猪多精受精的超微结构研究

AN ULTRASTRUCTURAL STUDY ON THE POLYSPERMIC FERTILIZATION IN THE PIG

应用发情期正常的哈尔滨自猪、杜哈猪和长杜哈母猪共6头。在交配后24小时、2天和3天分别取输卵管、子宫角,用杜氏磷酸缓冲液冲出胚胎。用扫描电镜和透射电镜,观察58个处于1～4细胞期和桑椹期胚胎。用蛋白酶除去1细胞期的透明带,观察细胞表面结构。扫描电镜观察结果证明,1.合子期细胞表面有许多密集的微绒毛,微绒毛之间见有精子头部附着,其顶体消失,头、尾部均被微绒毛包围,精子头部赤道区的质膜尚完整;2.在2细胞期的透明带外表面,有大量精子,有的已斜穿透明带;3.4细胞期的透明带仍可见到穿入的精子。4.桑椹胚透明带表面则仅见少量精子。用透射电镜观察连续超薄切片,发现在1细胞和4细胞阶段,各卵裂球内均可见到精子头部,其染色质仍处于凝聚状态。此外,在4细胞期各细胞的胞质内,可见到精子头部被包在吞噬泡内。4细胞期仍见有精子直接穿入卵裂球内。上述结果表明,猪虽有多精受精现象,但并不影响受精卵的早期分裂。卵裂球对进入的多余精子有自身清除能力。

58 embryos at 1, 2, 3 and 4 cell and morula stage were recovered from the oviduct and the uterine horn of the Ha-bai, Du-ha and Du-chang-ha pigs, 24 hours, 2 or 3 days of pregnancy, and were observed with SEM and TEM. The zona pellucida of 1 cell embryo was removed by treatment with 2.5％ pronase for visualization of the cell surface structure.The findings are as follows:1. The surface of the 1 cell stage embryo was densely populated with microvilli and sperm can be found on the surface with its head and tail surrounded by the microvilli and its plasma membrane of the equatorial segment of acrosome intact.2. Many spermatozoa were observed both on the surface and inside the zona pellucida of the 2 celled embryo.3. By the 4 cell stage, some of the spermatozoa had penetrated through the zona and got into the perivitelline space. 4. There were still some spermatozoa on the zona surface of the morula.5. The TEM observation revealed that the heads of supernumerary sperm were located within the cytoplasm of the blastomeres of the embryos from 1 to 4 cell stages and still not decondensed. Some of these sperm heads were actually found within the phagocytic vacuoles of the 4 celled embryos. The ultrastructure of these polyspermic embryos was normal.These results showed that polyspermy in the pig did not intefere with the cleavage of the embryo and the embryo possessed the ability to dispose the excessive sperms.