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  • 1
    Electronic Resource
    Electronic Resource
    S6 phosphorylation results from prothoracicotropic hormone stimulation of insect prothoracic glands: A role for S6 kinase (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 15 (1994), S. 332-338 
    Details
    ISSN: 0192-253X
    Keywords: Insect molting ; ecdysteroid ; S6 kinase ; rapamycin ; immunosuppressant ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The insect prothoracic glands are the source of steroidal molting hormone precursors and the glands are stimulated by a brain neuropeptide, prothoracicotropic hormone (PTTH). Previous work from this laboratory revealed that PTTH acts via a cascade including Ca2+/calmodulin activation of adenylate cyclase, protein kinase A, and the subsequent phosphorylation of a 34 kDa protein (p34) hypothesized, but not proven, to be the 56 protein of the 40S ribosomal subunit. The jmmunosuppressive macrolide, rapamycin, is a potent inhibitor of cell proliferation, a signal transduction blocker, and also prevents ribosomal S6 phosphorylation in mammalian systems. We demonstrate here that rapamycin inhibited PTTH-stimulated ecdysteroidogenesis in vitro by the prothoracic glands of the tobacco hornworm, Manduca sexta, with half-maximal inhibition at a concentration of about 5 nM. At concentrations above 5 nM, there was a 75% inhibition of ecdysteroid biosynthesis. Similar results, were observed with the calcium ionophore (A23187), a known stimulator of ecdysteroidogenesis. Most importantly, the inhibition of ecdysteroid biosynthesis was accompanied by the specific inhibition of the phosphorylation of p34, indicating that p34 indeed is ribosomal protein S6. In vivo assays revealed that injection of rapamycin into day 6 fifth instar larvae resulted in a decreased hemolymph ecdysteroid titer and a dose-dependent delay in molting and metamor-phosis. When S6 kinase (S6K) activity was examined using rapamycin-treated prothoracic glands as the enzyme source and a synthetic peptide (S6-21) or a 40S ribosomal subunit fraction from Manduca tissues as substrate, the date revealed that rapamycin inhibited S6K activity. The composite data suggest that rapamycin inhibits a signal transduction element leading to p34 phosphorylation that is necessary for PTTH-stimulated ecdysteroidogenesis in this insect endocrine gland, and lend further support to the concept that p34 is S6. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020150404
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Biosynthesis, secretion, and immunocytochemistry of trypsin modulating oostatic factor of Aedes aegypti (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 27 (1994), S. 27-38 
    Details
    ISSN: 0739-4462
    Keywords: hormone ; HPLC ; ovary ; antibody ; PAGE ; pulse-chase ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Trypsin modulating oostatic factor (TMOF) was followed by RIA in the ovary of female Aedes aegypti before and after the blood meal. The amount of TMOF in a pair of ovaries from females fed sugar for 3 days or blood for 24 h was low (1.7 ng). Between 24 and 48 h after the blood meal the amount of TMOF in the ovaries rapidly increased and reached a peak of 104 ng at 48 h. The amount of TMOF in the head of a female A. aegypti was very low (0.05 to 0.1 ng) during sugar and blood feeding. Immunocytochemical methodology identified the follicular epithelium as the site of biosynthesis of TMOF in the ovary. Females ovariectomized and fed a blood meal continued to synthesize trypsin for 64 h, whereas intact controls stopped at 40 h, indicating that a factor from the ovary regulates trypsin biosynthesis. Ovaries incubated in vitro with [3H]proline synthesized [pro-3H]TMOF that was identified by HPLC and by anti-TMOF serum. The ovary started to synthesize TMOF in vitro 24 h after the blood meal, and the synthesis reached a peak at 36 h and then declined. The synthesis of TMOF by the ovary is closely correlated with the termination of trypsin biosynthesis in the female mosquito's midgut. Ovaries that were pulsed with [3H]proline for 30 min synthesized [pro-3H]TMOF which was chased into the medium with unlabeled proline, indicating that the hormone is secreted by the ovary. These results indicate that TMOF is a secretory peptide, synthesized by the ovarian follicular epithelium and that it modulates trypsin biosynthesis in the mosquito's gut. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940270105
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    Paper (German National Licenses)
    Fulltext
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