Effect of sperm penetration in vitro on completion of first meiosis by bovine oocytes arrested at various stages in culture.
Bovine oocytes cultured for 12-20 h in TC-199 were incubated for 24 h in fertilization medium, Brackett and Oliphant medium with bovine serum albumin (10 mg ml-1), caffeine (5 mmoll-1) and heparin (10 micrograms ml-1), with or without frozen-thawed spermatozoa. High penetration rates (93-96%) and significantly (P < 0.001) higher maturation rates were obtained in oocytes incubated with (93-100%) than without (62-72%) spermatozoa. However, when oocytes at the germinal vesicle stage were cultured for 44 h fertilization medium, maturation of oocytes to metaphase II was reduced. However, all oocytes that were first cultured for 20 h and further for 24 h with spermatozoa were penetrated and 40% of the penetrated oocytes reached metaphase II. All of the remaining oocytes that did not mature arrested at the stages of condensed germinal vesicle (39%) or prometaphase I (22%). These results indicate that oocytes at metaphase I at and after sperm penetration are stimulated by sperm penetration to complete maturation.
Chian
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RC
Division of Animal Science, Faculty of Agriculture, Okayama University, Japan.
Niwa
K
K
Nakahara
H
H
D000818:Animals; D002417:Cattle; D005260:Female; D005307:Fertilization in Vitro; D008297:Male; D008540:Meiosis / Q000502:physiology*; D008677:Metaphase; D009865:Oocytes / Q000166:cytology*; D009866:Oogenesis / Q000502:physiology*; D013084:Sperm-Ovum Interactions / Q000502:physiology*