Hyttel P, Xu K P, Greve T
Department of Anatomy, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
Anat Embryol (Berl). 1988;178(1):41-6. doi: 10.1007/BF00305012.
Cumulus-oocyte complexes were collected from cows at an abattoir by aspiration from small (1-6 mm) follicles. The complexes were matured in vitro for 28 h. Subsequently, the cumulus cells and the zona pellucida were removed by enzyme treatment in a proportion of the complexes (zona-free ova). Both cumulus-enclosed and zona-free ova were inseminated in vitro and processed for scanning electron microscopy after different periods of culture. In the cumulus-enclosed ova the number of spermatozoa attached to and penetrating into the cumulus investment increased with increasing culture time. Practically all spermatozoa displayed intact acrosomes. In the zona-free ova clusters of spermatozoa attached to the ovum surface, and at 5 h a proportion of the spermatozoa had undergone the acrosome reaction, and their internalization into the ooplasma was initiated. The acrosome reaction was characterized by an increasing fenestration of the membrane coverings of the acrosomal region of the sperm head. During the sperm head internalization, where the ovum microvilli appeared to contact especially the equatorial segment and the postacrosomal region, the sperm head gradually disappeared from the ovum surface, and the microvilli at the site of internalization became more bulbous. Simultaneous abstriction of the second polar body was seen in some ova.
卵丘-卵母细胞复合体从屠宰场的母牛中通过从小（1-6毫米）卵泡抽吸获得。复合体在体外成熟28小时。随后，在一部分复合体（裸卵）中通过酶处理去除卵丘细胞和透明带。卵丘包被的卵和裸卵均在体外受精，并在不同培养时间后进行扫描电子显微镜处理。在卵丘包被的卵中，附着并穿透卵丘的精子数量随着培养时间的增加而增加。几乎所有精子都显示顶体完整。在裸卵中，精子簇附着在卵表面，在5小时时，一部分精子发生了顶体反应，并开始内化进入卵质。顶体反应的特征是精子头部顶体区域的膜覆盖物出现越来越多的窗孔。在精子头部内化过程中，卵微绒毛似乎特别接触赤道段和顶体后区域，精子头部逐渐从卵表面消失，内化部位的微绒毛变得更加膨大。在一些卵中可见第二极体同时排出。
