Mean Nitric Oxide Concentration Research Articles

Exploratory Data Analytics of Air Pollutant Data for Air Quality Management Application

Purpose: With escalating concerns over the detrimental impacts of air pollution on public health and the environment, this study embarks on a comprehensive exploration of air quality dynamics, focusing on Ogun state metropolis of Nigeria. The primary objective is to contribute to the burgeoning field of air quality management by harnessing the power of data analytics, exploratory data analysis, and advanced python programming libraries. The study seeks to address critical questions regarding the current state of air quality, major sources of pollution, government interventions, and individual contributions to better air quality. Methodology: The research employs Exploratory Data Analysis to unveil intrinsic patterns and trends within historical air quality datasets extracted from IoT devices located across Ogun state. This initial phase aims to discern key statistical parameters, including mean concentrations, variations, and correlations among various pollutants. Subsequently, the study employs Topic Modeling to extract latent themes and sentiments from qualitative data, specifically focusing on public opinions gathered through digital surveys. Resulting topics provide insights into public perceptions regarding air quality, pollution sources, and the efficacy of governmental interventions. Findings: Experimental result is revealing of the diversity of the dataset. The EDA returned a mean Particulate Matter concentration of approximately 12.65 µg/m³, while the mean Nitric Oxide concentration is approximately 13.56 µg/m³. Notable correlations include a strong positive correlation between PM2.5 and PM10 (0.69), indicating a substantial association between fine and coarse particulate matter. Additionally, there is a noteworthy positive correlation between NO and Nox (0.97), suggesting a high degree of correlation between nitric oxide and nitrogen oxide levels. However, negative correlations are observed, such as the substantial negative correlation between RH (relative humidity) and PM2.5 (-0.46), implying an inverse relationship between humidity and fine particulate matter levels. The study develops an innovative air quality management application. Unique Contribution to Theory, Practice and Policy: The application aims to empower both the public and policymakers with actionable insights, fostering informed decision-making and collaborative efforts towards improving air quality. It is highly recommended that industry experts should continue to imbibe ethical standards in data acquisition and deployment practices.

Impacts of COVID-19 Lockdown on Traffic Flow, Active Travel and Gaseous Pollutant Concentrations; Implications for Future Emissions Control Measures in Oxford, UK

The COVID-19 lockdown provided a unique opportunity to test the impacts of changes in travel patterns on air quality and the environment. Therefore, this study provides insights into the impacts of COVID-19 emergency public health “lockdown” measures upon traffic flow, active travel and gaseous pollutant concentrations (NO, NO2 and O3) in Oxford city centre during 2020 using time-series analysis and linear regression methods. Comparisons of traffic counts indicated pronounced changes in traffic volume associated with national lockdown periods. Car volume reduced by 77.5% (statistically significant) during the first national lockdown, with lesser changes in goods vehicles and public transport (bus) activity during the second lockdown. Cycle flow reduced substantively during the first lockdown only. These changes resulted in a reduction in nitric oxide (NO) and nitrogen dioxide (NO2) concentrations of 75.1% and 47.4%, respectively, at roadside, and 71.8% and 34.1% at urban background during the first lockdown period. In contrast ozone (O3) concentrations increased at the urban background site by 22.3% during the first lockdown period, with no significant changes in gaseous concentrations during the second lockdown at either roadside or urban background location. The diurnal pattern of peak mean NO and NO2 concentrations reduced in magnitude and was shifted approximately 2 h earlier in the morning and 2 h later in the evening (roadside) and 3 h earlier in the morning and 3 h later in the evening (urban background). Our findings provide an example of how gaseous air quality in urban environments could respond to future urban traffic restrictions, suggesting benefits from reductions in peak and daily NO2 exposures may be offset by health harms arising from increases in ground level O3 concentrations in the summer months.

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.

Effects of Dietary Crude Glycerin Concentration on Testicular Morphology and Oxidative Stress Markers and on Plasma Testosterone Concentrations

We evaluated the effects of feeding 6%, 12% or 18% crude glycerin, containing 80.5% glycerol, on testicular histomorphometry and markers of oxidative stress and on plasma testosterone concentrations in lambs. Body weight, testicular biometric measurements, gonadosomatic index and net weight of the testicles were higher for the treated groups (P<0.05) compared with a control group that did not receive dietary glycerin. The mean total length of seminiferous tubules was higher in the 6% group (P<0.05), while the mean total tubular and seminiferous epithelium volumes increased in all treated groups (P<0.05). The volume of Leydig cells increased in the 12% group, while their number per gram of testicle decreased (P<0.05). There was a decrease in mean nuclear diameter and mean volume of Leydig cells, and an increase in the mean number of these cells per gram of testicle, in the 18% group (P<0.05). Plasma testosterone concentrations were unaffected. There was desquamation of seminiferous epithelium and vacuolation of Sertoli cells in the treated groups. Variable degrees of spermatocyte necrosis and the presence of giant cells were seen in all groups and there was intense vacuolation of Sertoli cells in the 12% and 18% groups. Superoxide dismutase and catalase production increased most in the 12% and 18% groups (P<0.05), while glutathione production was higher in the 18% group (P<0.05). Mean nitric oxide concentration decreased in all treated groups (P<0.05), while malondialdehyde production was higher in the 18% group than in the control and 6% groups (P<0.05). We conclude that the inclusion of 6% glycerin in the diet of lambs results in changes in testicular morphology that have been previously associated with improved reproductive function, but without evidence of oxidative stress.

Nitric oxide (NO) in the Bohai Sea and the Yellow Sea

Abstract. Nitric oxide (NO) is a short-lived compound of the marine nitrogen cycle; however, our knowledge about its oceanic distribution and turnover is rudimentary. Here we present the measurements of dissolved NO in the surface and bottom layers at 75 stations in the Bohai Sea (BS) and the Yellow Sea (YS) in June 2011. Moreover, NO photoproduction rates were determined at 27 stations in both seas. The NO concentrations in the surface and bottom layers were highly variable and ranged from below the limit of detection (i.e., 32 pmol L−1) to 616 pmol L−1 in the surface layer and 482 pmol L−1 in the bottom layer. There was no significant difference (p&gt;0.05) between the mean NO concentrations in the surface (186±108 pmol L−1) and bottom (174±123 pmol L−1) layers. A decreasing trend of NO in bottom-layer concentrations with salinity indicates a NO input by submarine groundwater discharge. NO in the surface layer was supersaturated at all stations during both day and night and therefore the BS and YS were a persistent source of NO to the atmosphere at the time of our measurements. The average flux was about 4.5×10-16 mol cm−2 s−1 and the flux showed significant positive relationship with the wind speed. The accumulation of NO during daytime was a result of photochemical production, and photoproduction rates were correlated to illuminance. The persistent nighttime NO supersaturation pointed to an unidentified NO dark production. NO sea-to-air flux densities were much lower than the NO photoproduction rates. Therefore, we conclude that the bulk of the NO produced in the mixed layer was rapidly consumed before its release to the atmosphere.

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.

Effect of particulate air pollution and passive smoking on surrogate biomarkers of endothelial dysfunction in healthy children

Background:This study aimed to determine the association of ambient particulate matter (PM) on surrogate markers of endothelial function and inflammation in healthy children with or without exposure to second-hand smoke.Methods:This cross-sectional study was conducted in 2011 in Isfahan, which is the second largest and second most air-polluted city in Iran. The areas of the city with lowest and highest air pollution were determined, and in each area, 25 pre-pubescent boys with or without exposure to daily tobacco smoke at home were selected, i.e. 100 children were studied in total. Serum levels of C-reactive protein (CRP) and nitric oxide (NO) were measured.Results:Mean (SD) NO concentration was 7·87 (2·18) and 7·75 (2·04) μmol/L for participants not exposed and exposed to passive smoking, respectively, which is not statistically significant. The corresponding figures for CRP concentrations were 1·69 (0·89) and 2·13 (1·19) μg/ml (P = 0·04). Mean (SD) CRP concentration was significantly higher in children living in the highly polluted area than in those in the area of low pollution [2·11 (1·91) vs 1·60 (1·43) μg/ml, respectively, P = 0·02]. This difference was not significant for NO concentration. The regression analysis that examined the association between PM concentration (as independent variable) and CRP and NO levels (as dependent variables) in children not exposed to passive smoking demonstrated that increased PM was associated with a decrease in NO and an increase in CRP concentration. This finding shows that, regardless of passive smoking, PM10 concentration has a significant independent association with serum CRP and is inversely associated with NO levels.Conclusion:The findings suggest that in healthy children PM concentration has a significant independent association with biomarkers of endothelial dysfunction and inflammation.

Inhibitory role of S-nitrosoglutathione in the aggregation of frozen platelets, and its effect on the expression of membrane glycoproteins

The aim of this study was to explore the effects of S-nitrosoglutathione (GSNO) on the aggregation of frozen platelets, the platelet nitric oxide (NO) content and the expression of membrane glycoproteins. The level of frozen platelet aggregation was measured using a platelet aggregation analyzer, while the content of NO was measured by the nitrate reductase method and the expression of frozen platelet membrane glycoproteins was determined by flow cytometry. The level of frozen platelet aggregation was reduced from 35.47±2.93 to 24.43±3.07% following treatment with GSNO. The mean NO concentration in the 32 samples of frozen platelets treated with GSNO was 45.64±6.31 μmol/l, which was significantly higher compared with the concentration in the fresh liquid platelet group. There were no significant differences in the levels of PAC-1 in the fresh liquid platelet, frozen platelet and GSNO-treated frozen platelet groups; by contrast, significant differences were observed in the CD42b and CD62P levels. The platelet membrane glycoprotein expression levels in the frozen platelet and the GSNO-treated frozen platelet groups were not significantly different. The results of the study indicate that GSNO has potential as a cryoprotectant, due to its ability to increase the NO concentration in frozen platelets, inhibit platelet aggregation and maintain platelet function. It is likely that the molecular arrangement and structure of the frozen platelets were altered following GSNO treatment, or that the frozen platelets were affected by alternative mechanisms.

Insights on Vitamin D's Role in Cardiovascular Disease: Investigating the Association of 25-Hydroxyvitamin D with the Dimethylated Arginines

Accumulating evidence has stipulated a strong correlation between vitamin D (vitD) deficiency and cardiovascular disease (CVD); however, a mechanistic link is missing. This study investigated the association of vitD with endothelial dysfunction parameters. Subjects comprised male patients with verified coronary artery disease (CAD) (n=69) and age- and sex-matched controls (n=20). 25-Hydroxyvitamin D [25(OH)D] was determined using high performance liquid chromatography with ultraviolet detection whereas asymmetric and symmetric dimethylarginine (ADMA and SDMA, respectively) were determined by liquid chromatography-mass spectrometry. Nitric oxide (NO) was determined spectrophotometrically and high-sensitivity C-reactive protein (hs-CRP) was determined using enzyme-linked immunosorbent assay (ELISA). Comparison of mean 25(OH)D concentrations of patients and controls yielded a significant result (p=0.0002). 25(OH)D2 was dominant in patients whereas 25(OH)D3 was dominant in controls (p=0.003 and 0.001, respectively). Comparison of mean ADMA and SDMA concentrations of patients exhibiting normal and suboptimal vitD yielded insignificant results (p=0.692 and 0.998, respectively). Significant results were obtained from the comparison of mean hs-CRP and NO concentrations of patients exhibiting normal and suboptimal vitD (p=0.035 and 0.031, respectively). Results suggest involvement of vitD with the NO system, however not via modulation of the dimethylated arginines. A potential anti-inflammatory activity for vitD is also raised.

Serum nitric oxide concentrations in patients with multiple sclerosis and patients with epilepsy

Nitric oxide (NO), a neurotransmitter and a free radical, has been purported to be involved in numerous neurological diseases. We investigated the serum nitric oxide concentration in 30 patients with multiple sclerosis (MS), in 30 patients with epilepsy and in 30 control subjects. The aim was also to determine whether a statistically significant difference in serum NO concentrations exists between the groups of interest. The total serum nitric oxide concentration was measured using the Griess reaction after reducing nitrates to nitrites with elemental zinc. In the group multiple sclerosis, the mean NO concentrations were X±SEM=31.02±1.79μmol/l, in the control group X±SEM=25.31±1.44μmol/l and in the group epilepsy X±SEM=22.51±1.28μmol/l. Student's t test showed a statistically significant difference between subjects with multiple sclerosis and the control group (p=0.013), as well as between the groups multiple sclerosis and epilepsy (p=0.0002). This data confirms that NO may play an important role in the pathogenesis of multiple sclerosis, whereas its role in epilepsy still remains unclear.

Changes of nitric oxide and endothelin serum level after carotid balloon denudation or stent assisted angioplasty: an experimental and clinical observation

To observe the changes of nitric oxide (NO) and endothelin (ET) serum level in the Guangxi BA-MA minipigs whose carotid arteries were injured by balloon denudation and in the patients with carotid stent assisted angioplasty. Twelve Guangxi BA-MA minipigs were chosen. High fat/cholesterol feeding and endovascular balloon denudation were used to create a carotid artery atherosclerotic stenosis animal model. Blood samples were collected from peripheral veins before starting the procedure, and again, at 2 and 3 weeks after the procedure, respectively. Serum NO and ET concentrations of blood samples were tested. Nineteen patients with carotid artery stenosis who underwent stent assisted angioplasty were randomly selected, and their serum NO and ET were tested using the same methods as above. In the animal group, there was a significant decrease of mean NO concentration at 2 weeks after carotid injury (t-test, P < 0.05), however, no significant change of ET was observed. A very significant increase of ET was observed at 3 weeks after the procedure (t-test, P < 0.01). In the patient group, there were no significant differences among serum NO or ET concentration of peripheral vein blood before, immediately after, and 6 h after the endovascular treatment. In this study, a decrease of NO concentration and an increase of ET concentration of peripheral vein blood are found in BA-MA minipigs after carotid arteries are injured by balloon denudation, which might be a cue for the formation of atherosclerosis. However, no significant changes are observed in this group of patients who underwent carotid angioplasty treatment. Therefore, further studies are needed.

Nitric oxide in exhaled and aspirated nasal air as an objective measure of human response to indoor air pollution

The concentration of nitric oxide (NO) in exhaled and aspirated nasal air was used to objectively assess human response to indoor air pollutants in a climate chamber exposure experiment. The concentration of NO was measured before exposure, after 2, and 4.5 h of exposure, using a chemiluminescence NO analyzer. Sixteen healthy female subjects were exposed to two indoor air pollutants and to a clean reference condition for 4.5 h. Subjective assessments of the environment were obtained by questionnaires. After exposure (4.5 h) to the two polluted conditions a small increase in NO concentration in exhaled air was observed. After exposure to the reference condition the mean NO concentration was significantly reduced compared to pre-exposure. Together these changes resulted in significant differences in exhaled NO between exposure to reference and polluted conditions. NO in nasal air was not affected by the exposures. The results may indicate an association between polluted indoor air and subclinical inflammation. Measurement of nitric oxide in exhaled air is a possible objective marker of subclinical inflammation in healthy adults.

Ros Generation and Lipid Peroxidation in Professional Sportsmen (Extreme Sports Condition)

Introduction: Too intensive physical exercise may lower NO bioactivity as a result of excessive production of reactive oxygen species (ROS), such as superoxide anion radical (O 2 •– ). This can lead to the intense peroxidation of cell membrane lipids in erythrocytes. Aim of the study: The aim of the study was to evaluate the influence of dosed maximal exercise on the plasma nitric oxide content and the level of malonyl dialdehyde in red blood cells in professional sportsmen and in individuals of normal physical activity. Materials and Methods: 41 rugby players and 21 men of normal physical activity (control group) were the subject of the study. NO and MDA concentrations were determined in three time points: before an effort, 1 minute after dosed maximal exercise and after 30-minute restitution period. Nitric oxide (NO) concentration was evaluated with Griess’s indirect method and malonyl dialdehyde (MDA) concentration was measured with Placer’s method. Results: Mean NO concentration increased in the exercise phase and decreased after 30-minute restitution in all three studied groups. The highest MDA level was observed in the first minute of exercise in all studied groups. Conclusions: Results of determination of plasma NO concentration does not confirm reduction of its bioactivity. Plasma NO level rose 1 minute after maximal exercise in all three groups of studied subjects. In trained professional sportsmen, adapted to the physical effort, this kind of load enables protection of cell structures against peroxidation process by the antioxidant barrier, which is reflected by the lower concentration of malonyl dialdehyde (MDA) in the red blood cells in comparison to the control group.

Direct gas measurements indicate that the novel cyclooxygenase inhibitor AZD3582 is an effective nitric oxide donor in vivo

1. AZD3582 [4-(nitrooxy)butyl-(2S)-2-(6-methoxy-2-naphthyl)propanoate] is a COX-inhibiting nitric oxide donor that inhibits COX-1 and COX-2. It is as effective as naproxen in models of pain and inflammation, but causes less gastroduodenal damage. Nitric oxide (NO) is generated from AZD3582 in vitro, and this study sought to show that the drug donates NO in vivo. 2. In anaesthetised male New Zealand white rabbits, the endogenous NO concentration in exhaled air was reduced by N(G)-nitro-L-arginine methyl ester (L-NAME) (30 mg kg(- 1) i.v.) from 33.5+/-1.0 ppb (mean+/-s.e.m.; n=6 per group) to 3.0+/-1.0 ppb, while increasing blood pressure and reducing heart rate. AZD3582 (0.2, 0.6, 2.0 or 6.0 micromol kg(- 1) min(- 1)) given 30 min after L-NAME increased the concentration of NO in exhaled air (P<0.05), decreased blood pressure and increased heart rate in a dose-dependent manner versus L-NAME control values. The peak mean NO concentration obtained was 44+/-8.0 ppb. 3. In in situ-perfused rabbit lungs, L-NAME (185 micromol l(- 1)) reduced the NO concentration in exhaled air from 106+/-13 to 4.0+/-0.4 ppb (n=5). Addition of AZD3582 (6 micromol min(- 1)) to the perfusate produced an initial rapid increase in the NO concentration in exhaled air, followed by a sustained, but lower plateau. Infusion of L-NAME increased, and AZD3582 decreased, pulmonary arterial pressure. 4. In both anaesthetised rabbits and in the perfused lungs, brief periods of hypoxia increased NO concentrations generated by AZD3582. 5. We conclude that, in rabbits, AZD3582 donates NO in vivo with characteristics similar to those reported for nitroglycerin and isosorbide nitrates

Comparison of nitric oxide concentration in seminal fluid between infertile patients with and without varicocele and normal fertile men.

Elevated nitric oxide (NO) levels have been shown to have toxic effects on sperm function and motility. This study was conducted to compare NO levels in the seminal fluid of infertile men with varicocele with those of infertile and fertile men without varicocele. Semen samples were obtained from 40 infertile men with varicocele (group 1), 40 infertile men without varicocele (group 2), and 40 fertile volunteers without varicocele (group 3). NO levels in the seminal plasma of patients in each group were measured and compared. In infertile men with varicocele, semen parameters, including sperm count and motility, and grade of varicocele were also determined. Mean NO concentrations were 52.34 +/- 26.62 micromol/L, 37.06 +/- 20.39 micromol/L, and 33.7 +/- 18.99 micromol/L in groups 1, 2, 3, respectively. Concentrations in group 1 were significantly higher than were those in groups 2 and 3 (P = 0.001). In group 1, no significant correlations were seen between NO concentrations and grades of varicocele, sperm count, sperm motility, or ages of the patients. Data from the current study suggest a possible role of NO in damaging the sperm function in varicocele as demonstrated by an increased concentration of NO in the seminal fluid of infertile men with varicocele compared with the seminal fluid of fertile and infertile men without varicocele.

Dietary nitrate generates potentially mutagenic concentrations of nitric oxide at the gastroesophageal junction

Twenty-five percent of absorbed dietary nitrate is re-secreted in saliva, and 30% of this is reduced to nitrite by buccal bacteria. When saliva is swallowed, the acidic gastric juice reduces the nitrite to nitric oxide. The aim of this study was to examine the anatomic distribution of nitric oxide generation within the lumen of the upper gastrointestinal tract under basal conditions and after ingesting nitrate equivalent to that in salad portion. Using custom-made sensors, the dissolved luminal nitric oxide concentration and pH were measured at 1-cm increments for 2 minutes throughout the length of the stomach and distal esophagus in 15 Helicobacter pylori-negative healthy volunteers with and without ingestion of 2 mmol potassium nitrate. Serum nitrate and saliva nitrite concentrations were also monitored. The nitrate ingestion increased mean (range) serum nitrate from 30 micromol/L (18-49) to 95 micromol/L (32-152), mean salivary nitrite from 36 micromol/L (19-153) to 252 micromol/L (32-600), and mean peak luminal nitric oxide concentration from 4.7 micromol/L (1.4-7.8) to 23.2 micromol/L (2.1-50) (P < 0.05 for each). After nitrate, the peak nitric oxide concentration occurred in 11 of the 15 (73%) subjects within 1 cm distal to the gastroesophageal pH step-up point. The mean nitric oxide concentration over the 1-cm segment immediately distal to the gastroesophageal pH step-up after nitrate was 7.5 micromol/L (range, 0.5-30.7) and was significantly higher than at all other sites. Nitric oxide concentrations greater than 50 micromol/L were observed at the precise location where neutral esophageal pH fell to acidic gastric pH. Luminal generation of nitric oxide from dietary nitrate via salivary nitrite is maximal at the gastroesophageal junction and cardia. The high concentrations of nitric oxide generated may contribute to the high incidence of mutagenesis and neoplasia at this site.

The electrochemical and fluorescence detection of nitric oxide in the cochlea and its increase following loud sound

A nitric oxide (NO)-selective sensor (tip diameter 30 μm) was inserted into the perilymph of the basal turn of the guinea pig cochlea. The basal level and stimulation-induced changes of NO were measured. The mean (±S.E.M.) basal level of NO was 273±42.9 nM. Following perilymphatic perfusion of the artificial perilymph containing NO synthase (NOS) substrate L-arginine (100 μM) combined with cofactor (6 R)-5,6,7,8-tetrahydrobiopterin dihydrochloride (100 μM), a rapid and significant increase of NO to a mean concentration of 392±32.3 nM ( P<0.01, n=10) was recorded. In contrast, a significant decrease of mean NO concentration to 180±32.7 nM ( P<0.01, n=10) was observed following the perfusion of the NOS-inhibiting agent N G-nitro- L-arginine methyl ester (100 μM). No change in the NO concentration was found following the perfusion of either artificial perilymph or N G-monomethyl- D-arginine (100 μM) solution employed as controls. Broadband noise exposure (3 h/day at 120 dBA SPL) for three consecutive days produced an increase in NO concentration to 618±60.7 nM ( P<0.05, n=10) in the perilymph. In addition, by using specific dyes for NO, 4,5-diaminofluoresceine diacetate and for the reactive oxygen species (ROS), dihydrorhodamine 1,2,3, the distribution of NO in the whole mounts of the organ of Corti and the production of ROS in vivo in the organ of Corti were investigated in both control ( n=5) and noise-exposed ( n=5) animals. The more intense NO and ROS fluorescence was observed in both the inner and outer hair cells in the noise-exposed groups. It is proposed that both the basal level and the increase in NO concentration following the addition of substrate ( L-arginine) are produced by the constitutive NOS while the elevated NO and ROS following noise exposure indicate that NO may be involved in noise-induced hearing loss.

The relationship between varicocele and semen nitric oxide concentrations.

We investigated the relationship between seminal plasma nitric oxide (NO) concentrations and conventional semen parameters in patients with varicocele. Semen samples were obtained from infertile patients with varicocele (n = 55) and from normal controls (n = 48). The mean NO concentration in the seminal plasma of patients with varicocele was significantly higher than that of the controls (P < 0.01). A significant negative correlation was noted between NO and sperm motility (r = -0.29, P = 0.003), NO and sperm concentration (r = -0.26, P = 0.008) and NO and normal morphology (normal %) (r = -0.25, P = 0.01). It was concluded that increased NO production may influence sperm production, motility and morphology in patients with varicocele.

Exhaled nitric oxide level decreases after cardiopulmonary bypass in adult patients.

To measure exhaled nitric oxide (NO) and compare it with lung function after cardiopulmonary bypass (CPB) in adult patients. Pulmonary dysfunction is sometimes observed after CPB. Impaired production of NO may account for this dysfunction. Prospective, single-center, observational study. University hospital operating room, intensive care unit. Sixteen adult patients undergoing cardiac surgery with CPB. None except cardiac surgery with CPB. Exhaled NO was measured continuously by the chemiluminescence method and was expressed as the peak and mean NO concentrations, and the NO output (VNO). These parameters were calculated by averaging four sequential tidal NO values. The data were obtained serially from before CPB to 16 hrs after CPB. Lung function was evaluated by monitoring lung compliance, pulmonary artery pressure, and alveolar-arterial oxygen difference (P(A-a)O2). The cardiac index did not change except for a significant increase at 16 hrs compared with 6 hrs after CPB. Peak NO, mean NO, and VNO decreased from 15.4 +/- 2.0 ppb (before CPB) to 8.2 +/- 0.8 ppb (6 hrs after CPB), from 5.7 +/- 0.7 ppb to 2.8 +/- 0.6 ppb, and from 29.2 +/- 3.1 nL/min to 15.7 +/- 2.2 nL/min, respectively. These changes were associated with the increases in pulmonary artery pressure and alveolar-arterial oxygen difference, and the decrease in lung compliance. VNO recovered to the level measured before CPB 16 hrs after CPB, which was consistent with the physiologic recovery in pulmonary hypertension, lung compliance, and gas exchange. Measurement of exhaled NO as VNO, which was associated with lung dysfunction, may be an indicator of lung injury in adult patients after cardiopulmonary bypass.

A Method for the Standardized Offline Collection of Exhaled Nitric Oxide

Exhaled nitric oxide (ENO) is a noninvasive marker of airway inflammation. The purpose of this study was to compare a standardized offline ENO measurement apparatus with a validated on-line method. Asthmatic volunteers (n = 21) had ENO measured by the two following methods: (1) inhalation to total lung capacity (TLC) followed by exhalation at a constant flow (45 mL/s) against a high resistance, while monitoring nitric oxide (NO) and pressure on-line; and (2) inhalation to TLC and exhalation into mylar balloons via an apparatus that included the same resistance and flow rate as used in the on-line method. We also examined NO stability in mylar balloons over 48 h. ENO values (given as geometric mean in parts per billion [ppb]; 95% confidence intervals) differed between the on-line method (69.6; 42.6 to 113.8) and the offline method (49.5; 30.9 to 79.3), indicating that the offline method gave lower ENO measures than the on-line method (p < 0.001). Furthermore, this difference between measures increased with increasing mean values. The intraclass correlation coefficient (0.931), however, showed excellent correlation between the on-line and offline methods. Within-subject repeatability, as assessed by the coefficient of repeatability (CR), was good for both the on-line and offline methods (CR, 1.09 and 1.17, respectively). Geometric mean NO concentrations (95% confidence limits) in mylar balloons containing exhalate increased from a baseline of 55.8 ppb (36.9, 84.4) to 64.5 ppb (45.6, 91.1) and 69.5 ppb (51.4, 94.0) at 24 h and 48 h, respectively. The offline method gave reproducible ENO values that were consistently smaller than, but showed good correlation with, values obtained with on-line ENO collection. This method is suitable for offline collection, but the measured values are not interchangeable with those obtained by on-line measurement.