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 127 records · Page 7Linked to original sources
PubMed1990

Prothrombin time in the monitoring of oral anticoagulant: a comparison of results using different thromboplastins.

The objective of this report is to compare the prothrombin time performed with thromboplastin of different tissues and species in patients under oral anticoagulant therapy as well as the way of expressing the results. The results showed that the ISI of the thromboplastin of human and rabbit brain are very close to the IRP BCT/253 (1.2 vs 1.1) and RBT/79 (1.3 vs 1.4), respectively. In contrast, the rabbit lung thromboplastin showed the greatest differences in the ISI values (1.6 vs 1.4) and in the CV (6.1%). The authors found significant statistical differences with the results of the prothrombin time as expressed in activity percentage (p less than 0.001) in three plasma pools of patients under different oral anticoagulant level for all thromboplastins studied. However, if the results are expressed in terms of INR, the values obtained are almost the same. The results here reported would demonstrate that the prothrombin time as INR allows the use of only one scheme for oral anticoagulant control when the thromboplastin reagent is calibrated according to the recommendations of the WHO.

Administration, Oral↗
PubMed1989

[Control of anticoagulant therapy by using soluble thromboplastin].

The characteristics of soluble thromboplastin, a new coagulant agent, were under study. This drug is a high-molecular lipoprotein complex of human cadaver brain, purified by gel chromatography. The new preparation has been standardized and compared to thromboplastin preparations manufactured in this country and abroad. Soluble thromboplastin has been found fairly sensitive to reductions of the prothrombin factors levels, it may be used for monitoring the efficacy of indirect anticoagulant therapy, and conforms to WHO regulations for thromboplastin reference agents; this latter fact recommends this new drug as a thromboplastin reference agent in this country.

Anticoagulants↗
PubMed1989

The effect of some instruments for prothrombin time testing on the International Sensitivity Index (ISI) of two rabbit tissue thromboplastin reagents.

Two commercial rabbit tissue thromboplastins were calibrated against the International Reference Preparation for rabbit thromboplastin (coded RBT/79) by one laboratory using the manual technique, a semi-automatic electro-mechanical coagulometer and three different automatic photo-optical instruments. The calibration of the two reagents was performed in three and two different exercises, respectively, and showed good reproducibility of the procedure. The purpose of calibration is providing a formula for the assessment of the International Normalized Ratio (INR) for patients receiving oral anticoagulants. The World Health Organization (WHO) model for thromboplastin calibration leads to the equation INR = RISI, in which R is the prothrombin time ratio and ISI the International Sensitivity Index of the calibrated thromboplastin/instrument system. This equation was adequate for one reagent, but not for the other when it was used in combination with the four instruments. At therapeutic intensities of anticoagulation, the deviation from the WHO-model observed for the second reagent was clinically insignificant. The WHO model was fully adequate when the second reagent was used with the manual technique. For both thromboplastins, there were statistically significant differences in ISI between the four instruments. The largest difference--amounting to approximately 10%--was observed between two photo-optical instruments. The order of instruments with increasing ISI was the same for the two reagents. It is recommended that thromboplastin manufacturers specify the instruments used for calibration of their reagent.

Animals↗
PubMed1989

A Multi-centre study to evaluate method dependency of the international sensitivity index of bovine thromboplastin.

In The Netherlands, a particular coagulometer method for prothrombin time (PT) determination with reduced sample and reagent volumes is used by 62% of the laboratories controlling oral anticoagulant therapy. This "micro-method" has been calibrated against the manual tilt-tube technique for PT determination by six Dutch laboratories. Each laboratory tested 20 fresh normal blood samples and 60 fresh patient blood samples using both methods with the same batch of bovine thromboplastin reagent, according to a detailed protocol. Both methods were comparable as to their precision, but PTs measured by the micro-method were significantly prolonged (p less than 0.001, Student's t-test) as compared to the manual method. This effect is stronger for samples of normal subjects than for patients' samples. It was assumed that the International Sensitivity Index (ISI) of the bovine thromboplastin for the manual method was 1.00 in each laboratory. The ISI-values of the bovine thromboplastin for the micro-method determined by the six laboratories ranged from 1.00 to 1.07 (mean 1.03, SD 0.03). Our results indicate that any other laboratory, using this thromboplastin and the micro-method, should obtain accurate assessment of the International Normalized Ratio from their own mean normal PT and an ISI which is 3% higher than the ISI supplied by the thromboplastin manufacturer for the manual tilt-tube method.

Animals↗
PubMed1989

The effect of lipopolysaccharides (LPS) on generation of thromboxane A2 and thromboplastin activity in whole blood of males, females and females on oral contraceptives.

Heparinized blood sample taken from 81 healthy persons, 40 men and 41 women of whom 17 were on combined oral contraceptives, were incubated with 2 ng lipopolysaccharides (LPS)/ml blood. Quantitation of thromboxane B2 (TxB2) in the resultant plasma revealed a significantly (p less than 0.001) higher generation of TxB2 in men than in women. No sexual differences were observed in thromboplastin activity in unstimulated and LPS stimulated monocytes. Addition of liposomes together with LPS enhanced the synthesis of thromboplastin 2-10 fold and unveiled a higher synthesis of thromboplastin among men. No differences were observed in TxB2 and thromboplastin synthesis in blood collected from females or females using oral contraceptives. A significant correlation between TxB2 and the thromboplastin activity exists within the male (r = 0.46, p = 0.003) and the oral contraceptive (r = 0.57, p = 0.016) group after exposure to LPS. This study suggests that males exposed to LPS may generate more thromboxane A2 than females and thus be at higher risk of developing thrombosis.

Adult↗
PubMedDate not supplied

[Mechanism of heparin inactivation by thromboplastin (factor III)].

Thromboplastin (a commercial one and that obtained from different tissues) is shown to inactivate heparin in proportion to the quantity of thromboplastin or to the heparin:thromboplastin ratio. A degree of inactivation of heparin changes after the modification of protein component of thromboplastin by proteases, however there is no dependence between the protein amount in the preparation and its antiheparin activity. Inactivation of heparin by thromboplastin is stipulated by the formation of associations due to electrostatic interactions between the clusters of amino acid protein residues (which dissociate under physiological conditions as bases) and heparin sulphogroups. It is suggested that factor III circulating in blood flow participates in the creation of hemostatic potential not only as a result of its ability to catalyze thrombinogenesis, but also due to the decrease of the anticoagulant blood activity.

Animals↗
PubMed1983

Intravenous injections of tissue thromboplastin and phospholipase C in rabbits.

Previous experiments (Gollub et al. [10]. Giercksky et al.) have shown that phospholipase C (PLC) has a protective effect on rats and rabbits receiving thromboplastin infusions. As a step towards the possible use of PLC in humans, we have investigated further the use of PLC in rabbits. Infusions of human or rabbit thromboplastin caused a rapid fall in factors V and VIII. LD50 for our standard human thromboplastin preparation was estimated to be 1.5--1.8 ml/kg. Highly purified PLC was given as an intravenous bolus immediately before thromboplastin. No improvement of survival and only a slight difference in factors V and VIII were observed, in contrast to earlier observations in the rat. This may in part be due to differences in the susceptibility to PLC of the thromboplastins used. PLC was also more toxic in rabbits than in rats.

Animals↗
PubMed1983

Platelets stimulate thromboplastin synthesis in human endothelial cells.

Human umbilical vein endothelial cells in culture synthesize thromboplastin upon stimulation with phytohaemagglutinin (PHA) or the tumor promotor 12-O-tetradecanoyl-phorbol-13-acetate (TPA). The thromboplastin activity is further strongly enhanced in a time dependent reaction by the presence of gel-filtered platelets or platelet aggregates. This effect was demonstrable at platelet concentrations lower than those normally found in plasma, it may thus be of pathophysiological relevance. The thromboplastin activity increased with increasing number of platelets added. Cycloheximide inhibited the increase, suggesting that de novo synthesis of the protein component of thromboplastin, apoprotein III, is necessary. When care was taken to remove monocytes no thromboplastin activity and no apoprotein III antigen could be demonstrated in suspensions of gel-filtered platelets, platelets aggregated with thrombin or homogenized platelets when studied with a coagulation assay and an antibody neutralization technique.

Blood Platelets↗
PubMed1982

Interaction of Borrelia spirochetes with human mononuclear leukocytes causes production of leukocytic pyrogen and thromboplastin.

Relapsing fever caused by Borrelia spirochetes is characterized by episodes of spirochetemia, fever, and DIC. We examined the ability of Borrelia hermsii to induce production of leukocytic pyrogen and thromboplastin from human blood leukocytes in vitro. Organisms were found devoid of endotoxin by the Limulus assay. Human peripheral blood leukocytes were separated into MNC and PMN fractions and were incubated with two to five spirochetes per cell in 10% human serum. Supernatant fluids from MNC-spirochete mixtures produced mean increases in the temperature of rabbits of 0.80 degree to 1.35 degrees C, which were significantly higher than those caused by supernatant fluids of MNC or spirochetes alone (p less than 0.05). MNC-spirochete mixtures possessed seven to 15 times the thromboplastic activity of MNC suspensions alone, assayed with a modified one-stage prothrombin time. Supernatant fluids of PMNs and spirochetes, on the other hand, did not contain leukocytic pyrogen, and PMN suspensions did not produce thromboplastin. Cycloheximide (10 micrograms/ml), and inhibitor of protein synthesis, completely suppressed both pyrogen and thromboplastin production. Although intracellular spirochetes were observed within phagosomes of blood monocytes by electron microscopy, the production of leukocytic pyrogen and thromboplastin was not significantly altered by serum opsonins or by the inhibitors of phagocytosis cytochalasin B (5 micrograms/ml) or phenylbutazone (2 mg/ml). These results showed that Borrelia spirochetes stimulated human MNCs to produce increased amounts of leukocytic pyrogen and thromboplastin and that this stimulation required de novo synthesis of protein, was not mediated by endotoxin, and was not prevented by omitting opsonic proteins or by inhibiting phagocytosis.

Borrelia↗
PubMed1978

Thromboplastin calibration. Experience of the Dutch reference laboratory for anticoagulant control.

Standardization of the thromboplastin most commonly used for anticoagulant control in The Netherlands has been achieved by the Dutch Reference Laboratory for Anticoagulant Control. The system established for control indicates the performance characteristics of each batch of thromboplastin in patients relative to a national calibration batch. Calibration constants were assessed according to an ICTH/ICSH proposal and with a reproducibility of approximately 2% (CV). With the use of a given calibration constant of the International Reference Preparation of Thromboplastin (1.0) and after assessment of the calibration constant of the National Reference Preparation in international terms (0.93), the accuracy of calibration with the various modifications of the calibration procedure is of the order of magnitude of 3% (CV). On the basis of the calibration protocol, physicians will be provided with correlation tables containing, for their convenience, prothrombin (thromboplastin) times in terms of the reference thromboplastin (uniform, i.e., batch-independent, prothrombin times), conventional prothrombin activity (percentages), and in due course with International Calibrated Ratios. With this approach current practice in the prescription of oral anticoagulants will be maintained. Opportunity is given, however, to aim at internationally proposed therapeutically optimal target values.

Blood Coagulation Tests↗
PubMed1995

Recombinant thromboplastin inhibition assay for the detection of lupus anticoagulant.

Tissue thromboplastin inhibition assay (TTI) is a sensitive test for lupus anticoagulant (LA). We have performed TTI in 12 LA positive patients using a new recombinant human tissue factor (Innovin, IN) and compared it with Thromborel S (TH), a commonly used human placenta thromboplastin. The effect of using two different dilutions of each thromboplastin (1:10 & 1:26) was investigated. A 1:26 dilution discriminated better than the 1:10 and this was more evident for Innovin. The mean value obtained with a 1:26 IN dilution was statistically different from that observed with TH at the same dilution. Furthermore, when PT and TTI ratios were considered, differences were statistically significant and seemed to increase depending on thromboplastin dilutions. When we used IN at 1:26 all LA positive patients had a value > 1.2. Then we compared TTI at a 1:26 dilution with dilute Russell's Viper Venom Time (dRVVT) in 50 consecutive patients with suspected lupus anticoagulant not treated with warfarin or heparin. In these patients the diagnosis of lupus anticoagulant was carried out using dilute APTT mixing studies and a platelet neutralization procedure: four out of 50 patients thus tested were LA positive. When dRVVT or TTI-I 1:26 were used, five patients were positive for lupus anticoagulant. Innovin showed similar sensitivity of dRVVT for detection of lupus anticoagulant. It is likely that higher dilutions of thromboplastins could further improve the specificity of this method.

Adult↗
PubMed1996

A simplified procedure for thromboplastin calibration--the usefulness of lyophilized plasmas assessed in a collaborative study.

The International Sensitivity Index (ISI) of thromboplastins is determined by calibration using fresh plasmas from 60 patients stabilized on oral anticoagulants and 20 healthy subjects. This procedure is demanding, particularly for those who have no easy access to patients. The alternative use of a smaller number of lyophilized plasmas has already been considered, but one important issue, the number of repeated measurements to be carried out, has never been addressed. Two commercial rabbit thromboplastins, A and B, were calibrated in 3 laboratories against CRM 149R. On each of 10 working days, prothrombin times were measured for a different set of 8 fresh plasmas and for the same set of 8 lyophilized plasmas. The ISI values for both thromboplastins were estimated by orthogonal regression on fresh and lyophilized plasmas. The between- and within-laboratory CV values of the estimated ISI were taken as measures of precision of the calibration. In addition, ISI and CV were calculated daily on cumulative results obtained with lyophilized plasmas from day 1 to day 10. The ISI values for both thromboplastins calculated with lyophilized plasmas were not significantly different from those with fresh plasmas (mean of 3 laboratories: 1.42 vs 1.48 for A and 1.22 vs 1.20 for B). The between-laboratory precision of the calibration with lyophilized plasmas was not considerably different from that with fresh plasmas (CV for 3 labs: 5.2% vs 6.8% for A and 0.9% vs 2.2% for B). The ISI estimated with lyophilized plasmas on results of day 1 were not different from those of days 2 through 10. Good within-laboratory precision of the calibration (CV around 2%) was already achieved on day 3. In conclusion, this study shows that lyophilized plasmas pooled from normals and patients on oral anticoagulants can be used as substitutes for individual fresh plasmas to simplify the existing procedure for thromboplastin calibration.

Anticoagulants↗
PubMed1996

Two recombinant tissue factor reagents compared to conventional thromboplastins for determination of international normalised ratio: a thirty-three-laboratory collaborative study. The Steering Committee of the UK National External Quality Assessment Scheme for Blood Coagulation.

Recent advances in recombinant technology have led to the development of prothrombin time (PT) reagents containing recombinant tissue factor which has been lipidated to allow expression of procoagulant activity. In this study we have compared International Normalised Ratios (INRs) determined using two such reagents and conventional thromboplastins in widespread use in the UK. Lyophilised plasma samples from eight different warfarinised patients were distributed to 33 laboratories in the UK. Each participant determined prothrombin times on 20 local fresh normal plasmas (used to derive mean normal PT and calculate INR) and the eight lyophilised samples, using manual technique and the following thromboplastins; Recombiplastin (Ortho Diagnostics Ltd); Innovin (Baxter Diagnostics Ltd); the conventional thromboplastin in local use. For eight plasmas the mean INRs determined with different reagents were as follows: Innovin (33 laboratories) - 3.4; Manchester Reagent (MR = 8 laboratories) - 3.4; Recombiplastin (33 laboratories) - 3.7; Instrumentation Laboratory (IL = 13 laboratories) - 4.4. Mean INR results with Recombiplastin were on average 7% greater than those obtained with Innovin, 8% greater than results with MR and 18% less than INRs with IL thromboplastin. There was no significant difference between results obtained with Innovin and MR. In contrast INRs obtained with IL were markedly (mean 28%) greater than results obtained with Innovin. This study employed lyophilised plasma and it is possible that some of the relationships described are influenced by this. However, the lyophilisation process employed did not influence the relationship between INRs of warfarinised plasmas obtained by the four main reagents described, indicating that the results are relevant to routine clinical practice. In conclusion, our data show some important differences are present between INRs determined using Recombiplastin, Innovin and two conventional thromboplastins.

Humans↗
PubMed1981

The Australasian Reference Thromboplastin: I. A study in bleeding patients.

The prothrombin time, activated partial thromboplastin time, thrombin time, and skin bleeding time, with assays of factors II, VII, IX, and X, platelet count, and liver function tests were performed on a group of patients receiving long term warfarin therapy. There were 17 bleeding patients and 13 non-bleeding patients. A study was made, using the Australasian Reference Thromboplastin and 2 other thromboplastic reagents in common use. The Australasian Reference Thromboplastin was shown to be more sensitive to the coumarin induced coagulation defect than rabbit brain thromboplastin, and hence of more value in preventing haemorrhagic complications. The level of factor II assayed by the one stage method was a useful independent indicator of the intensity of oral anticoagulation, and correlated well with the development of bleeding.

Bleeding Time↗
PubMed1988

Thromboplastin release, but not content, correlates with spontaneous metastasis of cancer cells.

No previous studies on the possible contribution of cancer-cell procoagulants to metastasis have fulfilled all the criteria for attaining biologically relevant and readily interpretable data (Grimstad et al., 1986), viz: (1) Spontaneous metastasis from primary tumors should be assessed in syngeneic animals; (2) cloned cell lines should be used to correlate cell properties, because heterogeneity within the cell lines employed is a source of serious error; (3) enough clones, derived from the same original tumor, should be used to identify only nonrandom correlations. Observing these criteria, we examined the procoagulant activities of 19 murine fibrosarcoma cell clones and 4 uncloned cell lines with high to moderate or low potential for lung metastases formation. The procoagulant activity found was exclusively of the thromboplastin (tissue factor, factor III) type. It occurred in all cell homogenates, but the quantities did not correlate with metastatic potential. In contrast, all highly to moderately metastatic cell clones and lines from 2 different fibrosarcomas shed thromboplastin activity into the culture medium, whereas no weakly metastatic cells did. Histological examination further supported these indications that release of thromboplastin from cancer cells can promote metastasis by initiating blood clotting and thereby facilitating arrest of the cancer cells in target organ vessels. Examination of a third fibrosarcoma showed that release of thromboplastin activity is not necessary for metastasis in all tumors.

Animals↗
PubMed1984

Effects of inhibitors of arachidonic acid metabolism on thromboplastin activity in human monocytes.

Human isolated monocytes possess low levels of procoagulant activity, which was stimulated 10-30 fold by brief (2 hr) exposure to 10 micrograms/ml endotoxin. This activity was expressed in normal or factor XII-deficient plasma, but lost in plasma deficient in factors X or VII, indicating that it was due to thromboplastin. The stimulation of monocyte thromboplastin by endotoxin was inhibited in a dose-dependent manner by two phospholipase A2 inhibitors, 4-bromophenacyl bromide and quinacrine, and by two lipoxygenase inhibitors, eicosatetraynoic acid and nordihydroguaiaretic acid. Two cyclooxygenase inhibitors, aspirin and indomethacin, prevented endotoxin-induced increases in thromboxane B2 production but had no effect on thromboplastin production. These results suggest that a component in the sequence of lipid deacylation, arachidonic acid release, and metabolism via lipoxygenase may mediate the stimulation of monocyte thromboplastin activity by endotoxin.

Arachidonate Lipoxygenases↗
PubMed1984

Inhibition of the thromboplastin response of endothelial cells in vitro.

Confluent monolayers of human umbilical vein endothelial cells in culture responded with a 5-fold increase in thromboplastin (tissue factor) synthesis when exposed to 12-O-tetradecanoyl-phorbol-13-acetate (TPA) (50 ng/ml) or endotoxin (ETX) (25 micrograms/ml) for 16 hr. This induced thromboplastin synthesis was markedly inhibited by exposure of the cells to two different phosphodiesterase inhibitors, methylisobutylxanthine (MIX) and rac-4(3-butoxy-4-methoxybenzyl)-2-imidazole idinone (RO-20-1724) and to the transmethylation inhibitors 3-deazaadenosine (DZA) and 1-homocysteine thiolactone (Hcy) in combination. It was slightly (TPA) or not at all (ETX) inhibited upon exposure of the cells to the intracellular calcium antagonist 8-(N,N-diethylamino)-octyl 3,4, 5-trimethoxybenzoate hydrochloride (TMB-8). However, in the presence of MIX TMB-8 had a moderate additional inhibitory effect on TPA-induced thromboplastin response. The thromboplastin response of endothelial cells in vitro thus probably depends on transmethylation events for its full expression. It is also strongly modulated by the intracellular level of cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1982

Effect of immune complex-containing sera from patients with rheumatic diseases on thromboplastin activity of monocytes.

Monocytes isolated from peripheral blood of patients with various rheumatic diseases and circulating immune complexes (IC) developed a significantly higher thromboplastin (tissue factor) activity than normal cells when cultured in vitro without inducers, but normal cells responded more strongly with thromboplastin production upon stimulation with IC or phytohaemagglutinin (PHA). Sera from patients with rheumatic diseases and circulating IC induced a significant increase in the thromboplastin activity of normal monocytes. Lysozyme release from patient monocytes was significantly lower than the release from control cells when stimulated with IC. Patient sera contained higher amounts of lysozyme than normal sera, indicating lysozyme release in vivo. These data suggest that activation of monocytes in vivo by IC may take place. The increased expression of thromboplastin in monocytes/tissue macrophages may be important for the development of microvascular thrombosis and fibrin deposition seen in chronic inflammatory lesions.

Adolescent↗