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排序方式: 共有327条查询结果,搜索用时 15 毫秒
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During lung development, Fibroblast growth factor 10 (Fgf10), which is expressed in the distal mesenchyme and regulated by Wnt signaling, acts on the distal epithelial progenitors to maintain them and prevent them from differentiating into proximal (airway) epithelial cells. Fgf10-expressing cells in the distal mesenchyme are progenitors for parabronchial smooth muscle cells (PSMCs). After naphthalene, ozone or bleomycin-induced airway epithelial injury, surviving epithelial cells secrete Wnt7b which then activates the PSMC niche to induce Fgf10 expression. This Fgf10 secreted by the niche then acts on a subset of Clara stem cells to break quiescence, induce proliferation and initiate epithelial repair. Here we show that conditional deletion of the Wnt target gene c-Myc from the lung mesenchyme during development does not affect proper epithelial or mesenchymal differentiation. However, in the adult lung we show that after naphthalene-mediated airway epithelial injury c-Myc is important for the activation of the PSMC niche and as such induces proliferation and Fgf10 expression in PSMCs. Our data indicate that conditional deletion of c-Myc from PSMCs inhibits airway epithelial repair, whereas c-Myc ablation from Clara cells has no effect on airway epithelial regeneration. These findings may have important implications for understanding the misregulation of lung repair in asthma and COPD. 相似文献
3.
It is a challenging task to predict with high reliability whether plant genomic sequences contain a polyadenylation (polyA) site or not. In this paper, we solve the task by means of a systematic machine-learning procedure applied on a dataset of 1000 Arabidopsis thaliana sequences flanking polyA sites. Our procedure consists of three steps. In the first step, we extract informative features from the sequences using the highly informative k-mer windows approach. Experiments with five classifiers show that the best performance is approximately 83%. In the second step, we improve performance to 95% by reducing the number of features using linear discriminant analysis, followed by applying the linear discriminant classifier. In the third step, we apply the transductive confidence machines approach and the receiver operating characteristic isometrics approach. The resulting two classifiers enable presetting any desired performance by dealing carefully with sequences for which it is unclear whether they contain polyA sites or not. For example, in our case study, we obtain 99% performance by leaving 26% of the sequences unclassified, and 100% performance by leaving 40% of the sequences unclassified. This is clearly useful for experimental verification of putative polyA sites in the laboratory. The novel methods in our machine-learning procedure should find applications in several areas of bioinformatics. 相似文献
4.
M Baba R Pauwels P Herdewijn E De Clercq J Desmyter M Vandeputte 《Biochemical and biophysical research communications》1987,142(1):128-134
2',3'-Dideoxythymidine (ddThd) and its 2',3'-unsaturated derivative 2',3'-dideoxythymidinene (ddeThd) are potent and selective inhibitors of human immunodeficiency virus (HIV) in vitro. When evaluated for their inhibitory effects on the cytopathogenicity of HIV in MT-4 cells, ddThd and ddeThd completely protected the cells against destruction by the virus at a concentration of 1 microM and 0.04 microM, respectively. In this aspect, ddeThd was about 5 times more potent than 2',3'-dideoxycytidine (ddCyd), one of the most potent and selective anti-HIV compounds now pursued for its therapeutic potential in the treatment of AIDS. ddThd and ddeThd also suppressed HIV antigen expression at 1 microM and 0.04 microM, respectively. Their selectivity indexes, as based on the ratio of the 50% cytotoxic dose to the 50% antiviral effective dose, were 120 (ddeThd) and greater than 625 (ddThd). 相似文献
5.
Mini-F E protein: the carboxy-terminal end is essential for E gene repression and mini-F copy number control 总被引:5,自引:0,他引:5
F Bex P Piérard A Desmyter P Drèze M Colet M Couturier 《Journal of molecular biology》1986,189(2):293-303
Mini-F is a segment of the conjugative plasmid F consisting of two origins of replication flanked by regulatory regions, which ensure a normal control of replication and partitioning. Adjacent to the ori-2 origin is a complex coding region that consists of the E gene overlapped by three open reading frames with the coding potential for 9000 Mr polypeptides here designated 9 kd-1, 9 kd-2 and 9 kd-3. In this paper, we show that open reading frame 9 kd-3 is preceded by active promoter and Shine-Dalgarno sequences. The E coding region specifies: an initiator of replication, which acts at the ori-2 site; a function that negatively regulates the expression of the E gene; and a function involved in mini-F copy number control. To assign one of these functions to one of the overlapping coding sequence, we have isolated, characterized and sequenced mutations mapping in the E coding region. In this paper, we analyse two mutations (cop5 and pla25) that abolish the repression of the E gene. As these mutations affect the primary structure of protein E itself but not the 9 kd polypeptides, we conclude that protein E takes part in the negative regulation of its own synthesis. In addition, the localization of the cop5 and pla25 mutations indicates that the carboxy-terminal end of the E protein is involved in the autorepression function. The cop5 mutation causes an eightfold increase of the mini-F copy number. The pla25 mutation leads to the inability of the derived mini-F plasmid to give rise to plasmid-harbouring bacteria. The ways in which the cop5 and pla25 mutations may lead to such phenotypes are discussed in relation to the different functions mapping in the E coding sequence. 相似文献
6.
M. Couturier J. Janssens F. Bex A. Desmyter I. Bonnevalle 《Molecular & general genetics : MGG》1979,169(1):113-116
Summary In this paper, we report the construction in vitro of chimerae between lambdoid replacement vectors (Murray et al., 1977) and the miniF Apr plasmid: pSC138 (Timmis et al., 1975). F recombinants were shown to be chimerae between the and the F replicons. By genetical tests, we have demonstrated that both and F replication mechanisms are functional: the F recombinant behaves as a non defective plaque forming phage on sensitive bacteria and establishes itself as a stable plasmid on recA F- homoimmune bacteria. In the extra-chromosomal state, the F recombinant apparently retains the controlled autonomous replication and the FI incompatibility characteristics of the F plasmid. The potential experimental uses of these phages are discussed. 相似文献
7.
8.
Stijn Van Slycken Nele Witters Linda Meiresonne Erik Meers Ann Ruttens Pierre Van Peteghem 《International journal of phytoremediation》2013,15(7):677-689
Short rotation coppice (SRC) of willow and poplar might be a promising phytoremediation option since it uses fast growing, high biomass producing tree species with often a sufficient metal uptake. This study evaluates growth, metal uptake and extraction potentials of eight willow clones (Belders, Belgisch Rood, Christina, Inger, Jorr, Loden, Tora and Zwarte Driebast) on a metal-contaminated agricultural soil, with total cadmium (Cd) and zinc (Zn) concentrations of 6.5 ± 0.8 and 377 ± 69 mg kg?1 soil, respectively. Although, during the first cycle, on average generally low productivity levels (3.7 ton DM (dry matter) ha?1 y?1) were obtained on this sandy soil, certain clones exhibited quite acceptable productivity levels (e.g. Zwarte Driebast 12.5 ton DM ha?1 y?1). Even at low biomass productivity levels, SRC of willow showed promising removal potentials of 72 g Cd and 2.0 kg Zn ha?1 y?1, which is much higher than e.g. energy maize or rapeseed grown on the same soil. Cd and Zn removal can be increased by 40% if leaves are harvested as well. Nevertheless, nowadays the wood price remains the most critical factor in order to implement SRC as an acceptable, economically feasible alternative crop on metal-contaminated agricultural soils. 相似文献
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10.
Jurgen Vercauteren Gertjan Beheydt Mattia Prosperi Pieter Libin Stijn Imbrechts Ricardo Camacho Bonaventura Clotet Andrea De Luca Zehava Grossman Rolf Kaiser Anders S?nnerborg Carlo Torti Eric Van Wijngaerden Jean-Claude Schmit Maurizio Zazzi Anna-Maria Geretti Anne-Mieke Vandamme Kristel Van Laethem 《PloS one》2013,8(4)