Browsing by Subject "Stress (Physiology)"
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Item A biomechanical investigation of the possibility of relating static and dynamic work by means of a common parameter(1968-06) Khalil, Tarek M.Not AvailableItem A comparative study of some physiological parameters of static and dynamic work performed by the upper limb(Texas Tech University, 1967-08) Purswell, Jerry Lee.Item Acute stress effects on pig performance, immunity, and behavior(Texas Tech University, 1996-08) Hicks, Tiffanie AStress activates the hypothalamic-pituitary-adrenal axis (HPA). Corticotropin-releasing hormone (CRH) is the primary initiator of the stress response. The hypothalamus releases CRH which in turn stimulates the anterior pituitary to secrete adrenocorticotropin hormone (ACTH) and other peptides. Increased ACTH levels stimulate the adrenal cortex to release glucocorticoids. Stress not only effects the neuroendocrine and endocrine systems, but also alters behavior, immunity and overall physiology. The objectives of these studies were to (1) determine if physiological concentrations of various hormones had an effect on in -vitro NK cytotoxicity in pigs, and (2) to determine the effects of three common stressors (heat, cold and shipping) on pig performance, physiology and behavior. In experiment 1, peripheral blood was collected from 59 pigs to determine the effects of physiological concentrations of stress hormones on porcine natural killer cell (NK) activity. A standard cytotoxicity assay was utilized with peripheral blood mononuclear cells and 51Cr-labeled K-562 target cells. Hormones and concentrations were: porcine corticotropin releasing hormone (pCRH) at 0, 0.47, 4.7, 47 and 467 ng/mL; P-endorphin at 0, 0.001, 0.01, 0.1, 1, 10 and 100 ng/mL, Cortisol at 0, 3.6, 36 and 360 ng/mL, adrenocorticotropic hormone (ACTH) at 0, 0.045, 0.45, 4.5 and 45 ng/mL, epinephrine at 0, 0.022, 0.22, 2.2 and 21.9 ng/mL and norepinephrine at 0, 0.021, 0.21, 2.1, 20.6 ng/mL. Over the range of doses evaluated, pCRH, ACTH, Cortisol and norepinephrine had no significant effect on porcine NK activity. P-endorphin and epinephrine had significant (P < .01) effects on porcine NK activity. All doses of â-endorphin suppressed (P < .05) porcine NK activity. Porcine NK activity was greater (P < .05) when incubated with 0.22 ng/mL epinephrine than with 0.022 or 21.9 ng/mL epinephrine. These results suggest that physiological concentrations of CRH, ACTFI, Cortisol, and norepinephrine alone do not modulate pig NK activity. â-endorphin seems to be a potent suppressor of porcine NK activity. Epinephrine influenced pig NK activity in a dose-sensitive manner. In the second study, 132 weanling pigs were used to investigate the effects of three common stressors (and a control) and differing social status on behavior, immunity, plasma Cortisol and blood chemical measures. Eleven blocks of 12 pigs each were evaluated. Each block contained four pens, established at weaning, and examined for outcome of agonistic interactions. Pigs were labeled socially Dominant (DOM), Intermediate (INT) or Submissive (SUB). Two weeks later, random pens of pigs experienced either a control treatment (CON) or for 4 hours they were either shipped (SHIP), heat stressed (HEAT) with overhead heat lamps in their home pens, or cold stressed (COLD) by direct application of water and an air current. A battery of physiological and behavioral measures were collected. Treatments did not influence body weights, however, percentage weight change during SHIP was greater (P < .001) than for other treatments (.23, -2.9, .72, .91% ± .96 for CON, SHIP, COLD, HEAT, respectively). Serum glucose was elevated (P = .02) for SHIP pig compared with other treatments. Serum Cortisol was decreased (P = .03) for HEAT compared with COLD and SHIP pigs. Social status influenced (P < .01) body weights at weaning and throughout the study with body weights heaviest for DOM pigs than INT and SUB pigs. Social status also influenced serum globulin, albumin/globulin (A/G) ratio, and Cortisol concentrations. Globulin decreased, while A/G increased in DOM pigs. SUB pigs showed an increase in Cortisol compared to DOM and INT pigs. An interaction between social status and treatment occurred for NK cytotoxicity at 50:1 E:T (P = .06). Socially DOM and INT pigs had higher NK cytotoxicity than SUB, COLD pigs. An interaction was also observed between social status and stress treatment for lymphocyte blastogenesis under Phytohemagglutinin mitogen. Among HEAT pens, the INT pigs had lower lymphocyte proliferation than SUB pigs, but were not different from the DOM pigs. Among SHIP pens, the INT pigs had higher lymphocyte proliferation than either the DOM or SUB pigs. In conclusion, social status had large effects on plasma Cortisol, globulin, A/G ratio, body weight and weight changes, although only acute shipping stress resulted in weight loss. Many immune and blood measures were not changed among acutely stressed pigs, however, the relationship between social status and LTA and NK cytotoxicity was disrupted during acute stress. Pig behavior was largely influenced across all stress treatments. COLD pigs had greater overall activity, including, feeding, standing and attacking and they had less lying behavior. The HEAT and SHIP pigs had depressed activity levels and spent more time lying. During acute stress, behavioral symptoms appears to be the most accurate and reliable indicator of stress.Item Affiliation under stress as a function of self-evaluation of abilities(Texas Tech University, 1971-08) Keating, Patrick HenryNot availableItem An investigation of biomechanical, physiological and environmental heat stresses associated with manual lifting in hot environments(Texas Tech University, 1984-05) Hafez, Hala AdelNot availableItem Cardiodynamic adaptive mechanisms of two kinds of stress in right and left ventricles of rat heart(Texas Tech University, 1982-05) George, Colleen O'Connordefinition of stress according to Selye is, ...the rate of wear and tear in the body " (42). Selye's ideas are expressed in a model of a general adaptation to the environment mediated by individual organs, particularly those of the nervous and endocrine systems. Adaptation is defined in the context of acclimatization; that is, an individual organism exhibits physiological and/or anatomical adjustments to a change in its immediate environment. Three levels of the stress syndrome are the alarm reaction, resistance, and exhaustion. Couched in different terminology, Ursin, Evind, and Seymour (49) view stress as a type of coping which is defined as advantageous changes in behavior or physiological responses to noxious or adverse stimulation. In their model, stress is viewed in the context of problem solving. Two kinds of adverse stimulation that have been studied at length are exposure to hypoxia and exercise. In both situations, the circulatory system demonstrates adaptation to the stressors. In the case of chronic adaptation to hypoxia, well described changes include increases in hematocrit, hemoglobin, RBC coimt, O2 carrying capacity and specific gravity of the blood, and total blood volume (50). Pulmonary hypertension and right ventricular hypertrophy also develop. Chronic adaptation to exercise, on the other hand, has been observed to result in an increased capillary density in skeletal and cardiac muscle, increased heart volume and weight, increased blood volume and cardiac output during maximal work, and increased stroke volume during rest, submaximal, and maximal work (5). Other increases have been observed in maximal oxygen uptake and blood lactate tolerance during maximal work. Decreases have been noted in heart rate at rest and during submaximal work. Other decreases have been found in oxygen uptake and blood lactate at given submaximal work loads.Item Effect of freeze tunnel chilling time on pork quality(Texas Tech University, 1997-05) Springer, Michael PatrickNot availableItem The effects of stress on different stages of memory(2004) Beckner, Victoria Lemle, 1966-; Tucker, David M., 1953-; Markman, Arthur B.Research suggests that memory is influenced by stress and the associated rise of glucocorticoids, such as cortisol. While human studies have generally found a negative effect of stress and elevated cortisol on memory, animal studies have demonstrated a dose-dependent facilitative effect. These discrepant findings may be a result of methodological limitations in the human literature, which often confound the different stages of memory by elevating cortisol levels prior to encoding, consolidation and retrieval. The purpose of the current study was to parse the effects of an acute psychosocial stressor on these separate memory processes by varying the timing of the stressor. Based on recent evidence, we predicted that stress would enhance encoding and consolidation, but impair retrieval. 208 college students (63 male, 138 female, mean age = 18.9) were randomly assigned to a no-stress control group (n = 51) or one of three groups stressed at different time points: prior to stimulus presentation (encoding/ consolidation, n = 51), immediately after stimuli presentation (consolidation, n = 56), or just before memory testing 48 hours later (retrieval, n = 50). Salivary cortisol was measured at baseline and 20 minutes after the stressor. Both verbal and visual memory was measured at the 48-hr delay using a film stimulus developed by the investigator and with the WMS-III narrative. Results demonstrated that the group stressed prior to consolidation significantly outperformed controls on the film recognition at delay for verbal and total scores. This effect may have been related to cortisol response, as this was the only stress group to exhibit a significant increase in cortisol (40%) following the stressor. No significant differences in memory were found between the other stress conditions and controls. Within-group correlations between change in cortisol and memory were not significant, but exploratory analyses revealed a small but significant positive correlation for cortisol and verbal scores on the film recognition test across all groups (rxy = .18). Results support the hypothesis that stress enhances consolidation of new information, and provides the first evidence of this for verbal memory. Findings did not support a detrimental effect of stress on retrieval.Item Network mechanisms underlying susceptibility to helplessness and response to the antidepressant fluoxetine(2010-05) Padilla, Eimeira; González-Lima, Francisco, 1955-; Delville, Yvon; Domjan, Michael P.; Dominguez, Juan M.; Beevers, Christopher G.Depression and post-traumatic stress disorder are common psychiatric comorbidities related to stress. These conditions are frequently treated with antidepressants such as selective serotonin reuptake inhibitors (SSRI’s). However, there are individual differences in susceptibility to stress-induced psychopathologies and response to antidepressants. Therefore, there is a need to identify biologic factors that predict vulnerability to stress and response to treatment. Furthermore, few studies have examined the neural correlates of antidepressant treatment response in a stress-susceptible animal model. This dissertation had three specific aims: 1) to characterize behavioral predictors of stress vulnerability by studying three dimensions of temperament (reward dependence, novelty-specific activity and harm avoidance) before stress exposure using a stress-susceptible rat strain, 2) to identify the neural network effects of response and non-response to SSRI treatment using a stress-susceptible animal model, and 3) to determine the neurophysiologic correlates of helplessness susceptibility. This was examined via measurement of regional brain metabolic capacity and functional connectivity within relevant neural circuits, and measurements of corticosterone and heart rate. These effects were studied in rats that underwent inescapable shock exposure followed by escape testing. Holtzman rats showed greater predisposition to helpless behavior following inescapable shock compared to Sprague Dawley and Long-Evans strains. Also, increased activity in a novel environment and low heart rate appeared to be markers of helplessness susceptibility in Holtzman rats. Limbic-cortical network effects were identified that distinguished between responders and non-responders to antidepressant treatment in the Holtzman strain. Finally, hypermetabolism of the lateral habenula and a less interactive prefrontal-limbic cortex were identified in subjects with higher susceptibility towards helplessness within the Holtzman strain. Similar findings have been reported with other depression animal models and human neuroimaging studies. These findings support that the helpless dimension of mood disorders can be accurately modeled with the Holtzman rat strain and confirm that the lateral habenula and prefrontal cortex are key regions mediating the helpless phenotype and response to SSRI treatment.Item Overgeneral cognitive style : the impact on physical and emotional adjustment to life stress(2002-08) Gibbs, Bryce Neil; Rude, Stephanie SandraResearch has found that individuals who are depressed and have experienced past traumas tend to report vague or overly general autobiographical memories (AM) and evidence prolonged latencies to retrieve specific AM’s (Kuyken & Brewin, 1995; Kuyken and Dagleish,1995). Additionally, other researchers have demonstrated that individuals who possess AM deficits have associated difficulties with social problem solving (SPS) (Goddard, Dritschel, and Burton, 1996) and display overgenerality in their imaginings of the future, which has been linked to the hopelessness that often accompanies depression (Williams et al., 1996). Finally, in terms of trauma, researchers have speculated that deficits in AM prevent individuals who have experienced trauma from restructuring their traumatic schemata thereby engendering psychopathology (Harvey, Bryant, and Dang, 1998). Based on the aforementioned research, this dissertation investigated whether AM deficits act as “diatheses” that predispose individuals to psychopathology, especially those with histories of trauma and who are currently experiencing life stress (Abramson, Alloy, and Metalsky, 1988). A starting point for the study was the notion that overgeneral (OG) memory may exist as a broad means of avoiding painful affects associated with traumatic memories. To this end, it was hypothesized that OG memory as assessed by established assessments of this construct would be associated with OG memory as assessed by a narrative measure of overgenerality. Second, due to the associations between AM deficits and related cognitive abilities (i.e. SPS and OG imaginings of the future), it was hypothesized that individuals with AM deficits would experience greater physical and emotional distress over the course of the semester than those without this vulnerability. Third, in agreement with established “diathesis-stress” models, it was hypothesized that AM deficits would interact with life stress over the course of the semester and lead to greater levels of physical and emotional distress than in “stressed” participants without the diathesis. Finally, based on the theory that AM deficits hinder individuals from restructuring traumatic schemata, it was hypothesized that AM deficits would mediate the relationship between past trauma and current physical and emotional distress. Results supported the hypothesis that overgeneral memory and latencies to provide specific memories would interact with life stress to predict emotional distress over the course of a semester. However, overgeneral memory and latencies to provide specific memories did not independently predict physical or emotional distress over the course of the semester and were not found to mediate the relationship between past trauma and current distress.Item Relationship between static and dynamic strength at selected angles of the knee(Texas Tech University, 1967-08) Higginbotham, Robert BNot availableItem The assessment of the ability of various heat stress indices to predict safe work behavior(Texas Tech University, 1981-05) Chai, Chi-pingNot availableItem The effects of neonatal testosterone on the prepubertal female rat's response to different stressors(Texas Tech University, 1985-12) Smith, Constance JNot availableItem The modification of psychophysiological responses to stress in piano performance(Texas Tech University, 1984-12) Whitaker, Charlotte SibleyNot availableItem The relationship of stress prone personality types to presbycusis(Texas Tech University, 1979-05) Kinsey, Eva DeeNot available