[PECULIARITIES OF ESTIMATION OF THE BURN DAMAGE, USING THE MAGNET RESONANCE TOMOGRAPHY METHOD].

The method of magnet resonance tomography was applied for early diagnosis of the burn depth and dynamics of processes in the tissues in the course of its treatment and verification of occurring complications. Application of the method proposed for diagnosis and control of therapy have permitted to estimate expediency and determination of volume of early surgical treatment objectively.

Kink nucleation in the two-dimensional Frenkel-Kontorova model.

A computer simulation of thermofluctuation nucleation of kinks on dislocations and their dynamics is carried out in the framework of the two-dimensional Frenkel-Kontorova model. It is shown that at relatively low temperatures and applied stresses the kinks can appear as a result of developing instability of phonon modes localized in the vicinity of the dislocation. The transition from this mechanism to the ordinary thermofluctuation kink nucleation with temperature increase can reveal itself in the peculiarities of yield stress temperature dependence.

[Regulation of Na+-K+-ATPase: effect of Mg and Ca ions]. / Reguliatsiia Na+,K+-ATP-azy: éffekty ionov Mg i Ca.

The participation of Mg2+ and Ca2+ in complicated mechanisms of Na+, K(+)-ATPase regulation is discussed in the survey. The regulatory actions of Mg2+ on Na+, K(+)-ATPase such as its participation in phosphorylation and dephosphorylation of the enzyme, ADP/ATP-exchange inhibition, cardiac glycosides and vanadate binding with the enzyme, conformational changes induction during ATPase cycle are reviewed in detail. Some current views of mechanisms of above mentioned Mg2+ regulatory effects are discussed. The experimental evidence of Ca2+ immediate influence on the functional activity of Na+, K(+)-ATPase (catalytic, transport and glycoside-binding) are given. It's noted that these effects are based on the conformational changes in the enzyme and also on the phase transition in membrane induced by Ca2+. Unimmediate action of Ca2+ on Na+, K(+)-ATPase is also discussed, especially due to its effect on other membrane systems functionally linked with Na(+)-pump (for instance, due to Na+/Ca(+)-exchanger activation). It's concluded that Mg2+ and Ca2+ as "universal regulators" of the cell effectively influence the functional activity and conformational states of Na+, K(+)-ATPase.

[Inactivation of rat brain Na+ K+ ATPase by sodium dodecylsulfate: effect of pH, magnesium ions and temperature]. / Inaktivatsiia Na+, K+-ATPazy mozga krys dodetsilsul'fatom natriia: vliianie pH, ionov magniia, temperatury.

The relative stabilities to SDS inactivation of the rat brain Na(+)-ATPase catalytic subunit isoforms in the conditions of the surface charge modulation and temperature modification of the physical state of the membrane lipids were examined. The higher sensitivity of the Na+,K(+)-ATPase a1-isoform than a+ to SDS inactivation occurs under the conditions of the detergent treatment of microsomes at pH 7.5 and room temperature. The decrease in pH in ATP-free medium up to 6.2 or temperature elevation up to 37 degrees C eliminates the differences in SDS sensitivity of the Na+,K(+)-ATPase isoforms. The enhancement of the SDS binding with a subunit due to changes in membrane surface charge in the first case or increase of accessibility of the protein intramembrane regions for detergent due to the decrease of the packing density of the boundary lipids in the second case are supposed.

Inactivation of brain Na+,K(+)-ATPase catalytic subunit isoforms by sodium dodecyl sulfate.

Persistence of the brain and kidney Na+,K(+)-ATPase isozymes to SDS inactivation under different time and temperature conditions of microsome extraction with the detergent was compared. In contrast to enzyme preparations from medulla oblongata the higher sensitivity of the Na+,K(+)-ATPase alpha-isoform (in comparison to alpha +) to SDS inactivation accompanied by its, at least, partial removal from the membrane was found in the preparations from cerebral cortex. This difference in the sensitivity to SDS was eliminated after extraction of microsomes with the detergent at 37 degrees C. The interpretation of the results is based on the assumed differences in the structural organization of the boundary lipids of the neuronal Na+,K(+)-ATPase catalytic subunit isoforms.

[Effect of phospholipase A2 from Naja naja oxiana venom on activity of Na+,K+-ATPase isoenzymes in rat brain]. / Vliianie fosfolipazy A2 iz iada Naja naja oxiana na aktivnost' izofermentov Na+,K+-ATPazy mozga krysy.

The specific sensitivity of the isoforms of the rat brain Na+,K(+)-ATPase catalytic subunit to phospholipase A2 (PL A2) from Naja naja oxiana venom has been estimated on the basis of changes in the two-component dose response curve of ouabain inhibition of Na+,K(+)-ATPase activity. Moderate Na+,K(+)-ATPase inactivation of PL A2 is accompanied by a decrease of the apparent affinity for ouabain in comparison with the untreated enzyme without any significant changes in the isoform activity ratio in the preparation. This effect is eliminated by washing of the preparation with serum albumin and seems to be mediated by the effect of free fatty acids on the enzyme. At a high level of Na+,K(+)-ATPase inactivation, the alpha-isoforms is inactivated more rapidly than the alpha (+)-isoform.

[The thermally induced transformation of the protein-detergent complexes of the Na+,K(+)-ATPase catalytic subunits of the kidneys and brain in PAG electrophoresis]. / Termoindutsiruemaia transformatsiia belkovo-detergentnykh kompleksov kataliticheskikh sub''edinits Na+,K(+)-ATP-azy pochek i mozga pri élektroforeze v PAAG.

Electrophoretic properties of the protein bands of Na+, K(+)-ATPase catalytic subunits of the kidney and brain have been comparatively studied for some types of animals after heat treatment of the preparations in the presence of DS-Na. The diffuse protein zone with lower electrophoretic mobility after heat-induced conformational transformation of alpha appears on gels parallel with protein band alpha II which is typical of this process. The prolonged heat treatment causes more rapid electrophoretic degradation of the alpha-isoform of the Na+, K(+)-ATPase catalytic subunit of the brain in comparison with alpha +. The results of the investigations are discussed in the aspect of existence of heat-induced transformation of the protein-detergent complexes of catalytic subunits of the enzyme.

[Activity of Na+, K+-ATP-ase isoenzymes in the cerebral cortex and their sensitivity to sodium dodecyl sulfate in rat postnatal ontogenesis]. / Aktivnost' izofermentov Na+, K+-ATP-azy kory golovnogo mozga i ikh chuvstvitel'nost' k dodetsisul'fatu natriia v postnatal'nom ontogeneze krys.

The comparative study of activities of Na+, K(+)-ATPase alpha (+)- and alpha-isozymes in rat brain cortex in the postnatal period is conducted. It is shown, that the rates of isozymes expression are not different and levels of their activities reach maximum to the 30th day after birth. Na(+), K(+)-ATPase resistance to SDS inactivation increases with the age, that reflects possible changes in the peculiarities in structural organization of isozymes protein-lipid complex. Results are discussed from the view point of the adaptive changes in the process of structural-metabolic organization of biomembrane function occurring in ontogenesis.

[Receptor function stability of cerebral Na+,K+-ATPase under conditions of modification of their enzymatic activity]. / Stabil'nost' retseptornoi funktsii izofermentov Na+,K+-ATPazy mozga v usloviiakh modifikatsii ikh fermentativnoi aktivnosti.

Rat and bovine Na+, K(+)-ATP-ase and isozymes have been studied for their sensitivity to ouabain to evaluate the conformational stability of the receptor for cardioactive steroid and its interconnection with intramembrane organization of catalytic polypeptide under modification of native functional conformation of membrane-bound enzyme by treatment with agents known to affect the membrane integrity (such as SDS, heat, phospholipase A2). The higher sensitivity of alpha-isoform of Na, K-ATP-ase activity to detergent as compared to alpha + under their irreversible inactivation that is due to its preferential sollubilization from the membrane is discovered. The existence of differences between isozymes in the hydrophobic protein-lipid interaction has been supposed. The greater sensitivity of alpha-isozyme to disorganization of the enzyme native phospholipid environment with phospholipase A2 has been also established. It is shown that Na+, K(+)-ATP-ase receptor function of ouabain-sensitive and ouabain-resistant enzyme types is much more conservative in comparison with hydrolytic and resistant to possible disorders of protein-lipid interactions.

[Sensitivity of rat brain Na+,K+-ATPase catalytic subunit isoforms to Ds-Na]. / Chuvstvitel'nost' izoform kataliticheskoi sub''edinitsy Na+,K+-ATPazy mozga krysy k Ds-Na.

Analysis of the detergent effect on the dose response curve of ouabain inhibition of rat brain Na+,K(+)-ATPase revealed that the microsomal alpha(+)-isoform was more stable to inactivation by SDS than the alpha-isoform of Na+,K(+)-ATPase from brain cortex and renal outer medulla. Data from SDS-PAAG electrophoresis of membrane-bound Na+,K(+)-ATPase suggest that irreversible inactivation of the isozymes is accompanied by their removal from the membrane but the alpha-isoform is more sensitive to the solubilizing effect of SDS.

[Thermal sensitivity of Na+,K+-ATPase isoenzymes in the brain and kidney]. / Termochuvstvitel'nost' izofermentov Na+,K+-azy mozga i pochek.

Thermal stabilities of Na+, K(+)-ATP-ase preparations with different isozyme content from brain and kidneys of different animal species have been compared. The greater thermal lability of the alpha(+)-isoform of a catalytic subunit of Na+, K(+)-ATP-ase is established. The method of specific thermal inactivation of in brain preparations was used in comparative study of ouabain sensitivity of Na+, K(+)-ATP-ase isozymes from rat, cow and rabbit. It is concluded that the existing structural and functional model of the receptor site of Na+, K(+)-ATP-ase catalytic subunit is not sufficient for the complete explanation of the species heterogeneity of Na+, K(+)-ATP-ase affinity to heart glycosides.

[Ouabain sensitivity of Na+,K+-ATPase in neuronal membranes]. / Chuvstvitel'nost' Na+,K+-ATP-azy neironal'nykh membran k uabainu.

Na+, K(+)-ATPase preparations of the rat and bovine brain and kidney were studied for ouabain sensitivity. Differences in apparent affinities to inhibitor of alpha(+)- and alpha-isozymes of Na+, K(+)-ATPase catalytic subunit were detected only in rat tissues but not in bovine ones. It is concluded that glycoside-sensitive and glycoside-resistant enzymic forms are not fully identical to alpha(+)- and alpha-subunit forms of Na+, K(+)-ATPase.

[Thermolability of alpha+-isoform of the catalytic subunit of brain Na+,K+-ATPase]. / Termolabil'nost' alpha+-izoformy kataliticheskoi sub''edinitsy Na+,K+-ATP-azy mozga.

Thermal stabilities of Na+,K(+)-ATPase isozymes from the rat brain and kidney tissues are compared. It is established that heat treatment of Na+,K(+)-ATPase preparations from the brain decreases the high affinity component of the ouabain inhibition of the enzyme activity due to selective inactivation of alpha-isoform. Its higher thermal lability in comparison with alpha-isoform is confirmed.

[Isoforms of Na+,K+-ATPase catalytic subunit in animal tissues]. / Izoformy kataliticheskoi sub''edinitsy Na+,K+-ATP-azy v tkaniakh zhivotnykh.

The tissue and species distribution of Na+,K(+)-ATPase isoenzymes is considered. Criteria for identification of the above isoforms are presented as attributed to their structural and functional peculiarities. Specificity inherent in functional properties of isoenzymes of Na+,K(+)-ATPase and physiological significance of the latter are discussed.

[The role of magnesium ions in the regulation of the catalytic activity of kidney Na+,K+-ATPase]. / Rol' ionov magniia v reguliatsii kataliticheskoi aktivnosti Na+,K+-ATP-azy pochek.

Free Mg2+ is studied for its effect on the activation kinetics of pig kidney Na+, K+-ATPase by monovalent cations (nH and K0.5 for Na+ and K+ are determined). It is established that at the saturating concentration of complementary ion-activator an increase of free Mg2+ concentration up to 12 mM is accompanied by a rise of nH and K0.5 for Na+ and a fall of K0.5 for K+ without nH changes for this cation. The analysis of inhibition kinetics shows that free Mg2+ is a competitive inhibitor as to Na+ and noncompetitive as to K+. It is concluded that inhibition of Na+, K+-ATPase by free Mg2+ is a complex process including competition with Na+ at its binding sites and the "occluding" of enzyme at the stage, preceding dissociation of cation and also the weakening of subunit interactions in the enzyme.

[Kinetics of thermoinactivation of kidney Na+-,K+-ATPase]. / Kinetika termoinaktivatsii Na+-,K+-Atpazy pochek.

The studies of Na+,K+-ATPase (the fraction of microsomes and highly active preparation) thermoinactivation in kidneys at 50, 55 and 60 degrees C under conditions of the different ionic composition of the medium has shown that 20 mM K+ protects the enzymic complex from the thermal denaturation more effectively than 182 mM Na+ does. An increase in the Mg2+ concentration in the medium from 1 to 5 mM decreases Na+,K+-ATPase resistance to thermoinactivation. The enzyme half-life becomes almost thrice as low in this case. The results obtained are discussed from the standpoint of specificity of ion-induced conformational states of Na+,K+-ATPase and regulatory role of cations in the process of its functioning.

[Thermostability of brain Na+, K+ -ATPase in the presence of surface-active agents]. / Termostabil'nost' Na+, K+ -ATPazy mozga v prisutstvii poverkhnostno-aktivnykh veshchestv.

Stability of Na+, K+-ATPase (EC 3.6.1.3) of the brain microsomal fraction towards thermoinactivation was studied under the effect of surfactants--alkyl sulphates with the C8-C15 chain length of a hydrocarbon radical, desoxycholate, triton X-100, twin-80 and digitonin. It is shown that NaCl treatment of the enzyme before thermoinactivation, and also in the presence of surfactants, increases its resistance to the effect of temperature (octyl and decyl sulphates are an exception, in their presence transport ATPase preincubated with NaCl is completely inactivated). In the presence of most surfactants used in the maximum activating concentrations the activity of Na+, K+-ATPase remained at a considerably high level (80-110% of the initial one) and did not change essentially under NaCl pretreatment of the enzyme. Besides octyl and decyl sulphate, desoxycholate, was also an exception, in the presence of NaCl it inhibited sharply the Na+, K+-ATPase activity. An interrelation is found between the ability of surfactants to decrease the activity of transport ATPase and to solubilize proteins and lipids from the microsomal fraction.

[Immunochemical approach to explaining the molecular organization and mechanism of action of Na+,K+-ATPase]. / Immunokhimicheskii podkhod k vyiasneniiu molekuliarnoi organizatsii i mekhanizma deistviia Na+,K+-ATP-azy.

Application of immunochemical methods for elucidating the Na+, K+-ATPase molecular organization and mechanism of action is discussed. The data of some authors who have studied the purified preparations of Na+, K+-ATPase from different sources show that both the catalytic subunit of the enzymic complex and its sialoglycoproteid have antigenic determinants. Antibodies, binding with these determinants, may either change or produce no effect on the enzymic process, link with the active transport of Na+ and K+. Antibodies used as conformation-sensitive explorers may yield the interesting information on organization of the Na+, K+-ATPase complex in the membrane and its conformation in different functional states which simultaneously with the data of the kinetic analysis and reconstruction of this enzymic complex would contribute to deciphering the mechanism of the Na+ and K+ active transport through biomembranes.

[Catalytic properties of solubilized brain Na+,K+-ATPase]. / Kataliticheskie svoistva soliubilizirovannoi Na+, K+-ATP-azy mozga.

The results are presented of a kinetic study of solubilized Na+, K+-ATPase obtained by 0.2+ digitonin from the NaI treated microsome fraction of the bull brain. It is shown that in main kinetic parameters (KmATP, V, pH-optimum, optimal [Na+]/[K+] ratio, etc.) the solubilized Na+, K+-ATPase does not differ essentially from membrane-bound enzyme. These results evidence for the absence of changes in principle for the kinetic behaviour of Na+,K+-ATPase when solubilized with digitonin. Simultaneously there are certain differences for a temperature dependence (the bend position in the Arrhenius anamorphosis) of the solubilized enzyme and its sensitivity to the action of strophanthin K.

[Extraction of highly active preparations of "soluble" Na+, K+-ATPase from different membrane stuctures of the brain]. / Oderzhannia vysokoaktyvnykh preparativ "rozchynnoï" Na+, K+-ATF-azy z riznykh membrannykh struktur mozku

A successive treatment with sodium iodide and digitonin of the myeline, microsome and synaptosome fractions of the cattle brain tissue resulted in obtaining the preparations of "soluble", Na+, K+-ATPase with a rather high specific activity non-containing practically Mg2+-dependent ATPase. To estimate the degree of these preparations structural heterogeneity they were subjected to analytical ultracentrifugation and disc-electrophoresis in polyacrylamide gel. The data obtained suggest an insignificant degree of heterogeneity for the "soluble" Na+, K+-ATP-ase preparations.