Anticoagulant Activity of Crude and Phenolic Extracts of Dalbergia ecastaphyllum (L.) Taub. Dried Leaves

SummaryUnfractionated heparin potentiates the anticoagulant action of activated protein C (APC) through several mechanisms, including the recently described enhancement of proteolytic inactivation of factor V. Possible anticoagulant synergism between APC and physiologic glycosaminoglycans, pharmacologic low molecular weight heparins (LMWHs), and other heparin derivatives was studied. Dermatan sulfate showed potent APC-enhancing effect. Commercial LMWHs showed differing abilities to promote APC activity, and the molecular weight of LMWHs correlated with enhancement of APC activity. Degree of sulfation of the glycosaminoglycans influenced APC enhancement. However, because dextran sulfates did not potentiate APC action, the presence of sulfate groups per se on a polysaccharide is not sufficient for APC enhancement. As previously for unfractionated heparin, APC anticoagulant activity was enhanced by glycosaminoglycans when factor V but not factor Va was the substrate. Thus, dermatan sulfate and LMWHs exhibit APC enhancing activity in vitro that could be of physiologic and pharmacologic significance.

Download Full-text

Assays for Phospholipid-Dependent Formation of Thrombin and Xa: A Potential Method for Quantifying Lupus Anticoagulant Activity

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646437 ◽

1991 ◽

Vol 66 (04) ◽

pp. 453-458 ◽

Cited By ~ 15

Author(s):

John T Brandt

Keyword(s):

Specific Activity ◽

Anticoagulant Activity ◽

Factor Xa ◽

Clinical Importance ◽

Potential Method ◽

Quantitative Expression ◽

Increased Risk ◽

Apparent Association

SummaryLupus anticoagulants (LAs) are antibodies which interfere with phospholipid-dependent procoagulant reactions. Their clinical importance is due to their apparent association with an increased risk of thrombo-embolic disease. To date there have been few assays for quantifying the specific activity of these antibodies in vitro and this has hampered attempts to purify and characterize these antibodies. Methods for determining phospholipid-dependent generation of thrombin and factor Xa are described. Isolated IgG fractions from 7 of 9 patients with LAs were found to reproducibly inhibit enzyme generation in these assay systems, permitting quantitative expression of inhibitor activity. Different patterns of inhibitory activity, based on the relative inhibition of thrombin and factor Xa generation, were found, further substantiating the known heterogeneity of these antibodies. These systems may prove helpful in further purification and characterization of LAs.

Download Full-text

The Anticoagulant Properties of a Modified Form of Protein S

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647048 ◽

1988 ◽

Vol 60 (02) ◽

pp. 298-304 ◽

Cited By ~ 17

Author(s):

C A Mitchell ◽

S M Kelemen ◽

H H Salem

Keyword(s):

Monoclonal Antibody ◽

Anticoagulant Activity ◽

Activated Protein C ◽

Factor Xa ◽

Protein S ◽

Human Neutrophil Elastase ◽

Factor X ◽

Sds Page

SummaryProtein S (PS) is a vitamin K-dependent anticoagulant that acts as a cofactor to activated protein C (APC). To date PS has not been shown to possess anticoagulant activity in the absence of APC.In this study, we have developed monoclonal antibody to protein S and used to purify the protein to homogeneity from plasma. Affinity purified protein S (PSM), although identical to the conventionally purified protein as judged by SDS-PAGE, had significant anticoagulant activity in the absence of APC when measured in a factor Xa recalcification time. Using SDS-PAGE we have demonstrated that prothrombin cleavage by factor X awas inhibited in the presence of PSM. Kinetic analysis of the reaction revealed that PSM competitively inhibited factor X amediated cleavage of prothrombin. PS preincubated with the monoclonal antibody, acquired similar anticoagulant properties. These results suggest that the interaction of the monoclonal antibody with PS results in an alteration in the protein exposing sites that mediate the observed anticoagulant effect. Support that the protein was altered was derived from the observation that PSM was eight fold more sensitive to cleavage by thrombin and human neutrophil elastase than conventionally purified protein S.These observations suggest that PS can be modified in vitro to a protein with APC-independent anticoagulant activity and raise the possibility that a similar alteration could occur in vivo through the binding protein S to a cellular or plasma protein.

Download Full-text

Pharmacokinetics of Full Length and Two-Domain Tissue Factor Pathway Inhibitor in Combination with Heparin in Rabbits

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649604 ◽

1993 ◽

Vol 70 (03) ◽

pp. 454-457 ◽

Cited By ~ 14

Author(s):

Claus Bregengaard ◽

Ole Nordfang ◽

Per Østergaard ◽

Jens G L Petersen ◽

Giorgio Meyn ◽

...

Keyword(s):

Tissue Factor ◽

Tissue Factor Pathway Inhibitor ◽

Anticoagulant Activity ◽

Fold Increase ◽

Volume Of Distribution ◽

Full Length ◽

Heparin Binding ◽

Extrinsic Pathway ◽

C Terminus ◽

Tissue Factor Pathway

SummaryTissue factor pathway inhibitor (TFPI) is a feed back inhibitor of the initial activation of the extrinsic pathway of coagulation. In humans, injection of heparin results in a 2-6 fold increase in plasma TFPI and recent studies suggest that TFPI may be important for the anticoagulant activity of heparin. Full length (FL) TFPI, but not recombinant two-domain (2D) TFPI, has a poly cationic C-terminus showing very strong heparin binding. Therefore, we have investigated if heparin affects the pharmacokinetics of TFPI with and without this C-terminus.FL-TFPI (608 U/kg) and 2D-TFPI (337 U/kg) were injected intravenously in rabbits with and without simultaneous intravenous injections of low molecular weight heparin (450 anti-XaU/kg).Heparin decreased the volume of distribution and the clearance of FL-TFPI by a factor 10-15, whereas the pharmacokinetics of 2D-TFPI were unaffected by heparin. When heparin was administered 2 h following TFPI the recovery of FL-TFPI was similar to that found in the group receiving the two compounds simultaneously, suggesting that the releasable pool of FL-TFPI is removed very slowly in the absence of circulating heparin.

Download Full-text

The Significance of TFPI in Clotting Assays – Gomparison and Combination with other Anticoagulants

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649603 ◽

1993 ◽

Vol 70 (03) ◽

pp. 448-453 ◽

Cited By ~ 12

Author(s):

Ole Nordfang ◽

Hanne I Kristensen ◽

Sanne Valentin ◽

Per Østergaard ◽

Johnny Wadt

Keyword(s):

Tissue Factor ◽

Tissue Factor Pathway Inhibitor ◽

Antithrombin Iii ◽

Anticoagulant Activity ◽

Assay System ◽

Thrombin Inhibitor ◽

Clotting Time ◽

Normal Plasma ◽

Tissue Factor Pathway ◽

Plasma Heparin

SummaryThe anticoagulant activities of Tissue Factor Pathway Inhibitor (TFPI), heparin and hirudin were compared in intrinsic (APTT) and extrinsic (PT) activated clotting assays. In contrast to the thrombin inhibitor hirudin, heparin was 10 fold more potent in the APTT assay than in the PT assay, indicating that inhibition of intrinsic activation is important for the anticoagulant activity of heparin as measured in an APTT assay. TFPI was most potent in the PT assay and the effect of TFPI was most pronounced in the presence of other anticoagulants (heparin and hirudin). The activities of the two natural anticoagulants antithrombin III (ATIII) and TFPI were compared in a PT assay with very dilute tissue factor. In this assay system TFPI in normal plasma affected the clotting time more than ATIII in the plasma. However, when heparin was added ATIII was the major anticoagulant, but profound Prolongation of the clotting time was only seen when TFPI was also added. In an ATIII deficient plasma heparin did not augment the effect of TFPI, showing that the increased effect of TFPI in the presence of heparin is dependent on the anticoagulant activity of ATIII/heparin. The effect of TFPI at prolonged clotting times was also illustrated by the significant effect of blocking TFPI in the plasma from warfarin-treated patients. Thus TFPI is a major anticoagulant in normal plasma and the effect of TFPI is especially seen at prolonged clotting times.

Download Full-text

The Coagulation Abnormalities in Systemic Lupus Erythematosus

Thrombosis and Haemostasis ◽

10.1055/s-0038-1651288 ◽

1968 ◽

Vol 20 (03/04) ◽

pp. 457-464 ◽

Cited By ~ 17

Author(s):

L Gonyea ◽

R Herdman ◽

R. A Bridges

Keyword(s):

Systemic Lupus Erythematosus ◽

Ammonium Sulfate ◽

Lupus Erythematosus ◽

Anticoagulant Activity ◽

Species Specificity ◽

Sensitive Assay ◽

Systemic Lupus ◽

Coagulation Abnormalities

SummaryAn anticoagulant occurring in 4 of 6 patients with SLE has been demonstrated by a sensitive assay utilizing an ammonium sulfate fraction of serum. The anticoagulant functions as an inhibitor of the activation of prothrombin. No species specificity was demonstrable. The inhibitor behaves clinically and chromatographically as an immunoglobulin, although an attempt to demonstrate directly the antibody nature of the inhibitor was not successful.A severe, apparently independent, decrease in the level of prothrombin was observed in the patient with hemorrhagic symptoms. In contrast to the anticoagulant activity, the low prothrombin has persisted during treatment.

Download Full-text

Heparin Excretion in Intact and Hepatectomized Rats

Thrombosis and Haemostasis ◽

10.1055/s-0038-1650152 ◽

1981 ◽

Vol 45 (02) ◽

pp. 146-149

Author(s):

Ray Losito ◽

Harry Gattiker ◽

Ginette Bilodeau

Keyword(s):

Column Chromatography ◽

Normal Values ◽

Anticoagulant Activity ◽

Biliary Fistula ◽

Kinetics Of ◽

Intact Rats

SummaryMetabolism and kinetics of 3H-heparin were compared in intact and hepatectomized rats. Rats were divided into three groups: 1) intact rats with biliary fistulas and cystostomies 2) intact rats with only cystostomies and 3) hepatectomized rats with cystostomies. Radioactivity in blood, bile and urine besides anticoagulant activity in blood and urine were examined. In addition, column chromatography of urine was used to isolate possible metabolites. Seventy percent and 80% of the radioactive dose was found in the urine of intact rats at 24 hr and 48 hr. Close to 5% of the radioactivity was found in bile or rats with a biliary fistula after 48 hr. The APTT declined to near normal values at 1 hr whether rats had a biliary fistula or not. In contrast, only 25 % of the radioactivity could be excreted into the urine of hepatectomized rats in 24 hr; the APTT did not decline as fast and at 5 hr, it was still 100 seconds. Only one radioactive component could be isolated on chromatography from all urines of these animals and appears to be similar to the original heparin. Thus, the liver has an important role to play in regulating the anticoagulant effects and excretion of heparin.

Download Full-text

Anticoagulant Activity of Hirulog™, a Direct Thrombin Inhibitor, in Humans

Thrombosis and Haemostasis ◽

10.1055/s-0038-1651573 ◽

1993 ◽

Vol 69 (02) ◽

pp. 157-163 ◽

Cited By ~ 137

Author(s):

Irving Fox ◽

Adrian Dawson ◽

Peter Loynds ◽

Jane Eisner ◽

Kathleen Findlen ◽

...

Keyword(s):

Rational Design ◽

Therapeutic Potential ◽

Anticoagulant Activity ◽

Subcutaneous Administration ◽

Direct Thrombin Inhibitor ◽

Controlled Study ◽

Thrombin Inhibitor ◽

Thrombin Time ◽

Thrombotic Disease ◽

Dose Dependent

SummaryHirulog™ (BG8967) is a direct thrombin inhibitor built by rational design using the protein hirudin as a model (Maraganore et al. [1990]; Biochemistry 29: 7095–101). In order to evaluate the therapeutic potential for hirulog in the management of thrombotic disease, the tolerability and anticoagulant activity of the agent were examined in a study of human volunteers.In a randomized, placebo-controlled study (n = 54), the intravenous infusion of hirulog over 15 min showed a rapid, dose-dependent prolongation of activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT). There was a corresponding dose-dependent increase in plasma hirulog levels. The peptide was rapidly cleared with a half-life of 36 min and a total body clearance rate for the peptide of 0.43 1 kg−1 h−1. Similar activity was observed following subcutaneous injection but with sustained pharmacodynamic and pharmacokinetic behavior. There was a significant correlation between pharmacokinetic and pharmacodynamic variables for both intravenous (r = 0.8, p <0.001) and subcutaneous administration (r = 0.7, p = 0.002).To evaluate the possible interactions of aspirin on the tolerability and anticoagulant activity of intravenous hirulog, a cross-over design was employed in eight subjects. Aspirin administration did not modify the peptide’s activity. At the administered dose of 0.6 mg kg−1 h−1 for 2 h, hirulog infusion prolonged APTT from 230 to 260% baseline. The infusion of hirulog in subjects who had received aspirin was not associated with any significant changes in the template bleeding time.The final phase of the study examined the activity and tolerability of hirulog in ten subjects during prolonged intravenous infusions for up to 24 h. The peptide (0.3 mg kg−1 h−1) exhibited sustained anticoagulant activity with no evidence for a cumulative effect. During hirulog infusion, APTT was prolonged from 210 to 250% baseline.In all phases of the study, hirulog administration was generally well-tolerated.Our observations show that hirulog is an active antithrombin agent with excellent tolerability in humans. As a direct thrombin inhibitor, hirulog provides a novel approach for the management of thrombotic disease.

Download Full-text

Comparison of the Non-Specific Binding of Unfractionated Heparin and Low Molecular Weight Heparin (Enoxaparin) to Plasma Proteins

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649639 ◽

1993 ◽

Vol 70 (04) ◽

pp. 625-630 ◽

Cited By ~ 71

Author(s):

Edward Young ◽

Benilde Cosmi ◽

Jeffrey Weitz ◽

Jack Hirsh

Keyword(s):

Molecular Weight ◽

Unfractionated Heparin ◽

Plasma Proteins ◽

Low Molecular Weight Heparin ◽

Specific Binding ◽

Anticoagulant Activity ◽

Factor Xa ◽

Low Molecular Weight ◽

Heparin Binding ◽

Fixed Amount

SummaryThe non-specific binding of anticoagulantly-active heparin to plasma proteins may influence its anticoagulant effect. We used low affinity heparin (LAH) essentially devoid of anti-factor Xa activity to investigate the extent and possible mechanism of this non-specific binding. The addition of excess LAH to platelet-poor plasma containing a fixed amount of unfractionated heparin doubled the anti-factor Xa activity presumably because it displaces anticoagulantly-active heparin from plasma proteins. Although dextran sulfates of varying molecular weights also increased the anti-factor Xa activity, less sulfated heparin-like polysaccharides had no effect. These findings suggest that the ability to displace active heparin from plasma protein binding sites is related to charge and may be independent of molecular size. In contrast to its effect in plasma containing unfractionated heparin, there was little augmentation in anti-factor Xa activity when LAH was added to plasma containing low molecular weight heparin (LMWH), indicating that LMWH binds less to plasma proteins than unfractionated heparin. This concept is supported by studies comparing the anticoagulant activity of unfractionated heparin and LMWH in plasma with that in buffer containing antithrombin III. The anti-factor Xa activity of unfractionated heparin was 2-fold less in plasma than in the purified system. In contrast, LMWH had identical anti-factor Xa activity in both plasma and buffer, respectively. These findings may be clinically relevant because the recovered anti-factor Xa activity of unfractionated heparin was 33% lower in plasma from patients with suspected venous thrombosis than in plasma from healthy volunteers. The reduced heparin recovery in patient plasma reflects increased heparin binding to plasma proteins because the addition of LAH augmented the anti-factor Xa activity. In contrast to unfractionated heparin, there was complete recovery of LMWH added to patient plasma and little increase of anti-factor Xa activity after the addition of LAH. These findings may explain why LMWH gives a more predictable dose response than unfractionated heparin.

Download Full-text

The Anticoagulant Activity of 3.3’-(p-Alkylthio-Benzylidene)-Bis-4-Hydroxycoumarins and Their Oxidation Products

Thrombosis and Haemostasis ◽

10.1055/s-0038-1654103 ◽

1967 ◽

Vol 17 (01/02) ◽

pp. 277-286 ◽

Cited By ~ 2

Author(s):

Maria Gumińska ◽

M Eckstein ◽

Barbara Stachurska ◽

J Sulko

Keyword(s):

Biological Activity ◽

Anticoagulant Activity ◽

Oxidation Products ◽

Para Position ◽

Sulphur Atom ◽

Group I ◽

One Step

SummaryThe anticoagulant activity of 3.3’-(benzylidene)-bis-4-hydroxycoumarin derivatives has been estimated by one step Quick’s method. The derivatives contained the following groups in the para position of benzylidene residue: NCS- (I), CH3-S- (II), CH3-SO-(III), CH3-S02- (IV), C2H5-S- (V), C2H5-SO- (VI), C2H5-S02- (VII). All these compounds were much more active than 3.3’-(benzylidene)-bis-4-hydroxycoumarin itself.Compounds possessing the ethyl chain at the sulphur atom (V, VI, VII) were more active than methyl homologues (II, III, IV). Comparison of the activity of the series of thio-, sulphoxy-, and sulphonyl-derivatives showed that among methyl- and ethyl-derivatives those with the sulphoxy grouping (III, VI) displayed the greatest anticoagulant activity. The action of sulphonyl (IV, VII) and thio-derivatives (II, V) was weaker and shortest. The derivative with the NCS-group (I) possessed a relatively the lowest activity among the investigated compounds. 3.3’-(p-Ethylsulphoxybenzyl-idene)-bis-4-hydroxycoumarin (VI), with distinct biological activity reached about ½ of dicoumarol activity.

Download Full-text