Radioimmunoassays, development

Choice of Radioligand. A 11+C radiolabel will probably exist for most pesticides which will be considered for radioimmunoassay development. Such an intrinsic radiolabel will prove very valuable in titering antisera and possibly in numerous other steps from antigen synthesis through assay development. Unfortunately, for the actual assay, the commonly available 11+C radiolabels may not be of high enough specific activity. The theoretical limit on the specific activity of a single carbon atom is 63 mCi/mmole, and few pesticides have a specific activity of over 50 mCi/mmole even when they are labeled in... 

C. E. Cook, C. R. Tallent, E. Amerson, G. Taylor, and J. A. Kepler, Quirudine radioimmunoassay Development and characterization of antiserum. Pharmacologist, 17 A241 (1975). 

The prednisolone radioimmunoassay developed by Colburn and Buller (66) used an antiserum raised against prednisolone-21-hemisuccinate conjugated to... 

Another Radioimmunoassay method was reported for vinblastine and vincristine as follows ( 129) Radioimmunoassay developed for determining the neoplasm inhibitors vinblastine (I) and vincristine (II) in blood involves the use of antiserum raised in a rabbit immunized with (I) bovine... 

Glanzer, K. Appenheimer, M. Kruck, F. Vetter, W. Vetter, H. Measurement of 8-arginine-vasopressin by radioimmunoassay. Development and application to urine and plasma samples using one extraction method. Acta Endocrinol. (Denmark) 1984,106(Z), 317-329. 

The first immunoassay technique was the isotopic dilution radioimmunoassay, developed by Rosalyn Yalow and Solomon Berson for the detection of insulin in human blood. This work gained Yalow a share of the 1977 Nobel Prize for Physiology and Medicine, but Berson was not honored because of Nobel rules stating that the prize cannot be awarded posthumously. The following passage, translated from the presentation speech, explains the technique in simple terms ...As a result of mixing in a test tube a known quantity of radioactive insulin with a known quantity of antibodies against insulin, a... 

It is clear that the raising of antibodies to 6-oxo-PGF in rabbits and the use of this antisera for measuring 6-oxo-PGF by the uterus has been successful. The radioimmunoassay developed should also prove useful in measuring 6-oxo-PGF production by other tissues. 

Methods of detection, metabolism, and pathophysiology of the brevetoxins, PbTx-2 and PbTx-3, are summarized. Infrared spectroscopy and innovative chromatographic techniques were examined as methods for detection and structural analysis. Toxicokinetic and metabolic studies for in vivo and in vitro systems demonstrated hepatic metabolism and biliary excretion. An in vivo model of brevetoxin intoxication was developed in conscious tethered rats. Intravenous administration of toxin resulted in a precipitous decrease in body temperature and respiratory rate, as well as signs suggesting central nervous system involvement. A polyclonal antiserum against the brevetoxin polyether backbone was prepared a radioimmunoassay was developed with a sub-nanogram detection limit. This antiserum, when administered prophylactically, protected rats against the toxic effects of brevetoxin. 

Methodology. Several radioimmunoassays of human calcitonin (hCT) have been developed In the past 5 years (18-20). Their greatest utility has been In the definitive diagnosis of patients with medullary carcinoma of the thyroid gland (MTC) and, recently. In Identifying family members of these patients who have occult MTC. 

Utility. Insufficient data Is available on the measurement of 1,25(0H)2D3 for evaluation of Its utility In clinical medicine. A major breakthrough In methodology will be needed before routine application will be possible. This could come with the development of a battery of radioimmunoassays for the measurement of all of the vitamin D metabolites. So far, however, the development of antibodies to vitamin D and Its metabolites has been limited by apparently Irreversable changes In the Important B ring of the sterol which occur during Its conjugation to Immunogenic proteins. 

The first application of immunologically based technology to pesticides was not reported until 1970, when Centeno and Johnson developed antibodies that selectively bound malathion. A few years later, radioimmunoassays were developed for aldrin and dieldrin and for parathion. In 1972, Engvall and Perlman introduced the use of enzymes as labels for immunoassay and launched the term enzyme-linked... 

Since the development of radioimmunoassay (RIA), many assays that rely on the specificity of the antigen-antibody binding reaction have been developed because of their inherent sensitivity and specificity. A typical competitive binding... 

Antibody molecules have no inherent characteristic that facilitates their direct detection in immunoassays. A second important step in developing a successful immunoassay, therefore, involves the incorporation of a suitable marker . The marker serves to facilitate the rapid detection and quantification of antibody-antigen binding. Earlier immunoassay systems used radioactive labels as a marker (radioimmunoassay RIA) although immunoassay systems using enzymes (enzyme immunoassays EIA) subsequently have come to the fore. Yet additional immunoassay systems use alternative markers including fluorescent or chemiluminescent tags. 

Study of chemical pathways in method development. Isotope dilution methods. Radioimmunoassay very important in biochemistry and medicine. Neutron activation analysis used for trace elements in geo-chemistry, semiconductor technology, pollution studies and forensic science. Relative precision of counting 1% if 104 counts are recorded. Assessment of pollution by radionuclides. 

A most important technique which has been developed as an extension of the isotope dilution principle is that of radioimmunoassay (RIA). Analyses by this method employ substoichiometric amounts of specific binding immuno-chemical reagents for the determination of a wide range of materials (immunogens) which can be made to produce immunological responses in animals such as sheep or rabbits. It is possible to combine the specificity of an immunochemical reaction with the extreme sensitivity of radiotracer detection. Analytical methods based upon these principles have achieved wide applicability in the determination of organic compounds at trace levels. 

Table 10.1 A selection of compounds for which radioimmunoassays have been developed, indicating the wide applicability of the technique...

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