Teses / dissertações sobre o tema "Stress (Physiology)"
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1
Ashcroft, Felicity Jayne. "The physiology of Reg". Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288281.
2
Newman, Amy Elida Margaret. "Neurosteroids and stress physiology in adult songbirds". Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7532.
Resumo:
Stress increases adrenal glucocorticoid secretion, and chronic elevation of glucocorticoids can have detrimental effects on the brain. Dehydroepiandrosterone (DHEA) is an androgen precursor synthesized in the adrenal glands, gonads or the brain and has anti-glucocorticoid properties. However, little is known about the role of DHEA in the stress response, particularly in the brain. In Chapter 2, I validated a solid phase extraction technique for extracting steroids from lipid-rich brain tissue and plasma of songbirds. In Chapter 3, I demonstrated that acute stress had statistically significant effects on plasma corticosterone and DHEA in wild adult male song sparrows that were season and vein specific. For corticosterone, acute stress increased jugular levels more than brachial levels during the molt. For DHEA, acute stress did not affect brachial DHEA but decreased jugular DHEA during the breeding season and increased jugular DHEA during the molt. These results suggest that corticosterone and DHEA are locally synthesized in the brain during molt. In Chapter 4, I measured the effects of acute stress and season on corticosterone and DHEA in brain tissue and jugular plasma. Compared to jugular plasma, corticosterone levels were up to 10Ã lower in brain, whereas DHEA levels were up to 5Ã higher in brain and were highest in the hippocampus. Acute stress increased corticosterone levels in jugular plasma and brain, except during molt, when stress decreased corticosterone levels in the hippocampus. In Chapter 5, I tested the effects of corticosterone and DHEA treatments on the brain. Corticosterone and DHEA had additive effects on the volume, neuron number and recruitment of new cells into HVC. Elsewhere in the brain, DHEA increased BrdU+ cells only in the absence of corticosterone suggesting that corticosterone can interfere with the action of DHEA. Together, these studies demonstrate that acute stress and season have distinct effects on corticosterone and DHEA in plasma and brain. Furthermore, I demonstrate that corticosterone and DHEA can have additive effects on cell survival and recruitment in the adult brain and that, in some cases, corticosterone can inhibit the actions of DHEA in the brain.
3
Ericson, Elke. "High-resolution phenomics to decode : yeast stress physiology /". Göteborg : Göteborg University, Dept. of Cell and Molecular Biology, Faculty of Science, 2006. http://www.loc.gov/catdir/toc/fy0707/2006436807.html.
4
Michaud, Michael Robert. "Molecular physiology of insect low temperature stress responses". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1172184329.
5
Johnson, Philip Lee. "The dorsomedial hypothalamus : stress-related physiology and behaviour". Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421100.
6
Michaud, Michael R. "Molecular physiology of insect low temperature stress responses". The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1172184329.
7
Oliver, Georgina. "Stress and food choice". Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299341.
8
O'Neill, Mark. "Cardiovascular regulation under physiological stress". Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294358.
9
Peyton, Justin Tyler. "Genomic Platforms and Molecular Physiology of Insect Stress Tolerance". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440175145.
10
He, Ying 1972 Apr 20. "Impacts of metabolic stress-induced malnutrition and oxidative stress on biochemical changes in the slow- and fast-twitch skeletal muscles of rats". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33774.
Resumo:
To assess the changes in glycolysis of skeletal muscles within metabolic stress and to test whether metabolic stress-induced oxidative stress and malnutrition were associated with these changes, slow- (soleus) and fast-twitch extensor digitorum longus (EDL) muscles were studied in zymosan-induced critically ill, pair-fed and control rats for 7 days. Thiobarbituric acid reactive species (TBARS) concentrations were increased in both stressed and pair-fed rats. In slow-twitch muscle, the fructose-1,6-bisphosphate (F-1,6-P2)/fructose-6-phosphate (F-6-P) ratio was decreased in stressed rats and was not altered with increased food intake. F-1,6-P2/F-6-P ratio in soleus was correlated with both TBARS and muscle dry weight. In EDL, the F-1,6-P2/F-6-P was unaffected and neither oxidative stress nor muscle weight correlated with the ratio. In conclusion, metabolic stress-induced oxidative stress and malnutrition influenced glycolytic slowdown only in slow-twitch muscle.
11
Harris, Rachel Armstrong. "Stress : the physiology and psychology of a training situation". Thesis, Robert Gordon University, 1995. http://hdl.handle.net/10059/2350.
Resumo:
This thesis describes a study that aimed to assess the psychophysiological effects of offshore survival training, and to investigate whether responses of trainees differed according to age. A group of 99 subjects, randomly selected from across a wide age range, volunteered and subsequently were monitored during the training. The sample population were split into 2 groups according to the training course attended, refresher or combined survival and fire fighting course. Physiological and psychological measurements, chosen as indicators of stress, were performed on these subjects. Attention was centred on 4 particular events: helicopter underwater escape training (HUET); simulated platform abandonment using totally enclosed motor propelled survival craft; simulated platform abandonment into liferafts; and self rescue from a smoke filled room. State anxiety and urinary free cortisol were assessed early on each morning. Anxiety was also measured before the 4 chosen events. Early morning anxiety and urinary free cortisol were observed to peak on the first day of training, then each showed a very similar pattern of a decline to a plateau. On assessing all combined subjects' anxiety scores in sequence, values were found to be relatively lower towards the end of the course. These results suggested that subjects suffered from pre-course apprehensions that may have caused elevations in anxiety scores during the course. It was also found that subjects with high urinary free cortisol values on day 1, had relatively higher heart rates later in the course. Despite variation between the training courses, very similar mean heart rates were recorded in combined and refresher subjects. Relatively elevated heart rates were detected during the HUET brief. This was proposed to be the result of psychological activation, probably anxiety. Indicators of links among physiological and psychological measures were thus detected. Stronger and more consistent relationships may have been observed had more extensive data been available. Age effects were also detected, older refreshers had lower levels of anxiety, but found the course relatively more demanding. The lower anxiety levels were proposed to result from older refreshers having more training experience.
12
Esworthy, Ann. "Occupational stress in professional groups". Thesis, Cardiff University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302878.
13
Marasco, Valeria. "Pre- and post-natal stress programming : from genes to physiology". Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5000/.
Resumo:
In a variety of vertebrate species, early life environmental cues are important drivers of an individual’s phenotypic trajectories, priming physiological pathways, with consequences for growth, reproductive-related traits and lifespan. These phenotypic responses are believed to be adaptive in the short-term, but may impinge on health and survival over the long-term. Much of the work in this field has focused on the potential constraints imposed on animals after exposure to early life adversities, including nutritional deficit, sibling competition, and high predator pressure. Such stressful experiences can result in direct, but also indirect (via the maternal route) increases in the exposure to glucocorticoid stress hormones in the developing individuals. Glucocorticoids, whose production and secretion is regulated by the Hypothalamic-Pituitary-Adrenal axis (HPA axis), have been hypothesised to be the main candidates mediating the programming effects of developmental stress. Earlier predictions based on this assumption came from studies conducted in mammals. In mammals it is particularly difficult to manipulate exposure to circulating hormones in developing individuals because of the physiological intimacy between mother and offspring via the placenta and lactation. Here, I circumvent this complicating factor by using the precocial Japanese quail as a study species. In chapter 2 I measure corticosterone (B, the main avian glucocorticoid) stress responses to a standardised environmental stressor in growing quail aged 8- and 16-days-old. The results are consistent with those previously reported in other precocial birds, showing that the magnitude of the stress response (i.e. peak B within 30 min period) is higher in the 8- than the 16-day-old hatchlings. I find no differences in baseline B concentrations between the two groups. I then describe the main experiment in which I elevate B concentrations in ovo and/or in the endogenous circulation of the hatchlings (oral B administration from day 5 to day 19 post-hatching) in order to obtain four distinct phenotypes: pre-hatching B-treated birds, post-hatching B-treated birds, both pre- and post-hatching B-treated birds, and controls. I examine the specific and combined effects of pre- and post-hatching B on (1) growth trajectories and physiological stress responses before sexual maturity (post-hatch day 22) and upon adulthood (post-hatch day 64); (2) adult gene expression patterns within the hippocampus and hypothalamus, and (3) oxidative stress in the blood and the brain in the adults. The main results of Chapter 3 show that post-hatching B, regardless of pre-hatching experiences, decrease HPA axis responsiveness in the juveniles, but only in the female quail; whilst pre-hatching stress, when not combined with post-hatching B, increase HPA responsiveness in both sexes upon adulthood. I also show that both pre- and post-hatching B induce short-term alterations in triglyceride basal concentrations, which are linked with the sex and basal glucose concentrations of the birds; the effects of pre-hatching B exposure were visible also upon adulthood with sex-specific alterations on basal glucose concentrations. Overall these results suggest that early life stress can trigger both transient and permanent physiological changes, depending on the sex and the quality of both the pre- and post-hatching environment. In Chapter 4 I show that the gene expression responses to pre- and post-hatching B are overall subtle, results similar to those reported in previous genomic studies that have manipulated early life rearing environments. The effects are, however, distinguishable, strongly tissue-specific and involve well characterised key candidate genes in the regulation of the HPA axis. These data also suggest important novel regulatory mechanisms, likely linked with cellular redox state, which may be driving the long-term effects of developmental stress. Finally, in chapter 5, I show that developmental B induces alterations in the basal antioxidant defences upon adulthood. The magnitude of these effects, once more, depends upon the timing of exposure, interactions between the pre- and post-hatching B and the tissue examined. As there are no differences in terminal oxidative damage, these results suggest that the B-treated birds could avoid oxidative stress via altering body oxidative defences. In summary, my findings throughout this thesis, illustrate the complexity of glucocorticoid programming and the importance of integrating analyses at multiple levels, from physiology to genome-wide investigations. The results of this thesis also strengthen the importance of examining the effects of early life stress over differing life stages in order to consider the overall balance of costs and benefits that may ultimately affect Darwinian fitness and survival.
14
Smith, Carine. "Exercise, stress and immune system functional responses". Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16070.
Resumo:
Dissertation (PhD)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: Stress related to chronic exercise affects both the immune and endocrine systems, but there are still many issues that are poorly understood, particularly effects of stress on the functional capacity of immune cells. This thesis probed some of these issues using physiological models of physical and psychological stress. Both exercise training stress and chronic psychological stress in human subjects were shown to result in an up-regulation of spontaneous reactivity of white blood cells in vitro, using two different assays, namely a) a peripheral blood mononuclear cell (PBMC) culture assay measuring immune cell responsiveness and b) a relatively new flow cytometry technique for assessing activation status of cells by their expression of the surface marker CD69, in a lymphocyte subpopulation-specific manner. An up-regulation of immune cell activation in the absence of an additional stressor was associated with a decreased capacity to mount a response to a subsequent mitogen stimulus in vitro after chronic psychological stress and acute, extreme exercise stress. Another novel finding was that cortisol high-responders to chronic psychological stress exhibited a higher spontaneous reactivity of both CD4+ and CD8+ lymphocytes when compared to cortisol low-responders. This result indicates that chronic exposure to cortisol may decrease its usual inhibitory effect on spontaneous T lymphocyte responsiveness. After optimisation of an animal model of mild, psychological stress, we demonstrated (using an IL-6 antibody) that IL-6 is necessary for a full-blown cortisol response to chronic, intermittent mild stress. Results also suggest that IL-6 plays a role in regulation of its own secretion by PBMCs in response to a stressor, by maintaining the production of IL-1β in the face of stress. Basal serum corticosterone concentration was shown to be the main determinant of the magnitude of mitogen-stimulated PBMC secretion of IL-6 in vitro in the stress-free controls. However, after blocking of IL-6 in vivo, IL-1β was identified as a major regulator of IL-6 secretion by mitogen-stimulated PBMCs in vitro, independently of the presence or absence of stress. The implications of these novel findings are that proinflammatory cytokines are sensitively regulated during mild stress.Mean serum cortisol concentration at rest was not a useful tool to assess chronic exercise stress after training intervention. However, classification of athletes at baseline into two groups according to their resting serum cortisol concentration illustrated two distinct patterns for the responses of both cortisol and the cortisol:testosterone ratio to chronic stress. These studies on the effects of chronic stress on parameters of the endocrine stress-axis and the immune system led to the following main conclusions: a) chronic exposure to cortisol results in a decreased inhibition of spontaneous immune cell activity at rest, b) this increased spontaneous activation of immune cells at rest in the absence of a stressor, is associated with a suppression of immune capacity to respond to a subsequent challenge, c) the latter finding is not evident under stress-free conditions where cortisol promoted immune cell IL-6 secretion, and d) IL- 1β and IL-6 are involved in the regulation of each others’ secretion.
AFRIKAANSE OPSOMMING: Chroniese oefening-verwante stres beïnvloed beide the immuun- en endokriene sisteme, maar daar is nog baie aspekte wat swak begryp word, veral m.b.t. die effekte van stres op die funksionele kapasiteit van immuunselle. Hierdie tesis het sommige van dié vraagpunte ondersoek deur gebruik te maak van fisiologiese en psigologiese stres. Beide oefening program-verwante stres en chroniese psigologiese stres in proefpersone het ‘n op-regulering van spontane witbloedselreaktiwiteit in vitro tot gevolg gehad, wat d.m.v twee verskillende metodes aangetoon is, naamlik a) ‘n perifere bloed mononukluêre selkultuur (PBMS-kultuur) bepaling van immuunsel reaktiwiteit en b) ‘n relatief nuwe vloeisitometriese tegniek vir die assessering van aktiveringsstatus van selle, deur hul uitdrukking van die oppervlakmerker CD69, op ‘n limfosiet subpopulasie-spesifieke wyse. ‘n Opregulering van immuunselaktiwiteit in die afwesigheid van ‘n addisionele stressor is geassosieer met ‘n verlaagde kapsiteit om te reageer op ‘n latere mitogeniese prikkel in vitro, na chroniese psigologiese stres en akute, erge oefeningstres. Nog ‘n nuwe bevinding was dat kortisol hoog-respondeerders, in reaksie op chroniese psigologiese stres, ‘n hoër spontane reaktiwiteit van beide CD4+- and CD8+-limfosiete toon in vergelyking met kortisol laagresopndeerders. Hierdie bevinding toon aan dat chroniese blootstelling aan kortisol die inhiberende effek daarvan op spontane reaktiwiteit van T-limfosiete verminder. Na optimalisering van ‘n rotmodel van gematigde, psigologiese stres, het ons gedemonstreer (deur gebruik te maak van ‘n IL-6 teenliggaam) dat IL-6 nodig is vir ‘n volledige kortisolreaksie op chroniese, onderbroke, gematigde stres. Die resultate dui daarop dat IL-6 ‘n rol in die regulering van sy eie sekresie deur PBMSe in reaksie tot ‘n stressor speel, deur die handhawing van produksie van IL-1β in die teenwoordigheid van stres. Basale serum kortisolkonsentrasie is as die belangrikste beslissende faktor in die omvang van mitogeengestimuleerde PBMS sekresie van IL-6 in vitro in die stresvrye kontroles aangedui. Na blokkering van IL-6 in vivo, is IL-1β egter as ‘n belangrike reguleerder van IL-6 sekresie deur mitogeen-gestimuleerde PBMSe in vitro geïdentifiseer, onafhanklik van die teenwoordigheid of afwesigheid van stres. Die implikasie van hierdie nuwe bevindinge is dat proinflammatoriese sitokiene tydens gematigde stres sensitief gereguleer word.Die gemiddelde serum kortisolkonsentrasie in ‘n rustende toestand was nie ‘n gepaste instrument om chroniese oefeningstres na ‘n oefenprogram-ingreep te assesseer nie. Na basislyn klassifikasie van atlete in twee groepe volgens hul rustende serum kortisolkonsentrasie, is twee afsonderlike patrone vir die reaksie van beide kortisol en die kortisol:testosteroon verhouding egter aangetoon. Hierdie studies rakende die effekte van chroniese stres op parameters van die endokriene stres-as en die immuunsisteem het tot die volgende vernaamste gevolgtrekkings gelei: a) chroniese blootstelling aan kortisol het ‘n verlaagde inhibisie van spontane immuunselaktiwiteit tydens rustende toestande tot gevolg, b) hierdie verhoogde spontane aktivering van immuunselle tydens ‘n rustende toestand word geassosieer met ‘n onderdrukking van immuunkapasiteit om te reageer op ‘n daaropvolgende prikkel, c) laasgenoemde bevinding is nie sigbaar tydens stresvrye toestande, wanneer kortisol IL-6 sekresie bevorder, nie en d) IL- 1β en IL-6 is betrokke by die regulering van mekaar se sekresie.
15
Brindle, Ryan C. "Peripheral physiological mechanisms of cardiovascular stress reactivity". Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6428/.
Resumo:
This thesis aimed to increase understanding of the underlying physiological sources of the substantial inter-individual variability in heart rate (HR) and blood pressure (BP) reactions to acute psychological stress. This aim was achieved using a multi-method approach that included meta-analysis, laboratory studies, and prospective secondary analysis of epidemiological data. Chapter 2 implicated beta-adrenergic sympathetic activation and parasympathetic withdrawal in the cardiovascular stress response and showed that autonomic changes vary as a function of stress task, age, and sex. Chapter 3 demonstrated that individual differences in a unique HR complexity marker accounted for a significant amount of the observed variance in HR reactivity and that this effect was independent of task performance and changes in autonomic activity and respiration. Chapter 4 revealed that individual differences in resting physiological allostatic load related to HR reactivity such that higher allostatic load indicated lower reactivity. Finally, in Chapter 5, multivariate cluster analysis of HR, systolic and diastolic BP reactivity resolved a large sample into four homogenous clusters, each displaying significantly different reactivity patterns and risk of hypertension at 5-year follow-up. The research reported in this thesis confirms already suspected physiological sources of individual difference but also reveals novel sources that deserve further inquiry.
16
Radull, John. "On the use of metabolic rate measurements to assess the stress response in juvenile spotted grunter, Pomadasys commersonnii (Haemulidae, Pisces)". Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1007564.
Resumo:
Quantitication of stress requires the use of a stress indicator that is easy to measure, and which can be readily interpreted in terms of the potential long-term effects to an organism. This study evaluates the suitability of metabolic rate as an indicator of the stress response in fish. By comparing the metabolic with the cortisol stress response, the most commonly used indicator of stress in fish, it was possible to assess the suitability of metabolic rate as a stress indicator. Changes in metabolic rate were used to predict the long-term effects of transport-related stressors. This study also detennined the baseline metabolic rates of the tish. The standard and the active metabolic rates of juvenile P. cummersonnii were 0.16 ± 0.02 (mean ± S.D, n = 6) mg O₂g⁻¹h⁻¹, and 0.56 ± 0.04 mg O₂g⁻¹h⁻¹, respectively, whereas the routine metabolic rate for the fish was 0.25 ± 0.03 mg O₂g⁻¹h¹. The relationship between metabolic rate and body weight was described by the equation ϺO₂ = 0.64 W⁻°·³⁸. 24-h oxygen consumption measurements showed that juvenile P. commersonnii exhibited diel rhythmicity in oxygen consumption rate, the higher rates occurring at night and the lower rates during the daytime. The higher nocturnal metabolic activity may have been due to increased activity induced by an endogenous rhythm related to feeding. Diel rhythmicity has direct implications for the measurement of baseline metabolic rates since it could result in overestimation or underestimation of these rates. 24-h continuous oxygen consumption measurements enabled the detection of the rhythmicity in oxygen consumption rate, and thereby ensured a greater degree of accuracy in the estimation of these parameters. The metabolic stress response in juvenile P. commersonnii was best described by the equation, y = -0.0013 x² + 0.0364 x ÷ 0.3052, where x = time after application of stressor, and y = oxygen consumption rate. Using the derivative of this equation, the metabolic stress response was estimated to peak approximately 14 min after application of a simulated capture and handling stressor. Oxygen consumption increased by about 300 % as a result of the stress. Approximately 15 min after application of a similar stressor, plasma cortisol levels in stressed fish was 200 % higher than baseline levels. However, cortisol levels in fish sampled 30 min after the disturbance was similar to the baseline cortisol levels, indicating that full recovery had occurred. Although the patterns in the metabolic and cortisol stress responses were similar, metabolic rate could be measured continuously, thereby ensuring accurate interpretation of the data. Furthermore, increases in metabolic rate during the stress response are a culmination of physiological events from the primary to the tertiary levels of biological organization and are, therefore, easier to interpret in terms of long-term effects on the fish. Different transportation procedures elicited variable degrees of stress in juvenile P. commersonnii. The cost of metabolism attributed to the effects of capture and handling was twice as much as that attributed to acute temperature elevation. Acute temperature decrease resulted in a signiticant reduction in the oxygen consumption rate (ANOVA, P < 0.05). Oxygen consumption by the fish was not affected by fish density (ANOVA: F = 2.002, P = 0.5), or by oxygen depletion at dissolved oxygen concentrations above the critical level. Below this level, however, oxygen consumption decreased linearly with further decrease in dissolved oxygen concentration. These results showed that the highest energetic cost to juvenile P. commersonnii was incurred as a result of capture and handling. The results also showed that by subjecting fish to different stressors, it was possible to categorize them according to their relative metabolic costs to the fish. At 25º C, the effective concentration of 2-phenoxyethanol to fully anaesthetize (Stage IV, McFarland 1960) juvenile P. commersonnii was 0.4 ml l⁻¹ and the most appropriate concentration for deep sedation (Stage II, McFarland 1960) of the fish for at least 24 h was 0.2 ml l⁻¹. A maximum of 3 minutes was required by the fish to recover from the effects of the anaesthetic. There was no correlation between fish weight and the rate of induction of anaesthesia (r² = 0.001, p = 0.3). At the peak of the metabolic stress response, oxygen consumption was twice as high in the un-anaesthetized fish compared to the fish anaesthetized after the application of the simulated capture and handling stressor, suggesting that anaesthetization with 2-phenoxyethanol may have reduced the effect of the disturbance on the fish. Similar oxygen consumption rates for the fish anaesthetized prior to capture and the non-stressed fish suggested that the increases in metabolic rate could be linked to the struggling associated with attempts by fish to escape from the perceived stressor. Anaesthetization of juvenile P. commersonnii with 0.3 ml l⁻¹ 2-phenoxyethanol resulted in a more than 200 % increase in plasma cortisol concentration. The elevated levels of plasma cortisol in the anaesthetized fish suggested a manifestation of 2-phenoxyethanol as a stressor. At the time of capture, cortisol levels in fish that were anaesthetized prior to capture were the same as those measured in the disturbed fish at the peak of the stress response (ANOVA, p = 0.95), suggesting that the anaesthetized fish were already experiencing considerable stress at the time they were captured. Undisturbed juvenile P. commersonnii that were anaesthetized for 1 h also had cortisol levels that were five times higher than those measured in undisturbed-unanaesthetized fish, indicating that the duration of exposure to the anaesthetic had a significant effect on plasma cortisol levels. The results presented in this study demonstrate the usefulness of metabolic rate as an indicator of acute stress in fish. This was achieved by comparing the metabolic and the cortisol stress responses. The ease and accuracy with which oxygen consumption of fish could be measured made it possible to measure the stress response more accurately than by plasma cortisol concentration. It was also possible to monitor metabolic rate continuously over a long duration using polarographic oxygen sensors, thus enabling a better evaluation of the stress response. These results, thus, suggest that metabolic rate measurements could be a more practical way to quantify the effects of acute stressors on juvenile fishes. By detailing the profile of the metabolic stress response in P. commersonnii, this study makes a contribution towards understanding the physiological effects of stress in fishes. The study also contributes towards the quantification of baseline metabolic rates of this species under captivity. This study also contributes towards understanding the effects of 2-phenoxyethanol on the stress physiology of fish. By anaesthetizing fish under different conditions of stress, it was possible to evaluate the effect of 2-phenoxyethanol on the metabolic stress response. The ability of 2-phenoxyethanol to reduce physical activity of the fish, and thereby reduce the impact of acute stress on the metabolic stress response, makes it a good agent for the mitigation of stress during the capture and handling of fish. However, the increase in plasma cortisol concentration during prolonged anaesthetization using this drug suggests that the anaesthetic might be a stressor to fish and may, therefore, not be suitable for long-term sedation.
17
Nephew, Benjamin Charles. "Simultaneous modulation of behavioral, cardiovascular, and corticosterone responses to acute stress, with an emphasis on arginine vasotocin /". Thesis, Connect to Dissertations & Theses @ Tufts University, 2003.
Resumo:
Thesis (Ph.D.)--Tufts University, 2003.Adviser: L. Michael Romero. Submitted to the Dept. of Biology. Includes bibliographical references (leaves 158-180). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
18
Ade, Carl Jacob. "Cardiorespiratory and vascular function during stress". Diss., Kansas State University, 2013. http://hdl.handle.net/2097/15976.
Resumo:
Doctor of PhilosophyDepartment of Anatomy and Physiology
Thomas J. Barstow
The primary aim of this dissertation was to evaluate the factors that contribute to the cardiorespiratory and vascular responses following exercise conditioning and microgravity deconditioning. The first study of this dissertation (Chapter 2) revealed that exercise training in the head down tilt posture, which places increases central blood volume compared to upright, results in cardiorespiratory adaptations in both upright and head down tilt postures which are not completely expressed with exercise training in the upright posture. These findings suggest that augmentation of the ventricular volume load during exercise training may result in adaptations that transfer across multiple body positions. In the second and third studies measurements of blood velocity and flow were performed via Doppler ultrasound. In Chapter 3 we observed that in the brachial and femoral arteries blood moves with a slightly blunted parabolic velocity profile that is very stable across a range of mean arterial pressures and downstream limb resistances. We concluded that these findings support the current calculations of shear rate based on the assumptions of laminar flow. With these assumptions confirmed, the investigation in Chapter 4 could be performed. We observed that acute exposure to a sustained antegrade shear rate, via unilateral forearm heating, increased measurements of flow-mediated dilation and the overall rate of adjustment for forearm blood flow and vascular conductance during dynamic handgrip exercise. These findings suggest that one potential stimulus for improvements in vascular function and health following exercise conditioning may be exposure to elevations in antegrade shear. Lastly in Chapter 5 we changed focus to the cardiorespiratory deconditioning following long-duration microgravity exposure. We retrospectively reviewed and analyzed previous investigations of microgravity deconditioning and demonstrated that the decrease in maximal O2 consumption ( O2max) occurs as a function of duration of exposure and that both convective and diffusive O2 transport pathways substantially contribute to this decline. In addition we reviewed the current literature and highlighted potential mechanisms, across several organ systems, which may contribute to this decline in O2max. Collectively, these studies revealed the breath of plasticity for cardiorespiratory adaptations to a variety of stressors.
19
Dolbier, Christyn Lisette. "Promoting challenge appraisals of stress : effects on reactivity, immunity, and health /". Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
20
Aigrain, Jonathan. "Multimodal detection of stress : evaluation of the impact of several assessment strategies". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066681/document.
Resumo:
Il est maintenant largement accepté que le stress joue un rôle important dans les sociétés modernes. Le stress impacte en effet le corps et l'esprit à différents niveaux. De plus, le lien entre stress et maladie a été observé dans plusieurs études. Cependant, il n'y a pas encore de définition consensuelle du stress, et par conséquent il n'y a pas de manière consensuelle de le mesurer. Ainsi, bien que la qualité de la mesure joue un rôle majeur dans la réalisation de solutions robustes de détection du stress, les chercheurs doivent choisir une stratégie de mesure parmi un grand nombre de possibilités. Cette hétérogénéité impacte la validité des comparaisons faites entre les différentes solutions. Dans cette thèse, nous évaluons l'impact de plusieurs stratégies de mesure pour la détection du stress. Dans un premier temps, nous résumons comment différents domaines de recherche définissent et mesurent le stress. Nous décrivons ensuite comment nous avons collecté des données de sujets en situation stressante ainsi que plusieurs mesures du stress. Nous étudions également les liens entre ces différentes mesures. Par la suite, nous présentons les descripteurs comportementaux et physiologiques que nous avons extraits pour nos expériences. Enfin, nous présentons les résultats obtenus concernant l'impact des stratégies de mesure sur 1) la normalisation de données, 2) la performance des descripteurs pour la classification et 3) sur la conception d'algorithmes d'apprentissage automatique. De manière générale, nous défendons l'idée qu'il faut adopter une approche globale pour concevoir une solution de détection du stressIt is now widely accepted that stress plays an important role in modern societies. It impacts the body and the mind at several levels and the association between stress and disease has been observed in several studies. However, there is no consensual definition of stress yet, and therefore there is no consensual way of assessing it either. Thus, although the quality of assessment is a key factor to build robust stress detection solutions, researchers have to choose among a wide variety of assessment strategies. This heterogeneity impacts the validity of comparing solutions among them. In this thesis, we evaluate the impact of several assessment strategies for stress detection. We first review how different fields of research define and assess stress. Then, we describe how we collected stress data along with multiple assessments. We also study the association between these assessments. We present the behavioural and physiological features that we extracted for our experiments. Finally, we present the results we obtained regarding the impact of assessment strategies on 1) data normalization, 2) feature classification performance and 3) on the design of machine learning algorithms. Overall, we argue that one has to take a global and comprehensive approach to design stress detection solutions
21
Yao, Qing Angela, e 姚青. "Cellular stress pathways in cartilage biology and disease". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2015. http://hdl.handle.net/10722/209501.
22
Leipner, Jörg. "Chilling stress in maize: from physiology to genetics and molecular mechanisms". Zurich : ETH, Eidgenössische Technische Hochschule Zürich, Department of Agricultural and Food Science, 2009. http://e-collection.ethbib.ethz.ch/show?type=habil&nr=34.
23
Zhang, Wei. "Differential Impact of Age and Stress on Amygdala Physiology and Function". Thesis, Rosalind Franklin University of Medicine and Science, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3566591.
Resumo:
Occasional stress is a normal aspect of mammalian life. However repeated or prolonged stress exposure dysregulates stress responses and contributes to the onset or exacerbation of affective disorders such as anxiety, depression and post-traumatic stress disorder (PTSD). Understanding the underlying mechanism of the effect of stress on affective behaviors is essential for effective prevention and treatment of these disorders.
All affective disorders share a deficit in the regulation of emotion. The amygdala plays crucial role in this regulation and is adversely affected by stress. This suggests that stress precipitates abnormal affective state by altering amygdala function. While the effect of acute stress on the amygdala has been well described, less is know about the impact of repeated stress nor its age-dependency. We hypothesized that repeated stress leads to a hyperactive amygdala and impairs the amygdala function in regulating affective behaviors, and such impacts are greater during prepubescence than during adulthood. In this study, we subjected prepubescent (postnatal day, PND ∼30) and adult rats (PND ∼65) to repeated restraint stress. We then measured the effect of stress on amygdala physiology and amygdala-dependent behavior in prepubescent (PND ∼40) and adult (PND ∼75) rats. The results were compared between age-matched non-restraint and repeated restraint groups and across age. Repeated restraint stress increased basolateral amygdala (BLA) spontaneous population activity in prepubescent rats whereas it enhanced individual neuron activity in adult rats. In parallel with these physiological changes, repeated restraint stress enhanced initial expression of conditioned fear in both age groups, but impaired within session fear extinction only in prepubescent rats. Further studies demonstrated that repeated restraint stress reduced the BLA projection neuron inhibition by exogenous GABA in prepubescent rats. However, repeated restraint stress enhanced the BLA projection neuron excitation by exogenous glutamate in adult rats. In addition, repeated restraint reduced basal GABA transmission and enhanced mPFC-induced excitation of spontaneously active BLA projection neurons in both age groups. Together, these findings indicate that repeated restraint results in a generalized hyperactive and hyper-responsive amygdala. The distinct changes in amygdala physiology at different developmental stages might underlie age-dependent effect of stress on affective behaviors. Overall, this study leads to a better understanding of the pathophysiology of stress-related affective disorders and provide insight into age-specific treatment of these disorders.
24
Davidson, Sarah Rosemary. "Effects of ozone and water stress on plant growth and physiology". Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46273.
25
Higuchi, Hirokazu. "Environmental Physiology of Cherimoya(Annona cherimola Mill.)under Heat Stress Conditions". Kyoto University, 1999. http://hdl.handle.net/2433/78092.
Resumo:
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第7587号
農博第1026号
新制||農||773(附属図書館)
学位論文||H11||N3222(農学部図書室)
UT51-99-D204
京都大学大学院農学研究科熱帯農学専攻
(主査)教授 櫻谷 哲夫, 教授 杉浦 明, 教授 三野 徹
学位規則第4条第1項該当
26
Lia, Debora. "Role of alphaOGG1 in the Maintenance of Mitochondrial Physiology". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS125/document.
Resumo:
Les mitochondries sont des structures uniques dans la cellule mammifère. Ces organites portent leur propre génome (ADN mitochondrial, ADNmt) qui se compose d'une petite molécule qui codifie pour 13 polypeptides de la chaîne de transport d'électrons (ETC), 22 ARNt et 2 gènes d'ARNr pour sa propre synthèse protéique. Le MTDNA est proposé pour être plus susceptible au stress oxydatif que le génome nucléaire (ADNn) parce que non seulement il manque d'histones protectrices, mais aussi en raison de sa proximité avec les complexes ETC qui sont les principaux producteurs de ROS dans les cellules de mammifères. Parmi tous les types de dommages à l'ADNmt, les dommages oxydatifs sont les plus répandus et, de loin, les mieux étudiés. La voie de réparation de l'excision de base (BER) est un mécanisme de réparation d'ADN conservé de façon évolutive qui répare les dommages de base d'ADN non volumineux. Puisque la guanine a le potentiel redox le plus bas de toute autre base dans l'ADN, elle est facilement oxydée à la 8-oxoguanine (8-oxoG) qui est l’altération la plus fréquente induite par les ROS sur les deux, l'ADNc et l'ADNmt. Si la fourche de réplication contourne le 8-oxoG avant son élimination, un A est souvent inséré sur le brin d'ADN opposé et les réplications subséquentes corrigent la transversion de G à T. Lorsqu'il est associé à la cytosine, le 8-oxoG est éliminé de l'ADN par l'ADN glycosylase de 8-oxoguanine (OGG1) qui, de cette manière, initie le procédé BER. OGG1 est une glycosylase de ménage bi fonctionnelle qui, conjointement avec d'autres enzymes BER différentes, est présente dans les compartiments nucléaires et mitochondriaux, soulignant l'importance de maintenir l'intégrité de l'ADNmt pour le fonctionnement cellulaire normal. Il a été démontré que la surexpression d'une version recombinante d'OGG1, spécifiquement destinée aux mitochondries par un signal de ciblage mitochondrial supplémentaire (MTS) (OGG1-MTS), protège les cellules d'un stress oxydatif, probablement en raison d'une efficacité accrue dans la réparation De 8-oxoG dans l'ADNmt. L'objectif principal de notre projet est d'élucider si la perte spécifique de l'activité de réparation 8-oxoG dans les mitochondries (mais pas dans le compartiment nucléaire) a un impact sur les fonctions organelles et / ou sur la viabilité cellulaire et aussi pour dévoiler le mécanisme / s Derrière les effets protecteurs d'OGG1 sur la physiologie mitochondriale et la maintenance d'ADNmtMitochondria are unique structures within the mammalian cell. These organelles carry their own genome (mitochondrial DNA, mtDNA) which consists of a small molecule that codifies for 13 polypeptides of the electron transport chain (ETC), 22 tRNA and 2 rRNA genes for its own protein synthesis. MtDNA is proposed to be more susceptible to oxidative stress than the nuclear genome (nDNA) because not only it lacks protective histones but also because of its proximity to ETC complexes which are the main ROS producers in mammalian cells. Among all the types of mtDNA damage, oxidative damage is the most prevalent and, by far, the best studied. Base excision repair (BER) pathway is an evolutionarily conserved DNA repair mechanism that repairs non-bulky DNA base damages. Since guanine has the lowest redox potential of any other bases in DNA, it is readily oxidized to 8-oxoguanine (8-oxoG) that is the most frequent alteration induced by ROS on both, nDNA and mtDNA. If the replication fork bypasses the 8-oxoG before its removal, an A is often inserted on the opposite DNA strand and subsequent replications fix the G to T transversion. When paired with cytosine, 8-oxoG is removed from DNA by the 8-oxoguanine DNA glycosylase (OGG1) that in such a way initiates the BER process. OGG1 is a bifunctional housekeeping glycosylase that, together with other various BER enzymes is present in both nuclear and mitochondrial compartments, highlighting the importance of maintaining mtDNA integrity for normal cellular functioning. It has been demonstrated that the overexpression of a recombinant version of OGG1, specifically targeted to mitochondria by an additional Mitochondrial Targeting Signal (MTS) (OGG1-MTS), protects the cells from an oxidative stress, likely due to an increased efficiency in the repair of 8-oxoG in mtDNA. The main goal of our project is to elucidate if the specific loss of 8-oxoG repair activity in mitochondria (but not in nuclear compartment) has an impact on the organelles’ functions and/or on cell viability and also to unveil the mechanism/s behind the protective effects of OGG1 on mitochondrial physiology and mtDNA maintenance
27
Jones, C. A. "A study of stress susceptibility in pigs". Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372043.
28
Brown, Paul B., e Carolyn A. Zeiher. "Cotton Heat Stress". College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/210949.
Resumo:
Heat stress has been a subject of considerable concern among Arizona cotton growers due to a recent string of hot, humid summers. Research studies indicate heat stress develops when mean crop temperature exceeds 82.4F (28C). Serious heat stress develops when mean crop temperatures exceed 86E Several meteorological factors impact crop temperatures in Arizona; however, accurate estimates of crop temperature can be made using a model requiring air and dew point temperature. This model was used to evaluate heat stress conditions in Arizona over the past 10 years. Results from this evaluation show the past three years were difficult years for heat stress. Elevation and humidity levels are major factors impacting heat stress in any given year. Lower elevation areas are more prone to heat stress than high elevation areas such as Safford. Possible management options to minimize the impact of heat stress include early optimal planting dates, variety selection, field location and good water management.
29
Au, Tat-kuen Gerald. "Expectant fatherhood status, stress and health". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B29653629.
30
Shirangi, Seyedeh Ainaz. "Mécanismes osmorégulateurs chez les juvéniles d'esturgeon perse (Acipenser persicus) durant une acclimatation à la salinité de la mer Caspienne". Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT174/document.
Resumo:
Afin de repeupler la mer Caspienne, la propagation artificielle de l’esturgeon Acipenser persicus est maintenant une pratique courante avec rejets annuels de juvéniles directement en mer. Cependant, une forte mortalité est régulièrement observée suite à la libération directe en mer de juvéniles pesant 2-3 g. L'objectif a donc été d'analyser les capacités d’acclimatation de juvéniles de l’eau douce à l’eau saumâtre et d'identifier un moyen possible d’améliorer les taux de survie d’esturgeons de moins de 3 g.Dans une première partie, l'effet de transferts abruptes ou progressifs sur 5 jours de l'eau douce (ED) à une salinité de 11‰ (salinité de la mer Caspienne, CSW) a été étudié chez des juvéniles de 1 à 2 g, 2 à 3 g et de 3 à 5 g. Ont été mesurés les taux de mortalité, l'osmolalité plasmatique, l’expression et la localisation (branchies, reins, valvule spiralée, caecum pylorique) des principales protéines de transport : la Na+, K+-ATPase (NKA), la H+-ATPase vacuolaire (VHA), le Na+, K+, 2Cl- (NKCC) et la ‘Cystic Fibrosis Transmembrane conductance Regulator’ (CFTR). Une étude des changements d'expression génique et protéique de la NKA au niveau des branchies a également été effectuée. Enfin, une étude ultrastructurale (TEM et SEM) des cellules à chlorure branchiales a été effectuée.Dans une deuxième partie, un traitement hormonal avec le cortisol a été effectué afin d’améliorer la capacité d'acclimatation. Des juvéniles de moins de 2g ont été traités pendant 24h en ED avec des bains de cortisol à 3 concentrations différentes : 3, 5 et 7 mg.l-1. Les poissons ont été ensuite directement transférés de l'eau douce à la CSW et échantillonnés après 1, 4 et 9 jours après transfert en CSW. Les taux de mortalité, l'osmolalité plasmatique, le nombre et l’aire des cellules à chlorure des branchies ont été évalués.Ainsi, les poissons de plus de 3 g sont capables de survivre et s’acclimatent à la CSW. Malgré une augmentation initiale de l'osmolalité plasmatique après transfert de salinité, les juvéniles réduisent ensuite leur osmolalité plasmatique jusqu'à la pression osmotique de la mer Caspienne. Cependant, beaucoup de poissons de moins de 3 g ne peuvent survivre à l’augmentation brutale de salinité et la pression osmotique du sang des poissons survivants reste élevée. L’expression de la NKA et du NKCC, la taille et le nombre des cellules à chlorure des branchies sont également plus élevés. Les juvéniles pesants plus de 2 g augmentent aussi fortement leur activité de NKA branchiale après transfert de salinité. L'étude ultrastucturale a révélé des surfaces apicales similaires pour les cellules à chlorure branchiales des poissons en ED et acclimatés à la CSW. Le cytoplasme de ces cellules dans les poissons pesant plus de 2 g apparait plus dense et gonflé par rapport aux poissons pesant moins de 2 g. Cela pourrait être dû à l'allongement des replis de la membrane basale (réseau tubulo-vésiculaire) et/ou à une densité plus élevée des mitochondries. L’expression branchiale du gène NKA des poissons acclimatés à la CSW est apparue d'abord sur- puis sous-exprimée 4 jours après le transfert de salinité pour atteindre le niveau des poissons en ED. Au niveau intestinal et des reins, aucune différence n'a pu être détectée entre les différents groupes de poids suite au transfert de salinité. Malgré une osmolarité plasmatique réduite, le nombre et la taille des cellules à chlorure des poissons traités avec le cortisol montrent 9 jours après transfert, les mêmes tendances que celles observées pour les poissons non traités.Ainsi, cette étude a révélé que seuls les esturgeons juvéniles de plus de 3 g peuvent être directement rejetés en mer Caspienne. Pour les poissons de 2-3 g, un protocole spécial pendant le transfert de salinité doit être considéré alors que les poissons pesant moins de 2 g ne peuvent tolérer une augmentation de salinité même après un traitement au cortisolFor restocking purposes, artificial propagation of Persian sturgeon (Acipenser persicus) and annual releases into the Caspian Sea are now common practice. However, high mortality is regularly observed following the direct release of 2-3 g juveniles into the Caspian Sea. Therefore, the aim of the study was to analyse the acclamatory capacities of juvenile Persian sturgeons to elevated salinity and to identify a possible way to improve survival rates of juveniles weighting less than 3 grams.In the first part of this study, the effect of abrupt and 5-day gradual salinity transfers from freshwater (FW) to 11‰ Caspian Sea water (CSW) were investigated in juvenile Persian sturgeons with three different weight groups: 1-2 g (1.62 ± 0.27 g), 2-3 g (2.55 ± 0.41 g) and 3-5 g (4.28 ± 0.76 g). Daily mortality rates, plasma osmolality, immunofluorescence localization of the main ion transporter proteins such as Na+, K+-ATPase (NKA), Vacuolar H+-ATPase (VHA), Na+,K+,2Cl–(NKCC) and Cystic Fibrosis Transmembrane conductance Regulator (CFTR) at the gill, kidney, pyloric caecum and intestinal spiral valve levels, ultrastructural studies (TEM and SEM) of the gills for chloride cell changes and changes of branchial NKA gene and protein expression were measured 4 and 10 days after abrupt transfer to CSW and 9 and 15 days after the initial gradual transfer (i.e. 4 and 10 days after reaching CSW), respectively.In the second part of study, hormonal treatment with cortisol was used to enhance the acclimation capability of fish weighing less than 2g. Fish were treated with a cortisol bathing method using three different concentrations; 3, 5 and 7 mg.l-1 for 24 hours in FW. Fish were then directly transferred from FW to CSW (11‰) and sampled after 1, 4 and 9 days post-transfer to CSW. Daily mortality rate, plasma osmolality and branchial chloride cell number and area were evaluated.The obtained results showed that fish weighing more than 3g are able to survive and could successfully acclimate to CSW. Despite initial plasma osmolality increase after salinity transfer, juveniles could reduce their plasma osmolality down to the CSW osmotic pressure after 15 days of acclimation in CSW. However, fish under 3 g could not survive abrupt salinity increase, and blood osmotic pressure of the remaining surviving fish increased and remained elevated during the whole experimental period. At the gill level, higher chloride cell size and number, with also higher NKA and NKCC content were observed allowing juveniles weighing more than 2 g to sharply increase their NKA activity after salinity transfer. The electron microscopic study revealed similar apical surfaces for branchial chloride cells in FW and CSW-acclimated fish. It also indicated that the cytoplasm of these cells in fish weighing more than 2 g were denser and inflated compared to fish weighing less than 2 g. This could be due to the elongation of the basal membrane infoldings (tubulo-vesicular network) and/or a higher density of mitochondria. Because sequences of NKA and NKCC1 genes were not reported for sturgeon fish, two partial sequences of NKA (632 bp) and NKCC1 (538 bp) were obtained from this present study and were registered in Genbank. Branchial NKA gene of CSW-acclimated fish was firstly upregulated and then downregulated to the level for FW fish after 4 days following salinity transfer. At the kidney and intestinal level, no difference could be detected between the different weight groups during salinity transfer. Despite lower plasma osmolality, number and size of the chloride cells in treated fish with cortisol show the same trends as the untreated control fish after 9-days post transfer. Consequently, this study revealed that only Persian sturgeon juveniles weighing more than 3 g can directly be released into the Caspian Sea. Fish weighting 2-3 g need special care during salinity transfer and fish weighing less than 2 g cannot tolerate Caspian Sea salinity even after cortisol treatment
31
Marin, Marie-France. "Immediate and delayed effects of stress on a reactivitated declarative long-term memory trace". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116034.
Resumo:
In 1968, a study demonstrated that consolidated memories can be affected again if they are reactivated. Given the importance of the stress hormones glucocorticoids (GCs) on memory consolidation, the goal of the current study was to assess whether GCs had the capacity to affect a reactivated long-term memory and whether neutral and emotional memories were affected differently. At the first session, participants encoded a movie containing neutral and emotional scenes. Two days later, they recalled the story. Half of them were then exposed to a psychosocial stressor. Memory performance was assessed again right after the stressor and five days later. The stressed group recalled less neutral material five days after the stressor compared to controls. Immediately after the stressor, the stressed group recalled more emotional material than controls. Moreover, this enhanced memory trace was maintained across time. This highlights the importance of minimizing exposure to stressful contexts when reactivating emotional memories.
32
Lu, Buyu. "Hormones of stress and control of adipocyte biological "colour"". Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/46849/.
Resumo:
The family of “stress” peptides that includes CRH and UCNs are emerging as important regulators of the homeostatic mechanisms regulating energy balance and metabolism. These peptides exert well documented central anorectic and thermogenic actions in controlling food uptake and optimise energy losses. Furthermore, CRH acting through specific G-protein coupled receptors, CRH-R1 and R2 can target multiple peripheral tissues such as skeletal muscle and adipose tissue to influence important metabolic pathways. Two types of adipose tissue exist in mammals: WAT and BAT. Since WAT is the largest energy reserve in mammals and BAT can utilize energy through adaptive thermogenesis, one of the goals in this study was to identify the presence of CRH system components in adipose tissue. Real time RT-PCR and immunofluorescence demonstrated that CRH-Rs as well as CRH, UCN-I, and UCN-II are expressed in both WAT and BAT, raising the possibility that CRH and UCNs are important regulators of energy storage and adaptive thermogenesis. Also the functional roles of CRH-Rs in adipose tissue were investigated. Using an experimental paradigm the T37i fibroblast that can differentiate into brown adipocyte, it was demonstrated that CRH at low (nanomolar) but not high (submicromolar) concentrations stimulated a signaling pathway involving the AC/cAMP/PKA/AMPK signaling cascade that regulates downstream phosphorylation of HSL. This was associated with a significant translocation of HSL toward lipid droplets and association with perilipin, as demonstrated with immunofluorescence. Studies applying quantitative RT-PCR also suggested that CRH-R1 appears to regulate genes important for adaptive thermogenesis, whereas CRH-R2 likely regulates brown adipocyte formation. Further analysis using an experimental paradigm the 3T3L1 fibroblast that can differentiate into white adipocyte showed that exposure of 3T3L1 cells to UCN-II (a specific CRH-R2 agonist) or NBI-27914 (a CRH-R1 specific antagonist) were able to induce morphological and biochemical characteristics suggesting adipocyte differentiation to a “beige” phenotype in white preadipocytes/adipocytes. Thus, CRH-R1 and R2 could be of potential importance in maintenance of energy homeostasis. Moreover, in vivo analysis showed that CRH system seems to demonstrate a certain degree of plasticity in response to stress perturbation. For instance, HFD significantly repressed the expression of CRH-Rs and their agonists, whereas food deprivation dramatically increased their expression. The analysis of quantitative RTPCR demonstrated that this activation of CRH system might be associated with induction of ‘beige’ cells in white fat depots. Since CRH-R1 KO mice displayed a lean phenotype and resistance to HFD-induced fat accumulation and these phenotypes can be reversed by supplementation of corticosterone, role of CRH-R2 in adipose tissue of these KO mice was investigated. Data showed that CRH-R2 activation likely induced BAT activity and transdifferentiation from WAT to BAT in CRH-R1 KO mice. Corticosterone reversed these changes in KO mice via potential suppression of CRH-R2.
33
Hjellström, Mattias. "Drought Stress Signal Transduction by the HD-Zip Transcription Factors ATHB6 and ATHB7". Doctoral thesis, Uppsala University, Physiological Botany, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1857.
Resumo:
This work describes the regulation of drought stress responses in Arabidopsis thaliana and adresses the roles of the homeodomain-leucine zipper (HD-Zip) transcription factors in this regulation. The characteristics of ATHB6 and ATHB7, two genes encoding class I HD-Zip transcription factors were analysed.
Expression of ATHB6 and ATHB7 was transcriptionally activated in plants subjected to water deficit or exogenous treatment with abscisic acid (ABA).
Transgenic plants constitutively expressing the ATHB7 gene displayed a delayed elongation growth of the main inflorescence stem after transition to reproductive development. This phenotype is consistent with ATHB7 acting as a negative regulator of growth and development of the elongating stem in response to water availability.
Transgenic abi1-1 mutant plants constitutively expressing the ATHB7 gene displayed a reduced wiltiness as compared to monogenic abi1-1 mutants. These data are consistent with the ATHB7 protein having a central role in the drought stress response, regulating the water balance of the plant, and acting downstream to ABI1. Furthermore, the data is consistent with ATHB7 acting as a positive regulator of the drought stress response.
The ABA-induced expression of the ATHB7 gene displayed a dependence on the phytochrome system, suggesting an interplay between light and osmotic stress signaling in the regulation of the ATHB7 gene.
34
Spacht, Drew Evan. "Seasonal, habitat, and stress-related responses of insects in cold environments". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1588946793797684.
35
Keller, Michael T. "EFFECTIVENESS OF THE “DRAGON HEAT POLAR SEAT” IN PREVENTING HYPERTHERMIC STRESS IN ATHLETES". Cleveland State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=csu1407430494.
36
Degabriele, Robert, University of Western Sydney e of Informatics Science and Technology Faculty. "Stress and the immune network". THESIS_FIST_XXX_Degabriele_R.xml, 1999. http://handle.uws.edu.au:8081/1959.7/406.
Resumo:
The clonal selection/defence paradigm appears unable to reconcile immune function with homeostatic activity whereas organismic homeostasis is central to immune function in the network/autopoiesis paradigm. The aim of this investigation, therefore, was to test the proposition that immune function, that is not clonally driven (central immune system activity), contributes to organismic homeostasis in collaboration with psychoneural responses. In one experiment sheep were confined, either in groups or individually, and the time course of changes in cortisol levels, behaviour and T lymphocyte numbers were monitored. In another study, soldiers were monitored during the stressful experience of recruit training. The combined results suggest that, at least when the immune response is not clonally driven, the psychoneural system and the central immune system may not be operating independently of each other but rather as sub-networks of the organismic network. Consequently, homeostasis is properly characterised as a property of the whole organism. In autopoietic terms, then, homeostasis could be defined as the maintenance of network stability.Doctor of Philosophy (PhD)
37
Roberts, Jonathan Richard. "The role of cellular stress during cold ischaemic and reperfusion injury". Thesis, University of Plymouth, 2002. http://hdl.handle.net/10026.1/2433.
Resumo:
The elemental physiology of the highly complex and regulated cellular response to stress remains poorly understood. Hypothermia and reperfusion are necessary and unavoidable stresses associated with the procurement, storage and transplantation of organs such as the kidney. Signal transduction pathways and transcription factors are evolutionarily conserved mediators of stress responses. This project has investigated the activation of the transcription factors Nuclear Factor kappa B (NFκB), Activator Protein 1 (AP1) and the Heat Shock Factor I (HSF1) as well as the mitogen activated protein kinases (MAPK), p38, JNK and ERK 1 /2, during hypothermic and reperfusion stress in cultured endothelial cells (HUVECS) as a model of kidney graft endothelial cells. HUVECS were subjected to 72 hours of hypothermia at 4°C in a renal preservation solution. For reperfusion experiments cells were returned to 37°C after 30 minutes or 12 hours of hypothermia. NFκB was activated within minutes of a hypothermic insult, correlating with the phosphorylation of the p38 and ERK 1 /2 MAPKs (p<0.01). Inhibition of p38 had no effect on NFκB translocation, but inhibition of ERK 1 /2 prevented subsequent NFκB activation (p<0.01). In contrast AP1 was not significantly up-regulated until 12 hours of hypothermia and HSF1 was down regulated during hypothermia. The downstream effects of NFκB activation were investigated by measuring the production of the inflammatory cytokines IL-6, IL-8 and TNFα. All three cytokines were up-regulated during hypothermia and reperfusion and the inhibition of NFκB with a decoy oligonucleotide reduced the expression of these cytokines. HUVECS were not killed by hypothermia with greater than 95% cell viability for 48 hours. Similarly DNA fragmentation. an event that occurs during apoptosis was not seen during hypothermic or reperfusion stress in HUVECS. There was a consistent expression of the mitochondrial anti-apoptosis protein BCL-2 during hypothermia. HUVECS did not release von willebrand factor (VWF), a marker of endothelial dysfunction during hypothermia, however, cells did produce lactate after prolonged storage indicating a degree of hypoxia developed during hypothermic stress. To extrapolate the in vitro work to a clinical setting 17 preservation solutions were collected from cadaveric donor kidneys. Levels of lactate, VWF, IL-6, IL-8, TNFα and the anti-inflammatory IL-4 were measured. A large range in values was found for all markers in the 17 preservation solutions, however, no correlation was found between increasing cold or warm ischaemic times, early graft function or rejection with the markers chosen. IL-6 was significantly increased in donor kidneys that had experienced greater than 30 minutes warm ischaemia (p<0.05). The response of a donor kidney may be regulated by polymorphisms which the graft cells contain. Microsatellite polymorphisms in the NFκB and TNFα genes and restriction enzyme sites in the IL-6 and NAD(P)H genes were investigated in 50 donor DNA samples. No correlation was found with rejection episodes with any of these polymorphisms. However, in the 17 preservation solutions, donors with the IL-6 allele which is linked to high protein production had higher IL-6 levels than donors with the low production allele. The role of IL-6 in transplantation remains unclear. However, this study has demonstrated that IL-6 may be a useful marker of stress. The ability to block cytokines by inhibiting transcription factors such as NFκB may have a therapeutic potential in ischaemic injury.
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Al-Najafi, Mohammad Abdul Aziz. "Root shrinkage in relation to water stress". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279828.
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Aigrain, Jonathan. "Multimodal detection of stress : evaluation of the impact of several assessment strategies". Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066681.
Resumo:
Il est maintenant largement accepté que le stress joue un rôle important dans les sociétés modernes. Le stress impacte en effet le corps et l'esprit à différents niveaux. De plus, le lien entre stress et maladie a été observé dans plusieurs études. Cependant, il n'y a pas encore de définition consensuelle du stress, et par conséquent il n'y a pas de manière consensuelle de le mesurer. Ainsi, bien que la qualité de la mesure joue un rôle majeur dans la réalisation de solutions robustes de détection du stress, les chercheurs doivent choisir une stratégie de mesure parmi un grand nombre de possibilités. Cette hétérogénéité impacte la validité des comparaisons faites entre les différentes solutions. Dans cette thèse, nous évaluons l'impact de plusieurs stratégies de mesure pour la détection du stress. Dans un premier temps, nous résumons comment différents domaines de recherche définissent et mesurent le stress. Nous décrivons ensuite comment nous avons collecté des données de sujets en situation stressante ainsi que plusieurs mesures du stress. Nous étudions également les liens entre ces différentes mesures. Par la suite, nous présentons les descripteurs comportementaux et physiologiques que nous avons extraits pour nos expériences. Enfin, nous présentons les résultats obtenus concernant l'impact des stratégies de mesure sur 1) la normalisation de données, 2) la performance des descripteurs pour la classification et 3) sur la conception d'algorithmes d'apprentissage automatique. De manière générale, nous défendons l'idée qu'il faut adopter une approche globale pour concevoir une solution de détection du stressIt is now widely accepted that stress plays an important role in modern societies. It impacts the body and the mind at several levels and the association between stress and disease has been observed in several studies. However, there is no consensual definition of stress yet, and therefore there is no consensual way of assessing it either. Thus, although the quality of assessment is a key factor to build robust stress detection solutions, researchers have to choose among a wide variety of assessment strategies. This heterogeneity impacts the validity of comparing solutions among them. In this thesis, we evaluate the impact of several assessment strategies for stress detection. We first review how different fields of research define and assess stress. Then, we describe how we collected stress data along with multiple assessments. We also study the association between these assessments. We present the behavioural and physiological features that we extracted for our experiments. Finally, we present the results we obtained regarding the impact of assessment strategies on 1) data normalization, 2) feature classification performance and 3) on the design of machine learning algorithms. Overall, we argue that one has to take a global and comprehensive approach to design stress detection solutions
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Moore, Hannah E. "Characterizing Interactions between Habitual Caffeine Consumption and Stress Response Physiology in Female Students". Scholarship @ Claremont, 2014. http://scholarship.claremont.edu/scripps_theses/377.
Resumo:
Caffeine, one of the most commonly consumed substances worldwide, acts as a biogenic stressor and elicits both cardiovascular and endocrine stress responses. The most commonly described endocrine stress response is the hypothalamic-pituitary-adrenal (HPA) axis, whose final product is cortisol. Cortisol is well described as an indicator of stress levels, and it may be elevated chronically in persistently stressful situations. Its subsequent effects include blood pressure elevation, which is an indicator of cardiovascular stress reactivity. Research shows that cardiovascular and endocrine stress responses attenuate—albeit incompletely—with habitual caffeine consumption. However, when caffeine consumption and situational stressors are combined, stress reactivity is potentiated, raising concerns about long-term effects in populations who are regularly exposed to both.
Numerous sex-related factors complicate this area of research in female cohorts. Endocrine considerations, especially relating to fluctuating estradiol levels, are well known to affect both caffeine metabolism and stress reactivity. Prior studies, ranging from biochemical to epidemiological levels, have identified variability in caffeine metabolism and stress reactivity attributable to menstrual cycle phase and recent pregnancy. Cardiovascular stress reactivity patterns differ, furthermore, between males and females, a reality that translates to differences in cardiovascular disease risk and forms a critical area of future research with broad public health implications.
Based on extensive review of caffeine metabolism and stress reactivity literature, focusing on studies relevant to young females with varying habitual levels of caffeine consumption, I designed a study proposal to further characterize these physiological stress responses within this demographic. The core goal of the proposed study is to assess changes in plasma free cortisol concentration and blood pressure following an acute dose of caffeine (200 mg) at peak (40 min) and elimination half-life (160 min) caffeine plasma concentration time points. Average daily caffeine consumption (low, medium, or high) and menstrual cycle phase were included as additional parameters of interest in order to further characterize interactions within the selected demographic.
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Keerio, Mohammad Ibrahim. "High temperature effects on growth, physiology and nitrogen fixation in soybean". Thesis, Bangor University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484156.
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Sun, Annika C. "Novel functions of B7-H4 in β cell physiology and stress response". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52872.
Resumo:
Stress-induced failure and death of pancreatic β-cells are integral steps in the pathogenesis of type 1 and type 2 diabetes. Better understanding of the molecular interactions that influence β-cell function and stress signaling may therefore identify therapeutic targets to protect endogenous β-cells or transplanted islet grafts. B7-H4 is a negative co-stimulatory molecule that is expressed on the cell membranes of antigen presenting cells and down-regulates the immune response. Interestingly, pancreatic β-cells also express high levels of B7-H4 mRNA and moderate levels of B7-H4 protein. Of note, various tumor cells have up-regulated levels of B7-H4, which has been linked to metabolic and anti-apoptotic effects. This raises the intriguing possibility that B7-H4 may also regulate β-cell function, stress signaling, and survival independent of immune-regulation. In this study, we used mice with β-cell-specific overexpression of B7-H4, as well as B7-H4 knockout mice to examine the possible roles of B7-H4 in β-cell physiology and responses to endoplasmic reticulum (ER) stress. Cytosolic Ca²+ imaging showed that B7-H4 transgenic islets had increased sensitivity to sub-maximal glucose stimulation. Additional experiments indicated no differences in ER Ca²+ uptake/release or glucose metabolism, but revealed that B7-H4 transgenic islets are sensitized to tolbutamide and are resistant to diazoxide, suggesting changes at the ATP-sensitive potassium channels. The B7-H4-induced amplification of glucose-stimulated Ca²+ did not translate into detectable differences in in vitro insulin secretion or in vivo glucose tolerance, suggesting secondary control between rise in intracellular calcium and exocytosis of insulin granules. ER stress was induced in vitro using thapsigargin, and gene expressions were compared by real time quantitative PCR. Moderate ER stress induced the expression of key unfolded protein response genes, BiP, CHOP, and XBP1s to significantly higher levels in B7-H4 transgenic islets compared with wild type. However, the death of dispersed B7-H4 and wild type islet-cells did not differ following more severe and prolonged ER stress. Together, our findings demonstrate that over-expression of B7-H4 amplifies β-cell glucose-stimulated Ca²+ responses and the unfolded protein response during ER stress, revealing novel roles for B7-H4 in the pancreatic β-cell.Medicine, Faculty of
Medicine, Department of
Experimental Medicine, Division of
Graduate
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Jabbi, Mbemba. "Integrating the homeostatic imbalances genetics and physiology of stress and the emotions /". [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2007. http://irs.ub.rug.nl/ppn/301103569.
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Humphrey, Suzanne. "Effects of food-related stress conditions on salmonella morphology, physiology and virulence". Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544351.
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Rosa, Christina Michelle. "Sleep, Stress, and Sweat: Implications for Client Physiology Prior to Couple Therapy". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7578.
Resumo:
Physiological state greatly influences one’s ability to emotionally regulate and connect to a partner in couple therapy. As individuals encounter real or perceived threats in relationships, they are likely to experience sympathetic nervous system (SNS) responses of fight, flight, or freeze, thereby inhibiting the ability to connect with a partner or therapist made possible by the parasympathetic nervous system (PNS). This study, guided by the Polyvagal theory, examines the influence of client sleep, daily stress, and exercise on physiological baseline prior to a couple therapy session. Participants included 23 married couples who attended couple therapy at the Brigham Young University (BYU) Comprehensive Clinic. We examined the influence of client number of awakenings, sleep fragmentation index (SFI), daily stress time, and daily exercise time on measures of physiological baseline which included Galvanic skin response (GSR), respiratory sinus arrhythmia (RSA) and pre-ejection period (PEP) of the left ventricle of the heart. Three multi-level models were conducted to analyze the influence of sleep, stress, and exercise on GSR, RSA, and PEP respectively. Results indicated that daily stress significantly predicts PEP baseline as a measure of SNS fight-or-flight activation. A discussion of potential limitations, recommendations for therapists, and suggestions for future research are included.
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Fallahshahroudi, Amir. "Domestication Effects on the Stress Response in Chickens : Genetics, Physiology, and Behaviour". Doctoral thesis, Linköpings universitet, Biologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-137350.
Resumo:
Animal domestication, the process where animals become adapted to living in proximity to humans, is associated with the alteration of multiple traits, including decreased fearfulness and stress response. With an estimated population of 50 billion, the domesticated chicken is the most populous avian species in the world. Hundreds of chicken breeds have been developed for meat and egg production, hobby or research purposes. Multidirectional selection and the relaxation of natural selection in captivity have created immense phenotypic diversity amongst domesticates in a relatively short evolutionary time. The extensive phenotypic diversity, existence of the wild ancestor, and feasibility of intercrossing various breeds makes the chicken a suitable model animal for deciphering genetic determinants of complex traits such as stress response. We used chicken domestication as a model to gain insights about the mechanisms that regulate stress response in an avian species. We studied behavioural and physiological stress response in the ancestral Red Junglefowl and one of its domesticated progenies, White Leghorn. An advanced intercross between the aforementioned breeds was later used to map genetic loci underlying modification of stress response. The general pattern of the stress response in chickens was comparable with that reported in mammals, however we identified distinctive differences in the stress modulatory pathways in chickens. We showed that changes in the expression levels of several stress modulatory genes in the brain, the pituitary and the adrenal glands underlie the observed modified stress response in domesticated chickens. Using quantitative trait loci (QTL) mapping, several QTL underlying stress induced corticosterone, aldosterone and baseline dehydroepiandrosterone (DHEA) levels were detected. As a next step, we combined QTL mapping with gene expression (eQTL) mapping and narrowed two QTL down to the putative causal genes, SERPINA10 and PDE1C. Both of these genes were differentially expressed in the adrenal glands of White Leghorn and the Red Junglefowl, had overlapping eQTL with hormonal QTL, and their expression levels in the adrenal glands were correlated with plasma levels of corticosterone and al-dosterone. These two genes thus serve as strong candidates for further functional investigation concerning modification of the stress response during domestication. This dissertation increase the knowledge about genetics and physiology of the stress response in an avian species and its modification during domestication. Our findings expand the basic knowledge about the stress response in chicken, which can potentially be used to improve welfare through appropriate genetic selection.
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Alou, Abdourahamane 1959. "Vegetative physiology of cotton as related to the Crop Water Stress Index". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276939.
Resumo:
This study was undertaken to investigate Gossypium hirsutum L. reproductive physiology and metabolic activities as they relate to the Crop Water Stress Index. Five treatments were established based on the CWSI. These were the maximum stress levels allowed for each treatment. The indices investigated were .16, .35, .36, .40, and .62. Daily tagging of opened flowers in each treatment was conducted throughout the season. Diffusive resistance, transpiration, apparent photosynthesis, and yield were measured. There was no significant difference in treatment yield. Plants irrigated at stress level either below .30 or above .40, tended to yield relatively low compared to plants maintained between .30 and .40. Floral production, abscission and boll retention were negatively correlated to CWSI. Negative relationships were also found between apparent photosynthesis, transpiration, leaf area and CWSI. A two day lag response was observed between a decrease in CWSI values resulting from irrigation, and daily flowering increase.
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Sundblad, Patrik. "Effects of physical activity and gravitational stress on cardiovascular control /". Stockholm, 1999. http://diss.kib.ki.se/1999/91-628-3791-5/.
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Hare, Alexander. "Developmental Plasticity in Zebrafish (Danio Rerio): Effects of Early Life Exposure to a Stressor". Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36973.
Resumo:
Experience of stress and/or cortisol, the end-product of activation of the hypothalamic-pituitary-interrenal (HPI) axis, may serve as a cue to trigger developmental plasticity. In fish, most research in this area has focused on effects of maternal stress or maternal cortisol levels on development, particularly with respect to the HPI axis and stress responses, and little attention has been paid to the effects of an endogenous stress response during early life. In the current study, zebrafish (Danio rerio) at four developmental stages (4, 7, 15 or 35 days post fertilization, dpf) were subjected to an air exposure stressor twice a day for two days. Individuals stressed early in life exhibited decreased survival and growth, increased whole-body Na+ and Ca2+ concentrations, and altered HPI axis activity associated with changes in anxiety-related behaviour at 7 to 35 dpf, with most effects diminishing with increasing age. Stress at 7 dpf was particularly effective at eliciting phenotypic changes, suggesting this age represents a critical window for cortisol to influence development. Finally, stress at 35 dpf induced masculinization, suggesting that cortisol influences sexual differentiation in zebrafish. These findings demonstrate that early-life stress in zebrafish triggers developmental plasticity, with effects on physiology and behaviour mediated by the HPI axis in an age-dependent manner.
50
Buckley, John Paul. "Ratings of perceived exertion and pain in the assessment and prescription of exercise". Thesis, Keele University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269175.