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PubMed1975

Nonlinear phenomena in oscillatory systems of homogeneous reactions - experimental observations.

An oscillating system of homogeneous chemical reactions (oxidation of malonic acid by bromate with ceric/cerous ion system as the catalyst) was followed experimentally in several reactor configurations, operated both as close and open systems. Characteristic nonlinear phenomena observed include: damped oscillations of concentrations of reaction components in a well stirred batch reactor, undampted oscillations and sudden changes of oscillatory behaviour (jump to a new steady state) in CSTR and interaction of oscillations in the two connected CSTRs. In a tubular reactor stationary and travelling concentration waves were observed. In the system of CSTR connected with a tubular reactor spreading of waves from CSTR to the tubular reactor, and vice versa was followed. In the flow through tubular reactor the formation of non-monotomic concentration profiles was measured, which were basically stationary with respect to changing flow-rate. The course of oscillations in CSTR was simulated on the basis of a semiempirical reaction kinetics model. An attempt to simulate quantitatively the behaviour of the distributed system with the common type of Fickian diffusion balance equations failed. Difficulties in the proper description of the transport of ions through the concentration gradient and the gradient of the electrical potential found in this system are discussed.

Bromates↗
PubMed1977

Three steady state situation in an open chemical reaction system I.

In an isothermal continuously stirred tank reactor (open chemical reaction system) fed by sulphuric acid solutions of bromate, bromide and cerium (III) bistability (three steady state situation) is experimentally observed. This remarkable behavior, based on the instability of one steady state, has important consequences for the understanding of excitability and biochemical control mechanisms. The mass-balance equations for the reactor and the chemical mechanism of the reaction are combined into a simple mathematical model. The behavior of the resulting nonlinear differential equations is examined analytically and by a graphical integration procedure (method of isoclines). Using realistic kinetic data, the model shows the same behavior as observed in the experiment.

Bromates↗
PubMed1984

Studies on the promoting and complete carcinogenic activities of some oxidizing chemicals in skin carcinogenesis.

Six oxidizing chemicals were tested for promoting and complete carcinogenic activities in skin carcinogenesis using female Sencar mice. In the promotion tests, the chemicals were applied twice a week for 51 weeks after initiation with dimethylbenzanthracene (DMBA). In the tests for complete carcinogenic activities, the chemicals alone were applied for 51 weeks. Benzoyl peroxide was found to be a potent promoter as reported previously. Moreover, possible complete carcinogenic action of this chemical was found in this study. Potential promoting effect was suspected in sodium chlorite. Potassium bromate, ammonium persulphate, hydrogen peroxide and sodium hypochlorite were inactive either as a promoter or a complete carcinogen.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1993

Organotropic formation and disappearance of 8-hydroxydeoxyguanosine in the kidney of Sprague-Dawley rats exposed to adriamycin and KBrO3.

A form of oxidative DNA damage, 8-hydroxydeoxyguanosine (8-OHdG), was comparatively determined for 48 h in the kidney and liver isolated from Sprague-Dawley rats i.p. treated with Adriamycin; potassium bromate (KBrO3), hydroquinone and vitamin A. HPLC-ECD analysis system showed that Adriamycin and KBrO3, renal carcinogens, induced higher levels of 8-OHdG in the target organ of kidney (12-13.8 residues/10(4) dG(deoxyguanosine)) compared to those in the liver (3.4-3.8 residues/10(4) dG) and showed highly persistent levels (8 residues, 10(4) dG) in the kidney. The data suggest that the organotropic persistence of 8-OHdG may provide a useful marker for identifying target organ systems in oxidative chemical carcinogenesis and screening free radical-generating carcinogens.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2005

Polyoxometallates as inorganic templates for electrocatalytic network films of ultra-thin conducting polymers and platinum nanoparticles.

We develop a concept of fabrication of the multilayer network films on electrodes by exploring the ability of a Keggin-type polyoxometallate, phosphododecamolybdate (PMo(12)O(40)(3-)), to form stable anionic monolayers (templates) on carbon and metals including platinum. By repeated alternate treatments in the solution of PMo(12)O(40)(3-) (or in the colloidal suspension of polyoxometallate-protected Pt-nanoparticles) and in the solution of monomer (e.g. anilinium) cations, the amount of the material can be increased systematically (layer-by-layer) to form stable three-dimensional assemblies on electrode (e.g. glassy carbon) surfaces. In the resulting hybrid (organic-inorganic) films, the layers of negatively charged polyoxometallate, or polyoxometallate-protected (stabilized) Pt-nanoparticles, are linked or electrostatically attracted by ultra-thin layers of such positively charged conducting polymers as polyaniline (PANI), polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene), PEDOT. Consequently, the attractive physicochemical properties of polymers and reactivity of polyoxometallate or noble metal particles are combined. The films are functionalized and show electrocatalytic properties towards reduction of nitrite, bromate, hydrogen peroxide or oxygen. They are of importance to the chemical and biochemical sensing as well as to the biochemical and medical applications.

Aniline Compounds↗
PubMed2006

Activity of OGG1 variants in the repair of pro-oxidant-induced 8-oxo-2'-deoxyguanosine.

Cells are continuously exposed to damaging reactive oxygen species (ROS), which are produced from both endogenous and exogenous sources. 8-Oxodeoxyguanosine (8-oxodG) is an abundant base lesion formed during oxidative stress which, if not repaired, can give rise to G:C-->T:A transversions in DNA. The 8-oxoguanine DNA glycosylase-1 (OGG1)-initiated base excision repair (BER) pathway operates to remove 8-oxodG lesions. Ogg1 deletion and polymorphism may result in a hypermutator phenotype and susceptibility to oxidative pathologies including cancer. Limited and conflicting evidence exists regarding the repair capacity of a prevalent human OGG1 (hOGG1) polymorphism, the Cys326-hOGG1 variant. The formamidopyrimidine DNA glycosylase (FPG)-modified comet assay was used to investigate the ability of sodium dichromate, potassium bromate and Ro19-8022 (+light) to induce DNA damage in mogg1(-/-) null (KO) and wild-type (WT) mouse embryonic fibroblasts (MEFs) and to assess hOGG1 variant-initiated BER capacities under conditions of oxidative stress. Treatment of WT MEFs with these pro-oxidant agents induced direct DNA strand breaks in a concentration-dependent manner, whereas, identical treatment of KO MEFs produced no effect. In contrast, KO MEFs accumulated significantly more FPG-sensitive sites than WT MEFs. Expression of hOGG1 in KO MEFs restored the WT phenotype in response to all pro-oxidants tested. The results suggest OGG1-initiated BER generates direct DNA strand breaks detected by the conventional comet assay, thus it is important that researchers do not interpret these as direct damage per se but rather a reflection of the repair process. The data also indicate Cys326-hOGG1-initiated BER is transiently impaired with respect to Ser326-hOGG1 (wild-type)- and Gly326-hOGG1 (artificial)-initiated BER following pro-oxidant treatment, possibly via hOGG1 cysteine 326 oxidation. This finding suggests the homozygous cys326/cys326 genotype may be classified as a biomarker of disease susceptibility, which is in support of a growing body of epidemiological evidence.

Animals↗
PubMed2005

Heterogeneous photocatalysed degradation of two selected pesticide derivatives, triclopyr and daminozid in aqueous suspensions of titanium dioxide.

Heterogeneous photocatalysed degradation of two selected pesticide derivatives, triclopyr (1) and daminozid (2), has been investigated in aqueous suspensions of titanium dioxide by monitoring the change in substrate concentration employing the UV Spectroscopic analysis technique and depletion of Total Organic Carbon (TOC) content as a function of irradiation time. The degradation kinetics were studied under different conditions such as reaction pH, substrate and catalyst concentration, different types of TiO2 and in the presence of electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3) and ammonium persulphate (NH4)2S2O8 in addition to molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts. The pesticide derivative triclopyr (1) was found to degrade faster as compared to daminozid (2). An attempt was also made to identify the intermediate products formed during the photooxidation process using GC/MS analysis. Probable pathways for the formation of products have been proposed.

Ammonium Sulfate↗
PubMed2006

Heterogeneous photocatalyzed degradation of uracil and 5-bromouracil in aqueous suspensions of titanium dioxide.

Photocatalyzed degradation of uracil (1) and 5-bromouracil (2) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation of the compounds under investigation was studied using various parameters such as, different types of TiO2 powders, pH, catalyst concentration, substrate concentrations, and in the presence of electron acceptors like hydrogen peroxide (H(2)O(2)) and potassium bromate (KBrO(3)) besides molecular oxygen. Photocatalyst Degussa P25 was found to be more efficient for the degradation of both compounds as compared with other TiO2 powders such as UV100, PC500 and TTP.

Bromates↗
PubMed2005

Flow injection kinetic spectrofluorimetric determination of trace amounts of osmium.

A flow injection (FI) kinetic spectrofluorimetric method is described for the determination of osmium(IV) and the possible mechanism of catalytic reaction is discussed. The method is based on the fluorescence enhancing reaction of o-vanillin furfuralhydrazone (OVFH) with potassium bromate, which is catalyzed by Os(IV) in water medium at pH 6.10 and 45 degrees C. OVFH is newly synthesized and its ionization, IR and elemental analysis are established. Under these experimental conditions, the oxidized product of OVFH has excitation and emission maxima at 337 and 490 nm, respectively. The linear range of this method is 0-600 ng ml(-1) with the R.S.D. of 1.2%. The detection limit is 1.0 ng ml(-1) of Os(IV). A high analysis rate of 24 samples h(-1) is obtained by the FI method. The proposed method is applied successfully to determine Os(IV) in synthetic mixture and mineral samples, and the results are well consistent with the standard values.

Benzaldehydes↗
PubMed2002

Applications of ion chromatography with electrospray mass spectrometric detection to the determination of environmental contaminants in water.

Ion chromatography (IC) is widely used for the compliance monitoring of common inorganic anions in drinking water. However, there has recently been considerable interest in the development of IC methods to meet regulatory requirements for analytes other than common inorganic anions, including disinfection byproduct anions, perchlorate, and haloacetic acids. Many of these new methods require the use of large injection volumes, high capacity columns and analyte specific detection schemes, such as inductively coupled plasma mass spectrometry or postcolumn reaction with UV-Vis detection, in order to meet current regulatory objectives. Electrospray ionization mass spectrometry (ESI-MS) is a detection technique that is particularly suitable for the analysis of permanently ionized or polar, ionizable compounds. The combination of IC with MS detection is emerging as an important tool for the analysis of ionic compounds in drinking water, as it provides increased specificity and sensitivity compared to conductivity detection. This paper reports on the application of IC-ESI-MS for the confirmation and quantitation of environmentally significant contaminants, i.e. compounds with adverse health effects which are either regulated or being considered for regulation, such as bromate, perchlorate, haloacetic acids, and selenium species, in various water samples.

Acetates↗
PubMed1999

Combination of suppressed and non-suppressed ion chromatography with atmospheric pressure ionization mass spectrometry for the determination of anions.

Non-suppressed and suppressed ion chromatography in combination with atmospheric pressure ionization mass spectrometry are compared with special respect to sensitivity for the analysis of low-molecular-mass anions. Iodate, bromate, bromide, sulfate, thiosulfate and bromide could be separated by non-suppressed ion chromatography using a low-capacity anion-exchange column and ammonium citrate as mobile phase. Absolute detection limits between 0.4 and 0.7 ng could be achieved; employing a column requiring a flow-rate of 1 ml/min for optimum performance, splitting was necessary so that only 120 microliters/min entered the interface of the mass spectrometer resulting in detection limits between 0.03 and 0.06 mg/l. The same stationary phase (packed into a narrow-bore column which allowed operation without splitting) was suitable for the separation of oxyhalides in the suppressed mode with detection limits of 0.5 microgram/l (50 pg) with sodium carbonate as eluent. The method was applied to the analysis of drinking water for oxyhalides. The sample pretreatment for the removal of matrix anions (sulfate, chloride and hydrogencarbonate) is described.

Anions↗
PubMed2001

Effect of gravity field on the nonequilibrium/nonlinear chemical oscillation reactions.

Biological systems have evolved for a long time under the normal gravity. The Belousov-Zhabotinsky (BZ) reaction is a nonlinear chemical system far from the equilibrium that may be considered as a simplified chemical model of the biological systems so as to study the effect of gravity. The reaction solution is comprised of bromate in sulfuric acid as an oxidizing agent, 1,4-cyclohexanedione as an organic substrate, and ferroin as a metal catalyst. Chemical waves in the BZ reaction-diffusion system are visualized as blue and red patterns of ferriin and ferroin, respectively. After an improvement to the tubular reaction vessels in the experimental setup, the traveling velocity of chemical waves in aqueous solutions was measured in time series under normal gravity, microgravity, hyper-gravity, and normal gravity using the free-fall facility of JAMIC (Japan Microgravity Center), Hokkaido, Japan. Chemical patterns were collected as image data via CCD camera and analyzed by the software of NIH image after digitization. The estimated traveling velocity increased with increasing gravity as expected. It was clear experimentally that the traveling velocity of target patterns in reaction diffusion system was influenced by the effect of convection and correlated closely with the gravity field.

Bromates↗
PubMed1999

Nonequilibrium / nonlinear chemical oscillation in the virtual absence of gravity.

The Belousov-Zhabotinsky (BZ) reactions were used as typical examples of a nonlinear system far from equilibrium in connection with biological evolution. The virtual absence of gravity in the present work was given from the free-fall facility of Japan Microgravity Center (JAMIC) in Hokkaido. The reaction solution of BZ reaction was composed of bromate in sulfuric acid, 1,4-cyclohexanedione and ferroin to visualize the time development of patterns of chemical oscillations in the reaction-diffusion system. It is a bubble-free constitution in the aging of the reaction. Therefore, the setup constructed to collect image data via CCD cameras was simplified. The operation sequences of necessary devices were comprised of simple solid state relays which were started by a command from the operation room of JAMIC. The propagation profile of chemical patterns under microgravity of 10(-5) g was collected as image data for 9.8 s, and processed by a software of STM-STS2. In the aqueous solutions, propagation velocity of chemical patterns under microgravity was decreased to 80.9 % of that under normal gravity, owing to suppression of convection. On the other hand, in gel matrix, gravity did not influence the propagation velocity.

Bromates↗
PubMedDate not supplied

Hydroquinone: genotoxicity and prevention of genotoxicity following ingestion.

Plant-derived polyphenolics and other chemicals with antioxidant properties have been reported to inhibit the expression of genotoxic activity by pro-oxidant chemicals (Sai et al., 1992, 1994; Teel and Castonguay, 1992). In vitro and in vivo studies with ionizing radiation suggest that hydroquinone (HQ) may have similar protective effects (Babaev et al., 1994). The present study was conducted to determine whether HQ is capable of inhibiting the induction of micronuclei in the bone marrow of mice following exposure to an oxidant, potassium bromate or KBrO3 (Nakajima et al., 1989; Sai et al., 1992, 1994). To be able to interpret the results of this work, it was also necessary to determine whether HQ is itself genotoxic when fed in the diet. HQ diets (0.8%) fed to mice for 6 days reduced the background incidence of micronuclei compared with the basal diet. KBrO3 dosed ip (12.5-100 mg/kg) produced a dose-dependent increase in micronuclei as reported by others. Mice fed 0.8% HQ diets 6 days, and then dosed intraperitoneally with KBrO3, showed a 36% reduction in micronuclei across the range of KBrO3 dose levels. This effect was associated with a reduction in the background micronucleus response as well as a reduction in response to KBrO3. Statistical significance (P < or = 0.05), observed at a dose of 25 mg/kg KBrO3 in the mice fed the control diet, was abolished in the group fed 0.8% HQ. When mice were given 50 mg HQ/kg by oral gavage and then given 50 mg KBrO3/kg ip 20 min later, the micronucleus response induced by KBrO3, was lower in animals given HQ. The results of this study demonstrate that large doses of HQ may be given orally without induction of micronuclei or bone marrow depression, that HQ reduces the background micronucleus response in animals fed a basal diet, and that the HQ reduces the micronucleus response to KBrO3 as well as background incidence of micronuclei in KBrO3-dosed animals. The protective effect of HQ may be due to enzyme induction or a direct antioxidant effect of HQ against oxidants commonly present in the diet.

Administration, Oral↗
PubMed2003

Analysis of preneoplastic and neoplastic renal lesions in Tsc2 mutant Long-Evans (Eker) rats following exposure to a mixture of drinking water disinfection by-products.

Disinfection of surface water for human consumption results in the generation of a complex mixture of chemicals in potable water. Cancer risk assessment methodology assumes additivity of carcinogenic effects in the regulation of mixtures. A rodent model of hereditary renal cancer was used to investigate the carcinogenic response to a mixture of drinking water disinfection by-products (DBPs). Rats carrying a mutation in the Tsc2 tumor suppressor gene (Eker rats) readily develop renal preneoplastic and neoplastic lesions, and are highly susceptible to the effects of renal carcinogens. Male and female Eker rats were exposed via drinking water to individual or a mixture of DBPs for 4 or 10 months. Potassium bromate, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), chloroform, and bromodichloromethane were administered at low concentrations of 0.02, 0.005, 0.4 and 0.07 g/l, respectively, and high concentrations of 0.4, 0.07, 1.8 and 0.7 g/l, respectively. Low and high dose mixture solutions were comprised of all four chemicals at either low concentrations or high concentrations, respectively, Following necropsy, each kidney was examined microscopically for preneoplastic lesions (atypical tubules and hyperplasias) and tumors. While some of the mixture responses observed in male rats did fall within the range expected for an additive response, especially at the high dose, predominantly antagonistic effects on renal lesions were observed in response to the low dose mixture in male rats and the high dose mixture in female rats. These data suggest that current default risk assessments assuming additivity may overstate the cancer risk associated with exposure to mixtures of DBPs at low concentrations.

Animals↗
PubMed1999

Resveratrol, melatonin, vitamin E, and PBN protect against renal oxidative DNA damage induced by the kidney carcinogen KBrO3.

Free radical scavengers can protect against the genotoxicity induced by chemical carcinogens by decreasing oxidative damage. The protective effect of the antioxidants melatonin, resveratrol, vitamin E, butylated hydroxytoluene and 2-mercaptoethylamine, and the spin-trapping compound alpha-phenyl-N-tert-butyl nitrone (PBN) against oxidative DNA damage was studied in the kidney of rats treated with the kidney-specific carcinogen potassium bromate (KBrO3). KBrO3 was given to rats previously treated with melatonin, resveratrol, PBN, vitamin E, butylated hydroxytoluene, or 2-mercaptoethylamine. Oxidative damage to kidney DNA was estimated 6 hours afterwards by measuring 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo8dG) referred to deoxyguanosine (dG) by means of high performance liquid chromatography with electrochemical-coulometric and ultraviolet detection. Levels of oxo8dG in the renal genomic DNA significantly increased by more than 100% after the KBrO3 treatment. This increase was completely abolished by the treatment with resveratrol and was partially prevented by melatonin, PBN and vitamin E. Resveratrol and PBN also prevented the increase in relative kidney weight induced by KBrO3. These results show that various different antioxidants and a free radical trap, working in either the water-soluble or the lipid-soluble compartments, can prevent the oxidative DNA damage induced in the kidney by the carcinogen KBrO3.

Animals↗
PubMed2002

Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 x 3H2O.

Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 x 3H2O are recorded and analyzed. The observed bands are assigned on the basis of BrO3- and H2O vibrations. Additional bands obtained in the region of v3 and v1 modes in [Cu(H2O)6](BrO3)2 are due to the lifting of degeneracy of v3 modes, since the BrO3- ion occupies a site of lower symmetry. The appearance v1 mode of BrO3- anion at a lower wavenumber (771 cm(-1)) is attributed to the attachment of hydrogen to the BrO3- anion. The presence of three inequivalent bromate groups in the [Al(H2O)6](BrO3)3 x 3H2O structure is confirmed. The lifting of degeneracy of v4 mode indicates that the symmetry of BrO3- anion is lowered in the above crystal from C3v to C1. The appearance of additional bands in the stretching and bonding mode regions of water indicates the presence of hydrogen bonds of different strengths in both the crystals. Temperature dependent Raman spectra of single crystal [Cu(H2O)6](BrO3)2 are recorded in the range 77-523 K for various temperatures. A small structural rearrangement takes place in BrO3- ion in the crystal at 391 K. Hydrogen bounds in the crystal are rearranging themselves leading to the loss of one water molecule at 485 K. This is preceded by the reorientation of BrO3- ions causing a phase transition at 447 K. Changes in intensities and wavenumbers of the bands and the narrowing down of the bands at 77 K are attributed to the settling down of protons into ordered positions in the crystal.

Aluminum↗
PubMed2005

Quantitation of dityrosine in wheat flour and dough by liquid chromatography-tandem mass spectrometry.

A method for the quantitation of dityrosine in wheat flour and dough by high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) using an isotope dilution assay with the internal standard 3,3'-(13)C(2)-dityrosine in the single-reaction monitoring mode was developed. The method consisted of the release of protein-bound dityrosine by hydrolysis in 4 mol/L hydrochloric acid/8.9 mol/L propionic acid for 24 h at 110 degrees C after addition of the internal standard, cleanup by C(18) solid-phase extraction, and HPLC-MS/MS. The limit of detection of dityrosine was 80 ng/g of sample (0.22 nmol/g), and the limit of quantitation was 270 ng/g of sample (0.75 nmol/g). The method was sensitive enough to analyze wheat flour and dough and to study the effect of flour improvers on the dityrosine content. Furthermore, the effect of the mixing time was studied. The dityrosine concentration in the flour was 0.66 nmol/g. After we mixed a dough to peak consistency, the dityrosine concentration doubled and remained constant on further mixing. Overdoses of hydrogen peroxide and hexose oxidase (HOX, E.C. 1.1.3.5) resulted in a strongly increased dityrosine content, whereas no increase of the dityrosine concentration was found after the addition of ascorbic acid and potassium bromate. Calculation of the percentage of dimeric tyrosine showed that less than 0.1% of the tyrosine residues of wheat protein were cross-linked. Therefore, dityrosine residues seem to play only a very minor role in the structure of wheat gluten.

Alcohol Oxidoreductases↗