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Biomedical subjects

D A Vasilenko

Publications and source records attributed to D A Vasilenko.

10 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↗
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↗