Shimizu Takashi
Division of Biological Sciences, Graduate School of Science, Hokkaido University, 060, Sapporo, Japan.
Rouxs Arch Dev Biol. 1996 Feb;205(5-6):290-299. doi: 10.1007/BF00365807.
An antibody raised against a highly conserved peptide of γ-tubulin (Joshi et al. 1992) recognized a 50 kDa polypeptide in centrosomes in Tubifex embryos. Centrosomes labelled with this antibody are found at both poles of the first meiotic spindle and at the inner pole of the second meiotic spindle. At the transition to the second meiosis, there is no change in morphology of the centrosomes which are retained in the egg proper. In contrast, as the second meiosis proceeds from anaphase to telophase, centrosomes labelled with the antibody gradually become smaller, but are still recognized as tiny dots; each egg exhibits no more than one tiny dot. The first cleavage spindles exhibit a centrosome at one pole but not at the other. The spindle pole with a centrosome forms an aster which is inherited by the larger cell, CD, of the two-cell embryo; the centrosome-free spindle pole then becomes anastral and is segregated to a smaller cell AB. Centrosomes are present in the C and D cell lineages but not in the A and B lineages, at least up to the eighth cleavage cycle. During cleavage stages, centrosomes duplicate early in telophase of each mitosis, and their size changes in a cell cycle-specific fashion. Centrosomes which otherwise duplicate asynchronously in separate cells do so synchronously in a common cytoplasm. Centrosome duplication is inhibited by nocodazole but not by cytochalasin D. An examination of embryos treated with cycloheximide or aphidicolin also suggests that centrosome duplication during cleavages requires protein synthesis but no DNA replication per se. These results suggest that the centrosome cycle in Tubifex blastomeres is linked to the mitotic cycle more closely than is that in other animals.
一种针对γ-微管蛋白高度保守肽段产生的抗体（Joshi等人，1992年）在颤蚓胚胎的中心体中识别出一条50 kDa的多肽。用该抗体标记的中心体存在于第一次减数分裂纺锤体的两极以及第二次减数分裂纺锤体的内极。在向第二次减数分裂转变时，中心体的形态没有变化，它们保留在卵细胞本身中。相反，随着第二次减数分裂从后期向末期进行，用抗体标记的中心体逐渐变小，但仍可被识别为微小的点；每个卵细胞中不超过一个微小的点。第一次卵裂纺锤体在一极有一个中心体，另一极则没有。有中心体的纺锤体极形成一个星体，该星体由二细胞胚胎中较大的细胞CD继承；无中心体的纺锤体极随后变为无星的，并被分配到较小的细胞AB中。至少在第八次卵裂周期之前，中心体存在于C和D细胞谱系中，但不存在于A和B细胞谱系中。在卵裂阶段，中心体在每次有丝分裂末期早期复制，其大小以细胞周期特异性方式变化。原本在不同细胞中异步复制的中心体在共同的细胞质中同步复制。诺考达唑可抑制中心体复制，但细胞松弛素D则不能。用环己酰亚胺或阿非迪霉素处理胚胎的检查结果还表明，卵裂期间的中心体复制需要蛋白质合成，但本身不需要DNA复制。这些结果表明，颤蚓卵裂球中的中心体周期比其他动物中的中心体周期与有丝分裂周期的联系更为紧密。
