Dextran-70 inhibits equine platelet aggregation induced by PAF but not by other agonists

Glucosyltransferase TeGSS from Thermosynechococcus elongatus produces an α-1,2-glucan

Here, we enzymatically produced a novel α-1,2-glucan, glucosylsucrose, that has a chemical structure significantly different from that of other glucans. This structural difference suggests its potential to modulate new physiological activities compared to known glucans. The enzyme TeGSS catalyzes the synthesis of this α-1,2-glucan from sucrose and UDP-glucose (UDPG). Using NMR spectroscopy, we elucidated the chemical structures of TeGSS-synthesized glucosylsucrose tri-, tetra-, and penta-saccharides in which the monosaccharide units are linked by α-1,2-glycosidic bonds. We also report the crystal structures of TeGSS co-crystallized with UDP and glucosylsucrose tri- and tetra-saccharides. Site-directed mutagenesis of residues in and around the TeGSS catalytic center has allowed us to propose a concerted SNi mechanism of action. Finally, we developed an enzyme-coupled reaction involving TeGSS and SuSyAc that allows production of UDPG for the synthesis of α-1,2-glucan.

Dextran grafting on PTFE surface for cardiovascular applications

The modification of biomaterial surfaces with biomolecules influences the biological response. In this work, caboxymethyldextrans (CMD) with different degrees of substitution have been grafted to surfaces by introduction of amino moieties directly onto the substrate surface. Polytetrafluoroethylene was selected as a model substrate for biomaterial as it is already largely used for cardiovascular clinical applications. Firstly, CMD polymers were characterized by FTIR, ¹H-NMR, and conductimetric titration. Then, the coatings have been analyzed by XPS to confirm the grafting and determine the composition. Once characterized, biological performances of CMD coatings were investigated. The hemocompatibility was ascertained using the free hemoglobin method. The effects on endothelial and smooth muscle cell adhesion were also studied. Results indicated that CMD at a 0.2 substitution degree, significantly influenced the biological property of PTFE by exhibiting non-thrombogenic properties as well as enhancing endothelial cell adhesion along with limiting smooth muscle cell adhesion. This work suggested the creation of versatile pro-active biomaterials suitable for different biomedical applications.

Anti-thrombogenic properties of a nitric oxide-releasing dextran derivative: evaluation of platelet activation and whole blood clotting kinetics

Controlling platelet activation and clotting initiated by cardiovascular interventions remains a major challenge in clinical practice. In this work, the anti-thrombotic properties of a polysaccharide-based nitric oxide (NO)-releasing dextran derivative are presented. Total platelet adhesion, platelet morphology and whole blood clotting kinetics were used as indicators to evaluate the anti-clotting properties of this material. With a total NO delivery of 0.203±0.003 μmol, the NO-releasing dextran derivative (Dex-SNO) mixed with blood plasma demonstrated a significantly lower amount of platelet adhesion and activation onto a surface and reduced whole blood clotting kinetics. Nearly 75% reduction in platelet adhesion and a significant retention of platelet morphology were observed with blood plasma treated with Dex-SNO, suggesting this to be a potential anti-platelet therapeutic agent for preventing thrombosis that does not have an adverse effect on circulating platelets.

Ativação de plaquetas de eqüinos com laminite induzida e tratados com ketoprofeno, fenilbutazona e flunixin meglumina

Avaliou-se a ativação de plaquetas em 20 eqüinos com laminite induzida, tratados com ketoprofeno, fenilbutazona e flunixin meglumina. As alterações de plaquetas incluíram mudança de forma, alteração da relação entre os eixos maior e menor, aumento de perímetro, emissão de pseudópodes, aumento no número dealfa-grânulos e de grânulos de glicogênio e redução no número degama-grânulos. As plaquetas de eqüinos, quando ativadas, apresentaram perfil de organela diferente de plaquetas normais, e as drogas antiinflamatórias, não-esteroidais, demonstraram atividade na ativação plaquetária de eqüinos in vivo. O flunixin meglumina apresentou melhor atividade em modular a ativação plaquetária de eqüinos in vivo do que a fenilbutazona e o ketoprofeno.

Assessment of a platelet function analyser in horses: reference range and influence of a platelet aggregation inhibitor

The objective of this study was to assess whether a new human platelet function analyser (the PFA-100) could be used to evaluate platelet function in horses and detect acetylsalicylic acid (ASA)-induced platelet dysfunctions. Citrated blood samples from 40 healthy horses were processed to obtain reference values for closure time (CT) using cartridges with collagen-ADP (CT-ADP) and collagen-epinephrine (CT-EPI) as platelet agonists. In addition, CT-ADP and CT-EPI were also measured before and 24 h after oral ASA administration in another 12 healthy horses. The sensitivity and specificity of the test were also determined. In normal horses, means+/-SD value for CT-ADP was 85.1+/-13.1 s (median, 82 s), and CT-EPI ranged from 158 to >300 s (median 291 s). Calculated reference ranges were 60.5-115.9 s and 158.5->300 s for CT-ADP and CT-EPI, respectively. Administration of ASA significantly (P<0.001) prolonged CT-ADP values from 91.0+/-13 to 113.5+/-14.4 s, and CT-EPI values were also significantly (P<0.008) prolonged after ASA administration. Sensitivity and specificity results for ADP cartridges showed that a prolonged CT value would be highly suggestive of a platelet aggregation inhibition. In conclusion, ADP cartridges can be used in horses to assess primary haemostasis and may be a valuable test for the detection of platelet aggregation inhibition.

Actions and interactions of ADP, 5- HT, histamine and PAF on equine platelets

Platelets are thought to play a role in equine diseases such as acute laminitis and verminous arteritis and may be involved in allergic disease. Mediators implicated in the pathophysiology of these conditions activate platelets and responses may be enhanced by interactions between mediators. The present study compared platelet aggregation, thromboxane production and release of radiolabelled [(3)H]5- HT in response to 5- HT, histamine, ADP and PAF alone and in combination in vitro.PAF caused concentration-related aggregation, [(3)H]5- HT release and thromboxane production. In contrast, ADP caused aggregation and 5- HT induced the release of [(3)H]5- HT with little effect on other platelet functions. Histamine had little or no effect on equine platelets. Addition of 5- HT (10 microM) prior to ADP significantly displaced the aggregation response curve to the left. The profile of responses to PAF, ADP and 5- HT suggests differential activation of intracellular signalling pathways regulating these events. The enhanced response to ADP in the presence of 5- HT may have implications in thromboembolic disease in the horse.