| 1. |
- Braun, Judith, et al.
(författare)
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Full15N tracer accounting to revisit major assumptions of 15N isotope pool dilution approaches for gross nitrogen mineralization
- 2018
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 117, s. 16-26
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 The Authors The 15 N isotope pool dilution (IPD) technique is the only available method for measuring gross ammonium (NH 4 + ) production and consumption rates. Rapid consumption of the added 15 N-NH 4 + tracer is commonly observed, but the processes responsible for this consumption are not well understood. The primary objectives of this study were to determine the relative roles of biotic and abiotic processes in 15 N-NH 4 + consumption and to investigate the validity of one of the main assumptions of IPD experiments, i.e., that no reflux of the consumed 15 N tracer occurs during the course of the experiments. We added a 15 N-NH 4 + tracer to live and sterile (autoclaved) soil using mineral topsoil from a beech forest and a grassland in Austria that differed in NH 4 + concentrations and NH 4 + consumption kinetics. We quantified both biotic tracer consumption (i.e. changes in the concentrations and 15 N enrichments of NH 4 + , dissolved organic N (DON), NO 3 − and the microbial N pool) and abiotic tracer consumption (i.e., fixation by clay and/or humic substances). We achieved full recovery of the 15 N tracer in both soils over the course of the 48 h incubation. For the forest soil, we found no rapid consumption of the 15 N tracer, and the majority of tracer (78%) remained unconsumed at the end of the incubation period. In contrast, the grassland soil showed rapid 15 N-NH 4 + consumption immediately after tracer addition, which was largely due to both abiotic fixation (24%) and biotic processes, largely uptake by soil microbes (10%) and nitrification (13%). We found no evidence for reflux of 15 N-NH 4 + over the 48 h incubation period in either soil. Our study therefore shows that 15 N tracer reflux during IPD experiments is negligible for incubation times of up to 48 h, even when rapid NH 4 + consumption occurs. Such experiments are thus robust to the assumption that immobilized labeled N is not re–mobilized during the experimental period and does not impact calculations of gross N mineralization.
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| 2. |
- Keuenhof, Katharina, 1994, et al.
(författare)
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Multimodality imaging beyond CLEM: Showcases of combined in-vivo preclinical imaging and ex-vivo microscopy to detect murine mural vascular lesions
- 2021
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Ingår i: Methods in Cell Biology. - : Elsevier. - 0091-679X. ; , s. 389-415
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In imaging, penetration depth comes at the expense of lateral resolution, which restricts the scope of 3D in-vivo imaging of small animals at micrometer resolution. Bioimaging will need to expand beyond correlative light and electron microscopy (CLEM) approaches to combine insights about in-vivo dynamics in a physiologically relevant 3D environment with ex-vivo information at micrometer resolution (or beyond) within the spatial, structural and biochemical contexts. Our report demonstrates the immense potential for biomedical discovery and diagnosis made available by bridging preclinical in-vivo imaging with ex-vivo biological microscopy to zoom in from the whole organism to individual structures and by adding localized spectroscopic information to structural and functional information. We showcase the use of two novel imaging pipelines to zoom into mural lesions (occlusions/hyperplasia and micro-calcifications) in murine vasculature in a truly correlative manner, that is using exactly the same animal for all integrated imaging modalities. This correlated multimodality imaging (CMI) approach includes well-established technologies such as Positron Emission Tomography (microPET), Autoradiography, Magnetic Resonance Imaging (microMRI) and Computed Tomography (microCT), and imaging approaches that are more novel in the biomedical setting, such as X-Ray Fluorescence Spectroscopy (microXRF) and High Resolution Episcopic Microscopy (HREM). Although the current pipelines are focused on mural lesions, they would also be beneficial in preclinical and clinical investigations of vascular diseases in general.
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| 3. |
- Lintner, MIchael, et al.
(författare)
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From cars to the oceans: do water-soluble fuel compounds impact widespread marine microorganisms?
- 2024
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Ingår i: TMS – CFFR Foraminifera Joint Spring Meeting, 22-25th May, Köln, Germany.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Foraminifera are mainly marine single-celled organisms, which can be found in every marine habitat from shallow water areas to the deep sea. Due to the high population densities of foraminifera in all marine habitats and their high uptake of organic matter, it has been suggested that foraminifera form an important contribution to the global marine carbon and nitrogen cycle. In this research we focus on Nonionella sp. T1 which is a non-indigenous species in the Gullmar Fjord (Sweden) and has been reported for the first time in the Skagerrak in 2013. During laboratory experiments we investigated the effect of water-soluble fuel components of diesel a gasoline on the metabolism of foraminifera. Three different concentrations of the extracts (25, 50 and 100%) were applied in contrast to a control (0% extract) sample. The foraminifera were incubated for 3 days with a 13C and 15N enriched food source (Chaetoceros calcitrans) and later examined with different spectroscopic methods. The results showed that the metabolism is influenced by the presence of fuel extracts. The nitrogen uptake of the foraminifera was reduced (p>0.001) by the presence of fuel extract. The amount of carbon absorbed during the experiments in the gasoline series does not differ significantly (p=0.093) in contrast to the control group, but the uptake during incubation with diesel extract is significantly (p>0.001) lower. This pattern was also reflected by the C:N ratio which indicates a change in protein production depending on stressful conditions. Based on this research, it can be summarized that contamination with fuel in the marine environment causes significant damage to microorganisms, even if they live in benthic habitats and therefore do not come into direct contact with the fuel itself.
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