Abstract
The corpora allata (CA) synthesize and release juvenile hormone (JH) that in turn regulates insect growth, metamorphosis and reproduction. Rates of juvenile hormone (JH) fluctuate concurrently during ovarian cycles with cyclic growth and atrophy of allatal cells in the cockroach, Diploptera punctata. We established an in vitro long-term culture system allowing us to study factors regulating slow development of CA cells. The data indicate that rates of JH synthesis were highly correlated with changes in the sizes of CA cells, an indicator of amount of cellular machinery required for JH synthesis. Also, we found that the brain and ovaries both induced CA cell atrophy. By adding allatostatin I into the culture media, the results imply that allatostatin may be the candidate of the brain factor to shrink CA cells. In addition, results of treating CA with ovaries, ovarian extract or ovary-conditioned medium suggest that a putative peptidergic growth regulator or 20-hydroxyecdysone released from mature ovaries acts directly on active CA cells and induces the elevation of intracellular cGMP content. Consequently, elevated cGMP may inhibit protein synthesis or trigger massive and synchronous autophagic activities, resulting in cell atrophy and reduction of protein content. As a result of the depletion of cellular machinery, CA glands exhibit long-term depression in JH synthesis.