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D A Rusakov

Publications and source records attributed to D A Rusakov.

51 records · Page 3Linked to original sources
PubMed1990

[Changes in the processes of vesicular recycling in the hippocampal presynapses during the modelling of glutamate neurotoxicity].

In order to test directly morphofunctional changes in presynaptic terminals (PTs) of hippocampal slice preparations (28 day-old rats, Ca 1 neurons), their ultrastructure was studied electron-microscopically under 0.5 h exposure of 500 mumol/l. glutamate added into the incubation medium. The morphometrical and statistical stereological approach has demonstrated a sufficient rise in the mean number of exo/endocytosis caveolae per a PT (up to 13), an increase of PTs surface area (from 2.23 to 3.15 microns, on the average), whereas the mean PTs volume was practically unchanged as compared to the controls. These quantitative data have allowed estimating changes in physical and chemical presynaptic membrane parameters, correlating with the observed plastic alterations under increased extracellular glutamate concentration. It has been shown that the studied effects can take place during earlier stages of the long-term potentiation development.

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↗
PubMed1990

[A statistical assessment of the membrane area and of the number of active zones in presynaptic terminals].

Geometrical features of electron microgram profiles of presynaptic terminals (PTs) in the dorsal horn of the cat spinal cord were studied. The statistical approach which has permitted estimating the surface area of the closed membrane on the basis of parameters of its plane random sections is described. Mean surface area of the plasma membrane of observed PTs is estimated. The probability estimate of the mean number of active zones per each presynaptic bouton is considered. The obtained quantitative data are discussed for the possibility to describe physical processes occurring in presynapses.

Animals↗
PubMed1989

[Numerical characteristics of the structure of the vesicular apparatus of the synapses in the dorsal horn of the cat spinal cord].

Numerical parameters characterizing the structure of vesicular apparatus of presynaptic terminals were determined on the basis of the morphometrical investigation of the ultrastructure of 135 synapses from the dorsal horn of the cat spinal cord. Statistical estimates of the number of vesicles in the terminal was obtained (mean value 470). Bimodality of distribution of distances from a centre of each vesicle to the nearest site of the active zone has been demonstrated, that is regarded as a possible structural correlate of the two-pool model of the transmitter storage. The possibility of classification of synapses according to the spatial distribution of vesicles, relations between such distribution and parameters of the transmitter release and storage are discussed.

Animals↗
PubMed1989

[The geometrical characteristics of the presynaptic mitochondria and active zones of the dorsal horn of the spinal cord in the cat].

An electron microscopic study of the ultrastructure of 140 presynaptic terminals (PTs) in the dorsal horn of the spinal cord of cat was carried out. Some spatial characteristics of mitochondria and active zones (AZs) at these PTs were examined by the statistical stereological analysis. The distribution of spatial mitochondrial radii and active diameters were estimated. Mean values of following parameters were obtained: volume, surface area and the number of mitochondria, AZ area, volume of synaptic clefts at observed synapses. Relations of these morphometrical data to the transmembrane diffusion and accumulation of the ions were discussed.

Animals↗
PubMed1989

[Stereometric characteristics of the ultrastructure of presynaptic terminals in the dorsal horn of the cat spinal cord].

Ultrastructure of 240 axo-dendritic presynaptic terminals (PT) in the dorsal horn of the spinal cord of cat was investigated using the morphometrical statistic method. Parameters describing shape and average spatial radius of the three-dimensional PT (approximated by irregular ellipsoid) were estimated on the basis of the morphometry of random PT sections using ideas of the theory of probabilities. A lack of correlation between the synaptic operative zone localization and features of the terminals' shape was demonstrated. The distribution of the spatial PT radii was obtained. The obtained distribution elicited the relatively small variability of these parameters.

Animals↗
PubMed1987

[Changes in transmission efficiency in synapses of the dorsal horn of the cat spinal cord during repeated activation of cutaneous afferents].

Inhibition dynamics of certain components of the spinal cord potentials under low frequency stimulation of cutaneous nerves was studied in acute experiments on cats. The experimental data obtained were approximated by the theoretical curve on the assumption that the two-pool model of the transmitter storage was applicable. An increase of the mediator replenishment intensity during rhythmical stimulation has been demonstrated. The results obtained were similar to those obtained from monosynaptic reflex investigations, that demonstrates the likeness of action mechanisms for different afferent synapses.

Afferent Pathways↗
PubMed1987

[Effect of spinal cord irradiation with a low-intensity laser on synaptic transmission characteristics in the dorsal horn].

The effect of the monochromatic red light irradiation on the inhibition dynamics of repetitively evoked spinal cord potentials was studied in cats. It is suggested that the radiation increases the intensity of transmitter replenishment processes in the synapses of neurons involved into the generation of observed potentials (N1 component of the cord dorsum potential and monosynaptically evoked discharges of dorsal horn units).

Animals↗
PubMedDate not supplied

Synapses in hippocampus occupy only 1-2% of cell membranes and are spaced less than half-micron apart: a quantitative ultrastructural analysis with discussion of physiological implications.

Relatively little information exists regarding the spatial structure of synaptic neuropil in the brain. The present electron microscopic study employs unbiased stereological techniques and Monte Carlo simulations to characterise quantitatively the spatial organisation of synaptic circuitry in the dentate gyrus of the hippocampus, an area of particular importance in mechanisms of learning and the subject of a number of experimental neurobiological models of synaptic plasticity such as long-term potentiation. Firstly, tissue shrinkage/expansion resulting from embedding was assessed by imaging 300-microm thick hippocampal slices in the course of the entire embedding protocol, giving a value of 94.3 +/- 1.1% for distance measures and 84.3 +/- 2.8% for volumetric measures. Secondly, numeric synaptic density, Nv, was estimated using the disector. Thirdly, accumulated area of post-synaptic densities (PSDs) per tissue volume, Sv, and the overall cell membrane area per tissue volume, Sv*, were assessed using unbiased stereological rules coupled with image analysis of single sections. Finally, the mean area of individual PSDs was derived as a ratio Sv/Nv giving: 0.0394 microm2 for axo-spinous PSDs (thus representing approximately 1.3% of total cell membranes) and 0.0769 microm2 for dendritic shaft PSDs (approximately 0.25% of total cell membranes). From these data, the mean nearest neighbour distance between synapses was estimated using Monte Carlo simulations of a random 3D arrangement of synapses constrained by PSD sizes (a truncated Poisson process), giving a value of 0.48-0.51 microm. The physiological importance of the morphometric data obtained is discussed in terms of assessing (i) the role of synaptic environment in modifying synaptic efficacy and (ii) the plausibility of cross talk between synapses in relation to extrasynaptic neurotransmitter diffusion and transient depletion of extracellular Ca2+.

Animals↗
PubMedDate not supplied

[Quantitative changes in the ultrastructural elements of presynapses exposed to low-intensity laser radiation within the framework of a factorial model].

The ultrastructure elements of presynaptic terminals (PT) in a dorsal horn of cat spinal cord were studied morphometrically in norm and after helium-neon laser irradiation. The disperse computer analysis showed changes in a median terminal radius, the number and localization of synaptic vesicles, and no changes in the shape and length of the plasmalemma profile of the irradiated PT.

Animals↗
PubMedDate not supplied

[Structural and functional changes in spinal cord neurons following low-intensity laser irradiation].

In acute experiments with cats the dynamics of changes in the evoked activity of spinal neurons was determined during low-intensity laser irradiation of the cord. With histological preparations, in conditions of automatic processing of the morphometrical information, the data were obtained indicating the decrease in the post-impulse synaptic depression accompanied by the intensification of the nuclear plasmic exchange of the exposed neurons.

Animals↗