PubMed Health⌕ Search

Biomedical subjects

W J Xu

Publications and source records attributed to W J Xu.

9 recordsLinked to original sources
PubMed2003

Molecular diversity and multilocus organization of the parental lines used in the International Rice Molecular Breeding Program.

One hundred and ninety three parental lines obtained from 26 countries for an international rice molecular breeding program were evaluated using 101 well-distributed simple sequence repeat (SSR) markers. An overall genetic diversity of 0.68 and an average of 6.3 alleles per locus were revealed, indicating a high level of genetic variation in these lines. Cluster analysis of the 193 accessions showed three major groups and nine subgroups. Group I corresponded to the classical indica subspecies, whereas groups II and III belong to the japonica subspecies. Indica and japonica differentiation accounted for only 6.5% of the total variation in the entire sample and 93.5% was due to within-subspecies diversity. Differentiation among eco-geographic regions accounted for 24% of the diversity within the subspecies. Larger amounts of the eco-geographical differentiation were resolved within japonica than within indica. The largest indica-japonica differentiation based on the single locus level was detected by markers on chromosomes 9 and 12, while the smallest differentiation was detected by markers on chromosomes 4 and 8. Furthermore, genetic differences at the single-locus and two-locus levels, as well as components due to allelic and gametic differentiation, were revealed between indica and japonica and among the main geographic regions. The multilocus analysis in genetic diversity showed a higher proportion of variation caused by predominant non-random associations of different loci within and among the classified subspecies and geographic subdivisions. The results suggest that selection for eco-geographical adaptation on multilocus associations was largely responsible for the maintenance of the extensive variation in the primary gene pool of rice.

Alleles↗
PubMed2001

[Analysis and separation of chromium(III) oligomers by ion chromatography].

A method of analyzing chromium(III) oligomers in aqueous solution by means of TSK-Gel ion exchange analytical column and diode array detector was developed. The effects of determination conditions, elution and ionic strength on analysis were investigated carefully and the analytical condition was optimized. The samples were separated for 10 min by using TSK-Gel SP-5PW(75 mm x 7.5 mm i.d., 10 microns) as column, 3 mol/L NaClO4-0.03 mol/L HClO4 as mobile phase, and detected at the wavelength of 200 nm. The method was simple, rapid and repeatable. This method was also used to determine the concentration of each fraction under various conditions of preparing chromium(III) oligomers and rendering the optimized preparation parameters.

Chromatography, Ion Exchange↗
PubMed2000

[Micro determination of acrylonitrile in ambient air by gas chromatography].

Acrylonitrile in ambient air was collected by Tenax GC and then thermo-desorbed. It was separated on GDX-502 chromatographic column from other pollutants and determined by flame-ion ization detector. The minimum detectable concentration was 0.01 mg/m3 when 2 L ambient air was collected. The recoveries were 85.6%-105.4% and RSDs were 4.5%-6.2%.

Acrylonitrile↗
PubMed1999

[Effect of removable partial denture(RDP) generated occlusal interference on masticatory efficiency-A preliminary study]

OBJECTIVE:This study was primarily aimed to observe the effect of RPD-generated occlusal interference on masticatory efficiency.METHODS:In this study,masticatory performances of thirty-six patients treated with removable partial dentures were assessed by peanut-light absorption test before and after occlusal adjustment was performed.Then comparing the differences of masticatory efficiency when occlusal interferences on dentures were present or eliminated.RESULTS:Patients who received occlusal adjustment made significant improvement in their masticatory efficiency (P<0.01). Occlusion appeared to do directly influence chewing ability.CONCLUSION:The results showed that occlusal factor is one of the major factors responsible for denture quality and health of stomatognathic system. Occlusal adjustment is important and necessary in dental prosthesis.

Journal Article↗
PubMed1997

Regulation of tPA in endothelial cells exposed to cyclic strain: role of CRE, AP-2, and SSRE binding sites.

We have previously reported that exposure of cultured bovine aortic endothelial cells (EC) to 10% average strain resulted in an increase in tissue plasminogen activator (tPA) mRNA, immunoreactive tPA protein, and tPA activity in the medium. The present study was designed to examine the regulation of tPA gene expression in EC by cyclic strain. We performed a functional analysis of the tPA promoter by transfecting bovine aortic EC with a 1.4-kilobase (kb) construct of the human tPA promoter coupled to chloramphenicol acetyltransferase. We found that subjecting the EC to 10% average strain (and not 6% average strain) resulted in a 2.6-fold increase in activity of the 1.4-kb tPA promoter by 4 h. Analysis of deletion mutants of the promoter transfected into EC demonstrated a 60% drop-off in activity between position -145 and -105. Deoxyribonuclease I protection analysis of the segment downstream of position -196 suggested involvement of activator protein-2 (AP-2) and adenosine 3',5'-cyclic monophosphate-responsive element (CRE)-like binding sites, which was confirmed by electrophoretic mobility shift assays. Site-directed mutants of either the AP-2 or CRE-like regions resulted in a 65% decrease in activity compared with the wild type. Double mutations abolished basal transcription and any strain-induced activity. A shear stress responsive element (SSRE) binding site is present at -945, but site-directed mutants did not show any drop in activity compared with wild type by cyclic strain. These studies demonstrate that cyclic strain regulates tPA gene transcription in bovine aortic EC and that this transcriptional activation is dependent on factors that are similar to those activated with phorbol ester.

Animals↗
PubMed1993

Evaluation of the contingent replication assay (CRA) and its application to the study of the general transcription initiation factor, TFIIF.

The Contingent replication assay (CRA) is a rapid assay for the screening and isolation of cDNAs by protein-protein or protein-DNA interactions in mammalian cells. The method has been shown to enrich a plasmid containing a cDNA encoding the bacterial replication-related protein, R6K, from a mixture of two plasmids. In this report we present data illustrating the sensitivity and selectivity of the method. Using the small subunit of TFIIF (Rap30) as a target, we demonstrate the enrichment of a clone encoding the large subunit, Rap74, from a cDNA library. Additional cDNA clones including human Rap30 and an anonymous cDNA clone homologous to members of the human cdc2 kinase family were enriched and isolated by a modified screening approach. The structure of these additional clones suggest that the CRA enriches for products that interact not only directly with the target protein but also through bridging by endogenous proteins.

Animals↗
PubMed1993

[The treatment of intracranial germinomas].

31 patients with intracranial germinomas received radiotherapy. Of thom, 15 were operated on directly and 7 by CSF shunt, 6 by external ventricular drainage. After radiotherapy, symptoms were improved in 93.5% of the patients. 16 patients were followed up for 2 to 14 years, their results were satisfactory. We consider that initial treatment of germinoma mainly by radiotherapy may be more appropriate, as the tumors highly radiosensitive. If hydrocephalus developed, combined external ventricular drainage with radiotherapy should be performed, and the shunting operation may be avoided because of potential peritoneal seeding of germinomas. For recurrent germinoma, radiotherapy combined with chemotherapy may be useful.

Adolescent↗
PubMed1991

[Effects of morphine on cutaneous blood flow and substance P release evoked by electric stimulation of rat sciatic nerve].

Electric stimulation of the rat sciatic nerve containing sensory afferent fibers produced an increase in cutaneous blood flow. Morphine (10, 30 mumol.kg-1 ia infusion) inhibited the electric stimulation-induced increase of the cutaneous blood flow velocity, and its effect was antagonized by naloxone (2 mg.kg-1 ip). In order to investigate the cause of this effect, we determined immunoreactive substance P (iSP) levels in the sc perfusate of hind paw. We found that electric stimulation of the sciatic nerve led to a significant increase of iSP release into the sc perfusate. Morphine (30 mumol.kg-1 ia infusion) inhibited the electrical stimulation-induced release of iSP, and this effect was completely antagonized by naloxone (2 mg.kg-1 ip). These result suggest that morphine-induced inhibition of the electrical stimulation-evoked increase in cutaneous blood flow could result from inhibition of the release of SP from peripheral sensory nerve endings.

Animals↗