Biomedical subjects
Publications and source records attributed to V A Makarov.
A detailed theoretical and experimental analysis of the possible oscillatory regimes of the dissipative Toda-Rayleigh lattice system is provided. It is shown that the system has (N-1) oscillatory modes with different space-time scales and two rotatory modes. Using its analog electronic circuit implementation we also show with a simple and robust method how switching between modes occurs.
In order to choose the proper method for evaluating the antithrombin activity in samples of chitosan polysulphate (CP) with different polymerization degrees and sulphation degrees, we estimated the ability of direct anticoagulants to depress the coagulability of recalcified sheep blood using the third international heparin standard (A1 - in vitro system) and determined such activity on pharmacodynamic curve (A2 - in vivo system). The curve admits the kinetics of CP elimination to be nonlinear in case of intravenous injection to rabbits, as it is observed in heparin: Ct = C(o)exp(-K(e)lt), where Ct is the CP concentration at the time moment t; C(o) is the CP concentration at the injection moment; Kel is the elimination constant. Besides, it is assumed that there is a linear approximation of the anticoagulant effect on the dose, which finally makes it possible to calculate the specific activity A2: T = KTCt+T(in), where T is the time of clot formation at different time intervals after CP injection; T(in) is the time of clot formation prior to CP injection. T value was assessed in two tests: blood coagulation time (BCT) and activated partial thromboplastin time (APTT). No correlation was observed between A1 and A2. At the same time, the values of Kel and the period of semi-elimination, with the use of the biospecific cetylpyridinium chloride electrophores for the quantitative determination of CP in rabbit's blood taken at different time intervals after injection, showed a close correlation (r = .94, P < .05) between the same parameters, obtained with the help of the rectilinear pharmacodynamic plot in BCT test. Thus, experimentally, it was proven that the assumption of the CP nonlinear elimination and the CP effect-dose dependence was true, which is necessary for A2 calculation. Relatively low molecular weights (MW 61-82 kDa, polymerization degree 188-252 ) and high sulphation patterns (sulphur amounts 15.6-16.9%, sulphation degree 1.58-1.86) were slowly cleared and there was more antithrombin activity (30-52 IU/mg). We recommend the use of in vivo system for evaluating the antithrombin activity of the CP derivatives.
We show that firing activity (spiking) can be regularized by noise in a FitzHugh-Nagumo (FHN) neuron model when operating slightly beyond the supercritical Hopf bifurcation (in the "canard" region). We also provide the conditions for imperfect phase locking between interspike intervals and low amplitude quasiharmonic oscillations. For the imperfect phase locking no need exists of an external signal as it follows from the FHN intrinsic dynamics.
In order to correlate the reactivity and molecular structures of dithiocarbamates, the crystal structures of 6-dimethylamino-5-nitropyrimidin-4-yl N,N-diethyldithiocarbamate, C11H17N5O2S2, (Ia), and 6-methylamino-5-nitropyrimidin-4-yl N,N-diethyldithiocarbamate, C10H15N5O2S2, (Ib), and of the product of thermolysis of (Ib), namely 4-diethylamino-6-methylamino-5-nitropyrimidinium chloride monohydrate, C9H16N5(O2)(+).Cl(-).H2O, (II), have been determined from X-ray laboratory powder diffraction data. Conformational preferences in (Ia) and (Ib) were studied on the density functional theory (DFT) level. Deviation of the reaction centre of the molecule from planarity and breakage of the secondary S...O contact cause switching between two alternative pathways of thermolysis.
Hydration sites are high-density regions in the three-dimensional time-averaged solvent structure in molecular dynamics simulations and diffraction experiments. In a simulation of sperm whale myoglobin, we found 294 such high-density regions. Their positions appear to agree reasonably well with the distributions of waters of hydration found in 38 x-ray and 1 neutron high-resolution structures of this protein. The hydration sites are characterized by an average occupancy and a combination of residence time parameters designed to approximate a distribution of residence times. It appears that although the occupancy and residence times of the majority of sites are rather bulk-like, the residence time distribution is shifted toward the longer components, relative to bulk. The sites with particularly long residence times are located only in the cavities and clefts of the protein. This indicates that other factors, such as hydrogen bonds and hydrophobicity of underlying protein residues, play a lesser role in determining the residence times of the longest-lived sites.
Measurement of plasminogen, the key component of fibrinolysis system, is one of the basic methods for estimation of fibrinolysis. Methods based on the use of chromogenic substrates are often used in diagnosis. Plasminogen measurements are important for laboratory diagnosis of thrombophilia caused by deficiency or abnormalities of this fiber, for detection and evaluation of the DIC syndrome, and for monitoring the treatment by fibrinolytic preparations (streptokinase, t-PA, urokinase, etc.). An original chromogenic substrate having no foreign analogs has been created at Institute of Genetics and Selection of Industrial Microorganisms and Research Center of Hematology (Moscow). Unlike previously described plasmin substrates, pNa has been obtained by microbiological methods with Russian commercial enzymes subtilisine 72 and megaterine. This paper presents the results of plasminogen measurements in patients with DIC with the use of the original chromogenic substrate. The results were compared with those of tests with Berihrom-Plasminogen diagnostic kit (Behringwerke AG).
A gene of human tumor-associated antigen VNTR(MUC1) bound to streptavidin, an expression plasmid, and a highly effective hybrid protein-producing strain were constructed. It was shown that the streptavidin leader peptide ensures an effective secretion of the hybrid protein into the periplasmic space of Escherichia coli cells. The hybrid protein was isolated in a homogeneous state and its immunogenic properties were studied.
Using molecular dynamics simulations of fully hydrated proteins and analysis of crystal structures contained in the Protein Data Bank, we develop a transferable set of perpendicular radial distribution functions for water molecules around globular proteins. These universal functions may be used to reconstruct the unique three-dimensional solvent density distribution around every individual protein with a modest error. We discuss potential applications of this solvent treatment in protein x-ray crystallographic refinements and in theoretical modeling. We also present a fast, grid-based algorithm for construction of the perpendicular solvent density distributions.
Effects of the macromolecular solute on the translational mobility of surrounding solvent water, and Na+ and Cl- ions are investigated by molecular dynamics (MD) simulation. Using MD trajectories of myoglobin and d(C5T5) . d(G5A5) DNA decamer of high quality and length, we determine the average diffusion coefficients for all solvent species as a function of distance from the closest solute atom. We examine solvent mobility in the directions parallel and perpendicular to the solute surface and in proximity to three different classes of solute atoms (oxygens, nitrogens, and carbons). The nature and the magnitude of the solute effects on water diffusion appear to be very similar for protein and DNA decamer. The overall diffusion rate at the interface is lower than in the bulk. The rate is higher than the average in the direction parallel to the solute surface, and lower in the direction normal to the surface, up to 15 A away from the solute. The rate is also lower in the solvation shells of the macromolecules, producing characteristic depressions in the radial profiles of the diffusion coefficient that can be correlated with peaks in the corresponding radial distribution functions. The magnitude of these depressions is small compared to the overall change in solvent mobility at the interface. Similar features are observed in the radial profiles of the diffusion coefficient of sodium and chlorine ions as well.
Models of protein hydration are becoming increasingly more accurate in comparison with experimental data. The recent success of these models implies that the major features of the solvation layers are dominated by local correlations and that such correlations are universal. The excellent agreement between theoretical and experimental solvent electron density radial distributions marks a significant success in our ability to accurately model macromolecular hydration.
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Metabolites of polyunsaturated fatty acids, primarily arachidonic acid, are important physiological regulators of blood coagulation. In contrast to many other substances involved in coagulation, eicosanoids affect virtually all links of hemostasis; they are responsible for blood vessel wall thromboresistance and its acquisition of procoagulant properties in response to various agonists, regulate the extent of cell-to-cell interactions, modulate reactions of plasma hemostasis and blood fibrinolytic activity, and change hemodynamic parameters. Such complex effects of eicosanoids on thrombogenesis suggest that they are unique and extremely important biologically active substances that strongly determine the balance of anticoagulant and procoagulant factors.
Dopamine, histamine, serotonin, and serotonin analogs were acylated with arachidonic and eicosapentaenoic acids, and the reaction products were named as artificially functionalized fatty acids (AFFA). The amides of arachidonic acid with serotonin, dopamine, and histamine were found to inhibit human platelet aggregation induced by ADP, arachidonic acid and adrenaline. Amides of arachidonic and eicosapentaeonic acids with serotonin and dopamine protect sea urchin early embryos against cytotoxic action of serotonin and histamine antagonists. These effects are not connected with the possible hydrolytic cleavage of AFFA to their constituent polyenoic fatty acids and amines. Arachidonic acid dopaminamide was shown to be a substrate of soybean 15-lipoxygenase, whereas the arachidonic acid amides with serotonin and its derivatives were resistant to this enzyme. Moreover, arachidonic acid serotoninamide turned out to be an irreversible lipoxygenase inhibitor. Considerable amount of hydroxyl radicals (fluorescent assay) were found for the first time to accompany lipoxygenase oxidation of linoleic acid; arachidonic acid serotoninamide blocked this process completely. Therefore, it was concluded that AFFA possess specific biological activity and can be considered as a novel group of lipid bioregulators.
The paper reviews P. K. Anokhin's works whose physiological studies promoted solution of clinical medical problems. The use of his theory of functional systems enabled one to solve many issues of clinical physiology and practical medicine, such as the nature of pain and the mechanisms of anesthesia, that of narcotic sleep, the pathogenesis of hypertensive disease, the principles of compensation of dysfunctions in the body, medical strategy in the prevention of diseases, etc.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Protein C (PC) is an anticoagulant protein which, being activated by thrombin, degrades factors V/Va and VIII/VIIIa and releases a tissue-type plasminogen activator. Some Agkistrodon snake venoms contain PC activators which, in experiments, exert an anticoagulant action. An antithrombotic effect of the PC activator from the venom of A. blomhoffi ussuriensis on the model of thrombus formation in the arterio-venous shunt in rats was under investigation. Administration of the PC activator resulted in a dose-dependent prolongation of the thrombus formation time and a decrease in plasma PC activity, which were accompanied by a decrease in factor V activity and APTT prolongation. No reliable changes in the t-PA level, ADP- and epinephrine-induced platelet aggregation were observed. Platelet adhesion to glass beads diminished. We assume that the antithrombotic effect of the PC activator from the A. blomhoffi venom in the platelet-dependent thrombosis model is caused by PC activation and subsequent factor V inactivation as well as by platelet adhesiveness reduction.