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J C Yang

Publications and source records attributed to J C Yang.

At least 91 records · Page 5Linked to original sources
PubMed1997

Isolation of a genetic locus associated with metronidazole resistance in Helicobacter pylori.

We examined the molecular mechanism of metronidazole resistance by constructing a lambda-Zap II phagemid expression library with genomic DNA from a metronidazole-resistance strain of Helicobacter pylori. Twenty-two clones were found to have elevated MTZ resistances in XLOLR strain of E. coli. Phagemids belonging to the twenty two clones were extracted and then retransformed into the XLOLR strain of E. coli. After MTZ selection, five clones could confer metronidazole resistance consistently. According to Southern hybridization and DNA sequencing, the five clones contained a same locus, recA. In addition, transforming the five clones into BL21 strain of E. coli produced a higher resistance to MTZ. Interestingly, electroporation of one of the five phagemid clones into two MTZ sensitive H. pylori yielded MTZ resistant strains. Comparing amino acid sequence in MTZ resistant with sensitive isolates revealed two point mutations at this locus. Above results suggest that mutation in recA may be associated with metronidazole resistance of H. pylori.

Base Sequence↗
PubMed1997

The large subunit of RNA polymerase II is a substrate of the Rsp5 ubiquitin-protein ligase.

The E3 ubiquitin-protein ligases play an important role in controlling substrate specificity of the ubiquitin proteolysis system. A biochemical approach was taken to identify substrates of Rsp5, an essential hect (homologous to E6-AP carboxyl terminus) E3 of Saccharomyces cerevisiae. We show here that Rsp5 binds and ubiquitinates the largest subunit of RNA polymerase II (Rpb1) in vitro. Stable complex formation between Rsp5 and Rpb1 was also detected in yeast cell extracts, and repression of RSP5 expression in vivo led to an elevated steady-state level of Rpb1. The amino-terminal domain of Rsp5 mediates binding to Rpb1, while the carboxyl-terminal domain of Rpb1, containing the heptapeptide repeats characteristic of polymerase II, is necessary and sufficient for binding to Rsp5. Fusion of the Rpb1 carboxyl-terminal domain to another protein also causes that protein to be ubiquitinated by Rsp5. These findings indicate that Rsp5 targets at least a subset of cellular Rpb1 molecules for ubiquitin-dependent degradation and may therefore play a role in regulating polymerase II activities. In addition, the results support a model for hect E3 function in which the amino-terminal domain mediates substrate binding, while the carboxyl-terminal hect domain catalyzes ubiquitination of bound substrates.

Amino Acid Sequence↗
PubMed1997

Identification of tyrosinase-related protein 2 as a tumor rejection antigen for the B16 melanoma.

Recently, major advances have been made in the identification of antigens from human melanoma which are recognized by T cells. In spite of this, little is known about the optimal ways to use these antigens to treat patients with cancer. Progress in this area is likely to require accurate preclinical animal models, but the availability of such models has lagged behind developments in human tumor immunology. Whereas many of the identified human melanoma antigens are normal tissue differentiation proteins, analogous murine tumor antigens have not yet been identified. In this paper we identify a normal tissue differentiation antigen, tyrosinase-related protein 2 (TRP-2), expressed by the murine B16 melanoma which was found by screening a cDNA library from B16 with tumor-reactive cytotoxic T lymphocytes (CTL). A peptide conforming to the predicted MHC class I H2-Kb binding motif, TRP-2181-188, was identified as the major reactive epitope within TRP-2 recognized by these anti-B16 CTLs. By site-directed mutagenesis, it was shown that alteration of this epitope eliminated recognition of TRP-2. It was further demonstrated that a CTL line raised from splenocytes by repeated stimulation in vitro with this peptide could recognize B16 tumor and was therapeutic against 3-d-old established pulmonary metastases. The use of TRP-2 in a preclinical model of tumor immunotherapy may be helpful in suggesting optimal vaccination strategies for cancer therapy in patients.

Animals↗
PubMed1997

Comparison of tramadol and tramadol/droperidol mixture for patient-controlled analgesia.

PURPOSE: To compare the analgesic efficacy and side effects of tramadol vs tramadol and droperidol for post-operative patient-controlled analgesia (PCA). METHODS: Randomised, double-blind study. Thirty-four patients undergoing elective colorectal or head and neck surgery were allocated to Group 1 (n = 18, PCA bolus 10 mg tramadol) or Group 2 (n = 16, PCA bolus 10 mg tramadol + 0.1 mg droperidol). Anaesthesia was induced with fentanyl and thiopentone and maintained with O2, N2O plus enflurane or isoflurane with iv morphine at doses decided by the attending anaesthetists. Muscle relaxation was achieved with atracurium or vecuronium. Patients were observed four-hourly for pain using an 11-point verbal rating scale (VRS). Nausea and vomiting, and sedation were assessed using four-point scales post-operatively. Vital signs, request for rescue anti-emetic and analgesic, and overall satisfaction were recorded. RESULTS: The mean nausea scores were lower in Group 2 (1.00 +/- 1.33 vs 0.06 +/- 0.25 at 0-8 hr, 1.22 +/- 1.93 vs 0.06 +/- 0.25 at 8-16 hr, P < 0.01; 0.81 +/- 1.68 vs 0 at 32-40 hr, P < 0.05; Group 1 vs Group 2). The vomiting scores were also lower (0.50 +/- 1.04 vs 0 at 0-8 hr, 0.67 +/- 1.50 vs 0, at 8-16 hr, P < 0.05; Group 1 vs Group 2). Seven (39%) patients in Group 1, but none in Group 2 requested rescue anti-emetic (P < 0.01). There were no differences in VRS, sedation score, overall satisfaction or vital signs. CONCLUSION: Tramadol and droperidol combination is superior to tramadol alone for post-operative PCA. It provides a similar quality of analgesia with less nausea and vomiting and without an increase in sedation.

Adult↗
PubMed1997

Cytoreductive surgery before high dose interleukin-2 based therapy in patients with metastatic renal cell carcinoma.

PURPOSE: We defined the outcome of a strategy using cytoreductive surgery before high dose interleukin-2 (IL-2) therapy in patients with metastatic renal cell carcinoma. MATERIALS AND METHODS: During an 11-year period, 195 patients underwent cytoreductive surgery as preparation for high dose IL-2 based therapy. The renal primary and locoregional metastatic disease that could be safely resected was removed. RESULTS: Because of the large size 176 of 195 renal tumors (90%) were resected through transabdominal incision and in 45 patients (23%) a second additional significant procedure was performed. Five cases (2.6%) were unresectable and 2 (1%) perioperative deaths occurred. After surgery 121 of 195 patients (62%) were eligible for treatment with high dose IL-2 based protocols. Overall response rate to IL-2 based protocols was 18%. CONCLUSIONS: Cytoreductive surgery can be performed safely in patients with metastatic renal cell carcinoma. Although the impact of cytoreductive surgery on response to immunotherapy remains undefined, this combination of primary debulking and systemic IL-2 can result in durable complete tumor regression in some patients with metastatic renal cell carcinoma.

Adolescent↗
PubMed1997

Calcium phosphate as a gene carrier: electron microscopy.

Transfection of DNA into cultured cells by the calcium phosphate (CaPi)-mediated method provides a means of examining gene functions. Several factors in preparing the CaPi-DNA co-precipitates were speculated to be correlated with the transfection efficiency. To achieve a better understanding of the steps of CaPi formation and the effect of other components in the medium, this study was undertaken to examine the morphological changes of CaPi in the transfection medium. Transmission electron microscopy (TEM) was employed to investigate the reaction products of CaPi precipitates prepared in the presence or absence of plasmid DNA, Dulbecco's modified Eagle medium and calf serum. The effect of pH of the HEPES-buffered saline (HBS) in which CaPi was formed was also examined. Here we report the observations we obtained from TEM. The results showed that CaPi precipitates underwent several steps of conversion in the presence of other components in the cell culture medium. The pH of the HBS in which CaPi precipitates were formed also exerts a profound effect on the morphology of the CaPi solid phase, indicating that the associated compositional and structural changes occurred during the maturation of CaPi in the DNA transfection medium.

Calcium Phosphates↗
PubMed1997

cDNA cloning and sequence analysis of the Xenopus laevis egg envelope glycoprotein gp43.

The glycoproteins of the Xenopus laevis egg envelope function in fertilization and development. As the unfertilizable coelomic egg transits the pars recta region of the oviduct, it is converted to a fertilizable egg by limited proteolysis of the envelope glycoprotein gp43 to gp41. This conversion is caused by an oviductally secreted serine active site protease, oviductin. We cloned a cDNA for gp43 from an oocyte cDNA library. The cDNA encoded a 454 amino acid protein homologous to the ZPC family of glycoproteins previously shown to be present in mammalian and fish egg envelopes. Conserved ZPC domains and motifs present in the Xenopus sequence included a signal peptide sequence, an N-linked glycosylation site, and 12 aligned Cys residues. In mammalian and Xenopus sequences, a furin-like (convertase) site and a C-terminal transmembrane domain were present reflecting the biosynthesis of ZPC in these species via the secretory glycoprotein pathway. However, fish envelope glycoproteins lack these sequences since they are synthesized via a different route (in the liver, transported to the ovary, and assembled into the egg envelope surrounding the oocyte). Consensus amino acid residues were identified by sequence comparisons of seven ZPC family members; 19% of the amino acid residues were invariant and 48% of the residues were identical in at least four of the seven sequences. The consensus sequence was used to make structure-fertilization function predictions for this phylogenetically conserved family of glycoproteins.

Amino Acid Sequence↗
PubMed1997

Production of a cell wall-specific monoclonal antibody to Fibrobacter succinogenes.

A monoclonal antibody (mAb) was raised against Fibrobacter succinogenes and produced after fusion as ascites in BALB/c mice. An ELISA was used to test for specificity and sensitivity of the mAb to detect F. succinogenes. The mAb BD1 was tested for sensitivity and cross-reactivity in detecting F. succinogenes with ELISA. The lower limits for F. succinogenes detection in pure and mixed culture-using mAb BD1 with ELISA was 10(5) cells ml-1. Twenty-six other species of bacteria, including 12 cellulolytic species, were tested for cross-reactivity with the ELISA but none was detected. Electron micrographs of F. succinogenes cells with immunogold labelling showed that the mAb BD1 reacted exclusively with cell wall epitopes but not intracellular material, as confirmed by ELISA.

Animals↗
PubMed1997

Cloning and characterization of the genes encoding the murine homologues of the human melanoma antigens MART1 and gp100.

The recent identification of genes encoding melanoma-associated antigens has opened new possibilities for the development of cancer vaccines designed to cause the rejection of established tumors. To develop a syngeneic animal model for evaluating antigen-specific vaccines in cancer therapy, the murine homologues of the human melanoma antigens MART1 and gp100, which were specifically recognized by tumor-infiltrating lymphocytes from patients with melanoma, were cloned and sequenced from a murine B16 melanoma cDNA library. The open reading frames of murine MART1 and gp100 encode proteins of 113- and 626-amino acids with 68.8 and 77% identity to the respective human proteins. Comparison of the DNA sequences of the murine MART1 genes, derived from normal melanocytes, the immortalized nontumorgenic melanocyte line Melan-a and the B16 melanoma, showed all to be identical. Northern and Western blot analyses confirmed that both genes encoded products that were melanocyte lineage proteins. Mice immunized with murine MART1 or gp100 using recombinant vaccinia virus failed to produce any detectable T-cell responses or protective immunity against B16 melanoma. In contrast, immunization of mice with human gp100 using recombinant adenoviruses elicited T cells specific for hgp100, but these T cells also cross reacted with B16 tumor in vitro and induced significant but weak protection against B16 challenge. Immunization with human and mouse gp100 together [adenovirus type 2 (Ad2)-hgp100 plus recombinant vaccinia virus (rVV)-mgp100], or immunization with human gp100 (Ad2-hgp100) and boosting with heterologous vector (rVV-hgp100 or rVV-mgp100) or homologous vector (Ad2-hgp100), did not significantly enhance the protective response against B16 melanoma. These results may suggest that immunization with heterologous tumor antigen, rather than self, may be more effective as an immunotherapeutic reagent in designing antigen-specific cancer vaccines.

Amino Acid Sequence↗
PubMed1997

Identification of a T-cell receptor from a therapeutic murine T-cell clone.

Tumor-infiltrating lymphocytes (TIL) have been successfully used for the treatment of metastatic malignancies in clinical trials and in experimental animal models. Tumor-specific reactivity by TIL is mediated via receptors expressed on the surface of T cells (TcRs), which recognize tumor-associated antigens (TAA) presented in the context of MHC molecules on the surface of tumor cells. The current study was performed to identify the TcR alpha and beta chains from a tumor-specific therapeutic TIL clone that can be used to develop a preclinical animal model for genetically modifying lymphocytes and hematopoietic progenitors with TcR genes. TIL 205 was generated from a subcutaneous implant of MCA-205 fibrosarcoma and at 21 days was cloned by limiting dilution. TIL clone 8, obtained from a culture seeded at one cell/well, mediated specific lysis and specific secretion of gamma-interferon to MCA-205 and WP6, a subclone of MCA 205. No reactivity was observed against other syngeneic sarcoma lines. Anchor polymerase chain reaction analysis determined that antigen recognition by clone 8 was mediated by a TcR consisting of V alpha 3/J alpha 27 and V beta 8.2/D beta 2.1/D beta 2.4. Immunofluorescent staining with V beta subfamily specific monoclonal antibodies revealed that > 95% of the T cells in TIL clone 8 expressed V beta 8.2, confirming that TIL clone 8 was indeed a clone. In contrast, approximately 30% of the T cells in the parental TIL 205 expressed V beta 8.2. The transfer of as few as 500,000 TIL clone 8 cells in conjunction with the systemic administration of recombinant human interleukin-2 mediated regression of established 3-day WP6 lung metastases. Thus, clone 8 recognizes a biologically relevant tumor rejection antigen, making the V alpha 3/J alpha 27-V beta 8.2/D beta 2.1/J beta 2.4 TcR isolated from this clone useful as a probe for cloning the tumor-rejection antigen in the WP6 tumor as well as modeling, in mice, the TcR-based gene therapies being developed for humans.

Adoptive Transfer↗
PubMed1997

Studies of DEAE-dextran-mediated gene transfer.

DEAE-dextran-mediated gene transfer was studied for the introduction of pSV2neo DNA into Fisher-rat 3T3 (FR3T3) cells. Zeta (zeta) potentials of the DEAE-dextran-DNA complexes and FR3T3 cells were found to be dependent on the concentration of DEAE-dextran in the medium. The maximum transfection efficiency occurred at a DEAE-dextran/DNA ratio of 50:1 or thereabouts. The interaction between DNA and cells is determined by the adsorption process. The results obtained, along with the correlation between the kinetic adsorption behaviour of 3H-labelled DNA and the transfection efficiency, indicated that adsorption of DEAE-dextran-DNA complexes to the negatively charged cell surfaces, due to electrostatic and dispersion attraction, plays the decisive role in determining the DNA transfection efficiencies.

3T3 Cells↗
PubMed1997

Genetic analysis of the cytotoxin-associated gene and the vacuolating toxin gene in Helicobacter pylori strains isolated from Taiwanese patients.

OBJECTIVE: Two virulence factors encoded by the cytotoxin-associated (cagA) gene and the vacuolating toxin (vacA) gene of Helicobacter pylori are known to be associated with gastroduodenal pathologic conditions. In this report, nucleotide sequence of cagA and vacA and the serum antibody response to the CagA antigen in H. pylori isolates from Taiwanese patients were studied. METHOD: cagA and vacA were characterized in 173 H. pylori strains by polymerase chain reaction and DNA hybridization analyses. The presence of serum IgG antibodies against CagA was assessed by Helico-blot Western blot system. Sequence analysis of polymerase chain reaction-amplified vacA and cagA was performed for two strains. RESULTS: cagA was detected in all the isolates with peptic ulcers and gastric cancer. Of 54 strains with non-ulcer dyspepsia, 51 were found to be cagA+. Serum antibodies to CagA were detected for 99.2% of cagA+ strains compared with 0% of strains lacking cagA. vacA was detected in all isolates. Sequence analysis of vacA and cagA indicated that sequences of two Taiwanese strains were closely related to each other (95.9% and 97% nucleotide identity, respectively) but less homologous to the published strains (90.9% and 91.4% mean nucleotide sequence identity, respectively). CONCLUSIONS: The strong association (98%) of cagA+ strains with Taiwanese patients suggests that the cagA+ phenotype could not be used as a single marker of high-risk patients in Taiwan. Moreover, sequence analysis indicates that Taiwanese strains contain different genetic sequences from those in other geographic regions.

Adolescent↗
PubMed1997

An ongoing prospective randomized comparison of interleukin-2 regimens for the treatment of metastatic renal cell cancer.

PURPOSE: This article compares the pharmacokinetics, toxicity, and clinical efficacy of high-dose intravenous, low-dose intravenous, and intermediate-dose subcutaneous recombinant interleukin-2 (rIL-2) regimens in patients with measurable metastatic renal cell carcinoma. PATIENTS AND METHODS: This trial began as a two-arm randomized study comparing two bolus intravenous rIL-2 regimens. High-dose (720,000 IU/kg) and low-dose (72,000 IU/kg) rIL-2 were administered every 8 hours for up to 15 consecutive doses. Later, a third arm of outpatient subcutaneous rIL-2 (week 1: 250,000 IU/kg/day for 5 of 7 days; weeks 2-6: 125,000 IU/kg/day for 5 of 7 days) was added, and only concurrently randomized patients were compared. A sample of patients underwent pharmacokinetic studies of serum IL-2 levels following their first dose. Accrual to this study is ongoing and results are preliminary. RESULTS: In the two-arm comparison of high-dose versus low-dose intravenous rIL-2, 116 and 112 patients have been randomized, respectively, and the median follow-up is 52 months. Low-dose rIL-2 induced significantly less hypotension, thrombocytopenia, malaise, pulmonary toxicity, and neurotoxicity than high-dose rIL-2. The initial overall response rate (partial plus complete responses) was 19% with high-dose rIL-2 and 10% with low-dose rIL-2. Responses to high-dose rIL-2 tended to be more durable. With 54 to 56 patients randomized per arm in the three-arm comparison, the high-dose intravenous, low-dose intravenous, and subcutaneous outpatient rIL-2 regimens have produced response rates of 16%, 4%, and 11%, respectively. Subcutaneous rIL-2 therapy was infrequently associated with grade 3 or 4 toxicity (similar to low-dose intravenous rIL-2 therapy). Survival data remain incomplete with median follow-up in the three-arm trial at 27 months. DISCUSSION: The optimal IL-2 regimen for treating metastatic renal cell carcinoma is not known. Alternative regimens with much less acute toxicity than high-dose IL-2 can cause regression of renal cell carcinoma, but duration of therapy, chronicity of symptoms, and quality-of-life issues may be important in properly evaluating the tolerability of different regimens. Because the main benefit of IL-2 therapy is not its initial response rate but its induction of durable, complete responses, further accrual and follow-up will be necessary to compare properly the impact of these regimens on patient survival.

Carcinoma, Renal Cell↗
PubMed1996

RANTES secretion by gene-modified tumor cells results in loss of tumorigenicity in vivo: role of immune cell subpopulations.

An immunogenic murine fibrosarcoma cell line was genetically modified to express and produce the human RANTES chemokine stably. In in vitro chemotaxis assays purified recombinant human RANTES as well as human RANTES secreted by the modified murine tumor cells were strongly chemoattractant for mouse CD8+ /Thy-1+ tumor-infiltrating lymphocytes (TIL). RANTES production did not alter the growth of these cytokine gene-modified tumor cells in vitro, but injection of RANTES-secreting cells resulted in the abolition of the ability of those cells to form solid tumors in vivo. The growth of tumors could be restored by co-administration of monoclonal antibodies that inhibit the function of various subsets of immune cells. For example, depletion of CD8+ T cells by antibody administration resulted in complete restoration of solid tumor formation by RANTES-secreting cells, whereas depletion of the CD4+ T cell population resulted in a partial restoration of tumor formation. Additionally, administration of an anti-CR3 monoclonal antibody known to inhibit the in vivo migration of macrophages also completely restored the tumorigenicity of RANTES-secreting fibrosarcoma cells. Thus, the human RANTES chemokine can abolish tumorigenicity of an immunogenic fibrosarcoma in an in vivo murine model, and this process is mediated by various subpopulations of immune effector cells.

Animals↗
PubMed1996

Costimulation enhances the active immunotherapy effect of recombinant anticancer vaccines.

Activation of T lymphocytes in the absence of a costimulatory signal can result in anergy or apoptotic cell death. Two molecules capable of providing a costimulatory signal, B7-1 (CD80) and B7-2 (CD86), have been shown to augment the immunogenicity of whole-tumor cell vaccines. To explore a potential role for costimulation in the design of recombinant anticancer vaccines, we used lacZ-transduced CT26 as an experimental tumor and beta-galactosidase (beta-gal) as the model tumor antigen. Attempts to augment the function of a recombinant vaccinia virus (rVV) expressing beta-gal by admixture with rVV expressing murine B7-1 were unsuccessful. However, a double recombinant vaccinia virus engineered to express both B7-1 and the model antigen beta-gal was capable of significantly reducing the number of pulmonary metastases when administered to mice bearing tumors established for 3 or 6 days. Most important, the double recombinant vaccinia virus prolonged the survival of tumor-bearing mice. These effects were antigen specific. The related costimulatory molecule B7-2 was found to have a similar, although less impressive enhancing effect on the function of a rVV expressing beta-gal. Thus, the addition of B7-1 and, to a lesser extent, B7-2 to a rVV encoding a model antigen significantly enhanced the therapeutic antitumor effects of these poxvirus-based, therapeutic anticancer vaccines.

Animals↗