Coagulation In Presence Research Articles

P2Y12 antagonist ticagrelor inhibits the release of procoagulant extracellular vesicles from activated platelets.

Activated platelets release platelet extracellular vesicles (PEVs). Adenosine diphosphate (ADP) receptors P2Y1 and P2Y12 both play a role in platelet activation, The present hypothesis herein is that the inhibition of these receptors may affect the release of PEVs. Platelet-rich plasma from 10 healthy subjects was incubated with saline, P2Y1 antagonist MRS2179 (100 μM), P2Y12 antagonist ticagrelor (1 μM), and a combination of both antagonists. Platelets were activated by ADP (10 μM) under stirring conditions at 37°C. Platelet reactivity was assessed by impedance aggregometry. Concentrations of PEVs- (positive for CD61 but negative for P-selectin and phosphatidylserine) and PEVs+ (positive for all) were determined by a state-of-the-art flow cytometer. Procoagulant activity of PEVs was measured by a fibrin generation test. ADP-induced aggregation (57 ± 13 area under curve {AUC] units) was inhibited 73% by the P2Y1 antagonist, 86% by the P2Y12 antagonist, and 95% when combined (p < 0.001 for all). The release of PEVs- (2.9 E ± 0.8 × 10⁸/mL) was inhibited 48% in the presence of both antagonists (p = 0.015), whereas antagonists alone were ineffective. The release of PEVs+ (2.4 ± 1.6 × 10⁷/mL) was unaffected by the P2Y1 antagonist, but was 62% inhibited by the P2Y12 antagonist (p = 0.035), and 72% by both antagonists (p = 0.022). PEVs promoted coagulation in presence of tissue factor. Inhibition of P2Y1 and P2Y12 receptors reduces platelet aggregation and affects the release of distinct subpopulations of PEVs. Ticagrelor decreases the release of procoagulant PEVs from activated platelets, which may contribute to the observed clinical benefits in patients treated with ticagrelor.

Investigation on interaction of Achatinin, a 9- O-acetyl sialic acid-binding lectin, with lipopolysaccharide in the innate immunity of Achatina fulica snails

Achatinin, a 9- O-acetyl sialic acid (9- O-AcSA) binding lectin, has been demonstrated to be synthesized in amoebocytes of Achatina fulica snails. This lectin was affinity-purified from Achatina amoebocytes lysate (AAL); it appeared as a single band on native polyacrylamide gel electrophoresis (PAGE) and showed 16 identical subunits of M.W. 15 kDa on sodium dodecyl sulphate (SDS)-PAGE. It was found to be homologous with an earlier reported lectin, Achatinin-H, derived from hemolymph of A. fulica snails (Sen, G., Mandal, C., 1995. The specificity of the binding site of Achatinin-H, a sialic-acid binding lectin from Achantia fulica. Carbohydr. Res., 268, 115–125). Homology between both lectins was confirmed by their similar electrophoretic mobilities, carbohydrate specificity and cross reactivity on immunodiffusion. Achatinin showed in vitro calcium dependent binding to two 9- O-acetylated sialoglyoconjugates (9- O-AcSG) on lipopolysaccharide (LPS) ( Escherichia coli 055: B5) of M.W. 40 kDa and 27.5 kDa, which was abolished following de- O-acetylation. Based on the previously defined narrow sugar specificity of Achatinin towards 9- O-AcSAα2→6GalNAc [Sen, G., Mandal, C., 1995. The specificity of the binding site of Achatinin-H, a sialic-acid binding lectin from Achatina fulica. Carbohydr. Res., 268, 115–125], we conclude that LPS contains this lectinogenic epitope at the terminal sugar moiety. The Achatinin-mediated hemagglutination inhibition of rabbit erythrocytes by LPS further confirmed it. The lectin exhibited bacteriostatic effect on Gram-negative bacteria E. coli, DH5α and C600. AAL was earlier reported to undergo coagulation in presence of pg level of LPS (Biswas, C., Mandal, C., 1999. The role of amoebocytes in the endotoxin-mediated coagulation in the innate immunity of Achatina fulica snail, Scand. J. Immunol. 49, 131–138). We now demonstrate that Achatinin participates in LPS-mediated coagulation of AAL as indicated by enhanced release of Achatinin from the LPS stimulated amoebocytes and most importantly, by exhibiting a 77% decline in the coagulation of AAL when depleted of Achatinin. Level of Achatinin sharply declined (17-fold) following injection of LPS (20 μg per snail) to the snails, which was reversible by simultaneous injection of LPS and leupeptin implying the presence of LPS-mediated serine protease activity in Achatinin. This was substantiated when purified Achatinin in vitro showed serine protease activity in the presence of LPS followed by its complete blockage in the presence of leupeptin and phenyl methyl sulphonyl fluoride. Therefore, Achatinin, an abundantly available lectin at multiple sites of A. fulica, by virtue of its interaction with LPS, essentially plays a crucial role in the innate immune protection of A. fulica snails.

ELECTRO-OPTICAL STUDY OF OXIDE DISPERSIONS AND THEIR STABILIT

Oxide/solution interface is with the clear origin of the surface charge, obtained through ionization of surface hydroxyl groups. The oxide particles produced by flame hydrolysis present fractal aggregates built from nearly spherical particles with constant diameter (AI2O3, SiO2). In the process of acid hydrolysis particles with well defined form (spheres, rods, ellipsoids) and high monodispersity could be obtained (α-Fe2O3, α-β-FeOOH). Different types of oxides are investigated by the means of electric light scattering. An information on the electric surface properties of oxide/solution interface as well as in presence of various additives, particles dimensions and fractal structure is obtained. The process of slow coagulation in presence of bivalent electrolyte and surface active substance is studied electrooptically. The change of dynamic electric behaviour (induced dipole moment) in the processes of interaction is followed. Some considerations are made on the nonequillbium electric properties of the interface and the connection with suspension stability.

Contribution to kinetics of slow coagulation of lyophobic sols by viskometric method

Kinetics of slow coagulation of As2S3 sol was studied by means of the equation,k=1/t(1+b)log1+bx/1−x (Freundlich) by measuring the changes in viscosity during coagulation in presence of Lithium-, Sodium- and Potassium-Chlorides. It was observed that the change in viscosity with time was autocatalytic and the above equation gave satisfactory values of the velocity constants. The points of inflexions in the curves obtained by plotting the degree of coagulation against time were taken to denote the same kinetic stage of slow coagulation (d2x/dt2=0) brought about by adding different concentrations of the electrolyte. If the times corresponding to the points of inflexion are plotted against (C−a)−1, a straight line is obtained. This serves to verify the new equation,C=a+m·1/t/n+1/t, developed in a previous communcication for the relation between time ‘t’ of coagulation and the concentration ‘c’ of the electrolyte.