Browsing by Subject "male"
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Item Artificial Stimulation of Cephalic Cholinergic Sensory Neurons Induces Mating-Like Motor Responses in Male Caenorhabditis elegans(2012-12-06) Midkiff, JamesAll complex organisms possess a nervous system which they use to monitor environmental and internal stimuli. In higher vertebrates, the nervous system is comprised of billions of cells which form highly plastic neural networks from their synapses. These large neural circuits modulate complex behaviors. The nematode roundworm Caenorhabditis elegans uses a small but highly-interconnected nervous system to carry out complex behaviors. The nervous system of C. elegans is a tractable model to determine the effects of changes on a nervous system at the systemic, cellular, genetic, and molecular levels. The C. elegans male?s nervous system detects environmental conditions, mating cues, attractants, repellents, and the location and composition of possible food sources and integrates these inputs to compute the decision of whether or not to mate. Mating behavior in the C. elegans male is regulated at a number of steps by cholinergic signaling from various sensory and sensory-motor neurons, but a comprehensive model of how cholinergic signaling controls this circuit has not yet been elucidated. Previous studies have thoroughly dissected the cellular structure, neural connectivity, and signaling pathways of the male?s peripheral circuits located in the genital regions of the animal?s tail. However, no studies have been conducted to determine what role the cephalic cholinergic neurons have in regulating mating behavior. I hypothesized that cephalic cholinergic neurons exert regulatory control over the male-specific mating circuit. I inserted the transmembrane light-activated ion pore Channelrhodopsin-2 fused to YFP and expressed from the Punc-17small promoter into these neurons and selectively stimulated them using high-intensity blue light. Stimulation induced mating-like behaviors in the male tail consistent with behaviors seen during copulation with a hermaphrodite. Using behavioral assays, I demonstrated that these behaviors were male-specific and only occurred after direct stimulation in the absence of a hermaphrodite. Incidence of mating-like behaviors increased significantly as the worm aged, and the mating circuit retained a memory of the stimulus, indicated by the latency between stimulation and onset of mating-like behaviors. Brief food deprivation, which normally downregulates excitability of the mating circuit via UNC-103 ERG-like K+ channels, caused an unexpected increase in the number of blue light-stimulated behaviors displayed. Pharmacological assays using acetylcholine (ACh) agonists showed that stimulation of the cephalic cholinergic neurons increased propensity for spicule protraction in the presence of an ACh agonist, and partially restored the decline in spicule protraction associated with temporary food deprivation. I sought to identify the cephalic cholinergic neuron or neurons responsible for regulating mating-like behavior in the tail circuits. I looked for a reduction in mating-like behaviors after stimulation after removal of a cephalic cholinergic neuron pair via laser micro-ablation. Two cholinergic and chemosensory neuron pairs in the inner labial sensilla (IL2L/R and IL2VL/R) appear to generate and/or relay the signal that induces mating-like behaviors in the tail. I hypothesize that these neurons sense environmental cues before the male contacts a mate, and modulate lasting motivational changes within the male mating circuit.Item Evaluation of dietary factors associated with spontaneous pancreatitis in dogs(2009-05-15) Lem, Kristina YvonneThis study estimates the association between dietary factors and spontaneous pancreatitis in dogs. A case-control study was conducted using 198 dogs with a clinical diagnosis of pancreatitis and 187 control dogs with a diagnosis of renal failure without clinical evidence of pancreatitis. Information on signalment, weight, body condition, dietary intake, medical history, diagnostic tests performed, concurrent diseases, treatment, length of hospital stay, and discharge status was extracted from medical records for dogs admitted to the Texas A&M University Small Animal Clinic (TAMU SAC) during January 2000 to December 2005. Information on dietary intake, signalment, weight, medical, surgical and environmental history was collected for the same dogs through a telephone questionnaire conducted from November 2006 through January 2007. Descriptive statistics were calculated, tabular analyses performed, and logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI). Based on information extracted from the medical records, ingesting unusual food (OR=4.3; CI=1.7 to 10.7), ingesting table food (OR=1.5; CI=1.0 to 2.2), or exposure to both of these dietary factors (OR=2.1; CI=1.3 to 3.2) increased the odds of pancreatitis. Collected through the telephone questionnaire, ingesting unusual food (OR=6.1; CI=2.2 to 16.5), ingesting table scraps the week before diagnosis (OR=2.2; CI=1.2 to 3.8) or regularly throughout life (OR=2.2; CI=1.2 to 4.0), and getting into the trash (OR=13.2; CI=2.1 to undefined) increased the odds of pancreatitis. Multivariable modeling estimated the associations of exposure to one or more dietary factors reported through the telephone questionnaire (OR=2.6; CI=1.4 to 5.0), overweight (OR=1.3; CI=0.7 to 2.5), year of diagnosis (OR=3.5; CI=1.9 to 6.5), neuter status (OR=3.6; CI=1.4 to 9.5), non-neuter surgery (OR=21.1; CI=3.3 to 133.9) and an interaction term between neuter status and non-neuter surgery (OR=0.1; CI=0.01 to 0.4). Dietary factors increase the odds of spontaneous pancreatitis in dogs.Item Osteogenic effect of electric muscle stimulation as a countermeasure during hindlimb unloading(Texas A&M University, 2007-09-17) Alcorn, Justin DowRats that undergo hindlimb unloading (HU) as a simulation for space flight experience bone changes similar to astronauts in microgravity. The purpose of this research was to assess whether an exercise countermeasure would be effective in preventing or mitigating bone degradation during HU. Controlled electrical muscle stimulation was applied to the lower left hindlimb to simulate resistive exercise. Adult 6-mo. old male rats were assigned to 3 groups of 12 each: hindlimb unloaded (HU), aging cage control (CC), and baseline (BL). The CC group was pair-fed to match the nutritional intake of HU animals during the 28 days of the study. The left leg was exercised 3 days a week for the duration of the study, with the unexercised right leg serving as a contra-lateral control. Mechanical tests were conducted to assess the strength of cancellous bone in the proximal tibia metaphysis. Although isolated specimens of cancellous bone are not feasible, reduced platen compression (RPC) was employed to directly load only the cancellous core region of each specimen. There was no significant difference in ultimate stress or elastic modulus between BL, CC, and HU-Ex (exercised). However, HU-Ex results were dramatically and significantly higher than HU-No Ex (contra-lateral unexercised control) for both ultimate stress (68%) and elastic modulus (81%). It is also notable that ultimate stress was 32% higher (but not statistically significant) for HU-Ex compared to CC. The total bone mineral density in the tibial metaphysis was significantly larger, 11%, in the HUEx compared to the HU-No Ex group's values. The results clearly demonstrate the efficacy of the exercise protocol in preventing the substantial mechanical deterioration induced by HU.Item Percieved influence of societal dissonance, self-efficacy, African American male mentorship, and institutional support on the success of African American Males in a predominantly whie insitution of higher education(2009-05-15) Brown, Ronald WilliamFor the past decade the attainment gap in college admission and graduation rates between Black males and their White counterparts has continued to grow. A growing body of research has held that there is a negative correlation between educational attainment and the decline of the Black family structure. As the structure of the Black family has deteriorated due to the lack of a male presence, so have participation rates in higher education for African American males. It is established that environmental and cultural factors have a profound influence on human behaviors, including academic performance. What is less understood is how environmental and cultural factors influence the way in which Black males come to perceive education and how those perceptions influence not only their behavior but their performance in school. It is unknown why being African American and male causes this segment of the population to stand out in the most negative and disheartening ways, both in school and in society. This study measures the perceived influence of four factors (societal dissonance, self-efficacy, African American male mentorship, and institutional support) on the academic success of African American male students at a predominantly White institution of higher education.Item The effects of childhood sexual abuse on adult male attachments in close relationships(Texas A&M University, 2006-10-30) Altman, Daniel RaynerOver the past two decades society has become more aware of the prevalence and impact of childhood sexual abuse (CSA). While society has become more aware of this problem, there is still much that remains unknown. This is evident especially in regard to the effects of CSA on adult males. There are several reasons for this; one such reason is that males who come to therapy are rarely asked about sexual abuse histories. However, the effects of CSA are often quite severe for males. One area particularly affected is adult close relationships. Attachment theory offers a way to conceptualize how people interact in close relationships. In this study, the influence of CSA on adult male relationships was examined. Seven hypotheses examined were that males who were abused by a male, males who were abused for a longer period of time, males who were abused at an earlier age, males who perceived little support from their family with regards to the abuse, males who were abused by a family member, males who were abused more frequently, and males who were abuse more severely would be more likely to have an insecure attachment than other males. These CSA characteristics were measured by the Childhood Sexual Experiences Questionnaire and the Adult Attachment Questionnaire (AAQ). Although limitations to this study make it difficult to reject the null hypothesis and to make statements that these results reflect the population, findings generally confirm the stated hypotheses.