Potassium currents in cut skeletal muscle fibers from toad Bufo marinus: activation and decline under maintained depolarizations.
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N J Arispe
Publications and source records attributed to N J Arispe.
Sodium currents in skeletal muscle fibres from the toad Bufo marinus.
Single fibres from the sartorius muscle of the toad Bufo marinus were used to study ionic currents, using a fast voltage-clamp method. Sodium currents were analysed following Hodgkin-Huxley formulations. Internal caesium fluoride blocks delayed currents but produced shifts in the equilibrium potential of the early channel due to sodium accumulation. Delayed channels are very unstable when fluoride is used inside the fibre. These instabilities and equilibrium potential shifts were eliminated on replacing fluoride by aspartate in the internal solution. Late peaks of inward current, probably associated with activity at the tubular system, were occasionally observed for small depolarizations. The results are compared with those obtained for other amphibian species and used to explain more general electrophysiological properties of muscle fibres of this tropical toad.
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Nonlinear cable equations for axons. I. Computations and experiments with internal current injection.
Steady-state potential and current distributions resulting from internal injection of current in the squid giant axon have been measured experimentally and also computed from nonlinear membrane cable equation models by numerical methods, using the Hodgkin-Huxley equations to give the membrane current density. The solutions obtained by this method satisfactorily reproduce experimental measurements of the steady-state distribution of membrane potential. Computations of the input current-voltage characteristic for a nonlinear cable were in excellent agreement with measurements on axons. Our results demonstrate the power of Cole's equation to extract the nonlinear membrane characteristics simply from measurement of the input resistance.
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Nonlinear cable equations for axons. II. Computations and experiments with external current electrodes.
We have investigated the steady-state potential and current distributions resulting from current injection into a close-fitting channel into which a squid axon is placed. Hybrid computer solutions of the cable equations, using the Hodgkin-Huxley equations to give the membrane current density, were in good agreement with experimental observations. A much better fit was obtained when the Hodgkin-Huxley leakage conductance was reduced fivefold.
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