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Flucycloxuron, a novel benzoylphenylurea (BPU) derivative, exhibited insecticidal activity when injected into newly ecdysed pupae of Tenebrio molitor. Mortality occurs because of defective adult ecdysis. Treatment caused a reduction in both cuticle thickness and incorporation ofC-labelled precursor into chitin, although it had no significant effect on the protein synthesis. The potencies of other BPU compounds as inhibitors of chitin biosynthesis have been examined and results showed that diflubenzuron was less effective than either flucycloxuron or triflumuron. [ABSTRACT FROM AUTHOR]

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The cytological modifications of the epidermal cells secreting sternal and pleural cuticle of adult Tenebrio are studied, specially during the formation and evolution of the outer and inner epicuticle. Both layers are secreted by condensation of diffuse material just above the epidermal microvilli. There is no peculiar phase without microvilli when inner epicuticle is formed. During the secretion of pre-ecdysial cuticle, the epidermal cell is characterized by an heterolytic process which is demonstrated by peroxidase injection into the ecdysial space: horseradish peroxidase is absorbed by large pinocytic coated vesicles which discharge their content into multivesicular bodies, after the loss of their coat. The intensity of pinocytosis is studied by vesicles counts at different stages of the pupal life. These counts show a pinocytic peak when the inner epicuticle is formed. When the epicuticular barrier is completely secreted, exogenous peroxidase is no more absorbed, but morphological study and counts show that pinocytosis still occurs. This demonstrates that epidermis cannot absorb macromolecules arising from the digested old cuticle since digestion occurs after the completion of adult epicuticle. Locke's hypothesis about the 'control of the extracellular subcuticular environment' by pinocytosis is confirmed. The Golgi complexes are involved in lytic process with their small coated vesicles and in secretion of cuticular material with their large dense secretory vesicles, but according to vesicle counts, the secretory vesicles are not concerned in epicuticle formation since their apparition is posterior to the deposition of the inner epicuticle. Les modifications cytologiques des cellules épidermiques sécrétant la cuticule sternale et pleurale de l'adulte de T. molitor sont étudiées pendant la formation et l'évolution de l'épicuticule externe et interne. L'épicuticule externe et interne sont sécrétées de la même façon par condensation de matériel diffus au-dessus de l'apex des microvillosités. Un cycle hétérolytique est mis en évidence par l'emploi de peroxydase injectée dans l'espace exuvial: la peroxydase est captée par de grosses vésicules revêtues et incorporée dans des corps multivésiculaires apicaux. Par comptage des différentes populations de vésicules, des variations nettes dans l'intensité de la pinocytose sont mises en évidence. Ces variations semblent en rapport non pas avec la digestion de l'ancienne cuticule mais avec les différences de nature et de structure des composants cuticulaires. L'hypothèse du contrôle de la sécrétion épidermique par les phénomènes de pinocytose énoncée par Locke (1969) est confirmée. Des vésicules d'origine golgiennes sont secrétées surtout après la formation de l'épicuticule et ne sont donc pas à l'origine du matériel épicuticulaire, mais il est possible qu'elles jouent un rôle dans l'évolution ultérieure des structures épicuticulaires. [ABSTRACT FROM AUTHOR]

Copyright of Histochemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bursicon active hemolymph of Tenebrio, injected into host pupae deprived in bursicon, induces a 2-fold increase of cyclic AMP in the epidermis of the hosts 5 min after the injection. No increase is observed by injecting bursicon inactive hemolymph or insect Ringer. From these experiments it can be concluded that cyclic AMP is a second messenger of bursicon. [ABSTRACT FROM AUTHOR]