Biomedical subjects

Xin Xu

Publications and source records attributed to Xin Xu.

At least 91 records · Page 5Linked to original sources

PubMed2005

[Construction and expression of the major outer membrane protein PI of Neisseria gonorrhoeae in Escherichia coli].

OBJECTIVE: To construct Neisseria gonorrhoeae major outer membrane protein PI gene recombinants for expression of the target protein in E. coli. METHODS: Four clinic isolates of Neisseria gonorrhoeae were collected, and then the genome DNA of these strains was extracted. The gene encoding for PI of Neisseria gonorrhoeae was amplified by PCR, inserted into the cloning vector pBS-T; the recombinant plasmids pBS-T-PI-NG were constructed and sequence analysis was performed. Then PI gene fragments were inserted into expression vector pET30b to form pET30b-PI-NG recombinants. The PI protein expression was induced by adding IPTG in the inocula. The expressed proteins were analyzed by SDS-PAGE. RESULTS: The pET30b-PI-NG expression recombinants for four clinic isolates of Neisseria gonorrhoeae were constructed successfully; three of the four expression recombinants were expressed successfully. CONCLUSION: The expressed PI protein will be applied in the further research for PI antigenicity and immunological activity. This will be very helpful for the further construction of preventive vaccines directed against Neisseria gonorrhoeae infection.

Bacterial Vaccines↗

PubMed2005

[Cloning and expression of superoxide dismutase gene from Deinococcus radiodurans in E. coli].

OBJECTIVE: To construct expressing recombinant of Mn-SOD of Deinococcus radiodurans and express the target protein in E. coli BL21(DE3). METHODS: SOD gene was amplified by PCR from genomic DNA of Deinococcus radiodurans and inserted into expression plasmid pET-30a(+) to create the recombinant pET-SOD. After being analyzed by the restriction endonuclease, the plasmid was transformed into E. coli BL21(DE3), and the recombinant protein was expressed after induction by the isopropyl-beta-D-thiogalactopyranoside (IPTG) and was analyzed with SDS-PAGE. RESULTS: The recombinant plasmid pET-SOD was obtained, and the recombinant protein was highly expressed in E. coli BL21(DE3). The activity of recombinant superoxide dismutase was 51,800 U per gram of wet bacteria. CONCLUSION: This study has provided a foundation for further studies and applications of the recombinant Mn-SOD.

Cloning, Molecular↗

PubMed2005

[Trends and variation of CFC-11 in the atmosphere of Beijing].

In recent years, concentration of CFC in the atmosphere has undergone rapid changes especially in association with human activities. For the influence of CFC on climate changes and environment changes, the concentration of atmospheric CFC-11 in Beijing is continuously observed and analyzed by a gas chromatography-mass spectrometry. The seasonal variation concentration and trends of CFC-11 are reported. The results show that the seasonal variation of CFC-11 was basically similar from 1999 to 2003. There was one peak value in the seasonal variation of CFC-11 in 1999-2003. The highest monthly average concentration of CFC-11 was 1149.5 +/- 531.9 x 10(12) ( V x V(-1)) in summer and the lowest monthly average concentration of CFC-11 was 487.5 +/- 131.5 x 10(-12) (V x V(-1)) in spring. The annual average concentration of CFC-11 was increasing in Beijing atmosphere from 1995 to 1998, and the average increasing ratio was 17.9%. The annual average concentration of CFC-11 was slowly decreasing from 1999, and the average decreasing ratio was 10.7%. The average concentration of CFC-11 in the atmosphere of Beijing was 3 to approximately 5 times of the average concentration of CFC-11 in the atmosphere of Mauna Loa Station of U.S.A.

Air Movements↗

PubMed2005

Alterations of MLH1 and microsatellite instability in esophageal squamous cell carcinomas.

Human MLH1 is one of the DNA mismatch repair genes and located in chromosome 3p21.3. Alterations of the MLH1 were associated with various kinds of human tumors. The present study was to investigate allelic loss of MLH1 and microsatellite instability (MSI) in esophageal squamous cell carcinomas (ESCC), and to estimate the correlation between MSI status and allelic loss of the MLH1 gene. The MSI of 14 microsatellite markers and mRNA expression of MLH1 were assessed in a large cohort of patients with ESCC by using denaturing polyacrylamide gel electrophoresis (PAGE) and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques. Thirty-five percent of tumors displayed MSI in at least one tested marker. MSI in D3S1611, an intragenic marker of the MLH1, was observed in 66.7% of tumors. No down-expression of MLH1 was found at the transcriptional level. The presence of MSI did not correlate with tumor stage, degree of differentiation, lymphonode-metastasis, age and sex of the patients, neither with allelic loss of the MLH1 gene. The data suggested that LOH of MLH1 is common in ESCC, but not lead to the alteration of MLH1 at the level of RNA expression. MSI in tested microsatellite markers occurs frequently in ESCC but is not associated with allelic loss of the MLH1 gene.

Adaptor Proteins, Signal Transducing↗

PubMed2005

[A theoretical study of the influence of interaction between transition metal atoms and carbon monoxide on infrared and Raman intensities of the C--O stretching vibration].

The structures and the spectral properties of the transition metal M-CO complexes have been investigated by performing the calculation of the hybrid density functional theory approach. The calculated results show that for each M-CO complex the infrared intensity of the C--O stretching mode is significantly larger than that of the M-C stretching mode and the bending modes. The Raman scattering factor of the C--O stretching mode is the largest among three modes. Comparison of the calculated results indicates that the C--O modes of M-CO complexes, the metal atom of which belongs to the fourth periodic metals and the Cu group, have larger Raman scattering factors than those in the other M-CO comnplexes.

Algorithms↗

PubMed2005

[Altered expression of the HSD17B4 gene in esophageal squamous cell carcinoma and loss of heterozygosity analysis].

OBJECTIVE: To investigate the alteration of the gene HSD17B4 in esophageal squamous cell carcinoma and its potential significance. METHODS: The mRNA expression and loss of heterozygosity (LOH) of HSD17B4 in 40 primary esophageal tumors were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and microsatellite analysis with the intragenic marker D5S1384 of the gene. RESULTS: The frequencies of allelic loss of D5S1384 and the rate of down-regulation of gene HSD17B4 were 46.2% and 62.5%, respectively. CONCLUSION: HSD17B4 may be a candidate tumor suppressor gene associated with esophageal squamous cell carcinoma.

17-Hydroxysteroid Dehydrogenases↗

PubMed2005

[Experimental study of facial nerve regeneration through polytetraflouroethylene tube with Schwann cells self-planted].

OBJECTIVE: To observe the effect of using polytetraflouroethylene (e-PTFE) tube with self-Schwann cells implanted to repair facial nerve defect. METHODS: Enzymatic digest method was used to get pure Schwann cells in short time. The e-PTFE membrane tube was used to bridge the 1.0 cm defect of facial nerve and pure self-Schwann cells were injected into the tube. As control group, the e-PTFE tube without self-Schwann cells was used in the same way. Electric physiological and histological examinations were taken in different times. RESULTS: The effect of nerve regeneration of the experimental group was better than control group at any time. The nerve conduction velocity of the experimental group was 29.70 m/s in the 16th week, while the control groups was 23.00 m/s respectively at the same time. CONCLUSION: It is possible to obtain sufficient active Schwann cells by enzymatic digest method. Using e-PTFE tube to bridge the defect of facial nerve with self-Schwann cells implanted can get effect of nerve regeneration.

Facial Nerve↗

PubMed2005

[SO2-caused oxidative stress and modulation of some signal molecules in wheat].

By adding different concentration SO2 to culture boxes, this paper studied the responses of wheat seedling's superoxide anion radical O2*- and antioxidant enzymes to SO2. The results showed that when the concentration of SO2 was 10 and 40 microl x L(-1), the O2*- content and peroxidase (POD) and catalase(CAT) activities of wheat leaf were increased, while the activity of superoxide dismutase(SOD) was reduced. When the SO2 concentration was 50 microl x L(-1), the activities of POD and CAT were decreased, with the top end leaves appeared necrosis, and more fungi multiplied on green leaves. Presoaking wheat seeds with 1 mmol x L(-1) salicylic acid (SA) for 6 h or with 10 mmol x L(-1) H2O2 for 12 h could efficiently alleviate the oxidative stress caused by SO2, with the O2*- content decreased and the activities of test antioxidant enzymes increased. Under SO2 fumigation, ethylene significantly inhibited the activities of test enzymes, and promoted the O2*- production rate. When applying SA and ethylene at the same time, SA could almost completely eliminate the influences of ethylene on O2*- production and test enzyme activities.

Catalase↗

PubMed2005

[Using neural networks based template matching method to obtain redshifts of normal galaxies].

Galaxies can be divided into two classes: normal galaxy (NG) and active galaxy (AG). In order to determine NG redshifts, an automatic effective method is proposed in this paper, which consists of the following three main steps: (1) From the template of normal galaxy, the two sets of samples are simulated, one with the redshift of 0.0-0.3, the other of 0.3-0.5, then the PCA is used to extract the main components, and train samples are projected to the main component subspace to obtain characteristic spectra. (2) The characteristic spectra are used to train a Probabilistic Neural Network to obtain a Bayes classifier. (3) An unknown real NG spectrum is first inputted to this Bayes classifier to determine the possible range of redshift, then the template matching is invoked to locate the redshift value within the estimated range. Compared with the traditional template matching technique with an unconstrained range, our proposed method not only halves the computational load, but also increases the estimation accuracy. As a result, the proposed method is particularly useful for automatic spectrum processing produced from a large-scale sky survey project.

Algorithms↗

PubMed2005

[Measurement method research on trace volatile organic compounds in atmosphere].

An automated accumulation sampling system and a method of two-step Cryo-Concentrated System combined with Gas Chromatography/Mass Spectrometry (CCS-GC/MS) are introduced. The method is evaluated by a set of special experiments and the results are demonstrated. The lowest limit volume concentrations of the measurement is expanded from 10 (-6) to 10(-12) using CCS-GC/ MS instead of the normal method of GC/MS and the average response factor of 39 object compounds is 2.9 x 10(-12) x A(-1). When injection volume of air sample reaches 1000 cm3, the lowest limit is 7 x 10(-12) - 40 x 10(-12); CCS-GC/MS may identify all the objective chemical species in the atmosphere samples, with average 2.5s bias of retention time for 39 GC peaks. Within 0 - 400 x 10(-9), the concentration of all the objective compounds can be calculated by standard curve individually (average r2 above 0.99) and accurately. The recollect rate is 88% - 111%, at average of 100.8% +/- 5.6%; and the bias of precision is 2% - 14%, at average of 6.6%.

Air Pollutants↗

PubMed2005

[Heavy metal stabilization in municipal solid waste incineration fly ash using soluble phosphate].

The physico-chemical characteristics of municipal solid waste incineration fly ashes was analyzed. It indicated that the main elements of fly ashes are Ca, Cl, K, S and Si, and many heavy metals such as Pb, Zn, Cu, Mn and Cr can be found in fly ashes, and the heavy metal leaching toxicity such as Pb, Cu, Zn and Cd is much higher than the standards. A new kind of stabilization agent-soluble phosphate is chosen to treat with fly ash, different influence factors including agent dosage, curing time and pH are taken into consideration to test its stabilization for the stabilized fly ash. The experimental results indicate that fly ash treated with soluble phosphate can have excellent stabilization effect, and the leaching toxicity for Pb, Cd and Zn can be reduced by 97.5%, 91.6% and 95.5% at a phosphate dosage of 3%; curing time can not influence its stabilization; and, stabilized fly ash using soluble phosphate can keep long-term stabilization at a broad pH value.

Carbon↗

PubMed2005

A novel region of deletion on 13q33-q34 in esophageal squamous cell carcinoma.

Chromosome 13 presents frequent allelic loss in esophageal squamous cell carcinomas (ESCC). However, no ESCC suppressor gene has been identified from this chromosome. To define common deletion regions that possibly contain the ESCC suppressor gene(s), we performed a mapping of allelic loss in 50 esophageal squamous cell carcinomas using a panel of 25 microsatellite markers on chromosome 13q21-qter, which has rarely been studied for allelic loss. Loss of heterozygosity (LOH) with high frequencies (> or = 50%) was observed at markers D13S1494, D13S1323, D13S248, D13S1315, D13S285, and D13S1295, in which the peak LOH (69.2%) was at locus D13S248. Seven cases presented LOH at three consecutive markers D13S248, D13S1315 and D13S285, 4 of which also displayed LOH at another adjacent marker D13S1295. This overlapping region of deletion covers an interval of 6.36 Mb at 13q33.1-q34, whose deletion has not previously been reported in ESCC. Tumors of grade II showed significantly more frequent LOH at D13S248 than those of grade I. A significantly higher frequency of allelic loss at D13S152 was also found in tumors with lymph node metastasis compared to those without lymph node metastasis. The present study defined a novel region of allelic loss in 13q33-q34. LOH at D13S248 and D13S152 are associated with higher tumor grade and metastasis, respectively.

Adult↗

PubMed2005

[Clinical application of maxillary sinus lifting, bone graft and simultaneous placement of implant].

PURPOSE: To evaluate the results of two kinds of sinus lifting techniques with simultaneous implant placement. METHODS: 31 maxillary sinus underwent two kinds of sinus lifting techniques and simultaneously 42 implants placement. The sinuses were observed 1, 3, 6 months after the surgery. RESULTS: There were no implants loose or lost; X ray examination showed well osseointegration and no maxillary sinusitis. All the patients finished implant prosthesis in 6 months postoperatively. Through 6-36 months' follow-up, clinical results were satisfactory. CONCLUSION: With properly handling of indication and the operation skill, the results of two kinds of maxillary sinus lifting techniques with bone grafting and simultaneously implants placement are both satisfactory.

Bone Transplantation↗

PubMed2005

[Luminescence properties of Gd2O3:Eu3+ sol-gel thin films].

In this paper, the sol-gel method with Re2O3 (Re=Gd, Eu) as parent compounds was introduced to produce Gd2O3:Eu3+ thin films. From the luminescence intensities of the films doped with different Eu3+ concentration and annealed at different temperatures, it was found that the optimal dopant concentration and annealing procedure was 10% and 800 degrees C for 2 hours, respectively. By comparing the excitation spectra of the Gd2O3:Eu3+ film and powder, the authors found that the film has higher efficiency for energy transfer from host to dopant, which means that the film would be more suitable than the powder as a radio-luminescence material. In addition, it was first discovered that the luminescence of the film nearly disappeared after 2 hours annealing at 1000 degrees C. The phenomenon was explained with the results of SEM and XRD experiments.

Europium↗

PubMed2004

Ionic liquid media resulted in the first asymmetric aminohalogenation reaction of alkenes.

[reaction: see text] The first asymmetric aminohalogenation of functionalized alkenes has been established. The ionic liquid [bmim][BF4] was found to be the only effective media for success as normal organic solvents failed to give any product for this reaction. The reaction is also very convenient to perform by simply mixing the three reactants, cinnamates, N,N-dichloro-p-toluenesulfonamide, and catalyst, together with 4 A molecular sieves at room temperature in [bmim][BF4] in any convenient vial of appropriate size without special protection from inert gases. Good chemical yields (60-72%) and diastereoselectivities (up to 75% de) have been obtained with a good scope of substrates. The resulting individual diastereomers have been cleanly separated via column chromatography. The absolute stereochemistry of the reaction was unambiguously determined by X-ray structural analysis.

Alkenes↗

PubMed2004

Characterization of a specific phage-displayed Peptide binding to vasculature of human gastric cancer.

Antivascular therapy provides a promising method for anticancer therapy. But targeting to gastric cancer vessels is nonselective due in part to the lack of specific cell-surface receptors identified on target vascular cells. Herein we used in vivo screening of phage displayed peptide library to identify some peptides that bind selectively to endothelial cells of human gastric cancer rather than nonendothelial cells. After four rounds of selection, one phage was obtained with a cyclic 7-mer peptide CGNSNPKSC homing to human gastric adenocarcinoma . There was a 4.6 approximately 137.26-fold increase in the number of the selected phage in gastric cancer xenograft in comparision with control organs brain, heart, liver, spleen and kidney. Immunohistochemistry in mouse and human tissue showed that this phage peptide only bind to the endothelial cells of human gastric cancer. This peptide was observed only specific binding to HUVEC not to SGC-7901, Eca-109, LoVo and Hep-G2 by ELISA. The competitive and inhibitory result between the synthetic CGNSNPKSC peptide and the phage displaying the peptide CGNSNPKSC on HUVEC and in vivo was also confirmed its specific binding effect. This peptide may be a possible candidate for targeted drug delivery in antivascular therapy.

Angiogenesis Inhibitors↗

PubMed2004

Identification of a minimal deletion region on chromosome 5q in Chinese esophageal squamous cell carcinomas.

The existence of unknown tumor suppressor gene(s) other than the APC gene has been hinted on 5q for esophageal squamous cell carcinoma (ESCC). In order to define minimal deletion intervals on 5q in ESCC and investigate the potential tumor suppressor gene(s), 9 microsatellite markers scattering the region from 5q22 to 5q35 were chosen for loss of heterozygosity (LOH) analysis in 50 primary ESCC from northern China. The results showed that six cases presented coexistence of LOH for three consecutive adjacent chosen markers, suggesting a minimal deletion region covering approximately 272 kb located on 5q23 from D5S1384 to D5S1505. It was a novel deletion region that was so far never reported in ESCC. Significant higher frequencies of LOH were observed in tumors with lower pathological grade at the locus D5S820 and with lymph node metastasis at the locus D5S408. The data suggested the possibility that one or more putative candidate tumor suppressor gene(s) on 5q23 might play an important role in the development and/or progression of ESCC.

Adult↗

PubMed2004

The extended Perdew-Burke-Ernzerhof functional with improved accuracy for thermodynamic and electronic properties of molecular systems.

Density functional theory (DFT) has become the method of choice for many applications of quantum mechanics to the study of the electronic properties of molecules and solids. Despite the enormous progress in improving the functionals, the current generation is inadequate for many important applications. As part of the quest of finding better functionals, we consider in this paper the Perdew-Burke-Ernzerhof (PBE) functional, which we believe to have the best theoretical foundation, but which leads to unacceptable errors in predicting thermochemical data (heats of formation) of molecular systems [mean absolute deviation (MAD)=16.9 kcal/mol against the extended G2 data set of 148 molecules]. Much improved thermochemistry is obtained with hybrid DFT methods that include part of the Hartree-Fock exchange [thus B3LYP (Becke's three parameter scheme combining Hartree-Fock exchange, Becke gradient corrected exchange functional and Lee-Yang-Parr correlational functional) with MAD=3.1 kcal/mol and PBE0 (Perdew's hybrid scheme using PBE exchange and correlation functionals) with MAD=4.8 kcal/mol]. However we wish to continue the quest for a pure density-based DFT. Thus we optimized the four free parameters (micro, kappa, alpha, and beta) in PBE theory against experimental atomic data and the van der Waals interaction properties of Ne(2), leading to the xPBE extended functional, which significantly outperforms PBE for thermochemical properties MAD reduced to 8.0 kcal/mol while being competitive or better than PBE for predictions of geometric parameters, ionization potentials, electron affinities, and proton affinities and for the description of van der Waals and hydrogen bond interactions. Thus xPBE significantly enlarges the field of applications available for pure DFT. The functional forms thus obtained for the exchange and correlational functionals may be useful for discovering new improved functionals or formalisms.

Journal Article↗