The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
Stephen S. Tobe - One of the best experts on this subject based on the ideXlab platform.
-
Neuropeptide Regulators of Juvenile Hormone Production
Reference Module in Neuroscience and Biobehavioral Psychology, 2017Co-Authors: William G. Bendena, Barbara Stay, Stephen S. TobeAbstract:The Juvenile Hormone(s) of insects are the primary regulator(s) of growth, metamorphosis, and reproduction in most species. As a consequence, it is essential that Juvenile Hormone production be precisely regulated so that it is present only during appropriate periods necessary for the control of these processes. The presence of Juvenile Hormone at inappropriate times can result in disruption to metamorphosis and development and, in some cases, to disturbances in female reproduction. For this reason, complex mechanisms to regulate the production of Juvenile Hormone by the corpora allata have evolved and, in many cases, neuropeptides are the primary regulators.
-
The Role of Allatostatins in Juvenile Hormone Synthesis in Insects and Crustaceans
Annual review of entomology, 2007Co-Authors: Barbara Stay, Stephen S. TobeAbstract:Allatostatins are pleiotropic neuropeptides for which one function in insects is the inhibition of Juvenile Hormone synthesis. Juvenile Hormone, an important regulator of development and reproduction in insects, is produced by the corpora allata. Mandibular organs, the crustacean homologs of insect corpora allata, produce precursors of Juvenile Hormone with putatively similar functions. Three types of allatostatins in insects have been isolated: FGLamides, W(X)(6)Wamides, and PISCFs. All act rapidly and reversibly; however, although these types occur in all groups of insects studied, they act as inhibitors of Juvenile Hormone production in only some groups. Only the FGLamide-type peptides have been isolated in crustaceans, in which they may function to stimulate production of Hormone by the mandibular glands, as occurs in early cockroach embryos. Much remains to be learned in order to understand the role of allatostatins in the modulation of Hormone production.
-
factors affecting allatostatin release in a cockroach diploptera punctata nerve section Juvenile Hormone analog and ovary
Journal of Insect Physiology, 1994Co-Authors: Barbara Stay, J Sereg A Bachmann, Carrie A Stoltzman, Steve E Fairbairn, Stephen S. TobeAbstract:The effect of topical application of a Juvenile Hormone analog, 7S-hydroprene, on Juvenile Hormone synthesis and the release into the hemolymph of allatostatins (neuropeptides that inhibit Juvenile Hormone synthesis) was assayed in adult male Diploptera punctata in which nerves to the corpora allata were severed or left intact. Hormone production by corpora allata was measured in vitro radiochemically; allatostatins were quantified by radioimmunoassay. Corpora allata with nerves intact were strongly inhibited by 7S-hydroprene; those with severed nerves (denervated) were less inhibited. Hemolymph allatostatins were highly elevated (>3 nM) above normal (<0.04 nM) only in 7S-hydroprene treated animals with denervated corpora allata. This suggests that allatostatins are normally released at nerve terminals within the corpora allata and that following denervation of the corpora allata allatostatins are released into the hemolymph and inhibit Juvenile Hormone synthesis less effectively. When ovarioles were implanted into 7S-hydroprene treated males with denervated corpora allata, hemolymph allatostatins were markedly reduced; Juvenile Hormone synthesis was higher after implantation of vitellogenic ovarioles than when a previtellogenic ovary was implanted. Thus, Juvenile Hormone analog acts on the brain to release allatostatins and the ovary counteracts this action. These experiments indicate that both Juvenile Hormone and the ovary affect Juvenile Hormone synthesis through release of allatostatins.
-
factors affecting the biosynthesis and release of Juvenile Hormone bisepoxide in the adult blowfly calliphora vomitoria
Journal of Insect Physiology, 1992Co-Authors: Hanne Duve, Koichiro J Yagi, C G Yu, Alan Thorpe, Stephen S. TobeAbstract:Abstract The principal Juvenile Hormone produced by the corpus allatum of the adult blowfly Calliphora vomitoria has been identified as Juvenile Hormone bisepoxide. The precursor compounds, methyl farnesoate and Juvenile Hormone III are also synthesized and released from the isolated gland in vitro, but in small amounts (approx. 1% of the total radiolabelled products of the gland). In females given unrestricted access to sugar, water and meat immediately after eclosion, the rate of Juvenile Hormone bisepoxide production rises with the initiation of oocyte development, reaches high levels early in the first gonadotropic cycle and remains consistently high through successive cycles. Mature males on the same diet also produce Juvenile Hormone bisepoxide at high rates. Flies restricted to a sugar-and-water-only diet synthesize much lower levels of Juvenile Hormone bisepoxide (less than 50% of meat-fed flies). Partially-purified brain extracts of C. vomitoria contain material that is immunoreactive in an ELISA against the inhibitory neuropeptide, allatostatin 1, of the cockroach Diploptera punctata. This material is able to inhibit significantly the biosynthesis of Juvenile Hormone bisepoxide in flies, and also has strong inhibitory effects on Juvenile Hormone III biosynthesis by cockroach corpora allata in vitro. Cockroach allatostatins 1–4 at concentrations of 10−4–10−7 M have no significant effect on Juvenile Hormone bisepoxide release in the blowfly. Also tested at the same concentrations, and shown to have no significant effects on the synthesis and release of Juvenile Hormone-related compounds in either the blowfly or the cockroach were the vertebrate peptide Met5-enkephalin-Arg6-Gly7-Leu8 (YGGFMRGL) and its carboxyamidated analogue (YGGFMRGL-NH2). Similarly, the FMRFamide-related peptides, calliFMRFamides 1 and 5 and their non-amidated analogues, at concentrations of 10−4–10−6 M, had no effect on Juvenile Hormone bisepoxide biosynthesis and release. Forskolin (5 × 10−5 M) and 8-bromo-cAMP (10−4 M) appeared not to have an inhibitory influence on Juvenile Hormone bisepoxide release in the blowfly, suggesting that cAMP may not be the intracellular second messenger in this species. A presumed precursor of Juvenile Hormone bisepoxide, farnesoic acid, did not stimulate and increased production of Juvenile Hormone bisepoxide, but resulted in an increase in Juvenile Hormone III production.
J P Edwards - One of the best experts on this subject based on the ideXlab platform.
-
effects of diploptera punctata allatostatins on Juvenile Hormone biosynthesis and endogenous Juvenile Hormone iii levels in virgin and mated female periplaneta americana
Journal of Insect Physiology, 1995Co-Authors: Robert J Weaver, Z A Paterson, J E Short, J P EdwardsAbstract:Abstract Corpora allata from 4-day-old virgin and sexually mature female Periplaneta americana were tested for sensitivity to inhibition of Juvenile Hormone biosynthesis in vitro by four allatostatins from Diploptera punctata . Two of these allatostatins were also tested for their ability to lower Juvenile Hormone levels in vivo when injected in aqueous solution. In 4-day-old virgin females (showing comparatively low rates of Juvenile Hormone synthesis) corpora allata were sensitive to all four neuropeptides. Inhibition of Juvenile Hormone synthesis was roughly equivalent at the single dose tested (58–74% inhibition @ 10 −5 M). By contrast, corpora allata from mid-cycle sexually mature females (in which Juvenile Hormone synthesis approaches maximum rates) were sensitive only to D. punctata allatostatin 4. Investigation of the sensitivity of corpora allata to allatostatins 1 and 4 throughout the reproductive cycle revealed that at no stage did allatostatin 1 cause more than 25% inhibition of Juvenile Hormone synthesis. Allatostatin 4 however, caused a moderate inhibitory response early in the cycle (33–71%), rising to a highly significant response (81–97%) towards the end of maximal oocyte growth when endogenous (control) rates of Juvenile Hormone synthesis are naturally declining. The activities of the Diploptera allatostatins against Periplaneta corpora allata in vitro are matched by their actions in vivo . Injections of allatostatins 1 and 4 (100 μg/insect) into day-4 virgin P. americana were effective in bringing about a lowering of total body JH III levels 12 h post-injection. Similar injections of allatostatin 1 into mid-cycle mated females produced no apparent effect but injection of allatostatin 4 did result in a substantial reduction (50–70%) of endogenous total body JH III levels in these insects.
-
The use of a Juvenile Hormone binding protein for the quantitative assay of Juvenile Hormone
Insect biochemistry and molecular biology, 1995Co-Authors: A.v. Glinka, J P Edwards, R.p. Braun, G.r. WyattAbstract:Abstract The suitability of the haemolymph Juvenile Hormone binding protein (JHBP) of Locusta migratoria for use in a competition assay for Juvenile Hormone (JH) III has been investigated, and a simple quantitative assay procedure using this protein has been developed. JHBP partially purified from haemolymph of precocene treated adult locusts gives rapid and stable binding of [3H]10R-JH III, and can be separated from the unbound Hormone with hydroxylapatite (HAP). The sensitivity of the method is such that 0.15 pmol (40 pg) 10R-JH III gives 50% displacement of [3H]10R-JH III from the binding protein. Competition by JH II is about 5 times less and JH I about 10 times less than that by JH III, while JH III diol and acid compete at least 1000 times less strongly. A procedure for extraction and assay of JH from 50 μl haemolymph samples is described, the interference by non-specific haemolymph components is shown to be relatively small, and some data on JH III titres in maturing adult locusts are presented.
Barbara Stay - One of the best experts on this subject based on the ideXlab platform.
-
Neuropeptide Regulators of Juvenile Hormone Production
Reference Module in Neuroscience and Biobehavioral Psychology, 2017Co-Authors: William G. Bendena, Barbara Stay, Stephen S. TobeAbstract:The Juvenile Hormone(s) of insects are the primary regulator(s) of growth, metamorphosis, and reproduction in most species. As a consequence, it is essential that Juvenile Hormone production be precisely regulated so that it is present only during appropriate periods necessary for the control of these processes. The presence of Juvenile Hormone at inappropriate times can result in disruption to metamorphosis and development and, in some cases, to disturbances in female reproduction. For this reason, complex mechanisms to regulate the production of Juvenile Hormone by the corpora allata have evolved and, in many cases, neuropeptides are the primary regulators.
-
The Role of Allatostatins in Juvenile Hormone Synthesis in Insects and Crustaceans
Annual review of entomology, 2007Co-Authors: Barbara Stay, Stephen S. TobeAbstract:Allatostatins are pleiotropic neuropeptides for which one function in insects is the inhibition of Juvenile Hormone synthesis. Juvenile Hormone, an important regulator of development and reproduction in insects, is produced by the corpora allata. Mandibular organs, the crustacean homologs of insect corpora allata, produce precursors of Juvenile Hormone with putatively similar functions. Three types of allatostatins in insects have been isolated: FGLamides, W(X)(6)Wamides, and PISCFs. All act rapidly and reversibly; however, although these types occur in all groups of insects studied, they act as inhibitors of Juvenile Hormone production in only some groups. Only the FGLamide-type peptides have been isolated in crustaceans, in which they may function to stimulate production of Hormone by the mandibular glands, as occurs in early cockroach embryos. Much remains to be learned in order to understand the role of allatostatins in the modulation of Hormone production.
-
factors affecting allatostatin release in a cockroach diploptera punctata nerve section Juvenile Hormone analog and ovary
Journal of Insect Physiology, 1994Co-Authors: Barbara Stay, J Sereg A Bachmann, Carrie A Stoltzman, Steve E Fairbairn, Stephen S. TobeAbstract:The effect of topical application of a Juvenile Hormone analog, 7S-hydroprene, on Juvenile Hormone synthesis and the release into the hemolymph of allatostatins (neuropeptides that inhibit Juvenile Hormone synthesis) was assayed in adult male Diploptera punctata in which nerves to the corpora allata were severed or left intact. Hormone production by corpora allata was measured in vitro radiochemically; allatostatins were quantified by radioimmunoassay. Corpora allata with nerves intact were strongly inhibited by 7S-hydroprene; those with severed nerves (denervated) were less inhibited. Hemolymph allatostatins were highly elevated (>3 nM) above normal (<0.04 nM) only in 7S-hydroprene treated animals with denervated corpora allata. This suggests that allatostatins are normally released at nerve terminals within the corpora allata and that following denervation of the corpora allata allatostatins are released into the hemolymph and inhibit Juvenile Hormone synthesis less effectively. When ovarioles were implanted into 7S-hydroprene treated males with denervated corpora allata, hemolymph allatostatins were markedly reduced; Juvenile Hormone synthesis was higher after implantation of vitellogenic ovarioles than when a previtellogenic ovary was implanted. Thus, Juvenile Hormone analog acts on the brain to release allatostatins and the ovary counteracts this action. These experiments indicate that both Juvenile Hormone and the ovary affect Juvenile Hormone synthesis through release of allatostatins.
Robert J Weaver - One of the best experts on this subject based on the ideXlab platform.
-
effects of diploptera punctata allatostatins on Juvenile Hormone biosynthesis and endogenous Juvenile Hormone iii levels in virgin and mated female periplaneta americana
Journal of Insect Physiology, 1995Co-Authors: Robert J Weaver, Z A Paterson, J E Short, J P EdwardsAbstract:Abstract Corpora allata from 4-day-old virgin and sexually mature female Periplaneta americana were tested for sensitivity to inhibition of Juvenile Hormone biosynthesis in vitro by four allatostatins from Diploptera punctata . Two of these allatostatins were also tested for their ability to lower Juvenile Hormone levels in vivo when injected in aqueous solution. In 4-day-old virgin females (showing comparatively low rates of Juvenile Hormone synthesis) corpora allata were sensitive to all four neuropeptides. Inhibition of Juvenile Hormone synthesis was roughly equivalent at the single dose tested (58–74% inhibition @ 10 −5 M). By contrast, corpora allata from mid-cycle sexually mature females (in which Juvenile Hormone synthesis approaches maximum rates) were sensitive only to D. punctata allatostatin 4. Investigation of the sensitivity of corpora allata to allatostatins 1 and 4 throughout the reproductive cycle revealed that at no stage did allatostatin 1 cause more than 25% inhibition of Juvenile Hormone synthesis. Allatostatin 4 however, caused a moderate inhibitory response early in the cycle (33–71%), rising to a highly significant response (81–97%) towards the end of maximal oocyte growth when endogenous (control) rates of Juvenile Hormone synthesis are naturally declining. The activities of the Diploptera allatostatins against Periplaneta corpora allata in vitro are matched by their actions in vivo . Injections of allatostatins 1 and 4 (100 μg/insect) into day-4 virgin P. americana were effective in bringing about a lowering of total body JH III levels 12 h post-injection. Similar injections of allatostatin 1 into mid-cycle mated females produced no apparent effect but injection of allatostatin 4 did result in a substantial reduction (50–70%) of endogenous total body JH III levels in these insects.
Roger W. Meola - One of the best experts on this subject based on the ideXlab platform.
-
Effects of Juvenile Hormone on eggs and adults of the cat flea (Siphonaptera: Pulicidae).
Journal of medical entomology, 2001Co-Authors: Roger W. Meola, Susan R. Dean, Govindan BhaskaranAbstract:Juvenile Hormone III plays a major role in regulating feeding and reproduction in the adult cat flea, Ctenocephalides felis (Bouche ´). Both blood consumption and egg production increased in a dose-dependent manner up to a maximum at 1,250 ppm when fleas were continuously exposed to concentrations up to 12,500 ppm Juvenile Hormone. Histological studies demonstrated that Juvenile Hormone III also stimulated cellular differentiation of salivary gland epithelia, midgut epithelia, and fat body cells, enhancing the ability of the adult flea to digest blood and synthesize vitellogenins for the maturing oocytes. In unfed fleas, exposure of adults to concentrations of $1,000 ppm Juvenile Hormone III applied to filter paper resulted in membrane lysis and destruction of salivary gland and midgut epithelial cells, fat body cells, and ovarian tissue. Unlike Juvenile Hormone mimics, which have potent ovicidal effects in fleas, Juvenile Hormone had little effect in preventing egg hatch; 58% of the eggs laid by fleas treated with 12,500 ppm Juvenile Hormone III hatched, and a concentration of 30,000 ppm was required to reduce hatch to 2% in untreated eggs exposed to treated filter paper for 2 h. Compared with the Juvenile homone mimic pyriproxyfen, Juvenile Hormone III was less toxic to fed adult fleas. However, at a concentration of 12,500 ppm, Juvenile Hormone killed '45% of the adults and caused autolysis and yolk resorption in the developing oocytes. Thus, at high concentrations, Juvenile Hormone appears to have a pharmacological effect on fleas, which is highly unusual in insects.
-
Effect of Juvenile Hormone and Juvenile Hormone Mimics on Sperm Transfer from the Testes of the Male Cat Flea (Siphonaptera: Pulicidae)
Journal of medical entomology, 1997Co-Authors: Susan R. Dean, Roger W. MeolaAbstract:Sperm transfer into the epididymis was completed without a blood meal, when newly emerged male cat fleas, Ctenocephalides felis (Bouche), were exposed to filter papers treated with Juvenile Hormone III or the Juvenile Hormone mimics fenoxycarb, methoprene, or pyriproxyfen. As the concentration of Juvenile Hormone or the time of flea exposure to Juvenile Hormone or the Juvenile Hormone mimics increased, the percentage of fleas that transferred sperm also increased. The percentage of pyriproxyfen-treated males that transferred sperm reached 100% after 3 d; whereas, 7 d exposure to Juvenile Hormone, fenoxycarb and methoprene was required for 100% of the males to transfer sperm. Although sperm were present in the epididymis of treated fleas, insemination of females did not take place off the host either on Juvenile Hormone-treated filter paper or on Juvenile Hormone-treated dog hair.
