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Biomedical subjects

E A Beck

Publications and source records attributed to E A Beck.

At least 37 records · Page 2Linked to original sources
PubMed1985

Reactivity of small molecular forms of human factor VIII/von Willebrand factor with botrocetin and anti-factor VIII-coated latex particles.

Two recently developed tests for measurement of factor VIII/von Willebrand factor (FVIII/vWF), i.e. platelet agglutination by botrocetin and a kinetic latex antigen assay, were compared with ristocetin cofactor and electroimmunoassay, in respect with FVIII/vWF size-distribution. FVIII/vWF was measured in six cases of atypical von Willebrand's disease (type II), in gel-filtered fractions of normal cryoprecipitate and in the course of depolymerization of purified normal FVIII/vWF by disulfide reduction. Small molecular forms of FVIII/vWF from normal and variant type II plasma, and those derived by disulfide reduction of high-molecular weight FVIII/vWF, showed remarkably decreased reactivity in ristocetin-, botrocetin- and latex-assay. We conclude that for botrocetin-induced platelet agglutination, as well as for agglutination of antibody-coated latex particles, multiple interactions with repeating subunits of FVIII/vWF are required. As a practical consequence, the combined measurement of FVIII/vWF by the latex test and electroimmunoassay provides a simple tool for discriminating between the classical von Willebrand's disease and its variants.

Antibodies↗
PubMed1985

Fibrinogen Bergamo I (A alpha 16Arg----Cys): susceptibility towards thrombin following aminoethylation, methylation or carboxamidomethylation of cysteine residues.

An abnormal fibrinogen, denoted as "fibrinogen Bergamo I", has been characterized. Its defect consists in an exchange of arginine by cysteine in position 16 of the A alpha-chain, thus corresponding to that found in a number of other fibrinogen variants. The abnormal fibrinopeptide A cannot be split off by thrombin from intact fibrinogen Bergamo I. We describe three different chemical modifications of the cysteine A alpha 16, i.e. aminoethylation, methylation and carboxamidomethylation, and their effects on the susceptibility of fibrinogen Bergamo I towards thrombin attack. S-aminoethylation of the A alpha 16Cys renders the peptide bond A alpha 16-17 cleavable by thrombin. Following methylation or carboxamidomethylation, the A alpha 19-arginyl bond becomes accessible for thrombin. The chemically modified extended fibrinopeptide A can be readily separated from the normal fibrinopeptide A by HPLC. The latter two modifications are suitable alternative procedures for detecting the molecular defect A alpha 16Arg----Cys of fibrinogen.

Amino Acids↗
PubMed1985

Inhibition of human T lymphocyte proliferation in vitro by commercial factor VIII concentrates.

Several investigators recently described a T lymphocyte subset abnormality (reversed helper/suppressor cell ratio) in haemophiliacs, especially following previous substitution therapy. We studied in vitro the potential effects of two commercial factor VIII concentrates on incorporation of 3H-thymidine by isolated human peripheral blood lymphocytes after stimulation with either phytohaemagglutinin or monoclonal antibody OKT3. Dose-related inhibition of thymidine incorporation was found for both concentrates but none using the purified main protein constituents, i.e. factor VIII, fibrinogen or fibronectin. Furthermore, the 'inhibitor' was completely removed by dialysis.

Acquired Immunodeficiency Syndrome↗
PubMed1984

[Desamino-8-D-arginine vasopressin nose drops in the treatment of mild hemophilia A and von Willebrand's disease].

To permit home treatment in our patients we investigated the response to intranasal administration of 260 micrograms DDAVP in 28 patients with either mild hemophilia A or von Willebrand's disease. 6 patients with mild hemophilia A responded, and 6 did not. In the group with von Willebrand's disease 6 responded well, 4 responded partially and 6 did not respond. Knowledge of the severity of the disease did not allow us to predict the response, and therefore every patient should be tested individually. Intranasal DDAVP in our patients was used with success for bleeding into the knee joint, muscle hematoma and hematuria.

Arginine Vasopressin↗
PubMed1984

Interactions of purified rat factor VIII/von Willebrand factor with rat and human platelets--effect of albumin and ristocetin.

Rat platelets do not respond to ristocetin in their own plasma nor do they aggregate in the presence of bovine or porcine factor VIII von Willebrand factor (F VIII R:WF) or human F VIII R:WF in presence of ristocetin. However, rat plasma supports ristocetin induced aggregation of washed human platelets. In this study we report on purification of rat F VIII R:WF from cryoprecipitate. Similarly to porcine or bovine material, purified rat F VIII R:WF induced aggregation of human washed fixed platelets. This effect was enhanced by addition of ristocetin and was not modified by addition of albumin. Rat washed platelets were aggregated by ristocetin in the presence of rat or human F VIII R:WF provided that high concentrations of ristocetin are added in a system essentially free of extraneous proteins. Increasing concentrations of albumin dramatically reduced the ability of ristocetin to aggregate rat platelets while human platelet aggregation by human or rat F VIII R:WF was only moderately affected. These studies show that rat F VIII R:WF can interact with rat and human platelets. The lack of response of rat platelets to ristocetin in their own plasma is most likely due to a low sensitivity of rat platelets to this drug and to an inhibitory activity of plasma proteins on this reaction.

Animals↗
PubMed1984

Isolation of small molecular forms of Factor VIII/von Willebrand factor from plasma.

Cryoprecipitated factor VIII/von Willebrand factor (FVIII/vWF), freed of fibrinogen by clotting with calcium and Defibrase, was chromatographed on Sepharose CL-2B. Fractions containing lower-molecular-weight forms of FVIII/vWF comprised coprecipitated plasma proteins of similar molecular weights. The major contaminants, fibronectin and IgM, were removed by affinity chromatography on gelatin- and anti-IgM-agarose, respectively. Finally, pure low-molecular-weight FVIII/vWF protein was harvested in the void volume fraction of a Sepharose CL-6B column. The smallest multimers had the size of the tetramer of the basic subunit chain of FVIII/vWF.

Blood Coagulation Factors↗
PubMed1983

[Standardization problems in the monitoring of oral anticoagulants by Quick's thromboplastin time: an attempt to determine the state of the problem in Switzerland].

In comparison with British Comparative Thromboplastin, we examined 11 different reagents which are presently available in Switzerland for surveillance of oral anticoagulation. Frozen plasma samples obtained from 50 patients under oral anticoagulation for at least 6 weeks were used for comparison of the various reagents. From our results the following conclusions emerge: Our present results largely concur with those of a similar study which compared the therapeutic range of thromboplastin reagents available in Switzerland 6 years earlier; therefore, we assume that the reagents which were sold at that time and are now available in Switzerland have remained fairly constant. In contrast to this apparent agreement, the therapeutic ranges indicated by the producers of reagents are, at least in part, comparable neither with the therapeutic range established for the British Comparative Reagent nor among themselves. Thus, the intensity of the induced coagulation defect is obviously variable, depending on a given test system. The calculated "therapeutic range" for a given test system traditionally corresponds to an average risk of thrombosis or bleeding; this range is not of necessity identical with a target zone that has to be established either individually or for certain diseases. Once established, a target value defining the intensity of oral anticoagulation can be more conveniently reproduced by use of suitable control plasmas rather than with reference thromboplastins, at any rate by practitioners or non specialised hospital laboratories.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1983

[Fibrinogen Bern II: hereditary fibrinogen variant with amino acid substitution of arginine replaced by histidine in position 16 of the A alpha chain].

The number of described individuals with congenital dysfibrinogenemia continuously increases, but only a few fibrinogen variants have thus far been characterized with respect to their structural defect. Fibrinogen Bern II is a hereditary fibrinogen variant with impaired release of fibrinopeptide A (FPA) and a markedly prolonged coagulation time. It turned out that only half of the FPA was cleaved off at normal rate while the residual FPA was released much more slowly and incompletely, unless high thrombin concentrations were used. Amino acid analysis of normal and abnormal FPA revealed that the abnormal peptide, in contrast to the normal, contained histidine but hardly any arginine. It is therefore concluded that fibrinogen Bern II undergoes substitution of arginine in position 16 of the A alpha-chain by histidine. Thus, the structural alteration is identical with that of seven other recently described variants. The presence of 50% normal fibrinogen molecules provides the normal hemostasis in the heterozygous carriers of the Bern II-dysfibrinogenemia.

Afibrinogenemia↗
PubMed1983

[Hemostasis disorders with reduced activity of the von Willebrand factor in myeloproliferative syndromes].

Splenectomy performed in a patient with polycythaemia vera and incipient osteomyelofibrosis was complicated by severe postoperative bleeding. A transient decrease of factor VIII/von Willebrand factor (VIIIR:WF) was detected as a possible cause of the bleeding tendency. As a result of this observation the VIIIR:WF system was investigated in all patients with myeloproliferative disorders who are presently followed by this laboratory. Subnormal VIIIR:WF activity was found in 5 of 9 prospectively investigated patients with polycythaemia vera and in one of 12 patients with chronic myeloid leukemia. These results suggest that acquired defects of the VIIIR:WF system are, in addition to the well known functional abnormalities of blood platelets, quite common in myeloproliferative disorders, especially polycythaemia vera, and must be reckoned with before surgery in particular. When specific antibodies directed against VIIIR:WF have been ruled out, the etiology of the VIIIR:WF defect found in our patients remains unclear.

Blood Coagulation Factors↗
PubMed1983

Inhibition of fibrin polymerization by fragment d is affected by calcium, Gly-Pro-Arg and Gly-His-Arg.

Fibrinopeptides A and B were removed from purified human fibrinogen by bovine thrombin, whereas the snake venom protease batroxobin only split fibrinopeptide A from fibrinogen. Aggregation of the resulting desAB- and desA-fibrin monomers was evaluated by recording the turbidity of incubation mixtures. Fibrin assembly was strongly accelerated by increasing the calcium concentration from 10(-5) to 10(-3) M. Fragment D was obtained from fibrinogen by proteolytic degradation with plasmin in the presence of Ca2+. At a 4-fold molar concentration relative to fibrinogen, fragment D dramatically inhibited fibrin polymerization at up to 10(-4) M Ca2+. This anticlotting activity was, however, much less pronounced at 10(-3) M Ca2+. The thrombin clotting time, measured on human plasma, was prolonged by fragment D in a dose-dependent manner. In citrate-containing plasma, the fibrinogen clotting was significantly delayed by an equimolar concentration of fragment D. In barium sulfate-adsorbed oxalated plasma, containing 2.5 mM Ca2+, the same amount of fragment D hardly affected fibrin polymerization. We conclude that fragment D has no important anticlotting effect under physiological conditions. The synthetic peptide Gly-Pro-Arg, corresponding to the amino-terminal sequence of the fibrin alpha-chain, inhibited aggregation of both desA-fibrin and desAB-fibrin at 10(-3) M Ca2+. The inhibition of desAB-fibrin polymerization by Gly-Pro-Arg was abolished at 10(-5) M Ca2+. In addition, Gly-Pro-Arg depressed the anticlotting activity of fragment D at low calcium concentration. An analogue of the amino-terminus of fibrin beta-chain, Gly-His-Arg, strongly accelerated aggregation of desA-fibrin monomers, but only moderately enhanced polymerization of desAB-fibrin monomers at 10(-5) M Ca2+, both in the presence and in the absence of fragment D. This activating effect of Gly-His-Arg was abolished at 10(-3) M Ca2+. It is suggested that the binding of calcium, Gly-His-Arg, and possibly also Gly-Pro-Arg, induces a conformational change in fibrin monomers and thus accelerates the polymerization process.

Animals↗
PubMed1983

Silver staining of high molecular weight proteins on large-pore polyacrylamide gels.

A large-pore gel for electrophoresis in the presence of sodium dodecyl sulfate, composed of 2.55% polyacrylamide crosslinked with 2.75% methylenebisacrylamide, is described. This gel has a resolving power for very high molecular weight proteins and can be stained with silver. The gel is suitable for fractionation of factor VIII/von Willebrand factor directly from plasma samples. Visualization by silver staining revealed a series of covalently bound multimers with molecular weights of up to 8 X 10(6). The procedure described should be useful also for studies on other very high molecular weight proteins and nucleic acids.

Acrylamides↗
PubMed1982

Effect of calcium and synthetic peptides on fibrin polymerization.

Human fibrinogen was subjected to limited proteolytic attack by thrombin, batroxobin or Agkistrodon contortrix thrombin-like enzyme, yielding desAB-, desA- or desB-fibrin monomers, respectively. Turbidity curves demonstrated that, with all three enzymes, the polymerization process was strongly accelerated by increasing the calcium concentration from 10(-5) M to 10(-4) M. Synthetic peptide Gly-His-Arg (5 mM), an analogue of the aminoterminal sequence of fibrin beta-chain, inhibited aggregation of desB-fibrin monomers at physiological calcium concentration whereas it enhanced aggregation of desA- and desAB-fibrin monomers at calcium concentrations below 10(-4) M. On the other hand, Gly-Pro-Arg (1 mM) corresponding to the amino-terminus of fibrin alpha-chain, dramatically inhibited aggregation of both desA- and desB-fibrins, but it only moderately affected the polymerization of thrombin-induced monomers. We conclude that the observed effects of Gly-Pro-Arg and Gly-His-Arg are not due solely to their competition with fibrin amino-termini for the respective binding sites in the D-domain, but rather reflect conformational changes in fibrin monomers which affect the polymerization process.

Batroxobin↗
PubMed1982

[The 5q syndrome--a chromosome aberration with characteristic hematologic picture: preleukemia? Literature review and description of a personal case].

The case of a 74-year-old woman with macrocytic, refractory anemia, typical changes in the bone marrow and a 5q-chromosome in bone marrow cells is presented and the literature of this newly described hematological disorder is reviewed. The syndrome is characterized by partial deletion of the long arms of a chromosome No. 5 in bone marrow cells. The chromosomal anomaly is acquired and originates most probably from a pluripotent hematologic stem cell. Hematologic changes are (1) macrocytic, refractory anemia, (2) low to normal leukocyte counts, (3) normal to increased platelet number with marked anisocytosis and a high proportion of megathrombocytes, (4) normal to hypoplastic erythropoiesis and generally small megakaryocytes with nonlobulated nuclei in the bone marrow. In most of the reported cases (16 out of 19) with isolated 5q-anomaly, the clinical picture and laboratory findings remained stationary during a follow-up period of up to 6 years. In only 2 out of 19 cases did acute leukemia develop. In the presence of additional chromosomal abnormalities, all the cases developed acute leukemia and especially acute myelogenous leukemia. The diagnosis of 5q-syndrome in patients with refractory anemia is of prognostic significance, since it renders possible early recognition of a potentially malignant disorder and early detection of leukemic transformation.

Aged↗
PubMed1981

[Fibrinogen Bern I and fibrinogen Bern II: 2 hereditary fibrinogen variants with diverse biochemical properties].

Two inherited fibrinogen variants, fibrinogen Bern I and fibrinogen Bern II, have been partially characterized. The markedly prolonged thrombin clotting times observed with both variants result from impaired fibrin monomer aggregation. Complete correction of this polymerization defect at physiological calcium concentrations has been achieved for fibrinogen Bern I. This variant also exhibits a charge abnormality in the gamma-polypeptide chain, an increased sialic acid content and defective calcium binding by the C-terminal part of the molecule. Fibrinogen Bern II, on the other hand, exhibits a defect which, although located at a site important for polymerization, is not influenced by the binding of calcium ions.

Binding Sites↗
PubMed1981

Von Willebrand activity of low molecular weight human Factor VIII increases by binding to gold granules.

Human factor VIII/von Willebrand protein is a population of multimers which vary in size but contain apparently identical subunits. Large-molecular-weight forms possess higher ristocetin cofactor/von Willebrand activity than the native smaller oligomers. Disulfide reduction of large factor VIII multimers results in progressively decreasing molecular size and a loss of ristocetin cofactor activity. Small molecular forms of factor VIII were adsorbed onto gold granules (average diameter 20-30 nm) and thereby increased their ristocetin cofactor activity. The amount of adsorbed material and the extent of activation were dependent on the pH of the coiled suspension. The maximum recovery of von Willebrand activity was observed at pH 4.75. Aggregation of fixed human platelets by factor VIII-coated gold particles was dependent on ristocetin concentration and was not competitively inhibited by unbound low-molecular-weight factor VIII. These results suggest that the subunits of the native small factor VIII species possess potential binding affinity for platelet receptors, which is manifested following formation of large factor VIII polymers. We conclude that an optimal size of remarkably high molecular weight is required for efficient aggregation of platelets by factor VIII as occurs during the primary phase of hemostasis.

Adsorption↗