小鼠卵母细胞体外成熟及受精过程中细胞核的时空变化规律

用电镜方法研究小鼠卵母细胞的发育及受精虽然已有很多报道，但大多数是有关细胞质、尤其是皮质颗粒、高尔基复合体及线粒体的形态及分布变化的。从卵母细胞体外成熟培养、第一次减数分裂恢复到受精后第二次减数分裂完成，细胞核经历了复杂的变化，有关的系统研究却很少。本实验详细地研究了小鼠卵母细胞体外成熟及受精过程中两性生殖细胞内细胞核的时空变化规律。从卵巢中采集生发泡（ＧＶ）期卵母细胞，进行体外成熟培养，经超排获得的成熟卵母细胞去卵丘和透明带后，用于体外受精。于体外成熟培养及受精后的不同时间，用光镜及电镜方法观察细胞核变化及极体排放。结果表明，尽管大多数卵母细胞在体外培养２至４小时生发泡破裂（ＧＶＢＤ），但有１３．６％在培养８小时后仍处于ＧＶ期（图１）。电镜观察揭示，不发生ＧＶＢＤ的卵母细胞核的核仁由颗粒性纤维成分、空泡及纤维中心组成。有时核仁表面有空泡。只有核仁完全致密化、核仁周围有核仁相随染色质分布时，卵母细胞才获得恢复减数分裂的能力。ＧＶＢＤ发生时，随着核仁相随染色质向核膜侧扩散迁移，核仁越来越小；与此同时，核膜打折，染色质团块中央出现电子致密的芯。核仁的消失早于核膜的破裂，提示核仁成分可能参与核膜打折及破裂，体外培

Chronological and Morphological Progression of Nucleus during Mouse Oocyte Maturation and Fertilization in vitro

The chronological and morphological changes of the nucleus during mouse oocyte maturation and fertilization were systematically studied. Although most oocytes went through GVBD 2-4 hrs after culture, 13.6% remained at GV stage 8 hrs after culture.TEM observation revealed that nucleoli of oocytes which failed to go through GVBD were composed of fibrillar-granular component,small vacuoles and fibrillar centers or showed small vacuoles on nuclear surface. During GVBD, the nucleoli became smaller and smaller and finally disappeared with the nuclear-associated chromatin dislocated to the periphery. Nuclear membrane with attached chromatin became folded and electronic dense cores appeared in the center of chromatin clumps at the same time.The last event of GVBD was the disruption of nuclear membrane.At the end of the 5th hr after culture, meiosis progressed to prometaphase I.Chromosomes,distributed in the original GV area free of organelles,were surrounded by large quantity of mitochondria and small SER vesicles. At the end of the 12th hr after culture,48. 1% of the oocytes emitted PB1.Decondensing sperm head and early male pronuclcus(mPN)with condensed nucleoli were found 1-2 hrs after insemination.The formation and enlargement of female PN(fPN) occurred a little earlier than that of mPN. 33.3% finished syngamy at 8-9 hrs after insemination.The process of nucleolus formation was reverse to that in GVBD. The oolemma modification caused by cortical reaction could effectively inhibit polyspermy.in contrast,there were sperm binding to the oolemma where CGs failed to be released. In addition, PB2 was emitted 2-5 hrs after insemination. The difference between PB1 and PB2 as well as the abstriction of polar body were also discussed.