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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 395 (1982), S. 75-77 
    ISSN: 1432-2013
    Keywords: Excitation-contraction coupling ; Cell calcium ; Vascular smooth muscle ; Reversibly hyperpermeable cells ; Calcium indicators ; Aequorin ; Phenylephrine ; Angiotensin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The bioluminescent calcium indicator aequor in was successfully loaded into vascular smooth muscle cells ofAmphiuma tridactylum by either microinjection or a new method which makes the cells reversibly hyperpermeable. Both gave similar results; however, the latter method produced larger signals. Vasoconstrictors produced a sustained contraction and a light (calcium) response consisting of two component: a large transient followed by a smaller, sustained response. Electrical stimulation produced a light transient that was much briefer than the contraction. These results suggest that tension can be maintained in smooth muscle in the presence of lower calcium levels than those present during force development.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Excitation-contraction coupling ; Cell calcium ; Mammalian cardiac muscles ; Reversibly hyperpermeable cells ; Calcium indicators ; Aequorin ; Isoproterenol ; Caffeine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The bioluminescent calcium indicator aequorin was successfully loaded into mammalian working myocardium of ferrets by a chemical procedure which makes the cells reversibly hyperpermeable through exposure to Ethylenebis-(oxyethylenenitrilo) tetraacetic acid (EGTA). After undergoing the loading procedure, developed tension at Lmax was 103±26% of the control, which indicates that the muscles regained normal function. The configurations of the aequorin signals (i.e., calcium transients) and their responses to drugs were the same as reported after microinjection of aequorin. The peak of the Ca++ transient determined by the method of fractional luminescence at 3s intervals of stimulation, 2.5mM [Ca++]o, 22.5°C was 1.1μM; this value is similar to that reported for microinjection. These results indicate that the chemical loading procedure is a useful alternative to microinjection for loading aequorin into mammalian working myocardium.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2013
    Keywords: Aequorin ; Calcium indicators ; Cyanide ; Hypoxia ; Ferret ; Oxidative phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We used the bioluminescent Ca2+ indicator, aequorin to record intracellular calcium transients during reoxygenation of hypoxic ferret ventricular muscle in order to determine whether alterations in the amplitude and time course of isometric contraction are emdiated by changes in [Ca2+]i. Papillary muscles ≤1 mm in diameter were removed from the hearts of male ferrets and perfused with a bicarbonate-buffered physiologic salt solution at 30°C. Muscles were stimulated to contract isometrically at 0.33 Hz and were loaded with aequorin by a chemical procedure. Hypoxia was induced by changing the gas mixture bubbling the perfusate to 95% N2, 5% CO2; reoxygenation was accomplished by switching the gas mixture to 95% O2, 5% CO2. Hypoxia produced a decrease in peak Ca2+ and tension that was reversed by reoxygenation. However, the effects on tension of changes in oxygenation were greater than expected from the degree of change in [Ca2+]i. The time courses of the Ca2+ transient and isometric twitch moved in opposite directions and were respectively prolonged/abbreviated by hypoxia and abbreviated/prolonged by reoxygenation. These results indicate that changes in the amplitude and time course of the isometric twitch induced by hypoxia and reoxygenation cannot be attributed alone to changes in intracellular Ca2+ availability and are caused in part by a significant decrease in the calcium sensitivity of the contractile apparatus.
    Type of Medium: Electronic Resource
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