Marine mammals play an important role in ecosystem stability. However, anthropogenic activity is compounding pressure on many already vulnerable populations. A potential consequence of anthropogenic disturbance is physiological stress, which can impact metabolism, immunity, and reproduction, especially if it occurs repeatedly. Previous studies on marine mammals have focused on acute stress, but the impacts of repeated stress are poorly understood. Due to its accessibility on land during haul-outs, the northern elephant seal (Mirounga angustirostris) is a good system in which to study the effects of stress in marine mammals. Stress stimulates the release of glucocorticoid hormones, primarily cortisol. Elevated cortisol is a good indicator of acute stress, but it is an unreliable proxy for chronic stress, and cortisol measurements alone do not provide information on the downstream physiological consequences of chronic stress. Therefore, additional biomarkers may provide a more comprehensive understanding of the effects of repeated stress on marine mammals. I examined two approaches for assessing stress in response to administration of the hormone that stimulates secretion of cortisol (adrenocorticotropic hormone; ACTH): a non-targeted proteomics approach using blood plasma and a targeted gene expression approach examining blubber expression of glucocorticoid receptor (GR) and two of its regulators, FKBP5 and KLF9. For the first approach, I used the highly sensitive LC-MS/MS technique to detect changes in circulating plasma proteins in juvenile seals in response to repeated ACTH administration. I identified changes in relative abundance of proteins of interest in the plasma proteome that included those with roles in lipid, iron, and redox homeostasis, cortisol and thyroid hormone transport, adipogenesis, oxidative stress, blood pressure regulation, vitamin and mineral transport, and innate immunity. I then measured blubber expression of GR and its regulator genes in blubber of adult female seals undergoing early and late molting to examine changes during different life-history stages in response to acute stress induced by ACTH administration. Using RT-qPCR, I found that GR expression decreased in blubber, while expression of FKBP5 increased, suggesting negative feedback at the tissue level which may reduce sensitivity to cortisol during key life-history stages, such as molting, which require fasting. These data provide insights into the resilience of marine mammals to acute stress and novel biomarkers that may be used to study the effects of prolonged stress in wildlife.

Previous research has shown that excessive cardiovascular reactivity may be important in the development of coronary heart disease. The present study examines the role of masculine cognitive appraisal of stress as a mediator of cardiovascular reactivity in men. The reactivity of men who differed on a measure of cognitive appraisal of masculine gender role stress (MGRS) was compared using the cold-pressor test under conditions of high and low masculine performance challenge. Under conditions of minimal challenge, it was predicted that high and low MGRS men would not differ on reactivity. Under high challenge, high MGRS men were expected to show greater reactivity than low MGRS men. Since coping responses are related to appraisal of stressful situations and impact on cardiovascular reactivity, subjects' coping responses were also assessed. Analysis of results for systolic blood pressure confirmed the major predictions. High MGRS men showed greater systolic blood pressure reactivity than low MGRS men under high challenge and equal or less reactivity under low masculine performance challenge. In general, the high and low MGRS groups did not differ in their use of coping strategies as a function of the high and low challenge condition. The implications of MGRS appraisal for men's health are discussed. / Master of Science

Rhodopseudomonas palustris is a metabolically versatile phototrophic α-proteobacterium. The organism experiences a wide range of stresses in its environment and during metabolism. The oxidative an pH stresses of four ECF (extracytoplasmic function) σ-factors are investigated. Three of these, σ0550, σ1813, and σ1819 show responses to light-generated singlet oxygen and respiration-generated superoxide reactive oxygen species (ROS). The EcfG homolog, σ4225, shows a high response to superoxide and acid stress. Two proteins, one containing the EcfG regulatory sequence, and an alternative exported catalase, KatE, are presented to be regulated by σ4225. Transcripts of both genes show similar responses to oxidative stress compared to σ4225, indicating it is the EcfG-like σ-factor homolog and controls the global stress response in R. palustris.

Sport and dance injuries have increased despite improvements in coaching techniques and medical care. Other factors, including psychological ones, were therefore thought to play a role in injury vulnerability. Most of the attempts to explain how psychological variables can affect an athlete's predisposition to injury have been based on anxiety or stress concepts. In this survey type study an interactive approach to stress has been adopted with the goal of finding a relationship between stress and injury in a group of professional ballet dancers. No simple direct relationship was found. Multiple regression analysis was performed and a more complicated relationship between stress indicators and injury was found. When an attempt was made to investigate the significant interaction, no significant correlations were found. However, the correlations were found to be large and negative. This could indicate that if the sample size had been larger significant correlations may have been found. / Psychology / M.A. (Psychology)

Sport and dance injuries have increased despite improvements in coaching techniques and medical care. Other factors, including psychological ones, were therefore thought to play a role in injury vulnerability. Most of the attempts to explain how psychological variables can affect an athlete's predisposition to injury have been based on anxiety or stress concepts. In this survey type study an interactive approach to stress has been adopted with the goal of finding a relationship between stress and injury in a group of professional ballet dancers. No simple direct relationship was found. Multiple regression analysis was performed and a more complicated relationship between stress indicators and injury was found. When an attempt was made to investigate the significant interaction, no significant correlations were found. However, the correlations were found to be large and negative. This could indicate that if the sample size had been larger significant correlations may have been found. / Psychology / M.A. (Psychology)

Stressors in the aquaculture environment can lead to negative impacts on growth and immune health, resulting in susceptibility to infectious diseases. These stressors are expected to increase as the growth of aquaculture continues to rise to meet demands for quality fish protein. Isoflavones, as a crude extract or as a pure isolate, may be effective in modulating the stress response, promoting growth and immunity. The objective of these studies was to examine the effect of various pure isoflavone isolates and crude isoflavone extracts on stress, growth, and immunity. Nile tilapia (Oreochromis niloticus) were stressed by adding hydrocortisone to the feed. In a 7-week study, pure isoflavone isolates of genistein and puerarin were evaluated to determine their respective effects on stress, growth, and immunity. A separate 10-day physiological and 6-week growth study focused on crude isoflavone extracts from kudzu (Pueraria lobata), red clover (Trifolium pratense), and soybean (Glycine max) was performed to determine their respective effects on stress, growth, and immunity. Numerous physiological parameters of the fish were measured (serum cortisol concentration, blood glucose concentration, hematocrit, hepatosomatic index, plasma protein concentration, lysozyme activity, and spleensomatic<br>index) to determine the effects of these pure isoflavone and crude isoflavone extracts on the modulation of stress and immunity. Many growth parameters were examined (length, weight, condition factor, weight gain, specific growth rate, feed intake, feed conversion ratio, and protein efficiency ratio) as well to determine the effects of these pure isoflavones and isoflavone extracts on growth. The addition of isoflavone and crude isoflavone extracts to the diet of Nile tilapia ameliorated some of the negative consequences of stress. Compared to stressed fish fed commercial feed, genistein and puerarin added to the diet appeared to improve serum cortisol concentrations, which resulted in increased plasma protein, albeit at different durations of stress. Puerarin, as well as all three crude isoflavone extracts, significantly increased spleen-somatic index compared to non-supplemented stressed fish, although the crude isoflavone extracts did not appear to improve serum cortisol concentrations. Crude isoflavone extracts also showed overall increases in lysozyme activity compared to non-supplemented stressed fish, although this was not significant. Genistein, puerarin, and red clover showed increased growth rates, feed conversion ratio, and protein efficiency. Overall, pure isolates of isoflavone appear to be more effective in modulating stress, immunity, and growth than the crude isoflavone extracts, although red clover extract showed promises in the ability to modulate the stress response and improve growth and immunity. There are likely substantial interactions between the isoflavones in the crude extracts that cannot be fully understood by measuring the effects of single isoflavones. Regardless, isoflavone supplementation (pure or crude) appeared to generally have an overall positive impact on stressed Nile tilapia, requiring more research to better understand the effects and mechanisms behind these isoflavones.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 52-60). Also available on the World Wide Web.

We examined the effect of daily stress, age, and emotional stability/neuroticism on stress reactivity, using cortisol diurnal rhythms. We used data from the Normative Aging Study (Spiro & Bosse, 2001). The 72 men in this study ranged from 67-93 (M =79.29, SD =4.88). Multilevel modeling showed that higher daily stress predicted flatter cortisol diurnal rhythms, B = .09, p < .001, as did age, B = .01, p < .001, while those higher in neuroticism on the emotional stability/neuroticism measure showed steeper slopes for cortisol diurnal rhythms, B = -.04, p < .001. These results indicate that age and emotional stability/neuroticism levels explain some of the variance in individual differences in stress reactivity and provide a basis for future research focused on the effects of psychosocial variables on physiological outcomes. / Graduation date: 2013

Survival of teleost larvae requires growth and development which depend upon endocrine processes. In this dissertation I have examined the ontogeny of elements of the thyroid hormone (TH) and corticosteroid (CS) systems in red drum (Sciaenops ocellatus). Basal cortisol production was first detected 3 days post-hatch (DPH) and a cortisol stress response was present from 6 DPH forward. Changes in steroidogenic enzyme mRNA (CYP11B and CYP21) levels did not correlate with these events. The time necessary to reach peak cortisol levels as well as return to basal levels declined as larvae developed. A second set of studies examined ontogenetic patterns in levels of mRNAs encoding thyroid (soTR[alpha] and soTR[beta]) and corticosteroid (soGR) hormone receptors and assessed the regulation of these mRNAs by exogenous triiodothyronine (T3) and cortisol. soTR[alpha], soTR[beta] and soGR were expressed in all stages of red drum examined. soTR[alpha] levels increased during the time when surging TH levels have been reported. soTR[beta] levels did not differ significantly during development. soGR levels were strongly correlated with those of soTR[alpha]. T3 up-regulated soTR[alpha] and soTR[beta] levels in 7 DPH, but not older larvae. Cross-regulation of receptor mRNAs by exogenous treatment with T3 or cortisol was not observed. Finally, I assessed the influence of a common herbicide, atrazine, on receptor mRNA, TH levels and growth of red drum. In two experiments, red drum exposed to environmentally relevant levels of atrazine did not alter hormone receptor mRNA levels, or TH content. However, atrazine did depress growth in some instances. In conclusion, the expression patterns of hormone receptor mRNA in embryos suggests receptor proteins could be activated by maternal hormones prior to the onset of endogenous hormone production. A correlation between soTR[alpha] and soGR mRNA levels suggests coordinated function of TH and CS systems, although regulatory interactions between these systems were not evident under the conditions in this study. Patterns in soTR[alpha] and soTR[beta] mRNA levels support an important role for TH in the larval to juvenile transformation of red drum larvae. The results also support growing evidence indicating atrazine exposure effects larval growth and may impact their survival in the wild. / text

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. / text