ristocetin and Blood-Platelet-Disorders

Numerous laboratory tests are in use to detect congenital or acquired platelet function disorders. Platelet aggregometry, using ADP, collagen, arachidonic acid or ristocetin as inductor is the standard test system for diagnosis. It is also used to detect platelet non-response to antiplatelet therapy. Studies have demonstrated that laboratory assessment of platelet non response to aspirin or clopidogrel is associated with adverse outcomes, and they indicate the importance of adjusting antiplatelet therapy in patients with a low degree of platelet inhibition. Nevertheless, a standardized method for identifying these patients is still missing.

Topics: Adenosine Diphosphate; Arachidonic Acid; Aspirin; Blood Platelet Disorders; Clopidogrel; Collagen; Hemorrhagic Disorders; Humans; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Function Tests; Predictive Value of Tests; Prognosis; Ristocetin; Ticlopidine

Topics: Adenosine Diphosphate; Blood Platelet Disorders; Blood Platelets; Cell Membrane; Collagen; Cyclic AMP; Epinephrine; Hemostasis; Humans; Microtubules; Platelet Adhesiveness; Platelet Aggregation; Platelet Factor 3; Platelet Factor 4; Ristocetin; Serotonin; Thrombopoietin

Topics: Animals; Antigen-Antibody Complex; Blood Coagulation Factors; Blood Platelet Disorders; Blood Platelets; Blood Proteins; Cell Membrane; Collagen; Complement System Proteins; Cytoplasmic Granules; Factor VIII; Fibrin; gamma-Globulins; Glycoproteins; Humans; Lectins; Platelet Adhesiveness; Platelet Aggregation; Polylysine; Ristocetin; Syndrome; von Willebrand Factor

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Anemia, Megaloblastic; Anti-Inflammatory Agents; Blood Coagulation Disorders; Blood Coagulation Tests; Blood Platelet Disorders; Blood Platelets; Carbenicillin; Collagen; Epinephrine; Hemorrhage; Humans; Isoantibodies; Leukemia; Myeloproliferative Disorders; Platelet Aggregation; Postoperative Complications; Purpura, Thrombocytopenic; Ristocetin; Stress, Psychological; Uremia; von Willebrand Diseases

The thrombopoietin receptor agonist romiplostim is used for the long-term treatment of chronic immune thrombocytopenia (ITP). ITP patients have an increased thrombotic risk, which could be exacerbated if romiplostim increased platelet hyperreactivity or caused spontaneous platelet aggregation. To investigate this possibility, this study examined platelet function in romiplostim-treated ITP patients and healthy subjects. Light transmission platelet aggregometry utilizing arachidonic acid, collagen, epinephrine, ristocetin, ADP, and saline (to assess spontaneous aggregation) was performed for each subject. In addition, the ADP AC

Topics: Adenosine Diphosphate; Adult; Aged; Arachidonic Acid; Blood Platelet Disorders; Collagen; Epinephrine; Female; Humans; Male; Middle Aged; Platelet Aggregation; Purpura, Thrombocytopenic, Idiopathic; Receptors, Fc; Receptors, Thrombopoietin; Recombinant Fusion Proteins; Ristocetin; Thrombophilia; Thrombopoietin; Young Adult

A 75 year old patient presenting with mucocutaneous bleeding was diagnosed with acquired thrombasthenia. The diagnosis was based on lack of platelet aggregation with adenosine diphosphate (ADP), arachidonic acid and collagen, and normal aggregation induced by ristocetin.. To study the mechanism of platelet function inhibition in a patient with acquired thrombasthenia.. Aggregation assays of platelets from the patient and healthy controls were performed. In addition, anti-glycoprotein (GP) IIbIIIa antibodies bindingto normal in the presence or absence of the patient's serum was by flow cytometry.. Aggregation of normal platelets in the presence of patient's plasma was inhibited four- and 2.5-fold in the presence of ADP and arachidonic acid respectively, while collagen-induced aggregation was completely abolished. Ristocetin-induced aggregation was normal. The patient's serum inhibited binding of commercial anti-glycoprotein IIbIIIa antibodies to normal platelets twofold by flow cytometry. Treatment with anti-CD20 monoclonal antibody (rituximab) normalized the patient's platelet aggregation.. These results suggest that the patient developed inhibitory anti-GPIIbIIIa autoantibodies that caused acquired thrombasthenia.

Topics: Adenosine Diphosphate; Aged; Antibodies, Monoclonal, Murine-Derived; Arachidonic Acid; Autoantibodies; Blood Platelet Disorders; Collagen; Drug Monitoring; Female; Humans; Immunologic Factors; Lupus Erythematosus, Systemic; Platelet Aggregation; Platelet Function Tests; Platelet Glycoprotein GPIIb-IIIa Complex; Remission Induction; Ristocetin; Rituximab; Treatment Outcome

Some patients evaluated for chest pain with angiographically normal coronary arteries show coronary slow flow phenomenon (CSFP) on angiography. Slow flow of dye in epicardial coronary arteries is also not an infrequent finding in patients during routine coronary angiography. The precise pathophysiology of CSFP is not known yet.. This study investigates the presence of platelet function disorders in patients with CSFP.. The patient group included 24 patients with CSFP detected by coronary angiography via the TIMI "frame count" method, and a control group included 23 patients with normal coronary flow. Platelet aggregability induced by use of ristocetin, collagen, and adenosine diphosphate (ADP), was measured from all blood samples in both control and patient groups.. The ratio of platelet aggregability increased significantly in patients with CSFP compared with patients with normal coronary flow (ristocetin 57.6 +/- 15 vs. 45.4 +/- 17.1, collagen 62.9 +/- 16.4 vs. 48.9 +/- 25.3, ADP 59.4 +/- 18 vs. 42.4 +/- 15.2, p < 0.05).. Platelet aggregability is increased in patients with CSFP.

Topics: Adenosine Diphosphate; Blood Platelet Disorders; Collagen; Coronary Angiography; Coronary Circulation; Female; Humans; Male; Middle Aged; Platelet Aggregation; Ristocetin

Platelet function testing consisting of platelet aggregation and secretion often is requested in the clinical evaluation of patients with bleeding problems. At present, there are no uniform clinical laboratory standards for the performance or interpretation of these studies. The present report describes one laboratory's methods and interpretations of platelet aggregation and secretion studies of platelet-rich plasma using each of the common platelet agonists. Diagnostic categories for the evaluation of the platelet function testing are presented. The diagnostic categories then are applied to the evaluation of 61 patients referred to our medical center for these studies. The aims of this report are to present clinical platelet aggregation and secretion studies and to provide a working schema to evaluate these results. Our intent is to stimulate interest in the development of professional guidelines for platelet function testing in the clinical laboratory.

Topics: Adenosine Diphosphate; Arachidonic Acid; Blood Platelet Disorders; Blood Platelets; Clinical Laboratory Techniques; Collagen; Dose-Response Relationship, Drug; Epinephrine; Humans; Plasma; Platelet Aggregation; Reference Values; Ristocetin; Thrombin

Topics: Blood Platelet Disorders; Dimerization; Hemostasis; History, 20th Century; History, 21st Century; Humans; Platelet Aggregation; Ristocetin; von Willebrand Diseases; von Willebrand Factor

Menorrhagia is a common clinical problem and is unexplained in more than 50% of women. Although studies suggest that von Willebrand's Disease (VWD) is found in a substantial number of women with unexplained menorrhagia, the prevalence of platelet defects in women with menorrhagia is unknown. To determine the prevalence of platelet and other hemostatic defects, we evaluated women ages 17-55 diagnosed with unexplained menorrhagia. Seventy-four women (52 white, 16 black, six other) were studied. Bleeding time was prolonged in 23 women (31.5%). Maximal percent platelet aggregation was decreased with one or more agonists in 35 (47.3%) women. The most commonly found platelet function defects were reduced aggregation responses to ristocetin in 22 women and to epinephrine in 16 women. Sixteen of 22 women with reduced ristocetin aggregation had von Willebrand ristocetin cofactor (VWF:RCo) and von Willebrand factor antigen (VWF:Ag) > 60%. Platelet ATP release was decreased with one or more agonists in 43 (58.1%) women. Of the black women studied, 11/16 (69%) had abnormal platelet aggregation studies compared with 20/52 white women (39%) (P = 0.06). Black women with menorrhagia had a higher prevalence of decreased platelet aggregation in response to ristocetin and epinephrine than did white women (P = 0.0075, P = 0.02). Ten women (13.5%) had VWF:RCo and/or VWF:Ag < 60%. Using race and blood group specific ranges, 5 (6.8%) women had decreased VWF:RCo, VWF:Ag and/or collagen binding (VWF:CB). Mild factor XI deficiency was found in two women and one woman with mild factor V deficiency and one hemophilia A carrier were identified. We conclude that the prevalence of platelet function defects and other inherited bleeding disorders is substantial in a multiracial US population of women with unexplained menorrhagia.

Topics: Adolescent; Adult; Blood Coagulation Factors; Blood Coagulation Tests; Blood Platelet Disorders; Epinephrine; Female; Humans; Menorrhagia; Middle Aged; Platelet Aggregation; Platelet Function Tests; Prevalence; Racial Groups; Ristocetin; von Willebrand Diseases

We report three cases of platelet dysfunction characterized by defective Ca2+ ionophore-induced platelet aggregation without impaired production of thromboxane A2 (TXA2). The patients had mild to moderate bleeding tendencies, and their platelet aggregation and secretion induced by ADP, collagen, arachidonic acid, stable TXA2 (STA2) and Ca2+ ionophore A23187 was defective or much reduced. However, ristocetin- or thrombin-induced platelet aggregation was normal. The analysis of second messenger formation showed that inositol 1,4,5-triphosphate formation or Ca2+ mobilization induced by thrombin, STA2 or A23187 was normal. Furthermore, the phosphorylation of 47 kDa protein (pleckstrin) and 20 kDa protein (myosin light chain, MLC) in response to those agonists was normal. These findings suggest that the defective site in the patients' platelets lies in the process distal to or independent of protein kinase C activation, Ca2+ mobilization and MLC phosphorylation.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Adult; Arachidonic Acid; Blood Platelet Disorders; Blood Proteins; Calcimycin; Calcium; Collagen; Female; Humans; Ionophores; Male; Middle Aged; Myosin Light Chains; Phosphoproteins; Phosphorylation; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin; Thrombin; Thromboxane A2

Isolated platelet factor 3 (PF3) availability defect has been observed to be a common platelet functional disorder (PFD) in the Department of Haematology, All India Institute of Medical Sciences, New Delhi, India. One hundred and thirty-two patients were diagnosed to have this defect based on the presence of reduced PF3 availability, normal platelet aggregation with ADP, collagen, adrenaline, ristocetin, and arachidonic acid and normal PF3 content. PF3 availability was evaluated by measurement of Russel viper venom time (RVVT) on the patient's platelet-rich plasma (PRP) after incubation with ADP for 20 min. An RVVT value >19.0 s was considered diagnostic of reduced PF3 availability in patients with normal prothrombin and activated partial thromboplastin times. Isolated PF3 availability defect occurred in patients with ages between 2 and 65 yr and had a female preponderance (M:F=1:2). One fifth of the patients had a positive family history of similar mild bleeding diathesis, indicating an autosomal dominant pattern of inheritance. All patients presented with mild bleeding manifestations, the commonest symptom being appearance of recurrent ecchymotic spots. In females, menorrhagia was the commonest symptom. A pilot study was conducted on 45 patients to evaluate the therapeutic role of oral soya bean (50 g/d). The clinical response was evaluated after 3 months. Soya therapy resulted in disappearance of bleeding problems in 5 patients and reduction in frequency and severity of bleeding in 26 patients. A repeat PF3 availability test after 3 months of therapy showed complete correction in 4 and partial correction in 12 patients. It is evident from McNemer's test that both the clinical and the laboratory parameters (PF3 availability) showed a similar response to soya therapy (p>0.05). Pre-soya therapy mean PF3 availability values differ significantly from those after soya therapy (p<0.01). Thus, soya bean appears to have a therapeutic potential in isolated PF3 availability defect.

Topics: Adenosine Diphosphate; Adolescent; Adrenergic Agonists; Adult; Aged; Arachidonic Acid; Biomarkers; Blood Platelet Disorders; Child; Child, Preschool; Collagen; Epinephrine; Female; Glycine max; Humans; Male; Middle Aged; Phytotherapy; Pilot Projects; Platelet Aggregation; Platelet Factor 3; Ristocetin

We describe here the molecular basis of an isolated hereditary giant platelet disorder (GPD) which is not accompanied with thrombocytopenia or leukocyte inclusion. Platelet aggregation with ristocetin and botrocetin was almost normal in this patient. Flow cytometric analysis showed that the glycoprotein (GP) Ib/IX complex was expressed on the platelet membranes at decreased levels. The amount of platelet GPIb alpha and the plasma glycocalicin concentration, the water-soluble extracellular portion of GPIb alpha, were also decreased. The anti-GPIb alpha antibody coprecipitated GPIb beta and GPIX, although the ratios of these polypeptides to GPIb alpha was greatly decreased compared with the ratio in normal platelets. Immunoblot analysis under nonreduced conditions showed that most of the GPIb alpha in the patient's platelets was not disulfide linked with GPIb beta. DNA sequencing analysis showed compound heterozygosity for two independent single nucleotide substitutions: from Tyr (TAC) to Cys (TGC) at residue 88, and from Ala (GCC) to Pro (CCC) at residue 108 in her GPIb beta gene. These substitutions were not found in genomic DNA samples from 108 normal individuals. These mutations might result in decreased expression of the GPIb/IX complex and may influence the association of the complex with the membrane skeleton, consequently impairing normal platelet morphology. Furthermore, the phenotype caused by mutations in the subunits of the GPIb/IX complex could span the spectrum from a normal phenotype, to isolated GPD, to a full-blown bleeding disorder, such as Bernard-Soulier syndrome.

Topics: Adult; Blood Platelet Disorders; Blood Platelets; Crotalid Venoms; Cystine; Female; Humans; Male; Platelet Aggregation; Platelet Glycoprotein GPIb-IX Complex; Point Mutation; Protein Conformation; Ristocetin; von Willebrand Factor

Patient B.G. is a 29-yr-old female with a lifelong bleeding disorder characterized clinically by a highly increased bleeding time, menorrhagias, long-lasting bleeding after cuts and tooth extractions and large post-traumatic haematomas. Her coagulation tests were within normal range, platelet count was 140,000-160,000 per microliters, but platelet function was impaired as demonstrated by the absence of collagen-induced aggregation, although no abnormalities were detected in aggregation response to ADP and ristocetin. Morphologically her platelets were characterized by gigantic size-average profile area was about 2.5 times higher than that of control donors, and severe deficiency of alpha-granules-only 16% of their number in control donors. These features taken together indicated the diagnosis of grey platelet syndrome. As has been shown by quantitative immunoblotting, patient's platelets contained small amounts of alpha-granule membrane protein P-selectin-about 15% of that in control donors. The content of plasma membrane glycoproteins IIb-IIIa and Ib was not reduced, suggesting the specific deficiency of alpha-granule membrane protein. Thus, B.G. is the second patient described in the literature (see also Lages et al, J Clin Invest 1991: 87: 919-929) with combined deficiency of alpha-granules and P-selectin.

Topics: Adenosine Diphosphate; Adult; Bleeding Time; Blood Platelet Disorders; Blood Platelets; Cytoplasmic Granules; Female; Humans; Microscopy, Electron; P-Selectin; Platelet Aggregation; Platelet Glycoprotein GPIIb-IIIa Complex; Platelet Membrane Glycoproteins; Ristocetin; Syndrome

There are data suggesting that recombinant human erythropoietin (rHuEPO) may induce thromboses in hemodialysis patients, possibly due to alterations in platelet function. In an earlier study, we found evidence of platelet hyperfunction in several patients 4 to 8 weeks following the start of rHuEPO therapy, which was begun shortly after hemodialysis was initiated. Studies were performed to examine the effects of rHuEPO on whole blood platelet aggregation and adenosine triphosphate (ATP) release independent of changes in hematocrit or the uremic state. Eight hemodialysis patients without and four with a history of vascular access clotting had platelet aggregation tests performed at baseline while receiving rHuEPO, off rHuEPO for 2 weeks, and 4 to 6 weeks after restarting the drug. While the plasma EPO level decreased significantly after the 2-week period off rHuEPO (P < 0.0001), the hematocrit did not change at any of the three time periods. Whole blood platelet aggregation in response to adenosine diphosphate (ADP), collagen, and ristocetin was not significantly altered on or off rHuEPO in either patient group. Platelet hyperfunction, determined by aggregation or ATP release either spontaneously or in response to low-dose ADP or ristocetin, was not seen in any patient. These data suggest that the increase in access clotting is not the result of platelet hyperfunction induced directly by rHuEPO.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Adult; Aged; Aged, 80 and over; Blood Platelet Disorders; Collagen; Erythropoietin; Female; Hematocrit; Humans; Kidney Failure, Chronic; Male; Middle Aged; Platelet Aggregation; Recombinant Proteins; Renal Dialysis; Ristocetin

Topics: Adenosine Diphosphate; Bleeding Time; Blood Platelet Disorders; Blood Platelets; Blood Specimen Collection; Collagen; Diagnostic Errors; Electric Conductivity; Epinephrine; Humans; Platelet Aggregation; Platelet Count; Platelet Function Tests; Ristocetin

A case is reported of a 49-year-old woman with a mild bleeding tendency. Her bleeding time, platelet count and size, plasma ristocetin cofactor activity, von Willebrand factor (vWF) antigen, and vWF multimeric pattern are all within normal limits. Spontaneous platelet aggregation is observed when citrated platelet-rich plasma (PRP) is stirred in an aggregometer cuvette. This aggregation is completely is only slightly diminished by an antiglycoprotein (GP) IIb/IIIa or by an anti GPIb monoclonal antibody. The patient's PRP shows increased sensitivity to ristocetin. The distinct feature of this patient, also present in two family members studied, is that platelet aggregation is initiated by purified vWF in the absence of any other agonist. The vWF-induced platelet aggregation is abolished by anti-GPIb and anti-GPIIb/IIIa monoclonal antibodies and by EDTA (5 mmol/L). Apyrase inhibits the second wave of aggregation. Patient's platelets in PRP are four to six times more reactive to asialo vWF-induced platelet aggregation than normal platelets. The amount of radiolabeled vWF bound to platelets in the presence of either low concentration of ristocetin or asialo vWF was increased 30% compared with normal. The patient's platelet GPIb was analyzed by SDS page and immunoblotting and by binding studies with anti-GPIb monoclonal antibodies showed one band with slightly increased migration pattern and a normal number of GPIb molecules. Unlike the previously reported patients with pseudo or platelet-type von Willebrand disease, this patient has normal vWF parameters.

Topics: Antibodies, Monoclonal; Blood Platelet Disorders; Blood Platelets; Female; Humans; Macromolecular Substances; Middle Aged; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin; von Willebrand Factor

Thirty-four cases of inherited bleeding disorders are reported. All are Saudi patients from the Eastern Province of Saudi Arabia. There were 15 haemophiliacs, 1 factor VII deficiency, 1 factor X deficiency, 12 Glanzmann's thrombasthenia, and 5 unidentified platelet function disorders. Consanguinity was common among the families of these patients. Different age groups were affected and the severity of bleeding varied in the different conditions reported.

Topics: Adenosine Diphosphate; Adolescent; Adult; Arachidonic Acid; Arachidonic Acids; Blood Coagulation Disorders; Blood Platelet Disorders; Child; Child, Preschool; Collagen; Consanguinity; Epinephrine; Female; Humans; Infant; Male; Platelet Aggregation; Ristocetin; Saudi Arabia

We examined platelet aggregation in platelet-rich plasma (PRP) and in whole blood from two patients with Glanzmann's thrombasthenia. In PRP, aggregation was measured by monitoring the changes in light absorbance that occurred in response to aggregating agents; to measure platelet aggregation in whole blood, we used a platelet counting technique. In PRP, the patients' platelets showed defective aggregation in response to ADP, adrenaline, arachidonic acid (AA), and collagen, but normal agglutination occurred in response to ristocetin. In whole blood, however, platelet aggregation in response to the aggregating agents appeared to be either very similar to that which occurred in blood from normal subjects or only slightly reduced. There was a reduced response to all concentrations of ADP and to low concentrations of collagen but a normal response to all concentrations of adrenaline, AA, and higher concentrations of collagen. Conversely, there seemed to be an increased agglutination response to ristocetin. The abnormality in our two patients with Glanzmann's thrombasthenia probably lies in the inability of their platelets to form large, macroscopic aggregates rather than in platelet aggregation per se.

Topics: Adenosine Diphosphate; Arachidonic Acid; Arachidonic Acids; Blood Platelet Disorders; Collagen; Epinephrine; Humans; In Vitro Techniques; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin; Thrombasthenia

The Bernard-Soulier syndrome is an inherited bleeding disorder that is due to a deficiency in platelet glycoprotein Ib. Bernard-Soulier platelets fail to agglutinate in response to ristocetin despite normal levels of factor VIII:von Willebrand factor. We report a patient who developed severe refractory thrombocytopenia postsurgically while receiving procainamide therapy. Thrombocytopenia was immune mediated since the patient's platelets bore high levels of antiplatelet antibody. Radioimmunoprecipitation studies demonstrated that the autoantibodies had specificity for platelet glycoproteins Ib and V as well as platelet HLA. The patient's plasma as well as purified immunoglobulin G completely inhibited the ristocetin-induced aggregation of normal platelets but did not inhibit adenosine diphosphate-induced aggregation. The laboratory studies revealed that this patient suffered from antibody-mediated thrombocytopenia with unusual characteristics that we have called pseudo-Bernard-Soulier syndrome.

Topics: Aged; Antilymphocyte Serum; Autoantibodies; Bernard-Soulier Syndrome; Blood Platelet Disorders; Female; Humans; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin; Thrombocytopenia

Tissue plasminogen activator (TPA) converts plasminogen to plasmin within the fibrin clot, thus localizing activation of fibrinolysis. To determine the extent to which platelets promote activation of plasminogen by TPA, we studied the interaction of TPA and plasminogen with unstimulated platelets. Normal washed platelets incubated in the presence of physiologic concentrations of plasminogen (180 micrograms/mL) and TPA (20 ng/mL) failed to generate plasmin activity. In contrast, incubation of platelets with TPA concentrations achieved during thrombolytic therapy (40 to 800 ng/mL) produced a tenfold to 50-fold increase in plasmin activity. After exposure to plasminogen and 200 ng/mL of TPA for one hour, platelets failed to agglutinate in the presence of ristocetin. Incubation of platelets suspended in autologous plasma with 400 ng/mL of TPA for one hour also inhibited ristocetin-induced agglutination. Exposure of platelets to plasminogen and increasing concentrations of TPA correlated with a decrease in glycoprotein Ib (GPIb) and an increase in glycocalicin, as shown by immunoblotting. The glycoprotein IIb/IIIa (GPIIb/IIIa) complex and a 250,000-dalton protein also disappeared from washed platelets after incubation with plasminogen and 200 ng/mL of TPA for one hour. These platelets failed to aggregate in the presence of adenosine diphosphate (ADP) or gamma thrombin, although aggregation in response to calcium ionophore A23187 and arachidonic acid remained intact. However, aggregation in response to all four agonists was normal when platelets were incubated with TPA in the presence of autologous plasma. Platelets from a patient with Glanzmann's thrombasthenia also generated plasmin in the presence of TPA. Hydrolysis of GPIb and inhibition of ristocetin-induced agglutination occurred to a lesser extent with these platelets than with control platelets. We conclude that platelets provide a surface for activation of plasminogen by pharmacologic amounts of TPA. Plasmin generation leads to degradation of GPIb and decreased ristocetin-induced agglutination in normal and thrombasthenic platelets, as well as degradation of GPIIb/IIIa in normal washed platelets and inhibition of ADP and gamma thrombin-induced aggregation. These findings suggest that pharmacologic concentrations of TPA may cause platelet dysfunction due to plasmin generation on the platelet surface.

Topics: Adenosine Diphosphate; Blood Platelet Disorders; Blood Platelets; Glycoproteins; Humans; In Vitro Techniques; Membrane Proteins; Plasminogen; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin; Thrombasthenia; Tissue Plasminogen Activator

Topics: Agglutination; Animals; Blood Platelet Disorders; Blood Platelets; Glycoproteins; Membrane Proteins; Mice; Platelet Membrane Glycoproteins; Ristocetin; Thrombasthenia

We studied the degree of Ristocetin-induced platelet agglutination in 4 Chinese patients with Glanzmann's thrombasthenia. At Ristocetin concentrations of 1.2-2.0 mg/ml (final concentration) variable, abnormal responses were observed. The most notable feature in 3 of 4 patients studied was the phenomenon of dose dependent, cyclic platelet agglutination-disagglutination. However, this phenomenon could be reproduced in only one of the 2 patients who were investigated on 2 separate occasions. Variable, but often characteristic responses of thrombasthenic platelets to different concentrations of Ristocetin are a useful additional diagnostic marker for this disease.

Topics: Blood Platelet Disorders; Female; Hong Kong; Humans; Infant; Infant, Newborn; Male; Platelet Aggregation; Ristocetin

Platelet size on blood smear is compared with platelet size and shape in suspension (i.e., whole blood and citrated platelet-rich plasma [PRP]) for normal donors and 16 patients with hereditary "giant" platelet syndromes (HGPS), including Bernard-Soulier syndrome (BSS) (seven patients), Montreal platelet syndrome (MPS) (three patients), May-Hegglin anomaly (one patient) and Rafael platelet defect (one patient). In whole blood platelet shape is normal for HGPS, but in PRP for 10 of 16 patients with HGPS there is a decrease in the proportion of smooth, discoid-shaped platelets (discocytes [D]). The platelets of all patients with HGPS had abnormally large mean volume (VT) and increased size on peripheral blood smear. Furthermore, 12 of 16 patients with HGPS, including six of seven donors with BSS, had abnormally large discocytes. The measured size of HGPS shape-changed platelets was compared with the size predicted from the size of the D by assuming that the relationship between the size of shape-changed platelets and D was the same as observed for normal donors. In this manner it was shown that for all donors with BSS and MPS, the shape-changed platelets are disproportionately larger than the D. In contrast, in the remaining patients with HGPS the size of the shape-changed platelets was consistent with the size predicted from the D. Examination of VT for MPS as a function of time after addition of 10 mumol/L adenosine diphosphate to PRP revealed an abnormal time course, thereby pointing to an abnormality in the mechanisms that regulate platelet size during shape change. With the lone exceptions of BSS and MPS, the size of platelets on blood smear was well correlated with the total platelet plasma membrane surface area as measured by the osmotic spherocyte method. Our observations point to two distinct abnormalities in platelet size in HGPS: a disproportion between the size of D and "shape-changed" platelets, which may be related to an abnormal shape change and which is observed only for MPS and BSS, and an abnormal increase in platelet size on blood smear, which appears to reflect the increased amount of platelet plasma membrane in other HGPS platelets.

Topics: Adenosine Diphosphate; Adolescent; Blood Platelet Disorders; Blood Platelets; Blood Specimen Collection; Collagen; Epinephrine; Female; Humans; Male; Mathematics; Middle Aged; Pedigree; Platelet Aggregation; Ristocetin; Time Factors

Platelet-type von Willebrand's disease is a recently described disorder of primary hemostasis, possessing attributes both of von Willebrand's disease and of a qualitative platelet abnormality. This article discusses the clinical features, laboratory aspects, pathophysiology, and treatment of platelet-type von Willebrand's disease.

Topics: Blood Coagulation Tests; Blood Platelet Disorders; Cell Membrane; Dose-Response Relationship, Drug; Factor VIII; Humans; Platelet Aggregation; Platelet Function Tests; Ristocetin; von Willebrand Diseases; von Willebrand Factor

Topics: Adenosine Triphosphate; Blood Platelet Disorders; Blood Platelets; Cell Separation; Hematologic Tests; Platelet Aggregation; Ristocetin

Bernard-Soulier's syndrome (BSS) is a familial hemorrhagic disease that is not very common, but its hemostatic defects have not been explained satisfactorily. In this paper the authors comments on the lack of Ib and Is glycoproteins in the platelet membrane, which is the basic characteristic of platelets with BSS. These proteins contain large amounts of sialic acid and have been identified as the absent membrane marker in said patients. The role played by these alterations in the BSS platelets leads us to suppose that there are no other structural and functional defects in such platelets, other than those related to the absence of membrane marker mentioned. From the above, a discussion follows on the similarity of BSS with von Willebrand's disease and it is concluded that the BSS is due to a scarce molecular concentration of Ib and Is glycoproteins in the platelet membrane and not to a functional defect of such molecules. The case described in this paper is the first one to be published in this country and was studied using the most useful and recommendable tests known at present, to this end.

Topics: Adult; Blood Coagulation Tests; Blood Platelet Disorders; Blood Platelets; Cell Membrane; Female; Glycoproteins; Humans; Membrane Proteins; Microscopy, Electron; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin

We have studied the binding of Factor VIII/Willebrand factor (FVIII/WF) to the platelets of ten normal donors, five patients with Bernard-Soulier syndrome (BSS), three clinically normal patients heterozygous for BSS (BSS hetero), and three with Glanzmann's thrombasthenia (GT). The amount of 125I-FVIII/WF bound to the platelets was measured in the presence or absence of ristocetin, the results expressed as percentage of total radioactivity added. The time course of 125I-FVIII/WF showed that maximum binding to the platelets was observed at 30 min, and then a plateau was reached. The binding was ristocetin-dependent and was relative to the concentration of ristocetin added. At a final concentration of 0.5 mg/ml of ristocetin, specific binding to the normal platelets was 30.9 +/- 2.5 %; at 1.0 mg/Ml, specific binding was 34.7 +/- 3.2% in the normal donors. In the five BSS patients lacking platelet membrane Glycoprotein 1 (GPI), reduced binding of 125I-FVII/WF was observed. At a final concentration of 1 mg/ml of ristocetin, the mean value of the binding was 13.7 % (11.5 % -14.8 %); at a final concentration of 0.5 mg/ml of ristocetin, the mean value decreased to 5.6 % (2.9 %-7.2 %). In the three BSS hetero patients, binding was near normal, although there were reduced amounts of platelet membrane GPI. Binding was slightly decreased in the three thrombasthenic patients lacking GP IIb/IIIa.

Topics: Binding Sites; Blood Coagulation Factors; Blood Platelet Disorders; Blood Platelets; Factor VIII; Humans; Ristocetin; Syndrome; von Willebrand Factor

10 cases of pernicious anaemia are reported in which 6 had abnormal aggregation with epinephrine, 3 with fibrinogen, 2 with ADP, and 2 with ristocetin. 5 patients had thrombocytopenia and 3 of these had a prolongation of the bleeding time. These abnormalities were normalized after vitamin B12 treatment. After treatment, platelet size changed toward a smaller diameter, but platelet size, however, was not significantly different from the normal platelet size distribution.

Topics: Adenosine Diphosphate; Aged; Anemia, Pernicious; Blood Cell Count; Blood Coagulation Tests; Blood Platelet Disorders; Collagen; Epinephrine; Female; Fibrinogen; Hemoglobins; Humans; Male; Middle Aged; Platelet Aggregation; Ristocetin; Thrombocytopenia; Vitamin B 12

Platelets from a patient with eosinophilic leukaemia were not aggregated by ristocetin. The defect was not corrected by normal human plasma and was due to a platelet abnormality. The patient's platelets also showed a diminished sensitivity to aggregation by bovine factor VIIIVWF. The defect was not associated with a prolonged bleeding time. No abnormalities were detected in ADP, collagen or thrombin-induced platelet aggregation. Biochemical studies showed that the platelets were deficient in sialic acid. This deficiency was associated with a reduced staining for glycoprotein I following SDS-polyacrylamide gel electrophoresis. The results suggest an acquired platelet surface abnormality.

Topics: Adenosine Diphosphate; Blood Platelet Disorders; Blood Platelets; Blood Proteins; Collagen; Electrophoresis, Polyacrylamide Gel; Eosinophils; Factor VIII; Glycoproteins; Hemostasis; Humans; Leukemia; Male; Middle Aged; Platelet Aggregation; Ristocetin; Sialic Acids; Thrombin

Topics: Adenosine Triphosphate; Adolescent; Adult; Blood Coagulation; Blood Platelet Disorders; Child; Child, Preschool; Female; Humans; Male; Middle Aged; Ristocetin

In four patients, platelet aggregation with arachidonate was absent but was normal with "Labile Aggregation Stimulating Substance". ADP (10muM) aggregation was always reversible; collagen aggregation was absent and those induced by thrombin and ristocetin were normal. Collagen did not induce 14C-serotonin release but there was some release with thrombin. There was no thromboxan B2 synthesis in these platelets. Two patients showed hereditary hemostasis defect and the others acquired cyclo-oxygenase deficiency.

Topics: Adenosine Diphosphate; Adult; Arachidonic Acids; Blood Platelet Disorders; Blood Platelets; Collagen; Cytoplasmic Granules; Female; Humans; Lipoxygenase; Microsomes; Peroxides; Platelet Aggregation; Prostaglandins; Ristocetin; Thrombin

Two patients are described with chronic hypoglycaemia; the first having glucose-6-phosphatase deficiency (type I glycogen storage disease), and the second fructose 1:6-diphosphatase deficiency. Both cases were associated with a bleeding diathesis, a defect of platelet aggregation, and a deficiency of platelet adenine nucleotides. The effect on the platelet abnormalities of a period of normoglycaemia was studied in both patients. Correction of the platelet abnormalities occurred rapidly after stabilization of the blood glucose within the normal range. Normal function persisted for the duration of the normoglycaemia, facilitating diagnostic liver biopsy and surgical procedures. A biochemical explanation for the nucleotide deficiency is suggested.

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Triphosphate; Blood Platelet Disorders; Child; Collagen; Epinephrine; Female; Glucose; Humans; Hypoglycemia; Infant; Platelet Aggregation; Ristocetin

Nine probands with von Willebrand's disease, and their family members, totalling 43 people, were examined. Twenty-seven had a history of bleeding; 29 had an increased factor VIII activity:factor VIII related antigen ratio; 24 had a decreased factor VIII related antigen; 23 had a prolonged bleeding time; 19 had a reduced platelet adhesiveness; 16 had a decreased factor VIII activity; and 14 had an abnormal ristocetin-induced platelet aggregation. Eight members with both normal beleeding time and normal factor VIII activity were found to have other abnormal tests: elevated ratio of factor VIII activity to factor VIII related antigen in seven; decreased factor VIII related antigen in four; and reduced platelet adhesiveness in one. Therefore, ratio of factor VIII activity to factor VIII related antigen and factor VIII related antigen are more sensitive and may be used for the detection of heterozygous carriers of von Willebrand's disease. Although patients with thrombocytopathy may have a prolonged bleeding time, decreased platelet adhesiveness and reduced platelet aggregation by ristocetin, their factor VIII activity, factor VIII related antigen and ratio of factor VIII activity to factor VIII related antigen are normal and their abnormal ristocetin test cannot be corrected by the addition of factor VIII concentrate. Hemophilic subjects and hemophilic carriers, who are deficient in factor VIII activity, usually have a normal bleeding time, normal platelet adhesiveness, and normal ristocetin test. In contrast to patients with von Willebrand's disease, their factor VIII related antigen is normal or slightly increased and their ratio of factor VIII activity to factor VIII related antigen is significantly reduced. We conclude that ratio of factor VIII activity to factor VIII related antigen and factor VIII related antigen are not only more sensitive but also more specific for the diagnosis of von Willebrand's disease.

Topics: Antigens; Blood Coagulation Tests; Blood Platelet Disorders; Diagnosis, Differential; Factor VIII; Female; Hemophilia A; Heterozygote; Humans; Male; Pedigree; Platelet Adhesiveness; Platelet Aggregation; Ristocetin; von Willebrand Diseases

The authors report a case of chronic eosinophilic leukemia. Ristocetin did not aggregate patient's platelets in the absence of bleeding disorder. A possible relationship between arterial thrombosis observed in patients with eosinophilic leukemia and platelet abnormality is evoked.

Topics: Arteries; Blood Platelet Disorders; Cytoplasmic Granules; Diagnosis, Differential; Eosinophils; Hematopoiesis; Heparin Antagonists; Humans; Male; Middle Aged; Myeloproliferative Disorders; Platelet Adhesiveness; Platelet Aggregation; Ristocetin; Thrombosis; von Willebrand Diseases

A constitutional platelet function disorder in a twelve year-old girl characterized by a lifelong bleeding tendency, prolonged bleeding time, normal platelet count, normal clot retraction, normal platelet factor 3 activity and impaired platelet aggregation was reported. Platelet aggregation, studied turbidimetrically, was absent in the presence of usual doses of ADP (1-4 MUM) although a small wave of primary aggregation was obtained by very large ADP concentrations (25-50 muM). The platelets were also unresponsive to epinephrine, thrombin and diluted collagen suspensions. But an almost normal aggregation response occurred with strong collagen suspensions. The platelets responded to Ristocetin. Release of platelet ADP was found to be normal by collagen and thrombin, but impaired by kaolin. Platelet fibrinogen content was normal. The present case, investigated with recent methods, confirms the existence of a type of primary functional platelet disorder characterized solely by an aggregation defect, described in 1955 and 1962 under the name of "essential athrombia."

Topics: Adenosine Diphosphate; Blood Cell Count; Blood Platelet Disorders; Blood Platelets; Child; Clot Retraction; Epinephrine; Female; Humans; Nephelometry and Turbidimetry; Platelet Aggregation; Ristocetin; Thrombin; Thromboplastin

With thrombasthenic platelets, aggregation induced by ristocetin (R) and bovine fibrinogen (BF) is reversible, provided ATP is not added to the system. ADP inhibits BF and R induced aggregation, and when added after the onset of aggregation causes rapid disaggregation. ATP prevents these inhibitory and disaggregation effects of ADP. A mechanism is suggested whereby co-operative effects occur between receptors in the membranes of thrombasthenic platelets.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Blood Platelet Disorders; Cattle; Fibrinogen; Humans; Platelet Aggregation; Ristocetin

Topics: Blood Coagulation Tests; Blood Platelet Disorders; Consanguinity; Factor VII; Female; Genes, Recessive; Heterozygote; Homozygote; Humans; Immunoassay; Male; Pedigree; Ristocetin; von Willebrand Diseases

The antibiotic ristocetin, in concentrations of 1.0-1.5 mg/ml, aggregated normal platelets in citrated platelet-rich plasma by a mechanism in which the release reaction played only a minor role. Platelet aggregation by ristocetin in a concentration of 1.2 mg/ml was absent or markedly decreased in 10 patients with von Willebrand's disease. Lesser degrees of abnormality were obtained with a concentration of 1.5 mg/ml. The magnitude of the defect in ristocetin-induced platelet aggregation correlated well with the degree of abnormality of the bleeding time and the levels of antihemophilic factor (AHF, VIII(AHF)) procoagulant activity. In all patients, the defect in ristocetin-induced platelet aggregation was corrected in vitro by normal plasma. Correction was also obtained with a fraction of normal cryoprecipitate that eluted in the void volume with VIII(AHF) after chromatography on a gel that excludes molecules larger than 5 x 10(6). A similar fraction, devoid of VIII(AHF) activity, obtained from patients with von Willebrand's disease had no corrective effect, but fractions obtained from patients with hemophilia were just as effective as those obtained from normal subjects. The correction activity of plasma and partially purified factor VIII was inhibited by a rabbit antibody to human factor VIII but not by a human antibody against VIII(AHF) procoagulant activity. The studies provide further evidence that patients with von Willebrand's disease are deficient in a plasma factor that is necessary for normal platelet function. The activity of this factor appears to be associated with factor VIII but is unrelated to VIII(AHF) procoagulant activity.

Topics: Adenosine; Adenosine Diphosphate; Antibodies; Blood Coagulation Tests; Blood Platelet Disorders; Blood Platelets; Carbon Radioisotopes; Chromatography; Collagen; Cyanides; Edetic Acid; Factor VIII; Female; Glucose; Hemophilia A; Heparin; Humans; In Vitro Techniques; Male; Platelet Adhesiveness; Purpura, Thrombocytopenic; Ristocetin; Serotonin; von Willebrand Diseases

The platelets of three patients with the hereditary giant platelet syndrome of Bernard and Soulier failed to aggregate in response to either ristocetin or bovine fibrinogen. The results of aggregation experiments using mixtures of platelets and plasma suggest that a reaction between a plasma factor deficient in von Willebrand's disease and a platelet component lacking in our patients, and leading to platelet aggregation independently of adenosine diphosphate (ADP), is essential for normal haemostasis.

Topics: Adenosine Diphosphate; Adolescent; Blood Platelet Disorders; Child; Collagen; Female; Fibrinogen; Hemorrhage; Humans; Plasma; Platelet Adhesiveness; Prothrombin; Purpura, Thrombocytopenic; Ristocetin; Syndrome; Thrombin; von Willebrand Diseases

Topics: Blood Coagulation; Blood Platelet Disorders; Blood Platelets; Factor VIII; Hemorrhage; Humans; Platelet Adhesiveness; Purpura, Thrombocytopenic; Ristocetin; von Willebrand Diseases

Topics: Acute Disease; Adenosine Diphosphate; Blood Cell Count; Blood Coagulation Factors; Blood Coagulation Tests; Blood Platelet Disorders; Blood Platelets; Cell Survival; Epinephrine; Humans; Leukemia; Leukemia, Lymphoid; Leukemia, Myeloid, Acute; Phospholipids; Platelet Adhesiveness; Remission, Spontaneous; Ristocetin; Thrombocytopenia

Topics: Afibrinogenemia; Blood Platelet Disorders; Female; Fibrinogen; Humans; Male; Platelet Adhesiveness; Ristocetin; von Willebrand Diseases