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PubMed1998

Action of antitumoral platinum complexes on in vitro platelet functions.

This report presents a comparison of the effects of cis- and trans-diamminedichloroplatinum complexes on in vitro platelet functions. Pretreatment of platelets with cis-platinum (cisplatin) induced a slow, dose-dependent (0.1-0.45 mM), increase in the cytosolic Ca2+ concentration, pleckstrin (47 kDa) phosphorylation and serotonin secretion, as well as a slight shape modification with emission of a few pseudopodia. All these effects were remarkably increased in platelets exposed to trans-platinum (transplatin). The rise in cytosolic Ca2+ concentration and serotonin secretion evoked by stimulation of platelets with thrombin were not significantly influenced by cellular exposure to cis-platinum, whereas they were enhanced and inhibited, respectively, by exposure to trans-platinum. Trans-platinum also inhibited thrombin-promoted platelet aggregation to a greater extent than the cis-isomer. While the viscosity of platelet rich-plasma tended to decrease in the presence of cis-platinum, it tended to increase in the presence of trans-platinum. Taken together, these results indicate that the effects on platelet functions of the efficacious antitumor complex cis-platinum is rather different from that of the inactive complex trans-platinum. Therefore, the in vitro tests of platelet functions employed in this study might provide an index of antitumor drug toxicity and serve as a preliminary indicator of therapeutic efficacy.

Antineoplastic Agents↗
PubMed1988

Platelet reactivity: a contribution to age dependence studies.

The authors examined 230 healthy donors (20-90 years) as to basic biochemical and haematological parameters and those parameters characterizing the function of blood platelets. Besides well known age dependences of fibrinogen concentration, AT III, erythrocyte sedimentation, glucose, cholesterol, alpha-2-macroglobulin and circulating immunocomplexes the results are presented showing a pronounced dependence of primary haemostatic system upon age. Within the age groups 65-75 years and those above 75 years there was a significantly higher amount of circulating aggregates (increase up to 152%), elevated concentration of beta-thromboglobulin and F VIII R:Ag. The increased reactivity of platelets is detectable even by applying relatively simple tests such as the determination of heparin-neutralizing activity, aggregation response to lower concentrations of induces or the determination of the amount of circulating aggregates.

Adult↗
PubMed2000

Comparison of the O'Brien filter test and the PFA-100 platelet analyzer in the laboratory diagnosis of von Willebrand's disease.

Von Willebrand's disease (vWD) is the most common congenital haemorrhagic diathesis, characterized by the quantitative or qualitative disorder of von Willebrand factor (vWF). A number of methods have been used for the diagnosis of the disease, and the bleeding time determination is widely accepted as a screening test in spite of its low sensitivity. Our aim was to evaluate and compare the performance of two high shear systems (the O'Brien filter test and the PFA-100 device) in the screening and diagnosis of vWD. Thirty patients (n=13 type 1 with mild symptoms, n = 9 type 1 with severe symptoms, n = 2 type 2A, n = 3 type 2B and n = 3 type 3 vWD) and twenty controls were investigated. In mild vWD the platelet retention in the second phase of the filter test with citrated blood showed the highest sensitivity (91.6%). The sensitivity of the PFA-100 method with collagen-epinephrine cartridges in this group was 76.9%, while the bleeding time was prolonged only in 15.4% of the cases. In severe type 1, in type 2A and type 3 all functional tests reflected the bleeding tendency of the patients. In type 2B disease the bleeding time was prolonged only when the patient was thrombocytopenic, but both high shear systems revealed the disease independently of the presence of thrombocytopenia. The overall sensitivity of the bleeding time determination was 50% compared to the 80-90% sensitivity of the O'Brien filter test and the PFA-100 system. The sensitivity values of the filter test and the PFA-100 device with collagen-epinephrine cartridges were in the same range, but the collagen-ADP cartridges showed a lower (65.5%) sensitivity, though the results were specific and had high positive predictive value. We conclude that both high shear systems are suitable for the screening of vWD, and that they are superior to the traditional bleeding time determination in case of mild disease or type 2B vWD.

Adenosine Diphosphate↗
PubMed1989

Bleeding time. A guide to its diagnostic and clinical utility.

Although the bleeding time is the most widely used clinical test employed to assess platelet function, its indications are poorly defined. The test is commonly used as a preoperative screen to predict hemorrhage, but the data supporting this indication are contradictory at best. In this review we highlight the physiologic basis for the bleeding time and survey the literature for data supporting the valid indications for its use. The bleeding time is a useful test for assessing platelet function in patients with hemorrhagic disorders. Its utility in providing helpful clinical information in patients who do not have a known bleeding diathesis by history is minimal. Specific recommendations regarding the rational use of the bleeding time for the preoperative evaluation of patients are presented.

Bleeding Time↗
PubMed2006

Modified labeling technique for in vivo visualization of platelets in the cerebral microcirculation of Mongolian gerbils.

Activation of platelets induces interactions with platelets, endothelial cells, and leukocytes. In vivo observation of these interactions in the cerebral microcirculation is rare. The purpose of the present study was to develop a model enabling the in vivo observation of platelet kinetics in the cerebral microcirculation. Intravital fluorescence microscopy was performed in the Mongolian gerbil. Platelets of a donor were labeled ex vivo with carboxyfluorescein diacetat-succinimidylester (CFDA-SE), providing long-term fluorescence. Platelet function was tested ex vivo by flow cytometric analysis and in vivo by analyzing platelet-endothelium interactions. Labeled platelets stimulated with adenosine diphosphate ADP (200 micromol/L) or thrombin (1000 U/L) showed aggregation in flow cytrometric analysis, whereas unstimulated platelets were not aggregated. Irradiation of the brain surface after intravenous injection of the photosensitizing dye Photosan first induced rolling and firm adherence of platelets on arteriolar and venular endothelium, followed by the formation of a thrombus obstructing the vessel. Quantitative analysis (n x 100 microm(-1) min(-1)) before and after 6 mins of irradiation showed 2.6+/-3.2 versus 29.0+/-28.9 rolling, and 0.0+/-0.0 versus 1.7+/-2.3 firm adherent platelets in arterioles, and 3.9+/-3.3 versus 36.6+/-20.9 rolling and 0.0+/-0.0 versus 13.6+/-8.9 firm adherent platelets in venules. Thus, we conclude that ex vivo labeling of platelets with CFDA-SE does not activate platelets. Platelet aggregation and adhesion was achieved by platelet-specific stimulation such as ADP, thrombin or irradiation. In vivo assessment of physiologic and pathophysiologic mechanisms of platelets in the cerebral microcirculation can be achieved in this model.

Adenosine Diphosphate↗
PubMed1990

A critical reappraisal of the bleeding time.

Since its initial invention by the French worker Milian in 1901, the bleeding time has been put forward as a clinically useful test in three contexts: diagnosis (particularly of platelet disorders), prediction of clinically important bleeding, and assessment of the adequacy of various forms of therapy. Attempting a complete review of the published experience with this test, we assessed 862 articles. Original bleeding time data appeared in 664 of these articles, from which we tabulated 1083 distinct studies in humans. ROC analysis, which characterizes the sensitivity and specificity of the test, was applied in every instance in which published data were adequate (34 studies). ROCs from 27 studies of the bleeding time in association with aspirin ingestion reveal high variability in the ability of the bleeding time to detect aspirin intake, and provide evidence against claims that recently devised bleeding time methods have improved discriminatory ability based on improved reproducibility. Two ROCs from surgical studies, in which the bleeding time was used to try to predict abnormal bleeding, were statistically indistinguishable from that of a completely noninformative test. In ROCs from five studies of abnormal bleeding in uremia, the test performed approximately the same as the platelet count or hematocrit (taken singly); in one of these studies, prothrombin consumption was determined and was a better predictor of bleeding than bleeding time, hematocrit, or platelet count. In the settings of renal biopsy (one study) and massive transfusion (one study), data allowed estimation of predictive value: in no instance was there evidence that the bleeding time significantly altered a priori estimates (based on prevalence) of the risk of bleeding. Linear regression analysis was applied to data from 23 studies relating platelet count to bleeding time, to assess published claims that the bleeding time and platelet count follow a predictively useful linear relationship. In 22 of 23 instances, the inverse relationship between bleeding time and platelet count was associated with broad statistical scatter, making it impossible to predict precisely one variable given the other. The pathophysiology of an abnormal bleeding time remains poorly understood. The bleeding time is affected by a large number of diseases, drugs, physiologic factors, test conditions, and therapeutic actions, not all of them platelet-related. The test is likely to remain widely used for the diagnosis of inherited disorders of platelet function, such as von Willebrand's syndrome, despite the lack of clear criteria for its use in this context.(ABSTRACT TRUNCATED AT 400 WORDS)

Bleeding Time↗
PubMed1993

Effect of strenuous exercise on platelet activation state and reactivity.

BACKGROUND: It has been hypothesized that platelets are activated, or made more activatible, by strenuous exercise and that these changes may play a role in the genesis of exercise-induced coronary ischemia. Previous studies have yielded conflicting results but have used assays (eg, platelet aggregation, plasma platelet factor 4, and plasma beta-thromboglobulin) that are subject to methodological problems. METHODS AND RESULTS: In the present study, a whole blood flow cytometric method was used to study the platelet activation state and reactivity of 12 physically active and 12 sedentary individuals before and after standardized treadmill exercise testing. The peptide gly-pro-arg-pro (GPRP) was included in this assay to prevent fibrin polymerization and platelet aggregation, thus allowing the measurement of the reactivity to thrombin of individual platelets in the physiological milieu of whole blood. A panel of fluorescent-labeled monoclonal antibodies was used to monitor activation-dependent platelet surface changes: downregulation of glycoprotein (GP) Ib (6D1) and upregulation of GMP-140 (S12), the GPIIb-IIIa complex (PAC1), and GPIV (OKM5). In samples obtained before exercise, platelets not exposed to thrombin showed no evidence of in vitro activation. In the sedentary subjects, exercise caused a consistent and significant augmentation of the platelet activation state and reactivity as judged by the binding of 6D1 in the presence of thrombin 0.05 U/mL (P < .001), 0.005 U/mL (P = .001), and 0 U/mL (P = .004) and by the binding of OKM5 in the presence of thrombin 0.05 U/mL (P < .001), 0.005 U/mL (P = .029), and 0 U/mL (P = .035). Exercise increased the binding of PAC1 at only a single thrombin concentration (0.005 U/mL, P = .027) and did not alter the binding of S12 at any thrombin concentration. In contrast, in the physically active subjects, exercise failed to cause a consistent alteration in either platelet activation state or platelet reactivity. No significant differences were found between the 12 male and 12 female volunteers. CONCLUSIONS: Strenuous exercise in sedentary subjects but not physically active subjects resulted in both platelet activation and platelet hyperreactivity. These changes were more readily detected with monoclonal antibodies directed against GPIb (6D1) and, to a lesser extent, GPIV (OKM5) rather than those directed against the GPIIb-IIIa complex (PAC1) and GMP-140 (S12). Platelet activation by thrombin, generally regarded as the most physiologically important agonist, can be studied in whole blood in a clinical setting through the use of the peptide GPRP.

Adult↗
PubMed1999

Evaluation of the Clot Signature Analyzer as a hemostasis test in healthy volunteers exposed to low doses of aspirin.

Several variables affect bleeding time that make it difficult to obtain consistent measurements. The Clot Signature Analyzer (CSA) has been developed to assess in vitro hemostasis using well-controlled flow chambers. In this study, the equivalencies in the CSA parameters with the conventional bleeding time or platelet aggregation methods were evaluated in subjects exposed to aspirin. The CSA parameters, platelet hemostasis time (PHT) and collagen-induced thrombus formation (CITF), were compared to bleeding time (Surgicutt2) and collagen-induced platelet aggregation, respectively. Fifty-three healthy volunteers were given two doses of aspirin (81 and 243 mg) in one day. Following the baseline period, the volunteers took 81 mg of aspirin and then took 243 mg 2 hours later. The changes in each value from the baseline to that at either aspirin dose (2 hours after dosing) were evaluated. Platelet hemostasis time and CITF correlated well with bleeding time and aggregation, respectively, but PHT was not significantly increased after 81 mg of aspirin, whereas bleeding time was significantly increased. The variation in PHT was slightly higher than that of bleeding time. At 81 mg, CITF was significantly increased but aggregation was not, even though the variation was comparable. This suggests that PHT and CITF can simulate the changes in bleeding time and aggregation, respectively, but the sensitivity of PHT for detecting the changes in bleeding time was no better than the conventional method. Also, CITF was more sensitive than aggregation in detecting platelet response to collagen. In conclusion, the proposed CSA is not always suitable for detecting hemostatic abnormalities.

Adolescent↗
PubMed1985

Effect of Bordetella pertussis vaccine on bleeding time, whole blood coagulation time and platelet aggregation in animals.

Bordetella pertussis vaccine, a hypoglycemic agent significantly prolonged the bleeding time and whole blood coaguistion time in rabbits and dogs when administered intraperitonially. The vaccine also affects platelet aggregation in rats 4 days after its intraperitonial administration. The effect on platelet aggregation is thought to be due to its beta adrenargic receptor blocking action which may also contribute to the hypoglycemia.

Animals↗
PubMed2002

The effects of perioperatively administered colloids and crystalloids on primary platelet-mediated hemostasis and clot formation.

UNLABELLED: To explore whether routinely administered colloids and crystalloids influence the hemostatic system, we studied 60 patients undergoing knee replacement surgery during randomized intravascular fluid administration using 6% hydroxyethyl starch 200/0.5 (HES) or 4% modified gelatin (GEL) in addition to a basal infusion of lactated Ringer's solution (RL), or exclusively RL. In addition to routine coagulation tests, measurements of coagulation factors were performed. Also, functional measurements of the in vitro bleeding time by use of the platelet function analyzer (PFA-100 and ROTEG analysis (ROTEG(R); extrinsically and intrinsically [Ex; In] activated measurements of clotting time, CT [s]; clot formation time, CFT [s]; clot strength, A20 [mm]; fibrinogen component of the clot, FibA20 [mm]; and maximal clot elasticity) were used. Time dependency of variables was analyzed with a repeated-measures analysis of variance (all groups pooled); differences between groups were detected by comparing the calculated area under the curve (AUC(A-D)). For all variables, except ExCT, ExCFT, and InCFT, a significant time dependency was demonstrated, indicating that impaired platelet-mediated hemostasis and clot formation occurred with IV administration of fluids. Total clot strength, fibrinogen part, and clot elasticity decreased significantly more in the colloid groups than in the RL group (InA20: HES, -13.0 mm; GEL, -11.5 mm; RL, -1.3 mm; P = 0.042; FibA20: HES, -10.5 mm; GEL, -6.0 mm; RL, -1.3 mm: P < 0.0001; MCE: HES, -48; GEL, -35; RL, -15.8; P < 0.0001). The decrease in fibronectin concentrations was significantly smaller with GEL as compared with HES, whereas a weak trend toward a larger decrease in fibrinogen concentrations was observed with both colloids. Results show that colloid administration reduces final clot strength more than does RL alone, which also exhibited effects, albeit minor, on the coagulation system. The reduction in total clot strength was due to impaired fibrinogen polymerization, resulting in a decreased fibrinogen part of the clot and reduced clot elasticity. IMPLICATIONS: Our data suggest that during deliberate colloid administration, critically impaired fibrinogen polymerization and reduced fibrinogen concentrations might be reached earlier than expected. Therefore, maintaining fibrinogen concentrations seems essential when continuing blood loss is bridged by colloid infusion until transfusion triggers are reached, especially in patients already exhibiting borderline fibrinogen levels at baseline.

Aged↗
PubMedDate not supplied

Platelet function and coagulation in patients with hepatobiliary disorders receiving cefotetan prophylaxis.

Eighteen patients with hepatobiliary disorders undergoing invasive biliary tract investigations were given the cephalosporin cefotetan and platelet function and coagulation factors were monitored. No significant changes were observed in the group as a whole, although marked alterations were seen in three patients in association with clinical complications unrelated to the antibiotic. Although cefotetan is structurally similar to cephalosporins which have been associated with bleeding disturbances, it does not appear to induce such abnormalities in a high risk group of patients with normal renal function when given for five days intravenously at a dose of 1 g twice daily.

Adult↗