STABLE ISOTOPES IN BIOSCIENCES, THEIR MEASUREMENT AND MODELS FOR AMINO-ACID-METABOLISM

In order to follow the movement and quantify the metabolic fates of bi ologically important molecules in vivo, both tracers and kinetic model ing are required. For the study of intermediary metabolism in children , stable isotopically labeled substrates satisfy both the analytical a nd ethical requirements for tracer use in children. Stable isotope tra cers have been proven safe over more than a half-century of use in hum ans. In addition, mass spectrometric analysis of stable nuclide molecu lar position and isotopic enrichment in biological molecules is both h ighly specific and extraordinarily precise. Using stable isotope data to develop models of biological system dynamics in vivo is an essentia l element of estimating substrate events that take place in cells or o rgans otherwise inaccessible for ethical sampling in children. Further , modeling is also a critical component in the development and the tes ting of hypotheses about the structure of the biological system in que stion and the mechanisms which control its operational parameters.