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Biomedical subjects

E Ezan

Publications and source records attributed to E Ezan.

7 recordsLinked to original sources
PubMed1991

Practical method for optimizing radioimmunoassay detection and precision limits.

A model of the competitive radioimmunoassay standard curve, based on the Law of Mass Action, has been developed and used in conjunction with experimental and counting errors to predict the assay detection limit and precision profiles. We verified the model with hapten radioimmunoassays performed in our laboratory. The resulting computer program can be used to determine the optimum antiserum concentration--depending on its affinity--and labeled-antigen concentration--according to its specific activity and nonspecific binding. The graphical representation of this model provides radioimmunologists with a practical tool for assay optimization.

Antigen-Antibody Reactions↗
PubMed1991

Elimination of undesired cross-reactants by using mixtures of antibodies: experimental and theoretical evaluations of hapten radioimmunoassays.

This study shows that the specificity of radioimmunoassays can be improved by including a second antibody raised against an undesired cross-reactant. In a radioimmunoassay of prostaglandin E2 (PGE2) involving a monoclonal antibody, the cross-reactivity with 6-keto-prostaglandin E1 (6kPGE1) was decreased from 20% to 2% by including a high concentration of a polyclonal anti-6kPGE1. A similar increase in specificity was obtained in the assay of a larger hapten, luliberin (luteinizing hormone releasing hormone); the cross-reactivity of a luliberin analog was decreased 20-fold. Equations derived from the Law of Mass Action were used for the mathematical analysis and for the computer simulation of changes in assay affinity and specificity according to the quantity and quality of the mixed antibodies. The model gave values that agreed well with experimental data; it promises to be quite useful in designing specific radioimmunoassays.

Antibodies, Monoclonal↗
PubMed1990

Validation in rat plasma of a direct radioimmunoassay for a luteinizing hormone-releasing hormone antagonist (BIM 21009)

Rabbits were immunized with [Ac-D-beta-Nal1-, D-p-Cl-Phe2, D-Phe3, D-Arg6, Phe7, D-Ala10]LHRH (BIM 21009) coupled to bovine serum albumin using bis-diazotized benzidine. The best antiserum had an affinity of 5. 10(-10) M and a specificity directed against the C-terminal part of the molecule. The antiserum was not affected by native LHRH but reacted to some extent with detergents. Assay of free-peptide plasma after gel filtration on Ultrogel AcA 34 showed apparent immunoreactivity associated with albumin and lipoproteins. The sensitivity of direct assay was 0.4 ng/ml. Measurements of BIM 21009 after s.c. injection in rats showed the resistance of the peptide to elimination. The specificity of the determinations in plasma were checked by High Performance Liquid Chromatography.

Amino Acid Sequence↗
PubMed1989

Triton X-100 eliminates plasma proteins interference in a radioimmunoassay for luteinizing hormone-releasing hormone (LHRH) and LHRH analogues.

A method is described for the radioimmunoassay of native LHRH and DTrp6-LHRH, an LHRH analogue which does not require extraction of plasma samples. Interference by binding proteins normally present in plasma is removed by addition of Triton X-100 to the binding buffer at a concentration of 1% for LHRH and 0.15% for the LHRH analogue. This approach permits a direct estimation of the peptide level in unextracted plasma with quantitative recoveries for concentrations ranging from 0.015 to 10 ng/ml. Although the antiserum titre is reduced, the affinity of the antibody does not change at the detergent concentrations used in this study. This procedure is recommended for peptide assays in which the non-specific effects of plasma prevent a direct assay.

Animals↗
PubMed1986

ELISA for detection of human antibodies to Chlamydiae.

An enzyme-linked immunosorbent assay for the detection of human antibodies to Chlamydiae is described which exploits the cross-react properties between the genus-specific antigen of Chlamydiae and the ReLPS constituent of the outer membrane of a Salmonella minnesota mutant. Of 100 random sera tested by ELISA-ReLPS and immunofluorescence 78% showed an absolute correlation, 15% were positive in immunofluorescence and negative in ELISA and 7% were positive in ELISA and negative in immunofluorescence. Furthermore results obtained by the ELISA-ReLPS on 55 sera from patients with clinical evidence of Chlamydiae infection correlated well with the values obtained by an ELISA using Chlamydia-coated microtitration plates and by two immunofluorescence tests using Chlamydia trachomatis and Chlamydia psittaci as antigens. The method described here is sensitive, simple, reproducible and may be employed for epidemiological and pathogenetic studies of chlamydial infections.

Antibodies, Bacterial↗
PubMed1986

Radioimmunoassay of [D-Trp6]-luteinizing hormone-releasing hormone: its application to animal pharmacokinetic studies after single injection and long-acting formulation administration.

A sensitive radioimmunoassay (RIA) for [D-Trp6]-luteinizing hormone-releasing hormone (LHRH) has been developed. This assay allowed measurement of the LHRH analog in unextracted plasma with a minimum detectable concentration of 10 pg/ml. Validation of plasma assays was performed through Sep-Pak and HPLC purification. The in vivo fate of the peptide was investigated in dogs after subcutaneous or intravenous injections. In both cases, the LHRH analog showed longer plasma half-life than native LHRH with an elimination half-life superior to 80 min. Long-acting formulations were tested in dogs and rats: the day following administration, [D-Trp6]-LHRH plasma level rose to 2.9-4.6 ng/ml in dogs and 0.8-3.8 ng/ml in rats. From day 4 to day 30, [D-Trp6]-LHRH plasma level followed a plateau with concentrations of 0.3-0.8 ng/ml in dogs and 0.2-0.4 ng/ml in rats. In parallel, testosterone plasma concentration was reduced to castrate level between day 4 and day 7 in dogs and was significantly lowered in rats. This sensitive [D-Trp6]-LHRH RIA will be particularly useful for the evaluation of long-acting formulations in patients with advanced prostate cancer.

Animals↗