Control of neural crest cell dispersion in the trunk of the avian embryo

摘要: Abstract Many hypotheses have been advanced to explain the orientation and directional migration of neural crest cells. These include positive negative chemotaxis, haptotaxis, galvanotaxis, contact inhibition. To test directly factors that may control dispersion crest, I employed a variety grafting techniques in living embryos. In addition, time-lapse video microscopy has used study cells tissue culture. Trunk normally disperse from their origin at dorsal tube along two extracellular pathways. One pathway extends laterally between ectoderm somites. When either pigmented or isolated 24-hr cultures are grafted into space lateral somites, they migrate: (1) medially toward somites (2) ventrally intersomitic blood vessels. Once posterior cardinal vein aorta migrate both vessels for several somite lengths anterior-posterior axis. Neural do not immediately move somatic mesoderm body wall limb. Dispersion occurs only after nerves first invaded, which then follow. The other alongside space. were ventral position, notochord aorta, this axial level last somite, rapidly within 2 hr directions: dorsally, space, until moving stream host laterally, endoderm. All above experiments indicate neither preestablished chemotactic nor adhesive (haptotactic) gradient exists embryo since will reverse direction these pathways tube. For same reason, also show dispersal is directed passively by environmental controls, can clearly counter usual against such putative passive mechanisms. Although becomes channeled structures as tube, initial radial pattern suggests driven among Tissue culture studies demonstrate display paralysis when lamellipodia touch each other. best explanation embryo, therefore,