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A Review of the Human Vermiform Appendix and its Proposed Function

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Since its discovery in 1524, many people have characterized the vermiform appendix. Charles Darwin considered the human appendix to be a vestige and a useless structure. Others at the time opposed this hypothesis. However, Darwin's hypothesis became prevalent one until

Since its discovery in 1524, many people have characterized the vermiform appendix. Charles Darwin considered the human appendix to be a vestige and a useless structure. Others at the time opposed this hypothesis. However, Darwin's hypothesis became prevalent one until recently when there became a renewed interest in the appendix because of advancements in microscopes, knowledge of the immune system, and phylogenetics. In this review, I will argue that the vermiform appendix, although still not completely understood, has important functions. First, I will give the anatomy of the appendix. I will discuss the comparative anatomy between different animals and also primates. I will address the effects of appendicitis and appendectomy. I will give background on vestigial structures and will discuss if the appendix is a vestige. Following, I will review the evolution of the appendix. Finally, I will argue that the function of the appendix is as an immune organ, including discussion of gut-associated lymphoid tissue (GALT), development of lymphoid follicles in GALT and their comparison within different organs, Immunoglobulin A (IgA) function in the gut, biofilms as evidence that the appendix is a safe-house for beneficial bacteria, re-inoculation of the bowel, and protection against recurring infection. I will conclude with future studies that should be conducted to further our understanding of the vermiform appendix.

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Date Created
2018-05

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Language Used when Covering People with Disabilities

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News outlets frequently portray people with disabilities as either helpless victims or objects of motivation. Portrayal of people with disabilities has improved over the years, but there is still room to grow. News outlets tend to make disability the center

News outlets frequently portray people with disabilities as either helpless victims or objects of motivation. Portrayal of people with disabilities has improved over the years, but there is still room to grow. News outlets tend to make disability the center of the story. A story about a disabled person is primarily about their disability, with their other accomplishments framed by it.

As one example of the victimhood narrative, ABC News used to run a special called My Extreme Affliction as part of 20/20 until 2012. As the name implies, the specials covered people with disabilities, specifically extreme versions. One 2008 episode on Tourette’s syndrome described Tourette’s like it was some sort of demonic possession. The narrator talked about children who were “prisoners in their own bodies” and a family that was at risk of being “torn apart by Tourette’s.” I have Tourette’s syndrome myself, which made ABC’s special especially uncomfortable to watch. When not wringing their metaphorical hands over the “victims” of disability, many news outlets fall into the “supercrip” narrative. They refer to people as “heroes” who “overcome” their disabilities to achieve something that ranges from impressive to utterly mundane. The main emphasis is on the disability rather than the person who has it. These articles then exploit that disability to make readers feel good. As a person with a disability, I am aware that it impacts my life, but it is not the center of my life. The tics from my Tourette’s syndrome made it difficult to speak to people when I was younger, but even then they did not rule me.

Disability coverage, however, is still incredibly important for promoting acceptance and giving people with disabilities a voice. A little over a fifth of adults in the United States have a disability (CDC: 53 million adults in the US live with a disability), so poor coverage means marginalizing or even excluding a large amount of people. Journalists should try to reach their entire audience. The news helps shape public opinion with the stories it features. Therefore, it should provide visibility for people with disabilities in order to increase acceptance. This is a matter of civil rights. People with disabilities deserve fair and accurate representation.

My personal experience with ABC’s Tourette’s special leads me to believe that the media, especially the news, needs to be more responsible in their reporting. Even the name “My Extreme Affliction” paints a poor picture of what to expect. A show that focuses on sensationalist portrayals in pursuit of views further ostracizes people with disabilities. The emphasis should be on a person and not their condition. The National Center for Disability Journalism tells reporters to “Focus on the person you are interviewing, not the disability” (Tips for interviewing people with disabilities). This people-first approach is the way to improve disability coverage: Treat people with disabilities with the same respect as any other minority group.

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2019-05

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A Life History Model of Mammary Neoplasia Across Mammals

Description

Cancer rates vary significantly across tissue type and location in humans, driven by clinically relevant distinctions in the risk factors that lead to different cancer types. Despite the importance of cancer location in human health, little is known about tissue-specific

Cancer rates vary significantly across tissue type and location in humans, driven by clinically relevant distinctions in the risk factors that lead to different cancer types. Despite the importance of cancer location in human health, little is known about tissue-specific cancers in non-human animals. A comparison of cancer prevalence across the tree of life can give insight into how evolutionary history has shaped various mechanisms of cancer suppression. Here, we explore whether species-level life history strategies are associated with differences in mammary neoplasia rates across mammals. We propose that the same patterns of cancer prevalence that have been reported across species will be maintained at the tissue-specific level. We used a phylogenetic regression on 15 life history traits across 112 mammalian species to determine the correlation between a life history trait and how it relates to mammary neoplasia prevalence. A greater risk of mammary neoplasia was found in the characteristics associated with fast life history organisms and a lower risk of mammary neoplasia was found in the characteristics associated with slow life history organisms. With this analysis, a framework is provided for how different life history modalities can influence cancer vulnerability.

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2020-05

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The Effects of Natural Selection, Drift, and Genetic Background on Phenotypic Variation and Correlation in E. coli

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Phenotypic evolution is an essential topic within the general field of evolution. Theoretically, the outcome of phenotypic evolution may be influenced by factors such as genetic background and the interaction of natural selection and genetic drift. To gain empirical evidence

Phenotypic evolution is an essential topic within the general field of evolution. Theoretically, the outcome of phenotypic evolution may be influenced by factors such as genetic background and the interaction of natural selection and genetic drift. To gain empirical evidence for testing the effects of those factors, we used eight long-term evolved Escherichia coli populations as a model system. These populations differ in terms of genetic background (different mutation rates) as well as bottleneck size (small- and large-magnitude). Specifically, we used a plate reader to measure three growth-related traits: maximum growth rate (umax), carrying capacity (Kc), and lag time (Lt) for 40 clones within each population. For each trait we quantified the change in mean per generation, the change in variance per generation, and the correlation coefficient between pairs of traits. Interestingly, we found that the small and large bottleneck populations of one background displayed clear, distinguishing trends that were not present within the populations of the other background. This leads to the conclusion that the influence of selection and drift on a population’s phenotypic outcomes is itself influenced by the genetic background of that population. Additionally, we found a strong positive correlation between umax and Kc within each of the high-mutation populations that was not consistent with our neutral expectation. However, the other two pairs did not exhibit a similar pattern. Our results provide a novel understanding in the relationship between the evolution of E. coli growth-related phenotypes and the population-genetic environment.

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2020-05

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Beginning to investigate Lactase Persistence in Turkana

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Lactase persistence is the ability of adults to digest lactose in milk (Segurel & Bon, 2017). Mammals are generally distinguished by their mammary glands which gives females the ability to produce milk and feed their newborn children. The new born

Lactase persistence is the ability of adults to digest lactose in milk (Segurel & Bon, 2017). Mammals are generally distinguished by their mammary glands which gives females the ability to produce milk and feed their newborn children. The new born therefore requires the ability to breakdown the lactose in the milk to ensure its proper digestion (Segurel & Bon, 2017). Generally, humans lose the expression of lactase after weaning, which prevents them being able to breakdown lactose from dairy (Flatz, 1987).
My research is focused on the people of Turkana, a human pastoral population inhabiting Northwest Kenya. The people of Turkana are Nilotic people that are native to the Turkana district. There are currently no conclusive studies done on evidence for genetic lactase persistence in Turkana. Therefore, my research will be on the evolution of lactase persistence in the people of Turkana. The goal of this project is to investigate the evolutionary history of two genes with known involvement in lactase persistence, LCT and MCM6, in the Turkana. Variants in these genes have previously been identified to result in the ability to digest lactose post-weaning age. Furthermore, an additional study found that a closely related population to the Turkana, the Massai, showed stronger signals of recent selection for lactase persistence than Europeans in these genes. My goal is to characterize known variants associated with lactase persistence by calculating their allele frequencies in the Turkana and conduct selection scans to determine if LCT/MCM6 show signatures of positive selection. In doing this, we conducted a pilot study consisting of 10 female Turkana individuals and 10 females from four different populations from the 1000 genomes project namely: the Yoruba in Ibadan, Nigeria (YRI); Luhya in Webuye, Kenya; Utah Residents with Northern and Western European Ancestry (CEU); and the Southern Han Chinese. The allele frequency calculation suggested that the CEU (Utah Residents with Northern and Western European Ancestry) population had a higher lactase persistence associated allele frequency than all the other populations analyzed here, including the Turkana population. Our Tajima’s D calculations and analysis suggested that both the Turkana population and the four haplotype map populations shows signatures of positive selection in the same region. The iHS selection scans we conducted to detect signatures of positive selection on all five populations showed that the Southern Han Chinese (CHS), the LWK (Luhya in Webuye, Kenya) and the YRI (Yoruba in Ibadan, Nigeria) populations had stronger signatures of positive selection than the Turkana population. The LWK (Luhya in Webuye, Kenya) and the YRI (Yoruba in Ibadan, Nigeria) populations showed the strongest signatures of positive selection in this region. This project serves as a first step in the investigation of lactase persistence in the Turkana population and its evolution over time.

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Date Created
2019-05

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Strong Episodic Selection for Natural Competence for Transformation due to Host-Pathogen Dynamics

Description

Many bacteria actively import environmental DNA and incorporate it into their genomes. This behavior, referred to as transformation, has been described in many species from diverse taxonomic backgrounds. Transformation is expected to carry some selective advantages similar to those postulated

Many bacteria actively import environmental DNA and incorporate it into their genomes. This behavior, referred to as transformation, has been described in many species from diverse taxonomic backgrounds. Transformation is expected to carry some selective advantages similar to those postulated for meiotic sex in eukaryotes. However, the accumulation of loss-of-function alleles at transformation loci and an increased mutational load from recombining with DNA from dead cells create additional costs to transformation. These costs have been shown to outweigh many of the benefits of recombination under a variety of likely parameters. We investigate an additional proposed benefit of sexual recombination, the Red Queen hypothesis, as it relates to bacterial transformation. Here we describe a computational model showing that host-pathogen coevolution may provide a large selective benefit to transformation and allow transforming cells to invade an environment dominated by otherwise equal non-transformers. Furthermore, we observe that host-pathogen dynamics cause the selection pressure on transformation to vary extensively in time, explaining the tight regulation and wide variety of rates observed in naturally competent bacteria. Host-pathogen dynamics may explain the evolution and maintenance of natural competence despite its associated costs.

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Date Created
2016-05

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Modeling the Relationship Between Migration, Selection, and Drift in Populations of Blind Cave Fish

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The evolution of blindness in cave animals has been heavily studied; however, little research has been done on the interaction of migration and drift on the development of blindness in these populations. In this study, a model is used to

The evolution of blindness in cave animals has been heavily studied; however, little research has been done on the interaction of migration and drift on the development of blindness in these populations. In this study, a model is used to compare the effect that genetic drift has on the fixation of a blindness allele for varying amounts of migration and selection. For populations where the initial frequency is quite low, genetic drift plays a much larger role in the fixation of blindness than populations where the initial frequency is high. In populations where the initial frequency is high, genetic drift plays almost no role in fixation. Our results suggest that migration plays a greater role in the fate of the blindness allele than selection.

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Date Created
2014-05

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Cannabis: Cannabinoids, Physiology, and Receptor Evolution

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The Cannabis plant has historical roots with human beings. The plant produces compounds called cannabinoids, which are responsible for the physiological affects of Cannabis and make it a research candidate for medicinal use. Analysis of the plant and its components

The Cannabis plant has historical roots with human beings. The plant produces compounds called cannabinoids, which are responsible for the physiological affects of Cannabis and make it a research candidate for medicinal use. Analysis of the plant and its components will help build a better database that could be used to develop a complete roster of medicinal benefits. Research regarding the cellular protein receptors that bind the cannabinoids may not only help provide reasons explaining why the Cannabis plant could be medicinally relevant, but will also help explain how the receptors originated. The receptors may have been present in organisms before the present day Cannabis plant. So why would there be receptors that bind to cannabinoids? Searching for an endocannabinoid system could help explain the purpose of the cannabinoid receptors and their current structures in humans. Using genetic technologies we are able to take a closer look into the evolutionary history of cannabinoids and the receptors that bind them.

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Date Created
2014-05

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Cold populations of flies evolved larger bodies and larger wings made of larger cells

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We examined the evolutionary morphological responses of Drosophila melanogaster that had evolved at constant cold (16°), constant hot (25°C), and fluctuating (16° and 25°C). Flies that were exposed to the constant low mean temperature developed larger thorax, wing, and cell

We examined the evolutionary morphological responses of Drosophila melanogaster that had evolved at constant cold (16°), constant hot (25°C), and fluctuating (16° and 25°C). Flies that were exposed to the constant low mean temperature developed larger thorax, wing, and cell sizes than those exposed to constant high mean temperatures. Males and females both responded similarly to thermal treatments in average wing and cell size. The resulting cell area for a given wing size in thermal fluctuating populations remains unclear and remains a subject for future research.

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Date Created
2015-05

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Assessing the Evolutionary Divergence Between Four Multiple Myeloma Patient Tumors and Their Established Cell Lines

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Current studies in Multiple Myeloma suggest that patient tumors and cell lines cluster separately based on gene expression profiles. Hyperdiploid patients are also extremely underrepresented in established human myeloma cell lines (HMCLs). This suggests that the average HMCL model system

Current studies in Multiple Myeloma suggest that patient tumors and cell lines cluster separately based on gene expression profiles. Hyperdiploid patients are also extremely underrepresented in established human myeloma cell lines (HMCLs). This suggests that the average HMCL model system does not accurately represent the average myeloma patient. To investigate this question we performed a combined CNA and SNV evolutionary comparison between four myeloma tumors and their established HMCLs (JMW-1, VP-6, KAS-6/1-KAS-6/2 and KP-6). We identified copy number changes shared between the tumors and their cell lines (mean of 74 events - 59%), those unique to patients (mean of 21.25 events - 17%), and those only in the cell lines (mean of 30.75 events \u2014 24%). A relapse sample from the JMW-1 patient showed 58% similarity to the primary diagnostic tumor. These data suggest that, on the level of copy number abnormalities, HMCLs show equal levels of evolutionary divergence as that observed within patients. By exome sequencing, patient tumors were 71% similar to their representative HMCLs, with ~12.5% and ~16.5% of SNVs unique to the tumors and HMCLs respectively. The HMCLs studied appear highly representative of the patient from which they were derived, with most differences associated with an enrichment of sub-populations present in the primary tumor. Additionally, our analysis of the KP-6 aCGH data showed that the patient's hyperdiploid karyotype was maintained in its respective HMCL. This discovery confirms the establishment and validation of a novel and potentially clinically relevant hyperdiploid HMCL that could provide a major advance in our ability to understand the pathogenesis and progression of this prominent patient population.

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Date Created
2016-05