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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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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Rapid analysis using capillary supercritical fluid chromatography (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 73-77 
    Details
    ISSN: 0935-6304
    Keywords: Capillary supercritical fluid chromatography ; Fast analysis ; Nonvolatile analytes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary supercritical fluid chromatography (SFC) is proving to be a viable and useful separation method for thermally labile and nonvolatile materials. As with other capillary chromatographic techniques, very fast separations can be accomplished by sacrificing total efficiency and optimizing the conditions for rapid analysis. This is achieved using short, small-bore capillary columns, increased mobile phase linear velocities and very fast pressure programming rates. These principles are demonstrated for the rapid separation of selected component systems.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240090204
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    Paper (German National Licenses)
    Fulltext
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