[ULTRASTRUCTURAL ORGANIZATION OF CELLULAR ELEMENTS AND INTERCELLULAR CONNECTIONS IN STATOCYSTS OF TERRESTRIAL PULMONARY SNAIL H. LUCORUM].

The organ of mollusc equilibrium - statocyst appears to be the analogue of acoustic-vestibular system in vertebrate animals. In terrestrial pulmonary snail the epithelial lining of statocyst cavity is created by two types of the cells - a small amount of large cells, provided with kinocilia of sensitive cells and considerably a large number of small supporting or inserted cells, covered with the microvilli. By means of transmission and scanning electron microscopy the ultrastructure and intercellular connections of these cells were studied. The sensitive cells have in a certain way structured cytoplasm, which consists of three layers: ectoplasm, granular layer and hyaloplasm. Myelin-like bodies having the granular, vesicular and drop-like formations in the centre appear to be the special structure of the cytoplasm. In the cytoplasm there are areas, saturated with electron dense glycogen granules. On the electronograms sometimes it is observed how the pinocytic vesicles in the supporting cells are created from the diverticulum of plasmatic membrane of sensitive cells. The boundary areas of plasmatic membrane of adjacent cells (sensitive cells with supporting or supporting cells with the support) are also characterized by the presence of specialized contacts, which are analogous to desmosomes in the epithelial tissues, as well as by the existence of cellular desmosomes, interdigitations. Numerous lacunas have been revealed in the intercellular space, which are connected by the thin tubules and ducts resulting in the formation of a complicated configuration of extensive system of communicating with each other lacunae, which have the exit in statocyst cavity.

[LIGHT AND ELECTRON MICROSCOPY OF CELLULAR ELEMENTS IN STATOCYSTS OF TERRESTRIAL PULMONARY SNAIL HELIX LUCORUM].

Statocysts H. Lucorum appear to be the paired formations having a spherical form and locating on dorsolateral surface of pedal ganglia of subesophageal ganglionic complex. Using the method of reconstruction, as well as the method of scanning electron microscopy on paraffin and semithin slices it has been revealed that the epithelial lining of H. Lucorum appears to be a spatially ordered complex, consisting of 13 cell assemblies. in each of them one sensory cell is surrounded by the satellite cells. The sensory cell has a star shape on the front pole of statocyst because of many protoplasmic processes branching off from its body. The other 12 cells have polygonal shape and form three belts around the inside perimeter of statocyst: interior, middle or equatorial and posterior. There are 4 cells in each belt. The sensory cells forming anterior and posterior belts turned out to be displaced in relation to the cells of equatorial belt and for this reason the whole cell structure resembles a brickwork. The distribution of sensory cells on the inner surfce of statocyst creates the structural polarization of this formtion. First of all, this is evidenced by the presence of the sensory cell on the anterior pole of statocyst and by the absence of those on opposite, posterior pole. The topography of each sensory cell on the inner surface of statocyst, the sizes and shapes of the nuclei, the quantity of nucleoli, the peculiarities of cytoplasm vacuolation and interrelation of sensory and supporting cells have been established.

[Light microscopy of statocyst cell elements from Helix lucorum (space experiment aboard the orbital station "MIR")].

Statocyst epithelial lining of terrestrial pulmonary snail Helix lucorum is a spatially arranged structure consisting of 13 cell ensembles. Each ensemble has a sensory cell surrounded by companion cells. The sensory cell on the anterior statocyst pole is star-shaped due to multiple protoplasmatic protrusions on its body. The remaining 12 polygon-shaped cells form 3 tires along the statocyst internal perimeter: anterior, middle or equatorial and posterior. There are 4 cells in each tire. Topography of every sensory cell on the statocyst internal surface was described as well as cell nuclei size and form, nucleoli number and patterns of cytoplasm vacuolization. Space free of sensory cells is occupied by supporting or intercalary cells. Exposure to space microgravity over 40, 43, 102 and 135 days aboard the orbital station MIR affected morphology of the sensory cells. Specifically, this appeared as reductions in cell height and, consequently, extension of the statocyst cavity internal diameter and volume in the space-flown snails.

[Plasticity of stastocyst inertial mass in terraneous gastropods helix lucorum and pomatias rivulare in altering gravitational field (microgravity, hypergravity)].

Light and scanning electron microscopy was used to study the morphological parameters and ultrastructure of Helix lucorum statocysts and statoliths in Pomatias rivulare statocysts after 56, 93 and 110-day exposure to microgravity aboard the ISS. Increased gravity was simulated by 30-d centrifugation at 6 g. On the first day of recovery, many statoconia and statoliths were found to carry numerous warts. Moreover, statoconia grew in number significantly as compared with the ground control. On the contrary centrifugation caused massive destruction of statoconia. In a month after orbital flight and centrifugation morphology of both statoconia and stastoliths was nearly normal. These results evidence, that the gravitational field is an important factor for the abiotic medium responsible for building up the inertial mass in the equilibrium organ of animals.

Morphological peculiarities statoconia in statocysts of terrestrial pulmonary snail Helix lucorum.

Vast majority of statoconia in statocysts of Helix lucorum are of oval shape and have smooth surface. Each statoconium in its central part has a nucleus, a spherical mass of 1.5 µ in diameter, surrounded by concentric structures. Minority of statoconia are of subcircular, elongated, rectangular, triangular, irregular, and sometimes fanciful shape and are structured around several nuclei or around small statoconia consolidated by shared growth layers. Apart from statoconia, spherical formations lacking mineral composition of 0.3-2.5 µ in diameter were also found in the statocyst cavity. Similar formations were found in vacuoles of sensory cells of statocyst epithelial lining. It is hypothesized that statoconium nuclei and growth layers around them are of different origin: the nuclei are formed by statocyst sensory cells, while the mineral component is a result of activity of supporting cells.

Effects of electric stimulation and destruction of caudate nucleus on short-term memory.

The effects of stimulation and destruction of the caudate nucleus on the cat short-term memory were studied by the method of classical delayed reactions. Short-term memory improved, if electrical stimulation of the caudate nucleus before presentation of the conditioned signal caused desynchronization of the electrocorticogram in the prefrontal and temporal cortex. Unilateral destruction of the caudate nucleus leading to the development of hyperactivity and attention disorders deteriorated short-term memory.