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PubMed1989

Fluorometric methods employing low concentrations of ethidium bromide for DNA topoisomerase and endonuclease assays.

DNA topoisomerase activity can be rapidly assayed by measuring the change in ethidium bromide fluorescence intensity after treatment of closed duplex DNA with enzyme. The sensitivity of the fluorometric assay has been enhanced 3-fold by a 10-fold reduction in ethidium bromide concentration to 0.1 microgram/ml. The results of the fluorometric assays are in close agreement with agarose gel electrophoretic analyses of reacted DNA. A sensitive fluorometric method using 0.1 microgram/ml ethidium bromide has also been developed to determine the fraction of nicked and linear DNAs in a mixture containing closed duplex DNA by measuring the fluorescence intensities of ethidium-DNA complexes at pH 7.0 and pH 12.0. These methods make possible very rapid and sensitive measurements of DNA topoisomerase and endonuclease activities.

Bacteriophages↗
PubMed1990

S1-nuclease enhancement of the ethidium bromide binding assay of drug-induced DNA interstrand crosslinking in human brain tumor cells.

A modification, using S1-nuclease, of a simple and sensitive fluorometric assay with ethidium bromide was developed for the measurement of cellular DNA interstrand crosslinking induced by bifunctional alkylators. Cells are lysed and treated with proteinase K and sodium dodecyl sulfate followed by extensive dialysis to yield intact high-molecular-weight DNA, free of contaminating proteins, on which the crosslink assay is then performed. The assay depends on the differential binding of ethidium bromide to single- and double-stranded DNA. Because of the higher ethidium bromide binding capacity of double-stranded DNA, the fluorescence retained after a heating/cooling cycle is directly proportional to the drug-induced cellular DNA interstrand crosslinking. We demonstrate that the sensitivity of this assay can be increased up to fourfold by including an S1-nuclease digestion step. This modified technique is simple and suited to the quantitation of low levels of DNA-interstrand crosslinking in cells.

Alkylating Agents↗
PubMed1987

Inhibition of yeast mitochondrial F1-ATPase, F0F1-ATPase and submitochondrial particles by rhodamines and ethidium bromide.

ATP hydrolysis by F1-ATPase is strongly inhibited by cationic rhodamines; neutral rhodamines are very poor inhibitors. Rhodamine 6G is a noncompetitive inhibitor of purified F0F1-ATPase and submitochondrial particles, however, an uncompetitive inhibitor of F1-ATPase (KI approximately equal to 2.4 microM for all three enzyme forms). Ethidium bromide is a noncompetitive inhibitor of F0F1-ATPase, submitochondrial particles and also F1-ATPase (KI approximately equal to 270 microM). Neither of the inhibitors affects the negative cooperativity (nH approximately equal to 0.7). The non-identical binding sites for rhodamine 6G and ethidium bromide are located on the F1-moiety and are topologically distinct from the catalytic site. Binding of the inhibitors prevents the conformational changes essential for energy transduction. It is concluded that the inhibitor binding sites are involved in proton translocation. In F1-ATPase, binding of MgATP at a catalytic site causes conformational changes, which allosterically induce the correct structure of the rhodamine 6G binding site. In F0F1-ATPase, this conformation of the F1-moiety exists a priori, due to allosteric interactions with F0-subunits. The binding site for ethidium bromide on F1-ATPase does not require substrate binding at the catalytic site and is not affected by F0F1-subunit interactions.

Ethidium↗
PubMed1984

Nonspecific inhibition of enzymes by p-bromophenacyl bromide. Inhibition of human platelet phospholipase C and modification of sulfhydryl groups.

This study demonstrates that p-bromophenacyl bromide irreversibly inhibits, in a time- and dose-dependent manner, yeast alcohol dehydrogenase, bovine pancreatic alpha-chymotrypsin, human platelet phosphatidylinositol (PI)-specific phospholipase C, in addition to the neutral-active and calcium-dependent phospholipase A2 of human platelets. The PI-specific phospholipase C has maximal activity at pH 5,5 is calcium-dependent, and is strongly inhibited by sulfhydryl reagents 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and methylmethane thiosulfonate . Increasing concentrations of DTNB produced concomitant inhibition of phospholipase C activity and titration of sulfhydryl groups. In contrast, human platelet phospholipase A2 activity was unaffected by concentrations of DTNB that titrated sulfhydryl groups, and completely inhibited PI-specific phospholipase C activity. Treatment of cysteine with p-bromophenacyl bromide resulted in modification of the amino acid as demonstrated by paper chromatography, and loss of titratable sulfhydryl groups. These data show that p-bromophenacyl bromide inhibits a wide spectrum of enzymatic activities including PI-specific phospholipase C. This reagent modifies amino acid residues other than active-site histidines and therefore has a broader reactivity than previously considered. Thus, it should not be used as a selective inhibitor of enzymes in crude cellular experiments.

Acetophenones↗
PubMed1977

A comparison of ipratropium bromide, deptropine citrate and placebo in asthma and chronic bronchitis.

A new anticholinergic aerosol, ipratropium bromide, was compared in a double-blind cross-over trial with an established preparation, deptropine citrate, and placebo in 16 patients with defined asthma or chronic bronchitis. Ipratropium bromide produced a significantly greater and more rapid bronchodilation than did deptropine citrate or placebo in the doses used, and its effect was slightly greater in the asthmatic than in the chronic bronchitic group. No unwanted effects on secretion were seen with ipratropium bromide.

Adult↗
PubMed1983

Comparison of nebulized salbutamol with nebulized ipratropium bromide in acute asthma.

Twelve patients admitted to hospital with an acute attack of bronchial asthma were studied. Six were treated initially with nebulized salbutamol solution by inhalation and 1 hour later by ipratropium bromide given in the same way; the other six were treated first with ipratropium bromide and 1 hour later by salbutamol. Ipratropium bromide was shown to be as effective as salbutamol when used as the initial bronchodilator but salbutamol produced significant further improvement when given 1 hour after ipratropium.

Acute Disease↗
PubMed1986

Combination of oxitropium bromide and salbutamol in the treatment of asthma with pressurized aerosols.

The bronchodilator effect of a combination of 200 micrograms salbutamol and 200 micrograms oxitropium bromide, given as pressurized aerosols, was compared to that of 200 and 400 micrograms of salbutamol in a controlled experiment on adult patients with asthma. The combined and the high dose salbutamol treatments were equally effective with respect to the response measured 60 minutes after administration, and both were significantly superior to the low dose salbutamol treatment. Bronchodilation persisted longer following the combined treatment than following the low or high dose salbutamol treatment. The results suggest that enhancement of the early bronchodilator response obtained by adding oxitropium bromide to a conventional dose of salbutamol in patients with stable asthma reflects suboptimal dosing of salbutamol rather than differences between the agents in mechanisms of action, whereas enhancement in duration of response is related also to the pharmacological characteristics of oxitropium bromide.

Adult↗
PubMed1992

A randomized controlled trial of valethamate bromide in acceleration of labor.

A randomized controlled study of valethamate bromide administered by intramuscular injection in acceleration of labor was done in 60 consecutive primigravidae and 60 consecutive multigravidae admitted in labor at 2-4 cm cervical dilatation. There was no difference observed in the rate of cervical dilatation between those who received valethamate bromide and those who received normal saline. However, maternal tachycardia was observed in significantly more women primigravida RR 1.97, 95% CI 1.3-3.0; multigravida RR 2.16, 95% CI 1.3-3.6) who had received valethamate bromide.

Female↗
PubMed1981

Estimation of genetic risks of alkylating agents. VI. Exposure of mice and bacteria to methyl bromide.

Methyl bromide was studied in a forward mutation system of E. coli to evaluate the relationship between dose and mutagenic response. The compound had a high toxicity and a low mutagenic efficiency, as expected from the high s value. The mutagenic effectiveness was estimated to be 1 mutation per 10(8) surviving bacteria per mM . h, in reasonable agreement with expectation from reaction kinetic data. To study the possibilities of using hemoglobin alkylation for an estimation of DNA alkylation in vivo, mice were treated with 14C-labeled methyl bromide. The degree of alkylation of DNA, determined in liver and spleen, was considerably lower than expected (200 and 20 times, respectively) from the degree of alkylation of hemoglobin and from the relative reactivities of DNA and hemoglobin towards methyl bromide in vitro. when hemoglobin alkylation is used for quantitative risk estimations, a correction factor has to be applied by taking into account the difference between the dose in red blood cells and the dose in the compartments of DNA.

Alkylation↗
PubMed1988

Frequent administration by inhalation of salbutamol and ipratropium bromide in the initial management of severe acute asthma in children.

A study was performed to compare the efficacy and safety of two therapeutic regimens for the treatment of children presenting to the emergency department with acute asthma. A regimen of inhaled salbutamol alone was compared to inhaled salbutamol combined with ipratropium bromide. Twenty-five children ranging in age from 5 to 15 years were enrolled in the study. Children with FEV1 less than or equal to 55% predicted were eligible to participate in the study. Subjects were randomized in a double-blind fashion into one of two treatment groups. Both groups received an initial dose of salbutamol by nebulizer of 150 micrograms/kg (0.03 cc/kg), followed by six consecutive doses of 50 micrograms/kg (0.01 cc/kg) at 20-minute intervals. In one group of subjects, 250 micrograms (1.0 ml) of ipratropium bromide respirator solution was added to the salbutamol administered at the time of the initial inhalation, and at 40 and 80 minutes, whereas the remaining subjects received a placebo with salbutamol at those times. Formal one-way statistical ANOVA with change in percent predicted FEV1 as a response variable confirmed there was a statistically significant difference at all time points caused by drug regimen during the 150-minute observation period. There was no significant difference in side effects reported in the two groups. Significant additional bronchodilation achieved with salbutamol and ipratropium bromide together indicates that there is likely a substantial cholinergic element to the bronchospasm observed in acute exacerbations of asthma in the pediatric age group.

Administration, Inhalation↗
PubMed1989

Pulmonary effects of sulfur dioxide exposure and ipratropium bromide pretreatment in adults with nonallergic asthma.

In this study we examined the potential short-term effect of sulfur dioxide (SO2) on total respiratory resistance and forced expiratory volume in patients with nonallergic asthma. A group of nine adult subjects with nonallergic asthma, 55 years of age or older, were exposed to SO2 at 0, 0.5, and 1.0 ppm for 20 minutes at rest followed by 10 minutes during light-moderate exercise. The measures of pulmonary function assessed were FEV1, specific total respiratory resistance (SRT), and maximal expiratory flow rates at 50% (Vmax50) and 75% (Vmax75) of expired vital capacity. Measurements were made before exposure to SO2 (baseline), postresting exposure, postexercising exposure, and at 30 minutes thereafter (recovery). Repeat measure analysis of variance revealed a statistically significant dose-response effect of SO2 inhalation on FEV1 (p = 0.008), SRT (p = 0.033), Vmax50 (p = 0.017), and Vmax75 (p = 0.048). Eight subjects had repeat exposure to SO2 at 1.0 ppm after treatment with either placebo or ipratropium bromide, 60 micrograms by metered-dose inhaler. Inpratropium bromide treatment, compared to placebo treatment, resulted in a statistically significant improvement in all baseline measures of pulmonary function: FEV1 (p = 0.017), SRT (p = 0.027), Vmax50 (p = 0.018), and Vmax75 (p = 0.035). However, this drug did not significantly alter the proportionate change in pulmonary function caused by SO2 inhalation in these subjects. These findings indicate that adults with nonallergic asthma are sensitive to short-term low-level SO2 exposure and that treatment with 60 micrograms of ipratropium bromide causes significant bronchodilation but does not protect, completely, these patients from the effect of SO2 inhalation.

Aged↗
PubMed1981

Fluorometric determination of DNA and RNA in Chlamydomonas using ethidium bromide.

By using the fluorescence enhancement of ethidium bromide bound to nuclei acid, a very rapid, simple and sensitive assay of DNA in the green alga Chlamydomonas has been devised. Total fluorescence (DNA + RNA) was determined by complex formation with ethidium bromide in a cell lysate made by mixing cell samples with lauroyl sarcosinate, EDTA and NaOH and incubating the mixture for 5 min at room temperature followed by neutralization. For determination of DNA the RNA was digested by incubating the cell sample in te alkaline lysis solution for 45 min at 60 degrees C followed by neutralization, and complex formation with ethidium bromide. Quenching of the fluorescence due to cellular pigments was corrected for using an internal DNA standard.

Chlamydomonas↗
PubMed1982

Human fibroblast strains showing increased sensitivity or resistance to ethidium bromide.

The sensitivity of a number of human fibroblast cell strains towards the DNA intercalating and mutagenic agent ethidium bromide has been examined. Among the cell strains investigated, 3 were of fetal origin, 6 from clinically normal adult persons, 2 from Lesch-Nyhan individuals and 1 each from persons with 3 genetic disorders, xeroderma pigmentosum, Fanconi anemia and Bloom syndrome, which are known to predispose to cancer. Results of our studies show that cells derived from 2 otherwise normal individuals exhibits a marked sensitivity towards ethidium bromide as compared to the rest of the group. At the same time all 3 cell strains of fetal origin were found to be highly resistant to killing by this agent. These results are discussed in relation to the toxic/mutagenic effects of ethidium bromide.

Adolescent↗
PubMed1982

A correlation between ethidium bromide uptake and petite mutagenesis during the yeast cell cycle.

The intracellular uptake of radioactively labeled ethidium bromide is shown to exhibit a periodic increase at the beginning of each cell cycle in synchronously growing cultures of the yeast, Saccharomyces cerevisiae. These peak rates of ethidium bromide uptake coincide in time with both new rounds of bud formation and the initiation of nuclear DNA synthesis during each cell cycle. Moreover, the peak rates of ethidium bromide uptake are also shown to be correlated in time with the maximum rate of petite mutagenesis induction by this drug during successive cell cycles.

Biological Transport↗
PubMed1989

Ethidium bromide-mediated renaturation of denatured closed circular DNAs: mechanistic aspects and fractionation of DNA on a molecular weight basis.

When closed circular duplex DNAs are exposed to alkali in the presence of ethidium bromide, from 0 to 100% of the DNA can be recovered as the fully base-paired duplex (native) form upon neutralization of the solutions. The fraction of native DNA depends on the concentration of ethidium bromide, time of incubation, ionic strength and temperature of the solutions before neutralization as well as the molecular weight and superhelix density of the DNA. Limiting ethidium concentrations exist below and above which 0 and 100% of the DNA, respectively, is recovered as native material under a given set of incubation conditions regardless of the length of time of incubation before neutralization. The strong molecular weight dependence of the fraction of DNA recovered in the native form after a given time of pre-neutralization incubation at ethidium concentrations between the limiting values noted above allows larger DNAs to remain fully denatured upon neutralization while smaller DNAs in the same mixture are fully renatured. This permits the rapid fractionation of mixtures of closed duplex DNAs on the basis of molecular weight when a technique for the separation of denatured from fully base-paired DNA is applied to such mixtures. Such a separation has been demonstrated through the marked enrichment of plasmid cloning vector DNA containing cloned inserts in the fractions that remain denatured after neutralization of alkaline solutions of these DNAs containing ethidium bromide.

Bacteriophages↗
PubMed1994

Detection of small quantities of double stranded DNA by enhanced fluorescence of substituted aldehyde modified polydeoxynucleotide-ethidium bromide complexes.

A method for the detection of small amounts of double stranded DNA by a simple incubation procedure involving the reaction of the nucleotide bases in DNA with chloroacetaldehyde is described. Following incubation, the presence of DNA may be visualized by the orange fluorescence emitted when ethidium bromide (EtBr) is added. Alternatively, the aldehyde/DNA mixture may be separated by agarose gel electrophoresis and individual double stranded DNA visualized by exposing the gel to ethidium bromide and observing the orange ultraviolet light induced fluorescence of the aldehyde modified double stranded ethidium bromide complex (Waring, M.J. (1965) J. Mol. Biol. 13, 269-282). At least a 20-fold increase in the detection of double stranded DNA is possible by this procedure. An important aspect of this method is that the visualization of single stranded DNA is not enhanced.

Acetaldehyde↗
PubMed1987

Subchronic toxicity of propantheline bromide administered in the feed to Fischer 344/N rats and B6C3F1 mice.

Propantheline bromide, a drug used for the treatment of peptic ulcers, was studied in male and female Fischer 344/N rats and B6C3F1 mice for subchronic toxicity. The drug was administered in the feed for 13 weeks at 0, 220, 670, 2000, 6000, and 24,000 ppm in both species. Propantheline bromide caused a decrease in weight gain at 24,000 ppm in male and female rats and at 6000 and 24,000 ppm in male and female mice. All rats survived the treatment. The top dose of 24,000 ppm was fatal to mice. Clinical signs of toxicity (dilated pupils and decreased gastrointestinal emptying), similar to the atropine-like effects of propantheline bromide in man, were seen in male and female rats at 24,000 ppm. Hyperplasia of the transitional epithelium of the urinary bladder was seen in high-dose male rats at the end of 13 weeks.

Administration, Oral↗
PubMed1991

Formation of DNA adducts in F-344 rats after oral administration or inhalation of [14C]methyl bromide.

The genotoxic effects of methyl bromide were investigated in a DNA-binding study. [14C]Methyl bromide was administered to male and female F-344 rats orally, or by inhalation from a closed exposure system. DNA adducts were detected in the liver, lung, stomach and forestomach. [14C]3-Methyladenine, [14C]7-methylguanine and [14C]O6-methylguanine were identified using a combination of three different methods of hydrolysing DNA, followed by HPLC or gas chromatography-mass spectrometry. After both oral and inhalation exposure, the highest levels of methylated guanines, especially those of [14C]O6-methylguanine, were found in the stomach and forestomach of the rats. These results clearly demonstrate a systemic DNA-alkylating potential of methyl bromide.

Administration, Inhalation↗