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Biomedical subjects

Yan Gao

Publications and source records attributed to Yan Gao.

At least 37 records · Page 2Linked to original sources
PubMed2006

Laribacter hongkongensis isolated from a patient with community-acquired gastroenteritis in Hangzhou City.

We describe the isolation of Laribacter hongkongensis in Hangzhou City, People's Republic of China. One strain of bacterium, named LHHZ242, had many of the same phenotypic and genotypic characteristics as Laribacter hongkongensis described in previous publications. This discovery proves that Laribacter hongkongensis is also associated with community-acquired gastroenteritis outside Hong Kong.

China↗
PubMed2006

Growth arrest induced by C75, A fatty acid synthase inhibitor, was partially modulated by p38 MAPK but not by p53 in human hepatocellular carcinoma.

C75, a well-known fatty acid synthase (FAS) inhibitor, has been shown to possess potent anti-cancer activity in vitro and in vivo. In this study, we reveal that C75 is a cell cycle arrest inducer and explore the potential mechanisms for this effect in hepatocellular carcinoma (HCC) cell lines with abundant FAS expression: HepG2 and SMMC7721 cells with wt-p53, and Hep3B cells with null p53. The results showed FAS protein expression and basal activity levels were higher in HepG2 cells than in the other two HCC cell lines. Treatment with C75 inhibited FAS activity within 30 min of administration and induced G(2) phase arrest accompanied by p53 overexpression in HepG2 and SMMC7721 cells. By contrast, C75 triggered G(1) phase arrest in Hep3B cells, and RNA interference targeting p53 did not attenuate C75-induced G(2) arrest in HepG2 cells. Similarly, p53 overexpression via p53 plasmid transfection did not affect C75-induced G(1) phase arrest in Hep3B cells. However, we observed a clear correlation between p38 MAPK activation triggered by C75 and the induction of cell cycle arrest in all three HCC cells. Furthermore, treatment with the p38 MAPK inhibitor SB203580 reduced p38 MAPK activity and cell cycle arrest, and also partially restored cyclin A, cyclin B1, cyclin D1 and p21 protein levels. Collectively, it was p38 MAPK but not p53 involved in C75-mediated tumor cell growth arrest in HCC cells.

4-Butyrolactone↗
PubMed2006

Soluble multimer of recombinant endostatin expressed in E. coli has anti-angiogenesis activity.

The bioactivity, refolding, and multimer formation of endostatin, particularly of recombinant endostatin produced from bacteria, are proved challenging for clinical application. In order to determine the biological activity of recombinant endostatin multimer, first, we expressed endostatin in Escherichia coli and purified it with ion-exchange chromatography. The purified active protein could elicit multimer formation spontaneously, but still has comparable activity. Aim to determine the anti-angiogenic activity of multimer endostatin, by use of RP-HPLC, we then successfully separated endostatin monomer and multimer for subjecting to anti-angiogenesis assay. The results from CAM (chorioallantoic membrane) inhibition assay showed that both monomer and multimer suppressed CAM vascularization significantly. At the dosage of 0.8 microg, inhibition rates of multimeric and monomeric proteins were about 58% and 38%, respectively. Multimeric endostatin exerted a higher activity than monomeric endostatin (p < 0.05). However, when the protein dosage is less than 0.4 microg/ml, there is no significance between their inhibition rates (p > 0.05), although both of them show a high inhibition effect in contrast to control. The results from HUVEC proliferation assay also showed similar effects at dosages of 0.6 and 1.6 microg/ml, multimer exerted a higher activity on inhibition of HUVEC proliferation comparing with monomer (p < 0.05). In conclusion, our results suggest that endostatin multimer has a comparable or higher bioactivity and multimerization will not affect its bioactivity, implying that endostatin activity is insensitive to structure conformation contributed by disulfide bonds.

Allantois↗
PubMed2006

Growth mechanism, photoluminescence, and field-emission properties of ZnO nanoneedle arrays.

ZnO nanoneedle arrays have been grown on a large scale with a chemical vapor deposition method at 680 degrees C. Zn powder and O(2) gas are employed as source materials, and catalyst-free Si plates are used as substrates. Energy-dispersive X-ray and X-ray diffraction analyses show that the nanoneedles are almost pure ZnO and preferentially aligned in the c-axis direction of the wurtzite structure. The growth mechanism of ZnO nanoneedle arrays is discussed with the thermodynamic theory and concluded to be the result of the co-effect of the surface tension and diffusion. Photoluminescence spectrum of the as-grown products shows a strong emission band centering at about 484 nm, which originates from oxygen vacancies. Field-emission examination exhibits that the ZnO nanoneedle arrays have a turn-on voltage at about 5.3 V/microm.

Journal Article↗
PubMed2006

Alternative 3' UTR polyadenylation of Bzw1 transcripts display differential translation efficiency and tissue-specific expression.

BZW1 is a conserved regulatory factor for transcriptional control of histone H4 gene at the G1/S transition. In this study, three Bzw1 transcripts were identified in mice with two long forms (approximately 2.9 kb) expressed ubiquitously at low level, and a short transcript of 1.8 kb expressed at high level exclusively in testis. These different transcripts share the same 5' UTR and coding sequence, but differ in the length of 3' UTR by utilizing alternative polyadenylation sites. Different translation efficiencies were observed in the cells transfected with chimeric EGFP-Bzw1 genes tailed with different 3' UTRs. Our results demonstrate that Bzw1 transcripts are alternatively polyadenylated and expressed in tissue-specific pattern.

3' Untranslated Regions↗
PubMed2006

Clinicopathologic study of parotid involvement in 21 cases of eosinophilic hyperplastic lymphogranuloma (Kimura's disease).

OBJECTIVE: To investigate the clinicopathologic features of eosinophilic hyperplastic lymphogranuloma (Kimura's disease) in the parotid gland. STUDY DESIGN: The hematoxylin and eosin sections and clinical data of 60 patients with eosinophilic hyperplastic lymphogranuloma (Kimura's disease), including with parotid involvement, were reviewed. RESULTS: Of 60 cases of eosinophilic hyperplastic lymphogranuloma (average age, 42 years; average disease duration, 5.8 years), 35 cases (58%) were clinically seen to involve swelling of the parotid region. Parotid specimens were available in 21 cases and showed different microscopic changes. In mildly affected parotid samples, the histological features included infiltration of lymphocytes and eosinophils around the ducts of the interlobular connective tissues. In the moderately involved glands, the infiltrated area was enlarged and contained lymphoid follicles, resulting in adjacent acinar atrophy that was particularly obvious around the salivary ducts. In severe lesions, most acini were lost and only a few ducts remained. All cases with parotid involvement showed more severe pathological changes in the subcutaneous connective tissues and/or local lymph nodes. The parotid lesions often surrounded a central intraglandular lymph node with characteristic features of the disease; however, the salivary parenchyma was left alone. Nerve fibers affected by inflammatory lymphocytes and eosinophils were seen in 38/60 (63%) cases of eosinophilic hyperplastic lymphogranuloma (Kimura's disease) examined in this study. CONCLUSIONS: Eosinophilic hyperplastic lymphogranuloma (Kimura's disease) does not show primary parotid involvement, but instead, pathological changes in the parotid gland are a result of disease spread from the intraparotid lymph nodes and adjacent soft tissues. In addition, our observations suggest that the pruritus often associated with the disease may be due to nerve infiltration by lymphocytes and eosinophils.

Adult↗
PubMed2006

Preparation of roxithromycin-polymeric microspheres by the emulsion solvent diffusion method for taste masking.

Microspheres of roxithromycin with Eudragit S100 and silica were prepared by the emulsion solvent diffusion method to mask the bitter taste of the antibiotic. The effect of different polymers and drug-polymer ratios on the taste masking and the characteristics of the microspheres were investigated. It was found that Eudragit S100 was the best for masking the unpleasant taste of roxithromycin among the six kinds of polymers investigated. The results of DSC, X-ray diffraction and IR showed that there were several combinations of roxithromycin and Eudragit S100. The influence of other formulation factors, i.e. dichloromethane-acetone ratios and silica-polymer ratios on the properties of the microspheres were also examined. In conclusion, the results of the present study will be helpful for the preparation of oral forms of roxithromycin with an acceptable taste.

Acetone↗
PubMed2006

Functional roles of p12, the fourth subunit of human DNA polymerase delta.

Mammalian DNA polymerase delta (pol delta), a key enzyme of chromosomal DNA replication, consists of four subunits as follows: the catalytic subunit; p125, which is tightly associated with the p50 subunit; p68, a proliferating cell nuclear antigen (PCNA)-binding protein; and a fourth subunit, p12. In this study, the functional roles of the p12 subunit of pol delta were studied. The inter-subunit interactions of the p12 subunit were determined by yeast two-hybrid assays and by pulldown assays. These assays revealed that p12 interacts with p125 as well as p50. This dual interaction of p12 suggests that it may serve to stabilize the p125-p50 interaction. p12 was shown to be a novel PCNA-binding protein. This was confirmed by identification of a PCNA-binding motif at its N terminus by binding assays and by site-directed mutagenesis. The activities and reaction products of recombinant pol delta containing a p12 mutant defective in PCNA binding, as well as purified recombinant pol delta and its subassemblies, were analyzed. Our results indicate that p12 contributes to PCNA-dependent pol delta activity, i.e. the p12-PCNA interaction is functional. Our data indicate that both p12 and p68 are required for optimal pol delta activity. This supports the hypothesis that the interaction between pol delta and PCNA is a divalent one that involves p12 and p68. We propose a model in which pol delta interacts with PCNA via at least two of its subunits, and one in which p12 could play a role in stabilizing the overall pol delta-PCNA complex as well as pol delta itself.

Binding Sites↗
PubMed2006

Increased neuroglobin levels in the cerebral cortex and serum after ischemia-reperfusion insults.

Neuroglobin (NGB) is a newly discovered protein localized in neurons of the central and peripheral nervous systems in vertebrates. It functions to bind, store, and facilitate the utilization of oxygen in neuronal cells. Recent studies suggest that it may modulate hypoxic and ischemic injury. The major goal of the present study is to characterize the dynamic changes of NGB protein in the brain and serum in a global forebrain ischemia-reperfusion model using gerbils. The sensitivity and validity of serum NGB as a potential biomarker for brain injury were further evaluated. Global cerebral ischemia-reperfusion models were induced by bilateral carotid occlusion for 20 min followed with 2-, 8-, 16-, 24-, 48-, or 72-h reperfusion in forty-six Mongolian gerbils. Sham-operated and operated animals were sacrificed at the designated time after reperfusion. Brains were fixed for immunocytochemical study to evaluate the time-dependent expression of NGB, and the concentration of NGB in serum was measured by enzyme-linked immunosorbent assay. Our results showed that the expression of NGB was upregulated in the cerebral cortex but significantly downregulated in the hippocampus from 2 to 72 h of reperfusion after 20 min of bilateral common carotid arteries occlusion. The concentration of NGB in serum was significantly increased at 8 h and reached a peak at 48 h of reperfusion. There is a significant correlation between NGB levels in the serum and severity of neuronal damage in the gerbil brain. In summary, the upregulation of NGB in cerebral cortex and downregulation in hippocampus after reperfusion insults in the gerbil brain are consistent with the fact that cerebral cortex is more tolerant to hypoxic or ischemic injury than the hippocampus. Moreover, the changes of NGB levels in serum may be used to monitor the extent of brain damage in ischemic brain diseases.

Analysis of Variance↗
PubMed2006

Temperature dependence of the Raman spectra of individual carbon nanotubes.

Resonant Raman scattering (RRS) spectra of individual carbon nanotubes on a SiO2 substrate have been investigated first in the temperature range of 100-600 K (Phys. Rev. B 2002, 66, 115411). It was revealed by the intensity abnormality of the radial breathing mode (RBM) that the carbon nanotubes have a temperature-dependent density of electronic states. This means that the previously reported temperature coefficients of RBM of carbon nanotubes are smaller than their "real" ones for the bulk samples of single- or double-walled carbon nanotubes. Comparatively, the G line of individual nanotubes shows no observable difference relative to the bulk samples.

Journal Article↗
PubMed2006

Influence of rmhTNF on the chemotherapy treatment of small cell lung cancer.

The efficacy and safety of the recombinant mutant human tumor necrosis factor (rmhTNF) combined with chemotherapy vs chemotherapy alone in the treatment of patients with small cell lung cancer (SCLC) were evaluated in this study. The selected 37 patients with SCLC were divided into experimental group (n =18) and control group (n = 19). Both groups were subjected to EP regimen. While in the experimental group, a regimen of 4 x 10(6) U/m2 rmhTNF intramuscular injection was given once a day from the 1st to 7th day and 11th to 17th day on the chemotherapy cycle. Twenty-one days were as a chemotherapy cycle and all patients received treatment with 2 cycles. The response rate was 83.3% (15/18) in the experimental group and 63.2% (12/19) in the control group respectively (P < 0.05). The KPS score after treatment was 78.4 +/- 9.6 in the experimental group and 71.2 +/- 9.7 in the control group with the difference being significant (P < 0.05). No severe adverse effects occurred in the two groups. It was concluded that the curative effectiveness of the rmhTNF combined with chemotherapy in the treatment of SCLC was more satisfactory than chemotherapy alone. The former could obviously improve the quality of life of the patients with SCLC.

Adult↗
PubMed2006

In vivo and in vitro inhibitory effect of amniotic extraction on neovascularization.

PURPOSE: To prepare amniotic extraction (AE) and to test its antiangiogenic effect in vivo and in vitro. METHODS: AE was prepared and diluted to 50, 100, and 200 microg/mL concentrations. Alkali burn-induced corneal neovascularization (NV) was produced and topically treated with different concentrations of AE or 0.1% dexamethasone for 7 days. Normal saline was used as a control. Corneal NV was visualized by heart perfusion of Chinese ink and quantified as the percentage of corneal NV area to the whole corneal area. Human umbilical vein endothelial cells (HUVECs) were primarily cultured. The effects of AE on proliferation and tube formation of HUVECs were tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method and in vitro angiogenesis assay. Pigment epithelium-derived factor (PEDF) in AE was detected by Western blot. RESULTS: Relative corneal NV area in the control group was 56.6% +/- 9.9%, which was significantly reduced by 50 microg/mL AE (47.6% +/- 6.9%; P = 0.043) and 200 microg/mL AE (34.3% +/- 7.8%; P < 0.001) and by 0.1% dexamethasone (21.1% +/- 1.8%; P < 0.001). HUVEC cell proliferation was significantly decreased after treatment with AE at concentrations of 50 and 100 microg/mL compared with control (P = 0.036 and 0.001, respectively). The tube formation was significantly suppressed by 100 microg/mL AE (70.03% +/- 4.35%) compared with control (100% +/- 4.84%; P = 0.002). No expression of PEDF was detected in AE. CONCLUSION: AE inhibits NV induced by alkali burn. This effect may be elicited at least in part through the inhibiting activity of blood vessel endothelial cells and is not associated with PEDF.

Amnion↗
PubMed2006

Crystal structure of the MAP3K TAO2 kinase domain bound by an inhibitor staurosporine.

Mitogen-activated protein kinase (MAPK) signal transduction pathways are ubiquitous in eukaryotic cells, which transfer signals from the cell surface to the nucleus, controlling multiple cellular programs. MAPKs are activated by MAPK kinases [MAP2Ks or MAP/extracellular signal-regulated kinase (ERK) kinases (MEK)], which in turn are activated by MAPK kinase kinases (MAP3Ks). TAO2 is a MAP3K level kinase that activates the MAP2Ks MEK3 and MEK6 to activate p38 MAPKs. Because p38 MAPKs are key regulators of expression of inflammatory cytokines, they appear to be involved in human diseases such as asthma and autoimmunity. As an upstream activator of p38s, TAO2 represents a potential drug target. Here we report the crystal structure of active TAO2 kinase domain in complex with staurosporine, a broad-range protein kinase inhibitor that inhibits TAO2 with an IC50 of 3 mM. The structure reveals that staurosporine occupies the position where the adenosine of ATP binds in TAO2, and the binding of the inhibitor mimics many features of ATP binding. Both polar and nonpolar interactions contribute to the enzyme-inhibitor recognition. Staurosporine induces conformational changes in TAO2 residues that surround the inhibitor molecule, but causes very limited global changes in the kinase. The structure provides atomic details for TAO2-staurosporine interactions, and explains the relatively low potency of staurosporine against TAO2. The structure presented here should aid in the design of inhibitors specific to TAO2 and related kinases.

Animals↗
PubMed2006

Autoantibody against cardiac beta1-adrenoceptor induces apoptosis in cultured neonatal rat cardiomyocytes.

To clarify whether apoptosis is involved in the injury processes induced by autoantibody against cardiac beta1-adrenoceptor, we investigated the biological and apoptotic effects of antibodies on cultured neonatal rat cardiomyocytes. Wistar rats were immunized with peptides corresponding to the second extracellular loop of the beta1-adrenoceptor to induce the production of anti-beta1-adrenoceptor antibodies in the sera. Immunoglobulin (Ig) G in the sera was detected using synthetic antigen enzyme-linked immunosorbent assay and purified using the diethylaminoethyl cellulose ion exchange technique. Apoptosis of cardiomyocytes was evaluated using agarose gel electrophoresis and flow cytometry. Our results showed that the positive serum IgG greatly increased the beating rates of cardiomyocytes and showed an agonist-like activity. Furthermore, positive serum IgG induced cardiomyocyte apoptosis after treatment with beta1-adrenoceptor overstimulation for 48 h. The effects of monoclonal antibody against beta1-adrenoceptor were also found to be similar to those of positive serum IgG. It was suggested that the autoantibody could induce cardiomyocyte apoptosis by excessive stimulation of beta1-adrenoceptor.

Animals↗
PubMed2006

[Genetic analysis of the UGT1A1 gene mutation sites in a Chinese family suffered from Gilbert's syndrome].

To learn the variation in the gene for UGT1A1 enzyme, the genetic mechanism in a Chinese Han nationality family suffered from Gilbert's syndrome was studied. At first, genomic DNA from peripheral blood of the sufferer in this family was used for amplifying all of the five exons of the UGT1A1 gene by PCR, and then direct sequencing of the PCR product was applied to analyze gene mutation. The results showed that there existed a G-->A homozygous transition at nucleotide 211 leading the substitution of arginine for glycine at position 71 of corresponding protein product (G71R) and a T-->G homozygous transition at nucleotide 1456 leading the substitution of aspartic acid for tyrosine at position 486 of corresponding protein product (Y486D). No mutation was detected in promoter region and the splicing junction sites. The relevant mutation sites of the other family members were sequenced and identified to be heterozygous in the two above-mentioned mutation sites and in the TA repeat mutation in the promoter region. Furthermore, fresh blood samples were collected from all of the members to detect the serum bilirubin levels to determine the sufferer. The result was consistent with the mutation analysis. It could thus be inferred that this family was caused by mutation in the open reading frame of the gene UGT1A1.

Asian People↗
PubMed2006

[Immunohistochemical analysis of cell cycle-associated proteins p27 in oral cancer and precancer].

OBJECTIVE: To evaluate the expression of p27 protein in oral precancerous lesions and oral squamous cell carcinoma (OSCC). METHODS: Immunohistochemistry was used to detect p27, p53, murine double minute (MDM2) and p21 protein expression in a series of 13 specimens with simple hyperplasia, 44 with dysplasia and 48 with OSCC. An attempt was made to correlate the protein levels with clinicopathologic parameters and Ki-67 protein levels. RESULTS: Positive p27 staining was present in 79.55% of the dysplasia samples, as well as in 81.25% of the OSCC samples. p27 protein overexpression in OSCC group was significantly higher than that in leukoplakia group (P < 0.001). The extent of p27 expression was positively associated with Ki-67 expression (P < 0.001). Cases with p27 overexpression displayed concurrent expression of p53 and/or MDM2 (P = 0.034) in OSCC group. CONCLUSIONS: p27, p53, MDM2 and p21 may all play important roles in the genesis of OSCC. The alterations of one or more cell cycle regulators are prevalent in oral premalignant lesions and OSCC and the regulators can regulate each other.

Carcinoma, Squamous Cell↗