Patton D T
Department of Science, Bristol Polytechnic, U.K.
Anat Embryol (Berl). 1991;183(2):165-77. doi: 10.1007/BF00174397.
The vertebrate spinal cord shows a segmental pattern of dorsal and ventral nerve roots. It is believed that this peripheral neural segmentation depends on the segmentation of the somitic mesoderm into somites. I have studied the relationship between somite segmentation and the pattern of Rohon-Beard sensory neurite outgrowth from the spinal cord in Xenopus embryos. Most Rohon-Beard neurites grow out in fascicles from the spinal cord at the intersomite clefts, a smaller number of neurites growing out over the dorsal somite margins. Previous work on peripheral neural segmentation has relied on transplanting or destroying somitic mesoderm. Here a non-invasive technique has been used. The pattern of somite segmentation was disrupted by heat shocks, leading to regions of somite fusion where one or two intersomite clefts are absent. At the regions of somite fusion the number of sensory fascicles is then unchanged but their distribution is different. The segmental pattern of sensory fascicle outgrowth is replaced by a fairly even distribution of outgrowth fascicles. Two interpretations of the difference in fascicle outgrowth at fused and control somites are discussed. Firstly, that heat shocks have a direct affect on fascicle outgrowth. Secondly, that heat shocks affect fascicle outgrowth indirectly by disrupting somite segmentation.
脊椎动物的脊髓呈现出背侧和腹侧神经根的节段模式。据信，这种外周神经节段化依赖于体节中胚层分割成体节。我研究了非洲爪蟾胚胎中体节分割与脊髓中罗霍恩－比尔神经细胞的感觉神经突生长模式之间的关系。大多数罗霍恩－比尔神经突以束状从脊髓在体节间裂处生长出来，少数神经突在背侧体节边缘生长出来。先前关于外周神经节段化的研究依赖于移植或破坏体节中胚层。这里使用了一种非侵入性技术。体节分割模式因热休克而被破坏，导致出现体节融合区域，其中缺少一两个体节间裂。在体节融合区域，感觉束的数量没有变化但其分布不同。感觉束生长的节段模式被生长束的相当均匀分布所取代。讨论了融合体节和对照体节在束生长方面差异的两种解释。第一，热休克对束生长有直接影响。第二，热休克通过破坏体节分割间接影响束生长。
