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Biomedical subjects

X Wu

Publications and source records attributed to X Wu.

At least 127 records · Page 7Linked to original sources
PubMed2001

Subcellular targeting analysis of SDR-type hydroxysteroid dehydrogenases.

Most mammalian hydroxysteroid dehydrogenases known thus far belong to the protein superfamilies of short-chain dehydrogenases/reductases (SDR) and aldo-keto reductases (AKR). Whereas members of the AKR family are soluble, cytoplasmic enzymes, SDR-type hydroxysteroid dehydrogenases are also located to other subcellular compartments, i.e. endoplasmic reticulum, mitochondria or peroxisomes. Differential localization might play an important role in influencing the reaction direction of hydroxy dehydrogenase/oxo reductase pathways by determining the available nucleotide cofactor pool. Targeting signals for different subcellular organelles in human hydroxysteroid dehydrogenases have been identified, however, in several enzymes localization signals remain to be determined.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2001

Anti-malondialdehyde antibodies in MRL+/+ mice treated with trichloroethene and dichloroacetyl chloride: possible role of lipid peroxidation in autoimmunity.

Trichloroethene (TCE) and one of its metabolites dichloroacetyl chloride (DCAC) are known to induce/accelerate autoimmune (AI) response in MRL+/+ mice as evident from anti-nuclear, anti-ssDNA, anti-cardiolipin, and DCAC-specific antibodies in the serum (Khan et al., Toxicol. Appl. Pharmacol. 134, 155-160, 1995). In the present study, we measured anti-malondialdehyde antibodies (AMDA) in the serum of TCE- or DCAC-treated mice in order to understand the contribution of lipid peroxidation to this AI response. Female MRL+/+ mice (5 weeks old) received ip injections of 10 mmol/kg TCE or 0.2 mmol/kg of DCAC in corn oil (100 microl) every 4(th) day for 6 weeks, while controls received an equal volume of vehicle only, and AMDA was measured in the sera of these animals by an ELISA established in our laboratory. While TCE treatment caused only marginal induction of AMDA, DCAC treatment elicited a significant AMDA response. Furthermore, a time-response study of DCAC (0.2 mmol/kg, every 4(th) day, for 2, 4, 6, or 8 weeks) showed an induction of AMDA (3/4) after 4 weeks of treatment, which was even greater at both 6 and 8 weeks of DCAC treatment (5/5). These findings were further substantiated by the presence of AMDA in systemic lupus erythematosus-prone MRL-lpr/lpr mice as early as 6 weeks of age. Presence of AMDA, as observed in this study, not only indicates increased lipid peroxidation (oxidative stress), but also suggests a putative role of oxidative stress in inflammatory autoimmune diseases.

Acetates↗
PubMed2001

[Familial febrile convulsions is supposed to link to human chromosome 19p13.3].

OBJECTIVE: To localize the familial febrile convulsion (FC) genes on human chromosomes. METHOD: For 63 FC pedigrees, tetranucleotide repeat markers D19S253 D19S395 and D19S591 on the short arm of chromosome 19, as well as dinucleotide repeat markers D8S84 and D8S85 on the long arm of chromosome 8 were genotyped. Transmission disequilibrium test (TDT) and Lod score calculation were carried out. The data were processed by PPAP software package. RESULTS: All the alleles in every locus of FC probands and normal controls were in Hardy-Weinburg balance. Transmission disequilibrium was found on D8S84, D19S395 and D19S591 in FC families. chi(2) values were 4.0, 5.124 and 7.364 separately. Each P value was < 0.05, and significantly meaningful. The two-point Lod scores between D8S84 and FC, D8S85 and FC, D19S253 and FC, D19S395 and FC, D19S591 and FC are 0.00002, 0.000017, 0.58, 1.53 and 1.42 respectively. The multi-point Lod score among markers on chromosome 8q and FC was 0.88, while Lod score among markers on chromosome 19p and FC reached 2.78. The results by both the non-parameter (TDT) and parameter (Lod score) methods were consistant on a whole. CONCLUSION: FC is linked with chromosome region 19p13.3, but not with chromosome 8q.

Chromosome Mapping↗
PubMed2001

Toward a rational design of peptide inhibitors of ribonucleotide reductase: structure-function and modeling studies.

Mammalian ribonucleotide reductase, a chemotherapeutic target, has two subunits, mR1 and mR2, and is inhibited by AcF(1)TLDADF(7), denoted P7. P7 corresponds to the C-terminus of mR2 and competes with mR2 for binding to mR1. We report results of a structure-function analysis of P7, obtained using a new assay measuring peptide ligand binding to mR1, that demonstrate stringent specificity for Phe at F(7), high specificity for Phe at F(1), and little specificity for the N-acyl group. They support a structural model in which the dominant interactions of P7 occur at two mR1 sites, the F(1) and F(7) subsites. The model is constructed from the structure of Escherichia coli R1 (eR1) complexed with the C-terminal peptide from eR2, aligned sequences of mR1 and eR1, and the trNOE-derived structure of mR1-bound P7. Comparison of this model with similar models constructed for mR1 complexed with other inhibitory ligands indicates that increased F(1) subsite interaction can offset lower F(7) subsite interaction and suggests strategies for the design of new, higher affinity inhibitors.

Animals↗
PubMed2001

A model of interfacial inactivation for papain in aqueous organic biphasic systems.

A model was proposed to describe the effects of the main factors in aqueous-organic two-liquid-phase media on the stability of papain. The relationships between the half-life of papain activity and these factors including interfacial tension, stirring rate, phase volume ratio and temperature were investigated. The results showed that these factors had notable effects on papain stability except temperature. The correlation coefficient between the model and the experimental data were 0.829, which indicated the model is practicable.

Journal Article↗
PubMed2001

Management of extensive cervical nodal metastasis in nasopharyngeal carcinoma after radiotherapy: a clinicopathological study.

OBJECTIVES: To evaluate the efficacy of afterloading brachytherapy following radical neck dissection (RND) in the management of extensive cervical lymph node disease in nasopharyngeal carcinoma after radiotherapy; and to examine prospectively prognostic factors and the pathologic behavior of neck disease. PATIENTS: Twenty-seven patients with nasopharyngeal carcinoma who had extensive cervical lymph node metastasis following external radiotherapy were treated with RND. Thirteen of them also underwent afterloading brachytherapy with iridium wire (Ir 192). The RND specimens of the 27 patients were also examined with step serial whole-specimen sectioning. RESULTS: All patients survived and their wounds healed primarily. Pathologic examination revealed 183 tumor-bearing lymph nodes that contained tumors in the neck: level I, 4% (8/183); level II, 53% (96/183); level III, 34% (62/183); level IV, 5% (9/183); and level V, 4% (8/183). Extracapsular tumor extension was seen in 84% of patients. Multivariate analysis identified the number of tumor-bearing lymph nodes detected in the specimens to be the only significant factor that affected control of disease. Although the neck disease in the group of patients who had afterloading brachytherapy was more extensive, the 3-year actuarial tumor control for the groups with and without brachytherapy were 60% and 61%, respectively. CONCLUSIONS: Recurrent cervical lymph nodes after radiotherapy in nasopharyngeal carcinoma are extensive and RND is mandatory for a successful salvage. When the nodal metastasis infiltrate or adhere to surrounding tissue, afterloading brachytherapy with iridium wire can provide satisfactory local tumor control.

Adult↗
PubMed2001

High-throughput characterization for organic pollutants in environmental waters using a capillary electrophoresis chip.

To evaluate organic pollution in water, we did preliminarily studies on high-throughput characterization of organic pollution in water using microchip-based capillary electrophoresis (CE) with laseer-induced fluorescence (LIF) detection. The applied voltage was investigated to control the gated valve injection and CE separation for conventional cross type microchips using a self-made personal computer (PC)-based controller as the voltage supply. We obtained high-throughput data for the reproducible separation of fluorescein isothiocyanate (FITC)-labeled river-water samples using a zwitter-ion based buffer solution to avoid adsorption of the labeled sample onto the channel of a microchip made from quartz glass. We used real samples from the Hino River that flows into Lake Biwa, from ten sampling points and obtained several reproducible peaks in different separation patterns for each sample within 2 min. We successfully demonstrated high-throughput characterization of dissolved organic carbon (DOC) in environmental water using the microchip.

Carbon↗
PubMed2001

Expression of recombination-activating genes and terminal deoxynucleotidyl transferase and secondary rearrangement of immunoglobulin kappa light chains in rheumatoid arthritis synovial tissue.

OBJECTIVE: Lymphocytic infiltrates in rheumatoid arthritis (RA) synovium often resemble lymphoid follicles and contain clonally related Ig transcripts, suggesting in situ antigen-dependent B cell selection. Recent reports have shown expression of recombination-activating genes (RAGs) and concurrent secondary rearrangement of Ig genes in normal peripheral lymphoid organs (receptor revision). We sought to determine if RAG-mediated receptor revision of Ig kappa light chains occurs in B cells within the RA synovium. Because we previously reported enhanced N-region addition at V(L)-J(L) joins in clonally expanded light-chain transcripts from RA synovium, we also sought expression of terminal deoxynucleotidyl transferase (TdT), which is normally expressed only in B cell precursors or immature B cells. METHODS: Reverse transcription-polymerase chain reaction (PCR) was used to detect RAG and TdT transcripts from unselected and B cell-enriched synovial and peripheral blood mononuclear cells obtained from 12 RA patients. Activity of RAG protein was sought using ligation-mediated PCR to detect recombination intermediates, and immunohistochemistry was performed to identify RAG+ cells within synovia. RESULTS: We found evidence of RAG-mediated secondary Ig kappa light chain rearrangements in about one-third of RA synovia. TdT expression was found in several samples, but did not correlate with RAG expression. CONCLUSION: RAG-mediated secondary Ig rearrangements of kappa light chains may contribute to the local production of antibodies to autoantigens (e.g., rheumatoid factor) or exogenous antigens, or it may represent a failed attempt at immune tolerance. TdT expression suggests the presence of immature B cells in RA synovia. These findings have important implications for the local generation of antibodies in RA and other chronic inflammatory diseases.

Adult↗
PubMed2001

Secondary necrosis is a source of proteolytically modified forms of specific intracellular autoantigens: implications for systemic autoimmunity.

OBJECTIVE: Specific autoantigens targeted in systemic autoimmunity undergo posttranslational modifications, such as cleavage, during cell death that could potentially enhance their immunogenicity. In light of the increasing interest in the immunologic consequences of defective clearance of apoptotic cells, we sought to determine whether autoantigens cleaved during apoptosis undergo an additional wave of proteolysis as apoptosis progresses to secondary necrosis in the absence of phagocytosis. METHODS: Apoptosis was induced in Jurkat cells with etoposide, anti-Fas antibody, or staurosporine (STS), and in HeLa cells with STS. Progression to secondary necrosis was assessed morphologically and quantified by trypan blue uptake. Autoantigen proteolysis during cell death was examined by immunoblotting of cell lysates using highly specific human autoantibodies as detecting probes. RESULTS: Cells treated with the different apoptosis inducers underwent a rapid apoptosis that gradually progressed to secondary necrosis. During the initial apoptotic stages, several autoantigens, including poly(ADP-ribose) polymerase, topoisomerase I (or Scl-70), SSB/La, and U1-70 kd, were cleaved into their signature apoptotic fragments. Progression of apoptosis to secondary necrosis was associated with additional proteolysis of these and other autoantigens in a caspase-independent manner. Some autoantigens (e.g., ribosomal RNP, Ku, and SSA/Ro) appeared to be resistant to proteolysis during cell death. CONCLUSION: In the absence of phagocytosis, apoptotic cells may undergo secondary necrosis, a process associated with additional proteolytic degradation of specific autoantigens. Secondary necrosis may occur in vivo in autoimmune disorders associated with impaired clearance of apoptotic cells and serve as a source of modified forms of specific autoantigens that might stimulate autoantibody responses under proinflammatory conditions.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Anomalous overexpression of p27(Kip1) in sporadic pancreatic endocrine tumors.

BACKGROUND: Little is known about the cellular defects and molecular mechanisms leading to pancreatic endocrine tumors (PETs). p27(Kip1) is a universal cyclin-dependent kinase inhibitor (CDKI), which acts as a tumor suppressor and a negative regulator of cell cycle. From previous reports, quiescent cells show high levels of p27(Kip1) expression while neoplastic and proliferating cells show no detectable p27(Kip1) expression. We hypothesize that in malignant sporadic PETs, p27(Kip1) expression would be decreased compared with benign PETs and normal pancreatic tissue. METHODS: Western analysis was performed on 28 PETs (7 malignant, 21 benign), 2 nonendocrine cell lines, and 5 endocrine cell lines. Signal intensities were quantitated using densitometry and standardized to normal pancreas. RESULTS: Unexpectedly, increased p27(Kip1) expression as compared with control was seen in both benign and malignant tumors, as well as in all four pancreatic islet tumor cell lines, but not fibroblast or pituitary cell lines, evaluated. There was no difference in p27(Kip1) level between benign and malignant tumors. CONCLUSION: This represents the first report of anomalous p27(Kip1) overexpression in sporadic PETs, and is part of a growing literature describing the paradoxical overexpression of p27(Kip1) in human tumors that includes other endocrine tumors. These studies suggest a unique molecular pathway leading to endocrine tumorigenesis.

Animals↗
PubMed2001

Two signal transduction pathways involved in the catecholaminergic differentiation of avian neural crest-derived cells in vitro.

Molecules derived from the neural tube and found in chick embryo extract (CEE) and bone morphogenetic proteins (BMP) support the differentiation of neural crest-derived catecholaminergic (CA) neurons. We now report that intracellular signaling resulting in the activation of Map kinase (MapK) or translocation of Smad1 mediate the differentiation of CA neurons in response to CEE or BMP 4, respectively. The differentiation of CA neurons was significantly reduced by inhibiting MapK using PD98059 or by pan-specific blockade of tyrosine kinases using Herbimycin A. In the presence of BMP 4 and inhibitors of MapK signaling, differentiation of CA neurons was only moderately reduced. Independent of MapK, BMP 4 induced translocation of Smad1 from the cytosol to the nucleus and induced transcription of dHAND, a DNA binding protein required for the differentiation of CA neurons. The data suggest that CEE-derived factors and BMP4 support the differentiation of CA neurons via independent signaling pathways.

Animals↗
PubMed2001

Regression of human mammary adenocarcinoma by systemic administration of a recombinant gene encoding the hFlex-TRAIL fusion protein.

The tumor necrosis factor (TNF)-related apoptosis-inducing ligand, TRAIL, is a new member of the TNF family. It can specifically induce apoptosis in a variety of human tumors. To investigate the possibility of employing the TRAIL gene for systemic cancer therapy, we constructed a recombinant gene encoding the soluble form of the human Flt3L gene (hFlex) at the 5' end and the human TRAIL gene at the 3' end. Such design allows the TRAIL gene product to be secreted into the body circulation. We have also demonstrated that the addition of an isoleucine zipper to the N-terminal of TRAIL greatly enhanced the trimerization of the fusion protein and dramatically increased its anti-tumor activity. The fusion protein reached the level of 16-38 microg/ml in the serum after a single administration of the recombinant gene by hydrodynamic-based gene delivery in mice. A high level of the fusion protein correlated with the regression of a human breast tumor established in SCID mice. No apparent toxicity was observed in the SCID mouse model. In addition, the fusion protein caused an expansion of the dendritic cell population in the C57BL/6 recipient mice, indicating that the hFlex component of the fusion protein was functional. Thus, the hFlex-TRAIL fusion protein may provide a novel approach, with the possible involvement of dendritic cell-mediated anti-cancer immunity, for the treatment of TRAIL-sensitive tumors.

Adenocarcinoma↗
PubMed2001

High-level expression of human acidic fibroblast growth factor and basic fibroblast growth factor in silkworm (Bombyx mori L.) using recombinant baculovirus.

A hybrid of Autographa californica nuclear polyhedrosis virus and Bombyx mori nuclear polyhedrosis virus, which is infectious to both Spodoptera frugiperda and Bombyx mori, was prepared in our previous study. Two recombinant hybrid baculoviruses, carrying cDNAs of human acidic and basic fibroblast growth factors, respectively, were successfully constructed in this study, for the large-scale production of human aFGF and bFGF using silkworm as host. These recombinant viruses were used to inoculate silkworm larvae. After the infection, the recombinant proteins were not found in the hemolymph. Such nonsecretion from cells has also been observed in the established insect cell lines, Sf21 and Tn-5. Tissue distribution analysis indicated that the expressed products were mainly located in fat body and the production of the recombinant aFGF and bFGF was maximal at around 80 h postinfection. Therefore, silkworm larvae infected with recombinant viruses were dissected and fat bodies were collected for the purification of recombinant aFGF and bFGF. The expression levels in both cases were estimated to be as high as approximately 600-700 microg per larva. Furthermore, the recombinant proteins were characterized and their biological activities were evaluated by in vitro bioassay using cell culture.

Adult↗
PubMed2001

Anti-viral activity of hairpin ribozyme directed against HBV core region in vitro.

To study the preparation and cleavage of hairpin ribozyme (HpRz) directed against the transcript of HBV core region in vitro, HRz gene designed by computer targeting the transcript of HBV core gene was cloned into the vector p1.5 between 5'-cis-Rz and 3'-cis-Rz. 32P-labeled HpRz transcript proved whether the vector fit for the preparation of hairpin ribozyme. 32P-labeled pKC transcript containing HBV core region as targets-RNA was transcribed by using T7 RNA polymerase and purified by PAGE. Cold HpRz transcript was incubated with 32P-labeled target-RNAs under different conditions and radioautographed after denaturing polyacrylamide gel electrophoresis. The results showed that HpRz had the ability of cleavage at 37 degrees C and 12 mmol/L MgCl2 and the design of ribozyme was correct. It is concluded that HpRz prepared in vitro possesses specific catalytic activity, indicating that it is possible for HpRz to intracellularly inhibit the replication of HBV. It may be developed into a nucleic acid drug in the treatment of hepatitis B in the future.

Antiviral Agents↗
PubMed2001

Establishment of in vitro cellular model predicting histocompatibility in allograft.

A novel in vitro cellular model producting recipient-donor histocompatibility in allograft was developed to select the donor validity. Fifteen couples of blood samples of donor and recipient in human BMT were examined using the model, and skin allograft in mice was performed to test the model. The results showed that the less the differences of histocompatibility evaluated by the model were, the later GVHR in human BMT occurred and the longer the survival time of skin allografts in mice. It was suggested that the model could be used to predict correctly histocompatibility between donor and recipient.

Animals↗
PubMed2001

Antitumor efficacy of 26-fluoroepothilone B against human prostate cancer xenografts.

BACKGROUND: Epothilone compounds (e.g. epothilones A and B) represent a new structural class of microtubule inhibitors with the remarkable ability to inhibit tumor growth of multidrug-resistant cell lines at low nanomolar or even subnanomolar concentrations. Unfortunately, this therapeutic efficacy has only been achieved to date with a narrow therapeutic window. Hence, other structural analogs of compounds such as epothilone B are currently being synthesized in the hope that they will demonstrate equivalent antitumor efficacy with reduced systemic toxicity. PURPOSE: To evaluate the relative efficacy and toxicity of selectively modified epothilone compounds. METHODS: Compounds were initially screened for relative cytotoxicity against the human prostate cancer cell lines PC3, LNCaP, MDA PCa 2a and MDA PCa 2b. Growth inhibitory IC50 values of 0.5 to 4 nM were obtained. From this initial screen, one epothilone compound, 26-fluoroepothilone B, was chosen for further evaluation against the growth of s.c.-implanted MDA PCa 2b- and PC3-derived prostate tumors in athymic nude mice. The compound was administered intravenously at 2, 5 and 10 mg/kg after the tumors had reached 300 mm3. Two control groups were used: paclitaxel (40 mg/kg) and saline. RESULTS: Following treatment with 10 mg 26-fluoroepothilone B/kg, there was a sustained decrease in tumor size for 30 days reaching a maximal reduction of 80% when compared with tumor growth in the saline control group. Sustained suppression (> 20 days) of tumor growth was observed following the second drug injection. Although a maximal body weight loss of 30% occurred after the second injection, all mice completely regained their initial body weight in 20 days. A lower dose (2 mg/kg) produced a 58% maximal reduction in tumor size and a 20% body weight loss. Minimal inhibition of tumor growth, however, was obtained with paclitaxel at a maximally tolerated dose (40 mg/kg). Other epothilones tested were either less effective and/or more toxic than 26-fluoroepothilone B. This new fluorinated epothilone compound supports the growth of paclitaxel-dependent Tax-18 mutant CHO cells and produces microtubule bundles similar to those produced by paclitaxel, indicating that the two drugs share a similar mechanism of action. CONCLUSION: A new fluorinated epothilone compound, 26-fluoroepothilone B, has been described that stabilizes microtubule structures based on its support of growth of a mutant paclitaxel-dependent CHO cell line. Its antitumor activity against human prostate cancer in nude mice is superior to that of paclitaxel at equivalent toxic doses. Further research is required to determine optimal dosing strategies and to fully assess the compound's activity against other malignant diseases.

Animals↗
PubMed2001

Genetic interactions between the ESS1 prolyl-isomerase and the RSP5 ubiquitin ligase reveal opposing effects on RNA polymerase II function.

Transcription of protein-coding genes by RNA polymerase II (pol II) is a highly coordinated process that requires the stepwise association of distinct protein complexes with the C-terminal domain (CTD) of Rpbl, the largest subunit of RNA pol II. Interaction of these complexes with the CTD might be subject to regulation by proteins such as Ess1 and Rsp5. Ess1, a prolyl-isomerase, binds the CTD and is thought to play a positive role in pol II transcription by generating conformational isomers of the CTD. Rsp5, a ubiquitin ligase, binds the CTD and is thought to play a negative role in transcription by mediating Rpbl ubiquitination and degradation. In this paper, we demonstrate that ESS1 and RSP5 interact genetically and that these interactions occur via RPBI. We show that over-expression of RSP5 enhances the growth defect of ess1ts cells and this effect is reversed by introducing extra copies of RPB1. Over-expression of RSP5 also mimics the sensitivity of ess1ts mutant cells to the toxicity of plasmids carrying dominant-negative CTD mutations, whereas mutations in RSP5 suppress this effect. Using a modified two-hybrid assay, we also demonstrate that Essl and Rsp5 compete directly for binding to the CTD. The results suggest a model in which Essl and Rsp5 act opposingly on pol II function to control the level of pol II available for transcription.

Binding, Competitive↗