Biomedical subjects

Yong Xie

Publications and source records attributed to Yong Xie.

At least 37 records · Page 2Linked to original sources

PubMed2005

[Metallothionein and its isoform genes expression in the human pancreatic cancer cell strains and their function].

OBJECTIVE: To compare the expression of metallothionein (MT) genes and proteins in six human pancreatic cancer cell strains and two human pancreatic cancer drug-resistant cell strains and to explore the relationship between the expression of the MT and pancreatic cancer cell chemo-resistance. METHODS: Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to determine the MT isoform-specific mRNA, and cadmium/hemoglobin saturation-electrochemistry to determine MT protein levels. RESULTS: MT protein expression in the pancreatic cancer cell strains was encoded by MT-1A, MT-1B, MT-1E, MT-1F, MT-1G, MT-1X, and MT-2A genes. The expression of MT proteins was upregulated and MT-1B, MT-1E, MT-1X, MT-2A genes overexpressed in human pancreatic cancer drug-resistant cell lines (P < 0.05). CONCLUSION: Expressions of MT proteins and genes correlate with the proliferation and chemoresistance of human pancreatic cancer cell strains.

Cell Division↗

PubMed2004

Plasmid encoding papillomavirus Type 16 (HPV16) DNA constructed with codon optimization improved the immunogenicity against HPV infection.

Human papillomavirus Type 16 (HPV16) infections can cause neoplasia, which is thought to be closely associated with the development of cervical cancers. In the study, we attempted to construct a DNA plasmid encoding a HPV16 capsid protein (L1) and a HPV16 oncoprotein (E7), which was capable of preventing HPV16 infection and eliminating HPV16-infected cells. A plasmid, L1E7hpSCA1, encoding the L1 and E7 genes with the codon usage optimized for mammalian cell expression, was constructed. Mutations were introduced into the E7 gene sequence for reducing its oncogenicity. C57BL/6 mice were intramuscularly immunized at tibialis anterior (TA) muscles with the newly constructed L1E7hpSCA1 plasmid. The immune responses induced by the L1E7hpSCA1 plasmid (with codon optimization) and a control L1E7pSCA1 plasmid (without codon optimization) were compared. It is shown that the L1E7hpSCA1 was able to induce much stronger immune responses than the L1E7pSCA1. Sera obtained from immunized animals were found to contain anti-HPV16 antibodies as detected by ELISA and hemagglutination inhibition (HAI) assays. Cytotoxicity and interferon-gamma assays showed that spleenocytes from immunized animals were able to recognize and lyze E7 expressing tumor TC-1 cells. Moreover, the growth of E7 expressing tumor mass was inhibited in vaccinated mice. In vivo tumor protection test indicated that tumor formation was prevented in the experimental animals (67%) after vaccination with L1E7hpSCA1, while for the control group injected with L1E7pSCA1 only and the animal group injected with pSCA1 only, tumor formation was observed in all experimental animals. Our results suggest that the L1E7h gene (with codon optimization) is more effective against HPV16 than the L1E7 gene (without codon optimization). The L1E7hpSCA1 plasmid was able to provide protection against E7 expressing tumor, and it might have the potential to be a vaccine candidate for HPV prevention.

Animals↗

PubMed2004

Crystallization and preliminary X-ray crystallographic studies of dissimilatory nitrite reductase isolated from Hyphomicrobium denitrificans A3151.

Dissimilatory nitrite reductase isolated from Hyphomicrobium denitrificans A3151 (HdNIR) is a novel copper-containing nitrite reductase (CuNIR) composed of six identical subunits. One plastocyanin-like domain and one green CuNIR-like domain are connected to each other, suggesting that the HdNIR subunit structure resembles a complex of green CuNIR and pseudoazurin (or azurin). Recombinant HdNIR protein was crystallized using the hanging-drop vapour-diffusion method with PEG 4000 as the precipitant at pH 8.9. X-ray diffraction data were collected to 2.35 A resolution. The HdNIR crystal belonged to the tetragonal space group P4(1) (or P4(3)), with unit-cell parameters a = b = 221.9, c = 165.2 A, giving 12 molecules (two hexamers) per asymmetric unit and a solvent content of 64%. A mutant form of HdNIR, C260A, which lacks the type I copper ion in the CuNIR-like domain, was prepared and crystallized under wild-type HdNIR conditions. The C260A mutant crystal belonged to the cubic space group P4(3)32 (or P4(1)32), with unit-cell parameters a = b = c = 153.7 A, giving one molecule per asymmetric unit and a solvent content of 59%. X-ray diffraction data were collected to 3.5 A resolution. To solve the crystal structure of HdNIR, the multiwavelength anomalous dispersion (MAD) method and the molecular-replacement method are currently being used.

Crystallization↗

PubMed2004

Identification of insulin variants using Raman spectroscopy.

Drop coating deposition Raman (DCDR) spectroscopy is used to obtain high-quality normal Raman spectra from small volumes (10 microl) of dilute insulin solutions (3-400 microM) for spectral identification and chromatographic detection. The results are used to demonstrate the spectroscopic classification (identification) of three natural insulin variants-human, bovine, and porcine-that differ by between one and three amino acid residues. DCDR measurements were performed on solutions obtained from reverse phase high-performance liquid chromatography (RP-HPLC) eluent fractions, either before or after lyophilization. Classification is demonstrated using replicate DCDR measurements, followed by normalized Savitsky-Golay second derivative preprocessing and partial least squares training with either leave-one-out or batch-to-batch testing.

Amino Acid Sequence↗

PubMed2004

The Raman detection of peptide tyrosine phosphorylation.

Drop-coating-deposition-Raman (DCDR) is used to detect spectral changes induced by phosphorylation of tyrosine amino acid residues in peptides. Four peptides are investigated, with sequences derived from the human protein-tyrosine kinase, p60c-src, with Y-216, Y-419, and Y-530 phosphorylation sites. Although the spectra of the four peptides are quite different, tyrosine phosphorylation is found to invariably induce the collapse of a doublet at 820-850cm(-1) and the attenuation of a peak around 1205cm(-1). Moreover, amide III band shifts suggest that tyrosine phosphorylation may promote beta sheet formation, particularly in peptides that lack phenylalanine residues. The degree of tyrosine phosphorylation in peptide mixtures is determined using DCDR combined with partial least squares multivariate calibration with a 2% root mean standard error of prediction.

Amino Acid Sequence↗

PubMed2004

Inhibition of human B-cell lymphoma by an anti-CD20 antibody and its chimeric F(ab')2 fragment via induction of apoptosis.

Monoclonal antibodies (mAb) directed against CD20, either unmodified or in radiolabeled forms, have been successfully used in clinic as effective therapeutic agents in the management of non-Hodgkin's B-cell lymphoma. Despite all clinical success the exact mechanisms of action of various anti-CD20 antibodies remains mostly unclear. Several mechanisms have been proposed to be responsible for the therapeutic activity of anti-CD20 antibodies, including antibody-dependent cell-mediated cytotoxicity, complement-mediated cytotoxicity, and direct inhibition of tumor growth via induction of apoptosis. We previously produced an anti-CD20 mAb, HI47, and showed that the antibody effectively blocked human B-cell proliferation in vitro and inhibited xenografted B-cell lymphoma in nude mice. In this study, we engineered the chimeric versions of both the Fab and F(ab)'2 fragments of HI47 and produced the fragments in E. coli. Both fragments competed efficiently with HI47 for binding to CD20+ B cells, and inhibited proliferation of B-lymphoma cells in a dose-dependent manner. Mechanistic studies revealed that both antibody fragments induced significant degree of B-cell apoptosis that is independent of any cross-linking agents. Further, both the F(ab)'2 and Fab fragments when administered in vivo significantly inhibited the growth of human B-cell lymphoma xenografts in nude mice. The bivalent F(ab)'2 fragment showed consistently better efficacy compared to its monovalent Fab counterpart in inducing apoptosis and inhibiting B-cell lymphoma growth both in vitro and in vivo. Taken together, these observations suggest that HI47 and its fragments most likely exert their antitumor activity through induction of cell apoptosis, and cross-linking/dimerization of CD20 molecules on B- cell surface is an important, but not essential, process for therapeutic efficacy of HI47 and its fragments.

Animals↗

PubMed2004

T-cell epitopes in severe acute respiratory syndrome (SARS) coronavirus spike protein elicit a specific T-cell immune response in patients who recover from SARS.

The immunogenicity of HLA-A2-restricted T-cell epitopes in the S protein of the Severe acute respiratory syndrome coronavirus (SARS-CoV) and of human coronavirus strain 229e (HCoV-229e) was analyzed for the elicitation of a T-cell immune response in donors who had fully recovered from SARS-CoV infection. We employed online database analysis to compare the differences in the amino acid sequences of the homologous T epitopes of HCoV-229e and SARS-CoV. The identified T-cell epitope peptides were synthesized, and their binding affinities for HLA-A2 were validated and compared in the T2 cell system. The immunogenicity of all these peptides was assessed by using T cells obtained from donors who had fully recovered from SARS-CoV infection and from healthy donors with no history of SARS-CoV infection. HLA-A2 typing by indirect immunofluorescent antibody staining showed that 51.6% of SARS-CoV-infected patients were HLA-A2 positive. Online database analysis and the T2 cell binding test disclosed that the number of HLA-A2-restricted immunogenic epitopes of the S protein of SARS-CoV was decreased or even lost in comparison with the homologous sequences of the S protein of HCoV-229e. Among the peptides used in the study, the affinity of peptides from HCoV-229e (H77 and H881) and peptides from SARS-CoV (S978 and S1203) for binding to HLA-A2 was higher than that of other sequences. The gamma interferon (IFN-gamma) release Elispot assay revealed that only SARS-CoV-specific peptides S1203 and S978 induced a high frequency of IFN-gamma-secreting T-cell response in HLA-A2(+) donors who had fully recovered from SARS-CoV infection; such a T-cell epitope-specific response was not observed in HLA-A2(+) healthy donors or in HLA-A2(-) donors who had been infected with SARS-CoV after full recovery. Thus, T-cell epitopes S1203 and S978 are immunogenic and elicit an overt specific T-cell response in HLA-A2(+) SARS-CoV-infected patients.

Amino Acid Sequence↗

PubMed2004

Chemical segregation and reduction of Raman background interference using drop coating deposition.

A new application of the recently described drop coating deposition Raman (DCDR) method facilitates the segregation and independent spectral characterization of mixture components. The quality of the normal (un-enhanced) Raman spectra are significantly improved as a result of reduced spectral interference from fluorescent impurities and buffer compounds. Fluorescence of commercial amino acid (O-phospho-L-serine) and protein (myoglobin) samples is reduced by over an order of magnitude using DCDR, more effectively than prolonged photo-bleaching. Furthermore, DCDR is used to obtain high-quality Raman spectra of proteins, lysozyme, and insulin, derived from solutions with up to 1000-fold excess buffer concentration. Possible thermodynamic and kinetic contributions to the observed segregation phenomena are discussed.

Amino Acids↗

PubMed2004

CD80 transfected human hepatocellular carcinoma cells activate cytotoxic T lymphocytes to target HCC cells with shared tumor antigens.

Human HCC cell lines (BEL-7402, SMMC-7721 and QGY-7703) do not express CD80 molecules, although they express MHC class I molecules and ICAM-1. HCC's poor immunogenicity may therefore be due to lack of CD80 molecules. This study first investigated whether CD80 molecules could provide minimal co-stimulatory signal for establishing an efficient anti-tumor immunity in HCC and second, whether the transfection of CD80 into the BEL-7402 cell line could induce T cell activation for targeting other HCC cell lines expressing shared common antigens. The transfection of cDNA encoding CD80 into ICAM-1+ HCC BEL-7402 cells was confirmed by flow cytometrical analysis. The CD80-transfected cells could enhance the immunogenicity of BEL-7402 cells as detected by T cell proliferation assay, and also activated the T cells at a higher proliferation rate comparing with the BEL-7402 cells transfected with vector only. The CD80-transfected cell line was also found able to activate T cells which subsequently induced cell lysis of SMMC-7721, QGY-7703 and parent BEL-7402 cell lines as detected by cytotoxicity assay. It can be concluded that the cytotoxicity was due to MHC class I restricted CD8+ cytotoxic T lymphocytes, but not natural killer (NK) cells, since this cytotoxic effect could be blocked by anti-MHC class I antibody and the cytotoxicity was shown very low in NK-cell-sensitive K562 cell line. Electroporation of CD80 cDNA into human HCC cells could increase the expression of the functional CD80 molecules and enhance the immunogenicity of the genetically-modified HCC cells to activate T cells for targeting 3 HCC cell lines in an HLA-restricted manner.

Antigens, Neoplasm↗

PubMed2003

Raman detection of proteomic analytes.

The compatibility of nonenhanced Raman spectroscopy with chromatographic and mass spectroscopic proteomic sensing is demonstrated for the first time. High-quality normal Raman spectra are derived from protein solutions with concentrations down to 1 microM and 1 fmol of protein nondestructively probed within the excitation laser beam. These results are obtained using a drop coating deposition Raman (DCDR) method in which the solution of interest is microdeposited (or microprinted) on a compatible substrate, followed by solvent evaporation and backscattering detection. Representative applications include the DCDR detection of insulin derived from an HPLC fraction, nondestructive DCDR followed by MALDI-TOF of lysozyme, the DCDR detection of protein spots deposited using an ink-jet microprinter, and the identification of spectral differences between glycan isomers of equal mass (such as those derived from posttranslationally modified proteins).

Journal Article↗

PubMed2003

Observing stochastic resonance in an underdamped bistable Duffing oscillator by the method of moments.

The method of moments is applied to an underdamped bistable oscillator driven by Gaussian white noise and a weak periodic force for the observations of stochastic resonance and the resulting resonant structures are compared with those from Langevin simulation. The physical mechanisms of the stochastic resonance are explained based on the evolution of the intrawell frequency peak and the above-barrier frequency peak via the noise intensity and the fluctuation-dissipation theorem, and the three possible sources of stochastic resonance in the system are confirmed. Additionally, with the noise intensity fixed, the stochastic resonant structures are also observed by adjusting the nonlinear parameter.

Journal Article↗

PubMed2003

Crystallization and preliminary X-ray crystallographic studies of mavicyanin from Cucurbita pepo medullosa.

Mavicyanin isolated from Cucurbita pepo medullosa is a glycosylated protein containing a single polypeptide chain of 109 amino-acid residues and is a member of the phytocyanin subclass of cupredoxins. Non-glycosylated recombinant mavicyanin, which was expressed in Escherichia coli, was crystallized by the hanging-drop vapour-diffusion method with ammonium sulfate as the precipitant at pH 5.5. The crystals belonged to the hexagonal space group P6(1) (or P6(5)), with unit-cell parameters a = 64.0, c = 245.0 A, four molecules per asymmetric unit and a solvent content of 59%. X-ray diffraction data were collected to 1.6 A resolution. To solve the structure of mavicyanin, the MAD method as well as a Patterson search method using the structure of stellacyanin as a starting model are presently being utilized.

Ammonium Sulfate↗

PubMed2003

[Immunoinformatic analysis for the epitopes on SARS virus surface protein].

SARS virus is a recently found coronavirus, which cause human atypical pneumonia through the binding of its spike protein to the receptor on human cells. By using the methods of immunoinformatics, we analyzed the virus surface protein and found that the epitopes, which can be recognized by human immune system, are strikingly changed or disappeared to compare with other common human coronavirus. This result may imply that the escape of SARS virus from human immune surveillance may be the causality plays a very of SARS virus infection. The immunoinformatics is a powerful fool for us to in screen the epitope specificial for SARS virus and identifying the candidate sites for peptide vaccine of SARS virus.

Epitopes↗

PubMed2003

Nasal natural killer/T cell lymphoma with cutaneous involvement: case report and Chinese literature review reported in China mainland.

Nasal natural killer (NK)/T cell lymphoma is an Epstein-Barr virus (EBV) associated lymphoma that arises in the nasal area and aggressively invades surrounding tissues. Our patient was a 48-year-old male who had had nasal obstruction and nasal discharge for 2 years and infiltrating plaques and necrosis on his nasal dorsum for three months. He developed fever and fatigue two weeks before admission. Biopsy from both skin and nasal mucosa revealed atypical medium-sized tumor cells infiltrating into the dermis. Immunohistochemical studies revealed that the tumor cells were UCHL-1, cytoplasmic CD3, CD56, TIA-1, and granzyme B positive, and CD8 and CD20 negative. In situ hybridization for EBV-DNA was positive. Clonal TCRb and TCRg gene rearrangement were negative. The patient was treated with cyclophosphamide, vincristine, and prednisone (COP) and with local radiotherapy, but he died 20 days later. We reviewed the cases of nasal NK/T cell lymphoma reported in mainland China in the Chinese literature during the last 5 years.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2003

Optimizing detection sensitivity on surface-enhanced Raman scattering of transition-metal electrodes with confocal Raman microscopy.

Some points on how to improve the detection sensitivity of confocal Raman microscopy for the study of surface-enhanced Raman scattering (SERS) of transition-metal electrodes are discussed, including the careful design of the spectroelectrochemical cell, proper selection of the thickness of the solution layer, the binning of charge-coupled device (CCD) pixels, and appropriate setting of the notch filter. Various roughening methods for the Pt, Rh, Fe, Co, and Ni electrode surfaces have been introduced in order to obtain SERS-active surfaces. It has been shown that the appropriate roughening procedure and the optimizing performance of the confocal Raman microscope are the two most important factors to directly generate and observe SERS on net transition-metal electrodes.

Electrochemistry↗

PubMed2003

Parabolic bursting induced by veratridine in rat injured sciatic nerves.

A specific bursting, parabolic bursting induced by veratridine, has been observed in rat injured sciatic nerve. With the help of Plant model, the biophysical mechanism for such a phenomenon is revealed from the viewpoint of nonlinear dynamical theory. The slow sodium influx educed by veratridine and the calcium-dependent potassium outflux are regarded as the two slow variables, which are responsible for the parabolic bursting. Furthermore, the roles that veratridine plays in the emergence of the parabolic bursting, namely inhibiting the inactivation of sodium channels and eliciting the slow sodium influx, are clarified.

Animals↗

PubMed2002

[Effects of trimetazidine on serum oxygen free radicals in congestive heart failure].

OBJECTIVE: To investigate the level of serum superoxide dismutase (SOD) and maiondialdehyde (MDA) and left ventricular systolic function in congestive heart failure (CHF) and to evaluate the influence of trimetazidine on them. METHODS: Serum SOD and MDA were measured in 50 patients with heart function from grade two to four and 15 normal subjects. All the persons underwent echocardiography to determine the left ventricular end-systolic volume index (LVESVI) and the left ventricular ejection fraction (EF). The patients with CHF were randomly treated with trimetazidine plus routine therapy (n = 25) or routine therapy only (n = 25) for 8 weeks with evaluations made before and after the treatment. RESULTS: The SOD level and EF in the patients with CHF significantly decreased and the MDA level and LVESVI in those patients significantly increased compared with the normal subjects (P < 0.05); the severer the CHF, the greater the changes. After the treatment, the SOD level and EF increased significantly and MDA and LVESVI decreased significantly (P < 0.01) in both the trimetazidine and the conventional groups. And these changes were more obvious in the trimetazidine group than in the conventional group(P < 0.01). CONCLUSION: Oxygen free radicals play an important role in the pathophysiologic changes of CHF. The level of serum SOD and MDA can indicate the degree of CHF. Trimetazidine not only increases the level of SOD and decreases the level of MDA, but also improves the left ventricular systolic function.

Adult↗

PubMed2002

X-ray structure of Galdieria Rubisco complexed with one sulfate ion per active site.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the reactions of carboxylation and oxygenation of ribulose-1,5-bisphosphate. These reactions require that the active site should be closed by a flexible loop (loop 6) of the large subunit. Rubisco from a red alga, Galdieria partita, has the highest specificity for carboxylation reaction among the Rubiscos hitherto reported. The crystal structure of unactivated Galdieria Rubisco has been determined at 2.6 A resolution. The electron density map reveals that a sulfate binds only to the P1 anion-binding site of the active site and the loop 6 is closed. Galdieria Rubisco has a unique hydrogen bond between the main chain oxygen of Val332 on the loop 6 and the epsilon-amino group of Gln386 of the same large subunit. This interaction is likely to be crucial to understanding for stabilizing the loop 6 in the closed state and to making a higher affinity for anionic ligands.

Binding Sites↗