Biomedical subjects

Xin Yao

Publications and source records attributed to Xin Yao.

26 records · Page 2Linked to original sources

PubMed2005

Intranasal immunization with inactivated SARS-CoV (SARS-associated coronavirus) induced local and serum antibodies in mice.

SARS-CoV (severe acute respiratory syndrome-associated coronavirus) strain GZ50 was partially purified and inactivated with 1:2000 formaldehyde. In cell culture the inactivated virus blocked the replication of live virus by decreasing the TCID(5.0) of the live virus 10(3.6) to 10(4.6) times. Inactivated GZ50 was used to immunize mice intranasally either alone, or after precipitation with polyethylene glycol (PEG), or with CpG, or CTB as an adjuvant. The titer of serum neutralizing antibodies was up to 1:640. In mice immunized with adjuvants or PEG precipitated GZ50, specific IgA was detected in tracheal-lung wash fluid by immunofluorescence. Though serum antibodies were detected, no anti-SARS-IgA could be detected in mice immunized only with inactivated GZ50. The roles of adjuvants in intranasal immunization with inactivated. SARS-CoV is discussed.

Administration, Intranasal↗

PubMed2005

High replicative full-length lamivudine-resistant hepatitis B virus isolated during acute exacerbations.

During chronic HBV infections, exacerbations of disease usually occur without clearly understood mechanisms. In this study, full-length HBV genomes were analyzed from four chronic hepatitis B patients who developed resistance to lamivudine [-2'-deoxy-3'-thiacytidine, LMV] accompanied by acute exacerbation of disease. Paired full-length HBV isolates were cloned from the sera of patients prior to LMV treatment and after drug resistant breakthrough isolates emerged with exacerbation. Compared to the isolates before treatment, isolates from all four patients during exacerbation showed marked increase in replicative competence by cell transfection study. Viral genome amplification and direct sequencing was used further to study the sequence differences between the dominant species and the clones used for functional analysis. Apart from mutations at the YMDD motif, no shared mutations were shown between all isolates. The isolates from the one patient who recovered from the exacerbation showed a lower number of mutations, and in particular, lacked basal core promoter (BCP) mutations at 1762/1764. In contrast, BCP mutations were found in isolates from the other three patients. Thus, in patients with acute exacerbation, high replicative strains might be selected from the total HBV quasispecies during treatment, and amongst these strains, those with core promoter mutations were most likely to be associated with severe clinical exacerbations.

Amino Acid Substitution↗

PubMed2005

Large-scale preparation of human anti-third-party veto cytotoxic T lymphocytes depleted of graft-versus-host reactivity: a new source for graft facilitating cells in bone marrow transplantation.

Induction of donor type chimerism in mildly prepared hosts without graft-versus-host disease (GvHD) is a most desirable goal in bone morrow transplantation. We have recently demonstrated in a mouse model that donor veto cytotoxic T lymphocytes (CTLs) can facilitate the induction of donor type chimerism in sublethally irradiated recipients without causing GvHD if they are effectively depleted of alloreactivity against host cells by means of stimulation against a third party. We extend this approach to human cells, by preparing CTLs in two major steps: primary culture in the absence of interleukin 2, leading to death by neglect of antihost clones, and addition of interleukin 2 and subsequent dilution of antihost clones as a consequence of the expansion of the anti-third-party clones. CTLs prepared in this way specifically suppress host cytotoxic T cells directed against antigens of the donor, but not against fourth-party antigens, as demonstrated in a standard (51)Cr release assay. We conclude that human anti-third-party CTLs afford a new source of veto cells that are depleted of potential graft-versus-host-reactive clones. The cells generated by this approach could potentially be used to facilitate engraftment of allogeneic hematopoietic stem cells.

Animals↗

PubMed2005

Substitution of proline 306 in the reverse transcriptase domain of hepatitis B virus regulates replication.

The proline residue at position 306 in hepatitis B virus (HBV) reverse transcriptase (rtP306) has been suggested to constrain the conformation of the alpha-helices in the thumb subdomain that interacts with the viral DNA template-primer. To study the impact of residue rt306 in HBV replication further, 11 site-directed mutants were constructed that substituted rtP306 with different amino acids. The replicative competencies of these mutants were assayed by HepG2 cell transfection and real-time PCR. When rtP306 was substituted with glycine or threonine, the replication competency of these mutants was drastically reduced to 1.96 and 4.51% of the wild-type HBV level, respectively. When rtP306 was substituted with glutamic acid, the replicative competency of the mutant increased up to 9.4-fold compared with wild-type virus. The results also showed that changes in the replicative competency of these constructed mutants were not associated with functional changes of HBV enhancer I. These results indicate the importance of amino acid(s) at the interface between the thumb and palm subdomains in modulating the replicative competency of HBV isolates. This regulatory residue(s) could serve as a new target for the development of anti-HBV drugs.

Amino Acid Substitution↗

PubMed2004

A hybrid Hopfield network-genetic algorithm approach for the terminal assignment problem.

This paper presents a hybrid Hopfield network-genetic algorithm (GA) approach to tackle the terminal assignment (TA) problem. TA involves determining minimum cost links to form a communications network, by connecting a given set of terminals to a given collection of concentrators. Some previous approaches provide very good results if the cost associated with assigning a single terminal to a given concentrator is known. However, there are situations in which the cost of a single assignment is not known in advance, and only the cost associated with feasible solutions can be calculated. In these situations, previous algorithms for TA based on greedy heuristics are no longer valid, or fail to get feasible solutions. Our approach involves a Hopfield neural network (HNN) which manages the problem's constraints, whereas a GA searches for high quality solutions with the minimum possible cost. We show that our algorithm is able to achieve feasible solutions to the TA in instances where the cost of a single assignment in not known in advance, improving the results obtained by previous approaches. We also show the applicability of our approach to other problems related to the TA.

Algorithms↗

PubMed2004

[Inhibitory effects of antisense TGF beta1 on in vitro and in vivo proliferation of human bladder cancer cells].

OBJECTIVE: To investigate the inhibitory effects of antisense TGF beta1 on proliferation of human bladder transitional cell carcinoma in vitro and in vivo. METHODS: Human bladder carcinoma cell line EJ was transfected with pRevT beta-AS, a replication defective retroviral vector carried antisense TGF beta1 fragment. The growth of the transfected cells was observed in vitro and in vivo. TGF beta1 mRNA expression and protein expression were detected by RT-PCR and ELISA. The proliferative activity was evaluated by immunohistochemistry method. The ultrastructure of cells was observed by image analysis system and electron microscopy. Cell cycle was determined by flow cytometry. RESULTS: The expression of TGF beta1 mRNA and protein in EJ cells was inhibited by pRevT beta-AS, G(1) to S transition was restrained in cell cycle and cell proliferation decreased in vitro. The tumorigenesis and growth of EJ cells and DNA heteroploidy were reduced by antisense TGF beta1 in vivo. CONCLUSION: TGF beta1 plays a role in vitro proliferation and in vivo growth of bladder transitional cell carcinoma.

Animals↗

PubMed2004

[Gene transfer of a beta-adrenergic receptor kinase inhibitor up-regulates the level of beta2-adrenergic receptor and cyclic adenosine monophosphate in the asthmatic murine lung].

OBJECTIVE: To investigate the effects of gene transfer of a beta-adrenergic receptor (beta(2)AR) kinase inhibitor (betaARKct) on pulmonary beta(2)-adrenergic receptor and cyclic adenosine monophosphate (cAMP) following beta(2)AR agonist treatment in asthmaticmice, and to analyze the relationship between the routes of gene delivery and the changes of beta(2)AR and cAMP. METHODS: (1)Thirty-five BALB/c mice were sensitized and challenged by 10% and 5% ovalbumin respectively to establish the asthmatic model and then divided into 7 groups (5 each). Sterile saline was injected intramuscularly in the asthmatic control group (group B), while beta(2)AR agonist (salbutamol) was injected intramuscularly in other 5 asthmatic groups (group C, D, E, F, and G) so as to establish the asthmatic model with prolonged application of beta(2)AR agonist. In addition, 5 healthy mice served as the normal control group (group A). (2) The plasmid with the expression of betaARKct was constructed and gene transfer was performed through intravenous injection or intratracheal instillation in asthmatic mice. Intravenous injection with plasmid-betaARKct was performed in group D, but with plasmid-pcDNA 3.1 in group E. Intratracheal instillation with plasmid-betaARKct was performed in group F, but with plasmid-pcDNA 3.1 in group G. (3) The gene expression was measured with Western blot analysis. Radioimmunoassay was used to evaluate the changes of pulmonary beta(2)AR and cAMP. RESULTS: (1) The expression of transferred betaARKct gene was detectable in the lungs. The level of betaARKct expression was higher in the lungs of mice receiving intratracheal plasmid (group F) than those receiving intravenous plasmid (group D). (2) The levels of beta(2)AR and cAMP in group A were (109 +/- 11) fmol/mg and (3.50 +/- 0.50) pmol/L respectively; The levels of beta(2)AR and cAMP in group B were (81 +/- 3) fmol/mg and (1.50 +/- 0.20) pmol/L respectively; the differences between the two groups were significant (all P < 0.05). The levels of beta(2)AR and cAMP in group C were (63 +/- 3) fmol/mg and (0.90 +/- 0.10) pmol/L respectively, and the differences were significant, as compared with those in group A (all P < 0.01). (3) The levels of beta(2)AR and cAMP in group D were (86 +/- 11) fmol/mg and (2.01 +/- 0.10) pmol/L respectively after using plasmid-betaARKct to the asthmatic mice treated with beta(2)AR agonist, and the differences were significant, as compared with those in group C (all P < 0.05). The levels of beta(2)AR and cAMP in group F were (107 +/- 13) fmol/mg and (3.30 +/- 0.20) pmol/L respectively, and the differences were significant, as compared with those in group C (all P < 0.05). The extent of up-regulation of beta(2)AR and cAMP was higher in group F than that in group D (all P < 0.05). The levels of beta(2)AR and cAMP were (70 +/- 11) fmol/mg and (1.30 +/- 0.10) pmol/L in group E, (67 +/- 4) fmol/mg and (3.30 +/- 0.20) pmol/L in group G, respectively, and there were no significant differences between group C and E or G (all P > 0.05). CONCLUSIONS: The results indicated that there was down-regulation of beta(2)AR and cAMP in asthmatic mice (group B), especially in those treated with beta(2)AR agonist (group C). Gene transfer of betaARKct could inhibit the extent of the down-regulation of beta(2)AR and cAMP in asthmatic mice treated with beta(2)AR agonist. The route of gene delivery could also affect the degree of up-regulation of beta(2)AR and cAMP. Gene transfer of betaARKct may provide a novel approach to the therapeutic strategy for asthma.

Animals↗

PubMed2002

Replication efficiency and sequence analysis of full-length hepatitis B virus isolates from hepatocellular carcinoma tissues.

Prolonged replication of hepatitis B virus (HBV) in liver tissues of hepatitis B patients has been considered as an important risk factor for the development of malignancy. Few studies on full-length HBV sequencing in association with the replication efficiency of isolates from HCC tissues have been reported. To study the structural and functional genomics of HBV isolates from Chinese hepatocellular carcinoma (HCC) patients, full-length HBV genomes were amplified from 6 HBV-marker positive HCC tissues and used to transfect HepG2 cells. Five of 6 isolates showed high replicative efficiency. All isolates were of genotype C and "hot-spots" mutations were detected in the B cell and T helper (Th) cell epitopes of the envelope and the core region. In addition, the X region of 2 isolates contained a stop-codon mutation that was predicted to result in a truncated X protein. High replicative HBV immune escape mutants that persist in infected hepatocytes could be 1 of the important factors to initiate pathological processes for the development of HCC in Chinese patients.

Base Sequence↗