergence of cooperation from a single mutant during microbial life cycles. Journal of The Royal Society Interface, 12(108), 20150171-20150171.

[17] Nedelcu, A. M., Driscoll, W. W., Durand, P. M., Herron, M. D., & Rashidi, A. (2010). On The Paradigm of Altruistic Suicide In The Unicellular World. Evolution, 65(1), 3-20.

[18] Okasha, S. (2006). Evolution and the Levels of Selection.

[19] Pinker, S. (2015). The False Allure of Group Selection. The Handbook of Evolutionary Psychology, 1-14.

[20] Price, M. (n.d.). SCQ. Retrieved March 2, 2016, from http://www.scq. ubc.ca/the-controversy-of-group-selection-theory/ [21] Thompson, N. (2000). SHIFTING THE NATURAL SELECTION METAPHOR TO THE GROUP LEVEL. Behavior and Philosophy, 28, 83-101.

[22] Weis, S. M., & Cheresh, D. A. (2011). Tumor angiogenesis: Molecular pathways and therapeutic targets. Nature Medicine Nat Med, 17(11), 1359-1370.

[23] Wilson, E. O. (1973). Group Selection and Its Significance for Ecology.

BioScience, 23(11), 631-638.

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Spring 2016

Scanning Electron Microscopy of Phosphorus Phases in Marine Sediments Leonard Shaw Department of Geophysical Sciences, University of Chicago Conclusions made on the chemical nature of phosphorus in marine sediments produced with sequential extraction (SEDEX) are hindered by the necessity of inaccurately determining chemical associations of phosphorus by the methods used. Scanning election microscopy and energy dispersive X-ray spectroscopy (SEM/EDS) provide mineralogical and biogeochemical context to SEDEX results beyond the operational definitions of extraction procedures. SEDEX-produced results on sediments in the Cariaco Basin have shown how retention of phosphorus in marine sediments has changed from the oxidized or “oxic” conditions of the last glacial period to present non-oxidized or “anoxic” conditions. SEM/EDS analysis provides evidence towards the possible biogeochemical processes behind this shift in phosphorus retention and opens the possibility for other solid spectroscopic techniques in quantifying phosphorus chemical phases.

Because phosphorus is an important nutrient for all organisms, further understanding of the chemistry of marine phosphorus is crucial to understanding the processes that affect the survival and growth of marine ecosystems.

Introduction Phosphorus is a crucial nutrient for marine life, serving as a building block for photosynthesis. In certain regions of the ocean, phosphorus can be the limiting nutrient for biological productivity and thus directly impact the growth of marine ecosystems (Benitez-Nelson 2000, Bridger and Henderson 1983, Redfield 1958).

The removal of phosphorus from the ocean plays a major role in the bioavailability of phosphorus to marine ecosystems. Oceanic phosphorus primarily exists as either sinking particulate phosphorus and biologically available dissolved phosphorus.

Phosphorus bearing particles that sink to the deep

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ocean can be incorporated into marine sediments on the ocean floor. Although most phosphorus is released from sediments back into pore waters, some phosphorus is trapped in sediments for hundreds of years and effectively removed or “sequestered” from the marine phosphorus cycle.

The retention of phosphorus in marine sediments is dependent on the specific chemical compound or “phase” phosphorus exists in (Paytan 2007). Oceanic phosphorus can exist in or be associated with many different kinds of phases that can be either reactive or nonreactive. These phases can range from organic molecules such as polyphosphate and phosphonates to inorganic minerals such as those that include phosphate in their chemical formulas

Scientia such as apatite and minerals that can carry trace amounts of phosphorus that attach or adsorb onto their surfaces such as iron oxides and calcium carbonates. Reactive phases such as dissolved orthophosphate and polyphosphates are easily remineralized back into the water column and can carry phosphorus out of sediments. Chemically stable phases such as iron (oxy)hydroxides and carbonate fluorapatites promote the burial of phosphorus in sediments and can act as phosphorus sinks.

Studying the partitioning of phosphorus phases in marine sediments is crucial to understanding the biogeochemical processes involved in the oceanic phosphorus cycle.

Background Chemical extractions are techniques in which most or all of the chemical contents of a sediment sample are quantified by the complete or partial dissolution of sediments and analysis on solution extracts. Sequential extraction (SEDEX, Ruttenberg et al. 1992) is used to measure the partitioning of phosphorus phases in marine sediments. Sediments are dissolved with a sequential series of reagents to expose increasingly chemically stable or “refractory” phosphorus phases. Phosphorus in extracted sediment is separated among different reagent fractions, each representing a group of chemically similar phosphorus phases. For example, phosphorus released in an extracted solution produced by dissolving sediment in acetic acid is defined as a reagent fraction that characterizes phosphorus phases that are dissolvable in acetic acid. However, problems arise because phosphorus phases must be “operationally defined” by the specific reagent used to dissolve them (Nirel and Morel 1990). For example, phosphorus in the extraction solution where sediments are dissolved in acetic acid is defined as the reagent fraction that quantifies phosphorus carried by phases that are soluble in acetic acid such as calcium carbonates and calcium fluorapatite. However, just because the reagent fraction utilizes a reagent that dissolves a certain set of phases does not mean that all of the phosphorus in the respective extraction solution necessarily comes from those phases. It could be possible that some calcium carbonate and calcium fluorapatite, and the phosphorus associated with them, is dissolved in an earlier fraction. It is also

possible that the acetic acid fraction does not dissolve all of the calcium carbonate and calcium fluorapatite and that the remaining is dissolved in a later fraction where phosphorus is not defined to be associated with either calcium carbonate or calcium fluorapatite. Several additional problems arise due to the need for operational definitions. It can be impossible to distinguish between certain phases within a single reagent fraction. For example, a reagent fraction defined to quantify phosphorus released when sediments are dissolved with a strong base will include many different chemical compounds that are soluble in base solution such as organic molecules, biogenic silicate that originate from organic sources, and inorganic aluminosilicates.

As such, it cannot be determined whether most of the phosphorus from this fraction is carried by organic or inorganic phases. In addition, amounts of reagents used and times for reagent dissolution during chemical extraction are generally defined for specific sediment particles sizes as well as sediments from oceanic regimes where certain phases that may be analytically important to quantify elsewhere are not present. Further analytical context is required to figure out which specific phases are most responsible for phosphorus measured in the extracted solution for a reagent fraction.

Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS) offers an opportunity to provide the analytical context necessary to interpret SEDEX results. SEM/EDS can be used to image solid sediments and analyze chemical compositions of specific phases without using extraction techniques. SEM images show how phases are arranged within sediments. EDS identifies the specific phases by measuring chemical compositions of targeted regions. Although results from EDS are less comprehensive than those from SEDEX as only individually selected sediments can be analyzed, phase associations measured

by EDS analysis are not limited by the operational definitions of chemical extraction. Without using a supplementary technique independent of operational definitions, accurate scientific conclusions can be difficult to obtain from certain applications of SEDEX. The focus of this study is to provide mineralogical context to SEDEX results on the phosphorus phase partitioning of marine sediments in the Cariaco Basin. SEDEX results were produced in Whitehill

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Spring 2016 et al. 2008. Over the transition from the last glacial period to the current interglacial, Cariaco Basin sediments have shifted from oxic conditions to anoxic conditions. Oxic sediments promote the retention of phosphorus whereas anoxic sediments facilitate the release of phosphorus into pore waters and eventually the water column (Krom and Berner 1980, Sundby et al. 1992). SEDEX was used to study how the concentrations of various phosphorus phases differed between oxic and anoxic sediments. However, individual SEDEX fractions can include both reactive and chemically stable phases. In addition, phases unique to either anoxic or oxic conditions might not be represented by the operational definitions of SEDEX. This study investigates SEM/EDS analysis as a possible solution to these issues as well as the overall effectiveness of spectrometric techniques that are not limited by operational definitions.

Methods Sample Background Sediments were collected in February 1996 from the ODP Leg 165 Site 1002 in the Cariaco Basin, an anoxic pull-apart basin located off the northeast coast of Venezuela (Whitehill et al. 2008). Sediments come from two eight meter deep sediment cores, 1002 A and 1002 B. Sediments were maintained in frozen storage and were lyophilized and ground in preparation for analyses. A 125 µm fraction was filtered out for SEDEX extraction. Sediments extracted with SEDEX ranged from 0 to 800 cm in depth. Four 125 µm sediment samples were analyzed with SEM/EDS in this study. 2B-95 Frozen and 2B-95 Dried were collected at 245 cm depth from sediment core 1002 B. 5A-10 Frozen and 5A-85 Frozen were collected at 710 cm and 785 cm depth, respectively, from sediment core 1002A. The shift from oxic to anoxic conditions occurred at around 725 cm depth. Therefore, 2B-95 Frozen, 2B-95 Dried, and 5A-10 Frozen consist of anoxic sediments whereas 5A-85 Frozen consists of oxic sediments.

SEDEX was performed on both of these sediments in order to determine whether phosphorus uptake in sediments was different under anoxic and oxic sediments (Whitehill et al. 2008). The conclusions of those results argued that oxic sediments promoted phosphorus uptake and anoxic sediments did not. As such, less marine phosphorus would be sequestered

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Figure 1: Location of Coring Site (Lyons et al. 2003)

from the oceanic phosphoric cycle during anoxic sediment conditions.

SEM Preparation Epoxy mounts are used for holding sediments in place under the pressure of vacuum in the SEM imaging chamber. Each sediment sample was loaded onto an individual epoxy mount. Four labelled black Teflon ring holders were attached to a metal plate with double sided tape. A thin layer of sediments was applied to the double sided tape in each ring holder.

The epoxy formula used was watery under room temperature for easy application and hardened only under extensive heat. Epoxy was prepared by mixing 5.4 mL Araldite 502 resin, 4.6 mL DDSA hardener, and 5 drops of DMP-30 accelerator. Enough epoxy was added to the ring holders to cover all of the sediments. Epoxy mounts were heated at 351 K for three hours on a hot plate until the epoxy hardened.

Epoxy mounts were removed from the metal plate with a razorblade. Respective labels were added to the undersides of the epoxy mounts.

SEM analysis can only be performed on exposed and flat sediments because the electron beam produced by the SEM must come into contact with the sample sediment surface and can produce different values when hitting a surface at an angle.

The epoxy mount with sediment grains within had to be sanded to expose the sediment grains and polished to flatten out the scratched sanded surface.

A 120 grit silicon carbine grinding paper was used to remove the remaining tape on the mounts and expose sediment grains. An optical microscope was used to check when certain grains were exposed.

2B-95 Dried and 2B-95 Frozen were polished with 320 and 600 grit grinding papers. 2B-95 Frozen and 5A-85 Frozen were polished with 12, 9, 6, and 3 µm diamond lapping films as they possessed the most

Scientia exposed grains. These three samples were further polished with 9, 6, and 1 Âľm stone polishing laps.

5A-10 Frozen showed no exposed grains under the optical microscope and was not polished. Polishing with grinding paper and diamond lapping films was performed under running reverse osmosis (RO) water.

Stone polishing was performed with an oil lubricant. Samples were cleaned with isopropanol before and after stone polishing to prevent contamination of stone laps. All samples were gold coated for SEM/EDS analysis. Gold is an incredibly reflective material and allows for the reflection of electrons from the electron beam. Reflected electrons are then sent into a detector in the SEM where they are converted to photons and used to produce images.

SEM Imaging Analyses were conducted with a LYRA 3 Tescan Scanning Electron Microscope and an Oxford Instruments EDS detector. Wide view and resolution images were taken to track locations of targeted sediments in the epoxy mounts. Targeted sediments were imaged and analyzed at a 15 keV acceleration voltage to reduce charging effects.

Charging effects occur when too many electrons bombard the sample and begin to develop static electricity on the sample. A backscattered electron detector (BSE) was used to produce maps in which brightness contrast could be used as a measure for the atomic weights of different elements.

Backscattered electrons are electrons that slightly penetrate the sample surface and are reflected off of atoms within the sample. The atoms of heavier elements, those with greater atomic weight, attract and reflect more electrons than those of lighter elements, those with less atomic weight. Since electrons are converted to photons in the detection process, areas of the sediment grain surface with heavier elements will shine brighter than those with lighter elements. EDS analysis was conducted using AZtec microanalysis software. The software produced chemical spectra of targeted regions, chemical mappings, and corrected for gold coatings on samples. Chemical spectra are calculated graphs where the abundances of different elements at a particular point are compared. Although these abundances do not translate perfectly to molecular ratios, the presence or absence of certain elements

can be used to qualitatively identify phases. The chemical mappings are images where different elements are highlighted with artificial color so the spatial organization of different chemical phases can be determined, such as whether a phase serves as background material for other particles or whether it exists primarily as a distinct isolated particle.

The gold coating needs to be corrected because the artificial abundance of gold can obscure the abundances of elements of interest.

Results In order to confirm the results of SEDEX analyses on the Cariaco Basin sediments, differences between oxic and anoxic phases were primarily investigated.

Figure 2: Layered Map of Particle in 2B-85 Frozen. Calcium carbonates and iron sulfides are distributed within a silicate background. The matrix of spheres underneath the particle was identified as part of the doublesided tape that remained on the epoxy mount.

As the conclusions for the SEDEX results argued that ancient oxic sediments favored phosphorus uptake and modern anoxic sediments did not, oxic sediments were analyzed for evidence of phosphate minerals such as apatite.

Calcium carbonates, opal, aluminosilicates, and iron sulfides were the most abundant phases in imaged particles (Figure 2). Calcium carbonates were bright in BSE images and had smooth textures.

They were often organized in defined structures such as perfect circles, suggesting shell burial in sediments (Figure 3). Opals and aluminosilicates

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Spring 2016

Figure 3: Smooth Calcium Carbonate Particle (Left) and Calcium Carbonate Shell (Right) from 5A-10 Frozen

Figure 5: Silicate Particle in 5A-10 Frozen. Site 75 is an iron sulfide and all the other sites are silicate phases. Site 73, an opal, is more defined than sites 76 and 77, aluminosilicates. Site 71, a feldspar, is brighter than all of the other silicates.

Figure 4: Example of Calcium Carbonate Spectrum. This spectrum corresponds to a point on one of the shells in Figure 2

often composed the darker regions of sediment images and served as background material for other phases (Figures 5 and 6). Aluminosilicates were the more abundant silicate phase. Although both phases were often indistinguishable from one other in BSE images, opals were generally characterized as spatially defined particles instead of amorphous background material. Certain aluminosilicates such as feldspar were distinguished in BSE images, e.g. potassium in feldspar is a heavier element than silicon and oxygen and thus feldspars show up as brighter than other silicates. Iron sulfides were the only identified iron phase and were often the brightest phases in BSE images (Figure 7). They are characterized as circular clusters of small spherical crystals. Iron sulfides were found in all samples, including the oxic sediments in 5A-85 Frozen.

Calcium oxide, apatite, and heavy metal phases were relatively rare phases that showed up in

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Figure 6: The Spectra of Sites 71, 73, 75, and 76. As shown in spectrum 73, Opal is silicon dioxide and lacks major elements besides silica and oxygen. Spectra 71 and 76 can be interpreted as different phases since spectrum 71 possesses a much larger potassium peak, identifying it as a feldspar. Spectrum 75 is clearly an iron sulfide as only sulfur and iron are major elements.

analyzed sediment particles. These phases were discovered by mapping entire particles and noticing specific regions where either concentrations of common elements did not align in expected ways or high concentrations of rare elements appeared.

Calcium oxide was found the anoxic sediments of 5A10 Frozen when a calcium map did not correspond

Scientia

Figure 9: Layered Map of Particle in 5A-10 Frozen. Two bright green spots in the layered map indicate titanium phases (Left). Spectrum 83 identifies the titanium phase as titanium dioxide.

Figure 7: A group of iron sulfides (Left) and a close-up image of an iron sulfide cluster (Right). All iron sulfide spectra closely resembled spectrum 75 in Figure 6.

Figure 10: BS E Image and Phosphorus Map of Particle in 5A-85 Frozen.

The two bright yellow spots in the phosphorus map indicate apatites.

of 5A-85 Frozen. One of the apatites discovered was shown to have relatively high concentrations of rare earth elements, namely cesium, lanthanum, and neodymium (Figure 11). Multiple spectra and

Figure 8: Carbon, Calcium, and Oxygen Maps of Particle in 5A-10 Frozen.

The carbon mapping shows low concentrations of carbon throughout the particle, especially in comparison to the epoxy surrounding the particle (Left). Oxygen is generally evenly distributed throughout the particle, mostly due to the silicate background of the particle (Right). Specific calcium phases can be seen within the particle (Middle). Since the calcium phases do not correspond with high carbon concentrations nor low oxygen concentrations, the calcium phases are most likely calcium oxides.

with a carbon map, suggesting that there was a calcium phase that was not calcium carbonate(Figure 8). Titanium dioxide and apatite were found in particles where elemental maps pinpointed the locations of the respective phases (Figures 9 and 10). The apatites were found in the oxic sediments

Figure 11: BSE Image and Spectrum of Apatite in Particle in 5A-85 Frozen. The apatite pictured here corresponds to the upper of the two bright yellow spots in the phosphorus map in Figure 9. Spectrum 159 describes elements near the center of the apatite; cesium, lanthanum, and neodymium show clear peaks without interference from other elemental X-rays. Spectra 157 to 164 all showed similar concentrations of rare earth elements. Melding of particle with background and the presence of silicon and aluminum in the spectrum suggest that the apatite is slightly covered by an aluminosilicate phase.

the recalculations of each spectrum returned nearly identical abundances and proportions of these three rare earth elements, confirming their existence in the apatite.

Discussion Contextual Information for Cariaco Basin Sediments

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Spring 2016 Observations with the SEM and EDS agree with conclusions derived from SEDEX on the biogeochemistry of marine sediments in the Cariaco Basin. The abundance of iron sulfides in anoxic sediments supports the idea that anoxic sediments promote the release of phosphorus into pore waters and thus prevent phosphorus sequestration. Iron oxides are one of the primary carriers of phosphorus into sediments and facilitate the authigenic formation of carbon fluorapatite, an ultimate sink for phosphorus (Ruttenberg 1993). Under anoxic conditions, iron oxides are transformed into iron sulfides, releasing phosphate back into the water column (Rozan et al. 2002). In this manner, anoxic sediments prevent the retention of phosphorus.

The presence of some iron sulfide particles observed in the oxic sediments of sample 5A85 Frozen and the presence of calcium oxide and other oxidized minerals in the anoxic sediments of sample 5A-10 Frozen suggests that there was postlithogenic (after the deposition of modern anoxic sediments onto old oxic sediments) mixing between the oxic and anoxic layers, most likely caused by bioturbation, the mixing of sediments by burrowing organisms. However, several lines of mineralogical evidence do support the chemical differences between oxic and anoxic sediments. Apatites found in the oxic sediments support the idea that oxic sediments promote phosphorus sequestration. In addition, the presence of rare earth elements in one of the apatites suggests the possibility of a phase transformation that may be facilitated by oxic conditions. Rare earth elements are accumulated in ferromanganese nodules in the water column (Elderfield et al. 1981). Ferromanganese phases such as manganese iron oxides are some of the primary phosphorus phases in oxic sediments (Ruttenberg et al. 1993, Compton et al. 2000). As a result, phosphorus in the apatite with rare earth elements could have originated from these ferromanganese nodules. Isotopic measurements of the rare earth elements would be necessary to confirm the origins of phosphorus in the apatite.

SEDEX conclusions on these sediments argued that anoxic sediments facilitate the release of phosphorus into the water column because phosphorus concentrations quantified by SEDEX fractions defined to include reactive phases are greater in anoxic sediments than those in oxic sediments. The SEM/EDS observations provide

26

evidence that generally supports these conclusions outside of SEDEX operational definitions. However, the evidence of mixing between the anoxic and oxic layers could require a revisit of the conclusions made on the SEDEX results.

Future Investigation Results from EDS analysis of marine sediments provide context and indirect clues on processes behind phosphorus phase partitioning. In contrast, direct measurement of phosphorus in imaged phases would provide results that can be analytically compared to concentrations of phosphorus in SEDEX fractions. However, EDS lacks the accuracy and sensitivity required to measure phosphorus in silicates, carbonates, and other phases that are biogeochemically important to the global phosphorus flux but lack high phosphorus concentrations in individual particles. Wavelengthdispersive X-ray spectroscopy (WDS) has been shown to possess the accuracy necessary for measurements of phosphorus concentrations less than 100 Âľg per gram dry weight (Rao and Berner 1995). However, WDS requires extremely well-polished and flat samples. Sediments observed in this study were found to be thin enough that overpolishing often resulted in the removal of entire particles. Other spectroscopic methods that can analyze solid samples might be more suitable for analysis of thin marine sediments. Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) uses an ion beam to measure the chemical composition of sample surfaces. An ion beam has much more energy than an electron beam and can penetrate and remove enough sample such that excessively flat surfaces are unnecessary. When used alongside SEM/EDS, TOF-SIMS may prove an effective approach to the analysis of phosphorus phase partitioning.

Acknowledgements Sediment samples and background information on SEDEX research behind these samples were provided by Albert Colman. This project would not have been possible without his advice and mentorship. In addition, this project is part of an ongoing collaboration between the Marine Biological Laboratory and the University of Chicago investigating SEM/EDS and ICP-MS analyses on

Scientia phosphorus phase partitioning in the Sargasso Sea. Results from this project will be used in further studies on SEM analysis on the Sargasso Sea particle flux. Levke Kööp was an excellent lab technician and helped immensely in providing directions and troubleshooting for sample preparation and SEM/ EDS analysis.

About the Author Leonard Shaw is a third year Geophysical Sciences major.

References [1]

Benitez-Nelson, C. R. Earth Sci. Rev. (2000): 51, 109.

[2]

Bridger, W. A.; Henderson, J. F. Cell Adenosine Triphosphate Physiology; Wiley: New York, (1983).

[3]

Compton, J. Variations in the global phosphorus cycle. Marine Authigenesis: From Global to Microbial, SEPM Special Publication No.66 (2000).

[4]

Elderfield, Henry, C. J. Hawkesworth, M. J. Greaves, and S. E. Calvert. Rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments. Geochimica et Cosmochimica Acta 45, no. 4 (1981): 513-528.

[5]

Krom, M. D.; Berner, R. A. Limnol. Oceanogr. (1980): 25, 797.

[6]

Lyons, Timothy W., Josef P. Werne, David J. Hollander, and R. W. Murray. Contrasting sulfur geochemistry and Fe/Al and Mo/Al ratios across the last oxic-to-anoxic transition in the Cariaco Basin, Venezuela. Chemical Geology 195, no. 1 (2003): 131-157.

[7]

Nirel, P. M. V., and F. M. M. Morel. Pitfalls of sequential extractions.

Waterresearch 24, no. 8 (1990): 1055-1056.

[8]

Paytan, Adina, and Karen McLaughlin. The oceanic phosphorus cycle.

Chemical Reviews 107.2 (2007): 563-576.

[9]

Rao, Ji-Long, and Robert A. Berner. Development of an electron microprobe method for the determination of phosphorus and associated elements in sediments. Chemical geology 125, no. 3 (1995): 169-183.

[10] Redfield, A.C. The biological control of chemical factors in the environment. Am. Sci. 46, (1958): 205–222.

[11] Rozan, Tim F., Martial Taillefert, Robert E. Trouwborst, Brian T. Glazer, Shufen Ma, Julian Herszage, Lexia M. Valdes, Kent S. Price, and George W. Luther III. Iron‐sulfur‐phosphorus cycling in the sediments of a shallow coastal bay: Implications for sediment nutrient release and benthic macroalgal blooms. Limnology and Oceanography 47, no. 5 (2002): 1346-1354.

[12] Ruttenberg, Kathleen C. Development of a sequential extraction method for different forms of phosphorus in marine sediments.

Limnology and oceanography 37.7 (1992): 1460-1482.

[13] Ruttenberg, Kathleen C., and Robert A. Berner. Authigenic apatite formation and burial in sediments from non-upwelling, continental margin environments. Geochimica et cosmochimica acta 57.5 (1993): 991-1007.

[14] Sundby, B.; Gobeil, C.; Silverberg, N.; Mucci, A. Limnol. Oceanogr.

(1992): 37, 1129 [15] Whitehill, A. R., K. C. Ruttenberg, R. Briggs, T. W. Lyons, and A. S. Colman. Phosphorus burial in Cariaco Basin sediments through the last glacial-interglacial transition. In AGU Fall Meeting Abstracts, vol.

1, p. 1517. 2008.

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Acknowledgements The Triple Helix at the University of Chicago would like to thank the following individuals for their generous and continued support: Dr. Matthew Tirrell

Founding Pritzker Director of the Institute for Molecular Engineering

David Clark

Assistant Vice President for Student Life and Associate Dean of the College

Arthur Lundberg

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Student Involvement Advisor

We also thank the following departments and groups: The Institute for Molecular Engineering The Biological Sciences Division The Physical Sciences Division The Social Sciences Division University of Chicago Annual Allocations Student Government Finance Committee (SGFC) Chicago Area Undergraduate Research Symposium UChicago Undergraduate Research Symposium

Finally, we would like to acknowledge all our Faculty Review Board members and the mentors of our abstract authors for their time and effort.

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If you would like to learn more about Scientia and The Triple Helix, visit http://thetriplehelix.uchicago.edu or contact us at uchicago@thetriplehelix.org.

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Scientia

About The Triple Helix

at The University of Chicago

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We continue to work closely with an ever-increasing number of faculty members, and have notably acquired the generous support of the founding Pritzker Director of Chicago’s Institute for Molecular Engineering, Matthew Tirrell, and his department. We have expanded our local organization so that now, we can confidently say that there is a place here for each and every one of our fellow college students. We have consciously and dramatically increased the size of our production, marketing, and events teams, and have watched our group of talented writers and editors grow at unprecedented levels. In fact, we have further expanded the intellectual diversity of our chapter, with TTH members having declared for more than 30 of the University’s different major and minor programs. Finally, we are absolutely thrilled to present the newest issue of our journal of original undergraduate research, Scientia.

Over the years, TTH UChicago members have found themselves in research positions around campus, taking advantage of the hundreds of opportunities we are fortunate to have here. We found ourselves wishing, however, that there was an outlet where we could reach out to our peers on campus, to share our projects and project ideas – and to hear or read about their work as well. So we decided to create that outlet ourselves. This was the impetus for our journal, Scientia, which is the culmination of many of our members’ hard work. Since its inception, we have continued to strive for excellence in the diverse world of research by publishing the highest quality of undergraduate research. We hope you enjoy reading our latest issue!

Stephen Yu President of The Triple Helix, Inc.

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