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Biomedical subjects

W X Chen

Publications and source records attributed to W X Chen.

At least 19 recordsLinked to original sources
PubMed2001

Rhizobium yanglingense sp. nov., isolated from arid and semi-arid regions in China.

A novel rhizobial group, cluster 9, defined in previous research [Tan, Z. Y., Wang, E. T., Peng, G. X., Zhu, M. E., Martinez-Romero, E. & Chen, W. X. (1999). Int J Syst Bacteriol 49, 1457-1469], was further characterized by determination of DNA base composition, whole-cell protein SDS-PAGE analysis, DNA-DNA hybridization, 16S rRNA gene sequencing and host specificity. These isolates were collected from the wild legumes Amphicarpaea trisperma, Coronilla varia and Gueldenstaedtia multiflora growing in arid and semi-arid regions in northwestern China. Isolates within cluster 9 grouped into a single cluster above a similarity level of 90.6% in a cluster analysis based on protein SDS-PAGE, and they were differentiated from defined rhizobial species. Comparative analysis of 16S rRNA gene sequences showed that isolate CCBAU 71623T, representing cluster 9, was most related to Rhizobium gallicum and Rhizobium mongolense. The DNA-DNA homologies were lower than 42.4% among cluster 9 and defined species, including R. gallicum and R. mongolense. These data indicated that cluster 9 was a unique genomic species. Isolates within this cluster could share their host plants. They could not nodulate Galega orientalis and Leucaena leucocephala and formed ineffective nodules on Phaseolus vulgaris. This group could also be differentiated from defined species by phenotypic characteristics. It is therefore proposed as a new species, Rhizobium yanglingense, with isolate CCBAU 71623 as the type strain.

China↗
PubMed2001

[Study on intergenera fusion of protoplasts from Rhizobium leguminosorum and Sinorhizobium xinjiangnesis].

Penicillin and chloromycetin were regarded as the sign of resistance to antibodies of R. leguminosorum USDA2370 and S. xinjiangnesis CCBAU110 respectively. Using the protoplast fusion technique, USDA2370 and CCBAU110 were successfully fused. Fusion hybrid can inoculate in the leguminous of parental strains respectively. There were apparent differences between parents and fusion hybrid in cell morphology, colony and pattern of whole-cell protein. The values of DNA homology between fusion hybrid and USDA2370 and CCBAU110 were 56.6% and 10.2% respectively.

Bacterial Proteins↗
PubMed2000

Sinorhizobium meliloti associated with Medicago sativa and Melilotus spp. in arid saline soils in Xinjiang, China.

Of 42 rhizobial isolates from Medicago sativa and Melilotus spp. growing in arid saline fields in Xinjiang, China, 40 were identified as Sinorhizobium meliloti by a polyphasic approach. However, diverse groups were obtained from these isolates in numerical taxonomy and SDS-PAGE of proteins. They could grow at pH 10.5 and were tolerant to 2.5-4.0% (w/v) NaCl.

Bacterial Proteins↗
PubMed2000

[Analysis of 16S rDNA sequence and DNA-DNA hybridization of rhizobia isolated from Indigofera sp].

Based on the previous studies on numerical taxonomy and SDS-PAGE of whole-cell protein, the rhizobia strains isolated from Indigofera sp. in loess plateau area of North-west China constituted a new cluster, the 16S rDNA sequence of representative strain SHL042 was tested, and the phylogenetic tree was produced. In this tree, the strain SHL042, R. tropici A, R. tropici B, R. leguminosarum, R. etli, R. hananesis, R. mongolense and R. gallicum constituted a branch of phylogenetic. Within this branch, the similarity values of 16S rDNA sequences were 95.4%, 95.5%, 96.3%, 95.8%, 96.3%, 97.9% and 97.7% respectively. The values were more than 95%. This indicated that these species should belong to the same genus. The values of DNA homology in the new cluster were all more than 80%, but the values between SHL042 and the strains of these species were less than 50%. Thus, the strain SH714 represented a new rhizobia species.

Base Sequence↗
PubMed2000

[Detection of Epstein-Barr virus and human papillomavirus in sinonasal malignant neoplasms].

OBJECTIVE: To investigate the existance of Epstein-Barr virus (EBV) and papilloma virus(HPV) in sinonasal malignant neoplasms. METHOD: EBV and HPV (including HPV6,11,16,18,33) gene were detected in paraffin-embedded tissues with polymerase chain reaction(PCR) from 32 cases of sinonasal malignant neoplasms. RESULT: EBV was detected in 12(37.5%), HPV in 21(65.6%); The coinfection of EBV and HPV was found in 6 cases with stage III-IV by TNM; 10 cases of nasal polyps contained neither EBV nor HPV. CONCLUSION: Like HPV, there may be relationship between EBV and sinonasal malignant neoplasms. The coinfection of EBV and HPV is related to stage III-IV by TNM of sinonasal malignant neoplasms.

Adult↗
PubMed1999

Diversity of rhizobia associated with Amorpha fruticosa isolated from Chinese soils and description of Mesorhizobium amorphae sp. nov.

Fifty-five Chinese isolates from nodules of Amorpha fruticosa were characterized and compared with the type strains of the species and genera of bacteria which form nitrogen-fixing symbioses with leguminous host plants. A polyphasic approach, which included RFLP of PCR-amplified 16S rRNA genes, multilocus enzyme electrophoresis (MLEE), DNA-DNA hybridization, 16S rRNA gene sequencing, electrophoretic plasmid profiles, cross-nodulation and a phenotypic study, was used in the comparative analysis. The isolates originated from several different sites in China and they varied in their phenotypic and genetic characteristics. The majority of the isolates had moderate to slow growth rates, produced acid on YMA and harboured a 930 kb symbiotic plasmid (pSym). Five different RFLP patterns were identified among the 16S rRNA genes of all the isolates. Isolates grouped by PCR-RFLP of the 16S rRNA genes were also separated into groups by variation in MLEE profiles and by DNA-DNA hybridization. A representative isolate from each of these DNA homology groups had a separate position in a phylogenetic tree as determined from sequencing analysis of the 16S rRNA genes. A new species, Mesorhizobium amorphae, is proposed for the majority of the isolates, which belonged to a moderately slow- to slow-growing, acid-producing group based upon their distinct phylogenetic position, their unique electrophoretic type, their low DNA homology with reference strains representing the species within the genus Mesorhizobium and their distinct phenotypic features. Strain ACCC 19665 was chosen as the type strain for M. amorphae sp. nov.

Base Composition↗
PubMed1999

Characterization of bacteria isolated from wild legumes in the north-western regions of China.

Nodule isolates from 11 species of wild legumes in north-western China were characterized by numerical taxonomy, PCR-based 16S rRNA gene RFLP and sequence analyses, DNA-DNA hybridization, restriction patterns of nodDAB and nifH genes, and symbiotic properties. Based on the results of numerical taxonomy, most of the 35 new isolates were grouped into five clusters (clusters 7, 9, 12, 14 and 15). Clusters 7 and 12 were identified as Mesorhizobium amorphae and Agrobacterium tumefaciens, respectively, based on their high DNA homologies with the reference strains for these species, their 16S rRNA gene analysis and their phenotypic features. Results of 16S rDNA PCR-RFLP analysis showed that cluster 9 belonged to Rhizobium. Clusters 14 and 15 were identified as Mesorhizobium based on their moderately slow-growing, acid-producing characters and the high similarity of their 16S rDNA PCR-RFLP patterns to those of Mesorhizobium species. These two clusters were genomic species distinct from all described species based on analysis of DNA relatedness within this genus. The isolates in cluster 12 (Agrobacterium tumefaciens) failed to nodulate their original host and other selected hosts and they did not hybridize to nif or nod gene probes. The possibility of opportunistic nodulation of these isolates is discussed. Identical restriction patterns were obtained in the nif or nod gene hybridization studies from the three isolates within cluster 15, which were isolated from the same host species. The isolates from different host plants in each of clusters 9 and 14 produced different nodDAB RFLP patterns, but similar nifH RFLP patterns appeared (one band for each isolate). Different patterns were observed among different clusters from both the nod and nif gene hybridization studies. Crossnodulation was recorded among the isolates and the host plants in the same cluster and promiscuous properties were found among some of the hosts tested.

Bacteria↗
PubMed1998

Biological behavior of plasmid in Rhizobium sp. strain S25 from Tephrosia candida.

Rhizobium sp. strain S25 was isolated from the nodule on Tephrosia candida in Hainan Province, China. The strain showed high stress tolerance. The plasmid profile of strain S25, examined by the Eckhardt procedure, indicated that the strain harbors only one plasmid with an estimated size of 150 kb. The plasmid was shown to carry nod and nif genes by hybridization with probes of nodABC and nifHDK genes. Plasmid curing was carried out using the Bacillus subtilis sacB to generate derivatives of strain S25. In comparison with the parent strain S25, the cured derivative lost its ability to nodulate the host plant. Loss of the plasmid reduced significantly the strain's tolerance to acid, nitrous, and multiple antibiotics. The properties of the cured strain also indicated that the plasmid was involved in carbon and nitrogen metabolism. Reintroduction of the plasmid from S25 in the cured derivative restored its original biological phenotypes.

DNA, Bacterial↗
PubMed1998

Rhizobium huautlense sp. nov., a symbiont of Sesbania herbacea that has a close phylogenetic relationship with Rhizobium galegae.

The nitrogen-fixing rhizobial symbionts of Sesbania herbacea growing in the nature reserve at the Sierra de Huautla, Mexico, were isolated and characterized. All 104 isolates together with the type strain for Rhizobium galegae, HAMBI 540T, had similar 16S rRNA genes as revealed by PCR-RFLP analysis. Similarity in the sequences of the 16S rRNA genes placed the isolates on a phylogenetic branch shared with R. galegae. Among 66 randomly selected isolates, three closely related electrophoretic alloenzyme types (ETs) were identified, which were distinct from 10 ETs distinguished among 23 strains of R. galegae. A new species Rhizobium huautlense, represented by the Sesbania isolate SO2T, is proposed based upon low estimates of DNA relatedness between our chosen type strain and the type strains for the other species, the dissimilarity of the nucleotide sequence of the 16S rRNA genes, and their distinct ETs compared with R. galegae. The description of R. huautlense is significant because in the reconstruction of the phylogeny at R. huautlense there was a shift in the node of the branch of Agrobacterium vitis relative to that of R. galegae. The revised phylogenetic tree would tend to indicate common ancestry between R. galegae and Rhizobium leguminosarum.

Base Sequence↗
PubMed1997

Rhizobium hainanense sp. nov., isolated from tropical legumes.

A fast-growing rhizobial group isolated from leguminous plants in Hainan Province, a tropical region of China, is proposed as a new Rhizobium species on the basis of 16S rRNA gene sequencing. DNA-DNA hybridization, and phenotypic characterization. This new species belongs to the phylogenetic branch which includes Rhizobium leguminosarum. We propose the name Rhizobium hainanense sp. nov. for this species. The strain CCBAU 57015 (166) is the type strain; it has been deposited in the culture collection of Beijing Agricultural University, People's Republic of China.

China↗
PubMed1997

Phylogenetic and genetic relationships of Mesorhizobium tianshanense and related rhizobia.

The genetic and phylogenetic relationships for strains of Mesorhizobium tianshanense and its relatives were compared by an analysis of the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins, DNA-DNA hybridization, and full 16S rRNA gene sequencing. The strains of M. tianshanense formed a cluster which was distinct from those of other rhizobium species in the clustering analysis of SDS-PAGE. DNA-DNA relatedness between A-1BS (type strain of M. tianshanense) and the type or reference strains for Mesorhizobium loti, M. huakuii, M. ciceri, M. mediterraneum, and cluster U, an unnamed rhizobial group, ranged from 4.4 to 43.8%. The phylogenetic analysis based on the 16S rRNA gene sequences showed that M. tianshanense was closely related to the Mesorhizobium phylogenetic branch and could be distinguished from the other four species in this branch. These results further confirmed that these bacteria constitute a distinct rhizobial species.

Bacterial Proteins↗
PubMed1997

Repair of thyroid cartilage defect with bone morphogenetic protein.

The object of this research was to investigate whether a thyroid cartilage defect can be repaired by newly formed bone induced by bovine bone morphogenetic protein (bBMP). Bilateral thyroid cartilage defects measuring 0.5 x 0.6 cm were created in 25 adult rabbits. Experimental defects were implanted with ceramic bone particles combined with bBMP, or in controls, without bBMP. The animals were painlessly killed at 2, 4, 8, 12 and 16 weeks after implantation. The tissue responses were analyzed by routine histologic examination. An increase in the amount of new bone was observed in the interval from 4 to 12 weeks, and the defects were completely filled with new bone at 16 weeks, in contrast to a minimal new cartilage formation at the defect edges in controls. The results indicate that cartilage defects can be repaired by inducing new bone formation from mesenchymal cells in both perichondrium and muscular fascia.

Adult↗
PubMed1995

Isolation of differentially expressed sequence tags from steroid-responsive cells using mRNA differential display.

Transcriptional control of steroid-regulated gene networks by nuclear receptor proteins results in the coordinate expression of a limited number of target genes. Although much is known about the structure and function of steroid receptors, relatively few cell-specific steroid-regulated genes have been isolated and characterized. In this paper we describe results using mRNA differential display reverse transcriptase PCR (DDPCR) to identify and isolate short cDNA sequence tags from thymocyte and prostate cells under various hormone conditions. Using this technique we have isolated several differentially expressed sequence tags (DESTs) from the mouse thymocyte cell line WEHI 7.2. Two of these DESTs, GIG10 and GIG18, are rapidly induced by dexamethasone within 2 h of treatment. GIG10 is a novel sequence and GIG18 is the mouse homologue of a human expressed sequence tag isolated from activated B lymphocytes. We also used DDPCR to isolate DESTs from androgen-modulated rat ventral prostate tissue, one of which we characterized and found to correspond to the 3' end of prostatic spermine binding protein mRNA, a known androgen-regulated gene. Modifications of the original DDPCR protocol, which we found can potentially decrease the frequency of isolating false-positive DESTs, are described and the merits of DDPCR, relative to other differential cDNA cloning strategies, are discussed.

Androgens↗
PubMed1993

[The study and protection of mercury contamination in silver amalgam on patient's safety]

The mercury concentration of oeal gas was determinded.Comparison were made on 2 groups consisting of silver amalgam covered cases(n=15) and uncovered cases (n=29) immediately by vaseline after filling silver amalgam,and the concentration of Hg before polishing old silver amalgam and after polishing (n=10),The result showed there are very significant difference (P<0.01).The surface area of filling mercury amalgam did not relate to Hg concentration.The larger volume of polishing old mercury amalgam was,the higher concentration of Hg was.In addition,mercury concentrations of air in four consulting rooms before ventilation were higher than 3.1-6.6 times national hyienic standard,however,it was reduced to 1.2-2.1 times after ventilation.

Journal Article↗
PubMed1993

['Rotary-door' sternohyoid myocutaneous flap for laryngotracheal reconstruction in clinical and experimental studies].

Six dogs were made a 2.5 x 1.5cm tracheal defect in the cervical trachea. The tracheal defect was closed with a combined rotary-door sternohyoid myocutaneous flap and costal cartilage graft. One dog died from infection at the 5th postoperative day. Five dogs were completely healthy survival and killed up at 3-14 months after the surgery for postmortem examination. The sternohyoid myocutaneous flap was found to be incorporated completely into the defect. No cicatricial stricture were found. The tracheal lumen was widely patent. Histologic studies showed that the epithelium of myocutaneous flap nearly completely became ciliated columnar epithelium at the 14th postoperative months. Seventeen patients were included in this study. Sixteen were reconstructed for laryngotracheal stenosis and one for immediate reconstruction after conservative laryngeal surgery for malignant transformation of laryngeal papilloma. All patients have been successfully decannulated and have normal exercise tolerance. This study demonstrated the procedure is a useful and reliable technique for severe laryngotracheal stenosis and for reconstruction after conservative laryngeal surgery.

Adolescent↗
PubMed1993

Correlation of serum cholesteryl ester fatty acid composition with susceptibility to atherosclerosis in different species.

Fatty acid composition of serum cholesteryl esters (CEs) in Chinese and 9 species of laboratory animals was analysed. Polyunsaturated fatty acids (PUFAs) were the predominant fatty acids in CEs. A close correlation between PUFAs to saturated fatty acids ratio (P/S) in CEs and susceptibility to atherosclerosis (AS) was observed in different species. Animals with high P/S such as mice (13.0), tree shrews (9.0) and rats (9.0) were AS-resistant, and those with low P/S such as rabbits (2.9) were susceptible to AS. The P/S value in men (4.9) was between those of the above two kinds of animals, and similar to those of pigs (4.2) and monkeys (3.7). Marked physiological significance of the rich PUFAs in CEs may be expected. As the main constituent of low density lipoprotein (LDL), CEs may provide PUFAs for cells efficiently via LDL receptor. It is assumed that PUFAs in CEs may play an important role in the metabolism of cholesterol and the development of AS by regulating LDL receptor activity, platelet function and prostaglandin metabolism.

Adult↗
PubMed1993

Serum cholesterol determined by liquid chromatography with 6-chlorostigmasterol as internal standard.

We describe an accurate and precise method for determining serum cholesterol by high-performance liquid chromatography (HPLC). After addition of 6-chlorostigmasterol as internal standard, serum is treated with alcoholic potassium hydroxide. Subsequently the cholesterol and internal standard are extracted from the mixture into n-hexane and then derivatized to phenylurethanes for measurement by HPLC with ultraviolet detection. The effective chromatographic separation and the use of an appropriate internal standard make this procedure free from interferences by other serum sterols and precise. The mean cholesterol concentration in Standard Reference Material (SRM) 909 (human serum) assayed by this procedure (4.346 mmol.g-1 x L-1) agreed well with the value assigned by the National Institute of Standards and Technology (4.359 mmol.g-1 x L-1). Within-run and total CVs were 0.56% and 0.78%, respectively. Therefore the performance of this procedure is sufficiently good to allow its use as a candidate reference method for serum cholesterol determination.

Cholesterol↗