Neuron-glial contacts formed in the cerebellum during electrical stimulation in the presence of an NO-generating compound.

The molecular layer of the cerebellum of the frog Rana temporaria was studied by light and electron microscopy after electrical stimulation in the presence of an NO-generating compound. In these conditions, there was severe swelling of granule cell axon terminals (boutons) and astrocyte processes (AP), with loss of cytoplasmic elements. However, along with damaged structures, there were also undamaged structures: boutons with synaptic vesicles and AP with glycogen granules. It is suggested that these persisting viable AP may form 1) glial "wrappings" around damaged synapses or boutons and 2) neuron-glial contacts, which form when synaptic vesicles cross damaged bouton membranes to AP containing glycogen granules. It is also suggested that the presence of glycogen in AP in conditions of oxygen and glucose deficiency may provide a source of high-energy substrates such as glucose and ATP, thus providing conditions for neuron survival in pathological states (ischemia/hypoxia).

Energetic cooperation via ion-permeable junctions in mixed animal cell cultures.

Low ouabain concentration (1 x 10(-6) M) is shown to decrease intracellular K+ (K+in) and to increase intracellular Na+ (Na+in) in human fibroblast cell cultures. The same ouabain concentration was without effect upon K+in ad Na+in in rodent cultures such as BHK-21, mouse fibroblasts and rat glyoma C6 cells. K+in and Na+in in the mixed cultures of human and BHK-21 fibroblasts or human and mouse fibroblasts were found to be resistant to 1 x 10(-6) M ouabain whereas that of the mixtures of human and rat glyoma C6 cells proved to be ouabain-sensitive. The gap-junction-mediated dye transfer was revealed between human and BHK-21 cells. Such an effect was very small in the human-C6 cell mixed culture. It is concluded that cells with active ion pumps can support the maintenance of K+ and Na+ gradients in cells with inactive pumps, provided that effective ion transport via gap junctions takes place.

Factors affecting survival of reconstructed mouse embryos after nuclear transfer.

Reconstruction of mouse embryos was performed by injection of donor genetic material from differentiated cells of various types (cumulus cells, cardiomyocytes, and epithelial cells) into recipient cells (mature oocytes and zygotes). A medium for microsurgery was selected, which enhanced survival of both embryonic and somatic cells during the reconstructive manipulations. Special preparation of somatic cells to transplantation was carried out, which employed factors synchronizing the cells in a certain phase of the cell cycle in order to enhance their capacity to maintain the development of reconstructed embryos. The processes of nucleus reprogramming in specialized cells under the action of cytoplasmic factors of oocytes and zygotes were examined. During in vitro culturing of reconstructed embryos, the most successful development was observed in embryos implanted with donor material from cumulus cells. Mouse embryos reconstructed with a certain genome and subsequent production and use of stem cells are considered as the model system for developing the basic principles of replacement therapy.

Intercellular interactions as a basis for the expedient behaviour of multicellular systems.

Functional and structural aspects of intercellular interactions are considered. Chemical substances are universal mediators of intercellular interactions. Electrical and mechanical interactions are also involved in cell-cell cooperation. Functional peculiarities of the two principal types of intercellular interactions-ligand-receptor interactions and interactions based on permeable contacts-are compared. Examples of basic tissue processes are given (such as the mechanisms of embryonic induction and differentiation, regulation of cell proliferation, temporal and spatial regulation of the activity of differentiated cells, interactions between excitable cells) to illustrate the notion that the types of intercellular interactions are mutually complementary and fulfill different functions. Ligand-receptor interactions predominantly provide signal functions and ensure intertissue interactions, while the interactions based on permeable contacts mainly fulfill intratissue coordination relying on positional information and the exchange of energy and matter.

Ligand-receptor and junction-mediated cell-cell interactions: comparison of the two principles.

Two major forms of cell-cell interaction--namely, ligand-receptor interactions and junction-mediated interactions--have different functional implications and naturally supplement each other in the most important tissue processes. The former type of interaction may be defined as distant and mainly "intertissue"; as a rule it determines temporal coordination of cell functioning. The latter is local and preferentially "intratissue"; it determines spatial coordination of cell activity.

Analysis of electrical phenomena accompanying the growth of Neurospora crassa hyphae: theory and experiment.

To describe electrical phenomena observed in growth of Neurospora crassa hyphae, a theoretical model was developed considering the hypha as a one-dimensional electric cable with non-uniform longitudinal distribution of current sources reflecting the activity of proton pumps. A profile of the density of the pump current along the hypha is proposed, at which the results of simulation quantitatively coincide with the results of physiological experiments. The model values of energy coupling in the growth zones were estimated. The experimental dependence of the elongation rate of regenerating apical hypha fragments on their lengths was determined. Based on the comparison of these experimental results with the results of analysis of the model, the contribution of the axial metabolite transport, from the distal parts of the hypha to the apical part, to the dynamics of the apical cell growth was estimated. The possibility of evaluating the intensity of high-molecular-weight syntheses and/or accumulation of substances in granules was demonstrated. The growth rate of the regenerating hypha fragments was shown to correlate with the electric current flowing into the apical fragment 0.2-mm in length.