Molecular and Cellular Endocrinology, 75 (1991) 141-147 141 © 1991 Elsevier Scientific Publishers Ireland, Ltd. 0303-7207/91/$03.50 MOLCEL 02429 Developmental regulation of juvenile hormone synthesis: ovarian synchronization of volumetric changes of corpus allatum cells in cockroaches Ann-Shyn Chiang, Michal Gadot, Edina L. Burns and Coby Schal Department of Entomology, Cook College, Rutgers Unioersity, New Brunswick, NJ 08903, U.S.A. (Received 10 September 1990; accepted 25 October 1990) Key words: Blattella germanica; Cockroach; Corpora allata; 20-Hydroxyecdysone; Ovarian regulation; Juvenile hormone Summary The corpus allatum (CA) cells of adult Blattella germanica females undergo cyclic volumetric changes in relation to juvenile hormone (JH) synthesis. In intact females the size of CA cells changes synchronously during the gonotrophic cycle, resulting in cyclic JH synthesis. In ovariectomized females volumetric changes among CA cells become asynchronous, resulting in highly variable but high rates of JH synthesis. Injection of the steroid hormone 20-hydroxyecdysone into ovariectomized females with active CA resulted in a transient decline followed by an increase in both CA volume and JH biosynthesis. This response was due to a change in the size distribution of CA cells and not in the total number of CA cells. In ovariectomized females, CA cells can be re-synchronized into a uniform population of small inactive cells with injection of 20-hydroxyecdysone and implantation of an artificial egg-case, mimicking the successive events of ovulation, oviposition and pregnancy. Introduction Juvenile hormone (JH), synthesized by the cor- pora allata (CA), is essential for the expression of sexual behavior, synthesis of yolk proteins, and for the successful development of the ovaries and various ovarian tissues in many insects (Koeppe et al., 1985; Schal and Smith, 1990). The regulation of CA activity in insects during the gonotrophic cycle involves modulation by ovarian signals and by brain allatotropins and/or aUatostatins which are released in response to environmental (exter- Address for correspondence: Dr. Coby Schal, Department of Entomology, Cook College, Rutgers University, New Brunswick, NJ 08903, U.S.A. nal) and physiological (internal) stimuli. Also, rates of JH synthesis by the CA have been shown to be stimulated by the presence of young ovaries and inhibited by the presence of mature ovaries or egg case in many insects (reviewed by Engelmann, 1970; Cassier, 1979; de Kort and Granger, 1981; Feyereisen, 1985; Tobe and Stay, 1985; Khan, 1988; Raabe, 1989; Rankin, 1990). However, it is not clear how the CA respond to these regulatory factors that result in the cyclic release of JH during the gonotrophic cycle. It has been suggested that ecdysteroids, which are found in mature ovaries and in the hemo- lymph of adult females, are involved in the nega- tive feedback (Lanzrein et al., 1981; Stay et al., 1984; Weaver et al., 1984; Rankin et al., 1985). Removal of the ovaries abolishes the hemolymph