Oocyte activation and parthenogenetic development of bovine oocytes following intracytoplasmic sperm injection.
Development of bovine oocytes after intracytoplasmic sperm injection (ICSI) was investigated. Oocytes were matured for 24-26 h in vitro and injected with isolated sperm heads. When treated with 7% ethanol (v/v) for 5 min, 71.7% of ICSI oocytes were activated as shown by the resumption of meiosis and the formation of female pronuclei. However, 41.5% of injected sperm heads remained condensed at 18-20 h after injection into the ooplasm. The incidence of decondensing sperm and that of male pronuclei at this stage were 15.1% and 26.4%, respectively. A total of 55.5% of oocytes reached the 2-cell stage following sperm head injection and 54.7% after sham-ICSI; these percentages were not significantly different from those following in vitro fertilisation (IVF) (73.1%). The percentage of 2-cell embryos reaching the 8-cell stage following ICSI was 37.5%, and 27.6% after sham-ICSI, which were significantly lower (p < 0.01) than the equivalent percentage following IVF (62.4%). The percentages of parthenogenetic embryos reaching the 2-cell, 4-cell and 8-cell stages following ICSI were 56.4%, 48.9% and 30.0%, respectively. These results indicate that the low rate of normal embryonic development of bovine oocytes following ICSI is largely due to the parthenogenetic activation of the oocytes.
Li
X
X
Maebashi Institute of Animal Science, Livestock Improvement Association of Japan, Inc., Japan.
Hamano
K
K
Qian
X Q
XQ
Funauchi
K
K
Furudate
M
M
Minato
Y
Y
D000818:Animals; D002417:Cattle; D002875:Chromosomes; D002970:Cleavage Stage, Ovum; D005314:Embryonic and Fetal Development; D005260:Female; D008297:Male; D008858:Microscopy, Phase-Contrast; D009865:Oocytes / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D010312:Parthenogenesis / Q000502:physiology*; D013077:Sperm Head / Q000648:ultrastructure; D020554:Sperm Injections, Intracytoplasmic