RESUMO
In this study, we present evidence that neurogenic cells inhibit the differentiation of cardiogenic cells. When cells of the entire area pellucida at stage 5 were dissociated and reaggregated, the aggregates differentiated into neural tissues and other structures of any germ layer origin, except for heart tissues, despite the fact that the cardiogenic cells are already committed to differentiate. The phenomenon also occurs from stages 6 to 8, during which cells are in a higher state of commitment. Using combinations of different regions of the area pellucida, it was confirmed that neurogenic cells are responsible for the inhibition of cardiogenic cell differentiation. The inhibition is not species-specific because quail and chick neurogenic cells inhibit each other's cardiogenic cell differentiation. Direct contact between cardiogenic and neurogenic cells seems to be necessary for inhibition because cardiogenic cell differentiation takes place if cardiogenic and neurogenic cells are separated by a porous membrane. Dissociated neural tubes from early stages, but not dissociated telencephalon from 2-day-old chicks, also inhibit cardiogenic cell differentiation. These results suggest that neurogenic cells may sequester molecules necessary for the differentiation of cardiogenic cells rather than produce inhibitory molecules.
Assuntos
Coração/embriologia , Miocárdio/citologia , Sistema Nervoso/embriologia , Animais , Diferenciação Celular , Embrião de Galinha , Sistema Nervoso/citologia , Codorniz/embriologia , Especificidade da Espécie , Zona PelúcidaRESUMO
In vitro chondrogenesis is possible in the chick embryo from stage 4 of Hamburger and Hamilton (1951), only 18-19 hours of incubation, before somite formation. In stage 4 of Hamburger and Hamilton (1951) the chondroblasts are placed laterally to the primitive streak and notochord cells are not necessary for cartilage differentiation.
Assuntos
Cartilagem/embriologia , Diferenciação Celular , Gástrula , Animais , Células Cultivadas , Embrião de Galinha , Embrião de Mamíferos/citologia , Embrião não Mamífero , Idade Gestacional , Técnicas In Vitro , Morfogênese , Transplante HeterólogoRESUMO
Before the appearance of the morphological primordium of the nervous dissociated, reaggregate selectively "in vitro" and reach high levels of neural differentiation and organization. This property allows the experimental reproduction of the neural differentiation process. Before the appearance of the morphological primordium of the nervous system, its precursory cells carry the necessary information to put in action the basic characteristics of cell differentiation and structural organization, even isolated from the influence of mesoblastic cells.
