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  • 1
    ISSN: 1619-7089
    Keywords: Key words: Positron emission tomography ; 6-[18F]- fluoro-l-m-tyrosine ; Plasma metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. For the investigation of intracerebral dopamine metabolism, 6-[18F]fluoro-l-m-tyrosine (FmT) has been proposed as an alternative tracer that, unlike 6-[18F]fluoro-l-dopa, is not subjected to O-methylation. We have studied the time course of FmT and its labelled metabolites in plasma after intravenous injection into humans, employing a method that we have developed and validated to analyze labelled metabolites of FmT in plasma. The study population comprised 38 subjects, 14 of whom were taking an aromatic amino acid decarboxylase inhibitor (carbidopa), and obtained arterialized venous blood samples at various times after an intravenous injection of between 185 and 370 MBq of FmT. The major metabolite of FmT present in plasma was 6-[18F]fluoro-3-hydroxyphenylacetic acid. The time course of the fraction of radioactivity in plasma attributable to FmT was fitted well by the decay of two exponential functions. The fast component of the decay accounted for 40%–50% of the radioactivity and had a half-life of about 5 min. The slow component of the decay had a half-life of about 6 h in the subjects not taking carbidopa and 20 h in the patients taking carbidopa. When the total available FmT was calculated for each individual subject and expressed as a proportion of total radioactivity, this quantity did not differ significantly from that determined from the corresponding population mean. There was significantly more (15% on average) FmT available over the course of the 2-h experiment in the group pretreated with carbidopa. Our results demonstrate that the major metabolite in plasma after an intravenous injection of FmT is 6-[18F]fluoro-3-hydroxyphenylacetic acid. The clearance of FmT from plasma compares well with the clearance of intravenously administered levodopa. Carbidopa increases significantly the availability of FmT in plasma. These results verify, in a large number of human subjects, earlier analyses of FmT metabolism in other species. We validate a population-derived approach that can adequately describe the time course of FmT in plasma, alleviating the need for metabolite analysis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 69 (1997), S. 121-129 
    ISSN: 0268-2575
    Keywords: batteries ; nickel hydroxide electrodes ; metal hydride electrodes ; gas recombination ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: -This paper focuses on investigation of gas recombination in a positive-limited-sealed Ni-MHx cell. The positive electrodes were prepared by electrochemical impregnation of fibrous nickel plaques. The metal hydride negative electrodes were made by pasting the mixture of rare-earth hydrogen storage alloy powders, conducting and binding agents on foamed nickel substrates. The measurement of the positive capacity at different charge times was used to estimate the partial current for oxygen evolution at the same time. The effects of charge rate, electrolyte saturation level and initial state of charge of the positive electrodes on the recombination were investigated in sealed Ni-MHx cells. By determining the differential capacity of nickel hydroxide electrodes, an improved mathematical model was used to evaluate the gas recombination parameters during charge, overcharge, rest and discharge of the positive-limited-sealed Ni-MHx cell. The gas recombination during rest, discharge and overdischarge was also examined. The oxygen recombination on the nickel hydroxide electrodes can be neglected due to the consumption of water when the nickel hydroxide electrodes were discharged. The longer overdischarge produced an increase in cell pressure for the sealed Ni-MHx cell at an electrolyte unsaturated level and the evolving gas can be recombined by a following recharge operation. © 1997 SCI.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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