[Interdependent changes of the axon and Schwann cell in the process of reactive remodeling of a myelinated nerve fiber].

Using the inverted phase-contrast microscope, the living undamaged frog sciatic nerve fibers and the fibers mechanically injured to varying degrees, were studied. It was found that the swelling of myelin incisures (MI) (of Schmidt-Lanterman) occured according to the principles similar to those controlling the changes of the myelin gap (node of Ranvier) and depended on the swelling of a Schwann cell (SC) perikaryon. It was detected that this was a single process, which which could be united in a complex of nonspecific changes of a myelinated nerve fiber. It was also demonstrated that under the action of mechanical injury and hypotonic solution, swelling of MI, nodes of Ranvier and SC perikaryon occurred without modifications of outer fiber diameter, due to the pronounced local axon thinning. Electron microscopic study of the cytoskeletal axonal structures showed that there was not a simple local contraction of an axon, but a significant local increase in the density of cytoskeletal components of the axoplasm (by 200-275%). Reactive reversible remodeling of a myelinated fiber suggests a new type of interaction between the axon and SC, the mechanism of reversible translocation of liquid axoplasmic fraction to the glial cell cytoplasm.

[Two-nuclear neurons: sincitial fusion or amitotic division].

In the review the history of research two-nuclear neurons is stated and two hypotheses about mechanisms of their formation are analysed: by sincitial fusion or amytotic divisions. The facts of discrepancy of the former orthodox cellular theory categorically denying possibility sincitial of communications in nervous system and of sincitial fusion neurons are mentioned. As an example results of ultrastructural researches of occurrence sincitium in a cortex of the big brain of rats, in autonomic ganglions, in hypocampus and a cerebellum of adult animals are presented. The video data of the sincitial fusion of live neurons and the mechanism of formation multinuclear neurons in tissue culture are analyzed. Existing data about amytotic a way of formation two-nuclear neurons are critically considered. The conclusion becomes, that the mechanism of formation two-nuclear neurons is cellular fusion. Simultaneously the review confirms our representations about existence in nervous system sincitial interneural communications.

[Fusion of brain neurons in rat embryos].

Syncytial interneuronal connections were studied in the sensomotor cortex and caudate nucleus of twenty 14-22 day rat embryos. It was shown that with the extremely weak development of glial processes, many neuronal bodies and their processes were in the direct contact with each other. The contacting membranes in these areas formed oblong and dot-like contacts resembling gap and tight junctions. As a result, the intercellular cleft experienced varicose-like deformations. In the area of contacts, barely visible membrane pores were formed that broadened to form large perforations. The perforation margins presented the rounded shape of fused plasma membranes of adjacent neurons. Inside the perforations, residual vesicular membranous bodies were formed. The areas of the paired membranes between perforations were fragmented, thus increasing the number of residual vesicles, until the neurons fused with each other completely by unifying the neuroplasm of contacting cells. The results of these studies suggest that that the fusion of neurons in vertebrate brain cortex and brainstem nuclei could occur not only in pathology, but also in normal animals at the stage of embryonic development.

[Ultrastructure of the caudal mesenteric ganglion neurons during early development in kittens].

Electron microscopy was used to study the peculiarities of the development of nervous elements in the sympathetic caudal mesenteric ganglion (CMG) in the cat from the moment of birth until the end of the second month of life. The discordance in the rate of maturation of both neurons and their endings was observed. In newborn kittens, mature neurons, glial cells and synapses were observed together with many immature ones. In 14-day-old animals, the proportion of immature neurons decreased, while destruction of neurons was observed more frequently in this age. In CMG of the animals of all the age groups, axodendritic synapses were found most frequently and axosomatic synapses were observed more rarely. Finally, the ultrastructure of CMG in kittens become comparable to that of adult animals at the age of 60 days.

[Syncytial perforations of human neuronal embryo membranes].

An electron microscopy study of the anlage of cerebral cortex of human embryo has been carried with the aim of determining the presence of syncytial interneuronal connections in embryogenesis. It has been determined that, in part of the neurons, the glial embryo is absent and their external cell membranes are directly attached to each other by forming elongated or dotted tight junctions. Sometimes these junctions are perforated and, on their basis, the true syncytial interneuronal connections are formed. Natural structural properties of these connections are the following: formation of the base of tight membrane contacts, obligatory rounding of perforation edges, and the presence of residual particles in the form of spherical vesicles in the lumen of perforations. Results obtained allowed us to conclude that, in the anlage of cerebral cortex of embryos obtained during surgical abortion of pregnancy, apart from the formation of synaptic contacts, or until their formation, there is the possibility of syncytial interneuronal connections appearing. This should be considered during the transplantation of the developing brain.

[Syncytial cytoplasmic anastomoses between the neurites of caudal mesenteric ganglion cells in adult cats].

Since the majority of the published data on syncytial cytoplasmic anastomoses relate to the autonomic nervous system in the early postnatal period of development, when many nerve fibers are still poorly covered by glia or have no glial sheaths at all, it was suggested that such anastomoses were not present in adults due to the significant development of glia separating individual neurites from each other. To check this assumption, we have performed an electron microscopic study of the adult cat dorsal caudal mesenteric ganglion. The cell neurites were found to be frequently covered by glial sheaths. However, almost in every sample, the syncytial pores were detected between the contacting neurites lacking glial covering layers. Sometimes serial syncytially connected neurites were seen. Axo-dendritic synapses with presynaptic perforations outside the synaptic specializations were described in the autonomic nervous system for the first time. These observations therefore provide evidence of syncytial cytoplasm connections in normal adult animals, however this does not reject the neuronal doctrine.

[Development of rat stellate ganglion neurons, containing membrane muscarinic and purinoreceptors].

The aim of this study was to determine the localization and morphometric characteristics of the stellate ganglion (SG) neurons containing muscarinic and purinoreceptors in rats of different ages (newborn, 10-, 20-, 30-, 60-, and 180-day-old) using the immunocytochemical methods. The results obtained indicated that in all the animals studied, the major part of neurons contained immunopositive P2X2, P2X6 purinoreceptors and M1 cholinoreceptors since birth onwards. A few of the neurons containing P2X3 purinoreceptors were detected in all the stages of postnatal development; these neurons were scarce in rats up to 10 days of life, after which their number increased to reach a maximal value in 20-day-old animals and then declined again. No significant changes were found in the proportion of neurons expressing M1 cholinoreceptors and P2X2, P2X6 purinoreceptors during the ontogenesis. Thus, the muscarinic synaptic transmission was already present in SG of rats by the time of their birth, while the final set of purinoreceptors on the neurons of sympathetic ganglion was formed by the age of 30 days.

[Structural and functional changes in sympathetic ganglia following endotoxin and alpha1-antitrypsin exposure]. / Strukturno-funktsional'nye izmeneniia v simpaticheskikh gangliiakh pri deistvii v organizme éndotoksina i al'fa-antitripsina.

Structural and functional organisation of sympathetic ganglia under conditions of endotoxemia was studied in white rats, cats, and dogs. Submicroscopic characteristics of the changes occurring in the rat prevertebral sympathetic ganglia after endotoxin administration or application of endogenous proteinase inhibitor alpha 1-antitrypsin, were assessed as well as ultrastructural bases of the febrile rat ganglionic responses to antipyretic drug administration. Effects of endotoxin on synaptic transmission in inferior mesenteric plexus' ganglia of cats and on electrical activity in inferior mesenteric plexus' ganglia of dogs, were electrophysiologically demonstrated.