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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: Excitation-contraction coupling ; Cell calcium ; Cardiac muscle ; Thyroid hormone ; Aequorin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to determine the influence of thyroid hormone on tension development and the intracellular calcium transient in mammalian ventricular muscle. A hyperthyroid (H) state was induced in ferrets by subcutaneous injection ofl-thyroxine, 0.3 mg/kg daily, for 2–3 weeks. One-half of the age matched control group (C) were injected with vehicle. Aequorin was loaded into the cells of ferret papillary muscles by a chemical procedure. The muscles were stimulated at 0.33 Hz and isometric tension and the calcium transient were simultaneously recorded at 30°C. Peak isometric tension in mN/mm2 (±SD) was 15.4±7.2 and 16.2±7.9 for C (n=8) and H (n=9) respectively. The time to peak tension and time to 80% relaxation from peak of tension were reduced by 22% and 28% respectively in H compared to C. After stimulation, the calcium transient reached a maximum in 56±6 ms in C and in 47±5 ms in H. The time to 80% decay of the peak calcium transient was 95±8 ms and 68±5 ms for C and H respectively. The ratio of the aequorin luminescence at the peak of the calcium transient over the calculated maximum luminescence,L max, were compared and they were not different. At 22°C Log (L/L max) was −3.3±0.1 in C (n=4) and −3.4±0.3 in H (n=3). These results indicate that the thyroid state influences the time course of the calcium transient and are consistent with the abbreviation in the duration of contraction that is observed in the hyperthyroid state.
    Type of Medium: Electronic Resource
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