A 3- to 5-fold increase in Ca2+ accompanies cataract formation induced by selenite. The mechanism of selenite cataractogenesis involves calcium activation of calpain with subsequent proteolysis within the lens nucleus. This study was undertaken to investigate the biochemical mechanisms that lead to calcium accumulation in these circumstances. The components responsible for rat lens calcium regulation were defined by using either lens membrane vesicle preparations or intact lenses. Both Na+ gradient-dependent Ca2+ uptake and efflux occurred in lens membrane vesicles. Experiments with intact lenses showed that Na + ICa2 + exchange plays an important role in lens calcium regulation. ATP-dependent Ca2+ uptake and Ca2+ -dependent ATP hydrolytic activity have been characterized in lens membrane vesicles. Therefore, both Ca2+ -ATPase and Na + ICa2+ exchange participate in rat lens calcium regulation. Calcium accumulation in lenses treated by selenite may result from either increased influx (via non-selective cation channel), decreased efflux (via Ca2 +-ATPase and Na+ ICa 2+ exchange) or both. The selenite effects on the different components involved in lens calcium regulation were tested. / Ph. D.

En 1638, paraît en Angleterre un ouvrage de John Wilkins (1614 - 1672), traitant de la pluralité des Mondes et plus précisément de la découverte d’un nouveau Monde : la Lune. Grâce à une argumentation dialectique, l’auteur tente de montrer la similarité entre la Terre et notre satellite. Il s’appuie pour cela sur le modèle copernicien et sur les observations astronomiques de Galilée. De cette similarité, en résulte, selon lui, l’idée que la Lune est peut-être habitée comme la Terre, par des êtres qu’il nomme Sélénites. Il ajoute qu’il serait possible de s’y rendre, et de commercer avec les habitants. L’objectif de cette thèse est d’étudier la place des sciences du vivant dans les théories sur la pluralité des Mondes, principalement dans l’œuvre de John Wilkins, et les différentes implications littéraires, théologiques et philosophiques qui en découlent. / In 1638, a book is published in England by John Wilkins (1614-1672), dealing with the plurality of Worlds, and more specifically the discovery of a New World: the Moon. With a dialectical reasoning, the author tries to show the similarities between the Earth and the Moon. For this he uses the Copernican model and astronomical observations of Galileo. From these similarities, Wilkins suggests the idea that the moon could be harboring living beings like Earth and then conjecture on the nature of its inhabitants, the Selenites. He writes that it may be possible one day to reach the Moon and trade with its inhabitants. The purpose of our work is to study the living in the discourse on the plurality of worlds, and observe its place in the work of Wilkins.