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| carbon dioxide |
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| CHEBI:16526 |
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| A one-carbon compound with formula CO2 in which the carbon is attached to each oxygen atom by a double bond. A colourless, odourless gas under normal conditions, it is produced during respiration by all animals, fungi and microorganisms that depend directly or indirectly on living or decaying plants for food. |
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This entity has been manually annotated by the ChEBI Team.
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CHEBI:48829, CHEBI:3283, CHEBI:13282, CHEBI:13283, CHEBI:13285, CHEBI:13284, CHEBI:23011
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| ChemicalBook:CB5778186, eMolecules:474232 |
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more structures >>
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| Carbon dioxide is a chemical compound with the chemical formula CO2. It is made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature and at normally-encountered concentrations it is odorless. As the source of carbon in the carbon cycle, atmospheric CO2 is the primary carbon source for life on Earth. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater.
It is a trace gas in Earth's atmosphere at 421 parts per million (ppm), or about 0.042% (as of May 2022) having risen from pre-industrial levels of 280 ppm or about 0.028%. Burning fossil fuels is the main cause of these increased CO2 concentrations, which are the primary cause of climate change.
Its concentration in Earth's pre-industrial atmosphere since late in the Precambrian was regulated by organisms and geological features. Plants, algae and cyanobacteria use energy from sunlight to synthesize carbohydrates from carbon dioxide and water in a process called photosynthesis, which produces oxygen as a waste product. In turn, oxygen is consumed and CO2 is released as waste by all aerobic organisms when they metabolize organic compounds to produce energy by respiration. CO2 is released from organic materials when they decay or combust, such as in forest fires. When carbon dioxide dissolves in water, it forms carbonate and mainly bicarbonate (HCO−3), which causes ocean acidification as atmospheric CO2 levels increase.
Carbon dioxide is 53% more dense than dry air, but is long lived and thoroughly mixes in the atmosphere. About half of excess CO2 emissions to the atmosphere are absorbed by land and ocean carbon sinks. These sinks can become saturated and are volatile, as decay and wildfires result in the CO2 being released back into the atmosphere. CO2, or the carbon it holds, is eventually sequestered (stored for the long term) in rocks and organic deposits like coal, petroleum and natural gas.
Nearly all CO2 produced by humans goes into the atmosphere. Less than 1% of CO2 produced annually is put to commercial use, mostly in the fertilizer industry and in the oil and gas industry for enhanced oil recovery. Other commercial applications include food and beverage production, metal fabrication, cooling, fire suppression and stimulating plant growth in greenhouses.: 3
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Read full article at Wikipedia
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Mus musculus
(NCBI:txid10090)
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Source: BioModels - MODEL1507180067
See:
PubMed
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Saccharomyces cerevisiae
(NCBI:txid4932)
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Source: yeast.sf.net
See:
PubMed
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Escherichia coli
(NCBI:txid562)
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See:
PubMed
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Homo sapiens
(NCBI:txid9606)
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See:
DOI
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solvent
A liquid that can dissolve other substances (solutes) without any change in their chemical composition.
greenhouse gas
A gas in an atmosphere that absorbs and emits radiation within the thermal infrared range, so contributing to the 'greenhouse effect'.
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Escherichia coli metabolite
Any bacterial metabolite produced during a metabolic reaction in Escherichia coli.
Saccharomyces cerevisiae metabolite
Any fungal metabolite produced during a metabolic reaction in Baker's yeast (Saccharomyces cerevisiae ).
human metabolite
Any mammalian metabolite produced during a metabolic reaction in humans (Homo sapiens).
antagonist
Substance that attaches to and blocks cell receptors that normally bind naturally occurring substances.
mouse metabolite
Any mammalian metabolite produced during a metabolic reaction in a mouse (Mus musculus).
food packaging gas
A food additive that is a (generally inert) gas which is used to envelop foodstuffs during packing and so protect them from unwanted chemical reactions such as food spoilage or oxidation during subsequent transport and storage. The term includes propellant gases, used to expel foods from a container.
food propellant
A propellant that is used to expel foods from an aerosol container.
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refrigerant
A substance used in a thermodynamic heat pump cycle or refrigeration cycle that undergoes a phase change from a gas to a liquid and back. Refrigerants are used in air-conditioning systems and freezers or refrigerators and are assigned a "R" number (by ASHRAE - formerly the American Society of Heating, Refrigerating and Air Conditioning Engineers), which is determined systematically according to their molecular structure.
solvent
A liquid that can dissolve other substances (solutes) without any change in their chemical composition.
vasodilator agent
A drug used to cause dilation of the blood vessels.
anaesthetic
Substance which produces loss of feeling or sensation.
food packaging gas
A food additive that is a (generally inert) gas which is used to envelop foodstuffs during packing and so protect them from unwanted chemical reactions such as food spoilage or oxidation during subsequent transport and storage. The term includes propellant gases, used to expel foods from a container.
food propellant
A propellant that is used to expel foods from an aerosol container.
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View more via ChEBI Ontology
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carbon dioxide
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dioxidocarbon
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methanedione
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[CO2]
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MolBase
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Carbon dioxide
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KEGG COMPOUND
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CARBON DIOXIDE
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PDBeChem
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carbonic anhydride
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UM-BBD
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CO2
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KEGG COMPOUND
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CO2
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UniProt
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E 290
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ChEBI
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E-290
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ChEBI
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E290
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ChEBI
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R-744
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ChEBI
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119
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PPDB
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4256
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DrugCentral
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752
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MolBase
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C00011
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KEGG COMPOUND
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c0131
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UM-BBD
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CARBON-DIOXIDE
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MetaCyc
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Carbon_dioxide
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Wikipedia
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CO2
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PDBeChem
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D00004
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KEGG DRUG
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HMDB0001967
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HMDB
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124-38-9
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KEGG COMPOUND
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124-38-9
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NIST Chemistry WebBook
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124-38-9
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CAS Registry Number
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ChemIDplus
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1900390
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Reaxys Registry Number
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Reaxys
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989
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Gmelin Registry Number
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Gmelin
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Christa G, Zimorski V, Woehle C, Tielens AG, Wägele H, Martin WF, Gould SB (2014)
Plastid-bearing sea slugs fix CO2 in the light but do not require photosynthesis to survive.
Proceedings. Biological sciences 281, 20132493 [PubMed:24258718]
[show Abstract]
Several sacoglossan sea slugs (Plakobranchoidea) feed upon plastids of large unicellular algae. Four species--called long-term retention (LtR) species--are known to sequester ingested plastids within specialized cells of the digestive gland. There, the stolen plastids (kleptoplasts) remain photosynthetically active for several months, during which time LtR species can survive without additional food uptake. Kleptoplast longevity has long been puzzling, because the slugs do not sequester algal nuclei that could support photosystem maintenance. It is widely assumed that the slugs survive starvation by means of kleptoplast photosynthesis, yet direct evidence to support that view is lacking. We show that two LtR plakobranchids, Elysia timida and Plakobranchus ocellatus, incorporate (14)CO2 into acid-stable products 60- and 64-fold more rapidly in the light than in the dark, respectively. Despite this light-dependent CO2 fixation ability, light is, surprisingly, not essential for the slugs to survive starvation. LtR animals survived several months of starvation (i) in complete darkness and (ii) in the light in the presence of the photosynthesis inhibitor monolinuron, all while not losing weight faster than the control animals. Contrary to current views, sacoglossan kleptoplasts seem to be slowly digested food reserves, not a source of solar power. | Coelho Junior A, Parra JR (2013)
Effect of carbon dioxide (CO2) on mortality and reproduction of Anagasta kuehniella (Zeller 1879), in mass rearing, aiming at the production of Trichogramma spp.
Anais da Academia Brasileira de Ciencias 85, 823-831 [PubMed:23828359]
[show Abstract]
Eggs of Anagasta kuehniella (Zeller 1879) are widely used for mass rearing of Trichogramma spp. and other parasitoids and predators, largely commercialized in many countries. The aim of this study is to evaluate the effect of carbon dioxide (CO2) originated from larval metabolism on the biological parameters of A. kuehniella. For that purpose, we assess the production of carbon dioxide (CO2) per rearing tray of A. kuehniella and the effect of CO2 on the viability of egg-to-adult period and oviposition of A. kuehniella. Results allow to estimate that a rearing tray, containing 10,000 larvae between the 4th and 5th instars, produces an average of 30.67 mL of CO2 per hour. The highest egg production of A. kuehniella was obtained when the larvae were kept in rooms with lower concentration of CO2 (1,200 parts per million - ppm), producing 23% more eggs than in rooms with higher CO2 concentrations. In rooms with high density of trays (70 trays/room), CO2 concentration exceeded 4,400 ppm. The viability of the egg-to-adult period was not influenced by carbon dioxide. | Singh SK, Badgujar G, Reddy VR, Fleisher DH, Bunce JA (2013)
Carbon dioxide diffusion across stomata and mesophyll and photo-biochemical processes as affected by growth CO2 and phosphorus nutrition in cotton.
Journal of plant physiology 170, 801-813 [PubMed:23384758]
[show Abstract]
Nutrients such as phosphorus may exert a major control over plant response to rising atmospheric carbon dioxide concentration (CO2), which is projected to double by the end of the 21st century. Elevated CO2 may overcome the diffusional limitations to photosynthesis posed by stomata and mesophyll and alter the photo-biochemical limitations resulting from phosphorus deficiency. To evaluate these ideas, cotton (Gossypium hirsutum) was grown in controlled environment growth chambers with three levels of phosphate (Pi) supply (0.2, 0.05 and 0.01mM) and two levels of CO2 concentration (ambient 400 and elevated 800μmolmol(-1)) under optimum temperature and irrigation. Phosphate deficiency drastically inhibited photosynthetic characteristics and decreased cotton growth for both CO2 treatments. Under Pi stress, an apparent limitation to the photosynthetic potential was evident by CO2 diffusion through stomata and mesophyll, impairment of photosystem functioning and inhibition of biochemical process including the carboxylation efficiency of ribulose-1,5-bisphosphate carboxylase/oxyganase and the rate of ribulose-1,5-bisphosphate regeneration. The diffusional limitation posed by mesophyll was up to 58% greater than the limitation due to stomatal conductance (gs) under Pi stress. As expected, elevated CO2 reduced these diffusional limitations to photosynthesis across Pi levels; however, it failed to reduce the photo-biochemical limitations to photosynthesis in phosphorus deficient plants. Acclimation/down regulation of photosynthetic capacity was evident under elevated CO2 across Pi treatments. Despite a decrease in phosphorus, nitrogen and chlorophyll concentrations in leaf tissue and reduced stomatal conductance at elevated CO2, the rate of photosynthesis per unit leaf area when measured at the growth CO2 concentration tended to be higher for all except the lowest Pi treatment. Nevertheless, plant biomass increased at elevated CO2 across Pi nutrition with taller plants, increased leaf number and larger leaf area. | Scott DR, Marcus EA, Wen Y, Singh S, Feng J, Sachs G (2010)
Cytoplasmic histidine kinase (HP0244)-regulated assembly of urease with UreI, a channel for urea and its metabolites, CO2, NH3, and NH4(+), is necessary for acid survival of Helicobacter pylori.
Journal of bacteriology 192, 94-103 [PubMed:19854893]
[show Abstract]
Helicobacter pylori colonizes the normal human stomach by maintaining both periplasmic and cytoplasmic pH close to neutral in the presence of gastric acidity. Urease activity, urea flux through the pH-gated urea channel, UreI, and periplasmic alpha-carbonic anhydrase are essential for colonization. Exposure to pH 4.5 for up to 180 min activates total bacterial urease threefold. Within 30 min at pH 4.5, the urease structural subunits, UreA and UreB, and the Ni(2+) insertion protein, UreE, are recruited to UreI at the inner membrane. Formation of this complex and urease activation depend on expression of the cytoplasmic sensor histidine kinase, HP0244. Its deletion abolishes urease activation and assembly, impairs cytoplasmic and periplasmic pH homeostasis, and depolarizes the cells, with an approximately 7-log loss of survival at pH 2.5, even in 10 mM urea. Associated with this assembly, UreI is able to transport NH(3), NH(4)(+), and CO(2), as shown by changes in cytoplasmic pH following exposure to NH(4)Cl or CO(2). To be able to colonize cells in the presence of the highly variable pH of the stomach, the organism expresses two pH-sensor histidine kinases, one, HP0165, responding to a moderate fall in periplasmic pH and the other, HP0244, responding to cytoplasmic acidification at a more acidic medium pH. Assembly of a pH-regulatory complex of active urease with UreI provides an advantage for periplasmic buffering. | Sakakura T, Kohno K (2009)
The synthesis of organic carbonates from carbon dioxide.
Chemical communications (Cambridge, England)1312-1330 [PubMed:19259576]
[show Abstract]
Carbon dioxide (CO(2)) is an easily available, renewable carbon resource, which has the advantages of being non-toxic, abundant and economical. CO(2) is also attractive as an environmentally friendly chemical reagent, and is especially useful as a phosgene substitute. CO(2) is an "anhydrous carbonic acid" that rapidly reacts with basic compounds. Nucleophilic attack at CO(2) conveniently produces carboxyl and carbamoyl groups. Further reactions of these species with electrophiles lead to the formation of organic carbonates and carbamates. The present article deals with the synthetic technologies leading to organic carbonates using CO(2) as a raw material. | Mitteilungen der Ad-hoc-Arbeitsgruppe Innenraumrichtwerte der Innenraumlufthygiene-Kommission des Umweltbundesamtes und der Obersten Landesgesundheitsbehörden (2008)
[Health evaluation of carbon dioxide in indoor air].
Bundesgesundheitsblatt, Gesundheitsforschung, Gesundheitsschutz 51, 1358-1369 [PubMed:19043767]
[show Abstract]
For over 150 years, carbon dioxide has been an acknowledged indicator of indoor air quality. To estimate the air quality in mechanically ventilated buildings, DIN EN 13779 proposes four different levels of indoor carbon dioxide concentration. However, apart from the early guideline value of 1000 ppm carbon dioxide recommended by Pettenkofer in 1858, there is no actual guideline value for naturally ventilated buildings. Regarding recent intervention studies, the German Working Group on Indoor Guideline Values of the Federal Environmental Agency and the States' Health Authorities therefore recommends the following guide values, based on health and hygiene considerations: concentrations of indoor air carbon dioxide below 1000 ppm are regarded as harmless, those between 1000 and 2000 ppm as elevated and those above 2000 ppm as unacceptable. In addition to the recommendations for TVOC values, this further assists in the assessment of indoor air quality. | Milton CC, Partridge L (2008)
Brief carbon dioxide exposure blocks heat hardening but not cold acclimation in Drosophila melanogaster.
Journal of insect physiology 54, 32-40 [PubMed:17884085]
[show Abstract]
Carbon dioxide is a commonly used anaesthetic in Drosophila research. While any detrimental effects of CO2 exposure on behaviour or traits are largely unknown, a recent study observed significant effects of CO2 exposure on rapid cold hardening and chill-coma recovery in Drosophila melanogaster. In this study we investigated the effect of a brief CO2 exposure on heat hardening and cold acclimation in D. melanogaster, measuring heat knockdown and chill-coma recovery times of flies exposed to CO2 for 1 min after hardening or acclimation. CO2 anaesthesia had a significant negative effect on heat hardening, with heat knockdown rates in hardened flies completely reduced to those of controls after CO2 exposure. Chill-coma recovery rates also significantly increased in acclimated flies that were exposed to CO2, although not to the same extent seen in the heat populations. CO2 exposure had no impact on heat knockdown rates of control flies, while there was a significant negative effect of the anaesthetic on chill-coma recovery rates of control flies. In light of these results, we suggest that CO2 should not be used after hardening in heat resistance assays due to the complete reversal of the heat hardening process upon exposure to CO2. | De Rosa M, Gagliardi G, Rocco A, Somma R, De Natale P, De Natale G (2007)
Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy).
Geochemical transactions 8, 5 [PubMed:17448243]
[show Abstract]
We report on a continuous-measurement campaign carried out in Vulcano (Aeolian islands, Sicily), devoted to the simultaneous monitoring of CO2 and H2O concentrations. The measurements were performed with an absorption spectrometer based on a semiconductor laser source emitting around a 2-microm wavelength. The emitted radiation was selectively absorbed by two molecular ro-vibrational transitions specific of the investigated species. Data for CO2 and H2O concentrations, and CO2 soil diffusive flux using an accumulation chamber configuration, were collected at several interesting sampling points on the island (Porto Levante beach- PLB, Fossa Grande Crater - FOG- and Valley of Palizzi, PAL). CO2/H2O values, measured on the ground, are very similar (around 0.019 (+/- 0.006)) and comparable to the previous discrete detected values of 0.213 (Fumarole F5-La Fossa crater rim) and 0.012 (Fumarole VFS - Baia Levante beach) obtaid during the 1977-1993 heating phase of the crater fumaroles. In this work much more homogeneous values are found in different points of the three sites investigated. The field work, although carried out in a limited time window (25th-28th August 2004), pointed out the new apparatus is suitable for continuous gas monitoring of the two species and their ratios, which are important geochemical indicators of volcanic activity, for which other reliable continuous monitoring systems are not yet available. | Liang MC, Blake GA, Lewis BR, Yung YL (2007)
Oxygen isotopic composition of carbon dioxide in the middle atmosphere.
Proceedings of the National Academy of Sciences of the United States of America 104, 21-25 [PubMed:17190796]
[show Abstract]
The isotopic composition of long-lived trace molecules provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 parts per million by volume (ppmv) in the mesosphere. Here, we successfully reproduce the isotopic composition of CO(2) in the middle atmosphere, which has not been previously reported. The mass-independent fractionation of oxygen in CO(2) can be satisfactorily explained by the exchange reaction with O((1)D). In the stratosphere, the major source of O((1)D) is O(3) photolysis. Higher in the mesosphere, we discover that the photolysis of (16)O(17)O and (16)O(18)O by solar Lyman-alpha radiation yields O((1)D) 10-100 times more enriched in (17)O and (18)O than that from ozone photodissociation at lower altitudes. This latter source of heavy O((1)D) has not been considered in atmospheric simulations, yet it may potentially affect the "anomalous" oxygen signature in tropospheric CO(2) that should reflect the gross carbon fluxes between the atmosphere and terrestrial biosphere. Additional laboratory and atmospheric measurements are therefore proposed to test our model and validate the use of CO(2) isotopic fractionation as a tracer of atmospheric chemical and dynamical processes. | Piao S, Friedlingstein P, Ciais P, de Noblet-Ducoudré N, Labat D, Zaehle S (2007)
Changes in climate and land use have a larger direct impact than rising CO2 on global river runoff trends.
Proceedings of the National Academy of Sciences of the United States of America 104, 15242-15247 [PubMed:17878298]
[show Abstract]
The significant worldwide increase in observed river runoff has been tentatively attributed to the stomatal "antitranspirant" response of plants to rising atmospheric CO(2) [Gedney N, Cox PM, Betts RA, Boucher O, Huntingford C, Stott PA (2006) Nature 439: 835-838]. However, CO(2) also is a plant fertilizer. When allowing for the increase in foliage area that results from increasing atmospheric CO(2) levels in a global vegetation model, we find a decrease in global runoff from 1901 to 1999. This finding highlights the importance of vegetation structure feedback on the water balance of the land surface. Therefore, the elevated atmospheric CO(2) concentration does not explain the estimated increase in global runoff over the last century. In contrast, we find that changes in mean climate, as well as its variability, do contribute to the global runoff increase. Using historic land-use data, we show that land-use change plays an additional important role in controlling regional runoff values, particularly in the tropics. Land-use change has been strongest in tropical regions, and its contribution is substantially larger than that of climate change. On average, land-use change has increased global runoff by 0.08 mm/year(2) and accounts for approximately 50% of the reconstructed global runoff trend over the last century. Therefore, we emphasize the importance of land-cover change in forecasting future freshwater availability and climate. | Wise RG, Ide K, Poulin MJ, Tracey I (2004)
Resting fluctuations in arterial carbon dioxide induce significant low frequency variations in BOLD signal.
NeuroImage 21, 1652-1664 [PubMed:15050588]
[show Abstract]
Carbon dioxide is a potent cerebral vasodilator. We have identified a significant source of low-frequency variation in blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal at 3 T arising from spontaneous fluctuations in arterial carbon dioxide level in volunteers at rest. Fluctuations in the partial pressure of end-tidal carbon dioxide (Pet(CO(2))) of +/-1.1 mm Hg in the frequency range 0-0.05 Hz were observed in a cohort of nine volunteers. Correlating with these fluctuations were significant generalized grey and white matter BOLD signal fluctuations. We observed a mean (+/-standard error) regression coefficient across the group of 0.110 +/- 0.033% BOLD signal change per mm Hg CO(2) for grey matter and 0.049 +/- 0.022% per mm Hg in white matter. Pet(CO(2))-related BOLD signal fluctuations showed regional differences across the grey matter, suggesting variability of the responsiveness to carbon dioxide at rest. Functional magnetic resonance imaging (fMRI) results were corroborated by transcranial Doppler (TCD) ultrasound measurements of the middle cerebral artery (MCA) blood velocity in a cohort of four volunteers. Significant Pet(CO(2))-correlated fluctuations in MCA blood velocity were observed with a lag of 6.3 +/- 1.2 s (mean +/- standard error) with respect to Pet(CO(2)) changes. This haemodynamic lag was adopted in the analysis of the BOLD signal. Doppler ultrasound suggests that a component of low-frequency BOLD signal fluctuations is mediated by CO(2)-induced changes in cerebral blood flow (CBF). These fluctuations are a source of physiological noise and a potentially important confounding factor in fMRI paradigms that modify breathing. However, they can also be used for mapping regional vascular responsiveness to CO(2). | Nakahata K, Kinoshita H, Hirano Y, Kimoto Y, Iranami H, Hatano Y (2003)
Mild hypercapnia induces vasodilation via adenosine triphosphate-sensitive K+ channels in parenchymal microvessels of the rat cerebral cortex.
Anesthesiology 99, 1333-1339 [PubMed:14639145]
[show Abstract]
BackgroundCarbon dioxide is an important vasodilator of cerebral blood vessels. Cerebral vasodilation mediated by adenosine triphosphate (ATP)-sensitive K+ channels has not been demonstrated in precapillary microvessel levels. Therefore, the current study was designed to examine whether ATP-sensitive K+ channels play a role in vasodilation induced by mild hypercapnia in precapillary arterioles of the rat cerebral cortex.MethodsBrain slices from rat cerebral cortex were prepared and superfused with artificial cerebrospinal fluid, including normal (Pco2 = 40 mmHg; pH = 7.4), hypercapnic (Pco2 = 50 mmHg; pH = 7.3), and hypercapnic normal pH (Pco2 = 50 mmHg; pH = 7.4) solutions. The ID of a cerebral parenchymal arteriole (5-9.5 microm) was monitored using computerized videomicroscopy.ResultsDuring contraction to prostaglandin F2alpha (5 x 10(-7) m), hypercapnia, but not hypercapnia under normal pH, induced marked vasodilation, which was completely abolished by the selective ATP-sensitive K+ channel antagonist glibenclamide (5 x 10(-6) m). However, the selective Ca2+-dependent K+ channel antagonist iberiotoxin (10(-7) m) as well as the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (10(-4) m) did not alter vasodilation. A selective ATP-sensitive K+ channel opener, levcromakalim (3 x 10(-8) to 3 x 10(-7) m), induced vasodilation, whereas this vasodilation was abolished by glibenclamide.ConclusionThese results suggest that in parenchymal microvessels of the rat cerebral cortex, decreased pH corresponding with hypercapnia, but not hypercapnia itself, contributes to cerebral vasodilation produced by carbon dioxide and that ATP-sensitive K+ channels play a major role in vasodilator responses produced by mild hypercapnia. | Kaiser CS, Römpp H, Schmidt PC (2001)
Pharmaceutical applications of supercritical carbon dioxide.
Die Pharmazie 56, 907-926 [PubMed:11802652]
[show Abstract]
The appearance of a supercritical state was already observed at the beginning of the 19th century. Nevertheless, the industrial extraction of plant and other natural materials started about twenty years ago with the decaffeination of coffee. Today carbon dioxide is the most common gas for supercritical fluid extraction in food and pharmaceutical industry. Since pure supercritical carbon dioxide is a lipophilic solvent, mixtures with organic solvents, especially alcohols, are used to increase the polarity of the extraction fluid; more polar compounds can be extracted in this way. The main fields of interest are the extraction of vegetable oils from plant material in analytical and preparative scale, the preparation of essential oils for food and cosmetic industry and the isolation of substances of pharmaceutical relevance. Progress in research was made by the precise measurement of phase equilibria data by means of different methods. Apart from extraction, supercritical fluid chromatography was introduced in the field of analytics, as well as micro- and nanoparticle formation using supercritical fluids as solvent or antisolvent. This review presents pharmaceutical relevant literature of the last twenty years with special emphasis on extraction of natural materials. | Walle T, Walle UK, Halushka PV (2001)
Carbon dioxide is the major metabolite of quercetin in humans.
The Journal of nutrition 131, 2648-2652 [PubMed:11584085]
[show Abstract]
A previous study in ileostomy patients indicated that dietary glucosides of the flavonoid quercetin are hydrolyzed efficiently in the intestinal lumen, followed by absorption of a large fraction of the quercetin aglycone. To determine the fate of quercetin, we administered 1.85 MBq (50 microCi) of (14)C-quercetin both orally (100 mg, 330 micromol) and intravenously (iv; 0.3 mg, 1 micromol) to healthy volunteers. Serial plasma samples, urines and stools were collected for 72 h. Total radioactivity was determined by liquid scintillation spectrometry directly in plasma and urine and after repeated methanol extraction of stool homogenate samples. The oral absorption, based on total radioactivity, was surprisingly high, ranging from 36.4 to 53.0%. The biological half-life was very long, ranging from 20 to 72 h. The urinary recovery of total radioactivity ranged from 18.4 to 26.8% after the iv dose and from 3.3 to 5.7% after the oral dose. The corresponding fecal recoveries were only 1.5-5.0% and 1.6-4.6%, respectively. Thus, the total recovery of the (14)C-quercetin doses, in particular after oral administration, was very low. In search for the unaccounted for fraction of the (14)C-quercetin dose, we performed (14)CO(2) recovery studies in three volunteers (3 iv and 3 oral doses). At timed intervals, (14)CO(2) in expired air was trapped in hyamine hydroxide/thymolphthalein and analyzed for radioactivity. As much as 23.0-81.1% of the quercetin dose was recovered as (14)CO(2) in the expired air from these volunteers, after both oral and iv doses. The disposition of quercetin in humans is thus highly complex, requiring further studies. | Anderson CT, Breen PH (2000)
Carbon dioxide kinetics and capnography during critical care.
Critical care (London, England) 4, 207-215 [PubMed:11094503]
[show Abstract]
Greater understanding of the pathophysiology of carbon dioxide kinetics during steady and nonsteady state should improve, we believe, clinical care during intensive care treatment. Capnography and the measurement of end-tidal partial pressure of carbon dioxide (PETCO2) will gradually be augmented by relatively new measurement methodology, including the volume of carbon dioxide exhaled per breath (VCO2,br) and average alveolar expired PCO2. Future directions include the study of oxygen kinetics. | Woodcock RC (2000)
CO2 measurements for IAQ analysis.
Occupational health & safety (Waco, Tex.) 69, 56-8, 60, 62 passim [PubMed:10826146]
[show Abstract]
These examples illustrate the utility of carbon dioxide measurements as a diagnostic tool for indoor air quality. Carbon dioxide is sometimes said to be an unreliable indicator because of uneven mixing. However, even though mixing does occur slowly in very still air, in nearly all cases there is enough air movement that mixing is not a misleading factor for diagnostic purposes. Measurements do have to be recorded with enough context for proper interpretation. For example, to distinguish between the effects of natural and mechanical ventilation. Or to understand how the results are affected by the number of people in the building and what they are doing. Or how they relate to the nature and layout of the HVAC system and how it is adjusted or intended to be used. Carbon dioxide measurements say little about how healthy an indoor environment is. But they can tell a great deal about how comfortable it is and, with good observation, can give important clues as to where to look for factors that may be affecting health. The interaction of subjective and objective elements in the interpretation of CO2 measurements makes them a fascinating and powerful tool in the hands of a careful investigator. | Djurberg HG, Tjan GT, Al Moutaery KR (1998)
Enhanced catheter propagation with hypercapnia during superselective cerebral catherisation.
Neuroradiology 40, 466-468 [PubMed:9730350]
[show Abstract]
During arterial catherisation of a cerebral arteriovenous malformation it may be difficult or impossible to access the nidus of the malformation through its small, tortuous feeding vessels due to microcatheter impaction. Carbon dioxide, a most potent cerebral vasodilator, was temporarily added to the inspired gases of two anaesthetised patients undergoing superselective embolisation of an arteriovenous malformation, when the microcatheter had been impacted for a considerable time. Successful propagation of the microcatheter into the malformation was achieved in both patients after a relatively short period of hypercapnia. | Kral TA, Brink KM, Miller SL, McKay CP (1998)
Hydrogen consumption by methanogens on the early Earth.
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life 28, 311-319 [PubMed:9611769]
[show Abstract]
It is possible that the first autotroph used chemical energy rather than light. This could have been the main source of primary production after the initial inventory of abiotic organic material had been depleted. The electron acceptor most readily available for use by this first chemoautotroph would have been CO2. The most abundant electron donor may have been H2 that would have been outgassing from volcanoes at a rate estimated to be as large as 10(12) moles yr-1, as well as from photo-oxidation of Fe+2. We report here that certain methanogens will consume H2 down to partial pressures as low as 4 Pa (4 x 10(-5) atm) with CO2 as the sole carbon source at a rate of 0.7 ng H2 min-1 microgram-1 cell protein. The lower limit of pH2 for growth of methanogens can be understood on the basis that the pH2 needs to be high enough for one ATP to be synthesized per CO2 reduced. The pH2 values needed for growth measured here are consistent with those measured by Stevens and McKinley for growth of methanogens in deep basalt aquifers. H2-consuming autotrophs are likely to have had a profound effect on the chemistry of the early atmosphere and to have been a dominant sink for H2 on the early Earth after life began rather than escape from the Earth's atmosphere to space. | Frantz SW, Beskitt JL, Grosse CM, Tallant MJ, Dietz FK, Ballantyne B (1996)
Pharmacokinetics of ethylene glycol. I. Plasma disposition after single intravenous, peroral, or percutaneous doses in female Sprague-Dawley rats and CD-1 mice.
Drug metabolism and disposition: the biological fate of chemicals 24, 911-921 [PubMed:8869828]
[show Abstract]
The pharmacokinetics of [1,2-14C]ethylene glycol (EG) were evaluated in female Sprague-Dawley rats and CD-1 mice to characterize the plasma disposition after intravenous (IV), peroral (PO), and percutaneous (PC) doses. Rats were given doses of 10 or 1000 mg/kg by each route, and additional PO doses of 400, 600, or 800 mg/kg. Mice were also given IV and PO (bolus gavage) doses of 10 or 1000 mg/kg, and additional PO doses of 100, 200, or 400 mg/kg. PC doses in mice were 100 or 1000 mg/kg, and both species were given a 1000 mg/kg PC dose with a 50% (w/w) aqueous solution (2 ml/kg) to simulate antifreeze exposure. Results from this study have shown that orally-administered EG is very rapidly and almost completely absorbed in both rats and mice, with a bioavailable fraction of 92-100% in rats and similar percentages at the higher doses in mice. In contrast, the absorption of cutaneously applied EG is comparatively slow in both species. A species difference in the overall absorption of PC doses was demonstrated, with higher recoveries of 14C observed after PC doses in mice than for rats and a greater penetration of 14C after applying a 50% aqueous PC dose in mice than in rats, as evidenced by quantifiable plasma 14C concentrations only in mice. The major metabolites in both rats and mice are CO2 and glycolate. Oxidative metabolic pathways are saturated at high PO doses in both species, resulting in a shift from exhaled CO2 as the major excretion route to urinary excretion. The capacity to metabolize more completely EG to CO2 at low doses seems to be greater in the mouse than in the rat, as evidenced by the absence of urinary oxalate from EG-dosed female mice, and saturation of metabolic pathways at a comparatively lower dose in mice than for rats. This evidence suggests that dose-dependent changes in EG excretion in female Sprague-Dawley rats and CD-1 mice probably resulted from capacity-limited effects on EG metabolic pathways for the production of CO2 and a compensatory urine clearance of glycolate. Results from the present study corroborate previous observations in rats for the lower doses, but demonstrate a substantial difference in single-dose pharmacokinetics for IV and PO 1000 mg/kg doses in mice vs. rats. In summary, these data indicate that mice show a nonlinear plasma disposition of total radioactivity (EG and its metabolites) as dose is increased, whereas in rats plasma kinetics were linear over the dose range evaluated, whereas excretion kinetic patterns were nonlinear in both species as dose is increased. | Ellis MK, Naylor JL, Collins MA, Green T (1996)
Metabolism and disposition of difluoromethane (HFC32) in the mouse.
Human & experimental toxicology 15, 592-596 [PubMed:8818713]
[show Abstract]
1. Difluoromethane (HFC32) is under development as a replacement for chlorofluorocarbons (CFCs) in some refrigeration applications. 2. The metabolism and disposition of [14C]-difluoromethane ([14C]-HFC32) was determined in male Swiss mice as a consequence of a single 6 h inhalation exposure to atmospheres of 10 000 p.p.m. 3. Of the inhaled dose, about 1-2% was recovered in expired air, urine, faeces and carcass suggesting that systemic absorption of this hydrofluorocarbon from the alveolar air space of the lung into blood is poor. Upon cessation of exposure the majority of the systemically absorbed HFC32 was exhaled within 1 h. 4. Carbon dioxide was a major metabolite of HFC32. Carbon dioxide measured post-exposure accounted for about 0.3% of the inhaled dose. Urinary and faecal excretion of non-volatile metabolites accounted for about 0.34% and 0.07% of the inhaled dose, respectively. 5. Carbon monoxide could not be detected. 6. Total metabolism, measured as the sum of the radioactivity recovered in urine, faeces, as carbon dioxide and that retained in the carcass, amounted to about 0.8% of the inhaled dose, equivalent to 64% of the total radioactivity recovered. 7. Analysis of a range of tissues at 4 days post-exposure showed a relatively uniform distribution of radioactivity with the highest concentration in the lung, liver and kidney. There was no evidence of a specific retention in any organ or tissue. | Baudouin SV, Evans TW (1993)
Action of carbon dioxide on hypoxic pulmonary vasoconstriction in the rat lung: evidence against specific endothelium-derived relaxing factor-mediated vasodilation.
Critical care medicine 21, 740-746 [PubMed:8482095]
[show Abstract]
ObjectivesThe effect of hypercapnia on pulmonary vascular tone is controversial with evidence for both a vasoconstrictor and vasodilator action. The objective of this study was to investigate the possibility that this dual response to CO2 could be explained by a direct constrictor action on smooth muscle and an indirect dilator action via the release of endothelium-derived relaxing factor. The effect of ventilation with hypercapnia (FICO2 0.15) on pulmonary pressor response to hypoxia (FIO2 0.3) was investigated.DesignProspective, randomized study.SettingThe National Heart and Lung Institute, UK.SubjectsThe isolated, blood-perfused rat lung.InterventionsAngiotensin-II and a blocker of endothelium-derived relaxing factor synthesis, NG-monomethyl-L-arginine (L-NMMA).Measurements and main resultsThe vasomotor effect of hypercapnia depended on pulmonary arterial pressure. Under resting tone, CO2 acted as a mild constrictor (change in mean pulmonary arterial pressure from 14 +/- 2 to 15 +/- 2 mm Hg, n = 4; p < .05. At increased tone, induced either by hypoxia or Angiotensin-II, CO2 was a vasodilator. Thus, hypoxia increased mean pulmonary arterial pressure from 17 +/- 2 to 32 +/- 2 mm Hg (n = 8; p < .01), but simultaneous ventilation with hypoxia and hypercapnia reduced this by 16 +/- 1% (p < .01). Angiotensin-II (1 microgram) increased pulmonary arterial pressure from 14 +/- 2 to 39 +/- 5 mm Hg (n = 8; p < .01), but with hypercapnia, this angiotensin-induced pulmonary vasoconstriction was reduced by 18 +/- 6% (p < .001). The reduction in hypoxic pulmonary vasoconstriction induced by hypercapnia was not significantly different from that seen with Angiotensin-II hypercapnia. Blocking endothelium-derived relaxing factor synthesis using 30 microM NG-monomethyl-L-arginine did not significantly change either basal pulmonary arterial pressure or the response to hypercapnia, but increased hypoxic pulmonary vasoconstrictor by 24 +/- 4% (n = 4; p < .01). There was no significant difference between the change in hypoxic pulmonary vasoconstriction induced by hypercapnia after saline control (21 +/- 8% decrease) and the change in hypoxic pulmonary vasoconstriction caused by CO2 after 30 microM L-NMMA (25 +/- 10% decrease, p < .05, n = 8).ConclusionEndothelium-derived relaxing factor seems unlikely to specifically modulate CO2-induced vasodilation in the rat pulmonary circulation. | Beyer EM (1976)
A potent inhibitor of ethylene action in plants.
Plant physiology 58, 268-271 [PubMed:16659660]
[show Abstract]
Ag(I), applied foliarly as AgNO(3), effectively blocked the ability of exogenously applied ethylene to elicit the classical "triple" response in intact etiolated peas (Pisum sativumcv. Alaska); stimulate leaf, flower, and fruit abscission in cotton (Gossypium hirsutumcv. Stoneville 213); and induce senescence of orchids (Hybrid white Cattleya, Louise Georgeianna). This property of Ag(I) surpasses that of the well known ethylene antagonist, CO(2), and its persistence, specificity, and lack of phytotoxicity at effective concentrations should prove useful in defining further the role of ethylene in plant growth. | Byers RE, Baker LR, Sell HM, Herner RC, Dilley DR (1972)
Ethylene: A Natural Regulator of Sex Expression of Cucumis melo L.
Proceedings of the National Academy of Sciences of the United States of America 69, 717-720 [PubMed:16591971]
[show Abstract]
Sex expression in cucumber (Cucumis sativus L.) and muskmelon (C. melo L.) was correlated with endogenous ethylene production. Plants of gynoecious (all female) sex types of the two species produced more ethylene than monoecius (male-female) plants. C. melo plants of a gynoecious sex type that normally produce only pistillate (female) flowers, when grown with hypobaric ventilation to facilitate removal of endogenous gases by diffusion, produced perfect (hermaphroditic) flowers. When either the plant was returned to atmospheric pressure or when the reduced-pressure ventilating stream was supplemented with ethylene, the same plants produced pistillate flowers. Enrichment of the atmosphere at either normal or reduced pressure with CO(2), a competitive inhibitor of ethylene action, also resulted in development of perfect flowers. Foliar application of a benzothiadiazole, a postulated inhibitor of ethylene action, resulted in formation of perfect flowers on gynoecious plants of C. melo and of staminate (male) flowers on gynoecious C. sativus. Based on these findings, it is proposed that ethylene is an endogenous regulator of sex expression in C. sativus and C. melo. | Burg SP, Burg EA (1967)
Molecular requirements for the biological activity of ethylene.
Plant physiology 42, 144-152 [PubMed:16656478]
[show Abstract]
The molecular requirements for ethylene action were investigated using the pea straight growth test. Biological activity requires an unsaturated bond adjacent to a terminal carbon atom, is inversely related to molecular size, and is decreased by substitutions which lower the electron density in the unsaturated position. Evidence is presented that ethylene binds to a metal containing receptor site. CO(2) is a competitive inhibitor of ethylene action, and prevents high concentrations of auxin (which stimulate ethylene formation) from retarding the elongation of etiolated pea stem sections. It is suggested that CO(2) delays fruit ripening by displacing the ripening hormone, ethylene, from its receptor site. Binding of ethylene to the receptor site is also impeded when the O(2) concentration is lowered, and this may explain why fruit ripening is delayed at low O(2) tensions. |
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