Cell Assays Discretization

There should be specific, saturable binding to the receptor, accompanied by pharmacological characteristics appropriate to the functional effects, demonstrable using a radioactive, eg, tritium or iodine-125, ligand to label the receptor. Radioligand binding assays (1,6) have become a significant means by which to identify and characterize receptors and enzymes (see Immunoassays Radioactive tracers). Isolation of the receptor or expression of the receptor in another cell, eg, an oocyte can be used to confirm the existence of a discrete entity. 

Fluorescent labels, by contrast, can provide tremendous sensitivity due to their property of discrete emission of light upon excitation. Proteins, nucleic acids, and other molecules can be labeled with fluorescent probes to provide highly receptive reagents for numerous in vitro assay procedures. For instance, fluorescently tagged antibodies can be used to probe cells and tissues for the presence of particular antigens, and then detected through the use of fluorescence microscopy techniques. Since each probe has its own fluorescence emission character, more... 

This assay is a rapid one-step sandwich colorimetric immunoassay for quantitating histone-complexed DNA fragments (mono- and oligonucleosomes) with the size of discrete multiples of 180 bp in different types of cells in a microtiter plate (Boehringer Mannheim GmbH, Mannheim, Germany). 

As noted earlier, plasma from blood samples must be promptly stabilized and, if necessary, the acidified samples may be stored frozen at — 65°C. Because of the existence of oxyhemoglobin in whole blood or red cell suspensions, some consideration must be given to inactivate oxyhemoglobin or use an assay for total ascorbic acid content. With respect to tissue analysis, some discretion must be considered as to the degree of blood contamination. 

In mammalian cells, the genes are arranged on discrete chromosomes. There are many assays that have been developed in mammalian cells to measure the ability of specific chemicals and ionizing and UV radiations to induce damage to these chromosomes, referred to as chromosomal aberrations. In these assays, the cells are seeded, treated with the chemical... 

Some compounds may not actually reduce the amount of p24 released from the cell but cause the release of noninfectious virus particles. Such examples are the glycosidase inhibitors. In this assay, supernatants from the primary screen containing different concentrations of the drug are added to indicator cells and the extent of the CPE produced in the indicator cells gives a measure of the antiviral activity. C8166 and CEM cells form syncytia readily but MT2, MT4, and JM cells form syncytia that are more discrete and easier to count. 

Based on functional assays using cells transfected with the recombinant adrenoceptor, and on the effect of receptor environment on antagonist affinity, it has been proposed that the a,L adrenoceptor represents an affinity state of the adrenoceptor (Williams et al., 1996 Ford et al., 1997). This may explain why efforts to clone a discrete protein having characteristics have been unsuccessful. 

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