Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

C-reactive protein (CRP) is an acute phase reactant which shares numerous functional characteristics with the immunoglobulins. In the present study CRP was found to inhibit the aggregation of human platelets stimulated by either modified human immunoglobulin or thrombin. This effect did not involve chelation of calcium or cytotoxicity, and was overcome by larger amounts of the aggregating agents. CRP also inhibited the activation but not the activity of platelet factor 3 and the release of beta-glucuronidase. Thus, CRP can inhibit multiple platelet reactivities. We suggest that this property of CRP may play an important role in the control of platelet responsiveness during reactions of inflammation, defense, and repair.
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PMID:Effects of C-reactive protein on platelet function. I. Inhibition of platelet aggregation and release reactions. 5 27

It was previously demonstrated that C-reactive protein (CRP) inhibits platelet aggregation and release reactions, activation of platelet factor 3, and platelet-dependent clot retraction. Multiple considerations including selective inhibition of secondary wave aggregation suggested that CRP exerted its inhibitory effects by interfering with the release of endogenous ADP. In the present investigation, CRP was found by direct assay to inhibit the release of endogenous ADP and/or serotonin concomitant with inhibition of platelet aggregation stimulated by ADP, epinephrine, thrombin, and AHGG. CRP did not induce an increase in the basal level of platelet cAMP, suggesting independence of a direct effect upon this mediator system. Furthermore, CRP did not inhibit the aggregation and secretion induced by the antibiotic ionophore A23187, suggesting the absence of a direct effect upon the activation of platelet contractile elements. By contrast, CRP did inhibit both thrombin-induced release of malondialdehyde, a prostaglandin endoperoxide nonprostanoate endproduct, and platelet aggregation induced by the prostaglandin endoperoxide precursor arachidonic acid. These data, therefore, raise the possibility that CRP inhibits platelet reactivities by interfering with an aspect of porstaglandin metabolism, and that this occurs subsequent to the hydrolytic accumulation of arachidonic acid and prior to the movement of calcium from the platelet dense tubules. These studies support the concept that CRP serves to modulate platelet reactivities during acute inflammatory reactions.
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PMID:Effects of C-reactive protein on platelet function. III. The role of cAMP, contractile elements, and prostaglandin metabolism in CRP-induced inhibition of platelet aggregation and secretion. 7 Apr 75

It was recently demonstrated that C-reactive protein (CRP)4 inhibits the response of human platelets to heataggregated human gamma-globulin and thrombin and that this inhibition is characterized by a dose-dependent reduction in aggregation, activation of platelet factor 3 (PF3), and release of beta-glucuronidase. In the present experiments, CRP was found also to inhibit the ability of washed human platelets to aggregate in response to poly-L-lysine (PLL); in these experiments, the magnitude of the inhibitory effect was dependent upon the m.w. of PLL used as the stimulating agent, and was more effective with low (15,000 daltons) than with high (400,000 daltons) m.w. polymers. CRP similarly inhibited ADP- and epinephrine-stimulated platelet aggregation in platelet-rich plasma (PRP), and this was characterized by relatively minimal suppression of the primary wave of aggregation. CRP also inhibited the platelet aggregation induced by collagen in PRP, although it had no effect upon the adherence of platelets to collagen. Finally, CRP inhibited the activation of PF3 and the release of serotonin during stimulation of platelets with ADP, and this inhibition was temporally related to the onset of the secondary wave of aggregation. These experiments extend the platelet reactivities inhibited by CRP, show that CRP expresses its inhibitory capacity in platelet-rich plasma as well as upon isolated platelets, raise the possibility that CRP exercises its effects by inhibiting or interfering with the release and/or utilization of endogenous platelet ADP, and support the concept that CRP plays an important role in the control of platelet responsiveness to a variety of stimuli during acute inflammatory reactions.
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PMID:Effects of C-reactive protein on platelet function. II. Inhibition by CRP of platelet reactivities stimulated by poly-L-lysine, ADP, epinephrine, and collagen. 97 42

In seven patients who had to be dialysed between four and 13 times due to acute renal failure, low molecular weight heparin (LMWH) Fragmin was used for anticoagulation. According to dose-finding studies, 80-90 U kg-1 body weight of LMWH as a single bolus were administered initially, producing dose-related levels of 0.3-1.5 anti-factor Xa U ml-1 in plasma. Apart from the anti-Xa activity in the plasma, the thrombin anti-thrombin III complex (TAT complex) and a fibrin degradation product (D-dimer) were measured as parameters of a coagulation activation. A sufficient anti-coagulation during dialysis was supposed to exist at a normal range (5.0 micrograms l-1 or below) of TAT complex. Pathological TAT concentrations at the end of dialysis indicated the requirement of an increased dose for the next dialysis. These concentrations reflected a need for more heparin if, for example, inflammation, indicated by increasing C-reactive protein levels (CRP), occurred. The increase of TAT complex and D-dimer during dialysis showed a good agreement (p less than 0.001). Due to a single bolus application before dialysis, one measurement of TAT at the end of the dialysis was sufficient. The determination of the TAT complex concentration enabled a heparinization better adapted to the clinical situation of intensive-care patients undergoing acute dialyses, so that the coagulation system was not additionally activated by the extracorporeal circulation.
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PMID:The control of anti-coagulation in acute dialyses with sensitive laboratory parameters. 133 80

In a controlled pilot study of 32 critically ill patients, we have attempted prospectively to identify laboratory variables which can be used to select and monitor patients on antithrombin (AT) therapy. Patients with plasma AT levels less than 70% of normal were randomized to receive (AT group) or not to receive AT concentrate (non-AT group). The groups did not differ in median age, sex, median APACHE II and TISS scores, number of days spent in the Intensive Care Unit or mortality rate. At the time of inclusion all patients had activated coagulation and fibrinolysis demonstrated as high levels of soluble fibrin, thrombin-antithrombin complexes and fibrin-D-dimers (twice, four and ten times the upper reference range, respectively). In the AT group these levels decreased faster and the prothrombin complex concentration increased more rapidly to normal (i.e. the prothrombin time decreased). The level of C-reactive protein which was high in both groups on inclusion (139 and 98 mg/l, respectively) decreased by 40% in the AT group but did not change in the control group. Our study indicates that laboratory variables normalize faster in seriously ill patients who have activated coagulation and fibrinolysis when they receive AT concentrate and that the variables mentioned above seem to be useful for monitoring the treatment.
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PMID:Effect of antithrombin concentrate on haemostatic variables in critically ill patients. 146 8

Patients with unstable angina pectoris (UAP; n = 20) and acute myocardial infarction (AMI; n = 34) were studied in the acute phase of ischaemic heart disease. We found significantly higher levels of thrombin-antithrombin-III (TAT) complexes, lower levels of systemic tissue plasminogen activator (t-PA) activity, and higher levels of plasminogen activator inhibitor (PAI) activity in the AMI patients compared to the UAP patients. In contrast to these specific changes, general acute phase reactants such as C-reactive protein, fibrinogen and von Willebrand factor did not differ significantly between the two groups. Studies of the relationship between coagulation (TAT-complexes) and fibrinolysis data revealed a significant positive correlation between plasma antigen concentrations of TAT-complexes and t-PA (P less than 0.02), and between TAT-complexes and PAI-I (P less than 0.002). These observations indicate a common pathophysiological mechanism underlying the changes in coagulation and fibrinolysis, suggesting that coagulation activity and t-PA-related fibrinolysis are interrelated processes in vivo, and probably take place at the level of the endothelial cell.
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PMID:Interrelationship between coagulant activity and tissue-type plasminogen activator (t-PA) system in acute ischaemic heart disease. Possible role of the endothelium. 170 58

Cytostatic therapy is known to aggravate tumor-induced coagulopathy. Therefore, we have studied the effect of different chemotherapeutic regimens on the activation of coagulation and fibrinolysis in patients with non-Hodgkin's lymphomas or acute leukemias. In non-Hodgkin's lymphoma patients treated with an aggressive protocol (COL-BLAM) and in leukemia patients (TAD-9) fibrinopeptide A, prothrombin fragment (F1 + 2) and thrombin antithrombin III complexes (TAT) increased (Tables 4 and 6), while D-dimer did not deviate significantly. The ratio D-dimer/TAT consequently showed a significant decrease, indicating increased formation of thrombin after release of procoagulant factors, which is not paralleled by an activation of fibrinolysis. Both these groups were also characterized by an increase in uric acid and in C-reactive protein and plasminogen-activator inhibitor, two acute-phase reactants. In contrast, patients with non-Hodgkin's lymphomas treated with a less aggressive protocol (COP) showed no significant changes in hemostatic variables, uric acid, or acute-phase reactants. The release of procoagulant factors relates to the cytostatic sensitivity of the tumor and to a high tumor-cell destruction. Our results further emphasize the need for large-scale studies on antithrombotic prophylaxis in patients undergoing cytostatic treatment.
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PMID:Influence of cytostatic treatment on the coagulation system and fibrinolysis in patients with non-Hodgkin's lymphomas and acute leukemias. 171 7

It has been shown that lipoprotein(a) (Lp[a]) may interfere with the fibrinolytic system and that the Lp(a) level in an individual remains constant. To evaluate the effects of Lp(a) on the fibrinolytic system in patients with unstable angina, we measured plasma levels of Lp(a), the alpha 2-plasmin inhibitor-plasmin complex, and the thrombin-antithrombin III complex. The latter is a marker of thrombin generation, and the alpha 2-plasmin inhibitor-plasmin complex is an indicator of plasminogen activation. Venous plasma samples were taken from 18 patients with unstable angina and 18 patients with stable exertional angina who had been matched for clinical variables. On admission, plasma levels of Lp(a) were significantly higher in patients with unstable angina than in those with stable exertional angina (319 +/- 193 mg/l versus 191 +/- 141 mg/l, respectively; p less than 0.05). On admission, plasma levels of the alpha 2-plasmin inhibitor-plasmin complex and of the thrombin-antithrombin III complex were also significantly higher in patients with unstable angina than in those with stable exertional angina (0.78 +/- 0.42 micrograms/ml and 3.6 +/- 1.3 ng/ml versus 0.41 +/- 0.13 micrograms/ml and 1.9 +/- 0.5 ng/ml, respectively; p less than 0.01). In nine of the 18 patients with unstable angina, serial changes of plasma levels of Lp(a), the alpha 2-plasmin inhibitor-plasmin complex, the thrombin-antithrombin III complex, and the acute-phase proteins C-reactive protein and alpha 1-antitrypsin were examined for 3 weeks after admission.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Transient increase of plasma lipoprotein(a) in patients with unstable angina pectoris. Does lipoprotein(a) alter fibrinolysis? 183 67

C-reactive protein (CRP) is an acute phase inflammatory protein in man which binds to phosphocholine, chromatin, histones, and the 70-kDa protein of the U1 small nuclear ribonucleoprotein particle in a calcium-dependent, phosphocholine-inhibitable manner. CRP also binds to other proteins including fibronectin. The determinants involved in CRP binding to these diverse proteins have not been identified. The binding of CRP to histones was examined as these proteins are available in large quantity at high purity and subject to protease digestion with well characterized products. Histone H1 was digested with thrombin and trypsin to produce three distinct fragments, N-terminal, central globular, and C-terminal. CRP was shown only to bind to the C-terminal fragment. Binding to histone H2A was also examined. CRP binding was not diminished by cleavage of the C-terminal fragment but was greatly decreased when the central globular region of H2A was tested. Peptides were prepared to be identical to the N- and C-terminal fragments of H2A. The N-terminal (15 amino acid) fragment of H2A blocked CRP-induced precipitation of phosphocholine-coupled bovine serum albumin and histone H2A, whereas the C-terminal fragment showed no inhibition. Thus we have defined the first reported CRP binding determinant on a protein.
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PMID:Definition of a C-reactive protein binding determinant on histones. 198 77

C-reactive protein is the prototypic acute phase reactant. A self-complexed form (H-CRP) can induce isolated platelets to undergo aggregation, secretion of dense and alpha-granule constituents, and generation of thromboxane A2, but fails to function in platelet-rich plasma (PRP) as a direct agonist. In contrast, when PRP was activated with an amount of adenosine diphosphate (ADP) that produced only reversible platelet aggregation, the presence of H-CRP resulted in irreversible aggregation and the secretion of adenosine triphosphate (ATP). Following a maximum stimulus with ADP alone, where platelet secretion occurred late during the aggregation response, the presence of H-CRP shifted and increased the secretory burst to a time simultaneous with the onset of aggregation. This hypersecretion required H-CRP to be present prior to platelet stimulation or to be added within 15 to 30 seconds following the addition of ADP. H-CRP also potentiated platelet activation stimulated with epinephrine, thrombin, and collagen. When the synergism generated in PRP by H-CRP in the presence of ADP or epinephrine was compared to the synergism similarly produced by aggregated human IgG, collagen, or thrombin, it more closely resembled that of collagen, as reflected by the kinetics and characteristics of synergism and sensitivity to creatine phosphate/creatine phosphokinase or 5,8,11,14-eicosatetraynoic acid. These data provide a philosophically ideal niche for the acute phase (and C-reactive protein) in that a platelet-directed activity associated with this acute phase reactant is not utilized unless platelets are otherwise challenged.
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PMID:Platelet agonist synergism by the acute phase reactant C-reactive protein. 257 99


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