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PubMed2004

Highly selective spectrophotometric flow-injection determination of trace amounts of bromide by catalytic effect on the oxidation of m-cresolsulfonephthalein by periodate.

A new flow-injection method is reported for the determination of bromide. The method is based on catalytic effect of bromide on the oxidation of m-cresolsulfonephthalein by periodate in acidic media. The reaction was followed spectrophotometrically by measuring the decrease in absorbance at 528 nm. The influence of pH, reagent concentration and manifold variables on the sensitivity was studied. Under optimum conditions, a calibration graph was obtained in the range of 0.160-20.00 microg ml(-1) bromides with a limit of detection of 0.150 microg ml(-1) bromide. The relative standard deviation for ten replicate measurement of 1.0 microg ml(-1) bromide was 2.1%. The influence of potential interfering ions on the selectivity was studied. The method successes to measure bromide in the presence of other halide ions. The method was used to measure bromide in river water and tap water.

Bromides↗

PubMed1986

Mutagenicity of benzylic acetates, sulfates and bromides of polycyclic aromatic hydrocarbons.

Studies were performed to determine the direct mutagenicity of the acetates and some bromides and sulfates of hydroxymethyl polycyclic aromatic hydrocarbons in S. typhimurium strains TA98 and TA100. Benzylic acetates, bromides and sulfates were synthesized and characterized. The compounds tested were benzyl alcohol, 5-hydroxymethylchrysene, 1-hydroxymethylpyrene, 6-hydroxymethylbenzo[a]pyrene, 6-(2-hydroxyethyl)benzo[a]pyrene, 6-hydroxymethylanthanthrene, 9-hydroxymethylanthracene, 9-hydroxymethyl-10-methylanthracene, 7-hydroxymethylbenz[a]anthracene, 7-(2-hydroxyethyl)benz[a]anthracene, 12-hydroxymethylbenz[a]anthracene, 7-hydroxymethyl-12-methylbenz[a]anthracene, 12-hydroxymethyl-7-methylbenz[a]anthracene, 1-hydroxy-3-methylcholanthrene, 2-hydroxy-3-methylcholanthrene, 3-hydroxy-3, 4-dihydrocyclopental[cd]pyrene and 4-hydroxy-3, 4-dihydrocyclopental[cd]pyrene. The benzylic sulfate esters of 6-hydroxymethylbenzo[a]pyrene and 7-hydroxymethylbenz[a]anthracene were the most mutagenic compounds, whereas the aliphatic sulfate ester of 7-hydroxyethylbenz[a]anthracene did not cause an increase in mutations above background. All meso-anthracenic benzylic acetate esters were mutagenic in both strains with various degrees of activity, whereas the corresponding non-benzylic esters were inactive, as expected. Of the non-meso-benzylic acetate esters, only the 3-acetoxy-3, 4-dihydrocyclopenta[cd]pyrene was mutagenic. In the benzylic bromide series, only the eight mesoanthracenic were mutagenic, whereas benzyl bromide and 5-bromomethylchrysene were inactive. The aliphatic bromides, 6-(2-bromoethyl)benzo[a]pyrene and 7-(2-bromoethyl)benz[a]anthracene did not display significant activity. The potencies of the acetate esters more accurately reflect the mutagenicity because the rate of solvolysis did not compete with the reactivity of the esters with bacterial DNA. In the case of benzylic sulfates and bromides, the rate of solvolysis was very rapid and could have diminished the level of mutagenicity, depending on the assay conditions. These results demonstrate that meso-anthracenic benzylic acetates, sulfates and bromides are mutagenic, whereas benzylic acetate esters attached to other carbon atoms are inactive.

Acetates↗

PubMed2003

Trihalomethane formation by chlorination of ammonium- and bromide-containing groundwater in water supplies of Hanoi, Vietnam.

The occurrence and the fate of trihalomethanes (THMs) in the water supply system of Hanoi City, Vietnam was investigated from 1998 to 2001. The chlorination efficiency, THM speciation, and, THM formation potential (THMFP) was determined in the water works and in tap water. With regard to THM formation, three types of groundwater resources were identified: (I) high bromide, (II) low bromide, and (III) high bromide combined with high ammonia and high dissolved organic carbon (DOC) concentrations. Under typical treatment conditions (total chlorine residual 0.5-0.8 mg/L), the total THM formation was always below WHO, EU, and USEPA drinking water standards and decreased in the order type I > type II > type III, although the THMFP was > 400 micrograms/L for type III water. The speciation showed > 80% of bromo-THMs in type I water due to the noticeable high bromide level (< or = 140 micrograms/L). In type II water, the bromo-THMs still accounted for some 40% although the bromide concentration is significantly lower (< or = 30 micrograms/L). In contrast, only traces of bromo-THMs were formed (approximately 5%) in type III water, despite bromide levels were high (< or = 240 micrograms/L). This observation could be explained by competition kinetics of chlorine reacting with ammonia and bromide. Based on chlorine exposure (CT) estimations, it was concluded that the current chlorination practice for type I and II waters is sufficient for > or = 2-log inactivation of Giardia lamblia cysts. However, in type III water the applied chlorine is masked as chloramine with a much lower disinfection efficiency. In addition to high levels of ammonia, type III groundwater is also contaminated by arsenic that is not satisfactory removed during treatment. N-nitrosodimethylamine, a potential carcinogen suspected to be formed during chloramination processes, was below the detection limit of 0.02 microgram/L in type III water.

Ammonia↗

PubMed2000

The effects of pyridostigmine bromide and permethrin, alone or in combination, on response acquisition in male and female rats.

It has been hypothesized that concurrent exposure to pyridostigmine bromide and permethrin may have contributed to the development of neurocognitive symptoms in Gulf War veterans. The present experiment was designed to investigate the effects of pyridostigmine bromide and permethrin alone, or in combination, on the acquisition of a novel response, one measure of normal cognitive functioning. Male and female Sprague-Dawley rats were treated with pyridostigmine bromide (1.5 mg/kg/day, by gavage in a volume of 5 ml/kg) or its vehicle for 7 consecutive days. They then also received an intraperitoneal injection of permethrin (0, 15, or 60 mg/kg) before they were exposed to an experimental session during which they could earn food by pressing a lever in an operant chamber. Serum permethrin levels increased as a function of its dose, and were higher in rats treated with pyridostigmine bromide. Sex differences were observed as permethrin levels were higher in female rats than in male rats following the highest dose. Pyridostigmine bromide delayed response acquisition in male and female rats, and resulted in higher response rates on the inactive lever in female rats than in male rats. Although permethrin levels were higher in subjects treated with pyridostigmine bromide than in those treated with vehicle, there were no differences in the behavioral effects of permethrin. Whether or not these behavioral effects of pyridostigmine bromide are of central or peripheral origin will need to be determined in future studies, as its effects on motor activity and/or gastro-intestinal motility may have affected response acquisition.

Animals↗

PubMedDate not supplied

Background levels of bromide in human blood.

A total of 183 random, whole-blood specimens was collected from healthy individuals within the State of Queensland (Australia), and the bromide concentration was determined by wavelength-dispersive X-ray fluorescence spectrometry (WDXRF). The intensity of the tube Compton scatter line was used to account for differences in matrices between the aqueous calibration standard and whole-blood specimens. Technical details of the WDXRF method are included in the experimental section of the paper. The overall mean for bromide in human blood was 5.3 +/- 1.4 mg/L and ranged from 2.5 to 11.7 mg/L. Associations between bromide levels and variables including age, gender, weight, height, and postcode address were examined by ANOVA and Pearson's correlation. Data indicate that aged persons (45-65+ years) are more likely to have higher bromide levels than younger persons (15-25 years). Our results also suggest differences in bromide levels between the sexes in similar age groups. Average levels were higher in females in most age groups. The reason for this difference requires further detailed investigation. No correlation was observed between bromide levels and height or weight of donors. No significant differences in bromide levels were found in persons living in the highly populated southeast region of Queensland compared with those living in the less urbanized northern parts of the state.

Adolescent↗

PubMed1984

Effects of oral cyclotropium bromide, hyoscine N-butylbromide and placebo on gastric emptying and antral motor activity in healthy man.

Cyclotropium bromide, a new antimuscarinic agent, inhibits gastrointestinal motility in animals at lower doses than those required to inhibit gastric acid secretion and salivation. In man, cyclotropium bromide suppresses fasting and meal stimulated colonic motility. This study investigated the effects of single oral doses of 60 mg cyclotropium bromide, 60 mg hyoscine N-butylbromide and placebo on gastric emptying and on antral motor activity. Twenty four healthy men (mean age 25 years) participated in three experiments one week apart. The drugs were administered, in random double blind fashion, 30 minutes before the ingestion of a semisolid test meal labelled with 74 MBq (2 mCi) 99mTc sulphur colloid. A gamma camera coupled to a computer monitored gastric emptying together with amplitude, frequency, and propagation velocity of antral contractions. Cyclotropium bromide and, to a lesser degree, hyoscine N-butylbromide delayed gastric emptying and reduced contraction amplitude, but did not affect frequency and propagation velocity of antral contractions. Cyclotropium bromide was significantly more active than hyoscine N-butylbromide; the effects of hyoscine N-butylbromide differed significantly from placebo. Antral contractile activity was present all the time. After cyclotropium bromide, there was a significant correlation between antral contraction amplitude and gastric emptying. No adverse side effects occurred with any one treatment. In conclusion, cyclotropium bromide markedly inhibits gastric emptying and reduces antral contraction amplitude.

Adult↗

PubMed1996

Bromide dilution in adults: optimal equilibration time after oral administration.

Extracellular water is often estimated by bromide dilution. The time interval between oral administration of the dose and blood sampling varies considerably among studies. Because at least two processes are involved during equilibration (distribution of the dose and bromide leaving the body), we performed a bromide-dilution experiment and analyzed the decay data by fitting a biexponential curve. The experiment was carried out in 11 healthy adults (8 women and 3 men, age 21-39 yr). Bromide ingestion (60 mg Br/l estimated total body water) was followed by blood sampling at 2, 3, 4, 6, 10, 25, and 105 (or 170) h. The bromide concentration in serum ultrafiltrate was determined with high-performance liquid chromatography. The bromide concentration in serum after dose intake showed a significant decrease over time. One-exponent functions significantly fitted the data. The two-exponent functions fitted the data significantly better (F-test, P < 0.0001). A model combining the data from all subjects fitted just as well. Equilibration time can be defined as the time at which the first exponential function, which represents distribution of the dose, has decreased to 5% of its starting value. According to this model, the equilibration time of orally administered bromide should be 8.5-11.7 h. This can be achieved by an overnight equilibration.

Administration, Oral↗

PubMed1999

Rapacuronium bromide: a review of its use in anaesthetic practice.

UNLABELLED: Rapacuronium bromide (rapacuronium) is an aminosteroid, nondepolarising neuromuscular blocking agent (NMBA). At the recommended dose for endotracheal intubation (1.5 mg/kg), an intravenous bolus of rapacuronium has a rapid onset (approximately 1.2 to 1.8 minutes) and short duration of action (10.2 to 16.5 minutes) in adults undergoing elective surgery. Rapacuronium 1.5 mg/kg produced clinically acceptable intubating conditions in 68 to 89% of these patients at about 1 minute after administration. The onset, extent and duration of action and clinical efficacy of an intubating dose of rapacuronium appeared to be similar in the general adult population, adult patients with renal or hepatic dysfunction, patients undergoing Caesarean section, and elderly, paediatric or obese adult patients. Onset time with rapacuronium 1.3 to 2.5 mg/kg (0.9 to 1.8 minutes) was similar to or slower than that with a 1 mg/kg dose of the depolarising NMBA suxamethonium chloride (0.8 to 1.2 minutes). Intubating conditions were clinically acceptable about I minute after administration in 86 to 100% of patients with rapacuronium 1.3 to 2.5 mg/kg compared with in 88 to 97% of patients with suxamethonium chloride 1 or 1.5 mg/kg. Spontaneous recovery was slower with rapacuronium than with suxamethonium chloride, but neostigmine 0.04 or 0.05 mg/kg administered 2 or 5 minutes after rapacuronium 1.3 or 1.5 mg/kg accelerated recovery. In the few available comparative clinical trials, rapacuronium 1.5 mg/kg appeared to have a more rapid onset of action than the nondepolarising NMBAs mivacurium chloride 0.25 mg/kg, rocuronium bromide 0.45 or 0.6 mg/kg or vecuronium bromide 0.07 mg/kg, and a shorter duration of action than rocuronium bromide 0.45 or 0.6 mg/kg or vecuronium bromide 0.07 mg/kg. Additional boluses (< or =3) of rapacuronium 0.5 or 0.55 mg/kg after an intubating bolus of 1.5 mg/kg provided continued skeletal muscle relaxation during short surgical procedures in adult patients. However, these patients may recover more slowly than those who receive a single bolus of the drug. Bronchospasm was the most common treatment-related adverse event with rapacuronium 0.3 to 3 mg/kg (3.4% of adult patients). Tachycardia, injection site reaction and hypotension were also reported in small proportions of patients (1.6, 1.1 and 0.9%). The overall incidence of drug-related adverse events was similar with rapacuronium 1.5 or 2.5 mg/kg or suxamethonium chloride 1 mg/kg (8 vs. 6%) but bronchospasm, tachycardia and injection site reaction tended to occur more often with rapacuronium. CONCLUSIONS: At the recommended dose of 1.5 mg/kg, the nondepolarising NMBA rapacuronium has a rapid onset and short duration of action. It may provide a nondepolarising alternative to suxamethonium chloride for endotracheal intubation. Rapacuronium may be preferred over rocuronium bromide, vecuronium bromide or mivacurium chloride in this indication.

Animals↗

PubMed2001

Three cases of acute methyl bromide poisoning in a seedling farm family.

We encountered three patients (Patient I: 39-year-old man, Patient II: 34-year-old woman, and Patient III: 5-year-old girl) with acute methyl bromide poisoning, which had occurred as a result of exposure to the gas that leaked from methyl bromide cans stored in a warehouse of a seedling farm. Since all three patients exhibited almost the same initial symptoms, i.e., severe vomiting, tonic convulsions and clouding of consciousness, botulism was suspected at first. However, subsequent inquiry revealed that 27 cans of methyl bromide had been stored in the building that the patients lived in, and that the cans had been damaged a few days before the onset of the patients' illness by a thrashing machine that was being moved by them to another location. Inspection revealed that all the cans of methyl bromide had passed the expiry date and were corroded. Even though none of the cans had been used, three cans with a capacity of 750 g were found to be empty. Plasma bromide ion concentrations were determined to be high (72.9 microg/ml, 67.8 microg/ml and 91.5 microg/ml; normal level, < 5 microg/ml), and acute methyl bromide poisoning was diagnosed 8 days after admission of the patients to the hospital. Hemodialysis (peritoneal lavage in the case of the child) was performed immediately, after which the plasma bromide ion concentrations returned to normal and the general condition of the patients gradually improved.

Accidents, Occupational↗

PubMed2004

Investigation of the formation of chlorination by-products in water rich in bromide and organic matter content.

Bench-scale chlorination experiments with river water rich in bromide and organic matter content were performed in order to investigate the behavior and speciation of the chlorination by-products, especially the brominated ones, which are considered more harmful to human health than their chlorinated analogues. The analysis of the compounds was performed by means of gas chromatography. Statistical treatment of the results with Multifactor Analysis of Variance technique revealed the trends of each compound as function of pH, chlorine dose, reaction time and temperature. Brominated species of chlorination by-products predominated, due to the presence of bromide in the river water leading to preferable bromination than chlorination of the organic matter. Bromide incorporation factors were calculated for trihalomethanes and haloacetic acids, the major categories of compounds formed. While bromide incorporation factors decreased with increasing chlorine dose, the opposite was true for low range of chlorine dose, a fact that needs to be considered during treatment of waters with similar properties. Bromide incorporation factors decreased with increasing pH, especially for haloacetic acids. While the organic matter content can be sufficiently removed during water treatment, bromide ion still remains in the treated water. The results of the present study indicate that chlorination conditions should be optimized in order to minimize the incorporation of bromide into the chlorination by-products formed, which would increase their toxic effects on the water consumers.

Bromides↗

PubMed1981

Primary structure of 3-phosphoglycerate kinase from horse muscle. II. Amino acid sequence of cyanogen bromide peptides CB1-CB4 and CB6-CB14, sequence of methionine-containing regions, and complete sequence of the enzyme.

The amino acid sequences of 13 of the 14 cyanogen bromide peptides of horse muscle 3-phosphoglycerate kinase have been determined. These peptides together constitute 75% of the structure of the enzyme. Except for the smallest peptides, automated sequence analysis of the parent peptide was employed together with the automated or manual (5-dimethylaminonaphthalene-1-sulfonyl (dansyl)-Edman method) sequencing of relevant peptides obtained by proteolytic digestion. In the case of the five smallest peptides, all between 6 and 11 residues in length, sequences were derived from analyses of the intact peptides. CB14a, a peptide produced in low yield during the preparation of the cyanogen bromide fragments, was helpful in the sequence analysis of CB14. This peptide appeared to have arisen as the result of a cyanogen bromide cleavage on the carboxyl side of a tryptophanyl residue. The sequences of these 13 cyanogen bromide peptides, together with that of CB1, reported previously (Hardy, G. W., Darbre, A., and Merrett, M. (1981) J. Biol. Chem. 256, 10284-10292), have been combined with data obtained from the sequence analysis of tryptic peptides derived from the methionine-containing regions of the enzyme to determine the complete sequence. Isolation of these overlap peptides was facilitated by the labeling of methionyl residues with iodo[2-14C]acetic acid prior to tryptic digestion. Tryptophan-containing tryptic peptides were also isolated, and their sequence analysis enabled the positions of the four tryptophanyl residues to be established. In this way, the problem caused by tryptophan degradation during the preparation of the cyanogen bromide fragments was overcome. The NH2 terminus of CB1, the NH2-terminal cyanogen bromide peptide, was identified as N-acetyl serine by mass spectrometry. The alignment of the cyanogen bromide fragments of horse muscle 3-phosphoglycerate kinase described here is in complete agreement with that based on X-ray analysis of the enzyme reported previously (Banks, R. D., Blake, C. C. F., Evans, P. R., Haser, R., Rice, D. W., Hardy, G. W., Merrett, M., and Phillips, A. W. (1979) Nature 279, 773-777). The complete structure is comprised of 416 residues and has a molecular weight of 44,519.

Amino Acid Sequence↗

PubMed1977

Intoxication of cattle with sodium bromide-contaminated feed.

Five concentrations of bromide ion, sodium bromide, were incorporated into a pelleted ration and fed to 5 groups of cattle for 49 days. Another group of cattle was fed volunteer oat hay cut from a field that had been fumigated with methyl bromide. On analysis, the hay contained between 6,800 and 8,400 parts per million of bromide ion. Groups fed the pelleted ration containing the highest concentration of bromide and those eating the contaminated hay developed signs of motor incoordination between the 10th and 12th days. The sign of incoordination correlated with serum bromide concentrations of 30 mEq/L or more. Serum bromide concentrations and associated neurologic signs subsided markedly 14 days after feeding of the toxic feeds was discontinued.

Animal Feed↗

PubMed1996

Bromide toxicosis secondary to renal insufficiency in an epileptic dog.

Bromide toxicosis was diagnosed in an 8-year-old Labrador Retriever that had been treated for epilepsy with potassium bromide, at a dosage of 29 mg/kg of body weight/d. Clinical signs included hind limb weakness, ataxia, and disorientation. Renal insufficiency, diagnosed by determination of endogenous creatinine clearance, was believed to be responsible for the development of bromide toxicosis in this dog. Diuresis with physiologic saline solution and discontinuation of bromide and phenobarbital treatment resulted in rapid resolution of abnormal neurologic signs; however, serum bromide concentrations decreased dramatically during diuresis and seizures recurred. Although saline diuresis has been recommended for the treatment of bromide intoxication in human beings, more conservative measures, such as discontinuation of bromide and short-term fluid administration, may be more appropriate for epileptic dogs.

Animals↗

PubMed1995

Tiotropium bromide, a new long-acting antimuscarinic bronchodilator: a pharmacodynamic study in patients with chronic obstructive pulmonary disease (COPD). Dutch Study Group.

The objective of the present study was to investigate the dose-dependent bronchodilator efficacy and duration of action of the newly developed antimuscarinic agent tiotropium bromide in patients with chronic obstructive pulmonary disease (COPD). In a randomized, double-blind, placebo-controlled, crossover design, patients inhaled single doses of 10-80 micrograms tiotropium bromide and placebo, formulated in lactose powder capsules. The washout period between test doses was 72 h. Thirty five patients were enrolled in the trial (32 males and 3 females; mean age 64 yrs). Baseline forced expiratory volume in one second (FEV1) (mean 1.34 L) was less than 65% of predicted and was < 70% of forced vital capacity (FVC). All subjects had a smoking history of more than 10 pack-years. The mean reversibility of FEV1 after inhalation of 40 micrograms ipratropium bromide was 28%. Pulmonary function testing was performed before and at regular time intervals for up to 32 h after test drug administration. Compared to placebo, tiotropium bromide produced significant improvements in FEV1, FVC, peak expiratory flow rate (PEFR) and forced mid-expiratory flow (FEF25-75%). The bronchodilator response was almost immediate; peak improvement in FEV1 was reached 1-4 h after test drug inhalation, and the duration of action extended to 32 h after the 20, 40 and 80 micrograms doses. A clear dose-response relationship was seen for peak FEV1 and for the average FEV1 over differing time periods during the 32 h observation period, 80 micrograms of test drug being superior to the 10 micrograms dose. Peak improvement in FEV1 ranged 19-26% of test-day baseline for tiotropium bromide doses compared to 16% for placebo. The large improvement for placebo is probably due to carry-over effect which was significant. After excluding carry-over effect, the peak response to placebo decreased to 11%, whilst for tiotropium bromide doses it ranged 20-25%; standard error for mean difference was about 4%. There was no evidence of systemic anticholinergic effects. In this population of patients with COPD, tiotropium bromide was found to be a safe and long-acting bronchodilator, demonstrating a clear dose-response relationship following single dose administration.

Administration, Inhalation↗

PubMed1976

Factors affecting petite induction and the recovery of respiratory competence in yeast cells exposed to ethidium bromide.

When growing cultures of S. cerevisiae are treated with high concentrations of ethidium bromide (greater than 50 mug/ml), three phases of petite induction may be observed: I. the majority of cells are rapidly converted to petite, II. subsequently a large proportion of cells recover the ability to form respiratory competent clones, and III. slow, irreversible conversion of all cells to petite. The extent of recovery of respiratory competence observed is dependent on the strain of S. cerevisiae employed and the temperature and the carbon source used in the growth medium. The effects of 100 mug/ml ethidium bromide are also produced by 10 mug/ml ethidium bromide in the presence of the detergent, sodium dodecyl sulphate, and recovery is also observed when cells are treated with 10 mug/ml ethidium bromide under starvation conditions. Genetic analysis of strain differences indicates that a number of nuclear genes influence petite induction by ethidium bromide. In one strain, S288C, petite induction by 100 mug/ml ethidium bromide is extremely slow under certain conditions. Mitochondria isolated from from S288C lack the ethidium bromide stimulated nuclease activity found in D243-4A, a strain which shows triphasic kinetics of petite formation. This enzyme may, therefore, be responsible for the initial phase of rapid petite formation.

Acriflavine↗

PubMed2000

Experimental exposure of rat skin to methyl bromide: a toxicokinetic and histopathological study.

Methyl bromide was experimentally exposed to a 12 cm2 area of the back skin of Wistar rats for 30 s, and for 1, 3, and 5 min, and time courses of both changes in plasma bromide concentration and of histopathological changes were examined. To measure bromide ion, a head space gas chromatography was used. The concentration of plasma bromide ion showed a sharp increase immediately after the exposure in all exposed groups, reaching a peak level after 1 h, then decreased rapidly. The ion level gradually decreased after 72 h to 1 week, and returned to a normal level after 4 to 8 weeks. Calculating from a regressive curve, the biological half lives of plasma bromide ion were 5.0 days to 6.5 days. Histopathologically, the impairments to the epidermal cells, fibroblasts and blood vessels were observed in the early phase. These cellular changes could be due to the direct cytotoxicity of the compound. In the next phase, newly infiltrating cells showed degeneration and necrosis. Subsequently, an impairment of the collagen bundles was observed. Our experiments suggested an immediate permeation and rapid metabolization of methyl bromide in the skin and a multistep formation of the skin damage induced by the compound. These processes of methyl bromide-induced skin damage are quite different from chemical skin injuries caused by the representative causative agents such as alkaline and acid.

Animals↗

PubMed1979

Dependence of mammalian DNA replication on DNA supercoiling. I. Effects of ethidium bromide on DNA synthesis in permeable Chinese hamster ovary cells.

Chinese hamster ovary cells labelled with [14C]thymidine were made permeable, incubated with various concentrations of the intercalating dye ethidium bromide, and centrifuged through neutral sucrose gradients. The gradient profiles of these cells were qualitatively similar to those obtained by centrifuging DNA from untreated, lysed permeable cells through gradients containing ethidium bromide. The sedimentation distance of DNA had a biphasic dependence on the concentration of ethidium bromide, suggesting that the dye altered the amount of DNA supercoiling in situ. The effect of ethidium bromide intercalation on incorporation of [3H]dTMP into acid-precipitable material in an in vitro DNA synthesis mixture was measured. The incorporation of [3H]dTMP was unaffected by less than 1 microgram/ml of ethidium bromide, enhanced up to two-fold by 1--10 microgram/ml, and inhibited by concentrations greater than 10 micrograms/ml. Alkaline sucrose gradient analysis revealed a higher percentage of small DNA fragments (6--20 S) in the cells treated with 2 micrograms/ml ethidium bromide than in control cells. These fragments attained parental size within the same time as the fragments in control cells. In cells treated with 2 micrograms/ml ethidium bromide, a significant fraction of newly synthesized DNA resulted from new starts, whereas in untreated cells practically none of the newly synthesized DNA resulted from new starts. These results suggest that relaxation of DNA supercoiled structures ahead of the replication fork generates spurious initiations of DNA synthesis and that in intact cells the rate of chain elongation is limited by supercoiled regions ahead of the growing point.

Animals↗

PubMed1985

Disposition of [14C]methyl bromide in rats after inhalation.

Methyl bromide is used as a disinfectant to fumigate soil and a wide range of stored food commodities in warehouses and mills. Human exposure occurs during the manufacture and use of the chemical. The purpose of this investigation was to determine the disposition and metabolism of [14C]methyl bromide in rats after inhalation. Male Fischer-344 rats were exposed nose only to a vapor concentration of 337 nmol [14C]methyl bromide/liter air (9.0 ppm, 25 degrees C, 620 torr) for 6 hr. Urine, feces, expired air, and tissues were collected for up to 65 hr after exposure. Elimination of 14C as 14CO2 was the major route of excretion with about 47% (3900 nmol/rat) of the total [14C]methyl bromide absorbed excreted by this route. CO2 excretion exhibited a biphasic elimination pattern with 85% of the 14CO2 being excreted with a half-time of 3.9 +/- 0.1 hr (means +/- SE) and 15% excreted with a half-time of 11.4 +/- 0.2 hr. Half-times for elimination of 14C in urine and feces were 9.6 +/- 0.1 and 16.1 +/- 0.1 hr, respectively. By 65 hr after exposure, about 75% of the initial radioactivity had been excreted with 25% remaining in the body. Radioactivity was widely distributed in tissues immediately following exposure with lung (250 nmol equivalents/g), adrenal (240 nmol equivalents/g), kidney (180 nmol equivalents/g), liver (130 nmol equivalents/g), and nasal turbinates (110 nmol equivalents/g) containing the highest concentrations of 14C. Radioactivity in livers immediately after exposure accounted for about 17% of the absorbed methyl bromide. Radioactivity in all other tissues examined accounted for about 10% of the absorbed methyl bromide. Elimination half-times of 14C from tissues were on the order of 1.5 to 8 hr. In all tissues examined, over 90% of the 14C in the tissues was methyl bromide metabolites. The data from this study indicate that after inhalation methyl bromide is rapidly metabolized in tissues and readily excreted.

Animals↗