| Research Abstract |
Egg yolk protein humoral precursor, vitellogenin (Vg), is synthesized in the fat body under the control of juvenile hormone in most insects (ecdysteroids in some dipteran insects). In this research project, endocrinological control mechanisms of Vg synthesis induction (particularly by juvenile hormone) were investigated in tick system (Ornithodoros moubata) compared with a lady-beetle (Henosepilachana vigintioctopunctata). First of all, JH and JH analogues (JHA) were tested on the Vg induction in unengorged unmated female ticks. In spite of the reports on positive effect of JH by Pound ＆ Oliver (1979), we could not find any positive effect on the induction of Vg synthesis in our system (O. moubata). Precocene was also tested without any positive effect as results. An insecticide pyresroid, cypermethrine (CyM), which has been known as an effector on the neurosecretory cells to release neuro-hormone, however, was demonstrated to be active in the induction of Vg synthesis in unfed unmated
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female adults and also in males and nymphs. It is clear that CyM can be used in future as a good tool to investigate the control mechanisms of Vg gene expression.
we also studied on the jh sensitivity in diapausing lady-beetles to induce diapause termination and vg synthesis. the sensitivity to jh changed u-shape fashion during the diapause and the post-diapause.
For the future research on the gene level reguration of Vg synthesis, we started Vg cDNA cloning as the first step of the project. RNAs were extracted from the fat bodies dissected out from ticks and lady-beetles which were at the most active stage in Vg synthesis. Poly A(+) RNAs were selected by Oligo-dT cellulose column and cDNA libraries were prepared by Okayama-Berg method. Several Vg specific cDNA clones in the ticks and the lady-beetles were isolated by enzyme-immuno-detection using anti-Vg-IgG. Restriction maps of these Vg cDNA clones were investigated. These clones will be used as probes to study on mRNA determination, and also gene cloning. Less
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