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S M Bailey

Publications and source records attributed to S M Bailey.

At least 19 recordsLinked to original sources
PubMed2004

DNA and telomeres: beginnings and endings.

How a cell deals with its DNA ends is a question that returns us to the very beginnings of modern telomere biology. It is also a question we are still asking today because it is absolutely essential that a cell correctly distinguishes between natural chromosomal DNA ends and broken DNA ends, then processes each appropriately - preserving the one, rejoining the other. Effective end-capping of mammalian telomeres has a seemingly paradoxical requirement for proteins more commonly associated with DNA double strand break (DSB) repair. Ku70, Ku80, DNA-PKcs (the catalytic subunit of DNA-dependent protein kinase), Xrcc4 and Artemis all participate in DSB repair through nonhomologous end-joining (NHEJ). Somewhat surprisingly, mutations in any of these genes cause spontaneous chromosomal end-to-end fusions that maintain large blocks of telomeric sequence at the points of fusion, suggesting loss or failure of a critical terminal structure, rather than telomere shortening, is at fault. Nascent telomeres produced via leading-strand DNA synthesis are especially susceptible to these end-to-end fusions, suggesting a crucial difference in the postreplicative processing of telomeres that is linked to their mode of replication. Here we will examine the dual roles played by DNA repair proteins. Our review of this rapidly advancing field primarily will focus on mammalian cells, and cannot include even all of this. Despite these limitations, we hope the review will serve as a useful gateway to the literature, and will help to frame the major issues in this exciting and rapidly progressing field. Our apologies to those whose work we are unable to include.

Animals↗
PubMed2004

Strand-specific fluorescence in situ hybridization: the CO-FISH family.

The ability to prepare single-stranded chromosomal target DNA allows innovative uses of FISH technology for studies of chromosome organization. Standard FISH methodologies require functionally single-stranded DNAs in order to facilitate hybridization between the probe and the complementary chromosomal target sequence. This usually involves denaturation of double-stranded probes to induce temporary separation of the DNA strands. Strand-specific FISH (CO-FISH; Chromosome Orientation-FISH) involves selective removal of newly replicated strands from DNA of metaphase chromosomes which results in single-stranded target DNA. When single-stranded probes are then hybridized to such targets, the resulting strand-specific hybridization is capable of revealing a level of information previously unattainable at the cytogenetic level. Mammalian telomeric DNA consists of tandem repeats of the (TTAGGG) sequence, oriented 5'-->3' towards the termini of all vertebrate chromosomes. Based on this conserved structural organization, CO-FISH with a telomere probe reveals the absolute 5'-->3' orientation of DNA sequences with respect to the pter-->qter direction of chromosomes. Development and various applications of CO-FISH will be discussed: detection of cryptic inversions, discrimination between telomeres produced by leading- versus lagging-strand synthesis, and replication timing of mammalian telomeres.

Animals↗
PubMed2003

A phase I/II study of oral uracil/tegafur (UFT), leucovorin and irinotecan in patients with advanced colorectal cancer.

BACKGROUND: The aim of this study was to determine the maximum tolerated dose (MTD), toxicity profile and response rate of the oral 5-fluorouracil prodrug UFT (tegafur/uracil) and leucovorin (LV) in combination with irinotecan in patients with advanced or metastatic colorectal cancer. PATIENTS AND METHODS: Patients with histologically proven advanced or metastatic colorectal adenocarcinoma received first-line chemotherapy comprising UFT 250 mg/m(2)/day and LV 90 mg/day given on days 1 to 14, with escalating doses of irinotecan (200-300 mg/m(2)) administered intravenously on day 1 of a three-weekly cycle. Eligibility criteria were standard. The MTD was defined as the dose at which >33% of six patients experienced a dose-limiting toxicity (DLT) during cycle 1. RESULTS: A total of 32 patients were studied. Initially, six patients were treated at each of the irinotecan dose levels (200, 250 and 300 mg/m(2)) combined with UFT 250 mg/m(2)/day and LV 90 mg/day. DLTs consisting of grade 3 or 4 diarrhoea and febrile neutropenia were observed in one of 20 patients at 250 mg/m(2) and three of six patients at the 300 mg/m(2) irinotecan dose level. Having defined the MTD, the 250 mg/m(2) dose level was established as the recommended dose (RD) and expanded to 20 patients in whom treatment was generally well tolerated. The overall response rate was 19%, with five patients having a partial response (PR) and 18 stable disease (SD) out of 32 response-evaluable patients. CONCLUSION: UFT and LV can be safely combined with irinotecan. The RDs for future studies are UFT 250 mg/m(2)/day and LV 90 mg/day given on days 1-14, with irinotecan 250 mg/m(2) administered on day 1, every 3 weeks. This combination is well tolerated and active. Further investigation of UFT and LV in combination with irinotecan is warranted in patients with colorectal cancer.

Adenocarcinoma↗
PubMed2001

Strand-specific postreplicative processing of mammalian telomeres.

Telomeres are specialized nucleoprotein structures that stabilize the ends of linear eukaryotic chromosomes. In mammalian cells, abrogation of telomeric repeat binding factor TRF2 or DNA-dependent protein kinase (DNA-PK) activity causes end-to-end chromosomal fusion, thus establishing an essential role for these proteins in telomere function. Here we show that TRF2-mediated end-capping occurs after telomere replication. The postreplicative requirement for TRF2 and DNA-PKcs, the catalytic subunit of DNA-PK, is confined to only half of the telomeres, namely, those that were produced by leading-strand DNA synthesis. These results demonstrate a crucial difference in postreplicative processing of telomeres that is linked to their mode of replication.

Animals↗
PubMed2001

Involvement of NADPH: cytochrome P450 reductase in the activation of indoloquinone EO9 to free radical and DNA damaging species.

Evidence suggests that DT-diaphorase is involved in the activation and mechanism of cytotoxicity of the investigational indoloquinone anticancer drug EO9 under aerobic conditions. Data also implicate a role for other enzymes including NADPH: cytochrome P450 reductase, especially in low DT-diaphorase tumour cells and under hypoxic conditions. Here, we used purified rat NADPH: cytochrome P450 reductase to provide additional evidence in support of a role for this enzyme in activation of EO9 to generate free radical and DNA-damaging species. Electron spin resonance spectrometry studies showed that NADPH: cytochrome P450 reductase reduced EO9 to a free radical species, including a drug radical (most likely the semiquinone) and reactive oxygen species. Plasmid DNA experiments showed that reduction of EO9 catalysed by NADPH: cytochrome P450 reductase results in single-strand breaks in DNA. The information obtained may contribute to the understanding of the molecular mechanism of DNA damage and cytotoxicity exerted by EO9 and may be useful in the design of future bioreductive drugs.

Animals↗
PubMed2001

Ethanol and oxidative stress.

This article represents the proceedings of a workshop at the 2000 ISBRA Meeting in Yokohama, Japan. The chair was Albert Y. Sun. The presentations were (1) Ethanol-inducible cytochrome P-4502E1 in alcoholic liver disease, by Magnus Ingelman-Sundberg and Etienne Neve; (2) Regulation of NF-kappaB by ethanol, by H. Matsumoto, Y. Nishitani, Y. Minowa, and Y. Fukui; (3) Chronic ethanol consumption increases concentration of oxidized proteins in rat liver, by Shannon M. Bailey, Vinood B. Patel, and Carol C. Cunningham; (4) Antiphospholipids antibodies and oxidized modified low-density lipoprotein in chronic alcoholic patients, by Tomas Zima, Lenka Fialova, Ludmila Mikulikova, Ptr Popov, Ivan Malbohan, Marta Janebova, and Karel Nespor; and (5) Amelioration of ethanol-induced damage by polyphenols, by Albert Y. Sun and Grace Y. Sun.

Alcoholism↗
PubMed2001

Chronic ethanol consumption alters the glutathione/glutathione peroxidase-1 system and protein oxidation status in rat liver.

BACKGROUND: Alcohol-induced liver damage is associated with oxidative stress, which might be linked to disturbances in liver antioxidant defense mechanisms. The effect of chronic ethanol consumption on the mitochondrial and cytosolic glutathione/glutathione peroxidase-1 (GSHPx-1) system and oxidative modification of proteins was therefore studied in the rat. METHODS: Male Sprague-Dawley rats were fed liquid diets that provided 36% total calories as ethanol for at least 31 days. Pair-fed controls received isocaloric diets with ethanol calories substituted with maltose-dextrins. Mitochondrial and cytosolic fractions were prepared from livers and assayed for GSHPx-1 and glutathione reductase activities and total and oxidized concentrations of glutathione. Catalase activity was measured in the postmitochondrial supernatant. Levels of GSHPx-1, lactate dehydrogenase, and the beta subunit of the F1 portion of the ATP synthase protein were determined by western blot analysis. Concentrations of mitochondrial and cytosolic protein carbonyls were measured to assess ethanol-induced oxidation of proteins. RESULTS: Chronic ethanol consumption significantly decreased cytosolic and mitochondrial GSHPx-1 activities by 40% and 30%, respectively. Levels of GSHPx-1 protein in cytosol were unaffected by ethanol feeding, whereas there was a small decrease in GSHPx-1 protein levels in mitochondria isolated from ethanol-fed rats. Glutathione reductase activities were increased in both intracellular compartments and catalase activity was increased as a consequence of ethanol exposure. Cytosolic total glutathione was mildly decreased, whereas ethanol feeding increased mitochondrial levels of total glutathione. Chronic ethanol feeding significantly increased both cytosolic and mitochondrial concentrations of protein carbonyls by 30% and 60%, respectively. CONCLUSIONS: This study demonstrates that chronic ethanol-induced alterations in the glutathione/GSHPx-1 antioxidant system might promote oxidative modification of liver proteins, namely those of the mitochondrion, which could contribute to the adverse effects of ethanol on the liver.

Alcoholism↗
PubMed2000

Effect of low flow ischemia-reperfusion injury on liver function.

The release of liver enzymes is typically used to assess tissue damage following ischemia-reperfusion. The present study was designed to determine the impact of ischemia-reperfusion on liver function and compare these findings with enzyme release. Isolated, perfused rat livers were subjected to low flow ischemia followed by reperfusion. Alterations in liver function were determined by comparing rates of oxygen consumption, gluconeogenesis, ureagenesis, and ketogenesis before and after ischemia. Lactate dehydrogenase (LDH) and purine nucleoside phosphorylase (PNP) activities in effluent perfusate were used as markers of parenchymal and endothelial cell injury, respectively. Trypan blue staining was used to localize necrosis. Total glutathione (GSH + GSSG) and oxidized glutathione (GSSG) were measured in the perfusate as indicators of intracellular oxidative stress. LDH activity was increased 2-fold during reperfusion compared to livers kept normoxic for the same time period whereas PNP activity was elevated 5-fold under comparable conditions. Rates of oxygen consumption, gluconeogenesis, and ureagenesis were unchanged after ischemia, but ketogenesis was decreased 40% following 90 min ischemia. During reperfusion, the efflux rates of total glutathione and GSSG were unchanged from pre-ischemic values. Significant midzonal staining of hepatocyte nuclei was observed following ischemia-reperfusion, whereas normoxic livers had only scattered staining of individual cells. Reperfusion of ischemic liver caused release of hepatic enzymes and midzonal cell death, however, several major liver functions were unaffected under these experimental conditions. These data indicate that there were negligible changes in liver function in this model of ischemia and reperfusion despite substantial enzyme release from the liver and midzonal cell death.

Animals↗
PubMed2000

A second-stage partogram.

OBJECTIVE: To describe a second-stage partogram based on a system of scoring the descent and position of the fetal head and to use this system for studying progress in the second stage of labor and predicting mode of delivery and obstetric outcome. METHODS: A prospective observational study of 1413 women at term with a singleton, cephalic presentation. The position and station of the fetal head were observed and scored at diagnosis of the second stage of labor, 1 hour later, and then at 30 minute intervals until delivery was achieved. The score at diagnosis of the second stage of labor was assessed for its ability to predict eventual mode of delivery and duration of labor. A normogram was defined for nulliparas and multiparas and was used to define normal and abnormal progress in the second stage, associated factors in the first stage of labor, and mode of delivery. RESULTS: Increasing total score at the start of the second stage of labor is associated with increasing chance of spontaneous vaginal delivery (odds ratio [OR] 1.68 for nulliparas, 1.59 for multiparas), decreasing chance of instrumental vaginal delivery (OR 0.67 for nulliparas, 0.64 for multiparas), and emergency cesarean delivery (OR 0.39 for nulliparas). Abnormal progress as defined by the normogram is associated with use of epidural anesthesia, induction of labor, augmentation, dystocia, and increased incidence of operative delivery. No significant difference is found between normal and abnormal second stages of labor in fetal outcome as determined by Apgar scores. CONCLUSION: The second-stage partogram offers an objective basis for management of the second stage of labor.

Delivery, Obstetric↗
PubMed2000

Antioxidants and gadolinium chloride attenuate hepatic parenchymal and endothelial cell injury induced by low flow ischemia and reperfusion in perfused rat livers.

The objective of this study was to determine whether Kupffer cells contribute to parenchymal and endothelial cell damage induced by ischemia-reperfusion in perfused rat livers. Parenchymal and endothelial cell injury were determined by measuring activities of lactate dehydrogenase (LDH) and purine nucleoside phosphorylase (PNP), respectively, in the effluent perfusate of livers subjected to 60 min of low flow ischemia followed by 30 min of reperfusion. Upon reperfusion, LDH and PNP activities increased significantly within the first 10 min of reperfusion and remained elevated over control values throughout the duration of reperfusion. Pretreatment with gadolinium chloride, an inhibitor of Kupffer cell function, significantly decreased LDH and PNP efflux during reperfusion by approximately 60% and 50%, respectively. When Kupffer cells were stimulated by vitamin A pretreatment, PNP efflux was doubled during reperfusion. Vitamin E pretreatment attenuated LDH and PNP release by approximately 70% during reperfusion compared to enzyme release in untreated livers. Moreover, the water-soluble antioxidants superoxide dismutase and desferrioxamine reduced reperfusion injury, whereas catalase had no effect on enzyme release. These results demonstrate that superoxide anions released from Kupffer cells are involved in oxidative damage to endothelial cells as well as hepatocytes during the early stages of hepatic reperfusion.

Animals↗
PubMed1999

DNA double-strand break repair proteins are required to cap the ends of mammalian chromosomes.

Recent findings intriguingly place DNA double-strand break repair proteins at chromosome ends in yeast, where they help maintain normal telomere length and structure. In the present study, an essential telomere function, the ability to cap and thereby protect chromosomes from end-to-end fusions, was assessed in repair-deficient mouse cell lines. By using fluorescence in situ hybridization with a probe to telomeric DNA, spontaneously occurring chromosome aberrations were examined for telomere signal at the points of fusion, a clear indication of impaired end-capping. Telomeric fusions were not observed in any of the repair-proficient controls and occurred only rarely in a p53 null mutant. In striking contrast, chromosomal end fusions that retained telomeric sequence were observed in nontransformed DNA-PK(cs)-deficient cells, where they were a major source of chromosomal instability. Metacentric chromosomes created by telomeric fusion became even more abundant in these cells after spontaneous immortalization. Restoration of repair proficiency through transfection with a functional cDNA copy of the human DNA-PK(cs) gene reduced the number of fusions compared with a negative transfection control. Virally transformed cells derived from Ku70 and Ku80 knockout mice also displayed end-to-end fusions. These studies demonstrate that DNA double-strand break repair genes play a dual role in maintaining chromosomal stability in mammalian cells, the known role in repairing incidental DNA damage, as well as a new protective role in telomeric end-capping.

Animals↗
PubMed1999

Ethanol stimulates the production of reactive oxygen species at mitochondrial complexes I and III.

The aim of this study was to investigate the hepatocellular site of reactive oxygen species generation during acute ethanol metabolism. Reactive oxygen species production was detected using the 2',7'-dichlorofluorescein fluorescence assay and cell injury was determined by lactate dehydrogenase release. Incubation with 1 and 10 mM ethanol increased the production of reactive oxygen species by 72% and 151%, respectively, which was associated with mild decreases in cell viability. Antimycin, a mitochondrial complex III inhibitor, elicited a 17-fold increase in the levels of reactive oxygen species and markedly decreased hepatocyte viability and ATP levels. Ethanol increased reactive oxygen species production and the cytosolic NADH/NAD+ ratio in antimycin-treated cells. Rotenone, a mitochondrial complex I inhibitor that allows electron flow through the flavin mononucleotide (FMN), but prevents electron flow to complex III, significantly increased reactive oxygen species production in untreated cells, but decreased reactive oxygen species production in antimycin plus ethanol-treated cells. Diphenyliodonium, a mitochondrial complex I inhibitor that inhibits electron flow through FMN, attenuated reactive oxygen species generation in all groups. Fructose prevented cytotoxicity in all treatment groups. Though they do not eliminate the participation of other intracellular compartments, these results indicate that the NADH dehydrogenase complex, as well as complex III of mitochondria, are involved in ethanol-related production of reactive oxygen species.

Adenosine Triphosphate↗
PubMed1999

Effect of dietary fat on chronic ethanol-induced oxidative stress in hepatocytes.

BACKGROUND: Although oxidative stress and deficits in hepatic energy metabolism have been implicated as important factors in the initiation of alcoholic liver disease, their relative contribution to ethanol-induced cell death is not known. The purpose of this study was to examine the effects of chronic ethanol administration on hepatocyte reactive oxygen species (ROS) generation, energy state, and viability, as well as the effect of dietary fat on these parameters. METHODS: Male Sprague-Dawley rats were fed liquid diets that provided 36% total calories as ethanol, with fat as either 12% (low fat) or 35% (high fat) of total calories. Pair-fed controls received liquid diets in which maltose-dextrin was substituted for ethanol calories. The fluorescent probe 2',7'-dichlorofluorescin diacetate was used to detect ROS, lactate dehydrogenase leakage was used to assess viability, and ATP levels were used as a measure of the energy state. The effect of chronic ethanol feeding on these parameters was determined by incubating hepatocytes under a 5% oxygen-containing atmosphere or an atmosphere < or = 1% oxygen for 60 min. RESULTS: In general, chronic ethanol feeding stimulated ROS production and decreased ATP concentrations, which were associated with decreased viability in hepatocytes isolated from rats fed either high- or low-fat, ethanol-containing diets, compared to the corresponding controls. Incubation under an atmosphere < or = 1% oxygen and/or ethanol (10 mM) augmented these effects in both high- and low-fat control and ethanol-fed hepatocytes. The addition of antimycin to the incubations increased ROS production, decreased ATP concentrations, and accelerated loss of hepatocyte viability. Viability loss under all conditions used in this study was correlated with decreases in cellular ATP. CONCLUSIONS: Comparisons of incubations performed under the two oxygenation conditions revealed that viability loss was inversely associated with ROS production, which indicates that ATP loss and not ROS production was a better predictor of loss in cell integrity. This study also demonstrates that the level of dietary fat has only minor effects on generation of ROS and the cellular energy state. In contrast, ethanol consumption had significant effects on generation of ROS, energy state, and hepatocyte viability.

Adenosine Triphosphate↗
PubMed1998

Reduction of the indoloquinone anticancer drug EO9 by purified DT-diaphorase: a detailed kinetic study and analysis of metabolites.

DT-diaphorase has been implicated in the activation and mechanism of cytotoxicity of the investigational indoloquinone anticancer drug EO9. Here, we have used a highly purified DT-diaphorase isolated from rat Walker tumour cells to provide unambiguous evidence for the ability of this enzyme to catalyze reduction of EO9 and to provide a more detailed characterization of the reaction. Under the conditions used hypoxia had no effect on the initial rate of this reduction but did effect the nature and stability of metabolites formed. Electron spin resonance (ESR) spectrometry studies showed that DT-diaphorase reduced EO9 to a highly oxygen-sensitive metabolite that is probably the hydroquinone. In the presence of air, this metabolite is auto-oxidized to generate both drug- and oxygen-based radicals. Comproportionation:disproportionation reactions may also be involved in the generation of these radical species. The identification of these metabolites may contribute to the understanding of the molecular mechanism of DNA damage and cytotoxicity exerted by EO9.

Animals↗
PubMed1998

Acute and chronic ethanol increases reactive oxygen species generation and decreases viability in fresh, isolated rat hepatocytes.

Although reactive oxygen species (ROS) have been implicated in the etiology of alcohol-induced liver disease, neither their relative contribution to cell death nor the cellular mechanisms mediating their formation are known. The purpose of this study was to test the hypothesis that acute and chronic ethanol exposure enhances the mitochondrial generation of ROS in fresh, isolated hepatocytes. Acute ethanol exposure stimulated ROS production, increased the cellular NADH/NAD+ ratio, and decreased hepatocyte viability slightly, which was prevented by pretreatment with 4-methylpyrazole (4-MP), an inhibitor of alcohol dehydrogenase. Similarly, xylitol, an NADH-generating compound, enhanced hepatocyte ROS production and decreased viability. Incubation with pyruvate, an NADH-oxidizing compound, and cyanamide, an inhibitor of aldehyde dehydrogenase, significantly decreased ROS levels in acute ethanol-treated hepatocytes. Chronic ethanol consumption produced a sixfold increase in hepatocyte ROS production compared with levels measured in controls. Hepatocytes from ethanol-fed rats were less viable compared with controls, e.g., viability was 68% +/- 2% (ethanol) versus 83% +/- 1% (control) after 60 minutes of incubation. Antimycin A increased ROS production and decreased cell viability; however, the toxic effect of antimycin A was more pronounced in ethanol-fed hepatocytes. These results suggest that acute and chronic ethanol exposure exacerbates mitochondrial ROS production, contributing to cell death.

Alcohol Dehydrogenase↗
PubMed1997

Involvement of DT-diaphorase (EC 1.6.99.2) in the DNA cross-linking and sequence selectivity of the bioreductive anti-tumour agent EO9.

The chemistry of the mitomycin C-related drug indoloquinone EO9 would suggest that its mechanism of action is likely to involve DNA damage after reductive activation. The ability of this agent to induce DNA damage in intact cells has been examined using alkaline filter elution. After treatment with pharmacologically relevant concentrations of EO9, both DNA strand breaks and interstrand cross-links were detected in rat Walker tumour cells and human HT29 colon carcinoma cells. These cell lines express relatively high levels of DT-diaphorase (NAD(P)H: quinone acceptor oxidoreductase), which is believed to be involved in EO9 activation. The extent of DNA damage was increased by approximately 30-fold under hypoxia in BE colon carcinoma cells that express non-functional DT-diaphorase, but this dramatic hypoxia enhancement was not seen in HT-29 cells. These data are consistent with cytotoxicity studies that indicate that DT-diaphorase appears to be important in EO9 activation under aerobic conditions, but other enzymes may be more relevant under hypoxia. The involvement of DT-diaphorase in DNA damage induction was further investigated using cell-free assays. DNA cross-links were detectable in plasmid DNA co-incubated with EO9, cofactor and DT-diaphorase but not in the absence of this enzyme. In contrast, using a Taq polymerase stop assay, monofunctional alkylation was detected in plasmid DNA without metabolic activation, although the sequence selectivity was altered after reduction catalysed by DT-diaphorase.

Animals↗