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At least 145 records · Page 8Linked to original sources
PubMed1988

Platelets secrete a coagulation inhibitor functionally and antigenically similar to the lipoprotein associated coagulation inhibitor.

Stimulation with thrombin or the calcium ionophore, A23187 caused human platelets to release a coagulation inhibitor similar to the Lipoprotein Associated Coagulation Inhibitor (LACI). This was documented functionally, with clotting assays measuring tissue factor inhibition and factor Xa inhibition, as well as immunologically, in a competitive immunoassay. The total amount of LACI released by 3 x 10(8) platelets after two hours stimulation was 7% to 8% of the amount found in 1 mL of serum. Half of the LACI was released by five minutes. The LACI was present in the platelet supernatant and was not associated with the platelet membrane or shed vesicles. The tissue factor and factor Xa inhibitory activities that were released were neutralized by preincubating the platelet supernatants with specific rabbit polyclonal anti-LACI IgG. On Western blot, platelet LACI appeared to run as a doublet with a molecular weight (mol wt) 45,000 to 47,000. Blood samples obtained from the site of a wound (template bleeding time) demonstrated a progressive increase in LACI concentration. A cDNA probe, derived from endothelial cell LACI cDNA, hybridized selectively to 4.0 and 1.4 kb transcripts in a preparation of platelet mRNA.

Blood Platelets↗
PubMed1982

Monoclonal antibodies to porcine factor VIII coagulant and their use in the isolation of active coagulant protein.

Partially purified preparations of porcine factor VIII:C were used to immunize mice and spleen cells from the immunized animals were fused to NS-1 mouse myeloma cells. The ability of hybrid culture fluids to bind factor VIII:C was detected with a radiolabelled, affinity-purified, human antihuman VIII:C inhibitor. Three cloned hybrid lines have been obtained that preferentially bind to VIII:C when compared to von Willebrand factor binding. Two of these monoclonal antibodies partially inhibit VIII:C coagulant activity. The third antibody does not inhibit VIII:C, but it can be used as an affinity reagent to absorb dissociated VIII:C out of solution. Active coagulant can be recovered by elution in 50% ethylene glycol. The VIII:C obtained has a specific activity of 6 units/micrograms based on absorbance measurements. When analyzed on SDS gels, the unactivated VIII:C contains 3 bands of apparent molecular weight 166,000, 130,000 and 76,000. Thrombin treatment results in a 40 fold increase in activity and cleavage to products of 76,000, 67,000 an 50,000 and small amounts of lower molecular weight peptides. EDTA inactivation of the factor VIII:C results in the separation of the 166,000 and 130,000 chains from the 76,000 chain, suggesting a Ca++ dependent noncovalent interaction among the chains.

Animals↗
PubMed1997

Fibrinolysis, inhibitors of blood coagulation, and monocyte derived coagulant activity in acute malaria.

Different parameters of fibrinolytic systems like t-PA, PAI, D-dimer, and inhibitors of blood coagulation, i.e., protein C (PC), protein S(PS), and antithrombin III (AT-III), have been studied in cases of acute malaria due to Plasmodium falciparum and plasmodium vivax infection, and these patients were followed up. It was observed that the plasma PAI-1 was very high in cases of P. falciparum malaria infection as compared to normal controls and P. vivax infection. The changes in complicated cases of P. falciparum were remarkable as compared to uncomplicated ones. The PC, PS, and AT-III levels were also low in P. falciparum, particularly so in complicated cases, and were normal in P. vivax infection. The factor VIII R:Ag levels were invariably high in acute malaria. On follow-up of some of these cases the values came back to normal after the antiparasite treatment. The monocyte procoagulant activity was found to be significantly higher in P. falciparum infection as compared to that of P. vivax infection. All these findings therefore contribute towards the production of a hypercoagulable state in P. falciparum infection and partly explain the complications of P. falciparum infection like cerebral malaria.

Antithrombin III↗
PubMed2000

Coagulation inhibitors in sepsis and disseminated intravascular coagulation.

Sepsis is a syndrome that is increasing in frequency and continues to be associated with an unacceptably high mortality. DIC is an important and common sequel of sepsis, is implicated in the development of multiple organ failure, and has been shown repeatedly to connote a poor prognosis. Increasing understanding of the pathogenesis of DIC has suggested several novel therapies designed to correct deficiencies in inhibitors of coagulation. To date, small randomized, controlled studies of antithrombin III concentrates in sepsis and DIC have shown a trend to increased survival, but have not achieved statistical significance. Currently, a large randomized controlled trial of antithrombin III in sepsis is being conducted. Until more data are available, important questions remain as to its proper place in the treatment of sepsis, septic shock, and DIC. Similarly, therapy with protein C and tissue factor-pathway inhibitor has been beneficial in animal models of sepsis and DIC. The results of controlled clinical trials in humans are eagerly awaited.

Animals↗
PubMed1976

Coagulation profile and the ethanol gelation test with special reference to components consumed during coagulation.

In 753 consequtive blood samples (from the same number of patients) routinely examined for coagulation abnormalities, a positive ethanol gelation test was found in 160. In 7 samples with plasma fibrinogen below 150 mg/100 ml and a positive test, other laboratory signs of consumption coagulopathy (low thrombocyte count, low factor V, low antithrombin III, large amounts of FDP in serum and great discrepancies between Normotest and Thrombotest) were regularly observed. Also at normal or high fibrinogen levels, a positive ethanol gelation test was more frequently associated with low thrombocyte counts, low factor V and Normotest/Thrombotest discrepancy than was a negative test. In 46% of the samples with a positive test, fibrinogen was higher than 500 mg/100 ml (versus 4% in those with a negative test). In one-third of these samples, all other parameters gave normal results.

Blood Coagulation Disorders↗
PubMed1978

Alterations in the coagulation and fibrinolysis system in pregnancy, labour and puerperium, with special reference to a possible transitory state of intravascular coagulation during labour.

Various tests of hemostasis were carried out during pregancy, labour and the puerperium in a group of 259 women. Determinations were carried out in the 1st, 2nd and 3rd trimesters, in the period of dilatation, the expulsion period, the period of expulsion of the placenta and the immediate postpartum period of labour and on each of the first 5 days of the puerperium. It was confirmed that during pregnancy there is an elevation of the fibrinogen degradation products (FDP) levels with a proportional increase in the numbers of positive protamine sulfate and ethanol tests. The proportion of positive protamine sulfate and ethanol tests reaches a maximum in the expulsion of the placenta coinciding with the presence of soluble complexes heavier than fibrinogen as detected by polyacrylamide gel electrophoresis and by column chromatography. All this indicates that there is a transitory intravascular coagulation produced during labour reaching its maximum at the time of birth and tending to become normalized in the first few days of the puerperium.

Blood Coagulation↗
PubMed1982

Factor IX thrombogenicity: in vivo effects on coagulation activation and a case report of disseminated intravascular coagulation.

An episode of defibrination with bleeding following high dose Edinburgh Factor IX (D.E.F.IX) replacement in a patient with haemophilia B undergoing knee joint replacement is reported. We have also monitored plasma fibrinopeptide A levels in patients with haemophilia B following ten standard doses of D.E.F.IX (15-20 u/kg) and have been unable to document any change. Activation of the coagulation system, as previously noted, appears to be related to the use of Factor IX concentrates in high doses.

Adult↗
PubMed1981

[Effect of long-term plasmapheresis on blood composition. II. Changes in the concentration of coagulation factors, inhibitors, thrombocytes and its effect on routine tests of coagulation].

The influence of serial, double plasmapheresis on blood coagulation was evaluated in two groups of plasma donors submitted from three up to 306 plasmapheretic sessions. An average of 375 or 660 ml of plasma respectively were weekly harvested from the donors. No statistically significant changes were observed in platelet count, activity of factor V and factor VIII, fibrinogen, plasminogen, alpha-2-macroglobulin, antithrombin III and prothrombin time, irrespectively of the frequency and the number of plasmapheresis. The concentration of alpha-1-antitrypsin was already increased after 7 plasmapheresis in both groups of donors. KCCT was progressively shortened with the increasing volume of harvested plasma (p 0.05) and thrombin time was prolonged (p 0.05).

Blood Coagulation Factors↗
PubMed1980

[Asphyxial shock and disseminated intravascular coagulation (DIC) in animal experiments. 2. Morphometric tests and blood coagulation studies (author's transl)].

First intravascular coagula were detected as early as in the pre-acidotic phase of artificially hypoxic rabbit foetuses used by the authors in experimental studies. Growing acidosis in circulating blood has been accompanied by excessive increase of fibrin precipitation in the terminal blood track. Further increase of intravascular coagulation was found to be discontinued by predominance of secondary fibrinolysis at blood pH around 6.9. Rising hydrogen ion concentration, as a reflection of a consumptional reaction, was found to be accompanied by decline in both the fibrinogen level and thrombocyte count in the foetal blood, fully in parallel with the above DIC.

Animals↗
PubMed1980

Monitoring of blood coagulation in open heart surgery. II. Use of individualized dosages of heparin and protamine controlled by activated coagulation times.

Results are presented of individualized anticoagulatory management during open heart surgery in two groups of 20 patients comparing colloid versus non-colloid priming of the extracorporeal circuit. Advantages of individualized dosages of heparin according to a constructed dose response curve and controlled by measuring Activated Coagulation Times (ACT) were safer adaptation to individual variability in heparin sensitivity, reduction of incremental heparin doses during cardiopulmonary by-pass and nearly 50% reduction of protamine dosage as compared to conventional heparinprotamin protocols. No significant influence of the type of priming used in the extracorporeal circuit on coagulatory behaviour could be detected.

Adult↗
PubMed1998

Contact activation of blood coagulation: trigger properties and hysteresis. Kinetic recognition of foreign surfaces upon contact activation of blood coagulation: a hypothesis.

A mathematical model of contact activation of blood coagulation was developed and analysed. The model variables are concentrations of factor XIIa, kallikrein and activated high-molecular-weight kininogen. Concentrations of active factors were shown to depend on the activating signal value in a hysteretic manner. Within a range of relatively small signals, two (activated and non-activated) stable states coexist (bistability). Signals of the natural environment (surfaces of endothelial and blood cells) seem to be in the range of bistability; therefore, contact activation that persists for a short time can induce a transition of the system to the activated state, and, correspondingly, the formation of a clot. The system cannot return to the initial state, which is characterized by low activation levels, until the activating signals decrease significantly below those present in the circulation.

Blood Coagulation↗
PubMed1991

Effect of lipoprotein-associated coagulation inhibitor (LACI) on thromboplastin-induced coagulation of normal and hemophiliac plasmas.

Lipoprotein-associated coagulation inhibitor (LACI) is a plasma-derived protein that inhibits the tissue factor/factor VIIa/calcium/phospholipid complex in a factor Xa-dependent manner. Recombinant LACI (rLACI) added exogenously to plasma prolonged the activated partial thromboplastin time (APTT) and prothrombin time (PT) as a function of rLACI concentration in linear and curvilinear manners, respectively. Under these standard assay conditions, the amounts of rLACI required to double the APTT and PT were approximately 350- and 90-fold the plasma concentration of LACI, respectively. Likewise, addition of antibodies against LACI to pooled normal, factor VIII-deficient, or factor IX-deficient plasma had no effect on their respective APTTs and PTs, demonstrating the insensitivity of these assays to endogenous LACI. The prothrombin time assay was modified by using dilute thromboplastin. Unlike the standard prothrombin time assay, the clotting times were prolonged for factors VIII- or IX-deficient plasma relative to pooled normal plasma in this modified PT assay. Additionally, the degree of factor deficiency, as determined by the APTT assay, was correlated with that determined by the modified PT assay using dilute thromboplastin. When antibodies against LACI were added to pooled normal, factor VIII-deficient, or factor IX-deficient plasma and the prothrombin time assay initiated using dilute thromboplastin, the clotting times for antibody-treated plasma were shorter than for the corresponding plasma in the absence of antibodies. Moreover, the clotting times for factors VIII- and IX-deficient plasmas treated with antibodies raised against LACI were at least as fast as pooled normal plasma in the absence of LACI antibodies when dilute thromboplastin was used to initiate clotting. These results suggest that the prothrombin time assay using dilute thromboplastin may more accurately reflect what occurs in vivo and that LACI may play an important role in the prolonged bleeding of those with hemophilia A or B.

Antibodies, Monoclonal↗
PubMedDate not supplied

Coagulation protein function. IV. Effect of acetaldehyde upon factor X and factor Xa, the proteins at the gateway to the common coagulation pathway.

Acetaldehyde (AcH) (447 mM) exerts an inhibition on Factor Xa, as followed by a clotting assay, but does not inhibit the hydrolysis of the synthetic fluorogenic substrate, N-tBOC-Ile-Glu-Gly-Arg-7-amido-4-methylcoumarin. These data suggest that AcH, although not reacting at the catalytic site of Factor Xa nor at the binding site for the synthetic substrate, does interact with the functional groups on the enzyme that bind to its natural substrate, prothrombin. As a consequence of such interaction, the charge and conformation of Factor Xa is altered, thereby limiting effective activation of prothrombin. Additionally, alkylation of factor Xa may also affect its capacity to associate with Factor Va for the activation of prothrombin. AcH also reacts with Factor X, prolonging clotting times when the zymogen is activated with Russell's viper venom (RVV). It also reduces the rate of hydrolysis of the fluorogenic substrate after activation of the alkylated zymogen by RVV. These data lead to the considerations that AcH-modified Factor X is no longer as effectively activated by RVV due to an alteration of its charge/conformation. Additional possibilities include a likely alkylation of the Factor Xa moiety of Factor X by AcH such that the activation product has an altered charge/conformation compared to native Factor Xa, including possible alkylation of its binding site(s) for prothrombin. The reduced rate of hydrolysis of the synthetic fluorogenic substrate for Factor Xa by the alkylated, activated Factor X lends further support to the generation of a modified Factor Xa by RVV, which may have a lower binding or catalytic rate for the fluorogenic substrate. These results support the suggestion that chronic consumption of alcohol may prolong the reported coagulation times as a result of reaction of alcohol's primary metabolite, AcH, with clotting factors, thereby reducing their physiological potential.

Acetaldehyde↗
PubMed1999

Determination of coagulation factor VIII activity by a chromogenic substrate method on STA, an automated coagulation analyzer.

This study was aimed at evaluating the performance of a chromogenic factor VIII assay on STA, an automated coagulation analyzer. Additionally, a correlation study was conducted with an aPTT-based one-stage factor VIII clotting assay. Throughout the study the performance of the chromogenic assay was tested in two ranges of factor VIII activity: a high range with activity between 20% and 150% and a low range with activity below 20%. Inter-assay coefficient of variation ranged from 1.9% to 8.9% and intra-assay coefficient of variation from 0.5% to 11.4%, depending on factor VIII concentration. Day-to-day reproducibility was tested over a 5-day period; between-day imprecision ranged from 7.1% to 9.4%. The chromogenic factor VIII assay showed a good correlation with the clotting assay in both ranges. The correlation coefficients were 0.924 and 0.792 for the high and low range, respectively. A statistically significant difference in mean values was observed in the high range (p < 0.0001). Comparison between the chromogenic assay on STA versus on microplates showed a high correlation (0.991), which was highly significant (p < 0.0001). In conclusion, the chromogenic assay for factor VIII on STA shows good analytical performance. It correlates well with the one-stage factor VIII clotting assay, although significant differences between individual samples occur. Probably these are partly related to differences in measurement principle and standardization. Altogether, this precise and rapid assay is suitable for determination of factor VIII by an automated procedure.

Automation↗
PubMedDate not supplied

Determination of normal values using an automated coagulation timer for activated coagulation time and its application in dogs with hemophilia.

The present study was performed to determine normal values for the Medtronic HemoTec automated activated coagulation time (ACT) analyzer (Medtronic HemoTec Inc, Parker, CO, distributed in Switzerland by Convergenza AG, Vaduz, Liechtenstein), and to evaluate its ability to detect dogs with hemophilia. ACT was measured in 43 healthy dogs presented to the Companion Animal Hospital, University of Bern, Bern, Switzerland, with the Medtronic HemoTec ACT analyzer to determine normal values. The mean +/- 2 standard deviations (SDs) of the values obtained was defined as the normal range. ACT was measured 8-10 times on the same day in 6 dogs to determine repeatability. ACT also was measured in 11 dogs with hemophilia and compared with a conventional visual ACT measurement test and with the activated partial thromboplastin time (APTT). ACT values of the 43 dogs used to determine normal values ranged from 66.5 to 97.0 seconds (mean, 79.3 seconds; SD, 7.35 seconds; median, 78.5 seconds). A range of 64-95 seconds (mean +/- 2 SDs) was defined as the normal range for the tested device. Repeatability was poor (r = 0.256). ACT values measured with the automated device did not correlate with ACT values measured with a conventional visual test or with APTT Sensitivity of the test was 90.9%, specificity was 98.0%, and accuracy was 96.7%. Variability in the test results was large and may lead to incorrect results. The automated measurement device was not superior to the conventional visual method in evaluating dogs with hemophilia.

Animals↗
PubMed2006

A potent anti-coagulant RNA aptamer inhibits blood coagulation by specifically blocking the extrinsic clotting pathway.

A potent antidote-controlled aptamer, as an anticoagulant, has reportedly overcome the complications of acute bleeding by the administration of available anticoagulants. In the present study, we provide evidence that the aptamer binds specifically to factors IX and IXa and inhibits their functions. Furthermore, we demonstrated that the aptamer inhibits blood coagulation by interfering with the extrinsic pathway, blocking the complex of factor VIIa and tissue factor interactions with factor IX. The results from the previous and present studies suggest that the aptamer probably binds in the vicinity of the EGF1 and EGF2 domains of factor IX.

Anticoagulants↗