PubMed Health⌕ Search

Biomedical subjects

V I Pasechnik

Publications and source records attributed to V I Pasechnik.

At least 19 recordsLinked to original sources
PubMed1981

[Role of sterols in the interaction of polyene antibiotics with lipid membranes].

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.

Amphotericin B↗
PubMed1980

[Change in the properties of model membranes interacting with atherogenic and "antiatherogenic" classes of lipoproteins with varying physicochemical characteristics].

The work was undertaken for the purpose of studying the interaction of human blood plasma lipoproteins (LP) with bi-layer lipid membranes (BLM), which is regarded to be a model of nonreceptive interaction of LP with the cell membranes. The surface LP of very low density (LPVLD) layer is much "denser" in hyperalpha-lipoproteinemia than in hypoalpha-lipoproteinemia. It was found that atherogenic LP classes induce an increase in BLM conductivity in much lesser concentration than the subclasses of antiatherogenic LP of high density. LPVLD of individuals with their increased content in plasma increase the electrical capacity of BLM to a lesser extent than LPVLD of healthy individuals. In most experiments with LPVLD of individuals with their high level. BLM resilience diminished, whereas in experiments with LPVLD of persons with a normal LP spectrum, BLM resistance was found to be increased. It is thus shown that despite the absence of protein receptors in the BLM some of their physico-chemical characteristics change on interaction with blood plasma LP.

Adult↗
PubMedDate not supplied

[Kinetics of the reaction of hemoglobin with carbon monoxide. I. Relaxation measurements during photolytic illumination].

The relaxation curves in HbCO solutions to steady 1 and equilibrium 2 states were investigated at different temperatures and photolytic illumination intensities I. It was observed that in case of low I they were of identical shape and had more than one relaxation time. Increase of I leads to changes in the "tails" of curves 1 and in the initial parts of curves 2; the shape of curves 2 becomes simpler. The latter is interpreted as a result of a slow relaxation of the Hb molecules conformation to an equilibrium ligand-free state just after HbCO photodissociation.

Carbon Monoxide↗
PubMedDate not supplied

[Characteristics of relaxation experiments for proteins with "memory"].

Conditions of a linear relaxation experiment have been analysed for the proteins with "memory", i.e., the proteins whose stationary and equilibrium kinetic parameter values are changing but slowly after external perturbation. It is shown that to measure the equilibrium kinetic characteristics of these molecules one should decrease the degree of the external perturbation till the coincidence of the shape of the relaxation curves between stationary and equilibrium states after switching on and off the perturbation.

Carboxyhemoglobin↗
PubMedDate not supplied

[Kinetics of reactions between hemoglobin and carbon monoxide. II. Analysis of kinetic schemes in linear approximation].

The kinetics of hemoglobin (Hb) reactions with carbon monoxide were calculated for a number of classical schemes: with one, two, four binding sites and an allosteric scheme with T- and R-conformers. The developed theory predicts the existence of only one relaxation time for every scheme the values of which depends on the velocity constants, saturation degree and the Hb concentration.

Binding Sites↗
PubMedDate not supplied

[Receptor potential fluctuations in a pacinian corpuscle].

On the basis of the model proposed earlier fluctuations of the receptor potential and their dependence on the value of the latter are calculated. It is shown that the model of the corpuscle as a sum of independent mechanosensitive channels with fluctuating conductivity agrees satisfactorily with the experimental data.

Electrophysiology↗
PubMedDate not supplied

[Generation of capacitance current harmonics during electrostriction of inhomogeneous bilayers].

The mechanisms of generation of capacitance current harmonics arising from bilayer electrostriction are investigated theoretically in the case when fixed charges or dipoles are located inside the bilayer. If the elastic properties of the bilayer are inhomogeneous in a transversal direction, these charges or dipoles affect substantially the amplitude A2 of the second current harmonic and accordingly the magnitude of compensatory constant voltage VC, which shold be applied to the membrane to reduce A2 to zero. In membranes whose Young's modulus is minimum at the center of bilayer, the dependence of VC on depth of immersion of the charge xA into the bilayer represents a function with alternating signs, which is reduced to zero at the center of bilayer. In the case of a dipole source immersed into the bilayer, the appropriate dependence is oscillating as well, and its shape is a derivative of the corresponding dependence of VC for fixed charges with respect to a coordinate. Possible applications of the results are discussed.

Membrane Potentials↗
PubMedDate not supplied

[Use of transmembrane current harmonics originating from electrostriction for clarifying mechanisms of ion transport in prepartions of sodium-potassium ATPase].

The mechanisms of generation of transmembrane current harmonics arising due to electrostriction of the bilayer upon applying an alternating electric voltage to sodium/potassium ATPase sorbed on the support was studied. It is discussed what information can be obtained by measurements of transmembrane current harmonics to clarify the mechanism of ion transport in sodium/potassium ATPase preparations. It was shown that for studying the current harmonics upon electrostriction, the preparations should be sorbed on bilayer lipid membranes with a high modulus of elasticity. The kinetics of changes in the amplitude of the second current harmonics in response to an impulse addition of ATP to the preparation can have some specific features depending on the mechanism of ion transport.

Ion Transport↗
PubMedDate not supplied

[Post-radiation effect on the interhemispheric asymmetry in EEG and thermography characteristics].

Complex analysis of EEG and thermographic parameters carried out in 10 healthy subjects and 34 patients, Chernobyl clean-up participants revealed a correlation between EEG and brain temperature changes in the baseline state and during mental arithmetic. During cognitive activity the maximal increase in the average EEG coherence and temperature shifts in healthy subjects were observed in the left frontotemporal and right parietotemporal areas. In patients changes in both parameters under study were most pronounced, the interhemispheric relations were impaired. The visual analysis revealed "flat" and "hypersynchronous" EEG types in patients. The dominant pathologic activity in the betal range indicative of mediobasal and oral brainstem lesions was characteristic of the flat EEG. This type of activity was observed in 60% of patients. In these cases, a general decrease in EEG coherence and temperature was most pronounced in the left hemisphere. The hypersynchronou EEG type (40% patients) was characterized by paroxysmal activity in the theta and alpha ranges suggesting diencephalic brain lesions. In these cases, EEG coherence and temperature were more variable; changes in the right hemisphere were significant, be it increase or decrease. Our complex approach to investigation of brain activity in different aspects seems to be promising in estimation of the brain functional state both in healthy persons and patients in remote terms after exposure to radiation. The specific hemispheric temperature changes revealed in Chernobyl patients especially during cognitive activity can be the sequels of postradiation disorders of vascular neuro-circulation. The EEG findings suggest subcortical disorders at different levels (diencephalic or brainstem) and functional failure of the right or left hemispheres in remote terms after exposure to radiation.

Brain↗