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Biomedical subjects

Iu A Chizmadzhev

Publications and source records attributed to Iu A Chizmadzhev.

At least 19 recordsLinked to original sources
PubMedDate not supplied

[Rate of excitation propagation in a reduced Hodgkins-Huxley model. II. Slow relaxation of the sodium current].

The influence of sodium current activation on the value of nerve excitation conduction velocity is investigated on the basis of Hodgkin-Huxley model. The potassium activation and sodium inactivation are considered as slow processes which do not develop to an appreciable extent in the region of conduction velocity formation. The system of equations was derived and solved analytically after neglecting the dependency of sodium relaxation time on potential; the approximation of steady-state sodium activation was also used with the help of Hevyside function. The algebraic equation for conduction velocity was obtained; its solution has a simple analytical form in two limits of rapid and slow sodium current relaxation. The comparison with the experimental data has shown that at not very high temperatures the slow (compared to the potential dynamics) sodium current relaxation approximation is more appropriate. The dependency of impulse velocity on capacitance and conductance of the fiber was analyzed.

Electrophysiology↗
PubMedDate not supplied

[Rate of excitation propagation in a reduced Hodgkins-Huxley model. III. Integrodifferential equations].

The Hodgkin - Huxley system of equations is reduced to single integral-differential equation in neglection of slow variables dynamics. Two limiting cases of fast and slow sodium activation processes are considered. The first case leads to a nonlinear differential equation for the potential, the second one - to an ordinary differential equation with a known source as a function of coordinate. Such a simplification is due to approximation of steady-state sodium activation variable with the help of Heviside function. The validity of this approximation is discussed; the corresponding error is estimated by calculation of the second approximation for the source function.

Mathematics↗
PubMedDate not supplied

[Dynamic theory of enzymatic catalysis].

Formal kinetics of an enzymatic reaction is considered in terms of a dynamic scheme of catalysis. Conformation reconstructions of a liberated enzyme and e-s-complex are analysed upon the phase plane. An expression for the enzyme stationary activity depending on the rate of conformation reconstructions is obtained. The case of purely dynamic catalysis is analysed and possible initiation of enzymatic activity variation in time connected with initial synchronization of molecules is shown. This phenomenon is considered as a possible criterion of the dynamic character of enzymatic catalysis.

Catalysis↗