ORGANIZATION OF CYTOPLASMIC MICROTUBULES DURING MATURATION OF GOLDFISH OOCYTES

The organization of cytoplasmic microtubules during hormone-induced me iotic maturation of goldfish oocytes in vitro was examined by confocal immunofluorescence microscopy using an anti-tubulin antibody. The mic rotubule network was well distributed in fully grown immature oocytes. Once goldfish oocytes resumed meiotic maturation by a proposed matura tion-inducing hormone of this species (17 alpha, 20 beta-dihydroxy-4-p regnen-3-one, 17 alpha, 20 beta-DP), cytoplasmic microtubules serially re-organized. Soon after the onset of the germinal vesicle (GV) migra tion towards the animal pole, the former microtubule network disappear ed, followed by the appearance of a long perinuclear tail with high or dered microtubules extending from the vegetal surface of the GV. Incub ation of fully grown immature follilces in colcemid, an inhibitor of t ubulin polymerization, caused the disappearance of microtubules. Howev er, this treatment did not prevent either the 17 alpha, 20 beta-DP-ind uced migration of the GV or GVBD. Coincident with the breakdown of the GV (GVBD), numerous microtubules intruded into the GV from its vegeta l surface. Soon after GVBD, a disk-shaped ring consisting of microtubu le asters and a small ring with a radial array of microtubules in its center was observed at the animal pole region. In mature oocytes with meiotic spindles at the animal pole surface, cytoplasmic microtubules were concentrated in a small region around the animal pole showing com plicated microtubule arrays. The results presented define distinct cha nges in microtubule organization during the 17 alpha, 20 beta-DP-induc ed meiotic maturation of goldfish oocytes.