The occurrence of melatonin is known in nearly all organisms, but nothing is known exactly about its function outside of vertebrates. Long-term perifusions as well as short-term batch incubations of brains and moulting glands of the cockroach Periplaneta americana were used to identify the effect of melatonin on the release of prothoracicotropic hormone, a glandotropic neuropeptide in the brain, which stimulates the production of the moulting hormone ecdysone in the moulting gland. This is the first experimental evidence of a neurohormonal releasing effect of melatonin in the insect nervous system., Klaus Richter, Elmar Peschke, Dorothee Peschke, and Lit
The nature and rate of juvenile hormone (JH) biosynthesis and effects of allatostatins and allatotropin have been investigated in isolated corpora allata (CA) of adults and larvae of the noctuid tomato moth, Lacanobia oleracea. In adult female CA, mean rates of synthesis were relatively constant (10-16 pmol/pr/h) at all times. However, the range of JH synthesis by individual CA of similarly aged insects was quite large (2-30 pmol/pr/h). High performance liquid chromatography (HPLC) separation shows that adult female moth CA synthesise predominantly JH I and JH II. Rates of JH synthesis in vitro are dependent on methionine concentration. Synthetic Manduca sexta allatostatin (Mas-AS) caused a dose-dependent inhibition of JH synthesis by adult female CA but only to a max. of 54%, whilst 10 µM synthetic M. sexta allatotropin caused a 37% stimulation of CA activity. At 1 mM the cockroach allatostatin, Dip-allatostatin-2, had no significant effect on JH synthesis. In larval L. oleracea, rates of JH biosynthesis were very low., Neil Audsley, Robert J. Weaver, John P. Edwards, and Lit
The profile of hemolymph ecdysteroid was studied in the gram pod borer, Helicoverpa armigera, during larval-pupal transformation. The changes closely correspond to the developmental events occurring at metamorphosis. Two insect growth regulators, plumbagin and azadirachtin, significantly depleted the content and altered the profile of ecdysteroids at crucial stages, when applied at ED50 doses. The activity profiles of two fat body lysosomal enzymes, acid phosphatase and b-galactosidase, were also significantly affected by the insect growth regulators. It is suggested that plumbagin and azadirachtin treatments primarily modify the ecdysteroid titer, which in turn leads to changes in lysosomal enzyme activity causing overt morphological abnormalities during the metamorphic molt., Arulappan Josephrajkumar, Bhattiprolu Subrahmanyam, Srinivasan, and Lit