[Isolation and ways of acting of morphogenetic factors during early embryogenesis].

The attempts at isolation and characterization of the factors mediating the embryonic induction are summarized. A method is described in detail which allowed to isolate the purified form from the mixtures of chick embryonic tissues a vegetalizing protein factor which induces the mesoderm and endoderm in the ectoderm of amphibian gastrulae. Besides, its inhibitor was isolated which is also a protein; the inhibitors supposedly block the action of the most inducing factors but one or some of them. The isolation of the inducing factor in the pure form allowed to reinvestigate with the greatest precision the problem whether the induction is mediated by the contact of cell surfaces or the penetration of substances in the reacting cells and to show that the inducing factor penetrates in the cells upon the induction in the gastrula ectoderm. The effect of cyclic monophosphates and changes in potassium and sodium intracellular concentration as factors participating in the induction was also tested and it was shown that neither of these factors, contrary to the expectations, led to he induction phenomena. The importance of the vegetalizing factor concentration for the segregation of the primary ectodermal zone into ectodermal and mesodermal and, secondarily, nerve cellis discussed.