Biomedical subjects

X Xia

Publications and source records attributed to X Xia.

At least 37 records · Page 2Linked to original sources

PubMed2001

A chromosome 15 quantitative trait locus controls levels of radiation-induced jejunal crypt cell apoptosis in mice.

Jejunal crypt cells undergo apoptosis in response to ionizing radiation exposure. In mice the number of cells deleted by apoptosis is determined by several factors including the dose of radiation, the time of day the apoptosis level is quantified, and the strain of mouse irradiated. We previously found that the difference in radiation-induced apoptosis levels between C57BL/6J (B6) and C3Hf/Kam (C3H) mice is controlled by multiple genes, and this set of genes is distinct from that controlling thymocyte apoptosis levels in the same strain combination. Here, we report that a new quantitative trait locus on chromosome 15, Rapop5, partly accounts for the murine strain difference in susceptibility to radiation-induced jejunal crypt cell apoptosis. In addition, we show sexual dimorphism in the extent of radiation-induced jejunal crypt cell apoptosis, with female mice having higher levels.

Animals↗

PubMed2001

Ebp1, an ErbB-3 binding protein, interacts with Rb and affects Rb transcriptional regulation.

Ebp1, an ErbB-3 binding protein, inhibits the proliferation and induces the differentiation of human breast cancer cells. The mechanisms of these effects are unknown. Rb, the product of the retinoblastoma gene, is an important modulator of cell cycle progression and cellular differentiation. We report that Rb is a binding target for Ebp1. Ebp1 was localized to both the nucleus and the cytoplasm of logarithmically growing AU565 breast cancer cells and HeLa cells as determined by confocal immunofluorescent microscopy. Ebp1 was present in Rb immunoprecipitates derived from AU565 breast cancer cells. GST-Rb also bound endogenous Ebp1. Using GST-Ebp1 constructs, we determined that the 72 C-terminal amino acids of Ebp1 were sufficient to bind Rb. Dephosphorylation of Ebp1 enhanced the interaction of Ebp1 with Rb. The overexpression of Ebp1 in MCF-7 and AU565 (Rb(+)) cells inhibited the activity of the E2F1 regulated cyclin-E promoter. Ebp1 bound E2F1 indirectly via Rb in lysates of MCF-7 cells. The interaction of Ebp1 with Rb may prove to be an important mechanism of Ebp1 induced changes in cell proliferation and differentiation.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Electrochemical nanostructuring with ultrashort voltage pulses.

The application of nanosecond voltage pulses to electrodes provides three ways to conduct local electrochemistry on the micro- to nanometer scale. (1) The finite charging time of the double-layer capacity allows the machining of three-dimensional microstructures. (2) In an electrochemical scanning tunneling microscope, reactions are confined to the tunneling region, due to the depletion of the electrolyte in the tip--surface gap. (3) Ordering processes, following very fast electrochemical reactions, lead to unconventional island patterns on a surface.

Electrochemistry↗

PubMed2001

Effects of the oral spirochete Treponema denticola on interleukin-8 expression from epithelial cells.

This communication demonstrates that the interaction of the oral spirochete Treponema denticola 35405 with KB epithelial cells does not lead to the induction of interleukin-8 production as occurs with a variety of other bacteria. Utilizing the dentilisin protease mutant K1 of T. denticola, this property was demonstrated to be primarily a function of the expression of the protease by strain 35405.

Bacterial Proteins↗

PubMed2001

Intramuscular electroporation delivery of IFN-alpha gene therapy for inhibition of tumor growth located at a distant site.

Although electroporation has been shown in recent years to be a powerful method for delivering genes to muscle, no gene therapy via electro-injection has been studied for the treatment of tumors. In an immunocompetent tumor-bearing murine model, we have found that delivery of a low dose of reporter gene DNA (10 microg) to muscle via electroporation under specific pulse conditions (two 25-ms pulses of 375 V/cm) increased the level of gene expression by two logs of magnitude. Moreover, administration of 10 microg of interferon (IFN)-alpha DNA plasmid using these parameters once a week for 3 weeks increased the survival time and reduced squamous cell carcinoma (SCC) growth at a distant site in the C3H/HeJ-immunocompetent mouse. IFN-alpha gene therapy delivered to muscle using electroporation demonstrated statistically significant (P < 0.05) therapeutic efficacy for treating SCC located at a distant site, compared with interleukin (IL)-2 or endostatin gene, also delivered by electro-injection. The increased therapeutic efficacy was associated with a high level and extended duration of IFN-alpha expression in muscle and serum. We also discovered that the high level of IFN-alpha expression correlated with increased expression levels of the antiangiogenic genes IP-10 and Mig in local tumor tissue, which may have led to the reduction of blood vessels observed at the local tumor site. Delivery of increasing doses (10-100 microg) of IFN-alpha plasmid DNA by injection alone did not increase antitumor activity, whereas electroporation delivery of increasing doses (10-40 microg) of IFN-alpha plasmid DNA did increase the survival time. Our data clearly demonstrate the potential utility of electroporation for delivery of gene therapy to muscle for the treatment of residual or disseminated tumors.

Animals↗

PubMed2001

Enhancement of biodegradability of polychlorinated dibenzo-p-dioxins.

Enhancement of biodegradability of polychlorinated dibenzo-p-dioxins (PCDDs) was studied with new isolated bacterial strains from soil and oxic-sediments contaminated by PCDDs. The results indicated that mono- and di-chlorinated dibenzo-p-dioxins could be utilized as a sole carbon source and degraded by isolated bacterial strains, but tri-chlorinated dibenzo-p-dioxin (TrCDD) was hardly degraded. The biodegradability of TrCDD and tetra-chlorinated dibenzo-p-dioxin (TCDD) by the strain Pseudomonas sp. EE41, a new isolated one, could be enhanced through primary nutrient of co-metabolism of o-dichlorobenzene (o-DCB). In this case, TrCDD (1.2mg/l for 3 weeks) was degraded by 33.1% and the degradation rate enhanced more than 2 fold; also TCDD (0.1 mg/l for 3 weeks) biodegraded by 37.8%. Most highly chlorinated, Penta-, Hexa-, Hepta-, and Octa-chlorinated, dibenzo-p-dioxins (P-CDD, H6, H7-CDD and OCDD) tested in this study could not be degraded while accumulated in bacterial cells.

Biodegradation, Environmental↗

PubMed2001

AMADA: analysis of microarray data.

SUMMARY: AMADA is a Windows program for identifying co-expressed genes from microarray data. It performs data transformation, principal component analysis, a variety of cluster analyses and extensive graphic functions for visualizing expression profiles.

Algorithms↗

PubMed2001

2,4-dichlorophenoxyacetate/alpha-ketoglutarate dioxygenases from Burkholderia cepacia 2a and Ralstonia eutropha JMP134.

2,4-Dichlorophenoxyacetate (2,4-D)/alpha-ketoglutarate (alpha-KG) dioxygenase has been purified to apparent homogeneity from Burkholderia cepacia strain 2a, which utilizes 2,4-D as sole carbon source. The enzyme required ferrous ions, and was a homodimer composed of subunits having an Mr of approximately 32,000. The reaction catalysed consumed one mol each of 2,4-D, alpha-KG and dioxygen, with the production of one mol each of succinate, 2,4-dichlorophenol and glyoxylate. Maximum activity was exhibited at pH 7.8 and 25 degrees C, and reactivity was enhanced by the presence of ascorbate and cysteine. Mn2+, Zn2+, Cu2+, Fe3+ and Co2+ were inhibitory, and chemical modification of the dioxygenase revealed that thiol groups were essential for activity. The enzyme was active towards other substituted phenoxyacetates, but reacted most rapidly with 2,4-D. The apparent Michaelis constants for 2,4-D and alpha-KG were 109 and 8.9 microM, respectively. The properties of this enzyme are compared with those of the 2,4-D/alpha-KG dioxygenase from Ralstonia eutropha JMP134, which exhibits a differing N-terminal amino-acid sequence, and a different temperature 'optimum', pH optimum, substrate specificity and sensitivity to thiol-binding reagents.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2001

[Cloning and sequence analysis of truncated S gene from circulation of patients with chronic hepatitis B virus infection].

OBJECTIVE: To find different mutated status of HBV DNA in circulation from chronic HBV patients. METHODS: Specially designed primers and polymerase chain reaction method were applied to amplify the whole S gene of HBV from the serum of 2 patients. After being sequenced, 4 clones were compared with HBV adr subtype (China strain) to identify the mutant sites. RESULTS: Sequencing results implied that there was a truncated large/middle S gene in the serum of the patients. Besides that, HBsAg and HBV DNA polymerase defective clones were also detected. CONCLUSIONS: Truncated middle S gene is found in the circulation of patients with chronical HBV infection, suggestive of a poor prognosis.

Cloning, Molecular↗

PubMed2001

[Microbial degradation of polychlorinated dibenzo-p-dioxins].

PCDDs-degrading bacterial strains were isolated from soil and oxic-sediments polluted by PCDDs. One of them was identified as Pseudomonas sp. EE41. They are capable of growing on and degrade mono- and di-chlorinated dibenzo-p-dioxins as a sole carbon source. The biodegradability of TrCDD and TCDD can be enhanced through primary nutrient of co-metabolism of o-CDB, thus, 1,2,3-TrCDD and 2,3,7,8-TCDD were degraded by 33% (at the concentration of 1.2 mg/L, within 3 weeks) and 37.8% (at the concentration of 0.1 mg/L, within 3 weeks) respectively. Most highly chlorinated dibenzo-p-dioxins (P-CDD, H6-, H7-CDD and OCDD) tested in this study were accumulated in bacterial cells, but could not be degraded.

Biodegradation, Environmental↗

PubMed2001

[Screening and characterization of human phage antibody to hepatitis C core antigen].

OBJECTIVE: To screen and characterize human phage antibody (ScFv) against hepatitis C core antigen. METHODS: The recombinant phages were panned by core antigen that was coated in a microtiter plate. After three rounds of biopanning, 48 clones were determined specific to core antigen. The specificity of each ScFv colone was determined by ELISA. The coding gene for HCV protein ScFv has been sequenced. RESULTS: Phage antibody for HCV core protein had a specific combination character with core antigen of hepatitis C virus. The DNA sequence data showed that the ScFv gene included 774 bp. CONCLUSIONS: Human single chain antibody to hepatitis C core antigen has been identified by means of the phage display technology.

Amino Acid Sequence↗

PubMed2001

A bicistronic retroviral vector to introduce drug resistance genes into human umbilical cord blood CD34+ cells to improve combination chemotherapy tolerance.

OBJECTIVE: To study whether human umbilical cord blood CD34+ cells transduced with human aldehyde dehydrogenase class-1 (ALDH-1) and multidrug resistance gene (MDR1) have increases resistance to 4-Hydroperoxycyclo-phosphamide (4-HC) and P-glycoprotein effluxed drugs. METHODS: A bicistronic retroviral vector G1Na-ALDH1-IRES-MDR1 was constructed and used to transfect the packaging cell lines GP + E86 and PA317 by LipofectAMINE method, using the medium containing VCR and 4-HC agents for cloning selection and ping-ponging supernatant infection between the ecotropic producer clone and the amphotropic producer clone, we obtained high titer amphotropic PA317 producing cells with high titers up to 5.6 x 10(5) CFU/ml. Cord blood CD34+ cells were transfected repeatedly with supernatant of retrovirus containing human ALDH-1 and MDR1cDNA under the stimulation of hemopoietic growth factors. RESULTS: Bicistronic retroviral vector construction was verified by restriction endonuclease analysis. Polymerase chain reaction (PCR), reverse transcription (RT)-PCR, Southern blot, Northern blot, fluorescenceactivated cell sorting (FACS) method and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analyses showed that dual drug resistance genes have been integrated into the genomic DNA of cord blood CD34+ cells and expressed efficiently. The transgenes recipient cells confered 4-fold stronger resistance to 4-HC and 5.5 to 7.2-fold P-glycoprotein effluxed drug than untransduced cells. CONCLUSION: The bicistronic retroviral vector-mediated transfer of two different types of drug resistance genes into human cord blood CD34+ cells and co-expression provided an experimental foundation for improving combination chemotherapy tolerance in tumor clinical trial.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2001

Epidemiological investigation of Histoplasma capsulatum infection in China.

OBJECTIVE: To provide reliable information concerning the presence or the absence of Histoplasma capsulatum (H. capsulatum) infection in China, and data concerning this respect. METHODS: Three hundred normal people and 435 hospitalized patients, who lived in Hunan and Jiangsu provinces, and the Xinjiang Autonomous Region, were tested with yeast-phase histoplasmin (ALK/Berkerley Biologicals Laboratories, USA) and human pure protein derivative of tuberculin (PPD) on the volar surface of the forearm. Any reaction to the antigens over 5.0 mm in diameter of induration at 48-72 hours was considered positive. RESULTS: A total of 138 subjects (18.8%) in 735 patients reacted to histoplasmin with 5.0-45.0 (9.1 +/- 4.3) mm indurations. Significant differences of positive skin reaction rates in normal subjects were found in Hunan, Jiangsu and Xinjiang (8.9% vs 15.1% vs 2.1%). The overall positive rate of patients was 25.5%. Patients with tuberculosis [31.7% (78/246)] had a significantly higher positive skin reaction rate in comparison with those suffering from pneumonia [17.7% (11/62)], lung cancer [20.9% (9/43)], chronic obstructive pulmonary disease [17.3% (9/52)] and other diseases [12.5% (4/32)] (P < 0.01). Of 562 cases, 292 cases (52.0%) reacted to PPD with indurations of 5-50 (13.7 +/- 4.9) mm in diameter, 63 cases (11.2%) reacted to both histoplasmin and PPD, while 38 cases (6.9%) reacted to histoplasmin but not to PPD. CONCLUSIONS: The data suggest that there is H. capsulatum herd infection in China. The infection rate in Southeast China is higher than that in the Northwest, and the infection rate of patients with pulmonary tuberculosis is higher than that of normal persons and other pneumonopathy patients.

Adult↗

PubMed2001

[Study on drug resistance of Mycobacterium tuberculosis in different age group].

OBJECTIVE: To investigate drug resistance of Mycobacterium tuberculosis in different age group in recent five years, and to analyze the trends of drug resistance at present. METHODS: 1 948 cases of pulmonary tuberculosis with culture-positive were divided into youth group (18 approximately 39 years), middle age group (40 approximately 59 years) and old age group (>/=60 years). All of the strains of Mycobacterium tuberculosis were tested for resistance to INH, RFP, SM and EMB by the absolute concentration method. RESULTS: The rate of primary drug resistance in youth group was 36.1%, in middle age group 46.8%, in old age group 40.2%, there were no significant differences among them (P > 0.05). The rate of acquired drug resistance was higher in youth group than that in old age group (P = 0.019 6). The primary resistance rate to RFP in middle age group was 10.6%, much higher than that in youth group and in old age group. The acquired resistance rate to RFP in youth group was 63.6%, higher than that in middle age group and in old age group. The rate of primary multi-drug resistance in middle age group was 5.3%, higher than that in youth group (P = 0.011 2) and in old age group (P = 0.008 5). The rate of acquired multi-drug resistance in youth group was 55.2%, higher than that in middle age group (P = 0.031 9) and in old age group (P < 0.001). The drug resistance rate in using drugs 1 approximately 3 months group was 58.7%, higher than that in never using drug group (P < 0.001) and in using drugs < 1 month group (P = 0.047 2). The drug resistance rate had no significant difference between never using drug group and using drugs < 1 month group. The emergency of drug resistance in youth group was fastest in all age groups. CONCLUSIONS: Primary drug resistance or acquired drug resistance varies in different age group. It is suggested that the surveillance of drug resistance in different age group should be taken seriously, so as to provide an important basis for revising National Tuberculosis Programme (NTP).

Adolescent↗

PubMed2001

[Improvement of combination chemotherapy tolerance of human umbilical cord blood CD(34)(+) cells transducted with double drug resistance genes by a bicistronic retroviral vector].

OBJECTIVE: To explore whether human umbilical cord blood hematopoietic progenitor cells transduced with human aldehyde dehydrogenase class 3 (ALDH3) and multidrug resistance gene (MDR1) could increase resistance to 4-hydroxycyclophosphamide (4-HC) and P-glycoprotein effluxed drugs. METHODS: A bicistronic retroviral vector G1Na-ALDH3-IRES-MDR1 cDNA was constructed and transfected the packaging cell lines GP + E86 and PA317 by LipofectAMINE method, using the medium containing VCR and 4-HC for cloning selection and ping-ponging supernatant infection between ecotropic producer clone and amphotropic producer clone, cord blood CD(34)(+) cells were enriched with a high-gradient magnetic cell sorting system (MACS), and then repeatedly transfected with supernatant of retrovirus containing human ALDH3 and MDR1 cDNA under stimulation of hematopoietic growth factors. PCR, RT-PCR, Southern blot, Northern blot, FACS and MTT assay were used to evaluate the transfection and expression of the double genes. RESULTS: The purity of cord blood CD(34)(+) cells was approximately 91% and the recovery rate was 72%. The highest titer of recombinant amphotropic retrovirus in the supernatant was up to 6.5 x 10(5) CFU/ml. The efficiency of gene transduction was 18%, 20% and 16.7% tested by colony formation, PCR and FACS, respectively. Rhodamine 123 efflux showed 16% transduced cells with P-gp function. No helper virus was found by both nested PCR and rescue assay. The MTT analysis showed a 3.5 to 6.8-fold increase of resistance of transducted cells to cyclophosphamide and P-glycoprotein effluxes drug as compared with the nontransduced cells. CONCLUSION: The efficiency and co-expression of this dual genes transfer system provided a foundation for ameliorating combination chemotherapy toxicity in clinical trial.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2001

[The Immunophenotypical features of t (8; 21) (q22; q22) acute myeloid leukemia].

OBJECTIVE: To study the predictive value of immunophenotypical features in t (8; 21) (q22; q22) acute myeloid leukemia (AML). METHODS: Morphological/cytochemical, flow cytometric immunophenotyping, cytogenetic analyses (MIC) and RT-PCR were performed in 294 previously untreated AML. RESULTS: (1) In 294 AML patients, t (8; 21) AML were 21.8% (64); in AML-M(2), t (8; 21) AML were 54.7%; and in t (8; 21) AML, AML-M(2) were 81.3%. (2) Compared with control group, CD(19) and CD(34) expressions were higher, and CD(33) expression was lower (P < 0.001) in t (8; 21) AML. (3) If the cut-off value of CD(19) positive was >or= 20%, CD(19) positive rate was 13.6% (40/294) in AML, and 50% (32/64) and 3.5% (8/230) (P < 0.001) in t (8; 21) AML and control group. (4) CD(19)(+) and/or CD(34)(+) t (8; 21) AML accounted for 90.6% (58/64) of t (8; 21) AML and CD(19)(-)/CD(34)(-) for 9.6% (6/64). CONCLUSION: In t (8; 21) AML, especially M(2)/t (8; 21), CD(19) and CD(34) expressions were high. CD(19) was one of predictive markers of t (8; 21) AML.

Adolescent↗

PubMed2001

[Expression and drug resistance of human MGMT gene in hemopoietic cells mediated by bicistronic retroviral vector].

OBJECTIVE: To increase myeloid progenitors resistance to chemotherapy and prevent myelosuppression caused by alkylating agents. METHODS: Total cellular RNA was extracted from human liver and cDNA was synthesized by superscript reverse transcriptase, a polymerase chain reaction(PCR) was conducted. We obtained a full length cDNA fragment encoding human alkyguarine-DNA-alhyltransferase(MGMT). The PCR product was cloned into pGEMT-T vector and further subcloned into G1Na retrovirus expression vector. Then the recombinant plasmid was transduced into the packaging cell lines GP+E86 and PA317 by lipofect AMINE. RESULTS: By using the medium containing BCNU for cloning selection and ping-ponging supernatant infection between ecotropic produced clone and amphotropic producer clone, we obtained high titer amphotropic PA317 producer clone with the highest titer up to 8.6-10 CFU/ml. Human hematopoietic cells were infected repeatedly with this high titer virus under stimulation of hemopoietic growth factors IL-3, IL-6 and SCF. PCR, RT-PCR, Southern blot, Western blot and MTT analyses showed that MGMT gene has integrated into the genomic DNA of human hemopoietic cells and expressed efficiently. CONCLUSIONS: This study provides a foundation for application of gene therapy to tumor clinical trial.

Alkyl and Aryl Transferases↗

PubMed2001

A Negative Element Located in the Upstream Flanking Region of the Gene Encoding Arginyl-tRNA Synthetase (argS) from Escherichia coli.

The gene, argS, encoding the arginyl-tRNA synthetase (ArgRS) from Escherichia coli ( E.coli ) was overexpressed 1 000 fold in the transformant when E. coli TG1 was transformed with the recombinant plasmid containing argS and pUC18. In order to investigate the regulation of expression of E. coli argS, a series of deletion mutations was constructed. The results of SDS-PAGE showed that deletions of the whole 5' flanking region (argSdelta1) or the region in front of Shine-Dalgarno Sequence (argSdelta2) or the -10 region of promoter (argSdelta3), caused no overexpression of argS. If argS was deleted from 3' end of the flanking region (-189 nt) to the upstream of -10 region of promoter (argSdelta4), the -35 region (argSdelta5), -52 nt (argSdelta6), -70 nt (argSdelta7) and -122 nt (argSdelta8), respectively, the mutant gene was overexpressed to a level similar to that of argS bringing the full length 5' flanking region. However, in the expression of argSdelta4, argSdelta5, argSdelta6, some of ArgRS formed an inclusion body. By determination of RNA dot hybridization, the amount of mRNA produced in the transcription of argSdelta4, argSdelta5 and argSdelta6 was about 2--3 times than that of the wild type argS, argS delta7 and argS delta8. This indicated that the deletion of a 19 nt sequence (AATAGTGAAAACGGCAATA) located between -52 nt and -70 nt of the gene increased the transcription of argS. The 19 nt sequence is a negative region that represses transcription of argS. Deletion of the negative element may result in a faster production of ArgRS and the accumulation of some unfolding protein intermediates aggregating to form the inclusion body. The result by analysis of gel retardation shows that a factor binds to the negative element. Arginine induced specifically the transcription of argS and its effect correlated with the above negative element.

Journal Article↗