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  • 1
    Electronic Resource
    Electronic Resource
    Secondary combined resistance to the multidrug-resistance-reversing activity of cyclosporin A in the cell line F4-6RADR-CsA (1994)
    Springer
    Journal of cancer research and clinical oncology 120 (1994), S. 263-271 
    Details
    ISSN: 1432-1335
    Keywords: Multidrug resistance ; Reversibility ; Cyclosporin A ; Verapamil ; Dexniguldipine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Multidrug-resistant tumor cells can be resensitized by combined application of the selecting cytostatic drug and a chemosensitizer, such as cyclosporin A (CsA) or a calcium channel blocker. Since clinical trials on the circumvention of multidrug resistance (MDR) with chemosensitizers report disparate results, we investigated whether tumor cells of the MDR phenotype can develop additional resistance to the cytostatic chemosensitizer combination. Thus, the Adriamycin(ADR)-selected, P-glycoprotein-positive MDR Friend leukemia cell line F4-6RADR was exposed to stepwise increased concentrations of CsA at a constant level of 0.05 μg/ml ADR. The initial CsA concentration (plus 0.05 μg/ml ADR) to inhibit cell growth of F4-6RADR cells by 50% (IC50) was 0.04 μg/ml. By continuous incubation for more than 6 months, the IC50 for CsA (at constant ADR) was elevated to 3.6 μg/ml (90-fold), thus generating the variant F4-6RADR-CsA. The F4-6RADR-CsA cells were cross-resistant for cyclosporin H (CsH), a non-immunosuppressive derivative of CsA. As shown by immunocytochemistry as well as by the polymerase chain reaction and by Western blotting including densitometry, P-glycoprotein was preserved in the F4-6RADR-CsA variant and was expressed at a 4-fold higher level than in F4-6RADR cells. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis could detect no new proteins in F4-6RADR-CsA as compared to F4-6RADR. Interestingly, resistance of F4-6RADR-CsA cells remained reversible for the calcium antagonists verapamil and dihydropyridine B859-35 (dexniguldipine-HCl), indicating that CsA and these compounds interfere with the P glycoprotein function by different pharmacodynamic mechanisms. Transport studies with [14C]ADR, performed in the presence and absence of chemosensitizers, confirmed the good correlation of P-glycoprotein function with the pattern of resistance found in proliferation assays. Cellular accumulation of [3H]cyclosporin was reduced to 71% of that of the F4-6 controls in F4-6RADR-CsA cells, but remained at the level of controls in F4-6RADR cells. Results indicate that increased amounts of the P-glycoprotein — besides other, perhaps more important mechanisms that are as yet unknown — partially mediate CsA resistance in F4-6RADR-CsA cells. We have designated this new form of resistance “secondary combined resistance” (SCR). The results suggest that at least some clinical cases of insensitivity to chemosensitizers or of relapse after reversing therapy could be explained by SCR, and that resensitizing treatment of tumor patients should be based on the consideration of several chemosensitizers of different pharmacodynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01236382
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  • 2
    Electronic Resource
    Electronic Resource
    Untersuchungen zu den Sondeneigenschaften von 7-Hydroxy-cumarinen in micellarer Cetyl-triethyl-ammoniumbromid-Lösung - Hilfsmittel zur Beschreibung von micellaren Systemen (1986)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 328 (1986), S. 558-566 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Investigation on Probe Properties of 7-Hydroxy-coumarines in Micellar Cetyl-triethyl-ammoniumbromide Solution - Means for Characterization of Micellar SystemsAnions of 3-substituted 7-hydroxy-coumarines (1a-c) as fluorescence probes have been studied in this work. Acid-base equilibria in water and micellar solution of cetyl-triethylammoniumbromide (cmc = 0,72 mmol l-1), fluorescence properties and fluorescence quenching by octacyano-molybdate-IV have been investigated. It has been confirmed that probe and quencher are completely micellized. Fluorescence life times and quenching constants per one quencher molecule in the micell of about 108 s-1 have been determined. The kinetics of saponification of the probe 3-acetyl-7-hydroxy-coumarine at pH = 12 in micellar solution has been followed by probe fluorescence.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19863280415
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  • 3
    Electronic Resource
    Electronic Resource
    Conjugation reactions of polyaromatic quinones to mono- and bisglutathionyl adducts: Direct analysis by fast atom bombardment mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 329-332 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conjugation products of several reactive quinones with glutathione have been identified by fast atom bombardment mass spectrometry. Appropriate conditions have been developed which enabled the direct, dynamic mass spectral analysis of spontaneous, as well as glutathione transferase catalysed conjugation reactions. Applications to a series of quinones provided the direct detection and differentiation of the formation of mono- and bisglutathionyl adducts between regioisomeric quinone substrates in that only 1,4-quinones yielded bisglutathionyl adducts, which were not observed for the 1,2-isomers.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150605
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  • 4
    Electronic Resource
    Electronic Resource
    Untersuchungen an elektronenleitenden Oxidsystemen. XXI. Stabile spinelle ZnzNiMn2-zO4 und Vergleich mit Spinellen MgzNiMn2-zO4 (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 608 (1992), S. 166-172 
    Details
    ISSN: 0044-2313
    Keywords: Spinel ; zinc, nickel manganite spinel ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations on Electronically Conducting Oxide Systems. XXI [1] Stable Spinels ZnzNiMn2-zO4 and Comparison with Spinels MgzNiMn2-zO4Stable spinels are obtained in the result of substitution of ZnII for manganese in the series ZnzII NiIIMnzIVMn2-2zIIIO4 (O ≤ z ≤1). Different from spinels MgzII NiIIMnzIVMn2-2zIIIO4 (O ≤ z ≤1)they don't be submitted to decomposition in air during slow cooling at medium temperatures. ZnNiMnO4 (z=1) could not be prepared in a mono-phase state which is indicated by the composition of ZnNiMnO3.96 deduced from analysis by oxidimetric titration. The comparably small variation of the specific electrical conductivity and of the activation energy observed in the range O ≤ z ≤ 2/3 for ZnzNiMn2-z is discussed in relation to larger alterations in the series MgzNiMn2-zO4. Structural interpretation is proposed based on the comparison of the molar volume of spinels M Mn2O4 (M: Mn, Fe, Co, Ni, Cu, Zn, Mg).
    Notes: Die Substitution von ZnII anstelle von Mangan in der reihe ZnzII NiIIMnzIVMn2-2zIIIO4 (O ≤ z ≤1)ergibt stabile Spinelle, die im Unterschied zu Spinellen MgzIINiIIMnzIVMn2-2zIIIO4 (O ≤ z ≤1) beim langsamen Abkühlen im mittleren Temperaturbereich nicht dem Zerfall unter Sauerstoffaufnahme unterliegen. ZnNiMnO4 (z=1) konnte nach Bestimmung der mittleren Oxydationsstufe des Mangans nur in der Zusammensetzung ZnNiMnO3,96 und damit nicht völlig phasenrein erhalten werden. Die im Bereich O ≤ z ≤ 2/3 relativ geringe Änderung der spezifischen Leitfähigkeit und der Aktivierungsenergie wird im Vergleich mit einer stärkeren Variation der Eigenschaften in der Substitutionsreihe MgzNiMn2-zO4 diskutiert und im Zusammenhang mit einer Betrachtung der Molvolumina von M Mn2O4-Spinellen (M:Mn, fe, Co, Ni, Cu, Zn, Mg) strukturchemisch interpretiert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926080225
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  • 5
    Electronic Resource
    Electronic Resource
    Zur Wirkung kationischer Tenside auf das Spektrale Verhalten des sauren Triphenylmethanfarbstoffs Pentachrom Azurblau2″,6″-Dichlor-3,3′-dimethyl-4′-hydroxy-fuchson-5,5′-dicarbonsäure und seiner Metall-(III)-Komplexe - Micelleffekt oder ternäre Komplexbildung?Herrn Prof. Dr. Dr. h. c. H. G. O. Becker zum 60. Geburtstag gewidmet (1982)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 324 (1982), S. 299-308 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Effect of Cationic Detergents on the Spectral Properties of Pontachrome Azur blue and its Metal(III)-complexes - Micell Effect or Ternary Complex Formation?The results of studies of the metachromasy effect of pontachrome azur blue and its lakes, preferably with aluminium, and hexadecyl-, tetradecyl-, dodecyl- and decyltriethyl-ammonium-bromide, respectively can be explained on the basis of ternary complex formation. The surfactants can be applied at concentrations far below its critical micelle concentrations thus excluding micelle effects.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19823240214
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