Effects of microgravity (microG) on fertilization were studied in the urodele amphibian Pleurodeles waltl on board the MIR space station. Genetic and cytomorphologic analyses ruled out parthenogenesis or gynogenesis and proved that fertilization did occur in microG. Actual fertilization was demonstrated by the analysis of the distribution of peptidase-1 genes, a polymorphic sex-linked enzyme, in progenies obtained in microG. Further evidence of fertilization was provided by the presence of spermatozoa in the perivitelline space and in the fertilization layer of the microG eggs and by the presence of a female pronucleus and male pronuclei in the egg cytoplasm. Experiments in microG and in 1.4G, 2G, and 3G hypergravity showed for the first time that, compared to eggs in 1G, several characteristics of the fertilization process including the cortical reaction and the microvillus transformations were altered depending on the gravitational force applied to the eggs. Microvillus elevation, the most evident feature, was reduced on microG-eggs and amplified on eggs submitted to 2G and 3G. No lethal consequences of these alterations on the early development of microG-eggs were observed.

Résumé Cet article s'intéresse au rôle joué par l'intervention dans le processus d'empowerment de personnes en situation d'extrême pauvreté. Il se fonde sur une étude de cas d'une vingtaine de familles rejointes par le programme de santé publique Naître égaux – Grandir en santé (NÉ – GS). Il identifie d'abord les principales composantes qui se dégagent des processus d'empowerment observés. Par la suite, et c'est là le coeur de notre propos, l'article fait ressortir un certain nombre d'éléments pour qualifier l'intervention individuelle réalisée dans un tel contexte : une intervention à un moment clé de la vie ; une forte relation de confiance ; une intervention qui part du ou des projets des parents ; enfin, un accompagnement vers les services et ressources de la communauté en procurant le sentiment de posséder du pouvoir.

In vertebrates, only few experiments have been performed in microgravity to study the embryonic development from fertilization. To date, these concern only amphibian and fish. We report here a study on the embryonic development of Pleurodeles waltl (urodele amphibian) eggs oviposited in microgravity. The experiment was performed twice on board the Mir space station and the data obtained included video recording and morphological, histological and immunocytological analyses. The data confirm that the microgravity conditions have effects during the embryonic period, particularly during cleavage and neurulation, inducing irregular segmentation and abnormal closure of the neural tube. Moreover, we observed several abnormalities hither to undescribed corresponding to cortical cytoplasm movements, a decrease of cell adhesion and a loss of cells. These abnormalities were temporary and subsequently reversible. The young larvae that hatched during the flight displayed normal morphology and swimming behavior after landing. The results obtained in the urodele Pleurodeles waltl are in accordance with those observed earlier in the anuran Xenopus laevis and in the fish Oryzias latipes.

Tous droits réservés © Service social, 2002Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne. Résumé de l'article La naissance d'un enfant apporte dans chaque famille son lot de modifications significatives. Cette transition qui exige une adaptation importante est souvent associée à une plus grande vulnérabilité. Or, cette vulnérabilité peut être exacerbée par des circonstances particulières, dont celles qui découlent de l'expérience migratoire. Les équipes multidisciplinaires d'intervenantes peuvent-elles tenir compte de cette double réalité dans leur évaluation pour les services intégrés de soin de santé en périnatalité? Cette recherche a abordé ces questions en deux temps. D'abord par une étude exploratoire auprès de mères immigrantes (n = 91) en période périnatale afin d'explorer les relations entre les circonstances migratoires et les conditions de vie parentales, puis auprès d'intervenantes (n = 19) afin de saisir les facettes implicites du processus décisionnel qui les amène à diriger ou non vers la ressource appropriée une mère jugée vulnérable. Cette double perspective, complémentaire, propose un éclairage nouveau sur la dynamique particulière qui se dégage de l'expérience simultanée de la migration et de la maternité.

The FERTILE experiment was twice performed onboard the Mir space station during the Cassiopée and Pégase French space missions. The goal was to analyze the effects of microgravity on fertilization and embryonic development, and then on further development on the ground in the amphibian Pleurodeles waltl. The present paper reports development that occurred in the laboratory after landing. Recovered on the ground at the hatching stage, young larvae reared at room temperature underwent metamorphosis and became adults without obvious abnormalities. Of particular interest was the rearing temperature that induced a delayed metamorphosis for animals from the Cassiopée space mission, but not for animals from the Pégase mission. The rate of development and the morphology were analogous in these animals and in ground controls reared in a similar annual period. Analysis of offspring was performed using these animals. Males born in space were first mated with control ground-born females and then with females born in space. The mating gave progeny that developed normally. Depending on the methods used and on the limits of the analyses, the results clearly demonstrated that animals born in space were able to live and reproduce after return to the ground.