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  • 1
    Electronic Resource
    Electronic Resource
    Conductance increase by adrenaline in guinea pig taenia coli studied with voltage clamp method (1974)
    [s.l.] : Nature Publishing Group
    Nature 250 (1974), S. 432-433 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] This agrees with the results obtained from ionic flux experiments5. In contrast, however, it has been recently reported, on the basis of voltage clamp experiments, that adrenaline increases the negativity of the potassium equilibrium potential without causing significant changes in the membrane ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/250432a0
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of the Junction Potential of a Small Nerve (1960)
    [s.l.] : Nature Publishing Group
    Nature 188 (1960), S. 416-417 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Two microelectrodes were inserted (within 50 µ of each other) into a slow muscle fibre, one for recording the membrane potential and the other for passing current through the membrane. For the voltage-clamp experiment, a negative feedback amplifier system was connected to the microelectrodes ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/188416a0
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of ammonium chloride on membrane currents of acinar cells dispersed from the rat parotid gland (1992)
    Springer
    Pflügers Archiv 420 (1992), S. 297-301 
    Details
    ISSN: 1432-2013
    Keywords: Salivary gland ; Ammonium chloride ; Butyric acid ; Potassium current ; chloride current ; intracellular pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In acinar cells freshly dispersed from rat parotid glands, the effects of ammonium chloride (NH4Cl) on membrane currents were studied using the whole-cell clamp method. When membrane currents were recorded with command pulses to 0 mV, applied at 2-s intervals from a holding potential of −70 mV, NH4Cl (5–20 mM) transiently decreased outward currents and then slowly increased both outward and inward currents. After reaching a peak in about 40–50 s, both outward and inward currents gradually decreased in the presence of NH4Cl and, on its wash-out, the currents returned to the control level. Butyrate (5–20 mM) had little effect on the resting membrane currents, but markedly inhibited the response to NH4Cl. Tetraethylammonium (5 mM) strongly reduced both the resting and NH4Cl-induced outward currents, whereas it slightly potentiated the NH4Cl-induced inward current without affecting the membrane current at the holding potential. Without ATP in the patch pipettes, carbachol-induced membrane currents were relatively resistant to Ca2+ removal from the external medium, but NH4Cl-induced currents were quickly abolished in the absence of Ca2+. We conclude that intracellular alkalinization with NH4Cl increases Ca2+ influx and activates Ca2+-dependent outward K+ and inward Cl− currents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374462
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of calcium and temperature on tension in isolated canine coronary artery (1991)
    Springer
    Journal of anesthesia 5 (1991), S. 172-176 
    Details
    ISSN: 1438-8359
    Keywords: Coronary artery ; Calcium-induced contraction ; Hypothermia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of calcium and temperature on the tension of isolated canine coronary arterial strips were studied. In 20 mEq·l −1 K solution, the tension was significantly increased from 0 mg with 0 mEq·l −1 Ca to 33 ± 18 mg with 0.2 mEq·l −1 Ca at 37°C, from −40 ± 18 mg with 0 mEq·l −1 Ca to −17 ± 11 mg with 0.2 mEq·l −1 Ca at 30°C, from −77 ± 19 mg with 0 mEq·l −1 Ca to −52 ± 17 mEq·l −1 with 1 mEq·l −1 Ca at 25°C, from −88 ± 13 mg with 0 mEq·l −1 Ca to −41 ± 18 mg with 2 mEq·l −1 Ca at 20°C, from −125 ± 16 mg with 0 mEq·l −1 Ca to −116 ± 13 mg with 2 mEq·l −1 Ca at 15°C. Ca higher than 0.2 mEq·l −1 produced a dose-dependent increase in tension between 37°C and 15°C. In spite of the presence of 4 mEq·l −1 Ca, the development of tension was strongly supressed by lowering the temperature below 20°C, and completely inhibited at 10°C. The rate of a decrease in tension caused by cooling was about 5.5 mg·°C−1. This study demonstrated that Ca2+ produced a dose-dependent increase in tension in high-K solution, which was suppressed as the temperature was lowered. (Yoshida K, Fujii Y, Ina H, et al.: Effects of calcium and temperature on tension in isolated canine coronary artery. J Anesth 5: 172–176, 1991)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0054010050172
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of magnesium on isolated canine coronary arterial tension (1993)
    Springer
    Journal of anesthesia 7 (1993), S. 184-188 
    Details
    ISSN: 1438-8359
    Keywords: Coronary artery ; Contraction ; Magnesium ; Calcium ; Sodium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of magnesium on the tension of isolated canine coronary arterial strips were studied. In the solution containing K+ of 20 mEq·l −1, Ca2+ of 4 mEq·l −1, and Na+ of 127 mEq·l −1, the tension was 811 ± 111 mg with Mg2+ of 1 mEq·l −1, 494 ± 135 mg with Mg2+ of 10 mEq·l −1, 272 ± 126 mg with Mg2+ of 20 mEq·l −1, −52 ± 63 mg with Mg2+ of 30 mEq·l −1, −69 ± 80 mg with Mg2+ of 40 mEq·l −1. In the solution containing K+ of 20 mEq·l −1, Na+ of 12 mEq·l −1 and Ca2+ of 0 mEq·l −1, the tension was 102 ± 22 mg with Mg2+ of 1 mEq·l −1, 3 ± 35 mg with Mg2+ of 10 mEq·l −1, −49 ± 33 mg with Mg2+ of 20 mEq·l −1, −59 ± 49 mg with Mg2+ of 30 mEq·l −1, −65 ± 54 mg with Mg2+ of 40 mEq·l −1. The data demonstrated that Mg2+ above 30 mEq·l −1 inhibited the increase in tension caused by Ca2+ and Mg2+ above 20 mEq·l −1 inhibited the increase in tension caused by low Na+ concentration. (Yoshida K, Usui A, Hibi M, et al.: Effects of magnesium on isolated canine coronary arterial tension. J Anesth 7: 184–188, 1993)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0054030070184
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of sodium and temperature on tension in isolated canine coronary artery (1991)
    Springer
    Journal of anesthesia 5 (1991), S. 56-59 
    Details
    ISSN: 1438-8359
    Keywords: Coronary artery ; Sodium ; Hypothermia ; Tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of sodium and temperature on tension of isolated canine coronary arterial strips were studied. In 20 mEq·l −1 K solution, the strength of tension was inversely related to the Na concentration. At 37°C, the tension was significantly increased at 70 mEq·l −1 Na and below. The tension was gradually suppressed by lowering of the temperature from 37°C to 10°C. At 10°C, tension did not developed significantly at Na concentrations between 127 mEq·l −1 and 12 mEq·l −1. It was concluded that the decrease in Na concentrations increased the tension of the canine coronary artery and the lowering of temperature supressed the tension inducted by the decrease in Na concentrations. (Yoshida K, Fujii Y, Ina H, et al.: Effects of sodium and temperature on tension in isolated canine coronary artery. J Anesth 5: 56–59, 1991)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0054010050056
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of Ca2+ removal and of tetraethylammonium on membrane currents induced by carbachol in isolated cells from the rat parotid gland (1991)
    Springer
    Pflügers Archiv 419 (1991), S. 332-337 
    Details
    ISSN: 1432-2013
    Keywords: Salivary gland ; Muscarinic receptor ; Intracellular Ca ; Intracellular ATP ; Potassium current ; Chloride current ; Tetraethylammonium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In freshly dispersed rat parotid acinar cells, 10 μM carbachol increased outward currents at 0 mV and also inward currents at −70 mV recorded with the whole-cell clamp method using patch pipettes containing 1 mM EGTA. When EGTA in the pipette was increased to 2.4 mM, carbachol increased only outward currents and a further increase of EGTA to 4 mM blocked the carbachol response. Effects of changes in external K+ and Cl− concentrations suggested that outward currents were carried by K+ and inward by Cl−. Effects of Ca2+ removal from the medium differed between experiments with 0 and 5 mM ATP in the patch pipettes. When pipettes contained no ATP, responses evoked by repeated applications of 10 μM carbachol (0.5–1 min) at 1.5–4 min intervals decreased only slowly after Ca2+ removal, outward currents being reduced to 90±6% and inward currents to 47±11% (n=6) in 10 min. On the other hand, when 5 mM ATP was included in the electrodes, Ca2+ removal abolished the carbachol responses in about 5 min (n=4). It was also found that tetraethylammonium (5 mM) strongly reduced both currents, by blocking muscarinic receptors, while Ba2+ (2.4 mM) inhibited only the outward K+ current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371115
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  • 8
    Electronic Resource
    Electronic Resource
    A study of the crustacean axon repetitive responseSupported by NSF grant 24013.. III. A comparison of the effect of veratrine sulfate solution and potassium-rich solutions (1966)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 67 (1966), S. 181-196 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The crustacean single nerve fiber gives rise to trains of impulses during a prolonged depolarizing stimulus. It is well known that the alkaloid veratrine itself causes a prolonged depolarization; and consequently it was of interest to investigate the effect of this chemically produced depolarization on repetitive firing in the single axon and compare it with the effect of depolarization by an applied stimulating current or by a potassium-rich solution. It was found that veratrine depolarization, though similar in some respects to a potassium-rich depolarization of depolarizing current effect, was in many respects quite different.(1) At low veratrine concentration, less than 1 Mg%, the negative after potential following a spike action potential was prolonged and augmented. At higher concentrations or after a long period of time, veratrine caused a prolonged steady state depolarization of the membrane, the “veratrine response”. The prolonged plateau depolarization response could be elicited with or without an action potential spike by a short or long duration stimulating pulse, but only if the veratrine depolarization was prevented or offset by an applied conditioning hyperpolarizing inward current.(2) The “veratrine response” resembled the potassium-rich solution response in the plateau-like contour of the depolarization and the very low membrane resistance during this plateau phase. Like the potassium response, it was possible to obtain a typical hyperpolarizing response with an inwardly directed current pulse if applied during the plateau phase. During the negative after potential augmented with veratrine, however, this hyperpolarizing response was not observed.(3) In contrast to the potassium response, however, the “veratrine response” is intimately associated with the sodium concentration in the external medium. The depolarization in millivolts is linearly related to the log of the concentration of external sodium. Moreover, during veratrine action there is a continuous and progressive inactivation of the sodium mechanism which ultimately terminates repetitive firing and abolishes the spike action potential. Then even with conditioning hyperpolarization only the slow response may be elicited in veratrine, occasionally with a spike superimposed if sodium is present, but without repetitive firing.(4) It is concluded that veratrine action is the result of a chemical or metabolic reaction by the alkaloid in the membrane. It is suggested that veratrine may inhibit the sodium extrusion mechanism, or may itself compete for sites in the membrane with calcium and/or sodium. This explains the inhibiting effect of high calcium, the abolition of the “veratrine response” with low temperature and high calcium combined and the progressive inactivation of the sodium system.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040670121
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  • 9
    Electronic Resource
    Electronic Resource
    A study of the crustacean axon repetitive response: II. The effect of cations, sodium, calcium (magnesium), potassium and hydrogen (pH) in the external mediumThis research program supported by National Science Foundation Grant NSF-G-24013. (1965)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 65 (1965), S. 211-228 
    Details
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of sodium, calcium, potassium (magnesium), potassium, and hydrogen (pH) ion concentration in the external medium on the repetitive response and the transmembrane electrical parameters of the crustacean axon have been investigated. (1) The action potential is reduced with decrease in sodium ion concentration, the relationship is linear if the spike voltage is plotted against the log (Na0). The action potential amplitude does not increase significantly, above 135 mv, attained at Na0 = 452 mM, if Na0 is increased. (2) The repetitive response and oscillatory activity in general disappears as the sodium concentration is reduced to less than 150 mM. (3) The critical firing level increases with decrease in sodium, the relationship linear with respect to log (Nao). (4) The positive after potential amplitude is not affected by the sodium concentration. (5) The membrane resistance is not affected by sodium concentration. (6) Calcium lack results in decreased critical firing level and spontaneous firing, followed by a total and irreversible loss of excitability. The membrane resistance is markedly decreased. Polarizing current, if applied early after the onset of the calcium lack effect, may restore, at least partially, the excitability phenomenon. (7) Calcium excess increases membrane resistance, depresses excitability. Calcium concentration of 150 mM abolishes the repetitive response. (8) There is a 3.3+: 1 ratio Na:Ca for threshold level of repetitive response. Lower ratio figures, by reducing Na or increasing Ca or both, eliminates repetition. Increasing the ratio figure by increasing sodium or decreasing calcium or both augments oscillatory activity. This ratio is constant between the limits 400 mM Na:125, Ca to 90 mM Na:25 mM Ca. (9) Magnesium may substitute for calcium, the Na:Mg ratio for repetitive response threshold is 3.3:2. (10) Repetitive firing may be elicited over a wide range of pH values 4.2-10.5; membrane potential and resistance values decline invariably at pH values above 9.5 and below 4.5. (11) Repetitive firing is enhanced by increasing pH values, depressed by reducing pH values. (12) Effect of excess potassium produces depolarization, reduced membrane resistance, inactivation and abolition of repetitive firing, may be relieved by applied hyperpolarization. (13) Potassium lack results in membrane potential and resistance irreversible decline, permanent inactivation, total loss of excitability. Partial restoration by strong hyperpolarization if applied before effect is complete. Potassium replacement in solution only slows or temporarily arrests the overall membrane deterioration. (14) Conclusions - sodium controls spike, potassium controls after potential, calcium (magnesium) controls membrane permeability, pH controls amount of available ionized calcium. Repetitive firing requires proper ratio 3.3/1 of (Nao)/(Ca0), pH above 7.6 and potassium at 15 mM in solution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030650208
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  • 10
    Electronic Resource
    Electronic Resource
    A study of the crustacean axon repetitive response: I. The effect of membrane potential and resistance (1965)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 65 (1965), S. 195-209 
    Details
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The transmembrane electrical properties of the crustacean axon have been examined by a new technique which allows for quantitative evaluation of the electrical and excitable characteristics across a microscopic area, “patch,” of fiber membrane using external electrodes. Data from repetitive firing and from non-repetitive firing fibers compare as follows: (1) Membrane potential, resting, 82 mv repetitive; 67 mv non-repetitive; 70-75 mv transition level repetitive to non-repetitive. (2) Membrane potential, active, 132 mv, 50 mv overshoot repetitive; 100-120 mv, 30-50 overshoot, non-repetitive. (3) Membrane resistance, 7.6 × 106 ohms or 2300 ohms cm2 repetitive; 2.8 × 106 ohms or 880 ohms cm2 non-repetitive. (4) Membrane time constant, 2.5 ms repetitive; 1.5ms non-repetitive. (5) Membrane capacity 1.0μf repetitive; 1.7 μf non-repetitive. (6) Repetitive firing property may be restored to non-repetitive axons by increasing the Vm value with a polarizing inward current. This increases Rm also. (7) Non-repetitive fibers show considerable inactivation, give rise to “more or less” spikes particularly during refractory period following a spike, and respond to anode-break stimulation. Repetitive firing axons do not. (8) The action potential has two active components, one to depolarize (sodium) one to repolarize (potassium), both of which drive the membrane potential. toward predetermined levels. (9) The repetitive firing axons show little or nc inactivation with weak prolonged depolarization producing trains of spikes. There is a slow rise in critical firing level which ultimately causes the spike train termination. There is a slow increase in the undershoot (diphasic repolarization) amplitude.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030650207
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