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Iu A Darinskiĭ

Publications and source records attributed to Iu A Darinskiĭ.

At least 19 recordsLinked to original sources
PubMed1991

[A new mechanism of action of vasopressin on the neuronal membrane].

It is shown in this work that vasopressin at the concentrations of 1 x 10(-16) to 1 x 10(-6) mol/l decreased statistically significant the amplitude of the electrosensitive sodium and calcium ionic currents of the mollusc's Lymnaea stagnalis neuronal membrane. This peptide increased the amplitude of the fast potassium current at the concentration of 1 x 10(-16) and 1 x 10(-15) mol/l. It decreased the fast potassium current and did not change the slow potassium current at the concentrations more than 1 x 10(-9) mol/l.

Animals↗
PubMed1990

[The extrasynaptic effect of the neuropeptides vasopressin, oxytocin and vasotocin on the electrically controlled ion channels of the membrane in mollusk neurons].

Extrasynaptic effects of vasopressin, oxytocin, vasotocin on the membrane electrosensitive ionic channels were studied in model experiments using isolated somata from the CNS of mollusc Lymnaea stagnalis. The neuropeptide in concentrations of 1.10(-16)-1.10(-6) mol/l either blocked or induced biphasic dose-dependent effect on amplitudes of the membrane ionic currents.

Animals↗
PubMed1988

[Mechanism of the action of baclofen on the contractile activity of the myocardium and blood vessels].

The cardiovascular effects of GABA-analogous-baclofen (10(-5) M) have been investigated in the experiments on isolated myocardium and vessels of the rats. The spontaneous contraction of vena porta segments and contraction of papillary muscle and arterial rings segments induced by electrostimulation were registered. Baclofen induced the growth of arterial tonus, decreased the amplitude of phase contraction as well as resulted in positive inotropic effects in myocardium and vena porta. The obsidan did not influence the baclofen effects, but alpha-adrenolytic dihydroergotoxine inhibited the inotropic effects of the drug. It is supposed that hypertensive baclofen effect which is observed during system injection may be caused not only by central, but also by peripheral regulation of calcium change in the myocytes. The latter (possible) kind of regulation may consist in the drug binding with adrenoreceptor and/or direct influence on the calcium transport across sarcolemma.

Animals↗
PubMed1983

[Method for the intravital observation of neurons in a live spinal cord preparation].

A method was worked out permitting to study dynamics of structural changes in the liver spinal motoneurons of the frog. The possibility of comparative studies of the same cells on fixed and live preparations was demonstrated. The adjacent neurons in the live preparation differ in size, shape and staining intensity of vital dyes. The size of nonfixed motoneurons averages 1345 mkm. The nucleoplasmic ratio equals to 1:32. Upon mechanical lesion of neurons, numerous vacuoles appear in their cytoplasm, part of the cells are stained. The method permits to study the location of motoneuron dendrites as well as the distribution of nerve fibers with synapse-like thickenings which terminate on the cell. After fixation of the brain with the Carnoy liquid or 96 degrees ethanol, motoneurons shrink by 34.2% (the cytoplasm, nucleus and nucleolus by 34.7, 33.0 and 21.2%, resp.), However, the nucleoplasmic ratio does not change. Adjacent neurons decrease in size to various extent following the brain fixation (18-54%). No correlation was observed between the size of live neurons and the extent of their shrinkage after fixation.

Animals↗
PubMed1983

[Role of histological fixation of the brain in the detection of functional changes in the size of neurons].

In the experiments performed on frogs using vital and fixed preparations, the size and structure of the spinal motoneurons have been studied. In both cases the neighbouring neurons differ in size, form and staining intensity. After the brain is fixed in Carnoy fluid and in 96% alcohol, the neuron size decreases by 34%, cytoplasm--by 35%, nucleus--by 33% and nucleolus--by 22%. The nucleus--cytoplasm ratio does not change in the neurons after fixation. After fixation the neighboring neurons decrease to various degree (from 18 up to 54%). There is no correlation between the neuron size and degree of its decreasing after the brain fixation. In the vital preparations studied the size of the motoneurons subjected to an intensive, prolonged synaptic activation does not differ from that of the control. However, after the brain fixation, their size decreases by 49%. Thus, the degree of the neuron decrease after the brain fixation surves as an index of the vital activation intensity. The neurons injured or subjected to an intensive and prolonged activation only after fixation shrink and acquire a pyknomorphous appearance.

Action Potentials↗
PubMed1982

[Postactivation changes in the ultrastructure of motor neurons].

The prolonged high-frequency synaptic activation of the frog spinal motoneurons suppressing their firing, leads to an increase in the size of synapses and to a considerable shift in their ultrastructure. Restoration of the functional and morphological alterations in the cells after cessation of their rhythmical activation proceeds with different speed: the restoration of neurons' ability to generate synaptic and spike potentials in response to testing stimulation of afferents occurs much earlier than the restoration of the cells' ultrastructure and size. Neurons with obviously changed ultrastructure of soma and synaptic apparatus are capable of generating synaptic and spike potentials in response to stimulation. At the same time, the size of the neurons returns to normal either than the normalizing of cell ultrastructures whose speed of restoration varies as well.

Action Potentials↗
PubMed1982

[Morpho-functional changes in the frog neurons in ischemia].

After the full spinal cord ishemia in the frog, motoneuron lose their ability to generate spike potentials to a testing stimulation in 30 minutes. The size and structure of these neurons do not differ from those in the control ones. The ten minute high frequency stimulation of motoneurons affected by ishemia results in deep pathologic structural changes. The neuron dimensions decrease, and numerous picnomorphical, dark and vaculized neurons appear. The full ishemia leads to pathologic changes in the neuron structure. However, the number of picnomorphical and dark neurons is considerably less than that after the high frequency activation. Following the 90 minute ishemia, no postsynaptic or spike potentials occur in motoneurons as a response to their stimulation.

Action Potentials↗
PubMed1981

[Effect of a ginseng tissue culture preparation on morphofunctional changes in motor neurons upon activation].

Irritation for 10 min of the posterior spinal root in the frog Rana temporaria (electrical stimulation 50 imp/sec, threshold power 4) results in decreasing size of the motoneurons and their nuclei and in appearing pycnomorphous type of neurons. Simultaneously, peculiar changes in cellular ultrastructure connected with inhibition of protein synthesis are observed. When the ginseng preparation is administered to intact animals, an increased excitability of the spinal centers, as well as increasing volume of the motoneuronal nuclei and certain ultrastructural shifts demonstrating activation of protein synthesis and cellular energy are observed. When the ginseng preparation is preliminary administered to the frogs, before a high-frequency synaptic activation of the motoneurons, it protects the cells from pathological changes and pycnotic shrinkage.

Animals↗
PubMed1976

[Changes in the dimensions of motor neurons and their components with different forms of nerve center activation].

Experiments in frogs have shown that a prolonged orthodromic rhythmical activation of motoneurons induce changes in their size and staining. Under these conditions the size of all components of motoneurons (cytoplasm, nucleus, nucleolus) is changed. The cytoplasm size changes are more pronounced than those of the nucleus. Under prolongation of the low frequency stimulation (1 per sec.) of the dorsal roots the changes are of phasic character: an initial enlargement (10 minute-long stimulation) and a subsequent decrease of all the above spinal cord motoneuron components (25 minute stimulation). After the 10 minute high frequency stimulation (50 impulses per second) of nerve centers there occur a sharp decrease of the size of the cytoplasm and the nucleus.

Animals↗
PubMed1976

[The influence of synaptic processes on changes in neuronal structure].

Reactions of the spinal motoneurons to the afferent inflow were different in frogs: some neurons generated spike potentials during 10-min rhythmic stimulation (1/sec) of afferents, other neurons were switched on and off. The motoneurons and their synapses increased in size, their cytoplasmic matrix became lighter and ribosoms deteriorated. Antidromic activation did not entail modofocation of size or color of the cells. RNP granules were safe and local organellas degenerated. The role of synaptic processes in regulation of RNP metabolism and in intracellular reparation, was revealed.

Animals↗
PubMed1976

[Role of duration and intensity of activation of afferent fibers in regulating morphologic shifts in a neuron].

The afferent impulsation has a regulating influence on morphological and histochemical shifts in the neuron. The size and staining of spinal motoneurons of the frog are changed depending on the force and duration of the applied high frequency stimulation of afferent fibres. The threshold 10-minute-long activation results in the increased size and lighter staining of nerve cells. An increased force of high frequency stimuli causes darker staining and a decreased size of the motoneurons under study. One-minute-long activation of the afferent fibres by electric stimuli of 50 imp/sec failed to cause changes in the size and staining of nerve cells. Prolongation of the activation till 10 minutes results in a sharp decrease of the neuron size. Further activation of the afferent fibres for 2 hours causes pathological shifts in the structure of motoneurons: their vacuolization and melting. Besides, there appears a great number of dark stretched intensively stained nerve cells.

Animals↗
PubMed1975

[Changes in the ultrastructure of frog spinal cord motor neurons following low frequency stimulation of afferent fibers].

Effect of 10 min stimulation on the motoneurones ultrastructure depended on the amplitude of the ventral root biopotentials. In case of low amplitudes dilated endoplasmic spaces, Golgi complex cisterns were seen. Mitochondria were swollen and the number of free ribosomes increased. In the cytoplasm many "whorl--like" structures appeared. In case of high amplitude ventral root biopotentials, alterations were particularly evident in decrease in the ribosomes number, fragmentation of the endoplasmic reticulum. Electron density of the motoneurons was very low. After 25 min stimulation, the number of ribosomes increased in the motoneurons, the Golgi complex proliferated, very large mitochondria appeared. In the dendrites, swollen mitochondria often were adjacent to postsynaptic membranes. Electron density of the motoneurons was very high. The ultrastructural alterations of the motoneurons are supposed to be due to a change of cellular metabolism in the conditions of increased functional activity.

Animals↗
PubMed1975

[The mechanism of development of changes in the structure and histochemistry of a neuron].

The change of the neuron's functional state when the cells become unable to generate spike responses to orthodromic testing stimuli, was shown not to be reflected in the morphological pattern of motoneurons as revealed by means of Einarsson's RNA staining. High-frequency stimulation of the motoneurons generating neither postsynaptic nor spike potentials diminishes the neurons size and intensifies their staining. A strong activation of presynaptic endings followed by no active postsynaptic processes on the neuron's membrane was shown to be able to entail major morphological alterations.

Animals↗