RESUMO
Insulin pathways were demonstrated from invertebrates to vertebrates to be involved in the regulation of numerous processes including storage metabolism and reproduction. In addition, insulin system may integrate variations of environmental conditions like dietary restrictions. In the Pacific oyster Crassostrea gigas, reproductive and storage compartments are closely intricated in the gonadal area and their respective development was found to be dependant of trophic conditions. For these reasons, C. gigas is an original and interesting model for investigating the role of insulin control in the balance between storage and reproduction and the integration of environmental parameters. On the basis of sequence conservation, we identified three potential elements of the oyster insulin pathway, Ras, Pten and p70S6K and we investigated their expression levels in various tissues. In the gonadal area, we used laser microdissection in order to precise the targeted contribution of insulin signaling to the restoration of storage tissue and to the control of vitellogenesis. Food deprivation during gametogenesis reinitiation stage led to reduced proliferations of gonia and also to modulate insulin signal by transcriptional activation of insulin pathway elements.
Assuntos
Crassostrea/genética , Insulina/metabolismo , PTEN Fosfo-Hidrolase/genética , Proteínas Quinases S6 Ribossômicas 70-kDa/genética , Proteínas ras/genética , Sequência de Aminoácidos , Ração Animal , Animais , Crassostrea/metabolismo , Meio Ambiente , Feminino , Privação de Alimentos/fisiologia , Gônadas/fisiologia , Masculino , Dados de Sequência Molecular , PTEN Fosfo-Hidrolase/metabolismo , Proteínas Quinases S6 Ribossômicas 70-kDa/metabolismo , Homologia de Sequência de Aminoácidos , Transdução de Sinais/fisiologia , Ativação Transcricional/fisiologia , Vitelogênese/fisiologia , Proteínas ras/metabolismoRESUMO
The aim of this study is to describe the early stages of spermatogenesis of the Pacific oyster Crassostrea gigas using both light and electron microscopy. The gonad is formed by gonadal tubules invaginated in a connective tissue constituting a storage tissue. Myoepithelial cells surround each gonadal tubule and are associated with an acellular matrix delimiting the outer part of the tubule, the inner part is composed by intragonadal somatic cells associated with germinal lineage. Two types of spermatogonia are identified, where type I spermatogonia (Spg I) are large, scarce and pale cells leaned against the base of the tubule (nuclear diameter: 5.5+/-0.5 microm). Type II spermatogonia (Spg II) are clustered and dark cells which appear smaller than type I (nuclear diameter: 4.3+/-0.3 microm). The aspect of nuage-like material in cytoplasm is described from pale spermatogonia to primary spermatocytes (nuclear diameter: pachytene 3.6+/-0.3 microm, diplotene 3.4+/-0.3 microm), while no structure related to a chromatoid body was observed in oyster spermatocytes and spermatids.
Assuntos
Crassostrea/citologia , Gônadas/citologia , Gônadas/ultraestrutura , Espermatogênese , Animais , Crassostrea/embriologia , Gônadas/embriologia , Masculino , Meiose , Espermatogônias/citologia , Espermatogônias/ultraestruturaRESUMO
Immunological detection of glucagon-like peptides was performed in the cerebral ganglia of the mussel Mytilus edulis using an anti-vertebrate glucagon antibody. Two clusters of positive neurosecretory cells were observed, as well as stained nervous fibers. The effect of vertebrate glucagon on glucose incorporation into glycogen of reserve cells was tested using an in vitro microplate bioassay. Optimal incubation conditions were previously defined and an inhibitory effect of porcine glucagon was obtained for concentrations ranging from 10(-6) to 10(-9)M. It is postulated that the glucagon-like peptide may be implicated in the regulation of glucose metabolism in bivalves.