[Evaluation of absorbed doses of ionizing radiation by milk teeth enamel in children living in the Belarus Republic].

Mean doses of ionizing radiation, absorbed by children in the Byelarus Republic, were evaluated by EPR dosimetry of tableted samples of milk teeth enamel. A relationship between the doses absorbed by the children and density of radionuclide contamination of the territory of residence was detected. Based on the mean absorbed doses, doses which can be absorbed during 70 years of life were estimated.

[The effect of small doses of ionizing radiation on the physico-chemical characteristics of the membranes of peripheral blood lymphocytes of rats].

The fluorescence probe method was used for investigating the physical state of a total lipid phase of a bi-layer and an annular (near-protein) zone of the membrane lipids of lymphocytes in a peripheral blood of rats on the 10th day after a whole-body acute and chronic gamma-exposure to doses of 0.25, 0.5, and 1.

[The immunoglobulin content in the saliva of children living under different radioecological conditions].

Salivary specimens of 80 children aged 8-14 years from the Stolin District and of 34 children of the city of Minsk are examined by radial immunodiffusion in gel and by enzyme immunoassay. Residents of a region contaminated with radionuclides (soil contamination with 137Cs 185-555 kBq/m2) develop an imbalance in the production and secretion of specific salivary antibodies: the production of IgM in early periods of immune response is suppressed and the level of IgE is increased.

[Modifying effect of incorporated 137Cs on the mechanism of adrenergic control of myocardial contraction].

Incorporated 137Cs (absorbed dose of 0.26 Gy) causes decrease of myocardial's contractile function and inotropic response to beta-adrenagonists effect, isoproterenol-stimulated adenylate cyclase activity and beta-adrenoreceptors affinity. Adrenergic effects, mediated by alpha-adrenergic structures on heart contractile function, on the contrary, become stronger, that is due to the increase of the receptors' density on sarcolemma surface.

[Regulation of glucose transport in rat thymocytes after chronic gamma-irradiation].

Chronic gamma-irradiation (1 Gy, 100 mR/hr) increases cell titre in rat thymus and decreases glucose transport activation by phorbol ester. Animals kept in the Chernobyl evacuation zone over a period of 30 days exhibit reduced thymus cellularity and decreased PMA (200 nM) stimulation of glucose uptake by thymus cells.

[The effect of incorporated cesium-137 on the structure of the erythrocyte membranes].

The influence of incorporated cesium 137 (the absorbed doses of 0.26-0.08 Gy) on the erythrocyte membrane structure has been investigated.

[The immediate and late effects of ionizing radiation on the Ca2+-accumulating capacity of the plasma membranes of rat aorta smooth-muscle cells].

A study was made of Ca2(+)-accumulating ability of plasma membranes of nonstriated cells of rat aorta 3, 10, 30, 180 and 365 days after whole-body gamma irradiation with doses of 0.5, 1.0 and 4.

[Structural reorganization of the brain synaptic membranes and aging].

Results of the authors' studies and data from literature underlie the development of a notion on structural rearrangement of the brain synaptic membranes in aging. Reorganization results in conformational changes of the key membrane-bound enzymes and receptors underlying the age alterations of neuronal functions.

[The effect of low doses of gamma radiation on the structural-functional status of the membranes of aortic smooth muscle cells in rats].

Using the fluorescent probe and membrane filtration methods it has been shown that 3 days after gamma-irradiation of rats with a dose of 1 Gy microviscosity of membranes increases and their Ca2(+)-transport function decreases with a simultaneous increase in the affinity of Ca2(+)-pump for calcium. In 15 days, the characteristics under study do not differ from those of the intact controls.

[Age specificity of lipid fluidity in the sarcoplasmic reticulum of the rat heart].

The lipid fluidity in heart sarcoplasmic reticulum membranes prepared from adult (12 mo.) and old (24 mo.) rats has been measured by the fluorescence probe (DPPH) and spin probe (5NS) methods at 22 and 37 degrees C.

[Structural state of the cardiomyocyte sarcolemma in animals of different ages].

Cardiomyocyte plasmalemma membranes of adult (12 months) and old (24-26 months) rats have been studied. Ageing is accompanied with an essential decrease of the content of the membrane protein SH-groups. We have found an increase in the fraction of strongly immobilized spin-labeled SH-groups, a decrease in that of unsaturated lipids, as well as an increase in that of lysophosphatidylcholine in old rats membranes.

[Structural and functional changes in the synaptic membranes of the brain during aging].

Below 37 degrees the mobility of lipids in rat brain synaptic membranes evaluated by the spin probe method is higher in old (24-26 months) than in young (5-6 months) animals. The number of ouabain receptors in membranes increases with age, while maximum rate and Km values are not changed. The relation between structural state of membrane and properties of ouabain binding centers is discussed.

[Muscarinic cholinoreceptors of brain synaptic membranes from animals of various ages].

In old rats in contrast to young and mature ones the treatment of synaptic membranes with SH-reagent N-ethylmaleimide, cholinergic agonist carbamylcholine or both of them decreases the specific binding of labeled muscarinic antagonist 3H-quinuclidinylbenzylate. The age related change of receptor conformation with exposure of thiol groups responsible for antagonist binding is suggested.

[Age changes of structural state of synaptic membranes of brain].

In the brain synaptic membranes from old rats (24-26 months) in comparison with the mature ones (6-7 months) an increase was shown in disintegration rate with DDS Na, mobility of 5-, 16-doxyl-stearate spin probes and in thermosensitivity of acetylcholinesterase. The total number of SH-groups decreased. While protein composition remained constant lysophosphatidylcholine and saturated fatty acid content in old animals increased.

[Comparative study of beta-adrenoreceptors of rat brain synaptic membranes].

Affinity of beta-adrenoreceptors in the rat brain synaptic membranes to agonists isoproterenol and norepinephrine, as well as to antagonist 125I-hydroxybenzylpindolol is lower in young (1 month) and old (24--26 months) than in mature (8--12 months) rats. Desensitization toward isoproterenol is expressed in the young ones only. In the old but not in other groups simultaneous action of isoproterenol and N-ethylmaleimide decreases the following binding of the antagonist while the same agents added separately produced no effect.

[Effect of physiologic concentrations of local anesthetics of the procaine series on the structural and functional state of cerebral synaptosome membranes].

Studies are presented of the effect of procaine group anesthetics on rat brain synaptosome stability to dodecyl sulfate and on catalytic properties of the membrane bound alkaline phosphatase. The dose curves of detergent stability are characterized by two maxima, one at 3.10(-4) M for tetracaine, 2.

[Age changes in the allosteric properties of brain acetylcholinesterase].

d-tubocurarine and procaine have been shown to inhibit the acetylcholinesterase of rat brain homogenate by coupled and non-competitive mechanism respectively, which suggests binding to enzyme peripheral sites. Judging by values of Hill coefficient negative cooperativity in interactions between procaine sites is characteristic of all ages (n=0,8 and 0,53 for young and old rats) while such cooperativity for d-tubocurarine sites appears only at old age (n=1 and 0,6 for young and old animals). Values of Ki changed in opposite directions for each of the substances with aging.

[Structural rearrangements in synaptosomal membranes of the brain].

Studies were carried out on structural state of synaptosomes and synaptic plasma membranes from brain of rats and guinea pigs at 5--50C. In membranes from guinea pig brain there were two breaks at 8 and at 18--20C in the curves of temperature dependence of light scattering. At the same temperatures adhesive properties of membranes had changed in jump-like manner when evaluating the degree of aggregation at pH4.

[Comparative study of membrane-bound acetylcholinesterase in guinea pig and rabbit brains].

As a result of kinetic studies on acetylcholinesterase inhibition by allosteric effector d-tubocurarine it was shown that interaction between modifier and catalytic sites of rabbit and guinea pig acetylcholinesterase are different for these two species. Judging by the inhibition curves and sensitivity of d-tubocurarine theses differences involve enzyme microenvironment in the membrane. Addition to 7,15-10-6 M d-tubocurarune to solubilized preparation led to a significant fall in the value of Hill coefficient for enzyme-substrate interaction.