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61.
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. 相似文献62.
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. 相似文献
63.
GUILLAUME MARTI MATTHIAS ERB JULIEN BOCCARD GAÉTAN GLAUSER GWLADYS R. DOYEN NEIL VILLARD CHRISTELLE A M. ROBERT TED C. J. TURLINGS SERGE RUDAZ JEAN‐LUC WOLFENDER 《Plant, cell & environment》2013,36(3):621-639
Plants respond to herbivory by reprogramming their metabolism. Most research in this context has focused on locally induced compounds that function as toxins or feeding deterrents. We developed an ultra‐high‐pressure liquid chromatography time‐of‐flight mass spectrometry (UHPLC‐TOF‐MS)‐based metabolomics approach to evaluate local and systemic herbivore‐induced changes in maize leaves, sap, roots and root exudates without any prior assumptions about their function. Thirty‐two differentially regulated compounds were identified from Spodoptera littoralis‐infested maize seedlings and isolated for structure assignment by microflow nuclear magnetic resonance (CapNMR). Nine compounds were quantified by a high throughput direct nano‐infusion tandem mass spectrometry/mass spectrometry (MS/MS) method. Leaf infestation led to a marked local increase of 1,3‐benzoxazin‐4‐ones, phospholipids, N‐hydroxycinnamoyltyramines, azealic acid and tryptophan. Only few changes were found in the root metabolome, but 1,3‐benzoxazin‐4‐ones increased in the vascular sap and root exudates. The role of N‐hydroxycinnamoyltyramines in plant–herbivore interactions is unknown, and we therefore tested the effect of the dominating p‐coumaroyltyramine on S. littoralis. Unexpectedly, p‐coumaroyltyramine was metabolized by the larvae and increased larval growth, possibly by providing additional nitrogen to the insect. Taken together, this study illustrates that herbivore attack leads to the induction of metabolites that can have contrasting effects on herbivore resistance in the leaves and roots. 相似文献
64.
LAËTITIA BUISSON WILFRIED THUILLER SOVAN LEK PUY LIM GAËL GRENOUILLET 《Global Change Biology》2008,14(10):2232-2248
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. 相似文献
65.
Throughout the animal kingdom there are species that have two or more phenotypic forms or 'morphs', and many of these are amphibians. In North America, the red-backed salamander Plethodon cinereus can have either a red dorsal stripe or no dorsal stripe (lead-phase form), and evidence to date indicates the lead-phase form incurs a greater number of attacks from predators. In a recent collection of 51 P. Cinereus, blood smears of both color morphs (35 red-stripe, 16 lead-phase) were examined to obtain numbers of circulating leukocytes (via light microscopy), which can be used to indirectly estimate levels of stress hormones in vertebrates via a 'hematological stress index', which is the ratio between the number of two leukocyte types (neutrophils and lymphoeytes). Our results showed that lead-phase salamanders tended to have greater numbers of circulating neutrophils and lower numbers of circulating iymphocytes than red-stripe morphs, leading to higher average neutrophil-lymphocyte ratios in lead-phase individuals. Since the salamanders were held (refrigerated) for 7 days before sampling, we cannot be certain if this effect is a stress reaction to the captivity or the normal level for this morph. However comparison with two sets of related salamanders that were captured and sampled immediately indicates the red-stripe salamanders were either not stressed from the captivity at all, or their white blood cell distributions had returned to normal after 7 days of captivity. Taken together, our results indicate that lead-phase forms of P. Cinereus have higher stress levels than the red-stripe forms, which may be a consequence of their higher exposure to, and/or attacks from, predators. They may also indicate that the lead-phase form is less-suited to captivity than the red-stripe form of this species. 相似文献
66.
67.
A mycological survey was carried out on rice samples harvested in 1997 and 1998 from Entre Ríos province, belonging to the
main production area of Argentina. The relative density and isolation frequency of the prevalent fungi were statistically
compared between locations and harvest seasons. The genusAlternaria was the most prevalent component of the internal seedborne mycoflora in the two harvest seasons. Fungi belonging to the generaPhoma, Fusarium, Microdochium, Penicillium andAspergillus were also isolated. The predominant species of these genera wereAlternaria alternata, Phoma glomerata, Fusarium graminearum, Microdochium nivale, Penicillium citrinum and Aspergillus flavus. 相似文献
68.
Taxol from fungal endophytes and the issue of biodiversity 总被引:7,自引:0,他引:7
GA Strobel WM Hess E. Ford RS Sidhu X Yang 《Journal of industrial microbiology & biotechnology》1996,17(5-6):417-423
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. 相似文献
69.
70.
Evolution of the secondary structures and compensatory mutations of the ribosomal RNAs of Drosophila melanogaster 总被引:10,自引:0,他引:10
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.
相似文献