Embryonale Induktion und Hemmung der Ribonucleinsäure-Synthese durch Actinomycin D

Abstract

Blastoporal lip (presumptive notochord and myotomes) together with adjacent ectoderm (which is induced to form the neural system by the blastoporal lip) from early gastrulae was explanted and treated with 0,5—2,5 µg/ml actinomycin D for periods ranging from two hours to several days. The RNA synthesis is completely inhibited at 2,5 μg/ml Actinomycin D and partially inhibited at 0,5 μg/ml actinomycin D. At 2,5 µg/ml some notochordal cells are still formed, but the differentiation of neural tissue is completely inhibited. At 0,5 μg/ml actinomycin D notochord and muscle are more resistent than the neural tissue. The inducing capacity of the blastoporal lip is not diminished after treatment with actinomycin D. Actinomycin D must therefore impair the competence of the ectoderm to be induced by inhibiting the RNA synthesis. If tissues from tailbuds, which are already differentiating into muscle, notochord and spinal cord are explanted and treated with actinomycin D the differentiation is partially inhibited, but a differential sensitivity of these tissues is not observed. The overall rate of protein synthesis is somewhat enhanced after treatment with 0,5 μg/ml actinomycin D for 2 — 5 hours.