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March 10, 1951


JAMA. 1951;145(10):736. doi:10.1001/jama.1951.02920280048013

The availability of isotopes of many common chemical elements which may be followed in the animal organism has proved of great value in the medical sciences. Particularly is this true in investigations of the intricate processes of cellular metabolism. "Tracer" elements have made possible the elucidation of the metabolic pathways of many "essential metabolites," as is emphasized in a current review1 of this subject. Supplementary studies with various naturally occurring and artificially induced mutant strains of micro-organisms with their altered nutritional requirements have likewise proved of considerable aid in elucidating metabolic pathways.

In the review cited above, the Wisconsin investigators discuss the present knowledge of the metabolism of a number of specific "essential metabolites." The fact that two or more alternative pathways of metabolism are usually demonstrable is stressed. For example, studies with pyruvic acid labeled with radioactive carbon 14 as a "tracer" have demonstrated that at least eight