Comparative studies on early neural-type differentiation between isolated blastomeres of protochordate embryos and teratocarcinoma cell lines derived from mouse primitive ectoderm.

如前所述，当Halocynthia胚胎，原脊索动物，在早期发育阶段，1- 4-细胞，并进一步培养，直到正常的孵化时间，大的卵裂球的膜只表达表皮型兴奋性，而当卵裂停止后，8-细胞阶段，一些卵裂球显示神经型兴奋性。这种差异可能是由于8细胞期后卵细胞质因子的进一步分离和/或细胞间的相互作用造成的。在本项目中，一个单一的前动物卵裂球，其中包括假定的神经区域的8细胞胚胎，当解离，分裂逮捕和培养溶液中，分化完全表皮型判断膜兴奋性和免疫反应性。然而，当同一卵裂球与一个前植物卵裂球接触培养时，它显示出Na峰，其特征是Na和Na+。 关于我们 K通道，并且没有显示表皮抗原的表达，表明“神经诱导”在与单个相邻细胞相互作用期间导致单个细胞。前-动物卵裂球和前-植物卵裂球之间的这种诱导相互作用所必需的接触在接触变得无效之前和之后有一个关键时期，该时期在对照胚胎的64细胞期和中期原肠胚期之间。此外，一些代理人模仿诱导作用的前动物卵裂球被寻找和蛋白水解酶被发现开发Na尖峰完全相同的细胞-细胞接触诱导。最后，对哺乳动物胚胎系统和原脊索动物诱导系统进行了比较研究，并对来源于5日龄小鼠胚胎原始外胚层的克隆畸胎瘤细胞系的干细胞进行了化学诱导分化为神经元的研究。神经分化的早期阶段的特点是表达的钠通道，T型钙通道，和160 kD的神经丝蛋白在一个圆形的细胞没有轴突延伸。少

As previously reported, when the Halocynthia embryo, a protochordate, is cleavage-arrested at early developmental stages, 1- to 4-cell, and cultured further until the normal hatching time, the membrane of the large blastomeres expresses exclusively the epidermal-type excitability, while when cleavage-arrested after 8-cell stage, some of blastomeres show neural-type excitability. The difference can be caused by further segregation of egg cytoplasmic factors and/or cell-cell interaction after 8-cell stage. In the present project, a single anterior-animal blastomere which includes the presumptive neural region in the 8-cell embryo, when dissociated, cleavage-arrested and cultured in solution, differentiated exclusively to epidermal type judging from membrane excitability and immunoreactivity. However, when the same blastomere was cultured in contact with a single anterior-vegetal blastomere which includes the presumptive notochordal region, it displayed Na spikes, characterized by Na and … More K channels, and showed no expression of the epidermal antigen, suggesting "neural induction" resulted in a single cell during the interaction with a single neighboring cell. The contact necessary for this inductive interaction between an anterior-animal blastomere and an anterior-vegetal blastomere had a critical period before and after which the contact became ineffective and the period was between 64-cell stage and mid-gastrula stage of the control embryo. Further, some agents which mimic the inductive effects upon the anterior-animal blastomere were looked for and a proteolytic enzyme was found to develop Na spikes exactly identical with those induced by the cell-cell contact. Finally studying the mammalian embryonic system in comparison with the protochordate inductive system, the stem cells of cloned teratocarcinoma cell line derived from the primitive ectoderm of the 5 day mouse embryo was chemically induced to differentiate into neurons. The early stage of neural differentiation was characterized by expression of Na channels, T-type Ca channels, and 160 kD neurofilament protein in a round cell without neurite extension. Less