一种基于多特征的大肠杆菌启动子判别算法

主要对从一段DNA序列中提取出信息以判别其中是否含有启动子的问题进行了研究。首先从固定长度的序歹4中提取成分特征和结构特征,然后将这些特征输入到一个非线性分类器中进行判别。测试结果显示,在正集＆非编码区负集中,平均错误率降低为13．4％;在正集＆编码区负集中,平均错误率降低到17．0％。表明该方法是非常有效的。     

Overexpression of miR-26b-5p regulates the cell cycle by targeting CCND2 in GC-2 cells under exposure to extremely low frequency electromagnetic fields

The increasing prevalence of extremely low frequency electromagnetic fields (ELF-EMFs) exposure has raised considerable public concern regarding the potential hazardous effects of ELF-EMFs on male reproductive function. Increasing evidence indicates that miRNAs are necessary for spermatogenesis and male fertility. However, the regulation of miRNA expression and the roles of miRNAs in response to ELF-EMFs remain unclear. In our study, mouse spermatocyte-derived GC-2 cells were intermittently exposed to a 50 Hz ELF-EMF for 72 h (5 min on/10 min off) at magnetic field intensities of 1 mT, 2 mT and 3 mT. MiR-26b-5p was differentially expressed in response to different magnetic field intensities of ELF-EMFs. The host gene CTDSP1 showed an unmethylation status in GC-2 cells at different magnetic field intensities of ELF-EMF exposure. MiR-26b-5p had no significant, obvious influence on the cell viability, apoptosis or cell cycle of GC-2 cells. However, the overexpression of miR-26b-5p significantly decreased the percentage of G0/G1 phase cells and slightly increased the percentage of S phase cells compared to the sham group that was exposed to a 50 Hz ELF-EMF. Computational algorithms identified Cyclin D2 (CCND2) as a direct target of miR-26b-5p. MiR-26b-5p and a 50 Hz ELF-EMF altered the expression of CCND2 at both the mRNA and protein levels. Overexpressed miR-26b-5p in GC-2 cells can change the mRNA expression of CCND2 following 50 Hz ELF-EMF at 3 mT. These findings demonstrate that miR-26b-5p could serve as a potential biomarker following 50 Hz ELF-EMF exposure, and miR-26b-5p-CCND2-mediated cell cycle regulation might play a pivotal role in the biological effects of ELF-EMFs.     

High gene flow despite opposite chirality in hybrid zones between enantiomorphic door snails

We studied differentiation and geneflow patterns between enantiomorphic door‐snail species in two hybrid zones in the Bucegi Mountains (Romania) to investigate the effects of intrinsic barriers (complications in copulation) and extrinsic selection by environmental factors. A mitochondrial gene tree confirmed the historical separation of the examined populations into the dextral Alopia livida and the sinistral Alopia straminicollis in accordance with the morphological classification, but also indicated gene flow between the species. By contrast, a network based on amplified fragment length polymorphisms (AFLP) markers revealed local groups of populations as units independent of their species affiliation. Admixture analyses based on AFLP data showed that the genomes of most individuals in the hybrid zones are composed of parts of the genomes of both parental taxa. The introgression patterns of a notable fraction of the examined markers deviated from neutral introgression. However, the patterns of most non‐neutral markers were not concordant between the two hybrid zones. There was also no concordance between non‐neutral markers in the two genomic clines and markers that were correlated with environmental variables or markers that were correlated with the proportion of dextral individuals in the populations. Neither extrinsic selection by environmental factors nor intrinsic barriers resulting from positive frequency‐dependent selection of the prevailing coiling direction were sufficient to maintain the distinctness of A. straminicollis and A. livida. Despite being historically separated units, we conclude that these taxa now merge where they come into contact.     

Costs and Benefits of Mating in the Grasshopper Chorthippus parallelus (Caelifera: Acrididae)

Fitness consequences of different levels of mating benefits, viz., (1) virgin, (2) seldom mated, (3) free mating chances with the same male throughout the female's life span, and (4) free mating chances with three males always offered, were investigated in female meadow grasshoppers Chorthippus parallelus. No differences among the treatments were apparent in egg number per pod, total egg number per female, and hatching success of larvae. Seldom-mated females had offspring with the heaviest average larval dry weight. We did not find costs of mating in terms of reduced female longevity and residual dry weight between the treatments.     

Application of frequency ratio and logistic regression models for assessing physical wetland vulnerability in Punarbhaba river basin of Indo-Bangladesh

Growingly scarce ecologically viable flood plain wetland of the Punarbhaba river basin is further endangered due to flow modification through Komardanga dam. This work intends to discover physical vulnerability of the wetlands in Punarbhaba river basin of Indo-Bangladesh considering seven conditioning parameters, e.g., water presence frequency (WPF) map, flood inundation map, frequency of pixel being non-permanent, agriculture presence frequency (APF) map, fragmentation of wetland, normalized differentiation built up index (NDBI), and wetland changes (WC). Frequency Ratio and Logistic Regression models have been used for deriving the vulnerability of wetland for both pre (1988–1992) and post dam (1993–2016) periods. From computed FR models it is exhibited that out of the total wetland area (194.81 km²), 5.88% and 2.92% area are high and very highly vulnerable in pre-dam period but such vulnerable area is increased to 33.45% and 23.10% in post-dam state (total wetland: 126.11 km²). LR models also state that in pre-dam period, high and very high vulnerable wetland area were 5.02% and 3.82% (total wetland: 194.79 km²) and it is enhanced to 28.94% and 24.49% in post-dam state (total wetland: 126.11 km²). Extensions of agricultural land, squeezing of active flood plain, lowering flood frequency are dominant determinants for growing wetland vulnerability.     

Vertical structure of Erica umbellata,a representative species of European Ibero-Atlantic dry heaths

The canopy structure of Erica umbellata was studied in order to (a) quantify biomass allocation among several organ types, (b) analyse the possible changes in vertical structure related to season and plant size, and (c) evaluate the effectiveness of non-destructive measures to estimate biomass for a species that is declining in some areas, due to fire and other human disturbances. The study was conducted in NW Spain, sampling E. umbellata plants belonging to three size groups. Destructive (biomass) and non-destructive (frequency, height, diameter) measures were used to characterise the vertical distribution and abundance of photosynthetic, woody, reproductive and dead organs. Allometric equations were calculated to estimate total mass using non-destructive measurements. As E. umbellata increases in size, those organs with a higher renewal rate (leaves, new stems, flowers) increase in the upper strata. Seasonal differences are recorded for the reproductive organs and new stems. A sharp decrease in the green/total phytomass ratio (from 0.51 to 0.17) is observed as plant size increases. Organ biomass can be accurately predicted from total weight and it is also possible to estimate the total weight from non-destructive measures, which provides an easier way of recording data in the field.     

Variation in pollinator abundance and selection on fragrance phenotypes in an epiphytic orchid

Extraordinary floral variation is common among some orchids that employ deception to attract pollinators. This variation may be maintained by frequency-dependent selection where rare phenotypes are preferred. Over a 2-yr period, 1993-1994, we monitored the reproductive success of Tolumnia variegata, an obligately outcrossing epiphytic orchid, at three localities in Puerto Rico that differed in pollinator service. Plants varied in floral morphology and fragrance characteristics. Artificial arrays of varying frequencies of scentless and fragrant phenotypes were established to test for frequency-dependent selection. Where pollinators were rare (Cambalache, range of census average = 0-0.2 bees/h), 0.9-1.2% of the flowers were effectively visited (pollinarium removals and pollinations). At Tortuguero where 0.4-1.1 bees/h were observed, 4-9.2% of the flowers were visited. At Pi;atnones where bees were the most abundant (1.4-5.2 bees/h), 20.9-25.0% of the flowers were visited. A significant portion of the variance in all measures of reproductive success (male, female, and combined) was explained by differences among populations, which we attribute mostly to variation in pollinator abundance. Neither the fragrance phenotype nor its frequency had a significant effect on success as revealed by a split-plot ANOVA. There was a significant interaction between population and phenotypic frequencies in all our measures of reproductive success, but only for the 1994 flowering season. Thus, variation in floral fragrance phenotypes is not likely maintained by frequency-dependent selection. High levels of variation remain unexplained.     

圆蟾舌蛙鸣声特征分析

为研究体型较小的蛙类的鸣声特征,2012年7~8月,采用录音机和指向性话筒,在野外录制51只雄性圆蟾舌蛙(Phrynoglossus martensii)鸣声并对应测量了录音个体的体重、体长及头宽等体征数据。雄性圆蟾舌蛙的体重为(1.26±0.55)g,体长为(21.04±2.57)mm,头宽为(6.76±0.75)mm。该种蛙可发出广告鸣声和争斗鸣声。广告鸣声为单音节鸣叫,主频(3 782.25±167.78)Hz,3 100~4 349 Hz;基频(1 519.69±70.60)Hz,1 057~1 765 Hz。广告鸣声主频和基频均与体重、体长、头宽呈显著负相关,而音节间隔与体重和头宽呈正相关(相关性分析)。争斗鸣声主频(3 752.64±174.47)Hz,(3 304~4 081)Hz;基频(1 674.88±79.88)Hz,1 367~1 870 Hz。与广告鸣声相比,争斗鸣声的基频显著增高(t=﹣5.374,df=56,P0.001),音节时长和音节间隔显著降低(P0.05),而主频在两种鸣声类型中无显著差异(t=0.436,df=56,P=0.665)(独立样本T检验)。结果表明,作为体型较小的蛙类,体型影响了圆蟾舌蛙的鸣声结构和类型。     

抗生素对溶藻弧菌SXT/R391元件转移频率的影响北大核心CSCD

【目的】研究萘啶酸、诺氟沙星、卡那霉素3种抗生素对溶藻弧菌(Vibrio alginolyticus)SXT/R391元件ICEVal A056-1转移频率的影响。【方法】利用PCR检测溶藻弧菌A056中ICEVal A056-1的自我剪切、转移潜力。通过溶藻弧菌A056与大肠杆菌菌株VB111的接合实验,研究溶藻弧菌分别在含不同浓度萘啶酸、诺氟沙星、卡那霉素的LB培养基中培养15 min或30 min后,ICEVal A056-1转移频率的变化规律。【结果】溶藻弧菌A056细胞中有环状形式的ICEVal A056-1分子存在,具有水平转移潜力;溶藻弧菌A056在含40μg/m L萘啶酸的LB中培养30 min后,ICEVal A056-1转移频率是对照组的19.59倍;在含50μg/m L诺氟沙星的LB中培养15 min后,ICEVal A056-1转移频率是对照组的31.25倍;在含不同浓度卡那霉素的LB中培养30 min后,ICEVal A056-1转移频率与对照组没有显著差别。【结论】部分抗生素的使用可以明显促进溶藻弧菌ICEVal A056-1向大肠杆菌的转移,因此海洋环境中抗生素的滥用及随意排放很可能加剧ICEs(integrating conjugative elements)从溶藻弧菌到其他细菌的传播。     

Human cognitive performance in a 3 mT power-line frequency magnetic field

Extremely low frequency (ELF, <300 Hz) magnetic fields (MF) have been reported to modulate cognitive performance in humans. However, little research exists with MF exposures comparable to the highest levels experienced in occupations like power line workers and industrial welders. This research aims to evaluate the impact of a 60 Hz, 3 mT MF on human cognitive performance. Ninety‐nine participants completed the double‐blind protocol, performing a selection of psychometric tests under two consecutive MF exposure conditions dictated by assignment to one of three groups (sham/sham, MF exposure/sham, or sham/MF exposure). Data were analyzed using a 3 × 2 mixed model analysis of variance. Performance between repetitions improved in 11 of 15 psychometric parameters (practice effect). A significant interaction effect on the digit span forward test (F = 5.21, P < 0.05) revealed an absence of practice effects for both exposure groups but not the control group. This memory test indicates MF‐induced abolition of the improvement associated with practice. Overall, this study does not establish any clear MF effect on human cognition. It is speculated that an ELF MF may interfere with the neuropsychological processes responsible for this short‐term learning effect supported by brain synaptic plasticity. Bioelectromagnetics. Bioelectromagnetics 32:620–633, 2011. © 2011 Wiley Periodicals, Inc.