Browsing by Author "Evans, Mark"

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    Breath acetone concentration decreases with blood glucose concentration in type I diabetes mellitus patients during hypoglycaemic clamps
    (IOP Publishing, 2009-12-02T00:00:00Z) Turner, Claire; Walton, Christopher; Hoashi, Shu; Evans, Mark
    Conventional wisdom is that breath acetone may be markedly elevated in type 1 diabetes, but that this only occurs during poor blood glucose control and/or intercurrent illness. In contrast, little is known about breath acetone at more representative everyday blood glucose levels in diabetes. We used selected ion flow tube mass spectrometry to monitor the breath of eight patients with type 1 diabetes mellitus during 'insulin clamp' studies in which insulin and glucose were infused into patients to lower blood glucose levels in steps from normal values into the low glucose (hypoglycaemic) range. The concentration of acetone in breath and the blood sugar concentration of the patients were monitored at each blood glucose concentration. The blood glucose level at the start of the study was typically about 6 mM L-1, whereas the breath acetone concentration at this blood glucose level was unexpectedly variable, ranging from 1 part-per- million to 21 ppm, in contrast to what was previously believed, i.e. that type 1 diabetes mellitus is characterized by high acetone levels. In all eight patients, the breath acetone declined linearly with blood glucose concentration.
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    An exploratory comparative study of volatile compounds in exhaled breath and emitted by skin using selected ion flow tube mass spectrometry
    (John Wiley & Sons, Ltd, 2008-01-01T00:00:00Z) Turner, Claire; Parekh, Bhavin; Walton, Christopher; Španěl, Patrik; Smith, David; Evans, Mark
    This study examined the utilization patterns of key Carbon sources (CS, 24: including key sugars, aminoacids and fatty acids) in maize by strains of Aspergillus flavus and Fusarium verticillioides under different water activity (aw, 0.87-0.98 aw) and temperature (20-35°C) values and compared the niche overlap indices (NOI) that estimate the in vitro carbon source utilization profiles (Wilson and Lindow, 1994). The ability to grow in these key CS in minimal media was studied for 120 hrs in 12 hr steps. The NOI was calculated for inter-species (F. verticillioides – A. flavus) and for intra-species (A. flavus - A. flavus) using CS utilisation patterns over the range of interacting environmental conditions. 30°C, over the whole aw range examined, was found to be optimal for utilization of the maximum number of CS by A. flavus. In contrast, for F. verticillioides this was more so at 20°C; 25°C allowed a suboptimal usage of CS for both species. NOIs confirmed the nutritional dominance of A. flavus at 30°C, especially at lower aw levels and that of F. verticillioides at 20°C, mainly at 0.95 aw. In other conditions of aw, based on CS utilization patterns, the data indicated that A. flavus and F. verticillioides occupied different ecological niches. The variability in nutritional sources utilization between A. flavus strains was not related to their ability to produce aflatoxins (AFs). This type of data helps to explain the nutritional dominance of fungal species and strains under different environmental conditions. This could be useful in trying to find appropriate natural biocontrol microorganisms to compete with these mycotoxigenic