Nomura A, Maruyama Y K, Yoneda M
Department of Zoology, Faculty of Science, Kyoto University, Japan.
Dev Biol. 1991 Feb;143(2):289-96. doi: 10.1016/0012-1606(91)90079-i.
Starfish oocytes or eggs were inseminated at various times between first prometaphase and pronuclear stage, and were subsequently labeled with the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU) in order to detect the onset of DNA synthesis phase (S phase) during the first cell cycle using a monoclonal antibody against BrdU. The interval between fertilization and the first S phase was found to be constant (30-45 min, depending on batches) in eggs fertilized after formation of the first polar body. Eggs fertilized before first polar body formation, however, always entered the S phase 10-20 min after the second polar body formation. On the basis of these observations we conclude that (i) the chain of events triggered by fertilization, collectively called "postactivation process" for the first S phase, goes on in parallel with the process of maturation and (ii) only the final step of the postactivation process is arrested until the termination of meiosis. In eggs that had been fertilized before the first polar body formation, the female and male pronuclei exhibited uniformly distributed chromatin soon after the second polar body formation. In eggs that had been fertilized after the second polar body formation, however, the chromatin of the pronuclei remained fibrillar even during the S phase. Thus full decondensation of chromatin appears to depend on a certain advance in the postactivation process.
在第一次前中期和原核期之间的不同时间，对海星卵母细胞或卵子进行受精，随后用胸腺嘧啶类似物5-溴-2'-脱氧尿苷（BrdU）进行标记，以便使用抗BrdU单克隆抗体检测第一个细胞周期中DNA合成期（S期）的开始。在第一极体形成后受精的卵子中，受精与第一个S期之间的间隔被发现是恒定的（30 - 45分钟，取决于批次）。然而，在第一极体形成前受精的卵子，总是在第二极体形成后10 - 20分钟进入S期。基于这些观察结果，我们得出结论：（i）受精引发的一系列事件，统称为第一个S期的“激活后过程”，与成熟过程并行进行；（ii）激活后过程的最后一步直到减数分裂结束才会停止。在第一极体形成前受精的卵子中，第二极体形成后不久，雌、雄原核就呈现出均匀分布染色质。然而，在第二极体形成后受精的卵子中，即使在S期，原核的染色质仍保持纤维状。因此，染色质的完全解聚似乎取决于激活后过程的一定进展。
