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  • 1980-1984  (2)
  • 1960-1964  (2)
  • Polymer and Materials Science  (3)
  • Differenzierung  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of methylglyoxal bisguanylhydrazone on polyamine biosynthesis, growth, and differentiation of cultured keratinocytes (1980)
    Springer
    Archives of dermatological research 269 (1980), S. 61-68 
    Details
    ISSN: 1432-069X
    Keywords: Polyamines ; Keratinocytes ; Differentiation ; Methylglyoxal bisguanylhydrazone ; Psoriasis ; Polyamin ; Keratinocyten ; Differenzierung ; Methylglyoxal bisguanylhydrazone ; Psoriasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Der Putrescin-, Spermidin- und Spermingehalt in Subkulturen von menschlichen Vorhaut-Keratinocyten wurde während der Phase des schnellen Wachstums und der frühen Plateau-Phase bestimmt. Der höchste Wert wurde in der Wachstums-Phase gefunden. Zugabe von Methylglyoxal bis(guanylhydrazone) während der Wachstums-Phase resultierte in einer konzentrationsabhängigen Abnahme des intracellulären Spermidin- und Spermingehaltes und bei hoher Konzentration Zunahme des Putrescingehaltes. Diese Wirkungen reflektieren die Hemmung der S-adenosyl methionine Decarboxylase durch Methylglyoxal bis(guanylhydrazone). Eine Konzentration dieser Substanz von 8×10-6 M reduzierte den Einbau von radioaktivem Leucin in Eiweiß, reduzierte oder verhinderte die Ansammlung von DNA per Petrischale, inhibierte die mitotische Aktivität und erhöhte den Histidin/Leucin Einbau in Eiweiß. Letztere Wirkung wird als Induzierung der Epithelisierung angesehen. Alle diese Wirkungen waren reversibel, wenn die Inhibitor-Substanz nach 3 Tagen abgewaschen wurde. Hemmung der Enzyme der Polyamin Biosynthese können möglicherweise in der Psoriasistherapie wertvoll sein.
    Notes: Summary The putrescine, spermidine, and spermine content of subcultured human newborn foreskin keratinocytes was determined during growth and early plateau phase and found to be highest during growth. Exposure of the cells to methylglyoxal bis(guanylhydrazone) during growth phase caused a dose-dependent fall in intracellular spermidine and spermine levels and an increase in putrescine levels at higher concentrations. These effects reflect inhibition of S-adenosyl methionine decarboxylase by the drug. At 8×10-6 M the drug reduced incorporation of leucine into protein, lowered or stopped the accumulation of DNA per dish, inhibited mitotic activity, and increased the histidine/leucine incorporation into protein. The last effect is regarded as induction of keratinization. All these effects were reversible if the use of the drug was discontinued after 3 days. Inhibition of the enzymes of polyamine biosynthesis may have value in psoriasis therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404458
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric loss features of some epoxy resins (1963)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 7 (1963), S. 2003-2023 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: At temperatures far below the heat distortion point, the dissipation factor (and therefore power factor) of epoxy resins is comparably low - in the order of 0.001-0.01. Internally flexibilized, polyester-modified resins may have higher loss tangents, in the order of 0.01-0.10, even at room temperature. At temperatures far above the heat distortion point, anhydride curing agents give lower dissipation factors than do amines or acids. With anhydride cures, the higher molecular weight resins investigated cure faster than the lower molecular weight resins, give lower elevated temperature power factors and loss tangents, and are tougher. With any hardener-epoxy resin system, the optimum elevated temperature power factor, weight loss on aging and heat distortion point will probably depend on a close examination of the optimum hardener/resin ratio.With certain anhydride-cured low molecular weight epoxy resin systems, an increased rate of cure and lower elevated temperature power factor may be obtained by use of a small amount of higher molecular weight (polyhydroxy) epoxy resin. Attempts to compare the effect on power factor of changing the hydroxyl groups to less mobile dipoles by acetylation were unsuccessful, since the resulting acetoxy groups changed the cure mechanisms. However studies with resins of different molecular weights indicated that the effect of hydroxyl content on elevated temperature power factor is subordinate to other effects such as the rigidity of the cured resin system, rate of cure and ionic impurities. Acetylation of hydroxyl-containing epoxy resins may inhibit cure with some curing agents, due to side reactions of the resulting acetoxy group with specific hardeners.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1963.070070605
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  • 3
    Electronic Resource
    Electronic Resource
    The measurement of the tacticity of poly(vinyl chloride) by 13C nuclear magnetic resonance spectroscopy (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 879-891 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fourier transform 1H-decoupled 13C NMR spectra were obtained on seven poly(vinyl chloride), (PVC), samples in solution in o-dichlorobenzene. Four of the polymers were of the commercial type and the others were prepared by suspension polymerisation at +90°C, +5°C, and -30°C. Measurements of the spectra were used to assess the precision and accuracy with which information about the tacticity of PVC can be obtained from such spectra. The results show that the well-resolved α-carbon triad and β-carbon tetrad spectra obtained may be reliably analysed to give values of the probability of syndiotactic placement with a precision of about 0,005 for measurements on a single run on a single sample. The simplest and probably the most reliable method of measuring the areas under the peaks which correspond to specific triads ot tetrads is to use the spectrometer integrator, although results of slightly lower precision may be obtained by the use of a curve resolver. Consideration of possible systematic errors due to different T1 relaxation times, unequal nuclear Overhauser enhancement (NOE) factors, and incomplete dissolution of the polymer has shown that the only one of these which is possibly significant is that due to NOE, which is almost certainly less than 0,008, so that the absolute accuracies of the Pr values should be better than that. A more detailed study of the data shows that the polymers made at 5°C and -30°C are almost certainly non-Bernoullian and that firstoder Markov statistics can adequately describe the observed departures from Bernoullian statistics. These departures may have significant consequences for the physical properties of the polymers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840421
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  • 4
    Electronic Resource
    Electronic Resource
    Heat of fusion of polyvinyl fluoride and its interaction with diluentsPresented at the 136th National Meeting of the American Chemical Society, September 17, 1959. (1960)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 43 (1960), S. 383-388 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By employing a simple light-scattering technique to obtain a higher order Tyndall spectrum in mixtures of polyvinyl fluoride with dimethyl sulfoxide, γ-butyrolactone, and N-methylpyrrolidone, melting point data were readily obtained. From these data the heat of fusion per crystalline unit of polymer was found to be about 1800 cal., and the entropy of fusion per unit per bond, 1.9 cal./deg. Of the solvents investigated, N-methylpyrrolidone and dimethyl sulfoxide exhibited the most interaction with the polymer as indicated by interaction energy densities of -9.7 and -4.3 cal./cc., respectively.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1960.1204314209
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