NEURAL COMPETENCE AND CELL LINEAGE OF GASTRULA ECTODERM OF NEWT EMBRYO

Abstract

The change in the capacity to form neural structures was quantitatively analyzed in both intact and isolated ectoderms of Cynops pyrrhogaster gastrula. The frequency of explants with induced neural structures abruptly decreases between stage 12c and stage 13b in intact ectoderm and between 12 h and 18 h preculture in isolated ectoderm. The quantitative analysis also made clear that the size of the cell population of induced neural structures was gradually reduced with the aging of the ectoderm. Examination of the cell proliferation of early gastrula ectoderm confirmed that all ectodermal cells divided at least once within 18 h at 23.degree. C, after which the neural competence of the ectoderm completely disappeared. The relationships between neural competence and cell lineage (cell generation) of the ectoderm are discussed in the light of these findings.