The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Alexander S Raikhel - One of the best experts on this subject based on the ideXlab platform.
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microrna mir 275 is indispensable for blood digestion and Egg Development in the mosquito aedes aegypti
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Bart Bryant, Warren Macdonald, Alexander S RaikhelAbstract:The mosquito Aedes aegypti is the major vector of arboviral diseases, particularly of Dengue fever, of which there are more than 100 million cases annually. Mosquitoes, such as A. aegypti, serve as vectors for disease pathogens because they require vertebrate blood for their Egg production. Pathogen transmission is tightly linked to repeated cycles of obligatory blood feeding and Egg maturation. Thus, the understanding of mechanisms governing Egg production is necessary to develop approaches that limit the spread of mosquito-borne diseases. Previous studies have identified critical roles of hormonal- and nutrition-based target of rapamycin (TOR) pathways in controlling blood-meal–mediated Egg maturation in mosquitoes. In this work, we uncovered another essential regulator of blood-meal–activated processes, the microRNA miR-275. The depletion of this microRNA in A. aegypti females after injection of its specific antagomir resulted in severe defects in blood digestion, fluid excretion, and Egg Development, clearly demonstrating that miR-275 is indispensable for these physiological processes. miR-275 exhibits an expression profile that suggests its regulation by a steroid hormone, 20-hydroxyecdysone (20E). In vitro organ culture experiments demonstrated that miR-275 is induced by this hormone in the presence of amino acids, indicative of a dual regulation by 20E and TOR. This report has uncovered the critical importance of microRNAs in controlling blood-meal–activated physiological events required for completion of Egg Development in mosquito disease vectors.
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The small GTPase Rheb is a key component linking amino acid signaling and TOR in the nutritional pathway that controls mosquito Egg Development
Insect Biochemistry and Molecular Biology, 2010Co-Authors: Alexander S RaikhelAbstract:Mosquitoes transmit numerous devastating human diseases because they require blood feeding for Egg Development. Previously, we have shown that the nutritional Target-of-Rapamycin (TOR) pathway mediates blood meal activation of mosquito reproductive cycles. Blood-derived amino acid (AA) signaling through the nutrient-sensitive TOR kinase is critical for the transcriptional activation of the major yolk protein precursor (YPP) gene, vitellogenin (Vg), initiation of vitellogenesis and Egg Development. In this study, we provide in vitro and in vivo evidence that the Rheb GTPase (Ras Homologue Enriched in Brain), which is an upstream activator of TOR, is required for AA-mediated activation of the TOR pathway in the fat body of the mosquito Aedes aegypti. Using RNA interference (RNAi) methods, we showed that Rheb was indispensable in AA-induced phosphorylation of S6 kinase, a key downstream substrate of TOR activation. Rheb RNAi depletion resulted in significant downregulation of Vg transcription and translation in the mosquito fat body, which was monitored in vivo after blood meal or in vitro organ culture after AA stimulation. Egg Development was severely hindered in mosquitoes with a Rheb RNAi depletion background. This study represents a notable step in deciphering molecular pathways controlling reproduction of this important vector of human diseases.
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target of rapamycin dependent activation of s6 kinase is a central step in the transduction of nutritional signals during Egg Development in a mosquito
Journal of Biological Chemistry, 2005Co-Authors: Immo A Hansen, Geoffrey M Attardo, Alexander S RaikhelAbstract:Abstract Female mosquitoes are effective disease vectors, because they take blood from vertebrate hosts to obtain nutrients for Egg Development. Amino acid signaling via the target of rapamycin (TOR) pathway has been identified as a key requirement for the activation of Egg Development after a blood meal. We report the characterization of the TOR kinase and one of its major downstream targets, S6 kinase, of the yellow fever mosquito Aedes aegypti during Egg Development in adult females. Both TOR and S6K mRNA are expressed at high levels in the ovaries and in lower levels in fat body and other tissues. After a blood meal, the subcellular localization of TOR shifts from the cytoplasm to the plasma membrane of fat body cells. By detecting phosphothreonine 388 of mosquito S6 kinase, we show that TOR activity strongly increases in fat body and ovaries after a blood meal in vivo. Furthermore, phosphorylation of S6 kinase increases in in vitro cultured fat bodies after stimulation with amino acids. This increase is sensitive to the TOR inhibitor rapamycin in a concentration-dependent manner but not to the phosphatidylinositol 3-kinase/phosphatidylinositol 3-kinase-related kinase inhibitor LY294002, the MAPK inhibitor PD98059, or the translational inhibitor cycloheximide. RNA interference-mediated reduction of S6 kinase strongly inhibits the amino acid-induced up-regulation of the major yolk protein vitellogenin in vitro and effectively disrupts Egg Development after a blood meal in vivo. Our data show that TOR-dependent activation of S6 kinase is a central step in the transduction of nutritional information during Egg Development in mosquitoes.
Steven Russell - One of the best experts on this subject based on the ideXlab platform.
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gene expression during drosophila melanogaster Egg Development before and after reproductive diapause
BMC Genomics, 2009Co-Authors: Dean A Baker, Steven RussellAbstract:Despite the importance of Egg Development to the female life cycle in Drosophila, global patterns of gene expression have not been examined in detail, primarily due to the difficulty in isolating synchronised Developmental stages in sufficient quantities for gene expression profiling. Entry into vitellogenesis is a key stage of oogenesis and by forcing females into reproductive diapause we are able to arrest oogenesis at the pre-vitellogenic stages. Releasing females from diapause allows collection of relatively synchronous developing Egg populations and an investigation of some of the transcriptional dynamics apparent before and after reproductive diapause.
J. C. Freitas - One of the best experts on this subject based on the ideXlab platform.
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Antimitotic action of extracts of Petiveria alliacea on sea urchin Egg Development.
Brazilian Journal of Medical and Biological Research, 1994Co-Authors: E. L. A. Malpezzi, J. C. Freitas, S. C. Davino, L.v. Costa, Astréa M. Giesbrecht, Nidia F. RoqueAbstract:: The hydroethanol extract of the roots of Petiveria alliacea L. (Phytolaccaceae) has been investigated previously as an antitumor agent against mouse Ehrlich ascites. The extract and its methanol, butanol and ether fractions exhibited an antimitotic effect on sea urchin Egg Development. The aqueous fraction did not produce inhibition of cell cleavage. At the first cleavage the inhibition, at the lowest concentration (10 micrograms/ml), produced by the ether fraction was 42%, whereas the inhibition produced by the total extract and by the other fractions was only 5 to 10% showing that the ether fraction was the most active. Even at higher concentrations the butanol and methanol fractions inhibit the cleavage about 30%. At the first cleavage, the ED50 of the hydroethanol extract and of the ether fraction were 45.02 and 12.40 micrograms/ml, respectively. Furthermore, in the second cleavage, the hydroethanol extract was about twice as potent as the methanol or butanol fractions (ED50 of 22.40, 44.80 and 54.10 micrograms/ml, respectively).
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Antimitotic effect of an extract of the sea anemone Bunodosoma caissarum on sea urchin Egg Development.
Brazilian Journal of Medical and Biological Research, 1990Co-Authors: E. L. A. Malpezzi, J. C. FreitasAbstract:A methanolic extract of the sea anemone Bunodosoma caissarum has an antimitotic effect on sea urchin Egg Development. The extract produces a dose-dependent inhibition of cell cleavage. When the extract is added together with sperm to unfertilized sea urchin Eggs, the ED 50 is 0.60±0.03 mg/ml (x±SEM). When added shortly after fertilization, the extract produces the same kind of progressive inhibition but with an ED 50 of 0.98±0.16 mg/ml. In the first case, detachment of the vitelline layer is inhibited whereas in the second case the extract inhibits cleavage even when the membrane is present
Qiang Zhou - One of the best experts on this subject based on the ideXlab platform.
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nutritional signaling regulates vitellogenin synthesis and Egg Development through juvenile hormone in nilaparvata lugens stal
International Journal of Molecular Sciences, 2016Co-Authors: Kai Lu, Xia Chen, Xinyu Zhang, Mingxiao Chen, Qiang ZhouAbstract:Insect female reproduction which comprises the synthesis of vitellogenein (Vg) in the fat body and its incorporation into developing oocytes, needs a large amount of energy and food resources. Our previous studies found that juvenile hormone (JH) regulates vitellogenesis in the brown planthopper, Nilaparvata lugens. Here, we report on the role of JH in nutrient-regulated Vg synthesis and Egg Development. We first cloned the genes coding for juvenile hormone acid methyltransferase (JHAMT) which is involved in JH biosynthesis and methoprene-tolerant (Met) for JH action. Amino acids (AAs) induced the expression of jmtN, while showing no effects on the expression of met using an artificial diet culture system. Reduction in JH biosynthesis or its action by RNA interference (RNAi)-mediated silencing of jmtN or met led to a severe inhibition of AAs-induced Vg synthesis and oocyte maturation, together with lower fecundity. Furthermore, exogenous application of JH III partially restored Vg expression levels in jmtN RNAi females. However, JH III application did not rescue Vg synthesis in these met RNAi insects. Our results show that AAs induce Vg synthesis in the fat body and Egg Development in concert with JH biosynthesis in Nilaparvata lugens (Stal), rather than through JH action.
J-c. Brêthes - One of the best experts on this subject based on the ideXlab platform.
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Changes in yolk total proteins and lipid components and embryonic growth rates during lobster (Homarus americanus) Egg Development under a simulated seasonal temperature cycle
Marine Biology, 2004Co-Authors: V. Sibert, P. Ouellet, J-c. BrêthesAbstract:From August 2000 to June 2001, seven Egg-carrying female lobster ( Homarus americanus ) from the Îles de la Madeleine population (Gulf of St. Lawrence, Canada) were held under a simulated seasonal temperature cycle to monitor Egg Development from extrusion to hatching. For the first time, changes in the yolk components (total lipids and major lipid classes, total proteins) and embryo growth of single Eggs were monitored separately over the entire Development period. Under the controlled temperature conditions, Egg Development proceeded in three phases. (1) Autumn, from extrusion to early December, was marked by a rapid increase in the Perkins’s eye index and rapid declines in yolk total proteins and triacylglycerols (TAG). Embryo daily growth rate was estimated between 1 and 2 µg proteins day^−1. (2) Winter, from late December to early April (temperature stable at ca. 1°C) was characterized by a stationary phase in the evolution of the eye index and yolk lipid use, and embryo growth slowed significantly. (3) Spring, from late April to hatching in June was the period with the most rapid changes in yolk TAG and embryo growth rates >6 µg proteins day^−1 were recorded. Almost 65% of the live biomass (total proteins) of the hatching larvae was accumulated during the last few weeks of Development. An index of embryo growth efficiency was estimated as the slope of the relationship between embryo total proteins and yolk TAG during Egg Development. A relationship was found between the initial mean Egg dry weight and the embryo growth efficiency index suggesting that under the same experimental conditions bigger Eggs used yolk lipids more efficiently and sustained faster embryonic growth than smaller Eggs. The relationship may also explain why larger larvae originate from larger Eggs.