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Biomedical subjects

Yan Zhang

Publications and source records attributed to Yan Zhang.

At least 217 records · Page 12Linked to original sources
PubMed2005

Comparative proteome analysis of untreated and Helicobacter pylori-treated HepG2.

AIM: To investigate the pathological effect of Helicobacter pylori (H pylori) on human hepatic cells, proteomic methods were used to find and to identify proteins that were overexpressed in HepG2 cells treated by H pylori. METHODS: H pylori was co-cultured with HepG2 for 6 h. Two-dimensional gel electrophoresis was used to gain the protein expression pattern of untreated and H pylori-treated HepG2. After staining and image analysis, spots of interest were isolated and subjected to mass spectrometry. RESULTS: Seven proteins, which were up-regulated in H pylori-treated HepG2 cells, were identified. These proteins included integrin beta-1, protein kinase C alpha, LIM/homeobox protein Lhx1, eIF-2-beta, MAP kinase kinase 3, PINCH protein and Ras-related protein Rab-37, which involved in transcription regulation, signal transduction, metabolism and so on. CONCLUSION: H pylori may exert the pathological effect on HepG2 cells by up-regulating the expression of some proteins.

Carcinoma, Hepatocellular↗
PubMed2005

Up-regulation of telomere-binding TRF1, TRF2 related to reactive oxygen species induced by As(2)O(3) in MGC-803 cells.

In this work, our study focused on As(2)O(3) action in view point of telomere. Results showed that treatment of human gastric cancer MGC-803 cells with arsenic trioxide could cause up-regulation of telomeric repeat binding factor TRF1 and TRF2 mRNA and protein levels, and induced G2/M phase arrest and cell apoptosis. At the same time, telomere length shortening and telomerase inhibitory were not obvious. Flow cytometry measurements indicated that the increase of TRF1 and TRF2 proteins is related to oxidative stress by arsenic trioxide. Results also indicate that after arsenic trioxide treatment, p53 protein levels increased significantly and also could bind directly at the telomere t-loop junction. These findings demonstrate arsenic trioxide-induced cell cycle arrest and apoptosis might involve a novel pathway related to TRF1, TRF2 protein.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2005

Functional analysis of transcriptional repressor Otx3/Dmbx1.

Otx3/Dmbx1 is a member of paired class homeodomain transcription factors. In this study, we found that Otx3/Dmbx1 represses the Otx2-mediated transactivation by forming heterodimer with Otx2 on the P3C (TAATCCGATTA) sequence in vitro. The 156 amino acid region (residues 1-156) of Otx3/Dmbx1 is required for its repressor activity, and interacts directly with Otx2. Co-localization of Otx3/Dmbx1 and Otx2 in brain sections was confirmed by in situ hybridization. These data suggest that Otx3/Dmbx1 represses Otx2-mediated transcription in the developing brain. We also identified the consensus binding sequence [TAATCCGATTA and TAATCC(N2-4)TAATCC] of Otx3/Dmbx1.

Animals↗
PubMed2005

An electrochemical investigation of hemoglobin and catalase incorporated in collagen films.

Collagen, an electrochemically inert protein, formed films on pyrolytic graphite (PG) electrodes, which provided a suitable microenvironment for heme proteins to transfer electron directly with the underlying electrodes. Hemoglobin (Hb) and catalase (Cat) incorporated in collagen films exhibited a pair of well-defined and quasi-reversible cyclic voltammetric peaks at around -0.35 V and -0.47 V (vs. SCE) in pH 7.0 buffers, respectively, characteristic of the protein heme Fe(III)/Fe(II) redox couples. UV-vis spectra showed that the heme proteins in collagen films retained their near-native conformations in the medium pH range. The results of scanning electron microscopy (SEM) demonstrated that the interaction between heme proteins and collagen made the morphology of dry protein-collagen films different from the collagen films alone. The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (k(s)) and formal potential (E degrees ') of the films were estimated by using square wave voltammograms (SWV) and nonlinear regression analysis. The heme protein-collagen film electrodes were also used to catalyze the reduction of nitrite, oxygen and hydrogen peroxide, indicating potential applications of the films for the fabrication of a new type of biosensor that does not use mediators.

Animals↗
PubMed2005

[The investigation of genotype and expression of alpha1-AT in patients with COPD].

OBJECTIVE: To detect genotype and expression of alpha1-AT in the patients with COPD to investigate the effect of alpha1-AT on pathogenesis of COPD. METHODS: Detection of PiZ allele in exon V and S allele in exon III were performed by PCR-Amplification of Specific Allele (PASA). The levels of serum alpha1-AT in some of subjects were measured by Enzyme-Linked Immunoadsordent Assay (ELISA). RESULTS: The PCR production of S mutation was 285 base pair fragment. The PCR production of Z-mutation was 250 base pair fragment. The results showed that All subjects were PiMM genotype of alpha1-AT, including COPD and control group. The mean serum alpha1-AT concentration, in patients with COPD, was 2.3 g/L +/- 1.1 g/L. In control group, the mean serum alpha1-AT concentration was 2.7 g/L +/- 0.84 g/L. The levels of alpha1-AT in patients with COPD are significantly lower than that in control group (P = 0.012). RV/TL and degree of pursiness are negative correlation with the levels of alpha1-AT. The r value were -0.208 and -0.262 respectively. CONCLUSION: There was no difference in genetic polymorphism of alpha1-AT between the patients with COPD and controls. However, the levels of serum alpha1-AT were significantly lower in the patients with COPD compared with control subjects. alpha1-AT deficiency may be a factor of the pathogenesis of COPD. The mechanism of alpha1-AT deficiency needs to be addressed.

Aged↗
PubMed2005

Synthesis and biological evaluation of N-[4-[5-(2,4-diamino-6-oxo-1,6-dihydropyrimidin-5-yl)-2-(2,2,2-trifluoroacetyl)pentyl]benzoyl]-L-glutamic acid as a potential inhibitor of GAR Tfase and the de novo purine biosynthetic pathway.

The synthesis and evaluation of N-[4-[5-(2,4-diamino-6-oxo-1,6-dihydropyrimidin-5-yl)-2-(2,2,2-trifluoroacetyl)pentyl]benzoyl]-L-glutamic acid (2) as an inhibitor of glycinamide ribonucleotide transformylase (GAR Tfase) and aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase) are reported. The inhibitor 2 was prepared in a convergent synthesis involving C-alkylation of methyl 4-(4,4,4-trifluoro-3-dimethylhydrazonobutyl)benzoate with 1-chloro-3-iodopropane followed by construction of the pyrimidinone ring. Compound 2 was found to be an effective inhibitor of recombinant human GAR Tfase (K(i) = 0.50 microM), whereas it was inactive (K(i) > 100 microM) against E. coli GAR Tfase as well as recombinant human AICAR Tfase. Compound 2 exhibited modest, purine-sensitive growth inhibitory activity against the CCRF-CEM cell line (IC50 = 6.0 microM).

Antineoplastic Agents↗
PubMed2005

Synthesis and biological evaluation of alpha- and gamma-carboxamide derivatives of 10-CF3CO-DDACTHF.

Structurally-related, but non-polyglutamylatable, derivatives of 10-CF3CO-DDACTHF (1), which incorporate L-glutamine (2) and L-isoglutamine (3) in place of L-glutamate, were prepared and evaluated as inhibitors of recombinant human (rh) GAR Tfase. While the L-glutamate alpha-carboxamide derivative 3 was much less effective as a rhGAR Tfase inhibitor (K(i) = 4.8 microM) and inactive in cellular functional assays, the gamma-carboxamide derivative 2 was found to be a potent and selective rhGAR Tfase inhibitor (K(i) = 0.056 microM) being only 4-fold less potent than 1 (K(i) = 0.015 microM). Moreover, 2 was effective in cellular functional assays exhibiting purine sensitive cytotoxic activity (IC50 = 300 nM, CCRF-CEM) only 20-fold less potent than 1 (IC50 = 16 nM), consistent with inhibition of de novo purine biosynthesis via selective inhibition of GAR Tfase. Like 1, 2 is transported into the cell by the reduced folate carrier. Unlike 1, the functional activity of 2 is not dependent upon FPGS polyglutamylation.

Amides↗
PubMed2005

Design, synthesis, and biological evaluation of 10-methanesulfonyl-DDACTHF, 10-methanesulfonyl-5-DACTHF, and 10-methylthio-DDACTHF as potent inhibitors of GAR Tfase and the de novo purine biosynthetic pathway.

The synthesis and evaluation of 10-methanesulfonyl-DDACTHF (1), 10-methanesulfonyl-5-DACTHF (2), and 10-methylthio-DDACTHF (3) as potential inhibitors of glycinamide ribonucleotide transformylase (GAR Tfase) and aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase) are reported. The compounds 10-methanesulfonyl-DDACTHF (1, K(i) = 0.23 microM), 10-methanesulfonyl-5-DACTHF (2, K(i) = 0.58 microM), and 10-methylthio-DDACTHF (3, K(i) = 0.25 microM) were found to be selective and potent inhibitors of recombinant human GAR Tfase. Of these, 3 exhibited exceptionally potent, purine sensitive growth inhibition activity (3, IC50 = 100 nM) against the CCRF-CEM cell line being 3-fold more potent than Lometrexol and 30-fold more potent than the parent, unsubstituted DDACTHF, whereas 1 and 2 exhibited more modest growth inhibition activity (1, IC50 = 1.0 microM and 2, IC50 = 2.0 microM).

Antineoplastic Agents↗
PubMed2005

Photoreactions of 1-acetylisatin with alkynes: regioselectivity in oxetene formation and easy access to 3-alkylideneoxindoles and dispiro[oxindole[3,2']furan[3',3' ']oxindole]s.

[reaction: see text] Photoinduced reactions of 1-acetylisatin (IS) with diphenylacetylenes 1a-c, 1-(p-methoxyphenyl)propyne 2, and 1,4-diphenyl-1,3-butadiyne 3 gave beta,beta-disubstituted 3-alkylidene oxindoles 6-12 respectively via [2+2] cycloaddition of 3IS* with the alkyne and subsequent oxetene ring opening. Photoreactions of IS with phenylacetylenes 4a-d and cyclopropylacetylene 5 furnished the dispiroindole[3,2']furan[3',3' ']indoles 13 and 14. Compounds 13 and 14 are formed in tandem reactions initiated by [2+2] cycloaddition of 3IS* with the alkynes to give spirooxetenes Va and Vb, which upon spontaneous ring opening gave the alpha,beta-unsaturated aldehydes IVa and IVb. It is proposed that hydrogen abstraction of 3IS* from the C(O)-H functionality in IV followed by dissociation of the triplet isatin ketyl (A)-aldehyde acyl (B) radical pair and an oxygenphilic attack of the acyl radical B at the C3 carbonyl oxygen atom of a neutral IS gave the 2:1 (IS:4) radical C, which took part in an intramolecular radical cyclization to give the dispiroindole[3,2']furan[3',3' ']indoles 13 and 14. The regioselectivity in the [2+2] photocycloadditions of IS with 4 to afford the oxetene Va depends on the intervening of the more stable 1,4-diradical intermediates VI, which have a linear alpha-phenyl-substituted vinyl radical where the phenyl provides spin delocalization of the radical center at the sp carbon atom.

Acetylene↗
PubMed2005

Poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-g-poly(vinyl pyrrolidone): synthesis and characterization.

Pluronic poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers are grafted with poly(vinyl pyrrolidone) by free radical polymerization of vinyl pyrrolidone with simultaneous chain transfer to the Pluronic in dioxane. This modified polymer has both thermal responsiveness and remarkable capacity to interact with a wide variety of hydrophilic and hydrophobic pharmaceutical agents which is very attractive for medical applications. The chemical structure of the graft copolymers was characterized by FTIR and 1H NMR spectroscopy. Polymerization conditions such as initiators, feed ratio, and reaction times are studied to obtain the ideal graft copolymer.

Journal Article↗
PubMed2005

Miniature fiber-optic multicavity Fabry-Perot interferometric biosensor.

A fiber-optic sensor is designed based on multicavity Fabry-Perot interferometry for the study of optical thickness in self-assembled thin-film layers. This miniature sensor is applicable not only to the measurement of self-assembled polyelectrolyte layers but also to the immobilization of proteins such as immunoglobulin G (IgG). The binding of IgG and the corresponding antigen is observed, and the nonspecific binding characteristics are investigated. The optical thickness changes are used to evaluate the immobilization of the IgG and the immunological activities of the immobilized layers.

Biosensing Techniques↗
PubMed2005

Preferential growth of single-walled carbon nanotubes on silica spheres by chemical vapor deposition.

The preferential growth of single-walled carbon nanotubes (SWNTs) on silica spheres with various diameters was realized for the first time by chemical vapor deposition (CVD) of methane. SWNTs tend to wrap the silica spheres to form a new superstructure of uniform SWNT nanoclaws when the diameters of the silica spheres are larger than 400 nm. The SWNTs obtained on silica spheres have highly graphitic tubular walls as characterized by Raman spectroscopy and HRTEM. This is a new method to obtain tunable uniform elastic deformation of SWNTs, which may act as the model for the study about the effect of delocalized bending on the properties of SWNTs. In addition, the combination of SWNTs with monodispersed silica spheres could conveniently integrate SWNTs into photonic crystals.

Journal Article↗
PubMed2005

Ornithine decarboxylase gene is overexpressed in colorectal carcinoma.

AIM: To investigate the ornithine decarboxylase (ODC) gene expression in colorectal carcinoma, ODC mRNA was assayed by RT-PCR and ODC protein was detected by a monoclonal antibody against fusion of human colon ODC prepared by hybridoma technology. METHODS: Total RNA was extracted from human colorectal cancer tissues and their normal counterpart tissues. ODC mRNA levels were examined by RT-PCR. ODC genes amplified from RT-PCR were cloned into a prokaryotic vector pQE-30. The expressed proteins were purified by chromatography. Anti-ODC mAb was prepared with classical hybridoma techniques and used to determine the ODC expression in colon cancer tissues by immunohistochemical and Western blotting assay. RESULTS: A cell line, which could steadily secrete anti-ODC mAb, was selected through subcloning four times. Western blotting reconfirmed the mAb and ELISA showed that its subtype was IgG2a. RT-PCR showed that the ODC mRNA level increased greatly in colon cancer tissues (P<0.01). Immunohistochemical staining showed that colorectal carcinoma cells expressed a significantly higher level of ODC than normal colorectal mucosa (98.6+/-1.03% vs 5.26+/-5%, P<0.01). CONCLUSION: ODC gene overexpression is significantly related to human colorectal carcinoma. ODC gene expression may be a marker for the gene diagnosis and therapy of colorectal carcinoma.

Animals↗
PubMed2005

[Study on the modulation of estrogen receptor isoforms alpha in endometrial carcinoma cells using antisense oligodeoxyribonucleotides].

OBJECTIVE: To verify the roles of estrogen receptor alpha in the tumogenesis of endometrial cancer in relationship with estrogen and tamoxifen, and to explore an efficient way to modulate the expression of estrogen receptor (ER) isoform alpha to built up a model of endometrial cancer cells expressing predominant one isoform of ERs for ultimately probing therapeutical and preventive antiestrogen for endometrial cancer. METHODS: A series of oligodeoxyribonucleotides against regions of the human ERalpha was synthesized and tested in human endometrial cancer cell line (HEC-1B cells) that expressed functional ERalpha. The expressions of ER isoforms were detected by Western blot using specific antibody. The change of HEC-1B cell proliferation in response to 17beta-estradiol(E2) and tamoxifen(TAM) under the impact of antisense oligodeoxyribonucleotides (AS-ODN) was studied. RESULTS: (1) Transfection with AS-ODN directed against the human ERalpha significantly inhibited ERalpha protein expression. (2) The proliferation of endometrial cancer cell line HEC-1B could be increased by both E(2) and TAM. The cells lost the ability to proliferate in response to E(2) after being transfected with ERalpha-AS-ODN at hours 24, 48 and 72. After being transfected with ERalpha-AS-ODN, HEC-1B cells lost the ability to proliferate in response to TAM at hour 48. CONCLUSION: (1) AS-ODNs directed against the human ERalpha can inhibit the expression of ER alpha effectively. The method can be used to built up a model of endometrial cancer cells expressing predominant one isoform of ERs. (2) ERalpha may be the primary receptor in the proliferation of HEC-1B cells in response to 17beta-estradiol and tamoxifen.

Cell Proliferation↗
PubMed2005

An algorithm for identification of bacterial selenocysteine insertion sequence elements and selenoprotein genes.

MOTIVATION: Incorporation of selenocysteine (Sec) into proteins in response to UGA codons requires a cis-acting RNA structure, Sec insertion sequence (SECIS) element. Whereas SECIS elements in Escherichia coli are well characterized, a bacterial SECIS consensus structure is lacking. RESULTS: We developed a bacterial SECIS consensus model, the key feature of which is a conserved guanosine in a small apical loop of the properly positioned structure. This consensus was used to build a computational tool, bSECISearch, for detection of bacterial SECIS elements and selenoprotein genes in sequence databases. The program identified 96.5% of known selenoprotein genes in completely sequenced bacterial genomes and predicted several new selenoprotein genes. Further analysis revealed that the size of bacterial selenoproteomes varied from 1 to 11 selenoproteins. Formate dehydrogenase was present in most selenoproteomes, often as the only selenoprotein family, whereas the occurrence of other selenoproteins was limited. The availability of the bacterial SECIS consensus and the tool for identification of these structures should help in correct annotation of selenoprotein genes and characterization of bacterial selenoproteomes.

Algorithms↗
PubMed2005

The microbial selenoproteome of the Sargasso Sea.

BACKGROUND: Selenocysteine (Sec) is a rare amino acid which occurs in proteins in major domains of life. It is encoded by TGA, which also serves as the signal for termination of translation, precluding identification of selenoprotein genes by available annotation tools. Information on full sets of selenoproteins (selenoproteomes) is essential for understanding the biology of selenium. Herein, we characterized the selenoproteome of the largest microbial sequence dataset, the Sargasso Sea environmental genome project. RESULTS: We identified 310 selenoprotein genes that clustered into 25 families, including 101 new selenoprotein genes that belonged to 15 families. Most of these proteins were predicted redox proteins containing catalytic selenocysteines. Several bacterial selenoproteins previously thought to be restricted to eukaryotes were detected by analyzing eukaryotic and bacterial SECIS elements, suggesting that eukaryotic and bacterial selenoprotein sets partially overlapped. The Sargasso Sea microbial selenoproteome was rich in selenoproteins and its composition was different from that observed in the combined set of completely sequenced genomes, suggesting that these genomes do not accurately represent the microbial selenoproteome. Most detected selenoproteins occurred sporadically compared to the widespread presence of their cysteine homologs, suggesting that many selenoproteins recently evolved from cysteine-containing homologs. CONCLUSIONS: This study yielded the largest selenoprotein dataset to date, doubled the number of prokaryotic selenoprotein families and provided insights into forces that drive selenocysteine evolution.

Algorithms↗