Whole body UVA irradiation lowers systemic blood pressure by release of nitric oxide from intracutaneous photolabile nitric oxide derivates.

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(2)=0.74) with enhanced plasma concentration of nitrosated species, as detected by a chemiluminescence assay, with increased forearm blood flow (+26+/-7%), with increased flow mediated vasodilation of the brachial artery (+68+/-22%), and with decreased forearm vascular resistance (-28+/-7%). CONCLUSIONS: UVA irradiation of human skin caused a significant drop in blood pressure even at moderate UVA doses. The effects were attributed to UVA induced release of NO from cutaneous photolabile NO derivates.

Intercomparison of infrared cavity leak-out spectroscopy and gas chromatography-flame ionization for trace analysis of ethane.

Comparison of two different methods for the measurement of ethane at the parts-per-billion (ppb) level is reported. We used cavity leak-out spectroscopy (CALOS) in the 3 microm wavelength region and gas chromatography-flame ionization detection (GC-FID) for the analysis of various gas samples containing ethane fractions in synthetic air. Intraday and interday reproducibilities were studied. Intercomparing the results of two series involving seven samples with ethane mixing ratios ranging from 0.5 to 100 ppb, we found a reasonable agreement between both methods. The scatter plot of GC-FID data versus CALOS data yields a linear regression slope of 1.07 +/- 0.03. Furthermore, some of the ethane mixtures were checked over the course of 1 year, which proved the long-term stability of the ethane mixing ratio. We conclude that CALOS shows equivalent ethane analysis precision compared to GC-FID, with the significant advantage of a much higher time resolution (<1 s) since there is no requirement for sample preconcentration. This opens new analytical possibilities, e.g., for real-time monitoring of ethane traces in exhaled human breath.

Ultra sensitive trace gas detection for biomedical applications.

We present an overview of our recent progress on spectroscopic trace gas detection for biomedical applications. The latest developments of cavity-enhanced spectroscopy as well as magnetic rotation spectroscopy lead to unprecedented sensitivity and specificity. The current detection limits of our laser spectroscopic approaches are in the picomolar to nanomolar range, depending on the molecular compound. The time resolution of the measurements is down to the sub-second range. This very high sensitivity and time resolution open up exciting perspectives for novel analytical tasks in biomedical research and clinical diagnosis.

Time resolved simultaneous detection of 14NO and 15NO via mid-infrared cavity leak-out spectroscopy.

We present a ring-down absorption spectrometer based on a continuous-wave CO laser in the mid-infrared spectral region near lambda = 5 microm. Using a linear ring-down cavity (length: 0.5 m) with high reflective mirrors (R = 99.988 %), we observed a noise-equivalent absorption coefficient of 3 x 10(-10) cm(-1)Hz(-1/2). This corresponds to a noise-equivalent concentration of 800 parts per trillion (ppt) for (14)NO and 40 ppt for (15)NO in 1 s averaging time. We achieve a time resolution of 1 s which allows time resolved simultaneous detection of the two N isotopes. The delta(15)N value was obtained with a precision of +/-1.2 per thousand in a sample with a NO fraction of 11 ppm. The simultaneous detection enables the use of (15)NO as a tracer molecule for endogenous biomedical processes.

Parts per trillion sensitivity for ethane in air with an optical parametric oscillator cavity leak-out spectrometer.

Spectroscopic detection of ethane in the 3-microm wavelength region was performed by means of a cw optical parametric oscillator and cavity leak-out. We achieved a minimum detectable absorption coefficient of 1.6 x 10(-10) cm 1/square root of Hz, corresponding to an ethane detection limit of 6 parts per trillion/square root of Hz. For 3-min integration time the detection limit was 0.5 parts per trillion. The levels are to our knowledge the best demonstrated so far. These frequency-tuning capabilities facilitated multigas analysis with simultaneous monitoring of ethane, methane, and water vapor in human breath.

Online recording of ethane traces in human breath via infrared laser spectroscopy.

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-1. 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 1770 s. Our analyzer provides a promising noninvasive tool for online monitoring of the oxidative stress status.