Radioactive indicators

The use of radioactive tracers was pioneered by Georg von Hevesy, a Hungarian physical chemist, who received the Nobel Prize in 1943 for his work on radioactive indicators (1). Radioisotopes have become indispensable components of most medical and life science research strategies, and in addition the technology is the basis for numerous industries focused on the production and detection of radioactive tracers. Thousands of radioactive tracers have been synthesized and are commercially available. These are used worldwide in tens of thousands of research laboratories. 

G. Hevesy, Radioactive Indicators, Interscience PubHshers, New York, 1948. 

After treatment of XXXVI with aqueous barium hydroxide, the liquor contained formic, methoxyacetic, and ethoxyacetic acids, methoxyacetone, and ethoxyacetone, produced by the two modes of cleavage XXXVIa and XXXVIb. Formic acid was converted with red mercuric oxide to carbon dioxide this was recovered as barium carbonate, the radioactivity of which was a measure of the C14 incorporated into Cl of kojic acid in the biosynthetic process. The alkoxyacetones were removed from the liquor by steam distillation, and converted to iodoform and a mixture of methoxy- and ethoxy-acetic acids. The iodoform was recovered by filtration its radioactivity indicated the proportion of C14 incorporated into C4. The alkoxy-... 

Hevesy, G. (1947). Radioactive indicators in turnover studies. Advances in Enzmol. 7, 111-214. 

Absorption in the gastrointestinal tract of triethanolamine administered orally to Wistar rats is rapid 63% of the dose disappeared from intestines within 65 min (Kohri et al., 1982). In dermal toxicity studies, the peak blood levels of [i C]triethanolamine were observed 2 h after its application in C3H/HeJ mice (2000 mg/kg bw), whereas in Fischer 344 rats (1000 mg/kg bw), the blood levels (expressed as radioactivity) indicated that triethanolamine was absorbed less rapidly than by mice. Data from various studies in mice and rats (1000-2000 mg/kg bw) suggest that absorption of dermally administered triethanolamine is almost complete in 24 h (Waechter Rick, 1988, cited in Knaak et a/., 1997). 

Oz, M.C., Newbold, J.E., and Lemole, G.M., Prevention of radioactive indicator and viral particle transmission with an ointment barrier, Infect. Control Hosp. Epidemiol., 12, 93, 1991. 

Dyestuffs have been very much employed for this purpose, as they can be easily estimated. Radioactive indicators have also been employed, and also gases. 

Many of the most popular methods for determining the surface area of powders and porous materials depend on the measurement of adsorption. The early work of Paneth (1922) involved the use of radioactive indicators and dye adsorption. It had been noted by Marc (1911) that the uptake of dye by an inorganic powder tended to approach a certain saturation level. Paneth set out to show that this level of maximum adsorption corresponded to the formation of a unimolecular layer. In spite of a number of unsolved problems, dye adsorption soon became one of the most widely used techniques for die study of fine powders. 

Because °Po is the daughter of °Bi, and because it has been produced by the neutron irradiation of °Bi, an established procedure for its separation has involved its precipitation from acid solution with H2S. Measurements of the radioactivity indicated that the precipitation was essentially quantitative. Suggestions that the precipitate was P02S3 did not survive the scratiny of experiment. 

Radiotracers (also called radioactive indicators) Traces of radionuclides (or labelled compounds) added to follow (trace) the fate of elements or compounds Specific activity (Radio)activity per mass unit [Bq/g or Bq/mol]... 

The amount of vitamin B12 in the serum sample is determined as follows. The amount of radioactive [ Co]cobalamin bound to the beads is measured. The purpose of using the beads is to facilitate the separation of bound P CoJcobalamin from the nonbound [ Co]cobalamin remaining in solution (floating around versus sinking to the bottom of the test tube). High levels of bound radioactivity indicate that the scrum sample contains low vitamin levels. Low levels of bound radioactivity indicate that the scrum contains high levels of vitamin. Plasma folate is... 

Cardiovascular diseases. Thallium-201 is used in the diagnosis of coronary artery disease. The isotope is administered intravenously and delivered to the heart muscle in proportion to the blood flow. Areas of restricted flow are observed as having lower levels of radioactivity, indicating some t)rpe of blockage. 

A kinetic study, using a radioactive indicator method, of the conversion of thiazolidine derivatives into mercaptoalkyl-ureas under basic conditions has been reported. ... 

In 1913, George Hevesy introduced the use of radioactive indicators when he used radioactive lead to track the movement of lead from the soil into plants and then back to the soil. He later extended these studies to living animals. In 1935, he showed how elements and molecules are taken up and released continually by living cells, a process called the dynamic state of body constituents. 

The same year, Hevesy invented the tracer principle, which made it possible to study chemical reactions without disturbing what was being measured. A radioactive indicator (tracer) could be given to a living organism or put in a test tube in amounts so small that there was no effect on the process under study. The tracer was exactly the same chemically as the molecule that it was tracing. 

When George Karl von Hevesy developed the technique of isotope dilution analysis (chapter 3), his source of lead isotopes was the natural decay of radioactive substances. In his 1944 Nobel lecture, Hevesy related his utopian wish from that period, some two decades earlier [Imagine] the great progress which might be expected if radioactive indicators of the common elements were made available to chemical and biological research. This was the discovery of the Joliot-Curies made in 1934, a... 

Detection limits based on the production of and the measurement of 40 disintegrations per second of radioactivity produced in an irradiation at a thermal neutron flux of at least 5 X 10 neutrons/cm sec. The length of the irradiation period is controlled by the half-life of the radioactive indicator for each species. 

The information given in this document shows that activation anidysis can be used in most studies investigating the role of trace elements and substances. Its capability of providing an isotopic identifier for an elemental species and the subsequent measurement of that radioactive indicator permits a better understanding of and offers a potential control of the biological functions of a trace element. 

The upper curve (a) represents TCA-soluble radioactivity in discs incubated in presence of CH. Identical values are obtained for total radioactivity (TCA-soluble + protein) in the control discs (- CH results not shown). The constant radioactivity indicates linear increase of total uptake with exogenous concentration of L-Phe. Por control discs the inverse relation betv/een amounts of labelled L-Phe in the protein and TCA-soluble fractions becomes very clear comparing curves b and e. 

The radioactive indicator is added to the unknown sample and isotope exchange is allowed to take place then the reagent is added in a substoichiometric but known quantity. After the reaction is complete, the phases are separated and activities measured. In those cases where the activity of the equilibrium solution is measured, the unknown concentration can be... 

Chromatographic methods are frequently used to separate radioactive nuclides and labeled compounds and can be used to analyze complex systems by using radioactive indicators. The principle of separation is the same as in standard chromatographic methods... 

An increase in radioactivity indicated by condenser air removal system monitors, and blowdown system monitors will reveal reactor coolant leakage through steam generators tubes to the secondary side. Routine analysis of steam generator secondary water samples will also indicate increasing leakage of reactor coolant into the secondary system. 

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