Rationale: Human skin contains photolabile nitric oxide derivates like nitrite and S-nitroso thiols, which after UVA irradiation, decompose and lead to the formation of vasoactive NO. Objective: Here, we investigated whether whole body UVA irradiation influences the blood pressure of healthy volunteers because of cutaneous nonenzymatic NO formation. Methods and Results: As detected by chemoluminescence detection or by electron paramagnetic resonance spectroscopy in vitro with human skin specimens, UVA illumination (25 J/cm 2 ) significantly increased the intradermal levels of free NO. In addition, UVA enhanced dermal S-nitrosothiols 2.3-fold, and the subfraction of dermal S-nitrosoalbumin 2.9-fold. In vivo, in healthy volunteers creamed with a skin cream containing isotopically labeled 15 N-nitrite, whole body UVA irradiation (20 J/cm 2 ) induced significant levels of 15 N-labeled S-nitrosothiols in the blood plasma of light exposed subjects, as detected by cavity leak out spectroscopy. Furthermore, whole body UVA irradiation caused a rapid, significant decrease, lasting up to 60 minutes, in systolic and diastolic blood pressure of healthy volunteers by 11؎2% at 30 minutes after UVA exposure. The decrease in blood pressure strongly correlated (R

A method is described for rapidly measuring the ethane concentration in exhaled human breath. Ethane is considered a volatile marker for lipid peroxidation. The breath samples are analyzed in real time during single exhalations by means of infrared cavity leak-out spectroscopy. This is an ultrasensitive laser-based method for the analysis of trace gases on the sub-parts per billion level. We demonstrate that this technique is capable of online quantifying of ethane traces in exhaled human breath down to 500 parts per trillion with a time resolution of better than 800 ms. This study includes what we believe to be the first measured expirograms for trace fractions of ethane. The expirograms were recorded after a controlled inhalation exposure to 1 part per million of ethane. The normalized slope of the alveolar plateau was determined, which shows a linear increase over the first breathing cycles and ends in a mean value between 0.21 and 0.39 liter Ϫ1 . The washout process was observed for a time period of 30 min and was modelled by a threefold exponential decay function, with decay times ranging from 12 to 24, 341 to 481, and 370 to 1,770 s. Our analyzer provides a promising noninvasive tool for online monitoring of the oxidative stress status. alveolar slope; breath analysis; cavity leak-out spectroscopy; lipid peroxidation; oxidative stress; washout AMONG THE VARIOUS VOLATILE hydrocarbons found in breath, the alkanes ethane (C 2 H 6 ) and pentane (C 5 H 12 ) have been extensively studied since they were identified as end products of the oxidative degradation (lipid peroxidation) of polyunsaturated fatty acids. The process of lipid peroxidation has gained interest as one of the important features of free radical-induced damage in biology and medicine (29). During peroxidation of omega-3 and omega-6 fatty acids, ethane and pentane, respectively, are formed and excreted via the lungs and thus can be detected in exhaled breath. Because lipid peroxidation is considered as the major, probably the only endogenous source of pentane and ethane, these volatile compounds may serve as specific markers for oxidative damage (8,25).The first report of breath ethane as a marker of in vivo lipid peroxidation was published by Riely et al. in 1974 (24). During the past decade, several studies provided evidence that ethane and pentane in exhaled air are useful markers of in vivo lipid peroxidation under certain clinical conditions (1-4, 8, 19, 20, 26, 27). Because pentane is metabolized in the liver, ethane is considered as the more reliable marker (10).Despite the growing number of reports on breath ethane and pentane, the development of rapid and sensitive analysis techniques for measurements of these markers in exhaled breath still remains a challenge. Ethane and pentane fractional concentrations in expired air are in the parts per billion (ppb; 1:10 9 ) range, which is below the detection limit of most analytical methods.The technique usually applied for quantifying these hydrocarbons in exhaled breath is gas chromatography (...

We report on a very fast fitting algorithm for single exponential functions which is based on the method of successive integration. The algorithm corrects the systematic error of trapezoidal integration. The new algorithm needs only 150 μs for a dataset of 1536 points and is around 700 times faster than the nonlinear Levenberg–Marquardt fit provided by LABVIEW. This makes it suitable for real-time instrumental use. Beside the better time resolution, the acceleration allows more averaging, which leads to higher precision. In our experiment instrumental sensitivity was improved by a factor of 3.7.

No abstract