Biomedical subjects

Hong Tang

Publications and source records attributed to Hong Tang.

63 records · Page 4Linked to original sources

PubMed2002

Purification, crystallization and preliminary X-ray diffraction studies of a Ca2+-binding protein, human S100P.

S100P, a Ca(2+)-binding protein, is a member of the S100 family. Its presence is associated with the development of prostate cancer, but its cellular function is not known. Recombinant human S100P has been expressed and purified in bacterial cells and crystals of human S100P in the calcium-bound state have been grown using the vapour-diffusion technique with PEG 4000 as precipitant. Diffraction data have been obtained to a resolution of 2.0 A from a single frozen S100P crystal which belongs to the space group P4(1)2(1)2, with unit-cell parameters a = b = 60.8, c = 47.6 A.

Calcium-Binding Proteins↗

PubMed2002

Crystal structure of a staphylokinase: variant a model for reduced antigenicity.

Staphylokinase (SAK) is a 15.5-kDa protein from Staphylococcus aureus that activates plasminogen by forming a 1 : 1 complex with plasmin. Recombinant SAK has been shown in clinical trials to induce fibrin-specific clot lysis in patients with acute myocardial infarction. However, SAK elicits high titers of neutralizing antibodies. Biochemical and protein engineering studies have demonstrated the feasibility of generating SAK variants with reduced antigenicity yet intact thrombolytic potency. Here, we present X-ray crystallographic evidence that the SAK(S41G) mutant may assume a dimeric structure. This dimer model, at 2.3-A resolution, could explain a major antigenic epitope (residues A72-F76 and residues K135-K136) located in the vicinity of the dimer interface as identified by phage-display. These results suggest that SAK antigenicity may be reduced by eliminating dimer formation. We propose several potential mutation sites at the dimer interface that may further reduce the antigenicity of SAK.

Antigens, Bacterial↗

PubMed2002

Avian and Mammalian hepadnaviruses have distinct transcription factor requirements for viral replication.

Hepadnavirus replication occurs in hepatocytes in vivo and in hepatoma cell lines in cell culture. Hepatitis B virus (HBV) replication can occur in nonhepatoma cells when pregenomic RNA synthesis from viral DNA is activated by the expression of the nuclear hormone receptors hepatocyte nuclear factor 4 (HNF4) and the retinoid X receptor alpha (RXR alpha) plus peroxisome proliferator-activated receptor alpha (PPAR alpha) heterodimer. Nuclear hormone receptor-dependent HBV replication is inhibited by hepatocyte nuclear factor 3 (HNF3). In contrast, HNF3 and HNF4 support duck hepatitis B virus (DHBV) replication in nonhepatoma cells, whereas the RXR alpha-PPAR alpha heterodimer inhibits HNF4-dependent DHBV replication. HNF3 and HNF4 synergistically activate DHBV pregenomic RNA synthesis and viral replication. The conditions that support HBV or DHBV replication in nonhepatoma cells are not able to support woodchuck hepatitis virus replication. These observations indicate that avian and mammalian hepadnaviruses have distinct transcription factor requirements for viral replication.

3T3 Cells↗

PubMed2002

Mechanisms of inhibition of nuclear hormone receptor-dependent hepatitis B virus replication by hepatocyte nuclear factor 3beta.

The nuclear hormone receptors hepatocyte nuclear factor 4 (HNF4) and the retinoid X alpha (RXRalpha) plus the peroxisome proliferator-activated receptor alpha (PPARalpha) heterodimer support hepatitis B virus (HBV) replication in nonhepatoma cells. Hepatocyte nuclear factor 3 (HNF3) inhibits nuclear hormone receptor-mediated viral replication. Inhibition of HBV replication by HNF3beta is associated with the preferential reduction in the level of the pregenomic RNA compared with that of precore RNA. Hepatitis B e antigen (HBeAg), encoded by the precore RNA, mediates part of the inhibition of viral replication by HNF3beta. The amino-terminal transcriptional activation domain of HNF3beta is essential for the inhibition of HBV replication. The activation of transcription by HNF3 from HBV promoters downstream from the nucleocapsid promoter appears to contribute indirectly to the reduction in the steady-state level of 3.5-kb HBV RNA, possibly by interfering with the elongation rate of these transcripts. Therefore, transcriptional interference mediated by HNF3 may also regulate HBV RNA synthesis and viral replication.

3T3 Cells↗

PubMed2002

Hepatocyte nuclear factor 3beta inhibits hepatitis B virus replication in vivo.

Hepatitis B virus (HBV) transgenic mice expressing rat hepatocyte nuclear factor 3beta (HNF3beta) were generated by breeding HBV transgenic mice with transgenic mice that constitutively overexpress the rat HNF3beta polypeptide in the liver. HBV 3.5-, 2.4- and 2.1-kb transcripts were reduced 2- to 4-fold in these mice relative to the HBV transgenic mouse controls. In contrast, the abundance of viral replication intermediates was profoundly reduced in HBV transgenic mice by overexpression of HNF3beta. This results, in part, from the preferential reduction in the level of the pregenomic 3.5-kb RNA relative to the precore 3.5-kb RNA. Therefore, it is apparent that increased expression of HNF3beta modestly reduces viral transcription and dramatically inhibits replication in vivo in the HBV transgenic mouse. This suggests that altering the activity of this transcription factor in vivo in chronic HBV carriers might be therapeutically beneficial.

Animals↗

PubMed2002

[A methodological study of measuring quantitatively turbulent shear stree downstream of mitral stenosis in vivo using Doppler echocardiography].

In order to establish a method for measuring quantitatively turbulent shear stress (TSS) downstream of mitral stenosis in vivo based on Doppler echocardiography and computer-aided image analysis, we used doppler echocardiography to record the spectrum of flow velocity downstream of mitral valve at several locations in normal persons and in patients with mitral stenosis. With the computer-aided analysis of spectrum images, the magnitude of TSS was measured at the locations. The results demonstrate that no matter how severe the mitral stenosis is, the TSS and relative turbulent intensity(Irel) at the central locations of jet are lower than those at the marginal ones. A significant difference in the quantitative items of TSS, Irel and flow field uniformity between normal persons and patients with varying-degree of mitral stenosis was noticed (P < 0.05). There was a significant correlation between these items and effective orifice area (EOA), and we found that the smaller EOA is, the more severe the extent of stenosis is and the greater the magnitude of both TSS and Irel are, and that the highest magnitude of TSS is focused on the marginal area of jet. These results indicate that there is an obvious correlation between TSS(measured by Doppler echocardiography combined with computer-aided image analysis) and flow field uniformity. They can coincidently reveal the hemodynamic changes resulting from mitral stenosis of varied severeness, implying that our method could exactly depict the magnitude of TSS downstream of mitral stenosis in vivo and is non-invasive and good for anti-disturbance. The method can be used to analyze quantitatively TSS in the flow field of heart valve in patients with valvular diseases.

Adult↗

PubMed2002

[Hemodynamics monitoring of liver transplantation with color Doppler ultrasound].

By hemodynamic monitoring of liver transplantation with Color Doppler ultrasound, we observed the hemodynamic changes pre- and post-operatively and the patency of the anastomotic vessels, to detect or exclude the presence of complications, then assess the prognosis. We measured the hepatic blood flow after orthotopic liver transplantation in recent 6 cases, and observed the patency of anastomostic vessels and the hemodynamic improvement of the portal vein and hepatic arteries. The abnormal liquid and solid echoes were not found around the transplantated liver in all 6 cases. The echoes of hepatic parenchyma and tububes were normal. The direction and speed of blood flow were also normal. Five of anastomoses of portal vein in 6 cases were patent. The rest one was a little stenosed, and the speed of local blood flow was a little faster. There were 11 patent ones and 1 mildly stenosed in the 12 anastomoses of inferior venae cavae. The speed index(SI) and resistance index(RI) of hepatic arterial blood flow distal to the anastomoses were all normal. Liver transplantation is the redical therapying of portal hypertension, and the color Doppler ultrasound is the best non-invasived method for monitoring the hemodynamic changes of transplantated liver.

Adult↗

PubMed2001

Crystallization and preliminary crystallographic analysis of a metastasis-inducing protein, human S100A4.

A metastasis-inducing protein, human S100A4, cDNA was overexpressed in Escherichia coli. The recombinant protein was purified by three chromatographic procedures. Crystals were obtained using polyethylene glycol as a precipitant. The native S100A4 crystals did not diffract sufficiently well for data collection, but the SeMet S100A4 crystal, grown using similar conditions as for the native, was found to be stable during exposure to X-rays and diffracted to 4 A resolution in-house. The crystal belongs to space group P6 or P3. The unit-cell parameters are a = b = 47.1, c = 175.6 A, alpha = beta = 90, gamma = 120 degrees. Complete data will be collected using synchrotron radiation.

Crystallography, X-Ray↗

PubMed2000

DNA-based vaccination induces humoral and cellular immune responses against hepatitis B virus surface antigen in mice without activation of C-myc.

AIM:To develop a safe and effective DNA vaccine for inducing humoral and cellular immunological responses against hepatitis B virus surface antigen (HBsAg).METHODS:BALB/c mice were inoculated with NV-HB/s, a recombinant plasmid that had been inserted S gene of hepatitis B virus genome and could express HBsAg in eukaryotes. HBsAg expression was measured by ABC immunohis tochemical assay, generation of anti-HBs by ELISA and cytotoxic T lymphocyte (CTL), by MTT method, existence of vaccine DNA by Southern blot hybridization and activation of oncogene C-myc by in situ hybridization.RESULTS:With NV-HB/s vaccination by intramuscular injection, anti-HBs was initially positive 2 weeks after inoculation while all mice tested were HBsAg positive in the muscles.The titers and seroconversion rate of anti-HBs were steadily increasing as time went on and were dose dependent. All the mice inoculated with 100&mgr;g NV-HB/s were anti-HBs positive one month after inoculation, the titer was 1 1024 or more. The humoral immune response was similar induced by either intramuscular or intradermal injection. CTL activities were much stronger (45.26%) in NV-HB/s DNA immunized mice as compared with those (only 6%) in plasma-derived HBsAg vaccine immunized mice. Two months after inoculation, all muscle samples were positive by Southernblot hybridization for NV-HB/s DNA detection, but decreased to 25% and all were undetectable by in situ hybridiza-tion after 6 months.No oncogene C-myc activation was found in the muscle of inoculation site.CONCLUSION:NV-HB/s could generate humoral and cellular immunolo-gical responses against HBsAg that had been safely expressed in situ by NV-HB/s vaccination.

Journal Article↗