Effect of actinomycin and puromycin on the deoxyribonuclease activity in P. Lividus embryos at various stages of development

The pattern of DNAse activity in sea urchin Paracentrotus lividus during early embryonic development is altered by actinomycin.When the drug is added to the embryos soon after fertilization, the decrease of DNAse activity that normally occurs before the onset of gastrulation is prevented. If actinomycin is added when DNAse activity starts to decrease, the enzyme pattern remains the same as in the control. Addition of the drug at late gastrula stage, on the other hand, brings about a transient increase of activity with respect to that of untreated embryos.Puromycin has no effect on DNAse activity during the period from fertilization to the blastula stage, whereas it inhibits the increase of activity which occurs after gastrulation. The type of regulatory mechanism involved is discussed.