TY - GEN A1 - Lara, Mark J. A1 - Nitze, Ingmar A1 - Große, Guido A1 - McGuire, David T1 - Tundra landform and vegetation productivity trend maps for the Arctic Coastal Plain of northern Alaska T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Arctic tundra landscapes are composed of a complex mosaic of patterned ground features, varying in soil moisture, vegetation composition, and surface hydrology over small spatial scales (10-100 m). The importance of microtopography and associated geomorphic landforms in influencing ecosystem structure and function is well founded, however, spatial data products describing local to regional scale distribution of patterned ground or polygonal tundra geomorphology are largely unavailable. Thus, our understanding of local impacts on regional scale processes (e.g., carbon dynamics) may be limited. We produced two key spatiotemporal datasets spanning the Arctic Coastal Plain of northern Alaska (similar to 60,000 km(2)) to evaluate climate-geomorphological controls on arctic tundra productivity change, using (1) a novel 30m classification of polygonal tundra geomorphology and (2) decadal-trends in surface greenness using the Landsat archive (1999-2014). These datasets can be easily integrated and adapted in an array of local to regional applications such as (1) upscaling plot-level measurements (e.g., carbon/energy fluxes), (2) mapping of soils, vegetation, or permafrost, and/or (3) initializing ecosystem biogeochemistry, hydrology, and/or habitat modeling. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1035 KW - spatial-distribution KW - lake basins KW - microtopography KW - water KW - ice KW - accumulation KW - degradation KW - permafrost KW - dynamics KW - barrow Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-459875 SN - 1866-8372 IS - 1035 ER - TY - GEN A1 - Feldmann, Johannes A1 - Levermann, Anders T1 - Interaction of marine ice-sheet instabilities in two drainage basins BT - simple scaling of geometry and transition time T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Universität N2 - The initiation of a marine ice-sheet instability (MISI) is generally discussed from the ocean side of the ice sheet. It has been shown that the reduction in ice-shelf buttressing and softening of the coastal ice can destabilize a marine ice sheet if the bedrock is sloping upward towards the ocean. Using a conceptional flow-line geometry, we investigate the possibility of whether a MISI can be triggered from the direction of the ice divide as opposed to coastal forcing and explore the interaction between connected basins. We find that the initiation of a MISI in one basin can induce a destabilization in the other. The underlying mechanism of basin interaction is based on dynamic thinning and a consecutive motion of the ice divide which induces a thinning in the adjacent basin and a successive initiation of the instability. Our simplified and symmetric topographic setup allows scaling both the geometry and the transition time between both instabilities. We find that the ice profile follows a universal shape that is scaled with the horizontal extent of the ice sheet and that the same exponent of 1/2 applies for the scaling relation between central surface elevation and horizontal extent as in the pure shallow ice approximation (Vialov profile). Altering the central bed elevation, we find that the extent of grounding-line retreat in one basin determines the degree of interaction with the other. Different scenarios of basin interaction are discussed based on our modeling results as well as on a conceptual flux-balance analysis. We conclude that for the three-dimensional case, the possibility of drainage basin interaction on timescales on the order of 1 kyr or larger cannot be excluded and hence needs further investigation. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 511 KW - Pine Island Glacier KW - model PISM-PIK KW - West Antarctica KW - grounding-line KW - Thwaites Glacier KW - divide position KW - part 1 KW - stability KW - shelf KW - accumulation Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-408903 SN - 1866-8372 IS - 511 ER - TY - JOUR A1 - Henkel, Janin A1 - Coleman Mac Gregor of Inneregny, Charles Dominic A1 - Schraplau, Anne A1 - Jöhrens, Korinna A1 - Weiss, Thomas Siegfried A1 - Jonas, Wenke A1 - Schürmann, Annette A1 - Püschel, Gerhard Paul T1 - Augmented liver inflammation in a microsomal prostaglandin E synthase 1 (mPGES-1)-deficient diet-induced mouse NASH model JF - Scientific Reports N2 - In a subset of patients, non-alcoholic fatty liver disease (NAFLD) is complicated by cell death and inflammation resulting in non-alcoholic steatohepatitis (NASH), which may progress to fibrosis and subsequent organ failure. Apart from cytokines, prostaglandins, in particular prostaglandin E-2 (PGE(2)), play a pivotal role during inflammatory processes. Expression of the key enzymes of PGE(2) synthesis, cyclooxygenase 2 and microsomal PGE synthase 1 (mPGES-1), was increased in human NASH livers in comparison to controls and correlated with the NASH activity score. Both enzymes were also induced in NASH-diet-fed wild-type mice, resulting in an increase in hepatic PGE(2) concentration that was completely abrogated in mPGES-1-deficient mice. PGE(2) is known to inhibit TNF-alpha synthesis in macrophages. A strong infiltration of monocyte-derived macrophages was observed in NASH-diet-fed mice, which was accompanied with an increase in hepatic TNF-alpha expression. Due to the impaired PGE(2) production, TNF-alpha expression increased much more in livers of mPGES-1-deficient mice or in the peritoneal macrophages of these mice. The increased levels of TNF-alpha resulted in an enhanced IL-1 beta production, primarily in hepatocytes, and augmented hepatocyte apoptosis. In conclusion, attenuation of PGE(2) production by mPGES-1 ablation enhanced the TNF-alpha-triggered inflammatory response and hepatocyte apoptosis in diet-induced NASH. KW - suppress VLDL secretion KW - mice lacking KW - nonalcoholic steatohepatthis KW - insulin-resistance KW - rat hepatocytes KW - kupffer cells KW - E-2 KW - disease KW - expression KW - accumulation Y1 - 2018 U6 - https://doi.org/10.1038/s41598-018-34633-y SN - 2045-2322 IS - 8 SP - 1 EP - 11 PB - Nature Research CY - London ER - TY - GEN A1 - Henkel, Janin A1 - Coleman Mac Gregor of Inneregny, Charles Dominic A1 - Schraplau, Anne A1 - Jöhrens, Korinna A1 - Weiss, Thomas Siegfried A1 - Jonas, Wenke A1 - Schürmann, Annette A1 - Püschel, Gerhard Paul T1 - Augmented liver inflammation in a microsomal prostaglandin E synthase 1 (mPGES-1)-deficient diet-induced mouse NASH model T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - In a subset of patients, non-alcoholic fatty liver disease (NAFLD) is complicated by cell death and inflammation resulting in non-alcoholic steatohepatitis (NASH), which may progress to fibrosis and subsequent organ failure. Apart from cytokines, prostaglandins, in particular prostaglandin E-2 (PGE(2)), play a pivotal role during inflammatory processes. Expression of the key enzymes of PGE(2) synthesis, cyclooxygenase 2 and microsomal PGE synthase 1 (mPGES-1), was increased in human NASH livers in comparison to controls and correlated with the NASH activity score. Both enzymes were also induced in NASH-diet-fed wild-type mice, resulting in an increase in hepatic PGE(2) concentration that was completely abrogated in mPGES-1-deficient mice. PGE(2) is known to inhibit TNF-alpha synthesis in macrophages. A strong infiltration of monocyte-derived macrophages was observed in NASH-diet-fed mice, which was accompanied with an increase in hepatic TNF-alpha expression. Due to the impaired PGE(2) production, TNF-alpha expression increased much more in livers of mPGES-1-deficient mice or in the peritoneal macrophages of these mice. The increased levels of TNF-alpha resulted in an enhanced IL-1 beta production, primarily in hepatocytes, and augmented hepatocyte apoptosis. In conclusion, attenuation of PGE(2) production by mPGES-1 ablation enhanced the TNF-alpha-triggered inflammatory response and hepatocyte apoptosis in diet-induced NASH. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 483 KW - suppress VLDL secretion KW - mice lacking KW - nonalcoholic steatohepatthis KW - insulin-resistance KW - rat hepatocytes KW - kupffer cells KW - E-2 KW - disease KW - expression KW - accumulation Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-420879 SN - 1866-8372 IS - 483 ER - TY - JOUR A1 - Hartwich, Melanie A1 - Martin-Creuzburg, Dominik A1 - Wacker, Alexander T1 - Seasonal changes in the accumulation of polyunsaturated fatty acids in zooplankton JF - Journal of plankton research N2 - In aquatic food webs, consumers, such as daphnids and copepods, differ regarding their accumulation of polyunsaturated fatty acids (PUFAs). We tested if the accumulation of PUFAs in a seston size fraction containing different consumers and in Daphnia as a separate consumer is subject to seasonal changes in a large deep lake due to changes in the dietary PUFA supply and specific demands of different consumers. We found that the accumulation of arachidonic acid (ARA) in Daphnia increased from early summer to late summer and autumn. However, ARA requirements of Daphnia appeared to be constant throughout the year, because the accumulation of ARA increased when the dietary ARA supply decreased. In the size fraction 140 m, we found an increased accumulation of docosahexaenoic acid (DHA) during late summer and autumn. These seasonal changes in DHA accumulation were linked to changes in the proportion of copepods in this size fraction, which may have increasingly accumulated DHA for active overwintering. We show that consumer-specific PUFA demands can result in seasonal changes in PUFA accumulation, which may influence the trophic transfer of PUFAs within the food web. KW - accumulation KW - Daphnia KW - copepods KW - ARA KW - DHA Y1 - 2013 U6 - https://doi.org/10.1093/plankt/fbs078 SN - 0142-7873 VL - 35 IS - 1 SP - 121 EP - 134 PB - Oxford Univ. Press CY - Oxford ER -