Using a non-radioisotopic, quantitative TRAP-based method detecting telomerase activities in human hepatoma cells

INTRODUCTIONTelomerase is a ribonucleoprotein complex that plays a critical role in telomeremaintenance and cellular immortality. Telomerase has been considered as tumordiagnostic marker and potential target for cancer therapyll, 2]. A sensitive, reliableand quantitative assay is of high interest in this field. The development of a very sensitive Telomeric Repeat Amplification Protocol (TRAP) for measuring telomerajseactivity in cell extracts has been proved to be an important tool for…     

Environmental filtering rather than dispersal limitation dominated plant community assembly in the Zoige Plateau

Identifying the mechanisms that underlie the assembly of plant communities is critical to the conservation of terrestrial biodiversity. However, it is seldom measured or quantified how much deterministic versus stochastic processes contribute to community assembly in alpine meadows. Here, we measured the decay in community similarity with spatial and environmental distance in the Zoige Plateau. Furthermore, we used redundancy analysis (RDA) to divide the variations in the relative abundance of plant families into four components to assess the effects of environmental and spatial. Species assemblage similarity liner declined with geographical distance (p < .001, R ² = .6388), and it decreased significantly with increasing distance of total phosphorus (TP), alkali‐hydrolyzable nitrogen (AN), available potassium (AK), nitrate nitrogen (NO₃ ⁺–N), and ammonia nitrogen (NH₄ ⁺–N). Environmental and spatial variables jointly explained a large proportion (55.2%) of the variation in the relative abundance of plant families. Environmental variables accounted for 13.1% of the total variation, whereas spatial variables accounted for 11.4%, perhaps due to the pronounced abiotic gradients in the alpine areas. Our study highlights the mechanism of plant community assembly in the alpine ecosystem, where environmental filtering plays a more important role than dispersal limitation. In addition, a reasonably controlled abundance of Compositae (the family with the highest niche breadth and large niche overlap value with Gramineae and Cyperaceae) was expected to maintain sustainable development in pastoral production. These results suggest that management measures should be developed with the goal of improving or maintaining suitable local environmental conditions.     

莱州湾水母种类多样性及群集结构的季节变化

基于2011年5月至2012年4月(除冰期12月和翌年1—2月外)在渤海莱州湾逐月采集的数据资料,系统地开展水母种类组成、数量分布的周年季节变动,弥补自20世纪90年代以来该区域相关资料的不足,有利于掌握该水域水母(主要是小型水母)主要种类数量时空分布特点,促进莱州湾生物类群对生境改变响应的相关研究。结果显示:所有调查中,共出现水母30种,无全年出现的种类。各月中,莱州湾水母以8月种数最多,5月数量居多。各月水母总数量的80%多由1—2种优势种贡献所致;水母优势种类组成季节更替明显。3—5月优势种为八斑唇腕水母;6月为嵊山秀氏水母和贝氏真囊水母;7月为贝氏真囊水母、9月有细颈和平水母;10月为细颈和平水母和大西洋五角水母,8月和11月无明显的优势种,但8月细颈和平水母和曲膝薮枝螅水母数量较多。莱州湾小型水母聚集结构主要呈现季节性时间格局上的变动。春季有八斑唇腕水母为代表、在湾内分布的聚集组;夏季有以嵊山秀氏水母和贝氏真囊水母为代表、在湾口西侧和湾中部分布的聚集组,以及细颈和平水母为代表、在湾中底部分布的聚集组;秋季有四枝管水母和大西洋五角水母为代表、在湾口和中部分布的聚集组。水温对小型水母聚集结构分布具有较为重要的影响作用。大型水母在本调查出现较少。海蜇和沙海蜇出现于6—8月个别站位;海月水母7—10月均有出现,但高密集区出现在10月紧邻莱州湾的湾底水域。     

端粒酶RNA反义基因对肝癌细胞的影响

用RT-PCR的方法钓取端粒酶RNA基因的cDNA,并将其反向插入到逆转录病毒载体pLNCX上,构建hTR基因的反义表达质粒。将质粒经脂质体介导转染人肝癌SMMG-7721细胞中表达。结果表明hTR反义基因的表达有效地封闭或抑制肝癌细胞的端粒酶活性,抑制细胞的生长和增殖,延长细胞的倍增时间并促进细胞凋亡。     

Immortalization with telomerase of the Nestin-positive cells of the human pancreas

Cells expressing the neuronal stem cell marker Nestin are present in the human pancreas but the biological role of these cells has yet to be resolved. We report here the establishment with the catalytic subunit of human telomerase (hTERT) of a line of normal human cells representing this cell type. Primary human cells derived from the ducts of the pancreas were transduced with an hTERT cDNA. The infected cells became positive for telomerase, failed to senesce, and were still proliferating after more than 150 doublings. The immortalized cells were positive for the expression of Nestin (at both the mRNA and protein levels) and were found to be free of cancer-associated changes: diploid and expressing wild type p16(INK4a), p53, and K-Ras. An established line of normal human cells representing this cell type should be of great value to help define the biological properties of this novel cell type.     

The role of farm structure on bird assemblages around a Kenyan tropical rainforest

Although it is clear that the farmlands neighbouring fragmented forests are utilized by some forest birds, it is not clear how birds in general respond to farmland habitat mosaic. An effort was made to determine how bird density and foraging assemblages were influenced by farm structural characteristics and distance from forest edge. Thirty farms up to a distance of 12 km around Kakamega forest in western Kenya were studied. Farm structure entailed size, hedge volume, habitat heterogeneity, woody plant density, plant diversity and crop cover. Birds were surveyed using line transects and DISTANCE analyses and classified into six feeding guilds and three habitat associations. Size of farms increased away from the forest, as woody plant density, plant diversity, indigenous trees and subsistence crop cover declined. The most important farm structure variable was hedge volume, which enhanced bird species richness, richness of shrub‐land bird species and insectivorous bird density (R = 0.58, P < 0.01). Bird density increased with tree density while indigenous trees were suitable for insectivores and nectarivores. There were very few forest bird encounters. Agricultural practices incorporating maintenance of hedges and sound selection of agroforestry trees can enhance conservation of birds on farmland, though, not significantly for forest species.     

Telomeres,senescence, and hematopoietic stem cells

The replicative lifespan of normal somatic cells is restricted by the erosion of telomeres, which are protective caps at the ends of linear chromosomes. The loss of telomeres induces antiproliferative signals that eventually lead to cellular senescence. The enzyme complex telomerase can maintain telomeres, but its expression is confined to highly proliferative cells such as stem cells and tumor cells. The immense regenerative capacity of the hematopoietic system is provided by a distinct type of adult stem cell: hematopoietic stem cells (HSCs). Although blood cells have to be produced continuously throughout life, the HSC pool seems not to be spared by aging processes. Indeed, limited expression of telomerase is not sufficient to prevent telomere shortening in these cells, which is thought ultimately to limit their proliferative capacity. In this review, we discuss the relevance of telomere maintenance for the hematopoietic stem cell compartment and consider potential functions of telomerase in this context. We also present possible clinical applications of telomere manipulation in HSCs and new insights affecting the aging of the hematopoietic stem cell pool and replicative exhaustion. This work was supported by European Community Grant LSHC-CT-2004-502943 (MOL CANCER MED).     

Relations Between River Plant Richness in the Portuguese Floodplains and the Widespread Water Knotgrass <Emphasis Type="Italic">(Paspalum Paspalodes</Emphasis>)

We examined the variability of macroinvertebrate assemblage structure, species identities, and functional feeding group composition in relation to stream size, tributary position, and in-stream factors in a boreal watershed in Finland. Our study included three riffle sites in each of three stream sections in each of three stream size classes. Multi-response permutation procedure, indicator value method, and canonical correspondence analysis revealed clear differences in assemblage structure among the stream size classes, with a gradual increase of species richness as the stream size increased. Significant differences in assemblage structure were also found among the tributary river systems. The functional feeding group composition broadly followed the river continuum concept, i.e., headwaters were dominated by shredders, gatherers, or filterers, whereas scrapers increased in relative abundance with stream size. There was, however, considerable variation in the functional feeding group composition both among and within the headwater stream sections. Our findings refer to a strong influence of stream size on macroinvertebrate assemblages, but also factors prevailing at the scale of individual riffles should be considered in biodiversity conservation of lotic ecosystems.     

辽宁铁岭盆地早白垩世孢粉组合

铁岭盆地白垩系发育,1990年以来辽河油田公司在该区钻探了3口参数井,并在下白垩统采获了较丰富的孢粉化石,建立了3个早白垩世孢粉组合,自下而上为Cicatricosisporites-Concavissimisporites-Protoconiferus组合,Cicatricosisporites-Abdiverrucospora-Piceaepollenites组合以及Deltoidospora-Cicatricosisporites-Laevigato-sporites-Tricolpopollenites组合,分别产自九佛堂组、沙海组和阜新组。本文叙述了组合特征,通过与国内外孢粉组合的对比及特征分子的时代分布,确立了本区早白垩世生物地层层序及地质时代。孢粉植物群反映了温暖潮湿的热带-亚热带气候。     

不同稻作年限下土壤微生物学性质和线虫群落特征的变化

红壤地区旱地改水田后随稻作年限的增加土壤性质会发生改变,但缺乏对百年尺度内土壤动物群落特征变化的了解.本研究选取了旱改水后1 yr、10 yr、20 yr、50 yr和100 yr五个时序的田块,研究了稻作土壤微生物学性质及线虫群落特征的变化.结果表明,随着稻作年限的延长,土壤微生物生物量碳氮、基础呼吸、矿质氮、速效磷、线虫数量及线虫属数均随稻作时间增长而逐渐上升,在50 yr均达到显著水平(P＜0.05),在50-100 yr变化渐缓或有所下降.线虫群落中植食者的比例显著上升(P＜0.05),捕食/杂食者的比例有所下降但差异不显著.线虫通道指数也随稻作年限的增加而逐渐增长(P＜0.05),表明土壤食物网结构趋向于细菌通道.稻作年限对线虫群落成熟度指数和结构指数的影响并不一致.总之,土壤微生物学性质和线虫群落在旱改水50 yr时土壤各项性质均达到较高水平,随稻作年限的继续延长呈现稳定趋势.