bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Duration of Oral Anticoagulant Therapy: A Randomized Trial Comparing Four Weeks with Three Months of Warfarin in Patients with Proximal Deep Vein Thrombosis
Authors: Levine Mark N , Hirsh Jack , Gent Michael , Turpie Alexander G , Weitz Jeffrey , Ginsberg Jeffrey , Geerts William , LeClerc Jacques , Neemeh Jean , Powers Peter , Piovella Franco
Published: July 2018

The optimal duration of oral anticoagulant therapy for patients with acute proximal deep vein thrombosis (DVT) is uncertain. Based on the hypothesis that a normal impedance plethysmogram (IPG) following DVT defines a group of patients at low risk of recurrent venous thromboembolism (VTE), a trial was conducted to evaluate the efficacy of only four weeks of warfarin. Patients with venographically confirmed acute proximal DVT who had received four weeks of warfarin after initial heparin and whose four week IPG was normal were allocated to either continue warfarin (targeted International Normalized Ratio 2.0 to 3.0) for a further eight weeks or receive placebo. Patients with an abnormal four week IPG received warfarin for a further eight weeks. Based on clinical characteristics at the time of the qualifying thrombosis, all patients were classified as having either continuing or transient risk factors for recurrent VTE. During the eight weeks following randomization, nine (8.6%) of the 105 placebo patients developed recurrent VTE compared to one (0.9%) of the 109 warfarin patients, P = 0.009. Over the entire 11 months of follow-up, 12 placebo patients developed recurrence compared to seven warfarin patients, P = 0.3. Nineteen of the 192 patients with an abnormal four week IPG experienced recurrence during the nine months after discontinuing warfarin.

In the 301 patients who received three months of warfarin in the randomized trial or in the cohort study, all 26 recurrent events were in the 212 patients with continuing risk factors.

In conclusion, an IPG four weeks after proximal DVT is not a useful predictor for recurrent VTE; whereas the presence of continuing risk factors is a very strong predictor. Four weeks of oral anticoagulants may be all that is required in patients without continuing risk factors. Patients with continuing risk factors may require more than three months of oral anticoagulants.
Determining Survivals of Platelets and Fibrinogen Using HAP an Interactive Hemostasis Analysis Computer Program
Authors: Abramson Mark J , Stein Sidney F , Goldstein J H
Published: July 2018

An interactive computer program is described which permits computation of platelet survivals based on the gamma function model of Murphy. An additional feature permits the treatment of other labelled proteins, e. g. fibrinogen, disappearing via an exponential process. The program requires no prior computer background and typical determinations of survivals can be effected in about five min, representing a substantial enhancement to the gamma function program as currently provided by the International Committee for the Standardization of Hematology. Provision has also been made for modifications to meet individual needs. The program is described in sufficient detail, including sample calculations, to permit evaluation for possible applications.
A Native Whole Blood Assay for Blood-Materials Interaction
Authors: Dodds W Jean , DiNovo Jean M , Bergeron John A
Published: July 2018

A convenient, accurate, and reproducible method was developed and characterized to test the effects of particulate solids and soluble agents on native whole blood. The effects of citrate anticoagulation and of variation in flow and column parameters were characterized by ancillary experiments. The study utilized a relatively homogeneous strain of large rabbits that had received intravenous [C14]-serotonin as a platelet radiolabel. The assay included a 4 min contact time of either the test sample or saline control with freshly drawn arterial blood and was followed by a series of hemostatic measurements, both before and after passage of the blood through a standard 1 g glass bead column. Changes induced by soluble (ADP, ellagic acid, aspirin) and particulate (collagen) agents in the reactivity of this blood to the subsequent challenge of a large area of reactive surface revealed reproducible quantitative effects on platelets and clotting. Generally comparable results were obtained with native whole human blood when the glass bead surface was adjusted (2 g) for the species difference in coagulability and platelet reactivity.
The Effect of Local Anaesthetics and Antiarrhythmic Agents on the Responses of Rabbit Platelets to ADP and Thrombin
Authors: Anderson Esther R , Foulks J G , Godin D V
Published: July 2018

Local anaesthetics and antiarrhythmic agents produced changes in responses of rabbit platelets to ADP and thrombin that varied with the agent and its concentration. In high concentrations all local anaesthetics decreased aggregation rates. At lower concentrations several local anaesthetics increased aggregation rates. Depending on the agonist and local anaesthetic, increases were produced at all or only at low or high agonist concentrations. Local anaesthetics failed to influence shape change except at concentrations much greater than those which inhibited aggregation. Inhibition of aggregation by procaine was potentiated by small organic anions suggesting effects at different sites on the platelet membrane. The inhibitory effect of local anaesthetics was decreased by increasing Ca. Kinetic analysis indicated different mechanisms for this Ca effect, i. e., predominantly competitive for procaine or lidocaine and predominantly non-competitive for tetracaine or ethyl lidocaine. Local anaesthetics may affect aggregation by modifying the participation of Ca in this process.
Purification and Properties of an Abnormal Blood Coagulation Factor IX (Factor IXBm)/Kinetics of Its Inhibition of Factor X Activation by Factor VII and Bovine Tissue Factor
Authors: Østerud B , Kasper C K , Lavine K K , Prodanos C , Rapaport S I
Published: July 2018

An abnormal blood coagulation factor IX has been isolated from the blood of a hemophilia B patient with a variant of the disease (hemophilia Bm) characterized by a normal concentration of factor IX antigen, negligible factor IX coagulant activity, and a prolonged prothrombin time with bovine tissue factor. The isolated protein (factor IXBm) had the same apparent molecular weight as normal factor IX (55,000) and the same mobility on two dimensional immunoelectrophoresis as normal factor IX. Factor IXBm underwent limited proteolysis induced by activated factor XI, in the presence of Ca2+ ions, or induced by the reaction product of tissue factor, factor VII and Ca2+ ions. A timecourse study showed that activated factor XI cleaved factor IXBm and factor IX at similar rates. However, in contrast to normal factor IX, the limited protelysis of factor IXBm did not generate procoagulant activity.

In kinetic experiments purified factor IXBm behaved like a competitive inhibitor (Ki of 0.017 μM) of the activation of factor X by bovine tissue factor and factor VII. Normal factor IX was also found to inhibit the reaction but required a four-fold higher concentration to achieve the same inhibitory effects as factor IXBm.
Recent Investigations of the First Bleeder Family in Åland (Finland) Described by von Willebrand
Authors: Nyman D , Eriksson A W , Blombäck M , Frants R R , Wahlberg P
Published: July 2018

The still living members of the original bleeder family on the Åland Islands described by von Willebrand in 1926 have been reinvestigated by using modem laboratory techniques for the measurement of the Factor VIII complex and with regard to platelet aggregation. The low level of F VIII: C activity demonstrated in 1957 could be confirmed in some of the family members, who however all had only mild bleeding symptoms. More consistently, in 6 out of 10, a low F VIIIR: Ag was found; all of those also had a low F VIII: RCoF. In none of the members were excessively low values for any of the parameters found. However, the spectrum of the whole F VIII complex indicates that the original family described by von Willebrand belongs to von Willebrand’s disease, type I.
Evidence of a Hypercoagulable State in Patients with Acute Lymphoblastic Leukemia Treated with Low Dose of E.coli L-Asparaginase: A GIMEMA Study
Authors: Leone Giuseppe , Gugliotta Luigi , Mazzucconi Maria Gabriella , De Stefano Valerio , Belmonte Monica Mattioli , Dragoni Francesco , Specchia Giorgina , Centra Antonietta , Gamba Gabriella , Camera Andrea , Mandelli Franco
Published: July 2018

Blood coagulation abnormalities induced by administration of E. coli L-asparaginase were investigated in 25 patients with acute lymphoblastic leukemia treated according to the GIMEMA ALL 0288 trial. Dosage of L-asparaginase was relatively low (6,000 U/m2/day for 7 days total dose 42,000 U/m2) as compared to the conventional dosages (120,000-140,000 U/m2 over 10–14 days). A significant decrease in fibronogen, plasminogen, alpha2-antiplasmin and antithrombin III was observed from day IV of L-asparaginase and it was maximum on day VIII, with return to the baseline levels on day XV. Protein C levels had only a borderline reduction, while no modification of protein S or factor VII was observed. Two of the patients investigated developed thrombosis. The presence of a prothrombotic state induced even by this low dosage of E. coli L-asparaginase was suggested by a significant increase of sensitive markers of hypercoagulability such as fibrinopeptide A, thrombin-antithrombin complexes, and prothrombin fragment F1 + 2.
Platelet Coagulant Activities and Retinal Vein Thrombosis
Authors: Walsh Peter N. , Goldberg Richard E. , Tax Richard L. , Magargal Larry E.
Published: July 2018

To determine whether platelets play a role in the pathogenesis of retinal vein occlusion (RVO), platelets and coagulation were evaluated in 28 patients with RVO. Platelet coagulant activities concerned with the initiation and early stages of intrinsic coagulation were 2–4 fold increased in 9 patients with acute primary RVO but not in patients with acute secondary (10 patients) or chronic (9 patients) RVO. Platelet factor 3 activity, platelet aggregation, serotonin release by platelets and plasma coagulation were normal in all patients. Platelets may provide a trigger mechanism for venous thrombosis in the eye when local conditions permit.
The Activation of Plasma Factor XIII with the Snake Venom Enzymes Ancrod and Batroxobin Marajoensis
Authors: Walter M , Nyman D , Krajnc V , Duckert F
Published: July 2018

The snake venom enzymes Ancrod and Batroxobin marajoensis are able to activate human plasma factor XIII as shown by the formation of the γ-dimers. The concentration of γ-dimers increases with the concentration of the activating enzymes. Factor XIII activated by Ancrod or Batroxobin marajoensis is, however, unable to catalyse the incorporation of the amine dansylcadaverine into casein. The partially activated factor XIII is therefore not demonstrable by means of the artificial test system. This factor XIII loses little activity and remains activable by thrombin.
Spontaneous Atrial Thrombosis in Aged Syrian Hamsters
Authors: McMartin Donald N.
Published: July 2018

Many of the aging Syrian hamsters maintained in our Division spontaneously develop atrial thrombosis accompanied by a consumption coagulopathy. The 50% mortality level is reached earlier by females (16 months) than by males (24 months). The incidence of thrombosis increases with age, beginning at 13.5 months in females and at 21.5 months in males, and the overall incidence (73%) is nearly the same for both sexes. Bilateral ventricular hypertrophy was found in thrombosed hearts. The hearts of most aged hamsters, whether thrombosed or not, had myxoid valvular thickenings and myocardial degeneration. Myodystrophic changes included hypertrophied nuclei, cytoplasmic vacuolation, fiber atrophy, and finally replacement fibrosis. Thrombosis probably resulted from local blood stasis secondary to cardiac failure. These hamsters may be an especially useful model for comparative study of the effects of aging and myocardial degeneration on spontaneous thrombosis.
Intravascular Coagulation in Liver Transplantation – Is It Present or Not?
Authors: Bakker C M , Metselaar H J , Gomes M J , Porte R J , Groenland Th N , Schalm S W , Terpstra O T , Stibbe J
Published: July 2018

It is still not clear whether disseminated intravascular coagulation (DIC) contributes to the hemostatic disturbances in orthotopic liver transplantation (OLT). Theoretically the lack of hepatic clearance of procoagulant factors during the anhepatic period and the release of thromboplastic material from the graft might trigger DIC. During heterotopic liver transplantation (HLT) the host liver is left in situ and procoagulant factors may still be cleared; DIC, if present, may not occur until after reperfusion. The aim of the present study was to gain more insight into the underlying mechanism of the coagulation changes during liver transplantation by comparison of OLT and HLT. Thrombin-antithrombin-III complexes (TAT), and indicator of thrombin generation, fibrin degradation products (FbDP) and routine clotting times were assayed in 12 OLTs, 18 HLTs and in a control group of 10 partial hepatic resections (PHR).

TAT increased dramatically after reperfusion to 136 μg/l in OLT and to 94 μg/l in HLT (p n.s.). In contrast, FbDP levels increased only in OLT, to a maximum of 13.8 μg/ml. Routine clotting times changed mildly and similarly in both OLT and HLT.

Conclusions: Graft reperfusion triggers excessive thrombin formation, but there are no other signs of subsequent DIC. Any thrombin formed is probably rapidly inhibited by antithrombin-III. The rise in FbDP during OLT is the result of increased fibrinolysis, which occurred only in OLT and not in HLT.
Pentasaccharide and Orgaran® Arrest, whereas Heparin Delays Thrombus Formation in a Rat Arteriovenous Shunt
Authors: Vogel Gerard M T , van Amsterdam Ronald G M , Kop Wim J , Meuleman Dirk G
Published: July 2018

The mode of action of glycosaminoglycans (GAGs) towards thrombus formation in a rat arteriovenous shunt was studied by simultaneous examination of thrombus weight, platelet consumption and thrombin generation during 45 min of blood circulation. A comparison was made between the effects of heparin, the heparinoid Org 10172 (Orgaran®), and the chemically synthesized methoxy derivative of the antithrombin III binding pentasaccharide fragment of heparin (Org 31540).

All three compounds inhibited thrombus growth by 30% at a dose of 80 anti-Xa U/kg i. v. when assessed after 15 min of circulation through the shunt. In addition, a systemic decrease of 27% of platelet numbers in the placebo group was inhibited by heparin and Orgaran® with 63% and by pentasaccharide with 48%. At a later stage, after 45 min of circulation, at comparable plasma anti-Xa levels, thrombi which had formed in the presence of Orgaran® or pentasaccharide, but not in the presence of heparin, became less or non thrombogenic. This non-thrombogenicity was reflected by i) an inhibition of the local deposition of [51Cr]platelets of 75% with Orgaran® and of 57% with pentasaccharide, and ii) an inhibition of ex-vivo thrombus-induced thrombin generation in pooled rat plasma of 67% with Orgaran® and of 52% with pentasaccharide (inhibition compared to placebo).

Although the mechanism of inducing non-thrombogenicity of a (developing) thrombus by Orgaran® and pentasaccharide requires further investigation, the suppression of the local thrombin generation potency, measured by thrombus-induced thrombin generation in pooled plasma, is much more correlated with thrombus growth than systemic anticoagulant activity. This suppression is likely to be due to the anti-Xa activity, as reflected by the efficacy of the pure Xa inhibiting pentasaccharide. Limitation of thrombus growth adds to the prophylactic perspective of Orgaran® and pentasaccharide in preventing thrombosis.
Heparinised Clotting Factor Concentrates in Patients with Christmas Disease and Liver Disease
Authors: Preston F. E , Malia R. G , Lilleyman J. S , Blackburn E. K
Published: July 2018

Evidence has been sought of activation of the coagulation system in two groups of patients following the infusion of two heparinised clotting factor concentrates. No changes were detected in 13 patients with mild hepatic dysfunction. In six studies on patients with Christmas disease induced abnormalities occurred in only one. Activation of the coagulation mechanism did not occur in another individual who had received the same batch of material.
The Rapid Fibrin Plate – a Method for Plasminogen Activator Assay
Authors: Marsh N. A , Gaffney P. J
Published: July 2018

Most of the technical problems associated with the fibrin plate method have been overcome in recent years with the exception of the long incubation period. This study was carried out to investigate plasminogen-enrichment as a means of shortening this period.

Fibrin plates made up to contain 2.0 casein units of added plasminogen each, were opaque, firm, did not lyse spontaneously and yielded biometrically-valid parallel-line assays for streptokinase and urokinase after a 3 hour incubation period. Urokinase assays were more accurate than those for streptokinase probably because of the latter’s shallow dose-response curve. Plasminogen-enrichtment appears therefore to be a convenient way of producing a “rapid” fibrin plate requiring incubation for 3 hours compared with the usual 16 to 20 hours.
Platelet Aggregate Ratios – Standardization of Technique and Test Results in Patients with Myocardial Ischemia and Patients with Cerebrovascular Disease
Authors: Prazich Julie A. , Rapaport Samuel I. , Samples John R. , Engler Robert
Published: July 2018

The technique for measuring platelet aggregate ratios described by Wu and Hoak (1974) was evaluated in normal subjects. The following had no influence upon the test result: age, sex, fasting versu the postprandial state, and the degree of stasis prior to drawing the sample. Variance within subjects was small compared to variance between subjects (0.0009 versus 0.0053, p < 0.01). Platelet aggregate ratios were then measured in 36 patients with coronary artery disease hospitalized with acute chest pain. Their mean platelet aggregate ratio of 0.86 was identical to the mean ratio for 47 normal subjects. Greater variability was found within patients (between samples) than within the normal subjects. This observation raises doubts about the significance of a single measurement of platelet aggregate ratio in such acutely ill patients. Mean platelet aggregate ratios measured daily did not differ over a 7-day period between 11 patients who developed a myocardial infarction and 10 patients who did not. A normal mean platelet ratio was also found on a single measurement from 30 patients with a history of completed stroke (0.87) and from 11 patients with a history of transient ischemic attacks (0.92).
Defective Platelet Adhesion and Aggregation on Subendothelium Exposed in Vivo or in Vitro to Flowing Blood of Fawn-Hooded Rats with Storage Pool Disease
Authors: Tschopp Th. B , Baumgartner H. R
Published: July 2018

Citrated rat blood was exposed to either subendothelium or the fibrillar collagen of enzymatically modified subendothelium of rabbit aorta in a perfusion system under laminar blood flow conditions at a wall shear rate of 830 s−1. The resulting platelet surface interaction was estimated by a morphometric method.

With blood of fawn-hooded (FH) rats, which suffer from hereditary platelet “storage pool disease”, platelet spreading was slower on both exposed surfaces and resulted in a lower rate of surface coverage with platelets on subendothelium if compared with controls.

The rate of adhesion of FH-platelets to the fibrillar collagen, however, was slightly higher as compared to controls despite reduced platelet spreading. This was probably due to the absence of platelet thrombus formation observed with FH-rat blood, whereas massive platelet thrombus formation took place in the controls. It is suggested that platelets of controls which arrive near the surface are preferentially incorporated into the rapidly forming platelet thrombi rather than reaching the surface, and hence do not increase surface-coverage with adhering platelets.

The defective platelet adhesion and aggregation in the FH-rat was also apparent after desendothelialization of the aorta in vivo, although to a lesser extent, probably due to the extremely low thrombogenicity of rat aorta subendothelium.
Exterior and Interior Events in Early Stage of Thrombin-induced Platelet Aggregation
Authors: Hashimoto Shuichi , Shibata Sachiko , Kobayashi Bonro
Published: July 2018

Treatment of washed rabbit platelets with 1 u/ml of thrombin at 37° C resulted in a disappearance from platelets of a protein with 250,000 dalton molecular weight which was shown to be originated from plasma membrane. Parallel loss of adenyl cyclase was noted, and both reactions were complete within 30 sec. From the patterns of disc electrophoretograms, the importance of quick suppression of thrombin action in demonstrating the primary event was stressed.

Thrombin induced an apparent activation of membrane bound phosphodiesterase. This reaction was also complete within 30 sec. The cellular component which contained the enzyme activity was distinct from plasma membrane. Soluble phosphodiesterase was not influenced by thrombin at all.

These reactions required intact platelet cells to react with thrombin, and no reaction was detected when subcellular preparations were treated with thrombin.

Possibility of collaboration of changes in externally located synthetic enzyme with those in internally located degrading enzyme in the early phase of thrombin action on platelets was suggested.
Effect of Calcium ion on the interaction between Thrombin and Heparin. Thermal Denaturation
Authors: Machovich Raymund , Arányi Péter
Published: July 2018

Heat inactivation of thrombin at 54° C followed first order kinetics with a rate constant of 1.0 min−1 approximately. Addition of heparin resulted in protection against thermal denaturation and, at the same time, rendered denaturation kinetics more complex. Analysis of the biphasic curve of heat inactivation in the presence of heparin revealed that the rate constants of the second phase changed systematically with heparin concentrations. Namely, at 4.5 × 10−6M, 9 × 10−6M, 1.8 × 10−5M and 3.6 × 10−5M heparin concentrations, the rate constants were 0.27 min−1, 0.17 min−1, 0.11 min−1 and 0.06 min−1, respectively.

Sulfate as well as phosphate ions displayed also enzyme protection against heat inactivation, however, the same effect was obtained already at a heparin concentration, lower by three orders of magnitude.

The kinetics of enzyme denaturation was not affected by calcium ions, whereas in the presence of heparin the inactivation rate of thrombin changed, i. e. calcium ions abolished the biphasic character of time course of thermal denaturation.

Thus, the data suggest that calcium ions contribute to the effect of heparin on thrombin.
Studies of Heparin Affinity to Antithrombin III and Other Proteins in Vitro and in Vivo
Authors: Takeda Y , Kobayashi N
Published: July 2018

Properties of human, canine, and porcine heparin and S-35-heparin were first studied. Their electrophoretic mobility through 10 g % polyacrylamide gels, specific activity and their filtration patterns through Sephadex G-200 columns were closely similar. Then, S-35-heparin (0.5 mg) and cold heparin (27 mg) were simultaneously injected intravenously into 5 dogs and their plasma behavior was compared. The plasma half-lives of S-35-heparin averaged 1.18 ± 0. 13 (SD) hr and was identical with that of cold heparin, but the half-lives were much shorter and averaged 0.46 ± 0.08 (SD) hr in 5 dogs when S-35-heparin alone was injected. Studies were next made of heparin affinity to proteins including canine antithrombin III (AT) by the use of Sephadex G-200 chromatography, polyacrylamide gel electrophoresis, and S-35-heparin as a tracer. It was found that S-35-heparin-binding to alpha1, beta, and gammaglobulins and fibrinogen was readily separable upon addition of 5 mg cold heparin, but that the binding to AT was inseparable by addition of cold heparin or by electrophoresis. However, in canine plasma, both S-35-heparin and cold heparin were mostly bound to proteins other than AT, suggesting that this might be the case in vivo. To further substantiate this, studies were made of the comparative behavior of I-125-labeled AT (I-125-AT) and S-35-heparin in dogs with the idea that the plasma half-lives of both should be equal if they were irreversibly bound to each other. The plasma half-lives of I-125-AT averaged 2.10 ± 0.05 (SD) days in 5 male dogs and 1.99 ± 0.04 (SD) days in 5 female dogs, and were much different from the half-life values of S-35-heparin as given above. These results indicate that heparin in vitro is more tightly bound to AT than to other proteins, that heparin in vivo is not irreversibly bound to AT and suggest that it is mostly bound to proteins other than AT in vivo.
Heparin Elimination in Patients with Liver Cirrhosis
Authors: Teien Arne N.
Published: July 2018

Heparin (100 U/kg body-weight) was injected intravenously, and heparin concentration in plasma determined by polybrene titration. Mean heparin half-life was 117.8 min in a group of patients with liver cirrhosis and normal renal function (n = 6) as compared to 74.0 min in the normal group (n = 6). The difference between the two groups is statistically significant (p ≈ 0. 02). Heparin half-life was correlated to galactose half-life in the patients (r = 0.83, p = 0. 05). The findings suggest that heparin is metabolized in the liver. There was a significant fall in antithrombin III activities in the normals, but not in the patients. A possible explanation may be that the normal liver removes heparin bound to antithrombin III, and that this function is impaired in liver cirrhosis.
Thrombo-Embolism in Patients with Abnormally Short Activated Partial Thromboplastin Time
Authors: McKenna Rajalaxmi , Bachmann Fedor , Miro-Quesada Miguel
Published: July 2018

Patients with a shortened activated partial thromboplastin time (APTT) of less than 29 sec (≥2.5 SD below the mean) were followed for the development of peripheral deep vein thrombosis by clinical findings. Perfusion lung scans were performed in patients with clinical symptoms suggesting pulmonary embolism. 23 of 100 patients in this prospective study developed thrombo-embolism (TE). This represents a tenfold increase over the overall incidence of 2.2% in medical and surgical patients during the study period. Shortened APTT’s were encountered most commonly in patients with disseminated malignancy and in surgical patients. Post-op er ative patients with an APTT of ≤ 28 sec were at high risk for the subsequent development of TE (43 %). There was a correlation between frequency of shortened APTT, degree of shortening of the APTT and incidence of TE. Patients with APTT’s of ≤ 28 sec on at least three occasions or ≤ 25 sec on at least one occasion had a 53% incidence of TE. Prophylactic low dose heparin therapy is therefore recommended for all patients who show a persistent mild shortening of the APTT or a severe shortening of the APTT on at least one occasion during periods of high risk, e.g. during immobolization or after surgery.
Spurious Prolongation of the Activated Partial Thromboplastin Time
Authors: Okpara Robert A. , Carabello Joann , James Day H
Published: July 2018

The clinical and laboratory data of 8 patients (4 males and 4 females) with circulating anticoagulant were presented. Based on prolonged APTT, failure to correct the APTT with 50 % normal plasma and abnormal tissue thromboplastin inhibition test, the inhibitor was identified as “middle stage” – or the “lupus anticoagulant”. Thrombokinetics showed the maximal rate of change in optical density (VmaxΔOD) of plasma, resulting from clot formation to be significantly less in the plasma of patients with the inhibitor than in normal plasma. This was not completely corrected by mixing the patients’ plasma with 50% normal plasma.
Human Platelet Storage Organelles A Review
Authors: Fukami Miriam H. , Salganicoff Leon
Published: July 2018

Platelets contain numerous electron-dense subcellular organelles which have been referred to in the literature by various names such as α-granules, electron-dense and very electrondense granules, lysosomes, dense bodies, etc. Most of the organelles are secretory granules, since induction of secretion by appropriate stimuli causes degranulation of platelets and the appearance of the granule contents in the extracellular medium. Among the substances that are known to be stored and secreted by platelets are: serotonin, ATP, ADP, calcium, pyrophosphate, acid hydrolases, fibrinogen, vascular permeability factor, β-thromboglobulin, platelet factor 4 and growth factor.

The recent literature concerning the localization of the secreted substances within specific platelet organelles is reviewed here. Results from electron microscopy and microprobe analysis, selective secretion experiments, subcellular fractionation studies and studies on platelets from patients with storage pool deficiency indicate that there are as many as four types of storage organelles in human platelets.
Prostaglandin Endoperoxide – Thromboxane Synthesis and Dense Granule Secretion as Positive Feedback Loops in the Propagation of Platelet Responses during “The Basic Platelet Reaction”
Authors: Holmsen Holm
Published: July 2018

Platelets respond to a great variety of stimuli by a sequential display of shape change, aggregation, prostaglandin/thromboxane synthesis – dense granule secretion and α-granule secretion. It is suggested that these responses are independent of each other, and caused by an increase in the concentration of a second messenger, liberated to the cytoplasm through the interaction between an extracellular agonist and the platelet membrane. The extent of the propagation of responses is determined by the strength of the stimulus. Stimuli can be subdivided into 1) original, applied stimuli and 2) platelet-produced stimuli (substances secreted from dense granules, prostaglandins and thromboxanes); these stimuli may act synergistically. In this way the platelet has two apparently independent means of potentiating their response to external stimuli which act as two separate positive feedback loops.
Effects of Sodium Azide on Platelet Function
Authors: Stibbe Jeanne , Holmsen Holm
Published: July 2018

Sodium azide in low concentrations (0.1-10 μM) was found to have inhibitory effects on human platelet function. Primary aggregation induced by ADP, epinephrine, thrombin and the ionophore A 23187 was decreased. To evaluate the effect of azide apart from secondary processes, the platelets were treated with indomethacin to prevent prostaglandin/thromboxane synthesis for all inducers; in addition, effects of secreted ADP, in the case of thrombin and A 23187, was prevented by the presence of creatine phosphate plus creatine phosphokinase. ADP, epinephrine and A 23187, but not thrombin-induced primary aggregates, dispersed immediately upon addition of azide. Azide powerfully inhibited dense granule secretion induced by collagen, ADP and epinephrine as measured both by 14C-serotonin secretion and as judged by secondary aggregation. Shape change induced by ADP, thrombin or A 23187 was not affected. Azide had no effect on energy metabolism. Since the aggregation experiments were performed in the presence of indomethacin, and malondialdehyde formation from arachidonic acid was not affected by azide, it seemed unlikely that the inhibition by azide of platelet function was related to inhibition of synthesis of prostaglandins and thromboxanes. It is concluded that azide exerts its effects directly on the common pathway for platelet responses.

Abbreviations used: AA: arachidonic acid; PG-TX: PGG2, PGH2 and thromboxane A2; ETYA: 5, 8, 11, 14-eicosa-tetraynoic acid; MDA: malondialdehyde; PGE1 prostaglandin E1; db-c-GMP: dibutyryl 3’, 5’-cyclic guanosine monophosphate; ADP: adenosine diphosphate; c-AMP: 3’, 5’-cyclic adenosine monophosphate; CP: creatine phosphate; CPK: creatine phosphokinase; PRP: píatelet-rich plasma; PPP: platelet-poor plasma; GFP: gel filtered platelets.
The Role of Platelets in the Pathogenesis of Thrombosis and Hemorrhage in Patients with Thrombocytosis
Authors: Walsh Peter N. , Murphy Scott , Barry William E.
Published: July 2018

Some patients with thrombocytosis due to myeloproliferative diseases or other etiologies experience thromboembolic complications and others may bleed excessively. It seems unlikely that elevations in platelet count per se are a direct cause either of thrombosis or of hemorrhage. In an effort to ascertain whether variations in platelet function might determine whether an individual patient experiences thrombotic or hemorrhagic complications we have evaluated platelet function in 22patients with thrombocytosis due to a variety of etiologies. The results of platelet counts, bleeding time determinations, and studies of platelet aggregation were similar in patients with thrombosis, in patients with bleeding and in patients with neither complication. Therefore, detailed studies of platelet coagulant activities were carried out in 8patients. The results of platelet coagulant activity assays were normal in all 3patients with thrombocytosis and neither thrombotic nor bleeding complications and an additional 3patients with myeloproliferative diseases, normal platelet counts and no thrombohemorrhagic complications. In 2patients with thrombotic complications significant elevation of platelet coagulant activities concerned with the early phases of intrinsic coagulation were observed whereas in 2patients with severe hemorrhagic complications deficiences of either contact forming activity or collagen-induced coagulant activities were evident. This preliminary study suggests the possibility that variations in platelet coagulant activities concerned with the early stages of intrinsic coagulation may determine whether patients with thrombocytosis will experience bleeding or thrombotic complications.
Early Activation of Hemostasis during Cardiopulmonary Bypass: Evidence for Thrombin Mediated Hyperfibrinolysis
Authors: Teufelsbauer H , Proidl Sylvia , Havel M , Vukovich Th
Published: July 2018

In 14 consecutive patients undergoing cardiopulmonary bypass for coronary bypass surgery the time course of coagulation and fibrinolysis markers were measured, e.g. plasma levels of thrombin-antithrombin III (TAT) complexes, cross-linked fibrin degradation products (X1FDP) and plasmin-α2-antiplasmin complexes (PAP). TAT levels exceeded the 90% baseline percentile already during CPB (after opening of aortic clamp) in 10 patients, whereas PAP and X1FDP exceeded their 90% percentile in only one patient at this time. Concerning fibrinolysis markers PAP and X1FDP the majority of patients showed elevations higher than their 90% baseline percentile only 1 h postoperation. Correlation analysis revealed significant dependencies between TAT levels during and at the end of CPB and PAP levels 1 h postoperation (R = 0.55 and R = 0.56 respectively). Furthermore, 1 h postoperation X1FDP levels were significantly correlated with both TAT and PAP. Peak X1FDP levels at the same time correlated with blood loss via thoracic drains (R = 0.56). Thus, we suggest that hyperfibrinolysis in patients undergoing CPB is at least partly due to hypercoagulation. Clinically, this may implicate that intensified anticoagulation could prevent hyperfibrinolysis and reduce postoperative blood loss.
Detection of Asymptomatic Deep Vein Thrombosis by Real-Time B-Mode Ultrasonography in Hip Surgery Patients
Authors: Agnelli Giancarlo , Volpato Raul , Radicchia Stefano , Veschi Franca , Di Filippo Paolo , Lupattelli Luciano , Nenci Giuseppe G
Published: July 2018

The aim of this study was to prospectively evaluate the accuracy of real-time B-mode ultrasonography in the diagnosis of asymptomatic proximal deep vein thrombosis (DVT) in hip surgery patients. Venography was adopted as the gold standard. We studied 100 consecutive patients undergoing hip surgery: 60 patients for hip fracture and 40 patients for elective hip replacement. Bilateral real-time B-mode ultrasonography was performed prior to bilateral venography. The two diagnostic procedures were performed on the same day by different investigators unaware of the assigned prophylatic regimen for DVT Compressibility of the vein segment was adopted as the single criterion for DVT. Venography was performed and judged by radiologists unaware of the ultrasonography results. In 13 limbs venography was either impossible to perform or not adequate for judgement. Ultrasonography and an adequate venography was obtained in 187 limbs. A venography proven DVT was observed in 49 limbs (26.2%) and a proximal DVT in 21 limbs (11.2%). All the patients were asymptomatic for DVT. The sensitivity and specificity of real time B-mode ultrasonography for proximal DVT were 57% (95% confidence interval: C. I. 36–80) and 99% (C. I. 99–100), respectively and the positive and negative predictive values were 93% (C.I. 73–100) and 95% (C.I. 91–97), respectively. The sensitivity and specificity for overall DVT were 25% (C.I. 11–38) and 99% (C.I. 97–100), respectively and the positive and negative predictive values were 92% (C. I. 73–100) and 79% (C.I. 76–85), respectively. Our data indicate that realtime B-mode ultrasonography for its high specificity could make venography unnecessary in patients with positive results. However, because of its low sensitivity it cannot be used for the screening of DVT in asymptomatic patients, nor can it replace venography for outcome measurements in clinical trials on DVT prophylaxis.
A Six Year Prospective Study of Fibrinogen and Other Risk Factors Associated with Mortality in Stable Claudicants
Authors: Banerjee A K , Pearson J , Gilliland E L , Goss D , Lewis J D , Stirling Y , Meade T W
Published: July 2018

A total of 333 patients with stable intermittent claudication at recruitment were followed up for 6 years to determine risk factors associated with subsequent mortality. Cardiovascular diseases were the underlying cause of death in 78% of the 114 patients who died. The strongest independent predictor of death during the follow-up period was the plasma fibrinogen level, an increase of 1 g/l being associated with a nearly two-fold increase in the probability of death within the next 6 years. Age, low ankle/brachial pressure index and a past history of myocardial infarction also increased the probability of death during the study period. The plasma fibrinogen level is a valuable index of those patients with stable intermittent claudication at high risk of early mortality. The results also provide further evidence for the involvement of fibrinogen in the pathogenesis of arterial disease.
Antiphospholipid Antibody Positive Sera Enhance Endothelial Cell Procoagulant Activity – Studies in a Thrombosis Model
Authors: Oosting Janine D , Derksen Ronald H W M , Blokzijl Laya , Sixma Jan J , de Groot Philip G
Published: July 2018

The effect of sera and IgG from 12 patients with systemic lupus erythematosus (SLE) on the endothelial cell (EC) procoagulant activity (PCA) was investigated in an in vitro thrombosis model. Six of the 12 SLE sera contained antiphospholipid antibodies (aPL).

EC were stimulated for 8 h at 37° C with or without 50 pM tumor necrosis factor (TNF) in culture medium containing 20% patient or control serum. Then the endothelial cell matrix (ECM) was isolated and subsequently exposed in a perfusion chamber to circulating normal whole blood, anticoagulated with low molecular weight heparin (LMWH). The PCA of the ECM was determined as the amount of generated fibrinopeptide A (FPA) in samples taken before and after perfusion. Furthermore, cross sections were made of the perfused matrix and analyzed for platelet adhesion and aggregate formation.

All six aPL containing sera induced a small, but significant increase of ECM procoagulant activity. When added in combination with a low dose of TNF (50 pM), a synergistic enhancement of ECM procoagulant activity was found. The FPA generation was increased to 150–614% from the values obtained after stimulation with TNF and control serum. Also a shift towards the formation of larger platelet thrombi was observed. After stimulation with TNF and patient serum the surface of ECM covered with large aggregates (> 5 µm) was increased by 124–329% compared to the results obtained after stimulation with control serum and TNF. When patient sera were depleted from IgG the effects were strongly decreased.

These data show that the potentiation of TNF-induced PCA formation by aPL containing sera from patients with SLE leads to enhanced thrombus formation in an in vitro thrombosis model. This may help explain the increased thrombotic tendency in these patients.
The Prevalence of Factor XII Deficiency in 103 Orally Anticoagulated Outpatients Suffering from Recurrent Venous and/or Arterial Thromboembolism
Authors: Halbmayer Walter-Michael , Mannhalter Christine , Feichtinger Christine , Rubi Karl , Fischer Michael
Published: July 2018

One hundred and three patients suffering from recurrent venous thrombosis, recurrent arterial thromboembolism and/or recurrent myocardial infarction and 50 healthy subjects were tested for Hageman factor (FXII) coagulant activity and antigen. Among the 103 patients we identified 15 subjects with FXII deficiency (15%), 3 with protein C deficiency (3%) and 3 with protein S deficiency (3%). Combined FXII and protein C, protein S or antithrombin III deficiency was not observed. The 103 patients were devided into subgroups according to the type of thrombotic complication. Among patients with exclusively recurrent venous thromboembolism 8% (p = 0.153) were deficient in FXII. Among patients suffering from recurrent arterial thromboembolism and/or myocardial infarction, the incidence of FXII deficiency was significantly higher (20%, p < 0.003). In 67% of the patients with FXII deficiency a positive family history of thrombosis could be established. In contrast, only 32% of all venous and 28% of all arterial thrombosis patients had a positive family history. We believe that reduced levels of FXII should be considered as a risk factor in the development of thromboembolism. Consequently, more attention should be payed to the measurement of FXII when evaluating thromboembolic risk factors especially in cases of recurrent arterial thromboembolism and/or myocardial infarction.
Effect of Tissue Factor Pathway Inhibitor (TFPI) in the HEPTEST® Assay and in an Amidolytic Anti Factor Xa Assay for LMW Heparin
Authors: Kristensen Hanne I , Østergaard Per B , Nordfang Ole , Abildgaard Ulrich , Lindahl Anne Karin
Published: July 2018

Both the HEPTEST® and amidolytic anti factor Xa assays are currently being used for heparin activity detection in plasma from patients receiving standard heparin or low molecular weight heparin (LMWH). In this study we have investigated the influence of recombinant and endogenous Tissue Factor Pathway Inhibitor (TFPI) on these assays. The HEPTEST® determinations were performed on an ACL 300 R Clottimer using the APTT program which resulted in a longer incubation time with factor Xa than recommended by the manufacturer. rTFPI added to plasma prolonged the HEPTEST® clotting time markedly, but had only a little effect in the amidolytic assay. Antibodies against TFPI (anti-TFPI) abolished these effects. The effect of adding rTFPI and Logiparin® was additive. When anti-TFPI IgG was added to samples of normal plasma, a statistically significant shortening of the HEPTEST® clotting time was seen. When anti-TFPI was added to plasma samples from volunteers who had received Logiparin® by subcutaneous or intravenous injection, then the HEPTEST® clotting time was shortened considerably. For some samples the clotting time was halved. These experiments show that the HEPTEST® clotting time is prolonged not only by heparin-antithrombin III, but also by TFPI released by heparin injection.
Fibrin Clot Lysis by Thrombolytic Agents Is Impaired in Newborns due to a Low Plasminogen Concentration
Authors: Andrew M , Brooker L , Leaker M , Paes B , Weitz J
Published: July 2018

Although thrombolytic drugs have been extensively used in adults, there is sparse information on their effectiveness in newborns whose fibrinolytic system differs significantly from adults. The purpose of this study was to determine if low plasma levels of plasminogen in cord plasma limited the therapeutic effectiveness of thrombolytic agents. Urokinase (UK), streptokinase (SK) and tissue plasminogen activator (TPA) were compared for their ability to lyse washed 125I-labelled adult or cord fibrin clots suspended in cord or adult plasma. 125I-labelled fibrin clots were prepared by recalcifying cord or adult plasma spiked with labelled fibrinogen and then placed into cord or adult plasma which contained either saline or differing amounts of a specific thrombolytic agent. After a 60 min incubation, the remaining 125I-fibrin in clots released 125I-fibrin fragments, and concentrations of fibrinogen, α2-antiplasmin, and plasminogen in the bathing plasma were measured and compared to starting values. Cord fibrin clots were more resistant than adult fibrin clots to all thrombolytic drugs tested (p <0.001). On average, the cord system retained 27% more 125I-fibrin in clots, and released 32% less 125I-fibrin fragments into plasma. Fibrinogenolysis was also decreased in cord plasmas compared to adult plasmas. The degree of fibrinolysis and fibrinogenolysis in cord plasma increased to adult values when plasminogen concentrations were increased in the bathing plasma. Thus, cord fibrin clots have an impaired response to thrombolytic agents secondary to low levels of plasminogen. We speculate that the clinical response of newborns to thrombolytic agents is also impaired and will not be enhanced by increasing doses of thrombolytic agents but may be enhanced by increasing the concentration of plasminogen.
Synergistic Antithrombotic Properties of G4120, a RGD-Containing Synthetic Peptide, and Argatroban, a Synthetic Thrombin Inhibitor, in a Hamster Femoral Vein Platelet-Rich Thrombosis Model
Authors: Imura Yoshimi , Stassen Jean-Marie , Vreys Ingrid , Lesaffre Emmanuel , Gold Herman K , Collen Désiré
Published: July 2018

The synergistic antithrombotic properties of G4120, a synthetic Arg-Gly-Asp (RGD) containing peptide which strongly inhibits platelet aggregation, and of Argatroban, a synthetic thrombin inhibitor, were examined in a reproducible quantitative hamster femoral vein platelet-rich mural thrombosis model. Bolus injections of G4120 and Argatroban inhibit thrombus formation in a dose-dependent way; 50% inhibition (ID50) is obtained with 11 µg/kg G4120 and with 2 mg/kg Argatroban. Combined bolus injections of 3 µg/kg G4120 with 0.5, 0.75 or 1 mg/kg Argatroban and of 1 mg/kg Argatroban with 1.5 or 3 µg/kg G4120 caused linear dose-dependent inhibition of thrombus formation, whereas 3 µg/kg G4120 or 1 mg/kg Argatroban alone had very little effect (<20% inhibition). ID50 was obtained with the combination of 3 µg/kg G4120 and 0.5 mg/kg Argatroban, corresponding to an equi-effective fractional combination of 0.62 with a 95% confidence interval of 0.50 to 0.74. Alternatively the ID50 was obtained with the combination of 1 mg/kg Argatroban and 1.3 µg/kg G4120, corresponding to an equi-effective fractional combination of 0.52 with a 95% confidence interval of 0.18 to 0.86. In both instances these results are indicative of a significant synergistic interaction. Bolus injection of 10 mg/kg aspirin, 100 U/kg heparin or the combination did not inhibit thrombus formation.

The synergistic effect of the combination of platelet inhibiting RGD-peptides and synthetic thrombin inhibitors could be useful in the prevention of arterial occlusion with platelet-rich thrombus in patients with ischemic heart disease following thrombolytic therapy or angioplasty, although this combination is not expected to reverse platelet thrombus formation.