Une étude sur les déterminants biologiques, psychologiques et du travail de l'épuisement professionnel

Cette thèse de doctorat s’intéresse à mieux comprendre, d’une part, ce qui influence la sécrétion de cortisol salivaire, et d’autre part, ce qui influence l’épuisement professionnel. Plusieurs objectifs en découlent. D’abord, elle vise à mieux cerner la contribution des conditions de l’organisation du travail (utilisation des compétences, autorité décisionnelle, demandes psychologiques, demandes physiques, horaire de travail irrégulier, nombre d’heures travaillées, soutien social des collègues, soutien social des superviseurs, insécurité d’emploi) sur la sécrétion de cortisol salivaire, ainsi que le rôle modérateur de certains traits de personnalité (extraversion, agréabilité, névrosisme, conscience, ouverture d’esprit, estime de soi, centre de contrôle) sur la relation entre les conditions de l’organisation du travail et la sécrétion de cortisol salivaire. Par ailleurs, cette thèse vise à établir la contribution des conditions de l’organisation du travail sur l’épuisement professionnel, ainsi que le rôle modérateur des traits de personnalité sur la relation entre les conditions de l’organisation du travail et l’épuisement professionnel. Finalement, cette thèse vise à vérifier si la sécrétion de cortisol salivaire joue un rôle médiateur sur la relation entre les conditions de l’organisation du travail et l’épuisement professionnel, ainsi qu’à identifier les effets de médiation modérés par les traits de personnalité sur la relation entre les conditions de l’organisation du travail et la sécrétion de cortisol salivaire. Ces objectifs sont inspirés de nombreuses limites observées dans la littérature, principalement l’intégration de déterminants à la fois biologiques, psychologiques et du travail dans la compréhension de l’épuisement professionnel. La thèse propose un modèle conceptuel qui tente de savoir comment ces différents stresseurs entraînent une dérégulation de la sécrétion de cortisol dans la salive des travailleurs. Ensuite, ce modèle conceptuel vise à voir si cette dérégulation s’associe à l’épuisement professionnel. Finalement, ce modèle conceptuel cherche à expliquer comment la personnalité peut influencer la manière dont ces variables sont reliées entre elles, c’est-à-dire de voir si la personnalité joue un rôle modérateur. Ce modèle découle de quatre théories particulières, notamment la perspective biologique de Selye (1936). Les travaux de Selye s’orientent sur l’étude de la réaction physiologique d’un organisme soumis à un stresseur. Dans ces circonstances, l’organisme est en perpétuel effort de maintien de son équilibre (homéostasie) et ne tolère que très peu de modifications à cet équilibre. En cas de modifications excessives, une réponse de stress est activée afin d’assurer l’adaptation en maintenant l’équilibre de base de l’organisme. Ensuite, le modèle conceptuel s’appuie sur le modèle de Lazarus et Folkman (1984) qui postule que la réponse de stress dépend plutôt de l’évaluation que font les individus de la situation stressante, et également sur le modèle de Pearlin (1999) qui postule que les individus exposés aux mêmes stresseurs ne sont pas nécessairement affectés de la même manière. Finalement, le modèle conceptuel de cette thèse s’appuie sur le modèle de Marchand (2004) qui postule que les réactions dépendent du décodage que font les acteurs des contraintes et ressources qui les affectent. Diverses hypothèses émergent de cette conceptualisation théorique. La première est que les conditions de l’organisation du travail contribuent directement aux variations de la sécrétion de cortisol salivaire. La deuxième est que les conditions de l’organisation du travail contribuent directement à l’épuisement professionnel. La troisième est que la sécrétion de cortisol salivaire médiatise la relation entre les conditions de l’organisation du travail et l’épuisement professionnel. La quatrième est que la relation entre les conditions de l’organisation du travail et la sécrétion de cortisol salivaire est modérée par les traits de personnalité. La cinquième est que la relation entre les conditions de l’organisation du travail, la sécrétion de cortisol salivaire et l’épuisement professionnel est modérée par les traits de personnalité. Des modèles de régression multiniveaux et des analyses de cheminement de causalité ont été effectués sur un échantillon de travailleurs canadiens provenant de l’étude SALVEO. Les résultats obtenus sont présentés sous forme de trois articles, soumis pour publication, lesquels constituent les chapitres 4 à 6 de cette thèse. Dans l’ensemble, le modèle intégrateur biopsychosocial proposé dans le cadre de cette thèse de doctorat permet de mieux saisir la complexité de l’épuisement professionnel qui trouve une explication biologique, organisationnelle et individuelle. Ce constat permet d’offrir une compréhension élargie et multiniveaux et assure l’avancement des connaissances sur une problématique préoccupante pour les organisations, la société ainsi que pour les travailleurs. Effectivement, la prise en compte des traits de personnalité et de la sécrétion du cortisol salivaire dans l’étude de l’épuisement professionnel assure une analyse intégrée et plus objective. Cette thèse conclue sur les implications de ces résultats pour la recherche, et sur les retombées qui en découlent pour les milieux de travail.

Impacts des dépositions atmosphériques de fer sur les assemblages phytoplanctoniques et la production de diméthylsulfure dans le Pacifique Nord-Est contemporain et dans le contexte de l’acidification des océans

La croissance du phytoplancton est limitée par les faibles concentrations de fer (Fe) dans près de 40% de l’océan mondial. Le Pacifique subarctique Nord-Est représente une de ces zones limitées en fer et désignées High Nutrient - Low Chlorophyll (HNLC). Cet écosystème, dominé par des cellules de petite taille telles les prymnésiophytes, est caractérisé par de très faibles concentrations estivales de chlorophylle a et de fortes concentrations de macronutriments. Il a été maintes fois démontré que les ajouts de fer, sous différentes formes chimiques (habituellement FeSO4), dans les zones HNLC, stimulent la croissance et modifient la structure des communautés planctoniques en favorisant la croissance des cellules de grande taille, notamment les diatomées. Ces effets sur la communauté planctonique ont le potentiel d’influencer les grands mécanismes régulateurs du climat, tels la pompe biologique de carbone et la production de diméthylsulfure (DMS). Les poussières provenant des déserts du nord de la Chine sont reconnues depuis longtemps comme une source sporadique importante de fer pour le Pacifique Nord-Est. Malgré leur importance potentielle, l’influence directe exercée par ces poussières sur l’écosystème planctonique de cette zone HNLC n’a jamais été étudiée. Il s’agit d’une lacune importante puisque le fer associé aux poussières est peu soluble dans l’eau de mer, que la proportion biodisponible n’est pas connue et que les poussières peuvent avoir un effet inhibiteur chez le phytoplancton. Cette thèse propose donc, dans un premier temps, de mesurer pour la première fois l’effet de la fertilisation de la communauté planctonique du Pacifique Nord-Est par un gradient de concentrations de poussières désertiques naturelles. Cette première expérimentation a démontré que le fer contenu dans les poussières asiatiques est biodisponible et qu’une déposition équivalente à celles prenant place au printemps dans le Pacifique Nord-Est peut résulter en une stimulation significative de la prise de nutriments et de la croissance du phytoplancton. Mes travaux ont également montré que l’ajout de 0,5 mg L-1 de poussières peut résulter en la production d’autant de biomasse algale que l’ajout de FeSO4, l’espèce chimique utilisée lors des expériences d’enrichissement en fer à grande échelle. Cependant, les ajouts de FeSO4 favorisent davantage les cellules de petite taille que les ajouts de poussières, observation démontrant que le FeSO4 n’est pas un proxy parfait des poussières asiatiques. Dans un deuxième temps, je me suis intéressée à une source alternative de fer atmosphérique, les cendres volcaniques. Mon intérêt pour cette source de fer a été attisé par les observations d’une floraison spectaculaire dans le Pacifique Nord-Est, ma région d’étude, associée à l’éruption de 2008 du volcan Kasatochi dans les îles Aléoutiennes. Forte de mon expérience sur les poussières, j’ai quantifié l’effet direct de ces cendres volcaniques sur la communauté planctonique du Pacifique Nord-Est. Mes résultats ont montré que le fer contenu dans les cendres volcaniques est également biodisponible pour le phytoplancton. Ils ont également montré que cette source de fer peut être aussi importante que les poussières désertiques dans la régulation de la croissance du phytoplancton dans cette partie de l’océan global à l’échelle millénaire. Dans un troisième temps, j’ai estimé comment l’acidification des océans modulera les réponses des communautés planctoniques aux dépositions naturelles de fer mises en évidence lors de mes expériences précédentes. Pour ce faire, j’ai effectué des enrichissements de poussière dans de l’eau de mer au pH actuel de 8.0 et dans l’eau de mer acidifiée à un pH de 7.8. Mes résultats ont montré une diminution du taux de croissance du phytoplancton dans le milieu acidifié mais pas de changement notable dans la structure de la communauté. Les ajouts de poussières et de cendres, de même que les variations de pH, n’ont pas eu d’effet significatif sur la production de DMS et de son précurseur le diméthylsulfoniopropionate (DMSP), probablement en raison de la courte durée (4 jours) des expériences. L’ensemble des résultats de cette thèse montre que le fer contenu dans diverses sources atmosphériques naturelles est biodisponible pour le phytoplancton du Pacifique Nord-Est et que des taux de déposition réalistes peuvent stimuler la croissance de manière notable dans les premiers jours suivant une tempête désertique ou une éruption volcanique. Finalement, les résultats de mes expériences à stresseurs multiples Fer/acidification suggèrent une certaine résistance des communautés phytoplanctoniques à la diminution du pH prédite d’ici la fin du siècle pour les eaux de surface des océans.

Vulnerabilidade ao Stress e Autoestima em Professores do 1.º, 2.º E 3.º Ciclo

Introdução: O stress condiciona o comportamento e desenvolvimento pessoal, podendo ter consequências preocupantes ao nível individual e organizacional. Os professores são uma classe reconhecida como estando sujeita a elevados níveis de stress, fator que prejudica a qualidade do ensino em geral. Objetivos: Avaliar a vulnerabilidade ao stress; identificar os principais fatores de stress e avaliar a correlação entre autoestima e stress, em professores do 1.º, 2.º e 3.º ciclos do ensino básico. Metodologia: Estudo correlacional, com uma amostra constituída por 60 professores do 1.º, 2.º e 3.º ciclos de escolaridade, de escolas do concelho de Leiria. Para a análise das variáveis em estudo foram aplicados: um questionário sociodemográfico; a Rosenberg Self-Esteem Scale (RSES); o Questionário de stress nos professores: ensino básico e secundário (QSPEBS) e a Escala de vulnerabilidade ao stress (23 QVS). Resultados: O estudo revela que 65% dos professores percecionam a profissão como stressante e que 30% são vulneráveis ao stress. O principal fator de stress identificado foi comportamentos inadequados/indisciplina dos alunos. Verificou-se uma correlação negativa entre a autoestima e a vulnerabilidade ao stress dos professores. Conclusão: Conclui-se que, quanto mais elevada é a auto-estima, menor é a vulnerabilidade dos professores ao stress e que, apesar de não se registarem níveis significativos de vulnerabilidade ao stress na população docente, a maioria dos professores perceciona a sua atividade profissional como geradora de elevados níveis de stress, sendo os comportamentos inadequados/indisciplina dos alunos o fator que mais contribui para o stress nos docentes. / Introduction: Stress affects behavior and personal development, and may have severe consequences either at the individual or organizational level. Teachers are identified as a class exposed to high levels of stress, factor that affects the quality of education in general. Objectives: To assess stress vulnerability; identify key stressors and assess the correlation between self-esteem and stress in primary and secondary school teachers. Methodology: A sociodemographic questionnaire and three self-report measures were administered to a sample of 60 primary and secondary teachers from Leiria district: the Rosenberg Self-Esteem Scale (RSES); a teachers stress questionnaire for primary, secondary and high school (QSPEBS) and a scale to access stress vulnerability (23 QVS). Results: The study reveals that 65% of teachers perceive the profession as stressful and that 30% are vulnerable to stress. The main stressor identified is inappropriate/disruptive behavior of students. There is a negative correlation between self-esteem and vulnerability to stress of teachers. Conclusion: We conclude that a higher self-esteem leads to less stress vulnerability in teachers and that, despite the non-significant level of vulnerability determined in this study, most teachers perceive their activity as stressful, being inappropriate/disruptive behavior of students the factor that most contributes for that.

Equilíbrios Difíceis: stress laboral, equilíbrio trabalho/família e diferenças de género entre os colaboradores de uma empresa de tecnologias da informação

O stress é não apenas inerente para o ser humano, como indispensável para a sua sobrevivência. À medida que as sociedades humanas evoluíram, assim também se alteraram as principais fontes de stress. Actualmente o stress organizacional é uma das principais áreas de investigação, bem como as suas relações com a família e a vida pessoal. Em foco estão ainda as variáveis individuais que servem como moderadoras da experiência de stress, como o coping e o suporte social. Neste trabalho procurou-se conhecer os níveis de stress experienciados pelos colaboradores da Cisco Systems Lda, identificando diferenças de género e entre os tipos de trabalho. Pretendeu-se ainda relacionar o stress no trabalho com o equilíbrio trabalho/família, equlíbrio vida pessoal/trabalho, suporte social e coping. Através de um estudo não experimental transversal, descritivo/descritivo correlacional, com 42 sujeitos, utilizando o PMI – Pressure Management Indicator, foi possível identificar quatro factores, com α a partir de 0,531 para as variáveis moderadoras ate 0,904 para as variáveis stressoras. Os trabalhadores da amostra trabalham em média 49,7 horas por semana, apontando como principal razão “para que o trabalho seja feito”; 31,7% consideram estar a sofrer de pressão negativa iniciada há mais de 3 meses. Estão muito satisfeitos com a organização, mas sentem pressão devido ao volume de trabalho, ao relacionamento interpessoal e às dificuldades em desligar do trabalho quando em casa, fazendo uso de estratégias focadas no problema e de suporte social. Existem diferenças estatisticamente significativas entre homens e mulheres nas subescalas “Estado de espírito” e “Nível de confiança”, indicando níveis mais altos de segurança e satisfação com o seu estado mental para o grupo dos homens. No que respeita aos tipos de trabalho, foi possível identificar diferenças entre as categorias Sénior gerência/profissional e Manual/hábil nas subescalas “Nível de energia”, “Volume de trabalho” e “Equilíbrio vida/trabalho”. Existe correlação positiva entre as variáveis stressoras e a subescala “Equilíbrio trabalho/família” (r=0,890; p<0,000) e entre as variáveis stressoras e a escala de Coping (r=0,748; p<0,000), sugerindo que níveis de stress elevados interferem com a vida familiar e conduzem a maior utilização das estratégias de coping. Apesar das políticas de recursos humanos da empresa no sentido de promover a conciliação entre trabalho e vida pessoal e familiar, há ainda margem para intervir e melhorar. / Stress is not only inherent to the human being, it’s essential to survival. As the humans societies evolved, so did the major sources of stress. These days, organizational stress is one of the main areas of research, as it is it’s relation with family and personal life. Under the spotlight are also individual variables that moderate the stress experience, such as coping and social support. With this paper, we intended to know the levels of stress experienced by the workers of Cisco Systems Lda, identifying gender and work type differences. We were also intending to relate work stress with home/work balance, life/work balance, social support and coping. Using a cross sectional correlational study, with n=42, using the PMI, we were able to identify four factors, with α starting on 0,531 for moderator variables to 0,904 for stressor variables. The workers on this sample work an average of 49,7 hours per week, naming “to get the job done” as the main reason for it. 31,7% consider to be suffering from negative pressure that started more than 3 months ago. They are very satisfied with the organization, but feel pressure due to workload, interpersonal relationship and the difficulties in switching off from work when at home. They use mostly Problem focus strategies and social support.There are statically significative differences between men and women in the subscales “State of mind” and “Confidence level”, which indicate higher levels of security and satisfaction with their state of mind for men. Regarding work types, we were able to identify differences between senior Management and Manual categories on subscales “Energy level”, “Workload” and “Life/work balance”. There is a positive correlation between stressor variables and the subscales “Home/work balance” (r=0,890; p<0,000) and between stressor variables and Coping scale (r=0,748; p<0,000), suggesting that high levels of stress interfere with family life and lead to higher use of coping mechanisms. Despite the company’s human resources policies to promote the balance between work and personal and family life, there is still place to intervene and improve.

Information and communication technology demands at work : the association with job strain, effort-reward imbalance and self-rated health in different socio-economic strata

PURPOSE: The use of information and communication technology (ICT) is common in modern working life. ICT demands may give rise to experience of work-related stress. Knowledge about ICT demands in relation to other types of work-related stress and to self-rated health is limited. Consequently, the aim of this study was to examine the association between ICT demands and two types of work-related stress [job strain and effort-reward imbalance (ERI)] and to evaluate the association between these work-related stress measures and self-rated health, in general and in different SES strata. METHODS: This study is based on cross-sectional data from the Swedish Longitudinal Occupational Survey of Health collected in 2014, from 14,873 gainfully employed people. ICT demands, job strain, ERI and self-rated health were analysed as the main measures. Sex, age, SES, lifestyle factors and BMI were used as covariates. RESULTS: ICT demands correlated significantly with the dimensions of the job strain and ERI models, especially with the demands (r = 0.42; p < 0.01) and effort (r = 0.51; p < 0.01) dimensions. ICT demands were associated with suboptimal self-rated health, also after adjustment for age, sex, SES, lifestyle and BMI (OR 1.49 [95 % CI 1.36-1.63]), but job strain (OR 1.93 [95 % CI 1.74-2.14) and ERI (OR 2.15 [95 % CI 1.95-2.35]) showed somewhat stronger associations with suboptimal self-rated health. CONCLUSION: ICT demands are common among people with intermediate and high SES and associated with job strain, ERI and suboptimal self-rated health. ICT demands should thus be acknowledged as a potential stressor of work-related stress in modern working life.

”Stress Monitoring via Wearable Electrodermal Sensors”

Stress is a phenomenon that on some level affects everyone’s lives on a daily basis. The autonomic nervous system controls the varying levels of stress at any given time. The responses of the autonomic nervous system adjust the body to cope with changing external and internal conditions. During high-stress situations the body is forced into a state of heightened alertness, which passes when the stressor is removed. The stressor can be any external or internal event that causes the body to respond. Stress is a very versatile phenomenon that can be both a cause and an indicator of other medical conditions, for example cardiovascular disease. Stress detection can therefore be helpful in identifying these conditions and monitoring the overall emotional state of a person. Electrodermal activity (EDA) is one of the most easily implemented ways to monitor the activity of the autonomic nervous system. EDA describes changes occurring in the various electrical properties of the skin, including skin conductivity and resistance. Increased emotional sweating has been proven to be one possible indication of stress. On the surface of the skin, increased sweating translates to increased skin conductivity, which can be observed through EDA measurements. This makes electrodermal activity a very useful tool in a wide range of applications where it is desirable to observe changes in a person’s stress level. EDA can be recorded by using specialized body sensors placed on specific locations on the body. Most commonly used recording sites are the palms of the hands due to the high sweat gland density on those areas. Measurement is done using at least two electrodes attached to the skin, and recording the electrical conductance between them. This thesis implements a prototype of a wireless EDA measurement system. The feasibility of the prototype is also verified with a small group of test subjects. EDA was recorded from the subjects while they were playing a game of Tetris. The goal was to observe variations in the measured EDA that would indicate changes in the subjects’ stress levels during the game. The analysis of the obtained measurement results confirmed the connection between stress and recorded EDA. During the game, random occurrences of lowered skin resistance were clearly observable, which indicates points in the game where the player felt more anxious. A wireless measurement system has the potential of offering more flexible and comfortable long-term measuring of EDA, and could be utilized in a wide range of applications.

The impacts of environmental and anthropogenic stressors on largemouth bass: an integration of field and laboratory studies

Several environmental stressors can impact the physiology and survival of fishes. Fish experience natural fluctuations in temperature and dissolved oxygen, but variations in these parameters due to anthropogenic sources are typically greater in magnitude and duration. Changes in temperature and oxygen of anthropogenic origins may therefore have larger negative impacts on fish than those occurring during natural events. Physiological parameters are sensitive indicators of the impacts of stressors by providing insight into the manner in which fish are disturbed by the stressor. Fish may display cumulative physiological responses to successive stressors, but the concept of synergy among multiple thermal stressors is poorly understood. Further, some fish species can be subjected to competitive angling events, which expose fish to an array of additional stressors that can increase mortality. The impacts of these events may change over seasons as fish display seasonal changes in behavior and physiology. Latitudinal origin may also affect the physiological response and mortality of fish exposed to common environmental stressors as individual populations are adapted to local environmental conditions. This thesis focuses on addressing these potential impacts on physiological parameters and mortality of largemouth bass (Micropterus salmoides) and provides implications for management and conservation. Largemouth bass were relatively robust to abrupt changes in temperature and oxygen, but were perturbed from physiological homeostasis during large (12°C) temperature shocks and low (< 4 mg O2/L) levels of dissolved oxygen. Cumulative physiological impacts of multiple cold shocks were only slightly greater than the disturbances sustained during a single cold shock, suggesting largemouth bass are able to tolerate successive thermal stressors. Largemouth bass exhibited seasonal changes in physiological parameters but the responses of fish to angling tournaments were relatively similar across seasons when compared with seasonal controls. Mortality was low during angling tournaments held during four seasons and no apparent seasonal trends were observed. Lastly, largemouth bass from two latitudinally separated populations exhibited differences in their physiological responses to acute cold stressors and overwinter mortality, characterized by greater mortality and physiological disturbances of southern fish than northern fish. Knowledge gained from this study can be used to make management and conservation decisions regarding a host of environmental factors and provides insight into the mechanisms by which fish species can persist over large latitudinal ranges.

Development of gene expression-based biomarkers of exposure to metals and pesticides in the freshwater amphipod Hyalella azteca

Ecological risk assessment (ERA) is a framework for monitoring risks of exposure and adverse effects of environmental stressors to populations or communities of interest. One tool of ERA is the biomarker, which is a characteristic of an organism that reliably indicates exposure to or effects of a stressor like chemical pollution. Traditional biomarkers which rely on characteristics at the tissue level and higher often detect only acute exposures to stressors. Sensitive molecular biomarkers may detect lower stressor levels than traditional biomarkers, which helps inform risk mitigation and restoration efforts before populations and communities are irreversibly affected. In this study I developed gene expression-based molecular biomarkers of exposure to metals and insecticides in the model toxicological freshwater amphipod Hyalella azteca. My goals were to not only create sensitive molecular biomarkers for these chemicals, but also to show the utility and versatility of H. azteca in molecular studies for toxicology and risk assessment. I sequenced and assembled the H. azteca transcriptome to identify reference and stress-response gene transcripts suitable for expression monitoring. I exposed H. azteca to sub-lethal concentrations of metals (cadmium and copper) and insecticides (DDT, permethrin, and imidacloprid). Reference genes used to create normalization factors were determined for each exposure using the programs BestKeeper, GeNorm, and NormFinder. Both metals increased expression of a nuclear transcription factor (Cnc), an ABC transporter (Mrp4), and a heat shock protein (Hsp90), giving evidence of general metal exposure signature. Cadmium uniquely increased expression of a DNA repair protein (Rad51) and increased Mrp4 expression more than copper (7-fold increase compared to 2-fold increase). Together these may be unique biomarkers distinguishing cadmium and copper exposures. DDT increased expression of Hsp90, Mrp4, and the immune response gene Lgbp. Permethrin increased expression of a cytochrome P450 (Cyp2j2) and decreased expression of the immune response gene Lectin-1. Imidacloprid did not affect gene expression. Unique biomarkers were seen for DDT and permethrin, but the genes studied were not sensitive enough to detect imidacloprid at the levels used here. I demonstrated that gene expression in H. azteca detects specific chemical exposures at sub-lethal concentrations, making expression monitoring using this amphipod a useful and sensitive biomarker for risk assessment of chemical exposure.

The study of histopathological damage in heart and bulbus arteriosus in rainbow trout

This study investigated the pathological changes of heart and bulbus artrius of rainbow trout breeders in several group of ages and density. The aim of study was to consider the process and the intensity of the heart and bulbus arteriosus damages in accordance to gender, age and stocking density of trout in three fish culture center (Zarghezel, Niyak in Haraz Region,Mazandaran and Espiran in Tabriz city environs). In field research, the all records the feed and feeding type, rate of mortality, stocking density of spawners and per spawners fishes, water chemical and physical specification was screened. Stocking density was considered as the most important stressor. 10 fish specimens from 7 weight groups (less than 90g, 90 to 300g, 300 to 500 g, 500 to 1000g, 1 to 3 kg, 3 to 5 kg, over 5 kg), totally 210 specimens were sampled and heart and bulbus arteriosus were taken. Samples were fixed in 10 % formalin and transferred to pathology laboratory of veterinary faculty of Tabriz Azad University. Histopathological slides and H&E staining were prepared from these samples. In total, 47 male and 73 female samples showed cardiovascular injury (29 cases in extensive system, 41 cases in semi intensive system, 50 cases in intensive system). The most important was damages, edema and hyperemia in spongy layer of atrium and ventricle muscles, but degeneration the muscle fibers, moderate edema , minor vascular damage. Hemorrhage as the effect of severs vascular damage, thrombus, sever inflammation, sever degeneration in muscle fiber, necrosis and fibrose were further pathological changed. The results of this study showed that the severity of damage increased by increasing the age (weight) of fishes. This situation was seen in all three culturing system (extensive system, semi intensive system, recirculation system). Histopathological changes is obviously seen in samples over 500g, therefore the damages were found to be important (P<0.05). Pathological effects and its severity in recirculation system was significantly high (P<0.05). Comparison with two other culturing system, histopathological changed in heart and bulbus arterius between male and female was significantly different.

Une étude sur les déterminants biologiques, psychologiques et du travail de l'épuisement professionnel

Cette thèse de doctorat s’intéresse à mieux comprendre, d’une part, ce qui influence la sécrétion de cortisol salivaire, et d’autre part, ce qui influence l’épuisement professionnel. Plusieurs objectifs en découlent. D’abord, elle vise à mieux cerner la contribution des conditions de l’organisation du travail (utilisation des compétences, autorité décisionnelle, demandes psychologiques, demandes physiques, horaire de travail irrégulier, nombre d’heures travaillées, soutien social des collègues, soutien social des superviseurs, insécurité d’emploi) sur la sécrétion de cortisol salivaire, ainsi que le rôle modérateur de certains traits de personnalité (extraversion, agréabilité, névrosisme, conscience, ouverture d’esprit, estime de soi, centre de contrôle) sur la relation entre les conditions de l’organisation du travail et la sécrétion de cortisol salivaire. Par ailleurs, cette thèse vise à établir la contribution des conditions de l’organisation du travail sur l’épuisement professionnel, ainsi que le rôle modérateur des traits de personnalité sur la relation entre les conditions de l’organisation du travail et l’épuisement professionnel. Finalement, cette thèse vise à vérifier si la sécrétion de cortisol salivaire joue un rôle médiateur sur la relation entre les conditions de l’organisation du travail et l’épuisement professionnel, ainsi qu’à identifier les effets de médiation modérés par les traits de personnalité sur la relation entre les conditions de l’organisation du travail et la sécrétion de cortisol salivaire. Ces objectifs sont inspirés de nombreuses limites observées dans la littérature, principalement l’intégration de déterminants à la fois biologiques, psychologiques et du travail dans la compréhension de l’épuisement professionnel. La thèse propose un modèle conceptuel qui tente de savoir comment ces différents stresseurs entraînent une dérégulation de la sécrétion de cortisol dans la salive des travailleurs. Ensuite, ce modèle conceptuel vise à voir si cette dérégulation s’associe à l’épuisement professionnel. Finalement, ce modèle conceptuel cherche à expliquer comment la personnalité peut influencer la manière dont ces variables sont reliées entre elles, c’est-à-dire de voir si la personnalité joue un rôle modérateur. Ce modèle découle de quatre théories particulières, notamment la perspective biologique de Selye (1936). Les travaux de Selye s’orientent sur l’étude de la réaction physiologique d’un organisme soumis à un stresseur. Dans ces circonstances, l’organisme est en perpétuel effort de maintien de son équilibre (homéostasie) et ne tolère que très peu de modifications à cet équilibre. En cas de modifications excessives, une réponse de stress est activée afin d’assurer l’adaptation en maintenant l’équilibre de base de l’organisme. Ensuite, le modèle conceptuel s’appuie sur le modèle de Lazarus et Folkman (1984) qui postule que la réponse de stress dépend plutôt de l’évaluation que font les individus de la situation stressante, et également sur le modèle de Pearlin (1999) qui postule que les individus exposés aux mêmes stresseurs ne sont pas nécessairement affectés de la même manière. Finalement, le modèle conceptuel de cette thèse s’appuie sur le modèle de Marchand (2004) qui postule que les réactions dépendent du décodage que font les acteurs des contraintes et ressources qui les affectent. Diverses hypothèses émergent de cette conceptualisation théorique. La première est que les conditions de l’organisation du travail contribuent directement aux variations de la sécrétion de cortisol salivaire. La deuxième est que les conditions de l’organisation du travail contribuent directement à l’épuisement professionnel. La troisième est que la sécrétion de cortisol salivaire médiatise la relation entre les conditions de l’organisation du travail et l’épuisement professionnel. La quatrième est que la relation entre les conditions de l’organisation du travail et la sécrétion de cortisol salivaire est modérée par les traits de personnalité. La cinquième est que la relation entre les conditions de l’organisation du travail, la sécrétion de cortisol salivaire et l’épuisement professionnel est modérée par les traits de personnalité. Des modèles de régression multiniveaux et des analyses de cheminement de causalité ont été effectués sur un échantillon de travailleurs canadiens provenant de l’étude SALVEO. Les résultats obtenus sont présentés sous forme de trois articles, soumis pour publication, lesquels constituent les chapitres 4 à 6 de cette thèse. Dans l’ensemble, le modèle intégrateur biopsychosocial proposé dans le cadre de cette thèse de doctorat permet de mieux saisir la complexité de l’épuisement professionnel qui trouve une explication biologique, organisationnelle et individuelle. Ce constat permet d’offrir une compréhension élargie et multiniveaux et assure l’avancement des connaissances sur une problématique préoccupante pour les organisations, la société ainsi que pour les travailleurs. Effectivement, la prise en compte des traits de personnalité et de la sécrétion du cortisol salivaire dans l’étude de l’épuisement professionnel assure une analyse intégrée et plus objective. Cette thèse conclue sur les implications de ces résultats pour la recherche, et sur les retombées qui en découlent pour les milieux de travail.

Cortisol Reactivity and Observed Parenting among Mothers of Children with and without ADHD

Parenting is a robust predictor of developmental outcomes among children with ADHD. Early parenting predicts the persistence and course of ADHD and comorbid problems above and beyond risk associated with shared genetic effects. Yet, on average, mothers of children with ADHD are less positive and more negative in their parent-child interactions compared to mothers of non-disordered children. Little is known about psychobiological markers which may be associated with individual variations in maternal parenting in families of children with ADHD. Neurobiological models of parenting suggest that maternal cortisol levels following a stressor may be positively associated with hostile and intrusive parenting; however, to date no studies have examined maternal cortisol reactivity and parenting in school-age, or clinical samples of, children. Mothers’ regulation of physiological stress responses may be particularly important for families of children with ADHD, as parenting a child with chronically challenging behaviors represents a persistent environmental stressor. The current study sought to extend the existing literature by providing an empirical examination of the relationship between maternal cortisol reactivity following two laboratory stressors and parenting among mothers of children with and without ADHD. It was hypothesized that child ADHD group would moderate the relationship between cortisol reactivity and self-reported and observed parenting. Greater total cortisol output and greater increase in cortisol during the TSST were associated with decreased positive parenting and increased negative and directive parenting, with the exception of parental involvement, which was associated with increased cortisol output during the TSST. Conversely, cortisol output during the PCI was associated with increased positive parenting, increased parental involvement, and decreased negative parenting. In contrast to the TSST, a greater decrease in cortisol during the PCI indicated more positive parenting and parental involvement. These associations were specific to mothers of children with ADHD, with the exception of maternal directiveness, which was specific to comparison mothers. Findings add to our understanding of physiological processes associated with maternal parenting and contribute to an integrative biological, psychological, and cognitive process model of parenting in families of children with ADHD.

Hydrodynamism and its influence on the density of the decorator crab Microphrys bicornutus (Mithracidae) on intertidal rocky shores from a subtropical region

Hydrodynamism is an environmental stressor on marine communities with effects on populations of intertidal organisms. Microphrys bicornutus is a crab species associated with secondary substrates on rocky shores and little is known about its population dynamics and its relation to the shore hydrodynamics. The aim of this study is to describe the population structure of Microphrys bicornutus on intertidal rocky shores from the north coast of the São Paulo State, Brazil, and the influence of wave exposure on the density of this decorator crab. There was a greater density of M. bicornutus on sheltered than on exposed rocky shores, which is probably due to the hydrodynamic influence on M. bicornutus populations on rocky shores: directly ( by the physical stress caused by wave impact) and indirectly ( by determining the dominance of the secondary substrate) acting on the density of these crabs. Our results also suggest a vertical distribution of juveniles and adults, where the juveniles might be more abundant on the infralittoral fringe and, thus, more influenced by hydrodynamism than adults in the infralittoral.

Effect of high densities on growth, stress response and plasma amino acid levels in senegalese sole (Solea senegalensis, Kaup 1858)

Dissertação de mest. em Aquacultura e Pescas, Faculdade de Ciências do Mar e do Ambiente, Univ. do Algarve, 2006

Absence of LPA1 receptor results in altered pattern of limbic activation after tail suspension test

Stress serves as an adaptive mechanism and helps organisms to cope with life-threatening situations. However, individual vulnerability to stress and dysregulation of this system may precipitate stress-related disorders such as depression. The neurobiological circuitry in charge of dealing with stressors has been widely studied in animal models. Recently our group has demonstrated a role for lysophosphatidic acid (LPA) through the LPA1 receptor in vulnerability to stress, in particular the lack of this receptor relates to robust decrease of adult hippocampal neurogenesis and induction of anxious and depressive states. Nevertheless, the specific abnormalities in the limbic circuit in reaction to stress remains unclear. The aim of this study is to examine the differences in the brain activation pattern in the presence or absence of LPA1 receptor after acute stress. For this purpose, we have studied the response of maLPA1-null male mice and normal wild type mice to an intense stressor: Tail Suspension Test. Activation induced by behaviour of brain regions involved in mood regulation was analysed by stereological quantification of c-Fos immunoreactive positive cells. We also conducted multidimensional scaling analysis in order to unravel coativation between structures. Our results revealed hyperactivity of stress-related structures such as amygdala and paraventricular nucleus of the hypothalamus in the knockout model and different patterns of coactivation in both genotypes using a multidimensional map. This data provides further evidence to the engagement of the LPA1 receptors in stress regulation and sheds light on different neural pathways under normal and vulnerability conditions that can lead to mood disorders.

Profile of cortisol, glycaemia, and blood parameters of American Bullfrog tadpoles Lithobates catesbeianus exposed to density and hypoxia stressors

O objetivo deste estudo foi avaliar a resposta fisiológica (cortisol, glicemia e parâmetros sanguineos) de girinos de rã-touro (Lithobates catesbeianus) em diferentes densidades e após exposição aérea. Os animais utilizados no experimento estavam entre os estágios 31 a 39, na fase de pró-metamorfose sendo testados 1 girino/L (Tratamento 1), 5 girinos/L (Tratamento 2) e 10 girinos/L (Tratamento 3), conduzidos em 3 réplicas simultâneas durante 12 dias. O sangue foi retirado por rompimento do vaso caudal na condição de Normóxia - N (tempo zero) e Hipóxia - H (tempo de 15 minutos de exposição ao ar). Foi observado um aumento nos valores de cortisol, aos 4 e 8 dias de exposição aérea retornando aos valores basais ao final do experimento, apesar de não haver diferenças significativas. A glicemia não apresentou diferenças significativas quanto aos estressores aplicados. Os parâmetros hematológicos da série branca, principalmente, o número de linfócitos, neutrófilos e eosinófilos mostraram diferença significativa aos 12 dias de experimentação quando comparados com o momento zero; concluindo-se que, em condições controladas, o adensamento de até 10 girinos/litro e a exposição aérea por 15 minutos não apresentou danos aos girinos de rã-touro durante o período experimental. O padrão de resposta a estes estímulos talvez seja expresso em outro nível hormonal (corticosterona).