thromboplastin and Thrombocytopenia

Malaria remains a highly prevalent disease in more than 90 countries and accounts for at least 1 million deaths every year. Plasmodium falciparum infection is often associated with a procoagulant tonus characterized by thrombocytopenia and activation of the coagulation cascade and fibrinolytic system; however, bleeding and hemorrhage are uncommon events, suggesting that a compensated state of blood coagulation activation occurs in malaria. This article (i) reviews the literature related to blood coagulation and malaria in a historic perspective, (ii) describes basic mechanisms of coagulation, anticoagulation, and fibrinolysis, (iii) explains the laboratory changes in acute and compensated disseminated intravascular coagulation (DIC), (iv) discusses the implications of tissue factor (TF) expression in the endothelium of P. falciparum infected patients, and (v) emphasizes the procoagulant role of parasitized red blood cells (RBCs) and activated platelets in the pathogenesis of malaria. This article also presents the Tissue Factor Model (TFM) for malaria pathogenesis, which places TF as the interface between sequestration, endothelial cell (EC) activation, blood coagulation disorder, and inflammation often associated with the disease. The relevance of the coagulation-inflammation cycle for the multiorgan dysfunction and coma is discussed in the context of malaria pathogenesis.

Topics: Animals; Blood Platelets; Coma; Disseminated Intravascular Coagulation; Endothelium, Vascular; Erythrocytes; Fibrinolysis; Humans; Inflammation; Malaria, Falciparum; Plasmodium falciparum; Platelet Activation; Thrombocytopenia; Thromboplastin

Antiphospholipid antibodies are autoantibodies that can be detected in plasma or serum with phospholipid-dependent coagulation tests or solid-phase immunoassays. The presence of these autoantibodies is strongly associated with an increased risk for arterial and venous thrombosis, recurrent fetal loss and thrombocytopenia. This paradoxical association of the in vitro prolongation of clotting assays and in vivo thrombosis has stimulated the search for the real antigen to which the autoantibodies are directed. A large number of potential pathological mechanisms have been proposed, and although disturbance of a certain metabolic pathway by the antibodies can explain a thrombotic tendency in one patient, no general pathological mechanism explaining thrombosis in the whole patient population has been found. This suggests that the antiphospholipid antibodies are a heterogeneous group of autoantibodies and is supported by the recent observations that antiphospholipid antibodies are not directed against phospholipids alone but against a combination of phospholipids and phospholipid-binding proteins. Both the phospholipid and the protein are part of the antigen. For the detection of antiphospholipids in an ELISA set-up, beta 2-glycoprotein I is the protein cofactor. In the coagulation tests, beta 2-glycoprotein, as well as prothrombin, can act as cofactor. However, the presence of these two proteins as a part of the epitope of the antiphospholipid antibodies does not explain the thrombotic tendency in the patient group. We have found that more physiologically relevant cofactors such as protein C and protein S, for which it is known that a partial deficiency is correlated with a thrombotic tendency, can also act as cofactors for the binding of antiphospholipid antibodies. It is concluded that antiphospholipid antibodies are a heterogeneous group of autoantibodies with varying affinity for different protein-phospholipid complexes and that inhibition of the biological activity of the protein part of the complex determines the pathological capacity of the antibodies.

Topics: Abortion, Habitual; Antibodies, Antiphospholipid; Antibody Specificity; Antiphospholipid Syndrome; beta 2-Glycoprotein I; Endothelium, Vascular; Epoprostenol; Female; Glycoproteins; Humans; Lupus Coagulation Inhibitor; Monocytes; Phospholipids; Platelet Aggregation; Pregnancy; Protein C; Thrombocytopenia; Thromboembolism; Thrombomodulin; Thromboplastin; von Willebrand Factor

Topics: Afibrinogenemia; Anti-Infective Agents; Antigens; Blood Coagulation Disorders; Blood Coagulation Tests; Disseminated Intravascular Coagulation; Factor V; Factor VIII; Fibrin; Fibrinogen; Fibrinolysin; Fibrinolysis; Hemagglutination Inhibition Tests; Heparin; Humans; Prothrombin Time; Radioimmunoassay; Thrombin; Thrombocytopenia; Thromboplastin

Topics: Adenine Nucleotides; Aging; Anemia, Hemolytic; Animals; Blood Coagulation; Endotoxins; Erythrocytes, Abnormal; Fibrinogen; Hemolysis; Humans; Models, Biological; Platelet Adhesiveness; Purpura, Thrombotic Thrombocytopenic; Rabbits; Thrombin; Thrombocytopenia; Thromboplastin; Venoms

Topics: Adult; Blood Coagulation Disorders; Blood Coagulation Factors; Blood Coagulation Tests; Blood Flow Velocity; Child; Child, Preschool; Clinical Laboratory Techniques; Dextrans; Female; Fibrinolytic Agents; Glomerulonephritis; Hemangioma, Cavernous; Heparin; Humans; Infections; Liver Cirrhosis; Male; Mycoses; Parasitic Diseases; Pregnancy; Pregnancy Complications; Purpura; Shock; Thrombocytopenia; Thromboplastin; Uremia

Topics: Blood Coagulation Disorders; Blood Coagulation Factors; Blood Platelets; Cell Membrane Permeability; Fibrinogen; Fibrinolysis; Hemorrhagic Disorders; Humans; Leukemia, Myeloid; Leukemia, Myeloid, Acute; Thrombocythemia, Essential; Thrombocytopenia; Thromboplastin

Heparin-induced thrombocytopenia (HIT) is a potentially devastating form of drug-induced thrombocytopenia that occurs in patients receiving heparin for prevention or treatment of thrombosis. Patients with HIT develop autoantibodies to the platelet factor 4 (PF4)/heparin complex, which is termed the HIT Ab complex. Despite a decrease in the platelet count, the most feared complication of HIT is thrombosis. The mechanism of thrombosis in HIT remains poorly understood. We investigated the effects of the HIT Ab complex on tissue factor (TF) expression and release of TF-positive microparticles in peripheral blood mononuclear cells and monocytes. To model these effects ex vivo, we used a murine mAb specific for the PF4/heparin complex (KKO), as well as plasma from patients with HIT. We found that the HIT Ab complex induced TF expression in monocytes and the release of TF-positive microparticles. Further, we found that induction of TF is mediated via engagement of the FcγRI receptor and activation of the MEK1-ERK1/2 signaling pathway. Our data suggest that monocyte TF may contribute to the development of thrombosis in patients with HIT.

Topics: Anticoagulants; Autoantibodies; Cell-Derived Microparticles; Extracellular Signal-Regulated MAP Kinases; Female; Gene Expression Regulation; Heparin; Humans; Male; MAP Kinase Signaling System; Monocytes; Platelet Factor 4; Receptors, IgG; Thrombocytopenia; Thromboplastin; Thrombosis

Acute promyelocytic leukemia (APL) is associated with a high risk of bleeding and thrombosis. APL patients have an activated coagulation system, hyperfibrinolysis, and thrombocytopenia. APL cells express tissue factor (TF), a receptor and cofactor for factor VII/VIIa. This study had 2 goals. Firstly, we measured biomarkers of coagulation and fibrinolysis activation as well as platelet counts and bleeding in both mouse xenograft and allograft models of APL. Secondly, we determined the effect of inhibiting TF on the activation of coagulation in these models. We observed increased levels of plasma thrombin-antithrombin complexes (TAT), D-dimer, and plasmin-antiplasmin complexes, reduced platelet counts, and increased tail bleeding in both mouse models of APL. Fibrinogen levels decreased in the xenograft model but not in the allograft model. In contrast, the red blood cell count decreased in the allograft model but not in the xenograft model. Inhibition of APL-derived human TF with an anti-human TF monoclonal antibody reduced the level of TAT, increased platelet count, and normalized tail bleeding in a xenograft model. Inhibition of all sources of TF (APL cells and host cells) in the allograft model with a rat anti-mouse TF monoclonal antibody decreased the levels of TAT but did not affect the platelet count. Our study demonstrates that TF plays a central role in the activation of coagulation in both the xenograft and allograft mouse models of APL. These APL mouse models can be used to investigate the mechanisms of coagulopathy and thrombocytopenia in APL.

Topics: Animals; Antibodies, Monoclonal; Blood Coagulation; Blood Coagulation Disorders; Hemorrhage; Humans; Leukemia, Promyelocytic, Acute; Rats; Thrombocytopenia; Thromboplastin

Thromboembolism complicates disorders caused by immunoglobulin G (IgG)-containing immune complexes (ICs), but the underlying mechanisms are incompletely understood. Prior evidence indicates that induction of tissue factor (TF) on monocytes, a pivotal step in the initiation, localization, and propagation of coagulation by ICs, is mediated through Fcγ receptor IIa (FcγRIIa); however, the involvement of other receptors has not been investigated in detail. The neonatal Fc receptor (FcRn) that mediates IgG and albumin recycling also participates in cellular responses to IgG-containing ICs. Here we asked whether FcRn is also involved in the induction of TF-dependent factor Xa (FXa) activity by IgG-containing ICs by THP-1 monocytic cells and human monocytes. Induction of FXa activity by ICs containing IgG antibodies to platelet factor 4 (PF4) involved in heparin-induced thrombocytopenia (HIT), β-2-glycoprotein-1 implicated in antiphospholipid syndrome, or red blood cells coated with anti-(α)-Rh(D) antibodies that mediate hemolysis in vivo was inhibited by a humanized monoclonal antibody (mAb) that blocks IgG binding to human FcRn. IgG-containing ICs that bind to FcγR and FcRn induced FXa activity, whereas IgG-containing ICs with an Fc engineered to be unable to engage FcRn did not. Infusion of an α-FcRn mAb prevented fibrin deposition after microvascular injury in a murine model of HIT in which human FcγRIIa was expressed as a transgene. These data implicate FcRn in TF-dependent FXa activity induced by soluble and cell-associated IgG-containing ICs. Antibodies to FcRn, now in clinical trials in warm autoimmune hemolytic anemia to lower IgG antibodies and IgG containing ICs may also reduce the risk of venous thromboembolism.

Topics: Animals; Antibodies, Monoclonal, Humanized; Anticoagulants; Antigen-Antibody Complex; Heparin; Histocompatibility Antigens Class I; Humans; Immunoglobulin G; Male; Mice; Monocytes; Platelet Factor 4; Receptors, Fc; Thrombocytopenia; Thromboplastin

Though the presence of platelets-derived microparticles (MPs) have previously been described in heparin-induced thrombocytopenia (HIT), the mechanism of thrombosis in HIT remains poorly understood. We aimed to assess the presence and origin of MPs in patients with HIT and their possible contribution to HIT with thrombosis (HITT).. Forty-five patients with HIT and 45 matched hospitalized patients with not confirmed HIT (HIT-negative) were enrolled. Twelve HIT patients (27%) developed HITT. MPs expressing phosphatidylserine (Annexin V-MP), activated platelet-derived (P-Selectin+), activated leukocyte-derived (L-Selectin+), PF4-bearing and tissue factor-bearing (TF+) MPs were measured by flow-cytometry.. HIT patients showed significantly higher median levels of P-Selectin+, L-Selectin+, PF4-bearing, L-Selectin+/TF + MPs than HIT-negative; PF4-bearing MP showed the highest statistical difference. As compared to HIT patients, HITT patients showed a trend of higher median levels of all MP subtypes considered but the differences were not statistically significant. Only levels of activated-leukocyte/TF + MPs (L-Selectin + CD142+) were significantly higher (P = 0.015). Sensitive analyses showed that HIT patients with activated-leukocyte/TF + MPs above the cut-off (52 MP/µL) had an odds ratio (OR) for thrombosis of 3.78 (95%CI, 0.98-14.5, P = 0.045). The combination of activated-leukocyte/TF + MPs and PF4-bearing-MPs above the cut-off (1416 MP/uL) resulted in a higher risk of HITT (OR 4.49 (95% CI, 1.17-8.05, P = 0.014).. We showed for the first time the presence of circulating PF4-bearing MPs derived from activated platelets in patients with HIT; activated leukocyte/TF + MPs are associated with an increased thrombotic risk. Our findings confirm that HIT antibodies complexes may determine a TF-driven prothrombotic state through the activation of platelets and leukocytes. © 2017 International Clinical Cytometry Society.

Topics: Adult; Aged; Blood Coagulation; Blood Platelets; Cell-Derived Microparticles; Female; Flow Cytometry; Heparin; Humans; Leukocytes; Male; Middle Aged; Phosphatidylserines; Platelet Activation; Risk; Thrombocytopenia; Thromboplastin; Thrombosis

Platelet- and fibrin-dependent thrombus formation is regulated by blood flow and exposure of collagen and tissue factor. However, interactions between these blood-borne and vascular components are not well understood.. Here, we developed a method to assess whole-blood thrombus formation on microspots with defined amounts of collagen and tissue factor, allowing determination of the mechanical properties and intrathrombus composition. Confining the collagen content resulted in diminished platelet deposition and fibrin formation at high shear flow conditions, but this effect was compensated by a larger thrombus size and increased accumulation of fibrin in the luminal regions of the thrombi at the expense of the base regions. These thrombi were more dependent on tissue factor-triggered thrombin generation. Microforce nanoindentation analysis revealed a significantly increased microelasticity of thrombi with luminal-oriented fibrin. At a low shear rate, fibrin fibers tended to luminally cover the thrombi, again resulting in a higher microelasticity. Studies with blood from patients with distinct hemostatic insufficiencies indicated an impairment in the formation of a platelet-fibrin thrombus in the cases of dilutional coagulopathy, thrombocytopenia, Scott syndrome, and hemophilia B.. Taken together, our data indicate that (1) thrombin increases the platelet thrombus volume; (2) tissue factor drives the formation of fibrin outside of the platelet thrombus; (3) limitation of platelet adhesion redirects fibrin from bottom to top of the thrombus; (4) a lower shear rate promotes thrombus coverage with fibrin; (5) the fibrin distribution pattern determines thrombus microelasticity; and (6) the thrombus-forming process is reduced in patients with diverse hemostatic defects.

Topics: Blood Coagulation; Blood Coagulation Disorders; Blood Coagulation Tests; Blood Flow Velocity; Blood Platelets; Case-Control Studies; Collagen; Elasticity; Fibrin; Hemophilia B; Humans; Regional Blood Flow; Thrombocytopenia; Thromboplastin; Thrombosis; Time Factors

Bleeding tendency, coagulopathy and platelet disorders are recurrent manifestations in snakebites occurring worldwide. We reasoned that by damaging tissues and/or activating cells at the site of the bite and systemically, snake venom toxins might release or decrypt tissue factor (TF), resulting in activation of blood coagulation and aggravation of the bleeding tendency. Thus, we addressed (a) whether TF and protein disulfide isomerase (PDI), an oxireductase involved in TF encryption/decryption, were altered in experimental snake envenomation; (b) the involvement and significance of snake venom metalloproteinases (SVMP) and serine proteinases (SVSP) to hemostatic disturbances.. Crude Bothrops jararaca venom (BjV) was preincubated with Na2-EDTA or AEBSF, which are inhibitors of SVMP and SVSP, respectively, and injected subcutaneously or intravenously into rats to analyze the contribution of local lesion to the development of hemostatic disturbances. Samples of blood, lung and skin were collected and analyzed at 3 and 6 h. Platelet counts were markedly diminished in rats, and neither Na2-EDTA nor AEBSF could effectively abrogate this fall. However, Na2-EDTA markedly reduced plasma fibrinogen consumption and hemorrhage at the site of BjV inoculation. Na2-EDTA also abolished the marked elevation in TF levels in plasma at 3 and 6 h, by both administration routes. Moreover, increased TF activity was also noticed in lung and skin tissue samples at 6 h. However, factor VII levels did not decrease over time. PDI expression in skin was normal at 3 h, and downregulated at 6 h in all groups treated with BjV.. SVMP induce coagulopathy, hemorrhage and increased TF levels in plasma, but neither SVMP nor SVSP are directly involved in thrombocytopenia. High levels of TF in plasma and TF decryption occur during snake envenomation, like true disseminated intravascular coagulation syndrome, and might be implicated in engendering bleeding manifestations in severely-envenomed patients.

Topics: Animals; Blood Coagulation Disorders; Blood Coagulation Tests; Blood Platelets; Bothrops; Crotalid Venoms; Edetic Acid; Fibrinogen; Hemorrhage; Lung; Male; Metalloproteases; Prothrombin; Rats; Rats, Wistar; Serine Proteases; Serine Proteinase Inhibitors; Skin; Sulfones; Thrombocytopenia; Thromboplastin

Among circulating cell-derived microparticles, those derived from red cells (RMP) have been least well investigated. To exploit potential haemostatic benefit of RMP, we developed a method of producing them in quantity, and here report on their haemostatic properties. High-pressure extrusion of washed RBC was employed to generate RMP. RMP were identified and enumerated by flow cytometry. Their size distribution was assessed by Doppler electrophoretic light scattering analysis (DELSA). Interaction with platelets was studied by platelet aggregometry, and shear-dependent adhesion by Diamed IMPACT-R. Thrombin generation and tissue factor (TF) expression was also measured. The effect of RMP on blood samples of patients with bleeding disorders was investigated ex vivo by thromboelastography (TEG). Haemostatic efficacy in vivo was assessed by measuring reduction of blood loss and bleeding time in rats and rabbits. RMP have mean diameter of 0.45 µm and 50% of them exhibit annexin V binding, a proxy for procoagulant phospholipids (PL). No TF could be detected by flow cytometry. At saturating concentrations of MPs, RMP generated thrombin robustly but after longer delay compared to PMP and EMP. RMP enhanced platelet adhesion and aggregation induced by low-dose ADP or AA. In TEG study, RMP corrected or improved haemostatic defects in blood of patients with platelet and coagulation disorders. RMP reduced bleeding time and blood loss in thrombocytopenic rabbits (busulfan-treated) and in Plavix-treated rats. In conclusion, RMP has broad haemostatic activity, enhancing both primary (platelet) and secondary (coagulation) haemostasis, suggesting potential use as haemostatic agent for treatment of bleeding.

Topics: Adenosine Diphosphate; Animals; Bleeding Time; Blood Coagulation Disorders; Busulfan; Cell Separation; Cell-Derived Microparticles; Clopidogrel; Disease Models, Animal; Erythrocytes; Flow Cytometry; Hemostasis; Humans; Male; Platelet Aggregation; Rabbits; Rats; Rats, Sprague-Dawley; Thrombelastography; Thrombin; Thrombocytopenia; Thromboplastin; Ticlopidine

In systemic endotoxaemia, bacterial lipopolysaccharide causes the rapid expression of tissue factor (TF) and disseminated intravascular coagulation and in animal models, anticoagulants limit pathology and promote survival. Recent studies have emphasised the importance of TF expressed by mononuclear cells for initiating thrombin generation during endotoxaemia and suggested that endothelial cell TF is of little relevance. However, the precise importance of endothelium for intravascular thrombin generation has not been established. In this study, we compared the effect of equivalent levels of hirudin tethered to either endothelium or platelets and monocytes.. CD31-Hir-Tg mice express a vesicle-targeted, membrane-tethered hirudin fusion protein on endothelium, platelets and monocytes. Bone marrow chimeras between these mice and C57BL/6 were generated The level of intravascular hirudin expressed during endotoxaemia was quantified by inhibition studies using an anti-hirudin antibody and reference to the circulating thrombin anti-thrombin complexes generated in control mice given soluble hirudin.. Antibody inhibition studies indicated that individual chimeras expressed similar levels of hirudin fusion protein on endothelium alone as on platelets and leukocytes combined and accordingly, the levels of thrombin anti-thrombin complexes and fibrinogen in each chimera were similar, indicating equivalent inhibition of thrombin generation. However, mice with hirudin on endothelium alone developed significantly less thrombocytopenia. These results suggest a hitherto unrecognized role of endothelium in thrombin-dependent platelet sequestration during endotoxaemia. The data have implications for the development of therapeutic strategies based on targeted anticoagulation to limit disseminated intravascular coagulation.

Topics: Animals; Antibodies, Monoclonal; Blood Platelets; Endothelium; Endotoxemia; Hirudins; Humans; Immunohistochemistry; Lipopolysaccharides; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Monocytes; Recombinant Fusion Proteins; Swine; Thrombin; Thrombocytopenia; Thromboplastin; Transfection

Upregulation of tissue factor (TF) expression on activated donor endothelial cells (ECs) triggered by the immune response (IR) has been considered the main initiator of consumptive coagulopathy (CC). In this study, we aimed to identify potential factors in the development of thrombocytopenia and CC after genetically engineered pig liver transplantation in baboons. Baboons received a liver from either an α1,3-galactosyltransferase gene-knockout (GTKO) pig (n = 1) or a GTKO pig transgenic for CD46 (n = 5) with immunosuppressive therapy. TF exposure on recipient platelets and peripheral blood mononuclear cell (PBMCs), activation of donor ECs, platelet and EC microparticles, and the IR were monitored. Profound thrombocytopenia and thrombin formation occurred within minutes of liver reperfusion. Within 2 h, circulating platelets and PBMCs expressed functional TF, with evidence of aggregation in the graft. Porcine ECs were negative for expression of P- and E-selectin, CD106, and TF. The measurable IR was minimal, and the severity and rapidity of thrombocytopenia were not alleviated by prior manipulation of the IR. We suggest that the development of thrombocytopenia/CC may be associated with TF exposure on recipient platelets and PBMCs (but possibly not with activation of donor ECs). Recipient TF appears to initiate thrombocytopenia/CC by a mechanism that may be independent of the IR.

Topics: Animals; Animals, Genetically Modified; Cell-Derived Microparticles; Disseminated Intravascular Coagulation; Galactosyltransferases; Papio; Sus scrofa; Thrombocytopenia; Thromboplastin; Transplantation, Heterologous

Trypanosoma evansi infections in domestic animals are characterized by anemia and thrombocytopenia. The cause of the platelets decrease is unknown, but researchers suggest that thrombocytopenia may result from damage of the bone marrow, reduced survival of platelets, auto-immune thrombocytopenia, disseminated intravascular coagulation and splenic sequestration. Some of these causes have already been tested by our research group and found to be unrelated. Therefore, this study has the objective of testing the hypothesis that splenic sequestration might be responsible for thrombocytopenia in T. evansi-infected rats. A total of 28 rats assigned to four groups were used in the experiment. Group A rats were splenectomized and infected with T. evansi, group B rats were infected with T. evansi, group C rats were splenectomized, but not infected and group D rats were normal controls. Five days post-infection all rats were anesthetized and blood was collected in order to measure the number of circulating platelets, fibrinogen levels, prothrombin time (PT) and activated partial thromboplastin time (aPTT). The spleens of groups B and D were weighed at necropsy. The infected animals (groups A and B) showed a significant reduction in platelets and increased PT and aPTT when compared to negative control groups (groups C and D). Animals from group A showed increased levels of fibrinogen. The mean weight of spleen differed between group B (2.62g) and group D (0.55g). It was concluded that there is no relationship between thrombocytopenia and splenic sequestration in infection by T. evansi.

Topics: Animals; Female; Fibrinogen; Hypersplenism; Platelet Count; Prothrombin; Rats; Rodent Diseases; Spleen; Splenectomy; Thrombocytopenia; Thromboplastin; Trypanosoma; Trypanosomiasis

Amniotic fluid embolism (AFE) is a rare but catastrophic complication of pregnancy characterized by severe hypotension, cardiovascular collapse, and massive consumptive coagulopathy. Several animal models of this syndrome have been proposed, but most have yielded inconclusive results.. The objective of this study was to develop a suitable animal model of AFE.. Twelve rabbits in late gestation (25 days) were used. Amniotic fluid was collected from the fetal amniotic sacs after laparotomy, and autologous fluid was injected into 6 rabbits via the left auricular vein. Six other rabbits received saline (control group). Blood pressure, platelet counts, and coagulation variables were measured at baseline and at various intervals for 60 minutes after injection. The in vitro effect of amniotic fluid on coagulation was assessed by thrombelastographic (TEG) analysis.. Injection of amniotic fluid did not reproduce clinical signs of AFE and had no effect on activated partial thromboplastin time (aPTT), prothrombin time (PT), or Factor VIII activity. However, significant thrombocytopenia was observed 5 minutes after administration of amniotic fluid and resolved by 60 minutes. In vitro addition of amniotic fluid to blood resulted in accelerated clotting on TEG tracings.. The syndrome of AFE was not reproduced in this rabbit model. However, injection of autologous amniotic fluid induced a transient and severe thrombocytopenia. Moreover, TEG analysis indicated that amniotic fluid could initiate the coagulation cascade. Other factors such as the presence of meconium in amniotic fluid may be needed to provoke more severe clinical signs.

Topics: Amniotic Fluid; Animals; Blood Coagulation; Blood Coagulation Tests; Blood Pressure; Disease Models, Animal; Embolism, Amniotic Fluid; Female; Humans; Injections, Intravenous; Platelet Count; Pregnancy; Pregnancy Complications; Rabbits; Thrombelastography; Thrombocytopenia; Thrombophilia; Thromboplastin; Time Factors

Topics: Animals; Cell Movement; Factor VIIa; Genetic Predisposition to Disease; Hemophilia A; Hemorrhage; Inflammation; Leukocytes; Mice; Mice, Inbred C57BL; Recombinant Proteins; Thrombocytopenia; Thromboplastin; Wound Healing

A rare case is described of acute disseminated intravascular coagulation (DIC) following isolated mild head injury with acute subdural haematoma, coagulopathy onset preceding craniotomy. Surgical treatment of the cause followed by swift diagnosis and treatment soon after surgery enabled a good outcome. Post-operative recollection of subdural and extadural blood was treated by further surgery. DIC following isolated mild head injury without axonal damage is rare, but fatal if missed. Thrombocytopaenia in head injured patients should be investigated expediently. Post-operative interim imaging (if not standard practice) should also be considered to exclude haemorrhagic recollection requiring further surgery.

Topics: Adult; Brain; Craniotomy; Decompression, Surgical; Disseminated Intravascular Coagulation; Early Diagnosis; Emergency Medical Services; Head Injuries, Closed; Hematoma, Epidural, Cranial; Hematoma, Subdural, Acute; Humans; Male; Partial Thromboplastin Time; Plasma; Platelet Transfusion; Subdural Space; Thrombocytopenia; Thromboplastin; Tomography, X-Ray Computed; Treatment Outcome; Violence

Heparin-induced thrombocytopenia (HIT) is a severe complication of heparin therapy. IgG antibodies targeting the platelet factor 4-heparin complex activate platelets and generate microparticles with procoagulant activity.. To determine whether the thrombin generation assay is capable of detecting procoagulant activity induced by patient platelet-poor plasma (PPP) in donor platelet-rich plasma (PRP).. We explored two groups of patients; group 1 (n = 23): patients with a positive clinical and biological diagnosis of HIT; group 2 (n = 25): patients with a negative clinical and biological diagnosis of HIT. Mixtures of donor PRP and patient PPP (1:1) were incubated either with unfractionated heparin 0.2 U mL(-1) or with physiological saline. Thrombin generation was assessed by calibrated thrombinography. The effect of heparin on the mixtures was evaluated according to the ratio of the values with and without heparin (wH/woH) of the five thrombogram parameters.. With low heparin concentrations, plasma of group 1 activates donor platelets and generates procoagulant activity. A set of three ratios outside the cut-off values corresponds to the 'HIT thrombogram profile', characterized by a highly specific aspect of the thrombogram wH in relation to the thrombogram woH. None of the group 2 patients presented a HIT thrombogram profile. The results of thrombinography correlate well with the results of the platelet aggregation test.. Our studies illustrate the central paradox of HIT, namely enhancement of thrombin generation in the presence of heparin. The HIT thrombogram profile as it is defined in this study can detect the procoagulant activity of HIT IgG antibodies.

Topics: Blood Platelets; Female; Heparin; Humans; Immunoglobulin G; Male; Platelet Activation; Platelet Aggregation; Platelet Factor 4; Platelet-Rich Plasma; Recombinant Proteins; Thrombin; Thrombocytopenia; Thromboplastin

Lepirudin (r-hirudin) is one of the two alternative anticoagulants licensed to treat patients with heparin-induced thrombocytopenia (HIT). Manufacturer's guidelines state that lepirudin should be monitored using the activated partial thromboplastin time (APTT) ratio. However, several studies have demonstrated a plateau effect of higher concentrations of lepirudin on APTT ratios and variable results when comparing different APTT reagents. This study compares APTT ratios (using two different APTT reagents) with two other commercially available methods for directly quantifying plasma lepirudin levels: ecarin chromogenic assay and prothrombinase-induced clotting time in 95 samples from five patients receiving lepirudin anticoagulation for HIT.

Topics: Anticoagulants; Blood Coagulation; Blood Coagulation Tests; Endopeptidases; Fibrinolytic Agents; Heparin; Hirudins; Humans; Partial Thromboplastin Time; Recombinant Proteins; Thrombocytopenia; Thromboplastin

Microparticles (MPs) support coagulation and can be helpful in restoring the hemostatic system in thrombocytopenic patients. The anticoagulant properties of MPs shed during storage of platelets (PLTs) have not been studied yet.. Storage-induced MPs were harvested from outdated PLT concentrates. Whether factor (F)Va was present on the surface of these MPs was investigated. The activated protein C (APC)-catalyzed inactivation of MP-bound FVa was further determined. Also, inactivation of FVa at the surface of thrombin-activated PLTs and synthetic vesicles was determined.. MPs in stored PLT products carry FVa at their surface. APC-catalyzed inactivation of MP-bound FVa resulted in 42 +/- 2 percent residual FVa activity after 20 minutes. The residual activity of FVa on thrombin-activated PLTs was 25 +/- 3 percent. Plasma-derived FVa was rapidly inactivated in the presence of synthetic vesicles, with 5 +/- 4 percent residual FVa activity. When synthetic vesicles were added to the inactivation mixture of MP- or thrombin-activated PLTs, a residual activity of 5 to 10 percent was found. Furthermore, addition of excess plasma-FVa to storage-induced MPs resulted in a residual activity of 26 +/- 2 percent. Moreover, the APC-resistant phenotype of MPs was confirmed in plasma in which thrombin generation was measured in the absence and presence of APC. Residual FVa activity in the presence of MPs, PLTs, or synthetic vesicles was 87 +/- 6, 65 +/- 3, and 8 +/- 19 percent, respectively.. Together, these results suggest that the MP surface environment renders FVa resistant to APC. It is further concluded that the APC resistance of FVa at the surface of storage-induced MPs enhances their procoagulant nature.

Topics: Arginine; Blood Coagulation; Blood Platelets; Blood Preservation; Electrophoresis, Polyacrylamide Gel; Factor Va; Hemostasis; Humans; Protein C; Thrombocytopenia; Thromboplastin

This paper presents an analysis of 24 cases in which recombinant factor VIIa (rFVIIa) was used in the management of hemorrhage in patients with thrombocytopenia associated with hematologic malignancies. This is the largest case aggregation to date and focuses on preliminary experience in the off-label use of this hemostatic agent. Data were extracted from the international, Internet-based registry, www.haemostasis.com, accessed in September 2003. The search results were manually cross-checked against monthly summary reports. The physicians providing the cases were contacted individually to approve the use of their cases, supply any information missing from the database, and validate the data already held. Patients with acute myeloid leukemia, acute lymphoblastic leukemia, Hodgkin's disease, non-Hodgkin's lymphoma, Burkitt's lymphoma, B-cell or T-cell lymphoma, or aplastic anemia received rFVIIa at total doses of between 18 and 1040 mug/kg body weight. Bleeding stopped in 11 of 24 (46%) patients, markedly decreased in 8 of 24 (33%) patients, and decreased in 4 of 24 (17%) patients. In most patients, the response was achieved within 2.5 hours of administration of rFVIIa. The use of rFVIIa was generally well tolerated -- 1 case of ischemic stroke was considered to be possibly related to rFVIIa administration, but this has yet to be confirmed. A review of these 24 cases submitted to the www.haemostasis.com database suggests that rFVIIa is beneficial in the management of hemorrhage in patients with thrombocytopenia and hematologic malignancies. This warrants further investigation in rigorously controlled clinical trials.

Topics: Adolescent; Adult; Anticoagulants; Child; Child, Preschool; Factor VIIa; Female; Hemorrhage; Humans; Internet; Leukemia; Lymphoma; Male; Medical Audit; Middle Aged; Prothrombin; Thrombocytopenia; Thromboplastin

In the present study we assessed the effect of platelet counts and rFVIIa on thrombin generation, platelet activation and clot formation after tissue factor pathway activation in human plasma aiming to investigate the mechanism by which rFVIIa induces haemostasis in patients with severe thrombocytopenia. Plasma samples with platelet counts from 5 x 10(9)/l to 150 x 10(9)/l were spiked with rFVIIa (1 micro g/ml) or buffer. Clotting was initiated in the presence of diluted thromboplastin. Thrombin generation was assessed using the Thrombogram-Thrombinoscope trade mark assay. The kinetics of platelet activation was assessed using flow cytometry to measure the expression the P-selectin on platelet membrane of washed platelets suspended in defibrinated homologous PPP. Thromboelastography was used to evaluate the effect of platelets and rFVIIa on the kinetics of clot formation and clot's firmness. In the presence of low platelet counts the endogenous thrombin potential (ETP) and the maximum concentration of generated thrombin (Cmax) were reduced by 60%-70%. The lag-time of thrombin generation and the time required to reach the Cmax (Tmax) were prolonged, the velocity of platelet activation was decreased and thrombus formation was delayed. Recombinant FVIIa accelerated thrombin generation and platelet activation but it did not significantly modify ETP or Cmax. Recombinant FVIIa enhanced platelet activation in a TF and thrombin dependent manner since its effect on the studied parameters was abolished when TF was omitted or when hirudin was added into the experimental system respectively. Recombinant FVIIa normalized the velocity of clot formation but it did not modify clot firmness, which depended mainly on platelets' count. In conclusion, in experimental conditions simulating severe thrombocytopenia rFVIIa in the presence of low amounts of TF, accelerates thrombin generation, without increasing the maximum amount of generated thrombin, thus leading in enhanced platelet activation and rapid clot formation.

Topics: Blood; Blood Coagulation; Blood Platelets; Factor VII; Factor VIIa; Hemostasis; Humans; Kinetics; Platelet Activation; Platelet Count; Recombinant Proteins; Thrombelastography; Thrombin; Thrombocytopenia; Thromboplastin

Recombinant FVIIa (rFVIIa) has been shown to improve hemostasis in patients with thrombocytopenia and to prevent or control bleeding episodes in patients with inherited deficiencies of major PLT glycoproteins, but the mechanism of action is not well understood.. Effects of rFVIIa on hemostasis were explored with an in vitro perfusion technique. Blood samples, from healthy donors or from patients with congenital defects of PLT glycoprotein IIb-IIIa (GPIIb-IIIa), were anticoagulated with low-molecular-weight heparin. Experimental thrombocytopenia (<6000 PLTs/microL) was induced by a filtration procedure. rFVIIa was added to blood samples at therapeutic concentrations. A severe GPIIb-IIIa impairment was also induced by exposure of normal blood samples to a specific antibody. Perfusion studies were performed through annular chambers containing damaged vascular segments. The presence of fibrin and PLTs on the perfused subendothelium was morphometrically quantified.. Under conditions of experimental thrombocytopenia, addition of rFVIIa enhanced fibrin formation in a dose-dependent manner (p < 0.05). Improvements in local fibrin generation and partial restoration of PLT interactions were also observed after incubation of blood from patients with Glanzmann's thrombasthenia with rFVIIa at 5 microg per mL (180 microg/kg). Similar improvements were observed in blood samples incubated with antibodies to GPIIb-IIIa. rFVIIa in whole normal blood also enhanced fibrin formation but PLT deposition was unaffected. Evaluation of prothrombin fragments 1 and 2 in the perfusates confirmed that rFVIIa increased thrombin generation in all cases.. Our data indicate that rFVIIa promotes a procoagulant activity at sites of vascular damage. This mechanism could explain the beneficial hemostatic effect of rFVIIa in patients with thrombocytopenia or with Glanzmann's thrombasthenia.

Topics: Blood Coagulation; Blood Platelet Disorders; Blood Platelets; Factor VIIa; Fibrin; Hemostasis; Humans; Peptide Fragments; Platelet Glycoprotein GPIIb-IIIa Complex; Prothrombin; Recombinant Proteins; Thrombasthenia; Thrombocytopenia; Thromboplastin

The relationship between platelet and leukocyte activation, coagulation, and neointima development was investigated in noninjured murine blood vessels subjected to blood stasis. The left common carotid artery of C57BL/6J mice was ligated proximal to the bifurcation. Tissue-factor expression in luminal leukocytes progressively increased over 2 weeks. On day 3 after ligation, in addition to infiltrated granulocytes, platelet microthrombi and platelet-covered leukocytes as well as tissue-factor-positive fibrin deposits lined the endothelium. Maximal neointima formation in carotid artery cross sections of control mice equaled 28+/-3.7% (n=11) and 42+/-5.1% (n=8) of the internal elastic lamina cross-sectional area 1 and 2 weeks after ligation. In FVIII(-/-) mice, stenosis was significantly lower 1 (11+/-3.6%, n=8) and 2 (21+/-4.7%, n=7) weeks after ligation (both P:<0.01 versus background-matched controls). In u-PA(-/-) mice, luminal stenosis was significantly higher 1 (38+/-7.0%, n=7) and 2 (77+/-5.6%, n=6) weeks after ligation (P:<0.05 and P:<0.01, respectively, versus matched controls). In alpha(2)-AP(-/-) mice, stenosis was lower at 1 week (14+/-2.6%, n=7, P:<0.01) but not at 2 weeks. Responses in tissue-type plasminogen activator or plasminogen activator inhibitor-1 gene-deficient mice equaled that in controls. Reducing plasma fibrinogen levels in controls with ancrod or inducing partial thrombocytopenia with busulfan resulted in significantly less neointima, but inflammation was inhibited only in busulfan-treated mice. We conclude that stasis induces platelet activation, leading to microthrombosis and platelet-leukocyte conjugate formation, triggering inflammation and tissue-factor accumulation on the carotid artery endothelium. Delayed coagulation then results in formation of a fibrin matrix, which is used by smooth muscle cells to migrate into the lumen.

Topics: Afibrinogenemia; Animals; Blood Coagulation; Blood Platelets; Carotid Arteries; Cell Division; Disease Models, Animal; Endothelium, Vascular; Fibrin; Hemostatic Disorders; Inflammation; Leukocytes; Ligation; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Platelet Activation; Thrombocytopenia; Thromboplastin; Thrombosis; Tunica Intima

A mathematical model of the extrinsic or tissue factor (TF) pathway of blood coagulation is formulated and results from a computational study of its behavior are presented. The model takes into account plasma-phase and surface-bound enzymes and zymogens, coagulation inhibitors, and activated and unactivated platelets. It includes both plasma-phase and membrane-phase reactions, and accounts for chemical and cellular transport by flow and diffusion, albeit in a simplified manner by assuming the existence of a thin, well-mixed fluid layer, near the surface, whose thickness depends on flow. There are three main conclusions from these studies. (i) The model system responds in a threshold manner to changes in the availability of particular surface binding sites; an increase in TF binding sites, as would occur with vascular injury, changes the system's production of thrombin dramatically. (ii) The model suggests that platelets adhering to and covering the subendothelium, rather than chemical inhibitors, may play the dominant role in blocking the activity of the TF:VIIa enzyme complex. This, in turn, suggests that a role of the IXa-tenase pathway for activating factor X to Xa is to continue factor Xa production after platelets have covered the TF:VIIa complexes on the subendothelium. (iii) The model gives a kinetic explanation of the reduced thrombin production in hemophilias A and B.

Topics: Binding Sites; Blood Coagulation; Blood Coagulation Factors; Blood Flow Velocity; Blood Platelets; Humans; Models, Biological; Models, Theoretical; Platelet Activation; Thrombocytopenia; Thromboplastin

The pathogenesis of thrombosis in heparin-induced thrombocytopenia (HIT) was studied by investigating whether antibodies to heparin-platelet factor 4 (H-PF4) induced tissue factor (TF) synthesis by monocytes. Plasma from 5 patients with HIT containing IgG to H-PF4 was incubated with peripheral blood mononuclear cells without or with purified PF4 and heparin. Significant TF-dependent procoagulant activity (PCA) expressed by monocytes, measured with a factor Xa-based chromogenic assay, was induced after incubation of each HIT plasma sample. This monocyte PCA required the presence of PF4 and was inhibited by high concentrations of heparin. Furthermore, purified HIT IgG added to whole blood with PF4 and heparin also provoked significant synthesis of TF mRNA by monocytes, demonstrated by RT-PCR, and this effect was not observed with normal IgG. These findings strongly support the hypothesis that antibodies to PF4 developed in HIT trigger the production of tissue factor by monocytes, and this effect could account in vivo for hypercoagulability and thrombotic complications in affected patients.

Topics: Blood Coagulation; Heparin; Humans; Immunoglobulin G; Monocytes; Platelet Factor 4; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Thrombocytopenia; Thromboplastin

Thrombosis is a life-threatening complication that occurs in a subset of patients with heparin-induced thrombocytopenia (HITT). The pathogenic mechanisms underlying the variable occurrence of thrombosis in HITT is poorly understood. It was hypothesized that monocyte activation leading to tissue factor expression may play a role in promoting a thrombogenic state in HITT. This study demonstrates that a human platelet factor 4 (PF4)/heparin-specific murine monoclonal antibody (KKO) binds to peripheral blood-derived human monocytes in a PF4-dependent manner. KKO and antibodies from patients with HITT induce monocytes to synthesize and secrete interleukin-8 and induce cell-surface procoagulant activity, which is abrogated following treatment with antihuman tissue factor antibody. The findings suggest a novel mechanism by which PF4/heparin antibodies may promote a hypercoagulable state in patients with HITT. (Blood. 2001;98:1252-1254)

Topics: Antibodies, Monoclonal; Autoantibodies; Coagulants; Heparin; Humans; Interleukin-8; Monocytes; Platelet Factor 4; Thrombocytopenia; Thrombophilia; Thromboplastin; Thrombosis

Recombinant factor VIIa (rFVIIa; NovoSeven, Novo Nordisk, Copenhagen, Denmark) may help to promote hemostasis in patients with thrombocytopenia. We used two in vitro models of thrombin generation to evaluate this effect. The reconstituted model contained tissue factor (TF)-expressing monocytes, unactivated platelets, isolated plasma coagulation proteins, and calcium. Platelet activation and thrombin generation were measured in timed aliquots. In the plasma-based model, thrombin generation was measured continuously after the addition of lipidated TF and calcium to platelet-rich plasma using a slowly cleaved fluorescent substrate. Thrombocytopenic conditions were mimicked by decreasing the platelet density. In both systems, a platelet density-dependent lowering of the thrombin-generation peak was observed. Addition of rFVIIa to samples with low platelet density (6700 to 10000/microL) increased the initial thrombin generation in both systems without normalizing thrombin-generation curves. The magnitude of the rFVIIa effect was most pronounced in the plasma-based model. Platelet activation was not significantly delayed at low platelet density in the reconstituted model. Addition of rFVIIa to samples with low platelet density caused faster platelet activation, most likely as a consequence of the increased initial thrombin generation. The data suggest that rFVIIa may help to achieve hemostasis at low platelet densities by increasing the initial thrombin generation, thereby compensating for low platelet number.

Topics: Blood Platelets; Coagulants; Factor VII; Factor VIIa; Humans; Kinetics; Lipopolysaccharides; Models, Biological; Monocytes; Recombinant Proteins; Thrombin; Thrombocytopenia; Thromboplastin

Disseminated intravascular coagulation in humans is frequently associated with Gram-negative bacterial sepsis. Therefore, to examine the role and time frame of the in vivo induction of tissue factor (TF) by bacterial endotoxin, a reverse transcription polymerase chain reaction and a solid-phase ELISA assay were developed to monitor the in vivo production in rabbits, of TF mRNA and TF antigen by peripheral blood leukocytes (PBL).. : Healthy rabbits were injected intravenously with either 1, 10 or 50 microg/kg of Salmonella endotoxin. Blood samples were obtained both before endotoxin administration and at various time points thereafter, up to 24 h. Some experiments were also done to determine whether all-trans retinoic acid would ameliorate the signs of the endotoxin-induced disseminated intravascular coagulation.. PBL counts dropped significantly within 2 h of rabbits receiving the endotoxin, recovering to baseline levels by 24 h. Platelet counts decreased gradually over this same time frame. Fibrin deposition was noted in renal glomerular capillaries at 24 h. An increase (P<0.001) in PBL-associated TF mRNA levels was observed 2 h post-endotoxin (10 microg/kg, n = 8), followed by a gradual decline over the subsequent 24 h. The average increase in TF mRNA at 2 h was approximately 4.6-fold (P<0.001) over that seen at time 0. The amount of mononuclear cell associated TF antigen demonstrated a peak at 2 h post-endotoxin (10 microg/kg, n = 13), with levels approximately 9.6-fold greater than (P<0.001) baseline. Pre-treatment of rabbits with all-trans retinoic acid significantly (P<0.001) ameliorated the PBL-associated increase in TF mRNA and TF antigen levels.. These results suggest that low dose endotoxin (10 microg/kg) faithfully reproduces the non-overt activation of coagulation observed in primates and human volunteers, supporting the hypothesis that TF expression is involved in the in vivo initiation and propagation of disseminated intravascular coagulation. Moreover, all-trans retinoic acid may be effective in modulating in vivo the TF transcription induced by endotoxin.

Topics: Animals; Antithrombin III; Blood Cell Count; Disseminated Intravascular Coagulation; Drug Evaluation, Preclinical; Endotoxemia; Fibrin; Fibrinogen; Gene Expression Regulation; Kidney Glomerulus; Leukocytes; Lipopolysaccharides; Male; Rabbits; RNA, Messenger; Thrombocytopenia; Thromboplastin; Tretinoin

We determined the prevalence and relationship with clinical manifestations of antibodies to thromboplastin (aTP) in 92 patients with systemic lupus erythematosus (SLE). Thirty-two (35%) patients had aTP: 13 (14%) were positive for IgG aTP, 13 (14%) for IgM aTP, and 6 (7%) for both. Patients with aTP had an increased incidence of thrombosis (p = 0.01), thrombocytopenia (p < 0.001), hemolytic anemia (p < 0.001), and fetal losses (p = 0.03). When the IgG and IgM aTP isotypes were analysed separately, the IgG aTP were found to be associated with thrombosis (p < 0.001), thrombocytopenia (p < 0.001), and fetal losses (p = 0.02). The IgM aTP were associated with hemolytic anemia (p < 0.001). A correlation was found between the titers of aTP and those of anticardiolipin antibodies, in both IgG (p < 0.01, r = 0.6) and IgM (p < 0.01, r = 0.64) isotypes, and between the titers of IgG aTP and the diluted Russell's viper venom time used to detect the lupus anticoagulant (p < 0.001, r = 0.42). This test is a reliable, reproducible and sensitive assay for the detection of antiphospholipid antibodies, specially in those patients under anticoagulant therapy.

Topics: Adolescent; Adult; Aged; Anemia, Hemolytic, Autoimmune; Antibodies, Anticardiolipin; Antiphospholipid Syndrome; Autoantibodies; Case-Control Studies; Cohort Studies; Enzyme-Linked Immunosorbent Assay; Female; Fetal Death; Humans; Immunoglobulin G; Immunoglobulin Isotypes; Immunoglobulin M; Lupus Coagulation Inhibitor; Lupus Erythematosus, Systemic; Male; Middle Aged; Pregnancy; Reproducibility of Results; Sensitivity and Specificity; Thrombocytopenia; Thromboplastin; Thrombosis

A number of nonplatelet-specific cytokines that augment platelet recovery following chemo/radiotherapy have been described. The members of the interleukin 6 (IL-6) family have properties that influence the hematopoietic system beyond their modest thrombocytopoietic effects. Studies performed in a canine model with IL-6 have shown that this factor augments plasma fibrinogen and von Willebrand factor (vWf) concentrations and decreases the level of free protein S. IL-6 appears to decrease the bleeding time in thrombocytopenic dogs, although this effect does not seem to be due to a direct influence of the factor on endothelial vWf or tissue factor production. The factor does not directly alter platelet function in vitro, but when administered to dogs, it increases the sensitivity of the platelets to activation by thrombin. Normal platelets injected into IL-6-treated dogs, and platelets from IL-6-treated dogs injected into normal animals, survive normally. Following injection of either IL-6 or the more specific thrombocytopoietic cytokine thrombopoietin (TPO), IL-6 increases platelet responsiveness to thrombin-induced activation to a greater extent than does TPO. The data show that IL-6 has certain properties that might be construed as prohemostatic, and these properties may prove to be useful clinically.

Topics: Animals; Antibodies, Monoclonal; Bleeding Time; Blood Platelets; Chromatography, Gel; Dogs; Endothelium, Vascular; Fibrinogen; Humans; Interleukin-6; Mice; Platelet Activation; Platelet Aggregation; Protein Binding; Protein S; Recombinant Proteins; Thrombin; Thrombocytopenia; Thromboplastin; Thrombopoietin; Time Factors; von Willebrand Factor

Venous thrombosis was induced by ligature of the inferior vena cava in rats whose blood was made hypercoagulable by intravenous (IV) administration of tissue thromboplastin. From a dose-response showing that the administration of increasing doses of tissue thromboplastin resulted in a subsequent progressive increase of thrombus weight, two concentrations of tissue thromboplastin were chosen: a high dose (550 microL/kg, IV) where thrombus formation was optimal and a concentration (7 microL/kg, IV) where tissue thromboplastin-hypercoagulability was intermediate. In both experimental conditions, leukopenia provoked by a myelotoxic drug did not influence the development of venous thrombosis. However, after thrombocytopenia induced by an antiplatelet antiserum, a dramatic decrease in thrombus formation was observed in animals that had been pre-challenged with the lower dose of tissue thromboplastin, whereas decrease in platelet count did not affect venous thrombosis under high thrombogenic challenge. When administered orally 2 hours before thrombosis induction, the ticlopidine analogue clopidogrel showed dose-dependent inhibition of thrombus formation in animals that were pre-challenged with a low dose of tissue thromboplastin (ED50 = 7.9 +/- 1.5 mg/kg, orally) but remained ineffective against high tissue thromboplastin-induced venous thrombosis. We further determined the effect of heparin and hirudin, and showed that both of these drugs exhibited a more potent antithrombotic activity after injection of the lower dose of tissue thromboplastin than after injection of a high dose of tissue thromboplastin. Therefore, using our model of stasis and hypercoagulability, platelet activation played a major role in the development of venous thrombosis when the thrombogenitic stimulus was mild.

Topics: Animals; Blood Platelets; Clopidogrel; Disease Models, Animal; Heparin; Hirudins; Leukopenia; Male; Mechlorethamine; Partial Thromboplastin Time; Platelet Aggregation Inhibitors; Rabbits; Rats; Rats, Sprague-Dawley; Thrombocytopenia; Thrombophlebitis; Thromboplastin; Ticlopidine

We report two cases of renal vein thrombosis, unusual because of acute expression, right renal vein localization, absence of the usual renal or perirenal causes, surgical management and a never before reported etiology. In one case the thrombosis was secondary to primary antiphospholipid syndrome, in the other it was secondary to heparin associated thrombocythemia. In this case surgical management was performed during prostacyclin infusion.

Topics: Acute Disease; Autoantibodies; Blood Coagulation Disorders; Combined Modality Therapy; Epoprostenol; Female; Heparin; Humans; Male; Middle Aged; Phospholipids; Renal Veins; Syndrome; Thrombocytopenia; Thromboplastin; Thrombosis

Bernard-Soulier syndrome (BSS) was described in 1948 as a constitutional platelet disorder characterized by giant sized platelets, a prolonged bleeding time, and a defect in prothrombin consumption. The accurate mechanisms of these abnormalities remain unexplained, especially the defect in prothrombin consumption on which we focus in this paper. Several hypotheses are proposed: firstly, a defective reaction between the platelet membrane, where the phospholipid composition is abnormal, and the proteins which initiate thromboplastin generation such as collagen, factor XI; secondly, an abnormal reaction between thrombin, whose synthesis is increased, and its receptor, possibly glycoprotein V, which is defective; lastly, as factor VIII/vW binding is diminished, an abnormal dissociation of the complex VIII/vW-VIIIc at the site of the platelet membrane, which leads to an inactivation of factor VIIIc.

Topics: Binding Sites; Blood Coagulation Disorders; Blood Platelets; Cell Membrane; Collagen; Factor V; Factor VIII; Factor XI; Glycoproteins; Humans; Membrane Proteins; Platelet Factor 3; Platelet Membrane Glycoproteins; Thrombin; Thrombocythemia, Essential; Thrombocytopenia; Thromboplastin

Topics: Antibodies; Aspirin; Blood Coagulation Disorders; Blood Coagulation Factors; Blood Platelets; Cell Adhesion; Cell Communication; Cyclooxygenase Inhibitors; Disseminated Intravascular Coagulation; Epoprostenol; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinopeptide A; Humans; Indomethacin; Monocytes; Neoplasm Transplantation; Neoplasms; Syndrome; Thrombocytopenia; Thrombocytosis; Thromboembolism; Thromboplastin

When 125I-labeled canine prothrombin was given to normal adult dogs intravenously, it was calculated that 240% of the plasma prothrombin crossed the capillary barrier per day, 410% of the interstitial prothrombin returned to the blood stream daily, and 79% of the plasmatic prothrombin was catabolized per day. These data are in close agreement with those observed for bovine prothrombin in calves by Takeda (1970). When derived from normal dog prothrombin, prethrombin-1 is a mixture of 2 polypeptides, one larger than the other, and both present in about equal amounts. The longer peptide, "prethrombin-1-long," was catabolized twice as fast as prothrombin, and the shorter, "prethrombin-1-short," 4 times faster. Prothrombin fragment-1 was catabolized by the normal dog still more rapidly. The catabolism of prothrombin was not accelerated in 3 dogs receiving continuous infusions of a thromboplastic emulsion of dog brain. Nor was the level of prothrombin in their plasma remarkably altered.

Topics: Afibrinogenemia; Animals; Chromatography, Gel; Disseminated Intravascular Coagulation; Dogs; Iodine Radioisotopes; Kinetics; Prothrombin; Thrombocytopenia; Thromboplastin; Trichloroacetic Acid

Topics: Animals; Blood Cell Count; Blood Coagulation; Blood Platelets; Cattle; Prothrombin Time; Thrombocytopenia; Thromboplastin; Trypanocidal Agents; Trypanosomiasis, Bovine

Topics: Animals; Blood Cell Count; Blood Platelets; Complement C3; Complement System Proteins; Elapid Venoms; Female; Male; Mice; Mice, Inbred A; Mice, Inbred AKR; Mice, Inbred BALB C; Mice, Inbred CBA; Mice, Inbred DBA; Rabbits; Thrombocytopenia; Thromboplastin

Topics: Aged; Disseminated Intravascular Coagulation; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Humans; Male; Prostatic Neoplasms; Shock, Cardiogenic; Thrombocytopenia; Thromboplastin

Three techniques have been employed for the in vitro detection of circulating platelet antibodies in thrombocytopenic patients affected by 'idiopathic' form or by lupus erythematosus (SLE), the complement fixation test, the platelet factor 3 availability test and the serotonin release test. 29 of the 35 sera tested (82.8%) gave positive results for antiplatelet activity. In particular the serotonin release test allows to distinguish 4 groups of patients: a first group affected by idiopathic form; two groups with autoimmune thrombocytopenia and various degrees of serotonin release, and finally a fourth group which comprises subjects affected by SLE, with circulating immunocomplexes.

Topics: Autoimmune Diseases; Blood Platelets; Chronic Disease; Complement Fixation Tests; Humans; Isoantibodies; Lupus Erythematosus, Systemic; Serotonin; Thrombocytopenia; Thromboplastin

The effect of dipyridamole (Persantine) on the thrombocyte count and bleeding tendency in connection with open-heart surgery and perfusion was studied in 22 patients. A control series of 21 patients undergoing open-heart surgery was available. The treatment group received dipyridamole, 0.5 mg. per kilogram of body weight, in the beginning of cardiopulmonary bypass into the heart-lung machine and thereafter 10 mg. intravenously three times daily for 2 days. From the third day dipyridamole was administered by mouth, 75 mg. three times a day, until the patient was discharged from hospital. We found that dipyridamole had the effect of maintaining the thrombocyte count during cardiopulmonary bypass and the first and second postoperative days. Thereafter no significant difference was seen between the dipyridamole and control groups. The use of dipyridamole did not increase the postoperative hemorrhagic tendency. There were no significant differences in per- and postoperative blood loss and in bleeding and activated partial thromboplastin times between the groups.

Topics: Adolescent; Adult; Blood Cell Count; Blood Coagulation; Blood Platelets; Cardiopulmonary Bypass; Dipyridamole; Female; Heart Septal Defects, Atrial; Heart Septal Defects, Ventricular; Heart Valve Diseases; Hemostasis, Surgical; Humans; Male; Middle Aged; Postoperative Complications; Thrombocytopenia; Thromboplastin

Topics: Blood Coagulation Tests; Evaluation Studies as Topic; Fibrinogen; Heparin; Humans; Photometry; Prothrombin Time; Temperature; Thrombocytopenia; Thromboplastin

In an attempt to reveal certain aspects of the pathogenesis of the bleeding disorder in dengue hemorrhagic fever, hemostatic and platelet kinetic studies were carried out in 61 children with this disease. As has been shown by others, thrombocytopenia and hypofibrinogenemia were the two most prominent hemostatic defects constantly discovered. Increased intravascular clotting seemed to be one responsible factor, though not an outstanding one. This was evidenced by mildly and variably low factors II, V, VII, VIII, IX, X, and XII, and by mild to moderate increase of fibrin degradation products as well as low platelet counts and fibrinogen. In 11 cases platelet kinetic study revealed increased destruction as a main cause for the thrombocytopenia, most probably due to the underlying immunologic mechanism, i.e., via the immune complexes formed. Another factor was platelet dysfunction--the release of adenosine diphosphate.

Topics: Adenosine Diphosphate; Blood Cell Count; Blood Coagulation; Blood Coagulation Factors; Blood Platelets; Child; Dengue; Fibrin Fibrinogen Degradation Products; Fibrinogen; Hematocrit; Humans; Prothrombin Time; Thrombocytopenia; Thromboplastin

The clinical and laboratory features of a case of alphamethyldopa-induced thrombocytopenia are described. This is the second reported case in which the presence of alpha-methyldopa-induced platelet antibodies have been demonstrated.

Topics: Acute Kidney Injury; Antibody Formation; Aortic Aneurysm; Blood Coagulation Tests; Blood Platelets; Coombs Test; Female; Humans; Hypertension; Methyldopa; Middle Aged; Thrombocytopenia; Thromboplastin

When mice are injected intravenously with a large dose of vaccinia virus, prepared in the Ehrlich ascites carcinoma of the mouse, there is a precipitous loss of plasma fibrinogen and blood platelets. Death occurs usually within 24 hours. A specific role of the virus in this toxic syndrome can be demonstrated when heparin is employed to circumvent intravascular coagulation and fibrinogen loss. Heparin does not prevent a profound thrombocytopenia from occurring, but it modifies the rate of platelet loss. Toxicity is prevented when heparinized virus preparations are pretreated with beta-propiolactone or specific antibody, although a mild thrombocytopenia occurs. Thrombocytopenia does not occur in mice injected with heparinized material prepared from uninfected tumors. These studies indicate that the basic mechanism of vaccinia virus toxicity is an early interaction between infectious virus and blood platelets, with marked thrombocytopenia and consequential pathophysiologic changes.

Topics: Afibrinogenemia; Animals; Antibodies, Viral; Antiviral Agents; Ascitic Fluid; Blood Platelets; Erythrocyte Aggregation; Fibrinogen; Heparin; Lung; Mice; Propiolactone; Rabbits; Thrombocytopenia; Thromboplastin; Thrombosis; Trypsin Inhibitor, Bowman-Birk Soybean; Vaccinia virus

Topics: Animals; Atmospheric Pressure; Blood Coagulation Disorders; Decompression Sickness; Diving; Environment, Controlled; Fever; Fibrinogen; Hemostasis; Male; Platelet Adhesiveness; Prothrombin Time; Rats; Thrombocytopenia; Thromboplastin; Time Factors

Topics: Blood Coagulation Disorders; Blood Coagulation Tests; Factor VII Deficiency; Hemophilia A; Humans; Prothrombin Time; Thrombocytopenia; Thromboplastin; Vitamin K Deficiency

Topics: Adult; Blood Cell Count; Blood Platelet Disorders; Blood Platelets; Child; Child, Preschool; Clot Retraction; Female; Humans; Male; Middle Aged; Neoplasms; Prothrombin Time; Thrombocytopenia; Thrombocytosis; Thromboplastin

Topics: Blood Coagulation Tests; Blood Platelets; Cell Membrane; Humans; Microscopy, Electron; Osmotic Fragility; Pedigree; Platelet Aggregation; Potassium; Radioisotopes; Rubidium; Sodium; Thrombocytopenia; Thromboplastin

Topics: Adult; Aged; Antibody Formation; Arthritis, Rheumatoid; Aurothioglucose; Blood Coagulation Factors; Blood Platelets; Bone Marrow; Bone Marrow Cells; Dimercaprol; Drug Hypersensitivity; Drug Therapy, Combination; Female; Gold; Humans; Immunity, Cellular; Lipoproteins; Lymphocyte Activation; Male; Middle Aged; Prednisone; Thrombocytopenia; Thromboplastin

Topics: Animals; Blood Cell Count; Blood Platelets; Complement System Proteins; Factor V; Factor VII; Factor X; Fibrinogen; Immunologic Deficiency Syndromes; Rabbits; Thrombocytopenia; Thromboplastin; Time Factors

Topics: 5-Hydroxytryptophan; Abruptio Placentae; Animals; Blood Coagulation Factors; Desoxycorticosterone; Disease Models, Animal; Disseminated Intravascular Coagulation; Female; Fibrinogen; Fibrinolysis; Humans; Hypertension; Platelet Adhesiveness; Pre-Eclampsia; Pregnancy; Pregnancy Complications, Hematologic; Pulmonary Circulation; Rabbits; Rats; Thrombocytopenia; Thromboplastin

Topics: Adult; Antibody Formation; Blood Cell Count; Blood Coagulation Tests; Blood Platelets; Complement Fixation Tests; Hemorrhage; Heparin; Humans; Male; Middle Aged; Myocardial Infarction; Platelet Adhesiveness; Prothrombin Time; Thrombocytopenia; Thromboembolism; Thromboplastin; Thrombosis

Topics: Adult; Autoantibodies; Autoimmune Diseases; Complement Fixation Tests; Cyclophosphamide; Hodgkin Disease; Humans; Isoantibodies; Male; Prednisone; Remission, Spontaneous; Splenectomy; Thrombocytopenia; Thromboplastin

Topics: Animals; Ascorbic Acid; Ascorbic Acid Deficiency; Blood Coagulation Factors; Blood Platelet Disorders; Blood Platelets; Dicumarol; Factor VII; Glycine max; Hemorrhage; Hemostatics; Humans; Pedigree; Phospholipids; Plasma; Prothrombin; Prothrombin Time; Rabbits; Thrombocytopenia; Thromboplastin; Vitamin K; Vitamin K Deficiency

Topics: Blood Cell Count; Blood Coagulation Disorders; Blood Coagulation Tests; Blood Platelets; Fibrinogen; Hemorrhagic Disorders; Hemostasis; Humans; Liver Diseases; Prothrombin Time; Thrombin; Thrombocytopenia; Thromboplastin

Topics: Blood Coagulation Disorders; Blood Coagulation Tests; Blood Platelet Disorders; Hemostasis; Humans; Methods; Thrombelastography; Thrombocytopenia; Thromboplastin

Topics: Anti-Bacterial Agents; Blood Cell Count; Blood Coagulation; Blood Coagulation Disorders; Blood Coagulation Tests; Blood Platelets; Child; Cystic Fibrosis; Fibrinolysis; Gastrointestinal Hemorrhage; Hemoptysis; Hepatomegaly; Humans; Liver; Liver Function Tests; Lung; Prospective Studies; Prothrombin Time; Splenomegaly; Thrombocytopenia; Thromboplastin; Vitamin K

Topics: Blood Coagulation; Blood Coagulation Factors; Blood Coagulation Tests; Factor V Deficiency; Factor VII Deficiency; Factor XI Deficiency; Factor XIII; Hemophilia B; Hemostasis; Humans; Leishmaniasis, Visceral; Phospholipids; Prothrombin Time; Thrombocytopenia; Thromboplastin

Topics: Animals; Blood Cell Count; Blood Coagulation; Blood Platelets; Busulfan; Factor IX; Factor V; Factor VII; Female; Fibrinogen; Hematocrit; Hemoglobins; Male; Rabbits; Thrombocytopenia; Thromboplastin; Time Factors; Tissue Extracts

Topics: Acute Kidney Injury; Anemia, Hemolytic; Blood Coagulation Disorders; Blood Coagulation Factors; Blood Transfusion; Coronary Disease; Female; Heart Arrest; Hemorrhagic Disorders; Humans; Hyaline Membrane Disease; Infant, Newborn; Ischemia; Kidney Transplantation; Male; Obstetric Labor Complications; Pregnancy; Shock, Septic; Shwartzman Phenomenon; Thrombocytopenia; Thromboembolism; Thromboplastin; Toxemia; Wounds and Injuries

Topics: Blood Coagulation Disorders; Child; Erythrocyte Aggregation; Female; Humans; Infant; Infant, Newborn; Kidney Cortex Necrosis; Male; Meningitis, Meningococcal; Renal Veins; Thrombocytopenia; Thrombophlebitis; Thromboplastin

Topics: Adenine Nucleotides; Blood Coagulation Factors; Blood Coagulation Tests; Blood Platelet Disorders; Blood Platelets; Citric Acid Cycle; Erythrocytes; Female; Glycogen; Humans; Lipoproteins; Microscopy, Electron; Platelet Adhesiveness; Thrombin; Thrombocytopenia; Thromboplastin

Topics: Acidosis; Anticoagulants; Blood Coagulation Disorders; Blood Coagulation Factors; Blood Coagulation Tests; Blood Flow Velocity; Blood Transfusion; Blood Volume; Capillaries; Fibrinogen; Fibrinolysis; Humans; Prothrombin Time; Shock, Hemorrhagic; Thrombelastography; Thrombocytopenia; Thromboplastin

Topics: Animals; Antifibrinolytic Agents; Blood Coagulation; Blood Coagulation Tests; Fibrinogen; Fibrinolysis; Globulins; Liver; Liver Transplantation; Prothrombin Time; Swine; Thrombocytopenia; Thromboplastin; Transplantation, Homologous

Topics: Blood Cell Count; Blood Coagulation Disorders; Blood Coagulation Factors; Blood Coagulation Tests; Blood Platelets; Blood Pressure; Child; Child, Preschool; Factor V; Fibrinogen; Heparin; Humans; Hypotension; Infant; Infant, Newborn; Prothrombin Time; Rocky Mountain Spotted Fever; Sepsis; Shock, Septic; Thrombocytopenia; Thromboplastin

A family with congenital thrombocytopenia is described through four generations where the mode of inheritance appears to be an autosomal dominant. Spontaneous bruising of varying severity, menorrhagia, and profuse bleeding at operation necessitating transfusion were predominant in the history. Platelet function tests were performed on the various patients. Platelet aggregation by adenosine diphosphate (ADP) was found to be defective, though liberation of platelet factor III and platelet thromboplastic function were found to be normal when corrected for deficient numbers.

Topics: Adult; Blood Coagulation Tests; Blood Platelet Disorders; Female; Genes, Dominant; Hemorrhagic Disorders; Humans; Male; Menorrhagia; Thrombocytopenia; Thromboplastin

Topics: Biological Assay; Blood Cell Count; Blood Coagulation Disorders; Blood Coagulation Factors; Blood Coagulation Tests; Blood Platelet Disorders; Female; Fibrin; Humans; Immunoelectrophoresis; Male; Neoplasms; Thrombin; Thrombocytopenia; Thromboplastin

Topics: Adolescent; Adult; Blood Coagulation Disorders; Blood Coagulation Factors; Child; Child, Preschool; Factor VII; Factor VIII; Factor XIII; Female; Humans; Infant; Kaolin; Lymphoma, Non-Hodgkin; Male; Prothrombin Time; Pulmonary Embolism; Thrombocytopenia; Thrombophlebitis; Thromboplastin; Wiskott-Aldrich Syndrome

Topics: Animals; Blood Cell Count; Blood Coagulation; Blood Platelets; Diet; Fats, Unsaturated; Fatty Acids, Essential; Linoleic Acids; Oleic Acids; Rats; Thrombocytopenia; Thromboplastin; Thrombosis

Topics: Adolescent; Adult; Aged; Anticoagulants; Blood Coagulation Disorders; Blood Coagulation Factors; Child; Child, Preschool; Female; Fibrinogen; Histocytochemistry; Humans; Infant; Male; Meningitis; Meningococcal Infections; Middle Aged; Neisseria meningitidis; Prothrombin Time; Sepsis; Shock, Septic; Skin Manifestations; Thrombocytopenia; Thromboplastin

Topics: Blood Coagulation Tests; Blood Platelets; Hemolysin Proteins; Hemophilia A; Humans; Thrombocytopenia; Thromboplastin

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Blood Coagulation; Blood Coagulation Tests; Blood Flow Velocity; Blood Platelets; Blood Pressure; Coronary Vessels; Electrocardiography; Factor VIII; Heart-Lung Machine; Heparin; In Vitro Techniques; Phosphorus Isotopes; Prothrombin Time; Swine; Thrombocytopenia; Thromboplastin; Thrombosis

Topics: Anticoagulants; Enzyme Inhibitors; Immunoglobulins; Purpura; Purpura, Thrombocytopenic; Thrombocytopenia; Thromboplastin

Topics: Blood Platelet Disorders; Dicumarol; Drug Therapy; Factor V Deficiency; Factor VII Deficiency; Factor VIII; Factor XII; Hemophilia A; Hemophilia B; Hemorrhagic Disorders; Heparin; Humans; Hypoprothrombinemias; Prothrombin; Prothrombin Time; Serum Globulins; Thrombocytopenia; Thromboplastin

Topics: Blood Coagulation Tests; Hematologic Diseases; Hemorrhage; Humans; Leukemia; Thrombocytopenia; Thromboplastin

Topics: Hemophilia A; Hemorrhagic Disorders; Humans; Medicine; Sex Chromosome Disorders; Thrombocytopenia; Thromboplastin

Topics: Afibrinogenemia; Amniotic Fluid; Blood Coagulation Disorders; Embolism; Embolism, Amniotic Fluid; Female; Humans; Hyaluronoglucosaminidase; Pregnancy; Thrombocytopenia; Thromboplastin

Topics: Blood Coagulation Tests; Factor X; Fibrinolysis; Humans; Infant; Purpura; Purpura, Thrombocytopenic; Thrombocytopenia; Thromboplastin; Vitamin K 1

Topics: Blood Coagulation Tests; Genetic Diseases, X-Linked; Hemorrhagic Disorders; Humans; Leukemia; Leukemia, Hairy Cell; Lymphatic Diseases; Metabolism; Severe Combined Immunodeficiency; Thrombocytopenia; Thromboplastin

Topics: Blood Coagulation Disorders; Hemophilia A; Humans; Thrombocytopenia; Thromboplastin; Thrombosis; von Willebrand Diseases

Topics: Blood Transfusion; Hemophilia A; Humans; Purpura; Purpura, Thrombocytopenic; Thrombocytopenia; Thromboplastin

The intravenous injection of bacterial endotoxins alter the coagulation system of rabbits' blood in vivo. Twenty-four hours after the first injection the fibrinogen level rises to twice normal values. The second injection at this time causes a 30 to 40 per cent decrease in fibrinogen content in 4 hours. Twenty hours later it again rises to twice normal values. A marked decrease in whole blood coagulation times in silicone occurs 4 hours after both injections but rises to normal values 24 hours following each injection. The circulating platelets drop from average levels of 300,000/c.mm. to 150,000/c.mm. after the first injection. The platelets remain at this low level and decrease to less than 100,000 after the second injection. During this time no fibrinolytic or fibrinogenolytic activity can be detected. Also, there is no significant change in the one stage prothrombin times or antithrombin titres. The marked decrease in circulating fibrinogen at the time when intracapillary thrombi are formed suggests that the "hyaline" thrombi of the generalized Shwartzman reaction are composed, in part, of fibrin. There appears to be a relationship between the level of circulating fibrinogen at the time of injection of bacterial endotoxin and the extent of the thrombosis. The higher the preinjection fibrinogen level, the more extensive is the thrombosis. There is also a relationship between the amount of fibrinogen loss and the extent of thrombosis after the injection. The more extensive the thrombosis the greater is the postinjection decrease in circulating fibrinogen. A comparison between the response of the hemostatic mechanism to tissue thromboplastin and bacterial endotoxin indicates that the latter acts in a unique manner and not by way of a simple "thromboplastic" activity. From the hematological standpoint, "preparation" for the generalized Shwartzman reaction is accompanied by an increased circulating fibrinogen, leukocytosis, and thrombocytopenia.

Topics: Animals; Blood Coagulation; Endotoxins; Fibrinogen; Hypersensitivity; Rabbits; Shwartzman Phenomenon; Thrombocytopenia; Thromboplastin; Thrombosis

Topics: Blood Coagulation Factors; Blood Platelets; Coagulants; Cortisone; Thrombocytopenia; Thromboplastin