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PubMed2000

[Factor XIIa-inhibited diluted thromboplastin time can reflect coagulation process].

OBJECTIVE: To establish a screening test that can reflect two stages of coagulation process. METHODS: With FXII a being blocked, the effects of various dilution of thromboplastin on clotting time were observed. FX a activity was determined by chromogenic assay. RESULTS: (1) At high concentration of thromboplastin, FXII a-inhibited diluted thromboplastin time (FXII ai DTT) of pooled normal plasma and FXI deficient plasma was very similar, but at low concentration, FXII ai DTT was in order of FVIII and FIX deficient plasma > FXI deficient plasma > pooled normal plasma. (2) FXI consumption by immunologic method induced FXII ai DTT of pooled normal plasma prolonged, and addition of FXI to FXI deficient plasma shortened FXII ai DTT. (3) Alpha-thrombin blocked by hirudin at different time (10 - 80 seconds) resulted in decreased FXa generation, and the earlier the block, the more the decrease. Under the same condition, the amount of FXa generation was in order of platelet-rich plasma > platelet-poor plasma > FXI deficient plasma. CONCLUSION: (1) Our data support the two-stage hypothesis and confirm the important role of FXI in the amplification stage. (2) FXII ai DTT as a screening test for coagulation process may be practicable.

Blood Coagulation↗
PubMed2002

Thromboplastin-thrombomodulin-mediated time: a new global test sensitive to protein S deficiency and increased levels of factors II, V, VII and X.

BACKGROUND AND OBJECTIVES: A new test for screening the procoagulant capacity of plasma is described and evaluated. This test is based on the coagulation of plasma initiated by thromboplastin (Tp) in the presence of thrombomodulin (TM). In a previous paper we reported that this test had a significant phenotypic and genetic correlation with thrombosis susceptibility. The present report describes the characteristics of the test and its sensitivity to the concentration of some hemostasis factors. DESIGN AND METHODS: Plasma from normal subjects, from individuals with various disorders of hemostasis and plasma with different concentrations of factors II, V, VII, VIII, X, fibrinogen, protein C and protein S were studied. The thromboplastin-thrombomodulin-mediated time (Tp-TMT) is measured after mixing 100 mL of plasma diluted 1/10 at 37 C with 100 mL of a solution composed of 2 parts of thromboplastin, 1 part of thrombomodulin at 30 U/mL and 1 part of Owren's buffer. The results are expressed as the ratio of the patient's clotting time to that of the control. Values were compared with Student's t test and the Mann-Whitney test. Differences were considered statistically significant when p<0.05. RESULTS: In the control group women showed significantly lower values than men. Raised levels of factors II, V, VII and X reduced the coagulation time obtained with Tp-TM. Elevated concentrations of fibrinogen and factor VIII did not influence the test. The Tp-TMT was sensitive to protein S deficiencies, but not to protein C deficiencies. INTERPRETATION AND CONCLUSIONS: These results indicate that the effect of protein S on the test is through its anti-prothrombinase activity. IN CONCLUSION: Tp-TMT, which is correlated with thrombosis susceptibility, is sensitive to raised levels of factors II, V, VII and X, as well as to low levels of protein S, and may be an indicator of thrombosis risk.

Blood Coagulation↗
PubMed2003

The influence of exogenous magnesium chloride on the apparent INR determined with human, rabbit, and bovine thromboplastin reagents.

Magnesium ions can shorten the tissue factor-induced coagulation time. Some blood collection systems with sodium citrate are contaminated with variable amounts of magnesium and influence the results of the prothrombin time (PT) test. The aim of the study was to determine the dose-response relationship between exogenous magnesium chloride added to blood and the PT and the international normalized ratio (INR). Blood specimens from twenty patients on oral anticoagulant therapy were investigated. Four different types of thromboplastin reagents were used: recombinant human, human placenta, rabbit brain, and bovine brain combined with adsorbed bovine plasma. With all four reagents, exogenous magnesium induced a reduction of the apparent INR. Bovine thromboplastin was not as responsive to magnesium as the human and rabbit reagents. The magnitude of the INR deviation induced by 0.1 mmol/l magnesium in the blood was smaller than 10% in all patient samples. At 0.5 mmol/l magnesium in the blood, 10-35% of the patient samples had INR deviations greater than 10%, depending on the thromboplastin reagent used.

Animals↗
PubMed2004

[Obtaining active extracts for use in production of soluble thromboplastin].

Methods of obtaining (from cadaveric human brain) the highly-active extracts to be used later as raw-materials for thromboplastin manufacturing, which is applied to determine the prothrombin (thromboplastin) time of human plasma or blood, are described in the paper. The study resulted in defining the optimal requirements to choosing the raw-materials, storing regime, centrifuging and extraction. The thus elaborated technology of soluble thromboplastin manufacturing ensures the production of a reagent with a high sensitivity to a changing level of factors VII and X and to a reducing activity of the prothrombin complex, which is achieved through the impact of indirect anticoagulants.

Brain Chemistry↗
PubMed1992

Monitoring "mini-intensity" anticoagulation with warfarin: comparison of the prothrombin time using a sensitive thromboplastin with prothrombin fragment F1+2 levels.

Treatment with warfarin using a target International Normalized Ratio (INR) range of 1.7 to 2.5 is efficacious for many clinical indications, but the minimal intensity of anticoagulation required for antithrombotic protection has yet to be determined. To evaluate whether patients could be reliably monitored with a less intense regimen, we anticoagulated patients with warfarin for several months using a target INR range of 1.3 to 1.6 as determined by prothrombin time (PT) using a sensitive thromboplastin (Dade IS, International Sensitivity Index [ISI] = 1.3). Plasma measurements of F1+2, a marker of factor Xa action on prothrombin in vivo, were also obtained to determine the suppressive effect of warfarin on hemostatic system activity. Overall, 20 of 21 patients with a history of cerebrovascular events (mean age, 61 years) could be reliably regulated with warfarin in the target INR range. F1+2 levels were significantly suppressed from baseline in all patients, with a mean reduction of 49% (range, 28% to 78%). We found a significant relationship between the extent of suppression of prothrombin activation levels and the baseline measurements. A mean reduction of 65% was observed for those patients with baseline F1+2 greater than or equal to 1.5 nmol/L, but only 38% for baseline F1+2 less than or equal to 0.5 nmol/L. Overall, 68% of plasma samples obtained during stable anticoagulation were within the target INR range. PTs were also determined on all plasma samples with two thromboplastins of lower sensitivity (C+, ISI = 2.09; and automated simplastin, ISI = 2.10). Only 47% and 35% of PT determinations, respectively, were within the target range with these reagents. We conclude that prothrombin activation can be significantly suppressed in vivo with use of warfarin in an INR range of 1.3 to 1.6. This level of anticoagulation can be reliably achieved by monitoring PTs with a thromboplastin of high sensitivity.

Blood Coagulation↗
PubMedDate not supplied

[Interaction of human factor X with thromboplastin].

The binding of 125I-labeled human factor X to native and papaine-treated tissue tromboplastin in the presence of CaCl2 or EDTA was studied. The Scatchard analysis suggests the existence of high (Kd=l,8 x10(-9) M) and low affinity binding sites on the thromboplastin surface. The removal of Ca2+ reduced affinity of factor X to the high affinity sites. This was accompanied by some increase of their number. Proteolysis by papaine decreased affinity of high affinity sites and caused the increase of their number in the presence of Ca2+. In the absence of Ca2+ the affinity remained unchanged, but the number of sites decreased. At low concentrations of factor X positive cooperativity for high affinity binding sites was observed. It did not depend on the presence of Ca2+. The results indirectly confirm the role of hydrophobic interactons in Ca2+ dependent binding of factor X to thromboplastin and the fact that heterogeneity of this binding is determined by mesophase structure of the thromboplastin phospholipids.

Binding Sites↗
PubMed2006

Long-term stability of relationships between reference materials for thromboplastins.

Reference materials for thromboplastins are available from the World Health Organization (WHO) and the European Commission (EC). The long-term stability of the reference materials is an essential requirement and must be monitored. The relationship between two reference materials for rabbit thromboplastin, i.e. ERM-AD149 (EC) and RBT/90 (WHO), has been monitored in the period 1996-2002. No significant trend with time was detected. In addition, the relationship between ERM-AD149 and the reference material for bovine thromboplastin (i.e. OBT/79) has been determined in 1994 and in 2005 in multicentre studies (n = 11 and n = 9, respectively). No significant changes were observed in the relationships between these reference materials when all results were included (5% significance level).

Animals↗
PubMed1990

[A lyophilized reagent for standardization of the activated partial thromboplastin time].

Native partial thromboplastin, prepared from cadaver brain thromboplastin (a reagent), is a cephalin analog used to detect disorders in the first phase of coagulation. It was lyophilized with the aim of its stabilization, potential commercial manufacture, and introduction into practical clinical laboratories. Native emulsion was distributed into 0.2 ml penicillin flasks and lyophilized for 18-20 hrs in IZ-9 (CSR) or similar equipment at the maximum temperature of the product 5 degrees C. Lyophilized reagent is a white or slightly cream-colored powder. It retains its activity for at least a year as evidenced by the activated partial thromboplastin time test. The range of activities within one lot is less if commercial lyophilized donor reference plasma is used in the test. The reagent is stored in a refrigerator at 4-8 degrees C.

Blood Coagulation Tests↗
PubMed1990

Procoagulant (thromboplastin) activity in human bronchoalveolar lavage fluids is derived from alveolar macrophages.

Fibrin deposition in the alveolar space and the lung interstitium is a prominent feature of many types of inflammatory pulmonary diseases. Cells of the monocyte/macrophage line are the primary cells supplying procoagulant activity in inflammatory lesions. In the present study we found that both lung alveolar macrophages (LAM) and bronchoalveolar lavage fluids (BALF) from humans contained procoagulant activities. The procoagulant in BALF was associated with membrane vesicles which sedimented at 100,000 g for 1 h. By electron microscopy the BALF ultrasediment was seen to consist almost exclusively of membrane material and this was confirmed by monitoring the content of different marker enzymes for specific subcellular structures. Using macrophage membrane markers, at least part of the BALF-ultrasediment was shown to be derived from LAM. On the basis of phospholipase C sensitivity, antibody neutralization and the site of action of the procoagulant in the sequential activation of coagulation factors, both the LAM-associated and the BALF-associated procoagulant activity was identified as thromboplastin (tissue factor) or thromboplastin-factor VII complexes. This suggests that alveolar macrophages and the LAM-derived thromboplastin-containing microvesicles may contribute to intraalveolar and interstitial fibrin deposition in vivo and probably also have consequences for the development of pulmonary fibrosis.

Bronchoalveolar Lavage Fluid↗
PubMed1985

Thrombin induces thromboplastin synthesis in cultured vascular endothelial cells.

Cultured human umbilical vein endothelial cells responded to thrombin (10(-2) - 10 NIH u/ml) with a 2-5 fold increase in thromboplastin activity. The maximum response was reached after 4 hr in serum-free medium. The effect of thrombin was fully inhibited by the presence of 50% (v/v) fetal calf serum or more in the medium, by preincubation of thrombin with hirudin or by treatment of thrombin with N-bromosuccinimide or phenylmethylsulfonyl fluoride. The thrombin-induced thromboplastin activity was inhibited by incubation of the cells with cycloheximide (2 micrograms/ml) or actinomycin D (2 micrograms/ml) showing that the response depended on de novo protein and RNA synthesis. It was also suppressed by exposure of the cells to two different phosphodiesterase inhibitors, 3-butyl-1-methyl-xanthine (5 X 10(-4) M) and rac-4 (3-butoxy-4-methoxybenzyl)-2-imidazole (5 X 10(-4) M), to the transmethylation inhibitors 3-deazaadenosine (10(-5) M) and 1-homocysteine thiolactone (2 X 10(-5) M) in combination and to the intracellular calcium antagonist 8-(N,N-diethylamino)-octyl 3,4,5,-tri-methoxybenzoate hydrochloride (8 X 10(-5) M). Our results suggest that small amounts of thrombin can induce thromboplastin synthesis in endothelial cells in vitro and that this synthesis probably is regulated by the intracellular level of cAMP, by cytoplasmic Ca2+ and possibly also by transmethylation reactions.

1-Methyl-3-isobutylxanthine↗
PubMed1989

In situ-generated thrombin is the only enzyme that effectively activates factor VIII and factor V in thromboplastin-activated plasma.

We investigated the activation of the nonenzymatic protein cofactors factor VIII and factor V in plasma when coagulation was initiated by thromboplastin. With sensitive bioassays, we were able to measure specifically the generation of activated factor VIII and activated factor V in plasma. Our results showed that when plasma was triggered with a relatively high concentration of thromboplastin, factor VIII and factor V were completely activated at the clotting time of plasma. However, when the generation of thrombin, but not that of factor Xa, was delayed by addition of hirudin to the plasma, factor Va was generated only at the time thrombin generation overcame the hirudin inhibition. In addition, generation of factor VIIIa correlated with thrombin generation and not with factor Xa generation. Furthermore, addition of large amounts of factor Xa to hirudinized plasma did not show detectable factor VIII or factor V activation. We concluded that in plasma activated with thromboplastin the enzyme responsible for activation of factor V and factor VIII is thrombin, not factor Xa.

Blood Coagulation↗
PubMedDate not supplied

[Tissue thromboplastin in the human brain].

The studies by the scanning electron microscopy have shown that there are small amounts of membrane-like structures in the dry preparation of tissues thromboplastin obtained from the human brain. In water phospholipids of thromboplastin form hexagonal (H11) cylinders. Protein moiety of the tissue factor essentially influences on the phase state of phospholipids and on the dynamic properties of their fatty acid chains' radicals. The interaction of Ca2+ with the tissue thromboplastin does not change the phase state of phospholipids and at the same time rises rigidity of polar parts of phospholipids and their hydrophobic segments in the internal structures.

Brain Chemistry↗
PubMed1988

[The expression and degradation of tissue thromboplastin].

The highest disintegration rate of FITC-thromboplastin occurred in the organs rich in RES-cells. The half-disintegration period was found to be 58 +/- 12 min in liver, 98 +/- 48 min in spleen, 262 +/- 36 min in kidneys, 310 +/- 114 min in lung microcirculatory flow. Several pathways were found of the thromboplastin tissue local disintegration mediated via proteolytic and lipolytic enzymes released from endothelial cells and leucocytes: endocytosis of RES-cells followed by intracellular cleavage by lysosomal enzymes; and gradual blood transfer of thromboplastin particles from the organs with moderate disintegration rate to the organs capable of rapid disintegration.

Animals↗
PubMed1986

Mononuclear phagocyte thromboplastin, bacterial counts and endotoxin levels in experimental endogenous gram-negative sepsis.

The relationship between mononuclear phagocyte thromboplastin activity, microorganisms and levels of endotoxin in peritoneal fluid and splanchnic and systemic circulation was evaluated during experimental endogenous gram-negative peritonitis in the rat. Significant rise in thromboplastin activity of mononuclear phagocytes was demonstrated in all three compartments. This newly synthesized thromboplastin is a trigger for important biologic systems such as the coagulation cascade, and thus may play a major role in the development of disseminated intravascular coagulation so often occurring in gram-negative sepsis. It probably also participates in the formation of fibrous intraabdominal adhesions. Aerobic and anaerobic microorganisms together with endotoxin were detected already 1 1/2 hours after induction of peritonitis, and subsequently were found to increase in parallel fashion. Determination of endotoxin is a rapid and seemingly reliable method for early detection of gram-negative infection and thus may be of clinical value.

Animals↗
PubMed1986

Calibration of BCT/441, the ICSH reference preparation for thromboplastin.

An international collaborative exercise has been undertaken to calibrate a secondary international reference preparation (IRP) of thromboplastin on behalf of the International Committee for Standardization in Haematology (ICSH). This preparation of British Comparative Thromboplastin (BCT/441) is required because supplies of the WHO primary IRP (BCT/253) are necessarily limited. The calibration was performed at seven centres with only a small degree of interlaboratory variation. As a result of this study an ISI value of 1.04 has been assigned to the preparation. Opportunity was also taken to assess the reliability of a simplified calibration based on lyophilised plasmas. The results of the latter appeared reliable. BCT/441 will be available to officially designated National Control Laboratories for calibration of local thromboplastins to promote prothrombin time standardization in oral anticoagulant control.

Freeze Drying↗
PubMed1986

Utility of a modified calibration model for reliable conversion of thromboplastin times to international normalized ratios.

The combined thromboplastin reagent, Normotest, has been calibrated against the secondary international reference preparation for bovine thromboplastin, OBT/79. Three expert laboratories measured up to 62 patients on stabilized oral anticoagulant therapy and up to 20 normals in order to establish an INR-scale for Normotest. It was found that the model recommended by the WHO was less suited for the calibration of this thromboplastin. This is the first study in which three independent laboratories demonstrate a similar bias of the WHO calibration model. A modified model in which a correction factor is introduced was applied to the problem and proved to give a reliable calculation method for INR on Normotest. The mean coefficient of variation of INR calculated between measurements with Normotest and OBT/79 (scatter of data around calibration line) was 4.2-5.0% as compared to 5.1-5.7% for the WHO-method. A conversion scale for percent activities between Normotest and Thrombotest was established showing that the recommended therapeutic range of 5-10% Thrombotest (INR = 4.8-2.8) corresponds to 10-20% Normotest.

Anticoagulants↗
PubMed1985

Tissue thromboplastin generation in circulating mononuclear phagocytes and development of coagulation disorders during E. coli endotoxinaemia in pigs.

Tissue thromboplastin generation in monocytes was studied during various stages of Escherichia coli endotoxinaemia in pigs. The pigs were monitored in halothane anaesthesia and mechanically ventilated. Blood was sampled from the superior caval vein before and during endotoxin infusion and up to 6 hours after its start. Monnuclear leukocytes were harvested with Lymphoprep separation and monocyte counts were made, using TRITC-labelled sheep erythrocytes, acridine orange and a fluorescence microscope. Thromboplastin was quantified in a two-stage assay by incubating the test sample together with purified factor X, factor VII and Ca++. The generated factor Xa was thereafter assayed. There was statistically significant increase of tissue thromboplastin activity in monocytes after endotoxin infusion. Maximum level was reached at the end of the infusion and was maintained throughout the observation period. Decrease occurred in platelets, leukocytes, antithrombin III, fibrinogen and clotting factors V, VII and VIII, and clotting time was prolonged. These findings indicated significant disseminated intravascular coagulation. The endotoxin-stimulated monocytes with their elevated tissue thrombo-plastin activity thus may play an important part in development of the DIC which so often follows septicemia.

Animals↗
PubMed1973

A modified whole blood partial thromboplastin test for the assessment of heparinization.

Current methods of assessment of heparinization are either inconvenient as bedside procedures or lack correlation with the Lee-White whole blood clotting time over the therapeutic range. A new thromboplastin time (CAT time) has been developed to overcome these disadvantages by offering uniform contact activation. The test makes use of a partial thromboplastin activated by celite-adsorbed "contact factor", thus eliminating the activation phase of the activated partial thromboplastin time. Preliminary experiments suggest that this modification will be helpful in the study of "contact factor" deficiencies.

Blood Coagulation Tests↗