| Studies have demonstrated that the ability of in vitro matured (IVM) oocytes is far less than that of in vivo-matured (IVO) oocytes. In vitro, when oocytes are removed from follicles, they accomplish nuclear maturation quickly with insufficient cytoplastic maturity, and this may lead to the low developmental competence of IVM oocytes. Recently, to improve the quality of IVM oocytes, attempts were made to prevent precocious meiotic resumption and allow for adequate cytoplastic maturation in vitro. However, no report on this has so far been published in goats. In this study, ROS and BL-I, two specific and potent inhibitors of M-phase promoting factor (MPF) kinase activity, were used to block germinal vesicle breakdown (GVBD) of goat oocytes. The result are summarized as follows:1. Both drugs were effective and their action was dose-dependent. Regimens of 200 μM ROS, 100 μM BL-I, 100 μM ROS + 6.25 μM BL-I and 50 μM ROS + 25 μM BL-I blocked , respectively, 78.4%, 80.9%, 80.3% and 77.8% of oocytes in germinal vesicle (GV) stage during a 24-h culture period.2. Almost all (81.3%, 81.9%, 83.2% and 85.2%) of the inhibited oocytes resumed meiosis and reached the metaphase II (MII) stage after a further 24-h culture in maturation medium. When the matured oocytes after inhibition were activated with ionomycin and 6-DMAP, activation rates in the 4 treatment groups were 93.3%, 96.2%, 92.5% and 90.5% and not different (P>0.05) from that (97.8%) of control group. However, rates of cleavage and morulae of activated oocytes after inhibition were lower (P<0.05) than those of control oocytes. Cumulus expansion was also inhibited and the inhibitory effect was not reversible.3. After 8h inhibition by 200 uM ROS, cumulus expansions were fully reversible, and the rates of cleavage and morulae/blastocysts of activated oocytes were the same as those of control. After 16h inhibition, cumulus expansions were only partly reversible. The rate of cleavage was not affected, but the rate of morulae decreased and there was no blastocysts yielded.4. After inhibition, the GV chromatin configurations were different. After 8-h inhibition, GV2n, GV2c decreased and GV3n increased, GV3n was the dominant configuration. While after 24h inhibition, GV2n, GV2c, GV3n decreased and GV3c,GVBD increased, GV3c was the dominant configuration instead of GV3n.5.The inhibiting dose of ROS on DOs was higher than that on COCs. When DOs were inhibited with COCs or co-cultured with the cumulus cells after inhibition, cumulus cells could improve the maturation of goat DOs.6. The block rate of COCs was decreased from 75.5% to 44.3% when PMSG was added to the inhibition medium. However, addition of PMSG had no effect on block rates of DOS.7. Kinetics of maturation were accelerated after ROS removal, and the acceleration was more pronounced after 24 h of inhibition than after 8 h.8. Inhibition increased significantly the maturation competence and embryo development of goat oocytes isolated from small antral follicles, and the improvements were duration dependent.Han Dong, Animal Histology and Embryology Advisor: Pro. Tan Jinghe...
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