Thèses sur le sujet « Physiological stresse »

Mestrado em Biologia Aplicada
Em Portugal, cerca de 700,000 ha foram já plantados com clones de Eucalyptus globulus, selecionados pelas suas elevadas taxas de crescimento, alta produção de polpa e adaptabilidade ambiental. Contudo, a produtividade das plantações de E. globulus tem enfrentado sérias limitações, principalmente devido à fraca disponibilidade de água. A seca é um importante stress abiótico que afeta negativamente o crescimento e o desenvolvimento das plantas, causando um conjunto de respostas fisiológicas, bioquímicas e moleculares. Embora esteja disponível um grande número de estudos que descreve as respostas das plantas ao stress hídrico, apenas alguns trabalhos se debruçam sobre os mecanismos que permitem a recuperação. Além disso, vários estudos descrevem também como diferentes genótipos podem diferir na capacidade de lidar com a seca. Considerando que manter a produção durante o stress hídrico não é o mais relevante, mas sim a capacidade de sobreviver e recuperar rapidamente após a re-hidratação, o objetivo deste estudo foi compreender os mecanismos envolvidos na recuperação, de modo a selecionar coleções clonais adequadas a plantações sustentáveis num clima mediterrânico. Com essa finalidade, dois clones de E. globulus (AL-18 e AL-126) foram submetidos a um período de três semanas em stress hídrico, seguido por uma semana de recuperação. Um perfil fisiológico foi obtido para cada genótipo, pela avaliação do crescimento, estado hídrico, peroxidação lipídica, respostas do aparelho fotossintético, trocas gasosas e concentração de ABA. Os principais resultados deste trabalho levam a concluir que: i) os genótipos escolhidos foram altamente tolerantes às condições testadas; ii) os clones selecionados apresentaram uma resposta similar na maioria dos parâmetros testados (exceto MDA, pigmentos, parâmetros fotossintéticos e ABA); iii) o clone AL-126 foi o mais resiliente à seca, mantendo taxas de crescimento mais elevadas em stress e após re-hidratação.
In Portugal, about 700,000 ha have been established with Eucalyptus globulus clones selected for their high growth rates, high pulp yield and environmental adaptability. However, productivity in E. globulus plantations has encountered serious limitations, mostly because of water availability. Drought is a major abiotic stress negatively affecting plant growth and development that causes an array of physiological, biochemical and molecular responses in plants. Apart from the great number of studies reporting on plant responses to drought stress and on the mechanisms to overcome stressful conditions, only a few reports providing evidence about the capacity of recovery and the underlying processes during recovery from drought are available. Moreover, ecophysiological studies have reported that different genotypes differ in their capacity to cope with drought. Considering that maintenance of production during drought is not the most important consideration, but rather the capacity to survive and recover rapidly after rewatering, the aim of this study was to understand the underlying mechanisms in recovery in order to select suitable clonal collections for sustainable plantations in a Mediterranean climate. For this propose, two E. globulus clones (AL-18 and AL-126) were subjected to a three-week water stress period, followed by one week recovery. A physiological profile was obtained for each genotype, assessing growth, water status, lipid peroxidation, photosynthetic responses, gas exchanges and ABA concentration. The main results of this work led us to conclude that: i) the chosen genotypes were highly tolerant to the conditions tested; ii) the selected clones presented a similar response in most of the tested parameters (except for MDA, pigments, fluorescence parameters and ABA); iii) clone AL-126 was the most resilient to drought, maintaining higher growth rates under stress and after rewatering.

Exposure of broiler cockerels to between 35.0 to 37.8 C for 24 hr at 5 days of age increases their survival when exposed to a heat challenge at 6 weeks of age (35.0-37.8 C; RH 50% ). This' phenomenon does not resemble acclimation since the physiological changes known to occur in acclimated birds exposed to heat have not been observed in the neonatally stressed birds. A series of experiments were conducted to elucidate the mechanisms of neonatally induced thermotolerance. In Experiment 1, the erythrocyte protein profile of control and 5 days heated birds prior to and during exposure to acute heat were determined. Prior to juvenile heat exposure no differences in the erythrocytic protein profile of neonatally stressed and control birds were observed at any age (10, 17, 24, 31 and 38 days of age) when maintained under control conditions. However, upon exposure to an acute heat challenge (40.5 C; 52 days of age) temporal and differential expressions of proteins similar in molecular weight to heat shock proteins (HSPs) were observed between the neonatally stressed and control birds. In Experiment 2, the effects of neonatal heat stress at various ages (5, 8, 12, 16 days of age) on the protein synthesis profile of heart, brain (telencephalon, diencephalon, brain stem, cerebellum) and liver tissues during exposure to an acute heat challenge were studied. In addition, body temperature during neonatal heat exposure was monitored. A significant increase in body temperature was observed during neonatal heat stress. A steady increase in the magnitude of the temperature change was noticed up to 12 days of age. Body temperature of birds exposed to neonatal heat at 16 days of age was similar to that of birds heated at 5 days of age.
Ph. D.

During pregnancy, the basal activity is increased in both of our major stress response systems: the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis. At the same time, the reactivity towards stressors is reduced. These alterations sustain maternal and fetal homeostasis, and are involved in the regulation of gestational length. Although the feto-placental hormone synthesis produces the main endocrinological changes, also the central nervous system undergoes adaptation. Together, these profound adjustments have been suggested to make women’s mental health more vulnerable during pregnancy and postpartum period. The aim of this thesis was to examine factors connected to physiological stress responses during the late pregnancy in relation to pain, labour onset, emotional reactivity, and mental health. The first study examined the pain and sympathetic response during cold stress, in relation to time to delivery. Women with fewer days to spontaneous delivery had lower sympathetic reactivity, while no pain measure was associated with time to delivery. In the second study, acoustic startle response modulation was employed to study emotional reactivity during late gestation, and at four to six weeks postpartum. The startle response was measured by eye-blink electromyography, while the participants watched pleasant and unpleasant pictures, and positive and negative anticipation stimuli. A significant reduction in startle modulation by anticipation was found during the postpartum assessment. However, no startle modulation by pleasant, or unpleasant, pictures was detected at either time-point. The serum level of allopregnanolone, a neurosteroid implied in pregnancy-induced hyporeactivity, was analysed in relation to self-reported symptoms of anxiety and depression. Although the participants reported low levels of depression, the women with the highest depression scores had significantly lower levels of serum allopregnanolone. There was no correlation between allopregnanolone and anxiety scores. In the fourth study, the cortisol awakening response was compared between women with depression during pregnancy, women with depression prior to pregnancy, and women who had never suffered from depression. No group differences in cortisol awakening response during late pregnancy were found. The results are in line with the previously described pregnancy-induced hyporesponsiveness, and add to the knowledge on maternal stress hyporeactivity, gestational length, and maternal mental health.

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.

Because of the impact of stress on health, it is important to understand the variables that underlie cardiovascular reactivity to stress because it may lead to more focused targets of intervention for helping people to reduce or otherwise better manage their stress. The purpose of the present study was to answer the following questions: does lack of eudaimonic well-being (a combination of psychological and social well-being) predict increased cardiovascular reactivity to stress in a clinically distressed population? And does increased eudaimonic well-being protect against increased cardiovascular reactivity to stress when hedonic well-being (a combination of positive affect and life satisfaction) is low and depression and stress are high? If so, then it may be possible to reduce the effects of stress on health even if depression and stress are present. One hundred twenty-nine college students (ages 18-29) who were clinically distressed were administered a questionnaire that included questions about demographic variables and measures of hedonic and eudaimonic well-being, depression, and general perceived stress. After answering the questionnaire, a baseline reading of cardiovascular activity was taken. After the baseline reading, participants were subjected to the Trier Social Stress Test (TSST), an interpersonal stressor that consists of an anticipation period, a speech, and a math task. Measurements of cardiovascular activity were taken throughout the TSST. I predicted that lower levels of eudaimonic and hedonic well-being, mental health, and higher amounts of general perceived stress would predict increased cardiovascular reactivity to the TSST as measured by systolic blood pressure, diastolic blood pressure, and heart rate. Then, should the prior hypothesis be true, I predicted that higher eudaimonic well-being will suppress the effect of lower hedonic will-being, lower mental health, and higher general perceived stress on cardiovascular activity to acute stress. Results of the study found no effect of eudaimonic well-being, hedonic well-being, depression, and general perceived stress on cardiovascular reactivity during the TSST. The results suggest that there is no relationship between well-being, depression, and general perceived stress and cardiovascular reactivity to stress in a young college student population.

While a great deal of research has been directed towards the phenomena of excess post exercise oxygen consumption (EPOC), the effect of thermal stress on EPOC is not well defined. To assess the effect of heat stress on EPOC, seven healthy, active subjects (4 female, 3 male; 23.9 ± 2.0 years of age) performed 4 trials: one control (quiet rest) and one exercise (45 minutes of cycling at 65% VO2max workload) trial in moderate (23° C, 50% humidity) and hot (35° C, 50% humidity) environments. Oxygen consumption (V02), heart rate (HR) and rectal temperature (RT) were assessed pre, during and post control or exercise. Subjects were monitored until post exercise VO2 had returned to within ±2% of baseline. EPOC was determined by subtracting baseline VO2 from total V02 during the post exercise period. During the first 15 minutes (acute) post exercise, a significant EPOC (p = 0.0019) was seen in both exercise conditions over both control conditions. During the slow phase (> 15 minutes post exercise to baseline), there was no significant difference between the hot control (HC), moderate exercise (ME), or hot exercise (HE) EPOC. Total time post exercise until baseline was achieved was 35, 44, and 51 minutes for HC, ME, and HE respectively. HR was significantly elevated in both exercise conditions. During the acute post exercise period, HR in HE was elevated above MC, ME and HC (p < 0.05). RT was elevated in both exercise conditions during and post exercise. The present data indicate that heat stress does not have a significant effect on the magnitude or duration of EPOC.
School of Physical Education

While considerable information exists regarding the independent effects of caffeine and psychological stress on cardiovascular activity, there is relatively little information on their combined effects. Since caffeine may enhance cardiovascular responsivity to psychological stress, research on hemodynamic responses to caffeine-stress combinations may help elucidate mechanisms of hypertension development. In a series of studies, regular consumers of caffeine were exposed to laboratory and naturalistic stressors with and without prior caffeine intake. Among the findings were (1) caffeine and stress produced additive increases in blood pressure, (2) caffeine appears to potentiate beta-adrenergic responsivity to active coping, but not passive coping, stressors, (3) caffeine enhanced emotional responses to stress, and (4) cardiovascular responses to caffeine and stress in a naturalistic setting were similar to those observed in the laboratory. These results indicate that caffeine may enhance cardiovascular and psychological responses to stress, and that these responses may contribute to risk for essential hypertension.

The prefrontal cortex (PFC) is a brain region thought to mediate cognitive functions such as working memory. Chronic stress has been shown to reduce working memory. In this thesis study, the effect of chronic stress on PFC functions was assessed in adult rats.
First, contrary to previous evidences, chronic stress induces working memory performance alterations differentially in two populations of rats. One group displayed a decrease of performance only at 30 second delay, while the other had a decrease and increase at 0 and 30 seconds respectively.
Then, the effect of chronic stress on synaptic plasticity induction in the hippocampus-PFC network was investigated. High-frequency tetanic stimulation (HFS) of the dorsal hippocampus that induced long-term potentiation (LTP) in the prelimbic and infralimbic cortex in normal conditions was unable to induce LTP after chronic stress in the infralimbic cortex, whereas long-term depression (LTD) instead of LTP was induced in the prelimbic cortex.
Given that synaptic plasticity has been shown to depend on NMDA receptors in the PFC, NMDA subunit expressions before and after chronic stress was examined. There was a decrease of NR1 subunits expression in the prelimbic, but not infralimbic cortex. In contrast, the NR2A/NR2B ratio was increased in the infralimbic, but not prelimbic cortex. These results suggest that chronic stress disrupts PFC functions through dynamic modulation of distinct neural networks within the PFC.
Le cortex préfrontal (PFC) est une région du cerveau qui contrôle les fonctions cognitives comme la mémoire de travail. Dans cette thèse, l'effet du stress chronique sur des fonctions du PFC a été analysé chez des rats adultes.
Premièrement, les performances de la mémoire de travail ont été mesurées avant et après exposition au stress chronique. Nous avons constaté que le stress chronique induit des changements de performances de la mémoire de travail différemment selon deux populations de rats. Une des populations a démontré une diminution de performance seulement à 30 secondes de délai. Au contraire, l'autre a démontré une diminution de performance à 0 seconde et une amélioration de performance à 30 secondes.
En plus, nous avons évalué l'effet du stress chronique sur l'induction de la plasticité synaptique dans le réseau reliant l'hippocampe au PFC. Dans les conditions initiales, une stimulation tétanique à haute fréquence (HFS) dans l'hippocampe dorsal provoquait une potentialisation à long terme (LTP) dans le cortex prélimbique et infralimbique Or après exposition au stress chronique, une stimulation tétanique à haute fréquence n'a pas entraîné de potentialisation à long terme dans le cortex infralimbique. De plus, une exposition au stress chronique a provoqué l'apparition dans le cortex prélimbique d'une dépression à long terme (LTD) plutôt qu'une potentialisation à long terme.
Étant donné que la plasticité synaptique dépend des récepteurs de NMDA dans le PFC, nous avons examiné l'expression de sous-unité de NMDA avant et après exposition au stress chronique. En accord avec les changements synaptiques distincts de plasticité entre le cortex prélimbique et infralimbique après exposition au stress chronique, nous avons observé que l'expression de la sous-unité NR1 a diminué dans le prélimbique, mais non dans l'infralimbique. En revanche, le ratio de NR2A/NR2B a augmenté dans le cortex infralimbique, mais non dans le prélimbique. Ces résultats suggèrent que le stress chronique perturbe les fonctions du PFC par la modulation dynamique des réseaux distincts neurologiques dans le PFC.

Little research has been conducted on repeated days of recreational skiing. Repeated days of recreational skiing were thought to increase stress markers, induce fatigue, and hinder ski performance and enjoyment. PURPOSE: To examine the physiological changes that occur in recreational skiers from elevations below 460 meters over five days of vacation skiing. METHODS: Fourteen skiers, four females (Mean ± SD; Age (yrs): 41.3 ± 6.2), ten males (47.9 ± 11.2) participated in the study. Nine skiers were considered advanced skiers (7 males, 2 females) and five intermediate skiers (3 males, 2 females). Subjects arrived at Bridger Bowl Ski Area, Bozeman MT to ski for five days. Each subject filled out subjective scales, had their resting heart rate, systolic and diastolic blood pressure measured as well as blood drawn for creatine kinase analysis. Samples were taken on days 1, 3, and 5. Subjects skied for three hours in the morning at a self selected pace and on self selected runs. They came in for lunch and recorded their rating of perceived exertion (RPE). The researcher downloaded the data from the heart rate monitor. The subjects skied in the afternoon until a self determined end time and again recorded their RPE and gave the researcher their heart rate monitors; the researcher then gave directions for the following day. RESULTS: The variables of ski time, number of runs, heart rate, blood pressure, and subjective scales did not change significantly. However, RPE was significantly increased suggesting an increase amount of perceptual fatigue. Creatine kinase was did not increase until one outlier was removed. Significant creatine kinase (p=0.001) and RPE results strongly suggests that subjects were stressed even without a decrease in runs, or ski time. CONCLUSION: The current study supports previous research; repeated days of skiing was not a fatiguing enough event to hinder ski performance or enjoyment. Future studies should examine whether repeated days of skiing results in a positive contribution to physical fitness.

Cardiovascular disease is the leading cause of death in the western world. As accumulating evidence emerges that risk of developing cardiovascular disease increases with higher levels of blood pressure, the early detection of those with hypertension becomes an increasing priority. Blood pressure is influenced by numerous factors, including the properties of the large arteries. This thesis sought to examine the effects of acute physiological and psychological stress on indices of arterial function. During likely elevation of sympathetic outflow following isometric exercise, indices of conduit and central artery function indicated stiffening in excess of 10%. During and following acute mental stress the large arteries exhibited a similar stiffening response, despite decreased resistance in the peripheral vasculature. These decreases in arterial compliance resulted in increased amplitude and premature return of arterial pressure waves and lead to a 15% augmentation in central systolic pressure during both forms of stress. These findings may have important clinical implications as increased central pressure elevates left ventricular workload. During graded dynamic exercise, reduced arterial compliance was shown to have progressive influence on the interaction between the heart and the vasculature. These studies provide valuable insight into the cardiovascular response to physiological and environmental stress.

Transportation planners need to assess users\' stress conditions on cycling infrastructures given that highly stressful situations can discourage the use of this sustainable transport mode. Not many studies have addressed the relationships between these environmental factors and users\' emotional responses in terms of objective measures of stress. The aim of this study is to explore a new approach for planning and evaluating cycling infrastructure, based on smart sensors. This new approach focuses on the perspective of monitoring parameters intrinsic to the user, such as emotions. In this perspective, the indicators of stress levels are made from directly measuring cyclists\' physiological responses throughout the journey. This approach makes use of technological resources to extract information from users through sensors and imparts this information in an integrated way to improve infrastructures for cyclists. The data were collected using stress and noise sensors, accelerometers embedded in a smartphone and a GPS. Initially, the problem is posed and we discuss how the design and evaluation of cycle paths has been addressed in the literature. The proposed approach identifies the most relevant contributions and research gaps, such as the lack of research based on objective criteria and research that involves designing and evaluating infrastructure scenarios shared with motor vehicles. In the sequence, an objective method for assessing bicycle infrastructures combining environmental assessment with vertical acceleration measurements was proposed in order to improving data collection and other procedures required for assessing the main components of cycling infrastructures. Subsequently, a tool to characterize traffic stress of cycling routes, called the Level of Traffic Stress (LTS), was validated with physiological measures in the urban context of a mediumsized Brazilian city. It was observed that there is no correlation and little agreement between the parameters. It is also emphasized that even when incorporating information about the traffic speed to the LTS tool, it was not significantly related to stress from the perspective of the cyclist. In the final analysis the influence of noise, vibration, cycle paths and period of day on stress experienced by cyclists was investigated. An analysis of the p-values and odds ratio confidence intervals shows, with a 95% confidence level, that only the period of the day influenced stress, as confirmed by the data. In this case, the chances of having stress increased by 24% in the afternoon rush hour compared to the morning rush hour. This study showed the feasibility of stress assessment in cyclists using an objective measurement method, as well as quick identification of critical levels of stress.
Os planejadores de transporte precisam avaliar as condições de estresse dos usuários em infraestruturas cicloviárias, uma vez que situações de alto estresse podem desencorajar o uso deste modo de transporte sustentável. Poucas pesquisas têm questionado se existe alguma relação entre esses fatores ambientais e a resposta emocional em termos de medidas objetivas do estresse. O objetivo deste trabalho é explorar a incorporação de sensores inteligentes no planejamento e avaliação da infraestrutura cicloviária. Essa nova abordagem é focada na perspectiva de monitorar parâmetros intrínsecos ao usuário, como as emoções. Nesta perspectiva, os indicadores dos níveis de estresse são feitos a partir da medição direta de respostas fisiológicas em ciclistas ao longo do percurso. Essa abordagem aproveita os recursos tecnológicos para extrair informações dos usuários e permitir o uso dessas informações de forma integrada para melhorar a infraestrutura dos ciclistas. Os dados foram coletados por meio de sensores de estresse, de ruído e acelerômetros incorporados a um smartphone e GPS. Inicialmente é apresentado o problema e como o projeto e avaliação das ciclovias tem sido abordada na literatura. A abordagem proposta permitiu identificar as contribuições mais relevantes e as lacunas de pesquisa, tais como, a falta de pesquisas baseadas em critérios de objetivos e a falta de pesquisas que envolvam o desenho e a avaliação de cenários de infraestrutura compartilhados com veículos automotores. Em seguida foi proposto um método objetivo de avaliação de infraestruturas cicloviárias, combinando a avaliação ambiental com medições de aceleração vertical, a fim de melhorar a coleta de dados e outros procedimentos necessários para avaliar os principais componentes das infraestruturas cicloviárias. Na sequência uma ferramenta para caracterizar o estresse de tráfego de ciclovias, denominada Level of Traffic Stress (LTS), foi validada com medidas fisiológicas no contexto urbano de uma cidade brasileira de porte médio. Observou-se que não há correlação e há pouca concordância entre esses parâmetros. Ressalta-se ainda que, mesmo ao incorporar informações de velocidade de tráfego à ferramenta LTS, não foi significativamente relacionado com estresse medido sob a perspectiva do ciclista. Por fim, foi investigada a influência do ruído, vibração, presencia ou ausência de ciclovias e período do dia no estresse experimentado pelos ciclistas. Uma análise dos valores de p e dos intervalos de confiança das razões de chances mostraram, com um nível de confiança de 95%, que apenas o período do dia influenciou o estresse. Neste caso, as chances de ter estresse aumentaram em 24% na hora pico da tarde em comparação com a hora pico da manhã. Este estudo mostrou a viabilidade da avaliação do estresse em ciclistas por meio de um método de medida objetiva além da rápida identificação dos níveis críticos de estresse.

Abiotic and biotic stresses affect tree growth and play a major role in determining the geographic distribution of species. The objective of this study is to elucidate the following questions: (1) are GABA aminoacid and stomatal control good indicators of tolerance to water stress in Eucalyptus clones? In addition, what are the anatomical differences between drought-tolerant and drought-sensitive clones of Eucalyptus? (2) Are there differences of xylem vulnerability to cavitation in Pinus flexilis families susceptible and resistant to white pine blister rust (WPBR) and with different origins (high and low altitudes)? Two studies were carried out to elucidate the issues above. On chapters 1, eight Eucalyptus clones from different geographical and climatological conditions, three drought-sensitive (CNB, FIB and JAR), three drought-tolerant (GG, SUZ and VM), and two plastics (VER and COP), were studied in normal water supply (control treatment) and in water stress conditions (stress treatment). The first chapter concluded that GABA is an aminoacid very sensitive to water stress, but there was no relation between GABA concentration and tolerance to water stress of the clones. In addition, all clones decreased stomatal conductance with increasing vapor pressure deficit, and plastics and drought-tolerant clones (except GG) presented lower stomatal sensitivity to vapor pressure deficit under stress conditions than drought-sensitive clones. Besides, all clones showed differences on the anatomical parameters between, and only COP (plastic) and SUZ (drought-tolerant) showed homogeneous mesophyll and amphi-hipostomatic leaves. All clones increased the number of stomata and reduced leaf thickness of the leaves formed after water stress period. On the chapter 2, we studied 12 families of Pinus flexilis originating from high and lower altitudes, in which six families previously shown to contain the dominant C4 allele (resistant to WPBR) and six families without C4 allele (susceptible to WPBR). This study showed that the mean cavitation pressure (MCP) of Pinus flexilis varying between 3.63 a -4.84 Mpa, although there was a significant difference in vulnerability to cavitation comparing all families, this variable was not related to WPBR and origin region. These studies highlight that the physiological responses of plants under water stress conditions are important tools that can be used to complement the strategies of genotype selection in forest breeding programs.
Estresses abióticos e bióticos podem afetar o crescimento das árvores e desempenham um papel importante na determinação da distribuição geográfica das espécies. O objetivo deste estudo, foi elucidar as seguintes questões: (1) o aminoácido GABA e o controle estomático são bons indicadores da tolerância ao estresse hídrico em clones de Eucalyptus? E quais são as diferenças anatômicas entre clones de Eucalyptus tolerantes e sensíveis ao estresse hídrico? (2) existem diferenças de vulnerabilidade a cavitação do xilema entre famílias de Pinus flexilis suscetíveis e resistentes à ferrugem do pinho branco (WPBR) e com diferentes procedências (elevada e baixa altitudes)? Dois estudos foram desenvolvidos para elucidar as questões acima descritas. No capítulo 1, oito clones de Eucalyptus de diferentes procedências e condições climáticas, sendo três clones sensíveis ao estresse hídrico (CNB, FIB e JAR), três clones tolerantes ao estresse hídrico (GG, SUZ e VM) e dois clones plásticos (VER e COP), foram estudados sob duas condições distintas: sob adequado suprimento de água (tratamento controle) e sob condições de estresse hídrico (tratamento estresse). Do primeiro capítulo concluiu-se que o GABA é um aminoácido que possui alta sensibilidade ao estresse hídrico, no entanto, não houve relação entre a concentração de GABA e os níveis de tolerância ao estresse hídrico dos clones. Além disso, todos os clones reduziram a condutância estomática em relação ao aumento do déficit de pressão de vapor (DPV), sendo que, sob condições de estresse hídrico, os clones plásticos e tolerantes à seca (exceto o clone GG) apresentaram menor sensibilidade estomática ao DPV do que os clones sensíveis ao estresse hídrico. Além disso, todos os clones apresentaram diferenças anatômicas, sendo que, diferentemente dos demais, os clones COP (plástico) e SUZ (tolerante) apresentaram mesofilo homogêneo e folhas anfi-hipoestomáticas. Todos os clones aumentaram a quantidade de estômatos e reduziram a espessura foliar das folhas formadas após períodos de estresse hídrico. No segundo capítulo foram avaliadas 12 famílias de Pinus flexilis procedentes de regiões de baixa e alta altitudes, sendo seis famílias contendo um alelo dominante C4 (resistente à WPBR) e seis famílias sem o alelo C4 (suscetíveis à WPBR). Este estudo apresentou uma variação da pressão média da cavitação (MCP) para Pinus flexilis de -3,63 a -4,84 Mpa, e embora tenha havido uma diferença significativa da susceptibilidade a cavitação entre todas as famílias estudadas, esta variável não relacionou-se com a susceptibilidade a doença WPBR e com a região de procedência das famílias. Estes estudos comprovam que a avaliação das respostas fisiológicas das plantas sob condições de estresse hídrico são importantes ferramentas que podem ser utilizadas para complementar as estratégias da seleção de genótipos em programas de melhoramento florestal.

To determine the type of intervention which best mitigates thermal stress within a given context, two important factors need to be taken into account: the specific characteristics of the ambient environment (temperature, humidity, air speed and mean radiant temperature) and how the thermoregulatory control system will detect and potentially physiologically compensate the applied intervention. The purpose of the present thesis was to further explore these concepts and apply newly generated knowledge to the presently pressing context of human adaptation to heatwaves. The purpose of Studies 1-3 was to further mechanistically explore and characterise how the body detects and counteracts exogenous cooling and heating loads applied internally. Specifically, study 1 sought to confirm the existence of visceral thermoreceptors, which limit the effectiveness of cold fluid ingestion to defend against heat stress, by investigating whether hot and cold fluid ingestion modifies cold-defense thermoeffectors, independently of differences in core and skin temperature. The aim of Study 2 was to determine whether these thermoreceptors could adequately detect and counteract the relatively large internal heat sink provided by ice slurry ingestion by reducing whole-body heat loss responses during exercise. Study 3, investigated whether hot and cold fluid ingestion prior to a bout of exercise could delay the onset of sweating and vasodilation responses, independently of differences in core and skin temperature. Next, study 4 examined how ambient temperature, humidity and air speed interact to modify heat balance in distinctly different, but commonly experienced, simulated heatwave conditions. Finally, study 5 combined the information from studies 1-4 in order to determine the optimal cooling strategies during hot-dry heatwave conditions which could be applied in isolation or in conjunction with electric fan use and readily-available tap water.

People who have endured horrific events often bear predictable psychological harm. The symptoms of this harm can persist to produce a recognised clinical syndrome, Post-Traumatic Stress Disorder (PTSD). The lived reality of PTSD is a condition in which sufferers experience unbearable emotional reactions to traumatic reminders and exist in a persistent state of fear. Although the psychiatric and psychological construct of PTSD has been hotly contested, research and clinical opinion seem to converge around a state of enhanced sensitivity to threat, underpinned by chronic physiological hyper-arousal. This thesis has been concerned with the development of assessment measures that are sensitive to physiological hyper-arousal, including pupillometry and visual contrast sensitivity. In three experiments, a sample of 73 participants recruited from military, addiction and homelessness charity services were assessed for PTSD symptomology with the Clinician Administered PTSD Scale for DSM-V, and the self-report Impact of Event Scale-Revised. During passive viewing of emotive images, individuals with PTSD showed pupil responses that were influenced more by emotive stimuli than controls, and showed a reduced constriction of the pupil to light; revealing altered states of arousal. Due to methodological differences, a task assessing pupil responses to emotive sound clips failed to replicate this result. The assessment of visual contrast sensitivity revealed the heterogeneous nature of PTSD. Multi-dimensional assessment of symptom subscales showed that higher levels of re-experiencing symptoms were related to heightened visual sensitivity, but avoidant symptoms were related to lower sensitivity. Overall, the assessment of psychophysiological responses in PTSD demonstrated the utility of pupillometry for the assessment of PTSD, contributed to the literature on the regulation of the autonomic nervous system in PTSD, and highlighted the diversity of the clinical construct due to opposing effects of the symptom subscales.

The physiological responses to salt stress were measured in Chenopodium quinoa. In a greenhouse experiment, salt water was applied to the quinoa varieties, Chipaya and KU-2, and to the model halophyte Thellungiella halophila to assess their relative responses to salt stress. Height and weight data from a seven-week time course demonstrated that both cultivars exhibited greater tolerance to salt than T. halophila. In a growth chamber experiment, three quinoa cultivars, Chipaya, Ollague, and CICA 17 were hydroponically grown and physiological responses were measured with four salt treatments. Tissues collected from the growth chamber treatments were used to obtain leaf succulence data, tissue ion concentrations, compatible solute concentrations, and RNA for real-time PCR. Stomatal conductance and fresh weight were measured to determine the degree of stress and recovery. The expression profiles of SOS1, NHX1, and TIP2, genes involved in salt stress, showed constitutive expression in root tissue and up-regulation in leaf tissue in response to salt stress. These data suggest that quinoa tolerates salt through a combination of exclusion and accumulation mechanisms.

Salinity is a major abiotic stress in plant agriculture which reduces seed germination, vegetative growth, and flowering, and limits crop productivity world-wide. Salinity causes water deficit, ion toxicity, and nutrient deficiency in plants, which can result in cellular damage, growth reduction, and even death. Kentucky bluegrass (Poa pratensis L.) is the most widely used cool-season species in cool-arid climates; however it has relatively poor salt-tolerance. Thus the development of Kentucky bluegrass genotypes with increased salt tolerance is of interest to turf breeders. One impediment to selection towards this goal is finding an efficient and accurate method to evaluate the salt tolerance. The objective of this study was to examine physiological responses to salt stress and to evaluate the genetic diversity among the accessions used in the research. Salt-tolerant accessions PI371768 (768) and PI440603 (603) and salt-sensitive varieties Midnight and Baron were exposed to four levels of salinity imposed by irrigating with salt solutions of 0 dS m-1 (control), 6 dS m-1, 12 dS m-1, and 18 dS m-1 or 24 dS m-1. Soil salinity was measured using Acclima Digital TDT sensors and grass response to the stress was measured using turf quality ratings, stomatal conductance, leaf water potential and electrolyte leakage. In general, turfgrass quality, stomatal conductance, and leaf water potential decreased while electrolyte leakage increased under salinity stress. Midnight and Baron exhibited greater changes in these measurements, indicating more sensitivity compared to 768 and 603. The 6 dS m-1 treatment had little effect on the salt-tolerant accessions. Salt tolerance of 603 and 768 was confirmed and likewise, salt sensitivity of Baron and Midnight was confirmed. The genetic similarity of all cultivars used in this study was very high. All of the evaluation measurements were highly correlated, with water potential and electrolyte leakage being the most reliable and accurate methods due to the low standard deviations. Due to more repeatable methods and less user error, electrolyte leakage and turfgrass quality are recommended methods for screening salt tolerance of turfgrasses.

Psychology
Ph.D.
Although existing research has evaluated physiological and environmental risk factors for depression, these processes are often examined in isolation without considering the dynamic relationships in risk for depression. The present study evaluated physiological markers of resting and stress-reactive respiratory sinus arrhythmia (RSA and RSA reactivity) as predictors of depressive symptoms and interpersonal stress generation, a mutable and potent vulnerability for depression. Further, we examined whether stress generation predicted subsequent depressive symptoms. In a sample of late adolescents (N = 105; 18-22 years; 76% female), individuals who screened in for a history of clinical and subclinical depression participated in a micro-longitudinal assessment with a diagnostic interview, in-laboratory socio-evaluative stressor task, and two weeks of daily assessments of stressful events and depressive symptoms. First, results indicated that there were no clinical or physiological differences between individuals with a clinical or subclinical depression history. Our multilevel modeling analyses revealed that: 1) only lower levels of resting RSA predicted depressive symptoms over the two-week period; 2) only lower RSA reactivity predicted greater interpersonal stress generation, but not independent stressors; 3) interpersonal stress generation mediated the relationship between RSA reactivity and depressive symptoms, but not resting RSA and depressive symptoms; 4) sex differences only occurred in the relationship between resting RSA and depressive symptoms; and 5) there were no interactive effects of resting RSA and RSA reactivity on depression or interpersonal stress generation. These findings highlight the importance of assessing both resting RSA and RSA reactivity in the examination of depression and depression-related processes.
Temple University--Theses

The negative impacts of discriminatory events to the physiological and psychological stress of the recipient has been thoroughly documented. However, there is little to no evidence about the impacts to bystanders of these events, particularly White bystanders. Psychological impacts may emerge through academic achievement, which has implications for educational institutions and their diversity initiatives. This study examined the impact of witnessing discriminatory events on academic achievement, biological markers of distress, and emotional distress. Academic achievement was negatively impacted for participants in the microaggression and blatant racism conditions when compared to a control condition. Study participants also experienced negative emotional impacts. These were evident through a decrease of positive emotion and an increase of negative emotion throughout the study. Counter to the stated hypothesis, biological markers of distress did not demonstrate a negative impact from the discriminatory event. Microaggressions, specifically, were not found to have negative impacts on academic achievement. There were also no differences in the relationship between biological markers of distress and academic achievement among the three conditions. These findings suggest that discriminatory behavior negatively impacts White bystanders emotional state and academic achievement.

Initial experiments evaluated the impact of hematocrit on a birds ability to adapt to stress and what physiological mechanisms occurred to maintain oxygen carrying capacity (OCC). A final experiment was conducted to obtain proteomic evaluation of protein expression in monocytes of unstressed broilers. In initial experiments, ACTH treatment was applied to hematocrit separated broilers. Experiments evaluated effects of ACTH on broilers with low (19 to 22%, Experiment 1; 18-21%, Experiment 3), high (25 to 28%, Experiment 1; 24 to 27%, Experiment 3) or non-selected hematocrit levels (Experiment 2 and 3). After 4 d of ACTH, all treated birds had significantly increased (P < 0.1) pCO2, HCO3-, and corticosterone levels, indicating as stress raises pCO2, HCO3- must rise to maintain acid base balance. Birds not selected for hematocrit had significant drops in pO2 when given ACTH. Broilers compensate for low OCC through release of red blood cells from storage sites, indicated by decreases in organ hemoglobin and increases in hematocrit and blood hemoglobin when birds are given ACTH. Accelerated red blood cell formation does not appear to occur, because erythropoietin decreases following administration of ACTH to non-selected birds. ACTH induced stress, increased hemoglobin and hematocrit only in birds with low or non-selected hematocrit, suggesting high hematocrit birds prior to stress have an adaptive advantage during stress. Higher hematocrit prior to stress apparently provides ample OCC during stress. Unselected birds appear to require initiation of an inflammatory response to adapt to stress which can be noted by increases in total white blood cell count, monocytes, and heterophils and decreases in lymphocytes. High hematocrit birds appear less susceptible to stress effects by maintaining leukocytes at a constant level, while in non-selected birds lymphocyte percents drop. Proteomics was conducted on avian monocytes to reveal proteins related to immune functions, 3229 proteins were identified, with 46 involved in immune functions of professional antigen presenting cells. This protein data provides a means of comparing monocytes of stressed and unstressed animals in the future. In conclusion, evaluated hematocrit is advantageous in adaptation to stress through maintenance of high OCC, acid base balance and immune cells.

The welfare of domestic horses has been scrutinised by the scientific community in recent years. Traditional riding and stable management practices have been recognised to be at odds with the physical and behavioural adaptations of the horse. There is, therefore, a growing need to understand how modern horse management can impact on horse welfare. The first study in this thesis assessed the impact of common management practices on physiological stress in the horse. Faecal cortisol was higher in horses that were stabled and exercised, than turned out to grass with no exercise. The effect of exercise alone was also seen to increase levels of salivary cortisol. No change was seen in cortisol following short-term routine husbandry procedures such as exposure to the sound of electric coat clippers, but it was suggested that this required further investigation. The study confirmed exercise increased stress as reflected by cortisol concentration, and indicated that individual stabling may also contribute to elevated stress. The study recommended that horses may benefit from periods of rest and turn out to grass, to reduce stress levels and improve welfare. The measurement of stress for the purpose of welfare assessment is, however, best carried out using an integration of both physiological and behavioural measures. Behaviour scores offer non-invasive, quick and easy methods of assessing stress in domestic animals, but have typically been developed using only behavioural assessment of the stress response. In the second study a scale of behavioural indicators of stress was developed using behavioural and physiological measures for the purpose of assessing stress in stabled domestic horses. Principal component analysis of behavioural reactions and changes in salivary cortisol concentration in response to routine husbandry procedures, revealed three meaningful components that were used as the basis to the stress scale. Behavioural reactions to the husbandry procedures were further analysed by a panel of equestrian professionals using free choice profiling, and results were added to the appropriate components. The final scale comprised of four levels of stress (no stress, low, The welfare of domestic horses has been scrutinised by the scientific community in recent years. Traditional riding and stable management practices have been recognised to be at odds with the physical and behavioural adaptations of the horse. There is, therefore, a growing need to understand how modern horse management can impact on horse welfare. The first study in this thesis assessed the impact of common management practices on physiological stress in the horse. Faecal cortisol was higher in horses that were stabled and exercised, than turned out to grass with no exercise. The effect of exercise alone was also seen to increase levels of salivary cortisol. No change was seen in cortisol following short-term routine husbandry procedures such as exposure to the sound of electric coat clippers, but it was suggested that this required further investigation. The study confirmed exercise increased stress as reflected by cortisol concentration, and indicated that individual stabling may also contribute to elevated stress. The study recommended that horses may benefit from periods of rest and turn out to grass, to reduce stress levels and improve welfare. The measurement of stress for the purpose of welfare assessment is, however, best carried out using an integration of both physiological and behavioural measures. Behaviour scores offer non-invasive, quick and easy methods of assessing stress in domestic animals, but have typically been developed using only behavioural assessment of the stress response. In the second study a scale of behavioural indicators of stress was developed using behavioural and physiological measures for the purpose of assessing stress in stabled domestic horses. Principal component analysis of behavioural reactions and changes in salivary cortisol concentration in response to routine husbandry procedures, revealed three meaningful components that were used as the basis to the stress scale. Behavioural reactions to the husbandry procedures were further analysed by a panel of equestrian professionals using free choice profiling, and results were added to the appropriate components. The final scale comprised of four levels of stress (no stress, low, medium and high stress), and each category was further sub-divided into behaviour scores (SS). The scores represented accumulating levels of behavioural indicators of stress within each stress level, and provided indices of physiological stress. The scale offers an easy to use method of welfare assessment in horses, and reduces the need for additional physiological measures to be taken. The scale represented a novel approach to measuring stress, and was used in the final study to measure stress in horses stabled individually, group housed, and in horses moved from stabling to group housing. The effectiveness of the scale at measuring stress, was compared to the effectiveness of measures of heart rate variability (HRV) and faecal cortisol at measuring stress in the same horses. Lower levels of stress were recorded in group housed horses as measured by the SS, but measures of HRV and faecal cortisol showed no difference between those stabled or group housed. Stress levels were unaffected by the move to group housing, but SS declined significantly over the three weeks that the horses remained group housed. The physiological measures did not, however, reflect such a decrease in stress. Stress levels were also compared between horses housed in both environments whilst waiting to be fed. Group housed horses had lower stress levels as measured by the SS. Results provided by the SS were supported by relevant literature, and the scale appeared to be more sensitive than the physiological measures which did not yield significant results with the small sample sizes used in the study. The research confirmed short-term management practices horses are typically exposed to daily, can elevate their stress levels. Further research into which practices put horse welfare at a particular risk, and thus require modification or need to be avoided where possible, is necessary. The findings also suggest horse-owners may need to pay more attention to their horse's stress levels, to avoid repeated or on-going stress that can jeopardise health and welfare. The scale of behavioural indicators of stress would provide a suitable method by which stress could be monitored and thus become a part of horse management.

The purpose of this thesis was to determine optimal strategies for heat acclimation (HA) and to investigate whether HA attenuated the physiological responses, when acclimated, to acute hypoxia. Study one considered the optimal exogenous conditions for effective HA. Data identified that during acute exercise-heat stress a minimum degree of physiological strain was required to elevate blood extracellular heat shock protein (eHSP72, used as an indicator of cellular heat stress). The increase in eHSP72 was due to several endogenous factors achieved in 40°C/40% R.H., and not 20°C/63% R.H. or 30°C/51% R.H. Thus, the hottest external condition was used for subsequent HA methods. Study two tested the implementation of two isothermic HA models compared with a validated, traditional fixed intensity method (90 min; 50% V % O2peak). The isothermic models targeted and achieved specific core temperatures (Trec) (90 min; continuous = 38.5°C, day 1–10; progressive = 38.5°C day 1-5 then 39.0°C, day 6-10). Endogenous strain was sustained better using isothermic HA during long term timescales compared with the fixed intensity HA with a greater mean Trec and duration Trec≥38.5°C. During the early phases of acclimation, greater strain was not at the expense of greater work, or less palatable exercise intensity prescription, which were more favourable using isothermic versus fixed intensity methods, largely due to the greater initial heat production. Despite differences in the HA administration, no difference was found for resting or exercising phenotypic adaptations between methods. Additionally, using a progressive isothermic method offered no additional physiologically adaptive benefit in comparison to the fixed, or continuous isothermic methods. With Hsp72 increases being an important mechanism by which heat-hypoxic cross tolerance is augmented, study three demonstrated that the continuous isothermic HA methods from study 2 sustained the leukocyte Hsp72mRNA responses to the greatest extent. The sustained influence on physiological measures and HSP concentrations evoked by the long term continuous isothermic method, alongside the favourable administration, supported this method’s application for the final experiment, aimed at measuring the efficacy of optimised HA in reducing physiological strain during acute hypoxia. Study four data demonstrated accelerated physiological adaptations which accompany long term isothermic HA in comparison to normothermic training. Data collected within an acute hypoxic exposure during rest, then lowmoderate and moderate-high intensity exercise, identified physiological strain is reduced following HA, in comparison to normothermic training or when not acclimated, and that the Hsp72mRNA increase which occurred prior to HA was subsequently attenuated following the intervention. No increase in Hsp72 mRNA was observed in either pre or post trials in the normothermic training (control) group, suggesting insufficient stimuli to initiate the heat shock response within this group. This evidence supports the notion that HA provides a suitable strategy to decrease the physiological strain during acute hypoxic exposures.

The bond between pet and owner has been shown to decrease stress-related physical, mental, and emotional disorders by lowering blood pressure and heart rate. The purpose of this study was to examine whether a nonpet canine would have the same effect in reducing physical symptoms of stress as a known dog. Human-animal bond theory, Human pressor test. Data were analyzed using repeated measures, analyses of variance, and t tests. Results indicated that interaction with a strange dog lowered heart rate and blood pressure significantly faster in the experimental group than in the control group. The positive social change implications of this research include policy and procedural accommodations for the use of canines as comfort animals for individuals in stressful conditions.

The aim of this PhD research project was the understanding of some molecular and physiological mechanisms involved in stress signalling in plants. When plants are exposed to environmental growth conditions far from the ideals, plants are under stress. Under stress conditions, plant growth and crop yield could be severely affected. In general, adverse growth conditions are caused by plant pathogens (biotic stress) and not ideal environmental conditions (abiotic stress) such as heat, cold, drought, lack of nutrients, and heavy metals. Plants experiencing biotic and abiotic stresses activate signalling pathways that lead to changes in gene expression, thus, alteration of transcriptome, proteome and metabolome. All these processes are oriented to the acclimation of plants to the changed growth conditions. During my PhD I approached the study of two stress signalling mechanisms, one occurring as consequence of high concentration of cytokinins (CKs), a physiopathological condition (biotic stress), and the other one as consequence of cadmium-induced oxidative stress (abiotic stress). Concerning the first signalling pathway, I investigated the involvement of CK receptors in triggering the programmed cell death (PCD) signalling in Arabidopsis thaliana cell cultures treated with high concentrations of CKs. In order to do so, we generated cell culture lines from wild-type and three Arabidopsis mutants, knocked-out in genes coding for different CK receptors (cre1-2, ahk2-5 ahk3-7 and ahk2-5 ahk3-7 cre1-2). Then, we characterized some physiological parameters of these cell cultures; in particular, we determined the growth and death kinetics, and the CKs content. No evident differences in the growth and death kinetics of wild-type, single and double mutant cell culture lines were observed, except for a delay in increasing cell death in the late part of the triple mutant subculture cycle. Moreover, the levels of most CKs resulted increased to a different extent in the CK receptor mutant lines. Then, in order to define whether the CK-induced PCD mechanisms required the functionality of the CK receptors, wild-type and mutant cell cultures were assayed for their sensitivity to high concentrations of CKs. The results of these experiments revealed that the CRE1/AHK4 was the CK-receptor involved in triggering the PCD signals in Arabidopsis cell cultures exposed to high concentrations of CKs. Concerning the second signalling pathway, the role of Arabidopsis cytosolic GAPDH (GAPC-1 and GAPC-2) in cadmium-induced oxidative stress signalling was investigated. To this aim, Arabidopsis seedlings were exposed to cadmium, and I demonstrated that the levels of both nitrogen oxide (NO) and hydrogen peroxide (H2O2) increased leading to the induction of an oxidative stress condition. Under these stress conditions the up-regulation of both GAPC-1 and GAPC-2 occurred. Given that, the more affected gene was GAPC-1, I produced Arabidopsis transgenic lines expressing GAPC-1 transcriptional and translational reporters. The exposure of these transgenic lines to cadmium revealed that GAPC-1 is affected by oxidative stress both at the transcriptional and post-transcriptional levels. Moreover, in vitro analyses revealed that NO and H2O2 negatively affected the GAPDH catalytic activity in a time- and concentration-dependent manner. These results confirmed that the oxidative stress condition induced by the accumulation of NO and H2O2 can affect the catalytic activity of the GAPC-1 enzyme, activating a signal cascade that enhances its expression and then its accumulation. Furthermore, reducing the redox state with reduced glutathione restored the catalytic activity of the NO-inactivated recombinant GAPC-1, and also reduced the GAPC-1 promoter activity and GAPC-1 protein level in vivo. On the other hand, decreasing the glutathione pool in vivo (i.e. more oxidizing condition) led to the increase of GAPC-1 promoter activity and GAPC-1 protein level. Finally, prolonged oxidative stress conditions led to the GAPC-1 nuclear accumulation. All together these results demonstrate that GAPC-1 is an oxidative stress sensor, and its nuclear relocalization could be a key step in the oxidative stress signalling. The study of how plants perceive stress conditions, the mechanisms by which plants transmit stress signals, and finally the acclimation to adverse growth conditions could be important to understand how to reduce the negative effects of biotic and abiotic stresses on plant growth and ultimately crop yield.
Lo scopo di questa tesi di dottorato è stato lo studio dei meccanismi molecolari e fisiologici coinvolti nella trasduzione dei segnali di stress nelle piante. Quando le piante sono esposte a condizioni ambientali di crescita non ideali, si trovano in condizioni di stress. In queste condizioni, la crescita delle piante e la resa delle colture d’interesse agronomico sono di solito fortemente ridotte. In generale, le condizioni di crescita sfavorevoli sono causate da agenti patogeni (stress biotici) e da condizioni ambientali non ideali (stress abiotici) come caldo, freddo, siccità, carenza di nutrienti e metalli pesanti. Le piante esposte a stress biotici e abiotici attivano vie di segnalazione che inducono il cambiamento dell'espressione genica, quindi, l'alterazione del trascrittoma, proteoma e metaboloma. Tutti questi processi sono orientati all’acclimatazione delle piante alle condizioni di crescita avverse. Durante il mio dottorato di ricerca ho affrontato lo studio di due meccanismi di segnalazione dello stress, uno che si verifica in seguito ad esposizione ad elevate concentrazioni di citochinine (CKs), una condizione fisiopatologica (stress biotici), e l'altro in risposta a stress ossidativo indotto da alte concentrazioni di cadmio (stress abiotici). Per quanto riguarda il primo meccanismo di segnalazione, ho studiato il ruolo dei recettori citochininici nella via di segnalazione e induzione della morte cellulare programmata (PCD) in colture cellulari di Arabidopsis thaliana trattate con alte concentrazioni di CKs. Per far ciò, abbiamo generato colture cellulari da una linea wild-type e da tre linee mutanti (knock-out) di Arabidopsis, in geni che codificano per diversi recettori citochininici (cre1-2, ahk2-5 ahk3-7 e ahk2-5 ahk3-7-cre1-2). In seguito, abbiamo caratterizzato alcuni parametri fisiologici di queste colture cellulari, in particolare, abbiamo determinato la crescita e la cinetica di morte e il contenuto di CKs. Non sono state riscontrate differenze evidenti nelle cinetiche di crescita e morte tra cellule wild-type, e linee cellulari mutanti, ad eccezione di un ritardo nella morte cellulare nelle ultime fasi del ciclo di coltura del triplo mutante. Inoltre, sono stati misurati livelli più elevati di CKs nelle linee cellulari mutanti. Infine, per verificare se i recettori citochininici fossero coinvolti nell’induzione della PCD in seguito al trattamento con alte concentrazioni di CK, è stata analizzata la risposta delle colture cellulari wild-type e mutanti ad alte concentrazioni di CKs. I risultati di questi esperimenti hanno rivelato che il recettore CRE1/AHK4 sia quello coinvolto nel meccanismo di segnalazione e induzione della PCD in colture cellulari di Arabidopsis esposte ad alte concentrazioni di CK. Per quanto riguarda il secondo meccanismo di segnalazione, ho studiato il ruolo delle GAPDH citosoliche (GAPC-1 e GAPC-2) di Arabidopsis nelle vie di segnalazione indotte da stress ossidativo in presenza di alte concentrazioni di cadmio. A tal fine, sono state trattate piantine di Arabidopsis con alte concentrazioni di cadmio e i risultati hanno mostrato che tale trattamento induceva un aumento dei livelli di ossido nitrico (NO) e perossido d’idrogeno (H2O2), e tale aumento causava l’induzione di una condizione di stress ossidativo. In queste condizioni di stress si è osservato un aumento dell’espressione di entrambi i geni GAPC. Essendo GAPC-1 il gene che mostrava l’aumento di espressione maggiore, ho prodotto delle linee transgeniche di Arabidopsis che esprimevano stabilmente geni reporter trascrizionali e traduzionali per GAPC-1. L'esposizione di queste linee transgeniche al cadmio ha rivelato che GAPC-1 è influenzata dallo stress ossidativo sia a livello trascrizionale che post-trascrizionale. Inoltre, dalle analisi in vitro si è osservato che NO e H2O2 influenzavano negativamente l'attività catalitica GAPDH in modo tempo- e concentrazione-dipendente. Questi risultati hanno confermato che le condizioni di stress ossidativo indotte da un aumento delle concentrazioni di NO e di H2O2 possono influenzare l'attività catalitica di GAPC-1, attivando una via di segnalazione che porta a un aumento della sua espressione e quindi il suo accumulo. Riducendo lo stato redox con il glutatione ridotto, l'attività catalitica della GAPC-1 ricombinante inattivata dal trattamento con NO si ripristinava. Inoltre, la presenza di glutatione ridotto riduceva sia l’attività promotoriale di GAPC-1 che i livelli di GAPC-1 in vivo. Peraltro, riducendo il contenuto di glutatione in vivo (quindi imponendo una condizione più ossidante) si è osservato l'aumento dell’attività promotoriale di GAPC-1 ed un aumento dei livelli di GAPC-1. Infine, prolungate condizioni di stress ossidativo hanno portato all’accumulo di GAPC-1 all’interno del nucleo. Questi risultati dimostrano che GAPC-1 è un sensore di stress ossidativo, e la sua rilocalizzazione nucleare potrebbe essere un passaggio chiave per la segnalazione dello stress ossidativo. Lo studio di come le piante percepiscano le condizioni di stress, i meccanismi con cui le piante trasmettono segnali di stress, ed infine lo studio dei meccanismi di acclimatazione a condizioni di crescita sfavorevoli potrebbe aiutare ad intervenire per ridurre gli effetti negativi di stress biotici e abiotici sulla crescita delle piante e sulla resa delle colture di interesse agronomico.

The current study was designed to test the efficacy of a meditation-based intervention, mindfulness-based stress reduction (MBSR), for women with stage II breast cancer. This prospective randomized study examined the effects of psychological and sleep functioning in the MBSR treatment group compared to a control group. The treatment consisted of a group format focusing on training participants in mindfulness meditation and its application to daily life. Participants in the control group recorded the stress management activities they chose to engage in each day. Results indicated that over time all participants' psychological well-being improved regardless of experimental condition. The MBSR condition did not improve significantly more than the control condition. Within the MBSR group, however, those participants reporting greater mindfulness meditation practice improved on both sleep and psychological variables more than those who practiced less. Implications of the study findings are discussed and directions for future research are suggested.

HAN, CHAE JOON. Physiological Studies of Extremely Thermoacidophilic Microorganisms under Normal and Stressed Conditions. (Under the direction of Professor Robert M. Kelly.)

The purpose of this research was to study thermoacidophilic physiology for the purpose of developing a new strategy for metal and sulfur biotransformation processes. , an extremely thermoacidophilic archaeon growing mixotrophically on organic and inorganic substrates at pH 2.0 and 74C, was used as a model organism to address this issue. The manipulation of ?s energetics under thermally and chemically challenged states led to increase in specific leaching rates. A dual-limited continuous culture, at a dilution rate of 0.04 hr, was used to provide a steady-state operation at which the cellular and sub-cellular responses were monitored and the biocatalytic efficiency of cells was evaluated. Under the thermal stress, showed acquired thermotolerance and ?stressed-phase? growth at 81C, which is 2C is higher than its normal maximum growth temperature, and over-synthesized (~6-fold increase) a 66 kDa heat shock protein (MseHSP60), which is immunologically related to a molecular chaperone (Thermophilic Factor 55) from . More importantly, however, there was a significant increase in specific iron turnover rate presumably through disruption of cellular proton network. In addition, although less dramatic when compared to thermal stress effects, similar results could be obtained when was subjected to the chemical stress. By temporarily short-circuiting ?s proton network with uncouplers, the respiration capacity of cells was disrupted, leading to the increased Fe iron turnover rate. The work described here should propose a new approach for analyzing physiological responses under extreme growth conditions and thereby points to novel strategies for improving whole-cell catalytic efficiency of thermoacidophilic microorganisms.

This investigation sought to identify differences in the human psychophysiological stress response when mediated by affiliation, by assessing heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), electrodermal activity (EDA), serum Cortisol (SC) concentration, interleukin-2 (IL-2) concentration, and state anxiety among subjects who underwent an anagram solution task. Thirty male subjects from the University of North Texas were randomly assigned to one of two experimental conditions and asked to solve a series of difficult anagrams either alone or with a companion. Subjects assigned to the control condition were asked to copy permutations of the anagrams. Before, and immediately after the anagram/copying tasks HR, SBP, DBP were measured, blood samples drawn, and The State-Trait Anxiety Inventory (STAI) administered to all subjects. EDA was measured throughout all trials. Changes from baseline through the experimental period for all dependent variables were analyzed by employing difference scores derived from contrasting baseline and experimental measures. These scores were subjected to an analysis of variance (ANOVA) resulting in one significant between group effect among all dependent variables examined. Contrary to stated hypotheses, the alone condition significantly differed from the companion and control conditions by demonstrating a significant decrease in systolic blood pressure from baseline through the experimental period. It was concluded that the decrease in systolic blood pressure from baseline through the experimental period for the alone group was a result of chance sampling of individuals possessing unique psychophysiological response patterns. Appraisals of inter-group differences in response patterns across all dependent variables suggest that an insufficient stressor, and limitations in design, statistical analysis, and measurement may have contributed to this investigation's results. Implications of findings were discussed along with suggestions for future research.

Significant cultivar difference in many water stress responses of zoysiagrass (Zoysia japonica (Steud.) and Zoysia matrella (L.) Merr.) are shown in this study. Of the four cultivars, Palisades was the most water stress tolerant, had the most negative turgor loss point, and leaf rolled after loss of full turgor pressure. On the other end of the spectrum, Diamond was the least water stress tolerant, had the lowest full turgor pressure, the least negative turgor loss point, and leaf rolled at full turgor. Differences between Diamond, Cavalier, Palisades, and DALZ 8504 in leaf rolling, loss of full turgor, water release curve parameters, root characteristics and gene expression make zoysiagrass a prime candidate for further investigation into the mechanisms of water stress avoidance/tolerance. Enhanced antioxidant activity and stomatal control, along with root characteristics, most likely explain the cultivar difference in water stress tolerance of zoysiagrass. Palisades and DALZ 8504 maintained full turgor for significantly longer than Diamond and Cavalier, which may be associated with root characteristics and/or enhanced stomatal control as only those two cultivars showed enhanced expression of a stomatal control gene (phospholipase D). The apparent response (most apparent in turgid weight/dry weight ratios (TWDW)) of well watered plants to water stressed neighbor plants will likely be the most novel finding of this study. Well watered zoysiagrass and Kentucky bluegrass responded to water stressed neighbors by reducing TWDW. Significant increases in gene expression of a systemin degrading enzyme and of an integral membrane protein (signal receptor) were also observed in well watered plants. Results from this study indicate that this phenomenon is occurring and expose a dearth in scientific understanding that must be filled. Improving water stress tolerance through breeding for parameters like those discussed in this paper (delayed leaf rolling or loss of full turgor, enhanced stomatal control, enhanced antioxidant activity, deep rooting characteristics, etc.) may very likely produce turfgrasses that can survive and maintain desired aesthetic qualities using significantly less water.

Stress is a major health concern of the 21st century. It has been shown to be associated with a host of negative health outcomes, from a spectrum of several psychopathologies to cardiovascular disease. However, the exact mechanisms resulting in these disease states have not yet been identified. There are two main physiological systems solicited during an acute stress response: the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. Both the SNS and HPA have been hypothesized to interact, but the precise nature of their relationship is still under study. In addition to the biological response, there also is the subjective emotional experience of stress. As it is hypothesized to be the trigger of the endocrinological and physical responses, a relationship between these three variables is expected, though, literature on this topic has yielded inconsistent findings. The work in this thesis attempted to understand the relationship between the endocrinological, physiological and psychological responses during an acute stressor. To do so, we combined a pharmacological approach with the most widely used laboratory stress task - the Trier Social Stress Test (TSST). We suppressed these systems individually and together after which we exposed the participants to the TSST. Throughout the protocol a number of biomarkers of the SNS and HPA were assessed, including salivary cortisol and alpha-amylase, heart rate and blood pressure. State and trait subjective stress were also measured using questionnaires and visual analogue scales. Our first major finding suggested an inverse relationship between the biological systems, HPA and SNS. When one system was suppressed the other showed increased activity. Dysregulation of each of these systems have both been associated with adverse health consequences. Understanding how to keep an equilibrium between the HPA and SNS may thus be an important factor in the prevention of (psycho)pathologies like depression, or cardiovascular disease. We also observed a link between state subjective stress and the SNS. These findings were found to be in-line with the Two-Factor Theory of Emotion, which states that physiological arousal feeds back and contributes to the subjective emotion state. On the other hand, neuroticism was found to be associated with HPA axis activity. This may imply that neuroticism levels would be somewhat more of a threshold of threat detection. Logically it would not be associated with the SNS as it is a transient effect, but more with its biological analogue, the HPA axis. Future research in this field will surely yield interesting findings contributing to the understanding of its emotional component, inner workings and the etiology of its resulting disorders. Most importantly, it will broaden our understanding of this vast concept and hopefully contribute to the prevention of its associated negative health outcomes.
De nos jours, le stress est considéré comme un enjeu sociétal majeur qui continue de prendre de l'ampleur. Il a d'ailleurs été démontré qu'il a un impact néfaste considérable sur la santé et un lien direct avec plusieurs psychopathologies ainsi que les maladies cardiovasculaires. Cependant, les mécanismes par lesquels le stress cause un état pathologique n'ont pas encore été identifiés. Il y a principalement deux systèmes physiologiques sollicités au cours d'une réaction de stress : le système nerveux sympathique (SNS) et l'axe hypothalamo-pituito-surrénalien (HPS). Une hypothèse d'interaction entre les deux systèmes a été émise; par contre, la nature exacte de leur relation fait toujours l'objet d'études. En plus de la réponse biologique, il y a aussi l'expérience émotionnelle subjective du stress qui est considérée comme étant le déclencheur des réponses endocrines et physiques. Une relation entre ces trois variables semble donc logique, toutefois la littérature sur ce sujet récence plusieurs résultats contradictoires.Par conséquent, cette thèse tente de comprendre la relation entre les réponses endocrines, physiologiques et psychologiques lors d'une situation de stress.Pour ce faire, nous avons combiné une approche pharmacologique avec la tâche de stress psychologique la plus utilisée en laboratoire – le « Trier Social Stress Test » (TSST). Avant d'exposer les participants au TSST, nous avons inhibé les deux systèmes physiologiques, soit individuellement ou collectivement. Tout au long du protocole, plusieurs biomarqueurs des axes SNS et HPS, y compris le cortisol et l'alpha-amylase salivaires, la fréquence cardiaque et la pression artérielle ont été mesurés. Les différentes facettes du stress subjectif ont également été mesurées au moyen de questionnaires et d'échelles visuelles analogiques.Notre première constatation suggère une relation inverse entre les systèmes biologiques HPS et SNS. Lorsqu'un des systèmes est inhibé, l'autre montre une activité accrue. Le dérèglement de chacun de ces systèmes a été associé à des conséquences néfastes sur la santé. Le fait de mieux comprendre la façon de garder un équilibre entre les axes HPS et SNS peut donc être un facteur important dans la prévention des pathologies, comme la dépression et les maladies cardiovasculaires. Nous avons également observé un lien entre l'état subjectif du stress et le SNS. Ces résultats sont en accord avec la « Two-Factor Theory of Emotion » qui stipule que l'activité physiologique contribue à l'état subjectif du stress. D'autre part, l'inquiétude chronique a été associée à l'activité de l'axe HPS, ce qui suggère que le niveau de névrosisme pourrait agir comme seuil de détection du danger. Logiquement, il ne serait pas associé au SNS qui a un effet transitoire, mais plutôt à son analogue biologique, l'axe HPS.Les recherches futures dans ce domaine mèneront certainement à des résultats intéressants qui contribueront à la compréhension des composantes émotionnelles du stress, de son fonctionnement interne et de l'étiologie des troubles qui en résultent. Principalement, il permettra d'élargir notre compréhension de ce vaste concept et de contribuer à la prévention de ses effets néfastes sur la santé.

Cardiovascular disease is the leading cause of death in the western world. Hypertension is a major risk factor for cardiovascular diseases and blood pressure is in turn markedly influenced by large artery stiffness. Recently a number of studies have reported that apparently healthy normotensive individuals who exhibit an exaggerated systolic blood pressure response on exercise are at increased risk of developing subsequent sustained hypertension and cardiovascular disease. It is likely that an exaggerated systolic blood pressure response on exercise represents an abnormal response of the large artery during dynamic exercise. In this thesis the normal responses of large arteries to different types and intensities of exercise was investigated in healthy normotensive subjects. Whilst distensibility of limb conduit arteries was measured for up to 15 minutes following exercise aortic distensibility did not change. An exaggerated systolic blood pressure response on exercise was not observed in healthy subjects without other conventional cardiovascular risk factors, but was observed frequently in the presence of such risk factors. Subjects with an exaggerated systolic blood pressure response on exercise did not show increased limb conduit artery distensibility immediately following exercise (and by implication during exercise). Blockade of NO synthesis prevented the increase in limb conduit artery distensibility seen in the first few minutes following exercise, but did not abrogate the more sustained increase in arterial distensibility following exercise. Systemic blockade of NO synthesis caused marked changes in systemic haemodynamics at risk, but these were markedly attenuated during exercise. The impact of mental stress on arterial function was also assessed. Whilst peripheral microvessels vasodilated, large arteries stiffened and this largely accounted for the observed increase in blood pressure.

Attempts to assess psychological stress rely heavily upon subjective techniques which measure changes in perceived mental loading and situational awareness (Hart and Staveland 1988, Reid and Nygren 1988, Lemyre and Tessier 2003, 1998). Although quantitative methodologies do exist, for example monitoring changes in the cardiopulmonary system (Gelfand et al. 2004, Harada et al. 2006), such parameters are subject to influence by factors other than stress. Psychological stress is known to influence the effectiveness of the innate immune system, leading to an increased risk of infection and immune-related disease (Dhabhar et al. 1996, Boscarino et al. 1999, Altemus et al. 2006). Leukocytes, primarily neutrophils have been identified as an essential component of this mechanism - periods of increased psychological stress have been shown to stimulate neutrophils to release reactive oxygen species into surrounding healthy tissues (Mian et al. 2003). The exact biochemical pathways by which this occurs have not yet been fully elucidated. However, this mechanism has become the basis for a novel in vitro technique (McLaren et al. 2003) which has the potential and sensitivity to rapidly quantify and discriminate between changes in psychological stress, resulting from exposure to short-term low-level everyday life-stressors. Aims The overall aim of this research was to further explore the relationship between short-term psychological stress and altered immune responsiveness. Leukocyte coping capacity (LCC) is a luminol-dependent chemiluminescent technique for the assay of reactive oxygen species production in whole blood samples. The feasibility of applying this test as an objective, quantitative, diagnostic measure of altered mental workload (mental stress), in the assessment of ergonomics within automotive research and development was examined. Methods Leukocyte activity was determined from whole blood, using a luminol-dependent, in vitro, chemiluminescent technique referred to as Leukocyte Coping Capacity (LCC). 2 The technique measures reactive oxygen species production following phorbol 12-myristate 13-acetate (PMA) stimulation. Subjective psychological measures, including likert scales and the NASA task load index were employed to assess perceived stress and altered mental workload. Other traditional physiological parameters including heart rate, systolic and diastolic blood pressure and core body temperature were also measured. The ability of each parameter to detect and discriminate between related short-term stressors was investigated, and results were correlated with post-test changes in leukocyte activity. To investigate the mechanism of stress induced leukocyte activation, standard ELISA was used to assess post-stressor plasma concentration changes in nine mediators including Adrenaline, Noradrenaline, Cortisol, E-Selectin, L-Selectin, Interleukin-1β, Interleukin-6, Endothelin-1, and Tumour Necrosis Factor-α. All 5 studies involved the use of mental stressors that were associated with either driving or the ergonomics of driving. Participants were moderately fit and healthy, aged between 20 and 65 years. Study one assessed the ability of the LCC technique to objectively discriminate between two closely related stressors (performing a simple manoeuvre in two different vehicles). Study two investigated leukocyte sensitivity, by testing whether a quantifiable response was elicited following exposure to a low-level stressor lasting seconds. The third study was used to explore the mechanism of leukocyte activation following short-term low-level stress. In addition to testing the viability of leukocyte responsiveness as an objective quantitative ergonomic assay for use within the motor industry, study four investigated how the magnitude of leukocyte responsiveness changed following repeated exposure to the same stressor. The final study used leukocyte reactivity to investigate how mental loading was affected during the interaction with three different motor vehicle control interfaces, whilst simultaneously maintaining lane discipline within a simulated driving environment.

Bald Cypress (Taxodium distichum (L.) Rich.) is native to freshwater wetlands of Florida. The vitality of cypress within coastal freshwater wetlands is threatened by saltwater intrusion. Biomarkers to detect sub-lethal salinity stress were developed using a controlled greenhouse study. Cypress saplings maintained at elevated salinities of 4 and 8‰ exhibited a decrease in maximum quantum yield (MQY) and an increase in non-photochemical quenching (NPQ). Cypress leaves exhibited an increase in Na+, H2O2, and free proline content compared to plants maintained in freshwater. These biomarkers were used to detect salinity stress within a population of cypress associated with the lower St. Johns River where saltwater intrusion is occurring. Cypress in a basin swamp exhibited signs of salinity stress with low MQY and elevated NPQ values compared to Cypress at other sites. Cypress leaves at the basin swamp also had the highest Na+, lipid peroxidation, and proline content compared to plants at other sites. Detached Cypress leaf experiments were conducted to explore the mechanisms of salt tolerance. Detached cypress leaves were first exposed to elevated NaCl concentrations for 24, 48, or 72 hours. Elevated salinity caused a decrease in leaf transpiration for all times tested. Total peroxidase activity exhibited an increase in response to salt stress after 48 hours. Enhanced peroxidase activity was found to be associated with the induction of a ~37 kDa peroxidase isoform. Treatment of leaves with clofibrate caused an increase in activity of the ~37 kDa peroxidase. Pre-treatment of leaves with brefeldin A (BFA) blocked the induction of the ~37 kDa peroxidase associated with salt stress. Pre-treatment of Cypress leaves with diphenyliodonium (DPI) blocked the decrease in transpiration associated with salt stress, suggesting that H2O2 is enzymatically produced within the stomata in response to salt stress