Studies on platelet aggregation using the Born method in normal and uraemic dogs.
ABSTRACT Using the Born method, based on light transmission in platelet rich plasma, the minimum effective concentration (threshold values) of several platelet agonists for inducing maximum platelet aggregation was determined in healthy dogs. The final concentrations of aggregation agonists were as follows: adenosine diphosphate (ADP) (0.5-50 micromol/L; n = 75 healthy dogs), collagen (0.5-20 mg/mL; n = 75), thrombin (0.1-5 IU/mL; n = 75), ristocetin (1-10 mg/mL; n = 10), and epinephrine (5-50 micromol/L; n = 10). Reference values for maximum aggregation with a lower limit of > 80% were achieved for agonist concentrations 25 micromol/L ADP (80-98%), > or = 10 microg/mL collagen (80-96%), and > or = 1 IU/mL thrombin (80-97%). None of the concentrations of epinephrine and ristocetin used in this study induced quantitative aggregation in the whole group of healthy dogs. We also studied platelet aggregation in 14 uraemic dogs using selected concentrations of aggregation agonists. Aggregation was significantly decreased in uraemic dogs using intermediate agonist concentrations, i.e., in the region of the threshold concentration. In contrast, maximum aggregation was increased in uraemic patients compared to reference values using low concentrations of all three agonists (ADP: 1 micromol/L, collagen: 1 microg/mL, and thrombin: 0.1, 0.2 IU/mL).
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ABSTRACT: To review the mechanisms of platelet activation and options for diagnosing and treating platelet hyperactivity in relation to thrombosis in dogs and cats. Prospective, retrospective, and review articles, as well as textbook chapters in both human and veterinary medicine. Articles were primarily, but not exclusively, retrieved via Medline. In people, platelets are known to play a key role in the development of arterial thrombosis in numerous disease states and antiplatelet drugs are the cornerstone in the treatment of acute events and for prevention in patients at risk. For many years, aspirin was used as the sole antiplatelet drug in people, but the introduction of adenosine diphosphate receptor antagonists and integrin α(IIb) β(3) inhibitors has significantly improved outcome in selective groups of patients. The understanding of platelet activation in disease states has increased dramatically over the past decade. Simultaneously, a host of new methods for evaluating platelet function have been developed, which enable primarily researchers, but also clinicians to monitor the activity of platelets. Many of these methods have been validated for research purposes, but few have found their way to the clinics. Not a single correctly randomized clinical trial has been carried out with any antiplatelet drug for any indication in dogs or cats, and consequently, treatment is empiric and largely based on expert opinion or data from experimental studies. The pathogenesis of thromboembolic disease is complex and multifactorial and the role of hyperactive platelets in this etiology remains to be clarified in most of the diseases associated with thrombosis in dogs and cats. Until efficacy data from well-designed studies are available, antithrombotic therapy should consist of close monitoring, good supportive care, and judicious empirical use of antiplatelet agents.Journal of veterinary emergency and critical care (San Antonio, Tex. : 2001). 02/2012; 22(1):42-58.
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ABSTRACT: Abstract Background: Interest in natural compounds as sources of potentially new treatment options is growing rapidly. Preliminary screening of many different plant extracts showed that Wrightia tinctoria acts as a potent human platelet aggregation inhibitor. The aim of the present study was to isolate and characterize the active compound responsible for potent inhibition of human platelet aggregation in vitro.Methods: A 70% ethanolic extract derived from W. tinctoria seeds was fractionated with chloroform followed by ethyl acetate. The ethyl acetate fraction was further fractionated and purified through a series of three successive column chromatographic separations using silica gel, Sephadex LH-20, and C-18 columns. Liquid chromatography coupled to negative electrospray ionization tandem mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR) studies were performed in the structure determination of the active phenolic compound present in the ethyl acetate fraction of W. tinctoria seeds.Results: A phenolic compound has been isolated and identified as chlorogenic acid by LC-MS/MS and NMR studies. Chlorogenic acid showed concentration-dependent inhibitory effect on collagen-induced platelet aggregation in vitro with an IC50 of 0.2363 μg/μl.Conclusion: The present data suggest that chlorogenic acid can be developed as potential antiplatelet agent in the treatment of cardiovascular diseases in diabetes mellitus.Journal of Complementary and Integrative Medicine 01/2013; 10(1):1-8.
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ABSTRACT: To evaluate platelet-neutrophil aggregate (PNA) formation and neutrophil shape as indicators of neutrophil activation in dogs with systemic inflammatory diseases and after blood sample incubation with various platelet and neutrophil agonists. 20 dogs with systemic inflammatory response syndrome (SIRS) and 10 healthy Beagles. Neutrophils were isolated from blood samples directly after blood sample collection and after incubation of blood samples with phorbol myristate acetate, collagen, adenosine diphosphate, epinephrine, or various concentrations of lipopolysaccharide or arachidonic acid. CD61+ neutrophils as an indicator of PNA formation were evaluated, and neutrophil size and granularity were assessed via flow cytometry. Dogs with SIRS had more PNA formation, larger neutrophil size, and less granularity relative to control dogs, but no differences were evident when these dogs were grouped by whether they had sepsis (n = 6) or disseminated intravascular coagulation (12). A significant increase in PNA formation occurred after neutrophil incubation with all agonists, and incubation with phorbol myristate acetate elicited the strongest response. Neutrophils increased in size and decreased in granularity after incubation with all agonists except epinephrine. Incubation with lipopolysaccharide or arachidonic acid resulted in a dose-dependent effect on PNA formation and neutrophil shape. SIRS appeared to increase the degree of PNA formation and neutrophil shape change. Similar changes after neutrophil incubation with platelet agonists suggested that platelet activation has a role in PNA formation. Additional studies are necessary to determine the clinical importance and diagnostic value of PNA formation in dogs with SIRS and sepsis.American Journal of Veterinary Research 07/2012; 73(7):939-45. · 1.21 Impact Factor