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Biomedical subjects

J Landon

Publications and source records attributed to J Landon.

At least 91 records · Page 5Linked to original sources
PubMed1983

A novel immunoradiometric assay for human liver ferritin.

Rivanol, the cationic salt of an acridine base, has been used as a novel separation procedure in an immunoradiometric assay for human liver ferritin. The separation step is based on the differences in charge and molecular weight between the labelled antibody-ferritin complex and free labelled immunoglobulins. The resultant assay is simple, reproducible and sufficiently sensitive to determine serum concentrations of ferritin.

Antigen-Antibody Complex↗
PubMed1983

Direct determination of primidone in serum or plasma by a magnetisable solid-phase fluoroimmunoassay.

A solid-phase separation fluoroimmunoassay for primidone in plasma or serum was developed using antibodies coupled to magnetisable cellulose/iron oxide particles and a fluorescein-labelled primidone derivative as tracer. Endogenous fluorophores and other potentially interfering components in serum samples were reliably and completely removed at the time the antibody-bound and free fractions were being separated. The separation and wash steps were greatly facilitated by use of magnetic sedimentation. The assay reached equilibrium within 30 minutes; all normal reliability criteria were satisfied; and the results correlated closely with those of an established enzymoimmunoassay method. The assay is specific for primidone, and no detectable interference by all other commonly employed anticonvulsants was found at serum levels of 1 g/l.

Animals↗
PubMed1982

A novel non-separation fluoroimmunoassay for thyroxine.

It has proved possible to develop a novel non-separation fluoroimmunoassay for thyroxine employing antibodies both to thyroxine and to fluorescein incorporated into immune complexes by addition of a common species-specific anti-immunoglobulin G serum. The labelled hapten could bind to antibody of either specificity but not to both at the same time. Binding to anti-fluorescein markedly reduced fluorescence whereas binding to anti-thyroxine did not. Unlabelled thyroxine competed with the labelled hapten only for anti-thyroxine binding sites and, as a result, more of the labelled thyroxine was bound to anti-fluorescein with a decrease in total fluorescence.

Animals↗
PubMed1982

Development of Fluoroimmunoassays for the determination of individual or combined levels of procainamide and N-acetylprocainamide in serum.

A fluoroimmunoassay has been developed for the simultaneous determination of serum levels of procainamide and its active metabolite N-acetylprocainamide. It employs procainamide linked through its aromatic amino group to fluorescein isothiocyanate as tracer and an antiserum raised against procainamide conjugated to human thyroglobulin through the same position. Separation is rapidly and simply achieved by covalently linking the antiserum to magnetisable microparticles and use of a magnet. Specific magnetisable particle fluorimmunoassays were also developed for procainamide and for N-acetylprocainamide by the use of suitable immunogens and fluorescein-labelled tracers. That for procainamide uses an antiserum raised to a procainamide-enzyme conjugate and fluorescein-labelled p-aminobenzoic acid while the fluoroimmunoassay for N-acetylprocainamide employs an antiserum against a N-acetylprocainamide-enzyme conjugate and fluorescein-labelled p-acetamidobenzoic acid.

Acecainide↗
PubMed1982

Salivary cortisol determination: adaptation of a commercial serum cortisol kit.

The determination of cortisol levels in saliva offers a number of significant advantages as compared with plasma or serum measurements, and radioimmunoassay is the technique of choice because of the greater sensitivity required. To date, the assay of salivary cortisol has been limited to only a few centres employing 'in-house' reagents. We describe some simple modifications of a commercial kit, designed for the assay of cortisol in serum and urine, which allow direct and rapid determination of the steroid in saliva. These modifications enable any laboratory with access to a gamma counter to perform large numbers of salivary cortisol assays at relatively low cost.

Adult↗
PubMed1982

Fluoroimmunoassay of digitoxin in serum.

This fluoroimmunoassay for digitoxin in serum involves use of a sheep antiserum to digitoxin coupled to magnetizable solid-phase particles and fluorescein-labeled 3-O-succinyl digitoxigenin as tracer. Sodium salicylate blocks binding of the drug by binding proteins, and endogenous fluorophores and other interfering components in serum samples are reliably and completely removed at the separation and wash steps, which are facilitated by magnetic sedimentation. The method is sufficiently sensitive, precise, and specific for application to routine monitoring of digitoxin therapy, and results correlate closely (r = 0.992) with those of an established radioimmunoassay.

Digitoxin↗
PubMed1981

A two-site immunofluorometric assay for human placental lactogen.

A two-site immunofluorometric assay for human placental lactogen (HPL) in serum has been developed. Samples and standards are incubated for 10 min with an excess of sheep anti-HPL serum covalently coupled to particles of magnetisable cellulose. After sedimenting the particles and adsorbed hormone on a magnet the supernates are aspirated (or decanted) to waste. An excess of purified sheep anti-HPL immunoglobulin, labelled with fluorescein, is added and, after a further 20 min, the fluorescence remaining in the supernates, after sedimenting the particles, is inversely related to the initial concentration of HPL. Results correlate closely with those of an established radioimmunoassay (r = 0.92), within- and between-assay coefficients of variation are less than 10% and, employing a 200 microliter sample volume, the assay extends from a minimum detection limit of 0.02 mg/l throughout the entire range of values encountered in pregnancy to more than 10 mg/l.

Female↗
PubMed1981

Magnetisable solid-phase fluoroimmunoassay of human immunoglobulin G in serum.

A simple fluoroimmunoassay is described for the determination of immunoglobulin G (IgG) in serum. It employs IgG labelled with fluorescein and magnetisable polyacrolein/iron oxide particles covalently linked to goat anti-human IgG serum. Diluted patient sample or standard and fluorescein-labelled IgG are incubated for 30 min with solid-phase antibody, the antibody-bound and free antigen separated simply by means of a magnet and the fluorescence in the supernate (free fraction) determined, which directly reflects the IgG concentration of the standard or sample. Correlation studies with two other immunological methods showed good agreement.

Animals↗
PubMed1981

Magnetisable solid-phase separation fluoroimmunoassay for total oestriol in pregnancy serum.

A rapid separation fluoroimmunoassay for serum or plasma levels of total oestriol in pregnancy was established, based on the use of fluorescein-labelled oestriol and sheep anti-oestriol serum covalently linked to magnetisable particles. Equilibrium was attained within 10 min, and the fluorescence of the bound fraction of labelled ligand was quantitated fluorimetrically after elution from the magnetisable particles. Results for pregnancy serum samples correlated well with an established radioimmunoassay technique and the sensitivity, precision and accuracy were appropriate for clinical use. Advantages of this system as compared with radioimmunoassay include the speed and simplicity of end-point detection, prolonged shelf-life of the labelled reactant and absence of any health hazard. The separation step enabled the removal of any endogenous fluorophores or other interfering factors present in biological samples.

Animals↗
PubMed1981

Effect of temperature on the radioiodination of human growth hormone.

Studies have been undertaken to assess the effect of altering the temperature at which human growth hormone is radioiodinated on the incorporation of 125 Iodine and the immunoreactivity and stability of the labelled hormone. Employing highly purified monomeric hormone it proved possible, by the iodogen procedure, to prepare a labelled product of high specific activity irrespective of temperature. However, in radioiodinations performed at ambient temperature (20 to 25 degrees) significant amounts of the labelled hormone were in an aggregated form which was less immunoreactive than the 125 Iodine-labelled monomeric hormone. Such aggregation was largely prevented by radioiodinating at low temperature (0 to 4 degrees) and even the large monomeric peak was more immunoreactive (about 95% bound in antibody excess) than the monomeric peak from iodinations performed at room temperature (maximum binding 87%, or less).

Binding Sites, Antibody↗
PubMed1981

Direct determination of propranolol in serum or plasma by fluoroimmunoassay.

A fluoroimmunoassay for the determination of serum of plasma levels of propranolol was developed using antibodies to propranolol coupled to magnetizable solid-phase particles and fluorescein-labeled propranolol as tracer. The method was sufficiently sensitive, precise, and specific for application to routine monitoring of propranolol therapy, and gave good correlation (r = 0.99) with a widely used ultraviolet fluorometric method in the assay of patients' specimens. The fluoroimmunoassay involves the same instrumentation as the fluorometric assay and has practical advantages, including greater sensitivity (only 100 microliters of sample required), avoidance of an extraction step, and visible-wavelength fluorometry, which permits the use of disposable plastic apparatus throughout the entire procedure.

Animals↗