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排序方式: 共有276条查询结果,搜索用时 15 毫秒
81.
Ni Y  Su M  Lin J  Wang X  Qiu Y  Zhao A  Chen T  Jia W 《FEBS letters》2008,582(17):2627-2636
Chronic stress is closely linked to clinical depression, which could be assessed by a chronic unpredictable mild stress (CUMS) animal model. We present here a GC/MS-based metabolic profiling approach to investigate neurochemical changes in the cerebral cortex, hippocampus, thalamus, and remaining brain tissues. Multi-criteria assessment for multivariate statistics could identify differential metabolites between the CUMS-model rats versus the healthy controls. This study demonstrates that the significantly perturbed metabolites mainly involving amino acids play an indispensable role in regulating neural activity in the brain. Therefore, results obtained from such metabolic profiling strategy potentially provide a unique perspective on molecular mechanisms of chronic stress.  相似文献   
82.
The investigation of the importance of the genetics of Trypanosoma cruzi in determining the clinical course of Chagas disease will depend on precise characterisation of the parasites present in the tissue lesions. This can be adequately accomplished by the use of hypervariable nuclear markers such as microsatellites. However the unilocal nature of these loci and the scarcity of parasites in chronic lesions make it necessary to use high sensitivity PCR with nested primers, whose design depends on the availability of long flanking regions, a feature not hitherto available for any known T. cruzi microsatellites. Herein, making use of the extensive T. cruzi genome sequence now available and using the Tandem Repeats Finder software, it was possible to identify and characterise seven new microsatellite loci – six composed of trinucleotide (TcTAC15, TcTAT20, TcAAT8, TcATT14, TcGAG10 and TcCAA10) and one composed of tetranucleotide (TcAAAT6) motifs. All except the TcCAA10 locus were physically mapped onto distinct intergenic regions of chromosome III of the CL Brener clone contigs. The TcCAA10 locus was localised within a hypothetical protein gene in the T. cruzi genome. All microsatellites were polymorphic and useful for T. cruzi genetic variability studies. Using the TcTAC15 locus it was possible to separate the strains belonging to the T. cruzi I lineage (DTU I) from those belonging to T. cruzi II (DTU IIb), T. cruzi III (DTU IIc) and a hybrid group (DTU IId, IIe). The long flanking regions of these novel microsatellites allowed construction of nested primers and the use of full nested PCR protocols. This strategy enabled us to detect and differentiate T. cruzi strains directly in clinical specimens including heart, blood, CSF and skin tissues from patients in the acute and chronic phases of Chagas disease.  相似文献   
83.
纪和  赵广帅  刘珉  张鑫  崔嵬 《生态科学》2022,41(1):138-148
为分析评估京津风沙源治理工程区植被覆盖和气候要素变化,收集工程实施前、后各时期工程区域土地利用类型数据、MODIS产品植被覆盖(NDVI)数据和气象站点月值数据,利用最小二乘法拟合分析工程区NDVI和蒸散时空变化规律;利用MK非参数检验分析区域气候要素时空变化格局.结果表明(1)近25年来工程区土地利用类型变化不大,植...  相似文献   
84.
目的 了解我国医疗服务项目成本核算文献研究进展和政策推进情况。方法 检索中国知网、万方数据库、重庆维普数据库1978—2016年医疗服务项目成本核算相关文献和政策文件,进行内容分析。结果 通过对文献研究主题、数量与时间分布的三维匹配,将我国医疗服务项目成本核算演变历程分为起步(1979—1991年)、探索前期(1992—2001年)、探索中期(2002—2009年)、探索后期(2010年至今)4个阶段。结论 不同时期医疗服务项目成本核算政策推进均滞后于学术研究,缺乏政策导向性;医疗服务项目成本核算仍处于探索阶段,亟待标准化;核算技术标准化是医疗服务项目成本核算标准化的核心;未来医疗服务项目成本核算功能应向医疗质量安全成本一体化扩展;夯实核算基础与完善配套政策是开展医疗服务项目成本核算的关键。  相似文献   
85.
River restoration (RR) is widely practiced in both rural and urban contexts by combining various goals and measures. The theoretical discourse on RR not yet adequately reflects this breadth of restoration practice. In this study, we investigated 110 French RR projects implemented between 1980 and 2015. We analyzed projects considering eight key design features, main project motivation, restoration goals, project dates, costs, size, funding, river annual discharge, and implemented evaluation procedures. The study (1) provides a detailed account of the French RR effort, (2) compares restoration efforts in urban and rural contexts, and (3) establishes a RR project typology. The results also show that urban RR comprises a wider range of goals and measures than its rural counterpart, includes restoration of riparian habitats, and integrates ecological and social goals. A hierarchical multiple factor analysis yielded five types of projects, Fish RR (14% of the urban and 53% of the rural projects), Blue RR (4%, 7%), Water Framework Directive RR (36%, 40%), Flood protection RR (14%, 0%), and Human RR (32%, 0%). We suggest that the restoration community needs databases that use a project typology as developed in this study. This approach would take into account the multiple facets of RR projects, enabling more transparency into their communication and allow more suitable project comparisons.  相似文献   
86.
We derive and test some assumptions and predictions of the Sampling Effect Hypothesis (SEH) by examining the relationship between the traits of species in monoculture and their relative abundance in mixture, and by comparing polyculture performance with single-species plots. Although we found a positive relationship between production in monoculture and dominance in mixtures as predicted by the SEH, the relationship had low explanatory power. Counter to predictions, the species with the highest monoculture biomass were not able to strongly dominate all mixtures; instead the dominance of these species decreased with increasing species richness. On average, polycultures did not achieve greater biomass than (transgressively overyield) the species in each mixture, or at each site, that was most productive in monoculture. However, mixture yields did transgressively overyield both the monoculture biomass of the dominant species in the mixtures, and the weighted average of all monocultures (non-transgressive overyielding), both of which were positively related to increasing species richness. The varying responses of different overyielding tests resulted because resource partitioning and positive interactions were often counter-balanced by selection for species with lower biomass than the highest-yielding monocultures. Judging whether or not mixtures overyield therefore depends in part upon which species is the basis for comparison. We present a new general framework for overyielding analysis where every monoculture provides a potential comparison and from which the most relevant tests can be selected.  相似文献   
87.
It is well known that forest carbon or sink projects have not been included in theClean Development Mechanism (CDM), one of the flexible mechanisms created under the Kyoto Protocol. The main concern for postponing sink projects is related to issues of methodology and integrity. Project eligibility needs to be judged in a transparent manner if they are real, measurable,provide long-term benefits to mitigate climate change, and provide additional benefits to those thatwould occur in the absence of a certified project. One of the biggest challenges in implementing sink projects is fire risks and the associated biophysical and socio-economic underlying causes. This study attempts to assess fire probability and use it as a tool to estimate fire risk in carbon sink projects. Fire risks may not only threatenongoing projects but may also cause leakage of carbon stocks in other areas, especially in pro-tected areas. This exercise was carried out in the Berbak National Park located in Jambi Province, Sumatra, Indonesia and the surrounding areas. Fire probability is associated with (i) the means by which access to a given area is possible, and (ii) vegetation type or fuel load. Although most fires were intentionally ignited, fire escape iscommon and is enhanced by long spell of dry weather. When this occurs, secondary road was themost frequently used means, and it was certainly the case during 1997/1998 big fires when dam-age to natural vegetation (natural and secondary forests) was substantial. Burnt natural vegetationwas 120000 ha or 95% of the total burnt areas, and released more than 7 Mt of carbon into the atmosphere.  相似文献   
88.
Nodal基因的第一内含子中存在着顺式调控增强子元件   总被引:1,自引:1,他引:0  
小鼠nodal基因是在胚胎发育时期表达的一个基因,它在原肠期起着重要作用,并且参与左-右体轴的决定,413-d小鼠胚胎干细胞系3563在nodal基因的第一内含子中含有单拷贝逆转录病毒的插入。采用定量RNase保护法比较了该细胞系及其母源ES细胞CCE中nodal基因的表达量,CCE细胞中nodal mRNA的含量是3563ES细胞含量的2.3倍。这一结果提示原病毒在nodal基因第一内含子中的整  相似文献   
89.
白细胞介素1(IL-1)是一种重要的细胞因子,具有广泛的生物学活性。它通过与细胞表面的白细胞介素 1受体(IL-1R)结合而起作用。以杆状病毒为载体在昆虫细胞中克隆表达了小鼠I型可溶性白细胞介素1受体(sIL-1 RI)基因。以NIH/3T3细胞RNA为模板,采用RT-PCR方法扩增得到小鼠sIL-IRI的cDNA,克隆至杆状病毒转移载体pAcGP67B,将转移重组质粒与野生病毒ACNPV DNA共转染昆虫细胞Sf9,经同源重组得到重组杆状病毒rACNPV。应用经纯化的rAcNPV感染昆虫细胞Sf9,表达获得重组的sIL-1RI。经对亲和层析样品的SDS-PAGE分析和对IL-1β生物活性阻断作用实验证实,表达产物能够与其配基结合,并且能够分泌至细胞培养上清中。  相似文献   
90.
生态环境是和社会经济紧密联系、相互影响的复杂大系统 ,且其内部各因子之间存在大量的未知关系 ,神经网络为未知复杂系统的建模提供了一条全新的思路。运用 BP网络 ,就南水北调对湖北省襄樊市生态服务功能价值的影响进行了动态研究。研究显示 ,在调走约 1/3汉江水量后 ,襄樊的生态环境将受到严重的破坏 ,其后果是当地社会经济的可持续发展能力将受到损害和抑制。在分析案例的基础上 ,论证了神经网络在生态建模中的适用性 ,探讨了生态服务功能价值动态评价的技术趋势 ,并进一步提出了生态系统建模的新思路。  相似文献   
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