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  • 1
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This paper gives an overview of placebo-controlled studies of the effect of corticosteroid treatment on nasal blockage, based on objective measurements of nasal airway patency. A few studies of perennial rhinitis have indicated that pretreatment with an intranasal corticosteroid has a moderate effect on nasal hyperresponsiveness, measured as the histamine-induced increase of nasal blockage. Whereas the effect on allergen-induced early-phase symptoms is variable, the effect on the late-phase blockage is almost complete. In seasonal allergic rhinitis, a few studies have shown an effect of intranasal steroids on nasal airway resistance, nasal peak flow and on acoustic rhinometry, but there are no reports on the effect in adults with perennial rhinitis. In children with perennial disease, intranasal treatment results in increased nasal patency and, in one study, also in reduced mouth breathing and in an increased threshold for exercise-induced bronchoconstriction. In patients with nasal polyposis, intranasal steroids have an effect on nasal airway resistance and on nasal peak flow both before and after polypectomy. There is convincing evidence that intranasal corticosteroids provide a better effect than antihistamine on nasal blockage. Amazingly, there does not appear to be any report on the effect of systemic corticosteroid treatment on nasal airway patency, and it is therefore difficult to recommend this treatment in a rational dosage. In conclusion, there is a fairly good documentation in support of the efficacy of intranasal steroid treatment on nasal airway patency in rhinitis. An objective measurement of nasal airway patency ought to be the routine in controlled rhinitis trials.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 9 (1992), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the Completely Autotrophic Nitrogen removal Over Nitrite (CANON) process, aerobic and anaerobic ammonia oxidizing bacteria cooperate to remove ammonia in one oxygen-limited reactor. Kinetic studies, microsensor analysis, and fluorescence in situ hybridization on CANON biomass showed a partial differentiation of processes and organisms within and among aggregates. Under normal oxygen-limited conditions (∼5 μM O2), aerobic ammonia oxidation (nitrification) was restricted to an outer shell (〈100 μm) while anaerobic ammonia oxidation (anammox) was found in the central anoxic parts. Larger type aggregates (〉500 μm) accounted for 68% of the anammox potential whereas 65% of the nitrification potential was found in the smaller aggregates (〈500 μm). Analysis with ∼5 μM O2 microsensors showed that the thickness of the activity zones varied as a function of bulk O2 and NO−2 concentrations and flow rate.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 86 (1992), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A new method for accurate and easy measurement of denitrification in sediments is presented. The water overlying intact sediment cores was enriched with 15NO3− which mixed with the 14NO3− of the natural sources of NO3−. The formation by denitrification of single-labeled (14N15N) and double-labeled (15N15N) dinitrogen pairs was measured by mass spectrometry after a few hours incubation. Total denitrification including the formation of unlabeled (14N14N) dinitrogen could be calculated assuming random isotope pairing by denitrification of the uniformly mixed NO3− species. In contrast to previous approaches, by this method it is possible to measure denitrification of both NO3− diffusing from the overlying water and NO3− from nitrification within the sediment.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Depth distributions of O2 respiration and denitrification activity were studied in 1- to 2-mm thick biofilms from nutrient-rich Danish streams. Acetylene was added to block the reduction of N2O, and micro-profiles of O2 and N2O in the biofilm were measured simultaneously with a polarographic microsensor. The specific activities of the two respiratory processes were calculated from the microprofiles using a one-dimensional diffusion-reaction model. Denitrification only occurred in layers where O2 was absent or present at low concentrations (of a fewμM). Introduction of O2 into deeper layers inhibited denitrification, but the process started immediately after anoxic conditions were reestablished. Denitrification activity was present at greater depth in the biofilm when the NO3 − concentration in the overlying water was elevated, and the deepest occurrence of denitrification was apparently determined by the depth penetration of NO3 −. The denitrification rate within each specific layer was not affected by an increase in NO3 − concentration, and the half-saturation concentration (Km) for NO3 − therefore considered to be low (〈25μM). Addition of 0.2% yeast extract stimulated denitrification only in the uppermost 0.2 mm of the denitrification zone indicating a very efficient utilization of the dissolved organic matter within the upper layers of the biofilm.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-515X
    Keywords: acetylene block ; aquatic sediments ; denitrification ; N cycling ; 15N ; N2-flux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Measurements of denitrification using the acetylene inhibition,15N isotope tracer, and N2 flux methods were carried out concurrently using sediment cores from Vilhelmsborg sø, Denmark, in an attempt to clarify some of the limitations of each technique. Three experimental treatments of overlying water were used: control, nitrate enriched, and ammonia enriched water. The N2 flux and15N tracer experiments showed high rates of coupled nitrification/denitrification in the sediments. The acetylene inhibition method did not capture any coupled nitrification/denitrification. This could be explained by acetylene inhibition of nitrification. A combined15N tracer/acetylene inhibition experiment demonstrated that acetylene inhibition of N2O reduction was incomplete and the method, therefore, only measured approximately 50% of the denitrification due to nitrate from the overlying water. Similar rates of denitrification due to nitrate in the overlying water were measured by the N2 flux method and the acetylene inhibition method, after correcting for the 50% efficiency of acetylene inhibition. Rates of denitrification due to nitrate from the overlying water measured by the15N tracer method, however, were only approximately 35% or less of those measured by the acetylene inhibition or N2 flux methods.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 16 (2006): 2091–2122, doi:10.1890/1051-0761(2006)016[2091:MFMDDA]2.0.CO;2.
    Description: Denitrification, the reduction of the nitrogen (N) oxides, nitrate (NO3-) and nitrite (NO2-), to the gases nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2), is important to primary production, water quality and the chemistry and physics of the atmosphere at ecosystem, landscape, regional and global scales. Unfortunately, this process is very difficult to measure, and existing methods are problematic for different reasons in different places at different times. In this paper, we review the major approaches that have been taken to measure denitrification in terrestrial and aquatic environments and discuss the strengths, weaknesses and future prospects for the different methods. Methodological approaches covered include; 1) acetylene-based methods, 2) 15N tracers, 3) direct N2 quantification, 4) N2/Ar ratio quantification, 5) mass balance approaches, 6) stoichiometric approaches, 7) methods based on stable isotopes, 8) in situ gradients with atmospheric environmental tracers and 9) molecular approaches. Our review makes it clear that the prospects for improved quantification of denitrification vary greatly in different environments and at different scales. While current methodology allows for the production of accurate estimates of denitrification at scales relevant to water and air quality and ecosystem fertility questions in some systems (e.g., aquatic sediments, well defined aquifers), methodology for other systems, especially upland terrestrial areas, still needs development. Comparison of mass balance and stoichiometric approaches that constrain estimates of denitrification at large scales with point measurements (made using multiple methods), in multiple systems, is likely to propel more improvement in denitrification methods over the next few years.
    Keywords: Denitrification ; Greenhouse effect ; Nitrate ; Nitric oxide nitrogen ; Nitrous oxide ; Stable isotopes ; Water quality
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: 822728 bytes
    Format: application/pdf
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  • 9
    Publication Date: 2023-06-21
    Description: We investigated the intracellular dynamics of calcite and sulfur in the large sulfur-oxidizing, calcite-accumulating bacterium Achromatium, with an emphasis on oxygen exposure as a physiological control. For this purpose, morphological changes and possible accretion mechanisms of calcite granules in cells that were freshly collected from natural Achromatium-containing sediment were compared to cells from the same source after prolonged exposure to atmospheric oxygen. Intracellular sulfur is oxidized and removed in response to oxygen exposure. Calcite granules also undergo distinct oxygen-related dynamics; they alternate between tightly packaged, smooth granules with narrow but sharply defined interstitial spaces in atmospheric oxygen-exposed cells, and more loosely packaged granules with irregular, bumpy surface texture and larger interstitial spaces in cells that were not artificially exposed to oxygen. These results suggest that morphological changes of the calcite granules reflect their changing physiological role inside the cell. Sulfur oxidation and calcite dissolution appear to be linked in that proton generation during sulfur oxidation is buffered by gradual calcite erosion, visible in the smooth, rounded surface morphology observed after oxygen exposure. Our results support the hypothesis that calcite dynamics buffer the intracellular pH fluctuations linked to electron acceptor limitation during proton-consuming sulfide oxidation to sulfur, and electron acceptor abundance during proton-generating sulfur oxidation to sulfate.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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