[Alterations in neuroepithelial intermediate filaments during neurogenesis in the chick cervical spinal cord].

Intermediate filament proteins including nestin, vimentin and neurofilament were immunohistochemically studied during neurogenesis in the chick cervical spinal cord from stages 8 to 28. At stage 8, neuroepithelial cells of the neural groove contained a large amount of nestin in their cytoplasm and a little vimentin in the basal cytoplasmic areas, and no neurofilaments could be recognized at all. At stage 10, there was a marked decrease in nestin expression in the neural groove, and there was an increase in vimentin in neuroepithelial cells. At stage 15, when the neural tube was formed, small oval neuroblasts appeared in the peripheral area of the neuroepithelium. By employing double-immunostaining, three different neuroblasts could be identified; vimentin-positive and neurofilament-negative cells, neurofilament- and vimentin-double-positive cells, and neurofilament-positive and vimentin-negative cells. During the neuroblast stage, intracellular intermediate filaments were relayed from vimentin to neurofilaments. At stage 20, large polygonal cells containing a large number of neurofilaments could be recognized in the enlarged basal plate of the neural tube. At stage 28, neuronal processes developed in large polygonal cells and, although the staining intensity of the neurofilaments was slightly decreased in the soma, the neuronal processes contained a large number of neurofilaments. During neurogenesis in the chick cervical spinal cord, the intermediate filaments, nestin and vimentin, are present in neuroepithelial cells. During the neuroblast stage, vimentin and neurofilaments are observed together for a short time. Finally, in polygonal neurons, only neurofilaments are observed.