MORPHOLOGICAL AND FUNCTIONAL-CHANGES ACCOMPANYING THE ACQUISITION OF MEIOTIC COMPETENCE IN OVARIAN GOAT OOCYTE

In order to determine at which follicular size goat oocytes were capab le of resuming and completing meiosis, we evaluated their ability to m ature in vitro and measured their maturation promoting factor (MPF) ac tivity by histone H1 kinase assay. The results indicated that goat ooc yte meiotic competence developed progressively in follicles ranging fr om 0.5 to 3 mm; the oocytes acquired the ability to resume meiosis in follicles of 0.5-0.8 mm, to reach metaphase I (MI) in follicles of 1-1 .8 mm, and to reach metaphase II (MII) in follicles larger than 3 mm. The presence of MPF activity was first observed in oocytes arrested at early prometaphase I and reached a maximum level in oocytes blocked i n metaphase I (MI). In the second part of this study, RNA synthesis an d nucleolar changes were analyzed during the growth period. The acquis ition of meiotic competence was accompanied by nucleolar compaction an d a dramatic decrease in RNA synthesis. Changes in protein patterns we re also analyzed, but only slight differences were observed among oocy tes from the different classes. (C) 1994 Wiley-Liss, Inc.