[ISOMETRIC RETRACTION AND THE INVISIBLE PROCESSES OF NERVE CELLS].

Recently, a large number of physiological studies on stress and hibernation had described an unusual morphological phenomenon of the rapid disappearance and reapperance of apical dendrites of pyramidal neurons of the hippocampus, prefrontal cortex and other parts of the brain. In this article an attempt is maid to explain this phenomenon on the basis of morphological analysis of natural elastic properties of neuroplasm and structural kinetics of partially preserved processes of the living isolated neurons. The neuroplasm displacement with its bidirectional flow was identified in the processes. A new physiological phenomenon is described--the isometric retraction of nerve cell processes, during which the neuroplasm fluxes were directed to the opposite sides, leading to abrupt thinning of middle parts of the processes and to a thickening of both ends. It is suggested that the extremely attenuated processes can reach the submicroscopic sizes, becoming invisible in the light microscope. The repeated reversible "disappearance" and "appearance" of the processes was demonstrated supravitally in the culture of neurons and of C-1300 neuroblastoma cells. Reduction of the diameter of the processes to a limit of their visibility was demonstrated by the example of their natural stretching. The same effect was observed in the areas between the reversible varicosities of the processes. These areas became extremely thin, and then invisible. Becoming thinner, the processes were capable of sharp extension. A review of the available literature and our own data allow to conclude that the phenomenon of the disappearance of the apical dendrites was due to their isometric retraction, which lead to the emergence of "invisible processes".

Contractile activity of living isolated neurons and its inhibition by cytochalasin B.

Contractile activity of damaged neuronal axons of Lymnaea stagnalis and Planorbis corneus vulgaris mollusks and the possibility of inhibiting their retraction by cytochalasin B were studied. In experimental series I (control), the neuronal axons contracted in Ringer's fluid in 90% cases. In series II and III (cytochalasin B in concentrations of 0.02 and 0.2 mM), the percentage of non-contracting neurons was 50 and 70%, respectively. Presumably, the fiber retraction mechanism was involved in the formation of diastasis after nerve cutting and damage to conduction tracts. The nerve diastasis formed at the expense of not only elastic characteristics of the nerve sheath and glia, but also due to nerve fiber retraction. Experiments with cytochalasin B demonstrated that F-actin filaments were involved in the retraction of myelin-free nerve fibers.

[Enucleation, formation of cyto- and karyoplasts, and their fusion with neuronal body].

In this research that was performed on isolated neurons of mollusk Lymnaea stagnalis, using neuron enucleation, the cytoplast was obtained which was then fused with another neuron resulting in cybrid formation. The experiments performed have shown that the isolated neurons are able to fuse with each other, forming binuclear neurons; also, like all other cells, they could be enucleated with the formation of cyto- and karyoplasts and, after fusion, they can form cell body-cytoplast, cytoplasts-karyoplast, and other complexes. This is associated with the appearance of all doubtless indicators of fusion described for fusion of nerve cell bodies. This work demonstrates the possibility to artificially fuse the amputated neuroplasm fragment with neuronal cell body--the metabolic center of another cell. Theoretically, this means that in vivo amputated neuronal process also can be fused with a novel cell.

[A new view on the problem of nonneoplastic stenosis of the major duodenal papilla. Results of a prospective investigation].

The article contains results of a continuous prospective investigation of the normal course of the major duodenal papilla stenosis in 167 patients. It was revealed that the course of the disease was benign, pain syndrome became inconsiderable in the course of time, the degree of changes in biochemical analysis of blood was not significant. The development of complications (choledocholithiasis, acute pancreatitis, jaundice) was noted in 6-14% of the patients, depending on the presence or absence of GID. The data obtained allow suggestion of an algorithm of managing the patients.

[Neuron contractile and electrical activities as affected by colchicine].

The purpose of this investigation was to analyze the contractile activity of traumatized nerve cell processes and to try to inhibit their retraction by colchicine solution. Isolated living neurons of mollusks (Lymnaea stagnalis and Planorbis comeus vulgaris) were studied using phase contrast and time-lapse microvideorecording. In the control group, contractile activity of nerve cell processes in Ringers solution was detected in 92% of cases. Application of colchicine resulted in the inhibition of retraction of nerve fibers in 86% of neurons. In the experiments designed to study neuron electrical activity, leech Retzius neurons were used. It was found that ganglion incubation in colchicine solution of increased the frequency of spontaneous pulse activity from 0.22 to 0.75 imp/s. The amplitude of spontaneous potentials decreased from 46.9 to 37 mV, the threshold was reduced by 18%, spontaneous spike duration increased from 4.3 ms to 7.1 ms, while the latent period of the response to irritating stimulus increased from 25.0 to 37.9 ms. During the irritation with a frequency of 7-10 Hz, neuron generated higher frequency of pulse activity, than in norm. Thus, it was possible to show, that cochicine can inhibit the contractive activity of the traumatized nerve cell processes, preserving an electroexcitable membrane in a satisfactory state. These results suggest that it is possible to partially inhibit the nerve fiber retraction in vivo, thus preventing the diastasis increase in the nerves that impedes their contact surgical approximation and promotes the development of a massive scar in severed area.

Interneuronal membrane contacts and syncytial perforations in CA2 hippocampal area after brain trauma.

Membranes of pyramid neuron bodies located in CA2 hippocampal area were studied by electron microscopy after gunshot craniocerebral injury. In control group, asynaptic contacts and interneuronal syncytial perforations forming from tight junctions were observed. Contacts and perforations increased in size after trauma. Their number was maximum after severe gunshot injury. They reached their maximal size on days 5-7 after the injury.

[Glio-neuronal and glio-glial syncytial cytoplasmic connections in peripheral nerve trunks of the crayfish Astacus leptodactylus].

The paper considers various aspects of glial sheaths of neuritis in the crayfish peripheral nerve trunks and roots. There are revealed dotted glio-neurite tight junctions and a varicose deformation of the intercellular glio-neurite cleft. Rupture of membranes in the area of contact leads to formation of the glio-neurite pore (less than 10 nm) that is enlarged and forms wide (up to 240 nm) syncytial perforations. At the edge of perforation, either remnants of tight junctions are present or damaged membranes that fuse and are rounding. The lumen of perforations always contains residual membranous bodies in the form of vesicles. Their deviation from the median line can indicate a mutual translocation of substances of the glio- and neuroplasm. In the adjacent layers of the multilayer glial sheath there is noted a similar phenomenon of formation of the glio-glial syncytial connection terminating by fusion of neighbor glial layers, which is terminated by fusion of neighbor glial layers into the single lamina. The process begins from the varicose deformation of interglial clefts, which appears as a result of massive formation of dotted and expanded tight membranous contacts. As a result of transformation of ellipsoid varicose deformations into the spherical ones, syncytial pores (less than 10 nm) between them are formed, which are enlarged and break the paired gliolemmas into fragments. As a result, the adjacent glial layers are united. Since this process in intact animals occurs on the background of undamaged nerve structures, a suggestion is put forward about its reversibility and the functional nature.

Neuron division or enucleation.

The classical Bielschowsky-Gross neurohistological method was used to reproduce all the morphological phenomena interpreted by many authors as signs of neuron division, budding, and fission. It is suggested that these signs are associated with the effects of enucleation, which occurs in many cells of other tissue types in response to a variety of chemical and physical treatments. Studies were performed using neurons isolated from the mollusk Lymnaea stagnalis and exposed in tissue culture to the actin microfilament inhibitor cytochalasin B. Phase contrast time-lapse video recording over periods of 4-8 h demonstrated nuclear displacement, ectopization, and budding, to the level of almost complete fission of the neuron body. This repeats the pattern seen in static fixed preparations in "normal" conditions and after different experimental treatments. Budding of the cytoplasm was also sometimes seen at the early stages of the experiments. Control experiments in which cultured neurons were exposed to the solvent for cytochalasin B, i.e., dimethylsulfoxide (DMSO), did not reveal any changes in neurons over a period of 8 h. We take the view that the picture previously interpreted as neuron division and fission can be explained in terms of the inhibition of actin microfilaments, sometimes developing spontaneously in cells undergoing individual metabolic changes preventing the maintenance of cytoskeleton stability.

Syncytial cytoplasmic anastomoses between neurites in caudal mesenteric ganglion cells in adult cats.

The fact that most published data on syncytial cytoplasmic anastomoses are based on the autonomic nervous system in the early postnatal period of development, when many nerve fibers are poorly ensheathed by glia or have no glial sheaths at all, has led to the assumption that these anastomoses do not exist in adults because of the significant development of the glia and glial insulation of individual neurites from each other. We tested this assumption using electron microscopic studies of the caudal mesenteric ganglion in adult cats. A high level of glial ensheathing of neurites was observed. However, syncytial pores were seen between contacting neurites lacking glial sheaths in almost every specimen. This is the first report describing axodendritic synapses with perforations in the presynaptic zone outside the synaptic specializations in the autonomic nervous system. It is suggested that although syncytial cytoplasmic connections are seen in adult animals, they do not contradict the neuron theory.

[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.

[Neuronal division or enucleation].

In this work,using the classical neurohistological Bielschowsky-Gros method, all the morphological phenomena were reproduced that were earlier interpreted by many authors as the signs of neuron division, budding and fission. It is suggested that these phenomena are associated with the effect of enucleation demonstrated in many cells of other tissue types exposed to different physical and chemical factors. The experiments were conducted in tissue culture, using the isolated neurons of the mollusk Lymnnaea stagnalis, in which the neural cells were treated with actin microfilament inhibitor cytochalasin B. Phase-contrast time-lapse video recording during 4-8 hours demonstrated the effects of nucleus displacement, ectopy and bulging up to almost complete fission of neuronal body. These effects reproduce the images obtained in static fixed preparations under "normal" and various experimental conditions. Sometimes, at the early experimental stages, the bulging of cytoplasm was also detected. Control experiments in which the neurons were treated with the culture medium containing cytochalasin B solvent dimethyl sulfoxide, showed no changes in neurons during 8-hour period. It is suggested that the images, interpreted earlier as neuron division or fission, could be explained by inhibition of actin microfilaments, which sometimes may develop spontaneously in cells experiencing individual metabolic changes compromising the cytoskeleton stability maintenance.

[Blood serum of patients with secondary progressive multiple sclerosis changes neuron electric activity].

An effect of 20% blood serum estimated by the changes of background and excited spike activity of Retzius' neuron by Hirudo medicinalis, which does not contain myelin, has been studied in 2 groups of patients. The first group comprised patients with serum, containing antibodies to gangliosides, and the second one--patients without such antibodies. Incubation of Reitzius neurons in the serum with GM1-antibodies within 40 min resulted in the change of spike form, increase of cell stimulation threshold by average 20%, reduction of the frequency of spontaneous impulse activity by average 28%, decrease of the spikes number in response to the lower frequency (0.5 Hz) synaptic stimulation and inhibition of adaptation to the high frequency (10 Hz) stimulation. The use of the serum without GM1-antibodies caused a different change of the spike form and increased the stimulation threshold by 8% and sparser background impulse activity of the neuron by 40%. During low frequency synaptic activation of the neuron (0.5%), there was sensitivity disturbance and inhibition of the electric response to the high frequency stimulation. The results suggest that neuron injuries in multiple sclerosis may develop before morphological appearances of myelin lesions.