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  • 1
    Electronic Resource
    Electronic Resource
    Increase in the slow inward current by intracellularly applied nifedipine and nicardipine in single ventricular cells of the guinea-pig heart
    Amsterdam : Elsevier
    Journal of Molecular and Cellular Cardiology 16 (1984), S. 1173-1177 
    Details
    ISSN: 0022-2828
    Keywords: Adenosine 3',5'-cyclic monophosphate phosphodiesterase ; Dihydropyridine calcium antagonist ; Slow inward current
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0022-2828(84)80043-7
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibition of the slow inward current and the time-dependent outward current of mammalian ventricular muscle by gentamicin (1982)
    Springer
    Pflügers Archiv 394 (1982), S. 243-249 
    Details
    ISSN: 1432-2013
    Keywords: Papillary muscle ; Gentamicin ; Slow inward current ; Calcium ; Time-dependent outward current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aminoglycoside antibiotic, gentamicin (GM), depressed the plateau phase and shortened the duration of the action potential in guinea pig papillary muscle. Its effect on the membrane currents was studied by a single sucrose gap voltage clamp method. The slow inward current (is) was remarkably diminished by GM with little change in its time course, in the voltage-dependency of the steady-state inactivation and activation or in its reversal potential. The maximal amplitude of is, obtained by subtracting the Co2+-resistant current, was reduced to 57% by 0.1 mmol/l GM and almost reduced to zero by 1 mmol/l GM. The efficacy of GM in inhibiting is was reduced by increasing the external Ca2+ concentration from 1.8 to 5.4 or 10.8 mmol/l, but not by the application of adrenaline. The time-dependent outward current (iK) was also decreased by GM but only at higher concentrations. It is proposed that the depressant action of GM on is was due to a blockade of slow channels, whereby GM may have dislocated Ca from the binding sites at slow channels on the external surface of the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00589099
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Positive inotropic effect of 4-aminopyridine on dog ventricular muscle (1979)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 307 (1979), S. 207-212 
    Details
    ISSN: 1432-1912
    Keywords: 4-Aminopyridine ; Cardiac muscle ; Relaxation ; Action potential ; Catecholamines ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. In trabecular muscles obtained from the right ventricle of untreated dogs 4-aminopyridine (4-AP) (0.1–10 mM) increased the force of contraction elicited by electrical driving at 0.5 Hz. 2. This effect was associated with increases in mean velocities of force development and relaxation. The time to peak force was not changed by 4-AP and the relaxation time was increased by 3 and 10 mM 4-AP. 3. In ventricular muscles treated with the β-adrenoceptor blocking agent, pindolol, or in those obtained from dogs pretreated with reserpine the positive inotropic effect was reduced. 4. In such muscles 4-AP scarcely increased the mean velocity of force development and slightly increased the time to peak force. Marked prolongation of the relaxation time and a decrease in mean velocity of relaxation were characteristic of isometric contractions of such muscles in the presence of 4-AP. 5. These results indicate that the positive inotropic effect of 4-AP is sum of two effects, one being due to the release of endogenous catecholamines and the other to a possible direct action on cardiac muscle. 6. In muscles treated with pindolol or those obtained from dogs pretreated with reserpine 10 mM 4-AP elevated the resting force. 7. These observations suggest that 4-AP causes a persisting elevation of cytosolic Ca2+ in cardiac muscle cells. 8. In pindolol-treated muscles 4-AP prolonged the action potential duration. However, the prolongation of the action potential duration produced by 4-AP was much smaller than that of the relaxation time. Even with 10 mM 4-AP the resting membrane potential remained unchanged. 9. The above results suggest that the effects of 4-AP on the contraction and resting force of ventricular muscle may not be secondary to the effect on the transmembrane potential. 10. All the results taken together suggest that the primary action of 4-AP on ventricular muscle may not be to allow increased or prolonged entry of extracellular Ca2+ but rather may be either to promote the release of Ca2+ from intracellular binding or storage sites or to slow the binding of Ca2+ to intracellular structures. The prolongation of the action potential duration may be a consequence of change in calcium binding to the plasma membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00505935
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Disk-cathode flash X-ray tube driven by a repetitive two-stage Marx pulser (1993)
    Springer
    Medical & biological engineering & computing 31 (1993), S. S37 
    Details
    ISSN: 1741-0444
    Keywords: Cold-cathode diode ; Disk cathode ; Flash X-rays ; Photon energy control ; Pulsed X-rays ; Tube current control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Fundamental studies of a repetitive flash X-ray generator using a diskcathode radiation tube are described. The high-voltage pulser employed a modified two-stage surge-Marx circuit. The two condensers in the pulser were charged from 40 to 60 kV, and the electric charges were discharged to the X-ray tube repetitively to generate flash X-rays. The total capacity during the main discharge was 425 pF, and the maximum output voltage from the pulser was about 1·9 times the charged voltage. The flash X-ray tube of the demountable-diode type and was composed of a rodshaped anode tip made of tungsten, a disk cathode made of graphite and a tube body made of polymethylmethacrylate. The peak tube voltage was primarily determined by the anode-cathode (A-C) space, and the peak tube current was less than 0·5 kA. Thus the maximum photon energy could be easily controlled by varying the A-C space, and the tube current roughly increased according to increases in the charged voltage. The pulse width ranged from 40 to 100 ns, and the X-ray intensity was less than 1·1 μC kg−1 at 0·5 m per pulse. The repetition rate was less than 50 Hz, and the effective focal spot size was equivalent to the anode diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02446648
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    Paper (German National Licenses)
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