sc覺ent覺fic Spring 2013 | Volume 5 | Issue 2
Infection with the Dengue virus is a leading cause of death and infection in the tropics and subtropics. Full story on page 24. 1
scÄąentific Mission Statement: Founded in Spring 2008, Carolina Scientific serves to educate undergraduates by focusing on the exciting innovations in science and current research that are taking place at UNC-Chapel Hill. Carolina Scientific strives to provide a way for students to discover and express their knowledge of new scientific advances, to encourage students to explore and report on the latest scientific research at UNC-Chapel Hill and to educate and inform readers while promoting interest in science and research. From the Editors: We are pleased to present the newest issue of Carolina Scientific. As the organization matures, we aim to make science engaging and accessible for readers by highlighting new and exciting research being conducted at UNC-Chapel Hill. This work has been made possible by our dedicated staff, interesting by the researchers whose work is featured here and relevant by your desire to stay abreast of current research. In this issue you can learn about the categorization of words, the importance of oyster reefs in reducing climate change and a new protein important in pyroptosis. Enjoy!
Executive Board Keith Funkhouser, Editor-in-Chief Kelly Speare, Managing Editor Kelsey Ellis, Associate Editor Sneha Rao, Associate Editor Kati Moore, Associate and Design Editor Lauren Walls, Copy Editor Amber Gautam, Publicity Chair Kandace Thomas, Fundraising Chair Contributors Staff Writers Abby Becherer, Amanda Raymond, Anna van Venrooy, Cameron Doyle, Carlos Floyd, Cody Phen, Connor Davis, Erin Moore, Gayatri Rathod, Jasmin Singh, Joshua Sheetz, Kai Shin, Kelsey Ellis, Linran Zhou, Luciana Giorgio, Meghan McFarland, Michael Spicka, Mihir Pershad, Paul Lee, Sam Resnick, Vamsi Kolluru, Wylder Fondaw Copy Staff Amelia Lorenzo, Daniel Liauw, Diana Ford, Elizabeth Bartholf, Joshua Sheetz, Julia Filler, Lauren Westerhold, Matt Leming, Meghan McFarland, Prashanth Saisankar, Thalita Cortes
on the cover
Design Staff Connor Davis, Elizabeth Bartholf, Erin Moore, Julie Reiff, Kelci Schilly, Kelsey Ellis, Madelyn Roycroft, Paige Derouin, Pooja Ravindran, Wylder Fondaw
Image by Purdue University.
The Dengue virus shown here is a leading cause of death and infection in the tropics and subtropics. UNCâ€™s Rukie de Alwis is working to find a vaccine. See page 24 for the full story.
firstname.lastname@example.org carolinascientific.web.unc.edu facebook.com/CarolinaScientific @uncsci
Receptive to a Unique Approach
Dye-Sensitized Solar Cells
Research in the Svalbard Archipelago
Mapping the Amygdala
Bigger Is Not Always Better
Burning Down the House
What’s in a Word?
Preteen Puberty Problems
Anna van Venrooy
The Puzzle of Imperfect Mimicry
Navigating the Brain
Fluoride and Genes
Your Pocket Money’s Interest in Politics
Oyster Reefs: Friend or Food?
Dengue: Ninja of the Virus World
The Fat That Burns Fat
Stopping Cancer Cells in Their Tracks
The Psychological Constructionist Model Cameron Doyle
The Real Benefits of a Healthy Smile Paul Lee
“Nicking” Away at Multidrug Resistant Staph
Uncovering the Genome’s Insulin Instructions
Undoing the Past
More to Gold than Meets the Eye
F LU XO M I C S
Not Just Another -omics Science By Michael Spicka
he complete sequencing of the human genome was a pivotal feat in both our understanding of human biology and in classifying a new field of science itself. Research into our most basic human code has continued since the initial mapping of the genome, and the scientific community renamed this field of study “genomics.”1 The suffix -omics implies a comprehensive analysis; genomics looks at the genome as a whole rather than at individual genes.1 This mentality of understanding the puzzle holistically as more important than observing individual pieces has spread to other niches in the scientific community. Today we are faced with a myriad of -omics sciences. However, the -omics revolution originated from the central dogma in molecular biology, which states that genetic information is transcribed from DNA to RNA and then translated into functional proteins.2 The search for a way to quantify the central dogma gave rise first to genomics, then transcriptomics, and then proteomics. Metabolomics has emerged from the revelation that these previous -omics all study biological polymers, which are assembled from small molecules, such as nucleic and amino acids.2 Metabolism is the biological process that unites these three -omics sciences. Metabolomics quantifies the concentrations of the monomers of DNA, RNA, proteins, and the small molecules involved in energy production from metabolic pathways.2, 3 Lactic acid, for instance, is the molecule that makes your muscles sore after exercise. Similar to the build up of lactic acid causing fatigue, the symptoms of all ailments are primarily caused by increases or de-
creases in the small- molecule levels in a tissue.2 The end results of genetic information processing are proteins that drive metabolism. Therefore, the metabolome represents the concentrations of the entire set of low- molecular- weight compounds, also called metabolites, that are the by-products and substrates of enzymatic reactions.3 The goal of metabolomics is to create a profile of metabolism to help diagnose, elucidate etiology and find targets for drug therapies.2 Jeff Macdonald, Ph.D., has been working within metabolomics for a number of years, employing nuclear magnetic resonance spectroscopy (NMR) to identify and model meta-
“What was missing from the other -omics is dynamics.“ -Dr. Jeff Macdonald
bolic pathways. In 2010, Dr. Macdonald published a study in which he quantified and mapped the metabolome of the Eastern Oyster (Crassostrea virginica), which was a novel exploit in terms Jeff Macdonald, of metabolomics.4 These pathways, Ph.D. along with others currently being uncovered, serve as models that can be used in future experiments to determine the effects of environment, age, genetics, disease, and other factors on the metabolome.4 While Dr. Macdonald has had many successes within the field of metabolomics, he recognized that the metabolome does not paint the whole picture of a biological system. Analysis of the metabolome provides a mere glimpse of metabolic processes. In order to fully understand a metabolic network, it is necessary to quantify the rates at which metabolites flow through a particular pathway.5 “What was missing from the other -omics is dynamics. Biological pathways are Figure 1. The flow of genetic information from DNA to menot completely represented by a singular snapshot. It’s like tabolites and the associated -omics sciences used to quantify looking at a bucket of water with two drains attached at the the process. Image courtesy of Michael Spicka.
Figure 2. Left: Metabolome of the Eastern Oyster as it relates to functional anatomy. Right: An example of fluxomic data showing the concentrations of metabolites over a period of time. Images courtesy of Dr. Jeff Macdonald. bottom. Metabolomics takes a snapshot whereas fluxomics takes sequential snapshots and tells you which drain is flowing faster.”2 Fluxomics offers the closest direct measure of the metabolic phenotype by measuring the molar flux of metabolites through each reaction in a network. Essentially, fluxomics produces quantified data that completely describes in vivo enzyme activity5 and therefore allows a full understanding of the biological system. Fluxes cannot be directly measured; instead, they must be extrapolated from stoichiometric models.5 Dr. Macdonald measures flux data by introducing a stable carbon-13-labeled precursor (e.g., glucose or some biologically pertinent compound) to a system and using NMR to observe the carbon-13 progressing through the metabolic network. Only metabolites that are directly involved in a reaction with the precursor will show incorporation of the carbon13-labeled tracer.2 The system is observed for a specified period of time, and based on the concentration and organization of carbon-13 in the product, the fluxome is generated. Fluxomics answers questions that none of the other -omics can. When combined with genomics, transcriptomics, proteomics and metabolomics, a system-biology view of a sample can be achieved. Recently, Dr. Macdonald conducted a fluxomic study comparing metabolic activity in primary human and rat hepatocytes. In this experiment, both sets of cells were given carbon-13-labeled glucose and glutamine. Rat hepatocytes displayedcarbon-13 in glycolytic end products, indicating incorporation of the carbon-13 tracers; how-
ever, the human hepatocytes did not utilize the tracers.6 The human hepatocytes were metabolically active, though, and were found to be functioning via consumption of fats. From this information, Dr. Macdonald determined that the human cells were displaying a starved phenotype (as if there was no glucose present), and the rat hepatocytes displayed a fed phenotype (normal metabolism of glucose).6 Metabolomic data would have been identical for both sets of cells. Fluxomic data, however, allowed Dr. Macdonald to determine that the human hepatocytes were actually exhibiting a stressed phenotype meaning they were consuming fats even though glucose was present.2 Human hepatocytes in vivo regularly metabolize glucose, and therefore, this study was valuable to the pharmaceutical industry where primary human hepatocytes are often used for toxicology research.2 Along with the mapping of the human genome, a realization occurred that our world is best understood as a sum of its parts; the individual pieces are simply not enough. Countless -omics sciences have arisen to piece this great puzzle together. Genomics, proteomics and transcriptomics initially offered a decent model of the central dogma of biology. The addition of metabolomics provided a clearer view of biological networks, but there were still questions to be addressed. Today, labs like Dr. Macdonald’s are looking at biology from a new perspective known as fluxomics. Together, these -omics sciences allow us to view biological pathways as systems. With the power to manipulate samples and completely understand the effects, the applications are virtually limitless.
1. ‘Omics’ Sciences: Genomics, Proteomics, and Metabolomics. http://www.isaaa.org/resources/publications/pocketk/15/default.asp (accessed February 7th, 2013). 2. Interview with Jeffrey M. Macdonald, Ph.D. 02/08/13. 3. Ryals, J. Business Brieﬁng PharmaTech. 2004, pp 51–54. 4. Tikunov, A. P.; Johnson, C. B.; Lee, H.; Stoskopf, M. K.; Macdonald, J.M. Marine Drugs. 2010, 8, 2578-2596. 5. Krömer, J.; Quek, L.; Nielsen, L. Australian Biochemist. 2009, 40, 17-20. 6. Winnike, J. H.; Pediaditakis, P.; Wolak, J.; McClelland, R.; Watkins, P. B.; Macdonald, J. M. Stable Isotope Resolved Metabolomics of Primary Human Hepatocytes Reveals a Stressed Phenotype. Metabolomics. 2012, 8, 34-49.
Figure 3. Fluxomics allows for the measure of rates of a reaction. At t1 and t3 , both situations have the same concentration. However, at t2 it is evident that the concentrations are changing at different rates. Image by Keith Funkhouser.
G-protein coupled receptor kinase 2. Image courtesy of the European Bioinformatics Institute.
Receptive to a Unique Approach A different approach to studying a vastly important class of receptors has allowed one professor to stand out in the field of cell signaling. By Joshua Sheetz
affeine. Adrenaline. Light. Odor. Serotonin. Morphine. While each varies greatly in structure and biological outcome, all contain a similar defining characteristic: each of these acts as a ligand for a specific class of receptors. In order for organisms to respond to their environment, these ligands must interact with cell-membrane-bound receptors. In the science of cellular signaling, one particular class of receptors stands out. G protein-coupled receptors (GPCRs) are considered the most essential receptors to modern medicine. When it comes to cell signaling in eukaryotes, GPCRs are critical for initiating signal transduction. They function as “gatekeepers” for the cell and allow for specific molecules to attach, which passes the signal along through the bound intracellular G protein (Figure 1, left).1 The signal then goes through a complex protein pathway to achieve the desired response. Receptors in this class are both abundant and highly versatile. They have been found to interact with a diverse array of ligands, from large protein structures to simple molecules. Additionally, studies have identified four GPCRs in humans for light and hundreds for the olfactory response.2 Their abundance and versatility means that GPCRs are of high interest as drug targets. In fact, more than 40 percent of modern prescription drugs on the market work by targeting GPCRs.3 Following their initial discovery, it did not take long for scientists and pharmaceutical companies to realize their potential. The growing realization of their value has resulted in an explosion in GPCR and G protein research in the past two decades — ultimately becoming the topic of the 2012 Nobel Prize in Chemistry. Recipients Robert Lefkowitz, Ph.D. (Duke University) and Brian Kobilka, Ph.D. (Stanford University) were
pioneers in elucidating many of the complex protein interactions involved in G protein signaling.1 However, much of their work could not have been conducted if it had not been for another important characteristic of GPCRs. The receptors and their respective G proteins are highly conserved in evolution, meaning they exist in organisms ranging from unicellular yeast to complex human Henrik G. Dohlman, PhD. beings. At UNC-Chapel Hill, Henrik Dohlman, Ph.D., one of Lefkowitz’s former students, is conducting a series of studies on G protein regulation in Saccharomyces cerevisiae (baker’s yeast). Dohlman’s research during the mid-1990s was key to identifying regulators of G protein signaling (RGS) proteins, which are responsible for desensitization.2 Drawn to cell signaling by his interest in the receptor that triggers an “adrenaline rush,” Dohlman migrated towards the unfamiliar biochemical means behind desensitization. It was his unique approach that allowed him to push the boundaries of signaling knowledge. Examples of desensitization are all around us, as all GPCR systems exhibit a loss of function over time. In humans, exposure to light and smell results in decreased intensity of perception over time. Dohlman hypothesized that desensitization was caused by a modification involving GTP, a small molecule bound to the G protein. GTP is an energy source
Figure 1. Left: The transmembrane GPCR acts as a gateway for signaling. A ligand, such as a drug molecule, binds to the receptor, which causes GDP on the G protein to form GTP. This initiates a conformational change, breaks up the G protein and releases the two subunits to induce further signaling within the cell. Right: RGS proteins, such as Sst2, act by enhancing the breakdown of GTP into GDP. As a result, the G protein is unable to induce signaling and the cell experiences desensitization. Images courtesy of Joshua Sheetz. for certain enzymes that, when hydrolyzed to release a phos- realize there is no place further from Duke than Chapel Hill.”2 phate, induces a conformational change in the G protein. This Building on his previous desensitization work, Dohlphysical change deactivates the G protein, preventing it from man and his research group continue to explore alternative transmitting the signal. Usways in which G proteins ing yeast as a model organare regulated. In turn, his ism, Dohlman discovered “If receptors are the accelerators of cell contributions to biochemthat a distinctive protein, signaling, RGS proteins are the brakes. istry and pharmacology Sst2, was responsible for have opened doors for fuenhancing the breakdown They work in opposition to receptors to ture drug development. By of GTP, thus playing a large shut down signaling and are incredibly concentrating on a highly role in desensitization (Figregarded area of biochemure 1, right).4 Sst2 became important in receptor desensitization.” istry and adopting an exthe founding member of ceptional approach, he is - Dr. Henrik Dohlman RGS proteins. able to perform integrative “If receptors are the science. “It has been a reaccelerators of cell signaling, RGS proteins are the brakes,” warding experience,” Dohlman reflects. “We can answer quesDohlman asserts. “They work in opposition to receptors to tions using the power of yeast genetics that people working in shut down signaling and are incredibly important in receptor animal models and humans can only dream of doing.”2 desensitization.”2 Dohlman highlights his decision to study yeast as a vital part of making his research stand out. While there are hun- References dreds of labs investigating GPCRs and hundreds working with 1. Jogalekar, Ashutosh. G Protein-Coupled Recepyeast, he was one of the first researchers to focus on GPCRs tors (GPCRs) win 2012 Nobel Prize in Chemistry. in yeast. Yeast offered a less complex system than the mouse http://blogs.scientificamerican.com/the-curiousmodel for understanding protein interactions while maintain- wavefunction/2012/10/10/g-protein-coupled-receptors-gping relevance to human signaling. In order to conduct origi- crs-win-2012-nobel-prize-in-chemistry/ (accessed February nal research and differentiate himself from his mentor’s work, 3rd, 2013). Dohlman focused more on G proteins rather than receptors, 2. Interview with Henrik G. Dohlman, Ph.D. 2/1/13. switched kingdoms from animals to fungi and, after leaving 3. Filmore, D. Mod. Drug Discovery. 2004, 7, 24-28. Duke, attained a position on the west coast at the University of 4. Dohlman, H. G.; Thorner, J. J. Biol. Chem. 1997, 272, California, Berkeley. He jokingly remarks, “Eventually, I came to 3871-3874.
Dye-Sensitized Solar Cells:
A Light Forward
By Kai Shin
Image by Lance Cheung [CC BY-NC-ND 2.0].
ur sun, the source of the energy that fuels almost all life on earth, bombards our planet with as much energy in 20 days as is stored in all of Earth’s fossil fuels combined.1 Such vast power holds the promise of virtually limitless renewable energy if a feasible method of capturing it can be found. Usually sunlight is harnessed using photovoltaic cells that convert solar power into electric current. Photovoltaic cells utilize the photovoltaic effect, which is when a photon of light strikes a material and excites an electron from the “valence band,” the electron’s resting energy level, to the “conducting band,” a higher energy level where the electron is free to carry charge as electric current (Figure 1).2 The biggest obstacle inhibiting widespread production of solar power is the inefficiency of current technology in converting sunlight to electricity. Typical solar cells on the market today convert only 15 percent or less of received sunlight into electricity.3 Imagine trying to catch a waterfall with your bare hands, and you will have an idea of how much energy is lost.
In its effort to increase the amount of energy the United States receives from renewable sources like solar energy, the Department of Energy (DOE) has instituted the Energy Frontier Research Center (EFRC). Since 2009, UNC-Chapel Hill has operated as a leading center for solar fuels within the EFRC.4 One of the prominent researchers is Rene Lopez, Ph.D., whose laboratory is Rene Lopez, Ph.D. investigating the potential of solar energy as well as applications of the optical properties of certain materials in several new ways. “The EFRC here in particular is based around the idea of using solar light to directly create a kind of fuel,” says Dr. Lopez. “We aren’t doing just photovoltaics. It’s all about directly using electrons to create fuels.” The UNC-EFRC research is focused on developing devices called photo-electrochemical dye-sensitized solar cells (PESC’s) to harness solar energy and store it within the chemical bonds of a fuel. The primary target fuel in this case is hydrogen gas or H2, which can be created “through the oxidation of water and the reduction of resulting protons to create hydrogen gas,” according to Dr. Lopez.5 The UNC-EFRC aims to use sunlight to catalyze the splitting of water into hydrogen, which can be used in hydrogen fuel cells as an alternative to oil. Lopez’s group is working on improving the efficiency of dye-sensitized solar cells (DSSC) by testing various parameters of the fabrication procedure. The process starts when a metal oxide like titanium oxide (TiO2) is coated onto a transparent but conductive glass chip using a technique called
Figure 1. Illustration of the photovoltaic effect: light waves striking a surface can excite electrons into the higher energy conduction band where they are free to form an electric current. Image courtesy of S-kei [CC BY-SA 2.5].
Carolina Scientific pulsed laser deposition. A rapidly oscillating laser blasts off a plume of superheated particles that coats the surface of a precisely positioned conducting chip. The crystalline structure of this oxide varies greatly according to changes in its deposition environment, which affects its conductive properties (Figure 2). Furthermore, combining more than one metal oxide also changes the cell’s electrical properties. Next, each film is coated in a special dye designed to absorb light and encourage the excited electrons to jump directly to the conduction band of the metal oxide. Here, the distance that the electrons have
Research like Dr. Lopez’s opens up possibilities for a future where the world’s energy needs are met with clean, sustainable sources. to physically travel to go from the dye to the oxide and from there to the rest of the circuit affects how much charge is lost to chaotic processes. Finally, each film is covered by another conductive chip with an electrolyte bath sandwiched between the two slides. The electrolyte replenishes electrons to the dye to prevent it from breaking down after its electrons are excited into the conducting band. The result is a small device that generates a current and voltage potential when exposed to light. Each aspect of DSSC development is being examined to try and create an optimal combination of nanostructure and materials that maximizes the efficiency of the cell.6 In addition to creating fuel from solar energy, Dr. Lopez’s lab also looks into the optical properties of materials. One project, funded by the National Science Foundation and inspired by the microscopic wing structure of the blue morpho butterfly, looks at how the optical properties of its wing could be applied to electronic screens and other objects. The iridescent blue of the wing is a result of its complex microstructure, which essentially diffracts light to isolate the wavelength of blue light (Figure 3). Additionally, the wing structure makes its color angle independent, meaning the apparent color of its wings doesn’t change based on the angle of observation as a computer screen would.
Figure 3. The iridescent blue wings of the Morpho butterfly. Image courtesy of Gregory Phillips [CC BY-SA 3.0]. The end goal of this project is to recreate this effect in a material flexible enough physically to react to an electric field. Theoretically, such a material could be designed to display specific colors according to the ambient electric field. Imagine clothes that could be made to change color at the push of a button, camouflage that mimics one’s background or electronic screens that would not have to be plugged in. In Dr. Lopez’s words, “All the selling points are [there]; the challenge is to make it happen.”5 Indeed, the benefit of such energy-efficient technologies, combined with more efficient methods of exploiting solar energy, would be far-reaching as we move away from our dependence on limited fossil fuels. Research like Dr. Lopez’s opens up possibilities for a future where the world’s energy needs are met with clean, sustainable sources.
1. The George Washington Solar Institute, George Washington University. Frequently Asked Questions. solar.gwu.edu/ FAQ/solar_potential.html (accessed February 2nd, 2013). 2. University of Colorado at Boulder. Photoelectric Effect. phet.colorado.edu/en/simulation/photoelectric (accessed February 9th, 2013). 3. Grape Solar 250 Watt Monocrystalline Solar Panel. lowes. com. (accessed February 3rd, 2013). 4. University of North Carolina at Chapel Hill, Solar Fuels: UNC EFRC. efrc.unc.edu/. (accessed February 3rd, 2013). 5. Interview with Rene Lopez, Ph.D. 2/4/13. 6. Ghosh, R.; Hara, Y.; Alibabaei, L.; Hanson, K.; Rangan, S.; Bartynski, R.; Meyer, T. J.; Lopez, R. ACS Appl Mater Interfaces. 2012, 4(9), 4566-4570.
Figure 2. An electron microscope’s view of the metal oxide layer in a DSSC. Note the tree-like crystalline structure. Image courtesy of Dr. Lopez.
Research in the Svalbard Archipelago: How Microbial Communities’ Richness Can Influence Hydrolysis By Zijian Zhou
The Svalbard Archipelago. Image courtesy of Dr. Carol Arnosti.
he Arctic Ocean is one of the coldest oceans on Earth but is home to a diverse group of marine organisms. Like any living, dynamic environment, there are food chains. In these cold Arctic waters that have temperatures at or below 4 degrees Celsius, few decomposers can function. In the Arctic Ocean, decomposition of detrital organic matter is carried out predominantly by microorganisms. One of the focuses of Carol Arnosti, Ph.D.’s research group in the department of marine science at UNC-Chapel Hill is to investigate these microorganisms and their ability to decompose organic matter under permanently cold conditions. These microorganisms play an important role in the Arctic Ocean, and in the biosphere in general, by recycling nutrients locked up in dead organisms and making them available again. These microbial communities are composed of Figure 1. Svalbard Islands. many different types of bacteria, and their varying commuImage public domain.
nity composition is the reason why organic matter in the Arctic Ocean is decomposed differently than it is in more temperate waters like those off the coast of North Carolina.1 The organic matter that makes up the diet of these microorganisms comes from a variety of sources, including dissolved organic matter washed into the Arctic Ocean from the Eurasian rivers and dead marine animals Carol Arnosti, Ph.D. in the Arctic Ocean. Dead phytoplankton supply most of the organic matter in the form of polysaccharides, a type of complex carbohydrate. The Arnosti group focuses on the abilities of Arctic Ocean’s microbiological communities to break down these polysaccharides. The research involves extensive fieldwork conducted in collaboration with scientists from the Max Planck Institute for Marine Microbiology in Bremen, Germany. The project has been conducted mostly in the Svalbard archipelago in Norway. These islands are located in the Arctic Basin and are prime areas for sample collection. Seawater samples are collected by going to sea aboard a small research vessel and using Niskin bottles or buckets to collect water.1 Sediments are collected using a Haps corer, a cylindrical device that
Carolina Scientific penetrates the sediment layer to a depth of 20 to 35 cm and ensures that the collected sample retains its depth stratification.2 These samples are transferred to vials that are injected with various fluorescently tagged polysaccharides to determine how each of these substrates is hydrolyzed by seawater and sediment microbial communities. These polysaccharides make up a large portion of phytoplankton organic matter and include laminarin, xylan, fucoidan, arabinogalactan, pullulan and chondroitin sulfate.3 When bacteria hydrolyze polysaccharides, molecular size decreases as complex carbon chains are broken into smaller ones. The vials containing the samples are incubated and then analyzed using size-exclusion chromatography.1 Changes in the molecular size can be detected through the fluorescently marked hydrolyzed polysaccharide. A decrease in molecular size can only result from enzymatic hydrolysis of the substrate.3 Current results suggest that microorganism communities in Arctic waters hydrolyze a smaller range of substrates than those in more temperate waters. Microbial communities in temperate waters also degrade organic molecules at a rate which can be orders of magnitude higher than those in Arctic water. Microbial diversity increases towards more temperate waters (from poles towards the equator).3 The higher rates of hydrolysis observed in temperate waters cannot be attributed to temperature alone, because higher temperatures did not widen the range of organic matter that the bacteria decomposed. This is supported by the fact that not all hydrolysis activity of microbial communities in the Arctic Ocean is the same.3 Microbiological communities in the sediments of the Svalbard Archipelago demonstrate both higher rates of hydrolysis and the ability to degrade a greater range of organic molecules than do seawater communities. A comparison between sediment and seawater microbial communities shows the seawater community hydro-
lyzing only 5 out of the 7 polysaccharide samples and 2 out of the 3 algal extracts while all of the 10 substrates are hydrolyzed by the sediment communities. For most of these substrates, the hydrolysis rates of the sediment microbial communities are up to three orders of magnitude higher than those of seawater microbial communities. A possible reason for sedimentary microbial communitiesâ€™ ability to Figure 3. Dr. Arnosti and coldigest a wider range of leagues use a Haps corer to collect organic molecules may sediment samples. Image courtesy be that they consume of Dr. Carol Arnosti. what the seawater microbes cannot. As organic molecules sink through the water column, the seawater microbes digest a narrow range of organic molecules, forcing the sedimentary microbes to access the greater range of â€œleftoversâ€? for food.4 For temperate water communities as well as for the Svalbard sediment microbial communities, higher rates of hydrolysis and the ability to digest a wider range of organic substrates correlate with greater community richness. Shown in Figure 2, there is a greater diversity of microorganisms in sediment than in seawater at Svalbard. Studies by other groups researching a wide range of ocean environments, especially the International Census of Marine Microbes, support the idea that sedimentary marine microbial communities are, on average, more diverse than seawater communities. The Arnosti group has worked primarily in the Svalbard Archipelago and in a few temperate sites, so study of a wider range of sites in the Arctic Ocean is a major goal for future work.2 One implication of this research is the possible alteration of these Arctic Ocean microbial communities as ocean temperatures rise. At higher temperatures, bacterial diversity and decomposing ability can increase in these communities, leading to more rapid and extensive decomposition of organic matter to carbon dioxide (CO2) gas. This can dramatically affect the dynamic of the global carbon cycle and result in a higher amount of CO2 gas being generated. Since the amount of CO2 stored in the ocean dwarfs that in the atmosphere, small changes can lead to warmer temperatures and boost microbial colonies, leading to a positive feedback loop.
Figure 2. Greater microbial community richness in sediments. Image courtesy of Dr. Carol Arnosti.
1. Interview with Carol Arnosti, Ph.D. 02/09/13. 2. Email with Carol Arnosti, Ph.D. 02/12/13. 3. Arnosti, C.; Steen, A. D.; Ziervogel, K.; Ghobrial, S.; Jeffrey, W. H. PLoS one. 2011, 6(12), 1-6. 4. Teske, A.; Durbin, A.; Ziervogel, K.; Cox, C.; Arnosti, C. American Society for Microbiology. 2011, 77(6), 2008-2018.
Mapping the Amygdala Optogenetic Techniques and Fluorescent Proteins Used to Understand the Alcoholic Brain
By Anna van Venrooy
lcoholism is a disease that costs the United States $223.5 billion dollars annually, but the costs go beyond monetary value; alcoholism destroys lives, relationships and communities.1 Of course, participation in social or binge drinking in college does not classify someone as an alcoholic. According to the National Institutes of Health (NIH) website, an alcoholic experiences the symptoms of craving, tolerance and physical dependence.2 Alcohol exposure and genetic predisposition are risk factors that increase the likelihood of developing alcoholism.3 Alcoholism modifies a fundamental mechanism the brain uses to process emotions. Brain imaging (fMRI) studies on humans, as well as behavioral tests on rats, have shown the differences in an alcoholic’s brain and a social drinker’s brain.4 An fMRI displays which parts of the brain are stimulated when subjects are exposed to different visual stimuli. When alcoholics are shown pictures of alcoholic beverages, different parts of their brains light up when compared to non-addicts’, including the areas having to do with habituation (Figure 1). Exactly how ethanol exposure has manipulated brain circuitry is unknown, but experts in the fields of psychiatry, pharmacology and drug abuse are desperate to find out how to rewire the brains of alcoholics. Darin Knapp, Ph.D. and his colleagues at the Bowles Center for Alcohol Studies have Figure 1. Sagittal view of the dedicated their academic brain with the amygdala highcareers to understanding lighted in red. Image courtesy of the emotional aspects of Life Science Databases. withdrawal and the nega-
tive feedback circuits that cause the inevitable relapse of most alcoholics. Dr. Knapp earned his Ph.D. in biopsychology and behavioral neuroscience from Rutgers University and is currently an associate professor in the department of psychiatry. In Dr. Knapp’s lab, they supply rats with enough alcohol over a twoweek period to induce addiction and then observe the effects of Darin Knapp, Ph.D. withdrawal.3 After the rats are taken off the ethanol, they, like alcoholic humans, appear to be normal superficially, but when introduced to stress, their vulnerable state is exposed. Stress or temptation that does not affect a control rat causes anxiety and depression in an experimental rat. For example, a small puff of air aimed at the face will cause only alcoholic rats to whimper.3 Experiments like this support the idea that alcoholics process negative emotions differently from normal individuals, which has led to questions about the negative emotional circuits of the brain. The amygdala is known to be the negative response center of the brain, but the exact input and output mechanisms of the stress-induced anxiety during withdrawal is still a mystery.5 One of Dr. Knapp’s preliminary studies used viral vectors containing fluorescent tags eYFP (yellow) and eGFP (green) to map the nuclei, cell bodies and axonal projections to and from the amygdala.6 Another visualization technique stained the DNA and nucleus blue with DAPI to highlight various connections and show that the viral vector could be taken up by all parts of the circuit including the axons’ target cells (Figures 2 and 3). Axons can form long projections in the brain and the body. For example, there are nerve cells in your spinal cord that send axons to your toes. Normally, all axon projections appear as white, fatty fibers, and their various paths to different parts
Carolina Scientific How Does it Work? Rhodopsin-containing AAV is injected into the central amygdala. Light from fiber optic probes will be be projected into the amygdala to activate or inhibit specific neurons in various subregions of the structure. AAV (adeno-associated virus) is a vector that carries the genetic constructs coding for these proteins into the neurons. Other markers such as a green fluorescent protein (GFP) can be used to simply track projections of the neurons without the added feature of regulating functions of the amygdala. Image courtesy of Dr. Darin Knapp. of the brain are indistinguishable from one another with the naked eye. The fluorescent markers and stains are simply different colors that show where the axon is going and therefore what other parts of the brain it is giving orders to. Fluorescent markers help investigators determine which parts of the brain are “talking” to each other, but different techniques must be used to understand what they are saying and what “language” they are using. According to Dr. Knapp, the fluorescent markers “permitted identification of the local extent of transduc-
tion of cells at the site where the virus was injected.”3 The next step in their research is to determine if the terminals of the suspected neurotransmitters (glutamate, vasopressin and oxytocin) in the amygdala are involved in the circuit. To do this, they use pharmacology and the up-andcoming techniques of optogenetics.7 Optogenetics takes advantage of rhodopsins, a family of proteins that naturally occur in the retina of the human eye and are responsible for light detection. Specifically, optogenetics makes use of lightactivated channelrhodopsin-2 to test the activation or inhibition of specific terminals on a millisecond timeframe.8 The channelrhodopsin-2 is incorporated into the neurons of the amygdala by a viral vector after being microinjected. A beam of blue light then opens channels associated with the lightactivated channelrhodopsin-2, enabling in vivo regulation of a specific terminal (Figure 4). This novel technique will be used to better understand the input and output of the amygdala, which functions as the negative control center of the brain and is responsible for the emotional aspects of withdrawal. Ultimately, Dr. Knapp hopes that his research will help “isolate the pathways of intoxication and emotional regulation of agents such as alcohol.”3
Figure 2. Above: GFP (green) expression in the amygdala of neuron bodies and DAPI labeled nuclei (blue) 40 days after viral injection. Below: Yellow fluorescent protein (YFP) expression in the amygdala of neuron cell body membranes and projections. Cell nuclei are labeled blue with DAPI and center neuron labeled with both YFP and DAPI. Images courtesy of Dr. Darin Knapp.
1. Center for Dieses Control and Prevention: Excessive Drinking Costs U.S. $223.5 Billion. http://www.cdc.gov/features/alcoholconsumption/ (accessed January 31st, 2013). 2. National Institute on Alcohol Abuse and Alcholism. http://pubs.niaaa.nih.gov/publications/FamilyHistory/ famhist.htm (accessed on February 17th 2013). 3. Interview with Darin Knapp, Ph.D. 1/24/13. 4. Breese, G. R.; Sinha, R.; Heilig, M. Pharmacol Ther. 2011, 129, 149-171. 5. Knapp, D.J., Overstreet, D.H., Huang, M., Wills, T.A., Whitman, B.A., Angel, R.A., Sinnett, S.E.,Breese, G.R. Psychopharmacology, 2011, 218, 178-189. 6. Lee, R. Biology 395 Paper. 7. Bresse, G.; Knapp, D. Unpublished Grant c 8. Aravanis, A. M.; Wang, L. P.; Zhang, F.; Meltzer, L.A.; Mogri, M. Z.; Schneider, M. B.; Deisseroth, K. J Neural Engineering. 2007, 4, 143-156.
Bigger is Not Always Better
How Microbeam Radiotherapy May Revolutionize Cancer Treatment By Linran Zhou
A reasearch team at UNC is working to develop a system that may one day be used to deliver radiation with greater accuracy and safety to cancer patients.
hough there is an abundance of good news about the fight against cancer, the disease still stands as a daunting obstacle for medical research to overcome. According to the recent Annual Report to the Nation on the Status of Cancer, 1975-2009 (Figure 1), U.S. cancer death rates are continuing to drop across all sexes, major racial and ethnic groups and common cancer sites, giving reason to rejoice.1 However, cancer is still one of the leading killers in the United States, second only to heart disease.2 Furthermore, new challenges have presented themselves, such as the rise in human papillomavirus (HPV)-related cancers.1 The most frightening part might be the treatments patients must endure, each with serious risks. One common therapy used to treat cancers, especially when surgery is not an option, is radiation therapy. As the
Figure 1. All cancer death rates in the United States from 1975-2009, separated by sex. Image courtesy of National Cancer Institute.
name suggests, it uses high-energy emissions to kill cancerous cells, which can be delivered by an external machine, directly into or near the cells or systematically throughout the body. While radiation can be effective in eliminating malignant cells, it can cause debilitating side effects both during and after the treatment, as the radiation damages and kills all cells in the irradiated area.3 Acute side effects, which occur during the treatment period, include damage to tissues exposed to the radiation. The severity and symptoms depend upon which part of the body is treated. Chronic side effects of radiation therapy, which can appear and persist long after the treatment ends, include fibrosis (formation of scar tissue), infertility and even cancer.3 Although radiation therapy is a powerful and lifesaving treatment, the danger it poses is leading doctors and scientists to investigate safer and more effective ways to use it. One research team, led by Otto Zhou, Ph.D., of the department of physics and astronomy and Sha Chang, Ph.D., of the department of radiation oncology at UNC-Chapel Hill, are working to develop a system that may one day be used to deliver radiation with greater accuracy and safety to cancer patients. This system utilizes “microbeam radiation” which delivers X-ray radiation in the form of very thin, stagOtto Zhou, Ph.D. gered planes.4 “Rather than cover the entire tumor with radiation, if you deliver radiation in a way that they are in the form of parallel planes, but between the planes there is no radiation … , [researchers] found that they can kill the brain tumor with minimum damage to normal tissue,” said Dr. Zhou. The planes of radiation are about 300 microns thick and the spaces between them are large in
Carolina Scientific comparison — about one millimeter (Figure 2).4 Surprisingly, the concept of microbeam radiotherapy (MRT) has actually been around for quite some time, but microbeam radiation had previously only been produced by two synchrotron facilities in the world — the Brookhaven National Laboratory in Long Island, New York and the European Synchrotron Radiation Facility in France.4 Synchrotrons are massive (think Kenan Stadium or larger), circular machines that accelerate particles — in this case, electrons — until they reach velocities near the speed of light. Since the particles are moving in a circular path, their momentum changes continuously around the circle, releasing electromagnetic radiation.4 This method is impractical in treating patients because if the mechanical shutters allowing delivery of very short pulses fail, then the radiation would kill the patient.5 However, since previous literature suggests that microbeam radiation has therapeutic potential, Dr. Zhou and his team are trying to develop a desktop system that could be used in any lab or hospital (Figure 3). The team’s system produces microbeam radiation using a carbon nanotube cathode array, developed and patented by Dr. Zhou, and utilizes the principle of “electron field emission.”4 The system produces an emission current from the nanotube cathode of about 325 milliamperes per square centimeter of nanotubes by applying an electric field to the gate located above the cathode and emitting the electrons. The electrons are then bombarded against a molybdenum and tungsten anode held at a very high voltage compared to the cathode and gate. Using a focusing electrode, the beam is directed to a small focus spot on the anode, and through the photoelectric effect, X-rays are generated.5 A device called a collimator is used to block parts of the beam to form the planes and the spaces between them. Compared to conventional thermionic emission as a way of producing X-rays, which involves heating a metal filament to generate the electrons, the nanotube “cold cathode” method can produce X-rays at room temperature and from many different perspectives. The X-ray pulses can even be electronically controlled and synchronized with fine movements, such as heartbeats.4 Although the desktop system is far from treating humans, Dr. Zhou and his team are performing studies on mice to investigate the methods behind MRT. Previously, it was thought that hundreds of Gray (a unit for absorbed dose) of radiation were needed for MRT to work, such as the radia-
Figure 2. Stationary micro-beam lines shown on EBT2 Gafchromic© film from desktop MRT source. Image courtesy of Pavel Chtcheprov.
Figure 3. Desktop MRT system with integrated micro-CT. Image courtesy of Pavel Chtcheprov. tion generated at the synchrotron facilities. The desktop system currently delivers orders of magnitude less of a dose, but Dr. Zhou and his team are attempting to show that such high doses are not necessary.4 The next step is to produce a “second-generation” system that will improve treatment in small animals and then move on to larger animals.4 The project holds great potential for future cancer research. A number of hypotheses attempt to explain how microbeam radiation works. The treatment may be effective at destroying the vasculature of tumors, or it could work through a “bystander effect,” in which irradiating cells directly can cause the cells they communicate with to also display irradiated effects.5 “It’s not fully understood,” says Dr. Zhou. “One of the limitations is that it is very difficult for people to study them because there are only a few large synchrotron facilities where you can do the experiments. Part of our motivation is to build a system so that people can use them to study biology and why this works.”4
1. National Cancer Institute: Report to the Nation shows U.S. Cancer Death Rates Continue to Drop. http://www. cancer.gov/newscenter/newsfromnci/2013/ReportNation (accessed February 7th, 2013). 2. Leading Causes of Death. http://www.cdc.gov/nchs/ fastats/lcod.htm (accessed February 7th, 2013). 3. National Cancer Institute: Radiation Therapy for Cancer. http://www.cancer.gov/cancertopics/factsheet/Therapy/ radiation (accessed February 8th, 2013). 4. Interview with Otto Zhou, Ph.D. 2/8/13. 5. Interview with Pavel Chtcheprov, biomedical engineering graduate student. 2/7/13.
Before Dr. Miao’s most recent work, the enzyme caspase-11 was not known to have any beneficial function. Now, it is thought to play an important role in pyroptosis, a type of programmed cell death.
Burning Down the House: A New Player in Pyroptosis By Wylder Fondaw
lthough the phrase ‘cell death’ sounds bad, programmed self-destruction is imperative for life in a complex organism such as a mouse or a human. Infected cells can facilitate bacterial reproduction and dispersion, ultimately leading to the death of the organism. Pyroptosis, like apoptosis, is a form of programmed cell death. Dr. Edward Miao of the UNC School of Medicine’s Microbiology and Immunology department studies the role of a family of proteins called caspases that activate during bacterial infection and trigger pyroptosis. Once pyroptosis is induced, the cell lyses itself so that the bacteria are ejected “into the extracellular space, where they are phagocytosed and killed by neutrophils,” which are more effective at killing bacteria than macrophages (Figure 1).1 Dr. Miao likens pyroptosis to “a thief sneaking into the house, not knowing an alarm will go off to knock down the walls and expose him to capture by the police.”2 For such a vital process, pyroptosis is a relatively new topic of study with very little currently known about caspase pathways. Cells called macrophages are widely distributed throughout the body and constitute the immune system’s first line of defense. Macrophages engulf and slowly digest bacteria in a vacuole, but are often less efficient killers than neutrophils, which arrive in the second wave of defense.3,4 As a result, “many bacteria such as Salmonella typhimurium, Legionella pneumophila, and two species of Burkholderia bacteria have learned how to deal with macrophages.”3 S. typhimurium and L. pneumophila stay in the vacuole and inject proteins into the cell’s cytoplasm that do harm. Many bacteria have a structure known as a type III secretion system (T3SS) (Figure 2) that secretes virulence factors into the infected cell’s cytosol. The T3SS acts much like a syringe that injects virulence factors
into the cell that “reprogram host cell physiology to the benefit of the pathogen.”4 Hijacked cells also shelter the pathogenic bacteria so that more effective immune cells, such as neutrophils, cannot destroy them.1,3 If macrophages attempted to detect the virulence factors in order to trigger pyroptosis, bacteria would simply evolve new ones since bacteria’s short lifespan allows them to evolve much faster Edward Miao, M.D. than the organisms they target. Ph.D. Instead, macrophages are able to detect the pathogen’s rod and flagellin proteins, two indispensable structural elements from the bacteria that are unintentionally translocated into the host cell’s cytoplasm during virulence injection (Figure 2).4 The host cell takes advantage of “accidental injection of flagellin and rod proteins in order to detect these highly conserved and slowly evolving [bacterial] proteins.”5 Thus, macrophages are able to detect bacterial attack and activate caspase-1, the enzyme that triggers pyroptosis. Caspase-11 belongs to the same family of enzymes as caspase-1, but before Dr. Miao’s most recent work, caspase-11 was not known to have any beneficial function. To determine whether caspase-11 was capable of activating pyroptosis on its own, Dr. Miao injected the vacuole-escaping bacteria B. pseudomallei into mice lacking the ability to activate caspase-1 (Figure 3).4 Although these mice were unable to activate caspase-1, they still survived by performing pyroptosis in infected cells.1 Infected cells must be triggering pyroptosis in-
Figure 1. Mechanism of caspase-1 activated pyroptosis. Image courtesy of Dr. Miao. dependent of caspcase-1.4 Dr. Miao then began pursuing caspase-11 since “we don’t know what activates it and this pathway is important for protecting against a really nasty bug.”3 This nasty bug is the previously mentioned bacterium Burkholderia that escapes from macrophage containment vacuoles. Dr. Miao hypothesized that this escape process could be detected by caspase-11. To confirm this, Dr. Miao injected mice without caspase-11 with B. pseudomallei. These caspase-11 deficient mice were unable to trigger pyroptosis and quickly died, as did caspase-11 deficient mice injected with Burkhold-
eria thailandensis, a bacterium commonly found in soil that is related but avirulent. Thus, caspase-11 must be responsible for triggering pyroptosis in lethal B. pseudomallei infections.2,4 Even more remarkable is that bacteria that cause only mild symptoms in normal mice were lethal in mice lacking caspase-11. Dr. Miao’s work demonstrates that caspase-11 is important in the inflammasome pathway and has a clear function that can be beneficial or harmful depending upon the context of its activity. Caspase-1 was previously thought Figure 2. T3SS (the to initiate pyroptosis in both syringe-like structure) for vacuole-escaping and vacu- translocating virulence facole-residing bacteria, but Dr. tors into the host cell with Miao’s research indicates that accidental protein translocaspase-11 is responsible for cation of flagellin and rod detecting strains that escape proteins. Image courtesy of the vacuole while caspase-1 Dr. Miao. detects vacuole-residing bacteria. These caspase-11 triggering bacteria are so ubiquitous in places such as Southeast Asia that these parts of the world might be uninhabitable if not for the caspase-11 defense mechanism.3 Our understanding of the pathway that leads to caspase-11 activation and the mechanism through which it triggers pyroptosis will be a subject of continued investigation by Dr. Miao and other researchers as the study of inflammasomes catches fire.
1. Edward A. Miao and Jayant V. Rajan. Frontiers in Microbiology. 2011, Vol 2 pages 1-5. 2. Les Lang. Immune cell suicide alarm helps destroy escaping bacteria. http://news.unchealthcare.org/news/2013/ january/immune-cell-suicide-alarm-helps-destroy-escaping-bacteria (accessed February 2nd 2013). 3. Interview with Edward Miao MD Ph.D. 02/07/2013 4. Aachoui, Y.; Leaf, I. A.; Hagar, J. A.; Fontana, M. F.; Campos, C. G.; Zak, D. E.; Tan, M. H.; Cotter, P. A.; Vance, R. E.; Aderem, A.; Miao, E. A. Science. 2013, 339(6122), 975-978. 5. Edward Miao. Department of Microbiology and Immunology. http://www.med.unc.edu/microimm/directories/ faculty/immunology/edward-miao-ph.d (accessed January 30th, 2013). 6. Edward A. Miao, Jayant V. Rajan, Alan Aderem. Immunological Reviews. 2011, Vol 243 pages 206-212.
Figure 3. Shown in red are bacteria that have invaded host cells by escaping the containment vacuole and entering the cytoplasm. Image courtesy of Dr. Miao.
What’s in a
By Connor Davis
n elementary school, most people learn a few basic rules about language: A noun is a person, place or thing; a verb is an action; an adjective is a word used to describe a noun (Figure 1). However, research has shown that there is more to these lexical categories than just that. Jennifer Smith, Ph.D., a linguist at UNC-Chapel Hill, has shown that in some languages the speech sounds of words are just as important as their definitions when separating them into word categories. To help clarify this idea, consider the pronunciation of the word “record” as a verb and as a noun. While the stress in the word goes on the “o” in the verb form, it is placed on the “e” in the noun form. This same differentiation can be seen between the words “project” (verb) and “project” (noun). However, this pattern in English is only a tendency of the language; it is not an actual rule that dictates how English works.1 Jennifer Smith, In her 2001 paper titled “Lexical Ph.D. Category and Phonological Contrast,” Dr. Smith delves into several other languages to better support her argument. For example, Dr. Smith explains that in Fukuoka Japanese, any syllable of a noun may either be accented or the noun may have no accents at all (Figure 2). Verbs and adjectives, however, are not only required to have an accent, but the accent has a specific location on the penultimate syllable. Similarly in Spanish, accents can go anywhere on a noun as long as they stay on one of the last three syllables of the word. However, the accent placements are much more restricted on verbs, as they imply its conjugation.2 While these examples show how nouns and verbs can be differentiated by their speech sounds, adjectives are slightly different in that they tend to behave like either verbs or nouns. In particular, for languages that Figure 1. In elementary school, chil- treat adjectives more dren are typically taught that nouns like verbs, adjectives behave like verbs in are persons, places or things; verbs are action words; and adjectives are terms of their speech describing words. Image courtesy of sounds. Such languages include FuRobbiemuffin [CC BY-SA 3.0].
Figure 2. Above: Nouns from Fukuoka Japanese. The accent can go nearly anywhere within the word or can be missing entirely. Compare these words with (below) verbs and adjectives from Fukuoka Japanese, in which the accent must fall on the second-to-last syllable. This phonological restriction helps differentiate nouns from verbs and adjectives in the language. Images courtesy of Dr. Jennifer Smith. kuoka Japanese, in which adjectives can even be conjugated and take on tenses like verbs.1 On the other hand, in languages with adjectives that change to agree with the nouns they describe, adjectives behave more phonologically like nouns. For example, in Spanish, adjectives are modified depending on the gender and plurality of the noun being described.2 Consider the Spanish phrases “perro rojo,” “perros rojos,” “rosa roja” and “rosas rojas.” As can be seen from these phrases, the adjective, “rojo,” must be changed depending on the gender and number of the noun it modifies. From this observation, linguists can conclude that Spanish adjectives behave phonologically more like nouns than verbs. While Dr. Smith’s work has helped to explain how phonology and lexical categories are related,her work is part of a much larger goal. In an interview, Dr. Smith explained that her major line of research is seeing how different fields of linguistics interact with each other.1 Linguistics is a broad field of study composed of many subfields including phonology, phonetics, morphology, syntax, semantics and pragmatics. Some of these groups interact more extensively than others. For example, morphology (words and word-like units) and syntax (the order and functions of words in sentences and phrases) are intricately linked because morphology provides the words that syntax uses to put in the proper order in a sentence. In fact, these fields are sometimes just combined into one larger area of study — morpho-syntax. However, there are fewer interactions between the other subfields of linguistics. One would be hard-pressed to find links between pragmatics (the study of understanding language in context) and morphology. As Dr. Smith concisely puts it, “syllable structure doesn’t affect syntax.”1 Nonetheless, observing how these different fields of linguistics interact with each other significantly helps linguists understand how the brain turns mental grammar into speech. It also may help linguists move beyond the question “What’s in a word?” to deeper questions such as “What’s in a language?”
1. Interview with Jennifer Smith, Ph.D. 01/28/13 2. Smith, J. PETL 6: Proceedings of the Workshop on the Lexicon in Phonetics and Phonology. 2001, 61-72.
Preteen Puberty Problems By Amanda Raymond
ost people view the process of puberty in the same way. Children are snot-nosed kids in elementary school. Girls start changing during middle school, growing taller and developing curves. Then, something magical happens over the summer between middle and high school where short, squeaky-voiced boys transform into giants who sound like James Earl Jones (aka Mufasa and Darth Vader). Now imagine that magical process happening in elementary and middle school. New research has found that, like girls, boys today are entering puberty at an even earlier age. These early changes may signify environmental problems and young boys may not be mentally ready to hit puberty at such a young age. Marcia Herman-Giddens, P.A., Dr.P.H., a researcher at the UNC-Chapel Hill Gillings School of Global Public Health, performed her initial research observing instances of early puberty in girls and believed it was about time for researchers to look at the same phenomenon in boys. She worked in clinical practice at the Duke University Medical Center from the late 1970s until the 1990s and observed many girls developing “much earlier than the textbook said that they should be.” She found that the most consulted research about the average ages of children going through puberty was a British study from the 1960s. Herman-Giddens saw a need for a more current analysis of ages at which children were beginning puberty in the United States, for both girls and boys.1 “I got [federal] data on boys’ pubertal markers and analyzed that. Those data were not adequate for looking at the question of boys’ puberty, so then I realized, ‘Well, we need to do a study,’” Herman-Giddens explains.1
She conducted study in order to find out the age at which American boys were entering puberty, as well as when they reached sexual maturity according to external physical characteristics. The study included a wide range of male participants from various ethnicities and regions across the United States.2 Herman-Giddens and her colleagues measured the two earliest signs of puberty: pubic hair growth and testicular growth.3 Because this study was the first large study to measure testicular volumes in the United States, it can be used as a baseline for future studies. Observations of the changes in the participants were made by pediatricians and other clinicians who were trained in Tanner staging, a system of measuring pubic hair and genital growth. Tanner staging is a “five-stage visual method for assessing the development of secondary sexual characteristics,” from prepubertal (stage 1) to fully mature (stage 5).2 The clinicians were also trained to use
Early puberty most likely indicates environmental problems that are unhealthy for children today. Prader orchidometers, which measure the volume of testicles.4 Observations and measurements were made with informed consent and were limited to those that would normally occur during a routine physical exam. Herman-Giddens found that males in the United States are displaying their first signs of puberty at an earlier age than observed in previous research. She also found that African-American boys began puberty at a younger age than Caucasian or Hispanic boys. Caucasian and Hispanic boys entered stage 2 genital development at around 10 years old, while African-American boys entered the same stage at about age nine. They found almost the same phenomenon with pubic hair growth, with Caucasians and Hispanics entering stage 2 around the age of 11 and African-Americans entering that same stage around age 10. The data showed participants starting puberty from one and a half to two full years ahead of studies conducted several decades ago.2
According to Herman-Giddens, the age of puberty, like birth weights and height-to-weight ratios, is an important health determinant that can be very useful to physicians. She recommends that this kind of research should be done at least every 10–20 years.1 “It’s a very important public health indicator for the health of children just as height and weight, birth weights and those types of figures are,” she explained.1 Researchers are not exactly sure what is causing this age decrease when it comes to puberty. With females, it has been found that being overweight tends to be associated with early development, but the same cannot be said for males without further research. Earlier male development may be due to a number of factors, including environmental factors, exposure to chemicals, changes in diet, less physical activity and other modern lifestyle changes.2 Herman-Giddens also explained that, whatever the cause, early puberty most likely indicates environmental problems that are unhealthy for children today. In her words, “I find it disturbing that boys and girls are developing so early now.”1 Herman-Giddens believes there should be a focus on helping young boys cope with earlier puberty. The psychological maturity and capacity for rational judgment of children does not develop as fast as their bodies now do, so it is important that they and their parents are helped to understand their development process.5
1. Interview with Marcia Herman-Giddens, P.A., Dr.PH. 02/01/13. 2. Herman-Giddens, M. E.; Steffes, J.; Harris, D.; Slora, E.; Hussey, M.; Dowshen, S. A.; Wasserman, R.; Serwint, J. R.; Smitherman, L.; Reiter, E. O. Pediatrics. 2012, 130, e1058-e1068. 3. Puberty — Changes for Males. http://www.pamf.org (accessed February 2nd, 2013). 4. Orchidometer — Prader. http:// www.espmodels.co.uk (accessed February 2nd, 2013). 5. Neighmond, P. Like Girls, Boys Are Entering Puberty Earlier. http://www. npr.org (accessed February 10th, 2013).
“NICKING” AWAY AT MULTIDRUGRESISTANT STAPH BY GAYATRI RATHOD
he methicillin-resistant Staphylococcus aureus (MRSA) superbug outbreak in 1968 had the world scrambling for vaccines and taking extra precautionary hygienic measures to avert crises in hospitals and schools. Since then, the bacteria have continued to evolve to resist several common drugs. According to the U.S. Centers for Disease Control and Prevention, infec-
Figure 1. The golden-yellow colonies of Staphylococcus aureus surrounded by cellular debris. Image courtesy of NAID/NIH.
tion rates have rapidly increased during the past decade. Although healthcareassociated infections are decreasing, it is unlikely that the risk of developing community MRSA is following the same trend.1 Staphylococcus aureus, known as Golden Staph for its round, golden colonies (Figure 1), is an environmental, multidrug-resistant microbe that is spread primarily through patient contact, food and respiratory droplets and becomes a problem when it breaches the immune system.2 Deaths from hospital-acquired bacterial infections total 100,000 every year in the United States — almost twice the number of cases of breast cancer — making multidrug-resistant Staph a significant clinical problem. Studies of S. aureus show that polyester, the main component of hospital curtains, has the ability to sustain it for almost three months.2 Vulnerability to the glycopeptide antibiotic vancomycin was once established for Staph, diffusing some of the tension that had evolved from this sudden scare. The superbug has advanced a few steps ahead of modern medicine since genetic change in bacteria occurs rapidly given relatively low generation
times. Vancomycin-resistant wild strains (VRSA) of the particularly dangerous MRSA were discovered in a 2002 dialysis patient in Michigan,3 breaking the final line of antibiotic defense. From 2002 to 2010, ten different VRSA strains were isolated, eight of which stemmed from the United States.4 The key to approaching a solution for keeping this resistance under control now lies beyond the path of antibiotics and in the deeper understand- Matthew Redinbo, Ph.D. ing of the transfer of resistance genes by conjugation (Figure 3). Matthew Redinbo, Ph.D., a professor in the UNC-Chapel Hill department of chemistry, investigates the molecular mechanisms involved in resistance transfer. The Redinbo lab studied the DNA movement from bacterium to bacterium by looking at the interaction of the nicking enzyme in S. aureus (NES). NES functions as a gatekeeper protein
Figure 2. Left: NES cuts or hydrolyzes one strand of DNA at a specific nicking site sequence to create a gap so that outside DNA can be inserted in the genome. Right: There are two solutions for stopping transformation: (i) elimination of the loops on the NES and (ii) blocking the restriction sites on the genome. Images courtesy Gayatri Rathod. and it helps the transfer of antibiotic resistance genes into new Staph hosts by starting and stopping gene transformation between plasmids (Figure 2, left). The enzyme cuts a stand of DNA, and proteins that associate with NES drive the movement of the DNA. Dr. Redinbo’s perspective on exploring the means behind this genetic transfer is simple. He states, “We’re reductionists. We try to look at things on the chemical level, an atomic level.”5 A molecular analysis of the crystal structure of NES revealed two hairpin loops in the protein grasping the DNA at a specific site, pinching a portion of the plasmid.6 This nicked strand of DNA now has the ability to enter a new bacterial host. This makes the concerned region of NES a potential target for elimination,
reducing the DNA transfer across bacteria. Dr. Redinbo mentions that there were “other regions of NES that look more attractive for selective inhibitory functions.” Therefore, more structures of the NES are being collected for analysis.
be used to block the groove from binding to NES, preventing interaction between the DNA and protein altogether (Figure 2, right). In addition, the triggering of a disruption between a protein and DNA can be difficult, and most of the studies have been conducted in vitro. Therefore, the molecules are not yet known to work in vivo (in living cells). More research is needed to find a solution to this complex, multi-asset problem.4 Nevertheless, it is well worth the effort. “We don’t have the same protection from antibiotics that we’ve been used to,” Dr. Redinbo remarks, “so we need to address that by gaining an understanding of how bacteria becomes resistant to drugs such as vancomycin.”6
THE KEY TO APPROACHING A SOLUTION FOR KEEPING ANTIBIOTIC RESISTANCE UNDER CONTROL NOW LIES BEYOND THE PATH OF ANTIBIOTICS. He and his team were able to obtain a photograph of NES bound to the bacterial plasmid from S. aureus, revealing a groove in the DNA that NES tends to target. Since the NES is specific to a particular groove in the DNA,6 molecules could
Figure 3. Resistance genes spread when bacteria undergo DNA conjugation, picking pieces from other bacteria and reproducing. Image courtesy of Gayatri Rathod.
1. MRSA Statistics. http://www.cdc. gov/mrsa/statistics/index.html (accessed February 5th, 2013). 2. Neely, A. N.; Maley, M. P. J. Clin. Microbiol. 2000, 38, 724–726. 3. Gould, I. M. Lancet Infect Dis. 2010, 12, 816–818. 4. Chang, S.; Sievert, D. M.; Hageman, J. C.; Boulton, M. L.; Tenover, F. C.; Downes, F. P.; Shah, S.; Rudrik, J. T.; Pupp, G. R.; Brown, W. J.; et al. N. Engl. J. Med. 2003, 348, 1342–1347. 5. Interview with Matthew Redinbo, Ph.D. 2/05/2013. 6. Edwards, J. S.; Betts, L.; Frazier, M. L.; Pollet, R. M.; Kwong, S. M.; Walton, W. G.; Ballentine III, W. K.; Huang, J. J.; Habibi, S.; Del Campo, M.; et al. PNAS. 2012, 110, 1-6.
Friend or Food? By Kelsey Ellis
n a competition for Earth’s laziest organism, you might initially be tempted to put your money on the Eastern oyster, or Crassostrea virginica. After all, baby oysters, called spat, do not swim but instead drift with the currents until they settle somewhere suitable for growth. Once there, they attach themselves to the substrate and begin to grow their shells. Oysters even let their food, phytoplankton and bits of detritus, come to them. They simply filter these particles out of the water as they float by. But there is more to these shells than meets the eye, so don’t place your bets just yet. A single live oyster — one rough, grey shell — has been shown to filter up to five liters of water per hour. At their historical maximum, the oyster population of the Chesapeake Bay is estimated to have been capable of filtering the entire volume of the Bay in about a week.1 An oyster reef is not just a pile of shell; it is also a bustling habitat within its environment (Figure 1). A variety of creatures, including crabs, worms and other shelled invertebrates, make their homes within reefs. Larger organisms such as fish travel to reefs to feed upon these smaller creatures. Joel Fodrie, Ph.D. and his colleagues at UNC-Chapel Hill’s Institute of Marine Sciences (IMS) in Morehead City, NC are researching the extent of these ecosystem services among others. Understanding oyster reefs is an interdisciplinary endeavor at IMS, where different researchers tackle facets of oyster reef function. Dr. Fodrie himself has focused on fish use of the reefs and the potential for carbon burial within them. To accomplish this, he has extensively studied reefs built in Middle Marsh, NC, 15 years ago by another researcher. “When you build an oyster reef, you’re basically putting out a landing strip for oyster [spat] to land on, and you’ve got natural settlement that seeds the reef,” explains Dr. Fodrie.2 Old oyster shell
is piled in the intertidal zone and oyster spat from natural reefs settle on that shell and begin growing (Figure 2). Using this method, the reefs become “a manipulation of nature in the field. You’re basically going in and creating habitat in a very controlled design.”2 Dr. Fodrie has looked at how fish — specifically red drum — utilize reefs grown in mudflat, seagrass and saltmarsh landscape settings.3 “We wanted to revisit the reefs built in Middle Marsh … and see how fish use those reefs,” says Dr. Fodrie.2 Using acoustic signaling methods that allow a tagged fish to be tracked throughout the marsh, Dr. Fodrie and his lab found that red drum preferred to forage near the reefs along the edge of the saltmarsh as opposed to the comparable buffet of prey items found within reefs isolated on broad mudflats.3 This, Dr. Fodrie posits, may be because Joel Fodrie, Ph.D. the fish are edge predators and, as such, are “not willing to venture out into a desert of sand to look for habitat patches … they need habitat connectivity.”2 People often think of oysters as a delicious food and sometimes view them as habitat for other organisms. But, until recently, there was little impetus to include reefs in the list of “blue carbon” sinks, which include mangroves, marshes and seagrass beds. Dr. Fodrie and other researchers at IMS have set out to add them to this important group. Blue carbon sinks are marine environments that are able to sequester atmospheric carbon dioxide, sometimes indirectly, and in doing so decrease the amount of available carbon dioxide in the atmo-
Carolina Scientific sphere.4 On a large enough scale, this process can contribute to mitigation of anthropogenic climate change. An oyster reef contains not one but two types of carbon: organic and inorganic. The inorganic carbon comprises the oyster shell itself, while the food particles filtered out of the water and digested by oysters are the organic carbon. The creation of shell underwater forms carbonic acid, which “is basically CO2 in the water.”2 Phytoplankton and other detritus contain organic carbon that has been recently formed from CO2 through photosynthesis and other processes. When oysters digest these particles and bury them in the sediment through expelling their remnants, they are working to sequester that carbon. “You’ve got the organic and inorganic carbon in a competition of rates — do you have more inorFigure 2. One of the experimental mudflat oyster reefs in ganic (source CO2) or more organic carbon (sink CO2)?” says 2 Middle Marsh, NC. Image courtesy of Dr. Joel Fodrie. Dr. Fodrie. IMS researchers have discovered that reef location and inundation time determine whether reefs act as net suggests it’s more valuable in the ocean, but there’s a lot of sources or sinks of carbon, with shallow subtidal reefs and detail to fill in there.”2 saltmarsh-fringing reefs acting as sinks while mudflat reefs Oyster reefs provide a multitude of benefits to huact as sources.4 Though mudflat reefs have the highest oysmans besides being delicious. But in the last century, reefs ter density, this same proliferation of shell have experienced a precipitous decline increases the CO2 they emit relative to due to our activities. The oysters of the other reefs. Marsh-fringing reefs are also Chesapeake Bay now take almost a year “transforming habitat that was too deep to filter the amount of water that once for saltmarsh plants to grow, and they’re took them a week, and estimates sugincreasing [sediment] deposition locally gest that upwards of 80 percent of oys- Dr. Joel Fodrie and basically raising the seafloor. And as ter populations worldwide have been that happens, you become more interwiped out.1, 5 The work of Dr. Fodrie and tidal; you get more environments in which saltmarshes can others at IMS is to quantitatively demonstrate how useful persist and do well. And marsh is also a carbon sink.”4 intact oyster reefs are to people who might think of them The dual nature of oyster reefs, existing both as indionly as lazy (and tasty) piles of shell. In the future, Dr. Fodrie vidual organisms and a collective habitat, means that they is interested in examining how the present-day 10-squareserve many functions within an ecosystem. “The common meter reefs in Middle Marsh differ in function from much thread between both the fish and the carbon is that we’re larger reefs. Building reefs back to historical levels would really interested in the services reefs provide us,” Dr. Fodrie be a monumental task, but we may find that it is in our own explains. A common practice is to quantify these services by best interest to attempt to do so. giving them dollar values according to how they benefit humans and “actually try to say, is an oyster more valuable on a plate or is it more valuable in the ocean? And most analysis References
“Is an oyster more valuable on a plate or in the ocean?”
1. Newell, R. I. E. Ecological Changes in Chesapeake Bay: Are they the result of overharvesting the Eastern oyster (Crassostrea virginica)? In Understanding the Estuary: Advances in Chesapeake Bay Research; Lynch, M. P., Krome, E. C., Eds.; Chesapeake Research Consortium Publication: Gloucester Point, 1988; Vol. 129, pp 536-546. 2. Interview with Frederick Joel Fodrie, Ph.D. 01/30/13. 3. Kenworthy, M. D., et al. Fine scale habitat utilization of red drum (Sciaenops ocellatus) in a structurally complex intertidal landscape. Presented at the 2012 Benthic Ecology Meeting. 4. Fodrie, F. J, Rodriguez, A. B, Grabowski, J. H, Lindquist, N. L, Peterson, C. H, Piehler, M. F, and P. L Rodriguez (in preparation) Coastal shellfish reefs as carbon sources and sinks on a blue carbon scale. 5. Beck, M. W., et al. Oyster Reefs at Risk and Recommendations for Conservation, Restoration, and Management. Bioscience 2001, 61, 107-117.
Figure 1. An Eastern oyster reef. Shell growth is dependent on many factors, including water depth, temperature and biotic factors. Image courtesy of Dr. Joel Fodrie.
Areas infested with Aedes mosquito
Areas with Aedes mosquito and dengue epidemic activity
Ninja of the Virus World By Jasmin Singh
he dengue virus (Figure 1) is pretty sneaky. Its treatment has eluded our grasp since 900 B.C., when the first known case emerged in ancient China.1 What was once a disease prevalent in five countries has become an epidemic for over 100. With four different serotypes and only one target, dengue continues to infect the human population. Having seen the disease affect her family and friends during epidemics in her homeland of Sri Lanka, Rukie de Alwis, a fifth-year graduate student at UNC-Chapel Hill, is working to change this by finding a cure. Dengue is a disease of the developing world, found mainly in the tropic
and subtropical regions. Approximately 2.5 billion people, 40 percent of the world’s population, live in areas where there is risk of contracting the virus, according to the Centers for Disease Control and Prevention.2 The World Health Organization estimates that up to 100 million infections occur each year, with 22,000 deaths typically among children.2 Dengue is part of the virus family Flaviviridae (Figure 2) and consists of four serotypes, different versions of the disease named DENV 1 to 4.1 Viruses in this family are all transmitted through mosquitos, mainly Aedes aegypti and Aedes albopictus. These vectors carry all four serotypes and have spread all
over the world through globalization. “Since the mosquitoes have adapted to our daily lives, dengue is becoming an even bigger threat,” de Alwis said.1 Rukie de Alwis, a Like many fifth-year graduate viruses, dengue student in the de takes over the Silva lab at UNCmachinery of the Chapel Hill. cell (Figure 3). The virus attaches to the surface of the cell and binds to specific proteins with re-
Figure 1. The surface of exposed viral proteins assemble in a complex in a repeated pattern to form the dengue virion. Image courtesy of Rukie de Alwis. ceptors specific for receptor-mediated sponse,” de Alwis said.1 those that bind to more than one seroendocytosis, a process where cells inDe Alwis’ first breakthrough in- type. The fraction of protective antibodternalize molecules through the inward volved the characterization of the hu- ies produced compared to weakly neubudding of the plasma membrane. It man antibody response to dengue. tralizing those that offer no protection then uses various organelles to trans- “We urgently need to understand how was very low.1 That is when de Alwis delate its proteins, replicate its cided to characterize the viral genome and assemble more epitopes targeted by the provirus molecules. tective human antibodies. Since there is no The lab conducted vaccine, dengue is fought a study to characterize an- Rukie de Alwis through the body’s immune tibodies in the human imsystem (Figure 4). After the mune serum — the proteinvirus enters the body, the immune sys- the human body protects itself against rich liquid used to provide immunity to tem senses the threat and responds by dengue during a natural infection,” says a pathogen responsible for neutralizing creating antibodies. The major target of de Alwis.1 She found that after a natu- the virus.4 Samples were collected from these antibodies is the envelope pro- ral infection, humans produce a large eight volunteers who were exposed tein, which is responsible for viral at- amount of cross-reactive antibodies, to DENV2 or DENV3 infections. The retachment to host cells and the fusion of viral and host cell membranes. But the types of antibodies and where on the virus they bind are still not known, making the search for a vaccine even harder. The antibody response to dengue has been studied in mice and some primates, though de Alwis says that the experiments were not done under optimal conditions.1 Researchers have been focused on epitopes, regions on the antigen where an antibody attaches itself. Experiments found that the epitopes that the antibodies bind to in mice and primates differ from those in humans. The protection mechanism in humans does not use antibodies that target this region. This explained why mice and primates never got sick, yet humans do. “This left a gigantic hole in our under- Figure 2. The flavivirus family tree. The same family of mosquito, the Aedes, standing of the neutralizing epitopes carries Dengue, West Nile and Yellow Fever. The diseases can be linked back to a targeted by the human antibody re- common ancestor. Image courtesy of Rukie de Alwis.
“We urgently need to understand how the human body protects itself against dengue during a natural infection.”
sults from seven individuals showed that DENV-specific human antibodies consisted of distinct populations of serotypes. Their results found what could be the epitope that the human immune system targets when cells become infected.4 One major problem with dengue is that its symptoms, such as fever, joint pain and muscle aches, resemble those of other common illnesses like influenza. Such similarities make diagnosing dengue difficult for doctors because many developing countries do not have the proper equipment to test for the virus. This long waiting period between detection and diagnosis allows the virus to further infect the body, leading to a drop in blood pressure, platelet count and vascular leakage. If these symptoms are left unnoticed, the patient can die.3 Being infected with one serotype does not protect against the others. This is a trait seen in many diseases, including influenza. If a person becomes infected with DENV1, their body would create the necessary antibodies to fight it off. But these antibodies would not protect them from the other three serotypes. “It’s a pretty sneaky virus. If we were to make a vaccine, it must be able to fight off all four serotypes,” de Alwis said.1 The leading vaccine candidate against dengue from Sanofi Pasteur failed in phase II clinical trials in September of last year. The major setback was that the vaccine failed to protect against DENV 2 and was only 30 percent effec-
Figure 3. Once the virus has entered the blood stream, it enters cells and begins to take over its organelles. The virus copies its RNA and begins to replicate within the cytosol of the host cell. The virus itself is assembled on and buds off of the endoplasmic reticulum. Image courtesy of Rukie de Alwis. tive in the trial. Though the vaccine did protect for the other three serotypes, using it would increase the population’s chances of contracting DENV2.5 “If you make a vaccine that does not protect for all four, you are making the population more susceptible to disease,” de Alwis said.1 Though the costs of research and vaccine creation are high, de Alwis wishes to create an easily accessible vac-
cine for dengue that would save those in Sri Lanka and in other developing countries from an otherwise incurable disease. “We need to find a way to make a cost-effective vaccine that is affordable for people in developing countries,” de Alwis said.1 “If we can do that, then I have reached my goal.”
Figure 4. The dengue virus can use host antibodies and other receptors to sneak into the host cell and establish a productive infection. Image courtesy of Rukie de Alwis.
1. Interview with Rukie de Alwis. 02/01/13. 2. Centers for Disease Control and Prevention: Dengue Epidemiology. http://www.cdc.gov/dengue/epidemiology/index.html (accessed February 2nd, 2013). 3. Centers for Disease Control and Prevention: Dengue: Frequently Asked Questions. http://www.cdc. gov/dengue/fAQFacts/index.html (accessed February 2nd, 2013). 4. de Alwis, R.; Beltramello, M.; Messer, W. B.; Sukupolvi-Petty, S.; Wahala, W. M.; Kraus, A.; Olivarez, N. P.; Pham, Q.; Brien, J. D.; Tsai, W. Y.; et al. Plos. Neglect. Trop. D. 2011, 5, 1-8. 5. Seppa, N. Sci News. 2012, 182(8). 18.
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Uncovering the Genome’s Insulin Instructions By Sam Resnick
he U.S. Centers for Disease Control (CDC) designate type 2 and, to a lesser extent, type 1 diabetes as growing major health issues in the United States.1 Current trend analysis predicts that in as few as forty years, over one-third of Americans will be diagnosed with type 2 diabetes.1 Diabetes receives a plethora of attention from the media because of its association with poor diet and lack of exercise. It is hard to go a day without hearing how America’s image is becoming more tied to obesity and laziness. While nutrition and activity are significant factors in dictating who becomes affected by type 2 diabetes, genes also play a role, and numerous genetic factors still remain undiscovered. Diabetes is characterized by high blood glucose levels.1 In type 1 diabetes, immune cells attack the insulin-producing cells of the pancreas, rendering them unable to produce a sufficient amount of insulin to aid the uptake of glucose from the blood. On the other hand, in type 2 diabetes, both insulin production and glucose uptake are affected. More genetic analysis is needed to understand the disease. Karen Mohlke, Ph.D., a researcher in the UNC-Chapel Hill department of genetics, is taking advantage of newly available technology to understand the
Figure 1. An Illumina HumanExome BeadChip used in the study. Image courtesy of Illumina.
genetic basis of type 2 diabetes and other diseases. In a study that is the first of its kind, Dr. Mohlke, with collaborators from Finland and across the United States, was able to examine thousands of genetic variants in the proteincoding component of DNA, the Karen Mohlke, exome. These Ph.D. genetic variants are specific sequence changes in DNA, many of which are present in less than five percent of the population. After the completion of the Human Genome Project in 2001, a rush to understand the contents of the genome ensued. Soon after, researchers began to use genomewide association studies to understand the effects of variants in the genome.2 More recently, researchers have been sequencing exomes of study participants to identify new variants that may lead to disease. Last year, researchers compiled their findings of single-nucleotide variants that could potentially cause a change in the amino acid sequence of a protein. Many of these variants were compiled on a chip, the Illumina HumanExome BeadChip. The BeadChip can be applied to a sample of human DNA to determine which nucleotide is present at over 200,000 variant sites. A fluorescent signal indicates which nucleotide variant is present (Figure 1). In a study of almost 10,000 Finnish males, Dr. Mohlke examined the presence of these uncommon genetic variants in relation to a multitude of characteristics. Dr. Markku Laakso, a Finnish physician and epidemiologist, surveyed the subjects of the study and compiled hundreds of traits ranging
from blood pressure to the presence of certain insulin precursors in the blood. Proinsulin, the specific precursor to insulin measured in this study, is an indicator of the efficiency of a person’s insulinproducing machinery. “High proinsulin levels in the blood are associated with unhealthy islet beta cells,” says Dr. Mohlke in reference to the insulin-producing cells of the pancreas. Through statistical evaluation that compared the presence of genetic variants to varying levels of proinsulin in the blood, Dr. Mohlke and her team were able to identify genetic variants that appear to have an effect on insulin production. Not only did they identify new protein-coding variants in two genes previously believed to affect insulin production, they also found “variants in two genes that we did not previously know were involved with insulin processing.”3 The significance of this experiment goes beyond the discovery of genes that affect insulin production. The new information regarding genetic influences on insulin processing may help explain why people get diabetes. With this information, doctors may someday be able to predict who is more likely to get diabetes by examining their patients’ genomes. However, an additional victory in this project is showing that the use of genome-wide DNA analysis is an effective way to study the genetic basis of disease. “We believe that this experiment proves the utility of exome chip studies and sets the stage for further use of this technology,” says Dr. Mohlke.3
1. Centers for Disease Control and Prevention: Diabetes. http://www.cdc. gov/diabetes/ (accessed February 2nd, 2013). 2. Visscher, P.; Brown, M. A.; McCarthy, M. I.; Yang, J. Am. J. Hum. Genet. 2012, 90, 7-24. 3. Interview with Karen Mohlke, Ph.D. 1/24/2013. 4. Huyghe, J. R.; Jackson, A. U.; Fogarty, M. P.; Buchkovich, M. L.; Stančáková, A.; Stringham, H. M.; Sim, X.; Yang, L.; Fuchsberger, C.; Cederberg, H.; et al. Nat Genet. 2013, 45, 197-201.
Nature’s Not-So-Perfect Copycats:
The puzzle of imperfect mimicry By Vamsi Kolluru
Imitation is known as the sincerest form of flattery, but in the animal kingdom it is also a useful tool for survival. A mimic is a species that resembles another organism. Many species feature what are known as aposematic signals (such as bright coloration, spines or other displays) that warn potential predators to keep away unless they want to risk injury or death. When an animal adopts the aposematic signals of another animal to deter predators, it is classified as Batesian mimicry. The eastern coral snake is one animal that acts as a model for several mimicking organisms. This snake is very venomous while one of its mimics, the scarlet kingsnake, is not (Figure 1).3 This particular mimic-model relationship is the subject of a few rhymes to help people distinguish the two. “If red touches yellow, it can kill a fellow; if red touches black, it is a friend of Jack” is one of them.3, 4 This simple rhyme raises a question: Why has the scarlet kingsnake not evolved to exactly match the coloration of the eastern coral snake? David Kikuchi, a graduate student in David Pfennig, Ph.D.’s lab at UNC-Chapel Hill, is trying to answer that question. The coral snake and the scarlet kingsnake both display red, yellow and black rings, but the order of the rings is different. Some predators should therefore be able to make the distinc-
tion between the two species, and this pressure should have resulted in the evolution of the coral snake color pattern. Kikuchi says, “I thought that some kind of developmental constraint in combination with natural selection was preventing the mimic from becoming better.” Kikuchi thought that the scarlet kingsnake was in a better position than the alternate physical forms that could be selected for but was less fit than an ideal mimic. In this case fitness refers to the animal’s chance of surviving and producing offspring based on its likelihood of being attacked by a predator. Essentially the intermediate steps between scarlet kingsnake and coral snake coloration are likely to be less fit.3, 5 Kikuchi also postulated that predators either could not distinguish ring order (only color) or it was simply not worth their time to do so. Given the highly venom-
ous nature of the coral snake, it would be very risky for a predator to sit in front of the snake and determine whether its prey might be a harmless mimic.5 The David Kikuchi, a limited cognition graduate student of predators is in the Pfennig lab. also hypothesized to allow imperfect mimics to exist.3 To test this hypothesis Kikuchi designed an experiment where polymer clay replicas of the snakes were scattered throughout southeastern North Carolina. There were three types of replicas: a perfect mimic (looking like the coral snake), a good mimic (looking like the scarlet kingsnake) and a poor mimic
Carolina Scientific (serving as a control) (Figure 2, left). The poor mimic had the wrong amount of red and black, which has been shown to be less fit than the kingsnake’s coloring.5 The area selected for the experiment was the “sympatry-allopatry boundary.” This is essentially an ecological boundary between an area containing mainly scarlet kingsnakes (allopatry) and an area containing both coral and kingsnakes (sympatry). In this area the coral snakes are less abundant, and predators more likely to target poor mimics. Where the coral snakes are more abundant, it would be too risky to target a poor mimic, and they are avoided. Eighteen different sites were selected to place the replicas. At each site ten “triads” were placed, with each triad containing a perfect, good and poor mimic. The clay replicas were examined to determine whether they had been attacked. Significant damage to the replica (breaking, tearing, bite marks, etc.) or a missing model was recorded as predation. Good mimics were expected to be attacked more often than the perfect mimic, and the poor more than the good mimic.3 The results were not as expected — the good mimic and perfect mimic were attacked with equal frequency, while the poor mimic was attacked significantly more often (Figure 2, right). “I was really, really surprised by that … predators have lived with these snakes for thousands of years, maybe millions of years, and have never taken the time
Figure 1. The coloring of the non-venomous scarlet kingsnake (left) mimics that of the venomous coral snake (right). Images courtesy of David Kikuchi and J & T Reptiles and Exotics [CC BY 2.0]. to look at a snake and see that this one is different from this one,” says Kikuchi.5 One possible explanation for this result is that predators have developed a generalized response to reduce the risk of running into a venomous coral snake. This gives mimics some room for error.3 The evidence from this study strongly supports the hypothesis that mimics are taking advantage of predators’ limited cognition. This is the more likely explanation, as the predators where the experiment was conducted were likely able to distinguish mimics of different quality. 3 Mimicry is a vivid example of complex adaptations that can arise through natural selection. Imperfect mimicry highlights the important fact that evolution does not necessarily result in perfection, and as long as a trait
is not being selected against, there is no reason for the species to evolve further.5 Further research into this subject can shed more light on how such complex yet imperfect traits can arise.
1. Schnur, D. Animal Sciences. 2002. Vol. 3. 121-123. 2. Pagel, M. Mimicry. In Encyclopedia of Evolution. Oxford University Press, 2002. 3. Kikuchi, D. W.; Pfennig, D. W. Am. Nat. 2010, 176, 830-834. 4. Herpetology: Eastern Coral Snake. http://www.flmnh.ufl.edu/herpetology/fl-guide/micrurusffulvius.htm (accessed February 1st, 2013). 5. Interview with David Kikuchi. 1/31/2013.
Figure 2. Left: The three types of snake replicas used in the field experiment. Right: The frequencies of attack by predators for perfect, good, and poor mimics. Images courtesy of David Kikuchi.
navigating the BRAIN
Uncovering the neural basis of psychiatric disorders BY ERIN MOORE
he human brain is as intriguing as it is mysterious. For decades, scientists have attempted to understand the complex neural processes that underlie the pathological states observed in disorders such as autism spectrum disorder, schizophrenia and Alzheimer’s; but given the intricate map of signaling pathways comprising the billions of neuron connections in the brain, defining the specific neural mechanisms responsible for abnormalities in a psychiatric disorder is no easy feat. Patricia Maness, Ph.D. is up for the challenge, however. Dr. Maness, professor in the UNC-Chapel Hill School of Medicine’s department of biochemistry and the UNC Neuroscience Center, uses an interdisciplinary approach to examine the molecular underpinnings of neurodevelopmental disorders. Specifically, the Maness lab studies the mechanisms of neural recognition molecules expressed on the surface of developing neurons; these molecules play an important role in migration of neural stem cells and guidance of growth cones
Figure 1. The Maness lab has generated mice deficient in NrCAM to investigate the biological mechanisms underlying neurodevelopmental disorders such as autism. Image courtesy of Maggie Bartlett, NHGRI, public domain.
(Figure 3). As an axon conducts electrical impulses to send away from the cell body of a neuron, growth cones composed of actin filaments aid the axon to travel on appropriate pathways to specific cortical regions. Neuron-Glial-Related Cell Adhesion Molecule (NrCAM) plays an important role in growth cone guidance, and exploring its functions has been the subject of Patricia Maness, Ph.D. much of the Maness lab’s recent research. NrCAM is encoded by one of about 200 genes implicated as risk factors for autism spectrum disorder, a syndrome of neural development characterized by deficits in social behavior and cognition. While research suggests that autism arises from disconnections in cell-to-cell signaling that occurs between synapses and a significant genetic etiology of the disorder has been identified, the neural basis for autism remains poorly understood. Since NrCAM mutations have been observed at the autism “hot spot,” chromosome 7q31, investigating NrCAM function can lend insight into the elusive neural circuitry abnormalities associated with the disorder.1 To model loss of NrCAM function both at the behavioral and biochemical level, the Maness lab has created NrCAM “null” mice in which the gene encoding NrCAM is suppressed. These mice undergo a series of cognitive and social evaluations to compare the phenotype associated with NrCAM deletion to that observed in autism. Behavioral tests of sociability, for example, can model the reduced preference for social proximity observed in autistic children by giving mice the choice to spend their time with a “stranger mouse” or a novel object. The Morris water maze, which tests a mouse’s ability to locate an “escape platform” in a large circular pool, assesses cognitive and learning ability. Such evaluations ultimately showed that NrCAM null mice exhibited decreased sociability and reversal
Figure 2. Left: Increased spine density in mice deficient in NrCAM compared to wild type (WT). Image courtesy of Dr. Patricia Maness. Right: Comparison of spine morphogenesis over the lifetimes in normal subject, autism spectrum disorder, schizophrenia and Alzheimerâ€™s. Image reprinted with permission from Macmillan Publishers Ltd. learning as well as hypersensitivity to sensory stimuli.1 These behavioral studies provided evidence that the NrCAM domain is deficient in autism. But what happens at the molecular level causing autism-related cognitive and social abnormalities? To find the answers, Dr. Maness delved further into examining NrCAM function. A major biological role for NrCAM that the Maness lab has found relates to axon growth cone guidance. When NrCAM functions normally, for example, a somatosensory axon is directed to the somatosensory cortex, thanks in large part to the NrCAM signaling and interactions with proteins known as semaphorins, neuropilins and plexins. In NrCAM null mice, however, motor and somatosensory axons have been shown to misproject to the visual cortex, resulting in mice with visual impairments.2 Since Semaphorin-3F is known to direct axons in these cortical regions, these results enabled the Maness group to propose a mechanism by which NrCAM induces Sema3F axon guidance. Axon guidance is not the end Figure 3. Fluorescently labeled growth of the NrCAM and cones extending from an axon. Image Sema3F story. The from NIH Publication No. 97-4038, Maness group has public domain. also recently found
that NrCAM-null mice have increased spine density and as such NrCAM may play a role in regulating spine formation (Figure 2 left). Spines are small protrusions on the branched projections of neurons that form excitatory connections (synapses) allowing neurons to communicate. The postsynaptic density (PSD), an electron-dense structure containing receptors, organelles and signaling systems associated with synaptic transmission, lies at the distal tip of the spine head. Increased spine density has been proposed to account for the over-connectivity of local neural circuits observed in autism; moreover, elevated spine density has been observed in Fragile X syndrome while reduced spine density has been associated with Alzheimerâ€™s disease and schizophrenia (Figure 2, right).3 As NrCAM has already been shown to mediate Sema3F-induced axon guidance, the Maness lab is now exploring a function for NrCAM mediation of Sema3F involving both axon directing and spine retraction. To investigate this mechanism, the Maness group will analyze fluorescently labeled neurons of NrCAM mutants at early stages of neural development in mouse embryos. The lab can then quantitatively compare the spines of neurons from NrCAM null and wild-type genotypes. The next step is to treat the neurons with Sema3F protein and observe the effect on spine formation. Ultimately, Dr. Maness hopes to use the findings of NrCAM function to conduct future drug, environmental intervention, or behavioral studies relevant to autism.
Increased spine density has been proposed to account for the over-connectivity of local neural circuits observed in autism.
1. Interview with Patricia Maness, Ph.D. 1/14/13. 2. Demyanenko, G.P.; Riday, T.T.; Tran, T.S.; Dalal, J.; Darnell, E.P.; Brennaman, L.H.; Sakurai, T.; Grumet, M.; Philpot, B.D.; Maness, P.F. J Neurosci. 2011, 31, 1545-1558. 3. Penzes, P.; Cahill, M. E.; Jones, K. A.; VanLeeuwen, J. E.; Woolfrey, K. M. Nature neuroscience, 2011, 14(3), 285-293.
One size may not fit all when it comes to
Fluoride and Genes By Abby Becherer
ost people are aware that the addition of fluoride to our toothpaste, oral rinses and tap water works to prevent dental cavities, also known as dental caries. In fact, fluoridation of drinking water to prevent caries is considered one of the ten most important public health achievements of the 20th century, according to the U.S. Centers for Disease Control.1 However, most of us are unaware of the fact that getting the right amount of fluoride can be a balancing act, with deficient and excess fluoride both affecting our bodies adversely. What’s more, the appropriate amount of fluoride can be much more individualized than we might imagine. The research of Eric Everett, Ph.D., a professor in the department of pediatric dentistry and member of the Carolina Center for Genome Sciences at UNC-Chapel Hill, offers insight into how one’s genetic background influences the effects of fluoride in the body.2 While fluoride in drinking water at concentrations between 0.7 and 1.2 parts per million (equivalent to milligrams per liter) has a demonstrated positive effect on oral health by preventing caries, research also shows that fluoride concentrations between 2 and 4 ppm have the potential for adverse effects on teeth and bones.3 One condition that results from the intake of too much fluoride is dental fluorosis, a primary focus of Dr. Everett and his colleagues.2 As Dr. Everett explains, “Dental fluorosis is a common condition in humans, caused by excessive exposure to fluoride while our teeth are still de-
veloping in our gums.”2 Mild fluorosis has an unfavorable cosmetic effect, resulting in opaque white flecks on the surface of teeth. Severe fluorosis, however, is characterized by dark brown stains and pitted enamel. Unsurprisingly, the damage to enamel in severe dental fluorosis compromises the tooth’s structural integrity and the ability of enamel to protect the dentin, the bone-like component of teeth located below Eric T. Everett, Ph.D. the enamel (Figure 2).2, 3 Consider a case study of a village on Mt. Kilimanjaro where, despite similar diets that exposed them to an abnormally high amount of fluoride in the soil, dental fluorosis among the villagers ranged from mild to severe. This mysterious situation led Dr. Everett and his colleagues at the Indiana University School of Dentistry to carry out a study that compared dental fluorosis susceptibility among 12 inbred mouse strains.2 Their findings, published in 2002, demonstrated varied susceptibility and resistance to dental fluorosis among these different strains, providing compelling evidence that genetic background plays an important role in the development of dental fluorosis.4 Today, Dr. Everett and his team at the UNC School of Dentistry are closing in on the specific genes that are associated with dental fluorosis susceptibility and resistance. In humans, the window of opportunity to study fluorosis is limited because the formation of enamel by the cells known as ameloblasts occurs only once in our lifetime — during tooth development in childhood. Mice, on the other hand, are a perfect model to study dental fluorosis because, unlike humans, their enamel is continually produced as their incisor teeth are worn down.2 Ultimately, Dr. Everett and his colleagues are seeking to identify the genes responsible for susceptibility to fluorosis in mice, as these would be good candidate genes to study in humans. Dr. Everett’s lab uses traditional genetic approaches to map genes responsible for varying susceptibility to dental fluorosis. One strategy is to perform a two-generation cross
Fluoride treatments may need to be tailored to individuals rather than taking a one-size-fits-all approach.
Figure 1. Fluoride in tooth paste and tap water plays an important role in preventing dental cavities. Image courtesy of Thegreenj [CC BY-SA 3.0].
Parent 1 Fluoride-resistant strain
Parent 2 Fluoride-susceptible strain
Genetically identical hybrid offspring
Figure 3. A two-generation cross can be used to map fluorosis susceptibility and resistance genes. Mice in the second generation of offspring each have a unique combination of genes that can be “mapped” back to the original strains (Parents 1 and 2). These mice are then treated with fluoridated water and exhibit varying degrees of dental fluorosis. Using this information, along with the known genetic background of the mice, researchers can narrow in on the genes associated with dental fluorosis susceptibility and resistance. Image by Keith Funkhouser. between various inbred strains of mice and treat the offspring of the cross with fluoridated drinking water (Figure 3). “Because each strain has a unique collection of [genetic] markers, we can identify which alleles came from which original strain. And with large numbers of mice — several hundred — we can then begin to identify [important] places in the genome,” he explains. To date, Dr. Everett and his colleagues have narrowed their search down to two regions in mice on chromosomes 2 and 11. In the words of Dr. Everett, “It’s still a bit of work to dissect it out, but I think we’re getting pretty close.”2
The Everett lab is also studying the association between genetic background and fluoride’s effect on the cells that remove bone tissue, known as osteoclasts, as well as the interaction between fluoride and the parathyroid gland. The purpose of these projects, like their work on dental fluorosis, is to better understand the actions of fluoride in our bodies and how genetics affect the end result. Ultimately, this knowledge could be used to optimize the amount of fluoride in toothpaste, drinking water and food for people of different genetic backgrounds.2 In other words, fluoride treatments may need to be tailored to individuals rather than taking a one-size-fitsall approach. Fortunately, Dr. Everett, his colleagues and his collaborators have made enormous progress in recent years and are optimistic about our future understanding of the relationship between fluoride and genetic background.
Figure 2. Dentin is the bone-like component of teeth below the enamel. Image by Studio Dentaire.
1. Centers for Disease Control. MMWR Mortal. Wkly. Rep. 1999, 48, 241-243. 2. Interview with Eric T. Everett, Ph.D. 1/29/2013. 3. Committee on Fluoride in Drinking Water, National Research Council. Summary. In Fluoride in Drinking Water: A Scientific Review of EPA’s Standards; Butler, C., Ed.; National Academies Press: Washington, D.C. 2006; pp. 1-12. 4. Everett, E. T.; McHenry, M. A .K.; Reynolds, N.; Eggertsson, H.; Sullivan, J.; Kantmann, C.; Martinez-Mier, E. A.; Warrick, J. M.; Stookey, G. K. J. Dent. Res. 2002, 81(11), 794-798. 5. Everett, E. T. J. Dent. Res. 2011, 90(5), 552-560.
Your Pocket Money’s Intere$t in politic$ By Luciana Giorgio
Answering a few questions could change your perception of your economic standing and your political views at the same time.
group of social psychology researchers at UNC-Chapel Hill utilized an online sample of participants, supplied by Amazon.com, to understand what factors affect people’s political opinions. Two fourth-year doctoral students, Kristjen B. Lundberg and Jazmin L. Brown-Iannuzzi, guided by B. Keith Payne, Ph.D., are researching how perceptions of socioeconomic status influence people’s views on redistributive policies. Redistributive policies include programs in which the government taxes individuals from one socioeconomic status to help people of a lower socioeconomic status.1 Recent examples of these policies are Medicare and Medicaid. “It is natural for individuals to compare themselves to others,” says Brown-Iannuzzi.2 Using people’s natural instinct for self-comparison, they observed the power of perception of economic status over attitudes toward economic policies pertaining to inequality. For both studies, Lundberg and Brown-Iannuzzi hypothesized that “one’s personal economic status would influence one’s views of what constitutes as a ‘fair’ distribution of resources across all individuals.”3 Both Lundberg and Brown-Iannuzzi have previous experience with researching racial inequality and its effects on political opinions. From the idea that someone’s social status will influence his or her everyday decisions, Lundberg and Brown-Iannuzzi created two separate surveys that temporarily shifted the way the participants perceived their socioeconomic status. One study focused on a simulated situation and the other on a real-world situation. To reach a large and diverse sample of participants, these researchers distributed
their studies through the program Mechanical Turk (MTurk) on Amazon.com. MTurk allows Amazon.com users to volunteer to take surveys in exchange for monetary credit in their Amazon.com accounts. The first survey was based on an inKristjen Lundberg and Jazmin vestment game modBrown-Iannuzzi, doctoral students eled after real stock in the Payne lab. prices. Participants were given forty cents to invest in stocks from the list provided.3 Each stock had information that would allow the participants to feel as if they were making a real investment, which “was the challenging part,” says Lundberg.1 Then, participants were randomly assigned to either gain or lose money regardless of the investments they had made.3 If the participant gained money, he or she would be taxed for 20 percent of his or her earnings to counterbalance the money lost by others. If the participant lost money, he or she would be credited with 25 percent of his or her earnings. After the survey was over, the participants were asked whether they would change the redistribution rules of the game, meaning would they change the percentages given
Figure 1. Left: This graph demonstrates the support provided for a change in the redistribution policy of future investments in Study 1. People who gained more money during the game were less supportive of an increase in redistribution than those who lost money during the game. Right: This graph demonstrates the support provided for a change in the redistribution policy due to a change in perception of socioeconomic status in Study 2. Participants with higher subjective socioeconomic status were less supportive of redistribution than those with lower subjective socioeconomic status. Images courtesy of Kristjen Lundberg and Jazmin Brown-Iannuzzi. and taken away from the participants. The results of the study ferent socioeconomic classes can be reached. Brown-Iannuzzi showed that people who gained money in the study were less added, “This research highlights that the perception of sociosupportive of the concept of redistribution (Figure 1). economic status is not a static label,” as most people believe it The second study increased the generalizability of the to be.2 She went on to explain that right now the United States effect by creating a more real-world situation.3 Participants is based on a meritocratic philosophy (a belief that advancewere prompted to take a survey ment is reached through achieveon their spending habits. At the ment and ability), which stigmatizes end of the survey, the participants people with lower socioeconomic were told they either had more or status as incapable because they less monetary resources than their have not been able break through peers. Then participants were asked their socioeconomic class. Research whether they would support redissuch as this could develop a new, tributive policies. Those participants more flexible philosophy. Because - Kristjen Lundberg who were told they had greater the perception of socioeconomic monetary resources than their peers status can be manipulated, rather were less supportive of the policies than those who were told than considering socioeconomic status to have inherent disthey had fewer resources. positions, a more accurate approach would consider socioAs a result of this study, Lundberg and Brown-Iannuzzi economic class as a situation that changes with context. Unconcluded that a temporary manipulation in the perception derstanding the fluidity of perception will allow researchers of your socioeconomic status can influence your attitudes to- and policy makers to understand how individuals of different wards redistributive policies. “This is a very salient topic. After socioeconomic classes make decisions. the economic downturn, people are still struggling to find jobs while coping with being in a new socioeconomic status,” says Brown-Iannuzzi.2 Lundberg adds, “Given all the debate recently about proposed changes to taxation and welfare policies, understanding what motivates people’s support for or rejec- References tion of a policy is important.”2 Lundberg and Brown-Iannuzzi 1. Huntington, Eldridge. Public Policy. http://som.csudh. also say their research has only just begun. They have more edu/depts/adjunct/ehuntington/PUB304/CHAPT_4_pubplans to develop these studies further and keep researching lic_policy.htm (accessed February 14th, 2013). socioeconomic inequality and its effects on people’s attitudes 2. Interview with Kristjen Lundberg and Jazmin Brownand decisions. Iannuzzi, fourth-year doctoral students. 1/31/13. “We want to foster understanding. If you understand 3. Lundberg, K. B.; Brown-Iannuzzi, J. L.; Payne, B. K. (2013, why a person takes a particular stand on a political issue, it January). Attitudes toward income inequality as motivated may be easier to talk to each other and ultimately arrive at social cognition: The influence of economic outcomes on better solutions,” said Lundberg.2 Because socioeconomic support for redistribution. Poster presented at the SPSP status can be shifted so easily, an understanding between dif- Political Psychology Pre-Conference, New Orleans, LA.
“...understanding what motivates people’s support for or rejection of a policy is important.”
The Fat That Burns Fat
Using Quantum Physics in the Fight Against Obesity By Carlos Floyd
n mammals, not all fat is created equal. Brown adipose tissue (BAT) has an important and unique role in the metabolism of mammals, and the scientific community has only begun to investigate its properties within the past hundred years. White adipose tissue (WAT) and BAT differ in several respects, including the shapes of the nuclei and mitochondria. BAT has more mitochondria and fewer lipid stores than WAT (Figure 1). One of the most compelling aspects of this tissue is its function in non-shivering thermogenesis, which is the production of body heat that does not involve shivering. This attribute has won mammals, being endotherms, the evolutionary advantages of being able to survive the cold associated with nighttime and hibernal sleeps, as well as the impaired thermoregulatory ability that mammalian newborns temporarily have due to their immature skin.1 BAT accomplishes this by consuming glucose and other molecular energy sources (even the lipid droplets within the tissue itself ). In this way, BAT is a sort of fat that actually burns fat in the process of generating heat. Thermogenesis is accomplished in the mitochondria of BAT cells with the help of UCP1, a protein that is uniquely associated with BAT and helps to convert molecular energy
sources into heat as opposed to ATP, which is the normal product in the mitochondria of other tissues. The detection of BAT in humans and other animals has been a tricky endeavor, though, owing mainly to inadequate imaging techniques combined with the fickle nature of BAT itself. For example, previous studies on how common BAT is in humans have retrospecRosa Tamara Branca, tively analyzed hospitalsâ€™ PET scans Ph.D. of patients to look at areas of glucose uptake, which indicates the presence of BAT. Such efforts have indeed found symmetrically placed deposits of BAT in the neck and chest region in some subjects. However, trouble arises because BAT only takes up glucose when it is actively undergoing thermogenesis. Activation of thermogenesis is controlled by the sympathetic nervous system in response to being in an environment that is cold, but not so cold that shivering would be necessary, and hospital conditions do not typi-
Figure 1. A side-by-side comparison of BAT and WAT. BAT, on the left, consists of much more than just lipid droplets, as WAT does. The increased functionality of BAT in comparison to WAT reflects this. Images courtesy of Dr. Branca.
Figure 2. Left: The BAT of a lean subject, showing the relative amount of cytoplasm and other cell parts to the lipid deposits, which are the large white droplets. Right: The BAT of obese subjects, showing the large prevalence of lipid droplets compared to other parts of the tissue matrix — a feature that has also been revealed by NMR spectroscopy of such subjects. Images courtesy of Dr. Branca. cally fall into this range. In dedicated studies of prevalence, 16° C and light clothing is the combination used to stimulate BAT. The retrospective PET studies then grossly underestimated prevalence at two to seven percent, where more dedicated studies of different populations have revealed that 30 to 100 percent of a sampling of humans have BAT.2 Other techniques such as infrared thermography of the skin and MRI have been used to detect the elusive BAT, but with varying and generally poor results. Clearly, the development of a more reliable and informative technique is called for in investigating BAT. This is the goal of the research group overseen by Rosa Tamara Branca, Ph.D. who uses a novel approach to image BAT that also reveals important properties about its capacity for thermogenesis. The technique utilizes several properties of the stable Xenon isotope 129Xe in its gas phase. First, it is possible to cause 129Xe to be in a state of magnetic hyperpolarization by shining circularly polarized light at it. To say it is hyperpolarized just means that it is polarized to a degree more than it normally is, making the gas a candidate for detection by magnetic resonance techniques. The Branca lab uses both MRI and NMR spectroscopy in their studies of BAT. The second property of 129 Xe that makes it ideal for such experiments is its high solubility in fatty tissue; it is actually 10 times more soluble in fatty tissues than in lean muscle and blood. Additionally, BAT is highly vascularized, meaning that many blood vessels run through it, because of the increased demand for oxygen durFigure 3. 129Xe gas dissolved in ing thermogenesis and BAT deposits in an obese mouse the need to quickly reobtained by MRI. The BAT first distribute the heat that must be stimulated by controlling has been generated by the ambient temperature. Image thermogenesis. Because courtesy of Dr. Branca. the 129Xe is transmitted
in the blood stream after being breathed in, it is much more likely for the 129Xe to be taken up by BAT than by WAT tissue, where it would also be soluble but much less vascularized.3 So it is possible to detect via MRI where BAT is located in animals in vivo by allowing time for uptake of the 129Xe gas into the tissue deposits (Figure 3). It has also been shown that the location of the peak intensity frequency of resonance associated with the NMR spectrogram of 129Xe dissolved in BAT is temperature dependent, a feature that allows for the possibility of studying details of the thermogenic process in real time. In these ways, this approach to studying BAT provides a reliable method to determine both prevalence and several interesting properties related to the metabolic function of the tissue. One important result that has come out of these studies pertains to the structure and amount of activity of BAT in lean mice as opposed to obese mice. NMR spectroscopy of lean mice shows marked uptake of 129Xe in the blood and cytoplasm of BAT as well as in the lipid droplets; whereas only uptake in the lipid droplets is detected in the BAT of obese mice. This suggests that in obese mice, BAT is more similar in structure to WAT, which consists almost entirely of lipid droplets (Figure 2). In humans, BAT consists of more fat than in mice, and in some people, it is very similar to WAT. That BAT can resemble WAT in obese subjects helps to explain why prevalence can change from person to person as indicated by the previously mentioned studies. How it arises that BAT comes to resemble WAT is largely unknown and under investigation. Dr. Branca is hopeful that advances being made in her lab could lead to “a completely new way to fight obesity, by increasing energy expenditure as opposed to the classical way of just decreasing energy intake.”3
Brown adipose tissue (BAT) actually burns fat in the process of generating heat.
1. Nedergaard, J.; Bengtsson, T.; Cannon, B. Ann. N.Y. Acad. Sci, 2011, 1212, E20-E36. 2. Cannon, B.; Nedergaard, J. Physiol Rev, 2004, 84, 277359. 3. Interview with Rosa Tamara Branca, Ph.D. 1/30/13.
Vinculin, shown here in green, binds to the ends of actin filaments on the cell membrane to allow the cell to remain attached or to move. Image courtesy of Dr. Campbell.
in their tracks
By Mihir Pershad
By Firstname Lastname
ased on current rates, the Centers for Disease Control (CDC) predicts that 41 percent of men and women will be diagnosed with cancer at some point during their lifetime.1 That’s scary; it means that nearly half of all Americans, almost 123 million people, will develop some form of cancer in the span of their lifetime. According to the CDC, cancer is the number two killer in the United States, second only to heart disease.1 Because of this, cancer receives a significant amount of coverage from the media and is currently one of the most researched diseases in the nation. While we constantly hear stories about the discovery of new carcinogens, the growing cancer epidemic and new advances in chemotherapy, we hear little about one of the most important problems facing cancer patients today: tumor metastasis. Though cancer treatments have been
Figure 1. Dr. Campbell’s lab develops models of the structure of the vinculin-actin complex that facilitates cell movement in order to better understand the protein interactions. Image courtesy of Dr. Campbell.
shown to be highly effective on localized tumors, those that metastasize, or spread to other areas of the body, become much more difficult to treat and can lead to other serious complications in cancer patients.2 As one in three tumors will metastasize, metastasis presents an significant risk to patients and more research is needed to understand how to Sharon Campbell, Ph.D. prevent metastasis from occurring (Figure 2). Sharon Campbell, Ph.D., a researcher in the department of biochemistry and biophysics at the UNC School of Medicine, is taking advantage of new advances in nuclear magnetic resonance (NMR) technology to understand how proteins involved in the movement of cancer cells interact Peter Thompson, and how scientists can prevent a graduate student in the tumor metastasis by stopping Campbell lab. these cells from moving. In a pioneering study, Dr. Campbell, along with Klaus Hahn, Ph.D. of the UNC department of pharmacology, is seeking to discover the complete structure of the primary proteins involved in cell movement and adhesion (Figure 3). They hope to use these results to develop a model of how these proteins interact with signal cells to move or stay put. The protein at the focus of Dr. Campbell’s study is called vinculin, which is thought to control whether or not a cell will remain in one place or detach and move to a new location.3 Peter Thompson, a graduate student who works in Dr. Campbell’s lab, states that “if [scientists] can
Figure 2. Left: Cancer cells metastasizing from a tumor site. This movement is facilitated by the actin-vinculin complex, fluorescently tagged in red. Right: A cancer cell migrating through a blood vessel from the original tumor to a new site. Images courtesy of Dr. Campbell. determine how vinculin can activate other proteins that cause a cell to move, [they] can figure out ways to stop that activation,” thereby preventing metastasis and making cancerous tumors more manageable.4 In this study, Dr. Campbell used new advancements in two-dimensional nuclear magnetic resonance (NMR) technology to determine the amino acid sequence and overall shape of vinculin. She is now searching for a single genetic mutation that will interrupt vinculin’s ability to bind to proteins involved with cell movement without negatively affecting the function of the cell. “We can change just a single amino acid in vinculin and observe the structural change and change in protein interaction using NMR and other tests,” said Thompson, in reference to the experimental process (Figure 1).4 After each mutation, Dr. Campbell and her lab analyze the new structure of the protein and determine whether or not the affected cells are able to detach and move to a new location in the cell culture. So far, they have narrowed their focus from the entire protein to a single 60-amino-acid chain that forms the binding area of interest. Somewhere within this small region, they believe
there is an amino acid pivotal to vinculin’s ability to bind to other proteins and enable cell movement — a single amino acid that could be the key to preventing tumor metastasis. The significance of this project goes far beyond determining the structure of a single protein and understanding its interactions in the cell. The results of these experiments could play a pivotal role in understanding how cancerous tumors metastasize and discovering how to prevent that metastasis. “The end goal,” Thompson says, “is to be able to provide cancer patients with a viral vector that can transport a modified vinculin gene to the tumor cells and help contain the cancer by preventing tumor metastasis.”4 If scientists can develop a method for containing cancerous tumors within a single location, cancer patient survivorship could be significantly improved because oncologists would be able to treat a single tumor much more effectively than they can cancer that has spread throughout the entire body.2 Though the final goal may require years more of research, these trailblazing findings are significant in the fight to better understand cancer at the cellular level and prevent the metastasis of malignant tumors.
Results of these experiments could play a pivotal role in understanding how cancerous tumors metastasize.
Figure 3. Vinculin binds actin to integrins in the cell membrane, allowing for cell adhesion and movement. Image by Mihir Pershad.
1. Centers for Disease Control and Prevention: Cancer. www.cdc.gov/ cancer (accessed February 2nd, 2013). 2. Vigil, D.; Martin, T. D.; Williams, F.; Yeh, J. J.; Campbell, S. L.; Der, C.J. J. Biol. Chem. 2010, 45, 34729-34740. 3. Palmer, S.M.; Playford, M.P.; Craige, S.W.; Schaller, M.D.; Campbell, S.L. J. Biol. Chem. 2009, 11, 7223-7231. 4. Interview with Peter Thompson. 1/29/13.
The Psychological Constructionist An Approach to Understanding the Model Perception and Experience of Emotions By Cameron Doyle
ost of us can probably recall an instance where we have asked someone about their emotional state based on their facial expression only to find that they are not feeling the way we thought they were. Despite such experiences, it is commonly believed that emotions are discrete categories (e.g., anger, fear) that are associated with specific facial expressions. Growing evidence in the field of social psychology, however, suggests that this is not the case; our ability to experience and perceive emotions does not appear to be innate. According to UNC-Chapel Hill psychologist Kristen Lindquist, Ph.D., our perceptions of emotions are based on our knowledge of emotion words that we use to make meaning of general bodily feelings. This view is referred to as the psychological constructionist model of emotions. Dr. Lindquist’s hypothesis is that “emotions are products of more general psychological causes, which are constructed out of basic processes such as the ability to feel positive and negative sensations.” She is interested in “the human ability to make meaning of these more general sensations and to categorize them as emotions.”1 Notably, Dr. Lindquist and her colleagues have been the first to demonstrate that knowledge about emotion categories encoded in language helps people to make sense of their emotions. Prior to the development of the constructionist model, it was generally accepted
that emotions were universal, meaning that they existed as discrete categories in all humans; however, it has been determined that emotional states are not clearly defined across cultures, which supports the hypothesis that emotions may be linked to associations that we create based on language. Dr. Lindquist’s lab takes multiple approaches to testing her hypothesis about the con- Kristen Lindquist, Ph.D. struction of human emotions. She uses behavioral methods to understand how we act when we experience positive and negative sensations and how we make meaning of these sensations in terms of the emotion concepts that are available to us. The lab also takes psychophysiological measurements, which are used to determine how our bodily responses contribute to our categorization of emotional experiences. Dr. Lindquist uses neuroimaging techniques to measure brain activity during the experience of emotions to determine whether these activations reflect the involvement of affective processes and more general conceptual processes linked to language. In a study conducted at Boston College in 2006, Dr. Lindquist and her colleagues found that it is possible to temporarily reduce access to an emotion word by repeating it numerous times, making it difficult to perceive emotions that are associated with that particular word. This process is known as semantic satiation, and it was used in this context to provide evidence that emotion perceptions are supported by the words that we attach to them. The experiment involved a study phase where participants were primed with images of faces. These faces depicted configurations that are commonly associated with a particular emotion (e.g., anger). In the test Figure 1. In the study phase of the procedure, participants were shown faces phase, participants repeated the target emoto prime them for the test phase. Participants underwent either the semantion word (e.g., “anger”) 30 times for the satiatic satiation condition or the control condition. They were then asked to tion condition and three times for the control indicate which face they had seen previously. Researchers were interested in condition. As expected, in the satiation conparticipants’ response latency in the test phase. Image courtesy of Dr. Krisdition, participants experienced a temporary ten Lindquist. reduction in their ability to mentally access
Carolina Scientific the emotion word. During this period of limited access to the word (e.g., anger), participants were shown two images of a person’s face depicting the emotion (e.g., anger) either weakly or intensely. Participants were then asked to determine which face they had seen in the previous phase (Figure 1). The results showed that participants in the satiation condition took longer to elicit a response (Figure 2), indicating that along with a temporary reduction in access to the emotion word, the time it took them to perceive the emotion actually increased. Dr. Lindquist and her colleagues’ findings “constituted evidence consistent with the construction hypothesis: Satiating an emotion word appeared to change basic perceptual encoding of emotional faces . . . the fact that the task did not explicitly require conceptual knowledge implies that this knowledge is routinely active during emotion perception.”2 Dr. Lindquist has since completed additional studies assessing the relationship between language and emotion perception and is conducting some of these follow-up studies here at UNC. She hopes this research will expand on her findings related to the effect of language on emotion perception.
It could be possible to teach people how to make better distinctions between their states of affect and to thus better categorize their feelings. To further support the psychological constructionist model of emotions, Dr. Lindquist and Lisa Feldman Barrett, Ph.D. of Northeastern University analyzed existing research to find evidence of brain activity that corresponds with their “constructionist” hypothesis of emotion. Through the most extensive meta-analysis (an analysis of existing research) that has been conducted on this topic, they found that brain areas that are activated during emotion experiences and perceptions are many of the same areas that are associated with other psychological processes such as memory, attention, moral reasoning, and language (Figure 3). According to the report, “these findings are consistent with the hypothesis that brain
Figure 2. The results of the semantic satiation study show that participants who were in the satiation condition exhibited greater response latency than those in the priming condition F(1, 59) = 8.166, p = .006, X2 = .112. This constitutes the first evidence that emotion perceptions are constructed based on conceptual knowledge of emotion words. Image courtesy of Dr. Kristen Lindquist.
Figure 3. Areas of brain activation that are associated with emotion perceptions and experiences correspond to areas that are associated with other processes. This indicates that emotions are constructed as a result of brain activations for more basic psychological processes, not emotions specifically. Image courtesy of Dr. Kristen Lindquist. regions are implementing basic psychological operations that are not specific to any emotion per se, or even to the category ‘emotion.’”3 This information provides evidence that emotions are constructed in the mind as a result of basic feelings of affect (i.e., generally positive or negative feelings) and knowledge about emotions. Dr. Lindquist’s findings based on the psychological constructionist model of emotions have implications outside the laboratory. This information can help us to find ways to treat emotional disorders through the use of psychotherapy. It could be possible to teach people how to make better distinctions between their states of affect and to thus better categorize their feelings. Presumably, this knowledge would allow people with emotional disorders to properly regulate their emotions. Dr. Lindquist’s research also has important implications for learning about how the human mind functions in general. Constructionist models have been developed to explain many psychological processes, including memory and psychopathology.4,5 Interestingly, this implies that our minds could be responsible for constructing much more than just our emotions. Furthermore, these constructionist approaches have allowed psychologists such as Dr. Lindquist to make excellent use of modern technology to better understand the human mind. References 1. Interview with Kristen Lindquist, Ph.D. 01/29/13. 2. Gendron, M.; Lindquist, K. A.; Barsalou, L.; Barrett, L.F. Emotion. 2012, 12, 314-325. 3. Lindquist, K. A.; Barrett, L. F. Trends Cogn Sci. 2012, 16, 533-540. 4. Schacter, D. L. Am Psychol. 2012, 67, 603-613. 5. Kring, A. M. Emotion disturbances as transdiagnostic processes in psychopathology. In Handbook of Emotion, 3; Lewis, M., Haviland-Jones, J. M., Barrett, L. F., Eds.; Guilford Press: New York, 2008; 691-705.
Benefits of a Healthy Smile The Real
By Paul Lee
elieve it or not, proper brushing and flossing may one day save your life. While many of us are familiar with the dental benefits of proper oral hygiene, few of us know that it affects our overall health. Until recently, even physicians failed to recognize this significant relationship as patients were rarely referred to a dentist or gum specialist. However, Steven Offenbacher, DDS, PhD, MMSc and his colleagues at the Center for Oral and Systemic Diseases in the UNC School of Dentistry are helping to change this mindset. The research of Dr. Offenbacher, an OraPharma distinguished professor, the chair of the department of periodontology and director of the Center of Oral and Systemic Disease, explains how poor oral health influences the functioning of the body. The Centers for Disease Control and Prevention have recently reported that 47.2 percent of U.S. adults have some form of periodontal disease.1 Periodontal (or gum) disease comes in different levels of severity and is mainly caused by the buildup of hardened plaque called tartar, formed by bacterial flora in the mouth. Symptoms for periodontal disease can range from halitosis (bad breath) to inflammation, with
older people being more prone to the disease.2 This prevalent disease can also lead to painful inflammations within the oral cavity and even loss of teeth. A recent boom in research on periodontal disease has shown significant evidence that periodontal disease has consequences for our bodies far beyond our mouths. At the Center for Oral and SysSteven temic Diseases, Dr. Offenbacher and his Offenbacher, colleagues examine the levels of acuteD.D.S, Ph.D., phase reactants such as C-reactive proMMSc. tein (CRP) and Interleukin 6 (IL-6) in relation to conditions such as diabetes and heart disease. When bacteria invade oral tissue, they can create an inflammatory site of sepsis and seep into the bloodstream. Given this wide circulation, oral bacteria become a systemic challenge and trigger a hepatic acute-phase response (Figure 1). This response is the metabolic reaction to systemic tissue injury
Figure 1. Oral-systemic pathway. Image courtesy of Dr. Offenbacher.
Figure 2. Left: Current model of periodontitis-associated pregnancy complications. Right: Distrbution of intima-media thickness by periodontitis status and measurements of the innermost layers of the arterial wall. Images courtesy of Dr. Offenbacher. and is marked by considerable increases in plasma proteins, However, developing an effective treatment has its own chalsuch as CRP and IL-6, released by the liver.4, 5 Although this is lenges, as current literature presents conflicting evidence part of a natural response, periodontal disease can prolong regarding benefits of short-term therapy in pregnant moththis response and increase the likelihood of chronic diseases. ers. Dr. Offenbacher states, “As of now, there are a lot of miss“There is an underlying inflammatory characteristic to ing steps in knowledge dealing with treatment. We need to periodontal diseases; this trait puts you at risk for other chronic consider implementing a more comprehensive approach to conditions that exhibit similar pathoperiodontal disease.”3 With the sig3 genesis,” explains Dr. Offenbacher. nificance of periodontal disease in Studies have shown that increases in systemic health established, further these acute-phase proteins promote research needs to be done to deterbuildup of atheromatous plaques mine the benefits of long-term treat(lipid deposits) within the artements showing definite control of rial wall, possibly leading to serious infection and disease. complications.3 Even more, once the Although studies in this field - Dr. Steven Offenbacher bacteria enter the bloodstream, they are relatively new, the importance of also gain access to all vital organs in periodontal disease has already sugthe body and may cause direct harm. Studies have shown that gested much about the functioning of our bodies. With adpregnant mothers with periodontal disease are more likely to ditional research, doctors and dentists may soon be able to have preterm low birth weight deliveries. The current model work together to save the lives of high-risk patients. “Studies attributes this association to placental and fetal exposure to show that if you have periodontal disease, you are at a greater periodontal microbes such as C. rectus and possible placen- risk of death and other complications of health. What we can tal inflammation (Figure 2, left). Overall, patients with severe say for sure is that prevention is key,” explains Dr. Offenbachperiodontal disease have a risk of stroke and preterm delivery er.3 Could you ever need any more motivation to floss? approximately three times that of normal patients (Figure 2, right).3, 6 Today, Dr. Offen- References bacher and his team are 1. Periodontal Disease: Causes, Symptoms and Treatments. working on evaluating National Institute of Dental and Craniofacial Research. the systemic benefits of http://www.nidcr.nih.gov/NR/rdonlyres/10083F99-5030controlled periodontal 43AD-92F0-3E04D18CB664/0/PeriodontalGum_Eng.pdf treatments as well as (accessed February 1st, 2013). exploring therapy inter- 2. Eke, P. I.; Dye, B. A.; Wei, L.; Thornton-Evans, G. O.; ventions for high-risk Genco, R. J. J Dent Res. 2012, 10, 914-920. patients, such as those 3. Interview with Dr. Steven Offenbacher, DDS, Ph.D., admitted to the stroke MMSc. 1/30/13. unit. “There is a three- 4. Baumann, H.; In Vitro Cellular and Developmental Biolfold greater chance of ogy. 1989. 25, 115-126. morbidity for admit- 5. Offenbacher, S.; Beck, J.; Am Heart J. 2005, 149, 950-954 ted stroke-unit patients (Heart Disease). Figure 3. Invasion of bacteria with periodontitis; there 6. Offenbacher, S.; Boggess, K.; Murtha, A.; Jared, H.; Lieff, into oral tissue. Image courtesy of is room for intervention,” S.; McKaig, R.; Mauriello, S.; Moss, K.; Beck, J. Obstet GyneDr. Offenbacher. says Dr. Offenbacher.3 col. 2006, 107, 29-36 (Preterm Delivery).
“We need to consider implementing a more comprehensive approach to periodontal disease.”
Undoing the Past By Meghan McFarland
all it fate. Call it serendipity. Just don’t call it intuitive. A recent study has found that when it comes to counting our blessings, more might not always be better. According to a study done in 1991 by Arkes, Boehm and Xu, the more a person reflects on an event in his life, the more familiar and explainable it becomes1 — a reassuring idea when it comes to negative events, but a detrimental effect if you are looking for happiness in remembering positive events. Higher understanding of a positive event can result in less positive affect stemming from the positive event.2 Positive affect — not to be confused with a positive effect — consists of emotions such as excitement, self-assurance and cheerfulness, making it crucial to feeling gratitude and happiness.3 So, despite what you may have learned from every romantic comedy ever written, telling the story of your relationship might not make you as happy as What George Bailey didn’t realize: you would expect. mentally “undoing” the past can Luckily, with a strengthen your current relation- little faith, trust and ship. Image public domain. counterfactual thinking,
there is still a way to find gratitude for your relationship. Inspired by Frank Capra’s 1946 Christmas classic It’s A Wonderful Life, the idea of mentally “undoing” the positive events in your life — including meeting your one and only — can reinvigorate the gratitude and satisfaction you feel. When Clarence Odbody shows George Bailey what the world would be like without life’s blessings, rather than directly Sarah Algoe, Ph.D. asking him to count, Bailey realizes the value of little things in life, reviving his will to live.4 Beyond the heart-warming, moral-laden plot, however, lies valuable psychological insight. Frequently referred to as the “George Bailey Effect,” the method of thinking about the ways in which an event might not have occurred refreshes the surprise from the event, therefore increasing the positive effect.5 “One of the things I think is interesting is that it’s not intuitive to people at all,” says Sara Algoe, Ph.D. of UNC-Chapel Hill.6 Dr. Algoe and colleagues further the study and relate this effect specifically to relationship satisfaction. In the study, participants were required to have been in a romantic relationship for at least five years. To further narrow down the group, the chosen participants had reported a level of satisfaction with their relationship at or above the sample average.5 This was found by having participants answer 12 questions, including their happiness level on a scale of one (not at all happy) to seven (extremely happy). They also answered questions from commonly used relationship measures, such as “In general,
Carolina Scientific how satisfied are you with your relationship?”; “To what extent has your relationship met your original expectations?”; “How much do you love your partner?”; etc.5 Two weeks after these baseline measures were finished, participants were assigned to one of three conditions — the presence condition, the absence condition and the control. In the presence condition, participants spent 15 Image by Mushi [CC BY 2.0]. to 20 minutes writing about how they met their partners, began their relationship and ended up together.5 The absence condition focused on writing about how they may never have met their partners, begun dating and ended up together.5 The control condition had three versions — writing about a typical day, describing how they met a good friend or describing how they may never have met a good friend.5 No significant differences were found among the three control versions, so the data were combined into a single control group for analysis purposes.5 As hypothesized, individuals who participated in the absence condition saw the biggest increase in satisfaction with their relationship after imagining a world in which their partner did not exist.5 According to Dr. Algoe, “Some people might naturally do this and might naturally think, ‘It was fate — it was crazy! We were both in this one place at this one time. Can you imagine if it never happened?’ and those people actually do get a boost. But, with this experiment, we were able to sharpen the distinctions between the way people think they’re telling the story of their relationship and the actual ingredients, helping everyone else to get the most out of their experience.”6 One of the most interesting ideas about the results is that they are the opposite of Image courtesy of Peter Weis [CC0 1.0]. what people expect.
Within the study, 16 extra participants played the role of “forecasters” and were given a description of both the presence and absence conditions.5 When asked which condition they would prefer, 14 out of the 16 participants preferred the idea of the presence condition.5 Their reasoning involved such statements as, “I love telling The insightful angel Clarence Odpeople how we ended body taught about more than just up together because it how angels get their wings. Image is such a great story. It public domain. always makes me feel good about our relationship after I’ve told it.”5 Dr. Algoe is not far behind: “People just don’t predict it, because who wants to think of how they may never have met their partner?”6 Findings from this positive affect study may also have clinical applications. Dr. Algoe is building another study that focuses on the idea of “savoring” positive experiences and is hoping to encourage people to notice positive things in their everyday lives.6 She believes that this may lead to a snowball effect: “Over time, this may actually help to eliminate depressive symptoms and alleviate some worry that students go through in their college lives.”6 As it turns out, the angelic Clarence Odbody was onto something other than how angels earn their wings. So, if your well of happiness is running dry, try “undoing” the beginning of your relationship — you might gain a new perspective. As Odbody put it, “Strange, isn’t it? Each man’s life touches so many other lives, and when he isn’t around he leaves an awful hole, doesn’t he?”4
Individuals saw the biggest increase in satisfaction with their relationship after imagining a world in which their partner did not exist.
1. Arkes, H. R.; Boehm, L. E.; Xu, G. J Exp Soc Psychol. 1991, 27, 576-605. 2. Wilson, T. D.; Centerbar, D. B.; Kermer, D. A.; Gilbert, D. T. J Pers Soc Psychol. 2005, 88, 5-21. 3. Robbins, S. P.; Judge, T. A.; Campbell, T. C. Glossary. In Organizational Behavior, 1; Pearson, 2010. 4. Capra, F. (Producer & Director) 1946. It’s A Wonderful Life [Film]. Liberty Films: California. 5. Koo, M.; Algoe, S. B.; Wilson, T. D.; Gilbert, D. T. J Pers Soc Psychol. 2008, 5, 1217-1224. 6. Interview with Sara B. Algoe, Ph.D. 2/1/13.
More to Gold
Than Meets the Eye By Cody Phen
old is a very rare and versatile transition metal, and with the onset of recent economic instability, the value of gold has skyrocketed. Based on the current spot gold price of $1670.50, one gram of gold costs $53.71.1 This price reflects the inverse relationship gold has with the US dollar.2 As the value of the US dollar decreases, the value of gold increases dramatically. Besides playing a crucial role as an economic commodity, its breadth of properties such as malleability, excellent conduction of heat and electricity, ready formation of alloys with various metals, and resistance to corrosion reinforce gold’s value as a precious element. These properties are exploited in various industrial and practical applications such as jewelry, electronics, organic photovoltaics, and drug delivery in medical applications. However, with recent research on the properties and crystal structure of gold nanoparticles (Au25), chemists have realized there is much more to gold than meets the eye. Royce Murray, Ph.D., a Kenan professor in chemistry, and his colleagues determined the crystal structure of a gold nanoparticle in 2008. There are many different kinds of nanoparticles that are characterized simply by their diameter, but Dr. Murray says, “If you want to understand someFigure 1. There is one central thing, you have to get down gold atom and twelve other to the details.” The crystal gold atoms bonded to it form- structure of the thiolateing an icosahedron. This figure protected gold nanoparis known as the Au13 core. Imticle has three types of gold age courtesy of Dr. Murray. atoms.3 In chemistry, a mol-
ecule has a coordination number of the central atom, referring to the number of other atoms bound to it. In this particular nanoparticle, one central gold atom is bonded to a set of 12 gold atoms, giving it a coordination number of 12 (Figure 1).
“If you want to understand something, you have to get down to the details.” Dr. Royce Murray The 12 gold atoms on this Au13 core form the vertices of an icosahedron around the central Royce Murray, Ph.D. atom, whose coordination number is six (five bonds to gold atoms and one to a sulfur atom). Lastly, another set of 12 gold atoms is stellated on the 20 faces of the Au13 icosahedron (Figure 2, left).3 In total, 25 gold atoms make up a gold nanoparticle, thus giving it the chemical formula [Au25(SCH2CH2Ph)18] (Figure 2, right). The overall diameter of the gold core measured from the outermost gold atoms is 9.82 ± 0.04 Å. To put this into perspective, you would need roughly 7 x 1015 gold-core atoms to cover the surface area of a penny. That would be one shiny gold penny worth more than $134.28! The size and structure of the gold nanoparticles are very important because they play a crucial role in determining certain properties. Gold nanoparticles have the tendency to cluster together, reducing gold’s surface energy for effective chemistry to occur. In order to eliminate aggregation, gold nanoparticles are coated with thiolated ligands that help to “protect the nanoparticle from fusing with other nanoparticles” and minimize its surface energy.6 A ligand can be thought of as a platform on which the gold atom can perform and “shine” instead of being part of the “crowd.” This “monolayerprotecting (poly)ligand,” a term invented by Dr. Murray and his
Figure 2. Left: This ball-and-stick model is the complete Au25 nanoparticle. The gold spheres represent gold atoms and the orange spheres respresent the sulfur atoms. Right: This figure is the complete Au25 nanoparticle with its thiolate ligands attached [Au25(SCH2CH2Ph)18]. Images courtesy of Dr. Murray. colleagues, allows the synthesis of gold nanoparticles to be a particular size.3 For example, nanoparticles with less than 300 gold atoms can demonstrate certain distinct optical electronic properties compared to the bulk metal.4 Dr. Murray and his colleagues showed chemically how “ligand exchange” worked by adding and removing ligands in order to vary surface energy. He says, “Changing the ligands on the gold nanoparticles is a piece of cake.” In terms of practical applications of gold nanoparticles, he states, “A lot of people are interested in them as attaching drug substances to their surfaces and using the nanoparticle as a way for drug delivery.” Scientists and researchers are calling this new area of interest “nanomedicine.” Due to the gold nanoparticles’ extremely small size and their high versatility in surface chemistry, they are great agents to carry cancer drugs at high doses and kill cancer cells while leaving healthy tissue unharmed. The Boston Globe reports that these gold nanoparticles are currently being developed by CytImmune, a biopharmaceutical company, and will have three main elements incorporated: TNF (tumor necrosis factor, an effective cancer drug that is lethal at high doses), a second cancer drug and a molecule
Figure 3. Gold nanoparticles show promise in their potential for chemotherapeutic delivery. Shown here, the ligand is able to bind to a cell receptor and deliver the attached drug. Image adapted from Wang, et al. by Keith Funkhouser.
of ethylene glycol, which is designed to conceal the nanoparticle from the body’s immune system.5 The gold nanoparticle travels through the body, bypassing healthy tissue (small size) and barring the immune defenses from recognition (ethylene glycol attachment). When the ligand on the gold nanoparticle binds specifically to the receptor on a cancer cell, the cancer drug is released. This ligand-receptor interaction is the basis of nanomedicine. Nanomedicine is only one field making use of gold nanoparticles. The size and structure of the gold nanoparticle are reflective of the properties it exhibits and are paving the way to new frontiers, such as its facilitation in nanotechnology. With so many unique properties of the gold nanoparticle to exploit, maybe we should think about backing the U.S. dollar with silver instead.
1. Only Gold. http://www.onlygold.com/tutorialpages/ value_of_gold.asp (accessed February 3rd, 2013). 2. What is the relationship between US Dollars and Gold Prices? http://symmetricinfo.org/2011/03/what-is-the-relationship-between-the-us-dollar-and-gold-prices/ (accessed February 3rd, 2013). 3. Heaven, M. W.; Dass, A.; White, P. S.; Holt, K. M.; Murray, R. W. JACS. 2008, 130, 3754-3755. 4. Sardar, R.; Funston, A. M.; Mulvaney, P.; Murray, R. W. Langmuir. 2009, 25, 13840-13851. 5. Weintraub, K. Gold particles could deliver cancer drugs. http://www.bostonglobe.com/business/2012/12/24/ astrazeneca-waltham-unit-aims-use-gold-nanoparticlesdeliver-cancer-drugs-directly-tumors/Rq3b1KKx0hJWgkCxt5KVcO/story.html (accessed February 3rd, 2013). 6. Interview with Royce W. Murray, Ph.D. 2/1/2013. 7. Wang, Feng ; Wang, Yu-Cai; Dou, Shuang; Xiong, MengHua; Sun, Tian-Meng; Wang, Jun. ACS Nano 2011, 5, 36793692.
“Equipped with his five senses, man explores the universe around him and calls the adventure Science.” - Edwin Powell Hubble
Image by Ildar Sagdejev, [CC-BY-SA-3.0].
Spring 2013 | Volume 5 | Issue 2
This publication was funded at least in part by Student Fees which were appropriated and dispersed by the Student Government at UNC-Chapel Hill.