Predicting the carboxyhemoglobin levels resulting from carbon monoxide exposures.

Data from a series of human exposures to carbon monoxide (CO) were analyzed to determine the fit to the theoretical Coburn-Forster-Kane (CFK) equation which describes CO absorption and excretion. The equation was found to predict carboxyhemoglobin (HbCO) saturations for both men and women at exercise rates ranging from sedentary to 300 kpm/min when they were exposed to steady CO concentrations of 50, 100, and 200 ppm for 0.33-5.25 h. Methods for determining values of each of the variables in the CFK equation were collected and a rational, efficient procedure for solving the equation by trial and error was outlined. The CFK equation was then used to prepare a graph, relating HbCO saturation to exposure duration and concentration, and also to describe the effect of several variables on the rate of CO uptake and equilibrium HbCO levels, important considerations in the determination of permissible public, occupational, and experimental exposure to CO.     

Carbon monoxide uptake kinetics in unamended and long-term nitrogen-amended temperate forest soils

The effect of nitrogen (N) additions on the dynamics of carbon monoxide consumption in temperate forest soils is poorly understood. We measured soil CO profiles, potential rates of CO consumption and uptake kinetics in temperate hardwood and pine control plots and plots amended with 50 and 150 kg N ha-1 year-1 for more than 15 years. Soil profiles of CO concentrations were above atmospheric levels in the high-N plots of both stands, suggesting that in these forest soils the balance between consumption and production may be shifted so that either production is increased or consumption decreased. Highest rates of CO consumption were measured in the organic horizon and decreased with soil depth. In the N-amended plots, CO consumption increased in all but one soil depth of the hardwood stand, but decreased in all soil depths of the pine stand. CO enzyme affinities increased with soil depth in the control plots. However, enzyme affinities in the most active soil depths (organic and 0-5 cm mineral) decreased in response to low levels of N in both stands. In the high-N plots, affinities dramatically-increased in the hardwood stand, but decreased in the organic horizon and increased slightly in the 0-5 cm mineral soil in the pine stand. These findings indicate that long-term N addition either by fertilization or deposition may alter the size, composition and/or physiology of the community of CO consumers so that their ability to act as a sink for atmospheric CO has changed. This change could have a substantial effect on the lifetime of greenhouse gases such as CH4 and therefore the future of Earth's climate.     

Carbon monoxide poisoning

Carbon monoxide poisoning is a significant cause of illness and death. Its protean symptoms probably lead to a gross underestimation of its true incidence. Low levels of carbon monoxide aggravate chronic cardiopulmonary problems, and high levels are associated with cardiac arrhythmias and cerebral edema. Patients who survive acute poisoning are at risk of delayed neurologic sequelae. The measurement of carboxyhemoglobin levels does not reveal the tissue levels of carbon monoxide but is useful in determining therapy. Treatment includes the monitoring and management of cardiac arrhythmias and oxygenation. Hyperbaric oxygenation is beneficial, but there are currently no definite criteria for its use.     

Predictions of carbon monoxide and blood carboxyhemoglobin levels from motor vehicles exhaust emissions

This study aims at predicting Carbon monoxide (CO) emission rate as well as carboxyhaemoglobin (HbCO) levelsin Al-Ain City, United Arab Emirates (UAE). Also, several mathematical models are proposed for estimating both CO emission and HbCO levels. These models yield excellent agreements between observed and predicted data and can be easily coupled with atmospheric models. Carbon monoxide exposure from motor vehicles were measured over a 3-month period from September to December 1995 at three locations in the UAE. The study is based on a sample of 148 cars. The data revealed that the major characteristics of the cars surveyed were as follows: 69.5% of the cars were Japanese, 74.3% of the cars were 5 years old; 41% of the car was range rover or four-wheel-drive car, which indicates a higher proportion of powerful cars; 58.8% was used special fuel; 51.4% had regular maintenance for their cars and 52% of the cars had 4 cylinder engine capacity. Carboxyhaemoglobin (HbCO) levels in the UAE were predicted for 1-hour (1.720 ppm) and 8-hour (8.106 ppm) exposure times. Also, on an average driving of 80 km hr–1 per day, the CO emission rate was found to be 8.729 ppm. These findings indicate that the mean 1-hour and 8-hour Carboxyhaemoglobin (HbCO) levels do not exceed the permissible standards recommended by the WHO. Additionally, the results of stepwise multiple regression analyses revealed that the factors, such as, type of car, size of cylinder, size of car, and maintaining service of the car exerted the greatest influence on the amount and concentration of pollutant emission produced by car exhaust.     

A multicompartment model of carboxyhemoglobin and carboxymyoglobin responses to inhalation of carbon monoxide.

We have developed a model that predicts the distribution of carbon monoxide (CO) in the body resulting from acute inhalation exposures to CO. The model includes a lung compartment, arterial and venous blood compartments, and muscle and nonmuscle soft tissues with both vascular and nonvascular subcompartments. In the model, CO is allowed to diffuse between the vascular and nonvascular subcompartments of the tissues and to combine with myoglobin in the nonvascular subcompartment of muscle tissue. The oxyhemoglobin dissociation curve is represented by a modified Hill equation whose parameters are functions of the carboxyhemoglobin (HbCO) level. Values for skeletal muscle mass and cardiac output are calculated from prediction formulas based on age, weight, and height of individual subjects. We demonstrate that the model fits data from CO rebreathing studies when diffusion of CO into the muscle compartment is considered. The model also fits responses of HbCO to single or multiple exposures to CO lasting for a few minutes each. In addition, the model reproduces reported differences between arterial and venous HbCO levels and replicates predictions from the Coburn-Forster-Kane equation for CO exposures of a 1- to 83-h duration. In contrast to approaches based on the Coburn-Forster-Kane equation, the present model predicts uptake and distribution of CO in both vascular and tissue compartments during inhalation of either constant or variable levels of CO.     

Carbon monoxide gasing leads to alcohol production and butyrate uptake without acetone formation in continuous cultures ofClostridium acetobutylicum

Summary When continuous, steady-state, glucose-limited cultures ofClostridium acetobutylicum were sparged with CO, the completely or almost completely acidogenic fermentations became solventogenic. Alcohol (butanol and ethanol) and lactate production at very high specific production rates were initiated and sustained without acetone, and little or no acetate and butyrate formation. In one fermentation, strong butyrate uptake without acetone formation was observed. Growth could be sustained even with 100% inhibition of H₂ formation. Although CO gasing inhibited growth up to 50%, and H₂ formation up to 100%, it enhanced the rate of glucose uptake up to 300%. TheY _ATP was strongly affected and mostly reduced with respect to its steady-state value. The results support the hypothesis that solvent formation is triggered by an altered electron flow.     

Carbon monoxide attenuates aeroallergen-induced inflammation in mice

Carbon monoxide (CO) generated by catalysis of heme by heme oxygenase is increased in the exhaled air of asthmatic patients. Based on recent studies demonstrating that asthma is an inflammatory disease associated with increased oxidants and that CO confers cytoprotection in oxidant-induced lung injury and inflammation, we sought to better understand the functional role of CO in asthma by using an aeroallergen model. Mice were sensitized to ovalbumin, challenged with aerosolized ovalbumin, and maintained in either CO (250 parts/million) or room air for 48 h. The differential effects of CO on bronchoalveolar lavage (BAL) fluid cell types were observed, with a marked attenuation of BAL fluid eosinophils in the CO-treated animals at 24 and 48 h. A marked reduction of the proinflammatory cytokine interleukin-5 was observed in the CO-treated mice, with no significant changes for other proinflammatory cytokines. These differential effects of CO were also observed with leukotrienes (LTs) and prostaglandins in that CO significantly decreased BAL fluid PGE2, and LTB4 but exerted negligible effect on thromboxane B2 or LTC4/D4/E4. Our data suggest a putative immunoregulatory role for CO in aeroallergen-induced inflammation in mice.     

Carbon monoxide dehydrogenase activity in Bradyrhizobium japonicum

Bradyrhizobium japonicum strain 110spc4 was capable of chemolithoautotrophic growth with carbon monoxide (CO) as a sole energy and carbon source under aerobic conditions. The enzyme carbon monoxide dehydrogenase (CODH; EC 1.2.99.2) has been purified 21-fold, with a yield of 16% and a specific activity of 58 nmol of CO oxidized/min/mg of protein, by a procedure that involved differential ultracentrifugation, anion-exchange chromatography, hydrophobic interaction chromatography, and gel filtration. The purified enzyme gave a single protein and activity band on nondenaturing polyacrylamide gel electrophoresis and had a molecular mass of 230,000 Da. The 230-kDa enzyme was composed of large (L; 75-kDa), medium (M; 28.4-kDa), and small (S; 17.2-kDa) subunits occurring in heterohexameric (LMS)(2) subunit composition. The 75-kDa polypeptide exhibited immunological cross-reactivity with the large subunit of the CODH of Oligotropha carboxidovorans. The B. japonicum enzyme contained, per mole, 2.29 atoms of Mo, 7.96 atoms of Fe, 7.60 atoms of labile S, and 1.99 mol of flavin. Treatment of the enzyme with iodoacetamide yielded di(carboxamidomethyl)molybdopterin cytosine dinucleotide, identifying molybdopterin cytosine dinucleotide as the organic portion of the B. japonicum CODH molybdenum cofactor. The absorption spectrum of the purified enzyme was characteristic of a molybdenum-containing iron-sulfur flavoprotein.