| dc.description.abstract |
The present study examined the time-dependent effects of follicular cells onthe fertilizability of oocytes and their subsequent development toblastocysts. The percentages of oocytes reaching the metaphase-II stage ofmaturation rose from 51·3% after 16 h of culture to86·2% at 28 h (cumulus-intact oocytes; CIO) and, for the sametime points, from 65·4% to 83·3% (corona-enclosedoocytes; CO) and 54·3% to 88·9% (denuded oocytes;DO), respectively. When DO were cultured for more than 24 h beforeinsemination, fertilization rates were significantly lower compared with CIOand CO. The maximum rates of development to blastocysts were observed when theoocytes were cultured for 24 h in the CIO group (22·1%), 20 h inthe CO group (19· 7%) and 18 h in the DO group(9·2%), respectively. These results suggest that(i) the presence of cumulus cells or corona cells duringmaturation is not necessary for nuclear maturation of oocytes;(ii) the attachment of corona cells to the oocytesduring maturation is important for the further development to the blastocyststage, and (iii) the presence of attached cumulusand/or corona cells during maturation in vitroextends the maturation period required for further development to theblastocyst stage. |
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