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Biomedical subjects

U Seligsohn

Publications and source records attributed to U Seligsohn.

At least 37 records · Page 2Linked to original sources
PubMed2001

Identification of a region in glycoprotein IIIa involved in subunit association with glycoprotein IIb: further lessons from Iraqi-Jewish Glanzmann thrombasthenia.

The most frequent mutation causing Glanzmann thrombasthenia in Iraqi-Jews (IJ-1) is an 11-bp deletion in exon 13 of the glycoprotein (GP) IIIa gene. This deletion predicts a frameshift that results in the elimination of the C406-C655 disulfide bond and a premature termination codon shortly before the transmembrane domain. To determine the contribution of each of these alterations to the thrombasthenic phenotype, Chinese hamster ovary or baby hamster kidney cells were cotransfected with normal GPIIb complementary DNA (cDNA) and the following GPIIIa cDNAs: normal, cDNA bearing IJ-1 mutation, 2011T>A mutated cDNA predicting C655S (single-letter amino acid codes) substitution, and 2019A>T mutated cDNA predicting Stop657. Elimination of the C406-C655 disulfide bond by C655S substitution did not affect GPIIb/IIIa surface expression or binding of the transfected cells to immobilized fibrinogen, whereas elimination of the transmembrane and cytoplasmic domains in IJ-1 and Stop657 mutants prevented both surface expression and binding of the transfected cells to immobilized fibrinogen. Immunohistochemical staining and immunoprecipitation demonstrated that the elimination of amino acids 657-762 in IJ-1 and Stop657 prevented intracellular GPIIb/IIIa complex formation, and differential immunofluorescence staining of GPIIIa and cellular organelles suggested that the truncated uncomplexed GPIIIa protein was retained in the endoplasmic reticulum. Because the use of GPIIIa Stop693 and normal GPIIb cDNAs yielded GPIIb/IIIa complex formation, though with lower efficiency, it is suggested that amino acids 657-692 of GPIIIa are essential for the intracellular association of GPIIb and GPIIIa. (Blood. 2001;98:1063-1069)

Animals↗
PubMed2001

Identification and functional analysis of two novel mutations in the multidrug resistance protein 2 gene in Israeli patients with Dubin-Johnson syndrome.

Dubin-Johnson syndrome (DJS) is an inherited disorder characterized by conjugated hyperbilirubinemia and is caused by a deficiency of the multidrug resistance protein 2 (MRP2) located in the apical membrane of hepatocytes. The aim of this study was to identify the mutations in two previously characterized clusters of patients with Dubin-Johnson syndrome among Iranian and Moroccan Jews and determine the consequence of the mutations on MRP2 expression and function by expression studies. All 32 exons and adjacent regions of the MRP2 gene were screened by polymerase chain reaction and DNA sequencing. Two novel mutations were identified in exon 25. One mutation, 3517A-->T, predicting a I1173F substitution, was found in 22 homozygous Iranian Jewish DJS patients from 13 unrelated families and a second mutation, 3449G-->A, predicting a R1150H substitution, was found in 5 homozygous Moroccan Jewish DJS patients from 4 unrelated families. Use of four intragenic dimorphisms and haplotype analyses disclosed a specific founder effect for each mutation. The mutations were introduced into an MRP2 expression vector by site-directed mutagenesis, transfected into HEK-293 cells, and analyzed by a fluorescence transport assay, immunoblot, and immunocytochemistry. Continuous measurement of probenecid-sensitive carboxyfluorescein efflux revealed that both mutations impaired the transport activity of MRP2. Immunoblot analysis and immunocytochemistry showed that MRP2 (R1150H) matured properly and localized at the plasma membrane of transfected cells. In contrast, expression of MRP2 (I1173F) was low and mislocated to the endoplasmic reticulum of the transfected cells. These findings provide an explanation for the DJS phenotype in these two patient groups. Furthermore, the close localization of the two mutations identify this region of MRP2 as important for both activity and processing of the protein.

Biological Transport↗
PubMed2001

Thrombophilia as a cause for central and branch retinal artery occlusion in patients without an apparent embolic source.

PURPOSE: To assess the prevalence of vascular risk factors and thrombophilias in central and branch retinal artery occlusion in patients in whom an embolic source is not apparent. METHODS: The study group consisted of 21 consecutive patients with retinal artery occlusion (RAO) in whom Doppler ultrasonography of the carotid arteries and transthoracic or transoesophageal echocardiography were normal. Laboratory methods included polymerase chain reaction for detection of factor V G1691A, factor II G20210A and methylentetrahydrofolate reductase C677T mutations, assays of plasma levels of protein C, free protein S, antithrombin, fibrinogen and homocysteine; and tests for the presence of lupus anticoagulant and anticardiolipin antibodies. Controls for the laboratory tests were 243 healthy subjects. RESULTS: Nine of the 21 (43%) patients had at least one thrombophilic marker: 4 were homozygous for MTHFR C677T, 1 was heterozygous for factor V G1691A, 1 had a high titre of IgM anticardiolipin, 2 were heterozygous for factor V G1691A and homozygous for MTHFR C677T, and 1 had lupus anticoagulant, a high titre of IgM anticardiolipin, homozygosity for MTHFR C677T and hyperhomocysteinaemia. An interaction between vascular risk factors and thrombophilias seemed important since out of 14 patients with hypertension, diabetes and/or hypercholesterolaemia 7 (50%) had a thrombophilia. Homozygous MTHFR C677T was a significant risk factor with odds ratio of 3.18 (95% CI 1.20-8.47). The prevalence of factor V G1691A was also higher in the RAO patients versus controls with an odds ratio of 2.36 (95% CI 0.63-8.88), but this value did not reach significance, probably due to the small sample size. CONCLUSION: A search for thrombophilia in RAO is advisable in patients without evident source of emboli even when vascular risk factors are identified.

Acute Disease↗
PubMed2001

Methionine synthase A2756G and methylenetetrahydrofolate reductase A1298C polymorphisms are not risk factors for idiopathic venous thromboembolism.

Hyperhomocysteinemia is a defined risk factor for venous thromboembolism (VTE). Several polymorphisms of genes encoding for enzymes acting in the remethylation pathway of homocysteine metabolism, ie, methionine synthase (MS) A2756G, methylenetetrahydrofolate reductase (MTHFR) C677T and MTHFR A1298C, can cause increased homocysteine levels particularly in patients with deficiencies of folic acid, vitamin B6, or B12 and hence be potential risk factors for VTE. Indeed, homozygous MTHFR C677T was shown to be a mild risk factor for VTE by some, but not by all, investigators. In this study, we assessed the risk exerted by MS A2756G and MTHFR A1298C in a cohort of patients with idiopathic venous thromboembolism. Homozygosities for MS A2756G and MTHFR A1298C were not found to be statistically significant risk factors for VTE. In addition, no interactions were observed among MS A2756G, MTHFR A1298C and MTHFR C677T in conferring a risk of VTE.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed2001

High prevalence and impact of subnormal serum vitamin B12 levels in Israeli elders admitted to a geriatric hospital.

BACKGROUND: The elderly are known to have higher rates of low and subnormal vitamin B12 levels than younger persons. Vitamin B12 deficiency has been extensively studied in the elderly, but primarily in outpatient settings. There is a paucity of data regarding the prevalence of low and low-normal B12 in frail, hospitalized, elderly patients, and its implications. Additionally, there is little information regarding vitamin B12 status in Israeli elders. OBJECTIVES: The objectives of the study were to estimate the prevalence of low and borderline vitamin B12 levels among frail, hospitalized, elderly patients, and their clinical implications. METHODS: We conducted a chart review, using a retrospective cohort design. The participants were 895 patients admitted to Harzfeld Medical Center in Gedera, Israel. Records were abstracted for vitamin B12 and Folic Acid levels, gastric disease, and outcomes including death, cognitive impairment and neurologic disease. RESULTS: Six hundred and forty patients were eligible for the study. In 15% of the patients, vitamin B12 level was in the low range (<150pmol/L) and in 25% in the low-normal range (150-250pmol/L). Gastric disease and antacid use were not associated with the vitamin B12 status. Mortality was higher in the high vitamin B12 group (p=0.02), perhaps reflecting a selection toward higher acuity in this group. Cerebrovascular disease was more common in patients with lower vitamin B12 levels (p=0.046). CONCLUSIONS: Forty percent of hospitalized elderly patients have low or borderline serum levels of vitamin B12, which may contribute to cerebrovascular disease and cognitive decline.

Aged↗
PubMed2001

The role of factor XI in thrombin generation induced by low concentrations of tissue factor.

Thrombin generation has been studied in the plasma of severely factor XI deficient patients under conditions in which contact activation did not play a role. In platelet-rich as well as platelet-poor plasma, thrombin generation was dependent upon the presence of factor XI at tissue factor concentrations of between 1 and 20 pg/ml i.e. approximately 0.01 to 0.20% of the concentration normally present in the thromboplastin time determination. The requirement for factor XI is low; significant thrombin generation was seen at 1% factor XI; at 10%, thrombin formation was nearly normalised. A suspension of normal platelets in severely factor XI deficient plasma did not increase thrombin generation. This implies that there is no significant factor XI activity carried by normal platelets, although the presence of factor XI and factor XI inhibitors in platelets cannot be ruled out.

Blood Platelets↗
PubMed2000

Molecular characterization of four novel mutations causing factor VII deficiency.

INTRODUCTION: Hereditary deficiency of factor VII (FVII) is a rare coagulation defect. We previously studied the molecular basis of the FVII deficiency in Israeli patients and found that the majority of them bore the Ala244Val mutation. In the present study we further analysed FVII deficient patients. PATIENTS AND METHODS: Three patients with severe FVII deficiency (FVII activity < or =1%) and one with partial deficiency (25%) were studied. In all four patients, the FVII gene was amplified and sequenced. RESULTS: Four novel mutations have been identified: IVS 2+1G-->C Phe 24 deletion, Leu300Pro and Arg277His. Homozygosity for the IVS2+1G-->C mutation was lethal, whereas homozygosity for the Phe 24 deletion was accompanied by a severe bleeding tendency. FVII modeling showed that Phe 24 is located in the Gla domain. Both Arg 277 and Leu 300 are within the catalytic domain, although Arg 277 is also involved in tissue factor binding. CONCLUSION: We have analysed four mutations, two of which (IVS2+1G-->C, Phe 24 deletion) were associated with severe bleeding tendency in the homozygous state, facilitating prenatal diagnosis. Hypothetically, using FVII modeling, Arg 277 replacement by histidine may weaken the tissue factor, while deletion of Phe 24 and Leu300Pro mutation might be associated with abnormal folding of the Gla and catalytic domains, respectively.

Adolescent↗
PubMed2000

Abciximab in carotid stenting for postsurgical carotid restenosis: intermediate results.

PURPOSE: To report intermediate results of a pilot study in which the glycoprotein IIb/IIIa receptor antagonist abciximab was given to patients during percutaneous carotid stenting for recurrent internal carotid artery (ICA) stenosis. The objective was to prevent procedure-related cerebral embolic events and decrease the incidence of recurrent stenosis. METHODS: Sixteen patients (9 women; mean age 66.5 years, range 39-78) with severe ICA recurrent stenosis (>80%) underwent balloon angioplasty and stenting. Before the procedure, abciximab was administered intravenously as a bolus (0.25 mg/kg) followed by a 12-hour continuous infusion (10 microg/min). RESULTS: Fifteen patients received stents (14 Wallstent and 1 Strecker); 1 vessel was dilated with only 50% improvement in luminal diameter. Two stented arteries had residual stenosis (<30%) but satisfactory luminal diameter was achieved in the remaining 13 (81%) arteries. There were no neurological ischemic events during or following the procedure, nor were there any bleeding or peripheral vascular complications. Duplex surveillance studies up to 12 months revealed no significant recurrent stenosis in the treated vessels. CONCLUSIONS: The administration of abciximab in conjunction with percutaneous revascularization procedures for postsurgical carotid artery stenosis may reduce cerebral ischemic episodes. It may also attenuate restenosis in the treated artery.

Abciximab↗
PubMed1999

The human platelet alphaIIb gene is not closely linked to its integrin partner beta3.

alphaIIbb3 integrin is a heterodimeric receptor facilitating platelet aggregation. Both genes are on chromosome 17q21.32. Intergenic distance between them has been reported to be 125 to 260 kilobasepairs (kb) by pulsed-field gel electrophoresis (PFGE) genomic analysis, suggesting that they may be regulated coordinately during megakaryopoiesis. In contrast, other studies suggest these genes are greater than 2.0 megabasepairs (mb) apart. Because of the potential biological implications of having these two megakaryocytic-specific genes contiguous, we attempted to resolve this discrepancy. Taking advantage of large kindreds with mutations in either alphaIIb or beta3, we have developed a genetic linkage map between the thyroid receptor hormone-1 gene (THRA1) and beta3 as follows: cen-THRA1-BRCA1-D17S579/alphaIIb-beta3-qte r, with a distance of 1.3 centiMorgans (cM) between alphaIIb and beta3 and the two genes being oriented in the same direction. PFGE genomic and YAC clone analysis showed that the beta3 gene is distal and >/=365 kb upstream of alphaIIb. Additional restriction mapping shows alphaIIb is linked to the erythrocyte band 3 (EPB3) gene, and beta3 to the homeobox HOX2b gene. Analysis of alphaIIb(+)-BAC and P1 clones confirm that the EPB3 gene is approximately 110 kb downstream of the alphaIIb gene. Sequencing the region surrounding the human alphaIIb locus showed the Granulin gene approximately 18 kb downstream to alphaIIb, and the KIAA0553 gene approximately 5.7 kb upstream. This organization is conserved in the murine sequence. These studies show that alphaIIb and beta3 are not closely linked, with alphaIIb flanked by nonmegakaryocytic genes, and imply that they are unlikely to share common regulatory domains during megakaryopoiesis.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1999

Extensive venous and arterial thrombosis associated with an inhibitor to activated protein C.

Activated protein C resistance (APCR) in the absence of alterations in the factor V gene has been observed during pregnancy, in patients on oral contraceptives, in the presence of antiphospholipid antibodies, and in patients with ischemic stroke. We report a 49-year-old woman with recurrent major venous and arterial thromboses who displayed pronounced APCR, yet no changes in the activated protein C (APC) cleavage sites of factor V. The APCR values determined by four different assays were similar to those obtained in plasma from a homozygote for factor V Q506. Addition of IgG isolated from the patient's serum to normal plasma lowered the APCR ratio from 2.4 to 1.6. Incubation of patient's IgG with normal APC resulted in a profound change in the mobility of APC in crossed immunoelectrophoresis. APC was also shown to bind to patient's IgG immobilized on a protein A agarose column. Factor Va inactivation by APC was inhibited by patient's IgG, but not by control IgG in the presence or absence of either phospholipids or protein S. These results provide evidence for the existence of an acquired antibody against APC in the patient's plasma, which gave rise to the APCR phenotype and was probably responsible for the major thrombotic events. We suggest that acquired APCR due to anti-APC antibodies be considered a potential cause for severe venous and arterial thromboses.

Autoantibodies↗
PubMed1999

Synergistic effects of prothrombotic polymorphisms and atherogenic factors on the risk of myocardial infarction in young males.

Several recent studies evaluated a possible effect of the prothrombotic polymorphisms such as 5,10 methylenetetrahydrofolate reductase (MTHFR) nt 677C --> T, factor V (F V) nt 1691G --> A (F V Leiden), and factor II (F II) nt 20210 G --> A on the risk of myocardial infarction. In the present study, we analyzed the effect of these prothrombotic polymorphisms, as well as apolipoprotein (Apo) E4, smoking, hypertension, diabetes mellitus, and hypercholesterolemia, on the risk of myocardial infarction in young males. We conducted a case-control study of 112 young males with first acute myocardial infarction (AMI) before the age of 52 and 187 healthy controls of similar age. The prevalences of heterozygotes for F V G1691A and F II G20210A were not significantly different between cases and controls (6.3% v 6.4% and 5.9% v 3.4% among cases and controls, respectively). In contrast, the prevalence of MTHFR 677T homozygosity and the allele frequency of Apo E4 were significantly higher among patients (24.1% v 10.7% and 9.4% v 5.3% among cases and controls, respectively). Concomitant presence of hypertension, hypercholesterolemia, or diabetes and one or more of the four examined polymorphisms increased the risk by almost ninefold (odds ratio [OR] = 8.66; 95% confidence interval [CI], 3.49 to 21.5) and concomitant smoking by almost 18-fold (OR = 17.6; 95% CI, 6.30 to 48.9). When all atherogenic risk factors were analyzed simultaneously by a logistic model, the combination of prothrombotic and Apo E4 polymorphisms with current smoking increased the risk 25-fold (OR = 24.7; 95% CI, 7.17 to 84.9). The presented data suggest a synergistic effect between atherogenic and thrombogenic risk factors in the pathogenesis of AMI, as was recently found in a similar cohort of women.

Activated Protein C Resistance↗
PubMed1999

ERGIC-53 gene structure and mutation analysis in 19 combined factors V and VIII deficiency families.

Combined factors V and VIII deficiency is an autosomal recessive bleeding disorder associated with plasma levels of coagulation factors V and VIII approximately 5% to 30% of normal. The disease gene was recently identified as the endoplasmic reticulum-Golgi intermediate compartment protein ERGIC-53 by positional cloning, with the detection of two founder mutations in 10 Jewish families. To identify mutations in additional families, the structure of the ERGIC-53 gene was determined by genomic polymerase chain reaction (PCR) and sequence analysis of bacterial artificial chromosome clones containing the ERGIC-53 gene. Nineteen additional families were analyzed by direct sequence analysis of the entire coding region and the intron/exon junctions. Seven novel mutations were identified in 10 families, with one additional family found to harbor one of the two previously described mutations. All of the identified mutations would be predicted to result in complete absence of functional ERGIC-53 protein. In 8 of 19 families, no mutation was identified. Genotyping data indicate that at least two of these families are not linked to the ERGIC-53 locus. Taken together, these results suggest that a significant subset of combined factors V and VIII deficiency is due to mutation in one or more additional genes.

Amino Acid Substitution↗
PubMed1999

Fibrin-dependent platelet procoagulant activity requires GPIb receptors and von Willebrand factor.

Thrombin generation in platelet-rich plasma (PRP) involves complex interactions between platelets and coagulation proteins. We previously reported that the addition of fibrin to PRP enhances tissue-factor initiated thrombin generation by approximately 40%, and the current studies were designed to assess the mechanism(s) underlying thrombin generation in the absence and presence of fibrin. Blocking platelet GPIIb/IIIa + alphavbeta3 receptors with a monoclonal antibody (MoAb) inhibited basal thrombin generation, but did not affect the enhancement produced by fibrin. In contrast, blocking GPIb with any of three different MoAbs had no effect on basal thrombin generation, but essentially eliminated fibrin enhancement of thrombin generation. When thrombin generation was tested in PRP deficient in von Willebrand factor (vWF), both basal and fibrin-enhanced thrombin generation were markedly reduced, and the addition of factor VIII did not normalize thrombin generation. Botrocetin, which induces the binding of vWF to GPIb, enhanced thrombin generation. In all studies, the ability of PRP to support thrombin generation correlated with the production of platelet-derived microparticles and serum platelet-derived procoagulant activity. Thus, two separate mechanisms, both of which depend on vWF, appear to contribute to platelet-derived procoagulant activity: one is independent of fibrin and relies primarily on GPIIb/IIIa, but with a minor contribution from alphavbeta3; and the other is fibrin-dependent and relies on GPIb. These data may have implications for understanding the mechanisms of the abnormalities in serum prothrombin times reported in Bernard-Soulier syndrome, hemorrhage in von Willebrand disease (vWD), and the increased risk of thrombosis associated with elevated vWF levels.

Animals↗
PubMed1999

Analysis of prothrombotic and vascular risk factors in patients with nonarteritic anterior ischemic optic neuropathy.

OBJECTIVE: To determine whether genetic or acquired thrombophilias and other risk factors are associated with nonarteritic anterior ischemic optic neuropathy (NAION). DESIGN: Retrospective case-control study. PARTICIPANTS: Sixty-one patients with NAION diagnosed between 1984 and 1997. Ninety consecutive patients who visited the Eye Institute made up the control group. INTERVENTION: Protein C, protein S, antithrombin III, lupus anticoagulant, and three recently described prothrombotic polymorphisms (i.e., factor V G1691A, factor II G20210A, and methylenetetrahydrofolate reductase [MTHFR] C677T) were analyzed. In addition, risk factors for arteriosclerotic vascular disease were assessed. MAIN OUTCOME MEASURES: Parameters of thrombophilia. RESULTS: None of the thrombophilic markers (genetic and acquired) constituted a significant risk factor for NAION. Ischemic heart disease, hypercholesterolemia, and diabetes mellitus were discerned as risk factors for NAION with odds ratios of 2.9 (95% confidence interval [CI], 1.3-6.4), 2.6 (95% CI, 1.2-5.5), and 2.3 (95% CI, 1.1-4.8), respectively. Multiple logistic regression analysis indicated that ischemic heart disease and hypercholesterolemia exerted an additive risk for NAION with a combined odds ratio of 4.5 (95% CI, 1.4-14.5). However, none of these risk factors statistically predicted second eye involvement. CONCLUSION: NAION was not found to be associated with thrombophilic risk factors, yet it was related to ischemic heart disease, hypercholesterolemia, and diabetes mellitus.

Adult↗
PubMed1999

Role of aspirin in reducing the frequency of second eye involvement in patients with non-arteritic anterior ischaemic optic neuropathy.

PURPOSE: To retrospectively evaluate in patients with non-arteritic ischaemic optic neuropathy (NAION) whether aspirin reduces the frequency of second eye involvement. METHODS: In 52 patients who presented with NAION between 1984 and 1997 adequate information was available regarding use of aspirin, presence of risk factors and second eye involvement. RESULTS: Second eye involvement was noted in 8 of 16 patients (50%) who did not receive aspirin, in 3 of 8 patients (38%) who received 100 mg/day aspirin and in only 5 of 28 patients (18%) who received aspirin 325 mg/day. Moreover, mean time to second eye involvement was 63 months in patients who did not receive aspirin versus 156 months in patients who received aspirin 325 mg/day. CONCLUSION: Our results strongly suggest that aspirin at 325 mg/day may be effective in reducing the frequency of second eye involvement with NAION.

Adult↗
PubMed1999

Age estimates of two common mutations causing factor XI deficiency: recent genetic drift is not necessary for elevated disease incidence among Ashkenazi Jews.

The type II and type III mutations at the FXI locus, which cause coagulation factor XI deficiency, have high frequencies in Jewish populations. The type III mutation is largely restricted to Ashkenazi Jews, but the type II mutation is observed at high frequency in both Ashkenazi and Iraqi Jews, suggesting the possibility that the mutation appeared before the separation of these communities. Here we report estimates of the ages of the type II and type III mutations, based on the observed distribution of allelic variants at a flanking microsatellite marker (D4S171). The results are consistent with a recent origin for the type III mutation but suggest that the type II mutation appeared >120 generations ago. This finding demonstrates that the high frequency of the type II mutation among Jews is independent of the demographic upheavals among Ashkenazi Jews in the 16th and 17th centuries.

Alleles↗