Anti-Ecdysteroid Action of Some Imidazole Derivatives on Pupal-Adult Development of the Silkworm, Bombyx mori : Lepidoptera : Bombycidae

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Abstract
Some imidazole compounds, such as 1-benzyl-5-[(E)-2,6-dimethyl-1,5-heptadienyl] imidazole (KK-42) were applied to the newly ecdysed pupae of the silkworm, Bombyx mori to see their effects on the pupal-adult development, ovarian growth and ecdysteroid titers in hemolymph. KK-42 delayed the timing of pigmentation of compound eyes and adult emergence depending on stages and dosages applied. The critical periods for elongation of pupual life by KK-42 lasted 15 hr after larval-pupal ecdysis and a half maximal effect was induced at a dose of 5 .mu.g/pupa. Ovarian growth was also suppressed by the application of KK-42 at pupation. The strong inhibition was found in the imidazole derivatives carrying 1-benzyl and (E)-configuration of heptadienyl substituent. 20-Hydroxyecdysone injections clearly recovered the arrested pupal-adult development and retarded ovarian growth. However, no counteraction was brought about by an application of juvenile hormone analogue, methoprene. An application of KK-42 to the newly ecdysed pupae completely inhibited the increase of ecdysteroid titers in hemolymph and maintained at the low levels for several days after the treatment. The inhibition kinetics on hemolymph ecdysteroid levels gave a half effective dose of 1 .mu.g/pupa.

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