This investigation was undertaken to explore biochemical changes which may occur in heart tissue with age. In this connection, the cellular enzymes were of special interest.

Juvenile male blue crabs move into the tidal, freshwater James River during warmer months to feed and grow by undergoing molting. In crustaceans, growth and molting are hormonally controlled. The physiological effects of a multiple-stressor environment are determined by comparing the blue crab’s oxygen uptake after exposure to pure sand, James River sediment, or endosulfan-spiked sand. The effect of multiple stressors on molting is measured by the activity level of N-acetyl-ß-glucosaminidase (NAG), an enzyme in epidermal tissue important to molting. The oxygen uptake was decreased by exposure to James River sediment but not for exposure to endosulfan for seven days. Exposure to James River sediments over two days caused a similar suppression of epidermal NAG activity as exposure to endosulfan. These results indicate that the blue crab’s exposure to James River sediments and moderate hypoxia has the potential to cause short-term effects on physiology and long-term effects on growth.

De nouveaux enjeux émergent dans le domaine de la Santé en raison du vieillissement de la population et du développement inquiétant de la Maladie d’Alzheimer (MA). Chez le sujet sain ou pathologique, peu d’études ont porté sur le vieillissement du contrôle nerveux de la respiration, en dépit de son rôle crucial pour l’oxygénation du cerveau. Cette thèse présente des recherches translationnelles, réalisées chez la souris, pour étudier le vieillissement physiologique et pathologique du contrôle nerveux de la respiration. Chez des souris transgéniques, modèles reconnus de la MA et du syndrome de Rett, nous décrivons le développement de neuropathologies respiratoires graves, conduisant à un décès prématuré. Nous montrons pour la première fois qu’une tauopathie du tronc cérébral altère le fonctionnement des voies aériennes supérieures, la vocalisation et la respiration. De plus, nos travaux suggèrent un rôle délétère de l’anesthésie pour la MA et identifient des pistes thérapeutiques nouvelles. En conclusion, nos travaux chez la souris peuvent avoir des retombées particulièrement intéressantes notamment pour la MA. / New issues are emerging in the field of Health care due to ageing of the population and the alarming development of Alzheimer’s Disease (AD). In healthy or pathological living being, very few studies are dealing with the ageing of the respiratory nervous control, in spite of the crucial role of respiration for brain oxygenation. This thesis presents translational research performed in mice to examine the physiological and pathological ageing of the respiratory nervous control. In mice from two transgenic strains, recognized models for AD and Rett syndrome, we describe the development of drastic respiratory neuropathologies leading to premature death. In the AD mouse model, we show for the first time that brainstem tauopathy triggers dysfunctions of the upper airways, impairs vocalization and alters respiration and respiratory control. In addition, our work suggests a deleterious effect of anaesthesia for AD and identifies new therapeutic strategies. This mouse research could well contribute to significant improvements in AD care.