Ionic induction of the frog cement-gland cell from presumptive ectodermal tissues

Cells of the superficial layer which had been explanted from the presumptive ectoderm of Rana japonica early gastrulae at stage 10 differentiated into cement-gland cells (CGCs) when cultured in Barth9s solution containing 90–130 mM-NaCl, and into common epidermal cells and cilia cells when cultured in a solution containing 20–40 mM-NaCl. They failed to differentiate, however, when cultured in a solution in which NaCl is 15 mM or lower. The optimum condition for inducing the differentiation of CGC was stimulating them with a solution containing 130 mM-NaCl for 6–10 h at 18 °C, followed by culturing in a solution containing 15–40 mM-NaCl for 7 days. The greatest ability to react to the CGC-inducing stimuli resided in the superficial layer of the presumptive ectoderm of the embryo at stages 10–11. Under the optimum condition, the total volume of CGCs induced amounted to about 85% of the explanted tissue. High percentage comparable to this was obtained with stimulation by KCl, RbCl, sucrose or mannitol.