Wei Chen
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Wei Chen
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Blocking caspase-3 activity with a U6 SnRNA promoter-driven ribozyme enhances survivability of CHO cells cultured in low serum medium and production of interferon-beta.
Journal: Biotechnology and bioengineering
August/2/2004
Description

Apoptosis responding to various insults in bioreactors was observed to reduce cell viability and prevent cells from growing to high density. Inhibition of apoptosis in different ways has proved to be effective in keeping cells viable in high density and result in higher recombinant protein production. In apoptosis, death signals activate a family of proteinases, namely caspases, in a cascade and ultimately activate the final effector proteinase, caspase-3, which cleaves various substrates and drives the cells irreversibly to death. Caspase-3 is the executioner of an apoptotic cell and thus plays a central role in apoptosis. Therefore inhibition of caspase-3 may provide an effective way for apoptosis prevention. In this study, we designed a ribozyme targeted at the 451 nt of hamster caspase-3's open reading frame (ORF) and the ribozyme was proved to be effective in cleaving caspase-3 mRNA in vitro. Then, the ribozyme was cloned into a vector under the control of U6 snRNA promoter, an RNA polymerase III promoter, for high rate of transcription in vivo. The vector was transfected into an interferon-beta producing recombinant CHO cell line, and some clones were screened out that exhibited low caspase-3 production by Western blot analysis. One such clone was then further analyzed and it showed good anti-apoptosis property with respect to cell viability, cell density, and interferon-beta production.

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A spectroscopic off-on probe for simple and sensitive detection of carboxylesterase activity and its application to cell imaging.
Journal: The Analyst
April/30/2012
Description

A new resorufin-based spectroscopic probe, 7-(p-acetoxyphenylmethyloxy)-3H-phenoxazin-3-one (1), has been developed for detecting carboxylesterase activity. The probe is designed by introducing p-acetoxyphenylmethyloxy as a bifunctional moiety to resorufin. The p-acetoxyphenylmethyloxy moiety not only quenches the spectroscopic signal of resorufin, but also serves as a recognition unit for carboxylesterase. As a result, the prepared latent spectroscopic probe 1 shows very low background signal, which is rather desired for achieving sensitive detection. The specific cleavage of the carboxylic ester bond by carboxylesterase induces the hydrolysis of the probe, resulting in the release of resorufin and thereby the recovery of both color and fluorescence signal. This behaviour leads to the development of a simple and sensitive fluorescent method for assaying carboxylesterase activity, with a detection limit of 8.6 × 10(-5) U mL(-1), which is much more sensitive than the existing fluorescence approaches. Moreover, experimental results showed that the probe 1 is cell membrane permeable, and its applicability has been demonstrated for monitoring carboxylesterase activity in HeLa cells.

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[Cellular localization and tissue expression pattern of UCA1, a non-coding RNA].
Journal: Nan fang yi ke da xue xue bao = Journal of Southern Medical University
August/11/2011
Description

OBJECTIVE

To examine the subcellular location of UCA1, a non-coding RNA, analyze its tissue expression pattern, and investigate the relationship between UCA1 expression and bladder carcinoma progression.

METHODS

Electron microscopic in situ hybridization technique was employed to determine the subcellular localization of UCA1 gene. RT-PCR was used to detect its mRNA expression level in various tissues.

RESULTS

Electron microscopy identified scattered colloidal gold particles on the cell membrane and massive homogeneously distributed particles in the cytoplasm without specific aggregation in the cells; scattered particles were also detected in the cell nuclei. UCA1 gene was overexpressed in the chorionic villi, placenta and fetal bladder tissues. In adult human tissues, UCA1 gene was not expressed except in the heart and spleen. The expression level of UCA1 was increased in 8 common tumor tissues as compared with that in the corresponding normal tissues. UCA1 mRNA was not detected in normal bladder, normal kidney, renal cancer or hyperplastic prostate tissues, but highly expressed in cancerous bladder tissues.

CONCLUSIONS

UCA1 gene locates in the cytoplasm, and its mRNA expression level is closely correlated to the progression of bladder cancer, indication its potential as a specific molecular marker of bladder cancer.

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Fabrication of silver nanoparticle-doped hydroxyapatite coatings with oriented block arrays for enhancing bactericidal effect and osteoinductivity.
Journal: Journal of the mechanical behavior of biomedical materials
August/22/2017
Description

Implant-associated infection is a common postoperative complication and remains a serious problem in orthopedic surgery. This work describes the synthesis of silver nanoparticle-doped hydroxyapatite coatings with oriented block arrays (AgNP-BHAC). The resulting nanostructure was investigated using scanning electron microscopy, energy-dispersive spectrometry, transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. AgNP-BHAC exhibited excellent antimicrobial activity toward gram-negative Escherichia coli and gram-positive Staphylococcus aureus owing to the antibacterial effects of the silver nanoparticles. Human bone marrow stromal cells (hBMSC) culture revealed that the AgNP-BHAC exhibited better biocompatibility, and permitted improved cell proliferation, attachment, and osteoinductivity than uncoated Ti-6Al-4V titanium alloy, the favored material for biomedical applications. In summary, this study presents a convenient and effective method for the incorporation of silver into HA coatings with block morphology. This method can be utilized to modify a variety of metallic implant surfaces to improve their antimicrobial effects and reduce potential long-term cytotoxicity.

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Astilbin ameliorates experimental autoimmune myasthenia gravis by decreased Th17 cytokines and up-regulated T regulatory cells.
Journal: Journal of neuroimmunology
August/16/2017
Description

Astilbin, a major bioactive compound extracted from Rhizoma smilacis glabrae (RSG), has been reported to possess immunosuppressive properties. Our study first evaluated the effect of astilbin on experimental autoimmune myasthenia gravis (EAMG) in Lewis rats. The results showed that astilbin could attenuate the severity of EAMG by decreasing antigen-specific autoantibodies with up-regulation of regulatory T cells and down-regulation of Th17 cells. In addition to, astilbin also reduced the efficiency of the antigen presenting cells on which the expression of MHC class II decreased. These results suggest that astilbin might be a candidate drug for immunoregulation of EAMG, and provide us new treatment ideas for human myasthenia gravis (MG).

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Sorption of apolar and polar organic contaminants by waste tire rubber and its chars in single- and bi-solute systems.
Journal: Environmental pollution (Barking, Essex : 1987)
May/16/2011
Description

Single- and bi-solute sorption of organic compounds [1,3-dichlorbenzene (DCB), 1,3-dinitrobenzene (DNB) and 2,4-dichlorophenol (DCP)] on ground tire rubber and its chars was studied. The chars were prepared by pyrolyzing tire rubber at different temperatures (200-800 °C). Their surface area, aromaticity and hydrophobicity increase greatly with pyrolytic temperature, and the polymeric phase is partly converted into a condensed phase. The sorption of DNB and DCP increases with pyrolytic temperature and is characterized by a transition from a partition dominant to an adsorption dominant process. However, the sorption of DCB linearly decreases with the pyrolytic temperature. The enhanced adsorption of DNB and DCP on carbonized phase is primarily attributed to nonhydrophobic interactions such as π-π electron-donor-acceptor interactions and/or H bonding. The higher partition of DCB to polymeric phase is attributed to its high hydrophobicity. Competitive sorption between DCB and DCP on the tire chars is highly dependent on dissociation of the latter.

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Perception-based transparency optimization for direct volume rendering.
Journal: IEEE transactions on visualization and computer graphics
January/12/2010
Description

The semi-transparent nature of direct volume rendered images is useful to depict layered structures in a volume. However, obtaining a semi-transparent result with the layers clearly revealed is difficult and may involve tedious adjustment on opacity and other rendering parameters. Furthermore, the visual quality of layers also depends on various perceptual factors. In this paper, we propose an auto-correction method for enhancing the perceived quality of the semi-transparent layers in direct volume rendered images. We introduce a suite of new measures based on psychological principles to evaluate the perceptual quality of transparent structures in the rendered images. By optimizing rendering parameters within an adaptive and intuitive user interaction process, the quality of the images is enhanced such that specific user requirements can be met. Experimental results on various datasets demonstrate the effectiveness and robustness of our method.

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[Effects of schisandrin B on reversing multidrug resistance in human breast cancer cells transfected with mdr1 gene].
Journal: Zhonghua yi xue za zhi
March/16/2006
Description

OBJECTIVE

To investigate the multidrug resistance (MDR) reversal activity of schisandrin B (SchB) in transfected human breast cancer cell line MCF-7/MDR1.

METHODS

Human breast cancer cells of the line MCF-7 were cultured and transfected with mdr1 gene so as to establish a P-glycoprotein (P-gp) stable-expressing cell line MCF-7/MDR1. The expression of P-gp in the MCF-7/mdr1 cells was assayed by flow cytometry using fluorescent antibody. MCF-7 cells transfected with blank plasmid MCF-7/neo was used as controls. Adriamycin (ADR), verapamil (VER), pacilitaxel (taxol), and homoharringtonine (HHT) were added into the culture fluid of the MCF-7/mdr1 cells and MTT method was used to detect the IC(50) of these drugs. The culture fluid of the MCF-7/MDR1 cells was added with SchB of the concentrations of 2.5, 12.5, 25, and 50 micromol/L and then added with ADR1 cells, MTT method was used to calculate the reversal effect (RF) of SchB on the MDR phenotype of the MCF-7/mdr1 cells. MTT method was used to calculate the RF. Another culture fluid of MCF-7/mdr1 cells was added with 25 micromol/L SchB and then with ADR, vincristine (VCR), pacilitaxel, and HHT with that added with 10 micromol/L VER as control. After treatment with SchB the MF7/mgr1 cells were co-incubated with 5 micromol/L rhodamine (Rh)-123, then flow cytometry was used to detect the accumulation of Rh-123 within the cells. After treatment with 25 micromol/L SchB for 0, 0.5, 1, 6, 24, 48, and 72 hours flow cytometry was used to detect the P-gp expression in the MF7/mgr1 cells.

RESULTS

The transfected MCF-7/MDR1 cells overexpressed P-gp and exhibited resistance to multiple drugs, including ADR, VCR, pacilitaxel and HHT. SchB (25 micromol/L) significantly enhanced the sensitivity of the MCF-7/MDR1 cells to above mentioned chemotherapeutic agents, with a reversal factors of 6.03 to 23.94 times. The effect of SchB (25 micromol/L) on Rh-123 accumulation in MDR cells was equivalent to that of 10 micromol/L VER, however no significant difference was found in the effect of SchB (25 micromol/L) on the P-gp expression in the MCF-7/MDR1 cells.

CONCLUSIONS

SchB is able to restore the drug sensitivity in the transfected MCF7/MDR1 cells, with a possible mechanism of increasing the drug influx via inhibiting the P-gp function.

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Royal crown-shaped electride Li3-N3-Be containing two superatoms: new knowledge on aromaticity.
Journal: Journal of computational chemistry
February/8/2007
Description

The structure and aromaticity of a royal crown-shaped molecule Li(3)-N(3)-Be are studied at the CCSD(T)/aug-cc-pVDZ level. This molecule is a charge-separated system and can be denoted as Li(3) (2+)N(3) (3-)Be(+). It is found that the Li(3) (2+) ring exhibits aromaticity mainly because the Li(3) (2+) ring can share the pi-electron with the N(3) (-3) ring. The 4n+2 electron counter rule can be satisfied for the Li(3) (2+) subunit if the shared pi valence electron of N(3) (3-) subunit is also taken into account. This new knowledge on aromaticity of a ring from the interactions between subunits is revealed first time in this paper. Li(3)-N(3)-Be can be also regarded as a molecule containing two superatoms (Li(3) and N(3)), which may be named as a "superomolecule." Li(3)-N(3)-Be is a new metal-nonmetal-metal type sandwich complex. The N(3) (3-) trianion in the middle repulses the electron clouds of the two metal subunits (mainly to the Li(3) superatom) to generate an excess electron, and thus Li(3)-N(3)-Be is also an electride. This phenomenon of the repulsion results in: (a) the HOMO energy level increased, (b) the electron cloud in HOMO distended, (c) the area of the negative NICS value extended, and (d) the VIE value lowered. So the superomolecule Li(3)-N(3)-Be is not only a new metal-nonmetal-metal type sandwich complex but also a new type electride, which comes from the interaction between the alkali superatom (Li(3)) and the nonmetal superatom (N(3)).

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Adsorption of tetracycline to nano-NiO: the effect of co-existing Cu(ii) ions and environmental implications.
Journal: Environmental science. Processes & impacts
August/3/2014
Description

Nano-sized nickel oxide (nano-NiO) is a new nanomaterial that has shown great promise in many areas of application. Understanding its environmental fate and effects is critical for minimizing the potential environmental implications of this new material due to incidental and accidental releases in the future. In this study, we observed strong adsorption of tetracycline to nano-NiO and found that the adsorption affinity can be further enhanced by Cu(ii) ions - the observed distribution coefficient (Kd) values are 10(3.1) to 10(4.2) L kg(-1) in the absence of Cu(ii) and 10(3.0) to 10(5.5) L kg(-1) in the presence of Cu(ii); such adsorption affinities are even comparable to those of tetracycline to carbonaceous materials. The strong adsorptive affinities of nano-NiO for tetracycline are likely attributable to several mechanisms, including surface complexation, cation exchange, and electrostatic attraction. As a strong complexing agent, Cu(ii) can significantly enhance adsorption of tetracycline by serving as a bridging agent between tetracycline and nano-NiO. The findings of this study have important implications for the risk assessment of engineered nanomaterials - in aquatic environments nano-NiO (and likely other metal oxide nanomaterials) can strongly adsorb tetracycline antibiotics, resulting in the changes of environmental risks of the metal oxide nanomaterials and/or bioavailability of the adsorbed contaminants.

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