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PubMed1987

Stabilization of the reduced halocarbon-cytochrome P-450 complex of halothane by N-alkanes.

Under anaerobic conditions, various halogenated compounds, when metabolized by cytochrome P-450, form complexes which are spectrally detectable. Previous studies have shown that halothane forms such a complex with cytochrome P-450, and the result is a strong absorption at 470 nm. Stabilization of this proposed intermediate carbanion complex has never been demonstrated in a biological system. Data are presented which show that several organic solvents (C5-C7N-alkanes) will stabilize the complex formed between halothane and cytochrome P-450. Stabilization allowed the decay of the complex to be studied, and it is demonstrated that the product of decay was chlorodifluoroethylene, which substantiates the hypothesis that the complex is a two electron-reduced carbanion. Carbon tetrachloride and benzyl bromide, which also produce spectrally visible intermediate complexes, were not stabilized by this treatment. Stabilization of the halothane complex in a biological system may facilitate studies to identify precisely the halothane-cytochrome P-450 complex and to clarify the mechanisms of halothane reduction by cytochrome P-450.

Alkanes↗

PubMed1996

Applications of liquid chromatography-mass spectrometry interfacing systems in food analysis: pesticide, drug and toxic substance residues.

This paper reviews applications of different LC-MS techniques for the determination of xenobiotic substances in foods. Specific examples of contaminants discussed are pesticides, herbicides, insecticides and drugs; concerning toxic substances, mycotoxins, phycotoxins, cyanobacterial toxins, mutagenic and heterocyclic amines and beta-carbolines, arsenic, tin and inorganic halogen compounds, packaging materials and various epoxy resins are considered. Advantages and limitations are outlined for the different LC-MS interfacing systems (particle beam, thermospray, atmospheric pressure ionization with electrospray, ionspray and heated pneumatic nebulizer). The impact of developments in instrumental analysis on methodology and the limitations of the various LC-MS methods are discussed. Further, the coupling of LC with element-selective detection systems such as inductively coupled plasma mass spectrometry is discussed, with emphasis on speciation of trace toxic elements in foods.

Chromatography, Liquid↗

PubMed1989

Agonist and antagonist properties of benzazepine and thienopyridine derivatives at the D1 dopamine receptor.

Nine structurally related 1-phenyl-1H-3-benzazepine derivatives and two thienopyridines were tested for agonist and antagonist properties at the adenylate cyclase-coupled D1 dopamine receptor in homogenates of the striatum of the rat. The benzazepines SK&F 77434 and SK&F 82958, both of which contain a catechol ring, were agonists; the intrinsic activity of SK&F 77434 was similar to that of SK&F 38393, whereas SK&F 82958 was a full agonist. The remaining benzazepines inhibited the stimulation of adenylate cyclase by dopamine. Antagonist potency depended on the nature of the substituent at position 7 of the benzazepine molecule, 7-halogen compounds being the most potent. The Ki values, obtained from analysis of the antagonism of dopamine-stimulated adenylate cyclase, were significantly correlated with the Ki values for displacement of D1 ligands in binding experiments. Furthermore, antagonist activity of the resolved racemic benzazepine SK&F 83566 resided almost exclusively in the R-enantiomer. The thienopyridine derivatives SK&F 89641 and SK&F 89145 were partial agonists with greater efficacies than SK&F 38393.

Adenylyl Cyclase Inhibitors↗

PubMed1993

Lindane decreases forskolin-stimulated cyclic AMP accumulation but does not modify Gs in rat enterocytes.

Treatment of isolated rat enterocytes with the halogenated insecticide lindane (the gamma-isomer of hexachlorocyclohexane, HCCH) did not modify the general membrane fluidity (as estimated by a fluorescence polarization technique) nor the guanine nucleotide binding regulatory protein Gs (as studied by both ADP-ribosylation of its alpha subunit by cholera toxin and Gpp[NH]p stimulation of membrane adenylate cyclase activity). However, lindane decreased in a dose-dependent manner the effect of the diterpene forskolin on direct activation of the adenylate cyclase catalytic subunit. After 5 min of cell treatment with 0.5 mM lindane, the maximal stimulatory effect of forskolin (at 100 microM) decreased by about 50%. There was a certain degree of specificity since delta-HCCH was indeed more potent, whereas dieldrin and endrin (non-lindane related halogenated compounds) behaved as lindane, and alpha- and beta-HCCH were poorly efficient on the inhibition of forskolin stimulation of adenylate cyclase activity. A similar effect of lindane was observed on receptor-stimulated cyclic AMP accumulation by using vasoactive intestinal peptide instead of forskolin. The results on a non-receptor mediated effect of lindane on the adenylate cyclase catalytic subunit itself could be related to: (i) alterations of membrane microdomains surrounding this and other integral proteins which would result in modifications of their activities; and/or (ii) a reciprocal relation between the two main routes of signal transduction so that the activation of protein kinase C (or other Ca(2+)-dependent protein kinases) by lindane would lead to phosphorylation of the adenylate cyclase catalytic subunit.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗

PubMed2005

Speciation and biosynthetic variation in four dictyoceratid sponges and their cyanobacterial symbiont, Oscillatoria spongeliae.

Four species of marine sponges (Phylum Porifera, Order Dictyoceratida), which contain the filamentous cyanobacterial symbiont Oscillatoria spongeliae, were collected from four locations in Palau. The halogenated natural products associated with the symbiont were characterized from each sample, revealing that each species contained either chlorinated peptides, brominated diphenyl ethers, or no halogenated compounds. Analysis of the host sponges and the symbionts indicated that each species of sponge contained a distinct strain of morphologically similar cyanobacteria. Although cospeciation may be present in this group, we have identified that at least one host switching event has occurred in this symbiosis. Only the strain of O. spongeliae in the sponge containing the chlorinated compounds possessed genes involved in the biosynthesis of chlorinated leucine precursors, indicating that the chemical variation observed in these animals has a genetic foundation.

Animals↗

PubMed2003

Simultaneous determination of degradation products of nonylphenol polyethoxylates and their halogenated derivatives by solid-phase extraction and gas chromatography-tandem mass spectrometry after trimethylsilylation.

An efficient method for the simultaneous determination of the degradation products of nonylphenol polyethoxylates (NPnEOs, n = number of ethoxy units), i.e., nonylphenol (NP), NPnEOs (n = 1-3), nonylphenoxy carboxylic acids (NPnECs, n = 1-2, number of ethoxy units plus an acetate) and their halogenated derivatives (XNP, XNP1EO and XNP1EC; X = Br or Cl), in water samples were developed. After trimethylsilylation with N,O-bis(trimethysilyl)acetamide, all the analytes were determined by gas chromatography-tandem mass spectrometry (GC-MS-MS) with electron ionization (EI). The ion peaks of [M - 85]+ of the derivatives were selected as precursor ions and their product ions showing the highest intensities were used for the quantitative analysis. The instrumental detection limits were in the range from 2.1 to 11 pg. The recoveries of the analytes from the water samples were optimized by using solid-phase extraction (SPE). The deuterated reagents of octylphenol, octylphenol monoethoxylate and octylphenoxyacetic acid were used as the surrogates. The method detection limits (500 ml water sample) using C18 SPE were from 2.5 to 18 ng/l. The recoveries from spiked pure water and the environmental water samples were greater than 78%. The method was successfully applied to environmental samples. Remarkably, the concentrations of the halogenated compounds (CINP, CINP1EO and BrNP1EO) were detected at the hundreds of ng/l levels in the Neya river.

Gas Chromatography-Mass Spectrometry↗

PubMed2005

Improved analysis of volatile halogenated hydrocarbons in water by purge-and-trap with gas chromatography and mass spectrometric detection.

An analytical system composed of a purge-and-trap injection system coupled to gas chromatography with mass spectrometric detection (PTI-GC-MS) specific for the analysis of volatile chlorinated hydrocarbons (VCHCs) (chloroform; 1,1,1-trichloroethane; tetrachloromethane; 1,1,2-trichloroethylene; tetrachloroethylene) and trihalomethanes (THMs) (chloroform; bromodichloromethane; dibromochloromethane; bromoform) in water was optimised. Samples were purged and trapped in a cold trap (-100 degrees C) fed with liquid nitrogen (cryo-concentration). In order to make this method suitable also for only slightly contaminated waters, some modifications were made to PTI sample introduction, in order to avoid any air intake into the system. PTI, GC and MS conditions were optimised for halogenated compound analysis and limits of detection (LOD) were evaluated. The proposed method allows analysis of samples whose concentrations range from microg/L to ng/L. It is, therefore, applicable to drinking waters, in analyses required by law, and to slightly contaminated aqueous matrices, such as those found in remote areas, in environmental monitoring. Moreover, by changing cold trap temperature, even sparkling mineral waters can be analysed, thus avoiding CO2 interference during the cryo-concentration phase. Our method has been successfully used on real samples: tap water, mineral water and Antarctic snow.

Gas Chromatography-Mass Spectrometry↗

PubMed2005

Modulating effects of humic acids on genotoxicity induced by water disinfectants in Cyprinus carpio.

The use of chlorinated disinfectants during drinking-water production has been shown to generate halogenated compounds as a result of interactions of humic acids with chlorine. Such chlorinated by-products have been shown to induce genotoxic effects and consumption of chlorinated drinking-water has been correlated with increased risk for cancer induction in human populations. The aim of this work was to test the potential genotoxic effects on circulating erythrocytes of the fish Cyprinus carpio exposed in vivo to well-waters disinfected with sodium hypochlorite (NaClO), chlorine dioxide (ClO2) or peracetic acid (CH3COO2H, PAA), in the absence or presence of standard humic acids (HA). The effects were measured by use of the micronucleus (MN) and the single-cell gel electrophoresis (Comet) assays at different sampling times after a 3-day exposure period. The exposure to chlorine disinfectants without the addition of HA produced a clear toxic effect. Significant cytogenetic damage (i.e. MN induction) was detected in fish populations exposed to both NaClO and ClO2 with humic acids. In the Comet assay, a significant decrease of DNA migration was observed in erythrocytes of specimens after exposure to NaClO-disinfected water without HA. No effects were observed in any other experimental condition.

Animals↗

PubMed1997

Different distribution of fluorinated anesthetics and nonanesthetics in model membrane: a 19F NMR study.

Despite their structural resemblance, a pair of cyclic halogenated compounds, 1-chloro-1,2,2-trifluorocyclobutane (F3) and 1,2-dichlorohexafluorocyclobutane (F6), exhibit completely different anesthetic properties. Whereas the former is a potent general anesthetic, the latter produces no anesthesia. Two linear compounds, isoflurane and 2,3-dichlorooctofluorobutane (F8), although not a structural pair, also show the same anesthetic discrepancy. Using 19F nuclear magnetic spectroscopy, we investigated the time-averaged submolecular distribution of these compounds in a vesicle suspension of phosphatidylcholine lipids. A two-site exchange model was used to interpret the observed changes in resonance frequencies as a function of the solubilization of these compounds in membrane and in water. At clinically relevant concentrations, the anesthetics F3 and isoflurane distributed preferentially to regions of the membrane that permit easy contact with water. The frequency changes of these two anesthetics can be well characterized by the two-site exchange model. In contrast, the nonanesthetics F6 and F8 solubilized deeply into the lipid core, and their frequency change significantly deviated from the prediction of the model. It is concluded that although anesthetics and nonanesthetics may show similar hydrophobicity in bulk solvents such as olive oil, their distributions in various regions in biomembranes, and hence their effective concentrations at different submolecular sites, may differ significantly.

Anesthetics↗

PubMed2000

Characterization of a commercial gas chromatography-flame ionization detection system for the in situ determination of C5-C10 hydrocarbons in ambient air.

A commercial automated gas chromatograph with preconcentration on solid adsorbents (AirmoVoc HC1010) was coupled with a mass spectrometer in parallel with the flame ionization detection (FID) system and characterized for its suitability for quasi continuous measurements of atmospheric hydrocarbons (HCs) with a time resolution of 20 min. Of the 50 identified HCs in the range C5-C10, 15 elute in isolated peaks and 20 in groups of two or more HCs. The remaining 15 HCs suffer from coelution by oxygenated and halogenated compounds. Procedures to minimize and quantify the blanks and the memory from the adsorbents are described. Calibration was based on a custom-made diffusion source. The accuracy of this calibration (+/-10%, 2sigma) was verified by analysis of a certified 70-component standard (average deviation: -4.3+/-2%). During a field experiment in Summer 1998, the HC1010 system was compared with a custom-made GC system with cryogenic preconcentration and much better separation properties but lower time resolution. In ambient air, good agreement (2sigma deviation <14% or 10 ppt) was found for HCs and groups of HCs that are free from coelution with oxygenated compounds, whereas large discrepancies (in some cases more than a factor of three) were found for those HCs that coelute with oxygenated compounds, as identified by MS. Analysis of the mass spectra from those peaks via specific target ions showed much better agreement with the FID system of the reference GC within 25%.

Air Pollutants↗

PubMed2003

Fate of pharmaceuticals--photodegradation by simulated solar UV-light.

The fate of pharmaceuticals in surface waters under solar irradiation was investigated. Photodegradation of pharmaceuticals caused by sun irradiation may be of major significance in the natural elimination process. Based on a data compilation from the literature, the lipid lowering agent metabolite clofibric acid, the iodinated X-ray contrast media iomeprol, which contribute to the adsorbable organic halogen compounds, and the antiepileptic drug carbamazepine were selected. The irradiation experiments were carried out in batch experiments with simulated UV-sunlight. The photodegradation of the pharmaceuticals showed a pseudo-first-order kinetics. The objective of this investigation was to demonstrate that the extent of photoinduced degradation of pharmaceuticals can vary significantly for the different pharmaceuticals and it strongly depends on the water constituents present in solution. The influences of different initial pharmaceutical concentrations, the presence of other pharmaceuticals like carbamazepine or clofibric acid and the presence of natural organic matter on the photochemical degradation rate of pharmaceuticals in aqueous solutions were investigated. Analyses of the pharmaceuticals and their photodegradation products were carried out by high performance liquid chromatography with diode-array and fluorescence detection.

Carbamazepine↗

PubMed1996

Enhancement of chromosome aberrations by the combination of DNA substitution with halogenated deoxyuridine and streptonigrin treatments.

We treated CHO cells with streptonigrin (SN) alone, in combination with BrdUrd or IdUrd substitution, and with or without the addition of caffeine. The cells assessed for chromosome damage by SN were in the G2 period and the magnitude of the damage was expressed as monosubstituted chromatid breaks, bisubstituted chromatid breaks and boundary regions breaks (boundary regions indicate the point of exchange of mono- and bisubstituted chromatids). We found that the combination of BrdUrd or IdUrd substitution with SN treatments produced a remarkable increase in the frequency of breaks over the frequencies observed with the halogenated compound only. The effect was more evident with IdUrd than with BrdUrd, and more dramatic in bisubstituted than in monosubstituted chromatids. The frequency of boundary breaks in cells treated with BrdUrd plus SN was similar to the frequency of breaks in monosubstituted chromatids treated similarly. Conversely, the damage in boundary regions was almost similar to that in bisubstituted chromatids in cells challenged with IdUrd plus SN. The addition of caffeine to BrdUrd-substituted chromosomes gave rise to a marked enhancement of breakages with a gradient of chromatid damage that was: bisubstituted > monosubstituted > boundary regions. A further increase of chromatin breaks maintaining the gradient indicated above was obtained when the cells were treated with BrdUrd plus SN plus caffeine. We propose that BrdUrd and IdUrd substitution alone or in combination with caffeine treatments and with SN in its capacity to bind DNA, give rise to different chromatin structures capable of modulating the DNA damage induced along the chromatin fibril by the active oxygen species liberated by SN-DNA complexes.

Animals↗

PubMed2003

A microplate fluorimetric assay for measuring dehalogenase activity.

A fluorimetric assay was developed to measure halide release from halogenated compounds being degraded by microbes. The method relies on the property of halides to quench the fluorescence of 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ) by collision quenching. The assay shows a wide response to halide concentration (1-500 mM) and tolerates a wide pH range. Furthermore, it is simple to use, has the potential for automation and uses an inexpensive non-toxic reagent.

Biodegradation, Environmental↗

PubMed2001

Formation and detoxification of reactive intermediates in the metabolism of chlorinated ethenes.

Short-chain halogenated aliphatics, such as chlorinated ethenes, constitute a large group of priority pollutants. This paper gives an overview on the chemical and physical properties of chlorinated aliphatics that are critical in determining their toxicological characteristics and recalcitrance to biodegradation. The toxic effects and principle metabolic pathways of halogenated ethenes in mammals are briefly discussed. Furthermore, the bacterial degradation of halogenated compounds is reviewed and it is described how product toxicity may explain why most chlorinated ethenes are only degraded cometabolically under aerobic conditions. The cometabolic degradation of chlorinated ethenes by oxygenase-producing microorganisms has been extensively studied. The physiology and bioremediation potential of methanotrophs has been well characterized and an overview of the available data on these organisms is presented. The sensitivity of methanotrophs to product toxicity is a major limitation for the transformation of chlorinated ethenes by these organisms. Most toxic effects arise from the inability to detoxify the reactive chlorinated epoxyethanes occurring as primary metabolites. Therefore, the last part of this review focuses on the metabolic reactions and enzymes that are involved in the detoxification of epoxides in mammals. A key role is played by glutathione S-transferases. Furthermore, an overview is presented on the current knowledge about bacterial enzymes involved in the metabolism of epoxides. Such enzymes might be useful for detoxifying chlorinated ethene epoxides and an example of a glutathione S-transferase with activity for dichloroepoxyethane is highlighted.

Aerobiosis↗

PubMedDate not supplied

[Halogenated by-products of chlorination in tap water].

OBJECTIVE: The presence of trihalomethanes in the water systems of several Spanish cities has been demonstrated. The aim of this study was to analyze trihalomethane concentrations in the water provided for human consumption in the city of Barcelona. METHODS: We analyzed 151 water samples collected in 1998. The analyses were performed in the Public Health Laboratory of Barcelona using the purge-and-trap method and subsequent determination by gas chromatography and mass spectrometry. The results are presented according to the source of the water: the rivers of Llobregat or Ter, or a mixture of these. RESULTS: Trihalomethane concentrations in the water from Ter were relatively low, with a predominance of chloroform and bromodichloromethane, while concentrations in the water from Llobregat were much higher, with a predominance of bromoform and dibromochloromethane. Mixed water showed intermediate concentrations. The total concentrations reached in the water from Llobregat were above 100 microg/l. CONCLUSIONS: The results show the need to continue reducing organic pollution and halogenated compounds in the water used for human consumption in Barcelona.

Chlorine↗

PubMed1998

Effect of temperature and some common metals on the stability of volatile anaesthetic-Entonox mixtures.

Thermal stability of pressurised ready-to-use volatile liquid anaesthetic mixtures (halothane, isoflurane and enflurane) in Entonox (commercially available premixed 50% N2O, 50% O2 mixture) were investigated at temperatures of 20, 258, 400, 503 and 602 degrees C on glass, stainless steel, copper and aluminium by gas chromatography and GC-MS. It was found that most of the decomposition products formed were halogenated compounds and the observed thermal stabilities in glass, stainless steel and copper allowed a thermal treatment up to 250 degrees C without any decomposition problem. Aluminium was found to be the most effective metal at causing decomposition of the anaesthetic mixtures even at lower temperatures.

Aluminum↗

PubMed2002

Antimitochondrial antibodies in primary biliary cirrhosis: the role of xenobiotics.

Primary biliary cirrhosis is an enigmatic autoimmune disease of women characterized by antimitochondrial antibodies and destruction of intrahepatic bile ducts. The etiology of PBC is unknown, but we present data herein that the disease may be induced by xenobiotic (i.e. chemicals) exposure. In particular, we postulate that halogenated compounds will bind to the autoantigen, break tolerance, and lead to an intense mucosal response.

Animals↗

PubMed2001

Determination and mass spectrometric investigation of a new mixed halogenated persistent component in fish and seal.

An unknown component that caused an intense signal in sample extracts of fish tissue was enriched and investigated using a variety of mass spectrometric techniques coupled to gas chromatographic separation. With the help of electron capture negative ion mass spectrometry (ECNI-MS) and electron impact mass spectrometry (EI-MS) it was established that the component carries 2Br and 3Cl atoms and forms a molecular ion at m/z 396. A concentrated solution of this mixed halogenated compound (MHC-1) was investigated by gas chromatography interfaced to electron impact high-resolution mass spectrometry (GC/EI-HRMS). Using full scan and SIM techniques, the molecular formula of MHC-1 was established to be C10H13Br2Cl3. This points toward MHC-1 having a monoterpene backbone. No chemical with this molecular formula has been synthesized, but two components with this composition have been earlier isolated from marine algae.

Alkenes↗