[Simultaneous opposite axonal currents in neural process. Retraction hypothesis].

Bidirectional axonal current of organelles and molecules in the nerve fibers was demonstrated using radioautography, the horseradish peroxidase and in virology. However, the mechanism of this phenomenon and regulation of the currents direction in axoplasm still remain not entirely understood. In this article we used the model of living single neurons of mollusk isolated with fragment of neural process at its different levels. It was proved that the axoplasm has a mechanical tone, which is realized in the form of retraction up to complete axoplasm invagination in the neuron soma. The geometry changing of the living axon was treated as its transport neuroplasm mass. It turned out that the direction of axoplasm mass depends on the location of its adhesion sites. It is always simultaneous and bidirectional opposite, as it is the case with contractile muscle fibers.

[Contraction of the injured neuronal processes].

The investigation was performed on the isolated living neurons of a mollusk (Lymnaea stagnalis). The purpose of this study was to examine the contractile activity of the injured neuronal processes. Retraction of latter in Ringer's solution was found in 90% of the cases. The specific club-shaped structure (retraction bulb) served as a marker of contraction. The speed of process contraction fluctuated in different neurons from 0.03 to 9 microm/ min. As a result of usual linear contraction, the process diameter was increased on the average by 35%, while the cell body volume was increased on the average by 30%. The three forms of contractile activity were distinguished: linear contraction, isometric contraction (reduction of a process thickness with no change in its length) and mixed form of contraction. It is suggested that the mechanism of retraction takes part in the formation of diastasis after nerve sectioning and injury of the brain conducting pathways. Diastasis in the nerve is formed not only due to the elastic properties of its fibrous sheath and glia, but also as a result of nerve fiber retraction.

[Changes in molluscan neurons under the influence of proteolytic enzymes].

The goal of the work was to study the structure of neurons treated with proteases and to elucidate if this could lead to the formation of the interneuronal syncytial connections. In the first series of experiments, phase contrast observation of the living dissociated ganglionic neurons of the mollusc Lymnaea stagnalis treated with 0.4% pronase, demonstrated a retraction of nerve processes and a two-phase change of the cell body volume. At the first stage, the soma volume decreased, on the average, for 82.5 min by 12.1%; subsequently, the volume increased, on average, by 14.1%. Signs of neuronal vital activity in Ringer's solution were observed, on the average, for 828 min, while in pronase solution their duration was 1.4 times shorter. In the second series of experiments, the study of neuronal ultrastructure has demonstrated in many cases the integrity of mitochondria, rough and smooth endoplasmic reticulum (ER), Golgi complex, light and granular vesicles, nuclear structure, and the preservation of the optical density of neuroplasm. The cells making contacts after centrifugation form uniform intercellular clefts of about 20 nm. Point approaches of membranes were very rare. No signs of syncytial connections were detected. Elongation and fusion of smooth ER cisterns separated the fragments of soma from relatively undamaged cells. Some neurons were damaged, they contained numerous vacuoles formed by swollen mitochondria and ER cisterns. The nerve process fragments, detached during the dissociation, were surrounded by the normal plasma membrane.