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Biomedical subjects

X Chen

Publications and source records attributed to X Chen.

At least 235 records · Page 13Linked to original sources
PubMed2001

Direct nitric oxide imaging in cultured hippocampal neurons with diaminoanthraquinone and confocal microscopy.

A method for the direct measurement of intracellular nitric oxide (NO) production stimulated by penicillin G (PG) in cultured hippocampal neurons with diaminoanthraquinone (DAA) using laser scanning confocal microscopy (LSCM) was developed. Intracellular DAA fluorescence could specifically represent NO production based on two facts: (1) 3-morpholinosydnonimine, a NO donor, could dose-dependently increase DAA fluorescence; and (2) haemoglobin, a NO scavenger, could inhibit the increase of DAA fluorescence. The PG dose-dependently increased the intercellular level of glutamate (Glu, 5 min after stimulation) and the intracellular NO production (30 min throughout stimulation). The increase of NO production could be reversed by N(w)-nitro- l -arginine (a NO synthase inhibitor), and also by d (-)2-amino-5-phosphonovaleric acid, a subtype of Glu receptor antagonist. These results revealed that DAA could be used to indicate real-time and kinetic intracellular NO production of hippocampal neurons with higher sensitivity, specificity and accuracy.

2-Amino-5-phosphonovalerate↗
PubMed2001

Cytokine-induced metabolic dysfunction of MIN6 beta cells is nitric oxide independent.

BACKGROUND: An important obstacle to islet transplantation is graft injury due to local production of cytokines generated by host nonspecific inflammatory responses. The detrimental effects that cytokines impart on metabolic function have been associated with nitric oxide (NO) production and apoptosis. We tested the in vitro effects of interleukin (IL)-1 beta, tumor necrosis factor (TNF)alpha, and interferon (IFN)gamma on glucose-stimulated insulin release in the MIN6 beta-cell line and correlated metabolic dysfunction with NO production and rates of apoptosis. MATERIALS AND METHODS: MIN6 cells were cultured in the presence of IL-1 beta, TNFalpha, and/or IFN gamma. Insulin release was determined by radioimmunoassay. NO production was determined by the Griess reaction. Apoptosis was determined by measuring the sub-G(1) phase of DNA content of MIN6 cells by flow cytometry. RESULTS: Cytokine-induced suppression of glucose-stimulated insulin release was enhanced in a time-dependent manner. NO production was stimulated by IL-1 beta and augmented by TNFalpha and IFN gamma. N(G)-Monomethyl-l-arginine (l-NMMA) blocked cytokine-induced NO production but only partially attenuated suppression of glucose-stimulated insulin release. Apoptosis increased in the presence of cytokines and was slightly reduced when NO production was specifically inhibited. CONCLUSIONS: Proinflammatory cytokines suppressed glucose-stimulated insulin release in MIN6 cells. The dominant mechanisms involved NO-independent pathways.

Animals↗
PubMed2001

HSV amplicon-mediated neurotrophin-3 expression protects murine spiral ganglion neurons from cisplatin-induced damage.

Ototoxicity is a major dose-limiting side effect of cisplatin (DDP) administration due to its propensity to induce destruction of hair cells and neurons in the auditory system. Previous studies demonstrated that TrkC-expressing spiral ganglion neurons (SGN) are protected from the cytotoxic effects of DDP by localized delivery of the trophic factor neurotrophin-3 (NT-3). Successful in vivo implementation of such a therapy requires the development of an efficient gene delivery vehicle for expression of NT-3 within the cochlea. To this end, we constructed a herpes simplex virus (HSV) amplicon vector that expressed a c-Myc-tagged NT-3 chimera (HSVnt-3myc). Helper virus-free vector stocks were initially evaluated in vitro for their capacity to direct expression of NT-3 mRNA and protein. Transduction of cultured murine cochlear explants with HSVnt-3myc resulted in production of NT-3 mRNA and protein up to 3 ng/ml as measured over a 48-h period in culture supernatants. To determine whether NT-3 overexpression could abrogate DDP toxicity, cochlear explants were transduced with HSVnt-3myc or a murine intestinal alkaline phosphatase-expressing control vector, HSVmiap, and then exposed to cisplatin. HSVnt-3myc-transduced cochlear explants harbored significantly greater numbers of surviving SGNs than those infected with control virus. These data demonstrate that amplicon-mediated NT-3 transduction can attenuate the ototoxic action of DDP on organotypic culture. The potency of NT-3 in protecting spiral ganglion neurons from degeneration suggests that in vivo neurotrophin-based gene therapy may be useful for the prevention and/or treatment of hearing disorders.

Animals↗
PubMed2001

Induction of heme oxygenase-1 by Ginkgo biloba extract but not its terpenoids partially mediated its protective effect against lysophosphatidylcholine-induced damage.

In this study, we examined whether Ginkgo Biloba Extract and its terpenoid constituents protect against oxidative stress through actions on heme oxygenase (HO) gene expression and activity. HO-1 and glutathione peroxidase (GPx) gene expressions were examined by reverse transcription polymerase chain reaction (RT-PCR) analysis, HO activity and GPx enzyme activity were analysed by spectrophotometric assay. Pretreatment of H9c2 myocytes with 100-500 microgml(-1)Ginkgo Biloba Extract caused induction of HO-1 gene expression and a significant increase in HO activity; 30 microgml(-1)ginkgolide B and 30 microgml(-1)bilobalide had little effect. Treatment with Ginkgo Biloba Extract for 24 h also significantly increased GPx gene expression and GPx enzyme activity. Pretreatment with Ginkgo Biloba Extract, ginkgolide B and bilobalide protected myocytes against lysophosphatidylcholine (LPC)-induced damage. The protective effect of Ginkgo Biloba Extract against LPC-induced damage was partially suppressed by a HO inhibitor, Zinc protoporphyrin-IX (ZnPP-IX), while ZnPP-IX did not suppress the protective effect of ginkgolide B or bilobalide. Furthermore, pretreatment with hemin, biliverdin or bilirubin reduced cytotoxicity induced by LPC. These results suggest that induction of HO-1 by Ginkgo Biloba Extract but not its terpenoid constituents may play a beneficial role in oxidative stress. The mechanism of Ginkgo Biloba Extract-induced HO-1 gene expression and the increase in HO activity may be related to alteration of intracellular glutathione levels.

Animals↗
PubMed2001

Hazard of smoking initiation by age among adolescents in Wuhan, China.

BACKGROUND: Knowledge about age of smoking initiation among adolescents in China is helpful for exploring cultural differences in adolescent smoking behavior and informative for global tobacco control. However, little has been documented on this issue. METHOD: Adolescents (6,473) attending grades 7, 8, and 9 completed the baseline survey of a longitudinal, randomized smoking prevention trial. Data were collected in classrooms with a paper-and-pencil questionnaire. A survival model was used in the statistical analysis. RESULTS: The hazard of smoking initiation for boys showed a pattern previously observed in the United States: very low (<2%) before 7 years of age, increasing rapidly after age 10, and peaking at 14-15 years of age. The hazard for girls was below or around 1% until 12 years of age before it increased. The hazard levels were similar for adolescents both in urban and in rural areas, but higher for those in grade 7 than in grades 8 and 9. CONCLUSIONS: Chinese boys in Wuhan, China, experienced a hazard pattern of smoking initiation by age similar to those observed in the United States, while Chinese girls there experienced a rather low risk of smoking initiation. The hazard pattern suggests that the best time for smoking prevention is between 10 and 15 years of age. Adolescents in lower grades are at higher risk of early smoking initiation, suggesting a potential cohort effect in adolescent smoking initiation in Wuhan, China.

Adolescent↗
PubMed2001

A preliminary clinical study of three-dimensional ultrasonography in prenatal diagnosis.

To evaluate the clinical value of three-dimensional ultrasonography (3DUS) in prenatal diagnosis, 134 pregnant women with high-risk factors in second and third trimester were examined by 3DUS. The results showed that 3DUS could provide more diagnostic information, exclude the abnormalities and enhance the confidence level of physician in 102 normal pregnant women. 3DUS was helpful in the diagnosis in 17 (60.7%) of 28 cases of fetal anomalies. However, 3DUS was not useful in evaluating intrauterine growth retardation in 4 cases. It is concluded that 3DUS is helpful in prenatal diagnosis.

Adult↗
PubMed2001

Gene therapy of HSV-TK transferred by the EBV based expression vector on experimental hepatocellular carcinoma.

To study the therapeutic effects of herpes simplex virus thymidine kinase (HSV-TK) gene transferred by the EBV-based expression vector (pDR2) on experimental hepatocellular carcinoma, pDR2-TK gene was delivered into human hepatocellular carcinoma cell line SMMC-7721 by using liposome-mediated transfection technique, and then gene expression was detected by RT-PCR, and the killing effects were examined through MTT method. In the nude mice hepatoma model, the antitumor effects of pDR2-TK/GCV system was evaluated in terms of tumor growth. MTT results showed that the pDR2-TK/GCV had cytotoxic effect and about 70% SMMC-7721 cells were killed when GCV was at 1000 mumol/L. In vivo experiment showed that the tumor size in nude mice with transferred pDR2-TK gene was significantly smaller than that in control group (P < 0.01). On the 10th day the tumor in 3 mice (60%) disappeared completely after GCV treatment. It is concluded that the pDR2-TK/GCV system has marked killing effects on the experimental hepatocellular carcinoma.

Animals↗
PubMed2001

Use of the fibreoptic stylet scope (Styletscope) reduces the hemodynamic response to intubation in normotensive and hypertensive patients.

PURPOSE: To compare hemodynamic changes after tracheal intubation when using a new fibreoptic stylet scope (Styletscope) and a conventional laryngoscope in normotensive and hypertensive patients. METHODS: Normotensive (N; n=30) and hypertensive (H; n=30) patients undergoing general anesthesia participated in this study. Each group was divided into two groups. In one group, patients were intubated by using a stylet scope with a laryngoscope as an adjuvant (S; n=15 each), while patients in the other group were intubated using a laryngoscope by the usual technique (L; n=15 each). The time necessary for intubation, hemodynamic changes, and adverse effects were recorded. RESULTS: Patients in the normotensive groups (SN and LN groups) showed significant increases in both systolic and diastolic blood pressures from before induction to one minute after intubation; however, blood pressures in the SN group were significantly lower than those in the LN group. Both systolic and diastolic blood pressures increased after intubation in the LH group, but not in the SH group. Heart rates in all four groups showed significant increases, and there were no differences between heart rates in the stylet scope and laryngoscope groups or between the normotensive and hypertensive groups. The number of patients who complained of sore throat was greater in the laryngoscope groups. CONCLUSIONS: Tracheal intubation with a stylet scope can attenuate hemodynamic changes and reduce the incidence of sore throat in comparison with the conventional laryngoscope technique in both normotensive and hypertensive patients.

Anesthesia, General↗
PubMed2001

Production of compound A under low-flow anesthesia is affected by type of anesthetic machine.

PURPOSE: The purpose was to compare the concentrations of compound A in inspired gas breathed by patients produced by different types of anesthetic machines under prolonged sevoflurane low-flow anesthesia. METHODS: The anesthetic machines tested were Excel 210 SE (Datex-Ohmeda, Louisville, CO), Cicero (Dräger, Lübeck, Germany), and AS/3 ADU (Datex-Ohmeda, Louisville, CO). Anesthesia expected to last more than four hours was maintained with 2.0% sevoflurane and nitrous oxide (0.5 L x min(-1))/oxygen (0.5 L x min(-1)). The concentrations of compound A, obtained from the inspiratory limb of the circle system, were measured using a gas chromatograph. RESULTS: When Excel and Cicero were used, concentrations of compound A increased steadily from the baseline values to 28 and 29 (mean) ppm, respectively, at two hours after exposure to sevoflurane and became constant. There was no significant difference between the concentrations of compound A produced by these anesthetic machines. In contrast, the new anesthetic machine AS/3 was associated with lower concentrations of compound A (6 ppm at one hour, P <0.05 compared with Excel and Cicero), and the concentration did not change significantly thereafter. CONCLUSION: In spite of the use of a conventional carbon dioxide (CO2) absorbent with strong bases, the anesthetic machine AS/3 with a small volume of canister/soda lime (900 ml/700 ml) produced lower concentrations of compound A than those produced by the other machines.

Anesthesia, Inhalation↗
PubMed2001

Optical rubbery ormosils sensor for the detection of ammonia.

Rubbery ormosil films with immobilized aminofluorescein (AF) were investigated to develop an optochemical sensor for the determination of ammonia in water. The gel precursors with tetramethoxysilane (TMOS) and dimethyldimethoxysilane (DiMeDMOS) were deposited on glass supports, and characterized in terms of response to pH, and to dissolved ammonia at constant pH. After preconditioning the sensing film was stable for 6 months. The detection limit for ammonia in water was 0.2 microg mL(-1) (S/N 2), the response being linearly dependent on concentration in the range of 0.5 to 80 microg mL(-1) ammonia. The response time was less than 5 min. The effects of sodium chloride concentration, temperature, and coexisting metal ions and compounds were investigated.

Journal Article↗
PubMed2001

Ultrastructural localization of basigin in normal human epidermis.

Basigin is a glycosylated transmembrane protein belonging to the immunoglobulin superfamily. It is thought to play roles in intercellular recognition involved in cell differentiation. We previously demonstrated at the light microscope level a correlation between basigin expression and epidermal differentiation. In the present study, the ultrastructural localization of basigin in normal human epidermal keratinocytes was investigated by immunoelectron microscopy. The basigin labeling was strongest on membranes of basal cells, weaker on prickle cells, and absent in granular and horny cells. On the membrane of basal cells, labeling was observed on the apical and lateral sides but not on the dermal side. Gold particles were mostly observed on the surface of microvilli, especially on their tips. There were fewer on the intermicrovillous membrane and they were absent on the desmosome. These results are consistent with our previous report that basigin expression is correlated with differentiation of epidermal keratinocytes. Microvilli on basal and suprabasal keratinocytes might play roles in the differentiation of keratinocytes through basigin on the tips of microvilli.

Adult↗
PubMed2001

Chromosome landing at the bacterial blight resistance gene Xa4 locus using a deep coverage rice BAC library.

Xa4 is a dominantly inherited rice gene that confers resistance to Philippine race 1 of the bacterial blight pathogen Xanthomonas oryzae pv. oryzae in rice. In order to isolate the gene by positional cloning, a bacterial artificial chromosome (BAC) library was constructed from genomic DNA isolated from an Xa4-harboring accession, IRBB56. The library contains 55,296 clones with an average insert size of 132 kb, providing 14 rice genome equivalents. Three DNA markers closely linked to Xa4 were used to screen the library. The marker RS13, a resistance gene analogue that co-segregates with Xa4, identified 18 clones, of which four and six, respectively, were simultaneously detected by the other two markers, G181 and L1044. Fingerprinting and Southern analysis indicated that these clones overlapped and define an interval spanning 420 kb. In an F2 population derived from an indica variety, IR24, and its Xa4-containing near isogenic line (NIL), IRBB4, the susceptible plants were screened in order to map the Xa4 gene genetically and physically. Out of 24 insert ends isolated from the BACs in the contig, three revealed polymorphisms between IR24 and IRBB4. Two insert ends, 56M22F and 26D24R, flanked Xa4 on each side. Based on the overlap of the BACs, six overlapping clones were considered to include the Xa4 allele, one of which, 106P13, was chosen for further investigation.

Blotting, Southern↗
PubMed2001

An analysis of relationships among plant community phenology and seasonal metrics of Normalized Difference Vegetation Index in the northern part of the monsoon region of China.

This study focuses on relationships between the phenological growing season of plant communities and the seasonal metrics of Normalized Difference Vegetation Index (NDVI) at sample stations and pixels overlying them, and explores the procedure for determining the growing season of terrestrial vegetation at the regional scale, using threshold NDVI values obtained by surface-satellite analysis at individual stations/pixels. The cumulative frequency of phenophases has been calculated for each plant community and each year in order to determine the growing season at the three sample stations from 1982 to 1993. The precise thresholds were arbitrarily set as the dates on which the phenological cumulative frequency reached 5% and 10% (for the beginning) and 90% and 95% (for the end). The beginning and end dates of the growing season were then applied each year as time thresholds, to determine the corresponding 10-day peak greenness values from NDVI curves for 8-km2 pixels overlying the phenological stations. According to a trend analysis, a lengthening of the growing seasons and an increase of the integrated growing season NDVI have been detected in the central part of the research region. The correlation between the beginning dates of the growing season and the corresponding threshold NDVI values is very low, which indicates that the satellite-sensor-derived greenness is independent of the beginning time of the growing season of local plant communities. Other than in spring, the correlation between the end dates of the growing season and the corresponding threshold NDVI values is highly significant. The negative correlation shows that the earlier the growing season terminates, the larger the corresponding threshold NDVI value, and vice versa. In order to estimate the beginning and end dates of the growing season using the threshold NDVI values at sites without phenological data from 1982 to 1993, we calculated the spatial correlation coefficients between NDVI time-series at each sample station and other contiguous sites year by year. The results provide the spatial extrapolation area of the growing season for each sample station. Thus, we can use the threshold NDVI value obtained at one sample station/pixel for a year to determine the growing season at the extrapolation sites with a similar vegetation type for the same year.

China↗
PubMed2001

A low 13C-urea breath test value is associated with increased risk of gastric cancer.

PURPOSE: The 13C-urea breath test (UBT) is considered to be the most accurate way of diagnosing Helicobacter pylori infection. Values are affected by H. pylori infection and by the severity of atrophic gastritis. Our objective was to determine the association of UBT values with gastric cancer, and to evaluate the risk of gastric cancer in terms of UBT values. METHODS: Our study involved 413 consecutive patients who had undergone esophagogastroduodenal examination and the UBT test. RESULTS: Of the 398 patients with positive UBT results, atrophy and intestinal metaplasia scores in both antrum and corpus were significantly higher in patients with gastric cancer than in those with gastritis, duodenal ulcer, and gastric ulcer. The UBT value related to gastric cancer (22.01 +/- 1.89%o) was significantly lower than that for gastritis (35.19 +/- 1.53%o; P < 0.01), duodenal ulcer (29.01 +/- 1.97%; P < 0.05), or gastric ulcer (30.79 +/- 2.83%; P < 0.05). When the UBT values were less than 20%, increases in the risk of gastric cancer correlated with decreasing UBT values. CONCLUSIONS; These findings indicate that the UBT value related to gastric cancer is significantly lower than that for gastritis, duodenal ulcer, or gastric ulcer in H. pylori-positive patients. Low UBT values were associated with the risk of gastric cancer.

Biopsy↗
PubMed2001

Celite-activated viscometer Sonoclot can measure the suppressive effect of tranexamic acid on hyperfibrinolysis in cardiac surgery.

PURPOSE: To investigate the usefulness of the celite-activated viscometer Sonoclot for monitoring fibrinolytic status in cardiac surgery, we demonstrated the effectiveness of high doses of tranexamic acid, an antifibrinolytic agent, in reducing postoperative bleeding. METHODS: Thirty-two American Society of Anesthesiologists (ASA) physical status III patients who required cardiac surgery with cardiopulmonary bypass (CPB) were studied. Anesthesia was induced by a high dose of fentanyl and midazolam with oxygen and was maintained by the intermittent administration of these agents. Patients were divided into two groups: the control group (n = 15) and patients receiving tranexamic acid (TA; n = 17). The TA group received a high dose (50 mg/kg) of TA twice, once before and once after CPB. The percentage diminishing rate of the Sonoclot tracing 15 min after maximum clot signal (DR(15)) and the amount of postoperative bleeding were measured. RESULTS: After CPB, DR(15) in the control group (mean 28.3%) increased significantly by 45%, and the DR(15) in the TA group (16.1%) was significantly lower than that in the control group. The amount of postoperative bleeding in the TA group (546 ml) was significantly less, by 34%, than that in the control group (829 ml). CONCLUSION: Prophylactic administration of high-dose TA in cardiac surgery reduces postoperative bleeding, and this effect is consistent with changes in the diminishing rate using Sonoclot. The celite-activated viscometer Sonoclot is recommended for use in cardiac surgery for rapid assessment of fibrinolytic status.

Journal Article↗
PubMed2001

Applications of liquid chromatography-tandem mass spectrometry in drug and biomedical analyses.

BACKGROUND: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is one of the major tools for bioanalytical works. These instruments can be used for quantitative determination of plasma samples in pharmacokinetic studies. LC-MS/MS techniques frequently provide specific, selective and sensitive quantitative results often with reduced sample preparation and analysis time relative to other commonly employed techniques. METHODS: The applications of these instruments include analysis of nine corticosteroids illegally adulterated in traditional Chinese medicines, identification of drug metabolites of roxithromycin, propafenone and some glucuronide conjugates and the quantitative determination of plasma samples containing amlodipine, nitrendipine, flupirtine and their major metabolites. CONCLUSIONS: LCQ is ideally suited for the rapid identification of metabolites because it provides on-line LC/MS(n) capability, enabling multiple MS stages to obtain the maximum amount of structural information, while TSQ provides excellent precise and accurate results for quantitative assays at very low detection limits.

Amlodipine↗