Nitric Oxide Uptake Research Articles

Substantial uptake of nitrous oxide (N2O) by shoots of mature European beech

Similar to soils, tree stems emit and consume nitrous oxide (N2O) from the atmosphere. Although tree leaves dominate tree surface area, they have been completely excluded from field N2O flux measurements and therefore their role in forest N2O exchange remains unknown. We explored the contribution of leaf fluxes to forest N2O exchange. We determined the N2O exchange of mature European beech (Fagus sylvatica) stems and shoots (i.e., terminal branches) and of adjacent forest floor, in a typical temperate upland forest in Germany. The beech stems, and particularly the shoots, acted as net N2O sinks (−0.254 ± 0.827 μg N2O m−2 stem area h−1 and −4.54 ± 1.53 μg N2O m−2 leaf area h−1, respectively), while the forest floor was a net source (2.41 ± 1.08 μg N2O m−2 soil area h−1). The unstudied tree shoots were identified as a significant contributor to the net ecosystem N2O exchange. Moreover, we revealed for the first time that tree leaves act as substantial N2O sinks. Although this is the first study of its kind, it is of global importance for the proper design of future flux studies in forest ecosystems worldwide. Our results demonstrate that excluding tree leaves from forest N2O flux measurements can lead to misinterpretation of tree and forest N2O exchange, and thus global forest greenhouse gas flux inventories.

John W. Severinghaus, M.D., 1922 to 2021.

John W. Severinghaus, M.D., 1922 to 2021.

Alkali-modified biochar as a sustainable adsorbent for the low-temperature uptake of nitric oxide

Alkali-modified biochar as a sustainable adsorbent for the low-temperature uptake of nitric oxide

Electronic structure and mechanism for the uptake of nitric oxide by the Ru(iii) antitumor complex NAMI-A.

Nitric oxide (NO) has well known vasodilation effects in living organisms and its participation in the metastasis of cancer cells through the angiogenesis process has been demonstrated experimentally. Therefore, the uptake of NO has become one focus of investigation to produce anti-metastatic drugs. In this article we have investigated the uptake of NO by the ruthenium based metallodrug trans-tetrachloride(dimethylsulfoxide)imidazole ruthenate(iii) [Im]trans-[RuCl4(Im)(DMSO)], known as New Anti-tumor Metastasis Inhibitor-A (NAMI-A). Electronic structure calculations using Density Functional Theory, DFT, and State-Averaged Complete Active Space Self Consistent Field, SA-CASSCF, with second order perturbation theory corrections, NEVPT2 were carried out to investigate the mechanism involved in the uptake of NO by the Ru-based anticancer metallodrug NAMI-A. The calculations revealed that the reaction takes place at the triplet potential energy surface, with the singlet surface being ∼15 kcal mol−1 shifted to higher energies, and there is a surface crossing to form the most stable singlet product after the reaction takes place at the triplet surface. The spin pairing and electron transfer from the nitric oxide to the metallic fragment takes place at the region of the minimum energy crossing point between the two surfaces. The Ru–NO bond in the {Ru–NO}6 product has ∼10% of the RuIII–NO0 character. The SA-CASSCF/NEVPT2 calculations revealed that the uptake of NO by NAMI-A has a small energy barrier of ∼8 kcal mol−1 and, therefore a rate constant of 11.3 × 106 s−1 at 300 K. In addition, the reaction is thermodynamically favorable, with a Gibbs free energy of ∼30 kcal mol−1. These results show that the uptake of nitric oxide by the NAMI-A complex is kinetically and thermodynamically feasible in biological medium and, therefore, gives support to the anti-angiogenesis theory associated to the mode of action of NAMI-A and other related compounds.

Denitrification kinetics indicates nitrous oxide uptake is unaffected by electron competition in Accumulibacter

Denitrifying phosphorus removal is a cost and energy efficient treatment technology that relies on polyphosphate accumulating organisms (DPAOs) utilizing nitrate or nitrite as terminal electron acceptor. Denitrification is a multistep process, but many organisms do not possess the complete pathway, leading to the accumulation of intermediates such as nitrous oxide (N2O), a potent greenhouse gas and ozone depleting substance. Candidatus Accumulibacter organisms are prevalent in denitrifying phosphorus removal processes and, according to genomic analyses, appear to vary in their denitrification abilities based on their lineage. Denitrification kinetics and nitrous oxide accumulation in the absence of inhibition from free nitrous acid is a strong indicator of denitrification capabilities of Accumulibacter exposed long-term to nitrate or nitrite as electron acceptor. Thus, we investigated the preferential use of the nitrogen oxides involved in denitrification and nitrous oxide accumulation in two enrichments of Accumulibacter and a competitor – the glycogen accumulating organism Candidatus Competibacter. We modified a metabolic model to predict phosphorus removal and denitrification rates when nitrate, nitrite or N2O were added as electron acceptors in different combinations. Unlike previous studies, no N2O accumulation was observed for Accumulibacter in the presence of multiple electron acceptors. Electron competition did not limit denitrification kinetics or lead to N2O accumulation in Accumulibacter or Competibacter. Despite the presence of sufficient internal storage polymers (polyhydroxyalkanoates, or PHA) as energy source for each denitrification step, the extent of denitrification observed was dependent on the dominant organism in the enrichment. Accumulibacter showed complete denitrification, whereas Competibacter denitrification was limited to reduction of nitrate to nitrite. These findings indicate that DPAOs can contribute to lowering N2O emissions in the presence of multiple electron acceptors under partial nitritation conditions.

Atmospheric impact of nitrous oxide uptake by boreal forest soils can be comparable to that of methane uptake

AimsEnvironmental factors controlling nitrous oxide (N2O) uptake in forest soils are poorly known, and the atmospheric impact of the forest N2O sink is not well constrained compared to that of methane (CH4).MethodsWe compared nitrous oxide (N2O) and CH4 fluxes over two growing seasons in boreal forest soils located in Eastern Finland. Within a spruce forest, we compared plots with long-term nitrogen (N) fertilization history and non-fertilized plots, and additionally pine forest plots without a fertilization history. The flux data was complemented with measurements of climatic conditions and soil physical and chemical characteristics, in order to identify factors affecting N2O and CH4 fluxes.ResultsNon-fertilized spruce forest soils showed the highest cumulative N2O uptake among the sites, whereas the pine forest site displayed low cumulative N2O emission. Nitrous oxide uptake was favored by high soil silt and water content. The low temperature seasons, spring and autumn, had the highest N2O uptake, likely associated with high soil water content typical for these seasons. In the spruce forest the N2O uptake was seasonally decoupled from the CH4 uptake.ConclusionsApplying the Global Warming Potential (GWP) approach, the cooling effect of N2O uptake in the spruce forest was on average 35% of that of CH4 uptake showing that N2O uptake should be considered when evaluating the atmospheric impact of boreal forests.

Implementation of an Evidence-Based Practice Change to Offer Nitrous Oxide During Labor

ObjectiveThe aim of this evidence-based practice change was to implement use of nitrous oxide as a pain management option during labor and to examine women’s satisfaction with that option. DesignEvidence-based practice change guided by the model for evidence-based practice change. SettingLabor and delivery unit in a tertiary medical center in the southwestern United States. ParticipantsLaboring women who met eligibility criteria were offered the option of nitrous oxide during a 2-month period. MeasurementsProcess indicators to measure compliance with the practice change among staff, uptake of nitrous oxide among women, and women’s satisfaction with the choice to use nitrous oxide. ResultsNitrous oxide was offered to 26% (n = 55) of eligible women. Most of the 55 women who used nitrous oxide during the implementation period reported satisfaction with it and indicated that they would consider nitrous oxide for a future labor. ConclusionOur experience implementing a practice change to offer nitrous oxide to laboring women indicated that use of nitrous oxide was feasible in this setting and that women were receptive to this option, were satisfied with its use, and would use nitrous oxide for a future labor.

Effect of net gas volume changes on alveolar and arterial gas partial pressures in the presence of ventilation-perfusion mismatch.

The second gas effect (SGE) occurs when nitrous oxide enhances the uptake of volatile anesthetics administered simultaneously. Recent work shows that the SGE is greater in blood than in the gas phase, that this is due to ventilation-perfusion mismatch, that as mismatch increases, the SGE increases in blood but is diminished in the gas phase, and that these effects persist well into the period of nitrous oxide maintenance anesthesia. These modifications of the SGE are most pronounced with the low soluble agents in current use. We investigate further the effect of net gas volume loss during nitrous oxide uptake on low concentrations of other gases present using partial pressure-solubility diagrams. The steady-state equations of gas exchange were solved assuming a log-normal distribution of ventilation-perfusion ratios using Lebesgue-Stieltjes integration. It was shown that under these conditions the classical partial pressure-solubility diagram must be modified, that for currently used volatile anesthetic agents the alveolar-arterial partial pressure difference is less than that predicted in the past, and that the alveolar-arterial partial pressure difference may even be reversed during uptake in the case of highly insoluble gases such as sulfur hexafluoride. Comparing this with the situation described previously for nitrogen in steady-state air breathing, we show that for nitrogen, the direction of the alveolar-arterial gradient is opposite to the direction of net gas volume movement. Although gas uptake with ventilation-perfusion inequality exceeding that when matching is optimal is shown to be possible, it is less likely than alveolar-arterial partial pressure reversal. NEW & NOTEWORTHY Net uptake of gases administered with nitrous oxide may proceed against an alveolar-arterial partial pressure gradient. The alveolar-arterial gradient for nitrogen in the steady-state breathing air depends not only on the existence of a distribution of ventilation-perfusion ratios in the lung but also on the presence of a net change in gas volume and is opposite in direction to the direction of net gas volume uptake.

Desflurane with Isoflurane under low flow anaesthesia: A prospective randomized clinical comparative trial

Aim: To compare characteristics of Desflurane with Isoflurane under low flow anaesthesia using equilibration time. Material and methods: This prospective study was done the Department of AnaesthesiaMetro Hospital and Cancer Research Center, Jabalpur, Madhya Pradesh, India 100 healthy patients of either sex scheduled for routine surgeries, American Society of Anesthesiologists (ASA) physical status I and II, age 20–60 years, and hemoglobin more than 10 g/dL were include in this study. Patients were randomly allocated to two groups. Group I received desflurane as the inhalational anesthetic agent with minimal flow anesthesia (n=50). Group II received isoflurane as anesthetic agent with minimal flow anesthesia (n=50). Results: 100 adult patients were studied. The groups were randomly divided into two groups of 50 patients each. Mean of time taken for equilibration of the volatile anesthetic agent in the desflurane group was 5.23 ± 1.63 min and in the isoflurane group was 17.011±9.64 min, and the difference was statistically significant (P< 0.001). At 5, 20, 60, and 120 min, mean end-tidal concentrations (in kPa) of desflurane were not changed much and were 4.68 ± 0.80, 4.78 ± 0.62, 4.38 ± 0.61 and 4.15 ± 0.62, respectively. In the isoflurane group, variation were significant over time and were 0.77 ± 0.17, 0.93 ± 0.17, 0.73 ± 0.19 and 0.74 ± 0.19 at 5, 20, and 120 min intervals, respectively. Uptake of nitrous oxide was 80% and above by the time equilibration of any of the agents occurred. In both the groups, end-tidal to inspired nitrous oxide ratio was found to be 0.77 ± 0.14 in 5 min duration and 0.96 ± 0.03 by 12 min. Nitrous oxide concentration also fell over the time, and it was difficult to maintain nitrous oxide at 66 vol.% . It ranged between 42.30 ±4.57 and 61.20 ± 4.56. In long duration, minimal flow anesthesia nitrous oxide end-tidal concentration found to be <50%. At 80% uptake point of nitrous oxide, uptake of only desflurane was found to be nearly 80% at that time. Conclusion: we concluded that, with availability of agents like desflurane we can use minimal flow anesthesia more efficiently, with less drift in anesthetic gases and a clear-headed recovery and minimum operating room pollution.

Can Mathematical Modeling Explain the Measured Magnitude of the Second Gas Effect?

Recent clinical studies suggest that the magnitude of the second gas effect is considerably greater on arterial blood partial pressures of volatile agents than on end-expired partial pressures, and a significant second gas effect on blood partial pressures of oxygen and volatile agents occurs even at relatively low rates of nitrous oxide uptake. We set out to further investigate the mechanism of this phenomenon with the help of mathematical modeling. Log-normal distributions of ventilation and blood flow were generated representing the range of ventilation-perfusion scatter seen in patients during general anesthesia. Mixtures of nominal delivered concentrations of volatile agents (desflurane, isoflurane and diethyl ether) with and without 70% nitrous oxide were mathematically modeled using steady state mass-balance principles, and the magnitude of the second gas effect calculated as an augmentation ratio for the volatile agent, defined as the partial pressure in the presence to that in the absence of nitrous oxide. Increasing the degree of mismatch increased the second gas effect in blood. Simultaneously, the second gas effect decreased in the gas phase. The increase in blood was greatest for the least soluble gas, desflurane, and least for the most soluble gas, diethyl ether, while opposite results applied in the gas phase. Modeling of ventilation-perfusion inhomogeneity confirms that the second gas effect is greater in blood than in expired gas. Gas-based minimum alveolar concentration readings may therefore underestimate the depth of anesthesia during nitrous oxide anesthesia with volatile agents. The effect on minimum alveolar concentration is likely to be most pronounced for the less soluble volatile agents in current use.

ERJPodcast February 2017: ERS technical standards for the single-breath determination of nitric oxide uptake in the lung

As part of the February issue, the European Respiratory Journal presents the latest in its series of podcasts. Chief editor Marc Humbert discusses the new ERS task force document, on single-breath determination of nitric oxide uptake in the lung, with Prof. Gerald S. Zavorsky from the Georgia State University, USA.

Standardisation and application of the single-breath determination of nitric oxide uptake in the lung.

Diffusing capacity of the lung for nitric oxide (DLNO), otherwise known as the transfer factor, was first measured in 1983. This document standardises the technique and application of single-breath DLNO This panel agrees that 1) pulmonary function systems should allow for mixing and measurement of both nitric oxide (NO) and carbon monoxide (CO) gases directly from an inspiratory reservoir just before use, with expired concentrations measured from an alveolar "collection" or continuously sampled via rapid gas analysers; 2) breath-hold time should be 10 s with chemiluminescence NO analysers, or 4-6 s to accommodate the smaller detection range of the NO electrochemical cell; 3) inspired NO and oxygen concentrations should be 40-60 ppm and close to 21%, respectively; 4) the alveolar oxygen tension (PAO2 ) should be measured by sampling the expired gas; 5) a finite specific conductance in the blood for NO (θNO) should be assumed as 4.5 mL·min-1·mmHg-1·mL-1 of blood; 6) the equation for 1/θCO should be (0.0062·PAO2 +1.16)·(ideal haemoglobin/measured haemoglobin) based on breath-holding PAO2 and adjusted to an average haemoglobin concentration (male 14.6 g·dL-1, female 13.4 g·dL-1); 7) a membrane diffusing capacity ratio (DMNO/DMCO) should be 1.97, based on tissue diffusivity.

Nitrous oxide uptake in rewetted wetlands with contrasting soil organic carbon contents

Rewetting drained peatlands creates favorable reduced conditions for denitrification, but, the potential of restored peatlands to act as N2O sink is poorly characterized. We monitored N2O emissions in rewetted peatlands converted to rice paddies with a range of soil organic carbon (SOC) (6%, 11%, and 23%) during the growing season. Negative N2O emissions were repeatedly observed in all sites, which were not affected by nitrogen fertilization at 80 kg N ha−1. The highest consumption rates amounted to 8.2 tones CO2 eq ha−1 yr−1, 32% of the average CO2 emissions from drained peat soils. Porewater N2O concentrations were frequently less than the calculated in situ N2O equilibrium concentrations, suggesting diffusional constraints on atmospheric N2O into pore water. Redox potentials were correlated to N2O emission rates (r2 = 0.40, p < 0.01). However, relatively higher frequencies and magnitudes of negative N2O emissions were mostly observed during the period of water draw down for rice harvest activities, especially in the field with the highest SOC. It is likely that reducing water depth by drainage reduced the diffusional barrier for atmospheric N2O into the soil. In all, the capacity of rewetted peatlands to act as atmospheric N2O sinks can be significant and seemingly can be managed through manipulating water depths.

Robust global identifiability theory using potentials—Application to compartmental models

This paper presents a global practical identifiability theory for analyzing and identifying linear and nonlinear compartmental models. The compartmental system is prolonged onto the potential jet space to formulate a set of input–output equations that are integrals in terms of the measured data, which allows for robust identification of parameters without requiring any simulation of the model differential equations. Two classes of linear and non-linear compartmental models are considered. The theory is first applied to analyze the linear nitrous oxide (N2O) uptake model. The fitting accuracy of the identified models from differential jet space and potential jet space identifiability theories is compared with a realistic noise level of 3% which is derived from sensor noise data in the literature. The potential jet space approach gave a match that was well within the coefficient of variation. The differential jet space formulation was unstable and not suitable for parameter identification. The proposed theory is then applied to a nonlinear immunological model for mastitis in cows. In addition, the model formulation is extended to include an iterative method which allows initial conditions to be accurately identified. With up to 10% noise, the potential jet space theory predicts the normalized population concentration infected with pathogens, to within 9% of the true curve.

Abiotic dissolution and biological uptake of nitrous oxide in Mediterranean woodland and pasture soil

Soil is generally regarded as a net emitter of nitrous oxide (N2O). However, there are numerous field studies showing net uptake of N2O from soil in different ecosystems. Consumption of N2O may be abiotic (absorption by water; adsorption by soil matrix) and biotic (microbial reduction of N2O). This study is the first using undisturbed soil cores to determine the capacity of soil to consume N2O and discuss the fate of N2O.We exposed the base of undisturbed soil cores from Mediterranean pasture and woodland soil to elevated concentrations of N2O and sulphur hexafluoride (SF6; as tracer gas). Headspace concentrations of N2O and SF6 were determined over time and consumption rates of N2O were calculated ranging from 148.8 ± 19.8 ng N2O min−1 g−1 to 163.8 ± 17.2 ng N2O min−1 g−1 in woodland soil and from 117.2 ± 36.1 ng N2O min−1 g−1 to 145.1 ± 19.4 ng N2O min−1 g−1 in pasture soil. Absorption of N2O by soil water contributed 17–49% of the total N2O consumption. The remaining N2O consumed by the cores was due to adsorbtion by the soil matrix and/or reduction by microbes.Mediterranean soil from different ecosystems with different nitrogen (N) loads has a great potential to store and consume N2O, if exposed to an N2O elevated atmosphere.

Investigating uptake of N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O in agricultural soils using a high-precision dynamic chamber method

Abstract. Uptake (or negative flux) of nitrous oxide (N2O) in agricultural soils is a controversial issue which has proved difficult to investigate in the past due to constraints such as instrumental precision and methodological uncertainties. Using a recently developed high-precision quantum cascade laser gas analyser combined with a closed dynamic chamber, a well-defined detection limit of 4 μg N2O-N m−2 h−1 could be achieved for individual soil flux measurements. 1220 measurements of N2O flux were made from a variety of UK soils using this method, of which 115 indicated uptake by the soil (i.e. a negative flux in the micrometeorological sign convention). Only four of these apparently negative fluxes were greater than the detection limit of the method, which suggests that the vast majority of reported negative fluxes from such measurements are actually due to instrument noise. As such, we suggest that the bulk of negative N2O fluxes reported for agricultural fields are most likely due to limits in detection of a particular flux measurement methodology and not a result of microbiological activity consuming atmospheric N2O.

An estimate of the global sink for nitrous oxide in soils

A literature survey of studies reporting nitrous oxide uptake in the soils of natural ecosystems is used to suggest that the median uptake potential is 4 μg m(-2) h(-1). The highest values are nearly all associated with soils of wetland and peatland ecosystems. Globally, the consumption of nitrous oxide in soils is not likely to exceed 0.3 TgN yr(-1), indicating that the projected sink is not more than 2% of current estimated sources of N(2)O in the atmosphere.

Biogeochemistry of N2O Uptake and Consumption in Submerged Soils and Rice Fields and Implications in Climate Change

Submerged soils and rice fields are known sources of nitrous oxide (N2O) but also act as its sinks. Nitrous oxide uptake (movement from atmosphere into soil) and consumption (conversion of N2O to N2) in rice fields are both very significant, as they help decrease N2O concentration in the atmosphere. Rice soils had reportedly shown N2O uptake ranging from about 0.13 to 191 μg N2O-N m−2 hr−1 while in non-rice soils the same was about 0.0014–484 μg N2O-N m−2 hr−1. This review synthesizes the available information on N2O uptake and consumption in submerged soils vis-à-vis rice fields.

Soybean oil: a potentially new intravascular perfusate

Given that micelles of lipids are colloids, the hypothesis was generated that the rapid administration of large volumes of soybean oil micelles would be an effective perfusion fluid. We also hypothesized that oxygen loading would be enhanced due to the greater solubility of oxygen in lipids compared to water. A 100% lethal mouse model of blood loss was used to compare the ability of soybean oil micelles to that of Ringer's lactate, blood and other fluids, with respect to raising and maintaining the blood pressure for one hour. Oxygen on- and off-loading of various concentrations of soybean oil micelles was determined using mass spectroscopy. Nitric oxide uptake by micelles was also determined in a similar fashion. A 20% soybean oil emulsion was superior to Ringer's lactate in raising and maintaining blood pressure. A 20% soybean oil emulsion with 5% albumin added was superior to shed blood as well as solutions comprised of 5% albumin added to either normal saline or Ringer's lactate. There was a linear relationship between oxygen content and micelle concentration between 10% and 30%. Off-loading of oxygen from the micelles was nearly as fast as off-loading from water. Nitric oxide also loaded preferentially onto soybean oil micelles. (1) Soybean oil emulsions were superior to other fluids in restoring and maintaining the blood pressure; (2) oxygen-carrying ability of soybean oil micelles exceeds that of water and follows Henry's law between 10% and 30% w/v oil content; (3) nitric oxide was carried by the micelles; (4) animals receiving soybean oil micelles did not exhibit fat embolization; (5) colloids comprised of soybean oil-containing micelles may be used to replace blood loss and may be used to deliver oxygen and other potentially therapeutic gases such as nitric oxide to tissues.

Xylophagous termites: A potential sink for atmospheric nitrous oxide

To provide a better understanding of soil–atmosphere gas exchange processes, this study describes the atmospheric nitrous oxide (N2O) uptake by xylophagous termites and the biological process involved. The N2O consumption rates of three xylophagous termite species (Hodotermes mossambicus, Nasutitermes voeltzkowi and Hodotermopsis sjoestedti) were determined in incubation vials with ambient, artificially enhanced N2O concentrations in the headspace. Live individuals of the three termite species significantly decreased N2O concentrations (88%) in the headspace of the vials after 24 h incubation in the dark. The acetylene reduction assay method applied to N. voeltzkowi, a xylophagous termite species, showed a decrease in N2O uptake in acetylene-treated individuals, indicating the potential involvement of termite gut denitrifying microbes. The N2 formed is potentially subjected to assimilation via nitrogenase reductase into termite biomass through biological fixation as demonstrated by the reduction of acetylene to ethylene at an average rate of 18.21 ± 1.34 nmol C2H4 g−1 dw d−1. Further studies should focus on measurements of N2O-reductase (nosZ) gene activity in termite guts to gain a better understanding of the N2O reduction process in xylophagous termite species.