Platelet activation: ultrastructure and morphometry in platelet-rich plasma of horses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Platelet activation in experimental arterial thrombosis.

Platelet aggregates were studied in dogs with induced arterial thrombosis, by the method of Wu and Hoak. Blood was withdrawn from a jugular vein and from the femoral vein on the operated side 24 h after thrombus induction and immediately and 2 h after blood flow was restored by thrombectomy. Platelet activation was significant in dogs with obstructive arterial thrombosis and which tended to subside after thrombectomy. Activation or formation of platelet aggregates seemed to occur in the ischemic limb. It is suggested that this experimental model could be useful to test the action of anti-platelet drugs in vivo.

Avoiding leukocyte contamination and early platelet activation in platelet-rich plasma.

The objective of this study was to describe a new platelet-rich plasma (PRP) protocol with a reduced concentration of leukocytes and intact platelets. We collected 8 mL of venous blood (VB) from marginal ear veins of 10 male New Zealand white rabbits in acid dextrose citrate Vacutainer tubes. Tubes were centrifuged at 302g for 10 minutes. All plasma was collected in plastic tubes to avoid buffy-coat contamination and centrifuged at 2862g for 5 minutes. A 10% calcium chloride activator (10 PRP:2 CaCl2) was added to the lower third of this plasma (PRP), and the PRP gel was obtained. Mean platelet count was 317.7 x 10(3) +/- 39.9/microL in VB and 1344.9 x 10(3) +/- 347.5/microL in PRP. Leukocyte counts were 3.96 x 10(3) +/- 2.01/microL and 0.46 x 10(3) +/- 0.45/microL in VB and PRP, respectively. Mean platelet enrichment was 327.4 +/- 97.8%. All differences were statistically significant (P > .05). This protocol is practical and reproducible, resulting in a high concentration of intact platelets to help tissue repair and low levels of leukocytes.

Platelet aggregation and TGF-beta(1) plasma levels in pregnant women with preeclampsia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Platelet hyperaggregability in high-fat fed rats: A role for intraplatelet reactive-oxygen species production

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal structure of the platelet activator convulxin, a disulfide-linked alpha(4)beta(4) cyclic tetramer from the venom of Crotalus durissus terrificus

Convulxin (CVX), a C-type lectin, isolated from the venom of the South American rattlesnake Crotalus durissus terrificus, causes cardiovascular and respiratory disturbances and is a potent platelet activator which hinds to platelet glycoprotein GPVI. The structure of CVX has been solved at 2.4 Angstrom resolution to a crystallographic residual of 18.6% (R-free =26.4%). CVX is a disulfide linked heterodimer consisting of homologous alpha and beta chains. The heterodimers are additionally linked by disulfide bridges to form cyclic alpha(4)beta(4)heterotetramers. These domains exhibit significant homology to the carbohydrate-binding domains of C-type lectins, to the factor IX-binding protein (IX-bp), and to flavocetin-A (Fl-A) but sequence and Structural differences are observed in both the domains in the putative Ca2+ and carbohydrate binding regions. (C) 2003 Elsevier B.V. All rights reserved.

Análise dos traçados de ondas da agregação plaquetária em pacientes com doenças cardiovasculares em uso do ácido acetil salicílico comparados a doadores de sangue

A agregação plaquetária avalia a função das plaquetas através de diferentes vias de ativação plaquetária in vitro, fornecendo traçados de ondas equivalentes à propriedade física dessa agregação. Sabendo-se que a aspirina acetila irrever­sivelmente a enzima cicloxigenase prevenindo a geração de tromboxana A2, potente ativador da agregação plaquetária, esta droga tem sido analisada há mais de trinta anos na clínica médica em pacientes com doenças cardiovasculares como uma potente droga antitrombótica. Foram nossos objetivos obter traçados de ondas correspondentes às fases da agregação plaquetária para nossa padronização utilizando nosso grupo controle de doadores de sangue e compará-las com nosso grupo estudo, frente a diferentes agentes agonistas em diferentes concentrações: ADP 1µM e 3µM; AA, 0,5mM; ADR, 0,05 mg/mL, 0,025 mg/mL e 0,010 mg/mL. Os grupos analisados foram constituídos por 41 cardíacos e 40 doadores de sangue considerados controle. Dos cardíacos, 33 faziam uso regular do AAS na concentração de 200 mg/dia e oito na concentração de 100 mg/dia, sendo todos considerados hipertensos. A padronização da agregometria estava na dependência do encontro de traçados correspondentes a ondas de agregação, sendo esses obtidos em porcentagem no tempo de cinco minutos estandartizados pelo aparelho utilizado. Comparando os resultados entre os pacientes e o grupo controle, foi possível observar que, na presença dos agentes agregantes ADP 1µM e ADP 3 µM, ADR 0,05 mg/mL, 0,025mg/mL e 0,010 mg/mL, os pacientes apresentaram 1ª onda, mas não 2ª onda. Por sua vez, no caso do AA 0,5 mM não houve o encontro de traçados de ondas.

Influence of Antiplatelet Drugs in the Pathogenesis of Experimental Periodontitis and Periodontal Repair in Rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cardiovascular remodeling induced by passive smoking

Coronary heart disease (CHD) is the most common cause of death in many developed countries. The major risk factors for CHD are smoking, high blood pressure, diabetes, high cholesterol levels, and lack of physical activity. Importantly, passive smoke also increases the risk for CHD. The mechanisms involved in the effects of passive smoke in CHD are complex and include endothelial dysfunction, lipoprotein modification, increased inflammation and platelet activation. Recently, several studies have shown that exposure to tobacco smoke can result in cardiac remodeling and compromised cardiac function. Potential mechanisms for these alterations are neurohumoral activation, oxidative stress, and MAPK activation. Although the vascular effects of cigarette smoke exposure are well known, the effects of tobacco smoking on the heart have received less attention. Therefore, this review will focus on the recent findings as to the effects of passive smoking in acute and chronic phases of vascular and cardiac remodeling. © 2009 Bentham Science Publishers Ltd.

Inibição do receptor tipo-1 ativado por protease (PAR¹) na doença e reparo periodontal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

CrataBL, a lectin and Factor Xa inhibitor, plays a role in blood coagulation and impairs thrombus formation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Síntese, caracterização e avaliação farmacológica de derivados N-acilhidrazônicos para a prevenção de aterotrombose

Atherosclerosis is a chronic inflammatory disease characterized by accumulation of lipid and fibrous components in arterial vessels, giving rise to atheromas. Development of Atheromatou plaques leads to arterial steatosis, triggering ischemic events. Atherotrombosis has a strong correlation with atherosclerosis, where rupture of atheromatous plaques cause release of vessel wall's pro-thrombotic components, activating platelet aggregation and thromosis. Due to the major role played by platelets on thrombus-embolic conditions, drugs that inhibit platelet aggregation demonstrate great relevance for atherothrombosis prevention, reducing patient mortality. Currently, there are a variety of drugs acting on several different targets, preventing platelet activation. However, these therapies demosntrate side effects such as thrombocytopenia, neutropenia, hemorrhage and low oral availability. Thus, the application of molecular modifications such as hybridization can produce novel, more efficient antiplatelet aggregation inhibitors. In this project we describe the synthesis and characterization of novel N-acilhydrazone compounds, acting through multiple mechanisms such as platelet calcium chelation and nitric oxide donation by furoxanic subunits. Furthermore, we demonstrate that such compounds exhibit biological activity in in vivo bleeding time, in vitro antiplatelet aggregation and in vivo antinociceptive assays. Therefore, novel N-acilhydrazone compounds demonstrate potential as antiplatelet drugs for atherothrombosis prevention.

Effects of dipyrone, meloxicam, or the combination on hemostasis in conscious dogs

To compare the effects of dipyrone, meloxicam, and of the combination of these drugs on hemostasis in dogs. Prospective, blinded, randomized crossover study. Research laboratory at a veterinary teaching hospital. Six adult dogs. Animals received 4 intravenous treatments with 15-day washout intervals: control (physiological saline, 0.1 mL/kg), meloxicam (0.2 mg/kg), dipyrone (25 mg/kg), and dipyrone-meloxicam (25 and 0.2 mg/kg, respectively). A jugular catheter was placed for drug injection and for collecting samples for whole blood platelet aggregation (WBPA) and thromboelastometry assays at baseline, 1, 2, 3, 5, and 8 hours after treatment administration. The percent change from baseline of lag time and of the area under the curve (AUC) of impedance changes in response to collagen-induced platelet activation were recorded during WBPA. Thromboelastometry-derived parameters included clotting time, clot formation time, alpha-angle, and maximum clot firmness. The buccal mucosal bleeding time was evaluated by a blinded observer at baseline, 1, 3, and 5 hours after treatment injection. No significant changes in WBPA and thromboelastometry were recorded in the control treatment. Dipyrone significantly (P < 0.05) increased the lag time for 2 hours and decreased the AUC for 3 hours after injection. Meloxicam did not alter WBPA. Dipyrone-meloxicam significantly increased lag time for 2 hours and decreased the AUC for 5 hours after treatment injection. Experimental treatments did not differ from the control treatment for thromboelastometry and buccal mucosal bleeding time. While meloxicam does not alter hemostasis by the methods evaluated, dipyrone inhibits platelet aggregation for up to 3 hours. Meloxicam-dipyrone combination causes more prolonged inhibition of platelet function than dipyrone alone. Decreased platelet aggregation induced by dipyrone and dipyrone-meloxicam does not appear to impact the viscoelastic properties of the blood clot nor increase the risk of bleeding in dogs without preexisting hemostatic disorders.

Platelet-rich plasma stimulates cytokine expression and alkaline phosphatase activity in osteoblast-derived osteosarcoma cells

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)