Ultrastructural cytochemistry of the nucleus and nucleolus in growing rabbit oocytes.

Ultrastructural changes of the germinal vesicle during the growth of rabbit oocytes were studied by means of light and electron microscopy, 3H-uridine autoradiography, Ag-NOR staining and E-PTA staining. Particular interest was paid to the nucleologenesis and condensation of chromatin. In contrast to other mammalian species, chromosome condensation in rabbit oocytes occurred concomitantly with rRNA synthesis-dependent nucleolar compaction and preceded nuclear envelope breakdown and resumption of meiosis.