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Query: UMLS:C0220723 (PCA)
 4,687 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasma levels of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) and the in vitro ability of platelets to aggregate and of monocytes to express procoagulant (tissue factor) activity (PCA) were evaluated in five patients who are homozygous for familial hypercholesterolemia (FH) before and after a single and a regular 5-month cholesterol removal by low density lipoprotein (LDL) apheresis. The biweekly procedure resulted in a 25% to 30% reduction (approximately 150 mg/dl) in total and LDL cholesterol (both were greater than 550 mg/dl at the beginning of the study). The basal levels of t-PA antigen and fibrinolytic activity before and after 10 minutes of venous stasis, basal PAI activity, and PAI-1 antigen were comparable to controls and were not affected by LDL apheresis. Likewise, regardless of the cholesterol removal, the PCA of freshly isolated monocytes and that of monocytes incubated with lipopolysaccharide did not differ from control values. Finally, the pre-apheresis sensitivity of platelets to adenosine diphosphate, arachidonic acid, and collagen was 1.5 to 2 times the normal value. This ratio was unchanged throughout the 5-month procedure. We conclude that fibrinolysis and monocyte PCA are normal in FH patients, whereas platelet aggregation is abnormally high, and none of these parameters is significantly affected by a 25% to 30% reduction in total and LDL cholesterol by LDL apheresis. Furthermore, our data suggest that removal of cholesterol from plasma by LDL apheresis is important for gaining insight into the mechanisms involved in the ischemic complications of arteriosclerosis in FH patients.
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PMID:Hemostatic variables in homozygous familial hypercholesterolemia. Effect of regular plasma cholesterol removal by low density lipoprotein apheresis. 212 91

Nephrotic syndrome (NS) is associated with several disorders of hemostasis: thrombocytosis and platelet hyperaggregability; increased plasma levels of factors V and VIII, and of fibrinogen with blood hyperviscosity; decreased plasma levels of natural anticoagulants: free protein S, and antithrombin III compensated by increased levels of alpha 2-macroglobulin; lowered fibrinolytic activity. Intensity of hypercoagulability is related to the degree of hypoalbuminemia; however, the role of hypercoagulability in the increased incidence of thromboembolic events, including renal vein thrombosis, is not proved. Clotting disorders are due to urinary losses of anticoagulants or to increased liver synthesis of procoagulants stimulated by hypoalbuminemia. Moreover, changes in clotting factors levels may be due to intravascular thrombin formation (marked by increased plasma levels of fibrinopeptide A). During active phases of glomerulonephritides (GN) with NS, thrombin formation might in fact arise in glomeruli, following activation of the glomerular hemostasis system. Isolated glomeruli from human crescentic GN, rabbit nephrotoxic GN and rat HgCl2 autoimmune GN produce excessive amounts of procoagulant (tissue factor) activity (PCA). Sequential studies of the self-limited HgCl2 GN showed that glomerular PCA, proteinuria and glomerular fibrin deposits peaked concomitantly at the acme of the disease, suggesting that immunologically mediated glomerular damage had triggered the extrinsic coagulation pathway.
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PMID:Coagulation factors in nephrotic syndrome. 225 77

Fibrin is the primary constituent of the vegetation in infective endocarditis, and tissue factor expression is a major mechanism of coagulation activation on infected valves. To determine which cells may participate in coagulation activation in this setting, expression of procoagulant activity (PCA; shown to be tissue factor) was studied in cultured endothelial and stromal cells derived from human cardiac valves. Endothelial cells had negligible PCA (99 +/- 50 mU/10(5) cells, mean +/- 1 standard deviation) unless stimulated by lipopolysaccharide or interleukin-1, which increased PCA to 5,592 +/- 1,482 and 5,901 +/- 1,497 mU/10(5) cells, respectively, in 6 h. Incubation of cells with viable enterococci or viridans streptococci or with an enterococcal cell wall preparation did not induce PCA. Cultured valve stromal cells constitutively expressed high levels of PCA (14,276 +/- 8,738 mU/10(5) cells) which was not changed with exposure to interleukin-1. PCAs of stromal or stimulated endothelial cells from valves of both right and left sides of the heart were comparable. The results suggest that endothelial cells may contribute to fibrin deposition during infection if stimulated, but PCA is not directly induced by bacteria. Stromal cells could contribute PCA if exposed to blood in the course of valve injury.
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PMID:Effects of interleukin-1, lipopolysaccharide, and streptococci on procoagulant activity of cultured human cardiac valve endothelial and stromal cells. 249 62

The studies discussed have established that inflammatory or immune cytokines, such as IL-1, TNF, and LT, as well as bacterial endotoxin, can act directly on vascular endothelial cells to modulate two important functional properties. The first of these, the inducible expression of E-LAMs, provides a mechanism for the local regulation of leukocyte-vessel wall interactions. This endothelial-dependent mechanism may be relevant to a broad spectrum of pathologic processes, including inflammation, delayed hypersensitivity reactions, and atherogenesis. The second, modulation of endothelial tissue factor PCA and fibrinolytic components, has important implications for the local balance of prothrombotic and antithrombotic influences at the blood-vessel wall interface. Thus, under the influence of inflammatory stimuli, vascular endothelial cells may actively contribute to the development and maintenance of intravascular or perivascular fibrin. Although the endothelial effector mechanisms of these functional alterations are distinct, their induction by similar stimuli points to important interrelationships of leukocyte-vessel wall adhesion and thrombosis. Further understanding of the regulation of endothelial expression of E-LAMs and coagulant properties should contribute to our understanding of vascular disease.
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PMID:Inducible endothelial functions in inflammation and coagulation. 312 25

Using a canine model, leukocyte populations enriched for monocytes and lymphocytes were isolated from blood during three week periods after kidney allotransplantation corresponding to episodes of acute rejection. Relative to controls, these cells incubated in vitro for five hours were found to generate increased amounts of PCA (procoagulant activity) characterized as tissue factor, the extrinsic clotting pathway activator. Controls included comparable blood leukocyte populations isolated from kidney autograft recipients and healthy animals. Differences in results for these two control groups were insignificant. These contrasts observed between allografted animals and controls demonstrate that leukocyte PCA generation is stimulated by the allogeneicity of histoincompatible kidneys rather than by direct effects of organ transplantation or non-specific postoperative effects. Results of in vitro transfer experiments provide evidence that cellular stimulation or induction in vivo accounted for the PCA increases observed. Stimulation of leukocyte tissue factor generation as a consequence of allogeneic kidney transplantation may in part account for coagulopathies and fibrin deposition during kidney rejection.
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PMID:Increased tissue factor activity generation in vitro by canine blood leukocytes associated with allogeneic kidney transplantation and rejection. 388 34

Allogeneic stimulation of human lymphoid cells initiates a collaborative cellular pathway that relatively rapidly induces in monocytes the synthesis and cell surface expression of tissue factor, the initiating cofactor of the extrinsic coagulation pathway. T cells are required for the monocyte procoagulant generation, because the addition of autologous or allogeneic T cells fully reconstitutes the activity in otherwise nonresponding highly purified monocytes. Despite a strict T cell requirement, only low T cell to monocyte ratios are necessary for maximal PCA response. Our results further demonstrate that the collaborative signal from allogeneically stimulated T cells to effector monocytes is transferred by a soluble mediator rather than direct cell to cell contact. Other aspects of the present study include the observation that among normal peripheral blood lymphoid cells, monocytes elicit the strongest allogeneic PCA response. This response is clearly exceeded by that induced upon stimulation with Daudi lymphoblastoid B cells. Our data demonstrate the existence of a second distinct cellular pathway that mediates the lymphoid procoagulant response. This pathway differs from the previously characterized response to bacterial LPS in respect to: a) kinetics of T cell triggering; b) mediation by a soluble product; c) lack of genetic restriction of T cell; monocyte collaboration; and d) deficient capacity for direct T cell induction of the monocyte PCA response.
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PMID:A distinct "slow" cellular pathway involving soluble mediators for the T cell-instructed induction of monocyte tissue factor activity in an allogeneic immune response. 623 19

Human monocyte-derived interleukin 1 (IL-1) was found to be a potent inducer of procoagulant activity in cultured human vascular endothelium. IL-1-induced human umbilical vein endothelial cell procoagulant activity (HEC-PCA) was transiently expressed, manifest in intact cell monolayers, and required protein synthesis. Data obtained with coagulation factor-deficient plasma and a goat anti-human apoprotein III antiserum suggested that most, if not all, of IL-1-induced endothelial cell procoagulant activity is tissue factor-like. IL-1 induction of HEC-PCA may be important in the pathogenesis of intravascular coagulation in a variety of immunological and inflammatory conditions.
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PMID:Interleukin 1 (IL-1) induces biosynthesis and cell surface expression of procoagulant activity in human vascular endothelial cells. 633 68

Induction of tissue factor (TF) expression on monocytes and endothelial cells is central to the development of septic coagulopathy. Serum concentrations of endotoxin in septic patients who develop disseminated intravascular coagulation (DIC) do not, however, reach the levels that would directly stimulate TF expression on either monocytes or endothelium. We show, using an in vitro coculture system, that the interaction of monocytes with endothelium induces the expression of significant levels of TF. Unstimulated cocultures of monocytes (2 x 10(4)/well) and endothelial cells (2 x 10(4)/well) produced 35.3 +/- 8.5 mU of PCA/well, representing a 5-fold increase over the combined PCA of each cell type cultured alone (7.1 +/- 1.5 mU, n = 6, P < 0.001). Significant enhancement was also found in the presence of low concentrations of LPS. Induction of TF protein was confirmed by Western blotting. Fixation of monocytes with paraformaldehyde completely abolished TF induction in cocultures, whereas fixation of endothelium had no effect, suggesting that TF induction occurred in monocytes rather than endothelial cells. Induction of TF in cocultures could be further augmented by preincubating the endothelial cells with IFN-gamma. When endothelium was prestimulated with 500 U/ml IFN-gamma there was 142 +/- 11% increase over unstimulated cocultures (n = 5, P < 0.01). TF induction was inhibited by 32 +/- 6% in the presence of anti-ICAM-1 mAb (n = 5, P < 0.01). Our results suggest that monocyte interactions with vascular endothelium, regulated by inflammatory cytokines, and mediated by adhesive ligand binding, leads to the induction of functional monocyte TF protein, which may be responsible for the initiation of DIC in sepsis.
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PMID:Induction of tissue factor expression in human monocyte/endothelium cocultures. 854 49

The possible activation of monocytes to express tissue factor procoagulant activity (TF-PCA) during CPB (cardiopulmonary bypass) was investigated. 22 patients undergoing myocardial revascularization were randomly assigned to two groups. In group C, heparin-coated circuits (Duraflo II) and reduced systemic heparinization (ACT > 250s) were used. In group NC, non-coated circuits and standard heparin administration (ACT > 480s) were used. Adherent monocytes retrieved from the oxygenators immediately after bypass arrest showed a 2-3-fold increase in TF-PCA when compared to circulating cells pre-CPB (P < 0.01). When cell PCA was expressed as percent change from pre-CPB (baseline) values, circulating monocytes in group NC at CPB-arrest showed a 2-fold increase in PCA compared to group C (P < 0.05). Moreover, the percent increase in PCA of oxygenator-retrieved monocytes was 7-fold in group NC and 2-fold in group C (P < 0.008 and P < 0.004, respectively). Thus, heparin-coating of the extracorporeal circuit reduced induction of adherent cell TF-PCA by 70% (P < 0.05). Thus, monocyte TF-PCA may cause activation of the extrinsic coagulation pathway during CPB surgery. It is apparent that heparin-coating enhanced biocompatibility of extracorporeal circuits. Reduced systemic heparinization in group C proved to be safe. However, further reduction of heparin administration may not be advisable, since monocytes were still activated in the coated oxygenator.
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PMID:Induction of monocyte tissue factor procoagulant activity during coronary artery bypass surgery is reduced with heparin-coated extracorporeal circuit. 879 Jan 53

Heparin-coating improves the biocompatibility of blood contacting artificial surfaces. This led us to investigate the impact of heparin-coating (Carmeda AB, Stockholm) of polymetylmetacrylate on the expression of monocyte tissue factor procoagulant activity (TF-PCA) by surface adhesion. Also, the anticoagulant effect of heparin-coating in the presence or absence of adherent procoagulant monocytes was assessed. This is of particular interest, since activation of extrinsic coagulation by adherent monocyte TF-PCA may play a significant role in thrombin generation during extracorporeal circulation. Monocytes exposed to heparin-coated or non-coated polymetylmetacrylate expressed TF-PCA. The heparin coat did not affect the rate of monocyte adhesion. However, heparin-coating reduced the induction of TF-PCA of non-adherent and adherent monocytes by 17 and 33% (p <0.001 and p <0.0003), respectively. Heparin-coating in the absence of monocytes, totally inhibited the clotting of recalcified plasma (p <0.003). In contrast, in the presence of adherent monocytes expressing TF-PCA, surface-bound heparin did not inhibit clotting. However, inclusion of heparin in a plasma concentration of 8.9 IU/ml totally inhibited the activation of coagulation. It is apparent that heparin-coating of an artificial surface is an efficient means to inhibit coagulation of recalcified plasma, but much less so when procoagulant monocytes are adherent to the coated surface. The present findings are of clinical relevance, since monocytes will adhere to blood contacting surfaces of extracorporeal circuits or to implanted vascular prostheses and subsequently express TF-PCA, and this may promote thromboembolism.
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PMID:Monocyte procoagulant activity induced by adherence to an artificial surface is reduced by end-point immobilized heparin-coating of the surface. 949 80


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