PARTIAL THROMBOPLASTIN TIME TEST WITH KAOLIN. NORMAL RANGE AND MODIFICATIONS FOR THE DIAGNOSIS OF HAEMOPHILIA AND CHRISTMAS DISEASE

An engineered activated factor V for the prevention and treatment of acute traumatic coagulopathy and bleeding in mice

^superFVa arrests severe bleeding and prevents the development of ATC after trauma.

^superFVa therapy restores functional hemostasis when initiated after onset of ATC caused by traumatic bleeding.

Acute traumatic coagulopathy (ATC) occurs in approximately 30% of patients with trauma and is associated with increased mortality. Excessive generation of activated protein C (APC) and hyperfibrinolysis are believed to be driving forces for ATC. Two mouse models were used to investigate whether an engineered activated FV variant (^superFVa) that is resistant to inactivation by APC and contains a stabilizing A2-A3 domain disulfide bond can reduce traumatic bleeding and normalize hemostasis parameters in ATC. First, ATC was induced by the combination of trauma and shock. ATC was characterized by activated partial thromboplastin time (APTT) prolongation and reductions of factor V (FV), factor VIII (FVIII), and fibrinogen but not factor II and factor X. Administration of ^superFVa normalized the APTT, returned FV and FVIII clotting activity levels to their normal range, and reduced APC and thrombin-antithrombin (TAT) levels, indicating improved hemostasis. Next, a liver laceration model was used where ATC develops as a consequence of severe bleeding. ^superFVa prophylaxis before liver laceration reduced bleeding and prevented APTT prolongation, depletion of FV and FVIII, and excessive generation of APC. Thus, prophylactic administration of ^superFVa prevented the development of ATC. ^superFVa intervention started after the development of ATC stabilized bleeding, reversed prolonged APTT, returned FV and FVIII levels to their normal range, and reduced TAT levels that were increased by ATC. In summary, ^superFVa prevented ATC and traumatic bleeding when administered prophylactically, and ^superFVa stabilized bleeding and reversed abnormal hemostasis parameters when administered while ATC was in progress. Thus, ^superFVa may be an attractive strategy to intercept ATC and mitigate traumatic bleeding.

Characterization and pharmacological properties of a novel multifunctional Kunitz inhibitor from Erythrina velutina seeds

Inhibitors of peptidases isolated from leguminous seeds have been studied for their pharmacological properties. The present study focused on purification, biochemical characterization and anti-inflammatory and anticoagulant evaluation of a novel Kunitz trypsin inhibitor from Erythrina velutina seeds (EvTI). Trypsin inhibitors were purified by ammonium sulfate (30-60%), fractionation followed by Trypsin-Sepharose affinity chromatography and reversed-phase high performance liquid chromatography. The purified inhibitor showed molecular mass of 19,210.48 Da. Furthermore, a second isoform with 19,228.16 Da was also observed. The inhibitor that showed highest trypsin specificity and enhanced recovery yield was named EvTI (P2) and was selected for further analysis. The EvTI peptide fragments, generated by trypsin and pepsin digestion, were further analyzed by MALDI-ToF-ToF mass spectrometry, allowing a partial primary structure elucidation. EvTI exhibited inhibitory activity against trypsin with IC50 of 2.2×10(-8) mol.L(-1) and constant inhibition (Ki) of 1.0×10(-8) mol.L(-1), by a non-competitive mechanism. In addition to inhibit the activity of trypsin, EvTI also inhibited factor Xa and neutrophil elastase, but do not inhibit thrombin, chymotrypsin or peptidase 3. EvTI was investigated for its anti-inflammatory and anti-coagulant properties. Firstly, EvTI showed no cytotoxic effect on human peripheral blood cells. Nevertheless, the inhibitor was able to prolong the clotting time in a dose-dependent manner by using in vitro and in vivo models. Due to anti-inflammatory and anticoagulant EvTI properties, two sepsis models were here challenged. EvTI inhibited leukocyte migration and specifically acted by inhibiting TNF-α release and stimulating IFN-α and IL-12 synthesis. The data presented clearly contribute to a better understanding of the use of Kunitz inhibitors in sepsis as a bioactive agent capable of interfering in blood coagulation and inflammation.

Determinants of the thrombogenic potential of multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) are cylindrical tubes of graphitic carbon with unique physical and electrical properties. MWCNTs are being explored for a variety of diagnostic and therapeutic applications. Successful biomedical application of MWCNTs will require compatibility with normal circulatory components, including constituents of the hemostatic cascades. In this manuscript, we compare the thrombotic activity of MWCNTs in vitro and in vivo. We also assess the influence of functionalization of MWCNTs on thrombotic activity. In vitro, MWCNT activate the intrinsic pathway of coagulation as measured by activated partial thromboplastin time (aPTT) assays. Functionalization by amidation or carboxylation enhances this procoagulant activity. Mechanistic studies demonstrate that MWCNTs enhance propagation of the intrinsic pathway via a non-classical mechanism strongly dependent on factor IX. MWCNTs preferentially associate with factor IXa and may provide a platform that enhances its enzymatic activity. In addition to their effects on the coagulation cascade, MWCNTs activate platelets in vitro, with amidated MWCNTs exhibiting greater platelet activation than carboxylated or pristine MWCNTs. However, contrasting trends are obtained in vivo, where functionalization tends to diminish rather than enhance procoagulant activity. Thus, following systemic injection of MWCNTs in mice, pristine MWCNTs decreased platelet counts, increased vWF, and increased D-dimers. In contrast, carboxylated MWCNTS exhibited little procoagulant tendency in vivo, eliciting only a mild and transient decrease in platelets. Amidated MWCNTs elicited no statistically significant change in platelet count. Further, neither carboxylated nor amidated MWCNTs increased vWF or D-dimers in mouse plasma. We conclude that the procoagulant tendencies of MWCNTs observed in vitro are not necessarily recapitulated in vivo. Further, functionalization can markedly attenuate the procoagulant activity of MWCNTs in vivo. This work will inform the rational development of biocompatible MWCNTs for systemic delivery.

Acquired Factor VIII autoantibody: four cases demonstrating the heterogenous nature of this condition and problems involved in diagnosis and treatment

The development of an autoantibody to human Factor VIII is rare and presents many problems for diagnosis and treatment. We have seen several cases at our institution recently with widely heterogenous clinical and laboratory presentations. A wide range of treatment modalities were used in these cases with no gold standard of treatment or widely accepted guidelines existing. This has prompted us to examine all cases of this condition presenting at Fremantle Hospital over the last decade. We describe four cases which demonstrate the heterogeneity of this condition and its treatment and review the recent literature on the subject.

Characteristics of polylipid/Hb vesicles (ARC) (in vitro and in vivo test)

Polylipid/Hb vesicle, which is polymerized phospholipid vesicles (200 nm) encapsulating concentrated Hb solution, has been established by us as an artificial red cell (ARC). ARC can be easily adjusted to physiological conditions (viscosity, density and oncotic pressure etc) as the same of human blood. Our ARC has excellent blood compatibility (no effect on coagulation, no hemolysis and no red cell aggregation). Neither acute toxicity nor damage of internal organs was confirmed. Oxygen transporting capacity was almost the same as human blood, and the half life in blood stream was ca. 13 hrs.

Stability and blood compatibility of polylipid/Hb

The Polylipid/Hb vesicle is a new artificial red cell (ARC) based on liposome-encapsulated Hb. Advantages are derived from the stabilized liposomal bilayer membranes, obtained by polymerization of 1,2-bis(2,4-octadecadienoyl)-sn-glycero-3-phospho choline (DODPC). Furthermore, blood compatibility in vitro are good.

The ICTH/WFH study of the partial thromboplastin time in mild haemophilia

A study has been carried out in two stages to compare the sensitivity of different Partial Thromboplastin Time (P.T.T.) methods to partial deficiencies of factor VIII. In Stage 1, 63 laboratories throughout the world compared their own methods with a reference method, all using samples of the same three mild haemophilic plasmas. Wide variation was found between laboratories using the same method, especially for those methods which were not well standardised. There was fairly good agreement for the reference method. All methods correctly diagnosed the three mild haemophilic plasmas, but their factor VIII levels were rather low. Stage 2 was restricted to seven laboratories in Great Britain, comparing seven well-standardised commercial methods and the same reference method. A much wider range of abnormal plasmas was tested, and a variety of normal ones. P.T.T.'s for all plasmas (factor VIII levels from 5 to 58 iu/dL) fell outside the normal range by all methods, with a few exceptions. It was not possible to rank the methods in any order.

Sensitivity and precision of activated partial thromboplastin time (APTT) methods. A multicenter study

The Activated Partial Thromboplastin Time (APTT) test, Cephotest, was compared to other APTT methods in current use in 4 specialized coagulation laboratories. In 3 of 4 laboratories, the sensitivity of Cephotest was superior (P less than 0.001) to that of the local APTT method. There was no statistically significant difference between the APTT methods with regard to precision of repetitive testing. In each laboratory, the normal range of Cephotest was estimated on freshly collected plasma samples from healthy subjects. A mean value between 28.8 and 35.8 s, with a standard deviation of 1.1-3.3 s, was obtained. It is concluded that the composition of the APTT method if of importance for the sensitivity of this test, but does not influence the precision of repetitive testing to a significant degree. The use of a standardized reagent facilitates comparison of the results obtained with the APTT method from one laboratory to another.

An approach to the evaluation of hemostasis

Effective hemostasis may be adequately and quickly evaluated using tests that are readily available in the usual hospital laboratory. This evaluation includes peripheral smear for platelet morphology and number, platelet count, bleeding time, activated partial thromboplastin time (aPTT), prothrombin time (PT), and clot retraction. Normal results of these tests exclude all but the mildest disturbances of hemostasis.

Correction of abnormal coagulation in chronic liver disease by combined use of fresh-frozen plasma and prothrombin complex concentrates

The effect on abnormal coagulation tests of infusions of fresh-frozen plasma (F.F.P), prothrombin complex concentrates, and a combination of these treatments was compared in 30 patients with chronic liver disease undergoing needle biopsy. A single dose of F.F.P. (12 ml/kg body-weight) was found to be the least effective therapeutic regimen. The concentrate containing factors II, IX, and X was also not adequate, but the additional administration of factor-VII concentrate corrected the prothrombin-time (P.T.) and "Normotest" (N.T.) in most patients. However, this regimen did not correct the prolonged kaolin activated partial thromboplastin-time (K.P.T.T.). The results of tests for exploring both the extrinsic (P.T. and N.T.) and intrinsic (K.P.T.T.) coagulation systems only became normal after the combined administration of a lower dose of F.F.P. (8 ml/kg body-weight) and of both concentrates (12 units/ml). There was no clinical or laboratory evidence of thrombotic complications. No patient developed acute hepatitis or hepatitis-B surface antigen in the twelve months after biopsy. These results indicate that prothrombin-complex concentrates in combination with F.F.P. may therefore be used to allow liver biopsy to be performed safely in patients presenting with severe coagulation defects.

Simple screening tests for the diagnosis of isolated clotting factor defects. With special reference to 'contact factor' defects

Reagents may be prepared from normal plasma and used with the prothrombin time and partial thromboplastin time tests to distinguish isolated defects of factors I, II, VII, VIII, IX, X, XI, or XII.

Coagulation factors in chronic liver disease

Coagulation studies were carried out on 30 patients with chronic liver disease. The clotting defect was complex and involved factors V, VII, IX (Christmas factor), and prothrombin. Some patients showed a significant depression of factor IX in the presence of a normal one-stage prothrombin time. Thrombotest was found to be a good indicator of factor IX deficiency in this group of patients and may be of use as an additional liver function test. The screening of patients with liver disease for surgery or liver biopsy should assess the coagulation factors involved in both intrinsic and extrinsic thromboplastin generation.

The fibrinolytic enzyme system of the rat: the effect of aminonucleoside-induced nephrotic syndrome

Components of the fibrinolytic enzyme system were studied in rats rendered nephrotic by means of aminonucleoside of puromycin.

At the peak of the disease fibrinolytic activity was greatly decreased and this was due to decreased plasminogen and increased plasma antiplasmins. Plasma fibrinogen was also increased. Plasma activator levels remained relatively constant but there was a marked increase in urokinase excretion.

These changes could be explained from the loss of plasma proteins and abnormal protein metabolism associated with the nephrotic syndrome. Increases in plasma lipoproteins partly accounted for the increase in antiplasmins.

Despite the profound alterations to fibrinolytic components there was no evidence of increased intravascular fibrin deposition. This evidence does not support the theory that fibrinolysis is essential in the maintenance of a fibrinfree vascular tree.

Metabolic and blood coagulation changes during intravenous fat infusions

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Diagnosis of haemophilia: use of an artificial factor-VIII-deficient human plasma system

An artificial clotting system deficient in factor VIII has been made from normal human plasma. Factors XII and XI are supplied as ;activation product'. An eluate from Al(OH)(3), which has been incubated with normal plasma, supplies factors X and IX in their ;plasma' (unactivated) form with II. Factor V is provided as the supernatant after the Al(OH)(3)- treated plasma has been precipitated at one-third saturation with (NH(4))(2)SO(4). Fibrinogen is freed of factor VIII by freezing and thawing a lyophylized preparation and then added. Of these, activation product and the fibrinogen may be prepared in advance and stored frozen, and the eluate and supernatant may be made on the day of testing. A phospholipid source and CaCl(2)-solution are also required. In use, a patient's and a control plasma are first diluted in a mixture of the eluate, supernatant, and fibrinogen solution, and clotting times are recorded after completing the system by adding the phospholipid, activation product, and calcium chloride. The clotting times from the mixtures containing the patient's and the control plasmas may then be compared.

Partial thromboplastin time test with kaolin: diagnosis of haemophilia and Christmas disease without natural reference plasmas

Deficiencies of factor VIII (in haemophilia) and factor IX (in Christmas disease) prolong the partial thromboplastin time. If normal plasma is treated with alumina, the factor VIII remains but the factor IX is removed and can subsequently be recovered by elution of the alumina. If a long partial thromboplastin time is found on investigating a male patient whose history suggests a life-long bleeding disorder, the plasma may be retested after adding either alumina-adsorbed normal plasma or eluate. If the patient's partial thromboplastin time is shortened (relative to the control) by adding adsorbed normal plasma the patient is likely to be a haemophiliac; but if it is shortened by adding eluate then he is likely to have Christmas disease. Practical details for carrying out these manoeuvres are given and experiments on the validity of the test described.