Structure of glutamate receptor ion channels and mechanisms of their blockade by organic cations

Structural determinants of blocking the glutamate receptors of AMPA and NMDA subtypes, were studied. Close location of hydrophobic and ammonium groups is necessary for affective blocking of the NMDA receptor channels, whereas blockers of the AMPA receptor channels have a distance of about 10 angstroms between these two groups. Models of the channels meeting these topographic data have been devised using a molecular mechanics approach. The accomplished studies revealed molecular basis of channel blockade of the NMDA and AMPA receptors. This may allow designing predictable new blocking compounds with a desired selectivity.     

Components of the intracellular cyclic AMP system maintaining olfactory reception of amyl alcohol

In experiments on isolated olfactory epithelium, cAMP was shown to have an intracellular signal system which participates in pentanol olfaction transduction. Increase in the intracellular cAMP level is associated with adenylate cyclase activation due to G-protein stimulation by odorant coupled with it.     

Reasons causing a lag period in the oxidative phosphorylation process. Isn't ATP an internal uncoupler of ATP synthetase?]

The kinetics of oxidative phosphorylation catalyzed by bovine heart submitochondrial particles was studied in a range of MgATP and MgADP concentrations from 0.3 to 10 mM. It is shown that, at a low uncoupler concentration (0.9 microM of tetrachlorotrifluoromethylbenzimidazole, the lag period of the reaction increases from 12 s to 2-3 min, and KM for Pi increases severalfold; the value of Vmax remains practically unchanged. Increasing the [MgATP]/[MgADP] concentration ratio, with their total concentration being unchanged, leads to similar changes in the kinetics of oxidative phosphorylation. The value of delta pH generated on the membrane of AS particles at delta microH+ = 60 delta pH was measured using 9-aminoacridine. It was found that the electrochemical potential of H+ ions shows the same thermodynamic shift in the reaction of energy-dependent Pi -ATP exchange throughout the [MgATP]/[MgADP] concentration range studied, from 0.1 to 10: the synthesis on the ATP molecule is provided by the transmembrane transfer of two H+ ions. It was shown that the binding of ATP and/or ADP in the allosteric site, whose saturation is necessary for the functioning of ATP synthase, occurs with equal constants, 1-2 mM. It is concluded that the lag period in the synthesis of ATP indicates the monomolecular transition ATP hydrolase-->ATP sysnthase, which comes about by the action of transmembrane potential. The binding of MgADP or MgATP renders the enzyme structure "more coupled" or "less coupled", respectively. Structural distinctions manifest themselves in a kinetically different behavior of mitochondrial ATP synthase at [MgATP] > [MgADP] and [MgATP] < [MgADP] and do not suggest futile leakage of H+ through the membrane.     

Functional morphology of nuclear organizer regions of chromosomes and of nucleoli in cells of human multiple myeloma cell lines. II.Relationship between immunoglobulin E production and argentophilia of nuclear organizer regions of chromosomes in U 266 cell line

The IgE content in both cytoplasm and culture medium of U 266 myeloma cells, was studied by the enzyme-linked immunoassay in correlation with Ag-staining of NORs of chromosomes in their nuclei throughout 9 days after cell seeding. Proliferative activity of the cells was evaluated with 3H-thymidine labeling. The average values of both the cytoplasmic IgE content and its secretion level in U 266 cell population, being in logarithmic growth phase, were higher in S-phase cells as compared with G1-cells. On comparison of results of the present and previous (Turilova et al., 1998) studies it was revealed that U 266 myeloma cell line had a high stability of cell proliferation kinetics and IgE secretion and the dynamics of Ag-NORs-staining, while the number of argentophilic grains in the cell nuclei in the present experiment was higher to correlate with an enhanced IgE production. It is suggested that Ag-NORs-staining reflects the level of specific functional activity of cells in the U 266 line.     

Molecular biological monitoring of the polioviruses circulation in Belarus

A total of 135 polioviruses (PV), including 25 wild and 110 vaccine-related, isolated in Belarus in 1957-1999 were studied by the analysis of the polymorphism of the restriction fragments lengths of two distal regions of the genome: the region (480 oligonucleotide pairs) coding the N-terminal fragment of capsid protein VP1 (RLFP-1) and the region (291 oligonucleotide pairs) coding the N-terminal fragment of nonstructural protein of 3D-polymerase (RLFP-3D1). The genetic analysis of the viruses made it possible to determine 3 epidemiologically different periods of PV circulation: (1) the prevaccination period (1957-1959) when wild PV of all 3 serotypes circulated on the territory of Belarus; (2) the early period of the use of Oral Poliomielytis Vaccine (1960-1966), characterized by simultaneous circulation of wild and vaccine PV, as well as vaccine/wild recombinant PV; (3) the period of the elimination of wild PV of indigenous origin and the circulation of vaccine-related viruses (1967-1999). The characteristic feature of wild PV was their pronounced genetic variability. 8 genetic variants of PV1, including 4 genetic groups, 2 genetic variants of PV2 and 1 genetic variant of PV3 were detected; 2 vaccine/wild recombinant PV were detected in 1960 and 1966. More than 40% of the vaccine-related PV under study had altered genetic characteristics (mutations and/or recombinations. Reverse variability, linked with the loss of a number of signs of attenuation, was shown to be characteristic of vaccine PV1. Recombinants occurred most frequently among PV3 (44.9%) and PV2 (40.0%), their recombinations being formed mainly with PV1. Recombinants PV2/PV1 and PV3/PV1 were found to have high frequency of reversion in the "PV1" fragment of the genome; this frequency exceeded that in PV1 with the homotypical genome (66.7 and 44.4% in contrast to 12.5%).     

Changes in the expression of membrane markers and in the number of human blood monocytes after single and repeated courses of visible and infrared light at therapeutic doses

An attempt has been made to prove that the immunomodulating effect of therapeutic doses of polychromatic visible + infrared polarized (VIP) light at its application to a small body surface area is connected with a transcutaneous photomodification of a small amount of blood in superficial skin microvessels. For this purpose, in parallel experiments, using monoclonal antibodies, the membrane phenotype of circulating blood mononuclears was studied after irradiation of volunteers, of samples of their blood in vitvo, and of a mixture of the irradiated and non-irradiated autologous blood in a 1:10 volume ratio, thereby modeling events in vivo, when a small amount of the transcutaneously photomodified blood in the vascular bed contacts its main circulating volume. In this variant of experiment, a great similarity has been established of changes in expression of mononuclear membrane markers (CD3, CD4, CD8, CD20, CD16, HLA-DR and to a lesser degree of CD25); the ability has been proven of the photomodified blood to "translate" the light-induced changes to a much higher volume of non-irradiated blood, which might represent a mechanism of the systemic immunomodulating effect of phototherapy. Under conditions in vivo and in vitro, the most "reactive" were HLA-DR+, CD20+, CD16+, CD4+, and 0-cells. An increase of the total number of lymphocytes and monocytes has been shown by the end of the 10-day-long phototherapeutic course. The regulatory character of the single and course sessions of the VIP light on the blood immunocompetent cells is substantiated: depending on the initial state of the immune system, the VIP light can produce both stimulating and inhibitory effect on lymphoid cell subpopulations, which opens large possibilities of using this method for correction of immunological disturbances in diseases of different etiopathogenesis.     

Modification of redox sites of N-methyl-D-aspartate receptors affects changes in bioelectrical activity of olfactory cortex slices induced by anoxia in rats

The effects of the thiol oxidative agent 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) inhibiting NMDA receptors activity on changes of the evoked focal potentials generation (the NMDA and non-NMDA components EPSP) in response to long-term (LA) and short-term (SA) anoxic exposure which induced functional disturbances or promoted increasing of neurons resistance to LA, were studied on the rat olfactory cortex slices (Wistar-Kyoto). It was revealed that DTNB (200 mkM) effectively protected the depression of the EPSP generation induced by LA in the most tested neurons. In addition, DTNB eliminates the protective effect of the SA on focal EPSP generation evoked by LA. Nevertheless this dependence concerns the NMDA component and, to a lesser extent, the non-NMDA component EPSP. A possible role of changes of the NMDA receptor modulatory redox sites in mechanisms of functional disturbances and increasing neuronal resistance induced by hypoxic influences, is discussed.     

Cell markers in the recognition of acute myeloblastic leukaemia subtypes

The diagnosis of acute myeloblastic leukaemia (AML) is based on cell morphology, cytogenetic and molecular changes, cell markers and clinical data. Our aim was to establish whether morphology and cell markers are comparable in the evaluation of AML. Bone marrow smears were analysed, and flow cytometry and monoclonal antibodies were used to determine cell type and maturity. Morphology and cell markers correlated differently in different AML subtypes.