The activity of anthramycin and structurally related analogs as chemosterilants of the housefly, Musca domestica L., correlates closely with the action of these compounds as inhibitors of Escherichia coli RNA polymerase. Since inhibition of RNA polymerase by anthramycin reflects binding of this antibiotic to the DNA primer required for enzyme activity, we propose that the interaction of anthramycin with DNA may also account for its action as a chemosterilant.

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Oostatic hormone, prepared from mature female house flies, Musca domestica, was examined for its effect on processes mediated by egg development neurosecretory hormone (EDNH). When injected into newly emerged adult female mosquitoes, Aedes atropalpus, oostatic extracts inhibited vitellogenic growth of the ovaries. Comparison of oostatic activities in heads, thoraces, and abdomens of house flies showed that the major portion was present in the abdomens, apparently associated with the ovaries. In contrast to untreated vitellogenic females, no ecdysone or 20-hydroxyecdysone could be detected in female mosquitoes injected with the oostatic extract. Vitellogenic growth and ecdysteroid levels were suppressed in decapitated females injected with a mixture of extracts containing EDNH and oostatic activities. Since the normal vitellogenic and steroidogenic responses to EDNH can be suppressed by simultaneous injection of EDNH and oostatic material, it is suggested that oostatic hormone acts at a level subsequent to EDNH release. However, we cannot rule out at this time that EDNH release, itself, is also affected.