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Feng Zhou

Publications and source records attributed to Feng Zhou.

At least 19 recordsLinked to original sources
PubMed2007

Probing the responsive behavior of polyelectrolyte brushes using electrochemical impedance spectroscopy.

Cyclic voltammetry and impedance spectroscopy were employed to probe the responsive properties of polyelectrolyte brushes. Poly[(dimethylamino)ethyl methacrylate] (PDMAEMA) brushes over 100 nm thick on gold substrates were synthesized via surface-initiated atom-transfer radical polymerization and quaternized with methane iodide to obtain cationic brushes (Q-PDMAEMA). Q-PDMAEMA brushes respond to electrolytes by exhibiting swollen and collapsed states. Swollen brushes allow good permeability of electroactive probes, while collapsed states block electron transport. Electrolytes have different impacts on the electrochemical properties of Q-PDMAEMA. Some salts (NaNO3) cause brush collapse due to charge screening, while others such as those with more hydrophobic anions (ClO4-, PF6-, and Tf2N-) induce brush collapse because of solubility changes. The collapsed brushes exhibit intrinsically different resistance as probed with impedance. Charged screened brushes retain good permeability to electroactive probes. Strongly coordinating hydrophobic anions lead to insoluble brushes, resulting in a high resistance. These results show that electrochemical impedance spectroscopy is a powerful technique to probe the properties and structure of polyelectrolyte brushes.

Journal Article↗
PubMed2007

Multidrug resistance protein 4 protects bone marrow, thymus, spleen, and intestine from nucleotide analogue-induced damage.

Nucleoside-based analogues are mainstays in the treatment of cancer, viral infections, and inflammatory diseases. Recent studies showing that the ATP-binding cassette transporter, multidrug resistance protein 4, is able to efflux nucleoside and nucleotide analogues from transfected cells suggests that the pump may affect the efficacy of this class of agents. However, the in vivo pharmacologic functions of the pump are largely unexplored. Here, using Mrp4(-/-) mice as a model system, and the nucleotide analogue, 9'-(2'-phosphonylmethoxyethyl)-adenine (PMEA) as a probe, we investigate the ability of Mrp4 to function in vivo as an endogenous resistance factor. In the absence of alterations in plasma PMEA levels, Mrp4-null mice treated with PMEA exhibit increased lethality associated with marked toxicity in several tissues. Affected tissues include the bone marrow, spleen, thymus, and gastrointestinal tract. In addition, PMEA penetration into the brain is increased in Mrp4(-/-) mice. These findings indicate that Mrp4 is an endogenous resistance factor, and that the pump may be a component of the blood-brain barrier for nucleoside-based analogues. This is the first demonstration that an ATP-binding cassette transporter can affect in vivo tissue sensitivity towards this class of agents.

Adenine↗
PubMed2007

A macrokinetic model for myeloma cell culture based on stoichiometric balance.

A macrokinetic model for a myeloma cell line is proposed. The model describes the dynamic balances of lactate, alanine, ATP and NADH during the metabolsim of glucose, glutamine and other amino acids. The metabolic pathways mainly include glycolysis, glutaminolysis, the trcicarboxylic acid cycle, the formation and utilization of amino acids, the respiratory chain, cell growth and cell death. The metabolic shift of glucose is especially considered because of a change in the rate of glycolysis. Thus the model functions in three modes to describe the behaviour of the myeloma cell line. On the basis of this model the macrokinetic bioreaction rates such as the specific substrate consumption rate, the specific growth rate, the specific acetyl-CoA formation rate, as well as the specific oxygen uptake rate, are estimated. The specific substrate consumption rate and the specific growth rate are then coupled into a bioreactor model such that the key variables, i.e., the cell density, the substrate and metabolite concentrations, are obtained. Experiments with batch and fed-batch cultures of a myeloma cell line (X63-Ag8.653) were used to validate the model. The prediction of the model was simulated by the rolling prediction approach.

Cell Line, Tumor↗
PubMed2007

Some characteristics and purification of anti-(human ovarian carcinoma)xanti-(human CD3) single-chain bispecific antibody.

To obtain high-quality AhOC x AhCD3 [anti-(human ovarian carcinoma)xanti-(human CD3)] with high biological activity economically and easily, some characteristics and purification of AhOC x AhCD3, a single chain bispecific antibody, were investigated. During the present study, some important properties of AhOC x AhCD3, such as molecular mass, pI, solubility, stability, hydrophobic ability, molecular status and bioactivity were primarily studied. The molecular mass of AhOC x AhCD3 was determined to be approx. 58.0 kDa by SDS/PAGE (theoretical molecular mass: 56972.5 Da, calculated on the basis of the primary structure) and the pI was approx. 7.5+/-0.4 by IEF (isoelectric focusing; theoretical pI: 8.5, predicted by the ProtParam software tool) respectively. Experiments showed that the solubility of AhOC x AhCD3 increased with the pH increase and that the AhOC x AhCD3 was easily degraded into several fragments during the storage time of samples and the mixtures of both fragment B and fragment C retained normal bioactivity. Particularly, the soluble aggregate/polymer status of AhOC x AhCD3 with bioactivity was verified by non-reducing SDS/PAGE. After optimization of purification process, AhOC x AhCD3 with electrophoretic homogeneity was successfully obtained and the yield was approx. 20%. Some important properties of AhOC x AhCD3 were first observed and a procedure for soluble AhOC x AhCD3 purification in scale-up was first established. Some characteristics of AhOC x AhCD3, especially the stability of AhOC x AhCD3, are critical for the development of this protein pharmaceutical and useful for reference to other proteins.

Antibodies, Bispecific↗
PubMed2006

Multicomponent polymer brushes.

This article describes a general synthetic route to laterally distinctive multicomponent polymer brushes on gold. The procedure involves repeated surface patterning using microcontact printing (muCP) of initiator-terminated thiols without backfilling with inert thiols and surface-initiated atomic transfer radical polymerization steps. In between brush growth, the remaining initiator moieties are deactivated to avoid reinitiation on existing brushes. Optical and fluorescence microscopy, atomic force microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy have been used to characterize every step of this procedure. We found that brushes can be grown from initiator-modified surfaces that contain bare gold areas and that these areas remain available for further patterning using muCP. To demonstrate the flexibility of this approach, surfaces containing four different polymer brushes in patterns ranging from 2 x 4 microm lines to 20 x 20 microm squares were fabricated. The range of chemical functionalities incorporated includes cationic and anionic polyelectrolytes, as well as thermally responsive polymers.

Journal Article↗
PubMed2006

Application of multivariate statistical methods to water quality assessment of the watercourses in Northwestern New Territories, Hong Kong.

Multivariate statistical methods, i.e., cluster analysis (CA) and discriminant analysis (DA), were used to assess temporal and spatial variations in the water quality of the watercourses in the Northwestern New Territories, Hong Kong, over a period of five years (2000-2004) using 23 parameters at 23 different sites (31,740 observations). Hierarchical CA grouped the 12 months into two periods (the first and second periods) and classified the 23 monitoring sites into three groups (group A, group B, and group C) based on similarities of water quality characteristics. DA provided better results with great discriminatory ability for both temporal and spatial analysis. DA also provided an important data reduction because it only used six parameters (pH, temperature, five-day biochemical oxygen demand, fecal coliforms, Fe, and Ni) for temporal analysis, affording about 84% correct assignations, and seven parameters (pH, ammonia-nitrogen, nitrate nitrogen, fecal coliforms, Fe, Ni, and Zn) for spatial analysis, affording more than 90% correct assignations. Therefore, DA allowed a reduction in the dimensionality of the large data set and indicated a few significant parameters that were responsible for most of the variations in water quality. Thus, this study demonstrated that the multivariate statistical methods are useful for interpreting complex data sets in the analysis of temporal and spatial variations in water quality and the optimization of regional water quality monitoring network.

Discriminant Analysis↗
PubMed2006

Interaction of rice dwarf virus outer capsid P8 protein with rice glycolate oxidase mediates relocalization of P8.

Yeast two-hybrid and coimmunoprecipitation assays indicated that P8, an outer capsid protein of Rice dwarf phytoreovirus (RDV), interacts with rice glycolate oxidase (GOX), a typical enzyme of peroxisomes. Confocal immunofluorescence microscopy revealed that P8 was colocalized with GOX in peroxisomes. Time course analysis demonstrated that the localization of P8 in Spodoptera frugiperda cells changed from diffuse to discrete, punctuate inclusions during expression from 24 to 48 h post inoculation. Coexpression of GOX with P8 may target P8 into peroxisomes, which serve as replication sites for a number of viruses. Therefore, we conclude that the interaction of P8 with the GOX of host cells leads to translocation of P8 into peroxisomes and we further propose that the interaction between P8 and GOX may play important roles in RDV targeting into the replication site of host cells. Our findings have broad significance in studying the mechanisms whereby viruses target appropriate replication sites and begin their replication.

Alcohol Oxidoreductases↗
PubMed2006

Effects of beta-adrenoceptors overexpression on cell survival are mediated by Bax/Bcl-2 pathway in rat cardiac myocytes.

BACKGROUND: Chronic activation of beta-adrenoceptors (beta-ARs) results in cardiac myocyte injury, even death, and diminishes the number of beta-ARs. OBJECTIVES: To investigate the effects of overexpression of beta(1)- or beta(2)-AR on cardiomyocytes injured by isoprenaline (ISO). METHODS: We have used an adenoviral vector carrying the sequence for human beta(1)- or beta(2)-AR (Adv.beta(1), Adv.beta(2)) to increase the content of beta(1) or beta(2)-AR in isolated adult rat ventricular myocytes, and we have examined the cell survival and the expression of Bax and Bcl-2. RESULTS: With use of adenoviral vectors, the beta(1)- and beta(2)-AR contents of myocytes were increased 2.98- and 2.87-fold, respectively. Overexpression of beta(1)-AR sharpened the cellular injury of ISO. If beta(2)-AR activity was further blocked by addition of selective beta(2)-AR antagonist ICI118,551, the cells were more sensitive to the impairment of Adv.beta(1) + ISO. Overexpression of Adv.beta(2) partially inversed the cytotoxicity of ISO stimulation. The beneficial effects were strengthened by addition of CGP20712A, a beta(1)-AR-blocking agent. Western blot analysis demonstrated that both increasing beta(1)-AR and inhibition of beta(2)-AR increased the ratio of Bax/Bcl-2. Whereas, increasing beta(2)-AR and inhibition of beta(1)-AR decreased the ratio of Bax/ Bcl-2. Control adenovirus CGP had no effect on cell survival. CONCLUSIONS: Overexpression of Adv.beta(2) and/or inhibition of beta(1)-AR have protective effect on adult rat ventricular myocytes chronically stimulated by ISO. Overexpression of Adv.beta(1) and/or inhibition of beta(2)-AR are deleterious in the same state. The effects of beta-ARs on cell survival might be mediated by the Bax/Bcl-2 signal pathway.

Adenoviridae↗
PubMed2006

Anti-tumor immunity against nasopharyngeal carcinoma by means of LMP2A-specific cytotoxic T lymphocytes induced by dendritic cells.

OBJECTIVE: Adoptive immunotherapy with specific cytotoxicity T lymphocytes (CTLs) induced by dendritic cells (DCs) pulsed with tumor antigens plays a crucial role in the immunity against tumor. The purpose of this study was to assess the feasibility and efficacy of latent membrane protein 2A (LMP2A)-specific CTLs immunity against nasopharyngeal carcinoma (NPC) in vitro and in vivo. METHODS: DCs were generated by culturing the monocytes purified from human peripheral blood mononuclear cells (PBMCs) in cytokine cocktail containing granulocyte/macrophage colony-stimulating factor (GM-CSF), interleukin-4 (IL-4), and tumor necrosis factor-alpha (TNF-alpha). The phenotype of mature DCs was analyzed by fluorescence activated cell sorter (FACS). Mature DCs transfected with EBV-LMP2A recombinant adenovirus were co-cultured with autologous PBMCs to induce LMP2A-specific CTLs. The expression of the surface antigens such as CD3, CD4, CD8 and CD56 on CTLs were detected by FACS. The specific cytotoxicity of CTLs on target CNE cells expressing EBV-LMP2A was confirmed using cytotoxicity assay. The anti-tumor effect of LMP2A-specific CTLs in vivo was assessed in the mice tumor models implanted with CNE cells expressing EBV-LMP2A. RESULTS: Mature DCs expressed typically morphologic characteristics and high level of surface markers (CD1a, CD83, CD86, CD80 and HLA-DR). LMP2A-transfected DCs could induce LMP2A-specific CTLs consisting of a majority of CD4+ and CD8+ T cells. Cytotoxicity assay confirmed that the LMP2A-specific CTLs displayed significant cytotoxicity on target CNE cells compared with the controls. The study in vivo demonstrated that the treatment using these specific CTLs retarded the growth of established tumor in the treated mice. CONCLUSION: These findings suggest that DCs transfected with EBV-LMP2A recombinant adenovirus can elicit LMP2A-specific CTLs that have a specific killing effect on NPC in vitro and in vivo. The results provide experimental basis for the further immunotherapy of NPC in clinical trails.

Adenoviridae↗
PubMed2006

Effects of system parameters on making aluminum alloy lotus.

In the present article, stable biomimetic superhydrophobic surfaces on aluminum alloy are obtained by wet chemical etching following modification with crosslinked silicone elastomer, perfluorononane (C9F20), and perfluoropolyether (PFPE), respectively. The formation and structure of superhydrophobic surfaces were characterized by means of scanning electron microscopy (SEM), water contact angle measurement, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The effects of surface roughness resulted from the etching time, and the concentration of NaOH aqueous solution on the superhydrophobicity of the surfaces have been discussed in detail. The optimal surface roughness of starting material is about 0.05-0.5 microm and the resulting surface roughness should be controlled between 2.7 and 5.8 microm in order to realize the superhydrophobicity on aluminum alloy; if the concentration of NaOH aqueous solution is about 4 wt%, the best treatment time is between 2 and 4 h to form a surface roughness changing from 2.7 to 5.8 microm. The trapped air with the binary structure plays a key role in fabricating superhydrophobic surface on aluminum alloy. In other words, the unusual structure on the surface, which has a binary structure consisted of microprotrusions and nanoparticles, plays a very vital role in constructing of the stable biomimetic superhydrophobic surface on aluminum alloy.

Journal Article↗
PubMed2006

Signal transducers and activators of transcription 3 mediates up-regulation of angiotensin II-induced tissue inhibitor of metalloproteinase-1 expression in cultured human senescent fibroblasts.

BACKGROUND: Angiotensin II (Ang II), a principal effector of renin-angiotensin system (RAS) and increased in aging tissues, can stimulate JAK/STAT pathway via the G-protein-coupled Ang II receptor type I (AT1) and induce nuclear translocation of signal transducers and activators of transcription (STAT). To further explore the role of Ang II in aging, we examined the effect of Ang II on human replicative senescent diploid fibroblast WI-38 cells. METHODS: Human senescent WI-38 cells were incubated with Ang II, receptor antagonist PD123319, valsartan, STAT3 sense plasmid, and/or STAT3 antisense plasmids. Methods were applied including electrophoretic mobility shift assay (EMSA), Western blot, transfection, and laser scanning confocal microscopy. RESULTS: It was found that cultured human senescent WI-38 cells constitutively expressed tissue inhibitor of metalloproteinase-1 (TIMP-1), and Ang II induced TIMP-1 protein expression in both time- and dose-dependent manners. Ang II induced STAT-DNA binding activity also in both time- and dose-dependent manners. And supershift assay showed that the sis-inducing factor (SIF) band contained STAT3 proteins. STAT3 antisense oligonucleotides could inhibit both Ang II-induced STAT3-DNA binding activity as well as TIMP-1 expression. CONCLUSION: Ang II could up-regulate TIMP-1 expression through activating STAT3 signal pathway in human senescent cells, indicating that Ang II-STAT3-TIMP-1 pathway may be involved in the mechanism of sclerosis in aging tissues.

Angiotensin II↗
PubMed2006

Topography printing to locally control wettability.

This paper reports a new patterning method, which utilizes NaOH to facilitate the irreversible binding between the PDMS stamp and substrates and subsequent cohesive mechanical failure to transfer the PDMS patterns. Our method shows high substrate tolerance and can be used to "print" various PDMS geometries on a wide range of surfaces, including Si100, glass, gold, polymers, and patterned SU8 photoresist. Using this technique, we are able to locally change the wettability of substrate surfaces by printing well-defined PDMS architectures on the patterned SU8 photoresist. It is possible to generate differential wetting and dewetting properties in microchannels and in the PDMS printed area, respectively.

Adsorption↗
PubMed2006

Highly reversible and multi-stage cantilever actuation driven by polyelectrolyte brushes.

Microcantilever bending can be reversibly driven by conformational changes of phosphate containing polyelectrolyte brushes when exposed to different pH or salt solutions. The deflection of the cantilevers allows a detailed analysis of the properties of polymer brushes, while these systems are also a first step toward polymer-based nanoactuators.

Journal Article↗
PubMed2006

Observation of the second harmonic in Thomson scattering from relativistic electrons.

A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and gamma-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

Journal Article↗
PubMed2006

Proliferation and differentiation of duct epithelial cells after partial pancreatectomy in rats.

The proliferation and differentiation of pancreatic duct epithelial cells in remnant pancreas during regeneration after partial pancreatectomy in rats were studied, and the source of pancreatic stem cells was characterized. Partial (90 %) pancreatectomy was performed on 4- to 5-week-old Sprague-Dawley rats, and different duct epithelial cells and acinar cells were detected by immunohistrochemical stain method and scored using 5-bromo-2'-deoxyuridine (BrdU) labeling index (LI) at various time points after partial pancreatectomy. It was found that at 24 h after partial pancreatectomy proliferation started in the main, large and small duct cells, and persisted in small duct cells to day 5. There was significant difference between the experimental group and the control group (P<0.001). Acinar cells positive for BrdU were greatly increased and reached the peak LI on day 5. The destroyed lobular architecture almost totally recovered on day 7, and the newly islet cells appeared around the pancreatic ducts. These results suggest that regeneration after partial pancreatectomy is involved in proliferation and differentiation of pancreatic stem cells, and pancreatic stem cells may locate in the pancreatic ductules.

Animals↗