[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.

[Postnatal neurogenesis and regenerative capabilities of the central nervous system (review)].

Postnatal neurogenesis and regeneration opportunities of experimentally damaged areas of the cerebral cortex in various mammalian species were studied by the use of light and electron microscopy, autoradiography and transplantation. Back in the 70s of the 20th century by I. Mepisashvili and her school, it has been found that at the early stages of postnatal development of animals in the matrix area of the dorsolateral wall of the lateral ventricles there is a certain reserve of indifferent cells, which, like the embryonic period, by means of proliferation, migration and subsequent differentiation of their derivatives replenish the structure of the cortex with new glial and nerve cells and appear to be the major source of reparative regeneration of the CNS. The definite regularity in the rate of matrix cells implementation in the animals that occupy different levels of phylogenetic level (mouse, rat, rabbit, cat, dog) was established. It was found that in the immature-born animals (rabbit) the reserve of indifferent cells is maintained longer and their postnatal implementation takes place in a more extended period as compared to mature-born animals (guinea pig). The rates of the matrix cells implementation are in direct proportion to the functional load of the cerebral cortex. It has been demonstrated that these cells serve as the main source of regeneration of cortical lesions in the early postnatal period, while the defined biostimulants promote the intensification of this process. As a result of transplantation of the matrix of embryonic and early postembryonic cells in the experimentally damaged cortex of adult rats the quite successful restoration of the structure, characteristic of the relevant department of the cerebral cortex was observed.

[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.