Climate change hastens the turnover of stream fish assemblages

Stream fish are expected to be significantly influenced by climate change, as they are ectothermic animals whose dispersal is limited within hydrographic networks. Nonetheless, they are also controlled by other physical factors that may prevent them moving to new thermally suitable sites. Using presence–absence records in 655 sites widespread throughout nine French river units, we predicted the potential future distribution of 30 common stream fish species facing temperature warming and change in precipitation regime. We also assessed the potential impacts on fish assemblages' structure and diversity. Only cold-water species, whose diversity is very low in French streams, were predicted to experience a strong reduction in the number of suitable sites. In contrast, most cool-water and warm-water fish species were projected to colonize many newly suitable sites. Considering that cold headwater streams are the most numerous on the Earth's surface, our results suggested that headwater species would undergo a deleterious effect of climate change, whereas downstream species would expand their range by migrating to sites located in intermediate streams or upstream. As a result, local species richness was forecasted to increase greatly and high turnover rates indicated future fundamental changes in assemblages' structure. Changes in assemblage composition were also positively related to the intensity of warming. Overall, these results (1) stressed the importance of accounting for both climatic and topographic factors when assessing the future distribution of riverine fish species and (2) may be viewed as a first estimation of climate change impacts on European freshwater fish assemblages.     

Taxol from fungal endophytes and the issue of biodiversity

Fungi represent one of the most understudied and diverse group of organisms. Commonly, these organisms make associations with higher life forms and may proceed to biochemically mimic the host organism. An excellent example of this is the anticancer drug, taxol, which had been previously supposed to occur only in the plant genusTaxus (yew). However, taxol has been reported in a novel endophytic fungus—Taxomyces andreanae, but also has been demonstrated to occur in a number of unrelated fungal endophytes includingPestalotia, Pestalotiopsis, Fusarium, Alternaria, Pithomyces, Monochaetia and others. Thus, this report presents information on the presence of taxol among disparate fungal genera, and uses these observations as an additional argument to support efforts to study fungal endophytes and preserve their associated host plants.     

Small-subunit ribosomal RNA sequence from Naegleria gruberi supports the polyphyletic origin of amoebas

We have sequenced the small-subunit ribosomal RNA gene of the amoebo- flagellate protozoan Naegleria gruberi. Comparison of this sequence with the rRNA sequences of other eukaryotes resulted in a phylogenetic tree that supports the suggested polyphyletic origin of amoebas and suggests a flagellate ancestry for Naegleria.      

新疆维吾尔自治区20年问胃癌的临床特点分析

目的：分析新疆地区近20年来胃癌流行病学特征,探讨其变化规律及发展趋势。方法：回顾性分析和比较1991年、2001年、2011年经新疆维吾自治区人民医院胃镜及病理学诊断确诊为胃癌的病例的一般资料、病理学及内镜下特点,包括性别、年龄、病理类型、发病部位。结果：1991年组：胃癌检出率为2．48％,中位年龄为54岁,男女之比为3-3：1．0,发病部位以胃窦部癌为主,占39．1％;2001年组：检出率为2．39％,中位年龄为61岁,男女之比为3．0：1．0,发病部位以胃体部癌为主,占42．1％;2011年组：检出率为1．48％,中位年龄为63岁,男女之比为3．9：1．0,发病部位以贵门胃底部为主,占34．8％。三组病理学类型均以腺癌为主,检出率有逐年升高趋势,但差异无统计学意义（P〉0．05）。结论：（1）近20年来胃癌发病部位有上移现象,且胃癌检发病率有下降趋势;（2）男性胃癌患者发病率明显高于女性,且近20年来胃癌患者男女比例无明显改变;（3）近20年来胃癌发病中位年龄逐渐增高,且随着年龄的增长发病率逐渐升高,以中老年发病率最高;（4）癌患者病理类型仍以腺癌为主,且近20年来腺癌所占比例无明显变化.     

Purification of galectin-3 from ovine placenta: developmentally regulated expression and immunological relevance

Galectins, beta-galactoside-binding lectins, are extensively distributed in the animal kingdom and share some basic molecular properties. Galectin-3, a member of this family, is generally associated with differentiation, morphogenesis, and metastasis. In this study, galectin-3 was isolated from ovine placental cotyledons round the middle of the gestation period by lactose extraction followed by affinity chromatography on lactosyl-agarose, and separated from galectin-1 by size exclusion chromatography on a Superose 12 column. Under native conditions this lectin behaved as a monomer with an apparent molecular weight of approximately 29,000 and an isoelectric point of 9.0. The partial amino acid sequence of the peptides obtained by tryptic digestion of this protein followed by HPLC separation showed striking homology with other members of the galectin-3 subfamily. Furthermore, ovine placental galectin-3 exhibited specific mitogenic activity toward rat spleen mononuclear cells. Besides, this protein strongly reacted with a rabbit antiserum raised against a chicken galectin. Results obtained by Western blot analysis showed that its expression was greatly decreased in term placenta with respect to the middle of the gestation period, suggesting a regulated expression throughout development.      

Molecular dynamics of synthetic leucine-serine ion channels in a phospholipid membrane

Molecular dynamics calculations were carried out on models of two synthetic leucine-serine ion channels: a tetrameric bundle with sequence (LSLLLSL)(3)NH(2) and a hexameric bundle with sequence (LSSLLSL)(3)NH(2). Each protein bundle is inserted in a palmitoyloleoylphosphatidylcholine bilayer membrane and solvated by simple point charge water molecules inside the pore and at both mouths. Both systems appear to be stable in the absence of an electric field during the 4 ns of molecular dynamics simulation. The water motion in the narrow pore of the four-helix bundle is highly restricted and may provide suitable conditions for proton transfer via a water wire mechanism. In the wider hexameric pore, the water diffuses much more slowly than in bulk but is still mobile. This, along with the dimensions of the pore, supports the observation that this peptide is selective for monovalent cations. Reasonable agreement of predicted conductances with experimentally determined values lends support to the validity of the simulations.     

Evolution of the secondary structures and compensatory mutations of the ribosomal RNAs of Drosophila melanogaster

This paper examines the effects of DNA sequence evolution on RNA secondary structures and compensatory mutations. Models of the secondary structures of Drosophila melanogaster 18S ribosomal RNA (rRNA) and of the complex between 2S, 5.8S, and 28S rRNAs have been drawn on the basis of comparative and energetic criteria. The overall AU richness of the D. melanogaster rRNAs allows the resolution of some ambiguities in the structures of both large rRNAs. Comparison of the sequence of expansion segment V2 in D. melanogaster 18S rRNA with the same region in three other Drosophila species and the tsetse fly (Glossina morsitans morsitans) allows us to distinguish between two models for the secondary structure of this region. The secondary structures of the expansion segments of D. melanogaster 28S rRNA conform to a general pattern for all eukaryotes, despite having highly divergent sequences between D. melanogaster and vertebrates. The 70 novel compensatory mutations identified in the 28S rRNA show a strong (70%) bias toward A-U base pairs, suggesting that a process of biased mutation and/or biased fixation of A and T point mutations or AT-rich slippage-generated motifs has occurred during the evolution of D. melanogaster rDNA. This process has not occurred throughout the D. melanogaster genome. The processes by which compensatory pairs of mutations are generated and spread are discussed, and a model is suggested by which a second mutation is more likely to occur in a unit with a first mutation as such a unit begins to spread through the family and concomitantly through the population. Alternatively, mechanisms of proofreading in stem-loop structures at the DNA level, or between RNA and DNA, might be involved. The apparent tolerance of noncompensatory mutations in some stems which are otherwise strongly supported by comparative criteria within D. melanogaster 28S rRNA must be borne in mind when compensatory mutations are used as a criterion in secondary-structure modeling. Noncompensatory mutation may extend to the production of unstable structures where a stem is stabilized by RNA- protein or additional RNA-RNA interactions in the mature ribosome. Of motifs suggested to be involved in rRNA processing, one (CGAAAG) is strongly overrepresented in the 28S rRNA sequence. The data are discussed both in the context of the forces involved with the evolution of multigene families and in the context of molecular coevolution in the rDNA family in particular.      

聚酸酐控释制剂的研究进展

聚酸酐材料是一种良好的生物可降解材料,它可以作为药物载体将药物递送入人体的各个器官,如脑、骨骼、血管等,也可作为基因的载体对患者进行基因治疗。聚酸酐的合成工艺简单、成本低廉,可以满足不同的用途。它奇在人体内降解为对人体无害的二元酸而排除体内,具有良好的生物相容性。文中综述了聚酸酐的合成,聚酸酐控释制剂的制备工艺、降解、体内安全性和临床应用方面的研究进展,并提出了今后的发展方向。聚酸酐在医学方面的研究和应用必将日益广泛。     

Inferring functional modules of protein families with probabilistic topic models

Background  

Genome and metagenome studies have identified thousands of protein families whose functions are poorly understood and for which techniques for functional characterization provide only partial information. For such proteins, the genome context can give further information about their functional context.