Biomedical subjects

W Du

Publications and source records attributed to W Du.

At least 73 records · Page 4Linked to original sources

PubMed2000

[Determination of O6-methylguanine by high performance capillary zone electrophoresis].

In this paper, a method to determine O6-methylguanine in urine by high performance capillary zone electrophoresis has been established. O6-methylguanine was directly introduced into the capillary employing sodium borate at pH 9.0 as buffer. The capillary used was 75 microns i.d. x 57 cm. The calibration curve showed good linearity, r = 0.9987, CVs were 1.51% for intra-day and 1.93% for inter-day. The average recovery was 98.2%. In conclusion, this method is a simple, rapid, precise and reliable technique for O6-methylguanine measurement in urine.

DNA Adducts↗

PubMed2000

[The research development of single nucleotide polymorphism].

Single nucleotide polymorphism(SNP) is a novel set of polymorphism based on the single nucleotide variations at the genomic level, which distributes widely across the human genome and has high polymorphism information content (PIC). Now, tens of thousands SNPs have been discovered among the human genome and are introduced by many biological medicine networks. With the development of identification and analysis technique for SNP, especially the combination with DNA chips, they, as the third generation of genetic markers, are gradually fitable for fine-scale mapping of diseases, especially the complex diseases susceptibility genes and will eventually substitute for the most commonly used microsatellite markers presently.

Genetic Markers↗

PubMed2000

[Determination of kalium in husked seed food by suspension sampling-flame atomic emission spectrometry].

Suspension sampling technique was applied to flame atomic emission spectrometry and Kalium in husked rice, millet and husked Kaoliang successfully determined. A new method for rapid determination of kalium was developed. The samples were grinded and then made into agar suspension. NaCl solution was added to an appropriate amount of suspension for eliminating ionijation interference, and test solution prepared. The test solution was injected into air-acetylene flame. The working curve method was used for the determination. Results were consistent with those obtained by ashing method. RSD < 3.0%. Relative error of the two methods was less than +/- 1.8%. The t-test showed that no difference was found. This method is convenient, rapid and accurate.

Oryza↗

PubMed1999

Paclitaxel, cisplatin, and 5-fluorouracil for patients with advanced or recurrent squamous cell carcinoma of the head and neck.

BACKGROUND: The combination of cisplatin and 5-fluorouracil (5-FU) is considered standard therapy for patients with recurrent or metastatic squamous cell carcinoma of the head and neck (SCCHN). Paclitaxel has exhibited single-agent activity in patients with this disease. The authors conducted this study to evaluate the feasibility and efficacy of combining paclitaxel with cisplatin and 5-FU for patients with advanced or recurrent SCCHN. METHODS: Patients with recurrent, metastatic, or locally advanced SCCHN who had measurable or evaluable disease and no prior chemotherapy were eligible. The starting dose level consisted of paclitaxel 135 mg/m(2) on Day 1, cisplatin 75 mg/m(2) on Day 2, and 5-FU 1 gm/m(2)/day on Days 2-6. Due to Grade 4 mucositis, dose level 1 of 5-FU was reduced to 800 mg/m(2)/day on Days 2-6 (for 7 patients), and subsequently the 5-FU dose was adjusted to 1 gm/m(2)/day on Days 2-5 (for 17 patients). RESULTS: Twenty-five patients were enrolled, with a median age of 60 years and a median Southwest Oncology Group performance status of 1. Of the 25 patients, 16 had recurrent disease, 3 had metastatic disease at diagnosis, and 6 had untreated locally advanced SCCHN. Ninety-nine courses of therapy were administered, with a median of 5 courses. Major toxicities were neutropenia and mucositis. Significant neurotoxicity or nephrotoxicity were not observed. There were two treatment-related deaths (one each due to mucositis and neutropenic pneumonia), and these precluded further dose escalation. Fifteen of the 25 patients (60%) achieved a major response. Of significance is the response rate of 58% (11 of 19 patients) in those with recurrent or metastatic disease who had a duration of response ranging from 3 to 19+ months. Two of these 19 patients continue to be in remission of 19+ and 15+ months' duration, respectively. The median survival for patients with recurrent or metastatic disease was 6 months (range, 1-26 months), with a 1-year survival rate of 37%. CONCLUSIONS: The dose and schedule for the combination of paclitaxel, 5-FU, and cisplatin as determined in this study are feasible, with encouraging outcomes and activity in patients with recurrent or metastatic SCCHN. The results of this trial warrant larger-scale evaluation to determine the role of this combination in the management of patients with this disease.

Adult↗

PubMed1999

Geranylgeranylated RhoB mediates suppression of human tumor cell growth by farnesyltransferase inhibitors.

Farnesyltransferase inhibitors (FTIs) are in clinical trials, but their mechanism of action is not fully understood. We have shown that FTI treatment rapidly elevates the level of geranylgeranylated RhoB in cells and that this event is sufficient to inhibit cell cycle transit and reverse malignant transformation without affecting normal cells. However, because these observations were made in rodent fibroblast models in which transformation was driven by defined genetic alterations, it remained to be established whether RhoB-GG was relevant to the antineoplastic effects of FTIs in human epithelial tumor cells with diverse genetic backgrounds. In this study, we show that elevated levels of RhoB-GG are sufficient to block the proliferation of FTI-sensitive but not FTI-resistant human carcinoma cells. RhoB-GG induced the cell cycle kinase inhibitor p21(WAF1) in a p53-dependent manner, similar to FTI treatment, but this event was dispensable because RhoB-GG could still inhibit the growth of p53-null cells that lacked p21WAF1 activation. Consistent with actions beyond G1-phase arrest, certain cell lines exhibited accumulation in G2-M phase or an increased apoptotic index in response to RhoB-GG. We concluded that RhoB-GG suppressed human tumor cell proliferation by more than one mechanism and that it promoted apoptosis as well as inhibited cell cycle transit in malignant epithelial cells. These findings suggest how FTIs suppress the growth of human tumor cells that lack Ras mutations.

Alkyl and Aryl Transferases↗

PubMed1999

Multidrug resistance phenotype in high grade soft tissue sarcoma: correlation of P-glycoprotein immunohistochemistry with pathologic response to chemotherapy.

BACKGROUND: P-glycoprotein-mediated drug efflux has been implicated as an important mechanism of multidrug resistance (MDR) in cancer. Its role in chemotherapy resistance in soft tissue sarcoma is unclear. METHODS: Tumor specimens prior to and following neoadjuvant chemotherapy from 29 cases of high grade soft tissue sarcoma were analyzed with 2 monoclonal antibodies (C494 and JSB-1) that recognize different epitopes of P-glycoprotein. Staining intensity was graded 0 = negative, 1 = equivocal, 2 = moderate, 3 = strong. Only cases with Grade 2 or 3 staining intensity with both antibodies were considered MDR positive. The resection specimens were evaluated for tumor necrosis postchemotherapy. Pathologic response was graded as good for <15%, moderate for 15-50%, or poor for >50% posttreatment tumor viability. RESULTS: Of the 29 pretreatment specimens, 10 (34%) were MDR positive and 19 (66%) were MDR negative. Pathologic response to treatment was characterized as good in 6, moderate in 7, and poor in 16 patients. Of the MDR positive biopsies, 9 (90%) had poor response, compared with 7 (36%) in the MDR negative biopsy group (P = 0.0078). None of the cases with MDR positive biopsies had a good response, compared with 6 cases in which biopsies were MDR negative (32%) (P = 0.057). Only one MDR negative case became MDR positive posttreatment. CONCLUSIONS: Expression of MDR phenotype is found in approximately one-third of high grade soft tissue sarcomas. These preliminary data show a significant correlation between MDR phenotype and poor pathologic response to chemotherapy, and suggest that MDR induction by chemotherapy in soft tissue sarcoma is an uncommon event.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Activation of the PI3'K-AKT pathway masks the proapoptotic effects of farnesyltransferase inhibitors.

Farnesyltransferase inhibitors (FTIs) usually cause growth inhibition, but in certain preclinical settings they have been shown to induce apoptosis, a clinically desirable response. In this study, we show that the proapoptotic effects of FTIs in Ras-transformed cells are masked by activation of phosphatidylinositol 3'-kinase (PI3'K) or AKT, which are controlled by cytokines and integrins. The results implied that FTIs disrupt a signal that is crucial for survival of malignant cells, but not normal cells, if the PI3'K-AKT pathway is inactivated. Our findings have implications for clinical applications of FTIs where apoptotic responses would be preferred.

Alkyl and Aryl Transferases↗

PubMed1999

Mechanism for elimination of a tumor suppressor: aberrant splicing of a brain-specific exon causes loss of function of Bin1 in melanoma.

Loss of tumor suppressors that restrain important oncoproteins such as c-Myc may contribute to malignant progression. Bin1 is an adapter protein with features of a tumor suppressor that was identified through its interaction with and inhibition of the oncogenic properties of c-Myc. In this study, we analyzed the patterns of Bin1 expression in normal melanocytes and melanoma cells at different stages of tumor progression. Evidence is provided that Bin1 function is abrogated in melanoma cells by a mechanism based on aberrant splicing of a tissue-specific exon. Specifically, most melanoma cells inappropriately expressed exon 12A, which is spliced alternately into Bin1 isoforms found in brain but not into isoforms found in melanocytes and many other nonneuronal cells. Exon 12A sequences abolished the ability of Bin1 to inhibit malignant transformation by c-Myc or adenovirus E1A. Similarly, these sequences abolished the ability of Bin1 to induce programmed cell death in melanoma cells that endogenously expressed exon 12A. Our findings suggest that aberrant splicing of Bin1 may contribute to melanoma progression, and they define a mechanism by which the activity of a tumor suppressor can be eliminated in cells.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Effects of prenatal cocaine exposure on amphetamine-induced dopamine release in the caudate nucleus of the adult rabbit.

Acute amphetamine (AMPH) challenge has been used to probe the neurochemical and behavioral integrity of dopaminergic neurons under various conditions including prenatal cocaine exposure. In this study, we employed in vivo microdialysis to examine the effects of prenatal cocaine exposure on AMPH-induced dopamine (DA) release in the caudate nucleus of the awake adult rabbit. Pregnant rabbits were given intravenous injections of either saline or cocaine (4 mg/kg) twice a day from gestational day 8 (G8) through G29. Microdialysis was performed in adult saline and cocaine progeny at approximately postnatal day 70 (P70). There were no significant differences between cocaine and saline progeny in their basal concentrations of DA or its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). AMPH (5 mg/kg, i.v.) significantly increased extracellular DA in the caudate of both groups. However, AMPH-induced DA release was 2 to 3-fold greater in cocaine progeny than in the saline controls. Although, DOPAC decreased in both groups following AMPH injection, there was no significant group effect. In addition, there were no significant changes in concentrations of HVA. AMPH is known to release DA by a mechanism of exchange diffusion via the presynaptic DA transporter (DAT). Therefore, we examined the binding of [(3)H]WIN 35,428 to membrane fractions prepared from fresh caudate tissue to determine whether prenatal exposure to cocaine had altered the density (B(max)) or affinity (K(d)) of the DAT. While the B(max) for [(3)H]WIN 35,428 binding increased 3-fold between P3 and P120, there were no significant differences between saline and cocaine progeny at any age examined. The K(d) for [(3)H]WIN 35,428 binding did not change with postnatal age and did not differ between cocaine and saline progeny. These findings suggest that prenatal exposure to cocaine produces a long-term increase in the size of the presynaptic, AMPH releasable, cytoplasmic pool of DA.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1999

Bin1 functionally interacts with Myc and inhibits cell proliferation via multiple mechanisms.

The tumor suppressor Bin1 was identified through its interaction with the N-terminal region of Myc which harbors its transcriptional activation domain. Here we show that Bin1 and Myc physically and functionally associate in cells and that Bin1 inhibits cell proliferation through both Myc-dependent and Myc-independent mechanisms. Bin1 specifically inhibited transactivation by Myc as assayed from artificial promoters or from the Myc target genes ornithine decarboxylase (ODC) and alpha prothymosin (pT). Inhibition of ODC but not pT required the presence of the Myc binding domain (MBD) of Bin1 suggesting two mechanisms of action. Consistent with this possibility, a non-MBD region of Bin1 was sufficient to recruit a repression function to DNA that was unrelated to histone deacetylase. Regions outside the MBD required for growth inhibition were mapped in Ras cotransformation or HepG2 hepatoma cell growth assays. Bin1 required the N-terminal BAR domain to suppress focus formation by Myc whereas the C-terminal U1 and SH3 domains were required to inhibit adenovirus E1A or mutant p53, respectively. All three domains contributed to Bin1 suppression of tumor cell growth but BAR-C was most crucial. These findings supported functional interaction between Myc and Bin1 in cells and indicated that Bin1 could inhibit malignant cell growth through multiple mechanisms.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Elevation of alpha2(I) collagen, a suppressor of Ras transformation, is required for stable phenotypic reversion by farnesyltransferase inhibitors.

Farnesyltransferase inhibitors (FTIs) are a novel class of anticancer drugs that can reverse Ras transformation. One of the intriguing aspects of FTI biology is that continuous drug exposure is not necessary to maintain phenotypic reversion. For example, after a single exposure to FTIs, Ha-Ras-transformed fibroblasts revert to a flat and anchorage-dependent phenotype that persists for many days after processed Ras has returned to pretreatment levels. In this study, we show that persistence of the reverted state is mediated by elevated expression of the collagen isoform alpha2(I), a suppressor of Ras transformation the transcription of which is repressed by activated Ras and derepressed by FTI treatment. To our knowledge, this is the first report identifying an FTI-regulated gene which is linked to phenotypic reversion. The finding that extracellular matrix alterations can influence the kinetics of reversion supports our assertion that Rho-regulated cell adhesion parameters are a crucial determinant of the cellular response to FTIs.

Alkyl and Aryl Transferases↗

PubMed1999

The role of RBF in the introduction of G1 regulation during Drosophila embryogenesis.

The first appearance of G1 during Drosophila embryogenesis, at cell cycle 17, is accompanied by the down-regulation of E2F-dependent transcription. Mutant alleles of rbf were generated and analyzed to determine the role of RBF in this process. Embryos lacking both maternal and zygotic RBF products show constitutive expression of PCNA and RNR2, two E2F-regulated genes, indicating that RBF is required for their transcriptional repression. Despite the ubiquitous expression of E2F target genes, most epidermal cells enter G1 normally. Rather than pausing in G1 until the appropriate time for cell cycle progression, many of these cells enter an ectopic S-phase. These results indicate that the repression of E2F target genes by RBF is necessary for the maintenance but not the initiation of a G1 phase. The phenotype of RBF-deficient embryos suggests that rbf has a function that is complementary to the roles of dacapo and fizzy-related in the introduction of G1 during Drosophila embryogenesis.

Animals↗

PubMed1999

VEGF and VEGF type C play an important role in angiogenesis and lymphangiogenesis in human malignant mesothelioma tumours.

The vascular endothelial growth factor (VEGF) family is a novel regulator of endothelial cell proliferation. We assessed the mRNA expression of VEGF, VEGF type C (VEGF-C) and their receptors together with the microvessel density (VD) and microlymphatic vessel density (LVD) in pursuit of their connection and prognostic value in malignant pleural mesothelioma (MPM). We used four human MPM cell lines, 54 MPM tumours and five normal pleural tissues. Expression levels for receptors and ligands were assessed by semiquantitative reverse transcriptase polymerase chain reaction analysis. Microvessels were highlighted by immunohistochemical staining for factor VIII. The discrimination of lymphatics was performed by enzyme-histochemistry for 5'-nucleotidase after adequate inhibition of non-specific activity. The expression levels of VEGF, VEGF-C and VEGFRs were high in all MPM cell lines. The percentages of tumours with higher expression compared to the mean values of normal pleural tissues were 31.5% (17/54) for VEGF, 66.7% (36/54) for VEGF-C, 20.4% (11/54) for fms-like tyrosine kinase (flt)-1, 42.6% (23/54) for kinase insert domain-containing recepter (KDR) and 59.3% (32/54) for flt-4. Significant positive correlations were found between VEGF-C and flt-4, VEGF and KDR, VEGF and flt-1 in tumour tissues. The association between LVD and VEGF-C expression level was especially strong (P< 0.0001, r= 0.63). There were also significant correlations between LVD and flt-4, and VD and VEGF. No correlation, however, was found between LVD and nodal metastasis. VD was a negative prognostic indicator in this study. The associations between VEGFNEGF-C and vessel density suggest that these factors play an important role in angiogenesis and lymphangiogenesis in this tumour, and assessment of vascularity may be a useful prognostic indicator for MPM patients.

5'-Nucleotidase↗

PubMed1999

Accrual to breast cancer clinical trials at a university-affiliated hospital in metropolitan Detroit.

Despite the large number of available studies, most women with breast cancer do not participate in clinical trials, and this is especially true among lower income and minority women. In this study the authors surveyed the practice patterns of four medical oncologists who comprised the clinical breast service at a large urban university hospital to develop a better understanding of the clinical trials enrollment process for women with breast cancer. Of 136 new female breast cancer patients seen by the four physicians over a 7-month period, there were 47 women (34%) offered participation in a clinical trial, and 16 women (12%) were eventually enrolled. Women who were offered participation were more likely to be younger (p = 0.068) and to have earlier stage disease then were women not offered participation (p = 0.008). Women enrolled into a trial were also more likely to be younger, although this difference was not statistically significant (p = 0.114). Patient race was not associated with the accrual or enrollment process. Over half of the women were not offered participation in clinical trials because of the lack of available studies. Further work evaluating the process of patient enrollment and physician and patient barriers is necessary to develop effective strategies for recruitment into breast cancer clinical trials.

Breast Neoplasms↗

PubMed1999

Prognostic significance of p53 gene mutations in laryngeal cancer.

OBJECTIVE/HYPOTHESIS: We examined whether p53 gene mutations were predictive of clinical behavior in laryngeal cancer. STUDY DESIGN: Retrospective study of 45 patients with laryngeal cancer from 1985 to 1997. METHODS: DNA was extracted from tumor tissue and subject to polymerase chain reaction single-strand conformational polymorphism (PCR-SSCP) as well as DNA sequencing. The clinical outcome was correlated to the presence or absence of a p53 mutation. RESULTS: The p53 gene was analyzed by direct DNA sequencing and was found to be mutated in 33% (15/45) of patients. The presence of a p53 mutation was associated with a significant improvement in overall survival (80% vs. 43%, P < .03) and a trend toward improved disease-free survival (87% vs. 60%, P = .08). When other prognostic factors were adjusted, multivariate analysis revealed a trend toward improvement in overall survival as well as disease-free survival. CONCLUSION: Depending on the location of a p53 mutation, the suppressive functions or clinical outcome may or may not be affected. Fifty-three percent of mutations were detected in nonconserved regions as opposed to 17% as reported in colon cancer. In colon cancer, mutations in conserved regions of the p53 gene predicted a poorer survival, whereas nonconserved gene mutations were not predictive. In our group of patients. p53 mutations predicted a better prognosis, which may be due to a large proportion of mutations that lie within nonconserved areas. The predictive power of p53 gene mutations may depend on functional loss and inactivation of highly conserved areas and must be tested in a prospective trial.

Adult↗

PubMed1999

Green fluorescent protein as a reporter to monitor gene expression and food colonization by Aspergillus flavus.

Transformants of Aspergillus flavus containing the Aequorea victoria gfp gene fused to a viral promoter or the promoter region and 483 bp of the coding region of A. flavus aflR expressed green fluorescence detectable without a microscope or filters. Expression of green fluorescent protein fluorescence was correlated with resistance to aflatoxin accumulation in five corn genotypes inoculated with these transformants.

Aspergillus flavus↗

PubMed1999

Cell growth inhibition by farnesyltransferase inhibitors is mediated by gain of geranylgeranylated RhoB.

Recent results have shown that the ability of farnesyltransferase inhibitors (FTIs) to inhibit malignant cell transformation and Ras prenylation can be separated. We proposed previously that farnesylated Rho proteins are important targets for alternation by FTIs, based on studies of RhoB (the FTI-Rho hypothesis). Cells treated with FTIs exhibit a loss of farnesylated RhoB but a gain of geranylgeranylated RhoB (RhoB-GG), which is associated with loss of growth-promoting activity. In this study, we tested whether the gain of RhoB-GG elicited by FTI treatment was sufficient to mediate FTI-induced cell growth inhibition. In support of this hypothesis, when expressed in Ras-transformed cells RhoB-GG induced phenotypic reversion, cell growth inhibition, and activation of the cell cycle kinase inhibitor p21WAF1. RhoB-GG did not affect the phenotype or growth of normal cells. These effects were similar to FTI treatment insofar as they were all induced in transformed cells but not in normal cells. RhoB-GG did not promote anoikis of Ras-transformed cells, implying that this response to FTIs involves loss-of-function effects. Our findings corroborate the FTI-Rho hypothesis and demonstrate that gain-of-function effects on Rho are part of the drug mechanism. Gain of RhoB-GG may explain how FTIs inhibit the growth of human tumor cells that lack Ras mutations.

3T3 Cells↗

PubMed1999

[The relationship between IgA nephropathy and HBV infection].

OBJECTIVE: To clarify the correlation between hepatitis B virus (HBV) infection and the pathogenesis of IgA nephropathy. METHODS: Ninety-one cases of primary IgA nephropathy were investigated by using in situ hybridization(HBV DNA), immunohistochemistry (HBAg) and HBV DNA-HBAg double staining techniques. In some of the cases, Southern blot analysis and serologic HBV infectious markers were detected also. RESULTS: The positive rate of HBAg in renal tissue detected by immunohistochemistry was 69% (63/91) and that of the HBV DNA detected by in situ hybridization was 43% (39/91). Eighteen of 27 cases showed HBV DNA positive in Southern blot analysis, and all of the positive cases were identified to be the integrated form. Among them, 17 cases were HBAg detectable in renal tissue by immunohistochemistry and 16 cases were HBV DNA detectable by in situ hybridization simultaneously. The positive rate of the expression of HBcAg [77% (30/39)] and HBsAg [72% (28/39)] of the tubular epithelial cells with HBV DNA signals in nuclears by in situ hybridization was significantly higher than that of the cells without HBV DNA signals(10%, 21%). The double staining showed that most of the HBV DNA positive tubular epithelial cells coexpressed HBsAg and(or) HBcAg. CONCLUSION: The renal tissue of some of IgA nephropathy infected with HBV directly and express HBAg in situ.

Adult↗