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At least 397 records · Page 22Linked to original sources
PubMed1985

Serodiagnosis of acute B hepatitis: comparison between a competitive binding radioimmunoassay and an enzyme linked immunosorbent assay for IgM antibody to hepatitis B core antigen.

The standard radioimmunoassay for anti-HBc (CORAB) was modified for the differential detection of anti-HBc IgM by incorporation of a step in which anti-HBc IgG was preferentially absorbed by Staphylococcus aureus cells (Protein A). The ratio (R) of anti-HBc IgM to total anti-HBc was evaluated by computing the ratio of sample cpm's after and before protein A absorption. The R values of acute B hepatitis ranged from 0.9 to 2.1 (mean 1.3 +/- 0.3) while those of chronic HBsAg carriers ranged from 3.1 to 8.3 (mean 4.9 +/- 1.1). Adopting 2.1 as the upper limit of R value for acute B infection, this modified CORAB was shown to have excellent correlation with enzyme immunoassay, and to be capable of differentiating acute from persistent HBV infection in HBsAg positive patients, and discriminating acute B hepatitis from non-A, non-B hepatitis in HBsAg negative but anti-HBc positive acute hepatitis.

Acute Disease↗
PubMed1976

Serum glycoproteins in the liver diseases. I. Studies on sialic acid-free glycoproteins-improved competitive binding assay of desialylated glycoprotein by rat liver plasma membrane.

An improved method for quantitation of desialylated glycoproteins was developed. The assay was carried out in non-saturating condition other than saturating condition which has been used by the other authors. In the present method a lower radioactivity in the assay solution can be used. Standard curves obtained by adding an increasing amount of desialylated alpha1-acid glycoprotein to the assay solution made it possible to measure desialylated glycoproteins equivalent to 5-200 ng of desialylated alpha1-acid glycoprotein. Desialylated alpha1-acid glycoprotein used for the assay could be prepared in large scale by hydrolysis with 0.1 N-H2SO4.

Animals↗
PubMed1975

[Comparative studies on the clinical accuracy of two "competitive-binding-assays" for the determination of effective serum thyroxine].

160 sera of patients with normal or disturbed thyroid function was tested by ETR (Byk-Mallinckrodt) and Quantisorb (Abbott) for their metabolically effective thyroxine concentration. In 124 cases the in vitro findings were correlated with extensive clinical data, which had permitted to establish a definite judgement of thyroid function. 5,5--13,5 mug% were considered as normal values with Quantisorb, 0,8--1,18 (see article) with ETR. A critical evaluation of the test results showed a better distinction between normal and abnormal thyroid function with Quantisorb, which explains also the higher diagnostic accuracy of this kit (92,75% : 85,5%). "Grey-zones" between normal and abnormal thyroid function were found with both tests, they were smaller, however, with Quantisorb than with ETR. The Quantisorb kit can therefore be recommended for routine function tests in vitro, although the slightly greater laboratory work should be considered.

Adenoma↗
PubMed2000

Characterization of histamine H3 receptors in mouse brain using the H3 antagonist [125I]iodophenpropit.

We have characterized the binding of the histamine H3 receptor antagonist [125I]iodophenpropit to mouse brain. [125I]Iodophenpropit saturably bound to mouse brain membranes with a pKd-value of 9.31+/-0.04 nM and a receptor binding density of 290+/-8 fmol per mg protein. Saturation binding analysis revealed binding of [125I]iodophenpropit to a single class of sites, showing linear Scatchard plots and Hill coefficients not different from unity (nH=0.98+/-0.02). At a concentration of 0.25 nM [125I]iodophenpropit, specific binding represented about 75% of the total binding. Competition binding curves for H3 receptor antagonists were fitted best to a one-site model, showing pKi-values in general accordance with the pA2-values obtained in mouse cerebral cortex. Displacement of [125I]iodophenpropit by the H3 receptor agonists (R)-alpha-methylhistamine, immepip, imetit and histamine were fitted best to a two-site model. Competition binding curves of (R)-alpha-methylhistamine showed a rightward shift upon incubation with GTPgammaS (10 microM), indicating the involvement of G-proteins in H3 agonist binding. In contrast, competition binding curves of the antagonists iodophenpropit, thioperamide and burimamide were not affected by GTPgammaS (10 microM). Autoradiographic experiments showed that [125I]iodophenpropit binding sites were heterogeneously distributed, similarly to the distribution of histamine H3 receptors reported in rat brain. Highest densities were observed in the cerebral cortex, the striatum, the nucleus accumbens, the globus pallidus and the substantia nigra. In conclusion, we have demonstrated that in mouse brain, [125I]iodophenpropit selectively binds to histamine H3 receptors. We also observed that the mouse brain H3 receptors labelled by [125I]iodophenpropit displayed binding characteristics and a distribution similar to rat brain.

Animals↗
PubMed1989

Identification and characterization of a homogeneous population of beta 2-adrenergic receptors on human alveolar macrophages.

Human alveolar macrophages obtained by bronchoalveolar lavage were studied with the high specific activity beta-adrenergic ligand [125I]pindolol and found to possess a moderate density of beta-adrenergic receptors. Using macrophage membranes, the receptor density (Bmax) was 42 +/- 9 fmol/mg protein with an apparent equilibrium dissociation constant (Kd) of 44 +/- 9 pM (mean +/- SEM). With intact macrophages, the Bmax = 5,643 +/- 942 sites/cell with Kd = 29 +/- 9 pM. Competition binding studies with subtype-specific antagonists revealed an exclusive population of beta 2-adrenergic receptors. Incubation of intact macrophages with the beta-adrenergic agonist isoproterenol caused a 6-fold increase in intracellular cyclic AMP (cAMP). Prostaglandin E1 and forskolin, which activate adenylate cyclase via different mechanisms, afforded typical marked increases in macrophage cAMP. Saturation binding, competition binding, and cAMP accumulation studies may all be performed from a single sample of about 2 x 10(7) cells, which can be obtained by bronchoalveolar lavage. This should facilitate studies of in vivo regulation of human alveolar macrophage beta-adrenergic receptors with regard to immune function and mediator release, and as a possible reflection of lung parenchymal receptors.

Adrenergic beta-Agonists↗
PubMed1976

[Measurement of thyroxine binding globulin by competitive ligand binding assay (CLBA) (author's transl)].

The competitive ligand binding assay (CLBA) first described by Chopra et al. ((1972) J. Clin. Endocrinol. Metab. 35, 565-573) is a convenient routine method for the accurate measurement of thyroxine binding globulin in large numbers of serum samples. The assay is based on the partition of a constant quantity of radiolabelled T3 between a fixed quantity of rabbit T3 antibodies and the thyroxine binding globulin of the serum, after prior removal of T3 and T4 from the serum with an anion exchange resin (Amberlite IRA 400). In euthyroid subjects serum thyroxine binding globulin was 25.5 +/- 5.0 mg/1, in hyperthyroid patients thyroxine binding globulin was significantly decreased to 13.0 +/- 4.0 mg/1 and was significantly increased in hypothyroid patients to 36.8 +/- 6.2 mg/1 as well as in pregnant women to 41.3 +/- 6.2 mg/1. No difference was found between normal subjects and young women taking contraceptive pills with low oestrogen content. There were significant negative correlations between the thyroxine binding globulin in serum on the one hand side and the free T4-and free T3-fraction on the other. The low thyroxine binding globulin estimates in hyperthyroid patients increased gradually to normal during treatment with thyroid blocking drugs, the elevated thyroxine binding globulin in hypothyroid patients decreased to normal during treatment with thyroid hormones. The competitive ligand binding assay used here seems to be convenient as a routine method for the precise and reproducible measurement of thyroxine binding globulin in serum.

Animals↗
PubMed1988

Graphical analysis of binding data reflecting competition between two ligands for the same acceptor sites.

A theoretical expression is derived for the analysis of results from competitive binding studies in which two multivalent ligands compete for acceptor sites, and a linear transform is suggested for simple graphical representation and assessment of experimental results. The protocol is illustrated by application to competitive binding data, obtained by ultrafiltration, on the interactions of bovine serum albumin with two structurally similar organic anions, methyl orange and methyl red. In a second experimental study the present approach is then used to establish that lactate dehydrogenase and aldolase compete for the same myofibrillar sites of bovine cardiac muscle. Finally, numerically simulated behavior of systems with additional binding sites for either ligand is used to emphasize that the criterion for classical (complete) competition is agreement between an experimentally determined equilibrium constant for ligand binding and the apparent value deduced from competitive binding studies. Nevertheless, the present analysis of competitive binding data should still offer considerable scope for screening quantitatively the cross-reactivities of drug and antigen analogs for their respective specific protein-acceptor sites.

Animals↗