bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined Dys-Form of Homozygous Factor XI Deficiency and Heterozygous Factor XII Deficiency
Authors: Hellstern P. , Mannhalter C. , Köhler M. , Kiehl R. , von Blohn G. , Wenzel E. , Deutsch E.
Published: April 2009

A 12-year-old girl with lifelong hemorrhagic episodes was found to have both a dys-form of homozygous factor XI deficiency and heterozygous factor XII deficiency. The heredity of the coagulation defects was confirmed by family studies. Severe bleeding after dental surgery occurred in spite of replacement therapy and local measures including fibrin glue. Our findings suggest that the risk of bleeding in patients with homozygous factor XI deficiency must not be underestimated and that the most effective measure is the transfusion of sufficient amounts of fresh frozen plasma until at least the 5th postoperative day.
Lupus Anticoagulants and Thrombosis
Authors: Lechner K. , Pabinger-Fasching I.
Published: April 2009

25 patients with lupus anticoagulant (LA) and a history of thrombosis are described and the cases reported in the literature with this association are reviewed. From the combined data it is concluded that the prevalence of thrombosis in patients with LA is about 30%, the thrombosis sites are the leg veins in about 66%, the cerebral arteries in 25% and the peripheral arteries in 10% of the patients. High anticardiolipin levels are associated with a higher risk, while age of less than 10 years, low prothrombin activity and a platelet count of less than 50,000/μl is associated with a lower risk of thrombosis. Heparin and oral anticoagulants are effective in the treatment and prevention of thrombosis without untoward risk of bleeding.
Standardization of the Prothrombin Time in Oral Anticoagulant Control
Authors: van den Besselaar A.M.H.P.
Published: April 2009

The establishment of International Reference Preparations for thromboplastin together with a recommended methodology for use has permitted the definition of a universal scale for intensity of oral anticoagulation. This scale is called International Normalized Ratio (INR). INRs can be calculated by using calibrated thromboplastin/instrument systems. A calibration model has been developed together with statistical methods to test this model. The imprecision of calculated INRs has been estimated using information from international collaborative studies and proficiency testing programs. Normalized prothrombin times obtained with calibrated thromboplastin/instrument systems have been shown to provide safe patient care in clinical practice. The development of control plasmas with assigned INR equivalents will complete the standardization system. The INR scale will facilitate the process of consensus-making with respect to optimal therapeutic ranges for anticoagulant intensity. Finally, it will improve the continuity of anticoagulant control of travelling patients.
The Management of Stroke: Fears and Facts
Authors: Wintzen A.R.
Published: April 2009

The poor definition of stroke, the lack of exact knowledge of its aetiology and natural history, particulary in an individual case, and our limited insights into the effects of both medical and surgical treatment have up to now not broadened the fairly narrow rational basis for management of stroke patients. It is argued that, despite a vast literature on the subject, treatment is mainly conducted along emotional lines in practice. The only exception to this forms the secondary prevention of cardiogenic emboli.
An Analysis of the One-Stage Prothrombin Time
Authors: Talstad Ingebrigt
Published: April 2009

An analysis of the one-stage prothrombin time using thromboplastins highly (Thrombotest®) and slightly (Normotest®) sensitive to the Pivka (protein induced by vitamin K absence) inhibitor is presented. A one-tenth dilution of blood with 0.1 mol/l Na3 citrate was satisfactory even at an extreme packed cell volume (PCV). Whole blood and plasma were equally satisfactory as test materials; however, their accuracy and precision were greatly improved when a small sample size at a high coagulation activity and a large sample size at a low coagulation activity were used. The PCV correction method which corrected for the different Pivka inhibitor sensitivities of thromboplastins was preferable.
The Ratio MDA/MDAa as a New Index of Platelet Hyperactivity
Authors: Makris P.E. , Tsakiris D.A. , Papadopoulos A. , Balias A.
Published: April 2009

Since 1979, malonyldialdehyde (MDA) is considered a sensitive index of platelet hyperactivity. Stimulators of phospholipase A2 are used in the procedure of MDA production in order to obtain the final quantity (MDAa) which corresponds to the total amount of arachi-donic acid present; without stimulation the production of MDA is minimal in non-activated platelets (MDA non-activated). Therefore, the more the MDA/MDAa ratio approaches unity, the more activated are the thrombocytes. We utilized for the first time this new index for the investigation of hyperactive platelets, and we studied 56 persons (17 patients with thrombotic or thrombophilic disease as group A, 17 normals as group B and 22 diabetics without ketoacidosis as group C). We proved that the new index (MDA/MDAa) can be used to detect persons with functionally hyperactive platelets because large differences are found between the mean values of normals and the values of patients with established thrombotic disease, at a high confidence limit (x ± 3 SD covering 99% of the samples). Comparing the sensitivity of this new index with the other three methods used for the detection of hyperactive platelets [ratio of circulating platelet aggregates (CPA), aggregation with ADP, spontaneous aggregation] in groups B and C we found that only the ratio MDA/MDAa was able to reveal that (a) the two groups B and C are not identical (a statistical conclusion after comparison with the other methods) and (b) there were 5 diabetics in group C who had more hyperactive platelets than the others (these patients were not detected by any other method).
Simulation of Primary Haemostasis in vitro
Authors: Kratzer M.A.A. , Born G.V.R.
Published: April 2009

Primary haemostasis was simulated in vitro under standardized geometrical, rheological and biochemical conditions. The system was based on the hypothesis that adenine nucleotides, especially adenosine 5′-diphosphate, released from injured vessel wall cells play an important role for the initial platelet aggregation following lesion of small vessels. The device allows the reproducible measurement of in vitro bleeding time and volume in small samples of whole blood.
Detection of Abnormal Platelet Functions with an in vitro Model of Primary Haemostasis
Authors: Kratzer M.A.A. , Bellucci S. , Caen J.P.
Published: April 2009

A new technique, which simulates primary haemostasis in vitro was tested using blood from control persons and from patients with a defined abnormality of primary haemostasis. The device allows the reproducible measurement of in vitro bleeding time and volume in small samples of whole blood. Inhibition of platelet adhesion and aggregation can very sensitively be detected with the new technique, which allows its possible use in clinical or pharmacological applications.
Platelet Adhesion in Hyperlipidemic and Hypertensive Patients
Authors: Brook J.G. , Marmur A. , Berkovitch Y. , Aviram M.
Published: April 2009

Platelet adhesion was studied in whole blood using a simple stagnation flow method in patients at high risk for the development of atherosclerosis. Fourteen patients with hypercholesterolemia, 26 with hypertriglyceridemia and 25 normolipidemic hypertensive subjects were compared with 75 normal (normotensive and normolipidemic) subjects. Increased platelet adhesion was found in hypercholesterolemic (but not hypertriglyceridemic) patients only when native blood with no anticoagulants was used. In hypertensive patients, platelet adhesion was signficantly elevated, but remarkably reduced by beta-blocker drugs. Propranolol and atenolol significantly reduced platelet adhesion, but this effect was found to take a longer time than that required for significant blood pressure reduction.
Platelet Sensitivity to Adenosine Diphosphate and to Prostacyclin in Diabetic Pregnancies
Authors: Gerő G. , Rákóczi I. , Tihanyi K. , Oláh J. , Demeter J. , Gáti I.
Published: April 2009

Platelet sensitivity to adenosine diphosphate (ADP) and to prostacyclin (PGI2) was studied in normal and diabetic pregnant women. The threshold concentrations of ADP inducing the second phase of aggregation were used to determine the platelet sensitivity to PGI2. The sensitivity of platelets to ADP increased in both groups in the second trimester, thereafter it decreased both in normal and diabetic pregnancies. In contrast, sensitivity to PGI2 increased in the last trimester of pregnancy. No difference could be observed between diabetic and normal groups. The similarity of the results between the two groups could be explained by the normoglycaemic state of well-controlled diabetic pregnant women.
Acquired Thrombin Inhibitor in a Patient with Liver Cirrhosis
Authors: Barthels M. , Heimburger N.
Published: April 2009

An unusual thrombin inhibitor is described in a patient suffering from liver cirrhosis, associated with a polyclonal gammopathy. In all screening tests that are based on thrombin action, the plasma clotting time was prolonged; in contrast, a test using the thrombin-like enzyme thrombin coagulase was not influenced. A specific thrombin inhibitor, present in the patient’s plasma, was assumed. Fractionation experiments showed that the inhibitor was associated with the patient’s IgG fraction. The IgG fraction dose-dependently inhibited the action of thrombin on fibrinogen and the inhibition of thrombin by antithrombin III, but the amidolytic activity of thrombin was only little affected.
Local Hemostasis after Tooth Extraction in Patients with Abnormal Hemostatic Function
Authors: Baudo F. , de Cataldo F. , Gatti R. , Landonio G. , Muti G. , Scolari G.
Published: April 2009

Tooth extraction was carried out in 405 patients with various hemostatic disorders due to thrombocytopenia, chronic liver disease, hemophilia A and B, von Willebrand’s disease and oral anticoagulants. Human fibrinogen concentrate was used as local hemostatic agent. Prophylactic replacement therapy (platelets or plasma concentrates) and antifibrinolytic agents were not administered. Oral anticoagulants were not discontinued. Minor postex-traction bleeding occurred only in severe hemophilia A and occasionally in the oral anticoagulant group.
In vitro Aggregation of Normal Platelets: A Hypothetical First-Approximation Model for Light Extinction in Platelet-Rich Plasma
Authors: Boudreau D.A. , Rock W.A.
Published: April 2009

Aggregometer tracings of light transmission through platelet-rich-plasma are routinely used for the clinical evaluation of platelet function. The analytical relation between the changing aggregometer curve tracings of the light extinction and the aggregation process remains unknown. A first-approximation equation for this relation is proposed, based upon a highly simplified view of the in vitro aggregation process for normal platelets. The model described is capable of generating curves which show strong resemblance to those predicted by light scattering theory as well as those observed experimentally, including biphasic structures.
Defective Platelet Aggregation Induced by Platelet Activating Factor in Myeloproliferative Disorders: Deficiency of an Aspirin-Independent Mechanism?
Authors: Viero Piera , Cortelazzo Sergio , Barbui Tiziano , de Gaetano Giovanni
Published: April 2009

Platelets from 6 out of 10 patients with myeloproliferative disorders showed only a single reversible wave of aggregation when challenged with platelet activating factor (PAF). Preexposure to subthreshold concentrations of adrenaline resulted in a full irreversible response to PAF. Aspirin, however, removed this synergism. In the remaining 4 patients, PAF induced a full response but aspirin abolished the synergism with adrenaline in 2 of them. In platelets from all controls aspirin failed to abolish the synergism between PAF and adrenaline. It is suggested that patients with myeloproliferative disorders lack – to varying degrees -an aspirin-independent mechanism which amplifies the primary response to PAF. Such a mechanism could involve the products of arachidonic acid metabolism catalyzed by lipoxygenase.
Plasminogen Activator in Bronchoalveolar Fluid
Authors: Matsuo O. , Sakai T. , Bando H. , Okada K. , Nakajima S. , Takagi O. , Izaki S.
Published: April 2009

Plasminogen activator was purified from the soluble fraction of bronchoalveolar lavage fluid, and biological and immunological characteristics of the activator were examined by electrophoretic enzymography. The purified fraction showed a single band with a molecular weight of 53,000. The enzyme activity was eliminated in the presence of DFP and did not display fibrin affinity. Immunological tests revealed that the plasminogen activator reacted with IgG of antiurokinase but not with that of tissue-type plasminogen activator. However, the plasminogen activator cleaved S-2288 to a greater extent than S-2444 in contrast to urokinase.
Factor XI Kinetics after Plasma Exchange in Severe Factor XI Deficiency
Authors: Nováková I.R.O. , van Ginneken C.A.M. , Verbruggen H.W. , Haanen C.
Published: April 2009

Plasma exchange in a patient with factor XI deficiency allowed the determination of the factor XI disappearance time. The decay curve showed a biphasic pattern with a t½ of 12.3 h during the first 3 days, followed by a slower decay with a t½ of 121 h. After a loading dose by means of plasma exchange with fresh frozen plasma (FFP) up to a factor XI level of 65%, administration of 0.5 liter FFP every 12 h was necessary to maintain the factor XI concentration between 40 and 60%. The clearances of factor XI, calculated from the results of plasma exchange and from the maintenance dose, correlated very well and showed that the t½ of factor XI did not change after surgery. The patient underwent major surgery uneventfully but ultimately died 3½ weeks after operation from cerebral damage due to cardiac arrest, which occurred on the 2nd postoperative day.
Inhibition of Thrombin-Catalyzed Reactions in Blood Coagulation and Platelet Activation by Heparin Fractions in the Absence of Antithrombin III
Authors: Baruch Dominique , Lindhout Theo , Wagenvoord Rob , Hemker Coenraad
Published: April 2009

The antithrombin-III-independent effect of heparin was studied in the following thrombin-catalyzed reactions: activation of purified plasma factor V and partially purified plasma factor VIII:C, generation of factor Va from the platelets and, in the presence of collagen, of the platelet procoagulant activity. Five heparin fractions and a heparinoid were compared to crude heparin. Crude heparin was a more potent inhibitor of these reactions than the fractions or the heparinoid. The inhibitory action of heparin (fractions) appeared to be the result of the formation of a complex between heparin and thrombin that alters the specificity of thrombin towards high molecular weight substrates. The inhibition of these thrombin-dependent feedback reactions in blood coagulation might be of importance in the mechanisms for the dissociation between the antithrombotic and hemorrhagic properties of low molecular weight heparins.
In vivo Effects of Low Molecular Weight Heparins on Experimental Thrombosis and Bleeding
Authors: Hirsh Jack
Published: April 2009

Recent studies with heparin fractions indicate that it is possible to dissociate the antithrombotic and hemorrhagic effects of heparin and so improve its therapeutic potential. Heparin inhibits blood coagulation by 3 independent mechanisms by augmenting the effect of antithrombin HI (the major effect), by augmenting the inhibitory effect of thrombin or heparin cofactor II, and by disrupting the activation of blood coagulation on the platelet surface; it has an additional effect on hemostasis through its interaction with blood platelets. Some insight into the mechanism of heparin-induced bleeding has been provided by studies with low molecular weight heparins. These heparins have reduced antithrombin activity but retain anti-Xa activity and have antithrombotic properties in animals with a reduced risk of bleeding. There is evidence that the reduction in the bleeding risk is unrelated to the anticoagulant effect of these low molecular weight heparins, but that it may be related to the observation that they inhibit platelet function less than standard heparin. The very low molecular weight heparins (molecular weight 3,000 daltons), have virtually no anti-IIa activity and are relatively weaker antithrombotic agents than low molecular weight heparins of 5,000 daltons. A minimal amount of anti-IIa activity is required for full expression of the antithrombotic activities of these low molecular weight heparins.
Low Molecular Weight Heparin: A Better Drug?
Authors: Thomas Duncan P. , Barrowcliffe T.W. , Curtis A.D.
Published: April 2009

Preliminary clinical trials suggest that at least some low molecular weight (LMW) heparins are as effective as heparin in preventing post-operative deep vein thrombosis, and need only be injected once a day. However, a firm basis does not exist for assigning potency estimates to different LMW heparins. Caution is therefore necessary in determining appropriate dosages for various clinical indications. Until the problems of standardization and dosage are resolved, LMW heparins are unlikely to achieve their potential usefulness, or prove safer than standard heparin.
Biochemical and Pharmacological Studies on the Interaction of PK 10169 and Its Subfractions with Human Platelets
Authors: Brace L.D. , Fareed J. , Tomeo J. , Issleib S.
Published: April 2009

The interactions of heparin or its fractions with platelets that cause heparin-induced thrombocytopenia or in vitro platelet activation are poorly understood. We have shown that a low molecular weight derivative of heparin (PK 10169) and its subfractions can cause in vitro activation of platelets from normal human donors. This activation process is molecular-weight-dependent and involves the generation of thromboxane. We have also examined the effect of the serum from a patient with immune heparin-induced thrombocytopenia on normal donors’ platelets incubated with heparin, PK 10169 or subfractions of PK 10169. It was found that the patient’s serum induced aggregation of normal donor platelets in the presence of heparin, PK 10169 or certain subfractions of PK 10169. This process also appears to be mediated by thromboxane generation.
A New Low Molecular Weight Heparin Fragment (PK 10169): In vitro and in vivo Studies
Authors: Vinazzer H. , Woler M.
Published: April 2009

The depolymerized heparin fragment PK 10169 was compared with unfractioned mucosal sodium heparin. The inhibition of factors Xa and IXa by heparin and by PK 10169 was comparable on a weight base, whilst the inhibition of thrombin by PK 10169 was at least 5 times weaker than by heparin. Subcutaneous injection of PK 10169 was not followed by an increase of the thrombin time. The activated partial thromboplastin time was considerably less prolonged after PK 10169 than after heparin. Platelet count and platelet functions were not influenced by PK 10169. In vitro, the euglobulin lysis time (ELT) was shortened after addition of heparin to plasma but not after addition of PK 10169. After injection however, there was an equal shortening of the ELT by both substances. The half-life in circulation of PK 10169 was longer than the half-life of heparin. The advantages of PK 10169 over heparin are therefore the weaker influence on overall coagulation, the missing influence on platelet functions and the longer half-life in circulation.
Laboratory Studies on the Intravenous and Subcutaneous Administration of PK 10169 in Man
Authors: Fareed Jawed , Walenga Jeanine M. , Hoppensteadt Debra A. , Emanuele Martin
Published: April 2009

Intravenous and subcutaneous administration of PK 10169 in healthy human volunteers were studied utilizing numerous old and new laboratory methods for the monitoring of the effects of this agent. In the intravenous studies, individual groups of 10 healthy volunteers were administered with 2,500–12,500 anti-Xa units (25–125 mg) PK 10169 as a single bolus, and blood samples were drawn at 30 min, 1, 4 and 24 h after the administration of the drug. In the subcutaneous studies, 4,000 anti-Xa units (40 mg) b.i.d. of PK 10169 were administered to a group of 10 healthy individuals for 7 consecutive days, and blood samples were drawn 6 h after each dose. Citrated blood samples collected from both studies were centrifuged, plasma was frozen at -70 °C in aliquots, and various laboratory parameters were determined in batches. In the intravenous studies, the global clotting assays (activated partial thromboplastin time and thrombin time) were only prolonged at initial stages of treatment, whereas a marked increase in the antiprotease and antifibrinopeptide A generation activity titer was observed for periods of up to 24 h. In the subcutaneous studies, no significant prolongation of the global clotting assays was noted; however, the anti-Xa levels were significantly increased throughout the study period (7 days). Only a trace of anti-IIa activity was observed. In contrast, a strong antifibrinopeptide A generation activity was observed in all samples which persisted after the discontinuation of PK 10169. These studies suggest that PK 10169 may exert its clinical effects by multiple mechanisms which are only partially assessable by routine laboratory methods.
Pharmacokinetic Studies of Standard Heparin and Low Molecular Weight Heparin in Patients with Chronic Renal Failure
Authors: Follea G. , Laville M. , Pozet N. , Dechavanne M.
Published: April 2009

The disappearance of the anticoagulant activities of a standard commercial heparin and of a low molecular weight (LMW) heparin (PK 10169), administered as single intravenous injections, was studied in patients with chronic renal failure. Heparin and LMW heparin anticoagulant activities were determined by activated partial thromboplastin time (APTT) and chromogenic assays of anti-Xa and anti-IIa activities. Following heparin injection, a fast initial decay of anticoagulant activities preceded a slow convex disappearance curve, in semilogarithmic plots. These experimental data are in agreement with a model based on a predominant saturable mechanism of elimination of heparin in patients with renal failure. The disappearance of LMW heparin anti-Xa activity was obviously different, with linear or concave elimination curves, and longer apparent half-life. Taken together, our kinetic data and those previously reported in normal subjects strongly suggest that the mechanism of elimination of the LMW heparin studied is not saturable (at least for the tested dosages), and that the kidneys play a minimal role in the elimination.
Enoxaparine Low Molecular Weight Heparin: Its Use in the Prevention of Deep Venous Thrombosis Following Total Hip Replacement
Authors: Planes A. , Vochelle N. , Ferru J. , Przyrowski D. , Clerc J. , Fagola M. , Planes M.
Published: April 2009

The effect of Enoxaparin in the prevention of thromboembolism after total hip prothesis has been controlled by phlebography. 228 consecutives patients were studied with 4 dose regimens: 60 mg once a day, 40 mg once a day, and 30 and 20 mg twice a day. Conclusions: a total dose of 40 mg once a day or twice a day gives a rate of postoperative thrombosis of 8 %.
Studies of the Vitamin K-Dependent Carboxylase and Vitamin K Epoxide Reductase in Rat Liver
Authors: Suttie J.W. , Preusch P.C.
Published: April 2009

Vitamin K is required as a cofactor for a microsomal enzyme that converts glutamyl residues in precursor proteins to γ-carboxyglutamyl residues in completed proteins. These residues are essential for the biological function of prothrombin, factors VII, IX, and X, protein C, and protein S. Current data suggest that recognition of protein substrates by the carboxylase requires an unidentified protein-protein interaction in addition to the Glu substrate binding site. The primary vitamin K-dependent event has now been shown to be the abstraction of the γ-hydrogen of the substrate Glu residue with the concurrent formation of vitamin K 2,3-epoxide. Coumarin anticoagulants appear to inhibit the microsomal vitamin K epoxide reductase and one of a number of microsomal quinone reductases. They therefore block vitamin K action by preventing the recycling of vitamin K epoxide to the quinone and to the active cofactor form, the hydroquinone. Excess vitamin K can reverse a coumarin anticoagulant effect as the nonsensitive quinone reductase can continue to furnish the active coenzyme.
Role of Accessory Components in the Activation of Vitamin K-Dependent Coagulation Factors
Authors: van Rijn J.L.M.L. , Zwaal R.F.A. , Hemker H.C. , Rosing J.
Published: April 2009

Kinetic studies of prothrombin activation and intrinsic factor X activation carried out in the absence and presence of phospholipids and the protein cofactors Va or Villa have provided insight in the mechanism by which the accessory components enhance coagulation factor activation. In intrinsic factor X and prothrombin activation, phospholipids cause a drastic drop of Km for the substrates factor X and prothrombin, whereas the protein cofactors factor Va and factor Villa increase Vmax of the prothrombin- and factor X-activating reactions. The mode of action of factor Va in prothrombin activation is however somewhat more complex. Besides its stimulatory effect on the catalytic activity of factor Xa, Factor Va also plays an important role in the assembly of the prothrombin-activating complex at phospholipid surfaces especially when the latter have a low affinity for vitamin-K-dependent coagulation factors. This effect is likely accomplished by promoting the binding of both prothrombin and factor Xa to the procoagulant surface.
The Prothrombin Gene
Authors: MacGillivray Ross T.A. , Irwin David M.
Published: April 2009

Using recombinant DNA techniques, DNA fragments coding for bovine prothrombin mRNA have been cloned and characterized. Structural studies have revealed that prothrombin mRNA encodes a precursor protein having an amino-terminal extension of 43 amino acid residues. Using bovine prothrombin cDNA as a hybridization probe, the genes coding for human and bovine prothrombin have been isolated and partially characterized. The organization of the prothrombin gene is similar, but not identical to the organization of the genes coding for the other vitamin-K-dependent clotting factors.
Vitamin K and the Urogenital Tract
Authors: Vermeer C. , Soute B.A.M. , Ulrich M.M.W. , van de Loo P.G.F.
Published: April 2009

Solubilized microsomes from bovine liver, kidney and testis were compared with regard to their content of vitamin-K-dependent carboxylase, the presence of endogenous vitamin K as well as that of endogenous carboxylatable precursor proteins. The isolation and purification of these protein substrates was not successful. Using antibodies against various well characterized proteins containing gammacarboxyglutamic acid (Gla), we were able to identify precursors of the blood coagulation factors II, IX and X in liver microsomes. The nonhepatic proteins could not be identified in this way. Gla-containing proteins, however, were isolated from human sperm, urine and renal stones. It was demonstrated that – like osteocalcin – also the urinary Gla protein inhibits the precipitation of various calcium salts from supersaturated solutions. The concentration of the urinary Gla protein (16mg/l) in human urine is well above the concentration required for the in vitro inhibition of salt precipitation.
Osteocalcin: The Vitamin K-Dependent Ca2+-Binding Protein of Bone Matrix
Authors: Hauschka Peter V.
Published: April 2009

Osteocalcin is an abundant Ca2+-binding protein indigenous to the organic matrix of bone, dentin, and possibly other mineralized tissues. This protein contains 47–50 amino acid residues (molecular weight 5,200–5,900) depending on the species. Osteocalcin is distinguished by its content of three gamma-carboxyglutamic (Gla) residues. The vitamin-K-dependent biosynthesis of osteocalcin occurs in bone, and the protein is not homologous to the Gla-containing regions of known vitamin-K-dependent blood coagulation proteins. The two major structural features of osteocalcin which appear to control its function include: (1) the ‘Gla helix’, a compact Ca2+-dependent alpha-helical conformation, in which the three Gla residues are aligned to facilitate adsorption to hydroxyapatite, and (2) the ‘COOH-terminal beta-sheet’ which exhibits chemoattractant activity toward mononuclear leukocytes, specifically monocytes, the putative precursors of osteoclasts. While the biological function of osteocalcin is unknown, it appears to be a highly specific osteoblastic marker produced during bone formation, and is rapidly becoming a clinically important diagnostic parameter of bone pathology. This article reviews recent advances in the understanding of osteocalcin.
Vitamin K-Dependent Processes in Tumor Cells
Authors: Hauschka Peter V. , Haroon Yacoob , Buchthal Stephen D. , Bell Robert G.
Published: April 2009

Tumor cells are known to interfere with blood coagulation pathways of the host by producing procoagulants and other substances, thereby deriving certain advantages relating to tumor growth, metastasis, and angiogenesis. Anticoagulants may diminish these advantages under certain conditions. The interaction between coumarin anticoagulants and tumor cells has been reviewed with respect to procoagulants and their vitamin K-dependent properties. Evidence is also presented which suggests that vitamin K-dependent protein carboxylation is a general property of tumor cells.
Basis for Selection of Anticoagulant Drugs for Therapeutic Trials in Human Malignancy
Authors: Zacharski Leo R.
Published: April 2009

Evidence indicates that progression of the Lewis lung carcinoma in mice and small cell carcinoma of the lung in humans is retarded by warfarin administration. This suggests that vitamin K-dependent pathways are of importance in the pathogenesis of these tumors. Available data were reviewed for these tumor types in an attempt to explore mechanisms and to gain insights that might guide the selection of other coagulation-reactive drugs for testing in future controlled clinical trials in small cell carcinoma of the lung. While many differences exist between the Lewis lung tumor and small cell carcinoma of the lung, both are rapidly growing malignancies of pulmonary origin that metastasize early to kill the host after a short time. Both are favorably influenced by combination chemotherapy and radiation therapy as well as anticoagulant treatment. Peripheral blood changes indicative of disseminated intravascular coagulation occur in each of these tumor types, and tumor cells from both are capable of interacting with the coagulation mechanism. While many details concerning the host-tumor interaction remain to be elucidated, the considerable and diverse information available for these tumor types provides a secure base for future investigation. It is postulated that certain drugs in addition to warfarin might reasonably be studied in controlled clinical trials of small cell carcinoma of the lung and that drugs other than warfarin might be effective for tumor types that are not responsive to this agent.
Studies in Rats on in vitro Inhibition and in vivo Activity of Vitamin-K-Dependent Carboxylation
Authors: Cocchetto David M. , Bjornsson Thorir D.
Published: April 2009

Vitamin-K-dependent procoagulant activity was studied in vitro by characterizing vitamin-K-dependent carboxylation and in vivo by assessing prothrombin complex activity (PCA). The kinetics of endogenous substrate carboxylation were apparently first order. Inhibition of vitamin-K-dependent carboxylation versus antagonist concentration was determined for 2,3,5,6-tetrachloropyridin-4-ol (TCP), phenindione, 2,6-dichloroindophenol sodium (2,6-DIP), 2-chloro-1,4-naphthoquinone (chloro-K3), 2-chloro-3-phytyl-l,4-naphthoquinone (chloro-K1) and warfarin. These compounds represent different chemical classes of anticoagulants that exert their effects via vitamin K antagonism. The percent inhibition versus concentration plots exhibited a sigmoidal shape and were described by the logistic function. The following concentrations were associated with 50% inhibition of vitamin-K-dependent carboxylation: TCP = 1.23 ± 0.238 μM (mean ± SD), phenindione = 19.0 ± 11.2 μM, 2,6-DIP = 116 ± 39.2 μM, chloro-K3 = 146 ± 62.1 μM, chloro-K1 = 285 ± 89.3 μM and warfarin = 6.63 ± 2.82 mM The slope parameters of the percent inhibition versus concentration plots for chloro-K1 and phenindione were different from those for the other antagonists, suggesting a mechanism of action consistent with other data in the literature, i.e. competitive antagonism of the vitamin-K-dependent carboxylase. The relationships between in vitro parameters of vitamin-K-dependent carboxylation of precursor proteins and in vivo indices of rate of production of vitamin-K-dependent coagulation factors were studied in control animals and animals pretreated with compounds perturbing hepatic function. The in vivo rate of synthesis of prothrombin complex activity and the circulating levels of PCA were correlated with the in vitro first-order rate constant of vitamin-K-dependent carboxylation, but not with the amount of precursor proteins present. The results of these studies suggest that the rate of vitamin-K-dependent carboxylation is intimately involved in the regulation of levels and activity of vitamin-K-dependent coagulation factors.
Prostacyclin Is a More Potent Stimulator of Thrombolysis than Inhibitor of Haemostasis
Authors: Görög P. , Kovacs Iren B.
Published: April 2009

The effects of prostacyclin (PGI2) on haemostasis and thrombolysis in human blood were investigated in vitro using the ‘Haemostatometer’. In freshly drawn native blood samples, 5 ng/ml PGI2 greatly inhibited haemostasis but did not influence clotting time. The effect was potentiated in heparinised blood: 1 ng/ml PGI2 effect on haemostasis was still detectable, and the duration of the effect was prolonged. Thrombolytic activity was tested in heparinised blood by first allowing haemostasis and then measuring the time until rebleeding occurred through the consolidated haemostatic plugs. PGI2 at 0.5 ng/ml had no significant effect on haemostasis, but significantly decreased the time for spontaneous thrombolysis (p < 0.001). Comparable effects were demonstrated in blood samples containing 50 U/ml strepto-kinase. Increased thrombolysis also occurred when haemostatic plugs formed from control blood were perfused with blood containing 5 ng/ml PGI2. The results suggest that PGI2 has a thrombolytic effect independent of any contribution from the vessel wall and that it is a more potent stimulator of thrombolysis than inhibitor of haemostasis.
Prenatal Diagnosis of Hemophilia by Fetal Blood Sampling under Ultrasound Guidance
Authors: Forestier F. , Daffos F. , Solé Y. , Rainaut M.
Published: April 2009

In utero fetal blood sampling was performed in 55 cases for prenatal diagnosis of hemophilia A and B. Fifteen fetuses were found to be affected. However, with this new procedure, it was possible to demonstrate that fetuses were not hemophiliacs in 40 cases. Therefore, pregnancy was not interrupted; these infants were born and definitely proven to be normal. There were no diagnostic errors.
Salicylate Antagonism of Acetylsalicylic Acid Inhibition of Platelet Aggregation in Male and Female Subjects: Influence of Citrate Concentration
Authors: Philp R.B. , Paul M.L.
Published: April 2009

Platelets from volunteers were exposed for 1 min to sodium salicylate (SA) before and after the addition of acetylsalicylic acid (ASA) to produce ≥ 50% inhibition of aggregation induced by arachidonic acid (AA) or collagen. SA:ASA concentrations = 20:1. SA protection against ASA inhibition was always observed even if ASA exposure time was 15 min, whereas reversal could not be demonstrated once exposure of platelets to ASA exceeded a minimum of 3–10 min with AA as the stimulus. Reversal was even less effective when collagen was the stimulus. An apparent, increased sensitivity to SA reversal of ASA inhibition in females disappeared when citrate concentration was adjusted to compensate for lower packed cell volume. The proposed male dependency for protection in ASA treatment of thromboembolic disorders cannot be explained on the basis of differences in the SA-ASA competition at platelet cyclooxygenase and, if collagen is an important in vivo stimulus of platelet interaction with damaged vessel wall, the antagonism of ASA by SA may not be important.
Factors of the Hemostatic System in Diabetic Patients
Authors: Ostermann H. , van de Loo J.
Published: April 2009

Diabetes mellitus is associated with a variety of vascular complications like diabetic retinopathy, myocardial infarction, stroke and peripheral vessel disease. These complications are of utmost importance because they lead to disability and premature death of the patients. The pathogenesis of these lesions has been thought to depend at least partly on defects in the hemostatic system. Many alterations of the coagulation and the fibrinolytic system as well as of the reaction of platelets have been found in diabetics. In general these tend to suggest a state of slightly activated coagulation, of increased platelet reactivity and of decreased fibrinolysis. However, no conclusive picture of the role of hemostasis in the development of vascular lesions in diabetics has emerged yet, as contradictive results have been found by many investigators. The aim of this review article is to sum up the knowledge that has accumulated in the last years in controlled clinical trials concerning the state of the diabetic hemostatic system.
VA Cooperative Study on Antiplatelet Agents in Diabetic Patients after Amputation for Gangrene
Authors: Colwell John A. , Bingham Stephen F.
Published: April 2009

This paper review some of the issues faced by the investigators involved in a VA Cooperative Study on Antiplatelet Agents in Diabetic Patients after Amputation for Gangrene. The study was a negative one, and some of the reasons for this are considered. In addition, suggestive results in two subgroups, cerebrovascular disease and unexpected, sudden, or unobserved deaths, were found. The implications and interpretation of these findings are discussed.
Reduced Serum-Stimulatory Activity on Prostacyclin Production by Cultured Aortic Endothelial Cells in Diabetes mellitus
Authors: Inoguchi T. , Umeda F. , Watanabe J. , Ibayashi H.
Published: April 2009

Reduced prostacyclin (PGI2) production by the vascular wall has been proposed as a possible cause of macro- or microangiopathy in diabetes mellitus. In the present study, we confirmed the stimulatory activity on PGI2 (PSA) production in plasma-derived serum (PDS) by cultured aortic endothelial cells. Furthermore, the abnormality of PSA was examined in diabetic PDS. PSA in PDS from non-insulin-dependent diabetics significantly decreased as compared with that in PDS from age-matched control subjects. There was no difference in PSA in PDS between diabetic patients with and without vascular complications such as retinopathy and nephropathy. In addition, after treatment with dialysis, PSA in diabetic PDS was still not restored to that in normal PDS. These findings suggest that relatively heat-stable (56 °C, 30 min) and nondialyzable PGI2 stimulatory substance(s) may decrease in diabetic PDS. It is concluded that a reduction in PDS-stimulated PGI2 production by the vascular wall can play an important role in the pathogenesis of vascular lesions in diabetes mellitus.
Neurophysiological Variables and Fibrinolysis in Insulin-Dependent Diabetes Treated with an Aldose Reductase Inhibitor or Placebo
Authors: Jespersen Jørgen , Gram Jørgen , Christensen Jens Erik Just
Published: April 2009

In a double-blind study we randomized insulin-dependent diabetics (n = 19) into a group (n = 12) given daily 250 mg Sorbinil, a potent aldose reductase inhibitor reported to ameliorate diabetic neuropathy, and another group (n = 7) given placebo for 1 year. Objective, neurophysiological variables (biothesiometry, electromyography, nyctometri) were followed throughout the study and correlated with fibrinolytic variables in blood. We found that Sorbinil did not improve any of the selected neurophysiological variables. Neither did Sorbinil induce marked changes in the fibrinolytic activities of the extrinsic, tissue-type plasminogen activator (t-PA), or in the intrinsic factor XII-dependent or factor XII-independent (urokinase-like) plasminogen activator systems. We found no effect of Sorbinil on the activity of the fast-reacting inhibitor (PA-I) of plasminogen activator. Levels of PA-I in plasma influence the amounts of t-PA precipitated in euglobulins.
Defibrotide Is Antithrombotic and Thrombolytic against Rabbit Venous Thrombosis
Authors: Niada R. , Pescador R. , Porta R. , Mantovani M. , Prino G.
Published: April 2009

Defibrotide (D) is a polydeoxyribonucleotide of mammalian origin that has no anticoagulant activity or hemodynamic effects but has considerable profibrinolytic and antithrombotic activities under several experimental conditions. In this paper the dynamics of D’s antithrombotic effects after oral administration and D’s thrombolystic activity after intravemous infusion on venous collagen-induced thrombosis in the rabbit are reported. D administered orally (12.5, 25 or 50 mg kg-1), from 0 to 360 min before thrombus induction, was able to impede thrombus formation in the first 2 h of growth. There is a linear correlation between the dose of D and peak activity and a correlation, described by a power function, between the dose and the area under the experimental inhibition curve. D infused intravenously (20, 31.7 or 50 mg kg-1 h-1 × 6 h) into rabbits with 24-hour-old thrombi, had significant and impressive dose-related thrombolytic activity. There is a direct relationship between the thrombolytic effect and plasma levels. In this experimental model, urokinase infused intravenously (750, 1,500 or 3,000 IU kg–1 h–1) had the same thrombolytic activity as D; heparin (76 IU kg–1 h–1) was completely ineffective and PGI2 showed a modest activity at 60 nmol kg–1 h–1. The antithrombotic and thrombolytic activities of D may be partly due to its ability to promote release of plasminogen activator factor and of prostacyclin from vascular tissue.
Beneficial Effects of Defibrotide against Myocardial Ischemia and Decline of β-Adrenoceptor Function in the Rabbit
Authors: Berti F. , Rossoni G. , Niada R. , Omini C. , Pretolani M. , Mandelli C.
Published: April 2009

Defibrotide is a polydeoxyribonucleotide of mammalian origin which possesses profibrinolytic effect and PGI2-releasing capacity. Because of these properties, defibrotide has antithrombotic effects which are demonstrated in various experimental models of venous and arterial thrombosis.The present study indicates that defibrotide clearly protects against myocardial damage in the rabbit 3 days after total coronary artery occlusion. Furthermore, defibrotide prevents the decline of β-adrenergic receptor function, a phenomenon related to excessive circulating catecholamines that occurs during the myocardial infarct. Defibrotide prevents the dramatic fall of creatine phosphokinase activity in the ischemic ventricle: metabolic changes which reflect changes in the cells affected by prolonged ischemia. Assumptions about the mode of action of defibrotide are given particularly in consideration of the interaction between the fibrinolytic activity and the PGI2-releasing capacity of this substance.
Cardioprotective Effects of Defibrotide in Acute Lethal and Nonlethal Myocardial Ischemia in the Cat
Authors: Niada R. , Porta R. , Pescador R. , Mantovani M. , Prino G. , Berti F.
Published: April 2009

We evaluated the effects of defibrotide (D), a natural profibrinolytic and anti-thrombotic agent with endogenous PGl2-stimulating properties, on acute lethal and nonlethal myocardial ischemia (L-AMI and NL-AMI) in the cat. The coronary artery was occluded at 12–14 mm from its origin. In L-AMI, 12 of 15 control cats developed ventricular fibrillation and died; D (32 mg kg-1, bolus intravenously plus infusion) provided total protection against death and showed protective effects on plasma and myocardial creatine phosphokinase (CPK), hemodynamics and ECG. In NL-AMI, pretreatment of cats with D at the same dosage (intravenous infusion) reduced AMI-ST segment increases and AMI changes in hemodynamics. AMI-induced changes in lactate adenosine triphosphate and CPK in ischemic tissues were prevented by D. The beneficial effects of D in NL-AMI could be partly attributed to its stimulatory effect on vascular PGI2 release; the mechanism of the impressive protection by D observed in L-AMI has still to be elucidated.
Pharmacokinetics of Defibrotide in Healthy Volunteers
Authors: Noseda G. , Fragiacomo C. , Ferrari D.
Published: April 2009

A pharmacokinetic study of defibrotide, an antithrombotic polydeoxyribonucleotide extract, was performed in 5 healthy volunteers after rapid intravenous injection at three different doses: 0.5, 4 and 16 mg/kg. Defibrotide was given to 2 additional healthy volunteers by slow perfusion of 600 mg over 6 h, after a 200-mg intravenous bolus injection. The blood levels of defibrotide were determined by a method supplied by Crinos (detection of 6-desoxyribose). A one-compartment model was used to describe the kinetics of the drug in plasma. All the most important pharmacokinetic parameters (i.e. elimination constant, half-life, AUC and volume of distribution) were dose dependent. The half-lives were 9.8 min at 0.5 mg/kg, 14.2 min at 4 mg/kg and 21.1 min at 16 mg/kg. The dose-response curves for elimination indicated saturation. During slow infusion following the bolus injection a steady state was reached at 90–120 min, with a blood level of 10–15 μg/ml.
In vivo Effects of Defibrotide on Platelet c-AMP and Blood Prostanoid Levels
Authors: Çixmeci G.
Published: April 2009

Patients were treated with defibrotide (3 × 200 mg/day) for 7 days. Plasma PGI2 and TXB2 levels were measured by RIA using EDTA-aspisol as anticoagulant and cyclooxygenase inhibitor. Isolated platelet c-AMP levels were also determined by RIA, using EDTA-dipyridamole as anticoagulant and phosphodiesterase inhibitor. Blood PGI2 levels were found to increase significantly upon treatment while the increase in TXB2 levels was not significant. Blood PGI2/TXB2 ratio increased 51%, 30 min after intravenous injection and it remained 28% higher during therapy than the predrug blood level. Significantly higher platelet c-AMP levels were also obtained after the injection of drug (0.02 < p < 0.05).
Effectiveness of Defibrotide for Prophylaxis of Deep Venous Thrombosis after General Surgery: A Double-Blind, Placebo-Controlled Clinical Trial
Authors: Mozzi E. , Chiurazzi D. , Germiniani R. , Pacini F.
Published: April 2009

The prophylactic activity of defibrotide, a new extractive antithrombotic-thrombolytic agent of mammalian origin, was assessed by detection of deep venous thrombosis (DVT) in patients who underwent general elective surgery. 120 patients (aged 25–85 years, mean 55.6) were randomly assigned to defibrotide (60 patients) or to placebo (60 patients). The two groups were homogeneous for age, sex and risk factors for DVT. The active drug was given intravenously 200 mg four times a day, starting the day before the operation and then for the following 7 days. To detect DVT, 125I-fibrinogen was used, by conventional methods. Defibrotide reduced the frequency of DVT to 4/60 (7%) from 16/60 (27%) in the placebo group. The difference was highly significant (p < 0.01). Neither side effects nor anticoagulant activity were observed. On the basis of this evidence, defibrotide may be considered an effective and well-tolerated drug for prevention of DVT.