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Biomedical subjects

A Ius

Publications and source records attributed to A Ius.

At least 19 recordsLinked to original sources
PubMed2001

Analytical performance of luminescent immunoassays of different format for serum daidzein analysis.

Two sensitive competitive-type solid-phase immunoassays for serum daidzein analysis have been developed and optimized. The first is a chemiluminescent enzyme immunoassay that uses black polystyrene microtiter wells in which daidzein-specific antibodies raised in rabbits are immobilized and a daidzein derivative is coupled to horseradish peroxidase (HRP) as a label. The HRP activity of the antibody-bound tracer is measured with an enhanced chemiluminescent system (luminol/H2O2/enhancer). The second immunoassay is based on the use of bovine serum albumin-daidzein derivative immobilized on microtiter plates and a secondary anti-rabbit IgG-Fc fragment conjugated with 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (BCPDA). Formation of the complex Eu3+-BCPDA enables time-resolved fluorescence-mode detection of the amount of antibody bound to the immobilized antigen. Both methods fulfilled all the requirements of accuracy and precision. The detection limit was the same for each method, 10 pg/well; this is better than that of other immunoassays. The specificity of the two methods was different, because of their competitive-type mechanisms. The performance of the chemiluminescence method is better, because the cross-reactivity of the main interfering compound (genistein) was 5%, compared with 25% for the time-resolved fluoroimmunoassay.

4-Butyrolactone↗
PubMed2000

Selectively conjugated melittins for liposome time-resolved fluoroimmunoassay of theophylline in serum.

Theophylline (Th) has been selectively conjugated to the four amino groups of melittin (Mel) by solid phase peptide synthesis. The cytolytic activity of the resultant Th-Mel compounds was tested on liposomes trapping the bovine serum albumin (BSA) conjugate with 4,7-bis(chlorosulfophenyl)-1,10-phenanthrol ine-2,9-dicarboxylic acid (BCPDA). The loss of lytic activity was the highest for Th-K7-Mel. Th-G1-Mel retains almost the same lytic activity as Mel. A homogeneous liposome time-resolved fluoroimmunoassay (LITRFIA) of Th in serum has been carried out with Th-G1-Mel between 5 ng and 10 microg.

Amino Acid Sequence↗
PubMed2000

Quantification of glycoalkaloids in tomato plants by time-resolved fluorescence using a europium chelator entrapped in liposomes.

In the control of tomato transgenic cultivars it is important to determine the glycoalkaloid content, which requires the screening of many samples. We have developed a simple method for the extraction and determination of glycoalkaloids in the leaf and fruit extracts of tomatoes using a europium chelator entrapped in phosphatidylcholine-cholesterol containing liposomes. The concentration values were quantified from liposome lysis effected by glycoalkaloid action. The fluorescent signal is linear between 1 and 10 micrograms of tomatine, which makes the method useful for the analysis of tomato samples.

Chelating Agents↗
PubMed1999

Time-resolved fluoroimmunoassay for delta(9)-tetrahydrocannabinol as applied to early discrimination of Cannabis sativa plants.

In the cultivations of Cannabis, it is important to be able to distinguish fiber-type plants from drug-type plants by an easy observation of their phenotype. This study required the screening of many samples for their cannabinoid content. A simple and highly sensitive time-resolved fluoroimmunological method was developed for the determination of Delta(9)-tetrahydrocannabinol in the leaf extracts. The useful range of the calibration curve was between 10 pg and 25 ng of standard. Matrix effects were minimized by a high dilution of samples.

Animals↗
PubMed1996

Evaluation of three immunoassays for detection of Toxoplasma-specific immunoglobulin G and M.

A time-resolved immunofluorometric assay of the IgG specific for Toxoplasma gondii has been compared with two commercial methods, one automated enzyme linked fluorescent assay (VIDAS) and one automated colorimetric enzyme immunoassay (BEIA). The coefficients of variation were 3.4% and 7.4% within-assay (n = 12), and 9.2% and 8.1% between-assay (n = 10) for two sera at low and high concentrations of specific IgG. The regression lines obtained with 96 samples were y = 1.04x + 2.1 and y = 0.98x - 1.1. We also compared a time-resolved capture fluoroimmunoassay for Toxoplasma-specific IgM with a commercial immunoenzymatic assay (BEIA TOXO-M). The sensitivity and specificity were 100%, calculated from assays of 78 samples.

Animals↗
PubMed1995

Comparison of time-resolved fluoroimmunoassay and immunoenzymometric assay for clenbuterol.

A time-resolved fluoroimmunoassay (TR-FIA) for the direct determination of clenbuterol residues in horse urine using a highly specific monoclonal antibody has been compared with an immunoenzymometric assay (IEMA). The sensitivity of both methods was 10 pg; the calibration curve was linear between 10 and 10(5) pg for the TR-FIA and between 10 and 10(4) pg for the IEMA.

Animals↗
PubMed1994

Determination of aflatoxin B1 in agricultural commodities by time-resolved fluoroimmunoassay and immunoenzymometric assay.

A time-resolved fluoroimmunoassay (TR-FIA) and an immunoenzymometric assay (IEMA) were applied for the measurement of aflatoxin B1 in soya seeds, dried figs and raisins. The extraction procedure was simple and no clean-up was found to be necessary. Limits of detection were 0.5 microgram kg-1 for TR-FIA (range of linearity of calibration graph 2.5-5 x 10(4) pg; inter-assay relative standard deviation Sr < 5%) and 0.2 microgram kg-1 for IEMA (linear range 1.0-5 x 10(3) pg; Sr < 11%).

Aflatoxin B1↗
PubMed1993

The effect of the concentration ratio of avidin and biotin on a single step sandwich enzyme immunoassay.

The interaction between biotin and avidin, used in a single-step enzyme-immunoassay for ferritin determination, has been studied. The antigen is simultaneously bound by an antibody coated to a polystyrene bead and by an antibody coupled to biotin which reacts with avidin conjugated to peroxidase. We have assessed the optimal ratio between avidin, conjugated to peroxidase, and biotin, coupled to antibodies, to give rise to the best signal for a quantitative enzyme-immunoassay. We have found that a careful balance between biotinylated antibody and conjugated avidin is necessary for our purpose and a biotinylated antibody excess should be avoided since it causes a signal decrease. This ratio is uninfluenced by both the presence and the absence of the antigen. Thus, an avidin-biotin single-step methodology, which has proved to be reliable for routine use, was developed.

Antigen-Antibody Complex↗
PubMed1993

Comparison of two time-resolved fluoroimmunoassays (TR-FIA), as applied to oestriol in human serum and progesterone in bovine milk.

We compared two time-resolved fluoroimmunoassay systems for measuring free oestriol in human serum and progesterone in bovine milk. By reading the fluorescence of europium complex of 4,7-bis(chlorosulphophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid in solution, the measuring range is increased for both oestriol (10-50,000 ng/l instead of 25-50,000 ng/l) and for progesterone (10-50,000 ng/l instead of 25-10,000 ng/l). In addition, the interassay coefficients of variation were lowered from 9.5 to 5.7% for oestriol and from 7.5 to 5.4% for progesterone, at the smaller hormone concentrations detectable by each method.

Animals↗
PubMed1992

Affinity of europium-labelled proteins A and G for immunoglobulin G from seven mammalian species.

Proteins A and G were each labelled with two different europium chelates (p-isothiocyanatophenyl-ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid). Their affinities for IgG from rabbit, goat, horse, sheep, mouse, pig, and rat were then measured using time-resolved fluorescence. Protein G labelled with the second chelate was found to be especially effective in binding to goat and horse IgG.

Affinity Labels↗
PubMed1990

Time-resolved fluoroimmunoassay of progesterone in milk.

A direct, solid-phase, time-resolved fluoroimmunoassay for progesterone in cow's and goat's milk, using europium-chelate-protein A as a label, is described. The coefficients of correlation with the results by RIA were 0.987 and 0.989.

Animals↗
PubMed1989

Evaluation of time-resolved fluoroimmunoassay with Eu-labelled protein-A for serum progesterone.

Progesterone has been assayed in several serum samples by a time-resolved fluoroimmunoassay (TR-FIA). The solid phase was 11 alpha-hydroxyprogesterone hemisuccinate bound covalently to ovalbumin and adsorbed on wells of polystyrene. The assay was based on competitive reaction of solid phase-bound hormone and samples with specific antibody labelled in situ with protein-A prelabelled with europium. The bound Eu was dissociated from the solid phase by an enhancement solution and measured by time-resolved fluorometry. The coefficient of correlation between TR-FIA and RIA was 0.97.

Europium↗