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Results for “Methane”

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PubMed1992

Use of breath hydrogen and methane as markers of colonic fermentation in epidemiologic studies: circadian patterns of excretion.

Fermentation in the large bowel has been postulated to play a protective role against colon cancer. Hydrogen and methane are end products of this fermentation process and are absorbed into the bloodstream and excreted via expired air in the breath. Breath levels of hydrogen and, to a lesser extent, methane correlate strongly with colonic fermentation and may serve as useful biomarkers for this process. In a preliminary study to assess the usefulness of these two markers in epidemiologic studies, we followed the hourly excretion of the two gases in expired alveolar air for 48 hr in 20 healthy subjects, using a Quintron gas chromatograph equipped with a solid-state detector specific for reducing gases. All subjects excreted hydrogen, but 71% did not excrete methane. Possible atmospheric contamination of the samples was corrected for on the basis of breath carbon dioxide levels. A clear circadian pattern of excretion was observed for breath hydrogen, with a decrease during the early morning followed by a progressive increase during the rest of the day. Methane excretion was constant throughout the day. This study shows that four samples collected at convenient times (0600, 1300, 1800, and 2200 hr) are optimal to characterize individuals by their breath excretions of hydrogen and methane during a 24-hr period.

Biomarkers↗

PubMed2006

In situ study of mass transfer in aqueous solutions under high pressures via Raman spectroscopy: a new method for the determination of diffusion coefficients of methane in water near hydrate formation conditions.

A new method was developed for in situ study of the diffusive transfer of methane in aqueous solution under high pressures near hydrate formation conditions within an optical capillary cell. Time-dependent Raman spectra of the solution at several different spots along the one-dimensional diffusion path were collected and thus the varying composition profile of the solution was monitored. Diffusion coefficients were estimated by the least squares method based on the variations in methane concentration data in space and time in the cell. The measured diffusion coefficients of methane in water at the liquid (L)-vapor (V) stable region and L-V metastable region are close to previously reported values determined at lower pressure and similar temperature. This in situ monitoring method was demonstrated to be suitable for the study of mass transfer in aqueous solution under high pressure and at various temperature conditions and will be applied to the study of nucleation and dissolution kinetics of methane hydrate in a hydrate-water system where the interaction of methane and water would be more complicated than that presented here for the L-V metastable condition.

Algorithms↗

PubMed2004

Effect of Japanese horseradish oil on methane production and ruminal fermentation in vitro and in steers.

The effects of alpha-cyclodextrin-horseradish oil complex (CD-HR) on methane production and ruminal fermentation were studied in vitro and in steers. In the in vitro study, diluted ruminal fluid (30 mL) was incubated anaerobically at 38 degrees C for 6 h with or without CD-HR, using cornstarch as substrate. The CD-HR was added at various concentrations (0, 0.17, 0.85 and 1.7 g/L). Treatment affected neither the pH of the medium nor the number of protozoa. Total VFA increased in a linear manner (P = 0.02), and NH3-N decreased quadratically (P = 0.04) as the concentration of CD-HR increased from 0.17 g/L to 1.7 g/L. Molar proportions of acetate decreased in a linear manner (P = 0.03), and propionate increased linearly (P = 0.008) with increasing concentrations of CD-HR. Production of methane was inhibited up to 90%, whereas accumulation of dihydrogen was increased 36-fold by 1.7 g/L of CD-HR supplementation relative to controls. The effect of CD-HR on methane production, ruminal fermentation and microbes, and digestibility was further investigated in vivo using four Holstein steers in a crossover design. The CD-HR supplement was mixed into the concentrate portion of a (1.5:1) Sudangrass hay plus concentrate mixture that was fed twice daily to the steers. Ruminal samples were collected 0, 2, and 5 h after the morning feeding. No effects of CD-HR supplementation on ruminal pH (P = 0.63) or protozoal numbers (P = 0.44) were observed. Molar proportion of acetate was decreased (P = 0.04) and propionate was increased (P = 0.005) by CD-HR treatment. Molar proportion of butyrate was increased (P = 0.05) in CD-HR-supplemented steers. Ruminal NH3-N was decreased (P = 0.05) by treatment. Blood plasma glucose concentration was increased (P = 0.02) and urea-N was decreased (P = 0.04) with CD-HR supplementation. Daily DMI was decreased (P = 0.04), and apparent digestibility of DM (P = 0.13), NDF (P = 0.14), and CP tended (P = 0.14) to be increased by treatment. Methane production was decreased (P = 0.03) by 19%, and the number of methanogens was also decreased (P = 0.03). Although N retention (P = 0.11), total viable bacteria (P = 0.15), and sulfate-reducing bacteria (P = 0.17) were not significantly altered by treatment, tendencies for increases were noted with CD-HR supplementation. The number of cellulolytic (P = 0.38) and acetogenic bacteria (P = 0.32) remained unchanged by treatment. These results indicate that CD-HR supplementation can be used to decrease methane production in steers.

Animals↗

PubMed2006

Relationships of feedlot feed efficiency, performance, and feeding behavior with metabolic rate, methane production, and energy partitioning in beef cattle.

Residual feed intake (RFI) is the difference between the actual and expected feed intake of an animal based on its BW and growth rate over a specified period. The biological mechanisms underlying the variation in feed efficiency in animals with similar BW and growth rate are not well understood. This study determined the relationship of feedlot feed efficiency, performance, and feeding behavior with digestion and energy partitioning of 27 steers. The steers were selected from a total of 306 animals based on their RFI following feedlot tests at the University of Alberta Kinsella Research Station. Selected steers were ranked into high RFI (RFI > 0.5 SD above the mean, n = 11), medium RFI (RFI +/- 0.5 SD above and below the mean, n = 8), and low RFI (RFI < -0.5 SD below the mean, n = 8). The respective BW +/- SD for the RFI groups were 495.6 +/- 12.7, 529.1 +/- 18.6, and 501.2 +/- 15.5 kg. Digestibility and calorimetry trials were performed on a corn-or barley-based concentrate diet in yr 1 and 2, respectively, at 2.5 x maintenance requirements. Mean DMI (g/kg of BW(0.75)) during the measurements for high-, medium-, and low-RFI groups, respectively, were 82.7 +/- 2.0, 78.8 +/- 2.6, and 81.8 +/- 2.5 and did not differ (P > 0.10). Residual feed intake was correlated with daily methane production and energy lost as methane (r = 0.44; P < 0.05). Methane production was 28 and 24% less in low-RFI animals compared with high- and medium-RFI animals, respectively. Residual feed intake tended to be associated (P < 0.10) with apparent digestibilities of DM (r = -0.33) and CP (r = -0.34). The RFI of steers was correlated with DE (r = -0.41; P < 0.05), ME (r = -0.44; P < 0.05), heat production (HP; r = 0.68; P < 0.001), and retained energy (RE; r = -0.67; P < 0.001; energy values are expressed in kcal/kg of BW(0.75)). Feedlot partial efficiency of growth was correlated (P < 0.01) with methane production (r = -0.55), DE (r = 0.46), ME (r = 0.49), HP (r = -0.50), and RE (r = 0.62). With the exception of HP (r = 0.37; P < 0.05), feed conversion ratio was unrelated to the traits considered in the study. Feeding duration was correlated (P < 0.01) with apparent digestibility of DM (r = -0.55), CP (r = -0.47), methane production (r = 0.51), DE (r = -0.52), ME (r = -0.55), and RE (r = -0.60). These results have practical implications for the selection of animals that eat less at a similar BW and growth rate and for the environmental sustainability of beef production.

Animal Feed↗

PubMed1993

Breath methane excretion and intestinal methanogenesis in children and adults in rural Nigeria.

Breath methane excretion was measured in 274 healthy subjects from 2 rural communities in northern Nigeria. Studies in 24 adults showed a normal faecal flora with no enteric pathogens. Breath methane was detected in 122 (77%) of 159 adults, 19 (40%) of 47 older children (2-6 years), and 4 (8%) of 68 young children (< 2 years). Women were slightly more commonly breath methane-positive than men (82% versus 75%, respectively). Hyperventilation did not influence the specificity of the breath methane assay, although levels were circa 30% lower after deliberate hyperventilation. Methanogens were estimated by enrichment culture of faeces from 49 subjects. Of the subjects 76% had faecal methanogens estimated at > or = 10(2)/g, 45% at > or = 10(4)/g, and 16% at > or = 10(6)/g. There was no significant difference in distribution of methanogenic cultures between different age or tribal groups, and there were no obvious correlations between breath methane excretion and either the faecal carriage of methanogens per se or numbers present.

Adult↗

PubMed1995

The prediction of methane production of Holstein cows by several equations.

Ruminants are one of many sources contributing to atmospheric methane. The accuracy of seven published equations for methane prediction was evaluated using a data file consisting of 16 experiments (602 observations). Methane energy emissions ranged from .89 to 7.21 Mcal/d for Holstein cows. The DMI ranged from 9.7 to 28.7 kg/d for lactating cows and 4.0 to 12.9 kg/d for nonlactating cows. Mean dietary concentrations of ADF, CP, and ether extract were similar for lactating and nonlactating cows (20.9, 16.5, and 3.0% for lactating cows versus 21.2, 15.7, and 2.9% for nonlactating cows, respectively). Milk production ranged from 2.7 to 55.9 kg/d. Prediction equations were ranked by correlation coefficients and error of prediction. Prediction of methane energy loss from lactating and nonlactating Holstein cows with equations based on the daily total intake or intake of digested cellulose, hemicellulose, and nonfiber carbohydrates (OM - NDF - CP - ether extract) provided the highest correlation coefficients for reproducibility and the lowest errors of prediction. Predictions were poor for lactating cows when a quadratic function of DMI was used. In general, equations estimated methane production more accurately and precisely for nonlactating than for lactating cows.

Animals↗

PubMed1999

Influence of methane on infrared gas analysis of volatile anesthetics.

Contemporary multigas analyzers determine anesthetic gas concentrations using (near) infrared analysis at either 3.3 or 8-9 microns. Methane also absorbs infrared light at 3.3 microns, but not at 8-9 microns. Consequently, erroneous anesthetic agent readings may result when methane is present in the circuit (e.g. during closed circuit anesthesia), potentially compromising patient safety. We have analyzed in laboratory conditions the influence of different known methane concentrations (100, 500 and 1000 ppm) on the gas-analysis readings provided by some clinical monitoring devices that use infrared absorption for the measurement of inhalation anesthetic concentration. At 3.3 microns wavelength the influence on the measurement of halothane was important, whereas the influence on that of enflurane and isoflurane was less pronounced. For desflurane and sevoflurane measurements, the influence of methane at 3.3 microns wavelength proved to be minimal. At higher wavelengths (8-9 microns) no influence of methane could be demonstrated.

Anesthesia, Closed-Circuit↗

PubMedDate not supplied

[Assimilation of carbon dioxide and oxidation of methane in various zones of the Rainbow hyperthermophilic field zones].

Rates of carbon dioxide assimilation and methane oxidation were determined in various zones of the Rainbow Hydrothermal Field (36 degrees N) of the Mid-Atlantic Ridge. In the plume above the hydrothermal field, anomalously high methane content was recorded; the microbial population density (up to 10(5) cells/ml) was an order of magnitude higher than the background values; and the CO2 assimilation rate varied from 0.01 to 1.1 micrograms C/(1 day). Based on the data on CO2 assimilation, the production of organic carbon due to bacterial chemosynthesis in the plume was calculated to be 930 kg/day or 340 tons/year (about 29% of the organic carbon production in the photic zone). In the black smoke above active smokers, the microbial population density was as high as 10(6) cells/ml; the rate of CO2 assimilation made up 5-10 micrograms C/(1 day); the methane oxidation rate varied from 0.15 to 12.7 mu/(1 day); and the methane concentration ranged from 1.05 to 70.6 mu/l. In bottom sediments enriched with sulfides, the rate of CO2 assimilation was at least an order of magnitude higher than in oxidized metal-bearing sediments. At the base of an active construction site, whitish sediment was found, which was characterized by a methane high content (92 mu/dm3) and a high rate of oxidation (1.7 mu/(dm3 day)).

Carbon Dioxide↗

PubMedDate not supplied

[Anaerobic methane oxidation].

To clarify the biological mechanism of anaerobic methane oxidation, experiments were performed with samples of the Black Sea anaerobic sediments and with the aerobic methane-oxidizing bacterium Methylomonas methanica strain 12. The inhibition-stimulation analysis did not allow an unambiguous conclusion to be made about direct and independent role of either methanogenic or sulfate-reducing microorganisms in the biogeochemical process of anaerobic methane oxidation. Enrichment cultures obtained from samples of water and reduced sediments oxidized methane under anaerobic conditions, primarily in the presence of acetate or formate or of a mixture of acetate, formate, and lactate. However, this ability was retained by the cultures for no more than two transfers on corresponding media. Experiments showed that the aerobic methanotroph Mm. methanica strain 12 is incapable of anaerobic methane oxidation at the expense of the reduction of amorphous FeOOH.

Acetates↗

PubMedDate not supplied

[Methane oxidation in landfill cover soil].

Methane oxidation in the cover soil of the Khmet'evo municipal landfill in Moscow oblast was investigated. Methane emission from the experimental parcel of the site was highly inhomogeneous. At a depth of 45-60 cm, the pore gas mainly consisted of CH4 (60-70%) and CO2 (30-40%). In the upper horizons of the cover soil, the concentration of these gases sharply decreased. Techniques for estimation of the methane-oxidizing activity in the cover soil of the landfill were tested. The rate of methane oxidation in the soil, the factor limiting methane emission from the surface of the site, correlated with the cell number of culturable methanotrophic bacteria. The method of indirect immunofluorescence revealed ten known species of methanotrophic bacteria in enrichment cultures obtained from samples of the cover soil. Our results also indicate the presence of unknown psychrotolerant methanotrophs that are active at the low temperatures characteristic of Moscow oblast.

Cities↗

PubMed2006

[Short-term monitoring of methane emission regulation from a municipal solid waste landfill].

To understand the regulation and influencing factors of methane emission from landfills in China, rates of methane emission from Hangzhou Tianziling municipal solid waste landfill were measured by static chamber technique. The emission rates ranged from 3.67 to 36.65 mmol x (m2 x h)(-1) on average of the two tested points (No. 1 and No. 2) during 24-hour cycle. The max ratio of emission rates between the two tested points was 625. The difference with the rates of the two tested points could be explained by the depth of the cover soils. Rate of methane emission from each point correlated with atmospheric pressure and water content of landfill cover soils, and the result from stepwise regression was r2 = 0.89 for point No. 1, r2 = 0.76 for point No. 2. Rates of methane emission varied from -0.23 to 0.32 mmol (m2 x h)(-1) on average in 40-day test (points with same depth of cover soils). The low correlation (r2 = 0.15) with atmospheric pressure showed that atmospheric pressure was not the decisive factor. For some time, emission rates correlated with water content or temperature of the landfill cover soils significantly, but not obvious (r2 < 0.4) during the whole monitoring time. When atmospheric pressure was included, the results of stepwise regression were improved significantly, which showed that methane emission rates were influenced by different factors, but the effect of each factor was not the same at a different time.

Air Pollutants↗

PubMedDate not supplied

[Effect of inorganic electron acceptors on the bacterial formation of methane from cellulose].

The effect of nitrate, nitrogen oxide, sulphate, oxidized iron and manganese on the methane fermentation of cellulose was studied with the enrichment bacterial culture. The action of these oxidants on the enrichment culture growing on cellulose was compared to that on a pure methanosarcina culture in order to find out which stage of methane formation from cellulose was inhibited. Nitrate at the concentration of 2 g NaNO3 and more per litre of the medium inhibited the whole process of fermentation; at the concentration less than 2 g/l the production of methane was inhibited, and cellulose decomposition was accompanied with denitrification. Sulphate at the concentration of 2 g MgSO4 per litre had no effect on the formation of methane but the process was inhibited by the product of its reduction, i. e. sulphiade. Cellulose decomposition could be accompanied with sulphate reduction if sulphide produced in the process of the reduction were removed from the medium. In this case as well as in the presence of ferric iron, the production of methane was inhibited due to competition for the reducing agent.

Cellulose↗

PubMedDate not supplied

[Mechanism of methane oxidation by intact cells of obligate methylotrophs].

Ethane and propane were found to be competitive inhibitors of methane oxidation. Obligate methylotrophs can oxidize ethane only in the presence of methane, i.e. co-oxidation of ethane takes place. Studies on the kinetics of simultaneous oxidation of ethane and methane have shown that their oxidation is catalysed by one and the same enzyme system, within one and the same enzyme active site; therefore, the absolute substrate specificity is absent. The reactions of methane and ethane oxidation are coupled since ethane can be oxidized only after the reduced coenzyme had been provided by the reaction of methane oxidation.

Ethane↗

PubMedDate not supplied

[Methane in cadaver blood--homicide by natural gas or postmortem formation?].

A man had a quarrel with his wife. Suddenly he collapsed and became cyanotic. The woman supposed him to be dead. Because she was afraid of familiar requital, she opened the gas-cock of the cooking-range to pretend a suicide; methane emitted. The autopsy revealed a fresh cardiac infarction. Postmortem chemical analysis established methane in the blood. The question was, whether the methane had any importance for the death. By experimental inhalation of a methane-air-mixture (3%) we could expose, that the methane concentration in postmortem blood didn't have any relevance for the death.

Adult↗

PubMed2002

Methane activation and oxidation in sulfuric acid.

The H/D exchange observed when methane is contacted with D(2)SO(4) at 270-330 degrees C shows that the alkane behaves as a sigma base and undergoes rapid and reversible protonation at this temperature. DFT studies of the hydrogen exchange between a monomer and a dimer of sulfuric acid and methane show that the transition states involved in the exchange are bifunctional, that is one hydrogen atom is transferred from a hydroxy group in sulfuric acid to methane, while one hydrogen atom is abstracted from methane by a non-hydroxy oxygen atom in sulfuric acid. All the transition states include a CH(5) moiety, which shows similarities to the methanium ion CH(5) (+). The calculated potential activation energy of the hydrogen exchange for the monomer is 174 kJ mol(-1), which is close to the experimental value (176 kJ mol(-1)). Solvation of the monomer and the transition state of the monomer with an extra sulfuric acid molecule, decrease the potential activation energy by 6 kJ mol(-1). The acid-base process is in competition, however, with an oxidative process involving methane and sulfuric acid which leads to CO(2), SO(2), and water, and thus to a decrease of acidity and loss of reactivity of the medium.

Journal Article↗

PubMed2006

Solubility measurement of methane in aqueous solution of sodium dodecyl sulfate at ambient temperature and near hydrate conditions.

Solubility data of methane in aqueous solutions of sodium dodecyl sulfate (SDS) with different concentrations were measured at ambient temperature and near hydrate conditions. The critical micelle concentration (CMC) and the number of methane molecules dissolved in each micelle of the methane + water + SDS system were calculated and compared with those of the ethylene + water + SDS system. The results demonstrated that the micelles could be formed in the SDS concentration range where an efficient promotion effect on hydrate formation was previously reported; the micelle solubilization to methane molecules was remarkable near hydrate conditions, and the ethylene molecules could be solubilized in micelles in preference to methane molecules.

Journal Article↗

PubMed1999

Vascular plant controls on methane emissions from northern peatforming wetlands.

Methane emissions from wetlands are highly variable, both spatially and temporally and at scales ranging from microtopographic to regional differences. To comprehend this variation fully and also to predict responses to climate change, an understanding of the intimate linkage between carbon cycling and methane emission in these systems is needed. The presence of vascular plants has been recognized recently as one of the key factors controlling the scale of methane fluxes because it affects processes coupled to transport, production and consumption of methane. A wide area of research has therefore opened up, calling for investigations into details of the impact of vascular plants on methane emissions.

Journal Article↗

PubMedDate not supplied

QSAR modeling of oxidative stress in vitro following hepatocyte exposures to halogenated methanes.

Volatile halogenated aliphatic compounds are among those chemicals that can cause oxidative stress in vitro and in vivo. Relationships can be identified between the potential of these chemicals to elicit certain biological responses and their specific chemical descriptors, such as molecular orbital energies (LUMO) or partition coefficients (logP). A quantitative structure-activity relationship (QSAR) model has not been reported previously for the potential of a series of brominated and chlorinated methanes to induce oxidative stress in primary rat hepatocytes. By utilizing a novel in vitro methodology to expose cultures of rat primary hepatocytes to volatile chemicals, biological responses were assessed from exposures of hepatocytes to individual halogenated methanes. Indicators of lipid peroxidation, reactive oxygen species and cytotoxicity were measured. For the 10 brominated and chlorinated methanes tested, semi-empirical molecular orbital methods were used to calculate the physical/chemical descriptors used in the QSAR models. These models were used to explain the relative potential for a given halogenated methane to induce markers of oxidative stress or related damage in vitro. The results showed that certain descriptors, such as the molecular orbital energies, bond lengths, and lipophilicity are quantitatively correlated with induction of indicators for oxidative stress and cytotoxicity by halogenated methanes in primary rat hepatocytes.

Animal Testing Alternatives↗