Ovarian maturation in Leucophaea maderae: Juvenile hormone regulation of thymidine uptake into follicle cell DNA

Abstract

Our research demonstrates that juvenile hormone (JH I) stimulates thymidine incorporation into ovarian follicle cell DNA in the ovoviviparous cockroach, Leucophaea maderae. A rapid, quantitative method for monitoring 3H-thymidine incorporation into ovarian DNA, in vitro, is described. Cultured ovarian tissue from L. maderae incorporates 3H-thymidine into DNA at a linear rate between 16 and 120 min; analysis of the incorporated label revealed at least 98% of it to be in DNA. Using L. maderae females that had been mated 7 days after adult emergence, we monitored the following biochemical phenomena during the 18–22 day period of terminal oöcyte growth: (1) 3H-thymidine incorporation into ovarian DNA: (2) general protein synthesis in fat body; and (3) specific fat body vitellogenin synthesis. Decapitation of mated females with maturing oöcytes arrested both ovarian DNA synthesis and fat body vitellogenin synthesis. Substantial restoration of both types of synthesis was induced by injection of JH I. The resumption of thymidine incorporation into DNA was localized in the follicular epithelium of the terminal oöcyte. In decapitated virgin females, injection of JH I stimulated oöcyte growth and 3H-thymidine incorporation into ovarian DNA. Dose and time response curves indicate that peak stimulation of ovarian DNA synthesis occurred between 72 and 96 hr after administration of a single optimal dose of 25 μg JH I. The concurrent manifestation of 3H-thymidine uptake into ovarian DNA and activity within the fat body indicates that a similar hormonal mode of action may be operative with respect to both tissue types in virgin females.