Studies on the heterogeneity of cell populations in amphibian presumptive epidermis, with reference to primary induction

Abstract

The cell composition of the presumptive epidermis of Triturus pyrrhogaster gastrula was tested by means of isoelectric electrophoresis. Dissociated cells from the epidermis were electrophoretically divided into three zones; the cell numbers in the three zones in a cathode-to-anode direction, corresponded to 35, 41, and 24%, respectively, of the original cells. Epidermal cells neuralized by acidified Holtfreter's solution and cells dissociated from the forebrain of tail-bud embryos yielded electrophoretically a layer of cells at a position corresponding to a cathodal cell layer of the presumptive epidermis. Epidermal cells mesodermalized by bone marrow extract, and cells dissociated from dorsal blastoporal lip, were distributed electrophoretically into two layers at the levels corresponding to the two anodal cell layers of the presumptive epidermis. By means of neuralizing and mesodermalizing treatments, about 38 and 66% of the original dissociated cells of presumptive epidermis were recovered, respectively. Each of these percentages corresponds very closely to that of the cathodal zone and the two anodal zones in the original cell spectrum. These findings suggest the possibility of an originally inhomogeneous developmental potency for each cell species in the presumptive epidermis, and a selective killing effect of neuro-inducing substances on cell species which are destined to form mesodermal tissues and, conversely, a selective destruction by mesoderm-inducing substances of cell species destined to form neural tissue.