Description (adapted from the application): The Clinical Metabolism Core provides the personnel, methodology, and instrumentation for the centralized analysis of stable isotopic enrichment of biochemical compounds using state-of-the-art GC-MS and NMR spectroscopic methods. This core will focus on metabolites (amino acids, glucose, glycogen, urea, and glucuronide conjugates) purified from plasma, liver, or urine by ion exchange chromatography, and then analyzed by 13C, 1H or 31P NMR spectroscopy or derivatized for combined GC-MS (Gas Chromatographic-Mass Spectrometric) analysis. The primary purpose of the Clinical Metabolism core is to: 1) to make GC-MS and NMR analyses available to DERC participants, 2) to save money and effort by reducing duplication of personnel required to program and operate the spectrometers, 3) to provide standardized procedures to insure the accuracy of sample analysis and 4) to assist DERC participants in the design and interpretation of experiments which require GC-MS or NMR analysis.