模拟增温对西藏高原高寒草甸土壤供氮潜力的影响

过去几十年青藏高原呈现显著的增温趋势,冬季增温幅度显著高于生长季的季节非对称特征。气候变暖会对生态系统氮素循环产生重要影响,但关于全年增温与冬季增温对高寒生态系统氮循环的不同影响仍缺乏研究。在青藏高原高寒草甸区开展模拟增温试验,研究季节非对称增温对高寒草甸生态系统氮循环的影响。该试验布设于2010年7月,设置3种处理(不增温、冬季增温与全年增温)。研究结果发现,开顶箱增温装置造成了小环境的暖干化:显著提高了地表空气温度和表层土壤温度,降低了表层土壤含水量。冬季增温会加剧土壤中氮素的流失,所以在经历了冬季增温后土壤氮含量显著降低;在生长季节,土壤氮素周转速率受土壤水分的调控,在降雨较少的季节,增温引起的土壤含水量降低会抑制土壤氮周转速率。对于土壤微生物量而言,高寒草甸土壤微生物量碳表现出明显的季节动态,在生长季旺盛期较低,在生长季末期和初冬季节反而较高,这说明为了降低对土壤养分的竞争,高寒草甸植物氮吸收与土壤微生物氮固持在时间上存在分离。研究结果表明,冬季增温导致的土壤养分含量变化会影响随后生长季植物群落的生产力、结构组成与碳氮循环等过程,对生态系统过程产生深远的影响。     

Grazing simplifies soil micro‐food webs and decouples their relationships with ecosystem functions in grasslands

Livestock grazing often alters aboveground and belowground communities of grasslands and their mediated carbon (C) and nitrogen (N) cycling processes at the local scale. Yet, few have examined whether grazing‐induced changes in soil food webs and their ecosystem functions can be extrapolated to a regional scale. We investigated how large herbivore grazing affects soil micro‐food webs (microbes and nematodes) and ecosystem functions (soil C and N mineralization), using paired grazed and ungrazed plots at 10 locations across the Mongolian Plateau. Our results showed that grazing not only affected plant variables (e.g., biomass and C and N concentrations), but also altered soil substrates (e.g., C and N contents) and soil environment (e.g., soil pH and bulk density). Grazing had strong bottom‐up effects on soil micro‐food webs, leading to more pronounced decreases at higher trophic levels (nematodes) than at lower trophic levels (microbes). Structural equation modeling showed that changes in plant biomass and soil environment dominated grazing effects on microbes, while nematodes were mainly influenced by changes in plant biomass and soil C and N contents; the grazing effects, however, differed greatly among functional groups in the soil micro‐food webs. Grazing reduced soil C and N mineralization rates via changes in plant biomass, soil C and N contents, and soil environment across grasslands on the Mongolian Plateau. Spearman's rank correlation analysis also showed that grazing reduced the correlations between functional groups in soil micro‐food webs and then weakened the correlation between soil micro‐food webs and soil C and N mineralization. These results suggest that changes in soil micro‐food webs resulting from livestock grazing are poor predictors of soil C and N processes at regional scale, and that the relationships between soil food webs and ecosystem functions depend on spatial scales and land‐use changes.     

Microbial biomass and nitrogen cycling responses to fertilization and litter removal in young northern hardwood forests

The influence of site fertility on soil microbial biomass and activity is not well understood but is likely to be complex because of interactions with plant responses to nutrient availability. We examined the effects of long-term (8 yr) fertilization and litter removal on forest floor microbial biomass and N and C transformations to test the hypothesis that higher soil resource availability stimulates microbial activity. Microbial biomass and respiration decreased by 20–30 % in response to fertilization. Microbial C averaged 3.8 mg C/g soil in fertilized, 5.8 mg C/g in control, and 5.5 mg C/g in litter removal plots. Microbial respiration was 200 µg CO₂-C g^–1 d^–1 in fertilized plots, compared to 270 µg CO₂-C g^–1 d^–1 in controls. Gross N mineralization and N immobilization did not differ among treatments, despite higher litter nutrient concentrations in fertilized plots and the removal of substantial quantities of C and N in litter removal plots. Net N mineralization was significantly reduced by fertilization. Gross nitrification and NO₃ ^– immobilization both were increased by fertilization. Nitrate thus became a more important part of microbial N cycling in fertilized plots even though NH₄ ⁺ availability was not stimulated by fertilization.Soil microorganisms did not mineralize more C or N in response to fertilization and higher litter quality; instead, results suggest a difference in the physiological status of microbial biomass in fertilized plots that influenced N transformations. Respiration quotients (qCO₂, respiration per unit biomass) were higher in fertilized plots (56 µg CO₂-C mg C^–1 d^–1) than control (48 µg CO₂-C mg C^–1 d ^–1) or litter removal (45 µg CO₂-C mg C^–1 d^–1), corresponding to higher microbial growth efficiency, higher proportions of gross mineralization immobilized, and lower net N mineralization in fertilized plots. While microbial biomass is an important labile nutrient pool, patterns of microbial growth and turnover were distinct from this pool and were more important to microbial function in nitrogen cycling.     

Crosslinking of theDrosophila chorion involves a peroxidase

Summary TheDrosophila chorion contains an endogenous peroxidase activity which remains inactive until late stage 14 when it catalyzes the crosslinking of the chorionic proteins. Using explanted follicles developing in vitro, premature, but otherwise normal crosslinking can be induced with hydrogen peroxide and normal crosslinking can be prevented with peroxidase inhibitors. Inhibition or premature activation of the shell peroxidase allows characterization of chorionic filament specific proteins and establishes new criteria for the identification of eggshell components.     

Effect of Short-Chain Fatty Acids and Soil Atmosphere on Tylenchorhynchus spp.

Short-chain fatty acids can be produced under anaerobic conditions by fermentative soil microbes and have nematicidal properties. We evaluated the effects of butyric and propionic acids on death and recovery of stunt nematodes (Tylenchorhynchus spp.), a common parasite of turfgrass. Nematodes in a sand-soil mix (80:20) were treated with butyric or propionic acid and incubated under air or N₂ for 7 days at 25 °C. Amendment of soil with 0.1 and 1.0 µmol (8.8 and 88 µg) butyric acid/g soil or 1.0 µmol (74 µg) propionic acid/g soil resulted in the death of all nematodes. The composition of the soil atmosphere had no effect on the nematicidal activity of the acids. Addition of hydrochloric acid to adjust soil pH to 4.4 and 3.5 resulted in nematode mortality relative to controls (41% to 86%) but to a lesser degree than short-chain fatty acids at the same pH. Nematodes did not recover after a 28-day period following addition of 10 µmol butyric acid/g soil under air or N₂. Carbon mineralization decreased during this period, whereas levels of inorganic N and microbial biomass-N remained constant. Short-chain fatty acids appear to be effective in killing Tylenchorhynchus spp. independent of atmospheric composition. Nematode mortality appears to be a function of the type and concentration of fatty acid and soil pH.     

半乳糖凝集素‑3对骨关节炎成骨细胞矿化的作用研究

炎症反应以炎症因子为代表,是骨关节炎（osteoarthritis,OA）中软骨下骨发生病变的重要机制。炎症因子半乳糖凝集素?3（galectin?3,Gal?3）会引起软骨下骨OA样变,但机制尚不清楚。利用因膝关节OA行全膝关节置换患者的胫骨平台标本,培养成骨细胞。分别在正常氧和缺氧条件下用Gal?3处理成骨细胞后,检测骨钙素、ERRα和Sirtuin 1的表达情况。同时,给予矿化液培养的成骨细胞以Gal?3处理,28 d后使用茜素红染色检测成骨细胞矿化程度并进行定量分析。结果显示,Gal?3抑制成骨细胞骨钙素的表达,在缺氧条件下诱导ERRα和Sirtuin1的表达,在正常氧条件下Gal?3促进OA成骨细胞的矿化。正常氧条件下,Gal?3可以诱导OA成骨细胞的异常矿化,缺氧条件下Gal?3促进成骨,表明Gal?3在OA成骨细胞的矿化中扮演重要角色。     

Sulfated hyaluronic acid and dexamethasone possess a synergistic potential in the differentiation of osteoblasts from human bone marrow stromal cells

The development of novel bioactive biomaterials is urgently needed to meet the needs of an aging population. Both sulfated hyaluronic acid and dexamethasone are candidates for the functionalization of bone grafts, as they have been shown to enhance the differentiation of osteoblasts from bone marrow stromal cells in vitro and in vivo. However, the underlying mechanisms are not fully understood. Furthermore, studies combining different approaches to assess synergistic potentials are rare. In this study, we aim to gain insights into the mode of action of both sulfated hyaluronic acid and dexamethasone by a comprehensive analysis of the cellular fraction, released matrix vesicles, and the extracellular matrix, combining classical biochemical assays with mass spectrometry–based proteomics, supported by novel bioinformatical computations. We found elevated differentiation levels for both treatments, which were further enhanced by a combination of sulfated hyaluronic acid and dexamethasone. Single treatments revealed specific effects on osteogenic differentiation. Dexamethasone activates signalling pathways involved in the differentiation of osteoblasts, for example, CXC-motif chemokine receptor type 4 and mitogen-activated protein kinases. The effects of sulfated hyaluronic acid were predominantly linked to an alteration in the composition of the extracellular matrix, affecting the synthesis, secretion, and/or activity of fibrillary (fibronectin and thrombospondin-2) and nonfibrillary (transglutaminase-2, periostin, and lysyloxidase) extracellular matrix components, including proteases and their inhibitors (matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-3). The effects were treatment specific, and less additive or contrary effects were found. Thus, we anticipate that the synergistic action of the treatment-specific effects is the key driver in elevated osteogenesis.     

The iron mineralization of Spongia officinalis L. (Porifera,Dictyoceratida) and its relationships with the collagen skeleton

Lepidocrocite (γ FeOOH) granules are frequently found in the spongin fibers of some horny sponges. The granules also contain calcite and a small amount of goethite (α FeOOH). In the genus Spongia, the amount of iron is highly variable according to the habitat and to the age of the fiber. Some indications about the skeletal growth and structure can be inferred from the distribution of the biominerals and the arrangement of the crystallites: i.e. (1) Mineralization is a slow process in comparison with fiber formation; (2) Secondary connective fibers may have a discontinuous growth; (3) The collagen microfibrils display a definite arrangement in the successive spongin layers; (4) Although spongin is a collagen highly resistant in vitro to enzymatic digestion, the sponge is able to perform remodeling of its skeleton through autodigestion of the fibers.     

Sulphur mineralization and adsorption in soils

Summary Studies were conducted to determine the comparative sulphur mineralizing capacity of selected Malaysian and Iowan soils and to determine the amounts of available and adsorbed sulphate in a number of Malaysian soils. Results of the mineralization study indicated that more sulphur mineralised from Malaysian soils although their average contents of total sulphur were lower compared to Iowan Soils. For both sets of soils, significant correlations between contents of organic carbon and total sulphur existed indicating that most of the sulphur was in organic combination. Phosphate solution consistently extracted higher quantities of sulphate in comparison to chloride solution in the Malaysian surface soils implying that a portion of the sulphate existed in adsorbed form. Adsorption of sulphate in soils was found to be dependent on concentration of sulphate added and followed the Langmuir adsorption isotherm.     

Effect of legume-based cropping systems on nitrogen mineralization potential of Vertisol

The quantity and patterns of net mineralization of soil nitrogen (N) were studied in Vertisols under different cropping systems in the semi-arid tropical areas. Eight cropping systems were selected; three contained pigeonpea (PP), one contained PP and cowpea (COP), and two contained chickpea (CP) as legume component crops, one included sequence cropping with nonlegumes during the rainy and postrainy seasons, and one system was kept fallow (F) during the rainy season and sown to sorghum (S) during the postrainy season. Cropping systems with PP as a component crop increased mineralizable N(N _o ) content two-fold in the soil compared with fallow + sorghum (F+S)–F+S system. The N mineralization rate constant (k) was not significantly affected by previous cropping history of the soil; however, a numerically higher rate constant was observed in the COP/PP intercrop, followed by sequential S+safflower (SF) system as compared to the other soils. Mineral N accumulation curves for six soils were more accurately described by the exponential model than the linear model. The active N fraction (N _o /N_tot %) varied between 8 and 16% for different systems and a direct relationship was observed between N _o /N_tot and total N for the soils under diverse cropping systems.ICRISAT JA (1638)