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D A Vasilenko

Publications and source records attributed to D A Vasilenko.

13 recordsLinked to original sources
PubMed1991

The spatial pattern of the synaptic vesicular apparatus as a correlate of transmitter storage models.

A statistical stereological approach which allows one to derive a three-dimensional pattern of synaptic vesicle accumulation in relation to the active zone from an analysis of electron micrograms (random sections) of synapses is described. This approach is illustrated with a study of presynaptic terminals from the dorsal horn of the cat spinal cord, based on the morphometrical treatment of 105 micrographs containing 5190 synaptic vesicles. The spatial pattern obtained was found to have a bimodal shape, which can be considered a possible structural correlate of the two-pool model of transmitter storage. The connection of similar quantitative estimates with physiological data is discussed.

Animals↗
PubMed1990

[An evaluation of the spatial morphofunctional characteristics of the presynaptic endings in the lateral area of the base of the dorsal horn].

A statistical stereological pattern allowing estimation of populational three-dimensional characteristics of cell elements on the basis of the analysis of their plain sections has been developed. Using such an approach a morphometrical electron microscopic study of presynaptic terminals (PTs) within the lateral areas of the dorsal horn of the cat spinal cord was carried out. The estimated distribution of PT volumes, PT axolemma areas, sizes of active zones (AZ) have been obtained. The mean number of AZs per a PT, parameters of AZ localization with respect to the terminal axonal expansion have been estimated. The data obtained are compared with the morphometrical estimations for the another PT population studied previously. The connection between the parameters estimated and functional features of the studied synapses are discussed.

Animals↗
PubMed1990

[The structural correlations in the presynaptic terminals from the dorsal horn of the spinal cord].

The summarized data on three-dimensional parameters of ultrastructural elements of presynaptic terminals (PTs) in the dorsal horn of the cat spinal cord are presented. Interrelations of the following parameters were studied: mean volume and plasma membrane surface area of PTs; mean volume, surface area and number of mitochondria in the PTs; mean area and the number of active zones, mean number of synaptic vesicles per each observed PT. The data obtained were regarded as parameters reflecting the features of ion diffusion, transmitter release and vesicular recycling in PTs.

Animals↗
PubMed1988

[Spatial organization of the sources of the spino-reticulo-cerebellar pathway].

Quantitative characteristics of spatial distribution of HRP-labelled neurons projecting to the medullar lateral reticular nucleus (LRN) were calculated in the cat spinal cord. Mean quantities of the labelled units in the transverse 60 micron sections were 12.55 at C2-C4, 7.77 at C5-Th1, 1.07 at Th2-Th13 and 1.60 at L1-L7. levels. Two groups of spino-reticular units can be classified according to their localization density: lateral and ventromedial. Lateral neurons have mainly (but not exclusively) uncrossed projections to the LRN while ventromedial cells have predominantly crossed projections. The relative quantity of lateral neurons decreases in rostro-caudal direction and the quantity of ventromedial ones increases. Spatial distribution of spino-reticular neurons is correlated with their functional classification; the presence of lateral group of such cells at all segmental levels is regarded as argument against differentiation of specialized "ipsilateral forelimb tract." Functional organization of the spino-reticular system is compared with the organization of propriospinal intersegmental cell populations considering that a certain part of intersegmental units relaying activity of main cerebral descending systems send axon collaterals to the LRN.

Afferent Pathways↗
PubMed1979

[Polysynaptic effects in neurons of the cervical portion of the cat spinal cord induced by activation of long propriospinal pathways].

Effects evoked in cervical moto- and interneurons by stimulation of lateral (LF) and ventral (VF) funicles at low thoracic level were studied in anaesthetized cats; degeneration of descending supraspinal fibres was provided by preliminary cord sections. LF and (or) VF stimulation evoked PSPs (usually mixed) in 57 of 90 studied motoneurons. Monosynaptic EPSPs were "primary" actions in 9 motoneurons while poly(di)-synaptic EPSPs or IPSPs--in the rest. Intensity of excitatory synaptic action on motoneurons of proximal muscles was substantially higher than on "distal" ones. LF and VF stimulation excited interneurons localized in the ventral quadrant and had no action on interneurons situated more dorsally. The effects studied are suggested to be mainly a result of activation of long proporiospinal fibres ascending via LF and VF to the cervical enlargement; certain part of reactions is supposed to be transmitted via collaterals of descending propriospinal fibres to the cervical neurons.

Animals↗
PubMed1978

[Transformation of long reticulofugal impulse trains by interneurons monosynaptically linked to the reticulospinal tract].

Transmission of the reticulofugal activity via the interneurons localized in the ventromedial grey matter of the lumbar region and monosynaptically activated from the reticulospinal fibres was studied in anaesthetized immobilized cats. Interneurons usually generated stationary discharges when reticulospinal pathways were rhythmically stimulated with relatively low frequencies (up to 80-100/s); with further increase of stimulation frequency the discharges became non-stationary (initial high-frequency phase was followed by partial or complete discharge suppression). Maximal firing rate at the initial phase could not exceed 180-230 imp./s. The "transfer function" (the ratio of response frequency to stimulation frequency) reached 0.7-0.8 at low stimulation frequencies and decreased substantially at higher ones. Using mathematical modelling of the excitatory and post-activation inhibitory actions in these neurons, the parameters have been estimated which determine the transfer properties, of the interneuronal population relaying reticulofugal activity.

Animals↗
PubMed1978

Propriospinal neurones as a relay system for transmission of cortico-spinal influences.

1. Synaptic organization and transmission have been studied in the lateral group of short propriospinal neurones of the lumbar and cervical regions of the cat spinal cord. Special attention was paid to their role in the transmission of cortico-spinal volleys. 2. The majority of these neurones are mono- or oligosynaptically excited after pyramidal tract stimulation. Convergence of excitatory actions from rubrospinal and lateral reticulospinal tracts was typical for these cells. Neurones with relatively low-level and delayed effects from segmental afferents are frequent in this population. 3. Temporal summation is important for the transmission of descending vlleys through these neurones. Mutual excitatory and recurrent inhibitory connections are supposed to play a substantial role in their function. 4. Possible participation of the short lateral propriospinal system in the transmission, transformation and re-distribution of corticofugal signals to the segmental spinal mechanisms is discussed.

Animals↗
PubMed1977

[Transmission of reticulofugal activity through the ventromedial group of propriospinal neurons in cats].

Responses of propriospinal interneurons localized in the ventromedial regions of the cat lumbar cord to the reticulospinal tract stimulation were studied. Monosynaptic excitatory action usually accompanied by di- and polysynaptic components was found in most units. Strong single stimuli were able to evoke discharges only in some cells, while temporal summation was necessary in many others. Excitation of neurons was followed by a short postactivation inhibition limiting the maximal discharge frequency.

Action Potentials↗
PubMed1976

[Postactivation inhibition of processes in interneurons transmitting the activity of lateral "descending" systems].

After-discharge depression of excitability is found in the interneurons specialized on transmission of activities from "lateral" descending systems. Many of these cells are propriospinal units sending axons to the lateral funicle (LF). Anti- und orthodromic spike potentials in these cells are followed by significant hyperpolarization. In some cells post-activation depression increased with a rise in intensity of LF stimulation that evoked antidromic discharge; inhibitory post-synaptic potentials were recorded in several units after LF stimulation subthreshold for evoking such discharges. Existance of inhibitory synaptic connections between neurons of the investigated group similar to recurrent connections in the motoneuronal pools is supposed.

Action Potentials↗