Yan Liu

Southwest University in Chongqing, Pehpei, Chongqing Shi, China

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Publications (7)15.52 Total impact

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    ABSTRACT: As the main synthetic raw materials of polycarbonate, bisphenol A (BPA) and its analogues have been important issues in environmental pollution. The current studies focus mainly on BPA's estrogen effects and little on their cytotoxic effects. To assess the cytotoxicities of the five BPA analogues, we employed the MTS assay to determine the inhibition toxicity to MCF-7 (ER-), 2,4-dinitrophenylhydrazine assay to determine the release rate of lactate dehydrogenase (LDH) escaping into cell culture medium, and single cell gel electrophoresis assay (SCGE) to detect DNA damage. The dose-response curves (DRC) between the observed inhibition toxicities and concentrations of the BPA compounds in MTS assay were fitted by using the nonlinear least squares (NLS) and the results showed that all the dose-response relationships were effectively described by the Weibull or Logit function. The toxicities expressed by--lgpEC50 were BPB > BPC > TDP > BPE > BPA. LDH assay and SCGE assay showed that when the concentrations of BPA analogues were EC20, the MCF-7 cell proliferation was slightly inhibited due to its little damaged DNA, and at EC40 the cell proliferations were significantly inhibited due to the seriously damaged DNA, leading to the damage of cell membrane and release of LDH.
    Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 11/2012; 33(11):3935-40.
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    ABSTRACT: The bioluminescence inhibition of six triazine herbicides including desmetryne (DES), simetryn (SIM), velpar (VEL), prometon (PRO), metribuzin (MET), and aminotriazine (AMI) on Vibrio qinghaiensis sp.-Q67 (Q67) was determined to investigate the effects of exposure duration on the ecotoxicological relevance of triazine herbicides. Based on the short-term microplate toxicity analysis (MTA), a long-term MTA was established to assess the impact of exposure time on the toxicities of the herbicides. The results show that the long-term toxicities of DES and SIM are similar to their short-term toxicities, and the long-term toxicities of VEL, PRO, and MET are higher than their short-term toxicities, while AMI without short-term toxicity has a high long-term toxicity. In addition, a parabolic relationship was found between the pEC(50) (the negative logarithm of the EC(50), log 1/EC(50)) and the logarithm of octanol-water partition coefficient (logK(ow)). To better understand their toxicity process, the time-dependent toxicities of the six herbicides on Q67 were determined over a period of 12 h during which measurements were taken every 30 min to generate an integral effect surface related to both concentration and duration.
    Water Research 02/2009; 43(6):1731-9. DOI:10.1016/j.watres.2009.01.004 · 5.32 Impact Factor
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    ABSTRACT: Antiangiogenic therapy could destroy tumor vasculature and inhibit tumor growth. It might inhibit tumor growth significantly when used as a single treatment modality and its therapeutic benefit may even be greater when used in combination with established treatment modalities such as radiation therapy (RT). In the present report, we investigated the effect of recombinant human plasminogen kringle 5 domain (rhK5) in combination with ionizing radiation on angiogenesis, tumor growth and survival in a murine Lewis lung carcinoma (LLC) tumor model. Combined treatment using rhK5 and radiotherapy displayed obvious suppressive effect on LLC tumor growth as compared with single treatment with either modality (p < 0.05), and resulted in a more additive effect on tumor growth delay in this model. In addition, combined treatment significantly enhanced the survival of mice and no toxic effect, such as weight loss, was observed. The significant antitumor effect of rhK5 plus radiation was associated with a direct suppression effect on early neoangiogenesis and tumor cell apoptosis. Furthermore, the expression of VEGF and HIF-1alpha in tumor tissue correlated well with decreased vessel density. The results suggest that rhK5 significantly enhances the antitumor activity of RT and could be a potent adjuvant therapeutic approach to improve the efficacy of radiotherapy for lung cancer.
    International Journal of Cancer 12/2007; 121(11):2539-46. DOI:10.1002/ijc.22708 · 5.01 Impact Factor
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    ABSTRACT: Interleukin (IL)-2 is a pharmacologically important cytokine secreted by T-lymphocytes. Recombinant IL-2 (rIL-2) has been modified and produced in many systems. Mass production of rIL-2 is the prerequisite for its wide application. Using a site-directed mutagenesis strategy, we first generated a gene coding for a new type of mutant of human IL-2 (MhIL-2), in which we replaced the cysteine-125 in human IL-2 with alanine, the leucine-18 with methionine, and the leucine-19 with serine. Then we investigated the possibility of its production of MhIL-2 in a Pichia pastoris system. High-level secreted expression of MhIL-2 was achieved by methanol induction. When purified with ultrafiltration, cation-exchange chromatography, and Sephadex G100 gel filtration, about 100 mg of MhIL-2 with high purity was obtained from 1 L of ferment supernatant. Biologic activity assay revealed that the purified recombinant protein displayed increased activity on proliferation of IL-2-dependent CTLL-2 cells. These results suggest that MhIL-2 is an improved IL-2 mutant that might hold great promise for clinical use, and that P. pastoris is an excellent system for the mass production of biologically active hIL-2.
    Applied Biochemistry and Biotechnology 05/2006; 133(1):77-86. DOI:10.1385/ABAB:133:1:77 · 1.74 Impact Factor
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    ABSTRACT: Using the molecular electronegativity distance vector (MEDV) descriptors derived directly from the molecular topological structures, the gas chromatographic relative retention times (RRTs) of 209 polychlorinated biphenyls (PCBs) on the SE-54 stationary phase were predicted. A five-variable regression equation with the correlation coefficient of 0.9964 and the root mean square errors of 0.0152 was developed. The descriptors included in the equation represent degree of chlorination (nCl), nonortho index (Ino), and interactions between three pairs of atom types, i.e., atom groups -C= and -C=, -C= and >C=, -C= and -Cl. It has been proved that the retention times of all 209 PCB congeners can be accurately predicted as long as there are more than 50 calibration compounds. In the same way, the MEDV descriptors are also used to develop the five- or six-variable models of RRTs of PCBs on other 18 stationary phases and the correlation coefficients in both modeling stage and LOO cross-validation step are not lower than 0.99 except two models.
    Journal of Separation Science 02/2006; 29(2):296-301. DOI:10.1002/jssc.200301592 · 2.59 Impact Factor
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    ABSTRACT: Interleukin-2 (IL-2) was initially isolated as a T cell growth factor and had been shown to direct the expansion and differentiation of several hematopoietic cell types. Clinical studies using IL-2 in the treatment of AIDS have been encouraging, due to its critical role as a proliferative signal for activated T-lymphocytes. IL-2 has also undergone trials in the treatment of several types of cancer, based on its stimulation of cytotoxic, antitumor cells. Today, human IL-2 is produced completely by genetically engineered method, and it has been proved that genetically engineered recombinant human IL-2 has almost the same function and clinical effect as wild IL-2. In the former study, recombinant human IL-2 usually comes from E. coli, in this paper the mutant IL-2 was successfully expressed and purified in Pichia pastoris for the first time. As a eukaryote, Pichia pastoris has many of the advantages of higher eukaryotic expression systems such as protein processing, protein folding, and posttranslational modification, while being as easy to manipulate as E. coli or Saccharomyces cerevisiae. It is faster, easier, and less expensive to use than other eukaryotic expression systems such as baculovirus or mammalian tissue culture, and generally gives higher expression level. Expression conditions of human mutant interleukin-2(the codon for cysteine-125 of human IL-2 with alanine; the codon for leucine-18 with methionine; the codon for leucine-19 with serine) in the recombinant Pichia pastoris strain were optimized via test of some factors such as the rate of aeration, the inductive duration, the initial pH and the concentration of methanol. The results from tests showed that the most important parameter for efficient expression of interleukin-2 in recombinant Pichia pastoris strain is adequate aeration during methanol induction, and the optimum inductive condition for interleukin-2 expression was: more than 80% aeration, 2 days for induction, the initial pH of 6.0, the final methanol concentration of 1.0%. With this condition, the expressed IL-2 was secreted into fermentation broth and reached a yield of 30%, approximately 200 mg/L. Expressed interleutin-2 (MvIL-2) was isolated and purified by centrifugation, millipore filtration to concentration, Econo-PacS strongly acidic cation exchanger cartridge and molecular sieve chromatography and the yield of MvIL-2 was 27%. MvIL-2 was purified to electrophoretic purity by SDS-PAGE and only one peak being loaded on HPLC. Purified MvIL-2 protein had stimulating activity similar to the wild type of IL-2 as assayed by IL-2-dependent CTLL-2 cells. However, the stability of MvIL-2 was superior than that of IL-2 at different temperatures. The activity of obtained MvIL-2 was 4 - 5 times of the wild type of IL-2, So MvIL-2 had an advantage over wild type of rhIL-2 in storage stability and activity.
    Sheng wu gong cheng xue bao = Chinese journal of biotechnology 06/2005; 21(3):430-4.
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    ABSTRACT: The molecular holographic distance vector (MHDV) is employed to characterize the structures of 51 sub-stituted benzenes. 29 descriptors from 91 MHDV ones have nonzero values where 3 descriptors have only one nonzero sample and 1 descriptor only two nonzero samples. A genetic algorithm is used to select an optimal combination of the variables from the remaining 25 nonzero descriptors. Then the optimal descriptors are em-ployed to relate to the relative biodegradability using multiple linear regression method. The 6-variable linear model developed has high quality where the correlation coefficient of estimations and the root mean square error of estimations are 0.9604 and 0.280, respectively, and the correlation coefficient of predictions and the root mean square error of predictions for leave-one-out procedure are 0.9471 and 0.324, respectively.
    Journal- Chinese Chemical Society Taipei 04/2003; 50(2). DOI:10.1002/jccs.200300047 · 0.86 Impact Factor