The role of the notochord to the morphogenesis of chick embryos with special reference to the differentiation of somites and limbs

为了确定脊索、体节和四肢之间的发育关系，对鸡胚胎进行了各种显微外科手术。当脊索被移植到神经管的背中线上时，大多数胚胎发育时没有腹壁，因此暴露了内脏。此外，它们的四肢朝向胚胎的背侧生长，就好像胚胎的背腹方向发生了变化。所有这些实验操作的胚胎都在胚胎第10天之前死亡。由于脊索移植对形态发生有如此有害的影响，因此不可能直接确定脊索与肢体发育之间的关系。在我们解决这个问题之前，我们首先必须了解脊索和体节之间的发育关系。当体节不再受神经管和脊索的影响时，所有组成…的细胞术后10小时内死亡人数较多，24小时后神经管旁未见皮肌瘤和硬化瘤。然而，当体节被剥夺脊索时，硬化体细胞在24小时内死亡，留下一个被皮肌瘤包围的空隙。脊柱和肋骨不能在手术侧发育，因为它们来自于硬化症。虽然肌细胞的排列非常不规则，但到了第7天，它们就在中肾上方发育起来。相反，当只去除神经管时，小的皮肤肌瘤出现在神经管的远端；这些最终分化成小的肌细胞簇。这些结果表明，肌瘤的发育需要神经管或脊索的影响，而硬结的发育只需要脊索的影响。在充分了解肌瘤与神经管和脊索之间的发育关系之前，还需要更多的数据。较少

In order to determine the developmental relationships among the notochord, somites, and limbs, various micro-surgical manipulations were performed on chick embryos. When the notochord was transplanted onto the dorsal midline of the neural tube, the majority of the embryos developed without an abdominal wall and thus had exposed internal organs. In addition, their limbs grew toward the dorsal aspects of the embryo, as if the dorso-ventral orientation of the embryo had been changed. All such experimentally manipulated embryos were dead before embryonic day 10. Because transplantation of the notochord had such a deleterious effect on morphogenesis, it was impossible to determine the relationship between the notochord and limb development directly. Before we could address this issue, we firsts had to understand the developmental relationship between the notochord and somites. When somites were deprived from the influences of both the neural tube and notochord, all of the cells that compris … More e the somites were dead within 10 hours of operation ; after 24 hours, neither dermomyotomes nor sclerotomes were observed adjacent to the neural tube. However, when the somites were deprived of the notochord, the sclerotome cells had died within 24 hours, leaving a void surrounded by the dermomyotomes. The vertebral columns and ribs did not develop on the operated side because they derived from sclerotomes. Though the arrangement of muscle cells was quite irregular, however, they developed above the mesonephros by day 7. In contrast, when only the neural tube was eliminated, small dermomyotomes appeared distal to the neural tube ; these ultimately differentiated to small clusters of muscle cells.These results indicated that myotomes development requires influences from either neural tube or notochord, and sclerotome development requires only influences from the notochord. More data is required before the developmental relationship between the myotomes and the neural tube and notochord can be fully appreciated. Less