The study of volt-ampere characteristics of ionic channels formed by gramicidin A.

A method of measurement of the non-linearity coefficient of volt-ampere characteristics of the type i(U) approximately = U(1 + beta U2) has been developed for ionic channels formed by gramicidin A, using the third harmonic of the membrane current. The shape of the volt-ampere characteristics (VA) of ionic channels formed by gramicidin A did not depend on the antibiotic concentration in the membrane. The coefficient beta of non-linearity of VA of membranes modified by gramicidin A depended on electrolyte concentration "c" and it increased proportionally with the lg c from -17 V-2 at 0.03 mol/l KC1 to 8 V-2 at 3.4 mol/l KCl, and it was zero at co = 0.3 - 1 mol/l KCl. Egg lecithin and glycerol monooleate (GMO) membranes differ in their co values. The substitution of K+ for Li+ of the membrane solvent (n-heptane for n-hexadecane) did not influence the value of beta; the same applied for GMO membranes without any solvent. In a number of membranes, spontaneous change of the non-linearity coefficient with time observed after the membrane formation, as well as jumps of the non-linearity coefficient at a practically unchanged membrane conductivity. An analysis of some theoretical models of the ion transport through the channel has shown that, at voltages above 200 mV, these models provide rather small values of beta, or extremely high VA non-linearity.

[Influence of erythrocyte destruction kinetics on the dynamic behavior of the erythropoiesis system]. / Vliianie kinetiki raspada éritrotsitov na dinamicheskoe povedenie sistemy éritropoéza.

A simple mathematical model was used to analyse the influence of cell destruction kinetics on the dynamics of erythropoietic system. Two ways of erythrocyte destruction were compared: random destruction and destruction of cells at their maximum age. It has been shown that mostly used description of erythrocyte destruction as a random process results in a great stability increase (about three times in the critical feedback coefficient). Oscillations with large periods (20 divided by 200 days) may exist in the system.

[Change of constant electric field in man in the course of adaptation to hypokinesia]. / Izmenenie postoiannogo élektricheskogo polia cheloveka v protsesse adaptatsii k usloviiam gipokinezii.

A study was carried out of change kinetics of man's constant electric field in the course of adaptation to hypokinesia from normal physical load and vice versa. It has been shown that adaptation, a transitional regime from one physiological state to another, involves similar values of the electric potential difference between the fixed points of human skin.

[Change of current-voltage characteristics of amphotericin B ion channels accompanying its incorporation into the membrane]. / Izmenenie bol't-ampernoi kharakteristiki ionnykh kanalov amfoteritsina B pri ego vstraivanii v membranu.

Non-linearity of amphotericin B current-voltage characteristics is determined by means of the third harmonic generated in the membrane. A change of the sign of non-linearity is revealed during incorporation of antibiotic molecules into a membrane, i. e. the incorporation is not a simple increase of the number of similar ionic channels in the membrane.

[Role of sterols in the interaction of polyene antibiotics with lipid membranes]. / Rol' sterinov vo vzaimodeistvii polienovykh antibiotikov s lipidnymi membranami.

The problem whether the membrane sterols are indirect acceptors of polyenic antibiotics or they play the role of substances providing conditions (at the expense of putting in order the membrane phospholipids) for formation of conductive complexes (ionic canals) from the antibiotic molecules is discussed. The comparative study on the ability of sterols of various structure (ergosterol, 7-dehydrocholesterol, cholesterol, 5 alpha-cholestan-3 beta-ol) to interact with the membrane phospholipids and to increase the sensitivity of such membranes to amphotericin B showed no correlation between the levels of these properties. The value of the changes in the cross elasticity module (E) of artificial bilayer lipid membranes from egg lecithin on introduction of the above sterols into their composition was used as the criterion for the interaction level. The absence of correlation between the above properties of the sterols indicated that the role of the sterols in interaction of polyenic antibiotics with the membranes could not be considered as the only effect of the sterols on putting in order the phospholipids, which confirmed the hypothesis on the acceptor function of the sterols with respect to polyenic antibiotics. The study of the effect of amphotericin B on the elastic properties of the cholesterol-containing bilayer membranes isolated from egg lecithin showed tha the values of the longitudinal and cross elasticity modules of the membranes did not change during introduction into the membranes of the ionic canals.

[Study of the volt-ampere characteristics of ion channels by transmembrane current harmonics]. / Izuchenie vol't-ampernykh kharakteristik ionnykh kanalov po garmonikam transmembrannogo toka.

A method is proposed for measuring the coefficient of non--linearity beta of current--voltage characteristics of the class i (U) approximately U (1 + beta U2) of ionic channels formed by grammicidine A (Gra) and amphotericine B by the 3rd harmonics of the membrane current. For Gra A beta depends on the concentration of electrolyte c increasing lg c from -17 B-2 at 0.03 M to 8 B-2 at 3.4 M KCl turning to 0 at c0 = 0.3 divided by 1 M. The membranes of egg lecithin and glycerylmonooleate (GMO) differ in c0 value. Substitution of K+ ion for Li+, of the membrane solvent (n-heptane for n-hexadecane) and freezing of the GMO membrane do not affect beta.

[Thermal noise of Corti's organ hair cells]. / Teplovye shumy voloskovykh kletok kortieva organa

Thermal agitation of the hair cells stereocilia of Corti organ is estimated. It is shown that with threshold sound stimulus the signal-to-noise ratio for single stereocilium and for single hair cell is less than 1. Some methods are proposed for signal-noise discrimination.