Braun J, Stent G S
Department of Molecular Biology, University of California, Berkeley 94720.
Dev Biol. 1989 Apr;132(2):471-85. doi: 10.1016/0012-1606(89)90243-1.
We studied the development of the major extraganglionic components of the germinal plate in embryos of the glossiphoniid leech Helobdella triserialis to improve our understanding of the mechanism of segmental nerve formation. We examined the outgrowth of groups of axons from ganglionic neurons into the segmental nerves, the migration of peripheral neurons and epidermal specializations to their definitive sites, and the development of circular and longitudinal muscle fibers. We visualized axons, as well as neurons and epidermal specializations, by means of fluorescent cell lineage tracers injected earlier into blastomeres and muscle fibers by means of immunofluorescence. The development of cells in all groups was found to follow a stereotyped pattern. Axons of ganglionic neurons approach some identified peripheral neurons located along the segmental nerve paths but not, in general, epidermal specializations and muscle fibers. Near the somata of a subset of peripheral neurons they approach, axons cease or interrupt their growth. These findings identify a set of candidate guidance cells for axonal outgrowth in the leech, similar to those previously described in the developing nervous system of insects.
我们研究了三带水蛭Helobdella triserialis胚胎生发板主要神经节外成分的发育，以增进我们对节段神经形成机制的理解。我们检查了神经节神经元的轴突群向节段神经的生长、外周神经元和表皮特化结构向其最终位置的迁移，以及环形和纵形肌纤维的发育。我们通过早期注射到卵裂球中的荧光细胞谱系示踪剂来观察轴突，以及通过免疫荧光来观察神经元和表皮特化结构。发现所有组中的细胞发育都遵循一种固定模式。神经节神经元的轴突接近一些沿节段神经路径定位的特定外周神经元，但一般不接近表皮特化结构和肌纤维。在它们接近的一部分外周神经元的胞体附近，轴突停止或中断生长。这些发现确定了一组水蛭轴突生长的候选引导细胞，类似于先前在昆虫发育神经系统中描述的那些细胞。
