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Biomedical subjects

F N Serkov

Publications and source records attributed to F N Serkov.

At least 19 recordsLinked to original sources
PubMed1997

[Nikolaĭ Nikalaevich Sirotinin and his school].

In a brief review of 50-year scientific activity of professor N. N. Sirotinin and his students the authors emphasize that this broad-minded scientist contributed to development of such disciplines as microbiology, pathophysiology, high-altitude, aerospace medicine. However, his main goal was evolution of reactivity and resistance, approaches to perfection of human health and performance. Much attention was paid to effects of low partial oxygen pressure on human and animal body, to hypoxic states of different origin. Methods of hypoxytherapy and hypoxic training are widely used in Russia and abroad. The contribution of academician N. N. Sirotinin to modern pathophysiology, high-altitude and aerospace physiology, internal and sport medicine is highly appreciated in Russia.

Aerospace Medicine↗
PubMed1990

[The characteristics of the synaptic apparatus of the primary auditory area (A1) of the cat cerebral cortex].

Quantitative and qualitative comparative studies of the synaptic apparatus in different layers of the primary auditory cortex (AI) in cat were performed using an electron microscope. The total average density of axonal terminal profiles in this area was 255 terminals per 1000 microns2 of the slice area. These profiles occupied 8.9% of the total studied area of slices. 45.3% of axonal terminals in area AI formed synapses on spines, 48.5%--on dendrites and 6.2%--on neuronal somata. 83.9% of synapses were asymmetric, 16.1%--symmetric. The number of synapses in 1 mm3 of the neural tissue in area AI estimated by stereological methods was 322.8 x 10(6).

Animals↗
PubMed1989

[Changes in the synaptic apparatus of the associative area (field 5b) of the cat cerebral cortex following destruction of the lateral posterior thalamic nucleus].

Quantity of normal and degenerating axonal terminals (AT) in area 5b of the associative cortex of cat was studied 2, 4 and 30 days after the electrolytic lesion of the thalamic nucleus lateralis posterior (LP). It was established that the quantity of degenerating AT in area 5b two and four days after the LP lesion was 7.4 and 7.2%, respectively. Four days after LP lesions the quantity of normal AT diminished by 16.4%, which was a direct result of excitatory AT degeneration. 40% of vanished AT formed synapses on dendrites and 60%--on spines. The quantity of axosomatic synapses in area 5b did not change after the LP lesion. Consequently, neurons in area 5b receive direct excitatory, predominantly axospinal input from LP. 30 days after LP lesions the total number of AT in area 5b was lower by 100% as compared with the control. Results and peculiarities of reinnervation in area 5b after degeneration of thalamocortical synapses are discussed.

Animals↗
PubMed1989

[Characteristics of the synaptic apparatus of the parietal associative cortex (area 5b) in the cat brain].

An electron microscopic examination of the associative cerebral cortex (area 5b) in cat was performed. The average density of axonal terminal profiles in this area was 263 +/- 16 terminals per 1000 micron2 of the slice area. 75.5% of axonal terminals contained synaptic vesicles and had asymmetric or symmetric contacts with visible active zones. 8.4% of axonal terminals had contacts without visible active zones. 24.5% of axonal terminals contained synaptic vesicles, but had no visible contacts with neighbouring structures. 84.9% of axonal terminals contained round or slightly elongated vesicles, 7.8% --a mixture of round and elongated vesicles and 7.3%--thin elongated vesicles. Among the axonal terminals with visible synaptic contacts 46.6% were of the axo-spine type, 50%--of axo-dendritic type and 3.4%--of axo-somatic type. 77% of axo-somatic terminals contained elongated vesicles and had symmetric contacts and 23% contained round vesicles and had asymmetric contacts.

Animals↗
PubMed1984

[Neuronal and synaptic mechanisms of cortical inhibition].

Data are presented concerning the latencies, amplitude and durations of IPSPs evoked in neurons of different cortical regions by peripheral and thalamocortical fibre stimulations and intracortical microstimulation in cat. The duration of IPSPs developing due to single afferent stimulus ranged between 20 and 250 ms (60-80 ms as a rule). In response to intracortical microstimulation monosynaptic IPSPs of 5-10 ms duration arose parallel with IPSPs of 20-100 ms duration. Barbiturates and chloralose increased the duration of IPSP up to 300-500 ms. The latencies of 73% of IPSPs evoked in the auditory cortex neurons by thalamocortical fibres stimulation exceed the latencies of monosynaptic EPSPs evoked by the same kind of stimuli not more than by 1.2 ms. Conclusion is made that inhibition developing in neurons of the cortical projection areas in response to afferent volley is a direct one and is produced by cortical inhibitory interneurons. Some cortical neurons were inhibited by a recurrent mechanism. Only 2% of IPSPs developed monosynaptically. The synaptic delay of IPSP evoked by intracortical microstimulation ranged between 0.3-0.4 ms. The length of the inhibitory neuron axons in layer IV of the auditory cortex reached 1.5 mm. The excitation conduction velocity in these axons was calculated to be 1.6-2.8 m/s (2.2 m/s on the average).

Afferent Pathways↗
PubMed1984

[Intracellular reactions of neurons of the primary auditory area of the cerebral cortex in the cat to tones of different frequency and electric stimulation of nerve fibers of the spiral ganglion].

In experiments with nembutal-anaesthetized cats it was found that neurons in the AI auditory cortical area responded to sound stimulation by EPSP, EPSP-spike-IPSP, EPSP-IPSP and IPSP. The majority of neurons studied responded to tones of characteristic frequency or to above-threshold tones whose frequencies were close to the characteristic ones as well as to electrical stimulation of spiral ganglion fibres innervated a central part of the receptive field by the sequence: EPSP-spike-IPSP. Tones whose frequency differed significantly from the characteristic one and electrical stimulation of the peripheral parts of the receptive field evoked responses in the form of EPSP-IPSP or IPSP. The tone frequency band that under threshold stimulation evoked a spike in a neuron was significantly narrower than the tone frequency band that evoked EPSP or IPSP. Two types of IPSPs were observed: components of the EPSP-spike-IPSP sequence evoked by excitation of receptors in the centre of the receptive field and primary or following EPSP evoked only if receptors locating in peripheral parts of the receptive field were excited.

Animals↗
PubMed1984

[Characteristics of post-spike and lateral inhibition in neurons of the primary auditory cortex in the cat].

In experiments on cats anaesthetized with nembutal it was shown by intracellular recordings that neurons located in the primary auditory cortex respond to characteristic frequency tones or to electrical stimulation of spiral ganglion fibres innervating the centre of the neuronal receptive field by a short latency spike response followed by long-lasting (20-250 ms) poststimulus inhibition. The cause of this inhibition is an IPSP originating in the studied neuron after the spike. On the basis of close connection between poststimulus inhibition and preceding spike activity the conclusion is made that the inhibition is created by a recurrent mechanism. When tones of noncharacteristic frequencies were used or peripheral parts of the receptive field were stimulated, responses in form of EPSP-IPSP developed. They were followed by depression of neuronal background activity and its responses to test stimuli. It was shown that these effects are produced by the mechanism of lateral inhibition. The characteristics of these two kinds of inhibition are presented.

Action Potentials↗
PubMed1983

[Responses of neurons of the auditory cortex in the cat to exposure to tones of different frequencies and electrical stimulation of the corresponding portions of the cochlea].

The characteristic frequencies for responses of the primary auditory cortical neurons (zone AI) whose receptive fields were located in different parts of cochlear basilar membrane were determined in nembutal-anesthetized cats. It is shown that the higher the characteristic frequency of the neuron, the nearer its receptive field to the base of the cochlea. The receptive fields of neurons with characteristic frequency above 4 kHz were located over the first 10 mm of the basilar membrane. Receptive fields of neurons with characteristic frequencies lower than 4 kHz occupied the rest of the basilar membrane. Electrical stimulation of the centre of the receptive field evoked neuronal responses which corresponded to reactions of the same unit produced by the tone of the characteristics frequency. The more the frequency of the tone differed from the characteristic one or the greater the distance between the centre of the receptive field and the point of stimulation, the lower is the probability of the response. The size of the receptive field of neurons with low characteristic frequencies was wider than that of high-frequency neurons. Using paired stimuli it is shown that excitation of cortical neurons was followed by inhibition. This inhibition was more prolonged and effective in responses to tones of characteristic frequency.

Animals↗
PubMed1980

[Quantitative and qualitative characteristics of synapses in different layers of the auditory cortex].

The electron-microscopic examination of synapses in different layers of the cat auditory cortex was performed. 53% of them were located on dendritic spines, 37% on dendrites and 10% on neuronal soma. All synapses were separated into type I and type II according to Gray. The type I synapses amounted to 91% (69.5% were of type Ia and 21.5% of type Ib), the type II synapses constituted 9%. The type I synapses were located mainly on dendrites and dendritic spines, the type II--on neuronal soma, axon hillocks and large dendrites. 60 h after complete neuronal isolation of a portion of the auditory cortex 22.8% of synapses revealed signs of degeneration. No type II degenerating synapses were found. This indicates that they are formed by axons of intracortical neurons. Quantitative and qualitative composition of synapses in different layers of the auditory cortex is shown to be different.

Animals↗
PubMed1979

[Electrophysiologic study of conduction of afferent impulses through the medial geniculate body].

In experiments carried out on cats immobilzed with d-tubocurarine 280 neurons located in pars principalis of the medial geniculate body and 408 auditory cortical neurons located in AI were studied extra- and intracellularly in response to stimulation of the brachium of the inferior colliculus and geniculocortical fibres. It was shown that the initial stage of the reaction observed in the medial geniculate body neurons response to stimulation of the brachium of the inferior colliculus continue for 13.0 ms. Excitation of 72% of neurons participating in the reaction occurs during the first 3 ms after stimulation. 84% of IPSPs arouse in the same period of time. It is found that some medial geniculate neurons have axons entering the inferior colliculus. Substantial part of fibres in the brachium of the inferior colliculus comes to the auditory cortex without synaptic switching in the medial geniculate body. 76% of medial geniculate neurons from the group excited monosynaptically are thalamocortical relay neurons and the rest are interneurons. 90% of relay neurons in the medial geniculate body are excited monosynaptically. Many medial geniculate neurons respond to stimulation of the brachium of the interior colliculus by EPSP-IPSP sequence or by primary IPSPs. About 20% of primary IPSPs develop monosynaptically. The maximal amount of IPSPs comes into being disynaptically with the participation of inhibitory interneuron located at the input to the medial geniculate body. The inhibition observed in this case is direct afferent one.

Action Potentials↗
PubMed1976

[Reactions of medial geniculate body neurons to stimulation of the auditory cortex].

Extra- and intracellular responses of pars principalis neurons in the medial geniculate body to stimulation of the first (AI), second (AII) and third (AIII) auditory cortex were studied in experiments on cats immobilized with d-tubocurarine. In geniculate neurons both antidromic (45-50%) and orthodromic (50-55%) reactions occurred in response to the auditory cortex stimulation. The latencies for antidromic and orthodromic responses were 0.3-2.5 ms and 2.0-ms, respectively. Late responses appeared with a latency of 30-200 ms. 63% of neurons responded antidromically to both AII and AI stimulation, that confirms the suggestion on the projection of a considerable number of the geniculate neurons to both auditory zones. Orthodromic responses of geniculate neurons consisted either of 1-2 spikes or a burst of 8-12 spikes with a frequency of 300-600/sec. The bursts are supposed to be the responses of inhibitory geniculate neurons. Intracellular recording showed the following responses: antidromic spikes, EPSP, EPSP-spike, EPSP-spike-IPSP, EPSP-IPSP and initial IPSP. Above 50% of initial IPSPs had the latency of 2.0-4.0 ms. They are supposed to be produced with the participation of intermediate inhibitory neurons located in the medial geniculate body.

Animals↗
PubMed1975

[Monosynaptic inhibitory postsynaptic potentials of cerebral cortex neurons].

The auditory cortes of cats immobilized with d-tubocurarine was stimulated by monopolar macroelectrodes (tip diameter 100 mu) or micloelectrodes (tip diameter 100--15 mu). In both cases in cortical neurons located closely to the stimulation point IPSPs were recorded with latencies ranging between 0.4--1.2 and 1.4 6.0 ms. It is suggested that IPSPs of the first group are generated in response to direct stimulation of the bodies and axons of the inhibitory cortical neurons (monosynaptically). The amplitude of such IPSPs ranged in different neurons from 3 to 15 mV and their duration was between 4 and 15 ms. Many of them were complicated by later additional inhibitory volleys. 1.5% of all IPSPs generated in response to geniculocortical fibres stimulation had latencies between 0.8--1.3 ms. It is suggested that these IPSPs were also evoked monosynaptically.

Animals↗
PubMed1975

[The relationship between the second zone of the auditory cortex and the medial geniculate body and first auditory zone].

Extracellular and intracellular responses of the second auditory (AII) cortical neurons to stimulation of geniculocortical fibres and first auditory cortex (AI) were studied in experiments carried out on cats immobilized with d-tubocurarine. It is shown that in these neurons there appear antidromic, mono-, di- and polysynaptic spike potentials to geniculate and AI stimulation. The number of antidromic reactions was about twice as low as in AI under the same conditions. Di- and polysynaptic responses predominated among orthodromic reactions. Intracellular recording revealed EPSP, EPSP-IPSP and primary IPSP in AII neurons. Response latencies in AII neurons to AI stimulation were in the range of 0.75-6.0, 6.1-16.0, 18.0-23.0 and 60.100 ms. After the medial geniculate body was removed, the number of responses with a latency of 6.1-16.0 ms decreased considerably. In some neurons spike pontentials appeared both to geniculate and AI stimulation. Comparison of the response latencies at both types of stimulation showed that impulses from AI come in AII not only to the neurons that are inputs for MGB impulses but also to neurons in the sebsequent link of intracortical neuronal chain. In most AII neurons disynaptic IPSP appeared at AI stimulation. Only in one case IPSP with a latency of 1.0 ms was recorded being probably monosynaptic.

Animals↗