Low Concentrations Of Carbon Monoxide Research Articles

A carbon monoxide gas sensor using oxygen plasma modified carbon nanotubes

Carbon monoxide (CO) is a highly toxic gas that can be commonly found in many places. However, it is not easily detected by human olfaction due to its colorless and odorless nature. Therefore, highly sensitive sensors need to be developed for this purpose. Carbon nanotubes (CNTs) have an immense potential in gas sensing. However, CNT-based gas sensors for sensing CO are seldom reported due to the lack of reactivity between CO and CNTs. In this work, O2 plasma modified CNT was used to fabricate a CNT gas sensor. The plasma treated CNTs showed selectively towards CO, with the capability of sensing low concentrations of CO (5 ppm) at room temperature, while the pristine CNTs showed no response. UV spectra and oxygen reduction reaction provided evidence that the difference in sensing property was due to the elimination of metallic CNTs and enhancement of the oxygen reduction property.

Effect of Carbon Monoxide on Bacteria‐Stimulated Cytokine Production by Placental Explants

Preterm birth is frequently caused by an inflammatory response to ascending infections of the reproductive tract. Carbon monoxide (CO) has potent anti-inflammatory properties at subtoxic concentrations. Whether or not CO can modulate inflammatory responses by placental tissues is unclear. Placental explant cultures were incubated with heat-killed Escherichia coli or Ureaplasma parvum in the presence or absence of 250ppm CO for 24hr. Concentrations of cytokines relative viability of the cultures were quantified. Escherichia coli- and U.parvum-stimulated IL-1β production was significantly inhibited by CO supplementation. Escherichia coli-stimulated, but not U.parvum-stimulated, IFN-γ production was inhibited by CO. While CO inhibited PGE(2) production by unstimulated cells, no effects on bacteria-stimulated prostaglandin production were detected. CO had no effect on basal or E.coli-stimulated TNF-α production but enhanced TNF-α production by cultures stimulated with U.parvum. In addition, CO tended to improve the viability of the placental cultures. Low concentrations of CO tended to reduce proinflammatory cytokines and to promote the production of anti-inflammatory cytokines in a pathogen-specific manner. These properties suggest that CO may be useful for promoting a pro-pregnancy cytokine milieu by placental explants and may reduce the consequences of intrauterine infections.

Are rocket mud stoves associated with lower indoor carbon monoxide and personal exposure in rural Kenya?

Household use of biomass fuels is a major source of indoor air pollution and poor health in developing countries. We conducted a cross-sectional investigation in rural Kenya to assess household air pollution in homes with traditional three-stone stove and rocket mud stove (RMS), a low-cost unvented wood stove. We conducted continuous measurements of kitchen carbon monoxide (CO) concentrations and personal exposures in 102 households. Median 48-h kitchen and personal CO concentrations were 7.3 and 6.5 ppm, respectively, for three-stone stoves, while the corresponding concentrations for RMS were 5.8 and 4.4 ppm. After adjusting for kitchen location, ventilation, socio-economic status, and fuel moisture content, the use of RMS was associated with 33% lower levels of kitchen CO [95% Confidence Interval (CI), 64.4-25.1%] and 42% lower levels of personal CO (95% CI, 66.0-1.1%) as compared to three-stone stoves. Differences in CO concentrations by stove type were more pronounced when averaged over the cooking periods, although they were attenuated after adjusting for confounding. In conclusion, RMS appear to lower kitchen and personal CO concentrations compared to the traditional three-stone stoves but overall, the CO concentrations remain high. The rocket mud stoves (RMS) were associated with lower CO concentrations compared to three-stone stoves. However, the difference in concentrations was modest and concentrations in both stove groups exceeded the WHO guideline of 7 μg/m(3) , suggesting the unvented RMSs on their own are unlikely to appreciably benefit health in this population. Greater air quality benefit could be realized if the stoves were complemented with behavior change, including education on extinguishing fire when not in use as well as fuel drying, and cooking in locations that are separate from the main house.

Carbon Monoxide Modulates Apoptosis by Reinforcing Oxidative Metabolism in Astrocytes

Modulation of cerebral cell metabolism for improving the outcome of hypoxia-ischemia and reperfusion is a strategy yet to be explored. Because carbon monoxide (CO) is known to prevent cerebral cell death; herein the role of CO in the modulation of astrocytic metabolism, in particular, at the level of mitochondria was investigated. Low concentrations of CO partially inhibited oxidative stress-induced apoptosis in astrocytes, by preventing caspase-3 activation, mitochondrial potential depolarization, and plasmatic membrane permeability. CO exposure enhanced intracellular ATP generation, which was accompanied by an increase on specific oxygen consumption, a decrease on lactate production, and a reduction of glucose use, indicating an improvement of oxidative phosphorylation. Accordingly, CO increased cytochrome c oxidase (COX) enzymatic specific activity and stimulated mitochondrial biogenesis. In astrocytes, COX interacts with Bcl-2, which was verified by immunoprecipitation; this interaction is superior after 24 h of CO treatment. Furthermore, CO enhanced Bcl-2 expression in astrocytes. By silencing Bcl-2 expression with siRNA transfection, CO effects in astrocytes were prevented, namely: (i) inhibition of apoptosis, (ii) increase on ATP generation, (iii) stimulation of COX activity, and (iv) mitochondrial biogenesis. Thus, Bcl-2 expression is crucial for CO modulation of oxidative metabolism and for conferring cytoprotection. In conclusion, CO protects astrocytes against oxidative stress-induced apoptosis by improving metabolism functioning, particularly mitochondrial oxidative phosphorylation.

Neurodevelopmental Consequences of Sub-Clinical Carbon Monoxide Exposure in Newborn Mice

Carbon monoxide (CO) exposure at high concentrations results in overt neurotoxicity. Exposure to low CO concentrations occurs commonly yet is usually sub-clinical. Infants are uniquely vulnerable to a variety of toxins, however, the effects of postnatal sub-clinical CO exposure on the developing brain are unknown. Apoptosis occurs normally within the brain during development and is critical for synaptogenesis. Here we demonstrate that brief, postnatal sub-clinical CO exposure inhibits developmental neuroapoptosis resulting in impaired learning, memory, and social behavior. Three hour exposure to 5 ppm or 100 ppm CO impaired cytochrome c release, caspase-3 activation, and apoptosis in neocortex and hippocampus of 10 day old CD-1 mice. CO increased NeuN protein, neuronal numbers, and resulted in megalencephaly. CO-exposed mice demonstrated impaired memory and learning and reduced socialization following exposure. Thus, CO-mediated inhibition of neuroapoptosis might represent an important etiology of acquired neurocognitive impairment and behavioral disorders in children.

Hydrogen production via methanol steam reforming over Au/CuO, Au/CeO2, and Au/CuO–CeO2 catalysts prepared by deposition–precipitation

The production of hydrogen (H2) with a low concentration of carbon monoxide (CO) via steam reforming of methanol (SRM) over Au/CuO, Au/CeO2, (50:50)CuO–CeO2, Au/(50:50)CuO–CeO2, and commercial MegaMax 700 catalysts were investigated over reaction temperatures between 200°C and 300°C at atmospheric pressure. Au loading in the catalysts was maintained at 5wt%. Supports were prepared by co-precipitation (CP) whilst all prepared catalysts were synthesized by deposition–precipitation (DP). The catalysts were characterized by Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy (SEM). Au/(50:50)CuO–CeO2 catalysts expressed a higher methanol conversion with negligible amount of CO than the others due to the integration of CuO particles into the CeO2 lattice, as evidenced by XRD, and a interaction of Au and CuO species, as evidenced by TPR. A 50:50 Cu:Ce atomic ratio was optimal for Au supported on CuO–CeO2 catalysts which can then promote SRM. Increasing the reaction time, by reducing the liquid feed rate from 3 to 1.5cm3h−1, resulted in a catalytic activity with complete (100%) methanol conversion, and a H2 and CO selectivity of ∼82% and ∼1.3%, respectively. From stability testing, Au/(50:50)CuO–CeO2 catalysts were still active for 540min use even though the CuO was reduced to metallic Cu, as evidenced by XRD. Therefore, it can be concluded that metallic Cu is one of active components of the catalysts for SRM.

Novel Porous Composite Material Containing Catalytic Nanoparticles for Hydrogen Production from Biofuel

ABSTRACTIn this study, a novel flow-based method is presented to place catalytic nanoparticles into a reactor by sol-gelation of a porous ceramic consisting of copper-based nanoparticles, silica sand, ceramic binder, and a gelation agent. This method allows for the placement of a liquid precursor containing the catalyst into the final reactor geometry without the need of impregnating or coating of a substrate with the catalytic material. The so generated foam-like porous ceramic shows properties highly appropriate for use as catalytic reactor material, e.g., reasonable pressure drop due to its porosity, high thermal and catalytic stability, and excellent catalytic behavior.The catalytic activity of micro-reactors containing this foam-like ceramic is tested in terms of their ability to convert alcoholic biofuel (e.g. methanol) to a hydrogen-rich gas mixture with low concentrations of carbon monoxide (up to 75% hydrogen content and less than 0.2% CO, for the case of methanol). This gas mixture is subsequently used in a low-temperature fuel cell, converting the hydrogen directly to electricity. A low concentration of CO is crucial to avoid poisoning of the fuel cell catalyst. Since conventional Polymer Electrolyte Membrane (PEM) fuel cells require CO concentrations far below 100 ppm and since most methods to reduce the mole fraction of CO (such as Preferential Oxidation or PROX) have CO conversions of up to 99%, the alcohol fuel reformer has to achieve initial CO mole fractions significantly below 1%. The catalyst and the porous ceramic reactor of the present study can successfully fulfill this requirement.The results of the present study confirm that product gas mixtures with up to 75% hydrogen content and less than 0.2% CO content can be achieved, which is an excellent result. The reactor temperature can be kept as low as 220°C while obtaining a methanol conversion of up to 70%. The used PROX catalyst showed selective CO conversion rates above 99.5% for temperatures between 80 and 100°C in presence of large molar fractions of H2O and CO2.

Effects of exogenous carbon monoxide on radiation-induced bystander effect in zebrafish embryos in vivo

In the present work, the influence of a low concentration of exogenous carbon monoxide (CO) liberated from tricarbonylchloro(glycinato)ruthenium (II) (CORM-3) on the radiation induced bystander effect (RIBE) in vivo between embryos of the zebrafish was studied. RIBE was assessed through the number of apoptotic signals revealed on embryos at 25h post fertilization (hpf). A significant attenuation of apoptosis on the bystander embryos induced by RIBE in a CO concentration dependent manner was observed.

In Situ Infrared Molecular Detection Using Palladium-Containing Zeolite Films

In situ IR detection of carbon monoxide in the presence of hydrocarbons (methanol and pentane) using Pd-containing zeolite thin films is reported. The thin films are prepared by spin coating deposition of nanosized LTL and BEA type zeolites suspensions; the palladium clusters are introduced in the nanosized zeolites by ion exchange followed by γ radiolysis of the coating suspensions. The Pd-containing zeolite films with a thickness of 200 nm are exposed to a single gas (either CO or hydrocarbons) or gas mixtures in the presence of water (100 ppm), and the IR spectra are collected continuously at 25, 75, and 100 °C. The fast recognition of very low concentrations of CO (2-100 ppm) in the presence of highly concentrated vapors of methanol or pentane (400-4000 ppm) with the Pd-containing zeolite films is demonstrated. The detection of CO and hydrocarbons is instant, which is a function of the low thickness of the films, small size of the individual zeolite crystals, and regular size and high stability of the Pd clusters in the zeolite films. The heat of adsorption for all experiments is similar (15 kJ.mol(-1)), which is explained with weak interactions between the carbon monoxide and palladium clusters in the zeolite films at temperatures below 100 °C. The nanosized zeolites with homogeneously distributed Pd clusters deposited in thin films demonstrate high molecular recognition capacity toward low concentrations of carbon monoxide under real environmental conditions, i.e., in the presence of water and hydrocarbons.

Carbon Monoxide–Activated Nrf2 Pathway Leads to Protection Against Permanent Focal Cerebral Ischemia

Carbon monoxide (CO) is a gaseous second messenger produced when heme oxygenase enzymes catabolize heme. We have demonstrated that CO can be therapeutic in ischemia-reperfusion brain injury; however, it is unclear whether CO can also offer protection in permanent ischemic stroke or what mechanism(s) underlies the effect. Heme oxygenase-1 neuroprotection was shown to be regulated by Nrf2; therefore, we investigated whether CO might partially exert neuroprotection by modulating the Nrf2 pathway. To evaluate the potential protective effects of CO, we exposed male wild-type and Nrf2-knockout mice to 250 ppm CO or control air for 18 hours immediately after permanent middle cerebral artery occlusion. Infarct volume and neurologic deficits were assessed on day 7. Molecular mechanisms of Nrf2 pathway activation by CO were also investigated. Mice exposed to CO after permanent ischemia had 29.6±12.6% less brain damage than did controls at 7 days, although amelioration in neurologic deficits did not reach significance. Additionally, 18-hour CO treatment led to Nrf2 dissociation from Keap1, nuclear translocation, increased binding activity of Nrf2 to heme oxygenase-1 antioxidant response elements, and elevated heme oxygenase-1 expression 6 to 48 hours after CO exposure. The CO neuroprotection was completely abolished in Nrf2-knockout mice. Low-concentration CO represent a neuroprotective agent for combination treatment of ischemic stroke, and its beneficial effect would be at least partially mediated by activation of the Nrf2 pathway.

Emission of Carbon Monoxide During Composting of Municipal Solid Waste

Elevated concentrations of carbon monoxide (CO) have been observed at the enclosed municipal waste composting facility (ECF) in Edmonton, Canada. Elevated concentrations of CO in an enclosed facility pose a potential health risk to workers. The objectives in this study were to: (1) assess temporal and spatial variability of CO emissions from the composting bays in the ECF using Fourier Transform Infrared (FTIR) spectroscopy; and (2) identify any correlations between the CO emission rate and the physicochemical properties of the compost through bench-scale incubation experiments. Repeated gas measurements were taken above and within the compost bed in the ECF using a probe connected to an FTIR gas analyzer, which continuously collected concentration data. These preliminary field measurements showed maximum CO concentrations of 112 μL−1 within the compost. Autoclaved and non-sterilized compost samples from the ECF were incubated under aerobic and hypoxic conditions, and gas emissions were quantified using gas chromatography (GC). These trials showed a positive correlation between CO emission rate and incubation temperature for all samples, indicating a physico-chemical source of CO generation. Lower concentrations of CO were observed in the non-sterilized compost under both aerobic and anaerobic conditions, presumably due to the microbial metabolism of CO.

Carbon monoxide enhances early liver regeneration in mice after hepatectomy

Hepatocyte proliferation early after liver resection is critical in restoring liver mass and preserving function as the liver regenerates. Carbon monoxide (CO) generated by heme oxygenase-1 (HO-1) strongly influences cellular proliferation and both HO-1 and CO are accepted hepatoprotective molecules. Mice lacking functional HO-1 were unable to mount an appropriate regenerative response following partial hepatectomy (PHTx) compared to wildtype controls. We therefore hypothesized that exogenous administration of CO at low, nontoxic concentrations would modulate hepatocyte (HC) proliferation and liver regeneration. Animals treated with a low concentration of CO 1 hour prior to 70% hepatectomy demonstrated enhanced expression of hepatocyte growth factor (HGF) in the liver compared to controls that correlated with a more rapid onset of HC proliferation as measured by phospho-histone3 staining, increased expression of cyclins D1 and E, phosphorylated retinoblastoma, and decreased expression of the mitotic inhibitor p21. PHTx also increased activation of the HGF receptor c-Met, which was detected more then 9 hours earlier in the livers of CO-treated mice. Blockade of c-Met resulted in abrogation of the CO effects on HC proliferation. Corresponding with increased HC proliferation, treatment with CO maintained liver function with normal prothrombin times versus a 2-fold prolongation in controls. In a lethal 85% PHTx, CO-treated mice showed a greater survival rate compared to controls. In vitro, CO increased HGF expression in hepatic stellate cells, but not HC, and when cocultured together led to increased HC proliferation. In summary, we demonstrate that administration of exogenous CO enhances rapid and early HC proliferation and, importantly, preserves function following PHTx. Taken together, CO may offer a viable therapeutic option to facilitate rapid recovery following PHTx.

Carbon monoxide prevents hepatic mitochondrial membrane permeabilization

BackgroundLow concentrations of carbon monoxide (CO) protect hepatocytes against apoptosis and confers cytoprotection in several models of liver. Mitochondria are key organelles in cell death control via their membrane permeabilization and the release of pro-apoptotic factors.ResultsHerein, we show that CO prevents mitochondrial membrane permeabilization (MMP) in liver isolated mitochondria. Direct and indirect approaches were used to evaluate MMP inhibition by CO: mitochondrial swelling, mitochondrial depolarization and inner membrane permeabilization. Additionally, CO increases mitochondrial reactive oxygen species (ROS) generation, and their scavenging, by ß-carotene addition, decreases CO protection, which reveals the key role of ROS. Interestingly, cytochrome c oxidase transiently responds to low concentrations of CO by decreasing its activity in the first 5 min, later on there is an increase of cytochrome c oxidase activity, which were detected up to 30 min.ConclusionCO directly prevents mitochondrial membrane permeabilization, which might be implicated in the hepatic apoptosis inhibition by this gaseoustransmitter.

Integration Study of Micro Reformer and High Temperature PEM Fuel Cell

An integration platform assembling with methanol reformer and high-temperature proton exchange membrane fuel cell (PEMFC) was constructed in this present. The methanol micro reformer combines with catalytic reaction section and reforming section. Catalytic reaction section with Pt calalysis maintains the constant temperature envoriment for reforming process. SRM reforming results show the 74%~74.9% hydrogen and 23.5%~25.7% of carbon dioxide in the mixture product. Less than 2% of carbon monoxide was produced. Using the reforming product of low carbon monoxide concentration and the highest methanol conversion rate, a micro reformer links with fuel cell integration experiment was performed. Results show the high temperature PEMFC with 3 ~ 4W power output under methaol flow rate 15ml/hr. Due to the lower of hydrogen pressure supplying from the micro reformer, may cause the fuel cell power output become unstable.

Postconditioning of the Lungs with Inhaled Carbon Monoxide After Cardiopulmonary Bypass in Pigs

Administration of inhaled carbon monoxide before organ ischemic injury exerts protective effects in animal models. Because there are no data showing that this also works after an ischemic insult, our objective in this study was to investigate whether inhaled carbon monoxide attenuates cardiopulmonary bypass (CPB)-induced lung injury in a pig model. Animals were randomized to a SHAM group (n = 5), a SHAM group plus inhaled carbon monoxide (n = 5), standard CPB (n = 10), and to CPB plus inhaled carbon monoxide (n = 10). Carbon monoxide (250 ppm) was given for 1 hour after termination of CPB. Lung biopsies were obtained before CPB, immediately after separation from CPB, and for 5 hours after termination of CPB to determine expression of pulmonary heat shock proteins 70 and 90, cytokines, alveolar macrophage infiltration, and fluorogenic caspase-3 activity. At 5 hours after CPB, administration of inhaled carbon monoxide was associated with reduced pulmonary expression of the inflammatory cytokines tumor necrosis factor (CPB + CO 521 ± 77 vs CPB 821 ± 97 pg · mL(-1), P < 0.001) and interleukin-6 (304 ± 81 vs 860 ± 153 pg · mL(-1), P < 0.001), increased pulmonary expression of the cytoprotective heat shock protein 70 (CPB + CO 79 ± 14 vs CPB 36 ± 9 ng · mL(-1), P < 0.001) and the antiinflammatory cytokine interleukin-10 (CPB + CO 278 ± 40 vs CPB 63 ± 20 pg · mL(-1), P < 0.001), and with reduced pulmonary apoptotic protein caspase-3 activity (CPB + CO 0.73 ± 0.11 vs CPB 0.99 ± 0.1 RFU, P < 0.05). Carbon monoxide administration was associated with reduced histological evidence of lung injury and alveolar macrophage infiltration (78 ± 39 vs 145 ± 34 counts per field of vision, P < 0.001). These results suggest that administration of low concentrations of carbon monoxide after CPB ("postconditioning") protects the lung from CPB-related lung injury.

Mid-infrared laser spectroscopy for online analysis of exhaled CO

Carbon monoxide (CO) detection in human breath is the focus of much research because of CO's possible use as a marker molecule for different diseases. Detecting CO in human breath remains a tough challenge because of the low concentrations of CO (ppm range) that must be detected. Another problem is that many other molecules, which can be found in human breath, can interfere in these measurements. Additionally, a time resolution of less than 1 s is needed to resolve the CO curve of an exhalation. In this study 13CO instead of 12CO concentration is measured. The measurements are performed with a cavity leak-out spectroscopy system. The system's properties match the above-mentioned specifications for measurements, even of the rare isotopologue with high specificity, a time resolution of less than 1 s and a detection limit of 7 ppb Hz−1/2. Two investigations are presented here. The first is a measurement showing intraday changes between 9.5% and 23.3% of the exhaled CO level due to vigorous exercise. The second shows a long-term observation of the CO base level revealing natural variations in the recorded CO concentration. The covered time period is 25 weeks during which the differences between the minimum and maximum CO levels for each test case reached 84%.

A study on the integration of micro-reformer and high- temperature PEM fuel cell

This study presented an integration platform for a methanol reformer and high-temperature proton exchange membrane fuel cell (PEMFC). The methanol micro-reformer was combined with the catalytic reaction section and reforming section, whereas the catalytic reaction section with Pt catalysis maintained the constant temperature environment for a reforming process. SRM reforming results showed that 74 to 74.9% hydrogen and 23.5 to 25.7% of carbon dioxide in the mixture product, and less than 2% of carbon monoxide, was produced. Using the reforming product of low carbon monoxide concentration and the highest methanol conversion rate, a micro reformer link with a fuel cell integration experiment was performed. Results showed a high temperature PEMFC with 3 to 4 W power output under methanol flow rates of 15 ml/hr. Due to the lower hydrogen pressure supplied from the micro reformer, the fuel cell power output may become unstable. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/htj.20322

Microbiological, colour and sensory properties of fresh beef steaks in low carbon monoxide concentration

AbstractSteaks from gluteus medius m. (GM) and longissimus dorsi m. (LD) were packaged in atmospheres containing two low levels of CO (0.2 and 0.4%) in combination with 21% O2 or without oxygen. The other components of the modified atmosphere packaging systems were carbon dioxide (30%) and nitrogen (balance). Steaks were evaluated on 0, 7, 14 and 21 days of storage at about 2oC to investigate the effects of the gas mixtures on the microflora, instrumental (CIE L*a*b*) and visual colour and odour. The preservation of colour and odour of GM and LD steaks packaged under low carbon monoxide was best achieved using anoxic mixtures containing 0.2% CO and 30% CO2. Steaks packaged without oxygen retained a desirable colour and practically did not present a visible discoloration or perceptive off‐odour along the entire storage time. Colour stabilization with 0.2% CO and 30% CO2, without O2, following storage up to 21 days at 2°C did not increase microbial risk of products. The increase in CO from 0.2 to 0.4% had a negative effect on the colour of LD steaks which was regarded as ‘artificial’ by some panellists. The higher stability achieved in this study using 0.2% CO may result from increased stability of the colour from Bos indicus × Bos Taurus cross. Discoloration and off‐odour were evident in the GM and LD steaks packaged aerobically after 14 days of storage when the counts of deteriorant bacteria achieved approximately 6.5 to 9.7 log CFU/g. Highest bacteriostatic effect could be obtained if the volume of injected CO2 was sufficient to saturate the meat and keep in balance around the product during storage. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Evaluation of inhaled carbon monoxide as an anti-inflammatory therapy in a nonhuman primate model of lung inflammation

Carbon monoxide (CO) confers anti-inflammatory protection in rodent models of lung injury when applied at low concentration. Translation of these findings to clinical therapies for pulmonary inflammation requires validation in higher mammals. We have evaluated the efficacy of inhaled CO in reducing LPS-induced lung inflammation in cynomolgus macaques. LPS inhalation resulted in profound neutrophil influx and moderate increases in airway lymphocytes, which returned to baseline levels within 2 wk following exposure. CO exposure (500 ppm, 6 h) following LPS inhalation decreased TNF-α release in bronchoalveolar lavage fluid but did not affect IL-6 or IL-8 release. Lower concentrations of CO (250 ppm, 6 h) did not reduce pulmonary neutrophilia. Pretreatment with budesonide, a currently used inhaled corticosteroid, decreased LPS-induced expression of TNF-α, IL-6, and IL-8, and reduced LPS-induced neutrophilia by ∼84%. In comparison, CO inhalation (500 ppm, for 6 h after LPS exposure) reduced neutrophilia by ∼67%. Thus, inhaled CO was nearly as efficacious as pretreatment with an inhaled corticosteroid at reducing airway neutrophil influx in cynomolgus macaques. However, the therapeutic efficacy of CO required relatively high doses (500 ppm) that resulted in high carboxyhemoglobin (COHb) levels (>30%). Lower CO concentrations (250 ppm), associated with anti-inflammatory protection in rodents, were ineffective in cynomolgus macaques and also yielded relatively high COHb levels. These studies highlight the complexity of interspecies variation of dose-response relationships of CO to COHb levels and to the anti-inflammatory functions of CO. The findings of this study warrant further investigations for assessing the therapeutic application of CO in nonhuman primate models of tissue injury and in human diseases. The study also suggests that akin to many new therapies in human diseases, the translation of CO therapy to human disease will require additional extensive and rigorous proof-of-concept studies in humans in the future.

Acute Effects of Passive Smoking on Endothelial Function

Impairment of endothelial functions has been shown to occur after acute and chronic exposure to passive smoking (PS), as assessed by flow-mediated dilatation (FMD) of the brachial artery. A total of 61 participants, 30 male and 31 female, mean ages 26 (18-36) were enrolled in the study. All were clinically well and nonsmokers. All participants stayed for 30 minutes in the smoking room. Carbon monoxide (CO) level was 7.42 ± 0.98 ppm (4.71-10.50). Mean carboxyhemoglobin (COHb) levels of participants were significantly elevated after PS. Mean FMD was 18.6% ± 9% and decreased to 12.4% ± 7% after PS (P < .001). In the current study, with more number of participants at lower CO concentrations (7.42 ppm) and with smaller increase in COHb (51%) significant reduction (33%, P < .001) in FMD was observed.