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Biomedical subjects

J Amiral

Publications and source records attributed to J Amiral.

134 records · Page 8Linked to original sources
PubMed1984

A new method for the estimation of protein C by ELISA.

A new solid phase enzyme-linked immunosorbent assay (ELISA) was developed for the quantitation of human protein C antigen. Anti-protein C F(ab')2 fragments were adsorbed to polystyrene plates. The binding of serial dilutions of control or test plasma, containing protein C, was detected by incubation with peroxidase-labeled anti-protein. C-IgG followed by the addition of hydrogen peroxyde and 0-phenylenediamine. This ELISA is specific, sensitive (detection limit: 0.02%) and accurate (variation coefficient: 3 to 10%). When results are compared to those obtained by the Laurell technique (electroimmunodiffusion, EID), the correlation coefficient is 0.95 in all tested plasmas. Protein C antigen was measured by ELISA and EID in plasma from 40 controls, 14 patients with congenital protein C deficiency, 15 patients with liver cirrhosis and 40 dicoumarol-treated cases. In normal plasma, protein C ranged from 70 to 126%. In congenital deficiency, protein C was between 35 and 58% in 13 cases and 9% in one of them. In patients with liver cirrhosis and dicoumarol-treated cases, levels of protein C antigen were compared to those of other vitamin K dependent factors, i.e. Factors II and IX measured by EID and Factor X assayed by EID and ELISA. In liver cirrhosis, the amount of protein C was significantly lower than that of Factors II, IX and X. In short-term and long-term dicoumarol-treated patients, the highest correlation (r = 0.72) was observed between protein C and Factor X levels. In the plasma of patients undergoing oral anticoagulant therapy, protein C decreased more rapidly than Factors X or II and migrated in presence of calcium as a double peak, one with a normal mobility and one more anodal corresponding to the non carboxylated form of protein C.

Antigens↗
PubMed1984

Protein C level at birth.

The protein C level was determined, on cord blood, for 30 healthy newborns by electro-immuno assay using a monospecific antiserum. For the newborns the mean level of protein C related antigen is about one third of normal adults' mean level. There is a good correlation between Protein C related antigen and prothrombin related antigen. The low level of these vitamin-K-dependent proteins is probably a consequence of partial liver immaturity at birth. Using two-dimensional immuno-electrophoresis we were unable to detect subcarboxylated forms of protein C. However these abnormal forms could be seen in vitamin-K deficiencies of neonates.

Administration, Oral↗
PubMed1984

Assay of factor IX antigen using an enzyme immuno assay.

An Enzyme Linked immuno Sorbent Assay (ELISA) was developed for the measurement of factor IX:Ag. The results obtained in 90 control subjects, 56 hemophilia B patients and 40 patients under oral anticoagulant treatment were compared with factor IX:C and factor IX:Ag levels according to Electro Immuno-Assay (EIA). In healthy volunteers the mean factor IX:C level was 106.7 U/dl, the mean factor IX:Ag level was 96.8 U/dl according to EIA procedure and 101.5 U/dl according to ELISA method. Using ELISA, 10 hemophiliacs had no detectable antigen, and 13 had minute amounts of IX:Ag. All these patients are classified as B-. Among the others 21 had reduced antigen and are considered as BR and 12 had normal level of IX:Ag and are B+. Patients taking oral anticoagulants had not only a decreased factor IX:C level but also a reduced factor IX:Ag level which is always lower when using EIA procedure in the presence of EDTA than according to ELISA method.

Antigens↗
PubMed1984

Development and performance characteristics of a competitive enzyme immunoassay for fibrinopeptide A.

A simple nonisotopic method for the quantitation of FPA in biologic samples has been developed utilizing a competitive enzyme immunoassay technique. The performance characteristics of these assays have been investigated in both the experimental and clinical settings and were found to be satisfactory for the routine clinical application. This method is comparable to a commercially available RIA kit (Mallinckrodt, St. Louis, MO) in both the clinical and normal samples. This assay can be used in the diagnosis of hypercoagulable states associated with various diseases. Subclinical activation of coagulation can be readily assessed when the global tests, such as the prothrombin time, partial thromboplastin time, and thrombin time, have no value. This test is of value in the monitoring of the newer antithrombotic agents, such as the low molecular weight heparin fractions that do not effect the global assays, such as the partial thromboplastin time. Similarly, the risk of thrombosis associated with the use of procoagulant therapy, such as the activated prothrombin complex concentrates, can be readily assessed using this assay. It is proposed that the FPA measurement may also provide useful information on the quality control of various plasma-based therapeutic products, such as plasma concentrates or activated prothrombin complex concentrates. FPA generation tests are currently proposed for the screening of antithrombotic and prohemostatic agents.

Blood Coagulation Tests↗
PubMed1984

Application of enzyme immunoassays to coagulation testing.

Enzyme immunoassays are very useful for the detection of low concentrations of coagulation proteins and pathological markers in plasma. Analytes in the ng/mL range are measurable with good reproducibility with intra- and interassay CVs of less than 5% to 10%. "Sandwich" methods have been developed for von Willebrand factor (plasma concentration about 8 micrograms/mL, Factor IX (5 micrograms/mL), protein C (4 micrograms/mL), and Factor X (10 micrograms/mL). However, this technique is only suitable for macromolecules; for low-molecular-mass peptides such as fibrinopeptide A a competitive method is used. Normal concentrations of fibrinopeptide A are below 3 ng/mL, with greater values suggesting in vivo generation of thrombin; thus this test is quite useful in detecting thrombosis. Reagents for both the sandwich and competitive methods are commercially available and cost effective, and have a longer shelf-life than those for radioimmunoassays.

Binding, Competitive↗
PubMedDate not supplied

Standardization of immunoassays for antiphospholipid antibodies with beta 2GPI and role of other phospholipid cofactors.

Presence of beta 2 Glycoprotein I (beta 2GPI), in addition to phospholipids, is an absolute requirement for binding APA. This binding is frequently observed with beta 2GPI coated alone, however many APA react only with beta 2GPI complexed to phospholipids, but not with phospholipids alone. We demonstrate that a subgroup of rabbit polyclonal antibodies to human beta 2GPI binds to this protein only when it is coated on a solid surface, but not if it is in solution. In addition, beta 2GPI present in goat serum is strongly fixed by the coated phospholipids and the complexes formed bind as well APA as the rabbit antibodies to beta 2GPI. The diluent used for testing APA, has a strong incidence on APA's reactivity as it can be a source of beta 2GPI. Antibody binding to beta 2GPI, Prothrombin, Protein S, and Annexin V, coated in the presence or in the absence of phospholipids, was tested in 55 patients with the antiphospholipid syndrome. The strongest binding of antibodies was observed in 39 plasma to a mixture of phospholipids and purified human beta 2GPI, however 17 samples also presented a significant reactivity to beta 2GPI alone. Nine plasmas contained antibodies to Prothrombin, 4 to Protein S, 3 to Annexin V, and 1 to Protein C. We conclude that most of the APA are directed to a complex of beta 2GPI and phospholipids although in some patients antibodies to beta 2GPI alone or to other phospholipid binding proteins are present.

Animals↗