Kikuchi K, Nagai T, Ding J, Yamauchi N, Noguchi J, Izaike Y
Department of Genetic Resources II, National Institute of Agrobiological Resources, Ibaraki, Japan.
J Reprod Fertil. 1999 May;116(1):143-56. doi: 10.1530/jrf.0.1160143.
A large population (62-90%) of pig follicular oocytes can mature to metaphase II after culture for 48 h. However, a proportion (6-22%) remain in an immature stage at metaphase I (metaphase I-arrested). The main objective of this study was to determine whether the cytoplasm of metaphase I-arrested pig oocytes is capable of being activated by sperm penetration or parthenogenetic stimulation. After culture for 48 h, oocytes without a polar body (73% were shown to be at metaphase I after staining) and those with a polar body (94% were at metaphase II) were fertilized in vitro. A total of 69% and 62% of the oocytes were activated to form a female pronucleus, respectively, and the rate of polar body extrusion induced by fertilization in the activated oocytes was 90% (the first polar body) and 95% (the second polar body), respectively. When oocytes without and with a polar body were stimulated with an electric pulse, 53% and 81% of the oocytes were activated, respectively. The rate of polar body extrusion in the activated oocytes was 73% (the first polar body) and 79% (the second polar body), respectively. In contrast, young metaphase I oocytes cultured for 24 h had low (6%) or zero activation rate after in vitro fertilization or electric pulse stimulation. However, about one-third of the young metaphase I oocytes penetrated by spermatozoa after in vitro fertilization responded to electric pulse 12 h after insemination, and almost all (93%) were activated when they were stimulated 24 h after insemination. Patterns of polypeptide synthesis and histone H1 kinase activity were similar in metaphase I-arrested and metaphase II oocytes, and were characterized by increase in a 25 kDa polypeptide and by decrease in kinase activity. Although the first step of meiotic division is impaired, these results indicate that metaphase I-arrested oocytes are mature cytoplasmically.
大量（62% - 90%）猪卵泡卵母细胞在培养48小时后可成熟至减数第二次分裂中期。然而，仍有一部分（6% - 22%）停留在减数第一次分裂中期的未成熟阶段（减数第一次分裂阻滞）。本研究的主要目的是确定减数第一次分裂阻滞的猪卵母细胞的细胞质是否能够被精子穿透或孤雌激活。培养48小时后，没有极体的卵母细胞（染色后73%显示处于减数第一次分裂中期）和有极体的卵母细胞（94%处于减数第二次分裂中期）进行体外受精。分别有69%和62%的卵母细胞被激活形成雌原核，激活卵母细胞中受精诱导的极体排出率分别为90%（第一极体）和95%（第二极体）。当对没有极体和有极体的卵母细胞进行电脉冲刺激时，分别有53%和81%的卵母细胞被激活。激活卵母细胞中的极体排出率分别为73%（第一极体）和79%（第二极体）。相比之下，培养24小时的年轻减数第一次分裂中期卵母细胞在体外受精或电脉冲刺激后的激活率较低（6%）或为零。然而，体外受精后被精子穿透的年轻减数第一次分裂中期卵母细胞中，约三分之一在授精后12小时对电脉冲有反应，授精后24小时刺激时几乎所有（93%）都被激活。减数第一次分裂阻滞和减数第二次分裂中期卵母细胞中的多肽合成模式和组蛋白H1激酶活性相似，其特征是25 kDa多肽增加和激酶活性降低。尽管减数分裂的第一步受损，但这些结果表明减数第一次分裂阻滞的卵母细胞在细胞质上是成熟的。
