A JOURNAL BY THE TRIPLE HELIX AT THE UNIVERSITY OF CHICAGO
ABOUT THE TRIPLE HELIX
THE JOURNEY OF A NEUROEVANGELIST: AN INQUIRY WITH DR. PEGGY MASON YURI SUGANO
THE SYNERGISTIC EFFECT OF ANTIBIOTICS AND SILVER NANOPARTICLES ON DRUG-RESISTANT BACTERIA ANGELA SHA
PHOTO FEATURE: MARINE BIOLOGY LABORATORY
contents Produced by The Triple Helix at the University of Chicago Layout and Design by Bonnie Hu, Production Director Co-Editors-in-Chief: Zainab Aziz, Nikita Mehta Scientia Board: Zainab Aziz, Nikita Mehta, Josh Everts, Maritha Wang, Rita Khouri
ORGAN TRANSPLANTATION AND HOST IMMUNITY: AN INQUIRY WITH DR. MARIA LUISA ALEGRE
CLINICAL FEASIBILITY OF GLOBAL LONGITUDINAL STRAIN AND RELATIONSHIPS WITH SYSTOLIC AND DIASTOLIC FUNCTION
THE FUTURE OF WEARABLE DEVICES AND HUMAN-COMPUTER INTERACTIONS: AN INQUIRY WITH PROFESSOR PEDRO LOPES JARVIS LAM
BSCD UNDERGRADUATE RESEARCH SYMPOSIUM ABSTRACTS
ABOUt about the triple helix Dear Reader, The Triple Helix, Inc. (TTH) is the world’s largest student-run organization dedicated to evaluating the true impact of historical and modern advances in science. Of TTH’s more than 20 chapters worldwide, The University of Chicago chapter is one of the largest and most active. Our TTH chapter continues to proudly share some of the most distinct publications and events on campus, engaging the minds and bodies of our institution and the public as “a global forum for science in society.” Our mission, to explore the interdisciplinary nature of the sciences and how they shape our world, remains the backbone of our organization and the work we do. In addition to Scientia, we publish The Science in Society Review (SISR) and an online blog (E-Pub), while also creating events to discuss the most current, pressing topics at the intersection of science and our society. Our organization is driven by talented undergraduate individuals—writers, editors, and the executive board that come from all backgrounds and interests. The intellectual diversity of TTH members allows us to bring you the vast array of knowledge, research, and perspectives that we present in our works. We consciously strive to help each member grow, not only as a writer or editor, but also as a leader, who will continue to ask the very questions that lead us to innovation and advancement as a society. Over the years, TTH UChicago has expanded from just one journal and an online blog to a holistic outlet for all undergraduates on our campus. Everyone—whether in “the sciences” or not—is affected by it, contributes to it, and has to interact with it on a daily basis. We wanted to continue to grow the platform of “the sciences,” to make it accessible to everyone. We now have insightful opinion pieces through SISR, brief reportings through E-Pub, workshops and discussions through events, and original research and interviews with leading professors through Scientia—a whole ecosystem of knowledge that we hope challenges you to think and to actively join the ever-growing dialogue on “the sciences.” Today, I invite you to join us, The Triple Helix team, in celebrating the newest release of Scientia, one of our two biannual print publications. Scientia—unique to the UChicago chapter—was inspired by and continues to embody the motto of our university: Crescat scientia; vita excolatur (Let knowledge grow from more to more; and so be human life enriched). As you read our latest issue, I hope you are reminded of its essence and let your knowledge grow. Best wishes, Nila Ray President of The Triple Helix at the University of Chicago
about scientia Dear Reader, This edition of Scientia incorporates two sections that set it apart from our other issues— photographs from the Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts, and abstracts from the Biological Sciences Collegiate Division (BSCD) Undergraduate Symposium. Through its affiliation with the University of Chicago, the MBL has continued to develop its education-focused programs in recent years, in addition to maintaining its status as a premier research institution. The MBL has attracted scientists and educators from around the world by creating a vibrant and diverse environment where research can flourish. Our front cover features a student observing a squid under a dissecting microscope— this is one of the many activities that University of Chicago students may participate in during the MBL September courses. The MBL also offers fall “study abroad” programs and summer-long research fellowships, all opportunities for students to become more involved with the UChicago-affiliated research institute. In this issue, we also feature the works of Professors Peggy Mason, Pedro Lopes, and Maria Luisa Alegre, all prominent researchers in their fields, bringing unique perspectives to neurobiology, computer science, and immunology, respectively. Our student researchers present full-lengths on their work in cardiology and chemistry, reflecting the diverse topics pursued by undergraduate students. In our attempts to highlight both the depth and breadth of research being conducted by students at this university, our issue features a selection of abstracts from the BSCD Undergraduate Research Symposium, some of which are from senior thesis projects that will eventually be incorporated into publications. Scientia is always looking to broaden our scope and expand the reach of our publication. If you are completing a research project and want to see it in print, or if there is a professor performing eye-opening research that you would like to share, consider writing for us! We encourage all interested writers to contact a member of our team, listed in the back. In the meantime, please enjoy this edition of Scientia, presented by The Triple Helix. Sincerely, Nikita Mehta and Zainab Aziz Co-Editors-in-Chief of Scientia
inquiry THE JOURNEY OF A NEUROEVANGELIST: AN INQUIRY WITH DR. PEGGY MASON YURI SUGANO
Leading a research lab, teaching a neuroscience course, and directing an entire major might sound like three full-time jobs. Dr. Peggy Mason has been involved in all of those activities, and yet, has found time to collaborate with researchers across different fields in a new, expansive clinical research project. Her most recent project brought her to the UK, and for that reason, we had a lovely conversation over Skype. Dr. Mason’s research in empathy is well-known—it was the subject of an article in the Winter 2016 edition of Scientia. Dr. Mason is also responsible for teaching—her engaging classes have reached undergraduate, graduate, and
medical students at the University, along with thousands of others interested in neuroscience through her massive open online course (MOOC), “Understanding the Brain: The Neurobiology of Everyday Life.” In addition, she has been involved with the creation and development of the neuroscience major at the University. Professor Mason’s career in science began even before she knew it. Prior to college, she worked as a taxidermist in the Smithsonian Museum. She used to read the Smithsonian Magazine and was particularly enthusiastic about a column written by Stephen Jay Gould, an evolutionary
biologist at Harvard. Dr. Mason’s admiration for Gould was a major influencing factor in her decision to attend Harvard to pursue an undergraduate degree in biology. While in college, Dr. Mason received a full-ride scholarship to a graduate school. In spite of not knowing much about graduate school, Dr. Mason decided to go down this route, “I could do more studying and get paid for it. That’s a really cool gig.” Even though she grew up in a family filled with lawyers, Dr. Mason always wanted to be a scientist. With that in mind, she needed a subject to focus on. Dr. Mason was originally interested in evolution ecology, but she disliked
the classes she took in those areas. As a child, she experienced seizures, for which she visited a neurologist. She always thought the experience was entertaining and describes being fascinated by the little EEG electrodes on her head. Inspired by her childhood curiosity, Dr. Mason decided to look into neurobiology. She took a class with John E. Dowling—who currently teaches neuroscience at Harvard—with whom she ended up working on her senior thesis, performing cellular recording of cells in the retina. “I was recording from cells, flashing lights, cells were talking back to me; I was talking to cells. I was having a good time.” Graduate school turned out to be the right path for her. Another turning point in her life was her decision to complete her postdoctoral work at University of California, San Francisco. Part of this decision was motivated by her wish to be “a small fish in a big pond” by attending a large institution in a big city. As a result, when deciding where to set up her homebase, Chicago stood out. Moreover, Dr. Mason loved Hyde Park, where her mother had grown up. Dr. Mason ended up joining UChicago as a faculty member, and feels that it was and continues to be a good match for her. At UChicago, she continued to work on cellular recordings, or as she puts it, “continued to have fun conversations with cells”. As years went on, Dr. Mason became interested in the cellular basis of pain modulation. When she became a professor, she undertook adventurous paths with her research interests. That is precisely when her collaborator Inbal Ben-Ami Bartal, a highly renowned empathy researcher, proposed looking at the biological basis of empathy. This has been Dr. Mason’s primary research interest since then. Teaching has been a key part of Dr. Mason’s career. Since her arrival, she has taught medical
and graduate students, although her focus more recently has been on teaching undergraduates. “Most people’s favorite [for teaching] is grad school. It was never my favorite, I’m different that way”. She taught at the medical school for several years and even published a textbook, Medical Neurobiology (Oxford Press). Her first formal experience with undergraduates was teaching in the 2013 Neuroscience Study Abroad Program in Paris. This experience developed into an increasing interest for teaching undergraduates. Dr. Mason believes that she has not found the optimal way to teach undergraduates: “The optimal experience is to do something that is difficult, but still within your capacity.” This challenge motivated her to continue to teach at the University of Chicago’s center in Paris, in addition to leading the Fundamental Neuroscience course in the College alongside Professor Clifton Ragsdale. Dr. Mason’s love for teaching, however, extends beyond the University’s lecture halls. She was approached by Prof. Roy Weiss, Deputy Provost for Research, to start an open online course geared toward a general audience. Dr. Mason loved the idea from the outset, although she did not realize the impact it would have on her life. It was an enormous influence, leading her to meet people from all over the world. Meeting all these students has expanded her ideas, thoughts and interests in ways she would have never anticipated. Through the online course, Dr. Mason also met a person with whom she is currently spending a good portion of her time. In addition to empathy, Dr. Mason is currently working on an expansive clinical investigation on the neurobiological and genetic basis of a novel, unknown neurological condition that one of her former students has. Our conversation about teaching led us to the discussion
Picture of Stephen Jay Gould’s magazine, her biggest inspiration to go to Harvard.
of the neuroscience major, for which Dr. Mason has been appointed the inaugural director since 2016. The major started with Dr. Murray Sherman, Chair of Neurobiology. Murray used to teach undergraduates, and he would ask the students how many of them would be interested in a neuroscience major, often getting positive responses. Interested in making the idea a reality, he talked to Dr. Mason, the chair of the department’s teaching committee at the time. Dr. Mason wrote a proposal several years ago. The first attempt, however, “crashed and burned”. The Biological Sciences Division, at that time the only division with a single major, had dealt with different interests through specialization tracks. An ongoing debate involved whether neuroscience should be a specialization or a major of its own. After losing the first round, Dr. Mason became very discouraged and frustrated. Years later, John Maunsell, Director of the Grossman Institute for Neuroscience, Quantitative Biology, and Human Behavior revised the original proposal. He suggested the important addition of a laboratory course, which led to the major being approved in 2016.
Peggy exploring dissections of the brain. She is looking at the dissection of a sheep’s visual pathways.
Dr. Mason was appointed as the inaugural director, and she has been constantly working on developing and improving the major since then. Dr. Mason says part of the success is an idea she adopted from a friend at the Booth School of Business. In order to provide a platform for the students to have access to her, she holds weekly lunches so she is able to hear not only about their problems, but also their interests. This has allowed the department to promptly address course issues as they arise within the major. In only three years, the major has grown to over 150 students. As a consequence, Dr. Mason believes the next challenge is scalability, and how to deal with a major that continues to grow. In spite of her consideration for the major and students, Dr. Mason recently announced that she is stepping down as the
director of the major. Dr. Mason explained she feels pressure from her clinical project and needs to give this project most of her attention. “ I feel under the gun on my clinical project in particular. I just really feel as though I need to give that close to a hundred percent of my effort and wrap it up in the next year or two, and can’t do that if I am running the major.” Balancing research, teaching and directing a major is a considerable challenge, and Dr. Mason’s recent multidisciplinary clinical project has also been growing. “I want the students to know they are not the reason I am not doing this. I feel as though it is something of a divorce, and I do not want the students to feel in any way rejected. I can say, honestly, that the interaction with the students has been one of the most fruitful, growth-producing, and intellectually stimulating
experiences of my life. I have loved interacting with students, loved their ideas, interests and questions, their enthusiasm. I will miss that.”
YURI SUGANO is a firstyear transfer student at the University of Chicago majoring in Neuroscience.
full length The Synergistic Effect of Antibiotics and Silver Nanoparticles on Drug-Resistant Bacteria Angela Sha 1, Ning Fang 1 1 Georgia State University Chemistry Department
Abstract New classes of antibiotics are constantly being developed to address antibiotic resistance, but they do not provide a definitive solution. This lab conducted an investigation of the synergistic effects of antibiotics and silver nanoparticles on drug-resistant bacteria. A non-virulent, drug-resistant strain of E. coli was developed by using ampicillin to place evolutionary stress on the strain. The strain was also made resistant to other beta-lactam antibiotics, such as penicillin and amoxicillin. Different proportions of the minimum inhibitory concentration of differing antibacterial agents were applied to the bacteria, including ampicillin, silver nanoparticles, and ampicillincoated silver nanoparticles. The growth of the bacteria was measured through qualitative observation and a quantitative luciferase assay. A disk diffusion test was utilized to determine the minimum inhibitory concentration of each antibacterial agent. Toxicity tests were carried out on the antibacterial agents through an in vitro study on liver slices. The ampicillin-coated silver nanoparticles showed the lowest yield of cell growth, the lowest measured minimum inhibitory concentration, and a much lower cytotoxicity than silver nanoparticles. As such, the ampicillincoated silver nanoparticles were deemed to be the most effective antibacterial agent. The efficacy was likely due to the high enhancing effects of the different agents due to the different mechanisms used to combat bacteria. This research presents a new perspective on the age-old issue of antibacterial resistance.
Introduction Over time, multi-drug resistant strains such as MRSA, which evolve naturally via random mutation and natural selection, have become increasingly resistant to antibiotics. Beta-lactams (β-lactams), or groups of antibiotics that include penicillin, are examples of commonly used antibiotics that have become less efficient through the years. The purpose of this research was to determine how the unique antibacterial mechanism of nanoparticles interacts with antibiotics in antibioticresistant bacteria. Its antibacterial efficacy is defined as the lowest minimum inhibitory concentration (MIC) and lowest toxicity, on a drug resistant strain of bacteria. Silver nanoparticles, or Ag-NPs, have very distinct physical and chemical properties. The nanoparticles’ small size (1-100 nm) results in a large surface area to volume ratio, making their properties differ from silver as a bulk material . Ag-NPs have a high electrical and thermal conductivity, high chemical stability, and strong scattering and absorption properties . Their small size also allows them to “easily interact with other particles,” increasing antibacterial efficacy . Silver ions have been shown
to attack gram-negative bacteria, such as E. coli and S. aureas through multiple mechanisms . Their antiseptic properties are so strong that “one gram of Ag-NPs can give antibacterial properties to hundreds of square meters of substrate material” . Unlike antibiotics, which use toxicity to kill bacteria, Ag-NPs destroy the bacterium’s cell wall and suffocate it by disabling the enzyme through which the bacterium breathes oxygen, preventing bacteria from adapting to it and producing the protection mechanism that it has developed against the toxin in antibiotics . However, Ag-NPs are significantly more effective on gram-negative bacteria than gram-positive bacteria, because gram-positive bacteria are “composed of a thick layer (~20–80 nm) of peptidoglycan (linear polysaccharide chains cross-linked by short peptides)” while gram-negative bacteria consist of only a “[thin] layer of peptidoglycan (~7–8 nm) with an external layer of lipopolysaccharides” . The structure of gram-negative bacteria makes it easier for Ag-NPs to penetrate the cell wall. Pathogens have been unable to develop an immunity to silver, and have not yet developed the ability to neutralize Ag-NPs.
Figure 1. Creating a spatial growing environment.
In this study, we investigated the synergistic effect between antibiotics and Ag-NPs on drugresistant bacteria. Because Ag-NPs interact with a bacterial membrane composed of phospholipids and glycoproteins, we predicted that an enhancing effect would be observed in a combination of antibiotics and Ag-NPs. We chose to investigate the synergistic effect on Escherichia coli because it is one of the most commonly known microbes to develop drug resistance. Ampicillin is a more newly-developed class of antibiotic, known to be more effective than other forms of β-lactams like penicillin and amoxicillin, but many strains of E. coli have developed resistance to this class of antibiotic in recent years. Ag-NPs were chosen due to their higher synergistic effect with antimicrobial peptides than silver ions and gold nanoparticles. E. coli has commonly shown resistance to ampicillin, which suggests that it is resistant to penicillin and amoxicillin as well.
Methods Inducing Antibiotic Resistance in E. coli Evolutionary stress was placed upon E. coli bacteria to artificially introduce antibiotic resistance. A large petri dish was split into equal sections. MacConkey agar was used to ensure only gramnegative bacteria were tested. The antibiotics nested
in the agar nutrients ranged from zero dosage to suboptimal dosage to a dosage well above the MIC. This device, shown in Figure 1, was constructed to encourage the evolution of bacteria and allow migration and adaption in a spatially structured environment. With this method, the E. coli bacteria evolved by sharing, transferring, and exchanging antibiotic resistance both vertically and horizontally. As the reproduction rates of bacteria are extremely high, antibiotic resistance was witnessed occurring within a shorter period of time than in other types of species. Then, the E. coli bacteria strain was introduced to the spatial growing environment. Once the bacteria grew to the side of the petri dish with high antibiotic concentration, samples of the antibiotic-resistant E. coli were tested using disk-diffusion tests of ampicillin, amoxicillin, and penicillin, respectively. Disk diffusion tests spatially compare regions of inhibited bacterial growth, which allows for a measurement of sensitivity to antibiotics, the MIC. The measured MIC, over 32 µg/mL, demonstrated that the bacteria was drug-resistant. Because the strain was resistant to ampicillin, amoxicillin, and penicillin, it was concluded that the bacteria had likely developed β-lactamase, the enzyme necessary to break down the functional group of β-lactam antibiotics. Positive and Negative Control Groups A negative control test was conducted using the
1x MIC Ampicillin
1x MIC Ag-NP
1x MIC Amp. coated Ag-NP
10x MIC Ampicillin
10x MIC Ag-NP
100x MIC Ampicillin
100x MIC Ag-NP
10x MIC Amp. coated Ag-NP 100x MIC Amp. coated Ag-NP
Figure 2. Antibacterial agents applied to drug resistant E. Coli
common K-12 strain of E. coli bacteria on three disks containing 1x the MIC for ampicillin, ampicillin-coated Ag-NPs, and Ag-NPs. This showed zero growth for all antibiotics, which supports the conclusion that ampicillin, ampicillin-coated Ag-NPs, and Ag-NPs are all effective antibacterial agents against bacteria that are known to be not drug-resistant. A positive control test was conducted using drug-resistant E. coli on no antibacterial agent. The bacteria showed signs of regular growth experience by E. coli, indicating that cell death would be due to the independent variable, the antibacterial agent. Functionalization of Silver Nanoparticles Nanoparticles were functionalized with ampicillin by utilizing the thioether moiety present in the structure of ampicillin. The antibiotic was attached to the Ag-NPs by mixing 3.12 × 10 −4 M of ampicillin with Ag-NPs for 24 hours using a magnetic stir plate, a specific ratio modeled from previous studies . The functionalized nanoparticles were then dispersed in pH 7.0 bacterial growth media buffer, and stored away from light sources at 5°C. The previous test on the 9 different plates of agar was conducted 5 times to ensure replication of data.
Assessing Efficacy of Antibacterial Agents The drug-resistant bacteria were then transferred to 9 different plates of agar. The agar in the plates included 1x, 10x, and 100x the MIC concentration for only Ag-NPs, only ampicillin, and ampicillincoated nanoparticles. The antibacterial agents were pre-mixed into the agar solution to ensure even distribution. Results were qualitatively analyzed through observation of the bacteria after 24 and 48 hours. The data was quantified using a luciferase assay and a photometer. The luciferase assay contains a gene which codes for the luciferase enzyme. When ATP is used in the cell, the luciferase enzyme is excited and will act as a catalyst in the oxidation of luciferin, a compound which then gives off light as it is enhanced to an excited state. The assay tests the amount of ATP being used by a cell by measuring the fluorescence given off by the luciferase in the test sample and is a good quantification of the viability of a sample of cells. A low amount of fluorescence indicates a low amount of ATP usage, which in turn indicates that there are not as many living cells remaining. The luciferase assay was used to quantify the number of living cells for the effect of the antibacterial agents on E. coli.
Graph 1. Effect of Antibacterial Agent Used on the Amount of ATP Produced by E. coli
The MIC of the bacteria was assessed using the theoretical framework developed by Bonev, Hooper, and Parisot, known as the Oxford-Penicillin Cup Method .The intercept of the graph plot between the squares of the distances from the zone of inhibition and the concentration in the wafer was interpreted as the logarithm of the minimum inhibitory concentration. The effect of the antibacterial agents on precisioncut liver slices was then determined using toxicity assessments such as cell viability assays.
Results For analysis of the cultivated strain of E. coli, we relied mostly on qualitative observation. We observed that the control E. coli (non-drug-resistant) did not grow on any plates that contained antibacterial agents. After that, the same growth test was performed on the MDR strain, and it was observed that our cultivated strain grew on all the plates with varying concentrations of ampicillin, with slightly less growth on the plate with 100x the MIC concentration. This indicated that antibiotics had little to no effect on MDR bacteria. There was no visible growth for any concentration of ampicillin-coated Ag-NPs or Ag-NPs, indicating that these were more effective in killing bacteria. The qualitative data from the luciferase assay confirmed our visible results in terms of bacterial growth. In the data shown in Graph 1, the ampicillincoated Ag-NPs have the highest efficacy at inducing cell death at the lowest concentrations, indicated by lower amounts of ATP being produced by the bacterium. The MICs of the antibacterial agents were then
measured using disk diffusion tests, and determined using the Oxford Penicillin Cup Method (modified to include nanoparticles on the wafers placed in the agar plate). The logarithm of the zero-intercept through a linear regression of the data was determined as the MIC for each individual antibacterial agent; one example of this analysis is shown in Figure 3. Ampicillin-coated Ag-NPs needed a much lower concentration to inhibit bacterial growth, serving as a more effective antibacterial agent. Apoptosis and necrosis are two major forms of cell death observed in normal and disease pathologies. Although there are many assays for detection of apoptosis, there are relatively few assays available for measuring necrosis, a form of premature cell death caused by cell injury. A sign of necrotic cells is the permeability of plasma membrane, which can be quantified in tissue culture settings by measuring the release of the enzyme lactate dehydrogenase (LDH). When combined with other methods, measuring LDH release is a useful method for detection of necrosis, indicating cell viability. LDH activity was assessed in slice homogenates, and we report the amount detected in the medium as a percentage of the total content. A higher amount of LDH leakage was found for Ag-NPs than any of the other antibacterial agents, and this generally increased when a higher concentration of the agent was used. The methylthiazolydiphenyl tetrazolium bromide (MTT) reduction assay is a colorimetric assay that assesses cell metabolic activity and the cytostatic activity, or a shift from proliferation to quiescence, of potentially toxic materials. MTT is a yellow tetrazole that is reduced to purple formazan by NAD(P)H-dependent oxidoreductase enzymes. Therefore, the reduction of
Graph 2. MICs of Antibacterial Agents
this enzyme is dependent on the metabolic activity of the cell. Cells with a low metabolism, such as thymocytes, reduce very little MTT. This can therefore assay for different stages in the apoptotic process that happen before cell death. The Ag-NPs resulted in a greater MTT reduction than the ampicillin-coated Ag-NPs. From the MTT assay, there was no clear correlation between concentration of the agent and the reduction level. Glutathione is a tripeptide comprised of amino acids that serves as an antioxidant and detoxifier to boost an organismâ€™s immune system. It contains a thiol group, which attracts toxins, and is recycled within the body by undergoing a cycle of oxidation and reduction. A
Figure 3. Oxford Cup Penicillin Method Analysis
Graph 3. Effect of Antibacterial Agent on Lactate Dehydrogenase Leakage
glutathione reduction assay was completed on liver cells to analyze the effects of the antibacterial agents on the glutathione metabolism, where a deficiency in glutathione levels indicates a deterioration in the immune system. Thus, it is commonly used as an ethiological factor in testing for oxidative stress. Glutathione content remained around the same for all three antibacterial agents, with a decreasing trend due to increasing concentrations of the agents. The metallic nature of the nanoparticles may have increased the production of reactive oxygen species, leading to oxidative stress, and a time-dependent decrease of GSH content was observed.
Graph 4. Effect of Antibacterial Agent on Methylthiazolydiphenyl Tetrazolium Bromide Reduction
Discussion The purpose of this study was to assess the efficacy of differing antibacterial agents; more specifically, to determine the synergistic effect of antibiotic-functionalized Ag-NPs. The results of the study suggest that these synergistic effects exist on both an antibacterial and lower overall toxicity basis. From an antibacterial standpoint, ampicillin functionalized nanoparticles have a greater antibacterial efficacy than both ampicillin and AgNPs alone. This study reinforces the evidence from an earlier study of silver ions interacting with E. coli. This earlier study provides an analysis of the morphological changes in the E. coli after exposure to the silver ions: conglomeration of stimulated proteins, the inability of the bacterium to replicate due to damaged DNA, and interaction with thiol groups in proteins to inhibit enzyme activity . The Ag-NPs are able to attack antibiotic-resistant cells, which are resistant to the mechanism through which antibiotics induce cell death, because the Ag-NP’s employ a different mechanism of action. Antibiotics inhibit cell wall synthesis, which is easily combatted by the bacterium if it develops β -lactamase, which inactivates the antibiotic . The introduction of the bacteria to the spatial growing environment in this study mimics an evolutionary cycle, placing pressure on the bacteria to develop β-lactamase in order to survive in the environment. By evaluation of the control groups, the concept of β-lactamase as an enzyme that easily combats penicillin and other β -lactam antibiotics is affirmed. However, the reason for the greater efficacy in combination of the two is not only the different mechanism of action of the Ag-NPs, but the physical functionalization of the Ag-NPs on the ampicillin particles. Although the scope of this study was not to investigate the specific physical properties of functionalized Ag-NPs, or to characterize the particles, this would have provided further evidence as to the reason behind the synergy of the two particles. However, we theorize that Ag-NPs have a physical
Graph 5. Effect of Antibacterial Agent on Glutathione Concentration
property that prevents the inactivation of ampicillin through hydrolysis. Raman imaging indicates that random updates of the nanoparticles do not occur, which is likely as bacteria do not have endocytosis mechanisms . As the nanoparticles prevent random uptake of the ampicillin particles, this is likely the reason for their combined antibacterial efficacy, which supports these existing studies. As noted in the scope of the study, the toxic nature of Ag-NPs to human cells, due to the cause of deposition of proteins in vitro, was examined in the efficacy of the synergistic particles . This study examined in vitro liver slices. Ag-NPs target mitochondria, forming proteinaceous pores in mitochondrial membranes, which results in apoptosis . Antibiotics, on the other hand, interact with bacteria through a method which does not affect liver cells. The results of this experiment indicate that the interaction of the two, however, lowers the overall toxicity of the antibacterial agent in terms of LDH leakage and methylthiazolydiphenyl tetrazolium bromide reduction. The likely reason for this is due to the increased size of the entire particle, as an ampicillin-coated particle is much larger than a typical nanoparticle. This large size does not allow for the Ag-NPs to passively penetrate cell walls, as this is only possible for nanoparticles smaller than 5 nm, and these larger particles are likely internalized by endosomal mechanisms . More research towards the transport of ampicillin functionalized with Ag-NPs can be conducted to research the effect of size on cell uptake and toxicity. This research suggests that ampicillin-functionalized Ag-NPs may have potential to be commercialized in fields of medicine and materials science.
References 1. “Silver Nanoparticles: How They Are Bringing Antibacterial Properties to Household Appliances and Products.” AZO Materials. 2. Oldenburg, Steven J. “Silver Nanoparticles: Properties and Applications.” Sigma-Aldrich. Sigma Aldrich, n.d. Web. 15 Feb. 2017. 3. Feng, Q. L. and Wu, J . “A Mechanistic Study of the Antibacterial Effect of Silver Ions on Escherichia coli and Staphylococcus aureus”. J Biomed Mater Res. 52.4: 662-668. doi:10.1002/10974636(20001215)52:4<662::AID-JBM10>3.0.CO;2-3. (2000) 4. Bonev, B, et al. “Principles of Assessing Bacterial Susceptibility to Antibiotics Using the Agar Diffusion Method”. J Antimicrob Chemother. 61.6: 1295-1301. doi:10.1093/jac/dkn090. (2008) 5. Paterson D. L, et al. “Ampicillin/Sulbactam: Its Potential Use in Treating Infections in Critically Ill Patients”. Drugs. 67.13: 18291849. doi:10.2165/00003495-200767130-00003. (2007) 6. Brown, A. N, et al. “Nanoparticles Functionalized with Ampicillin Destroy Multiple-Antibiotic-Resistant Isolates of Pseudomonas aeruginosa and Enterobacter aerogenes and Methicillin-Resistant Staphylococcus aureus”. Appl Environ Microbiol. 78.8: 2768-2774. doi:10.1128/AEM.06513-11. (2012) 7. Stensberg, M. C. et al. “Toxicological Studies on Silver Nanoparticles: Challenges and Opportunities in Assessment, Monitoring, and Imaging”. Nanomedicine (Lond). 6.5: 879-898. doi:10.2217/nnm.11.78. (2011) 8. Allahverdiyev, A. M. et al. “Coping With Antibiotic Resistance: Combining Nanoparticles With Antibiotics And Other Antimicrobial Agents”. Expert Rev Anti-infect Ther. 9.11: 10351052. doi:10.1586/eri.11.121. (2011) 9. Jain, A and Mondal R. “TEM & SHV Genes in Extended Spectrum Beta-lactamase Producing Klebsiella Species Beta Their Antimicrobial Resistance Pattern.” Indian Journal of Medical Resources. 128.6 (2008): 759-64. Web. 15 Feb. 2017. 10. Lim, JY, et al. “A brief overview of Escherichia coli O157:H7 and Its Plasmid O157.” Journal of Microbiology and Biotechnology. 20.1 (2010): 5-14. Web. 15 Feb. 2017.
ANGELA SHA is a first-year student at the
University of Chicago majoring in Computer Science and minoring in Chemistry. She hopes to continue conducting research in the field of nanotechnology.
marine biological l aboratory
T H E S E P H OTO S W E R E TA K E N AT T H E M A R I N E B I O LO G I C A L L A B O R ATO RY (M B L) D U R I N G T H E S E P T EM B E R S U M M E R CO U R S E S A N D T H E FA L L S T U DY- A B ROA D P RO G R A M . T H E M B L I S A VI B R A N T CO M M U N IT Y D E D I C AT E D TO R E S E A RC H A N D E D U C ATI O N , A N D W E H O P E T H AT T H I S S E L EC TI O N O F P H OTO S I L LU S T R AT E S J U S T H OW S P EC IA L T H E M B L I S . Megan Costello
inquiry ORGAN TRANSPLANTATION AND HOST IMMUNITY: AN INQUIRY WITH DR. MARIA LUISA ALEGRE KATHERINE HOU
Why would the human body attack structures within it that are necessary for its function? This is the type of question that has always fascinated Dr. Maria Luisa Alegre, who originally studied medicine in Brussels. After working for 8 years as a practitioner in intensive care and
internal medicine, Dr. Alegre’s interaction with organ transplant patients led her to the University of Chicago. Here, she obtained her PhD in immunology in 1993. Since then, she has spent most of her time performing research on the various pathways involved in organ transplantation.
“As a physician treating transplant patients, I was interested in how the immune system works—in particular, in how these transplants are recognized as foreign,” Dr. Alegre explains. Organ transplants make up a vital class of treatment for individuals who face organ failure. In fact, for that category of patients, it is one of the only types of treatment available. However, these transplants can come with high risks. For instance, differences between the genetics of the donor and the genetics of the recipient can lead to transplant rejection when the immune system of the recipient recognizes the transplanted organ as foreign and responds by attacking it. Although pre-procedure preventative measures such as matching the donor’s genetics to the recipient’s genetics are taken, post-procedure treatments are usually necessary as well. The most common of which, unfortunately, involves placing the organ recipient on an immunosuppressive drug regimen that the patient is often kept on for the rest of their lives. That said, although these drugs largely exclude the patient from experiencing typical rejection-related symptoms, they can also come with complications. In particular, Dr. Alegre describes how they suppress the entire immune system. The activity of “good” immune system cells that target harmful pathogens is dampened in addition to the activity of the cells that mistakenly attack transplants as foreign. This leads into one of Dr. Alegre’s visions for how she wants her research to be applied. She ultimately wants “to suppress only the immune cells that recognize
Dr. Alegre’s current research group in the department of Immunology.
the transplant and leave the rest of the cells immunocompetent in order to fight infections and cancers.” The immune cells that Dr. Alegre refers to are members of the acquired immune system, which acts primarily through two complementary pathways. One pathway is comprised of B cells, which recognize antigens. Once activated by exposure to a foreign antigen, they generate antibodies that subsequently tag similar antigens, either inhibiting the pathogen directly or marking the pathogen for destruction. Meanwhile, T cells play a role in cell-mediated immunity. Dr. Alegre’s work mainly focuses on the latter category of cells. She has made considerable headway into how the activation of the transplantrecognizing T cells is initiated, and specifically into the transcription factors involved in the process. Focusing on a single transcription
factor called “Nuclear Factor Kappa B” (or NF-Kappa B), Dr. Alegre showed that its own suppression depresses the activity of the T cells that are typically involved in recognizing transplanted organs and initiating attacks on foreign agents. Now, Dr. Alegre’s focus has shifted slightly. Although she remains interested in how the NF-Kappa B pathway can be manipulated in pharmaceutical research, she currently works in two separate avenues of inquiry. The first avenue of inquiry is understanding how immunosuppressive therapies can be enhanced to be more selective in their inhibitory effects. The second is understanding the types of antigens that result from genetic differences between donor and recipient and how microbiota within the host might affect immune response after transplantation. Notably, such microbiota are the millions of
microbes that are found on and in us, from barrier surfaces like the skin and mucous membranes to the digestive or urinary tracts. Her reasoning for this environmental focus? “Well,” Dr. Alegre points out, “the genetics of the donor and recipient of an organ are fixed. But environment, if it plays a role in modulating immune response, is something that can be changed.” It is this potential for modification that Dr. Alegre sees as new and exceptionally exciting. If, she says, the mutual influence between a patient’s microbiota and immune system can be manipulated, then that could have direct applications for treatments in the clinic. Current knowledge already indicates that bacteria can “tune up” or “tune down” the activity of the immune system based on dietary effects. Dr. Alegre wants to take advantage of this inbuilt modulative force. She asks: is it possible to change the
microbiota to subsequently change the type of T cells that are activated? Can host microbiota be altered in a way that will make it easier for an organ to be accepted? Research on the immune response to organ transplantation and its possible connection to microbiota is rooted in Dr. Alegre’s near-exclusive focus on T cells. Although it now makes up a defining part of her career, her preference for this aspect of the acquired immune system happened through a matter of chance. During her PhD and postdoctoral training at the University of Chicago, she was supervised by two T-cell experts, Jeff Bluestone and Craig Thompson. She still recalls these experiences with great fondness and nostalgia. Yet, her interest in cell-mediated immunity is rooted much deeper than in just her PhD training. Even though the specific questions that she asks have evolved over her career, her broad area of interest hasn’t changed since her days as a doctor. It is this background in medicine that gives her a unique view on how her research can have applications in clinical settings. Too often, she says, there is a disconnect between the questions that basic researchers ask and the questions that clinicians want answered. “For me, having studied medicine, having seen the patients, having treated transplant patients, I’ve seen the problems from within the clinic. This dual training helps me find questions that are relevant and applicable to the improvement of human health.” This type of dual perspective, Dr. Alegre emphasizes, is deeply important. And, while the divide between basic researchers and clinicians has begun to narrow, there is still some ways to go in Dr. Alegre’s eyes. In her view, “because of differences in language, it’s hard to convey a clinical question in a way that a scientist would understand it. Or it’s hard to convey mechanistic pathways in a way that a clinician might understand it.” Her personal contribution to integration of these
two aspects of biomedical research materializes on two levels. Firstly, her own role as practitioner-turnedresearcher facilitates discussion between researchers and clinicians on a personal level. More broadly, Dr. Alegre’s membership in The American Transplant Foundation allows her to facilitate researcherclinician communication on a larger scale. There, typical activities that Dr. Alegre is involved in include seminars where clinicians and researchers present simultaneously to show both sides of a clinical problem. These seminars, Dr. Alegre hopes, will “link clinicians and researchers together so that the researchers know better where the big gaps in knowledge in the clinic are.” In terms of the future, Dr. Alegre maintains that she will keep advocating for clinician-researcher dialogue through integrated forums where both groups are present. In her research, she wants to focus on how easily transplantation tolerance, a state where the host immune system no longer attacks the organ transplant as foreign, is achieved, and whether it can be challenged by inflammation from acute infections. Yet, despite this outlined goal, she emphasizes, “We have so many questions, but there are only so many questions that you can tackle rigorously.” Beyond transplantation tolerance, Dr. Alegre hopes to investigate the differences in immune responses to organ transplants, tumors, and self-antigens. That said, these are just her intended projects. She recognizes the spontaneity involved in outlining new research topics, saying, “If you have a hypothesis, when your results are opposite to what you originally predicted, it’s almost more interesting. You’re surprised, and then you pursue something else.” Dr. Alegre has many questions she wants answered, and she hopes that more students will join her in cultivating an interest in research, the clinic, or both. When discussing her motivation for conducting research, she maintains
her excitement for solving clinical problems to improve patient wellbeing through biomedical research as an essential component of her drive to perform research. Dr. Alegre notes that “if people are curious and have a question that hasn’t been asked in the world before, being able to answer that question is incredibly thrilling.”
KATHERINE HOU is a first-year student at the University of Chicago planning to major in Biological Sciences and Economics.
full length Clinical Feasibility of Global Longitudinal Strain and Relationships with Systolic and Diastolic Function
Brian Yu 1 , Isabelle P. Lin 2, Betty Cornish 2, Linus Park 1, Steve S. Lin 2 1 Department of Medicine, Section of Cardiology, University of Chicago 2 Cardiovascular Ultrasound Laboratory, Saint Joseph Hospital
Abstract Global longitudinal strain (GLS) is an emerging echocardiographic technique that can detect myocardial abnormalities not delineated by traditional cardiovascular imaging. The purpose of this study was to characterize the feasibility of GLS and to relate GLS with measures of systolic and diastolic function. A total of 1159 consecutive transthoracic echocardiograms were retrospectively analyzed to obtain GLS and ejection fraction (EF), a measure of systolic function. Normal GLS was considered to be > 18% while normal EF was considered to be > 50%, as per guidelines. Out of all analyzed echoes, 632 of these had complete Doppler measurements and were further assessed for diastolic function. GLS measurement was possible in 818 of 1159 (70.6%) echocardiograms. A total of 317 of 818 (38.8%) had conflicting normal or abnormal assessments of EF and GLS. Of the disagreements, 315 of 317 (99.2%) were characterized by normal EF and abnormal GLS, while in the setting of abnormal EF, 159 of 161 patients (98.4%) had abnormal GLS. This may indicate GLS is a more sensitive measure of systolic function than EF. Linear regression revealed a correlation between the two parameters (R2 = .506, p < 0.0001). GLS is inversely related with an increasing grade of diastolic dysfunction (P < 0.005 for all comparisons, except for grade 1 vs. grade 2 diastolic dysfunction). Patients with abnormal GLS were more likely to have diastolic dysfunction (odds ratio = 13.87; 95% confidence interval, 6.7 to 29; p<0.0001). A GLS cutoff of -15.1% was found to differentiate between normal and abnormal diastolic function (area under the curve [AUC], a measure of diagnostic accuracy = 0.84). Next, diagnostic thresholds to differentiate between grades of diastolic dysfunction were identified. Grades 0 to 1 vs. grades 2 to 3 (AUC= 0.82) and grades 0 to 2 vs. grade 3 (AUC= 0.84) could be differentiated with good diagnostic accuracy. In conclusion, GLS is a feasible and clinically relevant parameter in cardiovascular disease.
Echocardiographic assessment of ejection fraction (EF) and left ventricular diastolic function (relaxation and filling of heart ventricles) play an integral role in the routine evaluation, management, and risk stratification of patients presenting with cardiovascular disease. In particular, EF is the clinical gold standard for diagnostic evaluation of left ventricular systolic function (contraction and emptying of the heart ventricles), but it is a volume-based imaging parameter that fails to describe the structural complexity of myocardial function. Similarly, there are difficulties in the interpretation of diastolic function. For instance, the American Society of Echocardiography (ASE) and European Association of Cardiovascular Imaging (EACVI) guidelines for diastolic function were updated in 2016 in order to simplify and standardize diastolic function assessment, with the ultimate goal
of increasing the accuracy and utility of guideline classification in clinical practice . Differentiating between individuals with normal and abnormal diastolic function, however, is still complicated by overlap between Doppler indices for diastolic function (values that quantify left ventricular relaxation and filling, important for diastolic function) in healthy and diseased individuals. Almost one in five patients are classified as indeterminate based on criteria stipulated by guidelines, thus frequently limiting their application . Moreover, the current 2016 guidelines can be viewed as too cumbersome for use in daily clinical practice . Echocardiography-based global longitudinal strain (GLS) is a specking tracking method for quantifying myocardial contraction with improved precision, reproducibility, and sensitivity for detecting
subclinical systolic dysfunction. In particular, GLS can be decreased despite preservation of systolic function as quantified by ejection fraction in a wide spectrum of diseased states, including heart failure with preserved ejection fraction (HFpEF), ischemic heart disease, surgical valvular disease (i.e. aortic stenosis and mitral regurgitation), hypertrophic and amyloid cardiomyopathy, and chemotherapy induced cardiotoxicity. Furthermore, in numerous studies involving broad based populations of asymptomatic at-risk patients, including patients with hypertension , diabetes mellitus , obesity , or the pathophysiological conditions listed above, GLS has consistently demonstrated increased prognostic yield over EF for prediction of cardiovascular outcomes [7,8]. The feasibility of GLS and its relationship with EF and left ventricular diastolic function has not been well characterized. The temporal and structural pathophysiological relationship between systole and diastole is highly complex, and may not be accurately described by the current cardiovascular disease paradigm in which diastolic impairment precedes systolic dysfunction. The aims of this present study, therefore, are to 1) assess the feasibility of GLS, 2) describe the relationship between GLS and EF, and 3) determine whether GLS can be related to diastolic function.
Methods Study Population The study population consisted of 1159 consecutive patients, identified from our echocardiography database of patients who underwent complete 2-dimensional transthoracic echocardiographic assessment between 2012 and 2016. Patients were excluded if images were of poor quality, image loops did not include 2-, 3-, and 4-chamber apical views, or if images did not allow for speckle tracking of left ventricle boundaries. Of the 1159 patients, 632 patients had complete and comprehensive echocardiographic assessments that allowed for diastolic function classification. An institutional review board approved the study protocol. Echocardiography All echocardiograms were performed at a single cardiac imaging center at a community hospital. Echocardiography was performed using the Vivid E9 ultrasound system (GE Healthcare, Chicago, Illinois) with a 2.5-Mhz transducer. Patients were examined with conventional 2-dimensional echocardiography. GLS was obtained with Automated Function Imaging software (GE Healthcare, Chicago, Illinois) for apical 2-, 3-, and 4- chamber views, while ejection fraction (EF) was determined via the Simpson’s Biplane method, which uses echocardiography to measure the area emptied during systole, or via visual estimation.
All echocardiograms were stored and reviewed with McKesson Imaging and Workflow Solutions (Orpheus Medical, New York, New York). Echocardiographic assessment was performed by one investigator and independently verified by a second observer, both blind to all other information. Assessment of Global Longitudinal Strain and Left Ventricular Diastolic Dysfunction Two-dimensional speckle tracking echocardiography was performed in 2-, 3-, and 4-chamber apical views. The endocardial border was traced by an automated function that defined a region of interest (ROI) at the end systole. The investigator visually assessed the detected ROI, and if necessary, manually modified the ROI to ensure proper tracking. Segments were excluded that were compromised by shadow or artifact. GLS was then calculated as an average peak strain from 3 apical projections and the ROI set to cover the entire left ventricle. If speckle tracking was not available for a single chamber view, GLS was averaged from remaining chamber views. Vendorrecommended protocol of -18% for cutoffs of normal and abnormal GLS (normal > -18%, abnormal < -18%) were followed, while normal EF was considered to be > 50%, as per guidelines. To avoid confusion, current guidelines that recommend presentation of strain data as referring to a change in deformation (increase in strain = more negative) are followed within this paper. Consequently, to simplify results and analysis, GLS is reported in absolute values. For assessment of diastolic function, from an apical 4-chamber view, transmitral pulsed-wave Doppler was obtained at the mitral leaflet tips, and peak early (E) and late (A) diastolic filling velocities, E/A ratio, and E-wave deceleration time were obtained. Peak early (e’) velocities were obtained and averaged from Doppler tissue imaging of the mitral annulus at the septal and lateral positions. Tricuspid regurgitation (TR) velocity and left atrial (LA) volume index measurements were also obtained. Classification of left ventricular diastolic function was determined by two blinded investigators, based on the 2016 update to ASE and EACVI guidelines . Statistical Analysis Data are presented as mean + SEM. Chi-squared tests, Fisher’s exact tests, Student’s t-tests, and Tukey’s tests are used as necessary to assess for differences in demographic characteristics, GLS, and other echocardiographic parameters. Receiver-operating characteristic (ROC) curves were constructed for diastolic dysfunction grades, and area under the curve was used to assess diagnostic potential of GLS. Results based on ROC curve analysis were used to find optimal GLS cutoffs to discriminate presence and grades of diastolic function. Optimal cutoff was calculated using Youden’s index, an index that optimizes the trade-off between sensitivity and specificity of the test.
Statistical significance was defined as P < 0.05, and all P values were two-tailed. All statistical analyses were conducted using SPSS version 25.0 (IBM, Armonk, USA) or GraphPad Prism version 7.0 (GraphPad Software, La Jolla, CA).
Results Patients The demographic and clinical characteristics of patients did not differ significantly between tertile of GLS, with the exception of age (Table 1). In general, the patients in this study were younger, the gender more balanced, and had fewer co-morbidities than patients enrolled in prior studies of GLS [5, 9, 10]. Tertile 1, the best tertile of strain, represents patients
with normal GLS, while Tertile 2 and 3 represent the intermediate and worst tertile of strain respectively. Feasibility of GLS and Relationship with EF GLS measurement was possible in 818 of 1159 (70.6%) echocardiograms. Among patients with available GLS, the mean GLS was 15.6% ± 4.7% and mean EF was 53.6% ± 11.7%. A total of 317 of 818 patients (38.8%) had disagreeing EF and GLS, defined as one abnormal and one normal assessment of EF or GLS. Of disagreements, 315 of 317 (99.2%) were characterized by normal EF but abnormal strain, while in the setting of abnormal EF, 159 of 161 patients (98.4%) had abnormal GLS. Linear regression analysis revealed a correlation between the two parameters (R2 = 0.5058, p < 0.0001).
Table 1. Patient Characteristics, Stratified According to Tertial of Global Longitudinal Strain*
*Plus-minus values are mean ± SD. This table only includes patients with available assessment of diastolic function. †P Values from one-way ANOVA for continuous variables and the Chi-squared test for categorical variables.
Figure 1. Relationship and association between Ejection Fraction and Global Longitudinal Strain. Panel A shows the entire dataset, plotting ejection fraction against global longitudinal strain. Graph is subdivided by clinically relevant categorizations of normality (EF > 50% and GLS < 18%).
GLS and Left Ventricular Diastolic Dysfunction Next, the possibility that GLS could differentiate between normal and abnormal left ventricular diastolic function was examined. In 145 of 288 echocardiograms (50.3%), GLS was abnormal despite normal diastolic function. Conversely, in only 24
of 179 echocardiograms (11.8%) was GLS normal in presence of diastolic dysfunction. Furthermore, there was increasingly abnormal GLS measurements corresponding to diastolic function, from normal (grade 0) to intermediate to abnormal diastolic function (inclusive of grades 1 to 3) (Figure 2). There was an increasing proportion of patients with tertile 3 and a corresponding decrease in patients with tertile 1 when comparing normal and abnormal diastolic function (Figure 3). Patients with indeterminate diastolic dysfunction have proportions of tertile 1 and tertile 3 between normal and abnormal diastolic function. Only 20 of 210 patients (9.5%) with diastolic dysfunction were in tertile 1, but 94 of 211 patients (44.8%) in tertile 3 had diastolic dysfunction. GLS and Grade of Left Ventricular Diastolic Dysfunction Additional analysis was performed to examine if GLS thresholds could differentiate between grade of diastolic dysfunction. ROC curves demonstrated that a GLS cutoff level lower than 15.1% was found to predict abnormal diastolic function, with an area under the curve (AUC, a measure of diagnostic performance) of 0.84 (Figure 4A and Table 2). ROC curves demonstrated an AUC of 0.82 and 0.84 for differentiating between grades 0 to 1 vs. grades 2 to 3
Figure 2. Global Longitudinal Strain According to Left Ventricular Diastolic Function. Tukeyâ€™s box plots of global longitudinal strain are stratified according to diastolic function (normal, indeterminate, abnormal grade 1, grade 2, and grade 3). The bottom and top of each box are 25th and 75th percentiles of strain distribution, respectively, and horizontal line in box represents the median. I-bars represent 1.5 interquartile range of the 25th and 75th percentiles; circles show outliers beyond this range. All comparisons are statistically significant (P<0.005 by Tukeyâ€™s multiple comparisons test), except for grade 1 versus grade 2 (P= 0.2707).
A. Distribution of Global Longitudinal Strain Tertiles by Diastolic Function
Tertile 1 Tertile 2 Tertile 3
C. Distribution of Grade of Diastolic Dysfunction by Tertile of Global Longitudinal Strain
Figure 3. Distributions of Left Ventricular Diastolic Dysfunction by Global Longitudinal Strain. Panel A shows distributions of tertiles of global longitudinal strain by diastolic function. Percentage of patients in tertile 3 increased from 15.1% in patients with normal diastolic function to 69% in patients with abnormal diastolic function. Percentage of patients in tertile 1 decreased from 47% in patients with normal diastolic function to 12% in patients with abnormal diastolic function (P < 0.0001 for heterogeneity). Panel B shows the percentage of patients with diastolic dysfunction according to classification (normal vs. abnormal) of global longitudinal strain. Threshold of abnormal global longitudinal strain was set at > -18%, according to vendor specifications. A small percentage of patients with normal global longitudinal strain had diastolic dysfunction (9.1%), while 45% of patients with normal diastolic function had abnormal global longitudinal strain (P < 0.0001 for heterogeneity). Panel C examines changes in distribution of grade of diastolic dysfunction by tertile of global longitudinal strain. Grade 3 diastolic dysfunction increased from 10% of patients in tertile 1 to 32% of patients in tertile 3 of global longitudinal strain (P < 0.0001 for heterogeneity).
and grades 0 to 2 vs. grade 3, respectively, indicating good diagnostic performance (Figure 4B, 4D, and Table 2). Optimal GLS cutoffs were identified: 14.6% for differentiation between grades 0 to 1 vs. grades 2 to 3 and 12.8% for differentiation between grades 0 to 2 and grade 3. By further adjusting the GLS cutoffs, negative predictive values (NPVs) were generated to act as â€œrule-outâ€? surrogates for the grade of diastolic dysfunction. For instance, a GLS cutoff at 16.73% for differentiation between grades 0 to 1 vs. grades 2 to 3 has an NPV of 93%. Similarly, a GLS cutoff at 18% for differentiation between grades 0 to 2 vs. grade 3 has an NPV of 100%, indicating that no participants in our study population with grade 3 diastolic dysfunction had a GLS of lower than 18%.
Discussion With its undisputed ability to measure subtle loss of longitudinal contraction and detect myocardial dysfunction not measurable by ejection fraction, GLS offers contemporary mechanistic insights into myocardial contractility that challenge the established paradigm that diastolic impairments precede systolic dysfunction. Several investigators have already reported that abnormal GLS can be present in atrisk asymptomatic patients with diabetes, obesity, hypertension, with presumably intact diastolic function. Wang et al. (2018) concluded that using an updated definition of myocardial function based on GLS can drive large-scale reclassification and enhanced identification of asymptomatic diabetic patients with Stage B heart failure . Consistent with these observations in previous studies, this is the first study to demonstrate that a GLS-based definition of left ventricular systolic dysfunction can and often does occur in the absence of diastolic dysfunction. Furthermore, GLS is inversely related to increasing grades of diastolic dysfunction. GLS thresholds can be identified that accurately rule out the presence of diastolic dysfunction, and indeed, differentiate between grades of diastolic dysfunction. The high accuracy of these GLS thresholds is especially notable in the context of the sampling process used in this study, namely, using a consecutive unselected sample population of this study and excluding solely based on study quality and completeness of GLS and diastolic data. Consequently, these findings suggest that GLS can be used for identification of left ventricular diastolic dysfunction in routine real-world clinical practice for a broad spectrum of patients. Furthermore, our findings demonstrate that GLS is relevant to left ventricular diastolic function, whereas prior studies have mainly focused on GLS as a technique for assessment of left ventricular systolic function [10, 12]. While the current standard of care for diagnosis of diastolic dysfunction is through Doppler
Figure 4. Receiver Operating Characteristic (ROC) Curves for Differentiating Between Classifications of Left Ventricular Diastolic Function by Global Longitudinal Strain. Shown are ROC curves for detection of normal or abnormal diastolic function (Panel A), normal to grade 1 or grade 2 to 3 diastolic dysfunction (Panel B), normal or grade 3 diastolic dysfunction (Panel C), and normal to grade 2 or grade 3 diastolic dysfunction (Panel D).
echocardiographic assessment, there are limitations to this approach. For instance, prior studies using Doppler echocardiography and invasive hemodynamic assessments suggest that single parameters such as the E/eâ€™ ratio are indicators of left ventricular filling pressure. However, followup studies have also shown single parameters for assessment of left ventricular diastolic function to be imprecise, with low specificity for patients with preserved EF, in particular. These studies support the current prevailing methodology based on a composite of 2-dimensional, spectral, and tissue Doppler indices for more accurate assessment of left
ventricular diastolic function [13, 14]. However, even with the simplifying updates made to the diastolic function guidelines in 2016, using multiple Doppler indices in the clinical setting can be time-intensive. Furthermore, potentially inconsistent or overlapping Doppler parameters necessitates the inclusion of the â€œindeterminateâ€? diagnosis. In our study sample, 141 of 632 individuals (22.3%) were classified as such, a similar rate to those in other studies [15, 16]. The high numbers of indeterminate diagnoses suggest a need for simplified, precise, and higher yield approach to identify the assessment of diastolic function in patients.
Table 2. Receiver Operating Characteristic (ROC) Curve Diagnostic Threshold Analysis for Left Ventricular Diastolic Dysfunction. GLS = global longitudinal strain; NPV = negative predictive value; PPV = positive predictive value.
Strain measurements aside from GLS have been identified for use in diagnosis of diastolic function. In particular, strain-rate imaging has been suggested as conferring prognostic information towards diagnosis of diastolic dysfunction independent of conventional Doppler indices . Specifically, left atrial (LA) strain has been identified as a potential tool for detecting and categorizing diastolic dysfunction . Other groups, however, suggest that strain rate imaging offers no incremental benefit to established indices, such as E/eâ€™, in patients with diastolic dysfunction but normal ejection fraction . Furthermore, in comparison with GLS, LA strain and strain-rate imaging are novel techniques still in the research stage of development . These findings highlight the need for a higher yield and streamline the methodology for diagnosis of diastolic function, in particular to reduce the number of indeterminate diagnoses. While the strengths and relative advantages of the speckle tracking technique over conventional 2-dimensional and Doppler indices are well documented, namely enhanced precision and reproducibility, there are still limitations to the use of strain. Despite collaborative efforts by the ASE and EACVI to standardize strain values across vendors, there are still vender-dependent differences in speckletracking software, leading to slightly varying strain measurements that make it inadvisable to generalize values across vendors. Limitations to our study include the lack of correlations with other measures of myocardial strain, including circumferential strain and strain rate, which were not available to further clarify the sequence of maladaptive pathophysiology in myocardial deformation and relaxation in the minority of patients who had normal GLS but abnormal diastolic dysfunction. Beyond GLS, however, there are unresolved limitations including increased variability and paucity of evidence supporting clinical utility, which continue to slow research into other deformation
indices. Future mechanistic studies including comprehensive myocardial deformation indices and invasive measures of diastolic function (including Ď„, a time constant of diastolic relaxation) will be required to advance the understanding of complex myocardial relationships during the cardiac cycle.
Conclusion Our results indicate that GLS is feasible in the clinical setting and associated with EF and severity of diastolic dysfunction. Importantly, GLS is frequently abnormal in absence of diastolic dysfunction. Conversely, when GLS is normal, diastolic dysfunction is uncommon. GLS has the potential to become a useful tool for systolic and diastolic assessment in clinical practice.
References 1. Nagueh S. F., et al. Recommendations for the Evaluation of Left Ventricular Diastolic Function by Echocardiography: An Update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr 29:4, 277-314. (2016) 2. Gottbrecht M. F., et al. Evolution of diastolic function algorithms: Implications for clinical practice. Echocardiography 35:1, 39-46. (2018) 3. van Dalen B. M., et al. A simple, fast and reproducible echocardiographic approach to grade left ventricular diastolic function. Int J Cardiovasc Imaging 32743-52. (2016) 4. Narayanan A., et al. Cardiac mechanics in mild hypertensive heart disease: a speckle-strain imaging study. Circ Cardiovasc Imaging 2:5, 382-90. (2009)
15. Clancy D. J., et al. Application of updated guidelines on diastolic dysfunction in patients with severe sepsis and septic shock. Ann Intensive Care 7. (2017) 16. Almeida J. G., et al. Impact of the 2016 ASE/EACVI recommendations on the prevalence of diastolic dysfunction in the general population. Eur Heart J Cardiovasc Imaging 19:4, 380-6. (2018) 17. Singh A., et al. LA Strain Categorization of LV Diastolic Dysfunction. JACC Cardiovasc Imaging 10:7, 735-43. (2017) 18. Kasner M., et al. Global strain rate imaging for the estimation of diastolic function in HFNEF compared with pressure-volume loop analysis. Eur J Echocardiogr 11:9, 743-51. (2010) 19. Collier P., et al. A Test in Context: Myocardial Strain Measured by Speckle-Tracking Echocardiography. J Am Coll Cardiol 69:8,
5. Jensen M. T., et al. Global longitudinal strain is not impaired in type 1 diabetes patients without albuminuria: the Thousand & 1 study. JACC Cardiovasc Imaging 8:4, 400-10. (2015) 6. Wong C. Y., et al. Alterations of left ventricular myocardial characteristics associated with obesity. Circulation 110:19, 3081-7. (2004) 7. Russo C., et al. Prevalence and prognostic value of subclinical left ventricular systolic dysfunction by global longitudinal strain in a community-based cohort. Eur J Heart Fail 16:12, 1301-9. (2014) 8. Biering-Sorensen T., et al. Global Longitudinal Strain by Echocardiography Predicts Long-Term Risk of Cardiovascular Morbidity and Mortality in a Low-Risk General Population: The Copenhagen City Heart Study. Circ Cardiovasc Imaging 10:3. (2017) 9. Ersboll M., et al. Early diastolic strain rate in relation to systolic and diastolic function and prognosis in acute myocardial infarction: a two-dimensional speckle-tracking study. Eur Heart J 35:10, 648-56. (2014) 10. Kamperidis V., et al. Left ventricular systolic function assessment in secondary mitral regurgitation: left ventricular ejection fraction vs. speckle tracking global longitudinal strain. Eur Heart J 37:10, 811-6. (2016) 11. Wang Y., et al. Diagnosis of Nonischemic Stage B Heart Failure in Type 2 Diabetes Mellitus: Optimal Parameters for Prediction of Heart Failure. JACC Cardiovasc Imaging 11:10, 1390-400. (2018) 12. Krishnasamy R., et al. Left Ventricular Global Longitudinal Strain (GLS) Is a Superior Predictor of All-Cause and Cardiovascular Mortality When Compared to Ejection Fraction in Advanced Chronic Kidney Disease. PLoS One 10:5. (2015) 13. Dokainish H., et al. Do additional echocardiographic variables increase the accuracy of E/eâ€™ for predicting left ventricular filling pressure in normal ejection fraction? An echocardiographic and invasive hemodynamic study. J Am Soc Echocardiogr 23:2, 156-61. (2010) 14. Dokainish H. Left ventricular diastolic function and dysfunction: Central role of echocardiography. Glob Cardiol Sci Pract 2015. (2015)
BRIAN YU is a fourth-year student at the
University of Chicago, majoring in Biology. He is applying to medical school this summer, with the aspiration of becoming a physician. Brian aims to continue biomedical research in medical school and beyond, with the hopes of uncovering discoveries that may help advance the field of medicine.
inquiry THE FUTURE OF WEARABLE DEVICES AND HUMAN-COMPUTER INTERACTIONS: AN ILLUMINATING TALK WITH PROFESSOR PEDRO LOPES JARVIS LAM
Imagine being able to use an ordinary-looking pen capable of guiding your hand movements, a pen that can direct your hand in plotting any graph once you have written down its equations. Welcome to Muscle Plotter, a futuristic device successfully
developed by Dr. Pedro Lopes, an Assistant Professor in the Department of Computer Science who works in the fields of human-computer interaction, virtual/augmented reality (VR/AR), and wearable computing. He leads a research group that takes human
body-computer interactions to the next level by developing interactive systems that utilize the user’s body for input and output. Dr. Lopes’ work lies at the forefront of his field, having captured the interest of media such as the MIT Technology Review, NBC, Discovery Channel, and Wired. Interactive devices have fascinated Dr. Lopes since he was an undergraduate student at the Instituto Superior Tecnico in Lisbon, known as Portugal’s most prestigious engineering school. He recalls, “At the time of my Master thesis, an overall research question was concerning what would happen to the interactions between humans and touch screen devices if one were to scale these touch screens to a much larger scale.” Intrigued by the question, Dr. Lopes created a table-sized touch screen for DJ-ing. By having actual DJ experts test out his device, Dr. Lopes gained some valuable insights. He notes: “While some people would still prefer the traditional turntables, many got very creative with the device, as it facilitated complex interactions that were not possible without the aid of computers.” His eventual solution was a hybrid device with actual turntables overlaid upon the touchscreen, allowing for a realistic feeling that offers a greater degree of complexity for manipulating records. Through the experiment, Dr. Lopes realized that a combination of the physical and virtual is often effective in providing an authentic interaction experience between computers and
From left to right: Spray can that shakes by itself. Cup that repels when too hot.
humans. This insight went on to fuel many of his best projects in building futuristic, interactive devices. For his doctoral degree, Dr. Lopes attended the Hasso Plattner Institute in Germany and worked under Professor Patrick Baudisch in his Human-Computer Interaction Lab. Here, Dr. Lopes began working on a new interactive system between humans and computers that utilize electrical muscle stimulation. “Look at the recent trajectory of modern electronic devices,” he explains. “We first had mainframe computers, then personal desktops and eventually portable laptops; these evolved into smartphones, and finally to wearable devices like smartwatches.” According to Dr. Lopes, the trend is that devices are becoming smaller, more personal, and more integrated into our body and daily life. He asks, “So what’s next? What’s even smaller, more direct, and more intimate? What is a step beyond carrying devices in your pockets and wearing devices on your body?” Pondering this question led Dr. Lopes to consider having computers connect directly to our body parts and “become an extended part of our muscles.” He developed an interactive system called the Muscle Plotter, which allows computers to communicate with human arm muscles through the use of electromyography (EMG), the technique for evaluating and recording the electrical activity produced by muscles, and electrical muscle stimulation (EMS), the practice of
eliciting muscle contractions using electrical impulses. In particular, the devices that Dr. Lopes built are best described as a set of wearable medical stimulators and pairs of electrodes capable of reading proprioceptive electrical inputs from muscles, and conversely, sending electrical signals to those muscles as outputs. By having computers interface directly with our arm muscles, two forms of human-computer interactions can happen. First, users can stretch or contract their muscles by actions such as reaching or grasping, sending electrical signals triggered by muscle tension to computers to execute pre-specified commands. For example, one can program a light bulb to switch off and on with the clench of a fist. However, the real significance lies in the other direction, where computers can send electrical signals back into the user’s body through the adhered electrodes to create “virtual” haptic sensations (tactile sensations) and guide muscle movements by triggering certain reflexes. For Dr. Lopes, the construction of these devices opens a window of novel ways that humans and computers can interact with one another. Exploring the real-life applications of these new interaction methods led Dr. Lopes to develop two other intriguing projects besides the Muscle Plotter. One such application is named VR Walls, which aims to provide a more realistic and immersive user experience in virtual reality by providing haptic sensations to virtual walls and other large forces
such as physical impacts, wind, or heavy objects. According to Dr. Lopes, one problem in virtual reality is the frequent mismatch between the users’ multiple sensory inputs which result in confusion. In other words, one might spot a very realistic wall in VR but not perceive it through the sense of touch. Dr. Lopes’ wearables provide the perfect solution; by sending electrical signals to users’ arms whenever they encounter a wall in virtual reality, computers can contract the users’ muscles and create a realistic force against their arms, simulating a VR wall. His second project, which won the CHI Best Paper Award, is named Affordance++. According to Dr. Lopes, every single tool we interact with is designed for a particular use, and that use is often communicated through its visual design. However, sometimes recognizing how one should use complex tools it is not intuitive. Dr. Lopes proposed to solve this problem by allowing objects to dynamically communicate their use through the proprioceptive sense, which led to his development of Affordance++. This concept is called affordance. For example, a pen is designed so that one can look at the pen and intuitively deduce that they should remove the cap before being able to write. “Take the spray can for example,” he demonstrates. “You give somebody the spray can and they may be able to figure out how to use it, but they may forget that you need to shake the can before spraying. If they were wearing Affordance++,
the moment they touch the can, the system immediately guides their hand to shake through electrical muscle stimulation.” Dr. Lopes has successfully tested out the use of Affordance++ on various tools such as door handles and avocado peelers, whose use may be more easily taught via muscle learning rather than visual. When asked about his awards, Dr. Lopes was humble: “Honored as I am, I believe the real satisfaction behind my work and what drives my lab forward is more the ability to answer questions like how can we engineer future devices to connect more personally and directly to our body. That is also partly why I have chosen to become an academic. I like the constantly learning approach to life and being able to choose what I want to work on in life.” A new addition to the University of Chicago faculty, Dr. Lopes is in the process of setting up his facility to begin taking part in new summer projects. One of his current projects is with Dr. Jun Nishida, a postdoctoral student in his research group. Together, they investigate the question of how to make EMS devices such as the Muscle Plotter feel more authentic: “When the plotter tells your hand to move in certain ways, usually you would feel that you had no agency and that you know that you are being controlled. We are interested in seeing if we can fool humans to think that they are the ones committing the actions during certain tasks by delaying and triggering EMS by the right timing.” To answer this question, Dr. Lopes conducted a simple study where people were made to catch dropping pens using an EMS device and subsequently asked whether they themselves or the machine caught the pen. He then varied the EMS response time with respect to humans’ normal reaction time and measured their feeling of agency for each timeframe. If the machine responded too quickly, people knew that the EMS devices performed the action; if the machine responded too late, then the subjects fail to catch the pen. From this experiment, Dr.
A wearable implementation using EMS and RFID.
Lopes found a “sweet time spot” that results in the optimal feeling of agency. Specifically, for this particular task and many of a similar nature, if an EMS device reacts only 80 milliseconds faster than humans’ normal reaction time, then the action is perceived normally. Future work in making EMS devices feel more authentic includes developing a VR system that uses an electroencephalogram (EEG) to measure users’ immersion by detecting multi-sensory mismatches in their prefrontal cortex. Regarding the ethical issues associated with his devices, Dr. Lopes recalls his art exhibition at Ars Electronica 2017, a sculpture with an opening to place a hand inside. When a hand enters the sculpture, it traps their hand and starts stimulating the hand muscles, forcing them to grab a lever and repeatedly pull it up and down, in turn generating the power needed to run the machine. “Quite the statement, isn’t it?” Dr. Lopes muses. Dr. Lopes believes in the multi-disciplinarity witnessed in the academic culture at UChicago, advocating for more collaboration between computer science and the arts. He hopes to raise campus awareness about the field of humancomputer interactions and further
integrate it into the research scene, one of his reasons for joining the university’s faculty. Regardless of their potential ethical implications, Dr. Lopes’ inventions will surely redefine the ways humans will interface with computers in the years to come, having laid the foundation for an entirely new subfield of human-computer interactions.
JARVIS LAM is a secondyear at the University of Chicago majoring in Computational and Applied Math. He is interested in the field of machine learning, computer vision, natural language processing and how it intersects with the study of the human mind. He plans to eventually work in strong AI.
bscd BSCD abstracts Optimizing BIN1 BioID2 in a Mouse Neuroblastoma Cell Line Aleksandra Recupero 1, Robert Andrew 1, and Gopal Thinakaran 1 1 Department of Neurobiology, University of Chicago The Bin1 gene has been identified through genome-wide association studies as the second most prevalent genetic susceptibility locus for late-onset Alzheimer’s disease. Although BIN1 has been implicated in the regulation of endocytosis and cell membrane dynamics, the function of BIN1 in the brain and its contribution to Alzheimer’s disease (AD) pathogenesis remain largely unknown. Therefore, in order to better understand the function of BIN1 and its isoform specific differences in AD, we sought to identify proteins that interact with BIN1 through the use of BioID2. BIN1 BioID2, or proximity-dependent biotin identification, utilizes a promiscuous biotin ligase-BIN1 fusion that biotinylates proteins proximal to BIN1. We cloned Bin1 isoform 1 and Bin1 isoform 9 into BioID2 and 13X Linker BioID2 vector backbones. Following sequence confirmation, the constructs were transfected into N2a cells to produce stable cell lines. Immunofluorescence staining of the stable cell lines revealed overexpression of BIN1 and biotinylated proteins in the same cells, indicating that the BIN1:BioID2 fusions are successfully biotinylating proteins within the cells. Next, primary cultures of neurons and oligodendrocytes will be transfected with the Bin1:BioID2 constructs. The biotinylated proteins will be recovered by streptavidin-conjugated beads, separated by SDS-PAGE, and identified through mass spectrometry. The identified proteins will provide a large dataset of proteins that either interact with or are present within the cellular environment of BIN1. The discovery of novel proteins that may interact with BIN1 will help elucidate the role of BIN1 as an AD risk gene.
On the Functional Significance of a NewlyObserved N-terminus Segment of the Mechanosensitive Channel MscS Allen Lu 1 , Bharat Reddy 1 , Navid Bavi 1 , and Eduardo Perozo 1 Department of Biochemistry and Molecular Biology, University of Chicago
MscS is a membrane protein linked to E. Coli’s hypo-osmotic shock response. Recent electron-microscopy data reveals an MscS region unresolved from the x-ray crystal structures, including an extension of TM-helices and a novel N-terminus fold. From this, I hypothesized that the N-terminus and TM-helices are located “higher” in the bilayer than previously modeled, and that this newly-observed region may be part of a novel gating mechanism. Individual downshock assays were performed on MJF465 (osmoregulating-channel-deficient E. Coli) transformed with different alanine point mutations of the newly-resolved region, including another mutant “Cryst” in which the region is cleaved. Mutants with significantly lower survival rates than cells with wild-type MscS were deemed functionally important and examined further in liposomes using patch clamp electrophysiology to determine their pressure-dependent open probability. These tests revealed many significant residues, including “Cryst,” suggesting the newly resolved region is indeed functionally important for gating. In particular, residues involved in intersubunit interactions seemed most relevant to relieving osmotic pressure. Because MscS is a force-from-lipid channel, the importance of the newly resolved region suggests the N-terminus and TM-helices are docked “higher up” in the bilayer rather than, as previously thought, along the helices. Therefore, previous models utilizing the incomplete crystal structure or incorrect docking location must be reinterpreted.
Optimizing Hospitalist Care: A Time in Motion Study Annie Feldkamp, Romy Portieles, and Andrew Schram 1 University of Chicago Medicine, Section of Hospital Medicine
Background: Doctors and patients are increasingly dissatisfied with the amount of time physicians spend with patients; this study sought to generate discrete and quantitative data on how much of physicians’ time is spent doing non-physiciancritical activities and how that affects the amount of time doctors spend with their patients. Currently, there are few studies that explore how doctors spend their time, and even fewer that collect data through direct observation. Methods: To better understand exactly how physicians’ time is spent, two research assistants conducted a time in motion study, directly observing 5 different hospitalist doctors at the University of Chicago Medical Center for one week. During this time, physician’s activities were recorded every minute of the day into a pre-prepared spreadsheet of possible tasks that included 6 general categories and 35 sub-categories of possible activities. Results: Altogether, 95 hours of hospitalist activity were recorded. After the observation period, and upon analyzing the data, physicians’ activities were broken down into physician-critical activities, non-critical activities, administrative activities, and time spent walking, as well as into time spent in direct patient care vs. indirect patient care. We found that on average, less than 20% of physicians’ time is spent directly caring for patients. Additionally, we found that doctors spend ~ 30 minutes per day on average doing non-critical work, with great variation from doctor to doctor, depending on the number of patients and the needs of each patient. Conclusion: Hospitalist physicians spend a significant portion of their days performing non-critical and administrative activities, thereby limiting the amount of time spent in direct patient care. As a result, hospitalist physicians spend very little time in face-to-face interactions with their patients. Interventions aimed at reducing the time spent in such non-critical activities have the potential to improve efficiency, quality of care, the doctor-patient relationship, and decrease physician burnout. Future opportunities for research could focus on the impact of shifting non-critical physician work to other types of healthcare providers.
Primary Succession on Slag Sites and Uncontaminated Soil: A Comparison Hengxing Zou 1 , Catherine Pfister 2 , and Alison Anastasioi 3 1 Department of Ecology and Evolution, University of Chicago, 2 Program on Global Environments
Slag, or waste from the steel-making process, contains large amounts of calcium, magnesium, iron and other heavy metals. Because of its composition, low pH and water retention ability, slag is considered an inhospitable environment to plants. Nevertheless, the spontaneously generated plant communities on slag are surprisingly diverse, but the assembly and structure of such communities is poorly studied. Previous studies have identified a slow process of succession due to low growth rate and slow accumulation of topsoil. Using two former industrial sites on the South Side of Chicago, IL, I investigated whether slag communities display similar patterns. All vegetation from plots on both slag and non-slag soil was removed to test whether primary succession differed over one growing season (4 months). To directly assess plant growth, selected species were planted on both sites and harvested. I show that primary succession differed on slag and non-slag soils. The recruitment process on slag, measured by percent coverage and number of recolonized species, was overall slower; however, the difference was not significant until 6-8 weeks of experiment, suggesting potential stage-dependent effects of slag on plant growth. Functional trait analysis found that graminoid and early successional species preferentially colonized slag plots. Furthermore, slag plots recovered slower from disturbance, suggesting a slow succession process that hinders natural recovery. However, slag also has the potential of hosting flora of analogous habitats native to the area, serving as a plant refuge. Restoration efforts should be informed by the low possibility of natural recovery of slag plots and slag’s potential as a native plant refuge.
Loneliness, Social Disconnectedness and Sleep in Older Adults Jade Benson 1, Veronica McSorley 1, Louise Hawkley 2, and Diane S. Lauderdale 1 1 University of Chicago, 2 National Opinion Research Center (NORC) at the University of Chicago
Objectives: The goals of this study were to (1) analyze whether social connectedness and loneliness are related to sleep in older adults, and (2) examine whether these variables differed for subjective and objective sleep measures. Methods: This study used the National Social Life, Health, and Aging Project (NSHAP) wave 2 data, which are nationally representative of community dwelling older adults born between 1920-1947. The sleep sub-study (n = 759) contained both subjective questions about sleep quality and objective sleep measurements through 72hr wrist actigraphy. A UCLA Loneliness Score was constructed from three questions to measure perceived loneliness. The Social Disconnectedness Score was calculated from eight measurements that describe network size, complexity, and interactions. OLS and ordinal logistic regression was used to examine whether sleep measures are associated with loneliness and social isolation, adjusted for potential confounders. Results: Increased loneliness is related to both worse objective and subjective sleep measurements, especially an increased insomnia symptom score after controlling for demographics and marital status (p = 0.001). Increased social isolation is related to worse objective sleep measures but not subjective sleep quality. The more socially isolated individuals are, the more interrupted their sleep is (wake after sleep onset-WASO; controlled for demographics and marriage, p=0.042) and their sleep is more fragmented (controlled for demographics, p = 0.039). Discussion: These results suggest that (1) loneliness is associated with how people experience sleep and objective sleep measures, and (2) social networks and interactions are only related to objective sleep measures.
Bystanders Bidirectionally Alter Helping Behavior in Rats John Havlik 1, Yuri Sugano 1, Maura Clement 1, and Peggy Mason 1 Department of Neurobiology, University of Chicago
The Bystander Effect is defined as decreased helping behavior in group settings. The effect has been observed in humans for over fifty years. The most prominent hypothesis on why the Bystander Effect occurs is that there is a “diffusion of responsibility” across groups of humans in emergency scenarios. A trapped rat was placed in a restrainer which could only be opened from the outside to create an effective distress scenario in which the Bystander Effect might be observed. The Bystander Effect was observed in the form of increased time taken to open a restrainer door for a trapped rat by a rat set free in the arena, when experimental confederates given an anxiolytic were also present in the arena. The presence of a strong Bystander Effect in rats calls into question the validity of the “diffusion of responsibility” hypothesis, which depends on higher cognitive function. We propose the effect occurs because rats and humans take the judgments of a group into account and integrate these judgments with their own reasoning when making decisions. More simply, a rat’s decision to help another rat is informed by the perceived decisions and actions of other rats present.
Identifying Neuronal Subtypes Expressing Drosophila DIP Proteins Katie DeLong 1, Meike Lobb-Rabe 1, James Ashley 1, and Robert Carrillo 1 1 Department of Molecular Genetics and Cell Biology, University of Chicago
Neurons form specific connections within neural circuits, yet the precise molecules and mechanisms underlying synaptic target recognition remain poorly understood. Dprs (defective proboscis extension response) and their cognate binding partners, DIPs (Dpr interacting proteins), are cell surface proteins and have been shown by our lab and others to be involved in circuit wiring of the Drosophila eye. DIP-ɑ significantly influences motor axon targeting in the peripheral nervous system and is co-expressed with DIP-η and ζ in several motor neurons. This co-expression suggests that these DIPs may play redundant roles in synaptic target recognition. Thus, we wanted to identify neuronal subtypes in the fly visual system which co-express these DIPs. We utilized a stochastic multi-colored FLP-out (MCFO) technique to determine expression of DIP-ɑ, η, and ζ. The technique allows us to identify distinct neuronal morphologies of single neurons. We compared the morphologies of the labeled neurons to a study by Fischbach and Dittrich 1989 that used Golgi labeling to characterize neurons within the optic lobe. This comparison allowed for the clear identification of subsets of neurons that expressed DIP proteins. DIP-ɑ, η, and ζ expression were found in laminal, trans-medulla, medulla, and trans-lobula cells. Of the neurons which co-expressed these DIPs, most functioned in motion processing, suggesting that these proteins may function in a subset of neurons within the motion detection circuit. Future studies will clarify how redundancy impacts neuronal wiring.
Voltage Mapping Across Neural Cell Membranes Using a DNA-Based Probe Katharine Henn 1, Anand Saminathan 2, and Yamuna Krishnan 1,2 Department of Neuroscience, University of Chicago, 2Grossman Institute for Neuroscience
In order to understand how neural diseases can be prevented, diagnosed, and treated, it is first necessary to understand the core mechanism of neural signal transduction: membrane voltage. Currently, calcium, small molecule, and protein-based imaging methods do not allow for absolute quantification of membrane potential changes that occur as action potentials propagate. In this project, we propose the characterization of a DNA-based fluorescent reporter that allows for quantitative, dynamic study of individual action potentials. The reporter contains a voltage sensitive fluorophore as well as a reference fluorophore for ratiometric quantification of membrane potential during action potential propagation. This project presents a probe that is targetable, adaptable, and able to be used for study of minute neuronal membrane potential changes on the millisecond scale as well as for populations of human neurons. The long-term goal of the project is to look at the relationship between membrane potential changes and organelle voltage, paying particular attention to the voltage dependence or independence of diseases, including cancer and neurodegenerative disease.
Caregiver Reconstruction of Children’s Errors: The Preservation of Complexity in Patterned Systems Madeline Meyers 1, Daniel Yurovsky 1 Department of Psychology, University of Chicago
Why do languages change? One possibility is they evolve in response to two competing pressures: (1) to be easily learned, and (2) to be effective for communication. In a number of domains, variation in the world’s natural languages appears to be accounted for by different but near-optimal tradeoffs between these pressures. Models of these evolutionary processes have used transmission chain paradigms in which errors of learning by one agent become the input for the subsequent generation. However, a critical feature of human language is that children do not learn in isolation. Rather, they learn in communicative interactions with caregivers who draw inferences from their errorful productions to their intended interests. In a set of iterated reproduction experiments with both children and adults, we show that this supportive context can have a powerful stabilizing role in the development of artificial patterned systems, allowing them to achieve higher levels of complexity than they would by vertical transmission alone. Yet, the systems retain equivalent transmission accuracies—they are equally easy to transmit to the new generation. Thus, the caregiver plays a dual role as both a teacher and a protector of the patterned system as whole, facilitating its evolution to an optimal balance of learnability and communicability.
Wnt Signaling in Schwann Cells Affects Peripheral Nerve Regeneration Nikita Mehta 1, Benayahu Elbaz 1, Anna Kolarzyk 1, Betty Soliven 1, and Brian Popko 1 The University of Chicago Center for Peripheral Neuropathy, Department of Neurology, University of Chicago
The peripheral nervous system (PNS) is unique in its ability to recover from nerve injury. In a process termed Wallerian degeneration, the axons and myelin distal to the site of injury degenerate and are cleared by Schwann cells and macrophages. Subsequently, Schwann cells dedifferentiate, proliferate, guide axons to their germane targets, redifferentiate, and myelinate the axons. Nevertheless, the molecular mechanisms controlling PNS regeneration are not fully understood. We have demonstrated a role of the canonical Wnt/-catenin signaling pathway in developmental myelination of the PNS. The ablation of APC, a critical inhibitor of Wnt signaling, from Schwann cells activates this pathway, leading to impaired developmental PNS myelination. These results suggest that Wnt signaling may also play crucial role in PNS regeneration. We used reporter mice to study Wnt pathway activation following sciatic nerve crush injury. Wnt signaling was strongly activated in Schwann cells as early as three days, and at least up to seven days post-crush injury. We have preliminary electrophysiology and electron microscopy data that suggests that the conditional ablation of APC in adult Schwann cells activates the Wnt pathway and delays recovery from peripheral nerve injury. Our data suggests that the activation of Wnt signaling in Schwann cells impedes PNS regeneration. We will next examine the potential of pharmacological mechanisms to inhibit Wnt signaling following PNS injury and to improve regeneration.
Investigating an Alzheimer’s Disease Risk Factor: The Role of BIN1 in Oligodendrogenesis Pedro Del Cioppo Vasques 1 , Pierre DeRossi 1 , Mitch Hansen 1 and Gopal Thinakaran 1 Department of Neurobiology, University of Chicago
Genome-wide association studies have identified BIN1 as a major genetic risk asystem (CNS) is still unknown. Previous studies from our lab have shown that BIN1 is predominantly expressed in the white matter of the brain by mature oligodendrocytes. Furthermore, brain imaging of patients with and without Alzheimer’s disease has demonstrated that myelin defects are present at the first stage of pathology and can be used as prognostic marker for the disease. Here, we explore the role of BIN1 in proliferation and maturation of oligodendrocytes by using genetically engineered mice to conditionally knock-out Bin1 during oligodendrocyte maturation. We used immunoblotting and immunohistochemistry experiments to apprehend the role of BIN1 in the maturation of oligodendrocytes. Finally, we induced an acute demyelination event in our mouse model using cuprizone diet, and analyzed by electron microscopy the role of BIN1 in the remyelination and the maintenance of myelin sheath surrounding axons. With successful characterization results of conditional Bin1 knockout mice in the white matter, we believe our study will bring new information the role of BIN1 in the CNS.
A Multi-Player Model of Bowerbird Marauding: A Simulation of Destruction Rachel Potter 1, Julia Smith 1, and Stephen Pruett-Jones 1 1 Department of Ecology & Evolution and the Committee on Evolutionary Biology, University of Chicago
Bowerbirds (Order: Aves, Family: Ptilonorhynchidae) are distributed in Australia and New Guinea. Male bowerbirds build complex structures, known as bowers, for the sole purpose of attracting females. Bowerbirds are unique among birds in that the male’s mating success is dependent on an externalized secondary sexual characteristic, the bower. Perhaps not surprisingly, male bowerbirds often destroy the bowers of their rivals, likely to increase their own mating success. However, a male’s decision to spend time away from his own bower can be costly, as he may miss opportunities to mate or defend his bower. Pruett-Jones and Pruett-Jones (1994; hereafter referred to as P-J & P-J 1994) developed a two-individual game theory model that examined bower destruction (marauding). They showed that a marauding strategy is superior to guarding, assuming a male interacts only with his nearest neighbor. In this study, we extended this work, and built an agent based model of interactions of males in a neighborhood, involving male-male interactions beyond the two male case of P-J & P-J (1994). We use the model to evaluate how the relative success of marauding and guarding strategies is impacted by the proportion of marauders in a population, inter-bower distance, and bower repair time. Importantly, in the multi-male version, it is still advantageous for bowerbirds to engage in marauding behavior. However, the degree to which marauding pays off is dependent on the frequency of marauding males in the population. Marauding is more beneficial when a smaller percentage of males exhibit that behavior. As bower repair time increased, the advantage to the marauder increased significantly, but inter-bower distance had a minimal effect on the payoff. This study confirms the results of the earlier game theory model of P-J & P-J (1994) but also suggests that it will be important to quantify the actual rates of marauding behavior in males of bowerbird species and how this rate varies across populations.
acknowledgements The Triple Helix at the University of Chicago would like to thank all of the individuals and departments on-campus that have continued to generously support and make our publications possible. Weâ€™d like to give a special thanks to our Student Involvement Advisor Tempris Daniels and all of the faculty members that provide their time and dedication to our student writers.
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the triple helix AT THE UNIVERSITY OF CHICAGO
The Triple Helix at UChicago offers a unique platform to share undergraduate research and inquiries about faculty through our journal Scient...
Published on Jul 7, 2019
The Triple Helix at UChicago offers a unique platform to share undergraduate research and inquiries about faculty through our journal Scient...