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Biomedical subjects

B C Liu

Publications and source records attributed to B C Liu.

At least 19 recordsLinked to original sources
PubMed2006

Mass and KLamda coupling of the N*(1535).

Using a resonance isobar model and an effective Lagrangian approach, from recent BES results on J/psi-->ppeta and psi-->pK+Lamda, we deduce the ratio between effective coupling constants of N*(1535) to KLamda and peta to be R=gN*(153)KLamda/gN*(1535)peta=1.3+/-0.3. With the previous known value of gN*(1535)peta, the obtained new value of gN*(1535)KLamda is shown to reproduce recent pp-->pK+Lamdanear-threshold cross section data as well. Taking into account this large N*KLamda coupling in the coupled channel Breit-Wigner formula for the N*(1535), its Breit-Wigner mass is found to be around 1400 MeV, much smaller than the previous value of about 1535 MeV obtained without including its coupling to KLamda. The implication on the nature of N*(1535) is discussed.

Journal Article↗
PubMed2001

Expression of telomerase subunits in normal and neoplastic prostate epithelial cells isolated by laser capture microdissection.

BACKGROUND: Vertebrates have special structures at the ends of their chromosomes, known as telomeres, which may provide the chromosomes with stability and protect them from exonucleolytic degradation. The shortening of telomeric DNA with each cell division may lead to cell cycle arrest and/or apoptosis of a normal human somatic cell. Telomerase, an RNA-dependent DNA polymerase, elongates the 3'-ends of telomeric DNA. Thus, the presence of telomerase activity may reflect a cell's potential immortal state. The telomerase complex is comprised of several subunits. In the current study, the authors describe the use of laser capture microdissection (LCM) to procure pure matched tumor and normal cell populations from histologic sections and to determine the expression of telomerase subunits in these purified samples. METHODS: Pure matched tumor and normal prostate epithelial cells were procured by LCM using fresh frozen tissue samples obtained from patients undergoing radical prostatectomy. RNA was extracted from LCM captured cells, and the subunits for telomerase were assayed by reverse transcriptase-polymerase chain reaction. RESULTS: In 18 samples that were captured with LCM, only the catalytic subunit of telomerase, or hTERT, was found to be discriminatory between tumor cells (17 of 18 specimens, 94.4%) and nontumor cells (none of 18 specimens). TP1, a protein that has been shown to be associated with telomerase activity, was expressed in 3 of 18 normal cells (16.7%) and 15 of 18 tumor cells (83.3%). The RNA subunit of telomerase, or hTR, was expressed in 10 of 18 normal cells (55.6%) and 18 of 18 tumor cells (100%). There was no apparent correlation between telomerase subunit(s) expression and Gleason sum score. CONCLUSIONS: Molecular analyses of LCM cells from prostate carcinoma patient samples demonstrated transcriptional up-regulation of all telomerase subunits in the prostatic epithelium. However, only the catalytic subunit of telomerase, hTERT, was found to be discriminatory between neoplastic versus normal cells (94.4% vs. 0%). This finding suggests that the hTERT subunit may be a useful marker for the detection of prostate carcinoma and/or a potential target for therapy.

Catalytic Domain↗
PubMed2001

Effects of L-arginine on the proliferation of human renal mesangial cells and production of extracellular matrix.

AIM: To investigate the effect of L-arginine (L-arg) on the proliferation of human mesangial cells and production of collagen. METHODS: The influence of L-arg on the cell proliferation was determined by MTT assay, immunocytochemical detection of expression of proliferative cell nuclear antigen (PCNA), and flow cytometrical analysis of cell cycle. Procollagen III and total collagen level in the supernatant and expression of collagen IV mRNA in human mesangial cells were determined by radioimmunoassay, hydroxyproline colorimetric assay, and reverse transcription polymerase chain reaction (RT-PCR). RESULTS: L-Arg induced inhibition of human mesangial cell lines (HMCL) in a concentration- and time-dependent manner. Immunocytochemical study for PCNA showed the number of cells was decreased, though the percentage of PCNA positive cells was increased in L-arg-treated group. Flow cytometrical analysis showed that cells in S and G2/-M phases were markedly increased in L-arg-treated group compared with those in control group. Furthermore, L-arg significantly inhibited the production of procollagen III and total collagen in the supernatants determined by radioimmunoassay and hydroxyproline colorimetric assay (P < 0.05 and 0.01, respectively) and inhibited the expression of collagen IV mRNA determined by RT-PCR (P < 0.01). CONCLUSION: L-arg could exert an inhibitory effect on the proliferation of human mesangial cells and production of extracellular components, which strongly suggested its potential therapeutic role in the chronic renal scarring.

Arginine↗
PubMed2000

Non-competitive inhibition of 5-HT3 receptor-mediated currents by progesterone in rat nodose ganglion neurons.

The effect of progesterone on the serotonin type 3 (5-HT3) receptor-mediated response was studied in acutely dissociated rat nodose ganglion neurons by using the whole-cell voltage-clamp technique. Progesterone rapidly and reversibly inhibited 5-HT-induced currents in a dose-dependent manner, with an EC50 of 31 microM and a maximal inhibition of 75%. Neither the 5-HT response nor inhibition of the 5-HT response by extracellularly applied progesterone was significantly affected by inclusion of a saturating concentration of progesterone in the electrode buffer, arguing that progesterone acted at the extracellular surface of the membrane. Progesterone also inhibited the 5-HT response non-competitively by a voltage- and agonist-independent mechanism that was distinct from that of open-channel blockers.

Animals↗
PubMed2000

Telomerase in human bladder cancer.

Biomarkers for human bladder cancer are currently available and more are being developed. However, the ultimate goal of diagnosing bladder cancer consistently in a noninvasive fashion has not yet been achieved. Telomerase is an enzyme that may play a role in maintaining telomere sequences in the ends of chromosomes and its activity may reflect the presence of immortal or cancer cells. In this article, we reviewed the potential applications of telomerase in the diagnosis, monitoring, and treatment of human bladder cancer.

Antineoplastic Agents↗
PubMed2000

Clearance of increased serum advanced glycosylation end products in patients with end stage renal disease by hemodialysis.

AIM: To study the effect of removal of hemodialysis using acetate membrane on serum advanced glycosylation end products (AGEP) in 36 patients (59.1 +/- 1.6) with end stage renal disease (ESRD). METHODS: Serum AGEP levels were determined with quantitative fluorescence spectrometry, flow injection analysis (FIA), and competitive enzyme-linked immunosorbent assay (ELISA) using a polyclonal antibody directed against AGEP. RESULTS: The serum AGEP levels in patients with ESRD quantified by fluorescence spectrometry, FIA, and ELISA were higher than those in controls [(25 +/- 5) vs (7.5 +/- 1.5), (6.1 +/- 1.8) vs (1.4 +/- 0.5), and (37 +/- 20) vs (9 +/- 10) kU/L, respectively] and markedly reduced to [(22 +/- 6), (4.2 +/- 1.4), and (19 +/- 14) kU/L, respectively] after hemodialysis. CONCLUSION: Increased serum AGEP levels in the circulation of patients with ESRD were reduced effectively by hemodialysis.

Aged↗
PubMed1999

[Changes in blood pressure in normal rats transplanted with kidney of SHR].

The experiments were performed on spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats of 12 weeks old. Systolic blood pressure in WKY recipients receiving an SHR or WKY rat kidney was observed and the influence of immuoinhibitor cyclosporin (CsA) on blood pressure was investigated. The systolic blood pressure (SBP) of tail artery was measured by tail cuff technique in 6 WKY recipients of one SHR kidney and 6 WKY recipients of a WKY kidney from before transplantation to 5 weeks after transplantation. At the time when kidneys were harvested for transplantation from 12-week-old SHR and WKY rats, the SBP in WKY recipients was not significantly different. The SBP in WKY recipients of an SHR kidney was significantly higher than that in WKY recipients of a WKY kidney at 3, 4 and 5 weeks after transplantation. The immunoinhibitor CsA exerted no effect on the arterial blood pressure in either intact or uninephrectomized SHR and WKY rats. The results indicate that the kidney of SHR plays an important role in the pathogenesis of genetic hypertension.

Animals↗
PubMed1998

Detecting human bladder carcinoma cells in voided urine samples by assaying for the presence of telomerase activity.

BACKGROUND: In an attempt to find a more sensitive and specific noninvasive assay for the detection of bladder carcinoma, the authors assayed exfoliated cells from patients' voided urine for the presence of telomerase, an enzyme that maintains a cell's chromosomal length and is thought to be active in the transformation of normal somatic cells into immortal human tumor cells. METHODS: The authors used a polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP) assay to determine the presence of telomerase activity in voided urine samples from patients with known but yet untreated bladder carcinoma (n = 104) and from patients with hematuria of benign causes (n = 47). For 88 of the patients with bladder carcinoma, cytology was determined independently of the telomerase results or the pathology findings. RESULTS: Of the 104 bladder carcinoma specimens, 88 (85%) tested positive for the presence of telomerase. Seventy-nine percent (23 of 29) of the Grade 1 tumors, 84% (32 of 38) of the Grade 2 tumors, and 87.5% (28 of 32) of the Grade 3 tumors were positive for telomerase activity. Five patients with carcinoma in situ (100%) were also positive. Telomerase activity was not found in 31 of 47 patients with bladder calculi, benign urethral stricture, benign prostatic hyperplasia, or inflammation. In the 16 patients (34%) who did have a false-positive result when tested for telomerase, all had either chronic or severe inflammation, including 1 patient with an inverted papilloma, 1 patient with cystitis cystica, and 1 patient with cystitis glandularis. However, for 35 normal, healthy volunteers whose voided urine samples were also assayed for the presence of telomerase activity, none was found. By comparison, only 51% (45 of 88) of the cytology samples from patients with bladder carcinoma yielded positive findings, whereas 49% (43 of 88) resulted in false-negative readings for tumors. Only 13% (3 of 23) of the Grade 1 tumors, 44% (14 of 32) of the Grade 2 tumors, and 82% (23 of 28) of the Grade 3 tumors were diagnosed by cytology. All five patients with carcinoma in situ were positive for cytology as well as for telomerase activity. When cytology was compared with the PCR-based telomerase assay in determining the presence of bladder carcinoma, the difference in the overall detection rates (85% for telomerase vs. 51% for cytology) was significant (P < 0.001). Furthermore, when telomerase activity was compared with cytology for low grade lesions (Grades 1 and 2), the difference in the detection rates (82% for telomerase vs. 31% for cytology) was also significant (P < 0.001). CONCLUSIONS: Urinary cytology yields poor results for low grade tumors. This study shows the possible application of the telomerase assay in detecting bladder carcinoma, in particular low grade tumors, in voided urine samples.

Adult↗
PubMed1998

Sensitivity and specificity of NMP-22, telomerase, and BTA in the detection of human bladder cancer.

OBJECTIVES: The recent introduction of novel molecular markers into clinical urology has created a need to evaluate the efficacy and utility of these potential markers. The ideal assay for bladder cancer should be noninvasive, sensitive, specific, and cost-effective. We compared the Matritech nuclear maxtrix protein (NMP)-22 assay, telomerase activity, and the Bard bladder tumor antigen (BTA) assay for the detection of human bladder cancer. METHODS: A single voided urine sample was obtained from patients with hematuria without bladder cancer and from patients with known bladder cancer before any treatment. Approximately 50 to 100 mL of voided urine sample was collected and aliquotted for the various assays. The results were compared to single cytologic results and ultimately to pathologic findings. RESULTS: In 47 patients with bladder cancer, the overall sensitivity was 81% for NMP-22, 80% for telomerase, 40% for BTA, and 40% for cytology. For Ta tumors (n = 31), sensitivity was 81% for NMP-22, 70% for telomerase, 32% for BTA, and 26% for cytology. For T1 or higher stage tumors (n = 13), sensitivity was 82% for NMP-22, 91% for telomerase, 64% for BTA, and 64% for cytology. The remaining 3 patients had carcinoma in situ (CIS). When tumors were stratified by tumor grade, grade I tumors (n = 16) were detected at 69% with NMP-22, 65% with telomerase, 13% with BTA, and 6% with cytology. Grade II tumors (n = 14) were detected at 86% with NMP-22, 72% with telomerase, 36% with BTA, and 36% with cytology. Grade III tumors (n = 14) were detected at 93% with NMP-22, 93% with telomerase, 79% with BTA, and 79% with cytology. Patients with CIS (n = 3) were detected at 67% with NMP-22, 100% with telomerase, 33% with BTA, and 67% with cytology. In 30 patients with hematuria but without bladder cancer, the overall specificity of the assays was 77% for NMP-22, 80% for telomerase, 73% for BTA, and 94% for cytology. CONCLUSIONS: In the population tested, NMP-22 and the telomerase assays gave similar sensitivity and specificity for the detection of bladder cancer, and appear to offer a greater sensitivity than the BTA assay and/or conventional cytology.

Aged↗
PubMed1998

Urinary telomerase and its possible role as a marker for bladder cancer.

Voided urine from patients with bladder cancer and from control patients with either hematuria or with no urologic conditions were examined for telomerase activity in order to explore the possibility that this activity could be used as a marker for the detection of bladder cancer. This assay was found to have an overall sensitivity in detecting bladder cancer of 85% (88/104) with 79% (23/29) grade 1 tumors, 84% (32/38) grade 2 tumors, 87.5% (28/32) grade 3 tumors, and 100% (5/5) carcinoma in situ testing positive. This compared favorably with urinary cytology which had an overall sensitivity of 51% and sensitivities of 13%, 44%, 82%, and 100% for grades 1, 2, 3 tumors and carcinoma in situ, respectively. The specificity of telomerase in patients with benign causes of hematuria was 66%, and in normal volunteers without urologic conditions, it was 100%. Assessment of nuclear matrix protein suggested comparable sensitivity and specificity. Evaluation of bladder tumor antigen showed less sensitivity for low-grade disease and less specificity, as it was influenced by inflammation and instrumentation. Telomerase thus seems to be a means whereby low-grade tumors may be detected in examination of voided urine and may offer an advantage in monitoring for recurrent disease.

Biomarkers, Tumor↗
PubMed1998

Role of dNTPs in mutagenesis.

The induced mutation frequency by alkylating mutagen glycidyl methacrylate (GMA) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated with or without perturbation of deoxyribonucleoside triphosphate (dNTP) pools; the influence of short treatment at different concentrations of GMA or MNNG on dNTP pools was also explored. The results indicated that the induced mutation frequency increased greatly at high dosages of mutagen (GMA approximately 64 micrograms/ml, MNNG approximately 8 micrograms/ml) and the perturbation on dNTP pools was carried out before the treatment of mutagen; the short treatment with mutagen could induce distinct fluctuations of dNTP pools, but different mutagen might have different effects on dNTP pools. According to the results of the present study and other reports in literature, we conclude that dNTP pools may be the targets of alkylating mutagens and the fluctuations of dNTP pools are closely associated with mutagenesis.

3T3 Cells↗
PubMed1998

Role of deoxyribonucleoside triphosphates (dNTPs) in cell transformation.

Deoxyribonucleoside triphosphate (dNTP) pools were measured in normal BALB/c3T3 cells, transformation-treated cells and transformed cells with reverse-phase HPLC. The fluctuation of dNTP pools was similar after transformation treatment with alkylating mutagen glycidyl methacrylate (GMA) or Nmethyl-N'-nitro-N-nitrosoguanidine (MNNG). However, the gap between deoxyguanosine triphosphate + deoxyadenosine triphosphate (dGTP + dATP) pools and deoxythymidine triphosphate + deoxycytidine triphosphate (dTTP + dCTP) pools was greatly intensified. The measurements also indicated that the dNTP pools in transformed cells were quite different from those in normal cells. The results suggested that dNTP pools may play an important role in cell transformation.

3T3 Cells↗
PubMed1998

p53 gene mutations in asbestos associated cancers.

The accumulation of mutant p53 protein in cancer cells was observed by immunohistochemistry analysis. DNA was extracted from paraffin-embedded tissue. Exons 5, 7 and 8 were amplified and studied by PCR-SSCP and sequencing analysis. Ten cases of asbestos associated cancer tissue were studied, of which five cases had adenocarcinoma, and the other five had mesothelioma, squamous carcinoma, small cell lung cancer, adenosquamous carcinoma and malignant lymphoma respectively. Employing monoclonal antibody PAb1801, five cases were found to be mutant p53 protein positive. Seven cases were found to have mutations by PCR-SSCP. A total of 7 cases (8 mutations) were found to be positive and 4 cases were found to be positive by both of these analyses. Of the 8 mutations found by SSCP analysis, 4(50%, 4/8) were clustered in exon 8. A high mutation frequency was noticed in adenocarcinoma (80%, 4/5). Sequencing analysis on two specimens revealed two hotspot mutations. In codon 234, TAC for tyrosin was mutated to AAC for asparagine by a T to A transversion of the first letter. In codon 273, CGT for arginine was mutated to AGT for serine by a C to A transversion of the first letter. In conclusion, the mutation of p53 gene is common in asbestos associated cancers. However, the mutational spectrum of asbestos associated cancers might be different from that of non-asbestos associated cancers.

Adenocarcinoma↗
PubMed1997

Applications of telomerase in urologic oncology.

Vertebrates have special structures at the ends of their chromosomes, known as telomeres, which are composed of 5- to 15-kb pairs of a guanine-rich hexameric repeat (TTAGGG)n. In normal somatic cells there is a progressive degradation of telomeres with aging. The cell can afford to lose only a finite number of these telomeres before significant sequences of the parent DNA are lost, resulting in chromosomal instability and cell death. However, germ-cell telomeres are maintained despite multiple rounds of replication. This suggests that they produce an enzyme that maintains their telomere length. This enzyme, a ribonucleoprotein, is called telomerase. In this review, we discuss the presence of telomerase activity in various human cancers and, in particular, in urologic tumors. We describe the potential clinical utility of detection of the presence of telomerase activity in cells from voided urine samples of patients with bladder cancer.

Enzyme Inhibitors↗
PubMed1997

Modulation of N-myc expression alters the invasiveness of neuroblastoma.

N-myc oncogene expression plays a pivotal role in the biology of neuroblastoma, a common childhood tumor. High N-myc expression is associated with advanced disease stage, and in animal models, increased expression results in increased metastatic potential. In normal embryologic development, N-myc expression is associated with neuroblast migration out from the neural crest. To further define the relationship between N-myc and metastasis, an in vitro assay was adapted to measure tumor cell attachment, motility, and proteolytic ability in neuroblastoma cell lines. These parameters were examined in a non-amplified, uniformly N-myc overexpressing cell line and its anti-sense N-myc expressing clones. These lines have been characterized previously, and have a decrease in N-myc expression, growth rate, and tumorigenicity relative to the parent line and vector-only control transfectant. Decrease in N-myc expression resulted in a non-proportional increase of tumor cell attachment, and a proportional decrease in both tumor cell motility and proteolytic ability. In further experiments, assay of a N-myc-amplified overexpressing cell line with an intrinsic heterogeneous pattern of expression demonstrated that motile cells expressed higher amounts of N-myc relative to the general population. Together these relationships indicate that N-myc plays a causative role in the invasive phenotype, and suggest that metastasis may, in part, result from the disruption of a developmentally important normal process.

Cell Adhesion↗