Detection of microtubule-forming capacity of the centrosome reveaed by its transplantation at meiosis and mitosis

为了研究第一次和第二次成熟分裂和第一次卵裂的差异，我们将每个分裂的中心体移植到海星成熟的卵母细胞或受精卵中。在合子中，从每个分裂中分离出来的中心体形成一个胚珠，诱导细胞质分裂，最终收到的合子在第一次卵裂后分裂成三个卵裂球。从任何分裂中分离出来的中心体也在成熟的细胞中形成了一个星座。然而，PLAR小体挤出总是正常发生的，即在受体卵母细胞中额外形成的星形胶质细胞从未诱导胞质分裂。用己二醇(HG)稳定有丝分裂原，结果表明，成熟后的原细胞体积比第一次卵裂时的小，用Clcemid处理后，第一次卵裂时的原细胞体积缩小，但不能产生胞质分裂。因此，在成熟和卵裂过程中，中心体在Are形成方面没有功能上的差异，但所产生的Aster的大小决定了是否诱导细胞分裂。当成熟的卵母细胞用1%左右的HG处理时，所得到的第一极体(PB1)的大小增大，有时甚至分裂。随着其尺寸的增大，分裂率明显增加，直径为正常PB1的1.6倍的增大的PB1的比例达到50%。微管免疫荧光染色显示，增大的PB1s有类似于第二次减数分裂时的减数分裂结构。当PB1移植时，受体受精卵中诱导出额外的STER，并且随着时间的推移，STER的数量从1个增加到2个。这些结果表明，PB1中的头体可以复制，但不组织有丝分裂装备，而在扩大的PB1中出现了这种情况。

In order to investigate differences among the first and second maturation divisions and the first cleavage, we transplanted a centrosome at each division into maturating oocytes or zygotes of the starfish, A.pectinifera. In the zaygtes, the cenrosome deried from every divisions formed an aster, which induced cytokinesis, and eventually the reciient zygote divided nto three blastomeres after the first cleavage. The centrosome derved from any division also formed an aster in maturing ocytes. However, the plar body extrusion always occurred normally ; namely, an aster additionaly formed in the recipient oocyte never induced cytokinesis. Stabilizing the mitotic aster with hexylene glycol (HG) treatment demonstrated clearly that the size of the aster at maturation was smaller than that at the first clevage Asters reduced in size at the first cleavage with clcemid treatment failed in nducing cytokinesis. Therefore, it is concluded that the centrosome has no functinal differencein aster formatin among maturation and cleavage, and, however, that the size of the resultant aster determines whether or not cell division is induced.When maturing oocytes were treated with HG at about 1%, the resultant first polar body (PB1) increased in size and sometimes divided. The division rate clearly increased when their size became larger, and the rate of enlarged PB1 whose diameter was 1.6 times larger than that of normal PB1 reached 50%. Staining microtubules immunofluorescently revealed that there was the itotic apparatus similar to that at the secnd meiosis in enlarged PB1s. When PB1 was transplanted, additional asters were induced in the recipient zygote, and the number of asters increased frm ne to two with time after its extrusion. These results indicate that the ceentrosome in PB1 may duplicate, but does not organize the mitotic appaatus, which appeared in enlarged PB1.