Bovine oocytes at the germinal vesicle stage were inseminated in Brackett and Oliphant's medium in the presence of BSA (10 mg ml -1), caffeine (5 mmol-1) and heparin (10 μg ml-1). When oocytes were transferred into tissue culture medium (TCM)-199 containing 10% fetal calf serum (FCS) with or without 6-dimethylaminopurine (6-DMAP; 2 mmol l-1) 8 h after insemination and cultured for 15-40 h at 39°C in 5% CO2 in air, 74-83% of oocytes were penetrated and polyspermy (67-80%) was common. At 40 h after culture in 6-DMAP-free medium, 65% and 63% of unpenetrated and penetrated oocytes, respectively, reached metaphase II or beyond. A few (6%) oocytes were activated and contained both male and female pronuclei. Sperm metaphase chromosomes were observed in 90% of the penetrated oocytes. Penetration by more than four spermatozoa greatly retarded the meiotic maturation of the oocyte. However, sperm chromosomes were never observed in oocytes cultured in 6-DMAP supplemented medium and oocyte maturation did not proceed beyond the stage of prometaphase I. These results demonstrate the possible participation of maturation-promoting factor in metaphase chromosome formation in spermatozoa.
|Number of pages||6|
|Journal||Journal of Reproduction and Fertility|
|Publication status||Published - 1993|
ASJC Scopus subject areas
- Developmental Biology
- Molecular Biology
- Obstetrics and Gynaecology