Youn B W, Malacinski G M
J Embryol Exp Morphol. 1981 Aug;64:23-43.
The intrasomitic changes in cell arrangement which accompany somite rotation during somitogenesis in Xenopus laevis were analysed with the scanning electron microscope (SEM). Longitudinal, horizontal fractures of whole embryos were examined at various dorsoventral levels of stage-22 to -24 embryos. Observations of the gross morphological features of somitogenesis, and the cellular changes which accompany somite segmentation and somite rotation were made. Several of these observations lead to modifications of previous models for the cellular basis of somitogenesis in Xenopus. Individual cellular rearrangements, rather than simultaneous block rotation of a whole somite, appear to be responsible for the 90 degrees rotation of myotomal cells within a single somite. Cellular arrangements in fused somites were also examined. Some ultraviolet-irradiated embryos displayed a complete lack of a notochord. The somites in those embryos were fused across the midline beneath the neural tube. The dorsal and ventral arms of the somites are not fused. Normal rotation occurs only in the dorsal and ventral arms while, in the majority of cases, cells in the fused region fail to rotate normally. In some cases, individual cells in the fused region undergo partial rearrangement. Those observations support the notion that individual cellular rearrangements account for the rotation of the whole somite.
利用扫描电子显微镜（SEM）分析了非洲爪蟾胚胎发育过程中，体节旋转时体节内部细胞排列的变化。在22至24期胚胎的不同背腹水平，对整个胚胎进行纵向、水平骨折检查。观察了体节形成的大体形态特征，以及伴随体节分割和体节旋转的细胞变化。其中一些观察结果导致了之前关于非洲爪蟾体节形成细胞基础模型的修正。单个细胞重排，而非整个体节同时进行块旋转，似乎是单个体节内肌节细胞90度旋转的原因。还检查了融合体节中的细胞排列。一些紫外线照射的胚胎完全没有脊索。这些胚胎的体节在神经管下方的中线处融合。体节的背侧和腹侧臂没有融合。正常旋转仅发生在背侧和腹侧臂，而在大多数情况下，融合区域的细胞不能正常旋转。在某些情况下，融合区域的单个细胞会发生部分重排。这些观察结果支持了单个细胞重排导致整个体节旋转的观点。
