Increases in summer droughts and nitrogen (N) deposition have raised concerns of widespread biodiversity loss and nutrient imbalances, but our understanding of the ecological role of ectomycorrhizal fungal (ECMF) diversity in mediating root functions remains a major knowledge gap. We used different global change scenarios to experimentally alter the composition of ECMF communities colonizing European beech saplings and examined the consequences for phosphorus (P) uptake (H PO feeding experiment) and use efficiencies of trees. Specifically, we simulated increases in temperature and N deposition and decreases in soil moisture and P availability in a factorial experiment. Here, we show that ECMF α diversity is a major factor contributing to root functioning under global change. P uptake efficiency of beech significantly increased with increasing ECMF species richness and diversity, as well as with decreasing P availability. As a consequence of decreases in ECMF diversity, P uptake efficiency decreased when soil moisture was limiting. By contrast, P use efficiencies were a direct (negative) function of P availability and not of ECMF diversity. We conclude that increasing summer droughts may reduce ECMF diversity and the complementarity of P uptake by ECMF species, which will add to negative growth effects expected from nutrient imbalances under global change.

Phosphorus (P) is often a limiting macronutrient in temperate forests, but knowledge on the phenological and physiological responses of beech (Fagus sylvatica L.) to P deficiency is scarce. In this study, young beech trees were excavated with intact soil cores from two German forests, Unterlüss (LUE) with low soil P and Bad Brückenau (BBR) with high soil P concentrations. The trees were transferred to identical climatic conditions. In the subsequent growth phase phenological stages during bud burst and leaf unfolding were recorded; biomass production and total P concentrations in different tissues were measured. Seasonal fluctuations in photosynthesis and of soluble P in wood and bark exudates were determined. BBR beeches grew faster and produced more and larger leaves than the LUE beeches. Leaf extension and unfolding were delayed in LUE compared with BBR beeches, but not the time point of bud break. All plant tissues of BBR trees contained higher total P concentrations than those of LUE trees. Strong seasonal fluctuations for P in exudates of beech transport tissues, wood and bark, indicated higher P supply in BBR than in LUE plants, especially at the beginning of the growth phase until leaf maturity. Photosynthetic activity of LUE beeches was lower than that of BBR beeches due to stomatal limitations as the result of anatomically smaller stomatal pore widths, but not as the result of acute biochemical limitation of photosynthesis. Our results suggest that developmental retardation and lower photosynthesis under low P availability may be adaptation mechanisms that adjust the acquisition and recycling of P resources to seasonal growth demand.

Ten Ag + -selective ionophores have been characterized in terms of their potentiometric selectivities and complex formation constants in solvent polymeric membranes. The compounds with π-coordination show much weaker interactions than those with thioether or thiocarbamate groups as the coordinating sites. Long-term studies with the best ionophores show that the lower detection limit of the best Ag + sensors can be maintained in the subnanomolar range for at least one month. The best ionophores have also been characterized in fluorescent microspheres. The so far best lower detection limits of 3× 10 −11 M (potentiometrically) and 2 × 10 −11 M Ag + (optically) are found with bridged thiacalixarenes.

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BackgroundHeme oxygenase-1 (HO-1), an antioxidant defense enzyme, has been shown to protect against oxidant-induced liver injury. However, its role on liver fibrosis remains unclear. This study aims to elucidate the effect and the mechanism of HO-1 in nutritional fibrosing steatohepatitis in mice.MethodsMale C57BL/6J mice were fed with a methionine-choline deficient (MCD) diet for eight weeks to induce hepatic fibrosis. HO-1 chemical inducer (hemin), HO-1 chemical inhibitor zinc protoporphyrin IX (ZnPP-IX) and/or adenovirus carrying HO-1 gene (Ad-HO-1) were administered to mice, respectively. Liver injury was assessed by serum ALT, AST levels and histological examination; hepatic lipid peroxides levels were determined; the expression levels of several fibrogenic related genes were assayed by real-time quantitative PCR and Western blot.ResultsMCD feeding mice showed progressive hepatic injury including hepatic steatosis, inflammatory infiltration and fibrosis. Induction of HO-1 by hemin or Ad-HO-1 significantly attenuated the severity of liver injury. This effect was associated with the up-regulation of HO-1, reduction of hepatic lipid peroxides levels, down-regulation of inflammatory factors tumor necrosis factor-alpha, interleukin-6 and suppressor of cytokine signaling-1 as well as the pro-fibrotic genes alpha-smooth muscle actin, transforming growth factor-β1, matrix metallopeptidase-2 and matrix metallopeptidase-9. A contrary effect was observed in mice treated with ZnPP-IX.ConclusionsThe present study provided the evidence for the protective role of HO-1 in ameliorating MCD diet-induced fibrosing steatohepatitis. Modulation of HO-1 expression might serve as a therapeutic approach for fibrotic steatohepatitis.

Phosphorus (P) is an important nutrient, whose plant-available form phosphate is often low in natural forest ecosystems. Mycorrhizal fungi mine the soil for P and supply their host with this resource. It is unknown how ectomycorrhizal communities respond to changes in P availability. Here, we used young beech (Fagus sylvatica L.) trees in natural forest soil from a P-rich and P-poor site to investigate the impact of P amendment on soil microbes, mycorrhizas, beech P nutrition, and photosynthesis. We hypothesized that addition of P to forest soil increased P availability, thereby, leading to enhanced microbial biomass and mycorrhizal diversity in P-poor but not in P-rich soil. We expected that P amendment resulted in increased plant P uptake and enhanced photosynthesis in both soil types. Young beech trees with intact soil cores from a P-rich and a P-poor forest were kept in a common garden experiment and supplied once in fall with triple superphosphate. In the following summer, labile P in the organic layer, but not in the mineral top soil, was significantly increased in response to fertilizer treatment. P-rich soil contained higher microbial biomass than P-poor soil. P treatment had no effect on microbial biomass but influenced the mycorrhizal communities in P-poor soil and shifted their composition toward higher similarities to those in P-rich soil. Plant uptake efficiency was negatively correlated with the diversity of mycorrhizal communities and highest for trees in P-poor soil and lowest for fertilized trees. In both soil types, radioactive P tracing (H333PO4) revealed preferential aboveground allocation of new P in fertilized trees, resulting in increased bound P in xylem tissue and enhanced soluble P in bark, indicating increased storage and transport. Fertilized beeches from P-poor soil showed a strong increase in leaf P concentrations from deficient to luxurious conditions along with increased photosynthesis. Based on the divergent behavior of beech in P-poor and P-rich forest soil, we conclude that acclimation of beech to low P stocks involves dedicated mycorrhizal community structures, low P reserves in storage tissues and photosynthetic inhibition, while storage and aboveground allocation of additional P occurs regardless of the P nutritional status.

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ABSTRACT:Tanshinol borneol ester (DBZ) is an experimental drug that exhibits efficacious anti-ischemic activity in rats. Although the specific metabolic properties of DBZ are still unknown, previous studies in rats have strongly suggested that DBZ is extensively metabolized after administration and thus probably acts as a prodrug. Because the enzymes involved in drug metabolism differ between humans and rats in isoform composition, expression, and catalytic activity, the pharmacokinetics of the same drug in the two species may also differ. Establishing the differences between DBZ metabolism in human and rat liver microsomes can help to predict DBZ pharmacokinetics in humans and aid in the assessment of its potential efficacy, toxicity, and mechanism of action. In this work, the microsomal stabilities and metabolic kinetics of DBZ in rat and human liver microsomes were compared, and the DBZ metabolites generated in human liver microsomes (HLMs) were identified. The results suggested that DBZ is more stable in HLMs than in rat liver microsomes (RLMs). The intrinsic clearance of DBZ in HLMs was 10-to 17-fold lower than that in RLMs, which indicates lower DBZ clearance in humans. Metabolite analysis suggested that DBZ is hydroxylated by liver microsomal enzymes, resulting in the production of five metabolites. Although the kinetics of metabolite formation in HLMs and RLMs were different, the same metabolites were generated, indicating that the same metabolic pathway is present in both species. The results obtained from this work suggest the potential for DBZ to act as a prodrug with anti-ischemic activity in humans.