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  • 1
    Language: English
    In: Water Research, 01 March 2018, Vol.130, pp.98-104
    Description: This study aimed to evaluate the effects of freezing and cold storage at 4 °C on bulk dissolved organic carbon (DOC) and nitrogen (DON) concentration and SEC fractions determined with size exclusion chromatography (SEC), as well as on spectral properties of dissolved organic matter (DOM) analyzed with fluorescence spectroscopy. In order to account for differences in DOM composition and source we analyzed storage effects for three different sample types, including a lake water sample representing freshwater DOM, a leaf litter leachate of representing a terrestrial, ‘fresh’ DOM source and peatland porewater samples. According to our findings one week of cold storage can bias DOC and DON determination. Overall, the determination of DOC and DON concentration with SEC analysis for all three sample types were little susceptible to alterations due to freezing. The findings derived for the sampling locations investigated here may not apply for other sampling locations and/or sample types. However, DOC size fractions and DON concentration of formerly frozen samples should be interpreted with caution when sample concentrations are high. Alteration of some optical properties (HIX and SUVA ) due to freezing were evident, and therefore we recommend immediate analysis of samples for spectral analysis.
    Keywords: Freezing ; Cold Storage ; Size Exclusion Chromatograpy (Sec) ; Dissolved Organic Nitrogen (Don) ; Dissolved Organic Carbon (Doc) ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 2
    Language: English
    In: Science of the Total Environment, 15 May 2016, Vol.553, pp.574-586
    Description: Streams represent active components of the carbon cycle as emitters of carbon dioxide (CO ) and methane to the atmosphere at a global scale. However, the mechanisms and governing factors of these emissions are still largely unknown, especially concerning the effect of land use. We compared dissolved and gaseous carbon dynamics in streams bordered by contrasting types of land use, specifically agriculture and forest. Carbon dioxide and methane partial pressures (pCO and pCH , respectively) in the water body and carbon emissions via both gases were studied for 24 h during four field expeditions. pCH did not differ between the two system types. pCO was constantly oversaturated in all streams and significantly higher in agricultural streams (annual mean 4282 ppm) compared to forest streams (annual mean 2189 ppm) during all seasons. However, emissions of CO were not significantly different between the stream types due to significantly higher gas transfer velocity in forest compared to agricultural streams. pCO was significantly positively correlated to the concentrations of dissolved organic carbon, dissolved nitrogen and soluble reactive phosphorus in the water. Furthermore, pCO was correlated to optical parameters of dissolved organic matter (DOM) quality, e.g., it increased with indicators of molecular size and an allochthonous fluorescent component identified by Parallel Factor Analysis (PARAFAC). This study demonstrates that different forms of land use may trigger a cascade of effects on the carbon production and emission of streams linked to changes in DOM quality.
    Keywords: Carbon Dioxide ; Methane ; Drifting Chamber ; Parafac Modeling ; Liquid Chromatography With Organic Carbon Detection (LC-OCD) ; Land Use ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    Language: English
    In: Science of the Total Environment, 01 June 2018, Vol.625, pp.519-530
    Description: A large part of the organic carbon in streams is transported by pulses of terrestrial dissolved organic carbon (tDOC) during hydrological events, which is more pronounced in agricultural catchments due to their hydrological flashiness. The majority of the literature considers stationary benthic biofilms and hyporheic biofilms to dominate uptake and processing of tDOC. Here, we argue for expanding this viewpoint to planktonic bacteria, which are transported downstream together with tDOC pulses, and thus perceive them as a less variable resource relative to stationary benthic bacteria. We show that pulse DOC can contribute significantly to the annual DOC export of streams and that planktonic bacteria take up considerable labile tDOC from such pulses in a short time frame, with the DOC uptake being as high as that of benthic biofilm bacteria. Furthermore, we show that planktonic bacteria efficiently take up labile tDOC which strongly increases planktonic bacterial production and abundance. We found that the response of planktonic bacteria to tDOC pulses was stronger in smaller streams than in larger streams, which may be related to bacterial metacommunity dynamics. Furthermore, the response of planktonic bacterial abundance was influenced by soluble reactive phosphorus concentration, pointing to phosphorus limitation. Our data suggest that planktonic bacteria can efficiently utilize tDOC pulses and likely determine tDOC fate during downstream transport, influencing aquatic food webs and related biochemical cycles.
    Keywords: Terrestrial Doc ; Agricultural Catchment ; Flood Pulse ; Hydrology ; Bacteria ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    Language: English
    In: Environmental science & technology, 17 February 2015, Vol.49(4), pp.2081-90
    Description: Agricultural management practices promote organic matter (OM) turnover and thus alter both the processing of dissolved organic matter (DOM) in soils and presumably also the export of DOM to headwater streams, which intimately connect the terrestrial with the aquatic environment. Size-exclusion chromatography, in combination with absorbance and emission matrix fluorometry, was applied to assess how agricultural land use alters the amount and composition of DOM, as well as dissolved organic nitrogen (DON) forms in headwater streams, including temporal variations, in a temperate region of NE Germany. By comparing six agriculturally and six forest-impacted headwater streams, we demonstrated that agriculture promotes increased DOC and DON concentrations, entailing an even more pronounced effect on DON. The major part of DOC and DON in agricultural and forest reference streams is exported in the form of humic-like material with high molecular weight, which indicates terrestrial, i.e., allochthonous sources. As an obvious difference in agricultural streams, the contribution of DOC and particularly DON occurring in the form of nonhumic high-molecular-weight, presumably proteinous material is clearly elevated. Altogether, DOM in agricultural headwaters is mainly complex-soil-derived and aromatic material with a low C:N ratio, which is more microbial processed than its counterpart from forest reference catchments. Our results emphasize the importance of agricultural land use on DOM loss from soils and identify agricultural soils as important DOC and particularly DON sources to headwater streams.
    Keywords: Agriculture ; Forests ; Humic Substances -- Analysis ; Nitrates -- Analysis ; Soil Pollutants -- Analysis ; Water Pollutants, Chemical -- Analysis
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 5
    Language: English
    In: Limnologica, January 2018, Vol.68, pp.82-91
    Description: Lowland streams are often revitalized by hydrologically reconnecting their surrounding terrestrial environment, which likely alters central ecosystem functions such as autotrophic and heterotrophic carbon and nutrient metabolism. However, such central ecosystem functions of stream reaches following revitalization have rarely been investigated. Here, we measured net-uptake of nitrate and of various dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) fractions (using size-exclusion chromatography, SEC), as well as fluorescence components (established by parallel factor analysis, PARAFAC) repeatedly along a revitalized 1.4 km reach of a Danish lowland stream during base flow conditions. Samples were taken at six stations every three hours for one day. We measured discharge at five of the six stations to calculate whole-stream net-uptake. Moreover, we continuously measured oxygen at the start and at the end of the reach to assess stream metabolism, and took piezometer samples from ten shallow groundwater sites to assess potential determinants of organic matter and nitrate metabolism. We found high metabolic activity within the stream reach with a gross-primary production of 4.8 and 3.6 g O m day and a production to respiration ratio of 0.8 and 0.9 at the start and end of the reach, respectively. Nitrate exhibited relatively constant high net-uptake rates of 0.41–0.52 g N m d , which varied little and were not related to the time of the day. Therefore, autotrophic nitrate uptake for was likely of minor importance, despite the apparently high primary production. In contrast, SEC DON and DOC fractions, as well as PARAFAC components did not suggest net-uptake or release. Instead, DOC and DON concentration were highly variable among the six stations and sampling times, a pattern that was not explainable by measurement errors but was likely related to the high variability of DOC and DON concentrations in the hyporheic zone and adjacent groundwater bodies. This pointed to a potentially high interaction with the hyporheic and riparian zone, underlining the strong linkage of DOM-related processes across the terrestrial-aquatic boundary. The high nitrate uptake points to the high retention potential of revitalized stream reaches, which, however, would need to be corroborated by further studies with reference reaches.
    Keywords: Stream Restoration ; Dissolved Organic Carbon ; Dissolved Organic Nitrogen ; Parafac ; Fluorescence ; Nutrient Spiraling ; Doc ; Don ; Oceanography ; Ecology
    ISSN: 0075-9511
    E-ISSN: 1873-5851
    Source: ScienceDirect Journals (Elsevier)
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  • 6
    In: Scientific Reports, 2015, Vol.5
    Description: Agricultural land covers approximately 40% of Earth's land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing.
    Keywords: Biology;
    ISSN: 20452322
    E-ISSN: 20452322
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  • 7
    Language: English
    Keywords: Ddc:550 ; 550 Earth Sciences ; 550 Geowissenschaften ; 570 Life Sciences ; Ddc:570 ; 570 Biowissenschaften; Biologie ; Dissolved Organic Material ; Agricultural Land Use ; Parafac ; Doc ; Don
    Source: Freie Universitat Berlin
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  • 8
    Language: English
    In: European Journal of Pharmacology, Feb 5, 2014, Vol.724, p.31(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ejphar.2013.12.014 Byline: Sandra Oster, Khaled Radad, Dieter Scheller, Marlen Hesse, Wladimir Balanzew, Heinz Reichmann, Gabriele Gille Abstract: In Parkinson disease the degeneration of dopaminergic neurones is believed to lead to a disinhibition of the subthalamic nucleus thus increasing the firing rate of the glutamatergic excitatory projections to the substantia nigra. In consequence, excessive glutamatergic activity will cause excitotoxicity and oxidative stress. In the present study we investigated mechanisms of glutamate toxicity and the neuroprotective potential of the dopamine agonist rotigotine towards dopaminergic neurones in mouse mesencephalic primary culture. Glutamate toxicity was mediated by the N-methyl-d-aspartic acid (NMDA) receptor and accompanied by a strong calcium influx into dopaminergic neurones for which the L-type voltage-sensitive calcium channels play an important role. The rate of superoxide production in the culture was highly increased. Deleterious nitric oxide production did not participate in glutamate-mediated excitotoxicity. Pretreatment of cultures with rotigotine significantly increased the survival of dopaminergic neurones exposed to glutamate. Rotigotine exerted its protective effects via dopamine receptor stimulation (presumably via dopamine D.sub.3 receptor) and decreased significantly the production of superoxide radicals. When cultures were preincubated with Phosphoinositol 3-Kinase (PI3K) inhibitors the protective effect of rotigotine was abolished suggesting a decisive role of the PI3K/Akt pathway in rotigotine-mediated neuroprotection. Consistently, exposure to rotigotine induced the activation of Akt by phosphorylation followed by phosphorylation, and thus inactivation, of the pro-apoptotic factor glycogen synthase kinase-3-beta (GSK-3-[beta]). Taken together, our work contributed to elucidating the mechanisms of glutamate toxicity in mesencephalic culture and unravelled the signalling pathways associated with rotigotine-induced neuroprotection against glutamate toxicity in primary dopaminergic cultures. Author Affiliation: (a) Department of Neurology, Technical University of Dresden, Fetscherstr. 74, 01307 Dresden, Germany (b) Department of Pathology, Faculty of Veterinary Medicine, Assiut University, 71515 Assiut, Egypt (c) UCB Pharma SA, Department of Parkinson's Disease and Movement Disorders, CNS Research, Chemin de Foriest, 1420 Braine-l'Alleud, Belgium Article History: Received 14 February 2013; Revised 9 December 2013; Accepted 10 December 2013
    Keywords: Aspartate ; Nitric Oxide ; Glucose Metabolism ; Glycogen Synthesis ; Glutamate ; N-methyl-d-aspartate ; Superoxides ; Glycogen ; Calcium Channels ; Parkinson Disease
    ISSN: 0014-2999
    Source: Cengage Learning, Inc.
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  • 9
    Language: English
    In: Journal of Quantitative Spectroscopy and Radiative Transfer, 2009, Vol.110(11), pp.930-949
    Description: This paper provides a survey of recent studies on the optical properties of aerosol and cloud particles that have been conducted at the AIDA facility of Forschungszentrum Karlsruhe (Aerosol Interactions and Dynamics in the Atmosphere). Reflecting the broad accessible temperature range of the AIDA chamber which extends from ambient temperature down to 183 K, the investigations feature a broad diversity of research topics, such as the wavelength-dependence of the specific absorption cross sections of soot and mineral dust aerosols at room temperature, depolarization and infrared extinction measurements of ice crystal clouds generated at temperatures below 235 K, and the optical properties of polar stratospheric cloud constituents whose formation was studied in chamber experiments at temperatures well below 200 K. After reviewing the AIDA research activity of the past decade and introducing the optical instrumentation of the AIDA facility, this paper presents illustrative examples of ongoing and already published work on optical measurements of soot aerosols, mineral dust particles, and ice crystal clouds.
    Keywords: Aida Chamber ; Extinction ; Light Scattering ; Light Absorption ; Depolarization ; Infrared Spectroscopy ; Polar Nephelometer ; Photo Acoustic Spectrometer ; Optical Properties ; Refractive Indices ; Soot Aerosol ; Mineral Dust ; Ice Crystals ; Non-Spherical Particles ; Physics
    ISSN: 0022-4073
    E-ISSN: 1879-1352
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  • 10
    Language: English
    In: European Journal of Pharmacology, 05 February 2014, Vol.724, pp.31-42
    Description: In Parkinson disease the degeneration of dopaminergic neurones is believed to lead to a disinhibition of the subthalamic nucleus thus increasing the firing rate of the glutamatergic excitatory projections to the substantia nigra. In consequence, excessive glutamatergic activity will cause excitotoxicity and oxidative stress. In the present study we investigated mechanisms of glutamate toxicity and the neuroprotective potential of the dopamine agonist rotigotine towards dopaminergic neurones in mouse mesencephalic primary culture. Glutamate toxicity was mediated by the N-methyl- -aspartic acid (NMDA) receptor and accompanied by a strong calcium influx into dopaminergic neurones for which the L-type voltage-sensitive calcium channels play an important role. The rate of superoxide production in the culture was highly increased. Deleterious nitric oxide production did not participate in glutamate-mediated excitotoxicity. Pretreatment of cultures with rotigotine significantly increased the survival of dopaminergic neurones exposed to glutamate. Rotigotine exerted its protective effects via dopamine receptor stimulation (presumably via dopamine D receptor) and decreased significantly the production of superoxide radicals. When cultures were preincubated with Phosphoinositol 3-Kinase (PI3K) inhibitors the protective effect of rotigotine was abolished suggesting a decisive role of the PI3K/Akt pathway in rotigotine-mediated neuroprotection. Consistently, exposure to rotigotine induced the activation of Akt by phosphorylation followed by phosphorylation, and thus inactivation, of the pro-apoptotic factor glycogen synthase kinase-3-beta (GSK-3-β). Taken together, our work contributed to elucidating the mechanisms of glutamate toxicity in mesencephalic culture and unravelled the signalling pathways associated with rotigotine-induced neuroprotection against glutamate toxicity in primary dopaminergic cultures.
    Keywords: Parkinson Disease ; Rotigotine ; Glutamate Excitotoxicity ; Pi3k/Akt Pathway ; Neuroprotection ; Pharmacy, Therapeutics, & Pharmacology
    ISSN: 0014-2999
    E-ISSN: 1879-0712
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