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P C Comp

Publications and source records attributed to P C Comp.

72 records · Page 4Linked to original sources
PubMed1984

Familial protein S deficiency is associated with recurrent thrombosis.

Recent studies have demonstrated that protein C deficiency is associated with recurrent familial thrombosis. In plasma, activated protein C functions as an anticoagulant. This anticoagulant response requires a vitamin K-dependent plasma protein cofactor, referred to as protein S. Since the anticoagulant activity of activated protein C is dependent on protein S, we hypothesized that patients lacking functional protein S might have associated thrombotic disease. Two related individuals with otherwise normal coagulation tests are described whose plasma is not effectively anticoagulated with activated protein C. Addition of purified human protein S to their plasma restores a normal anticoagulant response to activated protein C. We have developed a rapid one-stage clotting assay for protein S to quantitate the level of protein S in their plasma. Plasma is depleted of protein S by immunoadsorption with immobilized antiprotein S antibodies. The resultant plasma responds poorly to activated protein C, but is effectively anticoagulated in a dose-dependent fashion upon addition of purified protein S or small quantities of plasma. The affected individuals possess less than 5% protein S activity. Using Laurell rockets, protein S antigen was detected in the plasma but was at reduced levels of 13 and 18% in the two individuals. When the barium eluate of the patient plasma was chromatographed on quaternary aminoethyl Sephadex, a single peak of protein S antigen devoid of protein S anticoagulant cofactor activity was detected early in the chromatogram. In contrast, the barium eluate from normal donors separated into two peaks, one emerging early and also devoid of anticoagulant cofactor, and the second peak with anticoagulant activity emerging later. The first peak of protein S antigen, from both the normal donor and the patient, chromatographed in the region of the complement component C4-binding protein-protein S complex. These studies suggest that protein S deficiency may result in recurrent thrombotic disease.

Adolescent↗
PubMed1984

Heparin-protein C interaction.

Activated protein C is a vitamin K-dependent plasma protein which inhibits blood coagulation at the levels of factors V and VIII in the clotting cascade and which enhances blood clot lysis by raising the levels of circulating plasminogen activator. Activation of protein C occurs when thrombin binds to an endothelial cell associated cofactor, thrombomodulin. The thrombin-thrombomodulin complex rapidly activates the protein C. The activated protein C has a relatively long half-life in plasma and thus can serve as a circulating anticoagulant as well as elevate the levels of plasminogen activator. Heparin interacts with the protein C system in at least two distinct ways. First, the activation of protein C in vivo can be blocked by administration of low levels of heparin. The heparin brings about the inhibition of thrombin either before thrombin is bound to the cell-associated thrombomodulin or after the thrombin is complexed to the thrombomodulin. Secondly, activated protein C has its own unique inhibitor, activated protein C inhibitor. Inhibition of activated protein C by this inhibitor is stimulated by relatively high levels of heparin (5-10 u/ml). The physiologic significance of heparin-activated protein C inhibitor remains to be demonstrated.

Blood Proteins↗
PubMed1984

Determination of functional levels of protein C, an antithrombotic protein, using thrombin-thrombomodulin complex.

Protein C is a vitamin K-dependent plasma protein. Activated protein C is a potent anticoagulant and enhances blood clot lysis. We have developed a functional assay for protein C in human plasma. The measurement of protein C is accomplished by the addition of thrombomodulin, an endothelial-cell-associated cofactor for protein C activation, and thrombin in a 1:1 molar complex. The activated protein C formed in the plasma is immunoadsorbed with goat anti-human protein C IgG-agarose. The immunoadsorbed activated protein C retains the ability to hydrolyze chromogenic substrates, and after unbound plasma proteins are removed by washing, the bound activated protein C is quantitated by incubation with the substrate H-D-phe-pip-arg-p-nitroanilide (S-2238). Normal individuals have functional protein C levels of 3.9-5.9 micrograms/ml, with a mean value of 4.8 micrograms/ml. Individuals undergoing warfarin anticoagulation and patients with advanced liver diseases have decreased levels, as do certain patients with evidence of intravascular clotting. Functional protein C levels correlate well with immunologic levels of the protein in the patient groups studied. Heparin enhances the rate of activated protein C inhibition, as monitored by recovery of activated protein C by immunoadsorption. A patient with recurrent venous thrombosis and abnormal functional protein C activity, but normal levels of antigen, has been identified.

Adult↗
PubMed1982

Activation of protein C in vivo.

An endothelial cell-associated cofactor that greatly enhances the rate of protein C activation by thrombin has recently been described. The observation that the cofactor binds thrombin with unusually high affinity (K(d) = 0.5 nM) suggested that low level thrombin infusion into dogs might lead to the selective activation of protein C. Infusion of thrombin (1 U/min per kg body wt) into the jugular vein of dogs leads to the formation of a systemic anticoagulant activity within 5 min of starting the infusion. The plasma has a prolonged partial thromboplastin time and Factor X(a) clotting time, but there is no change in the thrombin clotting time. The systemic anticoagulant activity is identified as activated protein C for the following reasons: (a) anti-canine activated protein C IgG antibodies inhibit the anticoagulant activity; (b) the anticoagulant activity can be partially purified from the plasma of dogs infused with thrombin by barium citrate adsorption; (c) the anticoagulant has chromatographic properties on QAE Sephadex indistinguishable from those of activated protein C, and (d) the rate at which this anticoagulant is inhibited in citrated canine plasma is identical to that of canine activated protein C. The in vivo activation of protein C appears to be receptor mediated since it occurs at low thrombin concentration and since it can be progressively inhibited by simultaneous infusion of diisopropylphospho-thrombin with thrombin. The activation of protein C at low levels of thrombin is selective, since neither the platelet count nor the Factor V levels are altered. Thrombin infusion leads to an elevation in circulating plasminogen activator levels. This appears to be mediated through the activation of protein C since coinfusion of diisopropylphospho-thrombin with thrombin inhibits the increase in plasminogen activator levels. Pretreatment of dogs with dicumarol blocks both the formation of anticoagulant activity and the rise in plasminogen activator. When the dicumarol-treated dogs are supplemented with isolated protein C and thrombin is infused, the anticoagulant activity again appears and the circulating levels of plasminogen activator are again elevated. These studies illustrate that low levels of thrombin in vivo can activate protein C, which in turn can inhibit blood coagulation and initiate fibrinolysis by elevating circulating plasminogen activator levels.

Animals↗
PubMed1981

Generation of fibrinolytic activity by infusion of activated protein C into dogs.

Bovine-activated protein C, administered intravenously to dogs, increases the rate of lysis of whole blood clots. Protein C, bovine prothrombin, and diisopropylfluorophosphate-inactivated protein Ca do not increase the rate of lysis. Repeated infusions of protein Ca sustain rapid blood clot lysis, but neither elevate circulating fibrin-split products nor decrease circulating plasminogen levels. The administration of protein Ca results in the elevation of the levels of lysine-adsorbable plasminogen activator activity in the plasma. When partially purified concentrates of this activator are added to normal dog blood at the levels seen following protein Ca injection, the rate of clot lysis is similar to that seen after protein Ca injection. The addition of protein Ca to citrated whole blood in vitro, with the subsequent neutralization of protein Ca with antibodies, results in increased rates of lysis when plasma made from the treated blood is reinjected into the animal. The generation of fibrinolytic activity is dependent on both cellular and plasma components of blood. A model of protein Ca fibrinolytic activity has a minimum of two components: a secondary messenger formed by protein Ca action on blood cells and plasma, and the subsequent appearance of plasminogen activator in the animal in response to that messenger.

Animals↗
PubMed1981

A lysine-absorbable plasminogen activator is elevated in conditions associated with increased fibrinolytic activity.

A plasminogen activator, or class of activators, that absorbs to lysine-agarose is present in human plasma. We have developed a quantitative assay for this plasminogen activator. The assay involves removal of the activator from plasma with lysine-agarose affinity columns and subsequent measurement of the activity by the conversion of plasminogen to plasmin on standardized fibrin agar plates. Using this assay, we investigated three physiologic conditions that have in the past been associated with increased fibrinolytic activity to determine whether elevation of the LAPA was involved. Normal individuals undergoing strenuous physical exercise and others subjected to venous occlusion as well as patients with cirrhosis of the liver were examined. Treadmill exercise to maximal exertion produced up to 15-fold increases in the level of LAPA; venous occlusion produced similar elevation. Certain individuals did not show increase fibrinolytic activity in response to exercise or venous occlusion, as indicated by unchanged euglobulin lysis times. These fibrinolytic hyporesponders did not show an elevation of their LAPA levels. In the third group examined, patients with cirrhosis, 24 of 62 had elevated levels of LAPA. Supplementation of plasma from normal individuals with this plasminogen activator from exercised individuals and cirrhotics resulted in increased rates of clot lysis.

Adsorption↗
PubMed1979

Role of platelets in lysis of dilute plasma clots: requirement for metabolically active platelets.

The role of platelets in clot lysis has been investigated functionally with the use of dPRP clots formed at 4 degrees and shifted to 37 degrees. Clots handled in this manner lysed in 6 hr (+/- 1 hr), whereas clots formed at 4 degrees or at 37 degrees and held at those temperatures, or clots formed from dPPP did not lyse in less than 20 hr. dPRP clots having the shorter (6 hr) lysis time released 14C-5-HT at the time of the temperature shift. Preincubation of dPRP with antimycin A and 2-deoxy-D-glucose before addition of thrombin prolonged the clot lysis to 26 hr and inhibited release of 14C-5-HT at the time of the temperature shift. These studies demonstrate that metabolically active platelets are required to mediate the optimal clot lysis seen in the 4 degrees to 37 degrees system and that they continue to function (i.e., take up and release 5-hydroxytryptamine) after they have been incorporated into a clot. Thus the dPRP clot lysis system provides a model by which the timing and sequence of the interaction of metabolically active platelets with the fibrin framework of the formed clot can be studied.

Blood Coagulation↗
PubMed1979

Activated protein C inhibits platelet prothrombin-converting activity.

Bovine platelets that have been activated by thrombin facilitate the conversion of prothrombin to thrombin in the presence of calcium ions and factor Xa. Activated protein C, a vitamin-K-dependent plasma protein, inhibits this platelet prothrombin-converting activity. The inhibition is time dependent and is not reversed by increasing concentrations of factor Xa. However, factor Xa is able to protect the platelet prothrombin-converting activity from inactivation by activated protein C. The activated protein C causes a parallel loss of factor Xa receptor sites and platelet prothrombin-converting activity. Activated protein C may contribute to the regulation of clotting through inactivation of the platelet prothrombin-converting activity.

Animals↗
PubMed1979

The dilute whole blood clot lysis assay: a screening method for identifying postoperative patients with a high incidence of deep venous thrombosis.

A dilute whole blood clot lysis assay was used to identify patients with a high incidence of DVT. Of 191 orthopedic and urologic patients who underwent surgery, the over-all incidence of DVT as determined by 125I-fibrinogen leg scan was 35% in the 92 individuals with abnormal assays and 1% in the 99 patients with normal assays. The likelihood that an individual patient might have developed DVT increased progressively with the number of abnormal assays (p less than 0.001). The incidence of DVT increased from 28% in patients who had one abnormal assay, to 35% in patients with two abnormal assays, to 56% in patients with three abnormal assays. These studies establish the clot lysis assay as a simple means to screen for patients with a high incidence of DVT. A normal assay can eliminate patients from consideration for more extensive studies (venography, fibrinogen scan, impedance plethysmography), whereas those patients with one or more abnormal assays should be seriously considered for these additional studies.

Adult↗
PubMed1971

Properties of an extracellular -galactosidase secreted by Neurospora crassa.

An extracellular beta-galactosidase with an activity optimum at about pH 4 was found to occur in the filtrates of Neurospora crassa strain 74A when this mold was grown on certain sugars. This activity accounted for a substantial portion of the beta-galactosidase activity in the culture. The beta-galactosidase in the medium appeared to be a secreted, extracellular enzyme, not a product of cell lysis. The extracellular activity was found to have physical and kinetic properties similar to those of an intracellular beta-galactosidase previously found in Neurospora. Some conditions for the production and concentration of the enzyme are described.

Carbohydrate Metabolism↗
PubMedDate not supplied

Deficiency of plasma protein S, protein C, or antithrombin III and arterial thrombosis.

Protein C and protein S are vitamin K-dependent coagulation factors that together act as an anticoagulant, and antithrombin III is a plasma protein that inhibits several activated factors in the coagulation cascade. Although deficiencies of any of these three proteins have been associated with deficiencies of these factors. We report one patient with a protein S deficiency, another with a protein C deficiency, and a third with an antithrombin III deficiency, each of whom who had extensive arterial thrombosis. We suggest that deficiencies of these proteins may constitute risk factors for arterial thrombosis.

Adult↗
PubMedDate not supplied

Coagulolysis assay in the detection of deep vein thrombosis in the orthopedic patient. A preliminary report.

The recently developed coagulolysis assay was utilized in conjuction with fibrinogen uptake scanning to monitor 91 of 111 consecutive orthopedic patients scheduled for hip surgery or total knee replacement. Sixteen patients had abnormal coagulolysis assays and positive scans. Venography was performed in 15 of these patients, and deep vein thrombosis was documented in 12. Five patients developed pulmonary emboli, including one with negative venogram. Thus, over 80% of the patients in which both the coagulolysis assay and the fibrinogen scan were abnormal had additional documentation of deep vein thrombosis. In 41 patients, the coagulolysis assay was negative. Venograms were not routinely performed in this group. However, 3 patients developed pulmonary emboli indicating that deep vein thrombosis developed in this group. Only one patient had a normal coagulolysis with a positive fibrinogen scan. Venography documented a deep vein thrombosis. Thirty-three patients who had normal coagulolysis assays and negative fibrinogen scans also had no evidence of deep vein thrombosis or pulmonary embolism. The coagulolysis assay appears to be a safe, noninvasive study for the detection of deep vein thrombosis. There was only a one per cent false-negative incidence.

Blood Coagulation Tests↗