Evidence that cortical granule formation is a periovulatory event in marsupials

摘要: Formation of cortical granules was examined in superovulated oocytes from three marsupial species, brushtail possums (Trichosurus vulpecula) tammar wallabies (Macropus eugeniii) and grey short-tailed opossums (Monodelphis domestica) obtained during natural cycles Macropus eugenii. Superovulation induced by pregnant mares' serum gonadotrophin/gonadotrophin-releasing hormone (PMSG/GnRH) protocols ovulation removal pouch young. Oocytes were collected after ovariectomy or laparoscopically guided follicle aspiration into Hanks balanced salt solution (HBSS) supplemented with either 2.5% fetal calf (FCS) bovine albumin (BSA). Ovulated removing flushing the oviducts HBSS fixed immediately for electron microscopy. There no differences morphology timing formation between naturally cycling animals. Cortical absent germinal vesicle (GV) stage follicular before luteinizing (LH) surge all species. Dark granules, similar appearance to those seen eutherian mammals, found just beneath plasma membrane (9 per 100 microns membrane) preovulatory at vesicle, metaphase 1 anaphase stages. In addition, they contained a number less electron-dense (12 membrane). The cytoplasm rich Golgi complexes actively involved formation. Large numbers dark (90 only ovulated oocytes. A small lighter density also present This suggests that oocyte is following very different timetable granule accumulation mammals marsupials may not achieve cytoplasmic maturity until ovulation. significance these events fertilization development remains be established.