ABSTRACT
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.
Subject(s)
Helix, Snails/cytology , Microscopy/methods , Otolithic Membrane/cytology , Spacecraft , Weightlessness , AnimalsABSTRACT
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.
Subject(s)
Adaptation, Physiological , Gastropoda/ultrastructure , Otolithic Membrane/ultrastructure , Space Flight , Space Simulation/methods , Animals , Centrifugation/adverse effects , Female , Gastropoda/physiology , Hypergravity/adverse effects , Male , Microscopy, Electron, Scanning , Microscopy, Phase-Contrast , Otolithic Membrane/physiology , Space Simulation/instrumentation , Weightlessness/adverse effectsABSTRACT
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.
Subject(s)
Helix, Snails/cytology , Otolithic Membrane/ultrastructure , Animals , Georgia (Republic) , Microscopy, Electron , Otolithic Membrane/chemistryABSTRACT
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.
