不同发情周期阶段和不同体积卵泡的卵母细胞对体外受精及其发育的影响

EFFECTS OF DIFFERENT OESTROUS STAGES OF OVARIES AND SIZES OF FOLLICLES ON THE GENERATION OF BOVINE EMBRYOS IN VITRO

根据母牛卵巢黄体发育状态将实验用卵巢相应地划分为早期黄体(ELP)、功能黄体(LP)和退化黄体(LLP)三个试验组(实验1);实验2则按实验卵巢上卵泡的表面直径大小划分为小于2mm,2～6mm 和大于6mm 三组.采用注射器抽取法采集卵泡里的卵母细胞,然后按 Lu 等报导的方法进行体外成熟培养和体外受精。受精卵继续在体外条件下培养到囊胚阶段。实验2还进一步观察了囊胚体外发育到孵化囊胚的比率。结果表明,来自不同发情周期阶段的牛卵母细胞,经体外成熟培养后,各组体外受精分裂率(74.3%～78.4%)及体外囊胚发育率(27.7%～31.3%)均无显著差异;而来自表面直径小于2mm 卵泡的卵母细胞,其体外受精分裂率和体外囊胚发育率均显著地低于2～6mm 及大于6mm 组(P<0.01);来自直径大于6mm 卵泡的卵母细胞受精后的早期胚胎体外囊胚发育率均显著高于其余两组(p<0.01)。表明卵泡及其卵母细胞在体内的发育程度对其后体外受精及早期胚胎进一步发育的能力只有一定的影响。

Two experiments were separately conducted to determine the effects of oestrous stages of ovaries and sizes of follicles on in vitro development of in vitro matured (IVM)and fertilized(IVF)bovine oocytes.Oocytes were aspirated from ovaries at three different stages(Exp.1,8 replicates):early luteal phase,luteal phase,and late luteal phase according to Leibfried and First and from different sizes of follicles (<2 mm,2-6 mm and>6 mm in diameter,Exp.2,7 replicates).IVM and IVF were performed using the same methods as previously described by Lu et al.At 42-46 h after insemination,cleavage was evaluated and 2-8 cell embryos were co-cultured with granulosa cell monolayers under the same conditions as used in IVM.Blastocysts(BL) were recovered at 6-9 days after insemination and some BL from Exp.2 were evaluated for their further development to hacthed stage.The results showed that the cleavage rate (74.3%-78.4%)and BL development rate(27.7%-31.3%)among the three different phases of ovaries did not differ(P>0.05).However,the cleavage rate of the oocytes from<2 mm follicles(67.7%)was significantly lower than those from the other two groups(P<0.01).Also,there were significant differences among the three different sizes of follicles in BL development(P<0.01),but not in the development from BL to hacthed stage(P>0.05);and the highest percentage of BL(53.6%)came from >6 mm follicles.These results demonstrate that there may not be any effect of oestrous stage on the developmental capacity of IVM-IVF bovine oocytes.It also indicates that ooeytes from small follicles(<2 mm)may be less developmentally competent.