Takasaki Hiroko
Department of Biology, Osaka Kyoiku University, Tennoji-ku, Osaka 543, Japan.
Dev Growth Differ. 1987 Apr;29(2):141-152. doi: 10.1111/j.1440-169X.1987.00141.x.
Using 32-cell Xenopus embryos series of extirpation experiments were performed in order to clarify whether or not the dorsal equatorial blastomeres were committed to differentiate to the axial mesodermal structures. First, these blastomeres designated as B1, B1', C1 and C1' and C1' were labeled using the technique of HRP injection or vital staining. They produce descendants which become localized in the organizer region of the early gastrula. These cells form the prechordal plate, notochord, somites, pharyngeal endoderm and neural tube at early neurula stage. The results of extirpation of the medial two or four of these blastomeres show that the entire head lacks or the tissues and organs of the head greatly reduce. This indicates that already at the 32-cell stage they have been committed to autonomously differentiate to form the axial mesodermal tissues of the head and that their roles in the head formation can neither be replaced nor complemented by any other blastomeres surrounding them. It is also shown that the vegetal yolk cells do not seem to play essential roles for development of the axial organs of the head. On the basis of the present results a view of establishment of the organizer of Xenopus eggs is proposed.
为了阐明赤道面背侧的卵裂球是否已确定分化为轴中胚层结构，利用32细胞期的非洲爪蟾胚胎进行了一系列切除实验。首先，用辣根过氧化物酶注射或活体染色技术标记这些指定为B1、B1'、C1、C1'和C1'的卵裂球。它们产生的后代定位于早期原肠胚的组织者区域。在神经胚早期，这些细胞形成前索板、脊索、体节、咽内胚层和神经管。切除这些卵裂球中间的两个或四个的结果表明，整个头部缺失或头部的组织和器官大幅减少。这表明在32细胞期它们就已确定自主分化形成头部的轴中胚层组织，并且它们在头部形成中的作用既不能被周围的任何其他卵裂球替代，也不能由它们补充。研究还表明，植物性卵黄细胞似乎对头部轴器官的发育不起关键作用。基于目前的结果，提出了非洲爪蟾卵组织者建立的观点。
