Introduction on a forecasting model for infectious disease incidence rate based on radial basis function network / 中华流行病学杂志

It is important to forecast incidence rates of infectious disease for the development of a better program on its prevention and control. Since the incidence rate of infectious disease is influenced by multiple factors, and the action mechanisms of these factors are usually unable to be described with accurate mathematical linguistic forms, the radial basis function (RBF) neural network is introduced to solve the nonlinear approximation issues and to predict incidence rates of infectious disease. The forecasting model is constructed under data from hepatitis B monthly incidence rate reports from 1991-2002. After learning and training on the basic concepts of the network, simulation experiments are completed, and then the incidence rates from Jan. 2003-Jun. 2003 forecasted by the established model. Through comparing with the actual incidence rate, the reliability of the model is evaluated. When comparing with ARIMA model, RBF network model seems to be more effective and feasible for predicting the incidence rates of infectious disease, observed in the short term.

In vitro cytotoxicity of TCDD on SPC-A1 cells / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>The toxicology of TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) has been studied mainly with regard to the carcinogenicity of its metabolites, but its phototoxicity is not well understood. Although some studies have indicated the lethal phototoxicity of TCDD, this study was designed to investigate its effect on SPC-A1 cells.</p><p><b>METHODS</b>SPC-A1 cells were cultured in 1640 medium and treated with 10 nmol/L, 0.1 micromol/L, 1 micromol/L TCDD for either 24 h or 96 h at each concentration. SPC-A1 cells were co-cultured with TCDD at different concentrations. Then the cell morphology, DNA fragment electrophoresis, and cell cycle were analyzed by flow cytometry, and enzyme assays were used to observe the effect of TCDD on the morphology, growth rate, and enxyme change of SPC-A1 cells.</p><p><b>RESULTS</b>With the increasing concentrations of TCDD and prolongation of culture time, the morphology of SPC-A1 cells was changed from round shape to spindle, and the ability of SPC-A1 cells to adhere to wall was decreased. With debris emitted around the cells, the morphologic changes included reduction in cell volume. Nuclear chromatin condensation and PI were observed. With the increasing concentrations of TCDD, DNA ladder occurred. After treatment with TCDD, extraction of cancer cells exhibited typical DNA fragmentation, and flow cytometry analysis showed apoptosis in a dose-dependent manner. As the concentration of TCDD rose from 10 nmol/L to 1 micromol/L, the ratio of apoptotic cells increased from 10.76% to 21.82%.</p><p><b>CONCLUSIONS</b>TCDD has in vitro cytotoxicity on SPC-A1 cells, and the cytotoxicity is positively related to its concentration and culture time. TCDD may inhibit the growth and proliferation of SPC-A1 cells through the pathway of apoptosis introduction.</p>

A quantitative DNA methylation assay using mismatch hybridization and chemiluminescence / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To develop a quantitative method for methylation analysis of the p16 gene based on mismatch hybridization and chemiluminescence.</p><p><b>METHODS</b>Genomic DNA was modified by sodium bisulfite to convert all unmethylated but not methylated cytosines to uracil, and subsequently a pair of primer having no CpG sites was designed for amplification target DNA containing methylated or unmethylated CpG sites. The PCR product spanning CpG sites were hybridized with two oligonucleotide probes which perfectly matched the methylated and unmethylated CpG sequences respectively, and the hybrids were detected by chemiluminescent method. The percentage of methylated target sequences could be estimated by calculating the ratio of signals obtained with two probes.</p><p><b>RESULTS</b>The percentage of methylation of artificial mixtures DNA showed a linear relation. There was a negative correlation between the methyaltion index with p16 transcriptional mRNA of p16 gene in tumor cell lines.</p><p><b>CONCLUSION</b>Compared with existing methods, this assay is nonisotopic, rapid, simple, and can be widely applied to the study of DNA methylation.</p>

Study on the expression of DNA excision repair biomarkers in cispatin-treated lung cancer cell line / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the expression levels of ERCC2, UDG, and PCNA in cisplatin-treated A549 cell line.</p><p><b>METHOD</b>Comet assay, RT-PCR, and western blot were used to study the mRNA and protein expression levels of ERCC2, UDG, and PCNA.</p><p><b>RESULTS</b>When treated with IC(20) cisplatin, the DNA damage level increased as the cisplatin treated time increased within 24 h of cisplatin treatment. The tail state 12 h and 24 h after treatment was 5.02 +/- 0.68 and 7.22 +/- 0.53 respectively, which was significantly higher than those of the controls (2.73 +/- 0.29). The tail state 24 h after treatment was not significantly different from that of the controls. The DNA damage level decreased to normal after cisplatin treatment in 24 h (tail state 3.64 +/- 0.7). The expression levels of ERCC2, UDG, PCNA protein (4.37 +/- 0.57, 5.47 +/- 0.46, 2.21 +/- 0.47 respectively) and mRNA (0.71 +/- 0.08, 0.74 +/- 0.06, 0.82 +/- 0.09) were increased significantly within 24 h exposure and decreased to normal 24 h after cisplatin treatment. The 3 enzymes' mRNA and protein expression increased when treated with cisplatin, but the changes of protein level were slower than those of mRNA levels.</p><p><b>CONCLUSIONS</b>The DNA repair capability in A549 cells increases after cisplatin treatment. Cisplatin was a positive regulation of ERCC2, UDG, PCNA expression levels, which causes the increase of mRNA, and protein. The positive regulation only works in a short time and returns normal after 24 h of cisplatin treatment.</p>

Antisense ERCC1 RNA decreases the repair capability of damaged DNA in lung cancer cells induced by benzoapyrene / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of ERCC1 gene on the repair capability of damaged DNA in lung cancer A549 cells induced by benzo[a]pyrene.</p><p><b>METHODS</b>Recombinant plasmid expressing ERCC1 antisense RNA was constructed and transfected into A549 cells by Lipofectin reagent. The stable-transfected cell colonies were selected by hygromycin. Cell viability was determined by the MTT assay. The level of ERCC1 mRNA was measured by Northern Blot analysis. Single cell gel electrophoresis assay was applied to determine the cellular DNA damage and fifty cells for each group were counted.</p><p><b>RESULTS</b>Seven positive colonies expressing ERCC1 antisense RNA were screened. There was no growth rate difference between the antisense-transfected cells and the parental cells. The endogenous mRNA level in transfected colonies decreased in varied degrees, i.e. 12% approximately 86% of that of the parental cells in Northern Blot assay. After 24 h treatment of 10 micro mol/l benzo[a]pyrene, the repair capability for DNA damage in transfected colonies was reduced to 29% approximately 71% of that of the parental cells. Also, a statistically significant correlation was observed between expression of ERCC1 mRNA and repair capability (r = 0.84).</p><p><b>CONCLUSION</b>Antisense ERCC1 RNA decreased the repair capability for damaged DNA in lung cancer cells induced by benzo[a]pyrene.</p>

Improvement of chemically-activated luciferase gene expression bioassay for detection of dioxin-like chemicals / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To improve the chemically-activated luciferase expression (CALUX) bioassay for detection of dioxin-like chemicals (DLCs) based on the toxicity mechanisms of DLCs.</p><p><b>METHODS</b>A recombinant vector was constructed and used to transfect human hepatoma (HepG2). The expression of this vector was 10-100 folds higher than that of pGL2 used in previous experiments. The transfected cells showed aromatic hydrocarbon receptor (AhR)-meditated luciferase gene expression. The reliability of luciferase induction in this cell line as a reporter of AhR-mediated toxicity was evaluated, the optimal detection time was examined and a comparison was made by using the commonly used ethoxyresoufin-O-deethylase (EROD) activity induction assay.</p><p><b>RESULTS</b>The results suggested that the luciferase activity in recombinant cells was peaked at about 4 h and then decreased to a stable activity by 14 h after TCDD treatment. The detection limit of this cell line was 0.11 pmol/L, or 10-fold lower than in previous studies, with a linear range from 1 to 100 pmol/L, related coefficient of 0.997, and the coefficient of variability (CV) of 15-30%.</p><p><b>CONCLUSION</b>The luciferase induction is 30-fold more sensitive than EROD induction, the detection time is 68 h shorter and the detection procedure is also simpler.</p>

Catalysis of lyase-isomerase PecE/PecF for several apophycobiliproteins / 生物工程学报

Phycoerythrocyanin(PEC) lyase-isomerase PecE/PecF from Mastigocladus laminosus is the specific enzyme for biosynthesis of PEC alpha-subunit(alpha-PEC). In this work, the specificity of PecE/PecF on substrate apoproteins was reported. PecE/PecF could catalyse the reconstitution of phycocyanobilin(PCB) with apoproteins of alpha-PEC from two different subspecies of Mastigocladus laminosus, as well the site-directed mutated apoprotein of alpha-PEC with Trp at 128 to Phe in vitro, but could not catalyse the reconstitution of PCB with apoprotein of phycocyanin alpha-subunit(alpha-CPC) from Mastigocladus laminosus. The surfactant Triton X-100 had no effect for the reconstitution of alpha-PEC, while it could improve the reconstitution of PCB with apoprotein of alpha-CPC.