[Nucleolar vacuoles observed in rat oocytes]

Recently Merveille and al (1984) using light microscope have observed intranucleolar cavities in rat ovocytes from large antral follicles. They have showed that the frequency of these vacuoles increases when follicular growth is stimulated by gonadotropins. In this paper, the ultrastructure of the nucleolar cavities has been studied. Two types of cavities are visible in these nucleoli: 1. nucleolar "interstices" present at the periphery of the nucleoli in remnants of the granular component and of the dense fibrillar components; 2. nucleolar "vacuoles" which are located in the homogeneous substance forming the greatest part of the nucleolus. The nucleolar vacuoli generally are clear-cut and spherical. The density of their content is similar to the nucleoplasm but they don't communicate to the nucleoplasm. By means of cytochemical to detect Ag-NOR proteins (Ploton and al [1983]) and basic proteins (Sheridan and Barnett [1984]), dense fibrillar component of the nucleolus but no basic proteins may be seen in the wall of the cavity. Moreover no evidence of relation between the presence of the vacuoles and the process of follicular atresia has been found.