Biomedical subjects

Yao Luo

Publications and source records attributed to Yao Luo.

5 recordsLinked to original sources

PubMed2005

Quantification of dinor, dihydro metabolites of F2-isoprostanes in urine by liquid chromatography/tandem mass spectrometry.

The F2-isoprostanes (F2-IsoP) are a series of prostaglandin (PG)-F2-like compounds that are produced by free-radical-mediated oxidation of arachidonic acid. One F2-IsoP with potent biological activity is 15-F2t-IsoP and increased levels of 15-F(2t)-IsoP have been measured in several diseases. The major urinary metabolite of 15-F2t-IsoP (8-iso-PGF(2alpha)) is 2,3-dinor-5,6-dihydro-15-F2t-IsoP (15-F2t-IsoP-M). Previously, we developed a stable isotope dilution gas chromatography/negative chemical ionization/mass spectrometry (MS) assay for 15-F2t-IsoP-M, which, while highly sensitive, required time-consuming derivatization and thin-layer chromatography purification. We now report the development of a more rapid high-performance liquid chromatography method coupled to electrospray ionization-tandem mass spectrometry (LC/MS/MS) to analyze all of the dinor,dihydro metabolites of the F2-IsoP isomers (F2-IsoP-M). The precision of this assay was +/-5.0% and the accuracy 80%. The assay remained linear over a range of 1-100 ng injected onto the LC column. Levels of F2-IsoP-M determined by the LC/MS/MS assay method significantly correlated with levels of 15-F2t-IsoP-M determined by the GC/MS assay (R = 0.77y = 67.2x-0.5). The levels of F2-IsoP-M detected in spot urines from 40 normal subjects were 38.1+/-19.1 ng/mg creatinine (mean+/-SD). This method provides an accurate and rapid assay to assess oxidative status in vivo.

Chromatography, Liquid↗

PubMed2005

Functional analysis of the plant disease resistance gene Pto using DNA shuffling.

Pto is a serine/threonine kinase that mediates resistance in tomato to strains of Pseudomonas syringae pv. tomato expressing the (a)virulence proteins AvrPto or AvrPtoB. DNA shuffling was used as a combinatorial in vitro genetic approach to dissect the functional regions of Pto. The Pto gene was shuffled with four of its paralogs from a resistant haplotype to create a library of recombinant products that was screened for interaction with AvrPto in yeast. All interacting clones and a representative sample of noninteracting clones were sequenced, and their ability to signal downstream was tested by the elicitation of a hypersensitive response in an AvrPto-dependent or -independent manner in planta. Eight candidate regions important for binding to AvrPto or for downstream signaling were identified by statistical correlations between individual amino acid positions and phenotype. A subset of the regions had previously been identified as important for recognition, confirming the validity of the shuffling approach. Three novel regions important for Pto function were validated by site-directed mutagenesis. Several chimeras and point mutants exhibited a differential interaction with (a)virulence proteins in the AvrPto and VirPphA family, demonstrating distinct binding requirements for different ligands. Additionally, the identification of chimeras that are both constitutively active as well as capable of binding AvrPto indicates that elicitation of downstream signaling does not involve a conformational change that precludes binding of AvrPto, as previously hypothesized. The correlations between phenotypes and variation generated by DNA shuffling paralleled natural variation observed between orthologs of Pto from Lycopersicon spp.

Blotting, Western↗

PubMed2003

Determining a detectable threshold of signal intensity in cDNA microarray based on accumulated distribution.

In microarray data mining, one of the key problems is how to handle weak signals. Based on a bent piecewise linear accumulated distribution generally found in the microarray data, a new detectable threshold finding method is proposed to filter genes with unreliable information in this paper. More reliable and reproducible data is produced for the subsequent data mining.

DNA, Complementary↗

PubMed2003

[Validation of cDNA microarray technology].

cDNA microarray is a technological approach that has the potential to globally measure changes in mRNA expression levels. Self-comparison experiments with the same kind of tissue and differential expression experiments with the different kinds of tissue have been done to verify the reproducibility and the accuracy of this technique. The parameter of the reliability and the reproducibility of the microarray data were analyzed by correlation coefficient (R), coefficient of variation (CV) and false positive rate (FPR) etc. Meanwhile, the error resource also has been inspected. These results showed that generally the correlation coefficient of data from this cDNA microarray system was more than 0.9, the coefficient of variation was about 15%, and the false positive rate was below 3%. The result proves the accuracy of the cDNA microarray data. Consistence rate (CR) was advanced here as a new parameter to evaluate the reproducibility of two replicate experiments. It has some advantages over correlation coefficient and coefficient of variation. The influence of some important factors in the experiments, such as different concentration of spotted DNA, mRNA and total RNA, different batches of slides and different processes of labeling, have been investigated by comparing the results. It was shown that most of the false position produced by the experiment system could be reduced by replicate experiments.

Humans↗

PubMed2002

Cloning, mapping, and characterization of the human Rab3C gene.

Rab proteins are small molecular weight GTPases that control vesicular traffic in eukaryotic cells. A subset of Rab proteins, the Rab3 proteins are thought to play an important role in regulated exocytosis of vesicles. During the large-scale sequencing analysis of a human fetal brain cDNA library, we isolated a cDNA clone encoding a novel Rab protein, which showed 99% identity with previously isolated bovine Rab3C at the amino acid level It contained four conserved motifs characteristic of the Rab3 family. RT-PCR analysis indicated that human Rab3C was expressed in the human brain, placenta, and lung. By mapping, we localized the Rab3Cgene to human chromosome 5q13. The Rab3C gene consisted of 6 exons spanning more than 310 kb of human genomic DNA. Rab3A, Rab3B, and Rab3D have been mapped to three different chromosomes, suggesting that they are not transcripts of the same gene.

Amino Acid Sequence↗