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  • 25.55 Ek  (1)
  • 25.55.−e  (1)
  • vascular smooth muscle  (1)
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  • 1
    ISSN: 1573-4919
    Keywords: heart cells ; vascular smooth muscle ; Ca2+ channels ; insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of high K− concentration, insulin and the L-type Ca2− channel blocker PN 200-110 on cytosolic intracellular free calcium ([Ca2+]i) was studied in single ventricular myocytes of 10-day-old embryonic chick heart, 20-week-old human fetus and rabbit aorta (VSM) single cells using the Ca2+-sensitive fluorescent dye, Fura-2 microfluorometry and digital imaging technique. Depolarization of the cell membrane of both heart and VSM cells with continuous superfusion of 30 mM [K+]o induced a rapid transient increase of [Ca2+]i that was followed by a sustained component. The early transient increase of [Ca2+]i by high [+]o was blocked by the L-type calcium channel antagonist nifedipine. However, the sustained component was found to be insensitive to this drug. PN 200-110 another L-type Ca2+ blocker was found to decrease both the early transient and the sustained increase of [Ca2+]i induced by depolarization of the cell membrane with high [K+]o. Insulin at a concentration of 40 to 80 μU/ml only produced a sustained increase of [Ca2+]i that was blocked by PN 200-110 or by lowering the extracellular Ca2+ concentration with EGTA. The sustained increase of [Ca2+], induced by high [K+]o or insulin was insensitive to metabolic inhibitors such as KCN and ouabain as well to the fast Na+ channel blocker, tetrodotoxin and to the increase of intracellular concentrations of cyclic nucleotides. Using the patch clamp technique, insulin did not affect the L-type Ca2+ current and the delayed outward K+ current. These results suggest that the early increase of (Ca2+]i during depolarization of the cell membrane of heart and VSM cells with high [K+]o is due to the opening and decay of an L-type Ca 2+ channel. However, the sustained increase of [Ca2+]i during a sustained depolarization is due to the activation of a resting (R) Ca 2+ channel that is insensitive to lowering [ATP]i and sensitive to insulin.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: 25.55.−e ; 25.55 Ek ; 25.10.+s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Experiments on the reaction:3He+3He→4He+2He using a single four detector telescope have shown evidence for the production of deuteron pulses, consistent with the2He→2H+e++v fusion reaction in the final state. New measurements on the same reaction using improved techniques viz.A) a windowless3He gas target andB) α- d correlation detection with 5 ns resolving time and antipileup circuitry have been performed. Calibrations were obtained from the7Li+3He→2H+4He+4He reaction spectra. The correlation angles were 30° and 97° for the alphas and deuterons respectively. Deuteron pulses have been observed, correlated with alpha particles. A cross section of (1.7 ±0.5)nbsr−1MeV−1 was obtained consistent with previous measurements using a single telescope.
    Type of Medium: Electronic Resource
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