PubMed Health⌕ Search

Biomedical subjects

David Ross

Publications and source records attributed to David Ross.

At least 19 recordsLinked to original sources
PubMed2003

Kinetics of NAD(P)H:quinone oxidoreductase I (NQO1) inhibition by mitomycin C in vitro and in vivo.

The bioreductive activation of the antitumor quinone mitomycin C (MMC) by NAD(P)H: quinone oxidoreductase 1 (NQO1) is complicated by the ability of MMC to also act as a mechanism-based inhibitor of NQO1 in a pH dependent manner. Inhibition of NQO1 by MMC has been studied in purified enzyme preparations and in cultured cells but has not determined in vivo. In the studies presented here, NQO1 activity was measured in mouse tissues following treatment with MMC or the potent mechanism-based human NQO1 inhibitor 5-methoxy-1,2-dimethyl-[(4-nitrophenoxy)methyl]indole-4,7-dione (ES936). NQO1 activity was significantly decreased at 1, 2, and 4 h following MMC (10 or 20 mg/kg) treatment in kidney and lung but was unchanged in brain, heart, liver, and bladder. ES936 (1 mg/kg) treatment led to a significant and much more potent inhibition of NQO1 in all murine tissues analyzed except for bladder. To extrapolate these in vivo results from mice to humans, the species-specific kinetics of NQO1 inactivation by MMC was determined in vitro using mouse, rat, and human recombinant NQO1 proteins. Results showed the inactivation kinetics of mouse and human proteins by MMC were similar. Treatment of human and murine endothelial cells with MMC or ES936 showed similar inhibition of NQO1 activity. The aforementioned results clearly demonstrate that MMC can serve as a substrate for NQO1 in vivo; however, the metabolism resulting in enzyme inactivation is possibly tissue-specific. Furthermore, the kinetic similarities for inactivation between murine and human forms of NQO1 show these results are apropos to clinical use of MMC.

Animals↗
PubMed2003

Effect of caged fluorescent dye on the electroosmotic mobility in microchannels.

We report on measurements of electroosmotic mobility in polymer microchannels and silica capillaries with and without the addition of a caged fluorescein dye to the buffer. For PMMA microchannels, the mobility was found to increase from (2.6 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) to (4.6 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) upon addition of 1.2 mmol/L of caged dye. For PC microchannels, the mobility increased from (4.3 +/- 0.2) x 10(-4) cm2 V(-1) s(-1) to (5.4 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) upon addition of caged dye. For PDMS microchannels, the mobility increased from (4.3 +/- 0.2) x 10(-4) cm2 V(-1) s(-1) to (6.4 +/- 0.5) x 10(-4) cm2 V(-1) s(-1) upon addition of caged dye. For fused-silica capillaries, the mobility ((5.5 +/- 0.2) x 10(-4) cm2 V(-1) s(-1)) was unaffected by the addition of the caged dye.

Journal Article↗
PubMed2003

Interaction of human NAD(P)H:quinone oxidoreductase 1 (NQO1) with the tumor suppressor protein p53 in cells and cell-free systems.

NAD(P)H:quinone oxidoreductase 1 (NQO1) has been proposed to stabilize p53 via a redox mechanism involving oxidation of NAD(P)H as a consequence of the catalytic activity of NQO1. We report that treatment of HCT-116 human colon carcinoma cells with the NQO1 inhibitor ES936 had no effect on the levels of p53 protein. ES936 is a mechanism-based inhibitor of NQO1 that irreversibly blocks the catalytic function of the enzyme. This suggests that a redox mechanism involving NQO1-mediated NAD(P)H oxidation is not responsible for the stabilization of p53. We also examined the ability of the NQO1 protein to associate with p53 using co-immunoprecipitation experiments. Results from these experiments demonstrated co-immunoprecipitation of NQO1 with p53 and vice versa. The association between p53 and NQO1 was not affected by treatment of HCT-116 cells with ES936, demonstrating that the association was not dependent on the catalytic activity of NQO1. A comparison of isogenic HCT-116 p53+/+ and HCT-116 p53-/- cells demonstrated an interaction of NQO1 and p53 only in the p53+/+ cells. Experiments performed in an in vitro transcription/translation system utilizing rabbit reticulocyte lysates confirmed the interaction of NQO1 and p53. In these experiments a full-length p53 coding region was used to express p53 in the presence of recombinant NQO1 protein. An association of p53 and NQO1 was also observed in primary human keratinocytes and mammary epithelial cells. In studies where mdm-2 co-immunoprecipitated with p53, no association of mdm-2 with NQO1 was observed. These data demonstrate an association between p53 and NQO1 that may represent an alternate mechanism of p53 stabilization by NQO1 in a wide variety of human cell types.

Cell-Free System↗
PubMed2003

Rationales, obstacles and strategies for local outcome monitoring systems in substance abuse treatment settings.

The need for outcome monitoring systems (OMS) in substance abuse treatment is now such a pervasive position that it has achieved 'motherhood' stature. Yet, for a variety of reasons, implementation of systematic, ongoing monitoring continues to lag in most settings. The position taken in this article is that a local approach to monitoring is a viable alternative to large scale monitoring programs when such programs are unavailable. Moreover, local OMS can supplement these more generic programs by providing data that are more in tune with the orientation and program development of a specific setting. This article argues that local OMS can be developed with a reorganization of customary documentation procedures, a modest investment of personnel and specialized technical resources, a shorter-term view to outcome, and a commitment to evidence-based treatment.

Cost-Benefit Analysis↗
PubMed2003

Association of NAD(P)H: quinone oxidoreductase 1 (NQO1) C609T polymorphism with esophageal squamous cell carcinoma in a German Caucasian and a northern Chinese population.

NAD(P)H: quinone oxidoreductase 1 (NQO1) is an antioxidant enzyme, important in the detoxification of environmental carcinogens. A single base substitution (C --> T) polymorphism at nucleotide 609 (null-allele) of NQO1 gene impairs stability and function of the NQO1 protein. To investigate the association of this NQO1 polymorphism with susceptibility to esophageal squamous cell carcinoma (ESCC), the NQO1 C609T genotypes were determined by PCR-RFLP analysis in 450 patients with ESCC (257 German Caucasians and 193 northern Chinese) and 393 unrelated healthy controls (252 German Caucasians and 141 northern Chinese). Additionally, NQO1 protein expression was determined by immunohistochemistry in a subset of 74 ESCC (50 German, 24 Chinese). A significant difference in NQO1 C609T genotype distribution was observed between Caucasian healthy controls (C/C, 73.4%; C/T, 25.0%; T/T, 1.6%) and Chinese healthy controls (C/C, 34.0%; C/T, 49.7%; T/T, 16.3%) (chi(2) = 68.40, P < 0.001). The NQO1 T/T genotype significantly increased the risk for developing ESCC in both Caucasian subjects (OR = 4.62, 95% CI = 1.54-13.86) and Chinese subjects (OR = 1.81, 95% CI = 1.04-3.15), compared with the combined C/C and C/T genotypes. In Chinese subjects, this increased susceptibility was pronounced in patients with family history of upper gastrointestinal cancers (OR = 2.18, 95% CI = 1.14-4.17). Immunohistochemical analysis showed NQO1 protein expression in 53 carcinomas, whereas 21 carcinomas were negative. Negativity for NQO1 expression correlated strongly with the NQO1 genotype, being present in 8.6% of cases with C/C, 22.2% of cases with C/T and 100% of cases with T/T genotype (chi(2) = 16.60, P < 0.001). In summary, the association of the NQO1 C609T polymorphism with ESCC in genetically distinct populations makes a strong argument for its importance in carcinogenesis of ESCC in the German Caucasian and the northern Chinese population.

Adult↗
PubMed2003

EGF and TGF-alpha expression influence the developmental toxicity of TCDD: dose response and AhR phenotype in EGF, TGF-alpha, and EGF + TGF-alpha knockout mice.

The environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) produces cleft palate (CP) and hydronephrosis (HN) in mice. The etiology of these defects involves hyperproliferation of epithelial cells of the secondary palatal shelf and ureter, respectively. These effects correlate with altered expression of the epidermal growth factor receptor (EGFR), epidermal growth factor (EGF), and transforming growth factor-alpha (TGF-alpha). In this study, the developmental toxicity of TCDD was examined in EGF, TGF-alpha, and double EGF + TGF-alpha knockout (-/-) and wild type (WT) mice. The influence of background genetics in responsiveness to TCDD was examined using liver 7-ethoxyresorufin-O-deethylase (EROD) activity. Animals were dosed by gavage with 0, 0.2, 1, 5, 24, 50, 100, or 150 micro g TCDD/kg (5 ml/kg) body weight on gestation day 12. The mixed genetic background of WT, EGF (-/-), and EGF + TGF-alpha (-/-) made these mice less responsive to TCDD relative to C57BL/6J and TGF-alpha (-/-), which have a C57BL background. These results show that EGF and TGF-alpha are not required for response to TCDD; however, the specific ligand available to bind EGFR affects the responsiveness to TCDD. EGF (-/-) mice are less responsive for CP, but more sensitive to HN. TGF-alpha (-/-) mice were similar to WT in sensitivity for induction of CP and HN. The responses of EGF + TGF-alpha (-/-) mice were like the WT except at higher doses where sensitivity to CP increased, suggesting that the responses may be mediated by alternative ligands for EGFR that are not functional equivalents of EGF or TGF-alpha. In conclusion, the EGFR pathway is mechanistically important in responses of the embryo to TCDD. Specific ligands confer sensitivity or resistance that are target tissue-dependent.

Abnormalities, Drug-Induced↗
PubMed2003

Biochemical, cytotoxic, and genotoxic effects of ES936, a mechanism-based inhibitor of NAD(P)H:quinone oxidoreductase 1, in cellular systems.

The specific involvement of NAD(P)H:quinone oxidoreductase 1 (NQO1) in the bioactivation of quinone prodrugs has been shown through the use of the inhibitor of NQO1, dicoumarol. Disadvantages of using dicoumarol to inhibit NQO1 include its lack of specificity and its competitive mechanism of inhibition. The concentration of dicoumarol required for inhibition of NQO1 varies according to the substrate under evaluation, which may lead to either false conclusions of the involvement of NQO1 or the alteration of other cellular processes. We have reported previously on the chemical and biochemical properties of ES936, a mechanism-based inhibitor of NQO1 in cell-free systems. In this study, we investigated the effects of ES936 in cellular systems. ES936 (100 nM) inhibits more than 95% of NQO1 activity within 30 min and is stable in complete media at this concentration for a minimum of 2 h. The duration of inhibition is cell line-specific because a new protein must be generated for resumption of activity. ES936 abrogates the toxicity of streptonigrin, with greater effects seen in cell lines expressing higher levels of NQO1. ES936 does not inhibit other cellular reductases, nor does it alter cellular levels of acid-soluble thiols. Some evidence of DNA strand breaks was observed at the concentrations of ES936 required for the inhibition of NQO1 activity. From our studies, we propose the use of ES936 (100 nM) as a mechanism-based inhibitor of NQO1 in cellular systems and for use as a component of the routine activity assay for NQO1.

Animals↗
PubMed2002

Syphilis in pregnancy in Tanzania. II. The effectiveness of antenatal syphilis screening and single-dose benzathine penicillin treatment for the prevention of adverse pregnancy outcomes.

Treatment for maternal syphilis with single-dose benzathine penicillin (2.4 million units intramuscularly) is being implemented in many parts of sub-Saharan Africa. To examine the effectiveness of this regimen, a prospective cohort of 1688 pregnant women was recruited in Tanzania. Birth outcomes were compared among women treated for high-titer (n=133; rapid plasma reagin [RPR] titer > or = 1:8 and Treponema pallidum hemagglutination assay [TPHA]/fluorescent treponemal antibody [FTA] positive) and low-titer (n=249; RPR titer <1:8 and TPHA/FTA positive) active syphilis and 950 uninfected women. Stillbirth or low-birth-weight live births were observed in 2.3% and 6.3%, respectively, of women treated for high-titer active syphilis and in 2.5% and 9.2%, respectively, of seronegative women. There was no increased risk for adverse pregnancy outcome for women treated for high-titer active syphilis (odds ratio [OR], 0.76; 95% confidence interval [CI], 0.4-1.4) or low-titer active syphilis (OR, 0.95; 95% CI, 0.6-1.5), compared with seronegative women. Single-dose treatment is effective in preventing adverse pregnancy outcomes attributable to maternal syphilis.

Adolescent↗
PubMed2002

Syphilis in pregnancy in Tanzania. I. Impact of maternal syphilis on outcome of pregnancy.

To measure the impact of maternal syphilis on pregnancy outcome in the Mwanza Region of Tanzania, 380 previously unscreened pregnant women were recruited into a retrospective cohort at delivery and tested for syphilis. Stillbirth was observed in 18 (25%) of 73 women with high-titer active syphilis (i.e., women with a rapid plasma reagin titer > or = 1 :8 and a positive Treponema pallidum hemagglutination assay or indirect fluorescent treponemal antibody test result), compared with 3 (1%) of 233 uninfected women (risk ratio [RR], 18.1; P<.001). Women with high-titer active syphilis were also at the greatest risk of having low-birth-weight or preterm live births (RR, 3.0 and 6.1, respectively), compared with women with other serological stages of syphilis. Among unscreened women, 51% of stillbirths, 24% of preterm live births, and 17% of all adverse pregnancy outcomes were attributable to maternal syphilis. Syphilis continues to be a major cause of pregnancy loss and adverse pregnancy outcome among women who do not receive antenatal syphilis screening and treatment.

Adult↗
PubMed2002

Microfluidic temperature gradient focusing.

A new technique is described for the concentration and separation of ionic species in solution within microchannels or capillaries. Concentration is achieved by balancing the electrophoretic velocity of an analyte against the bulk flow of solution in the presence of a temperature gradient. With an appropriate buffer, the temperature gradient can generate a corresponding gradient in the electrophoretic velocity, so that the electrophoretic and bulk velocities sum to zero at a unique point, and the analyte will be focused at that point. The technique is demonstrated for a variety of analytes, including fluorescent dyes, amino acids, DNA, proteins, and particles, and is shown to be capable of greater than 10,000-fold concentration of a dilute analyte.

Journal Article↗
PubMed2002

Incidence of HIV infection in stable sexual partnerships: a retrospective cohort study of 1802 couples in Mwanza Region, Tanzania.

OBJECTIVE: To describe the dynamics of HIV transmission in stable sexual partnerships in rural Tanzania. DESIGN: Retrospective cohort study nested within community-randomized trial to investigate the impact of a sexually transmitted disease treatment program. METHODS: A cohort of 1802 couples was followed up for 2 years, with the HIV status of each couple assessed at baseline and follow-up. RESULTS: At baseline, 96.7% of couples were concordant-negative, 0.9% were concordant-positive, 1.2% were discordant with the male partner being HIV-positive, and 1.2% were discordant with the female partner being HIV-positive. Individuals living with an HIV-positive partner were more likely to be HIV-positive at baseline (women: odds ratio [OR] = 75.7, 95% confidence interval [CI]: 33.4-172; men: OR = 62.4, CI: 28.5-137). Seroincidence rates in discordant couples were 10 per 100 person-years (py) and 5 per 100 py for women and men, respectively (rate ratio [RR] = 2.0, CI: 0.28-22.1). In concordant-negative couples, seroincidence rates were 0.17 per 100 py in women and 0.45 per 100 py in men (RR = 0.38, CI: 0.12-1.04). Individuals living in discordant couples were at a greatly increased risk of infection compared with individuals in concordant-negative couples (RR = 57.9, CI: 12.0-244 for women; RR = 11.0, CI: 1.2-47.5 for men). CONCLUSION: Men were more likely than women to introduce HIV infection in concordant-negative partnerships. In discordant couples, incidence in HIV-negative women was twice as high as in men. HIV-negative individuals in discordant partnerships are at high risk of infection, and preventive interventions targeted at such individuals are urgently needed.

Adult↗
PubMed2002

Comparison of HIV prevalences in community-based and antenatal clinic surveys in rural Mwanza, Tanzania.

OBJECTIVES: First, to compare the prevalence of HIV infection among women in the general population and antenatal clinic (ANC) attenders in rural Mwanza, Tanzania, and second, to validate a method for adjusting HIV prevalence in ANC attenders to estimate the prevalence in the general female population aged 15-44 years. METHODS: A cross-sectional population survey was conducted in 12 rural communities of Mwanza Region between 1991 and 1992. From the same communities sequential ANC attenders were recruited on two occasions between 1991 and 1993. Consenting subjects were interviewed, examined, treated and a serum sample was tested for HIV. The HIV prevalence in women in the general population was compared with unadjusted and adjusted prevalences in ANC attenders. Parity-adjusted prevalences were obtained by applying correction factors to the observed prevalences in parous and nulliparous ANC attenders. RESULTS: A total of 5675 women aged 15-44 years from the general population and 2265 ANC attenders had complete socio-demographic and laboratory data. Unadjusted HIV prevalence was significantly lower in ANC attenders (3.6%) than women from the general population (4.7%, P = 0.025), but after adjustment there was no significant difference between the two groups (4.6 versus 4.7%, P = 0.95). CONCLUSION: In this rural population, the HIV prevalence in ANC attenders underestimated the prevalence among women in the general population, but this difference was eliminated by applying parity-based correction factors. Information on parity should be routinely collected in ANC-based HIV sentinel surveillance.

Adolescent↗
PubMed2002

Subcellular localization of NAD(P)H:quinone oxidoreductase 1 in human cancer cells.

NAD(P)H:quinone oxidoreductase 1 (NQO1) is implicated in both chemoprevention and bioactivation of DNA-damaging antitumor agents. NQO1 is mainly cytosolic, but distribution in other cellular compartments, particularly in tumor cells, is poorly defined. Nuclear NQO1 in HT29 human colon carcinoma and H661 human non-small cell lung cancer cells was observed using both confocal microscopy and immunoelectron microscopy. NQO1 was not detected in mitochondria, golgi, or endoplasmic reticulum. In addition, purified intact nuclei from HT29 cells contained immunoreactive NQO1, which was catalytically active as determined by conventional activity assay. In summary, we have confirmed the presence of nuclear NQO1, which has implications for chemoprotection and bioactivation of DNA-damaging antitumor agents.

Antineoplastic Agents↗
PubMed2002

Herpes simplex virus type 2 infection increases HIV incidence: a prospective study in rural Tanzania.

OBJECTIVES: To quantify the association between prevalent or incident Herpes simplex virus type-2 (HSV2) infection and the incidence of HIV seroconversion among adults in the general population in rural Tanzania. STUDY POPULATION: Adults aged 15-54 years sampled randomly from 12 rural communities in Mwanza Region, Tanzania and recruited to a randomized trial of improved treatment of sexually transmitted diseases. STUDY DESIGN: Unmatched case-control study nested within trial cohort. METHODS: Participants included 127 cases who seroconverted to HIV during the 2-year follow-up period and 636 randomly selected controls who remained HIV negative. Subjects were tested for HSV2 serology at baseline and follow-up, and associations between HIV and HSV2 were analysed with adjustment for socio-demographic and behavioural factors. RESULTS: After adjusting for confounding factors, a strong association between HSV2 infection and HIV seroconversion was observed in men (test for trend: P < 0.001), with adjusted odds ratios (OR) of 6.12 [95% confidence interval (CI), 2.52-14.9] in those HSV2 positive at baseline, and 16.8 (95% CI, 6.06-46.3) in those acquiring HSV2 infection during follow-up. A weaker association was observed in women (tests for trend: P = 0.14), with adjusted OR of 1.32 (95% CI, 0.62-2.78) and 2.36 (95% CI, 0.81-6.84), respectively. Population attributable fractions of incident HIV infection due to HSV2 were estimated as 74% in men and 22% in women. CONCLUSIONS: The results suggest that HSV2 plays an important role in the transmission of HIV infection in this population. There is an urgent need to identify effective HSV2 control measures in order to reduce HIV incidence in Africa.

Adolescent↗
PubMed2002

Interaction of the molecular chaperone Hsp70 with human NAD(P)H:quinone oxidoreductase 1.

NAD(P)H:quinone oxidoreductase 1 (EC; DT-Diaphorase, NQO1) is predominantly a cytosolic flavoenzyme that catalyzes a two-electron reduction. Using human tumor cell lines devoid of NQO1 enzymatic activity, we have previously identified a single nucleotide polymorphism (NQO1*2 allele) in the human NQO1 gene. This mutation has been characterized as a genetic polymorphism (NQO1*2), which leads to greatly diminished levels of protein due to rapid degradation of the NQO1*2 protein by the ubiquitin proteasomal pathway (UPP). In an attempt to decipher the mechanism responsible for the differential stability of wild-type NQO1*1 and mutant NQO1*2 proteins, we have investigated the interactions of these proteins with molecular chaperones of the Hsp family. Using co-immunoprecipitation studies (co-IPs), no association was observed between Hsp90 and either wild-type NQO1*1 or mutant NQO1*2 proteins. Hsp70, however, was found to associate with NQO1*1 protein in cells when co-IPs were performed with an anti-NQO1 antibody followed by immunoblotting with an anti-Hsp70 antibody or vice versa. Hsp40 could also be detected in the immunoprecipitated protein complex. Experiments were also performed using either the NQO1*1 or NQO1*2 coding regions in an in vitro transcription/translation system employing rabbit reticulocyte lysates (RRLs). Consistent with the cellular data, co-IP experiments in RRLs demonstrated an association of Hsp70 with wild-type NQO1*1 protein but not with NQO1*2 protein. To further elucidate the role of the association of Hsp70 with the NQO1*1 protein, site-directed mutagenesis was used to modify a proposed Hsp70 binding site near the N terminus of the NQO1 protein. We generated a plasmid containing an NQO1*1 coding region with a mutated Hsp70 binding site (isoleucine to aspartic acid at position 8, NQO1*1/I8D). In contrast to the NQO1*1 protein translated in RRLs, the NQO1*1/I8D protein did not associate with Hsp70, as demonstrated by co-IP, was catalytically inactive, and was degraded by the UPP. These data suggest that the association of Hsp70 with NQO1*1 may play an important role in the stability and functionality of the NQO1 protein.

Alleles↗
PubMed2002

Rapid microfluidic mixing.

A preformed T-microchannel imprinted in polycarbonate was postmodified with a pulsed UV excimer laser (KrF, 248 nm) to create a series of slanted wells at the junction. The presence of the wells leads to a high degree of lateral transport within the channel and rapid mixing of two confluent streams undergoing electroosmotic flow. Several mixer designs were fabricated and investigated. All designs were relatively successful at low flow rates (0.06 cm/s, > or = 75% mixing), but had varying degrees of success at high flow rates (0.81 cm/s, 45-80% mixing). For example, one design operating at high flow rates was able to split an incoming fluorescent stream into two streams of varying concentrations depending on the number of slanted wells present. The final mixer design was able to overcome stream splitting at high flow rates, and it was shown that the two incoming streams were 80% mixed within 443 microm of the T-junction for a flow rate of 0.81 cm/s. Without the presence of the mixer and at the same high flow rate, a channel length of 2.3 cm would be required to achieve the same extent of mixing when relying upon molecular diffusion entirely, while 6.9 cm would be required for 99% mixing.

Equipment Design↗
PubMed2002

Diet-induced obesity and hepatic gene expression alterations in C57BL/6J and ICAM-1-deficient mice.

The effects of high-fat feeding on the development of obesity were evaluated in intercellular adhesion molecule-1 (ICAM-1) knockout and C57BL/6J (B6) male mice fed a high-fat diet for < or =50 days. Serum and tissues were collected at baseline and after 1, 11, and 50 days on the diet. After 11 days on the diet, ICAM-1-deficient, but not B6, mice developed fatty livers and showed a significant increase in inguinal fat pad weight. At day 50, ICAM-1-deficient mice weighed less, and their adiposity index and circulating leptin levels were significantly lower than those of B6 controls. To better understand the early differential response to the diet, liver gene expression was analyzed at three time points by use of Affymetrix GeneChips. In both strains, a similar pattern of gene expression was detected in response to the high-fat diet. However, sterol regulatory element-binding protein-1, apolipoprotein A4, and adipsin mRNAs were significantly induced in ICAM-1-deficient livers, suggesting that these genes and their associated pathways may be involved in the acute diet response observed in the knockout mice.

Animals↗