Search results for "Juvenile Hormone"
showing 10 items of 50 documents
Notch and Numb are required for normal migration of peripheral glia in Drosophila
2006
Abstract A prominent feature of glial cells is their ability to migrate along axons to finally wrap and insulate them. In the embryonic Drosophila PNS, most glial cells are born in the CNS and have to migrate to reach their final destinations. To understand how migration of the peripheral glia is regulated, we have conducted a genetic screen looking for mutants that disrupt the normal glial pattern. Here we present an analysis of two of these mutants: Notch and numb. Complete loss of Notch function leads to an increase in the number of glial cells. Embryos hemizygous for the weak NotchB-8X allele display an irregular migration phenotype and mutant glial cells show an increased formation of …
Developmental profiles of epidermal mRNAs during the pupal-adult molt of Tenebrio molitor and isolation of a cDNA clone encoding an adult cuticular p…
1992
0012-1606 (Print) Journal Article; Changes in translatable mRNAs from the wing epidermis of the Coleoptera Tenebrio molitor have been investigated during metamorphosis by analysis of in vitro translated products. Striking differences between the patterns obtained from mRNAs extracted during pupal and adult cuticle secretion indicated that a drastic change in gene expression occurs during the pupal-adult transition. In addition to these stage-specific modifications, the mRNA patterns changed within each cuticular synthesis program (pupal or adult), especially at ecdysis. After tritiated leucine incorporation, some of the major radiolabeled cuticular proteins showed similar changes suggesting…
Covalent modificaition of juvenile hormone binding proteins by photoaffinity labeling: An unexpected gel shift effect
1994
The 32 kD juvenile hormone binding protein (JHBP) and two 80 kD proteins in larval Manduca sexta hemolymph were labeled with [3H]FDK, a photoaffinity analog of methyl farnesoate (MF). The labeling could be completely displaced by a 30-fold excess of either MF or JH II, demonstrating that [3H]FDK binds specifically to the JH binding sites of the 32 kD JHBP and the 80 kD proteins. In addition, a high molecular-mass protein was labeled with [3H]FDK; labeling could be displaced by excess MF but not by JH II, demonstrating the selectivity in binding MF. The 32 kD JHBP also appeared to weakly bind the potent juvenoid, methoprene, at the JH binding site. Covalent modification by [3H]FDK induced a …
Biological Activities of Natural Sesquiterpene Lactones and the Effect of Synthetic Sesquiterpene Derivatives on Insect Juvenile Hormone Biosynthesis
1998
Three natural sesquiterpene lactones have been assayed for their biological activity on locust (Locusta migratoria) nymphs. Since results obtained in vivo pointed to disruptions on juvenile hormone (JH)-regulated physiology, we tested the sesquiterpene lactones and a family of synthetic sesquiterpene derivatives for their ability to disturb the rate of JH biosynthesis by locust corpora allata (CA) in vitro. All the active compounds in vitro share a basic sesquiterpene double-ring structure as well as substituents with different chemical complexities. Compounds that shared an eudesmane base with different oxidation states on C3 and C12 carbon atoms were tested as JH biosynthesis inhibitors. …
Expression and characterization of the recombinant juvenile hormone epoxide hydrolase (JHEH) from Manduca sexta.
1998
The cDNA of the microsomal Juvenile Hormone Epoxide Hydrolase (JHEH) from Manduca sexta was expressed in vitro in the baculovirus system. In insect cell culture, the recombinant enzyme (Ms-JHEH) was produced at a high level (100 fold over background EH catalytic activity). As expected, Ms-JHEH was localized in the microsomal fraction with a molecular mass of approximately 50 kDa. Ms-JHEH showed a substrate and inhibitor spectrum similar to the wild type JHEH isolated from eggs of M. sexta. Its enzymatic activity was the highest for Juvenile Hormone III. Ms-JHEH hydrolyzed several trans-epoxides faster than cis-epoxides. A putative hydroxyl-acyl enzyme intermediate was isolated suggesting a …
Postembryonic development of Zophobas atratus Fab. (Coleoptera: Tenebrionidae) under crowded or isolated conditions and effects of juvenile hormone a…
1995
Abstract Pupation in Zophobas atratus is dependent on isolation and this provides a model for study of the onset of metamorphosis in beetles. We have analyzed the effects of isolation vs grouping on certain developmental parameters; the number of larval instars; their duration and weight. Sex differences were detected, such as the occurrence of regressive moults in females. Moreover, the development of Z. atratus is discussed in relation to Tenebrio molitor , the physiological timing of which appeared in part extendable to Z. atratus . Experiments show that 4–6 days of isolation are required for commencement of metamorphosis, as indicated by an immobile crooked posture observed at the end o…
Field application of the juvenile hormone analogue fenoxycarb against hopper bands of Locusta migratoria capito in Madagascar
1997
Summary Field trials have been carried out to examine the suitability of the JHA fenoxycarb in locust control. Laboratory tests have shown that a variety of JHAs, including fenoxycarb, applied to last instar larvae increased mortality, induced morphogenetic defects during metamorphosis, reduced fertility and provoked solitarisation of gregarious hoppers. The phase shift was indicated by green coloration and the acquisition of morphological and behavioural characteristics typical for solitary locusts. The present field experiments should clarify whether or not the effects observed in the laboratory are also observed with hopper bands in their natural habitat and if swarm formation and emigra…
Vitellogenesis inhibition in Oncopeltus fasciatus females (Heteroptera: Lygaeidae) exposed to cadmium
2005
Abstract Newly moulted females of the insect Oncopeltus fasciatus were exposed to cadmium (Cd) dissolved in the drinking water (50–400 mg l −1 Cd) for 5 days. Cd exposure delayed ovarian maturation and inhibited egg production. Exposure to Cd, moreover, decreased hemolymph levels of the two major vitellogenin polypeptides of O. fasciatus , VG1 and VG2, in a concentration-dependent way, probably by a reduction in their synthesis. The ovarian levels of VG1 and VG2 were also decreased in Cd-exposed females. It was next investigated whether Cd effects might be a consequence of the endocrine disruption of vitellogenin synthesis, which is controlled by juvenile hormone (JH). JH replacement therap…
The non-appearance of female-specific proteins in male Spilostethus pandurus)
1990
1. 1. Female-specific peptides can be detected by SDS-PAGE in the haemolymph when the female insects are 48 hr old. 2. 2. The age of the male insect at the moment of treatment with juvenile hormone I (JH I), JH III or ecdysone has no influence on the induction of the female-specific bands in male S. pandurus. 3. 3. Male insects exposed to the hormones for periods of time longer than 24 hr were also unable to show female-specific bands in their haemolymph. Consecutive treatments with JH were unable to induce these peptides in the males.
Effects of juvenile hormone analogues upon soldier differentiation in the termite Reticulitermes santonensis (Rhinotermitidae, Heterotermitinae).
2018
Under the influence of juvenile hormone analogues (JHAs), termite workers are induced to differentiate into soldiers. In Reticulitermes santonensis, such induced differentiation is often incomplete, resulting in intercaste production. The morphology of the structures most affected during differentiation was analyzed descriptively and biometrically in normal workers, presoldiers, and soldiers, and in experimental intercastes. We observed that intercastes form a morphological and biometrical continuum between workers and presoldiers (presoldier intercastes), and between presoldiers and soldiers (soldier intercastes). We also compared the biochemistry of the normal individuals and of the inter…