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  • Electronic Resource  (21)
  • 1995-1999  (11)
  • 1975-1979  (10)
  • Chemistry  (16)
  • Life and Medical Sciences  (3)
  • Aggression  (2)
  • 11
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 599-600 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 424-424 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 1349-1362 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This article reports the production of a surgical implant meeting several specific requirements such as biocompatibility, biodegradability, macroporosity, and flexibility. Porosity was controlled by an original method consisting of the aggregation of calibrated poly-D,L-lactide microparticles. The size of the interstices between the aggregated microspheres was in a direct relationship to the microsphere diameter. A first approach was based on coating the microspheres with poly(vinyl alcohol) followed by chemically crosslinking the coating layers that were in mutual contact. This method was disregarded because of the acute cytotoxicity of glutaraldehyde used as the crosslinking agent, the absence of macroporosity, and the complete lack of flexibility. A physical technique of aggregation was then tested, which relied on the plasticization of poly-D,L-lactide microspheres with triethylcitrate to the point where microspheres strongly adhered to each other when they were in contact. This method has proved to be straightforward and definitely superior to the chemical approach, particularly with respect to cytotoxicity, control of macroporosity, and flexibility. A polymer support was thus successfully produced which was biodegradable, macroporous (interconnected pores of 10-100 μm in diameter), and flexible. This potential medical device is presently being used for neuronal transplantation in the central nervous system. © 1995 John Wiley & Sons, Inc.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 89 (1976), S. 595-602 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The number of H+ ejected during passage of 2e- through each energy-conserving site of the mitochondrial respiratory chain (the H+/site ratio) was measured in three ways. In each case transmembrane movements of endogenous phosphate were minimized. (1) Measurement of the uptake of weak acids during loading of mitochondria with Ca2+ demonstrated that 2.0 weak acid anions were accumulated per Ca2+ ion. Since 1.7 to 2.0 Ca2+ ions were taken up per site, these data correspond to an H+/site ratio of 3.5 to 4.0. (2) More direct measurement of H+ ejection using the oxygen pulse technique demonstrated that the H+/site ratio was 3.0. In these experiments phosphate movements were prevented by addition of N-ethylmaleimide to inhibit phosphate-hydroxide antiport, by washing the mitochondria to remove endogenous phosphate, or by working at 5°C to reduce the rate of phosphate transport. When phosphate movements were allowed, H+/site ratios of 2.0 were observed. (3) Measurement of the initial steady rates of oxygen consumption and H+ ejection following addition of substrate to aerobic, substrate-limited mitochondria yielded H+/site ratios of 2.0, which were elevated to 4.0 when phosphate transport was prevented as described above.Previous determinations of the H+/site ratio were thus underestimates due to the unrecognized movements of endogenous phosphate; our results show that the H+/site ratio is at least 3.0 and may be as high as 4.0.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The isolation and characterization of a mutant murine T-cell lymphoma (S49) with altered purine metabolism is described. This mutant, AU-100, was isolated from a mutagenized populatio of S49 cells by virtue of its resistance to 0.1 mM 6-azauridine in semisolid agarose. The AU-100 cells are resistant to adenosine mediated cytotoxicity but are extraordinarily sensitive to killing by guanosine.High performance liquid chromatography of AU-100 cells extracts has demonstrated that intracellular levels of GTP, IMP, and GMP are all elevated about 3-fold over those levels found in wild type cells. The AU-100 cells also contain an elevated intracellular level of pyrophosphoribosylphosphate (PPriboseP), which as in wild type cells is diminished by incubation of AU-100 cells with adenosine. However AU-100 cells synthesize purines de novo at a rate less than 35% of that found in wild type cells.In other growth rate experiments, the AU-100 cell line was shown to be resistant to 6-thioguanine and 6-mercaptopurine. Levels of hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) measured in AU-100 cell extracts, however, are 50-66% greater than those levels of HGPRTase found in wild type cell extracts. Nevertheless this mutant S49 cell line cannot efficiently incorporate labeled hypoxanthine into nucleotides since the salvage enzyme HGPRTase is inhibited in vivo.The AU-100 cell line was found to be 80% deficient in adenylosuccinate synthetase, but these cells are not auxotrophic for adenosine or other purines. The significant alterations in the control of purine de novo and salvage metabolism caused by the defect in adenylosuccinate synthetase are mediated by the resulting increased levels of guanosine necleotides.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Nine independently derived clones of mutagenized rat hepatoma cells selected for resistance to 6-mercaptopurine (6-MP) or 6-thioguanine (6-ThioG) have been isolated. Each has severely reduced catalytic activity of hypoxanthine-guanine phosphoribosyltransferase (HPRT) and seven of them possess significantly increased activities of phosphoribosylpyrophosphate (PRPP) synthetase. The degrees of elevations of PRPP synthetase activities do not correlate with the degrees of deficiencies of HPRT activities.The cells from one of these clones, 1020/12, possess 40% of the normal HPRT catalytic activity and overproduce purines. We have extensively examined the cells from this clone. Immunotitration studies of 1020/12 cells indicate that there is a mutation in the structural gene for HPRT. Although they possess increased specific catalytic activities of the enzyme, PRPP synthetase, the catalytic parameters, heat stability, and isoelectric pH of PRPP synthetase from 1020/12 cells are indistinguishable from those of the enzyme from wild-type cells.The cause of purine overproduction by 1020/12 cells appears to be the elevated PRPP synthetase activity, rather than a PRPP “sparing” effect stemming from reduced HPRT activity. Support for this idea is provided by the observation that the complete loss of HPRT activity in a clone derived from 1020/12 cells does not further enhance the levels of PRPP synthetase or purine overproduction.We propose that the elevated levels of PRPP synthetase activity in these HPRT deficient cells result from a mutational event in the structural gene for HPRT, and that this causes the disruption of a previously undescribed regulatory function of this gene on the expression of the PRPP synthetase gene.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 95-97 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Carbon-13 chemical shifts of several benzimidazole- and benzoxazole derivatives have been measured. The signals of the homonuclear carbon atoms in unsymmetrical benzoheteroazoles can be assigned with the aid of additivity parameters. The structures of compounds obtained from the reaction of benzimidazoline- and benzoxazoline-2-thione with aryl cyanates were elucidated.
    Notes: Für verschiedene Benzimidazol- und Benzoxazolderivate wurden die chemischen Verschiebungen im 13C-NMR-Spektrum bestimmt. Mit Hilfe von Additivitätsparametern lassen sich die 13C-Signale der Benzokohlenstoffatome in unsymmetrischen Benzheteroazolen bestimmen. Die Struktur der Reaktionsprodukte aus Benzimidazolin- und Benzoxazolin-thion-(2) und Arylcyanaten werden abgeleitet.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 320 (1978), S. 1055-1056 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 0749-1581
    Keywords: 4-Methyl catechol ; Autoxidation ; Electron spin resonance spectroscopy ; Nucleophiles ; Semiquinones ; Allergic contact dermatitis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation of 4-methylcatechol by dioxygen and the subsequent reactions of the two nucleophiles OH- and MeO- with the oxidation products were studied by electron spin resonance (ESR) spectroscopy. These reactions are models for those of skin proteins with substituted 1,2-dihydroxybenzenes (catechols) which produce the severe allergic contact dermatitis associated with plants such as poison ivy, poison oakd and the Japanese lac tree. The rates of formation of the primary and secondary semiquinone radical anions show a large kinetic deuterium isotope effect (ca 10) at 20°C, which is ascribed to a slow deprotonation of the hydrogen bridged 4-methylcatechol monoanion. There is a marked difference in regioselectivity for OH- and MeO- substitution of the 4-methylcatechol monoanione; OH- reacts exclusively at the 3-position whereas MeO- attacks at the 5-position. This dissimilarity between two normally similar nucleophiles is also ascribed to the occurrence of hydrogen bridging between the substituting OH- at the 3-position and the adjacent quinone oxygen at the 2-position. The expected attack at the more electropositive 5-position occurs with MeO- because no such hydrogen bonding can occur. Disubstitution occurs for OH- but not for MeO-, probably reflecting the greater nucleophilicity of the former.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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