中药新药保肝作用的研究进展

肝脏作为代谢器官,在人体内发挥着重要作用。随着肝病的发病率逐年上升,如何有效的保肝护肝已成为医学界和药学界共同面一临的巨大挑战之一。化学药物在治疗肝病的同时常常伴随各种毒副作用甚至更进一步的肝损伤,而中药凭借其安全性和有效性的优势在肝病治疗领域受到越来越多的重视。中药护肝已有悠久的历史,近年来随着技术的进步,更多更好的新型中药逐步上市,相关研究不断增多。本文将就这些研究成果进行阐述。     

冰川退缩区不同演替阶段土壤溶解性有机质光谱特征及环境响应

溶解有机质(DOM)作为土壤中最活跃的有机组分,在土壤生物地球化学过程中起着关键作用,探讨植被演替过程中DOM的来源、组成、环境响应与累积规律,对预测土壤碳循环过程具有重要意义。本研究从海螺沟冰川退缩区植被原生演替序列选取演替年龄分别为12、30、40、50、80、120年的样地采集表层和亚表层土壤样本,测定DOM浓度并进行紫外-可见光光谱和三维荧光光谱分析,研究原生演替过程中DOM含量和组成的变化特征及其影响因素。结果表明: 土壤DOM浓度随演替年龄的增加而显著增加。土壤DOM中类蛋白组分、荧光指数和生物指数随演替时间的增加而减小,类腐殖质组分和腐殖化程度随演替过程不断增加,土壤DOM芳香化程度先增加后减小。pH值、铵态氮含量解释了62.2%的表层土壤DOM组分变异,土壤含水率和pH值解释了64.3%的亚表层土壤DOM组分变异,说明环境因素是影响海螺沟冰川退缩区原生演替过程中土壤DOM数量和组成的重要因子。     

Bacterial structures and ecosystem functions in glaciated floodplains: contemporary states and potential future shifts

Glaciated alpine floodplains are responding quickly to climate change through shrinking ice masses. Given the expected future changes in their physicochemical environment, we anticipated variable shifts in structure and ecosystem functioning of hyporheic microbial communities in proglacial alpine streams, depending on present community characteristics and landscape structures. We examined microbial structure and functioning during different hydrologic periods in glacial (kryal) streams and, as contrasting systems, groundwater-fed (krenal) streams. Three catchments were chosen to cover an array of landscape features, including interconnected lakes, differences in local geology and degree of deglaciation. Community structure was assessed by automated ribosomal intergenic spacer analysis and microbial function by potential enzyme activities. We found each catchment to contain a distinct bacterial community structure and different degrees of separation in structure and functioning that were linked to the physicochemical properties of the waters within each catchment. Bacterial communities showed high functional plasticity, although achieved by different strategies in each system. Typical kryal communities showed a strong linkage of structure and function that indicated a major prevalence of specialists, whereas krenal sediments were dominated by generalists. With the rapid retreat of glaciers and therefore altered ecohydrological characteristics, lotic microbial structure and functioning are likely to change substantially in proglacial floodplains in the future. The trajectory of these changes will vary depending on contemporary bacterial community characteristics and landscape structures that ultimately determine the sustainability of ecosystem functioning.     

Experimental analysis of retreat‐site selection by thick‐tailed geckos Nephrurus milii

Abstract Although animals use habitats non‐randomly in the wild, complex correlations among environmental features mean that proximate influences on habitat selection can be identified only by experimental manipulation of potential cues. Thick‐tailed geckos Nephrurus milii are large lizards that are widely distributed through southern Australia. These nocturnally active animals typically spend daylight hours under surface rocks. We presented captive geckos with alternative retreat‐sites (rock crevices) differing in attributes potentially relevant to habitat selection. The lizards showed strong preference for shelter‐sites that enhanced thermoregulation (warm rather than cool) and that reduced the animal's vulnerability to predators (narrow crevices with small openings and not containing the scent of a predatory snake). Horizontal rather than sloping crevices were also preferred. Overall crevice size and thickness of the overlying rock did not influence retreat‐site selection in the laboratory, but could be important in the field because of their influence on thermal regimes under rocks. The present study supports the idea that nocturnal reptiles base their selection of diurnal shelters on multiple aspects related to the fitness consequences of occupancy of alternative available retreat‐sites.     

Spatial distribution of discrete RAPD phenotypes of a root endophytic fungus, Phialocephala fortinii, at a primary successional site on a glacier forefront

Phialocephala fortinii is among the few identified hyphomycetes belonging to the Mycelium radicis atrovirens complex. This 'dark-septate endophyte' has a global distribution and colonizes a wide variety of host plants. In this study, the spatial distribution of discrete genets of P. fortinii on the forefront of a receding glacier was analysed using the randomly amplified polymorphic DNA (RAPD) technique to determine plants colonized and patterns of colonization. In two consecutive years of sampling, a total of 74 isolates of P. fortinii were obtained from nine plant species, typically ectomycorrhizal, ericoid mycorrhizal or non-mycorrhizal. The isolates showed substantial variation, sharing on average approx. half the RAPD markers. In the first year, three isolates belonging to a single genet were obtained from two plants separated by a distance of nearly 1.5 m. The continuity of this genet was assessed by a sampling the following year. No isolates similar to that, or any of the genets collected the year before were observed. Consequently, the identical isolates from the previous year were concluded to represent discontinuous ramets. Two additional large genets were observed during the second year of sampling, which inhabited roots of several plants representing three different species. These data suggest that the sharing of P. fortinii genets among plant species might play a fundamental role in adaptation and interaction within the whole plant community in a system undergoing primary succession.     

冰川消退带微生物群落演替及生物地球化学循环

冰川是生物圈重要组分之一。由于全球气候变化世界多地冰川加速消融,暴露原本被冰盖覆盖的区域,这些区域被称为冰川消退区域(glacier retreat area)或冰川前部区域(glacier foreland)。自暴露开始消退区随即发生初生演替,随着演替进行,物质循环逐步建立,生物量和土壤C、N总量逐步增加。生态系统C、N输入最初以矿化外来物为主,逐渐转变为以生物固C、固N为主。演替早期生态系统的发育主要受土壤C、N含量的限制,而演替后期的限制性营养物转变为P。演替区域土壤逐渐发育并促进生态位的分化,细菌、真菌、古菌,病毒及其他微生物群落的生物量和多样性不断增加直至达到该地区可承受的极值。随着生存条件的改善,不同生态策略物种的更替导致每个演替阶段微生物群落结构的差异。整体上,伴随演替进行微生物群落丰度、结构和活性呈现梯度性变化。气候变化对冰川消退带生态演替结果产生多方面的影响,而这些影响结果又综合反馈气候变化,因此目前难以准确估计气候变化对消退带生态演替的净效应。综述了近年冰川消退带微生物群落演替方面相关的研究结果,同时分别对该区域物质循环的建立、微生物群落演替和气候变化造成的影响这三个方面进行详细描述,并指出当前研究的不足。     

Rapid soil formation after glacial retreat shaped by spatial patterns of organic matter accrual in microaggregates

Global change contributes to the retreat of glaciers at unprecedented rates. The deglaciation facilitates biogeochemical processes on glacial deposits with initiating soil formation as an important driver of evolving ecosystems. The underlying mechanisms of soil formation and the association of soil organic matter (SOM) with mineral particles remain unclear, although further insights are critical to understand carbon sequestration in soils. We investigated the microspatial arrangement of SOM coatings at intact soil microaggregate structures during various stages of ecosystem development from 15 to >700 years after deglaciation in the proglacial environment of the Damma glacier (Switzerland). The functionally important clay‐sized fraction (<2 μm) was separated into two density fractions with different amounts of organo‐mineral associations: light (1.6–2.2 g/cm³) and heavy (>2.2 g/cm³). To quantify how SOM extends across the surface of mineral particles (coverage) and whether SOM coatings are distributed in fragmented or connected patterns (connectivity), we developed an image analysis protocol based on nanoscale secondary ion mass spectrometry (NanoSIMS). We classified SOM and mineral areas depending on the ¹⁶O^?, ¹²C^?, and ¹²C¹⁴N^? distributions. With increasing time after glacial retreat, the microspatial coverage and connectivity of SOM increased rapidly. The rapid soil formation led to a succession of patchy distributed to more connected SOM coatings on soil microaggregates. The maximum coverage of 55% at >700 years suggests direct evidence for SOM sequestration being decoupled from the mineral surface, as it was not completely masked by SOM and retained its functionality as an ion exchange site. The chemical composition of SOM coatings showed a rapid change toward a higher CN:C ratio already at 75 years after glacial retreat, which was associated with microbial succession patterns reflecting high N assimilation. Our results demonstrate that rapid SOM sequestration drives the microspatial succession of SOM coatings in soils, a process that can stabilize SOM for the long term.     

天山一号冰川前沿生态系统真菌群落结构演替及分布格局

【目的】分析真菌群落结构和多样性随着一号冰川退缩前沿年代序列的变化,揭示真菌群落的演替轨迹及环境因子对群落组成的影响。【方法】采用宏基因组学研究方法,结合生物信息学和统计学分析技术,对取自一号冰川末端表面冰尘,底部和前沿14个样品进行总DNA的提取,ITS基因的扩增并使用Illumina Miseq平台测序,通过相关生物地理化学特性综合分析在不同年代序列下真菌群落结构及其演替规律。【结果】经测序,筛选和质控分析获得185103条rawreads,占78.3%的非单序列在97%的相似度聚类分析共得到300个操作分类单元(OTU),共划分为6个门:子囊菌门(Ascomycota,52.7%)、担子菌门(Basidiomycota,16.9%)、壶菌门(Chytridiomycota,15.1%)、接合菌门(Zygomycota,2.4%)和球囊菌门(Glomeromycota,1.2%)。从演替初期到后期阶段虽然子囊菌的序列数逐渐下降而担子菌出现缓慢上升趋势,但子囊菌随着土壤年代序列的增加始终为优势类群,壶菌在冰川底部和前沿基层普遍存在且丰度仅次于子囊菌和担子菌。我们在缺乏植被的最新退缩基层发现依靠自养型宿主存活的活体营养菌,如Taphrinomycetes、Urediniomycetes和Ustilaginomycetes。从冰川底部和前沿基层检测到丰度较高的酵母菌,而粪生真菌(coprophilous fungi)仅仅出现在冰川前沿基层,共23个操作分类单元。球囊菌仅在前沿部分样品中存在,有着十分狭小的生态位分布。【结论】一号冰川前沿随着年代序列的增加真菌群落存在明显的演替轨迹和多样性的显著变化,不同生态位真菌类群组成的相似性较低且都存在明显的指示性真菌类群。     

Cultivation-independent and -dependent characterization of Bacteria resident beneath John Evans Glacier

Viable microorganisms are present in subglacial waters and sediment-laden ice beneath John Evans glacier in the Canadian high Arctic. The Bacterial communities resident in three subglacial samples were examined by amplifying 16S rRNA genes extracted from community DNA and from axenic isolates. Restriction fragment length polymorphism analysis of 341 clones produced 153 operational taxonomic units (OTUS), of which 25 dominant OTUS were sequenced. A subglacial water sample yielded Betaproteobacteria (25% of clones, particularly Comamonadaceae), Bacteroidetes (23%, particularly Flavobacterium) and Actinobacteria (14%). A second water sample had 51%Betaproteobacteria, 5%Bacteroidetes and no Actinobacteria, and a sediment sample was dominated by Betaproteobacteria (15%) and Bacteroidetes (38%). A collection of 158 morphologically distinct isolates was obtained on R2A agar using three incubation conditions: fully aerobic at 20 degrees C or 4 degrees C, or microaerobic at 20 degrees C. A total of 52 isolate OTUs were defined, comprising Bacteroidetes (predominantly Flavobacterium isolated at 4 degrees C), Betaproteobacteria (particularly Comamonadaceae), plus Actinobacteria and Alpha- and Gammaproteobacteria not detected as clones. Otherwise, the clone library and isolate collection results were quite comparable and supported earlier molecular studies at this site. Although additional undescribed diversity likely exists in these samples, combining culture-based results with molecular analysis increased the observed bacterial diversity and confirmed previous observations at this glacier and others.     

Variation in Microbial Community Composition and Culturability in the Rhizosphere of Leucanthemopsis alpina (L.) Heywood and Adjacent Bare Soil Along an Alpine Chronosequence

We compared the size, culturability, diversity, and dominant species similarity of the bacterial communities of Leucanthemopsis alpina (L.) Heywood rhizosphere and adjacent bare soil (interspace) along a chronosequence of soil development time (5, 50, and 70 years) in the forefield of the Dammaglacier (Switzerland). We found no evidence that the size of the bacterial community was significantly affected by either soil age or the presence of L. alpina. In contrast, the proportion of the bacterial community that could be cultured on nonselective agars, and which was taken as an indication of the proportion of r-selected populations, was significantly higher in the 50- and 70-year-old soils than in the 5-year-old soil, and was also significantly higher in the rhizosphere of L. alpina at all time points. RDA indicated significant correlations between the increased culturability of the bacterial community over time and increasing concentrations of labile N, and between the increased culturability in the rhizosphere and increased concentrations of labile C and N. HaeIII-amplified ribosomal DNA (rDNA) restriction analysis of a library of 120 clones of 16S rDNA revealed 85 distinct phylotypes. Hurlbert's probability of interspecific encounter (PIE) values derived from this library ranged from 0.95 to 1.0, indicating a very high genetic diversity. There was no significant difference in the PIE values of rhizosphere and interspace communities. Detrended correspondence analysis (DCA) of 16S ribosomal RNA (rRNA) denaturing gradient gel electrophoresis (DGGE) community profiles clearly distinguished the rhizosphere from the interspace community in the 5-year-old soils and also clearly distinguished between these communities and the rhizosphere and interspace communities of the 50- and 70-year-old soils. However, 16S rRNA DGGE revealed little difference between rhizosphere and interspace communities in the 50- and 70-year-old soils. The relative similarity of the 16S rRNA profiles strongly reflected labile carbon and nitrogen availability. Overall, our results suggest that improved C and N availability in the rhizosphere of L. alpina increases the size of r-selected bacterial species populations, but that the influence of L. alpina depends on soil age, being maximal in the youngest soils and minimal in the oldest. The reduced influence of L. alpina in the older soils may reflect a feedback between improved nutrient availability and reduced rhizodeposition.