[Morphological characteristic of spinal cord neurons in chick embryo development]

The objective of this study was to characterize morphologically the spinal cord neurons in Highsex-White Cross E-21 chick embryos at developmental days 10, 12, 15, 17 and 19. The total of 125 chick embryos were used. The study of the isolated neurons demonstrated the consistent changes of nucleocytoplasmic ratio and nuclear DNA content. Based on the perikaryon volume, three subpopulations of neurons were distinguished during the embryogenesis: small, medium, and large. This is indicative of heteromorphism. The differentiation of the neurons was characterized by a gradual reduction of the nuclear and perikaryon volumes and by the increase of nucleocytoplasmic ratio. The beginning of the differentiation in the histogenesis of the nervous tissue was accompanied by the massive death of undifferentiated nervous cells, which was most pronounced at developmental day 10, when 58% of neurons were eliminated; later this parameter was reduced to 2-5% (embryonic days 17-19).