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      Volatile Alkanes and Increased Concentrations of Isoprene in Exhaled Air during Hemodialysis

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          In this study we examined breath volatile hydrocarbon concentrations in exhaled air of hemodialysis patients. We assessed both C<sub>2</sub>–C<sub>5</sub> alkanes – among them ethane and pentane the production of which in man is essentially due to the action free radicals exert on polyunsaturated fatty acids – and isoprene, an unsaturated hydrocarbon the biosynthesis and biological effects of which are the subject of controversy and mounting interest. Twenty patients were studied. Evaluation was performed intrapatient in the breath of patients with chronic renal failure, before and after dialysis (20 patients) and, in the same cases, during hemodialytic treatment (10 patients). Breath concentrations of these volatile hydrocarbons, determined before dialysis, were not different from those of normal subjects. Dialysis did not modify the levels of the C<sub>2</sub>–C<sub>5</sub> saturated hydrocarbons ethane, propane, butane and pentane. Instead, there was a marked increase in isoprene in all patients (basal values rose by a mean of 270%). Since isoprene was not present in the fluids or filters used for dialysis and there were only traces in the ambient air, the isoprene must have been produced endogenously during hemodialysis. As no situation has previously been reported to increase endogenous production of isoprene in humans, patients in hemodialysis offer a unique opportunity to investigate in depth the medical, biological and toxicological aspects of isoprene.

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          Most cited references 8

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          Characterization of aspen isoprene synthase, an enzyme responsible for leaf isoprene emission to the atmosphere.

           Shane Silver,  R Fall (1995)
          Isoprene (2-methyl-1,3-butadiene) is a volatile hydrocarbon emitted from many plant species to the atmosphere, where it plays an important role in atmospheric chemistry. An enzyme extracted from aspen (Populus tremuloides) leaves was previously found to catalyze the Mg(2+)-dependent elimination of pyrophosphate from dimethylallyl diphosphate (DMAPP) to form isoprene (Silver, G. M., and Fall, R. (1991) Plant Physiol. 97, 1588-1591). This enzyme, isoprene synthase, has now been purified 4000-fold to near homogeneity. The enzyme had a native molecular mass of 98-137 kDa and isoelectric point of 4.7 and contained 58- and 62-kDa subunits, implying that it is a heterodimer. Partial amino acid sequences of the two subunits indicated they are closely related to each other and that they do not share a strong homology with any other reported proteins. The isoprene synthase reaction was dependent on Mg2+ or Mn2+, and the reaction products were shown to be isoprene and pyrophosphate with a stoichiometry close to 1:1. The Km for DMAPP was high at 8 mM, and the kcat of 1.7 s-1 was low, but similar to those of other allylic diphosphate-utilizing enzymes. It is argued that the isoprene synthase reaction may be much more efficient in vivo, where it is under light-dependent control. It seems probable that this unique enzyme, rather than non-enzymatic reactions, can account for the emission of hundreds of millions of metric tons of isoprene from plants to the global atmosphere each year.
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            Reactive oxygen species and airway inflammation

             Peter Barnes (1990)
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              The potential of the hydrocarbon breath test as a measure of lipid peroxidation


                Author and article information

                S. Karger AG
                August 1999
                04 August 1999
                : 82
                : 4
                : 331-337
                aInstitute of Internal Medicine and Oncological Sciences, bInstitute of Biochemistry and Medical Chemistry, and cDepartment of Surgery and Surgical Emergencies, Perugia University, Perugia; dNephrology and Dialysis Unit, San Giovanni Battista General Hospital, Foligno, Italy
                45448 Nephron 1999;82:331–337
                © 1999 S. Karger AG, Basel

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                Page count
                Figures: 4, Tables: 1, References: 57, Pages: 7
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                Original Paper

                Cardiovascular Medicine, Nephrology

                Breath test, Isoprene, Alkanes, Hemodialysis


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