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 If all you see are spots you need to have the CNRU Mass Spectrometry Core do your advanced research for you.
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Measuring Total Energy Expenditure in Nutrition Research.The CNRU Mass Spectrometry Core Facility offers assistance in methods development and mass spectrometry analysis to help researchers determine energy expenditure using doubly-labeled water stable isotope methods.Stable isotopes of hydrogen (deuterium oxide) and oxygen (oxygen 18) are routinely used to measure energy expenditure in free-living humans. The doubly-labeled water method using these isotopes is a form of indirect calorimetry that is completely safe, requires only periodic sampling of body fluids, is non-restrictive, and is ideally suited for measurement of energy expenditure in free-living or hospitalized patients. A typical energy expenditure study protocol using the doubly labeled water method starts with a baseline urine collection to determine pre-dose values for the hydrogen and oxygen isotopes. The subject is given a single oral bolus dose of heavy water (2H218O). After the administration of doubly labeled water (2H218O), the labeled hydrogen (2H2) is eliminated as water (2H2O), corresponding to water output, whereas the oxygen isotope would be eliminated as water (H218O) and as expired carbon dioxide (C18O2). By measuring the difference between the elimination rates of labeled oxygen and hydrogen, the carbon dioxide production rate can be calculated. The carbon dioxide production rate is then converted into energy expenditure using the respiratory quotient (RQ) of the food ingested during the observation period. Click for more information about the theory and models used for energy expenditure calculations. |
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