Representative labeling, radionuclides

A specialized application of microwave-assisted organic synthesis involves the preparation of radiopharmaceuticals labeled with short-lived radionuclides, particularly for use in positron emission tomography [70-72]. This represented an excellent application of microwave technology, where the products must be prepared quickly and in high radiochemical yield, on a small scale. 

Besides gamma emitters of iodine and technetium and C radionuclides, representative of p-emitters, are often utilized in protein labeling. 

Research in nuclear and radiochemistry comprises Study of radioactive matter in nature, investigation of radioactive transmutations and of nuclear reactions by chemical methods, hot atom chemistry (chemical effects of nuclear reactions) and influence of chemical bonding on nuclear properties, production of radionuclides and labelled compounds, and the chemistry of radioelements - which represent more than a quarter of all chemical elements. 

The term specific activity has several meanings. It may refer to any one of the following radioactivity per unit mass of an element, radioactivity per mass of labeled compound, or radioactivity per unit volume of a solution. The denominator of reference must be specified. In terms of radioactivity per unit mass, the maximum specific activity attainable for each radionuclide is that for the pure radionuclide. For example, pure C has a specific activity of 62Ci/mol or 4400Ci/kg. As usually available, is a tracer for compounds in which it represents only a small fraction of the total carbon, most of which is the natm-aUy occurring mixture of stable and stable C. If there is no stable element present, the radionucfide is said to be carrier free. 

Physiological labeling can be accomplished either by direct injection of a radionuclide into the body of an animal or by utilizing, in the laboratory or field, bait labeled with a radionuclide. The direct method relies on the ability of the investigator to capture an animal, and there is the uncertainty that the animal is representative of the population of interest. The bait procedure does not require initial capture, but here again the question is whether or not the animal is representative of the population under study. Both methods require another capture of the animal if a mark-recapture estimate of the population is desired, including the various assumptions inherent in the method of estimation. If the objectives of a study involve movement of a mammal, one might collect feces to see whether they contain the tag, rather than capture the live animal. 

We will now consider the use of radionuclide labels in physiological studies of aquatic invertebrates and vertebrates. Of those that involve invertebrates, we will consider a study of coral, sea urchin, and water fleas, while studies that involve vertebrates are represented by those investigating processes in rainbow trout. 

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