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Biomedical subjects

T Xie

Publications and source records attributed to T Xie.

At least 55 records · Page 3Linked to original sources
PubMed1997

A truncated poisson regression model with applications to occurrence of adenomatous polyps.

Adenomatous polyps are considered as the dominant precursor lesion of colorectal cancer. A phase III colorectal cancer prevention trial, conducted by the Arizona Cancer Center, concerns the ability of wheat bran fibre supplement to reduce the recurrence of adenomatous polyps. All participants in the study are to have had colorectal polyps detected and removed during a baseline (qualifying) colonoscopy within three months prior to enrolment. In this paper, our interest focuses on occurrence of adenomatous polyps at the baseline colonoscopy. We use a truncated Poisson model to fit these types of data. We develop a regression model to assess the effects of explanatory factors on the positive counting variable. We fit truncated Poisson parameters by a log-linear regression model and estimate regression parameters by the maximum likelihood procedure. Finally, we apply it to the baseline colonoscopy data from the Wheat Bran Fiber study.

Adenomatous Polyps↗
PubMed1997

G/A1947 polymorphism in catechol-O-methyltransferase (COMT) gene in Parkinson's disease.

High and low catechol-O-methyltransferase (COMT) activity is significantly determined by thermostability, which is caused by a valine/methionine108 polymorphism associated with polymorphic G/A1947 bases, in exon 4 of the COMT gene. Our allelic association study on this polymorphism did not find any statistically significant difference between our Chinese Parkinson's disease and that of control subjects. These results show that this polymorphism and hence the thermostability of COMT enzyme are not related to a risk of developing Parkinson's disease.

Aged↗
PubMed1997

High resolution single strand conformation polymorphism analysis using formamide and ethidium bromide staining.

Single strand conformation polymorphism (SSCP) analysis using ethidium bromide can be improved by adding formamide as the denaturant. This gives higher resolution than previous SSCP methods; it had 100% sensitivity in the discrimination of 14 PCR samples from two different genes, even for a long fragment close to the upper limit of 250 base pairs. This modified procedure is a rapid, simple, safe, and yet highly sensitive method for detecting structural differences in DNA fragments.

Catechol O-Methyltransferase↗
PubMed1997

Evaluation of cutoff levels for screening of gastric cancer using serum pepsinogens and distributions of levels of serum pepsinogen I, II and of PG I/PG II ratios in a gastric cancer case-control study.

This study was carried out to determine the cutoff levels of serum pepsinogen (PG) I, II and their ratio of PG I/PG II for gastric cancer to establish a better screening system. Optimal cutoff levels for gastric cancer screening using serum pepsinogens were determined using Youden's index. The sensitivity, specificity and Youden's index for gastric cancer cases were calculated according to sex, age and the stage of gastric cancer, and the maximum Youden's index in each category was adopted as the cutoff level for gastric cancer screening using serum pepsinogens. The maximal Youden's index in all gastric cancer cases was 0.37, corresponding to a cutoff level of PG I < 40 (micrograms g/l) and PG I/PG II < 3.5. The sensitivity and specificity for gastric cancer cases of these cutoff levels were 0.50 and 0.87, respectively. In future, better criteria for gastric cancer screening have to be examined with the estimation of Youden's index in addition to other epidemiological methods such as ROC (receiver operating characteristic) curves and/or cost benefit analyses.

Adult↗
PubMed1997

[Expression of ICAM-1 mRNA in HCC using in situ hybridization technique].

OBJECTIVE: To study the relationship between the intercellular adhesion molecule 1 (ICAM-1) mRNA expression of hepatocellular carcinoma (HCC) and its invasion and metastasis. METHODS: 34 cases of HCC and their pericarcinomatous tissues were studied on cryostat sections by in situ hybridization to investigate ICAM-1 mRNA expression. RESULTS: The ICAM-1 mRNA expression was stronger in the carcinomatous tissues of 19/21 invasive cases than that in the pericarcinomatous tissues, while in the 13 non-invasive cases, only 4 exhibited weak ICAM-1 mRNA expression. CONCLUSION: ICAM-1 mRNA expression may correlate with increased risk of invasion and metastasis of HCC.

Adult↗
PubMed1997

[Effects of sterigmatocystin on ras p21 expression and ultrastructure of human lung fibroblasts in vitro].

Effects of Sterigmatocystin (ST) on ras p21 expression and ultrastructure of human lung fibroblasts in vitro were studied with immunological flow cytometry and electron microscopy. The results showed that ras p21 expression in the ST treated cells was dramatically increased and the ultrastructural features of malignant cells, such as enlarged nuclei with bizzar nuclear membranne folds and predominant nucleoli, could be seen.

Carcinogens↗
PubMed1997

[Experimental and clinical research of cytolytic T lymphocytes specific for hepatocellular carcinoma].

To investigate a new kind of anti-tumor immunological cells and improve surgical results of hepatocellular carcinoma by anti-recurrence application, we activated T cells isolated from tumor infiltrating lymphocytes by double stimulating signals: the one was autologus HCC cells which were treated with IFN-gamma and TNF-alpha for enhancing expression of MHC class I and presented tumor antigen, and the other was costimulation signals which was from ICAM-1 and B7 molecules expressed on treated HCC cells as well as CD28 mAbs. Activated T cells which bound to HCC cells were expanded selectively as tumor specific cytotoxic T lymphocytes (TS-CTLs), their cytotoxic activity in vitro and anti-tumor effects in vivo were observed. Our results suggested that TS-CTLs expressed high cytotoxicity against autologous HCC cells with MHC class I restriction manner. Adoptive TS-CTLs treatment could decrease serum AFP level, inhibit ascites formation and prolong survival in SCID mice bearing human HCC. In clinical trail of 12 cases of HCC, TS-CTLs treatment was able to delay tumor recurrence after HCC resection. Our data demonstrated that TS-CTLs as new immunological treatment modality, are of great value in further application of tumor comprehensive management.

Adult↗
PubMed1997

TCM differential treatment of 30 cases of IgA nephropathy.

Thirty cases of IgA nephropathy having been diagnosed by biopsy with kidney puncture were selected. The treatment was based on the differentiation of syndromes in traditional Chinese medicine (TCM). The disease was divided into 4 stages: the initial stage with the lesion in the lung and kidney, the stable stage with the lesion in the spleen and kidney, the late stage with the lesion in the liver and kidney, and the recurrent stage. They were treated by TCM. Of them, 10 cases were completely alleviated, 13 markedly alleviated, 4 improved, and 3 ineffective, the total effective rate being 90%.

Adolescent↗
PubMed1997

[Study on the synthesis and secretion rate of transferrin in hepatoma and peritumor hepatocytes].

OBJECTIVE: To study the changes of synthesis and secretion of transferrin (Tf) in human hepatocellular carcinoma (HCC) cells and search the causes of reduced membrane-bond transferrin in HCC tissue. METHODS: By radioisotope incorporation and immunoprecipitation to determine the synthesis and secretion rate of transferrin in human HCC cells and peritumor hepatocytes. RESULTS: When compared with peritumor hepatocytes the quantity of transferrin synthesized was not changed in HCC cells, but its secretion rate was accelerated significantly while the transferrin storage was significantly decreased. CONCLUSION: The results suggest that HCC growth might be enhanced by increased Tf secretion and help explain the decreased membrane-bond form of Tf in HCC tissue.

Carcinoma, Hepatocellular↗
PubMed1997

[HLA-DR typing by standard serology and PCR-amplification with sequence-specific primers: a comparative study].

OBJECTIVE: DNA typing for HLA-DR by polymerase chain reaction with sequence-specific primers (PCR-SSP) compared with standard serology to evaluate the reliability and clinical practicability. METHODS: Double-blind typing for HLA-DR alleles was carried out using DNA typing by PCR-SSP and standard serology by microlymphocytotoxicity technique in 61 donors and 101 recipients of cadaveric transplantation. Matching time, sensitivity, specificity and clinical practicability were compared according to typing results by both methods. RESULTS: All 162 samples were able to be typed by PCR-SSP. A total of 308 alleles were detected (16 DR "blank"). The results of matching were confirmed by analysis with restriction endonucleases and Southern hybridization. The specificity and reproducibility were 100%. HLA-DR typing was performed in 5 hours by PCR-SSP or 20 hours by serology. The discrepancy rate between PCR-SSP and serological HLA-DR typing was 30.2% (35.6% for kidney recipients, 21.3% for donors). The discrepancies consisted of 8 loci being doubtful, 29 antigens being incorrectly interpreted by serology and 20 of serological "blanks" turning out to be definable alleles by the DNA method. CONCLUSIONS: Genotyping for HLA-DR by PCR-SSP offers the advantages of better reagent and sample availability, more rapid and greater accuracy, all of which would warrant that this approach was suitable for clinical practice in organ transplantation.

DNA↗
PubMed1996

The IRS 1 circumstellar disk, and the origin of the jet and CO outflow in B5.

We report the discovery of the inner edge of the high velocity CO outflow associated with the bipolar jet originating from IRS 1 in Barnard 5 and the first ever resolution of its circumstellar disk in the 2.6 mm dust continuum and C18O. From high spatial resolution observations made with the Owens Valley Millimeter Array we are able to locate the origin of the outflow to within approximately 500 AU on either side of IRS 1 and apparently at the edge of, or possibly within, its circumstellar disk. The orientation of the continuum disk is perpendicular to the highly collimated jet outflow recently seen in optical emission at much farther distances. The disk has been detected in C18O giving a disk mass approximately 0.16 M (solar). Our HCO+ and HCN maps indicate significant chemical differentiation in the circumstellar region on small scales with HCO+ tracing an extended disk of material. The 12CO interferometer maps of the outflow show two conelike features originating at IRS 1, the blue one fanning open to the northeast and the red one to the southwest. The vertices of the cones are on either side of the circumstellar disk and have a projected opening angle of about 90 degrees. The intrinsic opening angle is in the range of 60 degrees-90 degrees which leads to significant interaction between outflow and infall.

Astronomical Phenomena↗
PubMed1996

AP-2-mediated regulation of human NAD(P)H: quinone oxidoreductase 1 (NQO1) gene expression.

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a flavoprotein that catalyzes two-electron reduction and detoxification of quinones. We have shown previously that twenty-four base pairs of the human Antioxidant Response Element (hARE) mediate basal and xenobiotic-induced expression of the NQO1 gene [Li and Jaiswal, J Biol Chem 267: 15097-15104, 1992]. In the present report, we have characterized a second cis-element, AP-2, at nucleotide position -157 of the human NQO1 gene promotor that regulates basal and cAMP-induced transcription of the NQO1 gene. The NQO1 gene AP-2 mediated expression of the chloramphenicol acetyl transferase (CAT) gene and the binding of nuclear proteins to the AP-2 element were observed in HeLa (AP-2 positive) cells but not in human hepatoblastoma Hep-G2 (AP-2 deficient) cells, indicating the involvement of transcription factors AP-2 in the regulation of NQO1 gene expression. Affinity purification of nuclear protein that binds to the NQO1 gene AP-2 DNA element and western analysis revealed that AP-2 indeed binds to the NQO1 gene AP-2 element and regulates its expression HeLa cells. The involvement of AP-2 in the regulation of NQO1 gene expression was confirmed by the observation that cDNA-derived AP-2 protein in Hep-G2 cells increased in NQO1 gene AP-2 but not mutant AP-2 mediated expression of CAT gene in Hep-G2 cells.

Base Sequence↗
PubMed1996

Preferential transmission of the high activity allele of COMT in schizophrenia.

Catechol-O-methyl transferase (COMT) metabolizes a variety of catecholamines such as dopamine, adrenaline and noradrenaline. It exists in common high and low activity forms. The low activity form is the result of an amino acid substitution (val-108-met) which reduces the thermostability of the enzyme [Lotta et al. (1994) Biochemistry, 34, 4202-4210]. We have genotyped this polymorphism in 178 trios consisting of Han Chinese schizophrenic subjects and their parents in order to test the hypothesis that the high activity allele is transmitted more often to affected subjects. The data were analysed using the transmission disequilibrium test (TDT), a robust method of detecting linkage in the presence of allelic associations. Of the 131 parents heterozygous at this locus, 80 transmitted the high activity allele (val-108) to affected offspring, while the remaining 51 transmitted the low activity allele (p = 0.005, one-tailed). Combining this result with that of a previous TDT study of the same polymorphism in familial schizophrenia [Kunugi et al. (1996) submitted] gives significant evidence for linkage disequilibrium (p = 0.0015). However, val-108 is frequent in the Han Chinese population, and in the present sample, 239 of the 350 non-transmitted parental alleles were val-108 (68%). It is therefore unlikely that val-108 allele of COMT has a major effect on susceptibility to schizophrenia. Our results suggest that either val-108 is a minor risk factor for schizophrenia, that the COMT gene has additional polymorphisms with greater effect on risk, or that this region of chromosome 22 contains a susceptibility gene which is in linkage disequilibrium with the COMT gene.

Adolescent↗
PubMed1996

Factors affecting therapeutic effect of anti-CD3 and CD4 monoclonal antibody in acute renal allograft rejection.

Many factors can interfere with the therapeutic results for acute renal allograft rejection with anti-CD3 and CD4 MAbs. 1. When should we begin using MAbs and what about Scr levels while using MAbs? First-line treatment may be superior to rescue treatment; the earlier the better. 2. What is the level of blood concentration of CyA when rejection occurs? If the concentration of CyA is poor, the prognosis may be worse. 3. How do we maintain the dose of CyA during antirejection treatment with MAbs? Maintained use of CyA can play a coeffective role during antirejection treatment with MAbs. 4. What about the inhibiting degree of T-lymphocyte subsets after using MAbs? Whether CD3+ and CD4+/CD8+ decrease or not following the use of MAbs, the T-lymphocyte subsets may interfere significantly with the therapeutic results of MAbs. 5. The combined use of CD3 and CD4 MAbs seemed to get better results, especially for the intractable rejection cases. If we take care of the factors as referred to above, we may get a better therapeutic effect in reversing acute renal allograft rejection episodes with anti-CD3 and CD4 MAbs.

Acute Disease↗
PubMed1996

[DNA typing for HLA-DR in donor-recipients of cadaveric transplantation].

OBJECTIVE: To accurately allocate donor-recipients of HLA-matching and improve long-term graft survival, genotyping method for HLA-DR alleles by polymerase chain reaction with sequence-specific primers (PCR-SSP) was established and applied to renal transplantation. METHODS: Thirty primers were designed and synthesized according to the HLA-DR nucleotide sequences. Genomic DNAs were prepared by a rapid salting-out method. A rapid genotyping method of PCR-SSP was set up by PCR technique and applied to HLA-DR typing in 14 cell lines DNA and 171 individuals of donor-recipients of cadaveric transplantation. The amplification was accomplished by 34 cycles consisting of denaturation at 94 degrees C for 30 seconds, annealing at 60 degrees C for 50 seconds, and extension at 72 degrees C for 40 seconds. The specificity of matching was determined against a panel of standard DNA, analysis with restriction endonucleases and Southern hybridization. RESULTS: HLA-DR alleles of all 171 samples and 14 cell line DNAs were able to be typed by PCR-SSP. The size of specific products was consistent with the size of calculation. The overall time of genotyping was only 5 hours. No false positive or false negative typing results were discovered. The typing results were confirmed by analysis with endonucleases and hybridization. The specificity and reproducibility were 100%. CONCLUSIONS: Genotyping for HLA-DR by PCR-SSP is a rapid and accurate matching technique, suitable for organ transplantation, especially allocation of donor-recipients of cadaveric transplantation.

Alleles↗
PubMed1996

Rapid HLA-DR genotyping by PCR-amplification with sequence-specific primers.

OBJECTIVE: To establish a rapid genotyping for HLA-DR alleles by polymerase chain reaction with sequence-specific primers (PCR-SSP) for clinical application. MATERIAL AND METHODS: The subjects of study included 69 recipients, 43 unrelated donors and 5 cell lines. Genomic DNA was prepared from peripheral blood leukocytes by a salting-out method. Thirty primers were designed according to the HLA-DRB nucleotide sequences, and synthesized on a 391 DNA synthesizer. Twenty separate PCR reactions were performed for each sample. The amplification was accomplished by 34 cycles consisting of denaturation at 94 degrees C for 30 seconds, annealing at 60 degrees C for 50 seconds and extension at 72 degrees C for 40 seconds. The specificity of matching was determined by standard DNAs and Southern hybridization using DIG labeling probes. RESULTS: All 112 samples and 5 cell lines were able to be typed by PCR-SSP. No false positive or false negative typing results were obtained. The reproducibility was 100%. The size of the specific product was in concordance with the size of the designed primers. The overall time for genotyping was 4 hours. The typing results were confirmed by Southern hybridization. CONCLUSIONS: Genotyping for HLA-DR by PCR-SSP is a rapid and accurate matching technique suited for clinical application.

Alleles↗