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D A Moshkov

Publications and source records attributed to D A Moshkov.

At least 73 records · Page 4Linked to original sources
PubMed1989

[The ultrastructure of the individual nerve endings of the tonic fibers in the frog].

A regular diminution of specific areas of synaptic contacts and active zones (AZs) along the terminals towards the distal parts has been first shown. The discontinuity was found in the terminal nerve branch apposition to the muscle fiber as a result of periodic intercalation of the Schwann cell and its processes into the synaptic gap. A significant variability in shapes of active zones lengthways the terminal is revealed. It is suggested that all these structural features may reflect the functional properties of synapses on the tonic muscle fibres.

Animals↗
PubMed1989

[Ultrastructure of the Mauthner neurons in goldfish fry after their adaptation to vestibular stimulation].

The ultrastructure of the Mauthner cells (M-cells) of goldfish fries was investigated under four different functional states: a) intact (native fishes), b) fatigue (intact fishes subjected to a prolonged vestibular stimulation), c) adapted (intact fishes after a prolonged training session of the daily short vestibular stimuli), d) excited (adapted fishes subjected to a prolonged vestibular stimulation). It has been first found that the fatigue of the M-cells may result in destructive changes of their cytoskeleton. Besides, in the afferent synapses of both adapted and excited M-cells numerous dense-cored vesicles were revealed near the active zones. The data show the neuronal cytoskeleton to be the central target susceptible to damage upon stimulation. The training leads presumably to stabilization of the cytoskeleton ultrastructure. The dense-cored vesicles were suggested to play an active role in the process.

Adaptation, Physiological↗
PubMed1988

[Nonuniformity of the fine structure of various portions of the nerve terminal in frog somatic muscles as the basis for the variation in its efficiency].

The ultrastructure of serially sectioned single terminals of two neuromuscular synapses differing in efficacy in frog sartorius and cutaneous pectoris muscles was investigated. Their central (CP) and distal (DP) parts were studied morphometrically, and the data on the terminal ultrastructure in different muscles were compared. The areas of active zones (AZ) in CP of terminals in both the muscles were significantly larger than in DP. At the same time the number of AZ in CP specific terminal length of sartorius muscle exceeded that in DP, whereas at terminal of cutaneous pectoris muscle the AZ were arranged more uniformly along the whole terminal length. Some other structural features of these terminals were revealed exerting their influence on the efficacy of transmitter release. We suggest that changes of AZ dimensions may closely correspond to the efficacy both in different parts of the same terminal and in two different terminals.

Animals↗
PubMed1988

[Actin study of the synapses of surviving hippocampal slices during long-term potentiation].

A study was made of the synaptic actin ultrastructural localization in the hippocampal slices at long-lasting potentiation of area CA, using myosin subfragment-1 labeling. A specific qualitative ultrastructural sign of the potentiated hippocampal synapses was revealed for the first time - the formation in spines of rodlike bundles of actin filaments resembling the cilia. They penetrate the spine stalks to pass through the spine core towards the postsynaptic densities of active zones. The thinner bridges link the filament bundles with the actin cytoskeleton meshwork, with spine apparatus cisterns and with postsynaptic membranes of the active zones. Besides the increasing density of the presynaptic actin meshwork was shown. The changes in the actin cytoskeleton being taken into consideration, its contractile properties account for some morphofunctional features of the potentiated synapses known before and predict previously unknown ones.

Actins↗
PubMed1988

[Synapses with a different synaptic contact structure in the cerebellar cortex].

The ultrastructure of cerebellar axosomatic (inhibitory) and axo-dendritic (excitatory) synapses were studied on the Purkinje cells and in the lower molecular layer of guinea-pigs and rats, respectively. It was shown that synaptic contacts of excitatory and inhibitory synapses differed in the existence of desmosome-like structures near the active zones. The classification of synaptic functions according to the ultrastructure of specialized contacts, earlier developed to identify neurons of lower vertebrates, is supposed to be applicable to the nervous system of higher vertebrates.

Animals↗
PubMed1987

[The single nerve ending of the frog sartorius muscle: its ultrastructural characteristics and mediator secretion].

Electron microscopy and extracellular recordings were used for the investigation of structural and functional peculiarities of single frog sartorius muscle nerve terminal. It has been found that the diameter, length of the synaptic contact and quantity of synaptic vesicles decreased from proximal to distal parts of the nerve terminal. A number of varicosities, separated from each other by schwann cells, have been revealed along the course of the nerve terminal. This indicates the existence of an interrupted synaptic contact. Both the evoked and spontaneous transmitter release decreased from the initial to the end parts of the nerve terminal. The data obtained suggest that there is a correlation between structural heterogeneity and the differences in the transmitter release.

Animals↗
PubMed1987

[Differences in the cytoskeleton in inhibitory and excitatory synapses].

The cytoskeleton of afferent chemical synapses, with various ultrastructure of contact zones, was examined in the Mauthner cells of the goldfish. The synapses with combined active zones and desmosome-like specialized contacts possessed a well developed cytoskeleton consisting of filaments and microtubules oriented towards the synaptic apposition. Regular arrays of synaptic vesicles oriented in the same direction were observed beyond and near the active zones. The cytoskeleton of the synapses lacking desmosome-like formations was diffusely organized throughout the boutons. The distribution of vesicles in the vicinity of active zones was also not ordered. The role of cytoskeleton in organization of the two morphologically distinct synapses is discussed. A special function of cytoskeleton as an intermediary between synaptoplasm and membrane is regarded as a necessary basis for plasticity of excitatory rather than inhibitory synapses.

Animals↗
PubMed1986

[Detection of giant axospinal synapses in the hippocampus on semithin sections].

A histological study of plastic semithin hippocampal sections after the treatment of myosin with tannic acid and detergent and then with subfragment-1 has shown the neuronal dendrites to be covered with dark spine-like thickenings. Electron microscopic analysis of the same preparations has revealed that the electron dense discrete formations represent synaptic terminals, situated on the dendrites with a definite periodicity. We discuss the use of such a method for the quantitative calculation of synapses in nerve tissue at the combined histological and electron microscopic levels of investigation.

Animals↗
PubMed1986

[Cytochemical detection of actin in the structure of the synaptic apparatus of hippocampal field CA3].

Ultrastructural distribution of actin in dendrites, dendritic spines and presynaptic boutons of the hippocampal area CA3 of the guinea pig was investigated using decoration and immunocytochemical methods. The distribution of actin was non-homogeneous in all the parts of neurons. The highest concentration of this contractile protein was revealed in the spine cytoplasm. Here actin forms a dense cytoskeleton meshwork and is present also in postsynaptic densities. An intimate interaction between the spine actin cytoskeleton and the postsynaptic actin densities has been revealed. This feature may indicate the involvement of actin cytoskeleton in the organization and maintenance of dimensions, location and geometry of active zones.

Actins↗
PubMed1983

[Time-dependent changes in the structure of the synapses of hippocampal field CA3 after their potentiation].

The time-dependent quantitative ultrastructure of synapses in the stratum lucidum of the hippocampal CA3 area was investigated after the in vitro modulation of the synaptic efficacy by short tetanus applied to the fascia dentate (a so called long-term potentiation-LTP). Two distinct phases were shown in the structural alterations accompanying LTP. Firstly, significant reactive changes in the spine geometry and the active zone shape were observed. These changes reversibly disappeared during 2-3 hours of the subsequent incubation, whereas LTP became well pronounced at this time. Secondly, a substantial increase in the postsynaptic thickness was revealed. This morphological feature was matching more closely the time course of LTP, up to the disappearance of both structure and function within 5 hours or longer as a result of destructive changes during a prolonged in vitro incubation. We conclude that the increased postsynaptic thickness may structurally correspond to LTP.

Animals↗
PubMed1982

[Development of the structure and stability of Mauthner's neurons in Xenopus laevis tadpoles on the implantation of additional auditory vesicles].

The ultrastructure and functional changes of the Mauthner cells were studied in the X. laevis tadpoles under the conditions of the experimentally doubled source of their afferentation, an additional pair of ear vesicles. Additional afferent fibers grow from the receptors to the brain and form additional synapses on the soma of the Mauthner cells, indistinguishable by their morphology from the terminals of their own acoustic nerves. The altered interneuronal interactions lead, on one hand, to the accelerated maturation of the Mauthner cells and, on the other one, to the vacuolization of a part of the cytoplasm. The superafferentation of the Mauthner cells is characterized by a long-term marked decrease in the length of sections of the active zones of axosomatic synapses. It is suggested that this structural rearrangement provides for a marked increase in the stability of the Mauthner cells with respect to extreme natural stimulation which is noted in the tadpoles with the double vestibular system.

Animals↗
PubMed1981

[Histological, electron microscopic and biochemical study of the rat liver in experimental cardiomyopathy].

Morphological, electron microscopic, and biochemical studies of the livers of rats with experimental autoimmune cardiomyopathy were carried out. Morphological alterations of the liver included changes in hepatocytes, significant deposition of glycogen in liver cells, fatty dystrophy, signs of necrobiosis and necrosis in some parts of the liver. Electron microscopic studies of intracellular localization of glycogen revealed its accumulation in the cytoplasm, glycogen granules being represented mostly by alpha-particles. Lysosomes filled with glycogen were also demonstrated. These data are in good accord with the results of biochemical studies. The experimental results suggest possible causes of increased content of glycogen in the cytoplasm and lysosomes of liver cells in animals with experimental autoimmune cardiomyopathy, as compared with normal animals. The relationship between disorders in glycogen and lipid metabolism in this disease is discussed.

Animals↗
PubMed1980

[Ultrastructural study of the bases of postsynaptic potentiation in hippocampal sections by the freeze-substitution method].

Some morphological features of the pyramidal neurons depending on their physiological state were studied in the CA3 area of the guinea pig hippocampal slices by the freeze-substitution method. This method provided a better possibility to observe certain visible structural changes in the majority of fiber synapses in stratum lucidum after the rhythmic stimulation of dentate girus, compared to the conventional electron microscopy. The width of the spine stalks during the long-lasting potentiation in the tissue processed by the freeze-substitution method increased by 60%, being below 50% in conventional preparations. A correlation between changes in the post-synaptic densities and the physiological state of synapses was checked. A two-fold increase in the width of post-synaptic densities without changes in their length was found.

Animals↗