Saiki T, Hamaguchi Y
Biological Laboratory, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Japan.
Exp Cell Res. 1997 Nov 25;237(1):142-8. doi: 10.1006/excr.1997.3772.
The first polar body (FPB), which is formed at the first meiotic division during oogenesis, does not generally divide. We made a hypothesis that the amount of cytoplasm was not sufficient for the FPB to perform cell division, in spite of the same amount of genomes and centrosome as those of the secondary oocyte. To examine this hypothesis, hexylene glycol (HG) at a low concentration was applied to oocytes of the starfish Asterina pectinifera during the first meiotic division. Hence, FPBs were enlarged in their diameters, some of them divided once, and the division rate increased in proportion as their diameter extended. We further hypothesized that the difference between the second polar body (SPB) and the egg would be only the amount of cytoplasm and that if SPBs were enlarged, they would become eggs. When the secondary oocytes were treated with HG, large SPBs were obtained. Some of them, however, divided, and resultant daughter cells divided moreover, whereas eggs would not cleave unless they were fertilized. We discuss here the reason why the centrosome distributed during maturation division began to function in enlarged PBs.
第一极体（FPB）在卵子发生过程中的第一次减数分裂时形成，通常不再分裂。我们提出一个假设，尽管第一极体与次级卵母细胞具有相同数量的基因组和中心体，但由于其细胞质数量不足，不足以进行细胞分裂。为了验证这一假设，在第一次减数分裂期间，将低浓度的己二醇（HG）应用于多棘海盘车（Asterina pectinifera）的卵母细胞。结果，第一极体的直径增大，其中一些进行了一次分裂，并且分裂率随着直径的增大而成比例增加。我们进一步假设，第二极体（SPB）与卵子之间的差异仅在于细胞质的数量，并且如果第二极体增大，它们将变成卵子。当用HG处理次级卵母细胞时，获得了大型的第二极体。然而，其中一些进行了分裂，产生的子细胞还会进一步分裂，而卵子除非受精否则不会分裂。在此，我们讨论在成熟分裂期间分布的中心体为何在增大的极体中开始发挥作用的原因。
