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  • 1
    Electronic Resource
    Electronic Resource
    The effects of changing intracellular pH on calcium and potassium currents in smooth muscle cells from the guinea-pig ureter (1998)
    Springer
    Pflügers Archiv 435 (1998), S. 518-522 
    Details
    ISSN: 1432-2013
    Keywords: Key words Calcium ; Contraction ; Electrophysiology ; Guinea-pig ; pH ; Potassium ; Ureter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Guinea-pig ureteric smooth muscle is unusual in that intracellular acidification increases and alkalinization decreases force production. To help elucidate the mechanism underlying these effects on force we have investigated the effects of changing intracellular pH on both calcium and potassium currents in single cells isolated from the guinea-pig ureter to determine their possible role in force development. Depolarization to +40 mV resulted in a fast transient outward current which was inhibited by 4-aminopyridine but not tetraethylammonium. Intracellular alkalinization (20 mM trimethylamine) increased this current to 179 ± 24% of the control and resulted in the development of a slowly activating large outward current which was inhibited by tetraethylammonium and washout. Acidification (40 mM sodium butyrate) decreased the fast transient outward current to 58 ± 3% of the control and did not produce a slowly activating current. When potassium was replaced by caesium in the pipette solution, depolarization to 0 mV resulted in an inward calcium current which was abolished by nifedipine. Intracellular alkalinization increased this current to 126 ± 11% of the control whereas acidification had the opposite effect, decreasing it to 55 ± 10%. Furthermore, current-clamp experiments showed that intracellular alkalinization inhibited the amplitude of the action potential, therefore decreasing excitability of the cell. From our results, we suggest that the predominant effects of intracellular pH on force production in the guinea-pig ureter are mediated via the modulation of outward potassium currents (thereby reducing excitability of the tissue) rather than the effects on the inward calcium current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050547
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  • 2
    Electronic Resource
    Electronic Resource
    Changes of pH affect calcium currents but not outward potassium currents in rat myometrial cells (1995)
    Springer
    Pflügers Archiv 431 (1995), S. 135-137 
    Details
    ISSN: 1432-2013
    Keywords: pH ; uterus ; calcium current ; potassium current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneous contraction of uterine smooth muscle is enhanced by alkalinization and depressed by acidification. We have investigated the ionic currents responsible for this in single myometrial cells. Intracellular acidification (20 mM butyrate) at constant external pH depressed the magnitude of the calcium current to 58±6% of control, but had little effect on outward currents. Similar but slower effects were also observed when the extracellular pH was lowered to 6.9 (56±9% of control). Correspondingly, when the intracellular or extracelluar pH was elevated (20 mM NH4Cl or pH 7.9 respectively) the calcium current magnitude increased (165±15 % in NH4Cl; 136±2 % at pH 7.9) and there was, again, no effect on the outward currents. These observations are consistent with the effects of pH on spontaneous contractile activity being due to an effect on the membrane calcium current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374388
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  • 3
    Electronic Resource
    Electronic Resource
    Copolymers and Fibers from VinylidenedicarbonitrileLecture at the Meeting of the Gesellschaft Deutscher Chemiker, Section “Kunststoffe und Kautschuk”, on April 10th. 1962 at Bad Nauheim (Germany). (1962)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 1 (1962), S. 425-430 
    Details
    ISSN: 0570-0833
    Keywords: Copolymers ; Fibers ; Vinylidenedicarbonitrile ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vinyldendicarbonitrile (Vinylidene cyanide) on free redical catalyzed copolymerization shows a much stronger tendency to form 1:1 alternating copolymers than acrylonitrile. While bulk poly(vinylidene cyanide) fails to crystallize, despite its molecular symmetry, several alternating copolymers are readily crystallizable, notably those containing butadiene, isoprene, isobutylene, or vinylidene chloride. Fibers have been prepared from a number of the higher melting copolymers and examined for physical properties. Fibers from the vinyl acetate and vinyl chloride copolymers show expectional elastic behavior both when dry and wet. The fiber from the vinylidene cyanide |vinyl acetate alternating copolymer (Darvan® nytril fiber) is only moderately oriented and is characterized by exceptional softness and excellent elastic recovery and resilience, both when dry and wet.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196204251
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    Paper (German National Licenses)
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