Effect on fertilization and development by re-culture after freezing and thawing of bovine oocytes matured in vitro.
This study evaluated the effect of 6-h repeat culture before insemination of frozen-thawed, in vitro-matured oocytes on their fertilizability and developmental capacity. Immature oocytes were cultured for 18 h or 24 h and were frozen incrementally. Post-thaw oocytes were repeat cultured for 0 h (control) or 6 h before insemination. With fertilizability, the proportion of enlarged sperm head was significantly (P<0.05) higher in oocytes cultured for 24 h without repeat culture (24:0 h; 51.8%) than those cultured for 24 h with repeat culture (24:6 h; 26.1%) and nonfrozen oocytes (25.9%). However, the proportion of male pronucleus (MPN) in the group of 24:0 h (32.4%) was significantly (P<0.05) lower than that of nonfrozen oocytes (64.3%); the formation of the female pronucleus and MPN were also significantly (P<0.01) lower (17.2%) than that of nonfrozen oocytes (56.1%). Polyspermic oocytes cultured for 18 h with repeat culture for 6 h (18:6 h) were significantly (P<0.05) higher (47.5%) than for nonfrozen oocytes (25.6%). Development to 8-cell stage in the group of 18:6 h was significantly (P<0.05) lower (1.6%) than that of nonfrozen oocytes (18.5%). The cleavage rates in the groups of 24:0 h (16.3%) and 24:6 h (23.4%) were also significantly (P<0.05) lower than for nonfrozen oocytes (63.3%). Development to blastocysts was low (3.9%), but hatched blastocysts were observed in frozen-thawed oocytes cultured for 18:0 h. These results indicate the post-thaw 6-h repeat culture did not greatly improve the fertilizability and embryonic development of oocytes cultured for 18 h or 24 h before freezing. Frozen-thawed oocytes after 24 h in vitro maturation without repeat culture especially had impaired capacities for fertilizability and development.
Asada
M
M
Laboratory of Animal Genetics and Reproduction, Obihiro University of Agriculture and Veterinary Medicine, Japan.
Fukui
Y
Y
D000818:Animals; D001755:Blastocyst / Q000502:physiology; D002417:Cattle / Q000502:physiology*; D018929:Cell Culture Techniques; D004396:Coloring Agents / Q000737:chemistry; D015925:Cryopreservation / Q000592:standards / Q000662:veterinary*; D003451:Cryoprotective Agents / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary*; D016014:Linear Models; D008297:Male; D008858:Microscopy, Phase-Contrast / Q000662:veterinary; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D010078:Oxazines / Q000737:chemistry; D013094:Spermatozoa / Q000502:physiology
D004396:Coloring Agents; D003451:Cryoprotective Agents; D010078:Oxazines; C018437:aceto-orcein