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Biomedical subjects

A M Fischer

Publications and source records attributed to A M Fischer.

At least 73 records · Page 4Linked to original sources
PubMed1988

Thrombin binding properties of insoluble modified polystyrene: Part II.

Antithrombin III (AT III) inhibits thrombin via an arginine-serine interaction. Insoluble polystyrene resins grafted with arginyl methyl ester have been synthesized, and their interaction with thrombin tested. One of these resins was selected for its high affinity for thrombin. In this paper we report the characteristics of this thrombin resin interaction. Using this substituted polystyrene resin as a support for affinity chromatography, we have compared the binding of thrombin with that of other proteins (prothrombin, Factor IXa, trypsin and AT III). It was found that 0.7 mg of highly purified human thrombin (2,100 U/mg) was bound to 1 g of resin. This could only be eluted at high ionic strength (1.5 M) and the amidolytic and clotting activities of the eluted thrombin remained unchanged. The binding of thrombin to the resin involves the active site of the enzyme but also other residues since, when DIP thrombin was used, the inactive enzyme could be eluted at lower ionic strength (1.0 M). This resin seems to be specific for thrombin because it does not bind the other serine-proteases (trypsin or Factor IXa), prothrombin (the inactive precursor of thrombin) or AT III. The arginyl residues of the resin are important for the specificity of the interaction with Factor IIa since prolyl residues are totally ineffective. Chromatography performed on such a resin is a very efficient method of purifying thrombin, and may be very useful for the removal of thrombin as a contaminant of plasma protein fractions.

Antithrombin III↗
PubMed1988

General toxicity of water-soluble iodinated contrast media. Pathogenic concepts.

Despite many studies, the mechanism of the general accidents induced by the intravascular injection of water-soluble iodinated contrast media remains unclear. Two theories are proposed; until now, they have not been related to each other. Lalli emphasizes the role of a cerebral impact related to stress, which induces a chain of accidents that are perhaps more aggressive when the molecules cross the blood-brain barrier. Lasser has proposed a theory based on the biochemical catastrophies secondary to the damage of the vascular endothelium and the activation of the Hageman's factor XII. A true anaphylaxis has not been proven: specific immunoglobulins are only exceptionally found, and an actual primary activation of the complement system pathway with mediator release is a controversial phenomenon in vivo. The anaphylactoid collapses result from a chemotoxic effect that might be decreased by several kinds of pharmaceutical premedications; none of them are constantly efficient. The new low osmolar molecules have a very low general toxicity, but their use does not guarantee the lack of anaphylactoid reactions.

Anaphylaxis↗
PubMed1988

Treatment of severe Epstein-Barr virus-induced polyclonal B-lymphocyte proliferation by anti-B-cell monoclonal antibodies. Two cases after HLA-mismatched bone marrow transplantation.

We treated two children who developed Epstein-Barr virus-induced polyclonal B-cell proliferation after HLA-mismatched bone marrow transplantation for congenital immunodeficiency with two monoclonal anti-B-cell antibodies. Lymphoproliferative syndrome occurred between 50 and 60 days after bone marrow infusion, and was diagnosed by the presence of spontaneously growing B cells containing Epstein-Barr-nuclear antigen in the blood and bone marrow. The mouse monoclonal anti-B-cell antibodies used were a CD21-specific antibody recognizing the CR2 receptor on B cells (BL13, IgG1) and a CD24-specific antibody binding B cells at all steps of differentiation (ALB9 IgG1). Both antibodies were given intravenously (0.2 mg/kg/body weight.d for 10 days). All clinical and biological manifestations resolved within 3 weeks of treatment. Recurrence was not seen at 18- and 15-month follow-ups. T-cell function developed normally; B-cell function remained partially deficient in one patient 21 months after bone marrow transplantation. These results suggest that monoclonal anti-B-cell antibodies could be useful in controlling severe polyclonal lymphoproliferative syndrome in profoundly immunodeficient patients after bone marrow transplantation.

Antibodies, Monoclonal↗
PubMed1988

Treatment of type III von Willebrand's disease with solvent/detergent-treated factor VIII concentrates.

An intermediate purity concentrate of factor VIII, treated with solvent and detergent (SD), was successfully used for treatment of intracerebral hematoma in a newborn with type III von Willebrand's disease. At the present time, the SD process used for the preparation of this factor VIII concentrate seems to be one of the most effective methods for viral inactivation. In this product, the biological properties of factor VIII and von Willebrand factor are preserved. Thus, the intermediate purity factor VIII SD concentrate could be used instead of frozen cryoprecipitate, as a safer therapy in the treatment of von Willebrand's disease.

Bleeding Time↗
PubMed1987

Comparative effect of heparin and heparan sulphate on two abnormal antithrombin III type 3 variants.

Two families were found with an antithrombin III that was unresponsive towards heparin (type 3 AT III variants). The abnormal species were purified using affinity chromatography on Sepharose bound anti-AT III antibodies. This yielded active proteins, as judged by their progressive antithrombin activities. In an attempt to explain the thrombotic tendency observed in this abnormality we compared the effect of heparin and heparan sulphate on these abnormal AT III, since, unlike heparin, heparan sulphate is a naturally occurring anticoagulant in the human. In normal plasma the heparan sulphate used in this study had a heparin-like activity of 50 U/mg by anti-F.XA and anti-F.IIa amidolytic assays. Full expression of the heparin cofactor activity in normal plasma could be obtained at a final concentration of 0.024 mg/ml of heparan sulphate (equivalent to 0.007 mg/ml of heparin). At this concentration of heparan sulphate the two abnormal AT III still exhibit a heparin cofactor activity below 10%. This absence of binding of heparan sulphate to abnormal AT III of type 3 could explain why some patients with this abnormality suffer from thrombo-embolic episodes while their AT III acts normally in the absence of heparin.

Adult↗
PubMed1987

Prothrombin Poissy: a new variant of human prothrombin.

A new congenital dysprothrombinaemia is described in a newborn baby girl who presented severe bleeding from the second day of life. Routine coagulation tests showed very prolonged prothrombin time and activated partial thromboplastin time with about 2% prothrombin activity in a one-stage assay. Staphylocoagulase and Echis carinatus venom prothrombin assays were respectively 35% and 25%. The prothrombin antigen level was 47% and its migration in crossed immuno-electrophoresis was abnormal. Family study revealed the presence of both normal and abnormal prothrombin in the plasma of three family members: the father, the mother and the brother. Thrombin generation in a system free from natural inhibitors showed that the abnormal prothrombin was slowly and incompletely activated. The propositus is thought to be homozygous for a 'lazy' dysprothrombin.

Blood Coagulation Disorders↗
PubMed1986

Absence of transplacental passage of pentosan polysulfate during mid trimester of pregnancy.

Eight women who were going to have an abortion between the 18th and 23 week of gestation for chromosomal abnormalities or haemoglobinopathies received intravenously 50 mg of pentosan polysulfate (PSP). Maternal results of haemostasis prior and after the injection of the drug were compared. Fetal coagulation parameters were tested on samples obtained by direct puncture of the umbilical cord under ultrasound guidance, 30 min after injection. Results were compared to those of normal fetuses at the same stage of gestation, obtained in the same conditions. In mothers' plasma, 30 min after injection, APTT was prolonged, factor Xa generation was markedly impaired, and factor V level was deeply decreased. By contrast, no modifications of these parameters were observed in fetal plasma, 30 min after the injection of PSP to their related mothers when compared to control fetuses. Thus the absence of biological modifications induced by PSP injection could demonstrate that this drug does not cross through the placenta.

Blood Coagulation↗
PubMed1986

Thrombin purification by one-step preparative affinity chromatography on modified polystyrenes.

Insoluble polystyrenes substituted with sulphonate and L-arginyl methyl ester have been synthesized. Using their specific affinity for thrombin, we developed a simple one-step chromatographic procedure for thrombin purification. As a control, insoluble polystyrenes substituted only with sulphonate groups were tested. The results obtained confirmed the importance of the arginyl residues grafted onto these polymers to obtain an affinity matrix useful for purifying thrombin with a high specific activity and a good recovery.

Chromatography, Affinity↗
PubMed1986

High-performance affinity chromatography of human thrombin on modified polystyrene resins.

Cross-linked polystyrenes modified with L-arginyl methyl ester mimic the binding site of antithrombin III and thrombin substrates. They can be used as stationary phases in high-performance affinity chromatography of thrombin. Under isocratic conditions, thrombin is strongly adsorbed on the resins when the sodium chloride concentration is lower than 0.5 M. The bound enzyme can be selectively desorbed when the salt concentration is raised to about 1.2 M. With a linear salt gradient, the specific elution of thrombin can be effected with a high recovery of its enzymatic activity. The decomposition products of thrombin, when treated with sodium dodecyl sulphate, are not retained by the stationary phase. The effects of the flow-rate and salt gradient slope on the adsorption and desorption of alpha-thrombin demonstrate the importance of kinetic parameters.

Adsorption↗
PubMed1986

Antithrombin III Alger: a new homozygous AT III variant.

A qualitative abnormality of antithrombin III (AT III) was found in the plasma of a 41-year old patient. The plasmatic AT III antigen concentration was 130% and the progressive anti-F IIa and anti-F Xa activities were normal (105% and 137%). The plasma heparin cofactor activity was less than 10%, when measured by F IIa or F Xa inhibition. Crossed immunoelectrophoresis of AT III in the presence of heparin revealed in the plasma an abnormal slow-moving peak. When tested by affinity chromatography on heparin Sepharose, this abnormal AT III did not bind to heparin. Among the investigated relatives, 5 subjects had normal AT III levels, whatever the test used, the nine others having reduced levels of antithrombin heparin cofactor activity (45-61%) but normal levels of immunoreactive AT III (97-122%). Consanguinity was found in the family history. We therefore considered our patient as homozygous for an AT III molecular abnormality affecting the binding site for heparin.

Adult↗
PubMed1986

Affinity chromatography of thrombin on modified polystyrene resins.

Insoluble polystyrenes substituted with sulphonate and L-arginyl methyl ester (PAOM) present substituents mimicking the reactive binding site of antithrombin III. These materials have a specific affinity for thrombin. The binding of the enzyme is reversible and the eluted thrombin remains active. Consequently, these resins can be used as stationary phases in affinity liquid chromatography in order to purify thrombin with a high biological activity. The influence of different characteristics of such polymers (substitution ratio, average particle size, affinity constant, synthesis conditions) on the purification performance is studied. Human prothrombin complex concentrate is activated and applied onto the gel. A purified human thrombin of high specific activity is separated with a high recovery of biological activity of the enzyme.

Chromatography, Affinity↗
PubMed1986

Pharmacokinetics of warfarin in the nephrotic syndrome and effect on vitamin K-dependent clotting factors.

The behavior of warfarin, a drug tightly bound to albumin, was studied in patients with nephrotic syndrome (NS) to assess the influence of hypoalbuminemia on its pharmacokinetics and its effect on vitamin K-dependent coagulation factors. A single dose of warfarin (8 mg) was given orally to 11 nephrotic patients with normal or nearly normal renal function and to 11 controls. In every subject the following measurements were performed: albuminemia before (t0) warfarin administration; plasma warfarin and vitamin K-dependent coagulation factors (FII, FVII, FIX, FX) levels, before and at time intervals from 0 to 48 h after drug administration; warfarin urinary excretion from 0 to 24 h. Urinary warfarin excretion was null in 19 out of the 22 subjects and very low in two nephrotic patients and in one control. Low serum albumin in NS patients induced a twofold increase of unbound warfarin vs controls (3.5% vs 1.8%, p less than 0.001) which led to a threefold increase in plasma clearance of warfarin (9.70 vs 3.26 ml X min-1, p less than 0.001); as warfarin distribution volume showed only a slight (non significant) increase in NS patients, the elimination half-life was thus markedly shortened in NS patients vs controls (18 vs 36 h, p less than 0.01). Maximum warfarin effect on vitamin K-dependent factor levels occurred at 18 h in controls and 24 h in nephrotics, and these lowest values were similar, in spite of a higher level at 0 in NS patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Comparison between the effect of pentosan polysulphate heparin and antithrombin III injections in antithrombin III deficient patients.

Pentosan polysulphate is an heparin analogue which acts via an antithrombin III (AT III) independent pathway. We compared the effect of this drug to that of heparin and AT III infusions in AT III deficient patients. Four patients with AT III congenital deficiency received on three different occasions: (i) an infusion of human AT III concentrate (20 U/kg or 40 U/kg), (ii) an intramuscular injection of pentosan polysulphate (2 mg/kg), (iii) a subcutaneous calcium heparin injection (100 U/kg). AT III infusion inhibits the excessive thrombin generation (46% of inhibition) observed in the plasma of AT III deficient patients during at least 12 hours, but does not modify the factor Xa formation. On the contrary, pentosan polysulphate has a marked effect on both thrombin (62% of inhibition) and factor Xa generation (57% of inhibition) still present 8 hours after injection. Heparin injection has the same effect, more prolonged, as pentosan polysulphate on thrombin generation but is not so effective on impairing factor Xa generation (27% of inhibition). The marked effect of pentosan polysulphate on thrombin and factor Xa generation in these patients is due to its AT III independent mechanism of action.

Antithrombin III↗
PubMed1985

Anticoagulant activity of dextran derivatives. Part II: Mechanism of thrombin inactivation.

The mechanism of anticoagulant activity of dextrans substituted with carboxylic and benzylamide sulphonate groups is studied by various coagulation tests. These derivatives exhibit a heparin-like antithrombic activity which requires the presence of antithrombin III; however they are less effective than heparin on a weight basis. They also exert a direct antithrombic activity by an antithrombic III independent pathway; but this action is negligible compared to the thrombin inhibition observed in the presence of antithrombin III. Dextran derivatives have been prepared with antithrombic properties similar to those of heparin.

Antithrombin III↗
PubMed1984

Antithrombic properties of insoluble modified polystyrene: Part I.

Chlorosulfonated polystyrenes grafted with arginyl methyl ester have been synthetized and characterized by elemental analyses. When suspended in plasma or in fibrinogen solutions, these insoluble polymers cause an increase in the thrombin clotting time. Consequently the antithrombin activity observed is not dependent upon to the presence of antithrombin III. Binding between the resin and thrombin can be demonstrated. An approximative value of the affinity constant is calculated: 2.3 X 10(6) 1/M. At high ionic strength, thrombin can be desorbed and exhibits normal coagulation properties. The prolongation of the thrombin time therefore can be attributed to the thrombin-resin interaction.

Absorption↗