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  • General Chemistry  (5)
  • radioimmunoassay  (3)
  • Biliary Excretion  (2)
  • Nitrogenase regulation  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 290 (1975), S. 235-250 
    ISSN: 1432-1912
    Keywords: Nafenopin ; Biliary Excretion ; Hepatic Uptake ; Hypolipidemic Agents ; Dibromosulphthalein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats treated with the hypolipidemic agent, nafenopin (SU-13, 437) exhibit a higher plasma retention and a markedly reduced biliary excretion of organic anions, such as sulfobromophthalein (BSP) and its dibromo analog (DBSP), indocyaninegreen (ICG), succinylsulfathiazole (SST) and polar metabolites of bilirubin and the carcinogens 7, 12-dimethylbenzanthracene (DMBA) and 3,4-benz-pyrene (BP), despite an increase in liver mass and a profound choleresis. However, taurocholate is not affected in this manner, which supports the idea of a transport mechanism for taurocholate that differs from that of other organic anions. A pharmacokinetic study was made for DBSP in vivo. After nafenopin treatment, primary hepatic uptake (k12) and transport from liver into bile (k23) are reduced in vivo. Infusion studies indicate that biliary transport maximum (Tm) for DBSP is also decreased although the calculated hepatic storage (S) is only moderately affected. In the isolated perfused liver, hepatic clearance and biliary excretion of BSP are reduced by two-thirds. The time course of anion tranport inhibition and the hepato-biliary disposition of 14C-nafenopin suggest a direct effect of the drug. The extra liver mass induced by nafenopin appears to be hypo- or nonfunctional with respect to hepatic transport of organic anions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 290 (1975), S. 221-234 
    ISSN: 1432-1912
    Keywords: Biliary Excretion ; Choleresis ; Nafenopin Enterohepatic Circulation ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Administration of nafenopin (SU-13-437) to male rats for two days leads to a doubling of bile production and a 50% increase in liver weight. These two effects have been shown not to be directly interrelated. A marked decrease in biliary bile salt concentration suggests that the bile salt independent flow is stimulated. The extra bile produced is probably of canalicular origin since bile to plasma concentration ratios of erythritol are unchanged. At least three polar metabolites of nafenopin have been observed in rat bile. Obervations in rats with partial biliary fistulas indicate that the drug and its metabolites undergo extensive enterohepatic circulation. Our studies support the view that much of the enhanced bile flow is associated with the presence of nafenopin and/or its metabolites within the hepatobiliary system. However, the response is too extensive to be explained merely by osmotic choleresis. Induced structural changes in the liver may also account for some of this effect.
    Type of Medium: Electronic Resource
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  • 3
    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
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  • 4
    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
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 68 (1956), S. 181-182 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 104 (1992), S. 51-53 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 17 (1978), S. 246-254 
    ISSN: 0570-0833
    Keywords: NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 17O-NMR spectroscopy has found limited application as a structural probe due to the experimental problems associated with a quadrupolar nucleus having low natural abundance. A survey of data obtained from systematic studies of structurally related compounds shows, however, that large chemical shift differences are usually obtained for structurally nonequivalent nuclei, and that characteristic chemical shift values are observed for specific chemical environments. The present day availability of 17O enriched materials and Fourier transform NMR instrumentation should allow extensive application of the 17O-NMR technique to structural problems in the immediate future.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 90 (1978), S. 258-271 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die NMR-Spektroskopie des Isotops 17O, eines Quadrupolkerns mit geringer natürlicher Häufigkeit, wurde bisher wegen experimenteller Schwierigkeiten nur beschränkt zur Lösung chemischer Probleme herangezogen. Ein Vergleich der aus systematischen Studien strukturell verwandter Verbindungen erhaltenen Daten zeigt jedoch, daß nichtäquivalente Sauerstoffatome für gewöhnlich große Unterschiede in den chemischen Verschiebungen aufweisen und daß für 17O in spezifischen chemischen Umgebungen charakteristische Werte der chemischen Verschiebung beobachtet werden. Die gegenwärtige Verfügbarkeit von 17O-angereichertem Material und von Fourier-Transform-NMR-Geräten läßt für die nahe Zukunft eine ausgiebige Anwendung der 17O-NMR-Technik zur Lösung struktureller Probleme erwarten.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 31 (1992), S. 49-51 
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 30 (1995), S. 165-176 
    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
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