You Are What You Eat: Mass spectrometry in paediatric kinetic studies using stable isotopes

An overview will be presented about applications of stable isotopes in paediatric research. Mass spectrometry has proven to be an essential tool for unravelling kinetic studies in a large range of different research disciplines related to intestinal diseases, obesities, severe cerebral palsy, oxidative stress and foetal metabolism. Due to the diversity and complexity of the different metabolites involved in these studies, there is a high demand on sophisticated mass spectrometric instruments. Several new methods have been developed for measurement of isotopic labelled compounds in body fluids. 13C isotopic glucose enrichment in human plasma is analysed, using liquid chromatography isotope ratio mass spectrometry (LC/IRMS). Also new methods were developed for measuring the glutathione (GSH) fractional synthesis rate (FSR) in neonates after infusion of [1-13C]glycine as a tracer. For measuring energy expenditure and total body water composition in humans the doubly labelled water method is valuable technique. It usually involves blood or urine sampling, which might be difficult in neonates and children with cerebral palsy or other disabilities. We therefore aimed to validate a method making use of saliva samples analyzed by automated thermal conversion elemental analyzer in combination with isotope ratio mass spectrometry (TC/EA/IRMS). The different types of mass spectrometric instruments will be discussed here as well as several applications in paediatric research utilizing these techniques. The applications cover amino acid metabolism and body composition, energy expenditure, and the synthesis of specific proteins such as glutathione and albumin in different groups of children and even in foetuses. Finally, the aims and outline of this dissertation are covered

Een beschouwing over de waarde van verschillende onderzoekingsmethoden der booggangen

In dit proefschrift wordt gepoogd een inzicht te krijgen in de waarde van de vestibulaire onderzoekingsmethoden door middel van rotatoire en calorische prikkels. In een overzicht van de historische ontwikkeling van het rotatoire onderzoek wordt uitvoerig ingegaan op het onderzoek door middel van kleine gedoseerde draaiprikkels volgens Van Egmond, Jongkees en Groen, de cupulometrie. De grote betekenis van de onderzoekingen van de Utrechtse school wordt besproken

Milk protein oxidation in healthy subjects:A preliminary study

The role of protein oxidation in the regulation of whole body protein metabolism is unknown. Previously, it was observed that vigorous exercise led to increased protein oxidation. To further characterise 13C-milk protein oxidation in healthy subjects, the oxidation of ingested 13C-protein after an overnight fast was measured using a non-invasive 13C-protein breath test. This approach enables the analysis of 13C-protein oxidation kinetics and the effect of interfering factors. It was found that the estimated maximal 13C-milk protein oxidation was 0.07 g min−1, corresponding to a theoretical maximal oxidation capacity of ≈1.4 g kg body weight−1 d−1. No indications were found for preferential oxidation of non-essential amino acids. Combined ingestion of 30 g 13C-whey protein with 30 g glucose resulted in a 19% decrease of 13C-whey protein oxidation. It was concluded that exogenous 13C-whey protein oxidation can be affected by other co-ingested nutrients like glucose