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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogenase switch-off by ammonia in Rhodopseudomonas palustris: Loss under nitrogen deficiency and independence from the adenylylation state of glutamine synthetase (1981)
    Springer
    Archives of microbiology 130 (1981), S. 138-142 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogenase regulation ; Glutamine synthetase ; Ammonia switch-off ; Rhodopseudomonas palustris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogenase activity in Rhodopseudomonas palustris is subject to a rapid switch-off in response to exogenous ammonia. When cells were grown on limiting nitrogen and eventually became nitrogen deficient, nitrogenase synthesis was fully derepressed but the enzyme was insensitive to ammonia. The transformation of ammonia-sensitive to ammonia-insensitive cells was a slow, but fully reversible process. The switch-off effect in ammonia-sensitive cells paralleled changes in the adenylylation state of glutamine synthetase. Ammonia-insensitive cells, however, showed similar changes in glutamine synthetase activity although nitrogenase activity was unaffected. We conclude that nitrogenase regulation and adenylylation of glutamine synthetase are independent processes, at least under conditions of nitrogen deficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411066
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  • 2
    Electronic Resource
    Electronic Resource
    L-Methionine-SR-sulfoximine as a probe for the role of glutamine synthetase in nitrogenase switch-off by ammonia and glutamine in Rhodopseudomonas palustris (1983)
    Springer
    Archives of microbiology 134 (1983), S. 17-22 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; Nitrogenase regulation ; Glutamine synthetase ; Methionine suofoximine ; Rhodospirillaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methionine sulfoximine (MSX), an irreversible inhibitor of glutamine synthetase of Rhodopseudomonas palustris restored nitrogenase activity to cells in which nitrogenase had been completely inhibited by ammonia switch-off. After addition of MSX, there was a lag period before nitrogenase activity was fully restored. During this lag, glutamine synthetase activity progressively decreased, and near the time of its complete inhibition, nitrogenase activity resumed. Nitrogenase switch-off by ammonia thus required active glutamine synthetase. Glutamine itself caused nitrogenase inhibition whose reversal by MSX depended on the relative ratio of MSX to glutamine. Unlike ammonia, glutamine inhibited nitrogenase under conditions where glutamine synthetase activity was absent. This indicates that glutamine is the effector molecule in nitrogenase switch-off, for instance by interacting with the enzymatic system for Fe protein inactivation. The effects of glutamine and MSX were also dependent on the culture age. Possible explanation for this and for the competitive effects are a common binding site within the regulatory apparatus for nitrogenase, or, in part, within a common transport system. Some observations with MSX were extended to Rhodopseudomonas capsulata and agreed with those in R. palustris.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00429400
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of two juvenile hormone radioimmunoassays (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 23 (1993), S. 147-152 
    Details
    ISSN: 0739-4462
    Keywords: honey bee ; Apis mellifera ; juvenile hormone ; radioimmunoassay ; hemolymph ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Juvenile hormone from the hemolymph of adult worker honey bees of known age and behavioral status was extracted and analyzed by two different radioimmunoassays in two independent laboratoies. The assays are different in hapten attachment, radiolabeled tracer, and the method by which bound and unbound hormone are separated. Despite these differences in the methods, hormone determinations were in excellent agreement at lower levels (0-50 ng/ml) but diverged as the hormone concentrations increased (〉 50 ng/ml). The relative changes are in good agreement, with a correlation coefficient of 0.97. © 1993 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940230306
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  • 4
    Electronic Resource
    Electronic Resource
    Juvenile hormone regulation of hemolymph juvenile hormone binding protein in the black strain of the tobacco hornworm, Manduca sexta (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 30 (1995), S. 165-176 
    Details
    ISSN: 0739-4462
    Keywords: Lepidoptera ; radioimmunoassay ; enzyme immunoassay ; equilibrium dialysis ; monoclonal antibody ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Numerous studies have demonstrated regulation of specific lepidopteran proteins by pharmacological doses of insect juvenile hormone (JH). In this study, topical application of a 1 pg dose of JH I to fourth stadium larvae of the black (bl) mutant strain of the tobacco hornworm, Manduca sexta, induced a 50% increase in the titer of hemolymph juvenile hormone binding protein (hJHBP). Radioimmunoassay confirmed that JH titers were lower in bl larvae than in wild-type larvae at the time of JH treatment. Enzyme immunoassay analysis of hJHBP titers demonstrated that regulation by JH I was dose-dependent at doses up to 10 pg and that the response was saturated above 100 pg. Western blotting and equilibrium dialysis confirmed these results and demonstrated that hJHBP from bl larvae had the same molecular mass and displayed the same affinity for JH I as hJHBP isolated from wild-type larvae. Time course studies showed that regulation was complex: 1 2 h after JH I treatment, hJHBP titers were twofold lower in treated than in control bl larvae, while 44 h after treatment they were twofold higher. JH I regulation of hJHBP titers in bl larvae was independent of changes in total hemolymph protein. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940300207
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  • 5
    Electronic Resource
    Electronic Resource
    Recent advances in radioimmunoassay technology for the juvenile hormones (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 30 (1995), S. 295-306 
    Details
    ISSN: 0739-4462
    Keywords: radioimmunoassay ; JH I ; JH II ; JH III ; hemolymph ; insect hormone ; Manducasexta sexta ; Hyalophora cecropia ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Recent refinements in juvenile hormone radioimmunoassay technology now make this method significantly more sensitive and easier to use. Rabbit poly-clonal antisera against (10R) JH III and racemic JH II have been developed to determine hemolymph hormone titers in the low picogram range. The antisera display minimal cross-reactivity with JH metabolites, JH analogs, and hemolymph lipids. One antiserum recognizes racemic JH I, II, and (10R) III almost equivalently, exhibiting 50% displacement between 100 and 130 pg per tube. Another antiserum is JH II-specific and exhibits 50% displacement at 35 pg per tube. Assay sensitivity has been enhanced by using (10R,11S) [methyl-3H]-JH II of very high specific activity (〉 80 Ci/mmol) generated with Hyalophora cecropia accessory gland S-adenosylmethionine transferase and S-[methyl-3H]-adenosyl-L-methionine. Preparation of biological samples has been simplified with overall recoveries of JH from hemolymph ranging between 60 and 75%. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940300215
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