Biomedical subjects

Gang Chen

Publications and source records attributed to Gang Chen.

At least 109 records · Page 6Linked to original sources

PubMed2005

[Analysis of 618 cases of radical resection of rectal carcinoma].

OBJECTIVE: To investigate and analyse curative effects of Miles operation and anal sphincter preserving operation for rectal carcinoma in 20 years. METHODS: From 1984 to 2004, 618 cases of rectal carcinoma that underwent radical resection including Miles operation and anal sphincter preserving procedures were analysed retrospectively each 10 years, earlier 10 years from 1984 to 1994, and later 10 years from 1994 to 2004. RESULTS: Among the 618 cases, 492 (79.6%) were followed up. The median of the follow-up time was 5.4 years. In the earlier 10 years, local recurrence rate of post operation was 6.9% (14/201), for Miles operation and anal sphincter preserving procedures the local recurrence rate was 6.7% and 7.1% respectively. In the later 10 years, the local recurrence rate was 5.1% (15/291), 4.8% for Miles operation, 5.2% for anal sphincter preserving procedures. With the procedure of canular anastomosis of colon and rectal mucosa, the local recurrence rate was 4.9%. Overall five-year survival rate was 64.7% (130/201) in the earlier 10 years, 66.3% (59/89) for Miles operation, 63.4% (71/112) for anal sphincter preserving procedures. In the later 10 years, the five-year survival rate was 68.0% (198/291) in all, for Miles operation 66.3% (55/83), for anal sphincter preserving procedures 68.7% (143/208). With the procedure of canular anastomosis of colon and rectal mucosa, the five-year survival rate was 71.3% (62/87). CONCLUSIONS: The operation for rectal cancer should be chosen individually according to locus, biological character, and clinical stages. Anal sphincter preserving procedures are performed increasingly, and they provide the same five-year survival rate as Miles operation does, and the patient's quality of life can be improved obviously.

Adult↗

PubMed2005

Role of hTERT in apoptosis of cervical cancer induced by histone deacetylase inhibitor.

Human telomerase reverse transcriptase (hTERT) is the catalytic subunit of telomerase holoenzyme as well as the rate-limiting component of the telomerase enzyme complex. However, the role of the hTERT in apoptosis induced by histone deacetylase inhibitor has only been marginally addressed. For the first time, our study demonstrated that trichostatin A (TSA) briefly activated the proliferation of cervical cancer cell lines, HeLa and SiHa, within 12 h, but then inhibited cell growth after that time point. In response to TSA, hTERT expression, telomerase activity, and telomere length also underwent similar changes during the same time frame. Furthermore, the data in our study showed that cells transfected with dominant negative hTERT were more likely to undergo apoptosis induced by TSA than cells transfected with wild-type hTERT. The cyclin/cdk inhibitor p21waf1 was down-regulated by hTERT without changing the expression of p53. Results from this study suggest that the hTERT might be a primary target of TSA and the anti-apoptosis effect of hTERT might be carried out through a p21waf1-dependent and p53-independent pathway.

Apoptosis↗

PubMed2005

Low temperature bonding of poly(methylmethacrylate) electrophoresis microchips by in situ polymerisation.

A novel method for bonding poly(methyl methacrylate) (PMMA) electrophoresis microchips at the temperature below the glass transition temperature of PMMA based on in situ polymerization has been demonstrated. Methyl methacrylate (MMA) containing initiators was allowed to prepolymerize in an 85 degrees C water bath for 8 min and 15 min to produce a bonding solution and a dense molding solution, respectively. The channel plate of the PMMA microchip was fabricated by the UV-initiated polymerization of the molding solution between a nickel template and a PMMA plate at room temperature. Prior to bonding, the blank cover was coated with a thin layer of the bonding solution and was bonded to the channel plate at 95 degrees C for 20 min under the pressure of binder clips. The attractive performance of the PMMA chips bonded by the new approach has been demonstrated by separating and detecting dopamine, catechol, three cations, and three organic acids in connection with end-column amperometric detection and contactless conductivity detection.

Cold Temperature↗

PubMed2005

Signaling lymphocyte activation molecule-associated protein is a negative regulator of the CD8 T cell response in mice.

The primary manifestation of X-linked lymphoproliferative syndrome, caused by a dysfunctional adapter protein, signaling lymphocyte activation molecule-associated protein (SAP), is an excessive T cell response upon EBV infection. Using the SAP-/- mouse as a model system for the human disease, we compared the response of CD8+ T cells from wild-type (wt) and mutant mice to various stimuli. First, we observed that CD8+ T cells from SAP-/- mice proliferate more vigorously than those from wt mice upon CD3/CD28 cross-linking in vitro. Second, we analyzed the consequence of SAP deficiency on CTL effector function and homeostasis. For this purpose, SAP-/- and wt mice were infected with the murine gamma-herpesvirus 68 (MHV-68). At 2 wk postinfection, the level of viral-specific CTL was much higher in mutant than in wt mice, measured both ex vivo and in vivo. In addition, we established that throughout 45 days of MHV-68 infection the frequency of virus-specific CD8+ T cells producing IFN-gamma was significantly higher in SAP-/- mice. Consequently, the level of latent infection by MHV-68 was considerably lower in SAP-/- mice, which indicates that SAP-/- CTL control this infection more efficiently than wt CTL. Finally, we found that the Vbeta4-specific CD8+ T cell expansion triggered by MHV-68 infection is also enhanced and prolonged in SAP-/- mice. Taken together, our data indicate that SAP functions as a negative regulator of CD8+ T cell activation.

Animals↗

PubMed2005

[Capsule endoscopic diagnosis and treatment with intraoperative endoscopic assistance of vascular malformation of small intestine with bleeding].

OBJECTIVE: To evaluate the effect of capsule endoscopic examination in the diagnosis of vascular malformation of small intestine and discuss the operative method of this disease. METHODS: The clinical data of 11 cases of vascular malformation of small intestine by the capsule endoscopic diagnosis were analyzed retrospectively. RESULTS: All of the 11 cases received operation with the assistance of intra-operative endoscopic examination, and 10 cases were confirmed to suffer from vascular malformation of small intestine postoperatively. The methods of operation included dot-resection, wedge-shaped resection and segmental resection. CONCLUSIONS: The capsule endoscopic examination is optimal for the diagnosis of vascular malformation of small intestine. Dot-resection, wedge-shaped resection and segmental resection with the assistance of intra-operative endoscopic examination for the surgical intervention of this disease are recommendable.

Adult↗

PubMed2005

Bacterial adhesion to silica sand as related to Gibbs energy variations.

Bacterial adhesion to silica sand was related to variations in system Gibbs energy DeltaG(adh). Two typical Gram-positive bacterial strains of Streptococcus mitis and Lactobacillus casei were used as the model bacteria in this research. Impacts of solution chemistry and goethite coating of silica sand on bacterial adhesion were also explored. S. mitis and L. casei had negative DeltaG(adh) with both uncoated and goethite-coated silica sand, demonstrating their adhesion potentials to these substrate. After goethite coating, DeltaG(adh) decreased (negatively increased) for both S. mitis and L. casei. In the presence of rhamnolipid biosurfactant, DeltaG(adh) increased (negatively decreased) in answer to the increase of the rhamnolipid biosurfactant concentration. Bacterial percentage adhesion to silica sand corresponded to DeltaG(adh). This study demonstrated that bacterial adhesion to substrate could be explained in terms of bacterial, substratum and intervening medium physicochemical surface properties, which can be independently determined based on contact angle measurements.

Bacterial Adhesion↗

PubMed2005

Waveguide mode converter based on two-dimensional photonic crystals.

We propose and numerically analyze a novel mode converter based on two-dimensional photonic crystal waveguides with square arrays of cylindrical dielectric rods in air. The mode converter uses small perturbation defects to decouple various modes in the multimode waveguide, thereby permitting propagation of only one mode at any given frequency, which permits one-to-one mode conversion without exciting unwanted modes. The mode converter can efficiently convert a TM0 mode supported in a single-mode photonic crystal waveguide into a TM2 mode supported in the multimode waveguide that is laterally coupled to the single-mode waveguide section for a wide wavelength range. Influences of different sizes and positions of perturbation rods on the band structure of the multimode waveguide are studied.

Journal Article↗

PubMed2005

The role of epidermal growth factor receptor in ethanol-mediated inhibition of activator protein-1 transactivation.

A potential mechanism underlying ethanol-induced alterations in gene expression is the disruption of transcription factor activity. Growth factor receptors, particularly receptor tyrosine kinases, play an important role in modulating many biological effects of ethanol. We demonstrated here that the expression of epidermal growth factor receptor (EGFR) mediated the effect of ethanol on the activity of transcription factor activator protein-1 (AP-1). Ethanol had little effect on AP-1 activity in the fibroblast cells devoid of EGFR (B82); however, it significantly suppressed AP-1 activity in B82 cells that were stably transfected with either a wild-type EGFR (B82L) or a kinase-deficient receptor (B82M721) in a concentration-dependent manner. EGF activated AP-1 only in B82L cells; the activation was mediated primarily by Akt and ERK. Ethanol inhibited EGF-induced EGFR autophosphorylation, phosphorylation of ERK as well as Akt and its substrate GSK-3beta, and subsequently blocked EGF-stimulated AP-1 activation in B82L cells. On the other hand, ethanol had little effect on EGF-stimulated JNK activation. Phorbol ester 12-O-teradecanoyl-phorbol-13-acetate (TPA) activated AP-1 in B82L and B82M721 cells, but not B82 cells. TPA-induced activation of ERK and PKCdelta was dependent on the expression of EGFR although the intrinsic kinase activity of EGFR was not required. In contrast, TPA-induced phosphorylation of p38 MAPK, JNKs and other PKC isoforms was independent of EGFR. Ethanol selectively inhibited TPA-induced phosphorylation of ERK and PKCdelta, and modestly suppressed TPA-stimulated AP-1 activation in B82L and B82M721 cells. Thus, EGFR plays a critical role in the interaction between ethanol and AP-1.

Animals↗

PubMed2005

Immunosuppression with a combination of pg490-88 and a subtherapeutic dose of FK506 in a canine renal allograft model.

BACKGROUND: PG490-88 is a water soluble, semisynthetic derivative of a novel compound PG490 (triptolide) purified from the Chinese herb Tripterygium Wilfordii Hook F. In this study, we evaluated the immunosuppressive effect of PG490-88 alone or combined with FK506 in a dog renal transplantation model. METHODS: Recipient and donor male beagle dogs were obtained from different breeders to ensure MHC mismatching. PG490-88 and/or FK506 were administered orally based on protocol design. RESULTS: All dogs in the untreated group developed acute vascular rejection with a median survival time of 6 days. The grafts from this group presented with massive hemorrhage, IgM, IgG, and C4c deposition. Administration of PG490-88 0.06 mg/kg/day significantly prolonged graft survival to a median survival time of 11 days (P=0.038, vs. control). Treatment with FK506 0.3 mg/kg/day did not prolong graft survival with a median survival time of 9 days. Although FK506 0.6 mg/kg/day significantly prolonged survival, this dose was not tolerated by the dogs. The combination of PG 0.06 mg/kg/day and FK506 0.3 mg/kg/day significantly prolonged survival to a median survival time of 15 days (P=0.017, vs. control). Compared to the untreated control group, the pattern of acute humoral rejection was attenuated in renal allografts treated with PG490-88 and/or FK506. C4c deposition was significantly decreased in renal allografts treated with PG490-88 monotherapy and combination therapy. CONCLUSIONS: PG490-88 alone and combined with low dose FK506 significantly prolonged renal allograft survival in a dog model. This agent attenuated acute humoral rejection by inhibiting complement activation and T-cell infiltration.

Animals↗

PubMed2005

[Mechanism of inhibiting the proliferation of prostate cancer by finasteride: a study using cDNA microarray].

OBJECTIVE: To screen the genes related to finasteride treatment that reduces the proliferation of prostate cancer cells. METHODS: The prostate cancer cells of the line LNCaP sensitive to finasteride treatment were cultured. Finasteride was added into the culture fluid. A cDNA microarray consisting of 96 human genes was used to identify the genes showing differential expression. RESULTS: Finasteride significantly inhibited the proliferation of the prostate cancer cells of the line LNCaP. Twenty-nine genes out of the 96 genes showed differential expression under finasteride treatment 11 were upregulated and 18 were down-regulated, including those significant in cell metabolism, proliferation, apoptosis, and cell signal transduction, such as AKR1B1, PTEN, NKX3.1, PMEPA1, PSA, and XRCC2. CONCLUSION: Inhibiting the proliferation of prostate cancer cells by finasteride may involve the cooperative effect of multiple genes and pathways.

Antigens, Neoplasm↗

PubMed2005

Rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to coumarins: asymmetric synthesis of (R)-tolterodine.

[reaction: see text]. Rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to coumarins proceeded with high enantioselectivity in the presence of a rhodium catalyst (3 mol %) generated from Rh(acac)(C2H4)2 and (R)-Segphos to give the corresponding (R)-4-arylchroman-2-ones in over 99% ee. This asymmetric reaction was applied to the synthesis of (R)-tolterodine.

Benzhydryl Compounds↗

PubMed2005

Colloid-facilitated transport of cesium in variably saturated Hanford sediments.

Radioactive 137Cs has leaked from underground waste tanks into the vadose zone at the Hanford Reservation in south-central Washington State. There is concern that 137Cs, currently located in the vadose zone, can reach the groundwater. In this study, we investigated whether, and to what extent, colloidal particles can facilitate the transport of 137Cs at Hanford. We used colloidal materials isolated from Hanford sediments. Transport experiments were conducted under variably saturated, steady-state flow conditions in repacked, 20 cm long Hanford sediment columns, with effective water saturations ranging from 0.2 to 1.0. Cesium, pre-associated with colloids, was stripped off during transport through the sediments. The higher the flow rates, the less Cs was stripped off, indicating in part that Cs desorption from carrying colloids was a residence-time-dependent process. Depending on the flow rate, up to 70% of the initially sorbed Cs desorbed from colloidal carriers and was captured in the stationary sediments. Less Cs was stripped off colloids under unsaturated than under saturated flow conditions at similar flow rates. This phenomenon was likely due to the reduced availability of sorption sites for Cs on the sediments as the water content decreased and water flow was divided between mobile and immobile regions.

Adsorption↗

PubMed2005

Prevention of acute vascular rejection by a functionally blocking anti-C5 monoclonal antibody combined with cyclosporine.

BACKGROUND: Inhibition of the complement cascade at C5 prevents formation of pro-inflammatory molecules C5a and C5b-9, which play a key role in allograft rejection. The present study was undertaken to determine whether blocking terminal complement with anti-C5 monoclonal antibody (mAb) alone or combined with cyclosporine (CsA) would prevent acute vascular rejection (AVR) in a mouse cardiac allograft model. METHODS: C3H mouse hearts were transplanted into BALB/c mice and randomized into five groups with the following treatments: (1) no treatment; (2) CsA alone; (3) control mAb; (4) anti-C5 mAb alone; and (5) anti-C5 mAb and CsA. RESULTS: Allografts in untreated or control mAb-treated recipients were rapidly rejected at 8.0+/-0.6 and 8.2+/-0.8 days, respectively. These grafts exhibited typical AVR, characterized by vasculitis, hemorrhage, and thrombosis. A high level of complement activity was also demonstrated in these animals. High-dose CsA was not able to inhibit complement activation or AVR, and grafts were rejected in 15.5+/-1.1 days. Anti-C5 monotherapy completely inhibited complement activation and attenuated AVR, but grafts were rejected in 8.3+/-0.5 days by acute cellular rejection. In contrast, a combination of anti-C5 mAb and CsA successfully achieved indefinite graft survival (>100 days). This combined therapy completely inhibited terminal complement activation and prevented both humoral- and cellular-mediated rejection. CONCLUSIONS: Combination therapy of anti-C5 mAb and CsA achieves indefinite graft survival in a mouse cardiac allograft model. These data suggest that inhibition of terminal complement using anti-C5 mAb may be an effective therapeutic adjunct to prevent AVR in clinical transplantation.

Acute Disease↗

PubMed2005

Experimental and theoretical investigation of single Cu, Ag, and Au atoms adsorbed on Si(111)-(7x7).

Using scanning tunneling microscopy and first principles calculations, the adsorption sites of single Cu, Ag, and Au atoms on the Si(111)-(7x7) surface have been systematically investigated and identified. Despite their monovalence, these atoms were found to adsorb at high coordination sites, seeking to saturate the maximum number of dangling bonds. The stable adsorption sites were further observed to be distinctly different in the faulted and unfaulted half unit cells, showing an asymmetry that has never been observed for many other adsorbates.

Journal Article↗

PubMed2005

Combined liposome-mediated cytosine deaminase gene therapy with radiation in killing rectal cancer cells and xenografts in athymic mice.

PURPOSE: The aim of this study was to assess the antitumor efficacy of combination of cytosine deaminase (CD) suicide gene therapy with radiation and to grope for new therapeutic strategy for local recurrent rectal cancer. EXPERIMENTAL DESIGN: HR-8348 cell line of human rectal cancer was used to assess efficiency of transfection with plasmid pEGFP-N1 and PXJ41-CD. The cells were exposed to radiation followed by liposome-mediated transfection. Cell inhibition assay was done with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Antitumor efficacy of combined liposome-mediated CD suicide gene therapy with radiation was determined by treatment of nude mice bearing HR-8348 cancer cell xenograft. RESULTS: The efficiency of liposome-mediated CD gene transfection can be improved by radiation. With radiation at 2, 4, 6, and 8 Gy, the efficiency of liposome-mediated transfection increased from 21.3% to 62.2%, 78.0%, 83.2%, and 87.8%, respectively. CD expression was enhanced as well. Cancer cell inhibition experiment showed that combined liposome-mediated CD gene therapy with radiation had much stronger antitumor effect. With HR-8348 tumor xenograft model, suppression of tumor xenograft was observed. Compared with control group, tumor volume was inhibited by 81.5%, 48.5%, and 37.4%, respectively, in the combined CD/5-fluorocytosine with radiation group, CD/5-fluorocytosine group, and radiation group and the wet weight of tumor was decreased by 80%, 41.7%, and 37.7%, respectively. CONCLUSION: These findings suggested that combination of liposome-mediated CD gene therapy with radiation is a safer and efficient anticancer method. Its therapeutic efficacy may meet clinical treatment on local recurrent rectal cancer.

Animals↗

PubMed2005

Involvement of kv1 potassium channels in spreading acidification and depression in the cerebellar cortex.

Spreading acidification and depression (SAD) is a form of propagated activity in the cerebellar cortex characterized by acidification and a transient depression in excitability. This study investigated the role of Kv1 potassium channels in SAD using neutral red, flavoprotein autofluorescence, and voltage-sensitive dye optical imaging in the mouse cerebellar cortex, in vivo. The probability of evoking SAD was greatly increased by blocking Kv1.1 as well as Kv1.2 potassium channels by their specific blockers dendrotoxin K (DTX-K) and tityustoxin (TsTX), respectively. DTX-K not only greatly lowered the threshold for evoking SAD but also resulted in multiple cycles of spread and spontaneous SAD. The occurrence of spontaneous SAD originating from spontaneous parallel fiber-like beams of activity suggests that blocking Kv1 channels increased parallel fiber excitability. This was confirmed by the generation of parallel fiber-like beams with the microinjection of glutamate into the upper molecular layer in the presence of DTX-K. The dramatic effects of DTX-K suggest a possible connection between SAD and episodic ataxia type 1 (EA1), a Kv1.1 potassium channelopathy. The threshold for evoking SAD was significantly lowered in the Kv1.1 heterozygous knockout mouse compared with wild-type littermates. Carbamazepine and acetazolamide, both effective in the treatment of EA1, significantly decreased the likelihood of evoking SAD. Blocking GABAergic neurotransmission did not alter the effectiveness of DTX-K. The cyclin D2 null mouse, which lacks cerebellar stellate cells, also exhibited SAD. Therefore blocking Kv1 potassium channels establishes the conditions needed to generate SAD. Furthermore, the results are consistent with the hypothesis that SAD may underlie the transient attacks of ataxia characterizing EA1.

Acetazolamide↗

PubMed2005

Molecular analysis of TBL1Y, a Y-linked homologue of TBL1X related with X-linked late-onset sensorineural deafness.

Recent progress in sequencing the human Y chromosome has unveiled a series of X-Y homologous genes. In the present study, we focused on Transducin beta-like 1Y (TBL1Y), which is a Y-linked homologue of TBL1X that is related with X-linked late-onset sensorineural deafness. Recently, it has been shown that TBLR1, another homologue whose gene resides on chromosome 3, and TBL1X act as a corepressor/coactivator exchanger for several nuclear receptors and transcription factors. However, the expression pattern and function of TBL1Y remain unknown. The RT-PCR analysis of the TBL1 family revealed that TBL1Y was expressed in all 13 tissues examined but not in leukocytes. Among the cell lines tested, however, it was only expressed in NT2/D1 cells and in lymphoblasts transformed with Epstein Barr (EB) virus. To compare the functions of the TBL1 family, we generated a series of expression plasmids for GAL4DBD-fused proteins of the TBL1 family. We carried out dual luciferase assays using these plasmids in combination with a plasmid having a luciferase reporter gene harboring 5xGAL4 binding sites. Unlike the other constructs, GAL4DBD-fused TBL1Y did not repress the promoter activity. Moreover, we found three novel polymorphisms in the TBL1Y gene, IVS7+9G>A, G268C, and IVS7+1G>C, which is presumed to cause splicing error. These polymorphisms are found in males within Y-haplogroup O3 (XO3e), which is defined as the Y-haplogroup O3 excluding O3e, a branch of O3. The results show that TBL1Y differs from other members of the TBL1 family in expression and function, suggesting other roles in maleness.

Age of Onset↗

PubMed2005

Preparative isolation and purification of germacrone and curdione from the essential oil of the rhizomes of Curcuma wenyujin by high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) was applied to isolate and purify bioactive compounds in the essential oil of the rhizomes of Curcuma wenyujin. Two sesquiterpenes germacrone and curdione were successfully isolated and purified using two-phase solvent system composed of petroleum ether-ethanol-diethyl ether-water (5/4/0.5/1, v/v) in tail to head elution mode. 62 mg of germacrone and 93 mg of curdione were obtained from 658 mg of the essential oil each at over 95% purity. Their structures were identified by 1H NMR and EI MS.

Chromatography, High Pressure Liquid↗