Okada A, Yanagimachi R, Yanagimachi H
J Submicrosc Cytol. 1986 Apr;18(2):233-47.
The distribution and behavior of cortical granules (CGs) in hamster oocytes at various stages of maturation were examined using both light (phase-contrast) and electron microscopy. At the germinal vesicle stage, CGs were distributed almost evenly in the cortex of the oocyte. A 'small' CG-free area of the cortex, with prominent cytoplasmic protrusions, appeared twice during the progression of meiosis. The first time, immediately above the metaphase spindle of the first meiosis and secondly, above the metaphase spindle of the second meiosis. Both peripheral migration and exocytosis of CGs appeared to be responsible for the formation of CG-free cortex above the metaphase spindle of first meiosis. The development of CG-free cortex above the metaphase spindle of the second meiosis was definitely due to exocytosis of CGs. The CG-free cortex above the metaphase spindle of the second meiosis increased its size steadily even after the oocytes had been transported into oviducts. Concomitantly, the size of the perivitelline space increased. The enlargement of the perivitelline space in unfertilized oviductal oocytes seems to be attributed not only to the exocytosis of CGs, but also to an extrusion of non-CG materials by the oocytes and perhaps an accumulation of some materials secreted by the oviduct epithelium. The limited (premature) CG-exocytosis during oocyte maturation and prior to fertilization may alter the physico-chemical properties of the zona pellucida slightly in such a way that the zona can be penetrated only by a very 'strong' spermatozoon. The presence of the perivitelline space in the mature oocyte prior to fertilization seems to be essential or at least beneficial to normal fertilization. Distinct cytoplasmic protrusions appear on the cortex above the metaphase spindle. The plasma membrane covering these protrusions seems to represent the membrane synthetized by the oocyte in preparation for the extrusion of polar body.
利用光学（相差）显微镜和电子显微镜，研究了仓鼠卵母细胞在不同成熟阶段皮质颗粒（CGs）的分布和行为。在生发泡期，CGs几乎均匀地分布在卵母细胞的皮质中。在减数分裂过程中，皮质出现了一个“小”的无CGs区域，伴有明显的细胞质突起，出现了两次。第一次，在第一次减数分裂中期纺锤体的正上方；第二次，在第二次减数分裂中期纺锤体的上方。CGs的外周迁移和胞吐作用似乎都与第一次减数分裂中期纺锤体上方无CGs皮质的形成有关。第二次减数分裂中期纺锤体上方无CGs皮质的形成肯定是由于CGs的胞吐作用。即使在卵母细胞被转运到输卵管后，第二次减数分裂中期纺锤体上方无CGs皮质的大小仍在稳步增加。与此同时，卵周隙的大小也在增加。未受精输卵管卵母细胞中卵周隙的扩大似乎不仅归因于CGs的胞吐作用，还归因于卵母细胞对非CG物质的挤出，也许还有输卵管上皮分泌的一些物质的积累。卵母细胞成熟期间和受精前有限的（过早的）CGs胞吐作用可能会轻微改变透明带的物理化学性质，使得只有非常“强壮”的精子才能穿透透明带。受精前成熟卵母细胞中卵周隙的存在似乎对正常受精至关重要或至少是有益的。在中期纺锤体上方的皮质上出现明显的细胞质突起。覆盖这些突起的质膜似乎代表了卵母细胞为排出极体而合成的膜。
