Biomedical subjects

Yue Chen

Publications and source records attributed to Yue Chen.

121 records · Page 7Linked to original sources

PubMed2003

[Effect of intracellular-free Ca2+ concentration on transient magnesium-free treatment induced epileptic injury in developing cortical neurons of rats].

OBJECTIVE: To investigate the effect of intracellular-free Ca2+ concentration ([Ca2+]i) on injury following transient Mg(2+)-free treatment in vitro in developing cortical neurons. METHODS: Embryo cortical neurons of rats cultured for 6 d and 17 d were directly exposed to Mg(2+)-free media, or pretreated with NMDA receptor antagonists or calcium channel antagonist before being exposed to Mg(2+)-free media. MTT assay was used to study the injury of neurons. [Ca2+]i were measured using fluo-3, a fluorescent calcium-sensitive dye and laser-scanning confocal microscope, and calculated by the fluorescent intensity. RESULTS: Compared with control, MTT conversion rates decreased after transient (3 h) Mg(2+)-free treatment in neurons cultured for 6 d and 17 d in vitro, (59.1 +/- 6.87)% and (51.2 +/- 5.90)%, respectively. In neurons pre- and co-treated with 10 mumol.L-1 MK-801, 50 mumol.L-1 AP-5 and 10 mumol.L-1 nifedipine, MTT conversion rates were higher than those of neurons with only Mg(2+)-free treatment. Peak values of [Ca2+]i in neurons cultured for 6 d and 17 d were 2.4 +/- 0.23 and 3.2 +/- 0.32, respectively. Peak value of neurons 17 d in vitro was significantly higher than that of neurons 6 d in vitro (P < 0.05). In neurons pre- and co-treated with MK-801, AP-5 and nifedipine, [Ca2+]i were lower than those of neurons with only Mg(2+)-free treatment. CONCLUSION: Neuronal injury and [Ca2+]i changes following Mg(2+)-free-treatment-induced seizure were different between neurons 6 d and 17 d in vitro. It suggested that the age-dependent [Ca2+]i changes might play a role in an age-dependent manner of injury following Mg(2+)-free-treatment-induced seizure. NMDA receptor-Ca2+ pathway activation was crucial in the [Ca2+]i change and the cellular injury induced by Mg(2+)-free treatment.

Aniline Compounds↗

PubMed2003

[Cloning, eukaryotic expression and function assay of recombinant leukemia inhibitory factor gene LIF].

Leukemia inhibitory factor (LIF), a cytokine belonging to IL-6 family, which was discovered to inhibit the proliferation of murine myeloid leukemic cell line M1, has multiple functions in various biological processes. This factor is highly glycosylated when it binds to receptor to activate the signal transduction. Therefore, expression of LIF through eukaryotic system is the best way to obtain the correct glycosylation. In this study, human LIF cDNA with the sequence of signal peptide was cloned from adult blood cells by RT-PCR, and then subcloned into pcDNA3 for expression in HEK-293T cells. After transfection of the recombinant plasmid pcDNA3/LIF into HEK-293T cells, the conditioned medium containing the secreted LIF was obtained. The activity of the secreted LIF in the conditioned medium was detected through the phosphorylation of STAT3, EMSA and luciferase reporter (pGL2-APRE-luc) assays in Hep3B and 293T cells. Furthermore, to investigate the biological functions of the overexpressed recombinant LIF, a [(3)H]-thymedine incorporation assay was performed, and the results showed that the recombinant LIF inhibited the growth of M1 cells strongly. Taken together, all the function assays suggest that the recombinant LIF has the normal functions, suggesting that the recombinant LIF could be used for further studies.

Adult↗

PubMed2003

[The immunopotentiation of human B lymphocyte stimulator C-terminal peptide].

The cDNA of human B lymphocyte stimulator C-terminal peptide (C-BLyS) was amplified by nested PCR from cDNA library of human fetal brain. The expression plasmid pT7450-C-BLyS was constructed and transformed into E. coli BL21 CodonPlus (DE3) RIL which can recognize many rare codons. The C-BLyS protein was expressed as inclusion body in E. coli BL21 CodonPlus (DE3) RIL and the inclusion body of C-BLyS was denatured and then refolded by dialysis and purified by ion exchange chromatography. The refolded and purified C-BLyS can specifically bind with BCMA-Fc, a fusion protein of BLyS receptor and human IgG1 Fc. Furthermore, C-BLyS is proved to be an effective stimulator in mouse splenocytes proliferation in vitro and effective immunostimulant in vivo.

Animals↗

PubMed2002

Obesity may increase the incidence of asthma in women but not in men: longitudinal observations from the Canadian National Population Health Surveys.

To investigate the possibility of gender specificity for the effect of body mass index (BMI) on development of asthma, the authors used the longitudinal data from the first and second cycles of the National Population Health Survey, conducted in Canada in 1994-1995 and 1996-1997, respectively. Data from 9,149 subjects (4,266 men and 4,883 women) aged 20-64 years who reported no asthma at baseline were used in this analysis. The 2-year cumulative incidence of asthma was estimated by using a bootstrap procedure to take sampling weights and design effects into account. During the 2-year study period, 1.6% of the men and 2.9% of the women developed asthma. Average changes in body weight and BMI over the 2-year observation period were relatively small and were not associated with asthma incidence. However, baseline BMI was a significant predictor for asthma incidence in women. The adjusted odds ratio for women whose baseline BMI was at least 30.0 kg/m(2) versus 20.0-24.9 kg/m(2) was 1.9 (95% confidence interval: 1.1, 3.4), whereas the corresponding odds ratio of 1.1 (95% confidence interval: 0.3, 3.6) for men was not significantly different from unity. The authors concluded that obesity was related to development of asthma in women but not in men.

Adult↗

PubMed2002

Air pollution and disability days in Toronto: results from the national population health survey.

The influence of air pollution on disability days in Toronto during the period 1994-1999 was examined using data from Canada's National Population Health Survey. A model of disability days (the sum of days spent in bed and days when the respondent cut down on usual activities) during the 2 weeks prior to the interview was constructed by sequentially examining the influence of time period, personal characteristics, weather, and air pollution. After adjusting for these other factors, only the effects of carbon monoxide and particulate matter of median diameter less than 2.5 microm (PM2.5) were statistically significant (respectively, 30.8% (95% CI 1.2-69.0) and 21.9% (95% CI 3.8-43.0) increase in disability days for a change in concentration equal to the interquartile range of the 2-week average pollutant concentration). PM2.5 was more strongly associated with disability days in the warm season. Results of multipollutant models were difficult to interpret in that effect sizes appeared to be influenced by covariation among pollutants. With the exception of warm season results for PM2.5, findings were not sensitive to alternative analytical approaches. While these results are suggestive of significant effects of the urban air pollution mix at relatively low ambient concentrations, the precise contribution of individual pollutants could not be determined.

Air Pollutants↗

PubMed2002

Visual and cognitive control of attention in smooth pursuit.

In this chapter, we describe the role of attention in the control of smooth pursuit eye movements. As a voluntary and continuous eye movement, smooth pursuit is driven by both visual and cognitive signals. Here we show that whereas the entire process of smooth pursuit requires visual attention, the post-onset phase of the initiation and the maintenance smooth pursuit are under an additional sustained non-visual cognitive attention control. The temporal dynamics of these complementary controls of visual and non-visual cognitive attention support the continuous generation of smooth pursuit so that eye tracking of a moving target can be prompt and accurate.

Attention↗

PubMed2002

Fine particulate air pollution and all-cause mortality within the Harvard Six-Cities Study: variations in risk by period of exposure.

PURPOSE: We used Poisson regression methods to examine the relation between temporal changes in the levels of fine particulate air pollution (PM(2.5)) and the risk of mortality among participants of the Harvard Six Cities longitudinal study. METHODS: Our analyses were based on 1430 deaths that occurred between 1974 and 1991 in a cohort that accumulated 105,714 person-years of follow-up. For each city, indices of PM(2.5) were derived using daily samples. Individual level data were collected on several risk factors including: smoking, education, body mass index (BMI), and occupational exposure to dusts. Time-dependent indices of PM(2.5) were created across 13 calendar periods (< 1979, 1979, 1980, em leader, 1989, >/= 1990) to explore whether recent or chronic exposures were more important predictors of mortality. RESULTS: The relative risk (RR) of mortality calculated using Poisson regression based on average city-specific exposures that remained constant during follow-up was 1.31 [95% confidence interval (CI) = 1.12-1.52] per 18.6 microg/m(3) of PM(2.5). This result was similar to the risk calculated using the Cox model (RR = 1.26, 95% CI = 1.08-1.46). The RR of mortality was attenuated when the Poisson regression model included a time-dependent estimate of exposure (RR = 1.19, 95% CI = 1.04-1.36). There was little variation in RR across time-dependent indices of PM(2.5). CONCLUSIONS: The attenuated risk of mortality that was observed with a time-dependent index of PM(2.5) is due to the combined influence of city-specific variations in mortality rates and decreasing levels of air pollution that occurred during follow-up. The RR of mortality associated with PM(2.5) did not depend on when exposure occurred in relation to death, possibly because of little variation between the time-dependent city-specific exposure indices.

Air Pollutants↗

PubMed2002

The influence of ambient coarse particulate matter on asthma hospitalization in children: case-crossover and time-series analyses.

In this study, we used both case-crossover and time-series analyses to assess the associations between size-fractionated particulate matter and asthma hospitalization among children 6-12 years old living in Toronto between 1981 and 1993. Specifically, we used exposures averaged over periods varying from 1 to 7 days to assess the effects of particulate matter on asthma hospitalization. We calculated estimates of the relative risk of asthma hospitalization adjusted for daily weather conditions (maximum and minimum temperatures, and average relative humidity) for an incremental exposure corresponding to the interquartile range in particulate matter. Both bidirectional case-crossover and time-series analyses revealed that coarse particulate matter (PM10-2.5) averaged over 5-6 days was significantly associated with asthma hospitalization in both males and females. The magnitude of this effect appeared to increase with increasing number of days of exposure averaging for most models, with the relative risk estimates stabilizing at about 6 days. Using a bidirectional case-crossover analysis, the estimated relative risks were 1.14 [95% confidence interval (CI), 1.02, 1.28] for males and 1.18 (95% CI, 1.02, 1.36) for females, for an increment of 8.4 microg/m(3) in 6-day averages of PM10-2.5. The corresponding relative risk estimates were 1.10 and 1.18, respectively, when we used time-series analysis. The effect of PM10-2.5 remained positive after adjustment for the effects of the gaseous pollutants carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3). We did not find significant effects of fine particulate matter (PM2.5) or of thoracic particulate matter (PM10) on asthma hospitalizations using either of these two analytic approaches. For the most part, relative risk estimates from the unidirectional case-crossover analysis were more pronounced compared with both bidirectional case-crossover and time-series analyses.

Air Pollutants↗

PubMedDate not supplied

Studies on bone marrow stromal cells affinity of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate).

The objective of this study is to investigate the biocompatibility of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) with bone marrow stromal cells in vitro. The adsorption of fibronectin on the material was studied by enzyme-linked immunosorbent assay. After bone marrow stromal cells were seeded and cultured on PHBHHx, their proliferation was investigated by MTT. Differentiation of the cells was assessed by measuring alkaline phosphatase activity and by histochemical assay. The wettability and thermal property of PHBHHx films were also studied by contact angle goniometer, thermogravimetry and differential scanning calorimetry, respectively. The results show that bone marrow stromal cells can attach, proliferate and differentiate into osteoblasts on PHBHHx films. These results suggest that PHBHHx has good affinity with bone marrow stromal cells and may have potential applications in bone tissue engineering.

3-Hydroxybutyric Acid↗

PubMedDate not supplied

Integrated approach for manual evaluation of peptides identified by searching protein sequence databases with tandem mass spectra.

Quantitative proteomics relies on accurate protein identification, which often is carried out by automated searching of a sequence database with tandem mass spectra of peptides. When these spectra contain limited information, automated searches may lead to incorrect peptide identifications. It is therefore necessary to validate the identifications by careful manual inspection of the mass spectra. Not only is this task time-consuming, but the reliability of the validation varies with the experience of the analyst. Here, we report a systematic approach to evaluating peptide identifications made by automated search algorithms. The method is based on the principle that the candidate peptide sequence should adequately explain the observed fragment ions. Also, the mass errors of neighboring fragments should be similar. To evaluate our method, we studied tandem mass spectra obtained from tryptic digests of E. coli and HeLa cells. Candidate peptides were identified with the automated search engine Mascot and subjected to the manual validation method. The method found correct peptide identifications that were given low Mascot scores (e.g., 20-25) and incorrect peptide identifications that were given high Mascot scores (e.g., 40-50). The method comprehensively detected false results from searches designed to produce incorrect identifications. Comparison of the tandem mass spectra of synthetic candidate peptides to the spectra obtained from the complex peptide mixtures confirmed the accuracy of the evaluation method. Thus, the evaluation approach described here could help boost the accuracy of protein identification, increase number of peptides identified, and provide a step toward developing a more accurate next-generation algorithm for protein identification.

Algorithms↗

PubMedDate not supplied

Tagging-via-substrate strategy for probing O-GlcNAc modified proteins.

Identification of proteins bearing a specific post-translational modification would imply functions of the modification. Proteomic analysis of post-translationally modified proteins is usually challenging due to high complexity and wide dynamic range, as well as unavailability of efficient methods to enrich the proteins of interest. Here, we report a strategy for the detection, isolation, and profiling of O-linked N-acetylglucosamine (O-GlcNAc) modified proteins, which involves three steps: metabolic labeling of cells with an unnatural GlcNAc analogue, peracetylated azido-GlcNAc; chemoselective conjugation of azido-GlcNAc modified proteins via the Staudinger ligation, which is specific between phosphine and azide, using a biotinylated phosphine capture reagent; and detection and affinity purification of the resulting conjugated O-GlcNAc modified proteins. Since the approach relies on a tag (azide) in the substrate, we designated it the tagging-via-substrate (TAS) strategy. A similar strategy was used previously for protein farnesylation, phosphorylation, and sumoylation. Using this approach, we were able to specifically label and subsequently detect azido-GlcNAc modified proteins from the cytosolic lysates of HeLa, 3T3, COS-1, and S2 cell lines, suggesting the azido-substrate could be tolerated by the enzymatic systems among these cells from diverse biological species. We isolated azido-GlcNAc modified proteins from the cytosolic extract of S2 cells and identified 10 previously reported and 41 putative O-GlcNAc modified proteins, by nano-HPLC-MS/MS. Our study demonstrates that the TAS approach is a useful tool for the detection and proteomic analysis of O-GlcNAc modified proteins.

Acetylglucosamine↗

PubMedDate not supplied

Impact of particulate air pollution on quality-adjusted life expectancy in Canada.

Air pollution and premature death are important public health concerns. Analyses have repeatedly demonstrated that airborne particles are associated with increased mortality and estimates have been used to forecast the impact on life expectancy. In this analysis, we draw upon data from the American Cancer Society (ACS) cohort and literature on utility-based measures of quality of life in relation to health status to more fully quantify the effects of air pollution on mortality in terms of quality-adjusted life expectancy. The analysis was conducted within a decision analytic model using Monte Carlo simulation techniques. Outcomes were estimated based on projections of the Canadian population. A one-unit reduction in sulfate air pollution would yield a mean annual increase in Quality-Adjusted Life Years (QALYs) of 20,960, with gains being greater for individuals with lower educational status and for males compared to females. This suggests that the impact of reductions in sulfate air pollution on quality-adjusted life expectancy is substantial. Interpretation of the results is unclear. However, the potential gains in QALYs from reduced air pollutants can be contrasted to the costs of policies to bring about such reductions. Based on a tentative threshold for the value of health benefits, analysis suggests that an investment in Canada of over 1 billion dollars per annum would be an efficient use of resources if it could be demonstrated that this would reduce sulfate concentrations in ambient air by 1 microg/m(3). Further analysis can assess the efficiency of targeting such initiatives to communities that are most likely to benefit.

Adolescent↗

PubMedDate not supplied

Testing the harvesting hypothesis by time-domain regression analysis. II: covariate effects.

This article extends the previous work of Fung et al. (2004) investigating the ability of the time-scale log-linear regression model, proposed by Dominici et al. (2003), to detect mortality displacement (sometimes known as harvesting) in time-series data relating air pollution to excess mortality. We conducted a simulation study based on two different compartment models of the death process: pure frailty model and mixed frailty model. We assume that nonaccidental death only affects frail population in a pure frailty model and affects both frail people and other individuals in the mixed frailty model. With a pure frailty model and a moderate-size pollution effect, we identified a characteristic mortality displacement pattern in the different time-scale coefficients of log relative risk. However, once a covariate like temperature was introduced into the model, such a mortality displacement pattern disappeared. Furthermore, a false mortality displacement effect was present in the incorrectly specified model, when temperature was not taken into account. We believe that time-scale regression has limited value for detecting mortality displacement in time-series data.

Air Pollution↗