Measurement Of Nitric Oxide Concentration Research Articles

NO measurements in high temperature hydrogen flames: The crucial role of the hydrogen oxidation chemistry for accurate NO predictions

The current work investigates the formation of Nitric Oxide (NO) in hydrogen–air flames, over a wide range of flame temperatures. The use of hydrogen allows improved focus on the thermal-NO pathway by removing the complexity introduced by the prompt-NO pathway, which has been shown to be an important contributor to inaccurate predictions of absolute post-flame NO concentrations in hydrocarbon flames. This experimental study is conducted at atmospheric pressure using stoichiometric, premixed, laminar stagnation flames. Adiabatic flame temperatures ranging from 1600K to 2300K are achieved by varying the argon concentration in air. One-dimensional velocity, temperature, and NO concentration profiles are measured using non-intrusive laser diagnostics: Particle Tracking Velocimetry (PTV), NO multiline thermometry, and NO Laser Induced Fluorescence (NO-LIF), respectively. Results show that the experimental velocity profiles are incorrectly captured by the studied mechanisms, especially at low and high temperatures. This suggests that major inaccuracies are present in the hydrogen oxidation chemistry of the thermochemical models, regardless of their optimisation methodology. Furthermore, NO-LIF profiles show major discrepancies between all the studied mechanisms and the experiments, especially at elevated temperatures. The disagreement stems from an inaccurate description of the base chemistry of the models. These inaccuracies arise specifically from the description of the radical pool driving the flame behaviour and NO formation. This study demonstrates the need for model optimisation on experimental measurements using pure hydrogen 1D flames to obtain an accurate description of the hydrogen oxidation chemistry at play. This would lead to an improved description of the NOx sub-chemistry of any hydrogen, or hydrocarbon, combustion system.

Oral and nasal provocation test in chicken egg allergy—case report

IntroductionAllergy to chicken egg protein is a common form of food allergy. The most common clinical presentation includes gastrointestinal, skin, and respiratory symptoms. Differential diagnosis, including provocative tests, is critical in diagnosis.Case descriptionWe present a case of a 21-year-old patient with egg allergy, who underwent a double-blind food provocation test with placebo (evaluating subjective complaints from the gastrointestinal tract) and a titrated nasal provocation test using dry chicken egg content. We assessed the response of the nasal mucosa in the provocation test using the visual analogue scale (VAS), acoustic and optical rhinometry, as well as measurements of nitric oxide concentration in the exhaled air. During the provocation test, we measured the changes in the transverse section of the nasal passages, which were accompanied by subjective complaints measured with the VAS scale, using objective techniques. In the nasal provocation test with a dose of 20 µg of chicken egg protein, we observed an increase in the reactivity of the nasal mucosa and a decrease in the level of nitric oxide in the exhaled air from the upper airways (920 ppb before the provocation test and up to 867 ppb during the early stage of the allergic reaction). During the provocation tests, we recorded typical symptoms associated with the early stage of the allergic reaction; including nasal obstruction (1.2 cm), leakage of watery discharge (0.8 cm) in the food test, and itchy nose (1.1 cm) in the food test vs. the nasal test: 4.6, 2.8, and 3.5 cm, respectively.ConclusionsThe nasal mucosa provides convenient conditions for evaluation of the severity of allergy to common food allergens, including chicken egg allergens.

Nitric oxide concentration measurements in low-temperature, premixed hydrogen-air stagnation flames at elevated pressures

Understanding the formation of nitric oxide (NO) at elevated pressures closer to practical applications remains one of the challenges to improve nitrogen chemistry modelling. In the lean, premixed conditions favoured to mitigate the formation of thermal NO, secondary production pathways become significant. In an effort to better understand the importance of the NNH and N2O pathways, the present work reports NO concentrations obtained with laser-induced fluorescence (LIF) in near-stoichoimetric (ϕ=0.975), premixed, hydrogen-air stagnation flames at pressures of 2, 4, 6, and 8 atm. To minimize the formation of thermal NO and achieve stable flat flames, the premixed mixture is diluted with helium to maintain flame temperatures below 1800 K. Quantitative concentration measurements of ∼1.6–0.15 ppm are obtained as pressure, and dilution, increase. Particle tracking velocimetry (PTV) and multi-line NO-LIF thermometry provide velocity and temperature profiles, respectively, to complete the dataset. Experimentally-measured boundary conditions allow for direct comparison between simulations and experiments. Although discrepancy is observed between model predictions, recent thermochemical mechanisms exhibit a good agreement with the measured concentrations. Investigation of the formation mechanisms, performed with reaction pathway analysis, identifies the NNH pathway as the dominant production route with significant recycling of reactive nitrogen from NNH→N2O→N2. This recycling reduces with pressure as the pressure-dependent reaction of N2 with atomic oxygen is favoured. Limitations due to flame stability prevents investigations where a net production of N2O from N2 would be expected. This dataset, available for the development and validation of thermochemical mechanisms, is the first effort to measure NO concentration in supra-atmospheric hydrogen-air flames.

IS A DECREASED NITRIC OXIDE CONCENTRATION AFTER TRIAMCINOLONE ACETONIDE INTRAVITREAL INJECTION ONE OF THE REASONS FOR INTRAOCULAR PRESSURE RISE?

Diabetic macular edema is the most common cause of vision loss in patients affected by diabetes mellitus. For eyes with persistent retinal thickening despite anti-VEGF therapy, treatment with intravitreal triamcinolone may be considered, especially in pseudophakic eyes. The aim of this study was to examine aqueous humor nitric oxide concentration changes in pseudophakic eyes with persistent diffuse diabetic macular edema after intravitreal injection of triamcinolone acetonide, as well as the potential impact of these changes on the intraocular pressure values. In 10 pseudophakic eyes with persistent diffuse diabetic macular edema, paracentesis of anterior chamber with aspiration of aqueous humor and nitric oxide concentration measurements were done on the day of the intravitreal application of 20 mg triamcinolone acetonide, and after 1, 3, 6 and 9 months. Also, we were recording intraocular pressure values before the intravitreal triamcinolone acetonide injection and during the next 9 months. One month after the intravitreal triamcinolone acetonide injection, we noticed a decrease of nitric oxide concentration (45.37±5.55 µmol/L) by 31.79% compared to the initial values (66.52±7.66 µmol/L). After that, nitric oxide concentrations began to rise slightly, and at the end of the ninth month the mean nitric oxide concentration was similar to that recorded at the beginning of the study. Intraocular pressure values had increasing trend one month after the intravitreal triamcinolone acetonide injection (23.70±4.08 mm Hg) compared to the initial values (16.21±1.55 mm Hg), but after nine months these values returned to normal levels. Decreased concentration of nitric oxide could be one of the reasons for increased intraocular pressure after intravitreal application of triamcinolone acetonide in the treatment of diffuse diabetic macular edema.

Zero-dimensional and pseudo-one-dimensional models of atmospheric-pressure plasma jets in binary and ternary mixtures of oxygen and nitrogen with helium background

A zero-dimensional (volume-averaged) and a pseudo-one-dimensional plug-flow (spatially resolved) model are developed to investigate atmospheric-pressure plasma jets operated with He, He/O2, He/N2 and He/N2/O2 mixtures. The models are coupled with the Boltzmann equation under the two-term approximation to self-consistently calculate the electron energy distribution function. An agreement is obtained between the zero-dimensional model calculations and the spatially averaged values of the plug-flow simulation results. The zero-dimensional model calculations are verified against spatially resolved simulation results and validated against a wide variety of measurement data from the literature. The nitric oxide (NO) concentration is thoroughly characterized for a variation of the gas mixture ratio, helium flow rate and absorbed power. An ‘effective’ and a hypothetical larger rate coefficient value for the reactive quenching are used to estimate the role of the species N2(A3Σ, B3Π; v > 0) and multiple higher N2 electronically excited states instead of only N2(A3Σ, B3Π; v = 0) in this quenching. The NO concentration measurements at low power are better and almost identically captured by the simulations using the ‘effective’ and hypothetical values, respectively. Furthermore, the density measurements under the same operation conditions are also better predicted by the simulations adopting these values. It is found that the contribution of the vibrationally excited nitrogen molecules N2(v ⩾ 13) to the net NO formation rate gains more significance at higher power. The vibrational distribution functions (VDFs) of molecular oxygen O2(v < 41) and nitrogen N2(v < 58) are investigated regarding their formation mechanisms and their responses to the variation of operation parameters. It is observed that the N2 VDF shows a stronger response than the O2 VDF. The sensitivity of the simulation results with respect to a variation of the VDF resolutions, wall reaction probabilities and synthetic air impurity levels is presented. The simulated plasma properties are sensitive to the variation, especially for a feed gas mixture containing nitrogen. The plug-flow model is validated against one-dimensional experimental data in the gas flow direction, and it is only used in case an analysis of the spatially resolved plasma properties inside the jet chamber is of interest. The increasing NO spatial concentration in the gas flow direction is saturated at a relatively high power. A stationary O2 VDF is obtained along the direction of the mass flow, while a continuously growing N2 VDF is observed until the jet nozzle.

Relationship Between Air Pollution and the Concentration of Nitric Oxide in the Exhaled Air (FeNO) in 8-9-Year-Old School Children in Krakow.

The consequences of air pollution pose one of the most serious threats to human health, and especially impact children from large agglomerations. The measurement of nitric oxide concentration in exhaled air (FeNO) is a valuable biomarker in detecting and monitoring airway inflammation. However, only a few studies have assessed the relationship between FeNO and the level of air pollution. The study aims to estimate the concentration of FeNO in the population of children aged 8–9 attending the third grade of public primary schools in Krakow, as well as to determine the relationship between FeNO concentration and dust and gaseous air pollutants. The research included 4580 children aged 8–9 years who had two FeNO measurements in the winter–autumn and spring–summer periods. The degree of air pollution was obtained from the Regional Inspectorate of Environmental Protection in Krakow. The concentration of pollutants was obtained from three measurement stations located in different parts of the city. The FeNO results were related to air pollution parameters. The study showed weak but significant relationships between FeNO and air pollution parameters. The most significant positive correlations were found for CO8h (r = 0.1491, p < 0.001), C6H6 (r = 0.1420, p < 0.001), PM10 (r = 0.1054, p < 0.001) and PM2.5 (r = 0.1112, p < 0.001). We suggest that particulate and gaseous air pollutants impact FeNO concentration in children aged 8–9 years. More research is needed to assess the impact of air pollution on FeNO concentration in children. The results of such studies could help to explain the increase in the number of allergic and respiratory diseases seen in children in recent decades.

Back to basics – NO concentration measurements in atmospheric lean-to-rich, low-temperature, premixed hydrogen–air flames diluted with argon

Ideally, nitric oxide (NO) production pathways would be measured individually to understand the formation mechanisms at a fundamental level. Unfortunately, the four production routes in hydrocarbon combustion cannot be fully decoupled. Hydrogen combustion at low flame temperatures eliminates prompt-NO and mitigates thermal production, such that only the N2O and NNH pathways remain as significant production routes. The H2/O2 system, whose base chemistry has been studied in great detail, offers an excellent platform to validate nitrogen chemistry by limiting the possibility of error propagation during model calibration. The current work presents measurements of velocity, temperature, and NO concentration in premixed, jet-wall stagnation, hydrogen–air flames at atmospheric pressure, diluted with argon to maintain adiabatic flame temperatures below 1800 K. Measurements of reference flame speeds, Su,ref, obtained with particle tracking velocimetry, highlight the modeling differences in H2/O2 chemistry from a selection of thermochemical mechanisms, especially in lean flames affected by preferential diffusion. Laser induced fluorescence measurements in lean-to-rich flames (ϕ=0.7–1.5) yield concentrations of NO from 2 to 0.5 ppm, respectively. Simulated NO profiles cover one order of magnitude in predicted signal intensity. Fortunately, recent mechanisms with accurate descriptions of the N2O and NNH pathways predict NO concentrations within experimental uncertainties for multiple operating conditions.

The impact of ivacaftor on sinonasal pathology in S1251N-mediated cystic fibrosis patients.

ImportanceSinonasal symptoms in patients suffering from cystic fibrosis can negatively influence the quality of life and sinuses can be a niche for pathogens causing infection and inflammation leading to a decrease of lung function. Ivacaftor, a potentiator of the Cystic Fibrosis Transmembrane Conductance Regulator protein, has shown improvement in pulmonary function in cystic fibrosis patients with different forms of class III gating mutations. However, the effects of ivacaftor on sinonasal pathology have hardly been studied.ObjectiveTo determine the impact of ivacaftor therapy on sinonasal pathology in patients with cystic fibrosis with an S1251N mutation.DesignProspective observational mono-center cohort study, between June 2015 and December 2016.SettingA tertiary referral center in Utrecht, The Netherlands.ParticipantsEight patients with cystic fibrosis with an S1251N mutation, treated with the potentiator ivacaftor were investigated.ExposuresIvacaftor (Kalydeco, VX-770) therapy. Computed tomography imaging of paranasal sinuses. Nasal nitric oxide concentration measurements and nasal endoscopy.Main outcomes and measuresPrimary outcome is opacification of paranasal sinuses examined with computed tomography scan analysis and scaled by the modified Lund-Mackay score before and one year after treatment. Secondary outcomes are nasal nitric oxide concentration levels, sinonasal symptoms and nasal endoscopic findings before and approximately two months and in some cases one year after treatment.ResultsComputed tomography scan analysis showed a significant decrease in opacification of the majority of paranasal sinuses comparing the opacification score per paranasal sinus before and after one year of treatment with ivacaftor. Median nasal nitric oxide levels significantly improved from 220.00 (IQR:136.00–341.18) to 462.84 (IQR:233.17–636.25) (p = 0.017) parts per billion. Likewise, the majority of sinonasal symptoms and nasal endoscopic pathology decreased or resolved at two months after the use of ivacaftor.Conclusion and relevanceIvacaftor appears to improve sinonasal outcome parameters and thereby sinonasal health in patients with cystic fibrosis with an S1251N mutation.

Clinical Utility Of The Exhaled Nitric Oxide (NO) Measurement With Portable Devices In The Management Of Allergic Airway Inflammation And Asthma.

Nitric oxide (NO) is a potential bioactive gas produced continuously and constantly in the airways of healthy subjects. In allergic airway inflammation, the level of exhaled NO is usually increased and mediated by inducible nitric oxide synthase (iNOS) enzyme presenting in the epithelium and different inflammatory cells. The measurement of NO concentration in the airway is possible with portable devices which use an electroluminescence technique. In subjects with upper airway with allergic inflammation such as in allergic rhinitis, the measurement of nasal NO (nNO) may help to diagnose and manage the disease. In the lower airway, increased fractional exhaled NO (FENO) reflects directly the inflammatory process that occurs in the airways that are typically seen in asthma. It has been shown that there is a strong correlation between FENO levels and increased activity of airway inflammation mediated by immuno-allergic cells and mediators. Thus, FENO has higher specificity and sensitivity than other methods in diagnosing the severity of inflammation in asthmatic patients. Moreover, the correlation between increased FENO levels and a high risk of bronchial hyperresponsiveness has also been demonstrated. FENO is also a relevant biomarker to evaluate asthma status due to the change of its values occurring earlier than clinical manifestations and spirometry parameters. In addition, the measurement of FENO with portable devices helps to support the diagnosis of asthma, to follow-up the control of asthma and to personalize asthmatic patients for target treatment with biologic therapy. Therefore, measuring FENO with portable devices in the diagnosis and treatment of allergic airway inflammation, especially in asthma, is one of the most essential applications of NO biomarkers in exhaled breath.

Imaging the nonreactive collisional quenching dynamics of NO (A2Σ+) radicals with O2 (X3Σg -).

Nitric oxide (NO) radicals are ubiquitous chemical intermediates present in the atmosphere and in combustion processes, where laser-induced fluorescence is extensively used on the NO (A2Σ+ ← X2Π) band to report on fuel-burning properties. However, accurate fluorescence quantum yields and NO concentration measurements are impeded by electronic quenching of NO (A2Σ+) to NO (X2Π) with colliding atomic and molecular species. To improve predictive combustion models and develop a molecular-level understanding of NO (A2Σ+) quenching, we report the velocity map ion images and product state distributions of NO (X2Π, v″ = 0, J″, Fn, Λ) following nonreactive collisional quenching of NO (A2Σ+) with molecular oxygen, O2 (X3Σg -). A novel dual-flow pulse valve nozzle is constructed and implemented to carry out the NO (A2Σ+) electronic quenching studies and to limit NO2 formation. The isotropic ion images reveal that the NO-O2 system evolves through a long-lived NO3 collision complex prior to formation of products. Furthermore, the corresponding total kinetic energy release distributions support that O2 collision coproducts are formed primarily in the c1Σu - electronic state with NO (X2Π, v″ = 0, J″, Fn, Λ). The product state distributions also indicate that NO (X2Π) is generated with a propensity to occupy the Π(A″) Λ-doublet state, which is consistent with the NO π* orbital aligned perpendicular to nuclear rotation. The deviations between experimental results and statistical phase space theory simulations illustrate the key role that the conical intersection plays in the quenching dynamics to funnel population to product rovibronic levels.

Instantaneous planar measurements of nitric oxide concentration in a turbulent n-heptane spray flame

Instantaneous and mean nitric oxide (NO) concentrations are measured in a turbulent, lifted, n-heptane jet spray flame at an atmospheric pressure using planar laser-induced fluorescence (PLIF). The flame-front is simultaneously located using OH-PLIF. The NO excitation line with the least temperature-quenching dependence is selected, and the associated NO-LIF dependence is corrected. LIF optimization and data reduction are based on previous work [Mulla et al. Combust. Flame 203 (2019) 217–229] where the NO-LIF signal was simulated at the spray flame condition (temperature and gas composition from LES) using a spectroscopic model. In the present work, to reduce interferences from polycyclic aromatic hydrocarbons (PAH) and soot, the detection bandwidth is progressively reduced from broadband (F6), intermediate (F3), to narrowband (F1). F6 results in a significant interference, while F1 contains the least interference. Instantaneous NO mole fraction (χNO) is deduced from F1 dataset using a novel instant-wise mapped interference subtraction approach (F1-Inst). The conditional mean NO concentrations derived from F6, F3, F1, and F1-Inst are in agreement (within uncertainty limits); however, F1-Inst appears to be the most reliable. Instantaneous flame-structure (OH) and NO concentration fields are analyzed. The spray flame structure consists of the inner (B1) and outer (B2) flame branches. Local extinctions are observed along B1. Small-scale (<1 mm) extinctions do not alter the NO concentration, whereas large-scale extinctions result in a sharp (50–100%) χNO drop, possibly due to a reduced temperature. Instantaneous χNO along B2 shows a sharp growth until 55 mm height above burner (HAB), beyond which the growth saturates. The deceleration of NO growth and χNO reduction near the sooting region is most likely due to the soot-radiation induced temperature drop. Mean χNO along B1 measures ∼ 25 ppm with a small axial variation (20–30 ppm). Expected lower temperature and nearly constant χNO with residence time suggest the nitrous oxide and prompt NO formations routes. Mean χNO in the outer diffusion branch (B2) increases from 35 ppm at the flame-base to 75 ppm at 60 mm HAB. The NO growth and potentially high temperature in B2 indicate the thermal route of NO formation.

염증 유도제에 의한 바지락 Ruditapes philippinarum 치패의 nitric oxide 농도의 변이

염증 유도제에 의한 바지락 Ruditapes philippinarum 치패의 nitric oxide 농도의 변이

Performance of Amperometric Platinized-Nafion Based Gas Phase Sensor for Determining Nitric Oxide (NO) Levels in Exhaled Human Nasal Breath.

Nitric oxide (NO) levels in exhaled breath are a non-invasive marker that can be used to diagnose various respiratory diseases and monitor a patient's response to given therapies. A portable and inexpensive device that can enable selective NO concentration measurements in exhaled breath samples is needed. Herein, the performance of an amperometric Pt-Nafion-based gas phase sensor for detection of NO in exhaled human nasal breath is examined. Enhanced selectivity over carbon monoxide and ammonia is achieved via an in-line zinc oxide-based filter. Exhaled nasal NO levels measured in 21 human samples with the sensor are shown to correlate well with those obtained using a chemiluminescence reference method (R2 = 0.9836).

NO formation in premixed flames of C1–C3 alkanes and alcohols

The influence of alkane and alcohol molecular structures on nitric oxide (NO) pollutant formation trends is investigated through the study of C1–C3 alkanes and alcohols in premixed stagnation flames at atmospheric pressure. The flame diagnostics consist of one-dimensional (1-D) Planar Laser-Induced Fluorescence (PLIF) for measurements of NO and CH concentrations, 1-D NO-LIF thermometry, and 1-D Particle Tracking Velocimetry (PTV) for the determination of flame reactivity and burning rates. The results show that alcohols produce less NO than their alkane equivalents. This behaviour is linked to the lower flame temperatures of alcohol flames and the tendency of alcohols to produce lower concentrations of the CH radical, due to inhibition of the formation of methyl groups. These trends are captured in the available thermochemical models; however, there are discrepancies regarding the formation pathways of NO and its intermediates which are linked to variability in model rate coefficients. Further adjustments to all of the thermochemical models are needed to accurately capture the nature of NOx pollutant formation in premixed alkane and alcohol flames, and this experimental study provides target data for this effort.

Online Measurement of Exhaled NO Concentration and Its Production Sites by Fast Non-equilibrium Dilution Ion Mobility Spectrometry.

Exhaled nitric oxide (NO) is one of the most promising breath markers for respiratory diseases. Its profile for exhalation and the respiratory NO production sites can provide useful information for medical disease diagnosis and therapeutic procedures. However, the high-level moisture in exhaled gas always leads to the poor selectivity and sensitivity for ion spectrometric techniques. Herein, a method based on fast non-equilibrium dilution ion mobility spectrometry (NED-IMS) was firstly proposed to directly monitor the exhaled NO profile on line. The moisture interference was eliminated by turbulently diluting the original moisture to 21% of the original with the drift gas and dilution gas. Weak enhancement was observed for humid NO response and its limit of detection at 100% relative humidity was down to 0.58 ppb. The NO concentrations at multiple exhalation flow rates were measured, while its respiratory production sites were determined by using two-compartment model (2CM) and Högman and Meriläinen algorithm (HMA). Last but not the least, the NO production sites were analyzed hourly to tentatively investigate the daily physiological process of NO. The results demonstrated the capacity of NED-IMS in the real-time analysis of exhaled NO and its production sites for clinical diagnosis and assessment.

A practical approach to the theoretical models to calculate NO parameters of the respiratory system

Expired nitric oxide (NO) is used as a biomarker in different respiratory diseases. The recommended flow rate of 50 mL s−1 (FENO0.05) does not reveal from where in the lung NO production originated. Theoretical models of NO transfer from the respiratory system, linear or nonlinear approaches, have therefore been developed and applied. These models can estimate NO from distal lung (alveolar NO) and airways (bronchial flux). The aim of this study was to show the limitation in exhaled flow rate for the theoretical models of NO production in the respiratory system, linear and nonlinear models. Subjects (n = 32) exhaled at eight different flow rates between 10–350 mL s−1 for the theoretical protocols. Additional subjects (n = 32) exhaled at tree flow rates (20, 100 and 350 mL s−1) for the clinical protocol. When alveolar NO is calculated using high flow rates with the linear model, correction for axial back diffusion becomes negligible, –0.04 ppb and bronchial flux enhanced by 1.27. With Högman and Meriläinen algorithm (nonlinear model) the corrections factors can be understood to be embedded, and the flow rates to be used are ≤20, 100 and ≥350 mL s−1. Applying these flow rates in a clinical setting any FENO can be calculated necessitating fewer exhalations. Hence, measured FENO0.05 12.9 (7.2–18.7) ppb and calculated 12.9 (6.8–18.7) ppb. In conclusion, the only possibility to avoid inconsistencies between research groups is to use the measured NO values as such in modelling, and apply tight quality control to accuracies in both NO concentration and exhaled flow measurements.

Measurement of Exhaled Nitric Oxide Using End Tidal Value during Normal Breathing

Increased nitric oxide (NO) production in the expired air has been associated with a number of disease conditions and may reflect the severity of inflammation in the lungs. Measurement of exhaled NO concentration has been proposed as a novel clinical tool for assessing airway inflammation and response to drug therapy. In spite of international guidelines aimed at standardizing the measurement of exhaled NO, clinicians remain skeptical due to the necessity of a significant degree of subject collaboration required by the procedure to obtain meaningful measurements. We hypothesized that exhaled NO concentration may be best measured by using end tidal NO concentration during a breath by breath monitoring. We tested laboratory staff and monitored their NO concentration online using a fast response chemiluminescence NO analyzer during normal breathing at rest for 5 minutes. First we confirmed that the NO analyzer was adequately fast to record fully the swings during normal breathing. We then compared the average end tidal NO value (NOet) from 6 to 10 breaths, to the NO value obtained from the plateau from a single slow vital capacity maneuver as recommended by the ATS guidelines (NOplat). End of exhalation was identified using end tidal carbon dioxide measurement. NOet while breathing room air was 24.3 ± 4.2 (SE) ppb and was not significantly different compared to 22.4 ± 2.8 (SE) ppb using NOplat. Additionally breathing high level of NO of up to 88 ppb did not affect either NOet or NOplat significantly suggesting that both measurements are independent of inhaled NO concentration. NO value at end of exhalation was very reproducible from breath to breath and did not require any special effort on the part of the subject. We recommend using NOet measurement instead of the NOplat value that is highly dependent on the exhalation rate and cooperation of the subject. NOet is much easier to record in children, elderly and patients with respiratory disease. The main requirement for measuring NOet is to have a fast response NO analyzer to record the full swings in NO concentration during normal breathing and to have a way of identifying end exhalation.

일산화질소 (nitric oxide) 정량을 통한 바지락(Ruditapes philippinarum) 의 흔들림 스트레스 측정

본 연구는 바지락이 흔들림 스트레스에 노출될 경우 나타나는 생리적 변화를 측정하기 위하여 일산화질소량 (NO) 을 측정하였다. 이를 위하여 흔들림 방지 장치가 없는 그룹, NAME (NO 저해제) 를 주사한 그룹, 나일론 섬유 충전재(밀도 <TEX>$1kg/m^3$</TEX>) 로 흔들림이 방지된 그룹 등 총 3개 그룹으로 나눈 후 교반기에서 100 rpm으로 6시간동안 교반 한 후 DAF assay와 Griess assay를 이용하여 바지락 혈림프액의 NO 농도를 측정하였다. 조사결과 흔들림 스트레스에 노출된 바지락에서 NO 농도가 급격히 증가하였고 반면 NO 저해제가 주입된 바지락에서는 NO 농도가 감소하였다. 또한 흔들림 방지 장치가 들어간 그룹에서 NO 농도가 감소함이 확인되었다. 이러한 결과는 DAF assay와 Griess assay 실험에서 모두 동일하게 나타났다. 결론적으로 NO 측정은 바지락의 생리적 스트레스를 측정하는데 유용한 방법임이 확인되었으며, 형망에 의한 바지락 채취시나 수하식으로 양식할 경우 흔들림에 의한 스트레스를 방지할 수단이 필요함을 시사하였다. This study aimed to evaluate the effects of shaking stress in the hemolymph of the Manila clam Ruditapes philippinarum by quantification of nitric oxide (NO) levels. The clams were divided into 3 groups as follows: clams placed in a plain container (control), clams injected with nitro-L-arginine methyl ester (NAME, an NO inhibitor), and clams in a container filled with nylon fiber at a density of <TEX>$1kg/m^3$</TEX>. Subsequently, each group was placed in sea water and shaken at 100 rpm for 6 h. The concentration of NO was quantified by using DAF assay and Griess assay. Both the assays showed that while shaking significantly increased the NO concentration, the NO inhibitor reduced the NO concentration in the hemolymph of the clams tested. In addition, the nylon fiber, which was used as a filler, effectively prevented the increase in NO concentration. This result suggests that measurement of NO concentration is a useful tool for evaluation of physiological stress in marine bivalves. In addition, it should be considered that a filler is necessary when dredge fishing or the suspended clam culture method is developed.

An optical system for measuring nitric oxide using spectral separation techniques

An optical sensor based on differential absorption spectroscopy for real-time monitoring of industrial nitric oxide (NO) gas emission is described. The influence of gas absorption interference from sulfur dioxide (SO2) in the environment was considered and a spectral separation technique was developed in order to eliminate this interference effect. The absorption spectrum of SO2 around 226 nm was evaluated by the SO2 concentration obtained using the experimentally recorded absorption spectrum around 300 nm. The absorption spectrum of NO around 226 nm was obtained by subtracting the absorption of SO2 from the integral absorption spectrum of SO2 and NO. The concentration measurements were performed at atmospheric pressure. The technique was found to have a lower detection limit of 0.8 ppm for NO per meter path length (SNR=2) and be immune from the influence from SO2 on the NO measurement. The sensor based on this technique was successfully employed for in situ measurement of SO2 and NO concentrations in the flue gas emitted from an industrial coal-fired boiler.

Large conductance Ca2+-activated K+ channels modulate endothelial cell outward currents and nitric oxide release in the intact rat superior mesenteric artery

Endothelial cells (EC) control vascular smooth muscle cell (VSMC) tone by release of paracrine factors. VSMC may also influence the EC layer, and therefore, the present study hypothesized that the opening of large-conductance Ca2+ activated K+ (BKCa) channels may indirectly modulate EC hyperpolarization and nitric oxide (NO) release via myoendothelial gap junctions (MEGJ). To address this hypothesis ‘in situ’ EC ion current recordings, isolated VSMC patch clamp recordings, and simultaneous measurements of NO concentration and relaxation were conducted using segments of the rat superior mesenteric artery. In arteries constricted by α1-adrenoceptor activation, ACh (1μM) evoked EC outward currents, vasorelaxation, and NO release. In contrast to preincubation with iberiotoxin (IbTx, 100nM) application of IbTx after ACh decreased EC outward currents, NO release and vasorelaxation. Furthermore, in phenylephrine (Phe)-contracted arteries treated with a gap junction uncoupler, cabenoxolone (CBX), IbTx failed to decrease ACh-evoked EC outward currents. In addition, CBX decreased EC outward currents, time constant of the capacitative transients, input capacitance, and increased input resistance. In isolated VSMC CBX did not affect BKCa currents. Immunohistochemistry revealed only BKCa channel positive staining in the VSMC layer. Therefore, the present results suggest that BKCa channels are expressed in the VSMC, and that Phe by activation of VSMC BKCa channels modulates ACh-evoked EC outward currents, NO release and vasorelaxation via MEGJ in rat superior mesenteric artery.