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  • Polymer and Materials Science  (8)
  • Keratinocyten  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of vitamin A acid on cyclic nucleotides of cultured keratinocytes (1980)
    Springer
    Archives of dermatological research 267 (1980), S. 25-31 
    Details
    ISSN: 1432-069X
    Keywords: Vitamin A acid ; Keratinocytes ; Cyclic nucleotides ; Thymidine incorporation ; Cell cycle ; Vitamin A-Säure ; Keratinocyten ; cyclische nukleotide ; Thymidinaufnahme ; Cellcyclus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Primärkulturen von Meerschweinchenohr-Keratinocyten wurden mit Vitamin A-Säure behandelt zum Zeitpunkt des Ansetzens der Kulturen oder 14 h bzw. 14 Tage danach. In einem Zeitraum bis 50 h nach Behandlung wurde die intracelluläre Konzentration von den cyclischen Nukleotiden cAMP und cGMP mit einem Radio-Immunoassay in Intervallen bestimmt. Wenn die Zugabe der Vitamin A-Säure beim Ansetzen der Kulturen erfolgte, resultierte eine Welle von DNA-Synthese und eine Zunahme der DNA-Konzentration, die ihre Maxima zwischen 30 und 40 h nach Kulturansatz erreichte und zeitlich mit einer Abnahme der cAMP-Konzentration zusammenfällt. Dies könnte auf eine Keratinocyten-Subpopulation hinweisen. Die Zugabe von Vitamin A-Säure 14 h oder 14 Tage nach Kulturansatz führte zu sofortiger, wenn auch zeitlich begrenzter Abnahme der cAMP- und cGMP-Konzentration sowie einer Welle von Thymidin-Aufnahme die nicht mit einer Zunahme des DNA-Gehalts in der Petrischale verbunden war. Somit wirkt eine einmalige Behandlung mit Vitamin A-Säure nur dann Mitoseauslösend, wenn deren zugabe beim Ansetzen der Zellkultur erfolgte. Zu späteren Zeitpunkten verursacht Vitamin A-Säure Veränderungen in der Konzentration der cyclischen Nukleotide ohne bemerkbare Zellproliferation.
    Notes: Summary Primary cultures of guinea pig ear keratinocytes were treated with vitamin A acid at plating, or at 14 h or 14 days after plating. The intracellular content of the cyclic nucleotides cAMP and cGMP was determined by radioimmunoassay at intervals during a period of 50 h after treatment. When added at plating, vitamin A acid produced a wave of DNA synthesis and increase in DNA which was at maximum between 30 and 40 h after plating, and coincided with decreased cAMP levels. This may represent a subpopulation of keratinocytes in S phase. Treatment with vitamin A acid at 14 h or 14 days after plating resulted in an immediate but temporary fall in cAMP and cGMP, and a wave of thymidine uptake but no increase in DNA per dish. Thus, a single treatment with vitamin A acid is mitogenic only when applied at plating. At other times, it can cause changes in cyclic nucleotide content without any observable cell proliferation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00416918
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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Transfer constants from complete molecular weight distributions (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 403-412 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transfer constants to chain-transfer agent (CTA) and to monomer can be obtained by consideration of the complete molecular weight distribution, using the slope of a plot of the natural logarithm of number-molecular weight distribution against molecular weight, in the limit of high molecular weight and low radical flux (P. A. Clay, R. G. Gilbert, Macromolecules 28, 552 (1995)). This method is applied to the bulk polymerisations of methyl methacrylate (MMA) with added triethylamine (TEA) and with added tert-dodecylmercaptan (mixture of 2,4,4,6,6-pentamethylheptane-2-thiol and 2,2,4,6,6-pentamethylheptane-4-thiol, TDM). The transfer rate coefficients are found to be 74 (±20) dm3 · mol- · s-l at 60°C for TEA, and 56 (±13) dm3 · mol-1 · s-1 at 25°C for TDM.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1996.021970131
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    A study of methods for measuring the tacticity of poly(vinyl chloride) by proton magnetic resonance spectroscopy (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 2895-2912 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 60 MHz undecoupled α-, 90 MHz undecoupled β-, and 90 MHz decoupled α- and β-proton spectra were measured for seven poly(vinyl chloride) samples, four of these being commercial type polymers, the others were prepared at +75°C, +5°C and -30°C. The results were used to assess the preferred approach to the determination of tacticity. The reproducibility of the values from different solutions of a given polymer is significantly worse than that between a series of runs on a particular solution, showing that sampling errors are larger than those from instrumental sources. Although the 60 MHz spectra were found to be unsatisfactory when interpreted on a first order basis, curve fitting methods, which were similar to those used for the other types of spectra and involved the use of reasonable assumptions for chemical shifts and coupling constants, gave results of comparable precision to those from the two types of decoupled spectra and superior to those from the undecoupled 90 MHz spectra. The preferred approach is to combine the results from α- and β-proton spectra and to examine more than one solution of a given material. The applicability of Bernoullian propagation statistics was assumed in the majority of the curve fitting calculations; in the cases where this was not so the results were used to test this assumption and it has proved to be valid.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1978.021791209
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Transfer constants from complete molecular weight distributions (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 663-663 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980237
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation and polymerizability of substituted α,β,β-trifluorostyrenes (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 6 (1968), S. 711-717 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1968.150060322
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  • 10
    Electronic Resource
    Electronic Resource
    Pressure-related driving forces in the fully filled nonintermeshing twin screw extruder (1993)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 12 (1993), S. 353-360 
    Details
    ISSN: 0730-6679
    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
    Notes: Research in understanding the mechanisms behind driving forces in the fully filled nonintermeshing twin screw extruder concentrated on experimental analysis of the relation between stagger, screw speed, and cross-channel flow due to measured pressure differential in the nip region. A new measure of the pressure driving force was also sought out, to correlate new data to previous findings from visual studies. The first part of the study was to obtain the values for the dynamic pressure on both sides of the nip region. Further refinements to the equipment used in previous studies allowed closer placement of the transducers in the nip region. After the data were stored, analysis started by determining the δp values from the trace of the pressure differential. By plotting these values, we obtain a highly repeatable curve confirming that the greatest pressure flow occurs at small staggers. A simple 2-D model for pressure flow in the nip region was used to estimate the effect of the cross-channel pressure differential. Values for the cross-channel pressure flow were calculated and compared with the drag flow and found to be significant. © 1993 by John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1993.060120403
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