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Biomedical subjects

Gang Chen

Publications and source records attributed to Gang Chen.

At least 163 records · Page 9Linked to original sources
PubMed2005

[Effects of selected phages with specific peptide ligands on the biological behaviors of ovarian cancer cells].

OBJECTIVE: To evaluate the effects of the selected phages with the specific peptide ligands upon the biological behaviors of the ovarian cancer cells. METHODS: Two ovarian cancer cell lines, A2780 and SKOV3, were used in the study. They were divided into three groups respectively: study group, blank control group and negative control group. The effects of the phages were evaluated by trypan blue staining, flow cytometry, colony formation test, methyl thiazolyl tetrazolium (MTT) assay and Boyden chamber invasion assay. RESULTS: The average viability of ovarian cancer cells of study groups was (72.1 +/- 6.2)%, higher than that of negative control group (84.8 +/- 4.6, P < 0.05); the apoptosis ratio of the A2780 and SKOV3 cells of study groups increased (20.39% and 43.99% vs 0); the average colony formation rate of the ovarian cancer cells was of study groups 4%, lower than the control group (15%, P < 0.05); the inhibition rates of cell proliferation of A2780 and SKOV3 cells of study groups were 11.07% and 9.58%, significantly higher than that of their respective negative control (2.05% and 1.09%); the invasion index of the ovarian cancer cells decreased compared with the control. CONCLUSION: The selected phages down-regulate the growth, proliferation and invasion ability of the ovarian cancer cells to certain extent, the identified peptide ligands may play a role in tumorigenesis and metastatic transformation of ovarian cancers.

Apoptosis↗
PubMed2005

[The diagnosis and treatment of facial nerve schwannoma].

OBJECTIVE: To discuss the diagnosis and treatment of facial nerve (FN) schwannomas. METHOD: Two cases of FN schwannoma between 2002 and 2004 in Shanghai Sixth People's Hospital were reviewed. RESULT: Both cases were diagnosed during operation. CONCLUSION: Because of its rarity and various presentations, facial nerve schwannoma is difficult to diagnose. In addition of the common presenting symptoms and physical examination, radiographic studies can delineate the erosion area and the relationship with surrounding tissues. These studies are essential for preoperative planning. The main factors that influence on the recovery of facial nerve function after operation are the preoperative presence of facial nerve deficit and its duration. If the facial nerve deficit lasts over one year, the recovery of facial nerve function will be worse. However, the location and the preoperative grading of facial nerve function has nothing with the recovery.

Adolescent↗
PubMed2005

[Spectral signal recognition based on wavelet packet analysis].

Automated recognition of spectral signal is an importance part of spectral analysis, which jnvolves comparing spectral signals under the same conditions and obtaining relation of chemistry constitution according to similarity by pattern recognition method and computer technique, and is useful to determine the nature of spectral signal and validate spectral signal. This paper takes spectral signal according with Lambert-beer' law as object, introduces basic theory and method of recognition of spectral signal in brief, normalizes spectral signal to decrease difficulty, introduces wavelet analysis theory, puts forward the method of wavelet packet analysis to gain features of spectral signal, obtains formula to compute feature vector and error vector by statistics method, then makes use of binary tree' mode distinguishing step by step for quick recognition, and finally gives an example to explain.

Algorithms↗
PubMed2005

[Taohong Siwu decoction II inhibits the angiogenesis and the expressions of VEGF and KDR/FLK-1 in C57BL/6J mice bearing B16 melanoma].

OBJECTIVE: To investigate the effects of Taohong Siwu decoction II on B16 melanoma in mice and the underlying mechanism. METHOD: C57BL/6J mice bearing B16 melanoma were used in this study. The experimental groups were treated respectively with Taohong Siwu decoction II at doses of 2.5, 5 and 10 g x kg(-1) and cyclophosphamide at 0.05 g x kg(-1), Taohong Siwu decoction II at 10 g x kg(-1) plus cyclophosphamide at 0.025 mg x kg(-1). The tumor volume and weight, the expression of VEGF and KDR/FLK-1 and the amount of MVD were measured. RESULT: The tumor volume and weight, the expression of VEGF and KDR/FLK-1 and the amount of MVD were reduced significantly after treatment with Taohong Siwu decoction II at the doses of 5 and 10 g x kg(-1) and Taohong Siwu decoction II combined with cyclophosphamide as compared with normal saline-treated group (P < 0.01). CONCLUSION: Taohong Siwu decoction II can inhibit the growth of B16 melanoma in mice and attenuate the expressions of VEGF and KDR/FLK-1, suggesting that Taohong Siwu decoction II produces the antitumor effect via a possible antiagiogenisis mechanism.

Animals↗
PubMed2005

[Effect of transcriptional factor snail on epithelial-mesenchymal transition and tumor metastasis].

BACKGROUND & OBJECTIVE: Transcription factor Snail mediates epithelial-mesenchymal transition (EMT), and is associated with tumor metastasis. This study was designed to observe the enhancive effect of Snail and the reverse effect of antisense-Snail on EMT of tumor cells, and explore the role of Snail in tumor metastasis. METHODS: Snail cDNA was transfected into canine renal epithelial cell line MDCK; antisense-Snail was transfected into human breast cancer cell line MDA-MB231. The expression of epithelial markers E-cadherin, beta-catenin and Cytokeratin 18, mesenchymal marker Fibronectin, metastasis-related marker matrix metalloproteinase-2 (MMP-2), and RhoA were detected by Western blot. The metastatic potential of tumor cells was examined by in vitro cell wound model and Boyden chamber invasion assay. RESULTS: The invasion potential of MDCK cells was enhanced after transfection of Snail. The expression of E-cadherin, beta-catenin, and Cytokeratin 18 was significantly lower in Snail-transfected MDCK cells than in control cells (P < 0.05); the expression of Fibronectin, MMP-2, and RhoA was significantly higher in Snail-transfected cells than in control cells (P < 0.05). Inhibiting the expression of Snail with antisense-Snail in MDA-MB231 cells led to opposite results. CONCLUSION: Snail promotes EMT in normal epithelial cells, and inhibiting the expression of Snail may reverse EMT and suppress tumor metastasis.

Animals↗
PubMed2004

Cross-clade CD8 T-cell responses to HIV(IIIB) and Chinese B' and C/B' viruses in North American and Chinese HIV-seropositive donors.

HIV variation presents an obstacle to a global AIDS vaccine. Viral diversity and host variations in MHC expression both affect vaccine responses. Whether CD8 T cells from HIV-infected donors in 1 part of the world cross-recognize isolates from other regions will provide guidance about whether country-specific vaccines are needed. We compared recognition of HIV(IIIB) and representative B' (Thai B) and recombinant C/B' virus strains endemic in China by CD8 T cells from 7 HIV-infected North American donors and 4 Chinese donors. IFN-gamma production in response to HIV(IIIB) or the Chinese viruses was comparable. Although 1.6 +/- 0.8% of American donor CD8 T cells produced IFN-gamma above the background level in response to IIIB virus, 1.5 +/- 0.8% responded to B' virus, and 1.4 +/- 0.7% responded to C/B' virus. Responses to adherent cells infected with vaccinia viruses expressing B' and C/B' virus gag and env were also comparable in magnitude with responses to IIIB virus. Cytolysis of CD4 T cells infected with B' virus was comparable with lysis of cells infected with IIIB virus, but lysis of the more divergent C/B' virus was somewhat reduced. T cells, selected for IFN-gamma production to IIIB virus, also efficiently lysed cells infected with Chinese viruses. Therefore, cross-clade CD8 T-cell responses to IIIB virus and prevalent Chinese viral strains are common.

AIDS Vaccines↗
PubMed2004

Thermal radiation from photonic crystals: a direct calculation.

A classical simulation of equilibrium thermal emissivity from dispersive, lossy photonic crystals is presented. Normal emission results consistent with those assuming Kirchoff's law are obtained; i.e., a photonic crystal does not emit more than what a blackbody does. Significant enhancement, however, can be achieved over the radiation intensity from a uniform slab, indicating the potential usefulness of photonic crystals in incandescent lighting and thermal photovoltaic applications.

Journal Article↗
PubMed2004

Bulk modification of polymeric microfluidic devices.

The surface properties of microfluidic devices play an important role in their flow behavior. We report here on an effective control of the surface chemistry and performance of polymeric microchips through a bulk modification route during the fabrication process. The new protocol is based on modification of the bulk microchip material by tailored copolymerization of monomers during atmospheric-pressure molding. A judicious addition of a modifier to the primary monomer solution thus imparts attractive properties to the plastic microchip substrate, including significant enhancement and/or modulation of the EOF (with flow velocities comparable to those of glass), a strong pH sensitivity and high stability. Carboxy, sulfo, and amino moieties have thus been introduced (through the incorporation of methylacrylic acid, 2-sulfoethyl-methacrylate and 2-aminoethyl-methacrylate monomers, respectively). A strong increase in the electroosmotic pumping compared to the native poly(methylmethacrylate)(PMMA) microchip (ca. electroosmotic mobility increases from 2.12 to 4.30 x 10(-4) cm(2) V(-1) s(-1)) is observed using a 6% methylacrylate (MAA) modified PMMA microchip. A 3% aminoethyl modified PMMA microchip exhibits a reversal of the electroosmotic mobility (for example, -5.6 x 10(-4) cm(2) V(-1) s(-1) at pH 3.0). The effects of the modifier loading and the pH on the EOF have been investigated for the MAA-modified PMMA chips. The bulk-modified devices exhibit reproducible and stable EOF behavior. The one step fabrication/modification protocol should further facilitate the widespread production of high-performance plastic microchip devices.

Journal Article↗
PubMed2004

Enrollment of elderly patients in clinical trials for cancer drug registration: a 7-year experience by the US Food and Drug Administration.

PURPOSE: To analyze the age-related enrollment of cancer patients onto registration trials of new drugs or new indications approved by the US Food and Drug Administration from 1995 to 2002. PATIENTS AND METHODS: This study involved retrospective analyses of demographic data of cancer patients enrolled onto registration trials. The data on 28,766 cancer patients from 55 registration trials were analyzed according to age distributions of > or = 65, > or = 70, and > or = 75 years. The rates of enrollment in each age group for each cancer were compared with the corresponding rates in the US cancer population. The age distributions of the US cancer population were derived from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute for the period 1995 to 1999 based on the 2000 US Census. RESULTS: The proportions of the overall patient populations aged > or = 65, > or = 70, and > or = 75 years were 36%, 20%, and 9% compared with 60%, 46%, and 31%, respectively, in the US cancer population. Statistically significant under-representation of the elderly (P < .001) was noted in registration trials for all cancer treatment except for breast cancer hormonal therapies. Patients aged > or = 70 years accounted for most of the under-representation. CONCLUSION: Elderly were under-represented in the registration trials of new cancer therapies. Various strategies may be needed to evaluate cancer therapies for the elderly in prospective clinical trials and to improve cancer care in the elderly population.

Age Factors↗
PubMed2004

Intravascular thrombosis after hypoxia-induced pulmonary hypertension: regulation by cyclooxygenase-2.

BACKGROUND: Pulmonary hypertension induced by chronic hypoxia is characterized by thickening of pulmonary artery walls, elevated pulmonary vascular resistance, and right-heart failure. Prostacyclin analogues reduce pulmonary pressures in this condition; raising the possibility that cycloxygenase-2 (COX-2) modulates the response of the pulmonary vasculature to hypoxia. METHODS AND RESULTS: Sprague-Dawley rats in which pulmonary hypertension was induced by hypobaric hypoxia for 14 days were treated concurrently with the selective COX-2 inhibitor SC236 or vehicle. Mean pulmonary arterial pressure (mPAP) was elevated after hypoxia (28.1+/-3.2 versus 17.2+/-3.1 mm Hg; n=8, P<0.01), with thickening of small pulmonary arteries and increased COX-2 expression and prostacyclin formation. Selective inhibition of COX-2 aggravated the increase in mPAP (42.8+/-5.9 mm Hg; n=8, P<0.05), an effect that was attenuated by the thromboxane (TX) A2/prostaglandin endoperoxide receptor antagonist ifetroban. Urinary TXB2 increased during hypoxia (5.9+/-0.9 versus 1.2+/-0.2 ng/mg creatinine; n=6, P<0.01) and was further increased by COX-2 inhibition (8.5+/-0.7 ng/mg creatinine; n=6, P< 0.05). In contrast, urinary excretion of the prostacyclin metabolite 6-ketoprostaglandin F1alpha decreased with COX-2 inhibition (8.6+/-3.0 versus 27.0+/-4.8 ng/mg creatinine; n=6, P< 0.05). Platelet activation was enhanced after chronic hypoxia. COX-2 inhibition further reduced the PFA-100 closure time and enhanced platelet deposition in the smaller pulmonary arteries, effects that were attenuated by ifetroban. Mice with targeted disruption of the COX-2 gene exposed to chronic hypoxia had exacerbated right ventricular end-systolic pressure, whereas targeted disruption of COX-1 had no effect. CONCLUSIONS: COX-2 expression is increased and regulates platelet activity and intravascular thrombosis in hypoxia-induced pulmonary hypertension.

Animals↗
PubMed2004

Factors affecting thermodynamic stabilities of RNA 3 x 3 internal loops.

Internal loops in RNA are important for folding and function. The 3 x 3 nucleotide internal loops are the smallest size symmetric loops with a potential noncanonical base pair (middle pair) flanked on both sides by a noncanonical base pair (loop-terminal pair). Thermodynamic and structural insights acquired for 3 x 3 loops should improve approximations for stabilities of 3 x 3 and larger internal loops. Most natural 3 x 3 internal loops are purine rich, which is also true of other internal loops. A series of oligoribonucleotides containing different 3 x 3 internal loops were studied by UV melting and imino proton NMR. Both loop-terminal and middle pairs contribute to the thermodynamic stabilities of 3 x 3 loops. Extra stabilization of -1.2 kcal/mol was found for a GA middle pair when flanked by at least one non-pyrimidine-pyrimidine loop-terminal pair. A penalty of approximately 1 kcal/mol was found for loops with a single loop-terminal GA pair that has a U 3' to the G of the GA pair. A revised model for predicting stabilities of 3 x 3 loops is derived by multiple linear regression.

Base Pairing↗
PubMed2004

Preparative isolation and purification of syringin and edgeworoside C from Edgeworthia chrysantha Lindl by high-speed counter-current chromatography.

The bioactive compound syringin along with edgeworoside C were separated from the n-butanol extract of the stems and barks of Edgeworthia chrysantha Lindl (E. papyrifera) by high-speed counter-current chromatography (HSCCC) while it was difficult to purify each compound by silica gel column chromatography. Syringin was isolated from this plant for the first time. The two-phase solvent system used was composed of ethyl acetate-ethanol-water at an optimized volume ratio of 15:1:15 (v/v/v). Preparative HSCCC yielded, from 110mg of the partially purified extract, 28mg of syringin and 45 mg edgeworoside C each at over 96% purity by high-performance liquid chromatography analysis. Their structures were identified by electron impact ionization MS, 1H NMR and 13C NMR.

Coumarins↗
PubMed2004

Caste determination in a polyembryonic wasp involves inheritance of germ cells.

Social insects are characterized by the development of castes in which some colony members reproduce whereas others function as altruistic helpers. The conditional switch controlling caste formation usually involves environmental stimuli that act on processes that regulate development of individuals. Unlike other social species, embryos of polyembryonic wasps develop clonally to produce large numbers of genetically identical offspring and two morphologically distinct castes. All embryos in a clone exist in an identical environment, the host, yet develop into either reproductive larvae that mature into adult wasps or soldier larvae whose function is defense. Here, we report that caste determination in Copidosoma floridanum involves inheritance of germ cells. Expression of a C. floridanum homolog (Cf-vas) of the germ cell marker Vasa indicated that the B(4) blastomere in four cell-stage embryos is specified as a primordial germ cell. Vas expression later in development further indicated that embryos developing into reproductive larvae possess primordial germ cells whereas embryos developing into soldier larvae do not. Ablation of the B(4) blastomere resulted in most broods containing only soldiers whereas ablation of other blastomeres produced broods containing both castes. These results indicate that soldier larvae are obligately sterile and reveal a previously unknown role for germ cells in caste formation.

Amino Acid Sequence↗
PubMed2004

[The abnormity and clinical value of tyrosine kinase signaling pathway in lung adenocarcinoma].

OBJECTIVE: To study the abnormity and clinical value of tyrosine kinase signaling pathway in lung adenocarcinoma. METHODS: Total RNA was extracted form 10 lung adenocarcinoma samples and matched normal tissues. cDNA was labeled fluorescence during reverse transcription and hybridized on 20 slides of microarray with 13 824 genes. After washed and scanned, the cy3:cy5 ratios were obtained by computer analysis. Each experiment was repeated two times and the mean value was chosen. Cluster analysis and discriminant analysis were used to mine the pool data. The results were combined with clinical prognostic factors for further analysis. RESULTS: According to the abnormity of tyrosine kinase signaling pathway in lung adenocarcinoma, sample cluster divided the 10 samples into 3 groups and gene cluster divided all genes into 5 groups. Different prognosis samples had different characteristic genes. The patients with the best prognosis overexpressed some genes related to immunity and inhibition proliferation, and those with the worst prognosis overexpressed some genes related to proliferation while the genes related to immunity and inhibition proliferation were expressed at a low level. CONCLUSION: There are 3 type abnormity of tyrosine kinase signaling pathway in lung adenocarcinoma that are related to different biological behavior and different prognosis.

Adenocarcinoma↗
PubMed2004

Impact of lipopolysaccharide coating on clay particle wettability.

Impact of lipopolysaccharide coating on kaolinite and Na-montmorillonite wettability was investigated. Kaolinite had greater diiodomethane contact angles, smaller water and formamide contact angles than Na-montmorillonite. After lipopolysaccharide coating, diiodomethane and formamide contact angles decreased, while water contact angles increased for both kaolinite and Na-montmorillonite. The decrease and increase in liquid contact angles after lipopolysaccharide coating were most pronounced for lipopolysaccharide extracted from Pseudomonas aeruginosa, followed by Pseudomonas fluorescens and Echerichia coli. Clay particle wettability was determined by particle surface thermodynamic properties. Both kaolinite and Na-montmorillonite exhibited a monopolar surface and the monopolarity decreased after lipopolysaccharide coating, indicating an increase in hydration or surface wetness. The origins of interactions of clay particles with water molecules were discussed and related to clay particle water wettability.

Aluminum Silicates↗
PubMed2004

Glycogen synthase kinase 3beta (GSK3beta) mediates 6-hydroxydopamine-induced neuronal death.

The causes of sporadic Parkinson's disease (PD) are poorly understood. 6-Hydroxydopamine (6-OHDA), a PD mimetic, is widely used to model this neurodegenerative disorder in vitro and in vivo; however, the underlying mechanisms remain incompletely elucidated. We demonstrate here that 6-OHDA evoked endoplasmic reticulum (ER) stress, which was characterized by an up-regulation in the expression of GRP78 and GADD153 (Chop), cleavage of procaspase-12, and phosphorylation of eukaryotic initiation factor-2 alpha in a human dopaminergic neuronal cell line (SH-SY5Y) and cultured rat cerebellar granule neurons (CGNs). Glycogen synthase kinase-3 beta (GSK3beta) responds to ER stress, and its activity is regulated by phosphorylation. 6-OHDA significantly inhibited phosphorylation of GSK3beta at Ser9, whereas it induced hyperphosphorylation of Tyr216 with little effect on GSK3beta expression in SH-SY5Y cells and PC12 cells (a rat dopamine cell line), as well as CGNs. Furthermore, 6-OHDA decreased the expression of cyclin D1, a substrate of GSK3beta, and dephosphorylated Akt, the upstream signaling component of GSK3beta. Protein phosphatase 2A (PP2A), an ER stress-responsive phosphatase, was involved in 6-OHDA-induced GSK3beta dephosphorylation (Ser9). Blocking GSK3beta activity by selective inhibitors (lithium, TDZD-8, and L803-mts) prevented 6-OHDA-induced cleavage of caspase-3 and poly(ADP-ribose) polymerase (PARP), DNA fragmentations and cell death. With a tetracycline (Tet)-controlled TrkB inducible system, we demonstrated that activation of TrkB in SH-SY5Y cells alleviated 6-OHDA-induced GSK3beta dephosphorylation (Ser9) and ameliorated 6-OHDA neurotoxicity. TrkB activation also protected CGNs against 6-OHDA-induced damage. Although antioxidants also offered neuroprotection, they had little effect on 6-OHDA-induced GSK3beta activation. These results suggest that GSK3beta is a critical intermediate in pro-apoptotic signaling cascades that are associated with neurodegenerative diseases, thus providing a potential target site amenable to pharmacological intervention.

Animals↗