For many pathological states, microparticles are supposed to be one of the causes of hypercoagulation. Although there are some indirect data about microparticles participation in coagulation ...activation and propagation, the integral hemostasis test Thrombodynamics allows to measure micropaticles participation in these two coagulation phases directly. Demonstrates microparticles participation in coagulation activation by influence on the appearance of coagulation centres in the plasma volume and the rate of clot growth from the surface with immobilized tissue factor.Methods: Microparticles were obtained from platelets and erythrocytes by stimulation with thrombin receptor-activating peptide (SFLLRN) and calcium ionophore (A23187), respectively, from monocytes, endothelial HUVEC culture and monocytic THP cell culture by stimulation with lipopolysaccharides. Microparticles were counted by flow cytometry and titrated in microparticle-depleted normal plasma in the Thrombodynamics test.
Monocyte microparticles induced the appearance of clotting centres through the TF pathway at concentrations approximately 100-fold lower than platelet and erythrocyte microparticles, which activated plasma by the contact pathway. For endothelial microparticles, both activation pathways were essential, and their activity was intermediate. Monocyte microparticles induced plasma clotting by the appearance of hundreds of clots with an extremely slow growth rate, while erythrocyte microparticles induced the appearance of a few clots with a growth rate similar to that from surface covered with high-density tissue factor. Patterns of clotting induced by platelet and endothelial microparticles were intermediate. Platelet, erythrocyte and endothelial microparticles impacts on the rate of clot growth from the surface with tissue factor did not differ significantly within the 0-200·103/ul range of microparticles concentrations. However, at concentrations greater than 500·103/ul, erythrocyte microparticles increased the stationary clot growth rate to significantly higher levels than do platelet microparticles or artificial phospholipid vesicles consisting of phosphatidylcholine and phosphatidylserine.
Microparticles of different origins demonstrated qualitatively different characteristics related to coagulation activation and propagation.
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The problem of constructing axisymmetric nose parts having minimum aerodynamic drag in the range of large subsonic flight velocities under a given constraint on the aspect ratio is solved. The ...search for optimum shapes is based on the local linearization approaches, which were used in analyzing the results of simulations within the framework of Navier—Stokes equations and ensured the convergence with a limiting reduction in direct calculations of the numerical optimization process at large (more than 70) number of geometric parameters. The effect of additional restrictions imposed on the generator curvature on the drag is studied. The nose parts thus constructed and those having near-optimum characteristics are compared at subsonic and supersonic velocities; the latter forebodies are the Ryabouchinsky half-cavity and a truncated power-law body. The known feature of the bodies realizing zero or minimum wave drag at a given length, namely, the possibility of the formation of flat-faced nose as a region of boundary extremum, is confirmed.
The design of current X-ray diagnostic equipment used in neonatology and pediatrics is discussed. The parameters and functional capacities of these devices are analyzed. The technical requirements on ...the design of X-ray iagnostic equipment for neonatology and pediatrics under nonspecialist and nonhospital conditions are identified. A set of neonatal adaptations for X-ray imaging of extremely low birth weight neonates is proposed.
DNA aptamers (oligonucleotides) interacting with thrombin exosite I contain G-quadruplex, two T-T, and one T-G-T loops in their structure. They prevent exosite I binding with fibrinogen and thrombin ...receptors on platelet surface, thereby suppressing thrombin-stimulated formation of fibrin from fibrinogen and platelet aggregation. Earlier, we synthe-sized original antithrombin aptamer RE31 (5′-GTGACGTAGGTTGGTGTGGTTGGGGCGTCAC-3′) that contained (in addition to G-quadruplex) a hinge region connected to six pairs of complementary bases (duplex region). In this study, we compared properties of RE31 aptamer and its analogues containing varying number of bases in the duplex region and nucleotide insertions in the hinge region. Reduction in the number of nucleotides in the duplex region by 1 to 4 pairs (in comparison with RE31 aptamer) resulted in the decrease of the structural stability of aptamers (manifested as lower melting temperatures) and their ability to inhibit thrombin-stimulated fibrin formation in human blood plasma in tests of thrombin, prothrombin, and activated partial thromboplastin times. However, an increase in the number of bases by 1 to 2 pairs did not cause significant changes in the stability and antithrombin activity of the aptamers. Insertions into the hinge region of RE31 aptamer decreased its antithrombin activity. Investigation of RE31 antithrombotic properties demonstrated that RE31 (i) slowed down thrombin formation in human blood plasma (thrombin generation test), (ii) accelerated lysis of fibrin clot by tissue plasminogen activator in
in vitro
model, and (iii) suppressed arterial thrombosis in
in vivo
model. Based on the obtained data, RE31 aptamer can be considered as a potentially effective antithrombotic compound.
Current management of patients with acute coronary syndrome (ACS) includes a dual antiplatelet therapy with acetylsalicylic acid and a platelet P2Y12 receptor inhibitor. For patients without a high ...risk of bleeding, prasugrel and ticagrelor are preferred, since their effect is more pronounced, less dependent on metabolism of a specific patient, and occurs faster that the effect of clopidogrel. The prescription rate of platelet glycoprotein IIb/IIIa (GP IIb / IIIa) receptor inhibitors has considerably decreased. However, these drugs remain relevant in percutaneous coronary interventions in patients with a high risk of coronary thrombosis or a massive coronary thrombus, in thrombotic complications of the procedure, and in the "no-reflow" phenomenon. The intravenous route of GP IIb / IIIa inhibitor administration provides their effectiveness in patients with difficulties of drug intake or with impaired absorption of oral medications. This review presents clinical and pharmacological characteristics of various GP IIb / IIIa inhibitors and data of randomized clinical studies and registries of recent years that evaluated results of their use in patients with ACS.
Coagulation Activity of Membrane Microparticles Antonova, O. A.; Yakushkin, V. V.; Mazurov, A. V.
Biochemistry (Moscow). Supplement series A, Membrane and cell biology,
07/2019, Volume:
13, Issue:
3
Journal Article
Peer reviewed
Properties of membrane microparticles (MPs), as well as methods for their study are reviewed. Microparticles are vesicular fragments of a plasma membrane, which are detached from the surface of cells ...upon their activation and/or damage. An increase in intracellular calcium and subsequent remodeling of membrane cytoskeleton and redistribution of membrane phospholipids are key events leading to the MPs formation. Transfer of biologically active substances (proteins, lipids, and nucleic acids) from “parental” cell to other cells of the organism is the main function of MPs. MPs also have coagulation activity, that is, they are able to accelerate blood clotting. Procoagulant properties of MPs are determined by the expression on their surface of negatively charged phospholipids (first of all phosphatidylserine), which serve as substrates for assembling of coagulation complexes, and by the presence of tissue factor in some of them, the primary inducer of coagulation reactions. Methods of MPs counting and sizing are analyzed in this review with the indications of their limitations, advantages, and disadvantages. The main attention is focused on flow cytometry, the method that is most widely used in studies of MPs. The data on the coagulation activity of MPs originating from the blood cells (platelets, leukocytes, and erythrocytes) and endothelial cells are surveyed. Tissue factor-containing MPs derived from monocytes and endothelial cells have the highest capability to accelerate blood clotting. Information on the content of MPs of different cellular origin in the blood of healthy subjects and patients with thrombotic, inflammatory, and other diseases is presented.
Platelet functional activity was assessed in healthy volunteers (HV, n=92), patients with stable angina pectoris (SA, n=42) and acute coronary syndrome (ACS, n=73), treated with acetylsalicylic acid ...(ASA) + clopidogrel and ASA + ticagrelor, respectively. In all HV and patients we have compared parameters of platelet aggregation (maximum light transmission and velocity, Tmax and Vmax) and parameters, characterizing exposure of platelet activation markers, evaluated by flow cytometry. HV platelets were activated by 10 μM, 1 μM TRAP, and 20 μM, 5 μM, 2.5 μM ADP; patient platelets were activated by 10 μM TRAP and by 20 μM and 5 μM ADP. Strong and significant correlations between the aggregation and flow cytometry parameters (the r correlation coefficient from 0.4 up to >0.6) most frequently were registered in HV platelet during activation by 1 μM TRAP and in SA patients during platelet activation by 20 μM and 5 μM ADP. However, in many other cases these correlations were rather weak (r < 0.3) and sometimes statistically insignificant. In HV the differences in PAC-1 binding parameters between platelets activated by 10 μM TRAP (the strongest agonist) and all ADP concentrations were negligible (≤ 10%), while CD62P binding (at all ADP concentrations) and LTA parameters for (5 μM and 2.5 μM ADP) were significantly lower (by 40-60%). Antiplatelet therapy in patients decreased all parameters as compared to HV, but to varying extents. For 10 μM TRAP the MFI index for PAC-1 binding (40-50% decrease) and for both ADP concentrations the Tmax values (60-85% decrease) appeared to be the most sensitive in comparison with the other parameters that decreased to a lesser extent. The data obtained indicate a possibility of inconsistency between different LTA and flow cytometry parameters in assessing platelet activity and efficacy of antiplatelet drugs.
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