Cinemicrographic analysis of cytoplasmic and nuclear events associated with germinal vesicle breakdown in rat oocytes exposed to LH in vitro.

Cinemicrography, with Nomarski differential interference optics, was used to study the motion of cytoplasmic organelles and events leading to germinal vesicle breakdown (GVB) in rat oocytes perfused with a defined medium with or without LH. Initially, cytoplasmic organelles, 0-3--1-5 micrometer diam., appeared to move randomly and were uniformly distributed. A gradually increasing vigour of organellar movement, saltatory translocation of organelles and discontinuous convergent flow of groups of organelles around the nucleus were observed. Ultimately, most of the organelles, which possessed several properties indicative of lysosomes, accumulated around the nucleus. In the presence of 5--6 micrograms LH/ml perfusate, GVB was usually complete by 80 min, whereas in the absence of hormone, or in the presence of LH + antiserum to LH, GVB took up to 130 min. A sudden slight decrease in nuclear size, undulating activity in the nuclear envelope, and the appearance of intranuclear filaments indicated imminent GVB. The appearance of spherical bodies at the nucleolar surface, and the subsequent mobilization and collapse of the nucleolus in the nucleoplasm, were advanced events in the nuclear response. It is suggested that LH promotes GVB trought activation of lysosomes.