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Biomedical subjects

W Chen

Publications and source records attributed to W Chen.

At least 379 records · Page 21Linked to original sources
PubMed2000

[Phylogenetic analysis of two rhizobia new groups].

On the basis of numerical taxonomy, SDS-PAGE whole-cell protein analysis, 16S rDNA PCR-RFLP and DNA-DNA hybridization, the full length of 16SrDNA of two strains (XJ96060, XJ96408) were sequenced and compared with the 16S rDNA sequences of other members of the alpha 2 subclass of the Proteobacteria available from GenBank. An unrooted tree was produced to determine the phylogenetic relationships of two groups. The results showed that all strains were clustered into 6 branches, they were Sinorhizobium, Mesorhizobium, Agrobacterium-Rhizobium, Bradyrhizobium. Rhizobium, Azorhizobium. Group 1, 2 fell into Sinorhizobium branch.

Base Sequence↗
PubMed2000

[Cloning and expression of the gene encoding maltoologosyl trehalose synthase from Sulfolobus shibatae in E. coli].

2.2 kb DNA fragment encoding a novel enzyme, maltooligosyl trehalose synthase (MTSase) was amplified from Sulfolobus shibatae by using PCR technique. The amplified 2.2 kb DNA fragment was inserted into an expression vector, pBV220, to yield the recombinant plasmid pSBGT1. MTSase gene in pBSGT1 was expressed in E. coli. The molecular weight of expressed MTSase detected by SDS-PAGE was about 74 kD, which is conformed with that deduced from nucleotide sequence. The expressed MTSase protein accounted for about 4.4% of the total cell protein. The MTSase from transformants containing pBSGT1 is capable of decreasing DE value, forming non-reducing or less-reducing saccharides when allowed to act on reducing partial starch hydrolysates.

Cloning, Molecular↗
PubMed2000

[Cloning and expression of the gene encoding novel alpha-amylase from Sulfolobus shibatae in E. coli].

A novel alpha-amylase gene was amplified from Sulfolobus shibatae by using PCR technique. The amplified 1.7 kb DNA fragment was inserted into an expression vector pBV220 to yield the recombinant plasmid pSBAM. The novel alpha-amylase gene in pSBAM was expressed in E. coli. The production of the novel alpha-amylase activity reached over 8 units/100 mL of the culture. The molecular weight of this enzyme was about 61 kD by SDS-PAGE. The expressed novel alpha-amylase protein in E. coli DH5 alpha accounted for about 20% of the total protein in the recombinant cell. The cooperative action of the novel alpha-amylase and the maltooligosyltrehalose synthase from Sulfolobus shibatae was investigated and trehalose was detected by using HPLC analysis when using amylose and partial starch hydrolysates as substrates.

Cloning, Molecular↗
PubMed2000

[Cloning of a new catechol 1,2-dioxygenase gene (tfd C) from Plesiomonas and its expression in the E. coli].

A new catechol-1,2-dioxygenase gene (tfd C) was cloned from the Plesiomonas using the PCR method. Primers were designed according to the reported sequence of Catechol-1,2-dioxygenase (C120) gene from Alcaligenes eutroplus. The amplified fragment contained a 765 bp open reading frame (ORF), encoding a protein of 255 amino acids. The new tfd C gene shared a high homology with the one cloned from Alcaligenes eutroplus, showing only one base difference at 693 site (C-->A) and consequently one amino acid difference at 228 site (P-->T). The ORF was cloned to the plasmid pBluescriptII KS, which was transferred to E. coli JM109 and a positive clone, pBt2G, was then selected. A significant activity of C120 was detected in the positive clone. When the ORF was cloned to the plasmid pET-30a, which was transferred to E. coli BL21(DE3) plysS, the expected 33 kD protein was detected from a positive clone, pET30A, by SDS-PAGE. The C120 is a key enzyme in degrading aromatic pollutants in the environment. In order to use plants to degrade aromatic pollutants, the gene will be introduced into the turfgrass. To express the gene properly in plants, its translation initiation codon was modified from GTG to ATG. A similar activity of C120 was obtained following the modification.

Amino Acid Sequence↗
PubMed2000

[Studies on sanH and sanI--genes related to nikkomycin biosynthesis of Streptomyces ansochromogenes].

A 7.0 kb DNA fragment was cloned by reverse genetics, which was located in the gene cluster of nikkomycin biosynthesis of Streptomyces ansochromogenes. Besides sanF--a gene related to nikkomycin biosynthesis of S. ansochromogenes, the sequence of a 2.2 kb BglII DNA fragment upstream sanF was determined. This 2.2 kb DNA fragment cointains two complete open reading frames (ORF). ORF1 consists of 1233 base pairs, ORF2 consistis of 195 base pairs, and they encode proteins with 410 amino acids and 64 amino acids respectively, which were designated as sanH and sanI. In search of databases, the deduced products of sanH has 46% amino acid identities and 62% amino acid similarities in comparison with the cytochrome P450 of Streptomyces griseolus, and the deduced protein of sanI has 56% amino acid identities and 70% amino acid similarities with the ferredoxin of S. griseolus. The function of sanH gene was studied using strategy of gene disruption, and the result showed that the disruption of sanH didn't influence nikkomycin biological activity in S. ansochromogenes.

Amino Acid Sequence↗
PubMed2000

[The morphological variation in species of Anemarrhena asphodeloides].

In this paper, morphological studies modified the description in some literatures. The features of Anemarrhena asphodeloides Bunge growing in different districts vary. Carefully observation under Scanning Electron Microscope (SEM) showed that surface characters of leaves at the same developing stage, which were collected from cultivated plants formerly growing in different districts, vary greatly but regularly. It was found that the morphology of pollen grains were similar.

Anemarrhena↗
PubMed2000

[Surgical techniques to deal with lens nucleus' fragment of posterior capsular rupture during the phacoemulsification].

OBJECTIVE: To investigate some surgical techniques in dealing with a impending dropped nucleus when posterior capsular rupture during the phacoemulsification. METHODS: The postoperative results of 18 cases (18 eyes) whose posterior capsular of lens ruptured with a impending dropped nucleus during the phacoemulsification were studied retrospectively. Three surgical techniques to prevent lens nucleus' fragments dropping into the vitreous cavity were applied. They are consecutive phacoemulsification with lower flowing rate and lower irrigation, injection of viscoelastic substance with high elasticity and anterior segment vitrectomy with no irrigation. The follow-up was 12-24 months (average, 18.2 months). RESULTS: Except for a special case, no lens nucleus' fragments dropped into the vitreous cavity. Posterior chamber intraocular lens(IOL) was implanted primarily in all cases (18 eyes). Best corrected visual acuity was above 0.5 in 15 eyes (83.3%). The main complications included corneal edema and cystoid macular edema. CONCLUSION: With safety, effectiveness and less complications, these three surgical techniques are suitable to deal with different types of impending dropped lens nucleus' fragments during the phacoemulsification. It is advisable to apply these techniques in clinical practice.

Adult↗
PubMed2000

[Descending cervical mediastinitis: report of 15 cases].

OBJECTIVE: To analyze the cause, diagnosis and treatment of descending cervical mediastinitis. METHODS: Fifteen cases of descending cervical mediastinitis, which were treated from January 1985 to December 1997, were retrospectively reviewed. There were 10 males and 5 females, ranging in age from 2.5 to 82 years. RESULTS: The cause of descending cervical mediastinitis included odontogenic infection, suppurative tonsillitis, suppurative otitis media (cholesteatoma) complicating Mouret abscess, pharyngeal injury by foreign body and esophageal perforation. Different ways of drainage were adopted. Twelve cases were cured and three died. CONCLUSION: The key to successful management of descending cervical mediastinitis is early recognition, prompt and effective surgical drainage and appropriate antibiotics.

Adolescent↗
PubMed2000

The relationship between the N-glycosylation of acetylglucosaminyltransferase V and its activity.

OBJECTIVE: The goal of this paper is to investigate the relationship between the N-glycosylation of acetylglucosaminyltransferase V (GlcNAcT-V) and its activity and to know which site among the 6 N-glycosylation sites in the GlcNAcT-V gene is the most important. METHODS: Wild type of GlcNAcT-V was transfected into COS-7 cells and its activity was measured 48 h later. The first site (Asn 110) was mutated with site-directed mutagenesis and transfected into COS-7 cells. RESULTS: It was found that after the cells were added tunicamycin (TM, 1 microg/ml), the activity was 11.7% of the wild type. The activity of the cells with mutating GlcNAcT-V was about 12.0% of the wild type. RT-PCR showed that there was no significant change in mRNA expression among the three groups. CONCLUSION: The N-glycosylation is important for its activity. Our results suggest that the N-linked carbohydrates on GlcNAcT-V are required for the posttranscriptional activity of the enzyme.

Animals↗
PubMed2000

[Multiple types of chemokines expressed in mouse thymic stromal cell lines].

OBJECTIVE: To investigate semi-quantitative mRNA expression of SDF-1 alpha, IP-10, KC, MCP-1, and RANTES in thymic stromal cell lines of MTEC1, MTDC, D2SC, MTECB, TEC 1C8, TNC as well as in the primary thymic stromal cell cultures. The chemotactic activities of recombinant SDF-1 alpha, IP-10, MCP-1, and RANTES to mouse thymocytes were detected. METHODS: Using beta-actin as internal control, the mRNA of the chemokines listed above were amplified for 30 cycles with RT-PCR. The amplified products were observed by agarose electrophoresis, and each band was analyzed with integrated optical density. With the method of Boyden chamber assay, the chemotactic activities of recombinant SDF-1 alpha, IP-10, MCP-1, and RANTES were detected to thymocytes, and the chemotactic indices were calculated. RESULTS: The expression intensity of SDF-1 alpha, IP-10, KC, MCP-1, and RANTES varied from each other in the stromal cell lines detected. The PCR products of SDF-1 alpha and MCP-1 were not seen in D2SC or TEC 1C8, nor was the band of KC observed in TEC 1C8 either. The chemotactic indices of recombinant SDF-1 alpha, IP-10, MCP-1, and RANTES to thymocytes were 3.7, 4.5, 6.2, and 2.6, respectively. CONCLUSIONS: Different thymic stromal cell lines could express different types of chemokines with different expression intensities. To thymocytes, recombinant SDF-1 alpha, MCP-1, and IP-10 showed strong chemotactic activities, while the chemotactic activity of RANTES was very weak.

Animals↗
PubMed2000

[High level expression of foreign gene via multiple joined operons and a new concept on the restricted constant of total amount of plasmid DNA per cell of Escherichia coli].

OBJECTIVE: To examine the feasibility of linking operons in tandem to enhance expression of heterologous genes in Escherichia coli and to clarify the potential control mechanism of the total plasmid DNA amount in each host cell. METHODS: Two series of expression plasmids, CW11 and CW12, containing 1 to 4 and 1 to 3 heterologous gene operon(s), respectively, were constructed. The molecular size of the CW11 series varied from 5.47 kb to 12.26 kb in 2.25 kb increments. The CW12 series varied from 5.40 kb to 9.72 kb in 2.16 kb increments. Protein expression was analyzed via SDS-PAGE and laser scanning. Plasmid copy number was determined by incorporation with 3H-TdR([3H]-thymidine). RESULTS: No influence of the tandem-joined operons on host growth and plasmid stability was observed. Upon induction, the desired protein accumulated in the CW11 series were 46.0%, 54.8%, 56.1%, and 60.1% of total cell protein. In the CW12 series, the yields were 33.5%, 44.0%, and 47.1% of total cell protein. With increasing size, however, plasmid copy number decreased. Further calculation showed that the total amount of plasmid DNA per cell is restricted to some extent. There seems exists a mechanism to control the maximum level of total plasmid DNA amount in each host cell. CONCLUSIONS: Increasing the target gene dosage by tandem linking of operons enhanced the expression level of a desired protein. Although the size (kb) and the copy number of each plasmid are negatively interrelated, it seems that as for certain plasmids, their total DNA amount per cell is a restricted constant for a specific E. coli strain under identical incubation condition.

Cloning, Molecular↗
PubMed2000

[Influence on luminescence of Tb o-aminobenzolate complexes by second ligand].

Two Tb o-aminobenzolate complexes with different second ligands (phenanthroline and triphenyl phasphine oxide) were synthesized. Their structures and fluorescent properties were investigated by fluorescence spectroscopy and FTIR spectroscopy. The results indicate that the second ligand affected on the complexes luminescence by changing its structure.

Chelating Agents↗
PubMed2000

[Spectroscopic properties of 7-hydroxyquinoline in polymeric matrices].

In this paper, the absorption and fluorescence spectra of 7-Hydroxyquinoline (7HQ) in the copolymer of methyl methacrylate (MMA) and methacrylic acid (MAA) monomers were observed. The influence of different matrices on the species of 7HQ and the excited state proton transfer effect were investigated. The results showed that, as the number of carboxylic group in the matrix was increased, the relative contents of different species of 7HQ should be changed and the excited state proton transfer effect of 7HQ was enhanced.

Adsorption↗
PubMed2000

[Comparison between two spectral lines for the determination of Pb].

This article introduces the comparison between two sensitive spectral lines for the determination of Pb. The result proved that the sensitivity of 217.0 nm spectral line was increased by at least one time and the other indices also approached those of 283.3 nm spectral line. We concluded that it could be used to hygienic detection.

Environmental Pollution↗
PubMed2000

[Study on the stability of N-alkyl-N'-(sodium p-aminobenzenesulfonate) thiourea].

In this work, the stability of 13 kinds derivative of thiourea were studied by the UV absorption spectra and IR spectra of thiourea compounds in acidic medium at pH = 4.00, neutrality medium at pH = 7.00, basic property medium at pH = 10.00, under the influence of diffeveut store time, oxygen and sun light. Their structures were discussed and the changing rules of stability were developed.

Anti-Bacterial Agents↗