Biomedical subjects

Q Wei

Publications and source records attributed to Q Wei.

At least 145 records · Page 8Linked to original sources

PubMed1997

[The long-term therapeutic results of chemotherapy combined with radiotherapy in advanced nasopharyngeal carcinoma].

OBJECTIVE: To evaluate the effect of chemothrapy combined with radiotherapy in advanced nasopharyngeal carcinoma (NPC). METHODS: From Dec. 1989 to Dec. 1990, 76 patients with locally advanced NPC (stage III or IV) were treated with 3 cycles of cisplatin [PDD, 20 mg.(m2)-1.day-1, i.v. on days 1-5] and 5-Fluorouracil (5-Fu, 700 mg.(m2)-1.day-1 by continuous i.v. infusion on days 1-5 followed shortly thereafter by radiotherapy. Eighty-six patients treated with radiotherapy alone in 1989 were taken as control. The methods and time/dose schedule of radiotherapy were similar in the two groups. RESULTS: The response rate to chemotherapy was 89.3% [complete response (CR) 18.4%]. The overall 5-year survival was 48.7% in the combined treatment group and 33.6% in the control group (P > 0.05). The 5-year survival in the combined treatment group was 44.1% and 39.5%, in patients with T2N3 and T2-4N3 and 21.6% and 20.4% in the control group, respectively (P < 0.05). CONCLUSION: This prospective study demonstrates that PDD/5-Fu chemotherapy followed by radiotherapy can improve 5-year survival in patients with T2-4N3 nasopharyngeal carcinoma.

Adolescent↗

PubMed1996

Genetic elevation of monoamine oxidase levels in dopaminergic PC12 cells results in increased free radical damage and sensitivity to MPTP.

Production of hydrogen peroxide as a by-product of the breakdown of catecholamines by the enzyme monoamine oxidase (MAO) has been hypothesized to contribute to the increased proclivity of dopaminergic neurons for oxidative injury. We established clonal dopaminergic PC12 cell lines which have elevated MAO activity levels resulting from transgenic expression of the B isoform of the enzyme. Both MAO-A and MAO-B have relatively equivalent affinities for dopamine, and since PC12 primarily express the A and not the B form of the enzyme, this allowed us to distinguish the transgenic MAO activity in these cells from endogenous using the MAO-B specific substrate PEA. Elevation of MAO activity levels in the MAO-B+ cells resulted in higher levels of both free radicals and free radical damage compared with controls. In addition, increased MAO-B levels within PC12 cells caused a dose-dependent increase in sensitivity to the toxin MPTP. Our data suggests that oxidation of catecholamines by MAO can contribute to free radical damage in catecholaminergic neurons and that the low MAO-B activity levels found endogenously in these cells likely accounts for their relative resistance to MPTP toxicity.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1996

Reduced DNA repair capacity in lung cancer patients.

Although lung cancer is the paradigm of a tobacco-induced malignancy, host-specific factors modulate susceptibility to tobacco carcinogenesis. Variations in DNA repair may influence the rate of removal of DNA damage and of fixation of mutations. To test the hypothesis that genetically determined DNA repair capacity (DRC) modulates lung cancer susceptibility, we conducted a pilot case-control study of 51 patients with newly diagnosed, previously untreated lung cancer and 56 controls identified from local community centers and frequency matched to the cases on age, sex, and ethnicity. The subjects were ascertained and interviewed for an ongoing molecular epidemiological investigation of lung cancer susceptibility. We measured DRC in the subjects' peripheral blood lymphocytes by using the host-cell reactivation assay, which measures cellular reactivation of a reporter gene damaged by exposure to 75 microM benzo(a)pyrene diol epoxide. The mean level of DRC in cases (3.3%) was significantly lower than that in controls (5.1%) (P < 0.01). Only nine cases (18%) had DNA repair levels greater than the median value of repair in the controls. This median level of DRC in controls was used as the cutoff value for calculating the odds ratios. After adjustment for age, sex, ethnicity, and smoking status, the cases were five times more likely than the controls to have reduced DRC (odds ratio, 5.7; 95% confidence interval, 2.1-15.7). Younger cases (< 65 years) and smokers were more likely than controls to have reduced DRC. These findings suggest that individuals with reduced DRC are at an increased risk of developing lung cancer.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed1996

Benzo(a)pyrene diol epoxide-induced chromosomal aberrations and risk of lung cancer.

Benzo(a)pyrene is considered a classic DNA-damaging carcinogen and is one of a multitude of polycyclic aromatic hydrocarbons commonly found in tobacco smoke and in the ambient environment. In this report, we describe the characteristics of chromosomal aberrations induced in vitro by activated benzo(a)pyrene diol epoxide (BPDE) in lymphocyte cultures of 172 normal individuals ages 19-95 years and present the analysis of a pilot case-control study of 33 lung cancer patients and 96 selected controls without history of cancer and frequency matched on age (50-85 years) to the cases. The BPDE-induced chromosomal aberrations were predominantly single chromatid breaks, with few isochromatid breaks or exchange figures. In the 172 normal subjects, the frequencies of both spontaneous and BPDE-induced chromatid breaks were not correlated with age, sex, ethnicity, or tobacco use. However, the frequency of BPDE-induced chromatid breaks was significantly correlated with the frequency of spontaneous chromatid breaks (r = 0.19, P < 0.05). In addition, Hispanics had significantly higher mean BPDE-induced chromatid breaks than did non-Hispanic whites (P < 0.01). From the case-control analyses, the frequency of BPDE-induced chromosomal aberrations was significantly higher in cases (mean, 0.67 breaks/cell) than in controls (mean, 0.41 breaks/cell; P < 0.0001). An adjusted odds ratio of 6.53 (95% confidence interval, 3.74-11.4) for lung cancer was associated with increased frequency of these chromosomal aberrations. The higher rate of BPDE-induced chromosomal aberrations may be due to inefficient DNA repair. These findings warrant additional molecular epidemiological studies. The BPDE mutagen sensitivity assay will facilitate epidemiological studies of genetic susceptibility to smoking-related cancers.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed1996

In vitro induction of benzo(a)pyrene diol epoxide-DNA adducts in peripheral lymphocytes as a susceptibility marker for human lung cancer.

Given the same exposure, DNA adduct profiles can be considered as a phenotypic marker for carcinogen metabolism and DNA repair, which may reflect individual susceptibility to chemical carcinogenesis. Based on this notion, we have established a straightforward assay that measures induced DNA adducts in peripheral lymphocytes exposed in vitro to a model carcinogen, benzo(a)pyrene diol epoxide (BPDE) by 32P-postlabeling. To test the hypothesis that the levels of induced DNA adducts are a predictor for cancer risk, we conducted a pilot study of 21 lung cancer patients and 41 healthy frequency-matched controls. We found that the peripheral lymphocytes of cancer patients tended to accumulate higher levels of BPDE-DNA adducts than controls did (mean +/- SE of relative adduct labeling x 10(7) value; 59.6 +/- 12.0 versus 39.4 +/- 6.1 for cases and controls, respectively; P = 0.09). Using the tertile relative adduct labeling value of controls (10 adducts/10(7) nucleotides) as the cutoff point, 18 of 21 cases and 23 of 41 controls distributed above this level (odds ratio, 4.7; 95% confidence interval, 1.2-18.5). In logistic regression analysis, the level of induced adduct was an independent risk factor (odds ratio, 6.4; 95% confidence interval, 1.3-29.4) after adjustment for the potential confounding factors, i.e., age, sex, ethnicity, and smoking. Stratified analyses showed that greater differences in DNA adduct levels induced by BPDE between cases and controls were observed in individuals younger than 65 years and in nonsmokers. Despite the small sample size, the significant association between the level of BPDE-induced DNA adducts and risk for lung cancer suggests that this assay is a promising method for further investigations.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed1996

Mutagen sensitivity and risk of gliomas: a case-control analysis.

Although the risk factors contributing to the etiology of brain tumors remain largely unknown, this pilot study suggests that genetically determined sensitivity to environmental carcinogens may play a role in the pathogenesis of these tumors. In this study, we examined short-term lymphocyte cultures from 45 adult malignant glioma patients and 117 age-, sex-, and ethnicity-matched healthy controls for mutagen-induced chromatid breaks and evaluated their family history of cancer, smoking, and demographic variables to ascertain the association between mutagen sensitivity and risk of brain tumors. The mutagen selected was gamma-radiation. The mean number of induced breaks/cell was 0.72 (SD=0.45) for the cases and 0.45 (SD = 0.35) for the controls (P < 0.0001). Using the median number of induced breaks/cell in the controls as the breakpoint for defining mutagen sensitivity, we observed an unadjusted odds ratio of 5.36 (95% confidence interval = 2.12-13.69) for mutagen sensitivity and brain tumor risk and an adjusted odds ratio of 5.79 (2.26-14.83), when we controlled for epidemiological risk factors including smoking, race, income, and education. Although a larger study is needed to confirm this intriguing result, these preliminary findings suggest that increased sensitivity to radiation is an independent risk factor for gliomas.

Adult↗

PubMed1996

Fluorescence in situ hybridization method for measuring transfection efficiency.

We describe here the use of fluorescence in situ hybridization (FISH) to measure the transfection efficiency of the transient expression vector pCMVcat in lymphoblasts and fibroblasts. By using a pCMVcat probe, we can visualize the location of the plasmid after transfection and thus determine transfection efficiency. In this report, we show that, for transfection of pCMVcat by the diethylaminoethyl-dextran method, the transfection efficiency was about 15 and 70 times greater in fibroblasts and lymphoblasts, respectively, when measured by the FISH method as compared to the efficiency measured by cotransfection with pCMV beta gal. Based on these results, we conclude that the FISH method is a highly sensitive, specific and direct measure of transfection efficiency of a transient expression vector and that it may be useful for evaluating laboratory assays in which the quantitative aspects of transfection and the effect of plasmid DNA damage on transfection efficiency are important.

Cell Line↗

PubMed1996

DNA repair capacity correlates with mutagen sensitivity in lymphoblastoid cell lines.

This study describes a correlation between cellular DNA repair capacity and the frequency of mutagen-induced in vitro chromosomal breaks in selected lymphoblastoid cell lines. Two assays, host cell reactivation (HCR) assay for measuring cellular DNA repair capacity and in vitro mutagen sensitivity assay, have recently been shown to be useful biomarkers for such susceptibility. Increased in vitro mutagen sensitivity, measured by the number of induced chromatid breaks, has been postulated to reflect decreased capacity of DNA repair, as measured by the HCR assay. However, these two assays have not been examined in parallel to test this hypothesis. In this study, we performed both assays in 16 established lymphoblastoid cell lines derived from patients with xeroderma pigmentosum (n = 3), ataxia telangiectasia (n = 2), head and neck cancer (n = 3), and melanoma (n = 2), and from normal human subjects (n = 6) using UV light, 4-nitroquinoline-1-oxide (4-NQO; an UV-mimetic agent), and gamma-irradiation as the test agents. The measurements from the HCR assay correlated significantly with the frequency of chromatid breaks induced by either UV irradiation (r = -0.69; P < 0.01) or 4-NQO (r = -0.70; P < 0.01). Although published data suggest that damage induced by UV and 4-NQO may be repaired by different pathways, the two agents induced similar frequencies of chromatid breaks (r = 0.68; P < 0.01) in the tested cell lines. Our results also indicated that the HCR assay is not suitable to test agents that cause DNA strand breaks, such as gamma-irradiation, whereas the mutagen sensitivity assay is. Although reduced cellular DNA repair capacity correlated with increased frequency of mutagen-induced chromatid breaks in these cell lines, these two assays have different sensitivities in measuring the repair of damage induced by different carcinogens; therefore, the use of both assays is recommended for future molecular epidemiological studies of cancer susceptibility.

4-Nitroquinoline-1-oxide↗

PubMed1996

[Expression of retroviral transduced human beta-globin gene in mouse fetal liver cells].

A replication-defective retrovirus vector containing the human beta-globin gene and 36-base-pair HS2 enhancer (N2A beta E36) was constructed and transferred into psi-2 and PA317 packaging cell lines. Titers of amphotropic recombinant retrovirus ranged from 10(3) to 10(4) CFU/ml. Southern blot analysis indicated that intact human beta-globin gene was stably integrated into the genome of the target cells. Northern blot hybridization analysis showed that human beta-globin gene could be expressed in mouse fetal liver cells.

Animals↗

PubMed1995

Binding of vanadium (IV) to the phosphatase calcineurin.

X-band electron spin resonance spectroscopy was used to study the binding of vanadium (IV), or vanadyl, to the brain serine/threonine phosphatase-2B, calcineurin. Spectra were determined on frozen solutions of vanadyl and calcineurin at pH 7.4 in the presence of 20% (v/v) glycerol. The binding of vanadyl to the enzyme was established, and the data suggested the presence of two classes of sites, the higher affinity class of which contained two binding sites for vanadyl. The calcium-binding B subunit of the heterodimeric protein was also shown to bind vanadyl. The holoprotein appeared to be stabilized by vanadyl, and vanadyl enhanced enzymatic activity when assayed with or without calmodulin in the absence of calcium.

Animals↗

PubMed1995

Simultaneous amplification of four DNA repair genes and beta-actin in human lymphocytes by multiplex reverse transcriptase-PCR.

We describe here the development, optimization, and use of a non-radioactive, quantitative, multiplex reverse transcriptase-PCR technique to measure, in a single reaction, the relative levels of the transcripts of four DNA repair genes (XPCC, hMSH2, XRCC1, and ERCC1) and the beta-actin gene in lymphoblastoid cell lines and frozen peripheral blood lymphocytes. Expression of defective DNA repair genes was not detected in DNA repair-deficient human cell lines, whereas the intact genes were detected in repair-proficient cell lines and in lymphocytes from a normal donor. The assay was reproducible, and repeated determinations of the same samples generated highly consistent results for each target gene. This approach should facilitate molecular epidemiological studies that incorporate screening for germline alterations that may affect gene expression and for changes in the levels of gene expression.

Actins↗

PubMed1995

Prospective study of occupational asthma to laboratory animal allergens: stability of airway responsiveness to methacholine challenge for one year.

The stability of airway hyperresponsiveness was studied in a group of 178 young adults working with laboratory animals. At the time of their entry into the study, 132 of 178 subjects (74%) had less than 20% response to the inhalation of 25 mg/ml methacholine, whereas 26 (15%) had a methacholine dose causing a 20% fall in forced expiratory volume in 1 second after fewer than 80 breath units. The distribution of methacholine responsiveness did not differ at 6 months and 1 year; 155 of 178 volunteers (90.4%) responded during the repeated challenges to doses within one dilution of their results at entry. One hundred forty-one subjects were consistently unreactive during the year, and 17 were consistently reactive. Approximately equal numbers gained and lost reactivity. Those with consistently positive responses to methacholine were more likely to have skin test reactivity and chest symptoms. The presence of consistent chest symptoms was loosely associated with consistent methacholine responsiveness; 55% of those with consistent hyperresponsive airways had symptoms, and 24% of those who consistently had symptoms had hyperresponsive airways. We concluded that the methacholine response is relatively stable during the course of a year in laboratory animal workers who remain at their jobs and that the presence of a positive skin test response to laboratory animals or of chest symptoms does not change the pattern of stable responsiveness.

Adult↗

PubMed1995

DNA repair capacity for ultraviolet light-induced damage is reduced in peripheral lymphocytes from patients with basal cell carcinoma.

Sunlight exposure and certain host factors such as red hair and fair skin are established risk factors for non-melanoma skin cancers. Because deficient DNA repair capacity has contributed to the development of skin cancers in a rare genetic disease, xeroderma pigmentosum, we explored this deficiency as an etiologic factor in a recent population study. We used a new DNA repair assay, the host-cell reactivation, in a clinic-based case-control study to test the hypothesis that reduced DNA repair is the underlying molecular mechanism for the development of sunlight-induced basal cell carcinoma. The peripheral lymphocytes from 88 patients with primary BCC and 135 cancer-free controls were tested for their capacity to repair ultraviolet light-induced DNA damage in a reporter gene, chloramphenicol acetyl transferase. All subjects were between the ages of 20 and 60 years and were frequency matched by age (+/- 5) and sex. Among those who reported frequent sunbathing, poor tanning ability, a history of multiple sunburns, exposure to chemicals, or multiple medical irradiations, the BCC patients had significantly lower DNA repair capacity than controls (p < 0.05). DNA repair capacity was also found substantially lower in the basal cell carcinoma patients who had red hair and light skin (type I). Compared to controls, basal cell carcinoma cases with selected risk factors had a relative decrease in DNA repair capacity of 10-28%. These findings provided evidence that reduced DNA repair capacity is one of the underlying molecular mechanisms for sunlight-induced skin carcinogenesis in the general population.

Adult↗

PubMed1995

Vaccine-induced protection of chimpanzees against infection by a heterologous human immunodeficiency virus type 1.

The extraordinary genetic diversity of human immunodeficiency virus type 1 (HIV-1) is a major problem to overcome in the development of an effective vaccine. In the most reliable animal model of HIV-1 infection, chimpanzees were immunized with various combinations of HIV-1 antigens, which were derived primarily from the surface glycoprotein, gp160, of HIV-1 strains LAI and MN. The immunogens also included a live recombinant canarypox virus expressing a gp160-MN protein. In one experiment, two chimpanzees were immunized multiple times; one animal received antigens derived only from HIV-1LAI, and the second animal received antigens from both HIV-1LAI and HIV-1MN. In another experiment, four chimpanzees were immunized in parallel a total of five times over 18 months; two animals received purified gp160 and V3-MN peptides, whereas the other two animals received the recombinant canarypox virus and gp160. At 3 months after the final booster, all immunized and naive control chimpanzees were challenged by intravenous inoculation of HIV-1SF2; therefore, the study represented an intrasubtype B heterologous virus challenge. Virologic and serologic follow-up showed that the controls and the two chimpanzees immunized with the live recombinant canarypox virus became infected, whereas the other animals that were immunized with gp160 and V3-MN peptides were protected from infection. Evaluation of both cellular and humoral HIV-specific immune responses at the time of infectious HIV-1 challenge identified the following as possible correlates of protection: antibody titers to the V3 loop of MN and neutralizing antibody titers to HIV-1MN or HIV-1LAI, but not to HIV-1SF2. The results of this study indicate that vaccine-mediated protection against intravenous infection with heterologous HIV-1 strains of the same subtype is possible with some immunogens.

AIDS Vaccines↗

PubMed1995

Regulation of CD4 T cell reactivity to self and non-self.

While the thymus may be effective in inducing tolerance to lymphoid associated antigens, it is not as efficient in deleting T cells reactive to peripheral tissue specific antigens. Therefore, to maintain self tolerance to peripheral tissues, post-thymic mechanisms must be invoked. One important way to prevent autoimmune pathology mediated by autoreactive CD4 T cells is the diversion of clones to regulatory Th2 effector cells. However, many different factors contribute in vivo to the decision of stimulated CD4 T cells to develop into Th1 versus Th2 cells. For example, T cell signaling pathways may influence the types of cytokines produced by naive T cells, and studies have provided evidence for a genetic polymorphism among common mouse strains that can significantly influence the early cytokine production in stimulated naive CD4 T cells. The allele carried by the BALB/c strain promotes IL-4 production, and consequently provides resistance to autoimmune diabetes in our transgenic mouse model. In addition, antigen presenting cells can influence the development of stimulated CD4 T cells in part through the production of cytokines such as IL-12. The absorption of IL-12 in vivo can permit the expansion of Th2 type effector cells, and this phenomenon will also protect mice from autoimmunity. Finally, the relative potency of various class II positive antigen presenting cell types can influence the development of autoreactive T cells, with dendritic cells apparently being the strongest stimulator of Th1 responses. Consistent with this notion, a relB knockout mouse, which is missing dendritic cells, appears to drive Th2 development even in response to viral infection. In sum, these various influences over the Th1/Th2 decision in vivo may provide new targets for immunotherapy of autoimmune diseases.

Animals↗

PubMed1995

DNA repair and epidemiology of basal cell carcinoma.

In a molecular epidemiological study of DNA repair, host reactivation assay was used to measure the DNA repair capacity of cryopreserved lymphocytes from 88 primary basal cell carcinoma (BCC) patients and 135 cancer-free controls. In this study population, reduced repair of ultraviolet radiation-induced DNA damage contributed to the risk of sunlight-induced BCC. A family history of BCC is associated with low DNA repair. Repair of ultraviolet radiation-damaged DNA declines at a rate of approximately 1%/year in noncancerous controls. Reduced DNA repair is more likely seen in young BCC patients, indicating that BCC is a premature aging disease of the skin. The persistence of photochemical damage because of reduced repair results in point mutations in the p53 gene and allelic loss of the nevoid BCC gene located on chromosome 9q. Xeroderma pigmentosum appears to be a valid paradigm for the role of DNA repair in BCC in the general population.

Adult↗

PubMed1995

ESR study on calcineurin.

X-band electron spin resonance spectroscopy was used to investigate the binding of Mn2+ to the apo-forms of calcineurin and its A and B subunits. The results indicated the presence of 2 Mn2+ binding sites of different affinities (20 mumol/L and 60 mumol/L) in the calcineurin A subunit and 4 Mn2+ binding sites in the calcineurin subunit B, 2 high affinity and 2 low affinity binding sites with Kd's of 4 mumol/L and 90 mumol/L, respectively. Interestingly and quite surprisingly, Mn2+ binding to the holoenzyme was characterized by only 2 binding sites with Kd's of 7 mumol/L and 33 mumol/L. However, in the presence of calmodulin about 10 Mn2+ sites were detected, and the Mn2+ calmodulin-calcineurin complex exhibited enzymatic activity. These results, based on direct spectral measurements of the metal ligand, demostrate that Mn2+ binds to both free subunits of calcineurin in a manner distinct from binding to the holoenzyme. Also, the data suggest that conformational changes occur upon heterodimer formation and association of the holoenzyme with the regulatory protein calmodulin.

Animals↗

PubMed1995

[Effect of erythroid enhancer on the expression of beta-globin gene in mice erythroleukemia (MEL) cells].

Our previous works have verified that the beta-globin gene carrying large fragments of erythroid enhancer transferred by retrovirus vector caused the unstable provirus integration and low virus titer in infected cells, but the 36bp enhancer had not this negative effect. In order to circumvent this problem, we inserted the intact beta-globin gene (beta) or partially IVS II deleted beta-globin gene (delta beta) and truncated erythroid enhancer (36bp, 292bp and 341bp) into the N2A retrovirus vector. Recombinants were transfected into psi-2 ecotropic pachaging cells first, then the produced virus were used to infect PA317 amphotropic packaging cells. Virus supernatent from PA317 clonies with high virus titer and intact provirus integration was used to infect MEL cells. RNase protection assay was used to detect the expression of beta-globin gene. Results showed that not only the stable provirus integration and high virus titer of the transferred genes, but also the high levels expression of beta-globin gene carrying 292bp or 341bp erythroid enhancer were got.

Animals↗