Biomedical subjects

X Chen

Publications and source records attributed to X Chen.

At least 379 records · Page 21Linked to original sources

PubMed2001

[The role of Fos protein in modulation of dental pain in central nerve system].

OBJECTIVE: The aims of this study were to reveal the relationship between Fos protein expression, the transcription of preproenkephalin (PENK) mRNA, and the change of enkephalin (ENK) level initiated by experimental dental pain, and to understand the central modulation mechanism of dental pain. METHODS: The techniques of Immunohistochemistry in situ hybridization and radioimmunoassay were applied respectively to detect the expression of Fos, the transcription of PENK mRNA, and the change of ENK level in the experimental nucleus of the spinal tract of the trigeminal nerve, caudal part (sp5c) of rats. RESULTS: It was found that Fos protein expression was in a time-dependent manner. Fos appeared half hour after the pain stimulation, and its peak occurred two hours after the pain stimulation, but disappeared slowly four hours later. The transcription of PENK mRNA was seen two hours after the pain stimulation, its peak appeared four hours later and it disappeared eight hours later. The level of ENK increased significantly (P < 0.01) in the caudal part of the spinal tract of the trigeminal nerve four hours after pain stimulation. CONCLUSION: Fos protein may take a part in the central modulation of dental pain by initiating PENK mRNA transcription which led to the increment of ENK.

Animals↗

PubMed2001

[Clinical observation of TNF-alpha content in nasopharyngeal secretion of patients with nasopharyngeal carcinoma].

OBJECTIVE: To detect the changes of tumor necrosis factor-alpha (TNF-alpha) in nasopharyngeal secretion of patients with nasopharyngeal carcinoma(NPC). METHOD: The content of TNF-alpha in nasopharyngeal secretion was determined by radioimmunoassay (RIA) in 20 controls, 52 patients with NPC. RESULT: The average concentrations of TNF-alpha were (12.95 +/- 4.62) pmol/L in control group, (33.68 +/- 15.13) pmol/L in NPC group and (64.00 +/- 11.57) pmol/L in NPC with necrosis group. The content of TNF-alpha in nasopharyngeal secretion in control group was lower significantly than that of patients with NPC (P < 0.01). CONCLUSION: The level of TNF-alpha in nasopharyngeal secretion of NPC patients was higher than that of normal subjects. To detect the content of TNF-alpha in nasopharyngeal secretion is a useful test for the study and diagnosis of NPC.

Adult↗

PubMed2001

[Study on some metal elements levels and the T lymphocyte subset of the peripheral lymphocytes in patients with nasopharyngeal carcinomas].

OBJECTIVE: To study some metal elements levels and T lymphocyte subset of the peripheral lymphocytes in patients with nasopharyngeal. METHOD: Metal elements in the patients with nasopharyngeal and normal control were detected by the Atomic Absorption Spectrometer (Flame SHIMATZV.JAPAN). T lymphocyte subset were detected by the flow cytometry (FCM). RESULT: The level of copper was significantly higher and the level of zinc was significantly lower in patients with nasopharyngeal carcinomas than those in normal control group (P < 0.01 and < 0.05 respectively). The number of CD3/CD4 cell in the patients group were less than those in normal group(P < 0.01). CONCLUSION: The results of correlative analysis showed that there was a significant correlationship between the number of CD4 cells and levels of copper in peripheral lymphocytes of the patients group.

Adult↗

PubMed2001

[Cricohyoidoepiglottopexy: a report of 21 cases].

OBJECTIVE: To assess the indications, function preserving and long term results of cricohyoidoepiglottopexy (CHEP) in the treatment of laryngeal carcinoma. METHOD: Twenty-one patients were underwent this procedure during the period from 1993 to 1999 in our department. There were 20 glottic cancers (7 T1N0M0, 10 T2N0M0, 3 T3N0M0) and 1 supraglottic type (T2N1M0) according to the 1997 UICC system. In these cases, 15 were the aged over 60 years. RESULT: First decannulation rate was 95.24%, and majority completed in 28 days post-operation. No patient was with cannula all his life. All cases could finally take food by mouth without aspiration. Speech was also satisfactory. The overall 3-year and 5-year survival rates were 87.50% and 75.00% respectively. No patient experienced local recurrence. CONCLUSION: This procedure is presented as a useful alternative to partial vertical laryngectomy and total laryngectomy in select cases of laryngeal carcinoma.

Adult↗

PubMed2001

[The clinic treatment of traumatic optic neuropathy].

OBJECTIVE: To observe the visual outcome of traumatic optic neuropathy treated with optic canal decompression surgery and medication. METHOD: 15 patients, suffering from traumatic optic neuropathy, had received medication and optic canal decompression surgery through the approach of ethmoid and sphenoid sinus. The vision acuity was divided into 5 grades: no light perception, light perception, finger movement, counting fingers, vision > or = 0.1, the vision acuity improvements reaching 2 grades or more were determined as effective. All patients were followed up for intervals of 1 month and 6 months. RESULT: The total efficient rate is 57.4%, no intraoperative or postoperative complications were encountered. Being followed up 6 months, 2 cases, who underwent respectively the operation 8, 11 days after trauma, felt no light perception. CONCLUSION: The approach through ethmoid and sphenoid sinus have the merits such as safety, less damage and larger operative field. Timely medication, megacorticosteroid therapy mainly, may play a good role in alleviating optic nerve edema and restoring its function. Comprehensive therapy may be an ideal treatment to traumatic optic neuropathy.

Adolescent↗

PubMed2001

[Introduction of the chromogenic gene to the plant growth-promoting rhizobacteria of cucumber].

Using a bicomponent transposition system with the E. coli lacZY gene cloned between Tn7 termini, a sensitive, selectable marker based on expression of the E. coli lac operon genes encoding beta-galactosidase and lactose permease was transformed into the rifampicin resistant mutant of plant growth-promoting rhizobacteria of cucumber, Pseudomonas aeruginosa CN116 and Pseudomonas corrugata CN31, respectively. Transformants were conferred the ability to utilize lactose as a sole carbon source and the ability to cleave the chromogenis substrate X-Gal to show a specific blue color. Southern blotting analysis showed that lacZY gene was inserted into the genome DNA of target strains. Compared with the wild type strains, the cultural characters, morphological features, growth promoting and disease control effects of transformants were almost unchanged, except the new marked phenotype. This marker system enabled the detection of lac+ transformants at sensitivity of 10 CFU/g soil, which makes the further studies on PGPR more easily.

Cucumis sativus↗

PubMed2001

[Cloning and expression of the envelope glycoprotein gD gene of pseudorabies virus EA strain].

The envelope glycoprotein gD gene of pseudorabies virus Ea strain was cloned via PCR technique. Sequence analysis displayed 98% nucleotide sequence homology and 97% deduced amino acid sequence homology between our cloned gD gene and PRV Rice strain gD gene. The recombinant transfer plasmid pSX35A-gD was obtained by inserting D gene into the baculovirus transfer vector pSX35A with whole-phase promoter cassette, then transfected insect cell Hi5 with linearized AcMNPV-OCC- virus DNA, and formed recombinant baculoviruses AcMNPV-OCC(+)-gD by homologous recombination in insect cell. Recombinant baculoviruses infected insect cell Hi5 after being purified by plaque assay. Both SDS-PAGE and Western-blotting showed glycoprotein gD with a molecular weight of about 47 kD was expressed specifically, product was about 6.2% of total cellular protein, and expressed gD was of immunogenicity.

Animals↗

PubMed2001

[Subcloning and sequencing of DNA fragment related to salt tolerance in Sinorhizobium meliloti 042B].

A 4 kb ClaI DNA fragment related to salt tolerance from S. meliloti 042B was digested by HindIII down 2.4 kb fragment, and a 1.6 kb ClaII-HindIII fragment was retained on plasmid pML122. Then, the 2.4 kb DNA fragment was ligated with plasmid pBBR1-MCS2, and the recombinant plasmid was transformed to E. coli DH5 alpha, and transformant GS2 was obtained. Three-parental mating experiments were carried out with transformant GS2 as donor, salt sensitive strains GZ17 as recipient and pRK2013 as helper plasmid, then the transconjugant GG2 was selected on FY plates containing kanamycin and 0.4 mol/L NaCl. The remaining DNA fragment was self ligated with pML122 and then transformed into E. coli S17-1 and transformat GS0 was obtained. Two-parental mating experiment was carried out with transformant GS0 as donor and salt sensitive strain GZ17 as recipient, but no transconjugant was obtained on the FY plates. Then, the 2.4 kb HindIII DNA fragment was ligated into sequencing vector pGEM-7Zf(+) for sequencing. The result of sequencing and analysis showed that the 2.4 kb DNA fragment contained three ORFs. According to the result of sequencing, further subcloning was conducted and 1.9 kb HindIII-Sac II DNA fragment related to salt tolerance was obtained.

Amino Acid Sequence↗

PubMed2001

[Expression of human interleukin-12 in Baculovirus expression system].

Human Interleukin-12 (hIL-12) is a key immunoregulatory cytokine and the only heterodimeric cytokine found by far. It is a disulfide-linked heterodimer composed of a 35 kD light chain (P35) and a 40 kD heavy chain (P40). Two recombinant transfer vector plasmids pAcAB3-p35 (including hIL-12 p35 gene) and pAcAB3-p40 (including hIL-12 p40 gene) were constructed and co-transfected the insect cells Sf9 with AcNPV BaculoGold Linearized Baculovirus DNA. The obtained recombinant viruses, AcNPV-OCC(-)-hiL-12 (p35) and AcNPV-OCC(-)-hIL-12 (p40), were used to infect the Sf9 cells separately, and the supernatants of culture and cell lysate were examined by using SDS-PAGE and Western blot. Results showed that both hIL-12 p35 and p40 gene were successfully expressed in insect cells and secreted. The expression productions had immunogenicity.

Animals↗

PubMed2001

[The construction and application of promoter-signal peptide probe vector of lactic acid bacteria].

A promoter-signal peptide probe vector of lactic acid bacteria, designated pZLB based on pMG36e has been constructed. The vector contained a reporterd gene encoding for beta-lactamase, which lacked a promoter and a functional signal sequence. Sau3A restriction fragments (80-400 bp) from L. lactis ATCC 7962 total DNA were cloned into BamHI site of pZLB. A lot of different size framents were selected. These fragments promoted transcription and secretion of beta-lactamase in L. lactis. Sequence analysis revealed that inserted fragment in pZLBe7 contained typical promoter, SD sequence and atypical signal sequence.

Amino Acid Sequence↗

PubMed2001

[Rapid induction of senescence-like changes in human umbilic vein endothelial cells(HUVECs) by C6 ceramide].

Ceramide, a key molecule in sphingolipid metabolism and a candidate second messenger, has been shown to inhibit the activity of phospholipase D. This biochemical pathway has been implicated to regulate cell differentiation, apoptosis and cellular senescence. Ceramide is generated in response to a number of extracellular inducers(for example: TNF, IL-1 and Fas ligands etc.), and acts as a second messenger to mediate many of the effects of these inducers. HUVECs are the monolayer cells located inside the vein wall and play an important role in the regulation of vein physiology and blood function. It has been reported that the C6 ceramide can induce senescence of WI-38 HDF and promote the activity of beta-galactosidase, but, C2 ceramide has no such effect. In this study, we investigated the role of C6 ceramide in the senescence of HUVECs. 10 mumol/ml of C6 ceramide treatment for more than 72 hours can induce morphological alterations (such as: enlarged, flattened and irregular cell body), cell cycle arrested at G1 phase and the expression of the senescent histochemical marker-beta-galactosidase in HUVECs. These results showed that C6 ceramide could induce senescence-like changes of HUVECs. The detection of reactive oxygen species(ROS) and the anti-oxidative ability of the cells showed that the C6 ceramide induced senescence-like cells still have normal ability of anti-oxidation. Further investigations are ongoing.

Cell Cycle↗

PubMed2001

[Isolation and characterization of a plasmid pTS50, which encodes nisin resistance determinant in Lactococcus lactis TS1640].

Three nisin-resistant Lactococcus lactis strains were screened from 197 samples of fresh milk on a selective medium (M17) supplemented with nisin, lactose and bromocresol purple, and were confirmed to have the nisin resistance determinant (nsr) by PCR amplification. Physiological and biochemical tests as well as Lactococcus lactis specific 16S rDNA sequence analysis revealed that the three strains all belong to Lactococcus lactis subsp. lactis. A large plasmid, pTS50, was identified in L. lactis subsp. lactis TS1640 which encodes resistance to nisin following electroporation of the total plasmids DNA into L. lactis MG1363. The molecular weight of plasmid pTS50 was estimated to be 47 kb by restriction analysis of BamHI, EcoRI, HindIII, NcoI, PstI and nsr was localized on a 1.9 kb EcoRI fragment by Southern hybridization.

Animals↗

PubMed2001

[Isolation and identification of the broad spectrum antimicrobial peptide AP311 produced by Lactobacillus acidophilus].

The heat stable antimicrobial peptide (AP311) produced by Lactobacillus acidophilus was isolated and identified. The AP311 has broad spectrum of inhibition including many Gram-positive and Gram-negative bacteria. The inhibition activity of AP311 was lost upon treatment with trypsin, subtilisin, proteanase K, chymotrypsin and pepsin. Inhibition activity of AP311 was decreased with pH increasing. The AP311 is very stable at acidic condition (pH2-4) even if heating at 100 degrees C for 30 min. But it was inactivated at basic pH (pH12) and the activity was restored completely upon reversion to acidic. The AP311 was not precipitated and inactivated by various organic solvents, except n-butanol. When the precipitate was redissolved in 0.02 mol/L HC1, its activity was restored. Based on its proteinaceous nature, broad spectrum of inhibition, we propose that AP311 should be considered the broad spectrum antimicrobial peptide.

Anti-Bacterial Agents↗

PubMed2001

[Studies on the hydroxyl free radical-scavenging effect of combined selenium and germanium].

The effect of selenium, carboxyethyl-germanium sesquioxide (Ge-132) and the combination of selenium and Ge-132 on the production of hydroxyl free radical in liver microsomes of rats treated with Fe2SO4-NADPH system was studied with electron spin resonance technique (ESR). The results showed that the production of hydroxyl free radical was decreased significantly by adding selenium, Ge-132 and combined selenium and Ge-132, indicating a direct scavenging effect on hydroxyl free radical. It was also observed a enhanced scavenging effect at the low concentration of combined selenium and Ge-132.

Animals↗

PubMed2001

[Determination of domoic acid in water and aquatic animals by high performance liquid chromatography].

The content of domoic acid in water and in the body of some aquatic animals was detected by HPLC in order to find out the pollutant condition. The result showed that HPLC analysis was a simple and effective method for determining domoic acid in water and aquatic animals. Domoic acid has been found in some marine shellfish and not in seawater or freshwater. It is necessary to strengthen monitoring the contamination of domoic acid to prevent the toxin poisoning.

Animals↗

PubMed2001

[Study on cadmium-induced hepatocellular apoptosis in rats].

The effect of cadmium chloride on hepatocellular apoptosis in rats was studied in vivo at the doses of 5, 10 and 20 mumol/kg by using TUNEL (TdT-mediated dUTP Nick End Labelling), DNA ladder electrophoresis and flow cytometry. The results showed that TUNEL-positive cells could be detected in cadmium-treated rat liver cells. DNA fragmentation (ladder pattern) in cadmium-treated liver cells could be displayed by agarose gel electrophoresis. The rates of apoptotic cells in the liver of cadmium-treated rats at these doses were higher than those of control rats significantly. It was suggested that cadmium chloride could induce hepatocellular apoptosis of rats at certain doses in vivo.

Animals↗

PubMed2001

[Survey on the microbial pollution of pure water in water dispenser and its disinfection].

The counts of bacteria, total coliforms and fungi of pure water in the water dispensers were detected and the regular pattern of bacterial reproduction in water were studied after the dispensers and water were disinfected. The results showed the bacterial pollution in the water dispensers was serious and the bacteria counts increased with the time of using dispensers lasted. The disinfectant could killed effectively the bacteria in the water sources but it could not control the new bacteria polluted and reproduced while the water dispensers were in use. It was suggested that the bacteria polluted from air should be prevented by taking effective methods and selecting appropriate organic materials for making dispensers.

Escherichia coli↗

PubMed2001

The preliminary experimental study of induced differentiation of embryonic stem cells into corneal epithelial cells.

PURPOSE: To study preliminarily induced differentiation of embryonic stem cells into corneal epithelial cells in vitro. METHODS: Murine embryonic stem cells were co-cultured with Rabbit limbal corneal epithelial cells in Transwell system to induce differentiation. Mophological and immunohistochemical examination were implemented. RESULTS: The induced cells from embryonic stem cells have an epithelial appearance. The cells formed a network and were confluent into film gradually after being co-cultured with rabbit limbal corneal epithelial cells for 24-96 hours. The cells ranged mosaic structure and localized together with clear rim. Most of the cells showed polygonal appearance. Transmission electron microscope showed lots of microvilli on the surface of induced cells and tight junctions between them. These epithelial-like cells expressed the corneal epithelial cell specific marker cytokeratin3/cytokeratin12. CONCLUSION: The potential mechanism of the differentiation of murine embryonic stem cells into corneal epithelial cells induced by limbal corneal epithelial cell-derived inducing activity is to be further verified.

Animals↗