The toxicology of bromide ion

TwinF interface inhibitor FP802 stops loss of motor neurons and mitigates disease progression in a mouse model of ALS

Toxic signaling by extrasynaptic NMDA receptors (eNMDARs) is considered an important promoter of amyotrophic lateral sclerosis (ALS) disease progression. To exploit this therapeutically, we take advantage of TwinF interface (TI) inhibition, a pharmacological principle that, contrary to classical NMDAR pharmacology, allows selective elimination of eNMDAR-mediated toxicity via disruption of the NMDAR/TRPM4 death signaling complex while sparing the vital physiological functions of synaptic NMDARs. Post-disease onset treatment of the SOD1G93A ALS mouse model with FP802, a modified TI inhibitor with a safe pharmacology profile, stops the progressive loss of motor neurons in the spinal cord, resulting in a reduction in the serum biomarker neurofilament light chain, improved motor performance, and an extension of life expectancy. FP802 also effectively blocks NMDA-induced death of neurons in ALS patient-derived forebrain organoids. These results establish eNMDAR toxicity as a key player in ALS pathogenesis. TI inhibitors may provide an effective treatment option for ALS patients.

Crop bromide concentrations following methyl bromide fumigation for pale cyst nematode in southeastern Idaho

Methyl bromide (MeBr) is a sterilizing fumigant used to control quarantine pests that is restricted due to its detrimental atmospheric effects. The degradation of injected MeBr produces crop-available Br- . Up to five applications of MeBr were used in southeastern Idaho fields to combat the pale cyst nematode (Globodera pallida). Data regarding the uptake and partitioning of Br- in crops following MeBr application in the region were unavailable. Research determined background concentrations of Br- in alfalfa (Medicago sativa L.), barley (Hordeum vulgare L.), corn (Zea mays L.), potato (Solanum tuberosum L.), and wheat (Triticum aestivum L.) compared to MeBr-treated fields. Background Br- concentrations ranged from nondetectable (ND) to 33.0 mg Br- kg-1 ; vegetative tissue concentrations were greater than reproductive, except corn where there was no difference. Nearly all crops grown in MeBr-treated fields had greater Br- concentrations than background. Background-baled-alfalfa tissue Br- concentration was 33.0 mg kg-1 compared to 117.8 mg Br- kg-1 from a MeBr-treated field. Br- concentration in green alfalfa decreased from 79.8 to 36.5 mg Br- kg-1 at the final cutting in a MeBr-treated field, where time after application decreased crop Br- concentrations. Small grains had low Br- concentrations in reproductive tissue (1.7 mg Br- kg-1 ) compared to vegetative tissue (106.5 mg Br- kg-1 ). Corn stover concentration (12.7 mg Br- kg-1 ) was low relative to small-grain straw, but corn ear (5.8 mg Br- kg-1 ) was greater than small-grain reproductive tissue in the MeBr-treated field. Crop selection following MeBr applications should consider the likelihood of elevated Br- concentration for the plant fractions intended end use.

Removal and detoxification of pentahalogenated phenols using a photocatalytically induced enzymatic process

Poly-halogenated phenols generated from a range of industrial processes can find their way into rivers and ground water. Here we report on a potential treatment for reducing the toxicity of these aqueous pollutants using two highly toxic penta-halogenated phenols (pentachlorophenol (PCP) and pentabromophenol (PBP)) as surrogates. Solutions were passed through a glass column packed with a silica support fused with titanium dioxide (TiO2) and horseradish peroxidase (HRP) immobilized on its TiO2/glass surface (HRP-Tglass). TiO2 photocatalysis was activated through irradiation with UVB (320 nm) which in turn activated the HRP. Two operational flow rates (0.5 and 1.25 mL min-1; hydraulic retention times (HRTs) of 20 and 8 min, respectively), tested the effect of retention time on the extent of degradation and reduction in toxicity of the treated effluent. Microtox® was used to measure the toxicity of the substrate and its by-products at both flow rates. At the highest flow rate, dehalogenation was limited (removal of 37 % chlorine and 22 % bromine) and the toxicity of the reaction products increased. At the lowest flow rate, the longer exposure time resulted in approximately 97 % and 96 % transformation of PCP and PBP, respectively, a greater degree of dehalogenation (removal of 65 % chlorine and 70 % bromine) and a substantial decrease in toxicity of the treated solutions. The higher toxicity of effluent from the higher flow rate was attributed to the initial degradation products being more toxic than the substrates. With a longer HRT, these were then further broken down to less toxic products. Additional toxicity tests (Hydra hexactinella (Hydra) and Chinese Hamster Ovary (CHO) cell toxicity were conducted on the effluent from the lowest flow rate. Both were less sensitive than the Microtox test, with Hydra proving more sensitive than CHO. The novelty of this work is the toxicity risk assessment of the products resulting from the use of a spatially separated immobilized enzyme and photooxidation system. The system was robust and showed no decrease in treatment efficacy over 10 h.

Effects on rumen microbiome and milk quality of dairy cows fed a grass silage-based diet supplemented with the macroalga Asparagopsis taxiformis

The objective was to determine the effects on rumen microbiome and milk quality of reducing the methane (CH4) produced from enteric fermentation by the addition of Asparagopsis taxiformis (AT) to the diets of dairy cows. Six Nordic Red cows at 122 ± 13.7 (mean ± SD) days in milk, of parity 2.7 ± 0.52 and producing 36 kg ± 2.5 kg milk per day at the start of the trial were divided into three blocks by milk yield and assigned to an extra-period Latin-square change-over design comprising two dietary treatments. An extra period of observation was added to the Latin-square change-over design to control for carry-over effects. The dietary treatments were a diet consisting of grass silage and a commercial concentrate mixture (60:40) either not supplemented or supplemented with 0.5% AT on an organic matter intake basis. On average, daily CH4 production, CH4 yield, and CH4 intensity decreased by 60%, 54%, and 58%, respectively, in cows fed the diet supplemented with AT. Furthermore, hydrogen gas emitted by cows fed diets supplemented with AT increased by more than five times compared with cows fed a non-AT-supplemented diet. Feed intake was decreased and milk production altered, reflecting a decreased yield of milk fat in cows fed an AT-supplemented diet, but feed efficiency increased. Rumen fermentation parameters were changed to promote propionate rather than acetate and butyrate fermentation. The most prominent change in milk quality was an increase in bromine and iodine when the diet was supplemented with AT. The reduction in CH4 was associated with a shift from Methanobrevibacter to Methanomethylophilaceae in the archaeal population and a lower relative abundance of Prevotella in the bacterial population. Changes in milk fat odd-numbered and branched-chain fatty acids in the current study of AT supplementation support observed differences in ruminal archaeal and bacterial populations.

Ion Chromatography–High-Resolution Mass Spectrometry Method for the Determination of Bromide Ions in Cereals and Legumes: New Scenario for Global Food Security

The new scenario for global food production and supply is decidedly complex given the current forecast of an increase in food fragility due to international tensions. In this period, exports from other parts of the world require different routes and treatments to preserve the food quality and integrity. Fumigation is a procedure used for the killing, removal, or rendering infertile of pests, with serious dangers to human health. The most-used fumigants are methyl bromide and ethylene dibromide. It is important to bear in mind that the soil may contain bromide ions naturally or from anthropogenic source (fertilizers and pesticides that contain bromide or previous fumigations). Different methods (titrimetric, spectrophotometric, and fluorometric approaches) are available to rapidly determine the amount of bromide ion on site in the containers, but these are non-specific and with high limits of quantification. The increasing interest in healthy food, without xenobiotic residues, requires the use of more sensitive, specific, and accurate analytical methods. In order to help give an overview of the bromide ion scenario, a new, fast method was developed and validated according to SANTE 11312/2021. It involves the determination of bromide ion in cereals and legumes through ion chromatography–Q-Orbitrap. The extraction was performed by the QuPPe method, but some modifications were applied based on the matrix. The method described here was validated at four different levels. Recoveries were satisfactory and the mean values ranged between 99 and 106%, with a relative standard deviation lower than 3%. The linearity in the matrix was evaluated to be between 0.010 and 2.5 mg kg⁻¹, with a coefficient of determination (R²) of 0.9962. Finally, the proposed method was applied to different cereals and legumes (rice, wheat, beans, lentils pearled barley, and spelt) and tested with satisfactory results in EUPT-SMR16 organized by EURL.

Data on the clinical, analytical, and laboratory factors associated with negative anion gaps at an academic medical center

The anion gap is a calculated parameter derived from the difference between the major plasma cations and anions in serum/plasma or whole blood, with a widely used simple equation utilizing concentrations of sodium, chloride, and bicarbonate. While there is extensive literature on the clinical significance and causes of elevated anion gaps, there is comparatively less data on low anion gaps. Occasionally, anion gap calculations result in a negative number (-1 or less). From the published literature, causes of these 'negative anion gaps' include laboratory error, specimen contamination or interference, hypoalbuminemia, extreme hyperkalemia, bromism, and paraproteins from multiple myeloma or similar pathologic processes. The data in this article present results from retrospective review of clinical chemistry and blood gas analysis testing at an academic medical center. The data include electrolyte concentrations and anion gap values derived from a total of 2,948,574 specimens (2,841,863 serum/plasma specimens analyzed on Roche Diagnostics clinical chemistry analyzers, 93,987 whole blood specimens analyzed on Radiometer blood gas analyzers, and 12,724 whole blood specimens on point-of-care chemistry devices) from 371,925 unique patients, clinical area where testing was ordered (for serum/plasma samples), sex, and age. For serum/plasma specimens with a negative anion gap, the data additionally include information from detailed chart review of possible factors and disease conditions contributing to the negative anion gap, pattern of electrolyte abnormalities, presence or absence of hypoalbuminemia, and corrected anion gap (if hypoalbuminemia is present).

Synthesis, Physicochemical Characterization, and Cytotoxicity Assessment of Rh Nanoparticles with Different Morphologies-as Potential XFCT Nanoprobes

Morphologically controllable synthesis of Rh nanoparticles (NPs) was achieved by the use of additives during polyol synthesis. The effect of salts and surfactant additives including PVP, sodium acetate, sodium citrate, CTAB, CTAC, and potassium bromide on Rh NPs morphology was investigated. When PVP was used as the only additive, trigonal NPs were obtained. Additives containing Br- ions (CTAB and KBr) resulted in NPs with a cubic morphology, while those with carboxyl groups (sodium citrate and acetate) formed spheroid NPs. The use of Cl- ions (CTAC) resulted in a mixture of polygon morphologies. Cytotoxicity of these NPs was evaluated on macrophages and ovarian cancer cell lines. Membrane integrity and cellular activity are both influenced to a similar extent, for both the cell lines, with respect to the morphology of Rh NPs. The cells exposed to trigonal Rh NPs showed the highest viability, among the NP series. Particles with a mixed polygon morphology had the highest cytotoxic impact, followed by cubic and spherical NPs. The Rh NPs were further demonstrated as contrast agents for X-ray fluorescence computed tomography (XFCT) in a small-animal imaging setting. This work provides a detailed route for the synthesis, morphology control, and characterization of Rh NPs as viable contrast agents for XFCT bio-imaging.

From Silk Spinning to 3D Printing: Polymer Manufacturing using Directed Hierarchical Molecular Assembly

Silk spinning offers an evolution-based manufacturing strategy for industrial polymer manufacturing, yet remains largely inaccessible as the manufacturing mechanisms in biological and synthetic systems, especially at the molecular level, are fundamentally different. The appealing characteristics of silk spinning include the sustainable sourcing of the protein material, the all-aqueous processing into fibers, and the unique material properties of silks in various formats. Substantial progress has been made to mimic silk spinning in artificial manufacturing processes, despite the gap between natural and artificial systems. This report emphasizes the universal spinning conditions utilized by both spiders and silkworms to generate silk fibers in nature, as a scientific and technical framework for directing molecular assembly into high-performance structures. The preparation of regenerated silk feedstocks and mimicking native spinning conditions in artificial manufacturing are discussed, as is progress and challenges in fiber spinning and 3D printing of silk-composites. Silk spinning is a biomimetic model for advanced and sustainable artificial polymer manufacturing, offering benefits in biomedical applications for tissue scaffolds and implantable devices.

Census of halide-binding sites in protein structures

Motivation

Halides are negatively charged ions of halogens, forming fluorides (F⁻), chlorides (Cl⁻), bromides (Br⁻) and iodides (I⁻). These anions are quite reactive and interact both specifically and non-specifically with proteins. Despite their ubiquitous presence and important roles in protein function, little is known about the preferences of halides binding to proteins. To address this problem, we performed the analysis of halide–protein interactions, based on the entries in the Protein Data Bank.

Results

We have compiled a pipeline for the quick analysis of halide-binding sites in proteins using the available software. Our analysis revealed that all of halides are strongly attracted by the guanidinium moiety of arginine side chains, however, there are also certain preferences among halides for other partners. Furthermore, there is a certain preference for coordination numbers in the binding sites, with a correlation between coordination numbers and amino acid composition. This pipeline can be used as a tool for the analysis of specific halide–protein interactions and assist phasing experiments relying on halides as anomalous scatters.

Availability and implementation

All data described in this article can be reproduced via complied pipeline published at https://github.com/rostkick/Halide_sites/blob/master/README.md.

Supplementary information

Supplementary data are available at Bioinformatics online.

Inter-species variation in monovalent anion substrate selectivity and inhibitor sensitivity in the sodium iodide symporter (NIS)

The sodium iodide symporter (NIS) transports iodide, which is necessary for thyroid hormone production. NIS also transports other monovalent anions such as tetrafluoroborate (BF4-), pertechnetate (TcO4-), and thiocyanate (SCN-), and is competitively inhibited by perchlorate (ClO4-). However, the mechanisms of substrate selectivity and inhibitor sensitivity are poorly understood. Here, a comparative approach was taken to determine whether naturally evolved NIS proteins exhibit variability in their substrate transport properties. The NIS proteins of thirteen animal species were initially assessed, and three species from environments with differing iodide availability, freshwater species Danio rerio (zebrafish), saltwater species Balaenoptera acutorostrata scammoni (minke whale), and non-aquatic mammalian species Homo sapiens (human) were studied in detail. NIS genes from each of these species were lentivirally transduced into HeLa cells, which were then characterized using radioisotope uptake assays, 125I- competitive substrate uptake assays, and kinetic assays. Homology models of human, minke whale and zebrafish NIS were used to evaluate sequence-dependent impact on the organization of Na+ and I- binding pockets. Whereas each of the three proteins that were analyzed in detail concentrated iodide to a similar degree, their sensitivity to perchlorate inhibition varied significantly: minke whale NIS was the least impacted by perchlorate inhibition (IC50 = 4.599 μM), zebrafish NIS was highly sensitive (IC50 = 0.081 μM), and human NIS showed intermediate sensitivity (IC50 = 1.566 μM). Further studies with fifteen additional substrates and inhibitors revealed similar patterns of iodide uptake inhibition, though the degree of 125I- uptake inhibition varied with each compound. Kinetic analysis revealed whale NIS had the lowest Km-I and the highest Vmax-I. Conversely, zebrafish NIS had the highest Km and lowest Vmax. Again, human NIS was intermediate. Molecular modeling revealed a high degree of conservation in the putative ion binding pockets of NIS proteins from different species, which suggests the residues responsible for the observed differences in substrate selectivity lie elsewhere in the protein. Ongoing studies are focusing on residues in the extracellular loops of NIS as determinants of anion specificity. These data demonstrate significant transport differences between the NIS proteins of different species, which may be influenced by the unique physiological needs of each organism. Our results also identify naturally-existing NIS proteins with significant variability in substrate transport kinetics and inhibitor sensitivity, which suggest that the affinity and selectivity of NIS for certain substrates can be altered for biotechnological and clinical applications. Further examination of interspecies differences may improve understanding of the substrate transport mechanism.

Reactions of Methotrexate with Hypobromous Acid and Hypochlorous Acid

Methotrexate is a folate antagonist cytotoxic drug employed in the therapy of cancers and rheumatoid arthritis. Hypobromous acid (HOBr) and hypochlorous acid (HOCl) are generated by eosinophils and neutrophils at inflammation sites. The administered methotrexate may encounter HOBr and HOCl, and react with them to generate products. When methotrexate was incubated with HOBr or HOCl at pH 7.4 and 37°C for 30 min, a single product was generated almost exclusively in each case, identified as 3'-bromomethotrexate for HOBr and 3'-chloromethotrexate for HOCl. When methotrexate was incubated with HOCl in the presence of NaBr, the concentration of 3'-bromomethotrexate increased with decreasing concentration of 3'-chloromethotrexate in a dose-dependent manner with NaBr, probably due to the formation of HOBr. Free amino acids suppressed the reactions of methotrexate with HOBr and HOCl. Taurine suppressed the HOCl reaction but not the HOBr reaction. These results suggest that 3'-bromomethotrexate and 3'-chloromethotrexate may be generated from methotrexate at inflammation sites in humans, although their formation will be suppressed by coexistent amino acids.

A novel near-infrared fluorescent probe for detection of hypobromous acid and its bioimaging applications

Hypobromous acid (HOBr) is an important reactive oxygen species and has been recently found to be associated with a variety of diseases. However, owing to a lack of effective analytical tools, there is still limited understanding of its roles in living systems. Here, we present a new type of near-infrared fluorescent probe DCSN for HOBr detection. The designed probe exhibits high sensitivity with a low detection limit, excellent selectivity over other interfering species and low cytotoxicity. More interestingly, the fluorescence response behavior of the probe was different from the previous literatures due to the intramolecular charge transfer process. Moreover, we have successfully monitored HOBr in living cells by utilizing DCSN. This probe has potential to be used as a promising tool for better understanding the physiological functions of HOBr.

Role of Hypohalous Acids in Basement Membrane Homeostasis

SIGNIFICANCE

Basement membranes (BMs) are sheet-like structures of specialized extracellular matrix that underlie nearly all tissue cell layers including epithelial, endothelial, and muscle cells. BMs not only provide structural support but are also critical for the development, maintenance, and repair of organs. Animal heme peroxidases generate highly reactive hypohalous acids extracellularly and, therefore, target BMs for oxidative modification. Given the importance of BMs in tissue structure and function, hypohalous acid-mediated oxidative modifications of BM proteins represent a key mechanism in normal development and pathogenesis of disease. Recent Advances: Peroxidasin (PXDN), a BM-associated animal heme peroxidase, generates hypobromous acid (HOBr) to form sulfilimine cross-links within the collagen IV network of BM. These cross-links stabilize BM and are critical for animal tissue development. These findings highlight a paradoxical anabolic role for HOBr, which typically damages protein structure leading to dysfunction.

CRITICAL ISSUES

The molecular mechanism whereby PXDN uses HOBr as a reactive intermediate to cross-link collagen IV, yet avoid collateral damage to nearby BM proteins, remains unclear.

FUTURE DIRECTIONS

The exact identification and functional impact of specific hypohalous acid-mediated modifications of BM proteins need to be addressed to connect these modifications to tissue development and pathogenesis of disease. As seen with the sulfilimine cross-link of collagen IV, hypohalous acid oxidative events may be beneficial in select situations rather than uniformly deleterious. Antioxid. Redox Signal. 27, 839-854.

Extracellular chloride signals collagen IV network assembly during basement membrane formation

Basement membranes are defining features of the cellular microenvironment; however, little is known regarding their assembly outside cells. We report that extracellular Cl(-) ions signal the assembly of collagen IV networks outside cells by triggering a conformational switch within collagen IV noncollagenous 1 (NC1) domains. Depletion of Cl(-) in cell culture perturbed collagen IV networks, disrupted matrix architecture, and repositioned basement membrane proteins. Phylogenetic evidence indicates this conformational switch is a fundamental mechanism of collagen IV network assembly throughout Metazoa. Using recombinant triple helical protomers, we prove that NC1 domains direct both protomer and network assembly and show in Drosophila that NC1 architecture is critical for incorporation into basement membranes. These discoveries provide an atomic-level understanding of the dynamic interactions between extracellular Cl(-) and collagen IV assembly outside cells, a critical step in the assembly and organization of basement membranes that enable tissue architecture and function. Moreover, this provides a mechanistic framework for understanding the molecular pathobiology of NC1 domains.

Pre-steady-state Kinetics Reveal the Substrate Specificity and Mechanism of Halide Oxidation of Truncated Human Peroxidasin 1

Human peroxidasin 1 is a homotrimeric multidomain peroxidase that is secreted to the extracellular matrix. The heme enzyme was shown to release hypobromous acid that mediates the formation of specific covalent sulfilimine bonds to reinforce collagen IV in basement membranes. Maturation by proteolytic cleavage is known to activate the enzyme. Here, we present the first multimixing stopped-flow study on a fully functional truncated variant of human peroxidasin 1 comprising four immunoglobulin-like domains and the catalytically active peroxidase domain. The kinetic data unravel the so far unknown substrate specificity and mechanism of halide oxidation of human peroxidasin 1. The heme enzyme is shown to follow the halogenation cycle that is induced by the rapid H2O2-mediated oxidation of the ferric enzyme to the redox intermediate compound I. We demonstrate that chloride cannot act as a two-electron donor of compound I, whereas thiocyanate, iodide, and bromide efficiently restore the ferric resting state. We present all relevant apparent bimolecular rate constants, the spectral signatures of the redox intermediates, and the standard reduction potential of the Fe(III)/Fe(II) couple, and we demonstrate that the prosthetic heme group is post-translationally modified and cross-linked with the protein. These structural features provide the basis of human peroxidasin 1 to act as an effective generator of hypobromous acid, which mediates the formation of covalent cross-links in collagen IV.

Approach to the Patient With a Negative Anion Gap

When anion gap calculation generates a very small or negative number, an explanation must be sought. Sporadic (nonreproducible) measurement errors and systematic (reproducible) laboratory errors must be considered. If an error is ruled out, 2 general possibilities exist. A true anion gap reduction can be generated by either reduced concentrations of unmeasured anions such as albumin or increased concentrations of unmeasured cations such as magnesium, calcium, or lithium. This teaching case describes a patient with aspirin (salicylate) poisoning whose anion gap was markedly reduced (-47 mEq/L). The discussion systematically reviews the possibilities and provides the explanation for this unusual laboratory result.

Bromine is an essential trace element for assembly of collagen IV scaffolds in tissue development and architecture

Bromine is ubiquitously present in animals as ionic bromide (Br(-)) yet has no known essential function. Herein, we demonstrate that Br(-) is a required cofactor for peroxidasin-catalyzed formation of sulfilimine crosslinks, a posttranslational modification essential for tissue development and architecture found within the collagen IV scaffold of basement membranes (BMs). Bromide, converted to hypobromous acid, forms a bromosulfonium-ion intermediate that energetically selects for sulfilimine formation. Dietary Br deficiency is lethal in Drosophila, whereas Br replenishment restores viability, demonstrating its physiologic requirement. Importantly, Br-deficient flies phenocopy the developmental and BM defects observed in peroxidasin mutants and indicate a functional connection between Br(-), collagen IV, and peroxidasin. We establish that Br(-) is required for sulfilimine formation within collagen IV, an event critical for BM assembly and tissue development. Thus, bromine is an essential trace element for all animals, and its deficiency may be relevant to BM alterations observed in nutritional and smoking-related disease. PAPERFLICK:

The neurological effects of methyl bromide intoxication

Used primarily as a fumigant or as a substrate in chemical processes, methyl bromide is a highly toxic gas. The gas is usually absorbed by inhalation and effects on the lungs, gastrointestinal tract, skin, and brain are seen. Numerous instances of acute and chronic neurologic injury have been reported: acute poisoning results in seizures, myoclonus, ataxia or cerebral oedema beginning as early as 30 min after exposure while subacute or chronic intoxication presents with diverse slowly progressive neurological and neurobehavioral symptoms. Serum bromide levels may be elevated, but often return rapidly to normal. Electroencephalography may show frontally-predominant slow waves or polyspikes with following slow wave, and MRI reveals characteristic involvement in the dentate nucleus of the cerebellum, the brainstem, and the splenium of the corpus callosum. Symmetric and selective lesions in characteristic sites are observed on imaging and on histopathological examination. These are likely produced by methylation of intracellular lipids, protein and glutathione; production of toxic metabolites; defective neurotransmitter function; and abnormal oxidative phosphorylation. This article reviews the toxic effects of this gas, the pathophysiology and symptoms of its effects on the nervous system, and characteristic findings on MRI; and presents an illustrative case of methyl bromide intoxication due to exposure at a factory producing the compound commercially.

Synthesis, pharmacological studies and molecular modeling of some tetracyclic 1,3-diazepinium chlorides

Seven new 1,3-diazepinium chlorides exhibiting some structural similarities to the 1,4-benzodiazepines were synthesized. In a Hippocratic screen using mice, three of these salts, 3-methoxy-6-oxo-7,13-dihydro-6H-benzofuro[2,3-e]pyrido[1,2-a][1,3]diazepin-12-ium chloride (8a), 3-methoxy-9-methyl-6-oxo-7,13-dihydro-6H-benzofuro[2,3-e]pyrido[1,2-a][1,3]diazepin-12-ium chloride (8c) and 3-methoxy-11-methyl-6-oxo-7,13-dihydro-6H-benzofuro[2,3-e]pyrido[1,2-a][1,3]diazepin-12-ium chloride (8e) were examined for their effect on the central nervous system, and their activities compared to that of diazepam. On their own, salts 8a, 8c and 8e solicited no sedative effects on the behaviour of the animals. However, they elicited significant effects in combination with diazepam on diazepam-induced activities such as decreased motor activity, ataxia and loss of righting reflex. Compounds 8a and 8c were fitted into the pharmacophore/receptor model developed by Cook et al. with interaction at the L(1), H(1) and A(2) sites indicating that they are potential inverse agonists of the Bz receptor. The compounds displayed some affinity for the alpha1 isoform of the GABA(A)/BzR (L(Di) interaction) but are non-selective for alpha5 (no L(2) interaction). Results of binding affinity studies showed that compound 8a is mildly selective for the alpha1 receptor although not very potent (K(i)=746.5nM). The significant potentiation of diazepam-induced ataxia and decreased motor activity by compounds 8a and 8c in the Hippocratic screen may be associated with alpha1 selectivity.

Liquid-phase microextraction–gas chromatography–mass spectrometry for the determination of bromate, iodate, bromide and iodide in high-chloride matrix

In the determination of bromate and iodate, any free bromide and iodide present was quantitatively removed by anion exchange with silver chloride exploiting the differences in silver salts solubility product, being AgCl, 1.8 x 10(-10), AgBr, 5.0 x 10(-13), AgI, 8.3 x 10(-17), AgBrO(3), 5.5 x 10(-5) and AgIO(3), 3.1 x 10(-8). The oxyhalides were reduced with ascorbic acid to halides and converted to 4-bromo-2,6-dimethylaniline and 4-iodo-2,6-dimethylaniline by their reaction with 2-iodosobenzoate in the presence of 2,6-dimethylaniline at pH 6.4 and 2-3, respectively. Single drop microextraction (SDME) of the haloanilines in 2 microl of toluene and injection of the whole extract into GC-MS, or liquid-phase microextraction (LPME) into 50 microl of toluene and injection of 2 microl of extract, resulted in a sensitive method for bromate and iodate. The latter method of extraction has been found more robust, sensitive and to give better extraction in shorter period than SDME. Total bromine/iodine was determined without any treatment with silver chloride. High concentration of chloride in the matrix did not interfere. A rectilinear calibration graph was obtained for 0.05 microg-25 mg l(-1) of bromate/bromide and iodate/iodide, the limit of detection were 20 ng l(-1) of bromate, 15 ng l(-1) of iodate, 20 ng l(-1) of bromide and 10 ng l(-1) of iodide (by LPME in 50 microl of toluene). The method has been applied to seawater and table salt. From the pooled data, the average recovery of spiked oxyhalide/halide to real samples was in range 96.7-105.7% with RSD in range 1.6-6.5%.

DNA damage in leukocytes of workers occupationally exposed to 1-bromopropane

1-bromopropane (1-BP; n-propyl bromide) (CAS No. 106-94-5) is an alternative to ozone-depleting chlorofluorocarbons that has a variety of potential applications as a degreasing agent for metals and electronics, and as a solvent vehicle for spray adhesives. Its isomer, 2-brompropane (2-BP; isopropyl bromide) (CAS No. 75-26-3) impairs antioxidant cellular defenses, enhances lipid peroxidation, and causes DNA damage in vitro. The present study had two aims. The first was to assess DNA damage in human leukocytes exposed in vitro to 1- or 2-BP. DNA damage was also assessed in peripheral leukocytes from workers with occupational exposure to 1-BP. In the latter assessment, start-of- and end-of-work week blood and urine samples were collected from 41 and 22 workers at two facilities where 1-BP was used as a solvent for spray adhesives in foam cushion fabrication. Exposure to 1-BP was assessed from personal-breathing zone samples collected for 1-3 days up to 8h per day for calculation of 8h time weighted average (TWA) 1-BP concentrations. Bromide (Br) was measured in blood and urine as a biomarker of exposure. Overall, 1-BP TWA concentrations ranged from 0.2 to 271 parts per million (ppm) at facility A, and from 4 to 27 ppm at facility B. The highest exposures were to workers classified as sprayers. 1-BP TWA concentrations were statistically significantly correlated with blood and urine Br concentrations. The comet assay was used to estimate DNA damage. In vitro, 1- or 2-BP induced a statistically significant increase in DNA damage at 1mM. In 1-BP exposed workers, start-of- and end-of-workweek comet endpoints were stratified based on job classification. There were no significant differences in DNA damage in leukocytes between workers classified as sprayers (high 1-BP exposure) and those classified as non-sprayers (low 1-BP exposure). At the facility with the high exposures, comparison of end-of-week values with start-of-week values using paired analysis revealed non-sprayers had significantly increased comet tail moments, and sprayers had significantly increased comet tail moment dispersion coefficients. A multivariate analysis included combining the data sets from both facilities, log transformation of 1-BP exposure indices, and the use of multiple linear regression models for each combination of DNA damage and exposure indices including exposure quartiles. The covariates were gender, age, smoking status, facility, and glutathione S-transferase M1 and T1 (GSTM1, GSTT1) polymorphisms. In the regression models, start-of-week comet tail moment in leukocytes was significantly associated with serum Br quartiles. End-of-week comet tail moment was significantly associated with 1-BP TWA quartiles, and serum Br quartiles. Gender, facility, and GSTM1 had a significant effect in one or more models. Additional associations were not identified from assessment of dispersion coefficients. In vitro and in vivo results provide limited evidence that 1-BP exposure may pose a small risk for increasing DNA damage.

An unusual case of methyl bromide poisoning

A nonlethal poisoning case by methyl bromide in a young woman due to leakage of old fire extinguishers is described. The patient developed major action and intention myoclonus the day following exposure. Inorganic bromide concentrations in plasma were determined by inductively coupled plasma mass spectrometry. The initial plasma bromide level was 202 mg/L, 40-fold in excess than the commonly accepted tolerance limit, and decreased slowly to normal levels within 2 months. Although plasma inorganic bromide concentration is known not to be directly correlated to the severity of organic bromide poisoning, its determination was, in the present case, particularly useful to confirm the diagnosis. One year post-exposure, the patient showed no sign of central nervous system toxicity. While such a case of poisoning is particularly rare today, it illustrates, however, that the danger still exists in France although the destruction

Comparison of urinary bromide levels among people in East Asia, and the effects of dietary intakes of cereals and marine products

Groups of people with no occupational exposure to Br-containing chemicals (29-54 year old, mostly women) in Japan, China and Korea, respectively, offered spot urine samples. Those in China and Korea offered 24 h duplicates of foods of the day. Urine samples were analyzed for Br by ECD-gas chromatography (ECD-GC) after derivatization to methyl bromide, and the Br-U was adjusted for a specific gravity of 1.016. Food intake data were based on national statistics and supplemented by the food duplicate data. Mean Br-U was 5.4 and 6.5 mg/l for Japanese men and women, respectively. Mean levels were in a range of 1.8-2.8 mg/l for four groups of Chinese, and 8-12 mg/l for the four groups of women in Korea. Br-U levels among Korean women were close levels reported for occupational exposure to 1- or 2-bromopropane, or methyl bromide. Regression analyses showed that Br-U levels were influenced by the intake of marine products (such as sea algae, sea fish and shellfish) and fruits, and inversely relate to intakes of cereals and potato.

Impact of high bromide intake in the rat dam on iodine transfer to the sucklings

A significant impact of high bromide levels in the organism of the mother on iodine transfer to the sucklings was established in experiments with female Wistar rats. The observed decrease in iodine transfer to the young through mothers' milk and/or an increase in the bromide concentration in the milk, caused a decrease in body weight of the pups. Enhanced bromide levels also adversely affected the thyroid gland of the young. High bromide intake in the lactating dams caused a decrease in iodide accumulation in the mammary glands, and also an increase in iodide elimination through the kidneys.

Chloride-sensitive fluorescent indicators

Three fluorescent halide-sensitive quinolinium dyes have been produced by the reaction of the 6-methylquinoline heterocyclic nitrogen base with methyl bromide, methyl iodide, and 3-bromo-1-propanol. The quaternary salts, unlike the precursor molecule, are readily water soluble and the fluorescence intensity of these salts is reduced in the presence of aqueous chloride, bromide, and iodide ions, allowing halide solution concentrations to be determined using well-known Stern-Volmer kinetics. One of the dyes, dye 1, has a chloride Stern-Volmer constant of 255 mol(-1) dm(3) which is more than twice that of SPQ [6-methoxy-N-(3-sulfopropyl)quinolinium] used in recent physiological measurements to measure intracellular chloride levels. The dyes have been characterized using steady-state fluorescence spectroscopy and are compared to three similar dyes based on the 6-methoxyquinoline nucleus, reported earlier by the authors, and also to dyes reported by Krapf et al. (Anal. Biochem. 169, 142-150, 1988). The interference of aqueous anions and the potential for using these dyes in biological halide-sensing applications are discussed.

An unusual exposure to methyl bromide leading to fatality

INTRODUCTION

Methyl bromide has been responsible for deaths that usually occur from its accidental inhalation during fumigation.

CASE REPORT

We report an accidental fatality that occurred after methyl bromide seeped through underground conduits from a fumigated building to an adjacent guest house on the same property. The patient developed refractory seizures, intermittent fever, and multiorgan system failure before dying 19 days after exposure. The initial serum bromide was 27 mg/dL. Postmortem analysis detected methyl bromide concentrations of 2.9 mg/dL in the blood, 1.7 mg/dL in the bile, 24 micrograms/g in the liver, and 28 micrograms/g in the adipose tissue.

CONCLUSION

Methyl bromide, although applied under acceptable safety standards, led to the inadvertent death of a young woman. Extreme care must be used when fumigating to insure no unsuspected seepage routes exist.

Bromism from excessive cola consumption

BACKGROUND

Bromism is an unusual occurrence. Historically bromism has been known to occur with chronic ingestion of bromide salts used as sleep medications. In this case, excessive consumption of a cola with brominated vegetable oil caused a severe case of bromism.

CASE REPORT

The patient presented with headache, fatigue, ataxia, and memory loss which progressed over 30 days. He consumed 2 to 4 L of cola containing brominated vegetable oil on a daily basis before presenting with these symptoms. His significantly elevated serum chloride, as measured by ion specific methods, and negative anion gaps were overlooked during a prior hospitalization and emergency department visits. A focal neurologic finding of right eyelid ptosis led to an extensive evaluation for a central nervous system lesion. The patient continued to deteriorate, until he was no longer able to walk. A diagnosis of severe bromism was eventually made and his serum bromide was confirmed at 3180 mg/L (39.8 mmol/L). Despite saline loading the patient failed to improve but subsequent hemodialysis dramatically cleared his clinical condition, and reduced his serum bromide levels. The unilateral eyelid ptosis, a rarely reported finding in bromism, also resolved with hemodialysis.

CONCLUSIONS

A negative anion gap or an elevated serum chloride should prompt an evaluation for bromism. In this case hemodialysis dramatically improved the patient's clinical condition and reduced the half-life of bromide to 1.38 h.

Effect of increased bromide intake on iodine excretion in rats

The time course of iodine excretion in adult male rats substantially differs from bromine excretion. Bromine is excreted at a single rate, whereas iodine evinces two excretion rates. Even a strong increase in bromide intake in experimental animals failed to affect the rate of iodine excretion but it lowered the fraction of iodine accumulated in the thyroid gland by 20% probably by affecting the transport of iodide into the thyroid gland.

Systemic effects of inhalational methyl bromide poisoning: a study of nine cases occupationally exposed due to inadvertent spread during fumigation

Systemic methyl bromide (CH3Br) poisoning with signs and symptoms of varying severity developed in nine greenhouse workers after acute inhalational exposure on two consecutive days. Measurements of CH3Br, carried out at the site within hours after the accident, suggest that exposure on the second day may have been in excess of 200 ppm (800 mg/m3) CH3Br. All workers were admitted for observation. Seven of them were discharged after an uneventful overnight observation and residual symptoms, if any, subsided within three weeks of the accident. Two patients needed intensive care for several weeks because of severe reactive myoclonus and tonic-clonic generalised convulsions. These conditions were unresponsive to repeated doses of diazepam, clonazepam, and diphenylhydantoin but could be suppressed effectively by induction of a thiopental coma that had to be continued for three weeks. In some of the patients prior subchronic exposure to CH3Br, as shown by their occupational histories and high serum bromide (Br-) concentrations, is likely to have been a factor contributing to the severity of their symptoms. A direct association between serum Br- concentrations and the severity of neurological symptoms, however, seemed to be absent. An on site investigation into the circumstances leading to the accident showed the presence of an empty and out of use drainage system that covered both sections of the greenhouse. This was probably the most important factor contributing to the rapid and inadvertent spread of CH3Br.

The no-effect level of sodium bromide in healthy volunteers

1. A total of 0, 4 and 9 mg kg-1 body weight sodium bromide was administered orally to 45 healthy female volunteers. 2. The experiment lasted for six menstrual cycles: only during the first three cycles was bromide administered; 3. At the start, at the end of the administration period and at the end of the experiment a physical examination and haematological and routine clinical chemistry tests were performed. Except for nausea in relation to the intake of bromide, no adverse effects were observed. 4. The bromide concentration in plasma rose to 3.22 +/- 0.93 mmol kg-1 in the 4 mg kg-1 group and to 7.99 +/- 1.89 in the 9 mg kg-1 group by the end of the administration period. 5. Before and at the end of the experiment the thyroid hormones (T4, FT4, TBG, T3 and TSH) were analysed. No significant differences were observed between the groups. 6. Before, after three menstrual cycles and at the end of the experiment an EEG with a Visual Evoked Response was recorded. At the 4 and 9 mg kg-1 dose level in the alpha 1-band and the beta-bands significant changes were found (P < 0.1 and P < 0.05, respectively). The Visual Evoked Response showed no significant differences between the three groups. 7. From this experiment and previous experiments a no-effect level in humans for sodium bromide of 4 mg kg-1 body weight is proposed.

Low anion gap resulting from unexplained exposure to bromide in a patient with renal amyloidosis

A patient with nephrotic syndrome secondary to renal amyloidosis was consistently observed to have serum anion gap levels as low as -1 mEq/L and averaging approximately 2 mEq/L. Neither multiple myeloma nor extreme hypertriglyceridemia was present, and the patient's serum albumin concentrations were not low enough to depress the anion gap to this degree. An increased serum bromide level (below the range expected to produce clinical toxicity) was the apparent cause of the low anion gap. The patient's parents, who live in the same apartment, also manifested low anion gaps and inexplicably elevated serum bromide levels. Despite detailed investigation, no environmental or pharmacologic source of bromide was uncovered. Although the source of the bromide in the present instance remains elusive, this report illustrates the necessity to measure serum bromide when a low anion gap cannot be explained by other factors, even when there is no history to suggest bromide exposure.

Toxicity and carcinogenicity of potassium bromate--a new renal carcinogen

Potassium bromate (KBrO3) is an oxidizing agent that has been used as a food additive, mainly in the bread-making process. Although adverse effects are not evident in animals fed bread-based diets made from flour treated with KBrO3, the agent is carcinogenic in rats and nephrotoxic in both man and experimental animals when given orally. It has been demonstrated that KBrO3 induces renal cell tumors, mesotheliomas of the peritoneum, and follicular cell tumors of the thyroid. In addition, experiments aimed at elucidating the mode of carcinogenic action have revealed that KBrO3 is a complete carcinogen, possessing both initiating and promoting activities for rat renal tumorigenesis. However, the potential seems to be weak in mice and hamsters. In contrast to its weak mutagenic activity in microbial assays, KBrO3 showed relatively strong potential inducing chromosome aberrations both in vitro and in vivo. Glutathione and cysteine degrade KBrO3 in vitro; in turn, the KBrO3 has inhibitory effects on inducing lipid peroxidation in the rat kidney. Active oxygen radicals generated from KBrO3 were implicated in its toxic and carcinogenic effects, especially because KBrO3 produced 8-hydroxydeoxyguanosine in the rat kidney. A wide range of data from applications of various analytical methods are now available for risk assessment purposes.

Determination of peroxidative halogenation in mixtures of chloride and bromide

A method for the differentiation of chlorinated and brominated products from peroxidative oxidation of mixtures of the halides is presented. Chlorination or bromination of monochlorodimedone (MCD) by fungal chloroperoxidase (CPO) was measured by loss of MCD absorbance. Although the Vmax was similar for both halides [approximately 0.08 mM (2 min)-1], the apparent Km for chlorination was 10 times greater than that for bromination (5.88 vs 0.67 mM). Chlorination was also quantitated as I3- produced from N-chlorotaurine and I-. The Vmax [0.076 mM (2 min)-1] and apparent Km (6.31 mM) determined by this method agreed with those determined with MCD. Selective reduction by H2O2 of the I-oxidizing potential of N-bromotaurine allowed determination of the brominated product from the difference between the amounts of halogenated MCD and N-chlorotaurine. The brominated product predominated at saturating and at physiologic halide levels. Hence, it is suggested that Br- plays a significant role in halogenation even though in vivo levels of Cl- are equal to or greater than 1000 times those Br-.