Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “THROMBOPLASTIN”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1980

The British Comparative Thromboplastin: the relationship between lipid class composition and procoagulant activity.

Twenty-eight consecutive batches of the reference reagent British Comparative Thromboplastin (BCT) were produced in the National (UK) Reference Laboratory for Anticoagulant Reagents and Control (NRLARC) between 1969 and 1977. The relationship between procoagulant activity and lipid class composition in these batches at various stages of age deterioration on storage has been studied by a modification of the method of high pressure chromatography which allows better definition of the individual lipids. The free fatty acid concentration rose markedly while cconcentrations of phosphatidyl choline, phosphatidyl ethanolamine and phosphatidyl serine were reduced. An oxidative process is suggested and supported by the increase in malonaldehyde levels. The method of production of the BCT involves maceration of human brain which causes the breakdown of cell membranes and the release of many potentially oxidative materials from subcellular particles. The loss of procoagulant activity of BCT on storage may be due to the loss of phospholipid or to the increase of inhibitory degradation products, i.e. free fatty acid and malonaldehyde. The examination of the lipid class composition of tissue thromboplastin extracts appears useful, therefore, not only in determining the phospholipids necessary for procoagulant activity, but also in monitoring the deterioration of tissue thromboplastins on storage.

Humans↗
PubMed1985

Reduced thromboplastin activity in blood monocytes and reduced sensitivity to stimuli in vitro of blood monocytes from pregnant women.

The thromboplastin activity in blood monocytes from 18 normal third trimester pregnant women has been compared with a group of 20 healthy non-pregnant women. The thromboplastin activity in unstimulated monocytes from the normal pregnant group was on average 40% of the activity in the non-pregnant group (P less than 0.01). In endotoxin stimulated monocytes, the thromboplastin activity was also significantly lower in the pregnant group as compared to the non-pregnant group (P less than 0.001). Fibrinogen and factors V, VII and VIII were significantly higher in the pregnant than in the non-pregnant group, whereas no difference was observed in AT-III, prekallikrein and alpha 2-antiplasmin levels.

Adolescent↗
PubMed1988

Long-term stability of international reference preparations for thromboplastins.

Three certified reference materials for thromboplastins are available from the Community Bureau of Reference (BCR) of the European Commission for calibration of commercial thromboplastins used for control of oral anticoagulant therapy. The long-term stability of these reference materials has been monitored by two independent laboratories, using deep-frozen and lyophilized plasma samples. Prothrombin times and prothrombin time ratios measured on 19 occasions in the period 1981-86 have been analysed for trend with time. Although significant trends of prothrombin time and ratio (P less than 0.05) were observed, a consistent pattern of trends could not be recognized. The significant trends of prothrombin time and prothrombin time ratio are most probably due to changes in local laboratory conditions. There is no indication that the reference materials have deteriorated since the beginning of the study. It is recommended that long-term stability monitoring of thromboplastins be performed by at least two laboratories simultaneously.

Drug Stability↗
PubMed1988

Thromboplastin--sensitivity, precision and other characteristics.

A more sensitive or higher concentration of rabbit brain thromboplastin does not result in greater accuracy and precision of results in oral anticoagulant therapy and is unable to mimic the PIVKA sensitivity of human brain. In terms of International Normalized Ratios the British Comparative Thromboplastin and Manchester Comparative Reagent (both now discontinued) and the Manchester Reagent had the poorest sensitivity to factor VII of all the reagents studied. It is not possible accurately to calibrate rabbit brain against human brain thromboplastin in the upper therapeutic range and beyond.

Animals↗
PubMed1995

A comparison of five commercial thromboplastins: ISI re-evaluation on an automated coagulometer.

Five commercial rabbit brain thromboplastins were compared with an International Reference Preparation on an ACL coagulometer, using 90 patients stabilized on warfarin and 22 normal individuals. The prothrombin times were converted to INRs using the thromboplastin manufacturers' quoted ISI. The quoted ISIs were reassigned using orthogonal regression analysis and then used to recalculate INRs for patient and commercial INR control plasmas. This showed that the manufacturers' quoted ISIs and the INR control plasma results were inconsistent. With one thromboplastin the manufacturers quoted ISI changed from 1.17 to 1.05 whilst the control plasma results changed from an INR of 4.3 to an INR of 3.7 (manufacturer's INR, 3.3). In most routine laboratories ISI reassignment is not practical. We conclude that the availability of a reliable plasma calibrant is essential for the accurate calculation of INRs at a local level.

Animals↗
PubMed2006

International collaborative study for the calibration of a proposed international standard for thromboplastin, rabbit, plain.

BACKGROUND: A preparation of rabbit brain thromboplastin, provisionally coded 04/162, is proposed as a candidate for the World Health Organization (WHO) International Standard (IS) for thromboplastin (rabbit, plain), meant to replace the IS coded RBT/90 (rabbit, plain), stocks of which are now exhausted. RESULTS: The preparation was calibrated in an international collaborative study involving 21 laboratories from 13 countries and the calibration was performed against the existing WHO-IS (i.e. rTF/95 and OBT/79) and other Certified Reference Materials from the Institute for Reference Materials and Measurements of the European Commission (i.e. CRM149 S) and from the European Action on Anticoagulation (i.e. EUTHR-01). An additional candidate rabbit brain thromboplastin coded as 04/106 was also included in the study. On the basis of predefined criteria (the within- and between-laboratory precision of the calibration and the conformity to the calibration model), 04/162 was the preferred candidate. CONCLUSIONS: The assigned International Sensitivity Index value was 1.15 and the inter-laboratory SD and coefficient of variation were 0.057% and 4.9%, respectively.

Animals↗
PubMed1976

Protection of rats by phospholipase C from Bacillus cereus against the effects of intravenous infusions of purified tissue thromboplastin.

Infusions of purified tissue thromboplastin in rats cause the accumulation of fibrin and platelets in the lungs and produce marked changes in the platelet count and in the coagulation factors V, VII and VIII. Tissue thromboplastin in a dose corresponding to less than 2 mug of protein per rat is lethal when given as a bolus injection. Simultaneous i.v. administration purified phospholipase C effectively prevents all these changes and protects rats from otherwise lethal doses of tissue thromboplastin. The necessary doses of phospholipase C are well below the toxic level for phospholipase C alone.

Animals↗
PubMed1967

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.

Blood Coagulation Tests↗
PubMed1972

The partial thromboplastin (cephalin) time test.

Nine partial thromboplastin (cephalin) reagents have been compared in a parallel investigation of groups of patients on ;long-term' anticoagulants, a group with moderate haemophilia, and patients on heparin infusion. Results with the seven commercial reagents and a human cephalin extract have been correlated with those of a specially prepared and standardized reference preparation of human brain origin. The comparison was similar in principle to that of the prothrombin time thromboplastin standardization using the British Comparative Thromboplastin (BCT). Results, which for comparative purposes were expressed as ratio of patients' cephalin times to control cephalin times, varied greatly in all three groups. In the oral anticoagulant group some of the commercial reagents were particularly insensitive to the ;intrinsic' clotting defect. The correlation between the ;standardized preparation' and the other reagents was not good and the use of a reference cephalin material for quality control of cephalin time tests does not appear promising. In moderate haemophilia the commercial reagents were either relatively poor at picking out the clotting defect compared with the ;standardized preparation' or gave such a bad endpoint that the results were not dependable. The poor endpoint also limited the dependability of the results of all but the ;standardized preparation' and two of the commercial reagents in controlling heparin administration. In view of these standardization difficulties, which cannot apparently be resolved by the use of reference material, there is need for bulk, routine supplies of a sensitive, standardized cephalin reagent giving good reproducible endpoints. The method for the provision of such material in a recently introduced national supply scheme is described.

Blood Coagulation Tests↗
PubMed1995

Effect of thromboplastin and coagulometer interaction on the precision of the International Normalised Ratio.

AIMS: To examine the magnitude of thromboplastin and coagulometer interactions on the precision of International Normalised Ratio (INR) values when the manufacturers' recommended instrument specific International Sensitivity Index (ISI) values are adopted for the INR calculation. METHODS: The variability of INR values obtained from four automated phototopical coagulometers frequently used in North American laboratories was studied. When used with five commercial thromboplastins of moderate to high sensitivity (ISI values 0.92-1.97), 20 prothrombin time results were generated for each of a population of 98 patients on established warfarin treatment. RESULTS: The mean INR values of the patients ranged from 2.05 to 2.81, depending on which reagent/coagulometer combination was used. Within patient variation increased as the median INR value increased. The mean coefficient of variation of within patient INR values was 10%; the mean coefficient of variation of the prothrombin time results in seconds and prothrombin time ratio were 21 and 18%, respectively. CONCLUSIONS: There was considerable bias in the estimated ISI values of the thromboplastins compared with the manufacturers' instrument specific ISI value. Despite this apparent imperfection, our study clearly showed that the INR is preferable to other prothrombin time reporting formats for assessing the degree of anticoagulation for patients on warfarin treatment.

Adult↗
PubMed1984

Intracellular signal mechanisms in induction of thromboplastin synthesis.

Thromboplastin production in human monocytes gains steadily increasing significance as a pathogenetic factor in relation to human disease. A vast variety of stimuli can cause the induction of thromboplastin synthesis in monocytes, apparently through plasma membrane perturbation. Some of the possible signal compounds conveying information from the membrane to the intracellular-responding apparatus have been studied. Available data allow the conclusion that changes in intracellular concentrations of Ca2+, cyclic nucleotides and arachidonic acid metabolites as well as transmethylation reactions are of importance and modulate the integrated response which leads to increased synthesis and insertion of apoprotein III (the protein component of thromboplastin) in the plasma membrane.

Arachidonic Acid↗
PubMed1984

Clinical significance of increased thromboplastin activity on the monocyte surface--a brief review.

The importance of the blood coagulation sequence as an integral part in the pathogenesis of diseases inside as well as outside the blood vessels is becoming increasingly apparent. Mononuclear phagocytes have important functions in initiation of coagulation by producing several procoagulant substances, including thromboplastin, the potent trigger of the extrinsic pathway. Increasing evidence demonstrates the clinical importance of monocyte and macrophage thromboplastin synthesis in the pathogenesis of a variety of diseases. This review surveys the role of monocyte/macrophage thromboplastin in relation to inflammatory diseases, cancer, disseminated intravascular coagulation and diseases of the blood vessels, thrombosis and atherosclerosis.

Arteriosclerosis↗
PubMed1986

Thromboplastin activity in blood monocytes from oral contraceptive users.

The thromboplastin activity in blood monocytes from 13 women on oral contraceptives and from a reference group of 20 women not on oral contraceptives has been compared. The thromboplastin activity in endotoxin-stimulated monocytes from the oral contraceptive (OC) users was on average 54% of the activity in the reference group (p less than 0.05). The thromboplastin activity in unstimulated monocytes was also lower in the OC group than in the reference group although not statistically significant. Factor VII was significantly higher (p less than 0.05) in the OC group, whereas no difference was observed in fibrinogen and factor V levels.

Adult↗
PubMed1983

Characteristics of phospholipids associated with fibrins in partial thromboplastin test.

With the aim to obtain information on the role of individual phospholipids in the coagulation process, lipids associated with fibrins formed with partial thromboplastin reagents were examined. In the absence of the partial thromboplastin reagents, phosphatidylethanolamine and phosphatidylserine plus phosphatidylinositol in citrated plasma were incorporated preferentially into fibrin, although the main phospholipid associated with the fibrin was phosphatidylcholine. In the presence of the partial thromboplastin reagents, most phospholipids unseparable from the corresponding fibrins appeared to be derived from the reagents with little selectivity for individual phospholipids, except for lysophosphatidylcholine. These results suggest that phospholipids other than thromboplastic phospholipids may play some role in the coagulation process. The incorporation of lysophosphatidylcholine in the reagent into fibrins was significantly enhanced by the addition of activating agents (celite and ellagic acid), suggesting one role of the activating agents in fibrin formation.

Blood Coagulation↗
PubMed1987

A spectrophotometric method for the standardization of thromboplastin clot-promoting activity.

A simple spectrophotometric method for the quantitating of the clot promoting activity of thromboplastin in commercial preparations was developed. Thromboplastin activities were proportional to the maximum rate of clot formation. This was calculated from curves of absorption change during the coagulation of plasma coagulation control. The clot-promoting effects of thromboplastin in commercial preparations varied widely when assayed by this method.

Animals↗
PubMed1981

The Australasian Reference Thromboplastin: II. Are corrected prothrombin ratios valid?

A comparative study was made of 2 thromboplastins, the Australasian Reference Thromboplastin, and Simplastin, in a large group of patients on long-term Warfarin therapy. 373 individual samples were obtained. Calibration constants were obtained for those patients with prothrombin ratios within the therapeutic range, and for those well outside the therapeutic range, and found to be different. Study of the relationship between the 2 thromboplastins indicates that comparability is linear only within a specified limited range of prothrombin ratios. At the two extreme ends the relationship is curved, suggesting a logarithmic relationship. Attention is drawn to the need of caution in interpretation of corrected ratios calculated on a linear relationship especially when the ratio is above 4.0 as this may have clinical implications.

Coumarins↗
PubMed1987

Mononuclear phagocyte thromboplastin and endotoxin in patients with secondary bacterial peritonitis.

Endotoxin levels and mononuclear phagocyte thromboplastin activities in samples from peripheral blood and peritoneal fluid were determined in nine patients with secondary bacterial peritonitis (appendicitis with perforation, or diverticulitis) and in five control patients (uncomplicated duodenal ulcer or gallbladder stones). None or only negligible amounts of endotoxin, always less than 0.01 ng/dl (contamination), and no growth of bacteria were detected in controls. In the patients with peritonitis, peritoneal fluid samples always contained gram-negative bacteria, and large amounts (mean, 31.6 ng/dl) of endotoxin were seen. Plasma from these patients also contained endotoxin (mean, 0.56 ng/dl) despite negative blood cultures. Mononuclear phagocytes from controls had low thromboplastin values, whereas both circulating monocytes and peritoneal macrophages from peritonitis patients showed a substantial increase (multifold) of thromboplastin.

Adolescent↗
PubMed1998

Thromboplastin standardisation: calibrated lyophilised plasmas and coagulometer-specific international sensitivity indices.

The introduction of international reference preparations (IRP) of thromboplastins was an important step forward in the standardisation of laboratory monitoring of coumarin therapy for the treatment and prevention of thrombosis. In more recent years, the standard manual technique for prothrombin time (PT), which was used to monitor coumarin therapy, has been replaced gradually by a variety of different automated techniques in the laboratory. The international sensitivity index (ISI), assigned to a working thromboplastin by comparison to the IRP, is invalidated by the use of automated techniques, and is not necessarily consistent among analysers of the same type. Consequently, current recommendations are that individual laboratories should standardise their own thromboplastin with their routine method, using calibrated lyophilised plasmas which have international normalised ratios (INR) assigned to them.

Anticoagulants↗