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排序方式: 共有1108条查询结果,搜索用时 19 毫秒
61.
Alex R. Hastie Lingli Dong Alexis Smith Jeff Finklestein Ernest T. Lam Naxin Huo Han Cao Pui-Yan Kwok Karin R. Deal Jan Dvorak Ming-Cheng Luo Yong Gu Ming Xiao 《PloS one》2013,8(2)
Next-generation sequencing (NGS) technologies have enabled high-throughput and low-cost generation of sequence data; however, de novo genome assembly remains a great challenge, particularly for large genomes. NGS short reads are often insufficient to create large contigs that span repeat sequences and to facilitate unambiguous assembly. Plant genomes are notorious for containing high quantities of repetitive elements, which combined with huge genome sizes, makes accurate assembly of these large and complex genomes intractable thus far. Using two-color genome mapping of tiling bacterial artificial chromosomes (BAC) clones on nanochannel arrays, we completed high-confidence assembly of a 2.1-Mb, highly repetitive region in the large and complex genome of Aegilops tauschii, the D-genome donor of hexaploid wheat (Triticum aestivum). Genome mapping is based on direct visualization of sequence motifs on single DNA molecules hundreds of kilobases in length. With the genome map as a scaffold, we anchored unplaced sequence contigs, validated the initial draft assembly, and resolved instances of misassembly, some involving contigs <2 kb long, to dramatically improve the assembly from 75% to 95% complete. 相似文献
62.
AB Zarafi AM Emechebe AD Akpa O Alabi 《Archives Of Phytopathology And Plant Protection》2013,46(4):261-268
Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight. 相似文献
63.
Samuel Ko T.T. Kwok K.P. Fung Y.M. Choy C.Y. Lee S.K. Kong 《Free radical research》2013,47(3):295-304
Tumour necrosis factor-α(TNF-α) was found to be a cell cycle-independent apoptogenic cytokine in cultured fibroblast L929 cells. This assertion is based on the observations (1) TNF-α increased the number of cells with hypo-diploid DNA in a time dependent manner as revealed by flow cytometry, and (2) TNF-α induced DNA fragmentation as resolved by agarose gel electrophoresis. When cells were exposed to TNF-α (50ng/ml), a slow rise in intracellular free Ca2+ level and a delayed increase in the production of reactive oxygen species (ROS) (both observed 3h after the addition of TNF-α) were observed in fluo-3 and furared or dichlorofluorescein loaded cells, respectively. Interestingly, challenge of cells with TNF-α in the presence of BAPTA/AM, an intracellular Ca2+ chelator, decreased the release of ROS. Removal of ROS by 4-hydroxy 2,2,6,6-tetra-methyl-piperidinooxy (4OH-TEMPO) blocked the TNF-α-mediated Ca2+ rise. Moreover, when cells were exposed to TNF-α with both 4OH-TEMPO and BAPTA/AM, more viable cells were found than from treatment with either BAPTA/AM or 4OH-TEMPO. These results suggest that ROS and cellular Ca2+ are two cross-talk messengers important in TNF-α-mediated apoptosis. 相似文献
64.
We present the molecular structure of the IsiA-Photosystem I (PSI) supercomplex, inferred from high-resolution, crystal structures of PSI and the CP43 protein. The structure of iron-stress-induced A protein (IsiA) is similar to that of CP43, albeit with the difference that IsiA is associated with 15 chlorophylls (Chls), one more than previously assumed. The membrane-spanning helices of IsiA contain hydrophilic residues many of which bind Chl. The optimal structure of the IsiA-PSI supercomplex was inferred by systematically rearranging the IsiA monomers and PSI trimer in relation to each other. For each of the 6,969,600 structural configurations considered, we counted the number of optimal Chl-Chl connections (i.e., cases where Chl-bound Mg atoms are ≤ 25 Å apart). Fifty of these configurations were found to have optimal energy-transfer potential. The 50 configurations could be divided into three variants; one of these, comprising 36 similar configurations, was found to be superior to the other configurations in terms of its potential to transfer excitation energy to the reaction centres under low-light conditions and its potential to dissipate excess energy under high-light conditions. Compared to the assumed model [Biochemistry 42 (2003) 3180-3188], the new Chl increases by 7% the ability of IsiA to harvest sunlight while the rearrangement of the constituent components of the IsiA-PSI supercomplex increases by 228% the energy-transfer potential. In conclusion, our model allows us to explain how the IsiA-PSI supercomplex may act as an efficient light-harvesting structure under low-light conditions and as an efficient dissipater of excess energy under high-light conditions. 相似文献
65.
66.
The TMK1 gene from Arabidopsis codes for a protein with structural and biochemical characteristics of a receptor protein kinase. 总被引:10,自引:6,他引:10 下载免费PDF全文
C Chang G E Schaller S E Patterson S F Kwok E M Meyerowitz A B Bleecker 《The Plant cell》1992,4(10):1263-1271
Genomic and cDNA clones that code for a protein with structural and biochemical properties similar to the receptor protein kinases from animals were obtained from Arabidopsis. Structural features of the predicted polypeptide include an amino-terminal membrane targeting signal sequence, a region containing blocks of leucine-rich repeat elements, a single putative membrane spanning domain, and a characteristic serine/threonine-specific protein kinase domain. The gene coding for this receptor-like transmembrane kinase was designated TMK1. Portions of the TMK1 gene were expressed in Escherichia coli, and antibodies were raised against the recombinant polypeptides. These antibodies immunodecorated a 120-kD polypeptide present in crude extracts and membrane preparations. The immunodetectable band was present in extracts from leaf, stem, root, and floral tissues. The kinase domain of TMK1 was expressed as a fusion protein in E. coli, and the purified fusion protein was found capable of autophosphorylation on serine and threonine residues. The possible role of the TMK1 gene product in transmembrane signaling is discussed. 相似文献
67.
An Yun Guo Kwok Sui Leung Parco Ming Fai Siu Jiang Hui Qin Simon Kwoon Ho Chow Ling Qin Chi Yu Li Wing Hoi Cheung 《Experimental Animals》2015,64(4):425-433
Sarcopenia is an age-related systemic syndrome with progressive deterioration in skeletal
muscle functions and loss in mass. Although the senescence-accelerated mouse P8 (SAMP8)
was reported valid for muscular ageing research, there was no report on the details such
as sarcopenia onset time. Therefore, this study was to investigate the change of muscle
mass, structure and functions during the development of sarcopenia. Besides the average
life span, muscle mass, structural and functional measurements were also studied. Male
SAMP8 animals were examined at month 6, 7, 8, 9, and 10, in which the right gastrocnemius
was isolated and tested for ex vivo contractile properties and fatigability while the
contralateral one was harvested for muscle fiber cross-sectional area (FCSA) and typing
assessments. Results showed that the peak of muscle mass appeared at month 7 and the onset
of contractility decline was observed from month 8. Compared with month 8, most of the
functional parameters at month 10 decreased significantly. Structurally, muscle fiber type
IIA made up the largest proportion of the gastrocnemius, and the fiber size was found to
peak at month 8. Based on the altered muscle mass, structural and functional outcomes, it
was concluded that the onset of sarcopenia in SAMP8 animals was at month 8. SAMP8 animals
at month 8 should be at pre-sarcopenia stage while month 10 at sarcopenia stage. It is
confirmed that SAMP8 mouse can be used in sarcopenia research with established time line
in this study. 相似文献
68.
69.
Kyle Lapham Mark N. Kvale Jue Lin Sheryl Connell Lisa A. Croen Brad P. Dispensa Lynn Fang Stephanie Hesselson Thomas J. Hoffmann Carlos Iribarren Eric Jorgenson Lawrence H. Kushi Dana Ludwig Tetsuya Matsuguchi William B. McGuire Sunita Miles Charles P. Quesenberry Jr. Sarah Rowell Marianne Sadler Lori C. Sakoda David Smethurst Carol P. Somkin Stephen K. Van Den Eeden Lawrence Walter Rachel A. Whitmer Pui-Yan Kwok Neil Risch Catherine Schaefer Elizabeth H. Blackburn 《Genetics》2015,200(4):1061-1072
The Kaiser Permanente Research Program on Genes, Environment, and Health (RPGEH) Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort includes DNA specimens extracted from saliva samples of 110,266 individuals. Because of its relationship to aging, telomere length measurement was considered an important biomarker to develop on these subjects. To assay relative telomere length (TL) on this large cohort over a short time period, we created a novel high throughput robotic system for TL analysis and informatics. Samples were run in triplicate, along with control samples, in a randomized design. As part of quality control, we determined the within-sample variability and employed thresholds for the elimination of outlying measurements. Of 106,902 samples assayed, 105,539 (98.7%) passed all quality control (QC) measures. As expected, TL in general showed a decline with age and a sex difference. While telomeres showed a negative correlation with age up to 75 years, in those older than 75 years, age positively correlated with longer telomeres, indicative of an association of longer telomeres with more years of survival in those older than 75. Furthermore, while females in general had longer telomeres than males, this difference was significant only for those older than age 50. An additional novel finding was that the variance of TL between individuals increased with age. This study establishes reliable assay and analysis methodologies for measurement of TL in large, population-based human studies. The GERA cohort represents the largest currently available such resource, linked to comprehensive electronic health and genotype data for analysis. 相似文献
70.
Yan Han Man To Ling Huawei Mao Jian Zheng Ming Liu Kwok Tai Lam Yuan Liu Wenwei Tu Yu-Lung Lau 《PloS one》2014,9(1)
Although smokers have increased susceptibility and severity of seasonal influenza virus infection, there is no report about the risk of 2009 pandemic H1N1 (pdmH1N1) or avian H9N2 (H9N2/G1) virus infection in smokers. In our study, we used mouse model to investigate the effect of cigarette smoke on pdmH1N1 or H9N2 virus infection. Mice were exposed to cigarette smoke for 21 days and then infected with pdmH1N1 or H9N2 virus. Control mice were exposed to air in parallel. We found that cigarette smoke exposure alone significantly upregulated the lung inflammation. Such prior cigarette smoke exposure significantly reduced the disease severity of subsequent pdmH1N1 or H9N2 virus infection. For pdmH1N1 infection, cigarette smoke exposed mice had significantly lower mortality than the control mice, possibly due to the significantly decreased production of inflammatory cytokines and chemokines. Similarly, after H9N2 infection, cigarette smoke exposed mice displayed significantly less weight loss, which might be attributed to lower cytokines and chemokines production, less macrophages, neutrophils, CD4+ and CD8+ T cells infiltration and reduced lung damage compared to the control mice. To further investigate the underlying mechanism, we used nicotine to mimic the effect of cigarette smoke both in vitro and in vivo. Pre-treating the primary human macrophages with nicotine for 72 h significantly decreased their expression of cytokines and chemokines after pdmH1N1 or H9N2 infection. The mice subcutaneously and continuously treated with nicotine displayed significantly less weight loss and lower inflammatory response than the control mice upon pdmH1N1 or H9N2 infection. Moreover, α7 nicotinic acetylcholine receptor knockout mice had more body weight loss than wild-type mice after cigarette smoke exposure and H9N2 infection. Our study provided the first evidence that the pathogenicity of both pdmH1N1 and H9N2 viruses was alleviated in cigarette smoke exposed mice, which might partially be attributed to the immunosuppressive effect of nicotine. 相似文献