Biomedical subjects

F I Ataullakhanov

Publications and source records attributed to F I Ataullakhanov.

At least 19 recordsLinked to original sources

PubMed2005

Force production by depolymerizing microtubules: a theoretical study.

Chromosome movement during mitosis is powered in part by energy released through the depolymerization of kinetochore microtubules (MTs). Strong but indirect evidence suggests the existence of a specialized coupling between kinetochores and MT plus ends that enables this transduction of chemical energy into mechanical work. Analysis of this phenomenon is important for learning how energy is stored within the MT lattice, how it is transduced, and how efficient the process can be, given coupling devices of different designs. Here we use a recently developed molecular-mechanical model of MTs to examine the mechanism of disassembly dependent force generation. Our approach is based on changes in tubulin dimer conformation that occur during MT disassembly. We find that all of the energy of polymerization-associated GTP hydrolysis can be stored as deformations of the longitudinal bonds between tubulin dimers, and its optimal use does not require the weakening of lateral bonds between dimers. Maximum utilization of this stored energy and, hence, the generation of the strongest possible force, is achieved by a protofilament power-stroke mechanism, so long as the coupling device does not restrict full dissociation of the lateral bonds between tubulin dimers.

Biomechanical Phenomena↗

PubMed2005

Initiation and propagation of coagulation from tissue factor-bearing cell monolayers to plasma: initiator cells do not regulate spatial growth rate.

Exposure of tissue factor (TF)-bearing cells to blood is the initial event in coagulation and intravascular thrombus formation. However, the mechanisms which determine thrombus growth remain poorly understood. To explore whether the procoagulant activity of vessel wall-bound cells regulates thrombus expansion, we studied in vitro spatial clot growth initiated by cultured human cells of different types in contact pathway-inhibited, non-flowing human plasma. Human aortic endothelial cells, smooth muscle cells, macrophages and lung fibroblasts differed in their ability to support thrombin generation in microplate assay with peaks of generated thrombin of 60 +/- 53 nmol L(-1), 135 +/- 57 nmol L(-1), 218 +/- 55 nmol L(-1) and 407 +/- 59 nmol L(-1) (mean +/- SD), respectively. Real-time videomicroscopy revealed the initiation and spatial growth phases of clot formation. Different procoagulant activity of cell monolayers was manifested as up to 4-fold difference in the lag times of clot formation. In contrast, the clot growth rate, which characterized propagation of clotting from the cell surface to plasma, was largely independent of cell type (< or = 30% difference). Experiments with factor VII (FVII)-, FVIII-, FX- or FXI-deficient plasmas and annexin V revealed that (i) cell surface-associated extrinsic Xase was critical for initiation of clotting; (ii) intrinsic Xase regulated only the growth phase; and (iii) the contribution of plasma phospholipid surfaces in the growth phase was predominant. We conclude that the role of TF-bearing initiator cells is limited to the initial stage of clot formation. The functioning of intrinsic Xase in plasma provides the primary mechanism of sustained and far-ranging propagation of coagulation leading to the physical expansion of a fibrin clot.

Blood Coagulation↗

PubMed2005

Two subpopulations of thrombin-activated platelets differ in their binding of the components of the intrinsic factor X-activating complex.

Binding of fluorescein-labeled coagulation factors IXa, VIII, X, and allophycocyanin-labeled annexin V to thrombin-activated platelets was studied using flow cytometry. Upon activation, two platelet subpopulations were detected, which differed by 1-2 orders of magnitude in the binding of the coagulation factors and by 2-3 orders of magnitude in the binding of annexin V. The percentage of the high-binding platelets increased dose dependently of thrombin concentration. At 100 nm of thrombin, platelets with elevated binding capability constituted approximately 4% of total platelets and were responsible for the binding of approximately 50% of the total bound factor. Binding of factors to the high-binding subpopulation was calcium-dependent and specific as evidenced by experiments in the presence of excess unlabeled factor. The percentage of the high-binding platelets was not affected by echistatin, a potent aggregation inhibitor, confirming that the high-binding platelets were not platelet aggregates. Despite the difference in the coagulation factors binding, the subpopulations were indistinguishable by the expression of general platelet marker CD42b and activation markers PAC1 (an epitope of glycoprotein IIb/IIIa) and CD62P (P-selectin). Dual-labeling binding studies involving coagulation factors (IXa, VIII, or X) and annexin V demonstrated that the high-binding platelet subpopulation was identical for all coagulation factors and for annexin V. The high-binding subpopulation had lower mean forward and side scatters compared with the low-binding subpopulation ( approximately 80% and approximately 60%, respectively). In its turn, the high-binding subpopulation was not homogeneous and included two subpopulations with different scatter values. We conclude that activation by thrombin induces the formation of two distinct subpopulations of platelets different in their binding of the components of the intrinsic fX-activating complex, which may have certain physiological or pathological significance.

Annexin A5↗

PubMed2004

Complex dynamics of the formation of spatially localized standing structures in the vicinity of saddle-node bifurcations of waves in the reaction-diffusion model of blood clotting.

Local activation in a one-dimensional three-component reaction-diffusion model of blood clotting may lead to a formation of spatially localized standing structures (peaks) via several complex scenarios. In the first scenario, two concentration pulses first propagate from the site of activation, then stop and transform into peaks [Zarnitsina et al., Chaos 11, 57 (2001)]. Here, we examine this scenario, and also describe a different scenario of peak formation. In this scenario, two trigger waves propagate initially in opposite directions away from the site of activation. Then they stop and change direction of propagation toward each other to the activation site, where they interact and form a peak. Both of these scenarios of stable peak formation are observed in the vicinity of saddle-node bifurcation and may be viewed as a memory of the extinct wave modes.

Animals↗

PubMed2004

Running pulses of complex shape in a reaction-diffusion model.

In a one-dimensional reaction-diffusion model of an active medium, stable steady-state wave pulses of a new type are described. They are called multihumped because their waveforms contain several maxima of similar size. Presumably, the multihumped pulses arise via a bifurcation at which an unstable trigger wave disappears. The parameter governing this bifurcation is the diffusion coefficient for the model inhibitor. The model is analyzed by varying this parameter to determine the conditions for the emergence of multihumped pulses. The results of this analysis show how their waveform and dynamics of excitation depend on the inhibitor diffusion coefficient.

Biophysics↗

PubMed2004

Detection of stages of autoimmune hemolytic anemia by evaluating erythrocyte deformability and density.

Study of erythrocyte density and deformability in patients with hemolytic anemia, including long-term monitoring of 5 patients, helped us to characterize the pathological processes leading to changes in the erythrocyte population at different terms of the disease and to detect its main stages (agglutination, pathological dehydration, combination of pathological dehydration and microvesiculation, hemolytic crisis, and remission).

Adult↗

PubMed2003

Unstable trigger waves induce various intricate dynamic regimes in a reaction-diffusion system of blood clotting.

In this work we demonstrate that the unstable trigger waves, connecting stable and unstable spatially uniform steady states, can create intricate dynamic regimes in one-dimensional three-component reaction-diffusion model describing blood clotting. Among the most interesting regimes are the composite and replicating waves running at a constant velocity. The front part of the running composite wave remains constant, while its rear part oscillates in a complex manner. The rear part of the running replicating wave periodically gives rise to new daughter waves, which propagate in the direction opposite the parent wave. The domain of these intricate regimes in parameter space lies in the region of monostability near the region of bistability.

Blood Coagulation↗

PubMed2001

Immobilization of proteins in immunochemical microarrays fabricated by electrospray deposition.

Electrospray (ES) deposition has been applied to fabricate protein microarrays for immunochemical assay. Protein antigens were deposited as arrays of dry spots on a surface of aluminized plastic. Deposition was performed from water solutions containing a 10-fold (w/w of dry protein) excess of sucrose. Upon contact with humid air, the spots turn into microdroplets of sucrose/protein solution from which proteins were either adsorbed or covalently linked to clean or modified aluminum surfaces. It was found that covalent binding of antigens via aldehyde groups of oxidized branched dextran followed by reduction of the Schiff bonds gives the highest sensitivity and the lowest background in microarray-based ELISA, as compared to other tested methods of antigen immobilization. The minimum concentration of a primary mouse antibody detected in indirect ELISA with such antigen microarrays was approximately 0.3-1.0 ng/mL for ELF-97 or BCIP/NBT substrates of alkaline phosphatase.

Animals↗

PubMed2000

A substrate switch: a new mode of regulation in the methionine metabolic pathway.

We propose a simple mathematical model of liver S -adenosylmethionine (AdoMet) metabolism. Analysis of the model has shown that AdoMet metabolism can operate under two different modes. The first, with low metabolic rate and low AdoMet concentration, serves predominantly to supply the cell with AdoMet, the substrate for various cellular methylation reactions. The second, with high metabolic rate and high AdoMet concentration, provides an avenue for cleavage of excess methionine and can serve as a source of cysteine when its increased synthesis is necessary. The switch that triggers interconversion between the "low" and "high" modes is methionine concentration. Under a certain set of parameters both modes may coexist. This behavior results from the kinetic properties of (i) the two isoenzymes of AdoMet synthetase, MATI and MATIII, that catalyse AdoMet production; one is inhibited by AdoMet, whereas the other is activated by it, and (ii) glycine- N -methyltransferase that displays highly cooperative kinetics that is different from that of other AdoMet-dependent methyltransferases. Thus, the model provides an explanation for how different cellular needs are met by regulation of this pathway. The model also correctly identifies a critical role for glycine N -methyltransferase in depleting excess methionine in the high mode, thus avoiding the toxicity associated with elevated levels of this essential amino acid.

Animals↗

PubMed2000

Spatiotemporal dynamics of fibrin formation and spreading of active thrombin entering non-recalcified plasma by diffusion.

The spatiotemporal dynamics of clot growth was studied in non-stirred non-recalcified plasma where thrombin entered by diffusion. Under these conditions, the clot rapidly grew for 30-45 min and then stopped growing on reaching 0.4-0.5 mm in size. The dynamics of clot growth and its size almost did not depend on the thrombin concentration in the range from 50 to 400 nM. FITC-thrombin was shown to permeate the growing clot. The clot size in antithrombin-deficient plasma increases with decreasing antithrombin concentration, being 1.5 mm in the plasma depleted of antithrombin to 5% of its initial level. The data on the spatial distribution of amidolytic activity in the growth zone of the clot suggested that thrombin was not the sole source of this activity. Analysis showed that this additional activity arising during thrombin diffusion into plasma was largely accounted for by thrombin-alpha(2)-macroglobulin complex.

Antithrombins↗

PubMed2000

Deficiencies of glycolytic enzymes as a possible cause of hemolytic anemia.

The critical minimum values of Na,K-ATPase and glycolytic enzyme activities at which the erythrocyte viability is lost were calculated using the mathematical model of the erythrocyte, which included all reactions of glycolysis, adenylate metabolism, ionic balance, and osmotic regulation of erythrocyte volume. The criterion for cell death was an increase in its volume to the level at which it is sequestrated from the circulation or is lysed. In hemolytic anemia associated with hexokinase or pyruvate kinase deficiency, activities of these enzymes measured in patient erythrocytes appeared to be close to the calculated critical values. By contrast, in hemolytic anemia associated with phosphofructokinase, glucosephosphate isomerase, triosephosphate isomerase, or phosphoglycerate kinase deficiency, activities of these enzymes measured in patient erythrocytes were significantly greater than the calculated critical values. In this case, if the deficient enzyme were stable, i.e. its activity in the cell were low, but constant in time, the deficiency observed would not account for the erythrocyte destruction observed and the development of hemolytic anemia. It was shown, however, that in phosphofructokinase, glucosephosphate isomerase, triosephosphate isomerase, or phosphoglycerate kinase deficiency, hemolytic anemia can arise because of the instability of these enzymes in time.

Adenosine Triphosphate↗

PubMed2000

Anion permeability and erythrocyte swelling.

Permeability of cell membranes to cations may increase as a result of membrane oxidation or in certain pathologies. We studied the effects of nonselective increases in cell membrane permeability to univalent cations on the volume of erythrocytes incubated in phosphate-buffered saline (PBS) using amphotericin B (5-10 mg/l suspension) or gramicidin D (10-100 microg/l suspension) as the membrane permeabilizing agents. Both antibiotics caused K+ to leak, Na+ to accumulate intracellularly, and cell volume to increase. The interval needed to reach the equilibrium between the intracellular and extracellular ion concentrations ranged from 30 min to several hours, depending on the antibiotic concentration. In spite of a rapid disappearance of cation transmembrane gradients, cell volume increased relatively slow. Even 24 h after the membrane permeability was changed, the volume of most erythrocytes did not increase to the lytic values (about 1.6 times the normal volume). The slow increase in erythrocyte volume was accounted for by slow changes in the transmembrane Cl- gradient. 4,4'-Diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), a specific inhibitor of anion transport, while producing no effect on the transmembrane Na+ and K+ fluxes induced by the antibiotics, significantly inhibited the decrease in the transmembrane Cl- gradient and the increase in erythrocyte volume. Analysis of these data by means of mathematical modeling showed that it failed to satisfactorily describe the experimental kinetics of erythrocyte swelling in response to increases in the membrane permeability to univalent cations if its permeability to Cl was set to be constant. The satisfactory description of this kinetics could be achieved by assuming that the membrane permeability to anions decreased with increasing erythrocyte volume. The results obtained demonstrate that transmembrane anion transport may be considered to be a component of the mechanism responsible for the erythrocyte volume stabilization, because a significant decrease in the swelling rate allows the erythrocytes with damaged membranes to activate a relatively slow (metabolic) mechanisms of cell volume stabilization and/or repair their damaged membranes.

Amphotericin B↗

PubMed2000

Bioenergetics and mitochondrial transmembrane potential during differentiation of cultured osteoblasts.

To evaluate the relationship between osteoblast differentiation and bioenergetics, cultured primary osteoblasts from fetal rat calvaria were grown in medium supplemented with ascorbate to induce differentiation. Before ascorbate treatment, the rate of glucose consumption was 320 nmol. h(-1). 10(6) cells(-1), respiration was 40 nmol. h(-1). 10(6) cells(-1), and the ratio of lactate production to glucose consumption was approximately 2, indicating that glycolysis was the main energy source for immature osteoblasts. Ascorbate treatment for 14 days led to a fourfold increase in respiration, a threefold increase in ATP production, and a fivefold increase in ATP content compared with that shown in immature cells. Confocal imaging of mitochondria stained with a transmembrane potential-sensitive vital dye showed that mature cells possessed abundant amounts of high-transmembrane-potential mitochondria, which were concentrated near the culture medium-facing surface. Acute treatment of mature osteoblasts with metabolic inhibitors showed that the rate of glycolysis rose to maintain the cellular energy supply constant. Thus progressive differentiation coincided with changes in cellular metabolism and mitochondrial activity, which are likely to play key roles in osteoblast function.

Adenosine Triphosphate↗

PubMed2000

Mathematical analysis of the effects of geometric parameters and mechanical properties of erythrocytes on the filterability of nonuniform suspensions.

Approaches to determination of the pattern of erythrocytes distribution with regard to the rates of their passage through pores (3 microm in diameter) of a membrane filter by processing the data on changes in the flow rates of erythrocyte suspensions with time (filtration curves) are discussed. We considered the case when the suspension consisted of two subpopulations of erythrocytes differing in a single parameter. Using a model describing the erythrocyte passage through a pore and a model describing filtration of a nonuniform suspension, we analyzed the dependences of filtration kinetics of such suspensions on the relative contents of the subpopulations and their rheological characteristics. It has been shown that the filtration rates of the major subpopulation and the minor abnormal subpopulation, and their relative contents can be determined from the analysis of filtration curves. This can be done when the filtration rate of cells from the minor subpopulation is at least one order of magnitude lower than the filtration rate of cells from the major subpopulation. Thus we can register the presence of the minor subpopulation in the range of 0.5-1%. If filtration rates are recorded at different osmolalities, their analysis makes it possible to determine the surface area, intracellular viscosity, and membrane rigidity of cells of the major subpopulation and, in certain cases, the same parameters for the cells of the minor subpopulation.

Erythrocyte Deformability↗

PubMed1999

Volume stabilization in human erythrocytes: combined effects of Ca2+-dependent potassium channels and adenylate metabolism.

A mathematical model describing the possible role of Ca(2+)-dependent K+ channels and adenylate metabolism in volume stabilization of human erythrocytes was developed. The model predicts that the red blood cell volume can be stabilized either dynamically or stationary over a broad range of cell membrane permeabilities to cations. The dynamic stabilization results from the operation of Ca(2+)-dependent potassium channels. The erythrocyte volume changes less than 10% if the membrane permeability changes abruptly to a value in the range from half to sevenfold higher than the normal one. The stationary stabilization is achieved via controlling the adenylate metabolism. The stationary value of cell volume changes less than 10% when the membrane permeability varies from half the normal value to 15-fold higher than the normal value.

Adenosine Monophosphate↗

PubMed1999

[Detrimental effects of Daunorubicin and Doxorubicin on human erythrocytes in vitro].

In isotonic medium, daunorubicin in the concentration range of 0.5-5.0 mg/ml of cells and doxorubicin in the concentration range of 0.2-1.0 mg/ml of cells caused hemoglobin (Hb) and K+ to efflux from red blood cells (RBC), to increase RBC size and to lower their deformability. Hb and K+ efflux rates were proportional to the antibiotic concentrations and remained stable for a few hours. Hb efflux did not change significantly in the 4-21 degrees C range (exempt at an experimental concentration of daunorubicin of 5.0 mg/ml of cells) but soared sharply at 37 degrees C. At the daunorubicin and doxorubicin concentration of 0.2 mg/ml of cells, Hb and K+ efflux virtually did not differ from control values. At the antibiotic concentration of 1.0 mg/ml of cells, 37 degrees C, Hb efflux rate was 0.34-5.6%, while that of K+(-) 1.0-8.2%, per hour, of possible maximum value. For the daunorubicin level of 5.0 mg/ml of cells, the respective values were 10 and 17%. At the daunorubicin concentration of 5.0 mg/ml, at 4 degrees C, Hb efflux from RBC was significantly higher than at 21 degrees C. RBC malleability, which was determined as their ability to pass through membrane filters having 3 mm dia pores, did not differ significantly from control values for a few hours antibiotic concentrations not exceeding 0.3 mg/ml of cells. At the antibiotic concentration of 1.0 mg/ml and higher RBC deformability dropped to zero within 10 min. ATP level in RBC practically remained identical to control values during incubation with the antibiotics for several hours.

Antibiotics, Antineoplastic↗

PubMed1999

[Immobilized forms of daunorubicin in patients with acute leukemia].

AIM: To study pharmacokinetics of liposomal daunorubicine DaunoXome and daunorubicine (rubomycin) associated with red cells: to assess their effectiveness and toxicity in patients with acute leukemia. MATERIALS AND METHODS: 7 patients with resistant or recurrent acute leukemia entered the trial. Of them 2 patients had acute myeloid leukemia. They received DaunoXome in dose 100 mg in days 1, 2 and 3 of 7 + 3 program. 1 patient had pretreated acute promyelocytic leukemia. This patient received 5-day course of DaunoXome in a dose 100 mg in the presence of ATRA therapy. 4 patients were given single dose daunorubicin associated with autoerythrocytes in the courses RACOP and 7 + 3 in a dose 45 mg/m2. Concentrations of free, bound and liposomal daunorubicin were determined spectrofluorimetrically in chlorophorm extracts of plasm, blood, liquor and bone marrow specimens. RESULTS: Immobilization of daunorubicin on the red cells and liposomes changes pharmacokinetics of the drug: peak concentrations change and the area under the concentration curve increases. Tolerance of DaunoXome and daunorubicine associated with red cells was satisfactory in all the cases: clinical and echo-CG signs of cordiotoxicity were absent, myelotoxicity was similar to that of free daunorubicine. DaunoXome was effective in 2 of 3 patients with acute myeloblastic leukemia. CONCLUSION: The findings are of practical interest for physicians designing new programs of therapy of acute leukemia.

Adolescent↗

PubMed1999

Distributions of rheological parameters in populations of human erythrocytes.

We have previously proposed the osmofiltration method based on a modified Hanss hemorheometer to analyze distributions of erythrocytes in their ability to pass through membrane filters with 3 microns pores. Upon decrease in medium osmolality (u) the erythrocyte volume increases. When cell volume becomes V = Vcr at u = ucr, such cell loses its ability to pass through a 3 microns pore. The flow rate of erythrocyte suspension containing cells with different ucr through a filter gradually decreases with decreasing medium osmolality. This rate becomes zero at some u = omega, when the number of non-filterable cells in the applied sample approaches the number of pores in filter. Experimental determination of the dependencies of the filtration rate on medium osmolality for various hematocrit values allows to obtain omega for each hematocrit and, thereby, to assess the distribution of erythrocytes in ucr. Here, we propose a simplified version of this method, which allows screening of the erythrocytes in heterogeneous suspensions for the distribution in ucr by measuring omega for only two hematocrit values, 0.1% and 1%. Applications of the proposed method are exemplified by analysing the erythrocyte populations of healthy donors, of patients with microspherocytosis, hemochromatosis and normal erythrocyte populations in an acidic environment.

Erythrocyte Deformability↗