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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 45 (1989), S. 334-337 
    ISSN: 1420-9071
    Keywords: Benzodiazepine ; circadian rhythm ; gamma-aminobutyric acid ; inverse agonist ; suprachiasmatic nucleus ; triazolam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The benzodiazepine triazolam, the benzodiazepine inverse agonist, β-methyl carboline (β-CCM) or both, were administered to adult male hamsters under conditions of constant light. When given alone, triazolam induced phase advances in the circadian activity rhythm of about 90 min, while β-CCM when given alone, had no effect on phase of the activity rhythm. However, when triazolam and β-CCM were given at the same time, the magnitude of the phase advances induced by triazolam were attenuated to about 30 min. These data, in conjunction with previous results, provide pharmacological evidence for a GABAergic system involved in the regulation of a central circadian pacemaker.
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Calyculin-A ; Okadaic acid ; Protein phosphatase ; Root development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Emerging evidence suggests that protein phosphatases play an important role in the growth and development of higher plants. We report here on the effects of okadaic acid and calyculin-A, two specific and potent inhibitors of the type-1 and type-2A families of serine/ threonine protein phosphatases, on the growth and development ofArabidopsis thaliana L. roots. Application of these drugs in nanomolar ranges arrested root hair growth, severely affected the shape of cells within the zone of elongation and inhibited root growth rates. Root hair elongation was inhibited by concentrations of okadaic acid and calyculin-A as low as 3 nM. The pleiotropic effects of okadaic acid and calyculin-A point to multiple functions for type-1 and -2A protein phosphatases in controlling root growth and development.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 18 (1984), S. 542-545 
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Alumina ; Fused silica capillary columns ; Middle distillate fuel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application of capillary supercritical fluid chromatography (SFC) to the analysis of a middle distillate fuel is described. Small diameter (50μm i.d.) fused-silica capillary columns coated with crosslinked 50% phenyl polymethylphenyl siloxane provided high separation efficiency and good compatibility with flame ionization detection. High resolution separations of the chemical class fractions obtained by adsorption chromatography on alumina were obtained using carbon dioxide as the supercritical mobile phase and simple pressure programming techniques. In addition to the less polar fuel components, supercritical carbon dioxide allowed chromatography of the nitrogen-containing polycyclic aromatic hydrocarbon fraction and the hydroxylated polycyclic aromatic materials.
    Type of Medium: Electronic Resource
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