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Biomedical subjects

E Ezan

Publications and source records attributed to E Ezan.

49 records · Page 3Linked to original sources
PubMed1994

Effect of chronic converting-enzyme inhibition on kidney function of senescent hypertensive rats.

The age-related changes in the structure and the function of the kidney and the effect of chronic inhibition of angiotensin-converting enzyme (ACE) activity on these alterations were assessed in senescent, genetically hypertensive rats. Mean blood pressure was unchanged between 6 and 21 months, being 136 +/- 10 and 135 +/- 21 mm Hg, respectively. Hypertrophy of the glomeruli with a high incidence of glomerulosclerosis was reported in the 21-month-old animals. Renal blood flow, glomerular filtration rate, and filtration fraction were reduced between 6 and 21 months, whereas albuminuria and cGMP excretion were markedly enhanced with aging. Chronic ACE inhibition by administration of 0.3 mg/kg/day trandolapril from 18-21 months increased the life expectancy of the animals without affecting their mean blood pressure. The incidence of glomerular lesions and the excretion of enzymes that reflected the integrity of tubular and glomerular cells were not altered by ACE inhibition. On the other hand, the filtration fraction was restored in the 21-month-old treated animals, and the age-related albuminuria and rise in cGMP excretion were prevented by ACE inhibition. These results indicated that ACE inhibitor administered at the end of the life of senescent hypertensive rats was able to prevent some of the age-related changes in kidney function when glomerulosclerosis was already present.

Aging↗
PubMed1993

Enzyme immunoassay using a rat prolactin-alkaline phosphatase recombinant tracer.

This paper describes a competitive enzyme immunoassay of rat prolactin (rPrl) using a recombinant conjugate as a colorimetric tracer. rPrl was inserted into the N-terminal end of Escherichia coli alkaline phosphatase (AP), using an expression vector which allows insertion of foreign DNA sequences between codons +6 and +7 of the phoA gene. The assay was performed in 96-well microtiter plates coated with a mouse monoclonal antibody raised against rabbit immunoglobulin G. Each component (recombinant tracer, rabbit antiserum against rPrl, and rPrl standard) was added in a volume of 50 microL. The sensitivity of the assay was sufficiently high to allow titration of rPrl in plasma. The detection threshold was 15 pg (0.3 ng/mL) and the B/B0 50% value was 150 pg (3 ng/mL). The intraassay coefficient of variation was less than 10% over a wide range of rPrl concentrations (2.9-50 ng/mL). The interassay coefficient of variation was less than 15% for rat plasma samples in the concentration range of 4-40 ng/mL. The good parallelism observed between the standard curve and sample dilution curves showed that the immunoreactivity in rat plasma behaves like standard rPrl. Together with recovery experiments, these results indicated that assay without extraction is possible. A single immunoreactive peak that comigrates with standard rPrl is observed after molecular sieve fractionation of plasma samples. The reliability of the assay was confirmed by good correlation with conventional radioimmunoassay (r = 0.996, slope 0.978).

Alkaline Phosphatase↗
PubMed1993

Enzyme immunoassay for nomegestrol acetate in human plasma.

Currently available chromatographic assays of the progestative drug nomegestrol acetate in human plasma are not suitable for monitoring drug kinetics more than 24 h after clinical dosage. A specific and sensitive enzyme immunoassay was therefore developed. A 3(O-carboxymethyl)oxime derivative of nomegestrol acetate was synthesized and coupled to bovine serum albumin in order to raise polyclonal antibodies in rabbits. The enzymatic tracer was obtained by coupling the 3(O-carboxymethyl)oxime derivative to acetylcholinesterase (E.C.3.1.1.7.). HPLC fractionation of human plasma samples followed by enzyme immunoassay revealed the presence of cross-reacting metabolites. An automated procedure of metabolite separation was developed using silica bonded with diol groups (Diol Bakerbond column). This procedure ensured assay specificity. The quantification limit in human plasma was 0.1 ng/ml. Mean repeatability (intra-assay variation) and reproducibility (inter-assay variation) were 9 and 15%, respectively. The enzyme immunoassay allowed monitoring of the kinetics of nomegestrol acetate 144 h after oral administration of a single 5 mg dose. Values for human samples were in excellent agreement with those assayable by HPLC followed by u.v. detection.

Chromatography, High Pressure Liquid↗
PubMed1993

Enzyme immunoassays for a new angiotensin-converting enzyme inhibitor, zabicipril, and its active metabolite in human plasma: application to pharmacokinetic studies.

Zabicipril (S 9650) is a new angiotensin-converting enzyme inhibitor whose hydrolysis in vivo produces the pharmacologically active metabolite zabiciprilat (S 10211). Two competitive enzyme immunoassays specific for either zabicipril or zabiciprilat have been developed using acetylcholinesterase (E.C. 3.1.1.7) as label. Antibodies were raised in rabbits after immunization with lysil derivatives of zabicipril or zabiciprilat coupled with bovine serum albumin. Assays were performed in 96-well microtiter plates coated with a monoclonal antibody raised against rabbit immunoglobulin G, thus ensuring rapid separation of free and bound fractions of the tracer. The analysis does not require any extraction step. In the case of the assay of zabiciprilat, interference generated by endogenous angiotensin-converting enzyme (ACE) was eliminated by the addition of perindoprilat, another ACE inhibitor. Perindoprilat was not recognized by the antibodies (cross-reactivity < 0.01%) and did not affect assay efficiency. The specificity of the assays was checked by high-performance liquid chromatography of human plasma samples obtained after oral administration of 2 mg of zabicipril. No metabolites or endogenous substances were detected. The mean reproducibility was 15% for the assay of zabicipril and 19% for the assay of zabiciprilat. The quantification limits were 1.2 ng/ml for the zabicipril assay and 0.8 ng/ml for the zabiciprilat assay. These assays are therefore suitable for pharmacokinetic studies and drug monitoring in clinical studies.

Acetylcholinesterase↗
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↗
PubMedDate not supplied

Microdialysis study of bromocriptine and its metabolites in rat pituitary and striatum.

Bromocriptine, a D2 receptor agonist, was administered intravenously (1mg/kg) to anesthetized rats. Microdialysis probes were implanted in the pituitary and the striatum, known sites of D2 agonist action. Bromocriptine and its metabolites were monitored in plasma and tissue dialysates for 4 h. Drug analyses were performed using two different enzyme immunoassays specific for untransformed bromocriptine or a pool of parent drug plus hydroxylated metabolites. The metabolites/parent drug ratio for areas under the curve was 5.5 in plasma and 1 in the pituitary. No metabolites could be detected in the striatum. Bromocriptine penetration was at least 10-fold greater in the pituitary than in the striatum. The kinetics of bromocriptine in the pituitary and striatum did not parallel those in plasma, indicating that the prolonged action of bromocriptine reported by other authors may be due to slow dissociation from receptors.

Animals↗
PubMedDate not supplied

Pharmcokinetics in healthy volunteers and patients of NAc-SDKP (seraspenide), a negative regulator of hematopoiesis.

NAc-SDKP is a peptide being tested as a bone marrow hematopoiesis protector in chemotherapy trials in cancer patients. We studied the pharmacokinetics of NAc-SDKP in six healthy human volunteers and in five patients undergoing chemotherapy. Plasma concentrations of NAc-SDKP were monitored using a specific enzyme immunoassay. Because NAc-SDKP is an endogenous compound, a preliminary study was undertaken to determine intra- and interday baseline variations in healthy subjects. The baseline value (range 1.7-3.2 nM) differed between subjects, but was constant over time. The influence of the route of administration was studied in six healthy volunteers with 128 nmol/kg given as a 12-hr intravenous infusion or as a single subcutaneous or intramuscular injection. After cessation of intravenous infusion in healthy volunteers, NAc-SDKP was characterized by a quick elimination phase, with a mean half-life of 4.5 min. The volume distribution was 117 ml/kg and the area under the curve was 117 nM hr. After subcutaneous and intramuscular administrations, peak plasma drug concentrations occurred at 0.26 and 0.28 hr, with Cmax values of 156 and 110 nM, respectively. The bioavailabilities determined after subcutaneous and intramuscular administrations were 100 and 81%, respectively. NAc-SDKP pharmacokinetics was studied in patients after intravenous infusion over 48 hr of a dose of between 51.3 and 513 nmol/kg. Area under the curve values increased proportionately with the dose. Mean clearance was lower in patients than in healthy volunteers: 524 vs. 1120 ml/hr/kg, respectively.

Adult↗