Familial overexpression of beta antithrombin caused by an Asn135Thr substitution. (1/74)

We have investigated the basis of antithrombin deficiency in an asymptomatic individual (and family) with borderline levels (approximately 70% antigen and activity) of antithrombin. Direct sequencing of amplified DNA showed a mutation in codon 135, AAC to ACC, predicting a heterozygous Asn135Thr substitution. This substitution alters the predicted consensus sequence for glycosylation, Asn-X-Ser, adjacent to the heparin interaction site of antithrombin. The antithrombin isolated from plasma of the proband by heparin-Sepharose chromatography contained amounts of beta antithrombin (the very high affinity fraction) greatly increased (approximately 20% to 30% of total) above the trace levels found in normals. Expression of the residue 135 variant in both a cell-free system and COS-7 cells confirmed altered glycosylation arising as a consequence of the mutation. Wild-type and variant protein were translated and exported from COS-7 cells with apparently equal efficiency, in contrast to the reduced level of variant observed in plasma of the affected individual. This case represents a novel cause of antithrombin deficiency, removal of glycosylation concensus sequence, and highlights the potentially important role of beta antithrombin in regulating coagulation.  (+info)

Plasma antithrombin III deficiency in ischaemic stroke in the young. (2/74)

A deficiency of plasma antithrombin III has been identified as a potential risk factor for thrombosis. In a pilot study of 56 patients aged less than 40 years who presented with ischaemic stroke of unknown etiology, we detected only one case of plasma antithrombin III deficiency. Antithrombin III activity was estimated by a chromogenic assay. Hence, antithrombin III deficiency, though rare, should be considered while evaluating young patients with stroke of unknown etiology.  (+info)

Enhancement of heparin cofactor II anticoagulant activity. (3/74)

Heparin cofactor II (HCII) is a serpin whose thrombin inhibition activity is accelerated by glycosaminoglycans. We describe the novel properties of a carboxyl-terminal histidine-tagged recombinant HCII (rHCII-CHis(6)). Thrombin inhibition by rHCII-CHis(6) was increased >2-fold at approximately 5 microgram/ml heparin compared with wild-type recombinant HCII (wt-rHCII) at 50-100 microgram/ml heparin. Enhanced activity of rHCII-CHis(6) was reversed by treatment with carboxypeptidase A. We assessed the role of the HCII acidic domain by constructing amino-terminal deletion mutants (Delta1-52, Delta1-68, and Delta1-75) in wt-rHCII and rHCII-CHis(6). Without glycosaminoglycan, unlike wt-rHCII deletion mutants, the rHCII-CHis(6) deletion mutants were less active compared with full-length rHCII-CHis(6). With glycosaminoglycans, Delta1-68 and Delta1-75 rHCIIs were all less active. We assessed the character of the tag by comparing rHCII-CHis(6), rHCII-CAla(6), and rHCII-CLys(6) to wt-rHCII. Only rHCII-CHis(6) had increased activity with heparin, whereas all three mutants have increased heparin binding. We generated a carboxyl-terminal histidine-tagged recombinant antithrombin III to study the tag on another serpin. Interestingly, this mutant antithrombin III had reduced heparin cofactor activity compared with wild-type protein. In a plasma-based assay, the glycosaminoglycan-dependent inhibition of thrombin by rHCII-CHis(6) was significantly greater compared with wt-rHCII. Thus, HCII variants with increased function, such as rHCII-CHis(6), may offer novel reagents for clinical application.  (+info)

The prevalence of hereditary thrombophilia in the Trakya region of Turkey. (4/74)

The prevalences of deficiencies in antithrombin III (AT III), protein C (PC), protein S (PS) and in the activated protein C (APC) resistance in the thrombotic population of the Trakya region, Turkey were investigated. 37 patients with venous thrombosis (VT) and 17 patients with arterial thrombosis (ArT) were included in this study. The mean ages of the patients with VT and ArT were 46 years (range 20-70) and 38 years (range 32-40), respectively. The activity of AT III was measured by commercially available immuno-turbidimetric assay. The activities of PC and PS were determined by coagulometric assay. The APC resistance was measured using a modified APTT-based clotting assay. Among the VT patients, there were 2 cases (5.4%) with AT III, 5 (13.51%) with PC deficiency, 5 (13.51%) with PS deficiency and 2 (5.4%) with APC resistance. In the ArT patient group, there was 1 patient (5.88%) with AT III, 3 (17.64%) with PC deficiency, 1 (5.88%) with PS deficiency and no APC resistant patients, while there was one (2.08%) with PC deficiency and one (2.08%) with APC resistance in the control group (49 persons, mean age 41 years). The relative risk of thrombosis (odds ratio) was 1.7 in the deficiency of PC and 5.6 in the deficiency of PS. The data presented suggests that the prevalences of AT III, PC and PS deficiencies causing thrombophilia in the Trakya region of Turkey are higher than in other reported studies while the APC resistance is lower than in others. Further studies including more patients would be required to clarify these discrepancies.  (+info)

Complete antithrombin deficiency in mice results in embryonic lethality. (5/74)

Antithrombin is a plasma protease inhibitor that inhibits thrombin and contributes to the maintenance of blood fluidity. Using targeted gene disruption, we investigated the role of antithrombin in embryogenesis. Mating mice heterozygous for antithrombin gene (ATIII) disruption, ATIII(+/-), yielded the expected Mendelian distribution of genotypes until 14.5 gestational days (gd). However, approximately 70% of the ATIII(-/-) embryos at 15.5 gd and 100% at 16.5 gd had died and showed extensive subcutaneous hemorrhage. Histological examination of those embryos revealed extensive fibrin(ogen) deposition in the myocardium and liver, but not in the brain or lung. Furthermore, no apparent fibrin(ogen) deposition was detected in the extensive hemorrhagic region, suggesting that fibrinogen might be decreased due to consumptive coagulopathy and/or liver dysfunction. These findings suggest that antithrombin is essential for embryonic survival and that it plays an important role in regulation of blood coagulation in the myocardium and liver.  (+info)

Inherited thrombophilia in ischemic stroke and its pathogenic subtypes. (6/74)

BACKGROUND AND PURPOSE: One or more of the inherited thrombophilias may be causal risk factor for a proportion of ischemic strokes, but few studies have addressed this association or the association between thrombophilia and pathogenic subtypes of stroke. METHODS: We conducted a case-control study of 219 hospital cases with a first-ever ischemic stroke and 205 randomly selected community control subjects stratified by age, sex, and postal code. With the use of established criteria, cases of stroke were classified by pathogenic subtype in a blinded fashion. The prevalence of conventional vascular risk factors; fasting plasma levels of protein C, protein S, antithrombin III; and genetic tests for the factor V Leiden and the prothrombin 20210A mutation were determined in cases and control subjects. RESULTS: The prevalence of any thrombophilia was 14.7% (95% CI, 9.9% to 19.5%) among cases and 11.7% (95% CI, 7.4% to 17.0%) among control subjects (OR, 1.3; 95% CI, 0.7% to 2.3%). The prevalence of individual thrombophilias among cases ranged from 0.9% (95% CI, 0.1% to 3.4%) for protein S deficiency to 5.2% (95% CI, 0.3% to 9.1%) for antithrombin III deficiency; among control subjects, the prevalence ranged from 1.0% (95% CI, 0.1% to 3.6%) for protein S deficiency to 4.1% (95% CI, 0.2% to 7.8%) for antithrombin III deficiency. There were no significant differences in the prevalence of thrombophilia between cases and control subjects or between pathogenic subtypes of ischemic stroke. CONCLUSIONS: One in 7 patients with first-ever acute ischemic stroke will test positive for one of the inherited thrombophilias, but the relation is likely to be coincidental rather than causal in almost all cases, irrespective of the pathogenic subtype of the ischemic stroke. These results suggest that routine testing for thrombophilia in most patients with acute ischemic stroke may be unnecessary. Whether the thrombophilias may still be important in younger patients with ischemic stroke or in predicting complications (eg, venous thrombosis) and stroke outcome remains uncertain.  (+info)

Mesenteric venous thrombosis: a changing clinical entity. (7/74)

OBJECTIVE: Mesenteric venous thrombosis (MVT) and its clinical spectrum have become better defined following improvements in diagnostic imaging. Historically, MVT has been described as a morbid clinical entity, but this may not necessarily be true. Often, an underlying disease process that predisposes a patient to MVT can be found and potentially treated. This study was designed to evaluate the diagnostics and management of MVT and to review long-term results of treatment. PATIENTS: Thirty-one patients in whom MVT was diagnosed between 1985 and 1999 were retrospectively reviewed. Survivors were contacted for follow-up. There were 15 men and 16 women. Ages ranged from 22 to 80 years (mean, 49.1 years). Thirteen patients had documented hypercoagulability, 10 had a history of previous abdominal surgery, 6 had a prior thrombotic episode, and 4 had a history of cancer. MVT presented as abdominal pain (84%), diarrhea (42%), and nausea/vomiting (32%). Computed tomography (CT) was considered diagnostic in 18 (90%) of 20 patients who underwent the test. CT diagnosed MVT in 15 (100%) of 15 patients presenting with vague abdominal pain or diarrhea. Angiography demonstrated MVT in only five (55.5%) of nine patients. RESULTS: Seven of 31 patients died within 30 days (< 30-day mortality rate, 23%). Twenty-two patients (72%) were initially treated with heparin. Nine patients were not heparinized: four of them died, and two were later given warfarin sodium (Coumadin). Of the 31 patients, only one received lytic therapy. Three patients became symptom free without anticoagulation. Ten patients (32%) underwent bowel resection. Overall, 19 (79%) of 24 survivors were treated with long-term warfarin therapy. Long-term follow-up was obtained in 24 patients (mean, 57.7 months). Twenty-one (88%) of 24 survived in follow-up. CONCLUSION: The diagnosis of MVT should be suspected when acute abdominal symptoms develop in patients with prior thrombotic episodes or a documented coagulopathy. CT scanning appears to be the primary diagnostic test of choice. Anticoagulation is recommended. If diagnosed and treated early, MVT is not likely to progress to gangrenous bowel. Recent mortality rates for MVT are lower than previously published, perhaps because of earlier diagnosis and aggressive treatment or possibly because we now readily diagnose a more benign form of the disease, which is due to widespread use of CT scanning.  (+info)

Recombinant human transgenic antithrombin in cardiac surgery: a dose-finding study. (8/74)

BACKGROUND: Acquired antithrombin III (AT) deficiency may render heparin less effective during cardiac surgery and cardiopulmonary bypass (CPB). The authors examined the pharmacodynamics and optimal dose of recombinant human AT (rh-AT) needed to maintain normal AT activity during CPB, optimize the anticoagulant response to heparin, and attenuate excessive activation of the hemostatic system in patients undergoing coronary artery bypass grafting. METHODS: Thirty-six patients scheduled to undergo elective primary coronary artery bypass grafting and who had received heparin for 12 h or more before surgery were enrolled in the study. Ten cohorts of three patients each received rh-AT in doses of 10, 25, 50, 75, 100, 125, 175, or 200 U/kg, a cohort of six patients received 150 U/kg of rh-AT, and a control group of six patients received placebo. RESULTS: Antithrombin III activity exceeded 600 U/dl before CPB at the highest dose (200 U/kg). Doses of 75 U/kg rh-AT normalized AT activity to 100 U/dl during CPB. Activated clotting times during CPB were significantly (P < 0.0001) greater in patients who received rh-AT (844 +/- 191 s) compared with placebo patients (531 +/- 180 s). Significant (P = 0.001) inverse relations were observed between rh-AT dose and both fibrin monomer (r = -0.51) and D-dimer (r = -0.51) concentrations. No appreciable adverse events were observed with any rh-AT doses used in the study. CONCLUSIONS: Supplementation of native AT with transgenically produced protein (rh-AT) in cardiac surgical patients was well tolerated and resulted in higher activated clotting times during CPB and decreased levels of fibrin monomer and D-dimer.  (+info)

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