A cytochemical and ultrastructural analysis of in vitro maturation in amphibian oocytes

Changes undergone during the in vitro maturation of oocytes from 8 different amphibian species have been followed by cytochemical methods (Unna staining, Feulgen reaction, PAS reaction). Critical stages of maturation in Xenopus laevis have been studied by electron microscopy. Attention has been mainly focused on two types of structures: 1. 1. Large basophilic bodies, rich in RNA and glycogen, which form or accumulate at the basal end of the nuclear membrane under hormonal stimulation. They probably correspond to polysomal aggregates and they seem directly involved in the rupture of the germinal vesicle. When the basal nuclear membrane begins to open, the nuclear sap becomes invaded by ribosomes and glycogen and later on by mitochondria and small yolk platelets. 2. 2. Feulgen positive bodies, which correspond to the nucleolar organizers: they appear at the basal end of the nuclear membrane when the latter begins to break down. Later, they move toward the egg cortex, where they ultimately vanish. The effects of actinomycin, puromycin, cycloheximide, and hydroxyurea on the formation of these two kinds of nucleic acid-containing bodies have been studied. The significance of these observations is discussed. © 1970.Journal ArticleSCOPUS: ar.j