Search PubMed⌕ Search

Biomedical subjects

X C Chen

Publications and source records attributed to X C Chen.

At least 19 recordsLinked to original sources
PubMed2005

Radiation-induced root surface caries restored with glass-ionomer cement placed in conventional and ART cavity preparations: results at two years.

BACKGROUND: There are no published studies comparing the clinical performances of more-viscous glass-ionomer cement (GIC) restorations when placed using conventional and atraumatic restorative treatment (ART) cavity preparation methods to restore root surface caries. METHODS: One dentist used encapsulated Fuji IX GP and Ketac-Molar to restore 72 conventional and 74 ART cavity preparations for 15 patients who had received cervicofacial radiation therapy. Two assessors evaluated the restorations at six, 12, and 24 months for retention, marginal defects and surface wear, and recurrent caries. RESULTS: After two years, the cumulative restoration successes were 65.2 per cent for the conventional and 66.2 per cent for the ART cavity preparations, without statistical or clinical significance (P > 0.50). Restoration dislodgement accounted for 82.8 per cent and marginal defects for 17.2 per cent of all failures. There were no instances of unsatisfactory restoration wear or recurrent caries observed. Teeth with three or more restored cervical surfaces accounted for 79.3 per cent of all failures (P < 0.0001). CONCLUSIONS: For root surface caries restored with GIC, the use of hand instruments only with the ART method was an equally effective alternative to conventional rotary instrumentation for cavity preparation. Larger restorations had higher failures, usually from dislodgement.

Adult↗
PubMed2003

Microwave-induced thermal imaging of tissue dielectric properties.

A new imaging method, microwave-induced thermal imaging (MITI), was developed to differentiate tissue based on thermal and dielectric properties. Image contrast depends on temporal strain in tissue, which was determined by one-dimensional speckle tracking using a phase-sensitive, correlation-based technique. The underlying mechanisms were analyzed and experimental results on biologic tissue agreed well with theoretical predictions. Because of its strong contrast between water-bearing and lipid-bearing tissue, the technique may enhance existing intravascular ultrasound (IVUS) imaging systems to identify vulnerable arterial plaque.

Adipose Tissue↗
PubMed2002

CD4 T lymphocytes cause hepatocyte apoptosis by releasing Th1 cytokines in cellular immunological liver injury.

OBJECTIVE AND DESIGN: To investigate how lymphocytes induce hepatocyte apoptosis. MATERIALS AND METHODS: Liver injury was elicited by the trinitrobenzenesulfonic acid (TNBS) in picryl chloride (PCI)-sensitized mice. An ear swelling was also triggered with TNBS to confirm its eliciting ability. An in vitro assay for inducing hepatocyte apoptosis was established. RESULTS: TNBS significantly elicited liver injury as well as ear swelling in PCl-sensitized mice. In the liver injury, hepatocyte apoptosis was detected 6 h after TNBS treatment. Cyclosporin A inhibited both ear swelling and hepatocyte apoptosis. When spleen cells from PCl-sensitized mice were co-cultured for 24 h with those from normal mice that had been treated with TNBS for 20 min, the supernatant collected showed a strong apoptosis-inducing activity for hepatocytes. The apoptosis was significantly reduced when the spleen cells from PCl-sensitized mice were treated previously with anti-CD3 or anti-CD4 antibody. By treating the cells, galactosamine and cycloheximide also lowered the apoptosis-inducing activity and decreased TNF-alpha and IL-2 productions. However, galactosamine treatment of hepatocytes greatly facilitated their susceptibility to supernatant-induced apoptosis. By contrast, cycloheximide completely blocked the facilitation. CONCLUSIONS: CD4+ T cells in mice with liver injury may cause hepatocyte apoptosis by releasing cytokines including TNF-alpha and IL-2.

Animals↗
PubMed2001

Respiratory diseases in the first year of life in children born to HIV-1-infected women.

Our objective was to describe the respiratory complications, clinical findings, and chest radiographic changes in the first year of life in infected and uninfected children born to HIV-1-infected women. We prospectively followed a cohort of 600 infants born to HIV-1-infected women from birth to 12 months in a multicenter study. Of these, 93 infants (15.5%) were HIV-1-infected, 463 were uninfected, and 44 were of unknown status prior to death or loss to follow-up. The cumulative incidence ( +/- SE) of an initial pneumonia episode at 12 months was 24.1 +/- 4.7% in HIV-1-infected children compared to 1.4 +/- 0.6% in HIV-1-uninfected children (P < 0.001). The rate of Pneumocystis carinii pneumonia (PCP) was 9.5 per 100 child-years. The HIV-1 RNA load was not higher in the group that developed pneumonia in the first year vs. those who did not. Children who developed lower respiratory tract infections or PCP had increased rates of decline of CD4 cell counts during the first 6 months of life. Lower maternal CD4 cell counts were associated with higher rates of pneumonia, and upper and lower respiratory tract infections. The rates of upper respiratory tract infection and bronchiolitis/reactive airway disease in infected children were not significantly different than in uninfected children. At 12 months, significantly more HIV-1-infected than uninfected children had tachypnea and chest radiographs with nodular and reticular densities. There was no relationship between cytomegalovirus infection in the first year of life and radiographic changes or occurrences of pneumonia. In conclusion, despite a low incidence of PCP, rates of pneumonia remain high in HIV-infected children in the first year of life. The incidence of pneumonia in uninfected infants born to HIV-1-infected mothers is low. Chest X-ray abnormalities and tachypnea suggest that subacute disease is present in infected infants. Further follow-up is warranted to determine its nature.

Adult↗
PubMed2001

Forced expiratory flow in uninfected infants and children born to HIV-infected mothers.

The Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted HIV (P(2)C(2) HIV) Study is a multicenter study examining pulmonary and cardiac outcomes in offspring of HIV-infected mothers. This portion of the P(2)C(2) study tests the hypothesis that infants exposed to, but uninfected by, maternal HIV have normal maximal expiratory flow at functional residual capacity (V'max,(FRC)). We obtained 500 measurements of V'max,(FRC) by rapid thoracic compression in 285 children ages 6-30 mo in five U.S. centers. The data were compared with those from a healthy cohort of children described elsewhere. V'max,(FRC) rose with height in a linear relationship. The slope of the regression line in the exposed infants did not differ statistically from the slope in the comparison group, but the intercept was about 20% lower (p < 0.001). Height and weight were comparable in the two cohorts, and the differences between intercepts persisted after adjusting for birth weight and gestational age. However, maternal HIV infection cannot be assumed to be the cause as the cohorts may have differed in other variables, such as socioeconomic status and frequency of maternal smoking and drug use. Also, measurements varied substantially within and between our five centers, probably in part because of different racial and ethnic distributions. In summary, maternal HIV infection probably has only a modest effect, if any, on maximal expiratory flow at functional residual capacity in uninfected infants.

Age Factors↗
PubMed2001

Effects of endothelin receptor A antagonist FR139317 on rats with congestive heart failure.

AIM: To study the effects of a selective endothelin receptor A (ETA) antagonist FR139317 on rats with congestive heart failure. METHODS: A congestive heart failure model was established via left coronary artery ligation in adult male Wistar rats. The rats with congestive heart failure were treated with FR139317 at two doses (1 and 5 mg . kg-1 . d-1 respectively for 6 weeks) or with vehicle. Hemodynamics, plasma level of endothelin-1 (ET-1), and mortality rate of rats were measured. RESULTS: Both groups treated with FR139317 (high and low dose) have lower mortality rate (25.0 % and 28.6 % vs 50.0 %) and lower plasma level of ET-1 than that of vehicle [(3.6 +/- 1.2) ng/L and (4.9 +/- 1.5) ng/L vs (5.8 +/- 1.3) ng/L]. Comparing to vehicle group, left ventricular end-diastolic pressures of the FR139317-treated groups were improved significantly [(12 +/- 6) mmHg and (14 +/- 7) mmHg vs (22 +/- 9) mmHg]. FR139317 at a higher dose reduced the mean arterial pressure of the rats with congestive heart failure and decreased the plasma concentration of endothelin to a closer level of rats with normal heart function than lower dose. CONCLUSION: Selective ETA antagonist FR139317 improved the hemodynamics and reduced the plasma ET-1 level and the mortality of rats with congestive heart failure

Animals↗
PubMed2001

Cationic lipids enhanced cellular uptake and activity of bcl-2 antisense oligodeoxynucleotide G3139 in HL-60 cells.

AIM: To explore the effect of cationic lipid 1,3-di-oleoyloxy-2-(6-carboxy-spermyl)-propylamid (DOSPER) on cellular uptake and activity of bcl-2 antisense oligodeoxynucleotide G3139 in HL-60 cells. METHODS: The cell-associated mean fluorescence intensity and the percentage of cells with positive staining for Bcl-2 were measured by flow cytometry. The subcellular distribution of fluorescein isothiocyanate (FITC)-labeled G3139 was observed by fluorescence microscope and the bcl-2 mRNA level was detected by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: (1) DOSPER increased cellular uptake of G3139 into HL-60 cells greatly. When DOSPER/G3139 (microg : microg) was 2 : 1, the uptake of G3139 reached top after treatment for 2 h and increased about 20 times compared with application of G3139 alone. In the presence of DOSPER, G3139 was localized in nucleus and cytosol with a bright spotted fluorescence staining. However, G3139 was localized in cytoplasm with faint fluorescence in the absence of DOSPER. (2) Cell-associated G3139 could be effluxed out of cells. After treated with G3139 in the presence of DOSPER for 4 h, the cell-associated G3139 could be fitted by C(t)=68.2e(-0.60) t+31.8e(-0.02) t (% of initial value), with a half-life of approximately 1.1 h. In the absence of DOSPER, the cell-associated G3139 could be fitted by C(t)=64.8e(-2.27) t+35.2e(-0.04) t, with a half-life of about 18 min. (3) In the presence of DOSPER, G3139 1.0 micromol/L specially reduced bcl-2 mRNA level, and Bcl-2 protein decreased from 97 % +/- 4 % to 70.6 % +/- 2.1 %. CONCLUSION: DOSPER enhanced the activity of G3139 and it might be attributed to increase of the cellular uptake and change of the subcellular distribution of G3139.

Biological Transport↗
PubMed2001

Protective effect of ginsenoside Rg1 on dopamine-induced apoptosis in PC12 cells.

AIM: To explore the possible molecular mechanism of exogenous dopamine-induced apoptosis in PC12 cells and the protective effect of ginsenoside Rg1. METHODS: Flow cytometric assay was used to quantify the apoptotic cells and measure the percentage of cells with positive Bcl-2 and Bax proteins. The morphology of apoptotic cells was evaluated by transmission electron microscope. DNA fragmentation was observed by gel electrophoresis. Caspase-3 activity was determined by fluorescent spectrofluorometer and the expressive bcl-2 and bax mRNA by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Dopamine 0.15, 0.30, 0.45, and 0.60 mmol/L induced PC12 cell apoptosis from 1.1 % +/- 0.4 % (control) to 41 % +/- 3 %, 46.4 % +/ -2.7 %, 53 % +/ -3 %, and 64.5 % +/- 2.7 %, respectively. After treatment with dopamine 0.45 mmol/L following pretreatment with Rg1 10 micromol/L for 24 h, the percentage of apoptotic cells and caspase-3 activity decreased from 53 % +/- 3 % and 683 +/- 8 (mean fluorescence intensity, MFI) to 1.9 % +/- 0.6 % and 325 +/- 5, and the percentage of cells with positive Bcl-2 protein increased from 14.3 % +/- 1.1 % to 25.9 % +/- 1.6 %, however, the percentage of cells with positive Bax protein decreased from 48 % +/- 3 % to 35 % +/- 3 %, compared with group treated with DA 0.45 mmol/L alone. CONCLUSION: Ginsenoside Rg1 protected PC12 cells against apoptosis by inhibiting the activation of caspase-3 and regulating the ratio of Bcl-2 to Bax protein.

Animals↗
PubMed2001

[Possible mechanism of the protective effects of ginsenoside Rg1 on apoptosis in PC12 cells].

AIM: To explore the possible mechanism of the protective effect of ginsenoside Rg1 on dopamine-induced apoptosis in PC12 cells. METHODS: Flow cytometric assay was performed to quantify the apoptotic cells and detect the positive percentage of Bcl-2 and Bax proteins in PC12 cells. The expression of bcl-2 and bax mRNA was identified by reverse transcription polymerase chain reaction (RT-PCR). The CPP32 activity was measured by fluorescent spectrofluorometer. RESULTS: Dopamine-induced apoptosis in PC12 cells was inhibited by pretreatment with 10 mumol.L-1 Rg1. Simultaneously, the expression of Bcl-2 protein and mRNA were increased, and the Bax protein and mRNA were decreased. The activation of CPP32 was inhibited after pretreatment with Rg1. CONCLUSION: Rg1 protects against dopamine-induced apoptosis in PC12 cells and this effect might be attributed to its regulation of the ratio of Bcl-2 to Bax and its inhibition of the activation of CPP32.

Animals↗
PubMed2000

Thoracoabdominal compression and respiratory system compliance in HIV-infected infants.

The thoracoabdominal compression technique (TAC) is used to measure expiratory flow in infants. We investigated whether TAC caused a change in total thoracic compliance (Crs), resistance (Rrs), and respiratory system time constant (Trs). We studied 41 infants (mean age, 12.4 mo; SD, 7.5) from five centers studying longitudinal lung and cardiovascular function of infants from HIV-infected mothers. We measured Crs, Rrs, and Trs before and after TAC. Changes in Crs, Rrs, and Trs after TAC were not dependent on the length of time since TAC. Crs and Trs were reduced after TAC, p = 0.013 and p = 0.003, respectively, whereas Rrs did not change. When compared with uninfected infants, HIV-infected infants had a larger post-pre TAC percent decline in Crs (p = 0.003) and a post-pre TAC rise in mean Rrs (p = 0.03). These differences remained significant after adjusting for sex and age. When performing infant pulmonary function testing, TAC itself produces a temporary decrease in Crs and Trs that is more significant in infants at risk for abnormal lung volume or compliance. Therefore, the sequence of performing the infant lung function parameters should be the same each time the testing is repeated with TAC as the last parameter tested at each testing session.

Abdomen↗
PubMed2000

New chemical and biological aspects of S-nitrosothiols.

Nitric oxide (NO) possesses many physiological effects and S-nitrosothiols have been identified in a variety of tissues exhibiting many NO-like activities. This review focuses on the latest discoveries pertaining to the biological functions of S-nitrosothiols and the recent research progress in the chemical properties and biomedical applications of RSNOs.

Animals↗
PubMed2000

Effect of zinc intake on fetal and infant growth among Chinese pregnant and lactating women.

The relationship between maternal nutrient intake and fetal size or infant growth was studied in 1956 pregnant women, 599 parturients and 1043 lactating women, 318 non-pregnant women included as controls. The study was conducted in eight regions that were representative of all geographical areas of China. The diet was comprised primarily of cereal products with 70% to 85% of the zinc intake derived from plant sources. Women in the third trimester of pregnancy, parturients and lactating women consumed more food than non-pregnant women or women in the first two trimesters of pregnancy. Total energy, protein and iron intakes met the recommended allowances for each stage of reproduction. Calcium and zinc intakes, however, were 50% and 47% of the amount recommended, respectively. Only 7.2% of the women exceeded two-thirds of the recommended zinc intake. The mean intake of zinc was 6.5 mg to 9.0 mg each day among all the subjects. Correlation and stepwise regression analysis showed that maternal zinc intake was a predictor factor for fetal dimensions and birthweight. The results of this study show that fetal growth and birthweight are directly related to maternal zinc intake among Chinese women, and that there is no relationship between maternal zinc intake during lactation and infant height, weight, or weight gain from birth.

Adult↗
PubMed1999

Nursing as a career choice: perceptions of school students speaking Arabic, Serbo-Croatian, Spanish, Turkish or Vietnamese at home.

Australia is a multicultural society and nowhere is this more evident than in Sydney where 25% of the population speaks a language other than English. In one of the largest area health services in New South Wales, the five most frequently spoken languages at home are Arabic, Serbo-Croatian, Spanish, Turkish or Vietnamese, with these language groups comprising 12% of Sydney's population. Yet nurses speaking one of these five languages comprise less than 1% of the nursing workforce. A cost-effective method of addressing the shortage of nurses speaking languages other than English is to recruit students who already speak another language into the profession. This study examined high school students' perceptions of nursing in order to determine appropriate methods of recruiting students speaking one of these languages. Implications for the design of recruitment campaigns are also discussed.

Attitude to Health↗
PubMed1998

Effect of taurine on human fetal neuron cells: proliferation and differentiation.

The purpose of this study was to investigate the effect of taurine on human fetal brain neuron cell proliferation and differentiation using a glial-free, pure cerebral neuronal culture grown in a serum-free environment. We found that taurine was necessary for neuronal survival and neurite extension. Taurine, on the other hand, has a trophic effect on the human fetal brain cell, promoting both proliferation and differentiation. Results showed that DNA synthesis of the neurons was increased in a dose-dependent manner when neurons were cultured in the medium containing taurine (100-6400 microM). The protein content of neuronal cells was also significantly increased in the neurons treated with taurine as compared to the control. At day 15, the expression of neuron-specific enolase (NSE) was only detected in the neurons cultured in the medium containing taurine. These results establish taurine as a putative human fetal brain neurontrophic factor in the process of human brain development.

Brain↗
PubMed1998

Effects of repletion with zinc and other micronutrients on neuropsychologic performance and growth of Chinese children.

The knowledge that zinc is essential for growth and neuropsychologic performance and a report of zinc-responsive stunting in Chinese children prompted this project. This article summarizes findings from a 10-wk, double-blind, controlled trial of zinc repletion in 740 urban, 6-9-y-old first graders from low-income families in Chongqing, Qingdao, and Shanghai, People's Republic of China. Treatments were 20 mg Zn alone (Z), 20 mg Zn with micronutrients (ZM), and micronutrients alone (M). The M mixture was based on National Research Council guidelines. Nutrients that might interfere with zinc retention were excluded or given in lower amounts. Main outcomes were changes in neuropsychologic performance and knee height. Hemoglobin, serum ferritin, plasma and hair zinc, and whole blood and hair lead were also measured. Anemia was not common, and serum ferritin concentrations were usually within the range of normal. Mean baseline plasma zinc concentrations were marginal in children from Chongqing and Qingdao and normal in children from Shanghai. After treatment with ZM or M plasma zinc increased. Hair zinc tended to decrease after all treatments. Mean baseline whole blood lead concentrations were slightly below the limit considered excessive for children by the US Centers for Disease Control and Prevention. Neuropsychologic performance and growth were most improved after treatment with ZM. These findings were consistent with the presence of zinc and other micronutrient deficiencies.

Brain↗
PubMed1998

Effects of amiodarone on cardiac electrophysiology in right ventricular rapid pacing-induced heart failure dogs.

AIM: To study the effects of amiodarone (Ami) on cardiac electrophysiologic properties and ventricular fibrillation threshold (VFT) in right ventricular rapid pacing-induced congestive heart failure (CHF) dogs. METHODS: Dogs (n = 25) were randomly allocated into 3 groups: A) control group; B) CHF group induced by right ventricular rapid pacing (4 pulses.s-1) for 4-5 wk; C) CHF models p Ami 300 mg.d-1 for 4-5 wk. The electrophysiologic parameters and VFT were evaluated by electric stimulation and monophasic action potential (MAP) recording. RESULTS: In CHF models, ventricular MAP duration (MAPD90), ventricular late repolarization duration (VLRD), and intra-ventricular conduction time (IVCT) were prolonged by 43%, 318%, and 19%, respectively; the ratio of ventricular effective refractory period (VERP) to MAPD90 (VERP/ MAPD90) and VFT were decreased by 13% and 48% respectively; the dispersion of ventricular recovery time (RT-D) was increased by 185%. In CHF models, Ami had no effects on ventricular MAPD90, but increased VERP/ MAPD90, IVCT, and VFT by 15%, 10%, and 67%, respectively, shortened VLRD by 87%; and decreased RT-D by 87%. Ami had no significant influences on the hemodynamic parameters of the CHF dogs. CONCLUSION: Ami normalizes the cardiac electrophysiologic properties in CHF dogs.

Action Potentials↗
PubMed1997

A preliminary report: effects of zinc and micronutrient repletion on growth and neuropsychological function of urban Chinese children.

OBJECTIVE: Zinc is essential for growth and cognition of experimental animals. Past research found zinc repletion improved growth of stunted Chinese children. Therefore we measured effects of zinc repletion on growth and neuropsychological functions of children. DESIGN: Double-blind randomized controlled treatment trial. SETTING: Elementary schools in low income districts of Chongqing, Qingdao and Shanghai. SUBJECTS: Three hundred-seventy-two 6 to 9 year old first graders. INTERVENTIONS: Treatments were 20 mg zinc, 20 mg zinc with micronutrients, or micronutrients alone. The micronutrient mixture was based on guidelines of the US NAS/NRC. Treatments were assigned to classrooms of 40 or more children each, and administered by teachers 6 days per week for 10 weeks. MEASURES OF OUTCOME: Changes in knee height and neuropsychological functions. RESULTS: Zinc alone had the least effect on growth while zinc with micronutrients had the largest effect; micronutrients alone had an intermediate effect. Zinc-containing treatments improved neuropsychological functions, but micronutrients alone had little effect. CONCLUSIONS: The findings confirm the essentiality of zinc for growth of children, and show, for the first time, the essentiality of zinc for neuropsychological functions of children. In addition, the need for repletion of other potentially limiting nutrients in studies examining the effects of specific nutrients on growth and neuropsychological functions was confirmed.

Analysis of Variance↗