Efferent neurons of the auditory center in the midbrain of the frog Rana ridibunda

Individual cells which produce projections from the torus semicircularis in the frog have been visualized after injection of horseradish peroxidase (HRP) to various thalamic and isthmal areas. Labeled toral cells were observed if HRP had been injected to the posterodorsal areas of the thalamus or to the isthmal areas where lateral lemniscus fibers and cells of the premature lateral lemniscal nucleus are situated. Medium and large size cells in the rostrolateral torus semicircularis were mainly labeled. Thalamic injections of the HRP produced more labeled cells in the lateral part of the magnocellular nucleus, whereas isthmal injections produced labeled cells mainly in the lateral part of the laminar nucleus. A few HRP containing cells were observed in the principal nucleus of the torus. Specificity of the neuronal organisation of the auditory pathway in amphibians is discussed.     

Structure of the endotheliocytes of cerebral vessels of aquatic mammals

By means of scanning microscopy the relief of luminal surface of endotheliocytes, lining microvessels of various parts of the brain in the Pusa sibirica, Phoca vitulina and Delphinapterus leucas have been studied. Specialized formations of the cellular surface--various processes, projections, toruli have been revealed; their character in various parts of the brain in diving animals is determined by the blood stream conditions and their different sensitivity to oxygen deficiency during diving. The peculiarities, revealed in the structure of the cerebral vessels intima, are considered as one manifestations of the adaptive properties in the organism of diving animals, which had been developed in them during the process of a long evolution, while they adapted to the aquatic environment.     

Synthesis of polyglycerol phosphate by Bacillus stearothermophilus.

A particulate enzyme preparation from Bacillus stearothermophilus synthesized 1,3-poly(glycerol phosphage) from CDPglycerol at an optimum pH of 8.0 and the reaction was stimulated by divalent cations. Km for CDPglycerol was 0.18 mM. The synthesis was inhibited by CMP, CDP, and CTP and by concentrations of CDP-glycerol above 0.49 mM. The reaction was irreversible, The product had an average chain length of 8 glycerol units. About two thirds of the polymers were synthesized in entirety while the ramainder were attached to some acceptor by their phosphate end. The enzome was able to synthesize only a limited amount of polymer.     

Dynamic compression counteracts IL-1β induced inducible nitric oxide synthase and cyclo-oxygenase-2 expression in chondrocyte/agarose constructs

Background  

Nitric oxide and prostaglandin E₂ (PGE₂play pivotal roles in both the pathogenesis of osteoarthritis and catabolic processes in articular cartilage. These mediators are influenced by both IL-1β and mechanical loading, and involve alterations in the inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2 enzymes. To identify the specific interactions that are activated by both types of stimuli, we examined the effects of dynamic compression on levels of expression of iNOS and COX-2 and involvement of the p38 mitogen-activated protein kinase (MAPK) pathway.     

Stimulating effect of focused ultrasound on auditory fibers of the acoustic nerve in the frog Rana temporaria

After mechanical destruction of the receptor apparatus, application of focused ultrasound (frequency 2.34 mHz) to the auditory fibers of the frog elicited the electrical activity in the auditory midbrain centers (torus semicircularis). Action potentials evoked by focused ultrasound were similar to those evoked by activation of the intact contralateral labyrinth. After introduction of horseradish peroxidase into the destroyed auditory capsule, fibers activated by ultrasound were detected. Therefore electrophysiological and histochemical experiments reveal stimulating effect of focused ultrasound on the auditory fibers of the VIIIth nerve.     

The structural characteristics of the auditory portion of the cerebral cortex in the Baikal seal (Pusa sibirica) and the neuronal reaction to hypoxia]

Methods of light (Nissl, Golgi-Kopsch) and electron microscopy were used for studying the structural organization of the auditory portion of the cerebral cortex of Pusa sibirica. The auditory port of this kind of cortex is characterized by pyramidization of all the layers (layer IV included), thick layer I, two sublayers in layer III which is typical of other semiaquatic and aquatic mammals. Synaptoarchitechtonics of this part of the neocortex may be compared with that of other aquatic, semiaquatic and terrestrial mammals. The investigation of the state of neurons of the auditory portion of the cortex of Pusa sibirica during induced 18-min hypoxia has shown that the alterations in the neurons are of functional and reversible character. The axosomatic synapses remained most intact. The alterations in the auditory portion of the neo-cortex of Pusa sibirica evidences high level of adaptive reactions to hypoxia associated with the adaptation of these mammals to diving and fixed in the evolutionary process.     

Premature assembly of nucleolus-derived foci induced by a reversible hypotonic shock in metaphase CV1 and HeLa cells

The assembly of nucleolus-derived foci (NDF) in the cytoplasm of telophase cells is an early stage of nucleolus reassembly during mitosis. In current literature, significant attention is paid to the molecular composition of NDF and their participation in reassembly of the mature nucleolus. However, very little is known about mechanisms controlling the NDF formation. The authors have demonstrated for the first time that a reversible action of low ionic strength buffers (lypotonic shock treatment) on living mitotic human HeLa and green monkey CV1 cells triggers a premature assembly of NDF at metaphase. Like the true NDF, i. e., those assembled in telophase mitosis, NDF prematurally induced at metaphase contain RNA and proteins required for rRNA processing (fibrillarin, B23/nucliophosmin, C23/nucleolin), but lack UBF, an auxiliary factor of RNA polymerase I. We have assumed that a reversible action of hypotonic shock on metaphase cells may result in temporal increase in intracellular [Ca2+](i) that, in its turn, may induce a premature assembly of NDF under isotonic conditions. The structural integrity of the mitotic spindle apparently plays an essential role in the response of metaphase cells to hypotonic shock treatments.