Biomedical subjects

N S Veselovskiĭ

Publications and source records attributed to N S Veselovskiĭ.

18 recordsLinked to original sources

PubMed1986

[Electroregulated sodium channels of the somatic membrane of sympathetic neurons].

Electrically-operated sodium channels in the somatic membrane of isolated neurons from the rat superior cervical ganglion have been studied by means of intracellular dialysis technique under voltage clamp conditions. It was shown that in this preparation sodium currents can be carried by two independent systems of sodium channels. The mathematical analysis of voltage-dependent TTX-sensitive fast sodium currents was performed by the Hodgkin-Huxley formalism; their kinetic properties were compared with those described in other objects. TTX-sensitive sodium channels in the somatic membrane of sympathetic neurons were found to be highly selective for Na+ ions. Kinetic and voltage-dependent characteristics of slow TTX-resistant sodium current were also described. This component of the sodium current was observed only in a few neurons (not more than 2%).

Animals↗

PubMed1986

[Changes in the calcium action potentials of the neurons of the spinal ganglia in the rat in response to divalent cation substitution in the extracellular medium].

Rat dorsal root ganglion neurons were investigated by intracellular microelectrodes using current clamp technique. After elimination of sodium ions from the extracellular medium and addition of TEA pure "calcium" action potentials were recorded. Progressive and selective disturbance of such potentials was observed during continuous intracellular recording indicating a decrease in the calcium conductance while sodium and potassium conductances remained uneffected. Such a disturbance is supposed to be due to excessive influx of calcium, strontium or barium ions into the cell. The calcium component of the action potential was also dependent on the stimulation frequency, such dependence being different for strontium or barium solutions. Possible participation of current-dependent inactivation in the origin of this phenomenon is discussed.

Action Potentials↗

PubMed1986

[Sodium and calcium channels of the somatic membrane of neuroblastoma cells during artificially induced differentiation].

Sodium and calcium channels passing inward currents were studied by intracellular dialysis technique and voltage clamp in the somatic membrane of neuroblastoma cells during their morphological differentiation induced by increasing pH of the culture medium up to 8.0-8.2. Kinetic and voltage-dependent properties of sodium and calcium channels of differentiated cells and cells grown in the suspension culture were identical. Densities of sodium currents in the somatic membrane of neuroblastoma cells grown in suspension culture were about 7.3 +/- 0.8 microA/microF and from 37 +/- 5.2 microA/microF to 54.7 +/- 3.6 microA/microF of differentiated cells at different terms of cultivation. Densities of calcium currents in the membrane of cells grown in suspension were about 1.4 +/- 0.2 microA/microF, while in differentiated cells they ranged from 1.1 +/- 0.2 to 2.8 +/- 0.4 microA/microF at different terms of cultivation. Induction or reduction of differentiation by varying pH of the culture medium produced reciprocal changes in densities of sodium and calcium channels.

Animals↗

PubMed1986

[Effect of replacing calcium ions with barium ions in studies of the inward currents of mammalian neurons].

The effect of replacement of Ca2+ ions by Ba2+ ions in the external artificial solution on a high-threshold calcium current of the somatic membrane of rat dorsal root ganglion neurons was studied by intracellular dialysis technique and voltage clamp method. The conductance of the corresponding channels for Ba2+ ions assessed by the increase in the maximal current amplitude was shown to increase about twice. The decrease of the maximal current amplitude in the course of dialysis associated with the washout of the intracellular content slowed down considerably, probably, due to the removal of the blocking effect of intracellular Ca2+ on the calcium channels. The link of high-threshold calcium channels with cyclic nucleotide metabolism was not disturbed after the replacement of Ca2+ by Ba2+. The data obtained are discussed within the framework of existing ideas about the functioning of calcium channels in excitable membranes.

Animals↗

PubMed1986

[Changes in the ionic mechanisms of the electro-excitability of the somatic membrane of rat sensory neurons during ontogenesis. Distribution of ion channels of the inward current].

Distribution of different types of ionic channels carrying inward currents was studied in the somatic membrane of rat dorsal root ganglion neurons within three age groups: 5-9 days, 45 days and 90 postnatally. The number of neurons whose membrane contained simultaneously four types of inward current channels ("fast" tetrodotoxin-sensitive and "slow" tetrodotoxin-resistant sodium low- and high-threshold calcium one's) was progressively reduced in successive groups. The first group contained 14.5%, the second 5% and the third group 1% of such neurons. These changes were due to disappearance of "slow" sodium and low-threshold calcium channels from the membrane; the number of neurons whose somatic membrane contained only two types of inward current channels ("fast" sodium and high-threshold calcium) has increased, respectively.

Aging↗

PubMed1986

[Changes in the ionic mechanisms of the electro-excitability of the somatic membrane of rat sensory neurons during ontogenesis. Density ratios of inward currents].

Correlations between densities of different types of inward currents in the somatic membrane of dorsal root ganglion neurons were studied in three age groups of rats (5-9 days, 45 days and 90 days postnatally). A linear dependence between the densities of high-threshold calcium and slow sodium currents was found. No correlation was observed between the densities of different inward currents in neurons with low-threshold calcium inward current. An inverse dependence was observed between the densities of transmembrane currents in cells having only two types of channels ("fast" sodium and high-threshold calcium ones). Neurons exhibiting slow TTX-resistant sodium and/or low-threshold calcium channels did not show inverse dependence between the densities of "fast" sodium and high-threshold calcium currents.

Aging↗

PubMed1986

[Changes in the ionic mechanisms of the electro-excitability of the somatic membrane of rat sensory neurons during ontogenesis. Relation between calcium channels and intracellular metabolism].

A change in the relationship between high-threshold calcium channels and intracellular metabolism of cyclic nucleotides during postnatal development was found in experiments on rat dorsal root ganglion neurons. In the first age group (5-9 postnatal days) intracellular administration of cAMP-ATP-Mg2+ complex has resulted in restoration of the maximal amplitude of high threshold calcium current for 70% of neurons, whereas in the second (45 days) and third (90 days) age groups this effect was observed only in 26% and 10% of neurons, respectively. Kinetic and voltage-dependent characteristics of high-threshold calcium current in these three age groups were identical. The effect of introduction of cAMP-ATP-Mg2+ complex was different for neurons with different combination of inward currents. Neurons which possessed only two types of inward currents--"fast" sodium and high-threshold calcium ones, show no effect. Conventional effect of the intracellular cAMP injection occurred always in neurons which had exhibited a "slow" (TTX-resistant) sodium inward current together with the two main inward currents.

Adenosine Triphosphate↗

PubMed1986

[Isolation, identification and properties of the calcium component of the action potential in isolated neurons of the spinal ganglia of the rat].

Electrophysiological properties of isolated dorsal root ganglion neurons from adult rats were studied by intracellular microelectrodes. All investigated cells were separated into two groups according to the duration of their action potential and the shape of its falling phase. The calcium component of the action potential could be separated by placing the cells into sodium-free, calcium- and TEA-containing medium. The presence of this component was revealed in all studied neurons.

Action Potentials↗

PubMed1985

[Deactivation of calcium currents in the soma of spinal ganglion neurons after elimination of the depolarizing shift in the membrane potential].

Kinetic and voltage-dependent characteristics of deactivation of calcium inward currents with the removal of membrane depolarization were studied in the somatic membrane of rat dorsal root ganglion neurons by intracellular dialysis technique. The "tail" of low-threshold calcium current could be described reliably by one exponent with time constant tau 1-1.2-1.8 ms at repolarization to --90 mV. The "tail" of the high-threshold calcium current represented a sum of several exponents; the time constant of the main component tau h was in the range of 250-380 microseconds. tau 1 and tau h remained practically unchanged for repolarization potentials in the subthreshold region; however, they increased if it was in the range of potentials at which the corresponding component of the calcium current started to activate. A dependence of tau 1 and tau h on the duration of depolarizing shift was observed. The results obtained are discussed in the framework of a three-level kinetic model of calcium channels.

Animals↗

PubMed1984

[Calcium currents of differentiated mouse neuroblastoma cells].

Differentiated neuroblastoma cells (clone N18TG2-A1) were investigated by means of intracellular dialysis technique. A slow component of the potential-dependent inward current was observed in these cells. Changes in current amplitude produced by changes in the ionic composition of intra- and extracellular media showed that this component is carried by calcium ions. The calcium inward current was observed in all investigated cells. It could be activated by membrane depolarization to the level of -70 - -65 mV and reached maximum amplitude at -30 - -40 mV. Kinetic parameters of this current were studied. A conclusion is made that calcium current in differentiated neuroblastoma cells is similar to the fast component of the calcium current in normal neurons of rat dorsal root ganglion.

Animals↗

PubMed1984

[Morphologic differentiation of neuroblastoma cells induced by dimethyl sulfoxide].

Morphological features of neuroblastoma cells cultured in the presence of 1.0% dimethyl sulfoxide (DMSO) were investigated. The induced differentiation was characterized by appearance of long axon-like processes (neurites), cell size enlargement and inhibition of cell growth. Quantitative criteria for cell differentiation depending on survival time in the modified medium were estimated. The increase of total length of neurites was linear with time, the rate of their extension being 20.0 +/- 3 micron/h. The area of differentiated cell soma is 6-7 times higher than that of control cells. Increase of the DMSO concentration to 2.0% did not intensify neurite growth and enlargement of cell size but suppressed mitosis. Morphological criteria of cell differentiation are compared with probable functional changes in these cells.

Cell Differentiation↗

PubMed1983