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G Sas

Publications and source records attributed to G Sas.

18 recordsLinked to original sources
PubMed1992

Antithrombin Budapest 3. An antithrombin variant with reduced heparin affinity resulting from the substitution L99F.

The molecular basis and functional properties of a variant antithrombin (AT) protein. AT Budapest 3, were studied. A single base substitution was identified in codon 99, CTC----TTC, altering the normal leucine to phenylalanine. The proband presented with a history of venous thrombotic disease and was found to be homozygous for the mutation. The variant protein demonstrated reduced heparin affinity and reduced antiproteinase activity in the presence of either unfractionated heparin or the AT-binding heparin pentasaccharide, when compared to normal AT. A small change in the isoelectric point was also identified. The substituted amino acid residue of AT Budapest 3 is located near to the proposed AT heparin binding site, and it is suggested that reduced heparin affinity of the variant protein may result from substitution-induced distortion of positive charge geometry in the binding site and/or changes in its position relative to the rest of the inhibitor molecule.

Amino Acid Sequence↗
PubMed1992

Antithrombin III Budapest: a single amino acid substitution (429Pro to Leu) in a region highly conserved in the serpin family.

Antithrombin III (AT) is a major plasma serine protease inhibitor and a member of the serpin family of proteins. We have characterized the molecular and genetic basis of AT Budapest, an inherited variant of AT that is associated with thrombotic disease in affected family members. A single amino acid substitution, 429Pro to Leu, was identified, occurring in a region of the molecule that is highly conserved in members of the serpin family. Two forms of variant protein were present in approximately equal amounts in the plasma of the propositus, who is homozygous for the mutation. One form, which had apparently normal Mr, bound heparin strongly and retained some residual thrombin inhibitory activity. The other form had only weak heparin affinity and no antiproteinase activity, and had slightly decreased mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under nonreducing conditions; this normalized in the presence of a reducing agent, suggesting it was caused by a change in conformation. Additional support for a difference in conformation of the two forms of variant was provided by the finding that the fraction that bound heparin-Sepharose was recognized by a monoclonal antibody raised against normal AT, whereas the weak-affinity fraction was not.

Amino Acid Sequence↗
PubMed1992

Pleiotropic effects of antithrombin strand 1C substitution mutations.

Six different substitution mutations were identified in four different amino acid residues of antithrombin strand 1C and the polypeptide leading into strand 4B (F402S, F402C, F402L, A404T, N405K, and P407T), and are responsible for functional antithrombin deficiency in seven independently ascertained kindreds (Rosny, Torino, Maisons-Laffitte, Paris 3, La Rochelle, Budapest 5, and Oslo) affected by venous thromboembolic disease. In all seven families, variant antithrombins with heparin-binding abnormalities were detected by crossed immunoelectrophoresis, and in six of the kindreds there was a reduced antigen concentration of plasma antithrombin. Two of the variant antithrombins, Rosny and Torino, were purified by heparin-Sepharose and immunoaffinity chromatography, and shown to have greatly reduced heparin cofactor and progressive inhibitor activities in vitro. The defective interactions of these mutants with thrombin may result from proximity of s1C to the reactive site, while reduced circulating levels may be related to s1C proximity to highly conserved internal beta strands, which contain elements proposed to influence serpin turnover and intracellular degradation. In contrast, s1C is spatially distant to the positively charged surface which forms the heparin binding site of antithrombin; altered heparin binding properties of s1C variants may therefore reflect conformational linkage between the reactive site and heparin binding regions of the molecule. This work demonstrates that point mutations in and immediately adjacent to strand 1C have multiple, or pleiotropic, effects on this serpin, leading ultimately to failure of its regulatory function.

Adolescent↗
PubMed1979

Specificity in the factor VIII response to vasopressin infusion in man.

Structural requirements of the systemic factor VIII response to intravenous vasopressin in man has been investigated using vasopressin analogues. With the analogues available the receptor specificity of this phenomenon could not be distinguished from those associated with the previously described plasminogen activator release or antidiuretic effects of this hormone. Further studies using 1-desamino-[8-D-arginine]vasopressin showed a dose-related release of both procoagulant and antigenic components of the factor VIII complex. The newly released factor VIII could not be distinguished from circulating factor VIII on the basis of molecular size, electrophoretic mobility or in vitro stability despite apparent differences in the duration of response of the procoagulant and antigenic components in vivo.

Adult↗
PubMed1978

[Cholesterol deficiency. A pathogenetic factor in chronic anemias? Preliminary report of a study in three states (author's transl)].

It has been shown in several studies that there is a statistically confirmed connection between cholesterol and Hb levels in the sense that hypocholesterolemia and anemia occur together particularly frequently. This was demonstrated in an epidemiological cross-section study of 3958 patient data, and also that in a retrospective case control study of 159 anemias there wasa concurrent hypocholesterolemia. It is explained by the fact that cholesterol deficiency leads to rigidity of the erythrocytes.

Aged↗
PubMed1975

Further investigations on antithrombin III in the plasmas of patients with the abnormality of antithrombin III Budapest.

Antithrombin III (AT-III) was studied in a thrombophilic family with an abnormal AT-III molecule (antithrombin III Budapest) using a modified crossed immunoelectrophoresis technique, gel filtration, 'rocket' immunoelectrophoresis and a heparin cofactor assay. When agarose was applied in the first phase of the crossed immunoelectrophoresis, the normal and the pathological AT-III revealed identical electrophoretic mobility. However, when heparin was mixed with agarose in the first phase of electrophoresis, the propositus' plasma displayed a different AT-III pattern from normal plasma. His plasma contained the first component of the normal plasma (Immune Antithrombin III1, IAT-III) in a concentration of only 5% of normal, and a protein in high concentration which although immunoreactive to AT-III antisera, had an electrophoretic mobility similar (but not identical to that of IAT-III2. This abnormal protein had no heparin cofactor activity and a molecular size greater than normal plasma AT-III. Unlike AT-III, the addition of heparin did not change the molecular size of the pathogic AT-III molecule significantly. The abnormal protein was present in lower concentrations in the patient's children and at the time of study they had no clinical or laboratory evidence of intravascular coagulation.

Adult↗
PubMed1975

Investigations on antithrombin III in normal plasma and serum.

Studies on antithrombin III (AT-III) were made by a modification of the two dimensional crossed immunoelectrophoresis technique and gel filtration. Mixing various quantities of heparin with agarose in the first phase of electrophoresis, AT-III from normal human plasma and serum revealed a heterogeneity which depended on the heparin concentration in the agarose gel. At heparin concentrations higher than 16 u/ml, AT-III displayed three components with different electrophoretic mobilities. The component with the highest mobility (designated immunoantithrombin III1 : IAT-III1) dominated in plasma. In normal serum, however, the quantity of this component was decreased and the two other peaks with a slower electrophoretic mobility (IAT-III2 and IAT-III3) became more evident. Normal human plasma and serum were filtered on Sephadex G-200 and the AT-III concentration measured in the fractions by rocket immunoelectrophoresis. The peaks of AT-111 were found in the same fractions for both plasma and serum and were coincident with the albumin peak of the plasma proteins. However, in the case of serum the AT-III concentration decreased less sharply in those fractions with higher molecular weight than in the corresponding plasma fractions. Analysis of these fractions by crossed immunoelectrophoresis revealed that the two components with slower electrophoretic mobility (IAT-III2 and IAT-III3) had higher molecular size than IAT-III1, that the concentration of IAT-III2 and IAT-III3 was significantly higher in serum, and that the high molecular weight components in plasma and serum were qualitatively identical. It is concluded that high molecular weight complexes between AT-III and activated coagulation factors may be present in normally circulating blood and that their detection and possibly quantitation can be achieved using the heparin/agarose crossed immunoelectrophoresis system.

Antithrombin III↗
PubMed1975

In vitro spontaneous thrombin generation in human factor-IX concentrates.

A series of in vitro studies designed to ascertain the potential in vivo thrombogenicity of human factor IX-containing concentrates is described. Using concentrates obtained from several different Centres the fibrinogen clotting time with some preparations was less than 6 h and/or the recalcification time of normal plasma was shortened. In some preparations, however, the plasma recalcification time was lengthened. Further studies revealed that all diluted factor-IX concentrates generated thrombin after recalcification, and that the rate of thrombin generation appeared to be characteristic of a particular preparation. This characteristic has been designated the TGt50, which is the incubation period in minutes, after recalcification, required to obtain a 50 s clotting time of a fibrinogen substrate. The TGt50 was found to correlate most strongly with recalcification time of celite exhausted plasma (P less than 0.001), but no correlation was observed between it and the immunological antithrombin III or factor-VIII antigen levels. Evidence is presented which suggests that the thrombin generation test and recalcification time of celite exhausted plasma may represent suitable in vitro quality control assays for factor-IX concentrates.

Blood Coagulation↗