The effects of altered heat stress on voluntary pacing strategies during prolonged cycling

Central Governor Model (CGM) suggests that perturbations in the rate of heat storage (AS) are centrally integrated to regulate exercise intensity in a feed-forward fashion to prevent excessive thermal strain. We directly tested the CGM by manipulating ambient temperature (Tam) at 20-minute intervals from 20°C to 35°C, and returning to 20°C, while cycling at a set rate of perceived exertion (RPE). The synchronicity of power output (PO) with changes in HS and Tam were quantified using Auto-Regressive Integrated Moving Averages analysis. PO fluctuated irregularly but was not significantly correlated to changes in thermo physiological status. Repeated measures indicated no changes in lactate accumulation. In conclusion, real time dynamic sensation of Tam and integration of HS does not directly influence voluntary pacing strategies during sub-maximal cycling at a constant RPE while non-significant changes in blood lactate suggest an absence of peripheral fatigue.

Posttraumatic stress disorder symptoms might be destroying your intimacy : a test of mediational models in a community sample of couples

The present research focused on the pathways through which the symptoms of posttraumatic stress disorder (PTSD) may negatively impact intimacy. Previous research has confirmed a link between self-reported PTSD symptoms and intimacy; however, a thorough examination of mediating paths, partner effects, and secondary traumatization has not yet been realized. With a sample of 297 heterosexual couples, intraindividual and dyadic models were developed to explain the relationships between PTSD symptoms and intimacy in the context of interdependence theory, attachment theory, and models of selfpreservation (e.g., fight-or-flight). The current study replicated the findings of others and has supported a process in which affective (alexithymia, negative affect, positive affect) and communication (demand-withdraw behaviour, self-concealment, and constructive communication) pathways mediate the intraindividual and dyadic relationships between PTSD symptoms and intimacy. Moreover, it also found that the PTSD symptoms of each partner were significantly related; however, this was only the case for those dyads in which the partners had disclosed most everything about their traumatic experiences. As such, secondary traumatization was supported. Finally, although the overall pattern of results suggest a total negative effect of PTSD symptoms on intimacy, a sex difference was evident such that the direct effect of the woman's PTSD symptoms were positively associated with both her and her partner's intimacy. I t is possible that the Tend-andBefriend model of threat response, wherein women are said to foster social bonds in the face of distress, may account for this sex difference. Overall, however, it is clear that PTSD symptoms were negatively associated with relationship quality and attention to this impact in the development of diagnostic criteria and treatment protocols is necessary.

The effects of thermal stress on glucoregulation during exercise in participants with Type 1 Diabetes Mellitus

Type 1 Diabetes Mellitus (T1DM) is an autoimmune disease that destroys pancreatic beta cells, affecting glucose homeostasis. In T1DM, glucoregulation and carbohydrate oxidation may be altered in different ambient temperatures; however, current literature has yet to explore these mechanisms. This study examines the effects of 30 minutes of exercise at 65% VO2max in 5ºC, 20ºC and 35ºC in individuals with T1DM. No significant differences were observed for blood glucose across the 3 conditions (p = 0.442), but significance was found for core temperature, heat storage, and sweat rate (p < 0.01). Blood glucose was also shown to vary greatly between individuals among conditions. The mechanisms behind the differences in blood glucose may be due to the lack of significant glucagon production among conditions. These findings suggest that T1DM individuals may exercise submaximally for 30 minutes in different ambient temperatures without significant differences in glucoregulation.

The Relationship between athlete motivation, strategies used to cope with stress and affective outcomes in Canadian University athletes

Motivation to perform and coping with stress during performance are key factors in determining numerous outcomes of sporting performance. However, less evidence is in place assessing their relationship. The aim of this investigation was to assess the relationship between athlete motivation and the coping strategies used to deal with stress during their sporting performance, as well as the relationship between motivation and affect and coping and affect. One hundred and forty five university athletes completed questionnaires. Regressions revealed that two of the three self determined levels of motivation, identified and integrated regulation, predicted increased task-oriented coping strategies. Two of the three non-self determined levels of motivation, amotivation and external regulation, significantly predicted disengagement-oriented coping. Additionally, intrinsic motivation and task-oriented coping predicted increase positive affect. Increased disengagement-oriented coping predicted decreased positive affect. Disengagement-oriented coping significantly predicted increased negative affect. These findings increase understanding of motivations role in predicting athletes coping.

Intracellular antioxidant and DNA repair enzymes as correlates of stress resistance and longevity in vertebrates

In animals, both stress resistance and longevity appear to be influenced by the insulin/insulin-like growth factor-l signaling (lIS) pathway, the basic organization of which is highly conserved from invertebrates to vertebrates. Reduced lIS or genetic disruption of the lIS pathway leads to the activation of forkhead box transcription factors, which is thought to upregulate the expression of genes involved in enhancing stress resistance, including perhaps key antioxidant enzymes as well as DNA repair enzymes. Enhanced antioxidant and DNA repair capacities may underlie the enhanced cellular stress resistance observed in long-lived animals, however little data is available that directly supports this idea. I used three. experimental approaches to test the association of intracellular antioxidant and DNA base excision repair (BER) capacities with stress resistance and longevity: (1) a comparison of multiple vertebrate endotherm species of varying body masses and longevities; (2) a comparison of long-lived Snell dwarf mice and their normallittermates; and (3) a comparison of hypometabolic animals undergoing hibernation or estivation with their active counterparts. The activities of the five major intracellular antioxidant enzymes as well as the two rate-limiting enzymes in the BER pathway, apurininc/apyrimidinic (AP) endonuclease and polymerase ~, were measured. These measurements were performed in one or more of the following: (1) cultured dermal fibroblasts; (2) brain tissue; (3) heart tissue; (4) liver tissue. My results indicate that antioxidant enzymes are not universally upregulated in association with enhanced stress resistance and longevity. I also did not find that BER enzyme activity was positively correlated with longevity, in an inter-species context, though there was evidence for enhanced BER in long-lived Snell dwarf mice. Thus, while there were instances in which enhanced antioxidant and BER enzyme activities were associated with increased stress resistance and/or longevity, this was not universally the case, indicating that other mechanisms must be involved. These results suggest the need to re-examine existing 'oxidative stress' hypotheses of longevity and probe further into the molecular physiology of longevity to discover its mechanistic basis.

Protein Turnover in Rat Skeletal Muscle During In Vitro Hypo-Osmotic Stress

Hypo-osmolality influences tissue metabolism, but research on protein turnover in skeletal muscle is limited. The purpose of this investigation was to examine the effects of hypo-osmotic stress on protein turnover in rat skeletal muscle. We hypothesized increased protein synthesis and reduced degradation following hypo-osmotic exposure. EDL muscles (n=8/group) were incubated in iso-osmotic (290 Osm/kg) or hypo-osmotic (190 Osm/kg) modified medium 199 (95% O2, 5% CO2, pH 7.4, 30±2 °C) for 60 min, followed by 75 min incubations with L-U[14C]phenylalanine or cycloheximide to determine protein synthesis and degradation. Immunoblotting was performed to assess signalling pathways involved. Phenylalanine uptake and incorporation were increased by 199% and 169% respectively in HYPO from ISO (p < 0.05). This was supported by elevated phosphorylation of mTOR Ser2448 (+12.5%) and increased Thr389 phosphorylation on p70s6 kinase (+23.6%) (p < 0.05). Hypo-osmotic stress increased protein synthesis and potentially amino acid uptake. Future studies should examine the upstream mechanisms involved.

Chronic mild social stress increases neurogenesis in adolescent male rats

Once thought to occur only during specific periods of development, it is now clear that neurogenesis occurs in the rat hippocampus into adulthood. It is wellestablished that stress during adulthood decreases the rate of neurogenesis, but during adolescence, the effects of stress are much less understood. I investigated the effect of short-term or chronic stress during adolescence (daily lhr isolation and change of cage partner from postnatal day (PND) 30-32 or 30-45) on hippocampal neurogenesis. In experiment 1, rats were administered Bromodeoxyuridine (BrdU) daily on PND 30-32, or 46-48, to mark neurogenesis at the beginning of the stressor or after the stressor had ceased, respectively. Neither short-term nor chronic stress had an effect on proliferation or survival (evidenced by BrdU and Doublecortin (Dcx) immunohistochemistry respectively) of cells born at the beginning of the stress procedure. Compared to controls, BrdU-labeling showed chronic stress significantly increased proliferation of cells generated after the stressor had ceased, but survival of new neurons was not supported (Dcx-Iabeling). However, it may be that BrdU injections are inherently stressful. In experiment 2, the stressor (described above) was applied in the absence of BrdU injections. Ki67 (a marker of proliferation) showed that stress transiently increased cell proliferation. Dcx-Iabeling showed that stress also increased neuron survival into adulthood. Labeling with OX.,.42 (a marker of macro phages) suggested that the immune system plays a role in neurogenesis, as stress transiently decreased the number of activated microglia in the hippocampus. It can be concluded that in the adolescent male rat, chronic mild stress increases neurogenesis.

A Survey of hMLH1 mRNA Splicing Profiles in Human Cell Lines: Comparing Primary Cultured Fibroblasts Before and After Oxidative Stress and Transiently versus Stably Demethylated Colon Cancer Derived Cell Lines

Most human genes undergo alternative splicing and loss of splicing fidelity is associated with disease. Epigenetic silencing of hMLH 1 via promoter cytosine methylation is causally linked to a subset of sporadic non-polyposis colon cancer and is reversible by 5-aza-2' -deoxycytidine treatment. Here I investigated changes in hMLHI mRNA splicing profiles in normal fibroblasts and colon cancer-derived human cell lines. I established the types and frequencies of hMLHI mRNA transcripts generated under baseline conditions, after hydrogen peroxide induced oxidative stress, and in acutely 5-aza-2' -deoxycytidine-treated and stably derepressed cancer cell lines. I found that hMLHI is extensively spliced under all conditions including baseline (50% splice variants), the splice variant distribution changes in response to oxidative stress, and certain splice variants are sensitive to 5- aza-2' -deoxycytidine treatment: Splice variant diversity and frequency of exon 17 skipping correlates with the level of hMLHI promoter methylation suggesting a link between promoter methylation and mRNA splicing.

Disambiguating the Effects of Social Instability Stress in Adolescence on Learning and Memory Tasks that Involve the Medial Prefrontal Cortex and Hippocampus

Exposure to chronic stress can alter the structure and function of brain regions involved in learning and memory, and these effects are typically long-lasting if the stress occurs during sensitive periods of development. Until recently, adolescence has received relatively little attention as a sensitive period of development, despite marked changes in behaviour, heightened reactivity to stressors, and cognitive and neural maturation. Therefore, the purpose of the present study was to investigate the long-term effects of chronic stress in adolescence on two spatial learning and memory tasks (Morris water maze and Spatial Object Location test) and on a working memory task (Delayed Alternation task). Male rats were randomly assigned to chronic social instability stress (SS; daily 1 hour isolation and subsequent change of cage partner between postnatal days 30 and 45) or to a no-stress control group (CTL). During acquisition learning in the Morris water maze task, SS rats demonstrated impaired long-term memory for the location of the hidden escape platform compared to CTL rats, although the impairment was only seen after the first day of training. Similarly, SS rats had impaired long-term memory in the Spatial Object Location test after a long delay (240 minutes), but not after shorter delays (15 or 60 minutes) compared to CTL rats. On the Delayed Alternation task, which assessed working memory across delays ranging from 5 to 90 seconds, no group differences were observed. These results are partially in line with previous research that revealed adult impairment on spatial learning and memory tasks after exposure to chronic social instability stress in adolescence. The observed deficits, however, appear to be limited to long-term memory as no group differences were observed during brief periods of retention.

Interaction between stress and immunity during a week leading to competition in young athletes

This study examined changes in the salivary concentrations of immunoglobulin A (sIgA), cortisol (sC), testosterone (sT) and testosterone-to-cortisol ratio (T/C) in 23 competitive swimmers, 11-15 years old, during a week leading to competition as compared to a control (non-competitive) week. Results showed no effect of week or day, and no significant week-by-day interaction for sIgA, sC and T/C. In contrast, sT significantly decreased during the week of competition, along with a 7%, non-significant decrease in the weekly T/C. The latter suggests that the swimmers were in a catabolic state due to their training, but this did not have a negative effect on their performance Since sC did not change over the two weeks and according to the sport anxiety scale, competition stress was relatively low in these peri-pubertal athletes, it is concluded that in the absence of high cortisol levels mucosal immunity is unaffected in young athletes prior to competition.

Exploring Academic (Di)stress and Help-Seeking in Faculty of Education Students

This is a study of education students’ conceptions of and experiences with academic stress and help-seeking. The study explored teacher education and Master of Education students’ academic stress by examining causes of academic stress and how these stressors affect students’ academic and university experiences. Stress-related help-seeking was also a focus of this study, and was explored using inquiries regarding where participants sought stress-related support. Additionally, exploring students’ use of the Internet for stress-related information or support was a goal of this study. These research goals were pursued using a qualitative methodology that applied grounded theory design. Consequently, data were used to develop a theory that would contribute to existing literature. Specifically, participant descriptions related to causes of and responses to academic stress aligned with Maslow’s (1954) theory of human motivation and Alderfer’s (1969) E. R. G. theory, and led to theoretical contributions that took a hierarchy of student needs and motivation into consideration.

Assessment of Stress During Handling and Transport

The article focuses on assessing the stress levels of animals when transported and handled. The paper was presented at a symposium titled Effects of Stress in Farm Animals at the American Society of Animal Science 87th annual meeting, July 1995.

Optimal and Robust Designs of Step-stress Accelerated Life Testing Experiments for Proportional Hazards Models

Accelerated life testing (ALT) is widely used to obtain reliability information about a product within a limited time frame. The Cox s proportional hazards (PH) model is often utilized for reliability prediction. My master thesis research focuses on designing accelerated life testing experiments for reliability estimation. We consider multiple step-stress ALT plans with censoring. The optimal stress levels and times of changing the stress levels are investigated. We discuss the optimal designs under three optimality criteria. They are D-, A- and Q-optimal designs. We note that the classical designs are optimal only if the model assumed is correct. Due to the nature of prediction made from ALT experimental data, attained under the stress levels higher than the normal condition, extrapolation is encountered. In such case, the assumed model cannot be tested. Therefore, for possible imprecision in the assumed PH model, the method of construction for robust designs is also explored.

Reduce Stress of Handling to Improve Productivity of Livestock

The article focuses on stress factors, which include: Genetic Background, Individual Differences, Past Experiences. The conclusion of the article states "reducing handling stress of animals will improve their weight gain, reproductive performance, and ability to resist disease".

Effects of Cerebral Blood Flow and PETCO2 on Cognitive Function During Passive Heat Stress

This thesis tested whether cognitive performance during passive heat stress may be affected by changes in cerebrovascular variables as opposed to strictly thermally-induced changes. A pharmacological reduction in cerebral blood flow (CBF) using indomethacin along with a hypocapnia-induced CBF reduction during passive heat stress (Tre ~1.5°C above baseline) were used to investigate any cerebrovascular-mediated changes in cognitive performance. Repeated measures analysis of variance indicated that One-Touch Stockings of Cambridge (OTS) performance was not affected by a significant reduction in CBF during passive heat stress. More specifically, OTS accuracy measures did not change as a result of either a reduction in CBF or increasing passive heat stress. However, it was found that OTS response time indices improved with increasing passive heat stress independent of CBF changes. In conclusion, a significant reduction in CBF does not cause additional changes in performance of an executive functioning task during severe passive heat stress.