| 1. |
- Sun, Tao, et al.
(författare)
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A test of manganese effects on decomposition in forest and cropland sites
- 2019
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 129, s. 178-183
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Tidskriftsartikel (refereegranskat)abstract
- Litter of plant origin is the main source of soil organic matter, and its physical and chemical quality and decomposition rates are key variables in the prediction and modelling of how litter-derived carbon (C) is cycling through the ecosystem. However, the biological control factors for decomposition are not well understood and often poorly represented in global C models. These are typically run using simple parameters, such as nitrogen (N) and lignin concentrations, characterizing the quality of the organic matter input to soils and its accessibility to decomposer organisms. Manganese (Mn) is a key component for the formation of manganese peroxidase (MnP), an important enzyme for lignin degradation. However, the functional role of Mn on plant litter decomposition has been rarely experimentally examined. Here, using a forest and a cropland site we studied, over 41 months, the effects of Mn fertilization on MnP activity and decomposition of eight substrates ranging in initial lignin concentrations from 9.8 to 44.6%. Asymptotic decomposition models fitted the mass loss data best and allowed us to separately compare the influence of Mn fertilization on different litter stages and pools. Across substrates, Mn fertilization stimulated decomposition rates of the late stage where lignin dominates decomposition, resulting in smaller fraction of slowly decomposing litter. The increased MnP activity caused by Mn fertilization provided the mechanism explaining the stimulated decomposition in the Mn-addition treatments.
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| 2. |
- Yang, Yalan, et al.
(författare)
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Chemodiversity of Cyanobacterial Toxins Driven by Future Scenarios of Climate Warming and Eutrophication
- 2023
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Ingår i: Environmental Science and Technology. - 0013-936X. ; 57:32, s. 11767-11778
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Tidskriftsartikel (refereegranskat)abstract
- Climate change and eutrophication are two environmental threats that can alter the structure of freshwater ecosystems and their service functions, but we know little about how ecosystem structure and function will evolve in future scenarios of climate warming. Therefore, we created different experimental climate scenarios, including present-day conditions, a 3.0 °C increase in mean temperature, and a “heatwaves” scenario (i.e., an increase in temperature variability) to assess the effects of climate change on phytoplankton communities under simultaneous stress from eutrophication and herbicides. We show that the effects of climate warming, particularly heatwaves, are associated with elevated cyanobacterial abundances and toxin production, driven by a change from mainly nontoxic to toxic Microcystis spp. The reason for higher cyanobacterial toxin concentrations is likely an increase in abundances because under the dual pressures of climate warming and eutrophication individual Microcystis toxin-producing ability decreased. Eutrophication and higher temperatures significantly increased the biomass of Microcystis, leading to an increase in the cyanobacterial toxin concentrations. In contrast, warming alone did not produce higher cyanobacterial abundances or cyanobacterial toxin concentrations likely due to the depletion of the available nutrient pool. Similarly, the herbicide glyphosate alone did not affect abundances of any phytoplankton taxa. In the case of nutrient enrichment, cyanobacterial toxin concentrations were much higher than under warming alone due to a strong boost in biomass of potential cyanobacterial toxin producers. From a broader perspective our study shows that in a future warmer climate, nutrient loading has to be reduced if toxic cyanobacterial dominance is to be controlled.
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| 3. |
- Chen, Ying, et al.
(författare)
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Enhanced colonic tumorigenesis in alkaline sphingomyelinase (NPP7) knockout mice.
- 2015
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Ingår i: Molecular Cancer Therapeutics. - 1538-8514. ; 14:1, s. 259-267
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Tidskriftsartikel (refereegranskat)abstract
- Intestinal alkaline sphingomyelinase (alk-SMase) generates ceramide and inactivates platelet-activating factor (PAF) and is previously suggested to have anticancer properties. The direct evidence is still lacking. We studied colonic tumorigenesis in alk-SMase knockout (KO) mice. Formation of aberrant crypt foci (ACF) was examined after azoxymethane (AOM) injection. Tumor was induced by AOM alone, a conventional AOM/dextran sulfate sodium (DSS) treatment, and an enhanced AOM/DSS method. beta-catenin was determined by immunohistochemistry, PAF levels by ELISA and sphingomyelin metabolites by mass spectrometry. Without treatment, spontaneous tumorigenesis was not identified but the intestinal mucosa appeared thicker in KO than in wild type (WT) littermates. AOM alone induced more ACF in KO mice but no tumors 28 weeks after injection. However, combination of AOM/DSS treatments induced colonic tumors and the incidence was significantly higher in KO than in WT mice. By the enhanced AOM/DSS method tumor number per mouse increased 4.5 times and tumor size 1.8 times in KO compared to WT mice. While all tumors were adenomas in WT mice, 32% were adenocarcinomas in KO mice. Compared to WT mice, cytosol expression of beta-catenin was significantly decreased and nuclear translocation in tumors was more pronounced in KO mice. Lipid analysis showed decreased ceramide in small intestine and increased sphingosine-1-phosphate in both small intestine and colon in nontreated KO mice. PAF levels in feces were significantly higher in the KO mice after AOM/DSS treatment. In conclusion lack of alk-SMase markedly increases AOM/DSS induced colonic tumorigenesis associated with decreased ceramide and increased sphingosine-1-phosphate and PAF levels.
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| 4. |
- Hervey-Jumper, Shawn L, et al.
(författare)
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Interactive Effects of Molecular, Therapeutic, and Patient Factors on Outcome of Diffuse Low-Grade Glioma.
- 2023
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Ingår i: Journal of clinical oncology : official journal of the American Society of Clinical Oncology. - 1527-7755. ; 41:11, s. 2029-2042
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Tidskriftsartikel (refereegranskat)abstract
- In patients with diffuse low-grade glioma (LGG), the extent of surgical tumor resection (EOR) has a controversial role, in part because a randomized clinical trial with different levels of EOR is not feasible.In a 20-year retrospective cohort of 392 patients with IDH-mutant grade 2 glioma, we analyzed the combined effects of volumetric EOR and molecular and clinical factors on overall survival (OS) and progression-free survival by recursive partitioning analysis. The OS results were validated in two external cohorts (n = 365). Propensity score analysis of the combined cohorts (n = 757) was used to mimic a randomized clinical trial with varying levels of EOR.Recursive partitioning analysis identified three survival risk groups. Median OS was shortest in two subsets of patients with astrocytoma: those with postoperative tumor volume (TV) > 4.6 mL and those with preoperative TV > 43.1 mL and postoperative TV ≤ 4.6 mL. Intermediate OS was seen in patients with astrocytoma who had chemotherapy with preoperative TV ≤ 43.1 mL and postoperative TV ≤ 4.6 mL in addition to oligodendroglioma patients with either preoperative TV > 43.1 mL and residual TV ≤ 4.6 mL or postoperative residual volume > 4.6 mL. Longest OS was seen in astrocytoma patients with preoperative TV ≤ 43.1 mL and postoperative TV ≤ 4.6 mL who received no chemotherapy and oligodendroglioma patients with preoperative TV ≤ 43.1 mL and postoperative TV ≤ 4.6 mL. EOR ≥ 75% improved survival outcomes, as shown by propensity score analysis.Across both subtypes of LGG, EOR beginning at 75% improves OS while beginning at 80% improves progression-free survival. Nonetheless, maximal resection with preservation of neurological function remains the treatment goal. Our findings have implications for surgical strategies for LGGs, particularly oligodendroglioma.
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