| 1. |
- Munch, Marie W., et al.
(författare)
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Effect of 12 mg vs 6 mg of Dexamethasone on the Number of Days Alive Without Life Support in Adults With COVID-19 and Severe Hypoxemia The COVID STEROID 2 Randomized Trial
- 2021
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Ingår i: Journal of the American Medical Association (JAMA). - : AMER MEDICAL ASSOC. - 0098-7484 .- 1538-3598. ; 326:18, s. 1807-1817
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Tidskriftsartikel (refereegranskat)abstract
- Question What is the effect of 12 mg vs 6 mg of dexamethasone on the number of days alive without life support at 28 days in patients with COVID-19 and severe hypoxemia? Findings In this randomized trial that included 1000 patients with COVID-19 and severe hypoxemia, treatment with 12 mg/d of dexamethasone resulted in 22.0 days alive without life support at 28 days compared with 20.5 days in those receiving 6 mg/d of dexamethasone. This difference was not statistically significant. Meaning Compared with 6 mg of dexamethasone, 12 mg of dexamethasone did not statistically significantly reduce the number of days alive without life support at 28 days. This multicenter randomized clinical trial compares the effects of 12 mg/d vs 6 mg/d of dexamethasone in patients with COVID-19 and severe hypoxemia. IMPORTANCE A daily dose with 6 mg of dexamethasone is recommended for up to 10 days in patients with severe and critical COVID-19, but a higher dose may benefit those with more severe disease. OBJECTIVE To assess the effects of 12 mg/d vs 6 mg/d of dexamethasone in patients with COVID-19 and severe hypoxemia. DESIGN, SETTING, AND PARTICIPANTS A multicenter, randomized clinical trial was conducted between August 2020 and May 2021 at 26 hospitals in Europe and India and included 1000 adults with confirmed COVID-19 requiring at least 10 L/min of oxygen or mechanical ventilation. End of 90-day follow-up was on August 19, 2021. INTERVENTIONS Patients were randomized 1:1 to 12 mg/d of intravenous dexamethasone (n = 503) or 6 mg/d of intravenous dexamethasone (n = 497) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was the number of days alive without life support (invasive mechanical ventilation, circulatory support, or kidney replacement therapy) at 28 days and was adjusted for stratification variables. Of the 8 prespecified secondary outcomes, 5 are included in this analysis (the number of days alive without life support at 90 days, the number of days alive out of the hospital at 90 days, mortality at 28 days and at 90 days, and >= 1 serious adverse reactions at 28 days). RESULTS Of the 1000 randomized patients, 982 were included (median age, 65 [IQR, 55-73] years; 305 [31%] women) and primary outcome data were available for 971 (491 in the 12 mg of dexamethasone group and 480 in the 6 mg of dexamethasone group). The median number of days alive without life support was 22.0 days (IQR, 6.0-28.0 days) in the 12 mg of dexamethasone group and 20.5 days (IQR, 4.0-28.0 days) in the 6 mg of dexamethasone group (adjusted mean difference, 1.3 days [95% CI, 0-2.6 days]; P = .07). Mortality at 28 days was 27.1% in the 12 mg of dexamethasone group vs 32.3% in the 6 mg of dexamethasone group (adjusted relative risk, 0.86 [99% CI, 0.68-1.08]). Mortality at 90 days was 32.0% in the 12 mg of dexamethasone group vs 37.7% in the 6 mg of dexamethasone group (adjusted relative risk, 0.87 [99% CI, 0.70-1.07]). Serious adverse reactions, including septic shock and invasive fungal infections, occurred in 11.3% in the 12 mg of dexamethasone group vs 13.4% in the 6 mg of dexamethasone group (adjusted relative risk, 0.83 [99% CI, 0.54-1.29]). CONCLUSIONS AND RELEVANCE Among patients with COVID-19 and severe hypoxemia, 12 mg/d of dexamethasone compared with 6 mg/d of dexamethasone did not result in statistically significantly more days alive without life support at 28 days. However, the trial may have been underpowered to identify a significant difference.
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| 2. |
- Sarneel, Judith M., et al.
(författare)
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Reading tea leaves worldwide : decoupled drivers of initial litter decomposition mass-loss rate and stabilization
- 2024
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Ingår i: Ecology Letters. - : John Wiley & Sons. - 1461-023X .- 1461-0248. ; 27:5
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Tidskriftsartikel (refereegranskat)abstract
- The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models.
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| 3. |
- Andersen, Emil Alexander Sherman, et al.
(författare)
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Nitrogen isotopes reveal high N retention in plants and soil of old Norse and Inuit deposits along a wet-dry arctic fjord transect in Greenland
- 2020
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Ingår i: Plant and Soil. - : Springer. - 0032-079X .- 1573-5036. ; 455:1-2, s. 241-255
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Plant growth in the Arctic is often nutrient limited due to temperature constraints on decomposition and low atmospheric input of nitrogen (N). Local hotspots of nutrient enrichment found in up to 4000-year-old archaeological deposits can be used to explore the recycling and long-term retention of nutrients in arctic ecosystems.Methods: We investigated old Inuit and Norse deposits (known as middens) and adjacent tundra ecosystems along a wet-dry fjord gradient in western Greenland to explore the isotopic fingerprinting of plant and soil carbon and nitrogen (C-13/C-12 and(15)N/N-14) derived from human presence.Results: At all locations we observed a significant isotopic fingerprint in soil and plant N related to human deposits. This demonstrates a century-long legacy of past human habitation on plant and soil characteristics and indicates a surprisingly high N retention in these ecosystems. This is consistent with the significantly higher plant biomass in areas with archaeological deposits.Conclusion: Vegetation composition and N in plants and soils displayed marked differences along the wet-dry fjord gradient. Furthermore, the profound nutrient enrichment and organic matter accumulation in archaeological deposits compared to surrounding tundra demonstrates a century-long legacy of past habitation on plant and soil characteristics as well as efficient N cycling with surprisingly limited N loss.
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| 4. |
- Andresen, Louise C., 1974, et al.
(författare)
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Moderate nitrogen retention in temperate heath ecosystem after elevated CO2, drought and warming through 7years
- 2023
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Ingår i: European Journal of Soil Science. - 1351-0754 .- 1365-2389. ; 74:4
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) dynamic is one of the main controlling factors of responses to climate change in N-limited terrestrial ecosystems, which rely on nutrient re-cycling and retention. In this study we investigate the N partitioning in ecosystem compartments of a grassland heath, and the impact of multiple climate change factors on long-term N retention after 15N pulse labelling. The impacts of elevated carbon dioxide (eCO2), warming and drought and the treatments in combination on ecosystem N retention was investigated in a field scale manipulation experiment. A six-year time-course was assessed by pulse-labelling with the stable N isotope 15N and by sampling after 1 day, 1 year and 6years. After the six years we observed that the total ecosystem retained 42 % of the amended 15N across treatments (recovery of the amended 15N in the pool). The fate of the applied 15N was mainly stabilisation in soil, with 36 % recovery, while the plant compartment and microbial biomass each retained only 1-2 % of the added 15N. This suggests a moderate retention of N, for all treatments, as compared to similar long-term studies of forest ecosystems. A decreased ammonium and vegetation N pool combined with higher 15N retention in the soil at eCO2 treatments suggests that eCO2 promoted processes that immobilize N in soil, while warming counteracted this when combined with eCO2. Drought treatments contrastingly increased the vegetation N pool. We conclude that as the organic soil layer has the main capacity for N storage in a temperate heathland-grassland, it is important for buffering nutrient availability and maintaining a resilient ecosystem. However, the full treatment combination of drought, warming and eCO2 did not differ in 15N recovery from the controls, suggesting unchanged long-term consequences of climate change on retention of pulse added N in this ecosystem.
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| 5. |
- Andresen, Louise C., 1974, et al.
(författare)
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Patterns of free amino acids in tundra soils reflect mycorrhizal type, shrubification, and warming
- 2022
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 0940-6360 .- 1432-1890. ; 32:3-4, s. 305-313
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Tidskriftsartikel (refereegranskat)abstract
- The soil nitrogen (N) cycle in cold terrestrial ecosystems is slow and organically bound N is an important source of N for plants in these ecosystems. Many plant species can take up free amino acids from these infertile soils, either directly or indirectly via their mycorrhizal fungi. We hypothesized that plant community changes and local plant community differences will alter the soil free amino acid pool and composition; and that long-term warming could enhance this effect. To test this, we studied the composition of extractable free amino acids at five separate heath, meadow, and bog locations in subarctic and alpine Scandinavia, with long-term (13 to 24 years) warming manipulations. The plant communities all included a mixture of ecto-, ericoid-, and arbuscular mycorrhizal plant species. Vegetation dominated by grasses and forbs with arbuscular and non-mycorrhizal associations showed highest soil free amino acid content, distinguishing them from the sites dominated by shrubs with ecto- and ericoid-mycorrhizal associations. Warming increased shrub and decreased moss cover at two sites, and by using redundancy analysis, we found that altered soil free amino acid composition was related to this plant cover change. From this, we conclude that the mycorrhizal type is important in controlling soil N cycling and that expansion of shrubs with ectomycorrhiza (and to some extent ericoid mycorrhiza) can help retain N within the ecosystems by tightening the N cycle.
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| 6. |
- Baggesen, Nanna, et al.
(författare)
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Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a subarctic heath
- 2021
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 27:12, s. 2928-2944
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Tidskriftsartikel (refereegranskat)abstract
- Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long‐term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem‐level net BVOC fluxes were measured in the experimental plots using proton‐transfer‐reaction time‐of‐flight mass spectrometry (PTR–ToF–MS). The warming treatment increased monoterpene and isoprene emissions by ≈50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%–75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.
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| 7. |
- Barthelemy, Hélène, et al.
(författare)
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Short- and long-term plant and microbial uptake of 15N-labelled urea in a mesic tundra heath, West Greenland
- 2024
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Ingår i: Polar Biology. - : Springer Nature. - 0722-4060 .- 1432-2056. ; 47:1, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial animals are key elements in the cycling of elements in the Arctic where nutrient availability is low. Waste production by herbivores, in particular urine deposition, has a crucial role for nitrogen (N) recycling, still, it remains largely unexplored. Also, experimental evidence is biased toward short-term studies and Arctic regions under high herbivore pressure. In this study, we aimed to examine the fate of N derived from urine in a nutrient poor tundra heath in West Greenland, with historical low level of herbivory. We performed a pulse labelling with 15N-urea over the plant canopy and explored ecosystem N partition and retention in the short-term (2 weeks and 1 year) and longer-term (5 years). We found that all vascular plants, irrespective of their traits, could rapidly take up N-urea, but mosses and lichens were even more efficient. Total 15N enrichment was severely reduced for all plants 5 years after tracer addition, with the exception of cryptogams, indicating that non-vascular plants constituted a long-term sink of 15N-urea. The 15N recovery was also high in the litter suggesting high N immobilization in this layer, potentially delaying the nutrients from urine entering the soil compartment. Long-term 15N recovery in soil microbial biomass was minimal, but as much as 30% of added 15N remained in the non-microbial fraction after 5 years. Our results demonstrate that tundra plants that have evolved under low herbivory pressure are well adapted to quickly take advantage of labile urea, with urine having only a transient effect on soil nutrient availability.
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| 8. |
- Berner, Logan T., et al.
(författare)
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The Arctic plant aboveground biomass synthesis dataset
- 2024
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Ingår i: Scientific Data. - : Springer Nature. - 2052-4463. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Plant biomass is a fundamental ecosystem attribute that is sensitive to rapid climatic changes occurring in the Arctic. Nevertheless, measuring plant biomass in the Arctic is logistically challenging and resource intensive. Lack of accessible field data hinders efforts to understand the amount, composition, distribution, and changes in plant biomass in these northern ecosystems. Here, we present The Arctic plant aboveground biomass synthesis dataset, which includes field measurements of lichen, bryophyte, herb, shrub, and/or tree aboveground biomass (g m−2) on 2,327 sample plots from 636 field sites in seven countries. We created the synthesis dataset by assembling and harmonizing 32 individual datasets. Aboveground biomass was primarily quantified by harvesting sample plots during mid- to late-summer, though tree and often tall shrub biomass were quantified using surveys and allometric models. Each biomass measurement is associated with metadata including sample date, location, method, data source, and other information. This unique dataset can be leveraged to monitor, map, and model plant biomass across the rapidly warming Arctic.
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| 9. |
- Gregersen, Ida, et al.
(författare)
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Legumain in Acute Coronary Syndromes : A Substudy of the PLATO (Platelet Inhibition and Patient Outcomes) Trial
- 2020
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Ingår i: Journal of the American Heart Association. - : WILEY. - 2047-9980 .- 2047-9980. ; 9:17
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The cysteine protease legumain is increased in patients with atherosclerosis, but its causal role in atherogenesis and cardiovascular disease is still unclear. The aim of the study was to investigate the association of legumain with clinical outcome in a large cohort of patients with acute coronary syndrome. METHODS AND RESULTS : Serum levels of legumain were analyzed in 4883 patients with acute coronary syndrome from a substudy of the PLATO (Platelet Inhibition and Patient Outcomes) trial. Levels were analyzed at admission and after 1 month follow-up. Associations between legumain and a composite of cardiovascular death, spontaneous myocardial infarction or stroke, and its individual components were assessed by multivariable Cox regression analyses. At baseline, a 50% increase in legumain level was associated with a hazard ratio (HR) of 1.13 (95% CI, 1.04-1.21),P=0.0018, for the primary composite end point, adjusted for randomized treatment. The association remained significant after adjustment for important clinical and demographic variables (HR, 1.10; 95% CI, 1.02-1.19;P=0.013) but not in the fully adjusted model. Legumain levels at 1 month were not associated with the composite end point but were negatively associated with stroke (HR, 0.62; 95% CI, 0.44-0.88;P=0.0069), including in the fully adjusted model (HR, 0.57; 95% CI, 0.37-0.88;P=0.0114). CONCLUSIONS: Baseline legumain was associated with the primary outcome in patients with acute coronary syndrome, but not in the fully adjusted model. The association between high levels of legumain at 1 month and decreased occurrence of stroke could be of interest from a mechanistic point of view, illustrating the potential dual role of legumain during atherogenesis and acute coronary syndrome. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00391872.
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| 10. |
- Hicks, Lettice C., et al.
(författare)
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Simulated rhizosphere deposits induce microbial N-mining that may accelerate shrubification in the subarctic
- 2020
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 101:9
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is exposing high-latitude systems to warming and a shift towards more shrub-dominated plant communities, resulting in increased leaf-litter inputs at the soil surface, and more labile root-derived organic matter (OM) input in the soil profile. Labile OM can stimulate the mineralization of soil organic matter (SOM); a phenomenon termed “priming.” In N-poor subarctic soils, it is hypothesized that microorganisms may “prime” SOM in order to acquire N (microbial N-mining). Increased leaf-litter inputs with a high C/N ratio might further exacerbate microbial N demand, and increase the susceptibility of N-poor soils to N-mining. We investigated the N-control of SOM mineralization by amending soils from climate change–simulation treatments in the subarctic (+1.1°C warming, birch litter addition, willow litter addition, and fungal sporocarp addition) with labile OM either in the form of glucose (labile C; equivalent to 400 µg C/g fresh [fwt] soil) or alanine (labile C + N; equivalent to 400 µg C and 157 µg N/g fwt soil), to simulate rhizosphere inputs. Surprisingly, we found that despite 5 yr of simulated climate change treatments, there were no significant effects of the field-treatments on microbial process rates, community structure or responses to labile OM. Glucose primed the mineralization of both C and N from SOM, but gross mineralization of N was stimulated more than that of C, suggesting that microbial SOM use increased in magnitude and shifted to components richer in N (i.e., selective microbial N-mining). The addition of alanine also resulted in priming of both C and N mineralization, but the N mineralization stimulated by alanine was greater than that stimulated by glucose, indicating strong N-mining even when a source of labile OM including N was supplied. Microbial carbon use efficiency was reduced in response to both labile OM inputs. Overall, these findings suggest that shrub expansion could fundamentally alter biogeochemical cycling in the subarctic, yielding more N available for plant uptake in these N-limited soils, thus driving positive plant–soil feedbacks.
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