152 research outputs found

    Evolution and Distribution of Phenotypic Diversity in the Venom of Mojave Rattlesnakes (Crotalus scutulatus)

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    Intraspecific phenotype diversity allows for local adaption and the ability for species to respond to changing environmental conditions, enhancing survivability. Phenotypic variation could be stochastic, genetically based, and/or the result of different environmental conditions. Mojave Rattlesnakes, Crotalus scutulatus, are known to have high intraspecific venom variation, but the geographic extent of the variation and factors influencing venom evolution are poorly understood. Three primary venom types have been described in this species based on the presence (Type A) or absence (Type B) of a neurotoxic phospholipase A2 called Mojave toxin and an inverse relationship with the presence of snake venom metalloproteinases (SVMPs). Individuals that contain both Mojave toxin and SVMPs, although rare, are the third, and designated Type A + B. I sought to describe the proteomic and transcriptomic venom diversity of C. scutulatus across its range and test whether diversity was correlated with genetic or environmental differences. This study includes the highest geographic sampling of Mojave Rattlesnakes and includes the most venom-gland transcriptomes known for one species. Of the four mitochondrial lineages known, only one was monophyletic for venom type. Environmental variables poorly correlated with the phenotypes. Variability in toxin and toxin family composition of venom transcriptomes was largely due to differences in transcript expression. Four of 19 toxin families identified in C. scutulatus account for the majority of differences in toxin number and expression variation. I was able to determine that the toxins primarily responsible for venom types are inherited in a Mendelian fashion and that toxin expression is additive when comparing heterozygotes and homozygotes. Using the genetics to define venom type is more informative and the Type A + B phenotype is not unique, but rather heterozygous for the PLA2 and/or SVMP alleles. Intraspecific venom variation in C. scutulatus highlights the need for fine scale ecological and natural history information to understand how phenotypic diversity is generated and maintained geographically through time

    The Proposed Regulatory Changes to Fannie Mae and Freddie Mac: An Analysis

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    A Design Process Centric Application of State Space Modeling as a Function of Communications and Cognitive Skills Assessments.

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    Humans have a reliable basic probabilistic intuition. We utilize our probabilistic intuition in many day-to-day activities such as driving. In fact any interaction that occurs in the presence of other independent actors requires some probabilistic assessment. While we are good at sorting between rare and common events, determining if these events are statistical significant is always subject to scrutiny. Quite often the bounds of statistical significance are at ends with the ā€˜common senseā€™ expectation. While our probabilistic intuition is good for first moment effects such as driving a car, throwing a football and understanding simplistic mathematical models, our probabilistic intuition fails when we need to evaluate secondary effects such as high speed turns, playing golf or understanding complex mathematical models. When our probabilistic intuition is challenged misinterpretation of results and skewed perspectives of possible outcomes will occur. The work presented in this dissertation provides a mathematical formulation that will provide a guide to when our probabilistic intuition will be challenged. This dissertation will discuss the development of the Process Failure Estimation Technique (ProFET). A multitude of potential team parameters could have been selected, interpersonal communication effectiveness and cognitive skill assessments seemed the most obvious first steps. This is due to the prolific discussion on communication and the general acceptance of the cognitive testing as an indicator of performance potential. The teams skill set must be variable with respect to time in order to accomplish the required objectives of each phase of the design process. ProFET develops a metric for the design process that is sensitive to the team composition and structure. This metric is applied to a domain that is traditionally devoid of objective scoring. With the use of ProFET more informed decisions on team structure and composition can be made at critical junctions of the design process. Specifically, ProFET looks at how variability propagates through the design activities as opposed to attempting to quantify the actual values of design activities, which is the focus of the majority of other design research.PhDNaval Architecture and Marine EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116679/1/jdstrick_1.pd

    Phylogeography of the cottonmouth, Agkistrodon piscivorus, using AFLP and venom protein profiles.

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    The objective of this study was to examine population structure in cottonmouths (Agkistrodon piscivorus) using Amplified Fragment Length Polymorphism (AFLP) and compare genetic and venom protein profiles in Texas. AFLP profiles using 622 fragments were generated for 105 individuals to understand the level of variation within Agkistrodon. In Texas, there was a significant lack of gene flow detected and support for the isolation of Concho Valley individuals. Cottonmouths showed the greatest genetic variation when compared to other Agkistrodon species but there was not complete support for two species of cottonmouths as currently proposed. RP-HPLC was used to examine venom protein profiles in 86 Texas cottonmouths. Relative peak heights were analyzed using PCA and the MANOVA demonstrated separation of populations based on profiles (p<0.001). Genetic and venom variation did not follow the same pattern indicating that there may be other selection pressures acting on the venom proteins

    The effectiveness of blended learning environments for the delivery of respiratory care education [abstract]

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    Abstract only availableIt has been reported that the major weakness of online learning environments is the lack of consistent, efficient communication with the course instructor. In an attempt to provide the learner with the ā€œbest of both worlds,ā€ some educators have opted to integrate additional course materials via internet classrooms to enhance learning while still maintaining the face-to-face interaction between instructor and learner. The researchers hypothesized that there is not a difference in academic outcomes between students who complete a course in a traditional environment and those who complete the course in a blended environment nor is there a difference in student satisfaction between the two methods of course delivery. Methods: Data collection included a retrospective review of the demographic and course information. Quantitative data analysis of the data was performed in SPSSĀ® using the Mann-Whitney test and the Spearman rho correlation. Qualitative data analysis was performed via open coding of subjective student comments. Results: The data obtained by retrospective review of demographics and course outcomes was analyzed to determine significant differences. None of the variables showed a statistically significant difference (p=0.05). Further testing revealed an expected positive relationship between pre-existing GPA and the final examination grade as well as the final examination grade and the course grade (p=0.05). No other positive relationships were noted in course outcomes, student satisfaction or subjective comments. Conclusions: It can be assumed by the data presented that there is no difference in academic outcomes when comparing the traditional classroom setting to the blended classroom setting. These results favor the continuing practice of blended learning environments as a viable option for course delivery in health care education, specifically respiratory care.School of Health Professions Research Mentorshi

    Oral History Conversation With Chuck Samuelson (Kitchens for Good)

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    This was a conversation with Chuck Samuelson who runs a social organization (Kitchens for Good)

    Enhancing workplace wellness efforts to reduce obesity: A qualitative study of low-wage workers in St Louis, Missouri, 2013-2014

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    INTRODUCTION: The objective of this study was to examine workplace determinants of obesity and participation in employer-sponsored wellness programs among low-wage workers. METHODS: We conducted key informant interviews and focus groups with 2 partner organizations: a health care employer and a union representing retail workers. Interviews and focus groups discussed worksite factors that support or constrain healthy eating and physical activity and barriers that reduce participation in workplace wellness programs. Focus group discussions were transcribed and coded to identify main themes related to healthy eating, physical activity, and workplace factors that affect health. RESULTS: Although the union informants recognized the need for workplace wellness programs, very few programs were offered because informants did not know how to reach their widespread and diverse membership. Informants from the health care organization described various programs available to employees but noted several barriers to effective implementation. Workers discussed how their job characteristics contributed to their weight; irregular schedules, shift work, short breaks, physical job demands, and food options at work were among the most commonly discussed contributors to poor eating and exercise behaviors. Workers also described several general factors such as motivation, time, money, and conflicting responsibilities. CONCLUSION: The workplace offers unique opportunities for obesity interventions that go beyond traditional approaches. Our results suggest that modifying the physical and social work environment by using participatory or integrated health and safety approaches may improve eating and physical activity behaviors. However, more research is needed about the methods best suited to the needs of low-wage workers

    Trait differentiation and modular toxin expression in palm-pitvipers

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    Background Modularity is the tendency for systems to organize into semi-independent units and can be a key to the evolution and diversification of complex biological systems. Snake venoms are highly variable modular systems that exhibit extreme diversification even across very short time scales. One well-studied venom phenotype dichotomy is a trade-off between neurotoxicity versus hemotoxicity that occurs through the high expression of a heterodimeric neurotoxic phospholipase A2 (PLA2) or snake venom metalloproteinases (SVMPs). We tested whether the variation in these venom phenotypes could occur via variation in regulatory sub-modules through comparative venom gland transcriptomics of representative Black-Speckled Palm-Pitvipers (Bothriechis nigroviridis) and Talamancan Palm-Pitvipers (B. nubestris). Results We assembled 1517 coding sequences, including 43 toxins for B. nigroviridis and 1787 coding sequences including 42 toxins for B. nubestris. The venom gland transcriptomes were extremely divergent between these two species with one B. nigroviridis exhibiting a primarily neurotoxic pattern of expression, both B. nubestris expressing primarily hemorrhagic toxins, and a second B. nigroviridis exhibiting a mixed expression phenotype. Weighted gene coexpression analyses identified six submodules of transcript expression variation, one of which was highly associated with SVMPs and a second which contained both subunits of the neurotoxic PLA2 complex. The sub-module association of these toxins suggest common regulatory pathways underlie the variation in their expression and is consistent with known patterns of inheritance of similar haplotypes in other species. We also find evidence that module associated toxin families show fewer gene duplications and transcript losses between species, but module association did not appear to affect sequence diversification. Conclusion Sub-modular regulation of expression likely contributes to the diversification of venom phenotypes within and among species and underscores the role of modularity in facilitating rapid evolution of complex traits
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