Mita I, Satoh N
J Exp Zool. 1982 Sep 20;223(1):67-74. doi: 10.1002/jez.1402230111.
The aim of this study is to explore the control mechanism which regulates the timing of gastrulation. We wished to know whether the timing is rigidly determined within the constituting cells of the embryo of whether it is changed by intercellular communication systems. Starfish-fused double-embryos were formed by contact between pairs of denuded eggs with different cleavage schedules, one egg in each pair being distinguished with vital stain. Electron microscopy revealed identical ultrastructural characteristics in every cell contact: Septate junctions were found not only between cells in the contact area between the two counterparts constituting a fused embryo but also between cells within a counterpart. In fused embryos formed from stained eggs and unstained eggs with the former having started the first cleavage 30 min earlier than the latter, the stained counterparts began to invaginate about 30 min earlier than the unstained. When fused embryos were produced by putting stained eggs in contact with unstained eggs which had begun the first cleavage 2 hr later than the stained eggs, gastrulation of the stained counterparts took place about 2 hr earlier than that of the unstained counterparts. These results suggest that the timing of gastrulation is fixed within the cells of an embryo and cannot be altered in spite of the cell-to-cell communication that appears to exist.
本研究的目的是探索调节原肠胚形成时间的控制机制。我们想知道这个时间是在胚胎的组成细胞内严格确定的，还是会因细胞间通讯系统而改变。通过将具有不同卵裂时间表的一对去膜卵相互接触形成海星融合双胚胎，每对中的一个卵用活体染料进行区分。电子显微镜显示每个细胞接触处都有相同的超微结构特征：不仅在构成融合胚胎的两个对应部分的接触区域的细胞之间发现了分隔连接，而且在一个对应部分内的细胞之间也发现了分隔连接。在由染色卵和未染色卵形成的融合胚胎中，前者比后者早30分钟开始第一次卵裂，染色的对应部分比未染色的对应部分早约30分钟开始内陷。当通过将染色卵与比染色卵晚2小时开始第一次卵裂的未染色卵接触产生融合胚胎时，染色对应部分的原肠胚形成比未染色对应部分早约2小时。这些结果表明，原肠胚形成的时间在胚胎细胞内是固定的，尽管似乎存在细胞间通讯，但也无法改变。
