Mono- and polysynaptic connections between identified neurons in the system of the passive avoidance reflex of the snail.

The structure of the synaptic connections between identified sensory and giant command neurons of the parietal ganglia of the snail is examined. It is shown that the excitatory postsynaptic potential arising in the giant neuron in response to the generation of a single action potential in the presynaptic neuron consists of several monosynaptic components and may include polysynaptic components. It is hypothesized that monosynaptic components of the elementary excitatory postsynaptic potential that differ in the duration of the latent period and the dynamics of habituation may be associated with the activation of synaptic buttons on axon terminals of varying length.

[The mono- and polysynaptic connections between identified neurons in the system of the passive defensive reflex in the edible snail]. / Mono- i polisinapticheskie sviazi mezhdu identifitsirovannymi neironami v sisteme passivno-oboronitel'nogo refleksa vinogradnoi ulitki.

A structure of synaptic connections between the identified sensory and giant command neurons of Helix lucorum was studied. It was found that EPSPs arising in the giant neuron as responses to single action potentials generation in sensory neuron consist of several monosynaptic and several polysynaptic components having different magnitude, latencies, and plasticity. The latencies of monosynaptic components are determined by different presynaptic terminals' lengths.

Monosynaptic connection: identifiable synapses in the CNS of the edible snail.

The microanatomy of the pre- and postsynaptic neurons and the structure of the monosynaptic connection LPa7-LPa3 are described on the basis of planar reconstruction of sections of preparations of the CNS of the edible snail with neurons marked by heavy metal salts. Some physiological features of the presynaptic neuron and the monosynaptic connection were studied. The criteria for the identification of the LPa7 neuron according to its position in the ganglion, to the physiological reaction of LPa3, and to its microanatomy were determined. The position in the ganglion of three other neurons which form monosynaptic connections with LPa3 is described. The plasticity of the LPa7-LPa3 connection is demonstrated. The possibility of the realization of plasticity through the cutting off of individual synapses composing the connection is hypothesized. The results of 65 experiments on the identification of LPa7, the physiological characteristics of this cell, and its monosynaptic connection with LPa3, are summarized in this study. One preparation with a monosynaptic connection is reconstructed.

[The monosynaptic connection: identified synapses in the CNS of the edible snail]. / Monosinapticheskaia sviaz': identifitsiruemye sinapsy v TsNS vinogradnoi ulitki.

By electrophysiological and microanatomical methods of analysis of snail CNS small neurones it was shown that a number of neurones form a monosynaptic connection (MSC) with the gigantic polyfunctional neurone LPa3. By using cobalt and nickel staining, the structure of MSC cells LPa7--LPa3 was studied. Six identified synapses in two LPa3 processes zones were found. Physiological analysis showed that the revealed MSC was plastic. The described MSC with identified synapses is convenient for studying synaptic transmission mechanisms.

[Effect of ultrasound on the membrane potential and embryonic development of sea urchin eggs]. / Vliianie ul'trazvuka na membrannyi potentsial i émbrional'noe razvitie iaitsekletok morskogo ezha.

Eggs of sea urchin Strongylocentrotus intermedius were exposed to continuous wave ultrasonic energy at a frequency of 2 MHz for 3 min. Ultrasonic treatment results in the appearance of monstrous embryos that die at the latest stages of their development. The number of dead embryos sharply grows with the increase in the spatial average intensity from 0.4 W/cm2 up to 1.6 W/cm2, when it comprises 100%. Dramatic decrease from 99% to 17% in the absolute value of transmembrane potential for both fertilized and unfertilized eggs was observed after ultrasonic treatment. These results seem to be caused by the action of stable cavitation. The given estimations show that for ultrasonic intensities more than 0.2 W/cm2 and providing the presence of gaseous bubbles in the vicinity of eggs shell the value of shear stress in an egg shell becomes great enough to cause the cytoplasmic gel fragmentation.

[Postmortem changes in the ultrastructure, cytoplasmic proteins and nuclear chromatin of rabbit nerve cells]. / Posmertnye izmeneniia ul'trastruktury, belkov tsitoplazmy i khromatina iader nervnykh kletok krolika.

Changes in the set of water soluble cytoplasmic and chromatin proteins have been studied in the rabbit neocortex, cerebral trunk, liver and muscles by means of electrophoresis in polyacryl gel with sodium dodecisulfate, 12 and 24 h after the animals are decapitated, when the material is kept in cold and at room temperature. Ultrastructure of pyramidal neurons in layer V of the rabbit sensomotor cortex has also been studied immediately after death and after 24 hours' preservation of the material at 4 degrees C and at room temperature. It has been stated that the ultrastructural changes in the nucleus and in the set of chromatin proteins in the cerebral cells are rather small even 24 h after death. Cytoplasmic structure and spectrum of the cytoplasmic proteins undergo much greater changes. Chromatin proteins of the cerebral cell nuclei, especially those of the neocortex, much better withstand the postmortem proteolysis than the cells in the liver and muscles, and cytoplasmic proteins of the cerebral cells are less stable than in other tissues. A possibility to perform analogous investigations in section material of the human brain and possible mechanisms of adaptive character on unequal stability of proteins in various tissue cells are discussed.