共查询到20条相似文献,搜索用时 31 毫秒
1.
Sample phenotype clusters in high-density oligonucleotide microarray data sets are revealed using Isomap,a nonlinear algorithm 总被引:2,自引:0,他引:2
Background
Life processes are determined by the organism's genetic profile and multiple environmental variables. However the interaction between these factors is inherently non-linear [1]. Microarray data is one representation of the nonlinear interactions among genes and genes and environmental factors. Still most microarray studies use linear methods for the interpretation of nonlinear data. In this study, we apply Isomap, a nonlinear method of dimensionality reduction, to analyze three independent large Affymetrix high-density oligonucleotide microarray data sets. 相似文献2.
Background
Synthesis of cationic hydrous thorium dioxide colloids (ca. 1.0 to 1.7 nm) has been originally described by Müller [22] and Groot [11] and these have been used by Groot to stain acidic glucosaminoglycans for ultrastructure research of different tissues by conventional transmission electron microscopy. 相似文献3.
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Background
For gene expression data obtained from a time-course microarray experiment, Liu et al. [1] developed a new algorithm for clustering genes with similar expression profiles over time. Performance of their proposal was compared with three other methods including the order-restricted inference based methodology of Peddada et al. [2, 3]. In this note we point out several inaccuracies in Liu et al. [1] and conclude that the order-restricted inference based methodology of Peddada et al. (programmed in the software ORIOGEN) indeed operates at the desired nominal Type 1 error level, an important feature of a statistical decision rule, while being computationally substantially faster than indicated by Liu et al. [1]. 相似文献5.
Vladimir Makarenkov Alix Boc Jingxin Xie Pedro Peres-Neto François-Joseph Lapointe Pierre Legendre 《BMC evolutionary biology》2010,10(1):250
Background
Non-parametric bootstrapping is a widely-used statistical procedure for assessing confidence of model parameters based on the empirical distribution of the observed data [1] and, as such, it has become a common method for assessing tree confidence in phylogenetics [2]. Traditional non-parametric bootstrapping does not weigh each tree inferred from resampled (i.e., pseudo-replicated) sequences. Hence, the quality of these trees is not taken into account when computing bootstrap scores associated with the clades of the original phylogeny. As a consequence, traditionally, the trees with different bootstrap support or those providing a different fit to the corresponding pseudo-replicated sequences (the fit quality can be expressed through the LS, ML or parsimony score) contribute in the same way to the computation of the bootstrap support of the original phylogeny. 相似文献6.
Brandon W Higgs John Dileo Wenling E Chang Haley B Smith Olivia J Peters Rasha Hammamieh Marti Jett Jordan C Feidler 《BMC microbiology》2006,6(1):48-12
Background
The lack of detailed understanding of the mechanism of action of many biowarfare agents poses an immediate challenge to biodefense efforts. Many potential bioweapons have been shown to affect the cellular pathways controlling apoptosis [1–4]. For example, pathogen-produced exotoxins such as Staphylococcal Enterotoxin B (SEB) and Anthrax Lethal Factor (LF) have been shown to disrupt the Fas-mediated apoptotic pathway [2, 4]. To evaluate how these agents affect these pathways it is first necessary to understand the dynamics of a normally functioning apoptosis network. This can then serve as a baseline against which a pathogen perturbed system can be compared. Such comparisons can expose both the proteins most susceptible to alteration by the agent as well as the most critical reaction rates to better instill control on a biological network. 相似文献7.
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Background
DNA sequencing is used ubiquitously: from deciphering genomes[1] to determining the primary sequence of small RNAs (smRNAs) [2–5]. The cloning of smRNAs is currently the most conventional method to determine the actual sequence of these important regulators of gene expression. Typical smRNA cloning projects involve the sequencing of hundreds to thousands of smRNA clones that are delimited at their 5' and 3' ends by fixed sequence regions. These primers result from the biochemical protocol used to isolate and convert the smRNA into clonable PCR products. Recently we completed a smRNA cloning project involving tobacco plants, where analysis was required for ~700 smRNA sequences[6]. Finding no easily accessible research tool to enter and analyze smRNA sequences we developed Ebbie to assist us with our study. 相似文献9.
Background
Many bacteria swim by rotating helical flagellar filaments [1]. Waterbury et al. [15] discovered an exception, strains of the cyanobacterium Synechococcus that swim without flagella or visible changes in shape. Other species of cyanobacteria glide on surfaces [2,7]. The hypothesis that Synechococcus might swim using traveling surface waves [6,13] prompted this investigation. 相似文献10.
Background
In the clinical context, samples assayed by microarray are often classified by cell line or tumour type and it is of interest to discover a set of genes that can be used as class predictors. The leukemia dataset of Golubet al.[1] and the NCI60 dataset of Rosset al.[2] present multiclass classification problems where three tumour types and nine cell lines respectively must be identified. We apply an evolutionary algorithm to identify the near-optimal set of predictive genes that classify the data. We also examine the initial gene selection step whereby the most informative genes are selected from the genes assayed. 相似文献11.
Danival J de Souza Annie Bézier Delphine Depoix Jean-Michel Drezen Alain Lenoir 《BMC microbiology》2009,9(1):29-8
Background
Microorganisms are a large and diverse form of life. Many of them live in association with large multicellular organisms, developing symbiotic relations with the host and some have even evolved to form obligate endosymbiosis [1]. All Carpenter ants (genus Camponotus) studied hitherto harbour primary endosymbiotic bacteria of the Blochmannia genus. The role of these bacteria in ant nutrition has been demonstrated [2] but the omnivorous diet of these ants lead us to hypothesize that the bacteria might provide additional advantages to their host. In this study, we establish links between Blochmannia, growth of starting new colonies and the host immune response. 相似文献12.
Orla O'sullivan John O'Callaghan Amaia Sangrador-Vegas Olivia McAuliffe Lydia Slattery Pawel Kaleta Michael Callanan Gerald F Fitzgerald R Paul Ross Tom Beresford 《BMC microbiology》2009,9(1):50
Background
The recently sequenced genome of Lactobacillus helveticus DPC4571 [1] revealed a dairy organism with significant homology (75% of genes are homologous) to a probiotic bacteria Lb. acidophilus NCFM [2]. This led us to hypothesise that a group of genes could be determined which could define an organism's niche. 相似文献13.
Identification of coherent patterns in gene expression data using an efficient biclustering algorithm and parallel coordinate visualization 总被引:1,自引:0,他引:1
Background
The DNA microarray technology allows the measurement of expression levels of thousands of genes under tens/hundreds of different conditions. In microarray data, genes with similar functions usually co-express under certain conditions only [1]. Thus, biclustering which clusters genes and conditions simultaneously is preferred over the traditional clustering technique in discovering these coherent genes. Various biclustering algorithms have been developed using different bicluster formulations. Unfortunately, many useful formulations result in NP-complete problems. In this article, we investigate an efficient method for identifying a popular type of biclusters called additive model. Furthermore, parallel coordinate (PC) plots are used for bicluster visualization and analysis. 相似文献14.
Background
The Trypanosoma brucei cell cycle is regulated by combinations of cyclin/CRKs (cdc2 related kinases). Recently, two additional cyclins (CYC10, CYC11) and six new CRK (CRK7-12) homologues were identified in the T. brucei genome database [1,2]. 相似文献15.
Karel Kellens Wim Dewulf Michael Overcash Michael Z. Hauschild Joost R. Duflou 《The International Journal of Life Cycle Assessment》2012,17(2):242-251
Purpose
This report presents two case studies, one for both the screening approach and the in-depth approach, demonstrating the application of the life cycle assessment-oriented methodology for systematic inventory analysis of the machine tool use phase of manufacturing unit processes, which has been developed in the framework of the CO2PE! collaborative research programme (CO2PE! 2011) and is described in part 1 of this paper (Kellens et al. 2011). 相似文献16.
17.
Nilima Gandhi Miriam L. Diamond Mark A. J. Huijbregts Jeroen B. Guinée Willie J. G. M. Peijnenburg Dik van de Meent 《The International Journal of Life Cycle Assessment》2011,16(8):774-787
Purpose
Previous methods of estimating characterization factors (CFs) of metals in life cycle impact assessment (LCIA) models were based on multimedia fate, exposure, and effect models originally developed to address the potential impacts of organic chemicals. When applied to metals, the models neglect the influence of ambient chemistry on metal speciation, bioavailability and toxicity. Gandhi et al. (2010) presented a new method of calculating CFs for freshwater ecotoxicity that addresses these metal-specific issues. In this paper, we compared and assessed the consequences of using the new method versus currently available LCIA models for calculating freshwater ecotoxicity, as applied to two case studies previously examined by Gloria et al. (2006): (1) the production of copper (Cu) pipe and (2) a zinc (Zn) gutter system. 相似文献18.
Mayken W Wadman Ronald P de Vries Stefanie IC Kalkhove Gerrit A Veldink Johannes FG Vliegenthart 《BMC microbiology》2009,9(1):59
Background
Aspergillus niger is an ascomycetous fungus that is known to reproduce through asexual spores, only. Interestingly, recent genome analysis of A. niger has revealed the presence of a full complement of functional genes related to sexual reproduction [1]. An example of such genes are the dioxygenase genes which in Aspergillus nidulans, have been shown to be connected to oxylipin production and regulation of both sexual and asexual sporulation [2–4]. Nevertheless, the presence of sex related genes alone does not confirm sexual sporulation in A. niger. 相似文献19.
Madoka Koyanagi Julie A Kerns Linda Chung Yan Zhang Scott Brown Tudor Moldoveanu Harmit S Malik Mark Bix 《BMC evolutionary biology》2010,10(1):223
Background
Interleukin-4 (IL4) is a secreted immunoregulatory cytokine critically involved in host protection from parasitic helminths [1]. Reasoning that helminths may have evolved mechanisms to antagonize IL4 to maximize their dispersal, we explored mammalian IL4 evolution. 相似文献20.