ELIMINATION OF 1-CELLS BY ALKYLATING CYTOSTATIC AGENTS AND THEIR EFFECT ON EMBRYONIC DEVELOPMENT IN HYDRACTINIA ECHINATA

When applied in short-timed sublethal doses the alkylating agents Trenimon, Dichloren and Mitomycin C bring about cytolysis of the I-cells of Hydractinia echinata. Their effective range is different: Mitomycin causes lysis of I-cells only, additionally destroys Dichloren differentiating nerve cells, Trenimon cnidoblasts too. In relation to differentiated cells I-cells show an increased rate of DNA-synthesis and an increased RNA-turnover. In order to approach the point of attack on the nucleic acid metabolism, the regression lines of alkylating and other antimetabolites have been determined for the inhibition of egg-cleavage and of metamorphosis. The following correlations have been found. 1. 1. Only alkylating agents that block metamorphosis in low concentrations lead to lysis of I-cells. 2. 2. The more resistant cleavage is in comparison to metamorphosis, the more specifically are the I-cells destroyed. Since metamorphosis is initiated by newly produced nucleic RNA and since during cleavage DNA-synthesis occurs, whereas RNA-synthesis stops, these results are interpreted as indieating that RNA-synthesis reacts in a more sensitive way and that the specific sensitiveness of the I-cells depends on their high synthetic activity on the RNA level. © 1968.