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Results for “Ferrous Compounds”

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PubMed1992

Spectroscopic characterization of heme A reconstituted myoglobin.

The focus of this study was to examine the functional role of the unusual peripheral substitution of heme A. The effects of heme A stereochemistry on the reconstitution of the porphyrin have been examined in the heme A-apo-myoglobin complex using optical absorption and resonance Raman and electron paramagnetic resonance spectroscopies. The addition of one equivalent of heme A to apo-Mb produces a complex which displays spectroscopic signals consistent with a distribution of high- and low-spin heme chromophores. These results indicate that the incorporation of heme A into apo-Mb significantly perturbs the protein refolding.

Animals↗

PubMedDate not supplied

Iron-mediated DNA damage: sensitive detection of DNA strand breakage catalyzed by iron.

Oxidative DNA damage is involved in mutagenesis, carcinogenesis, aging, radiation effects, and the action of several anticancer drugs. Accumulated evidence indicates that iron may play an important role in those processes. We studied the in vitro effect of low concentrations of Fe(II) alone or Fe(III) in the presence of reducing agents on supercoiled plasmid DNA. The assay, based on the relaxation and linearization of supercoiled DNA, is simple yet sensitive and quantitative. Iron mediated the production of single and double strand breaks in supercoiled DNA. Iron chelators, free radical scavengers, and enzymes of the oxygen reduction pathways modulated the DNA damage. Fe(III)-nitrilotriacetate (NTA) plus either H2O2, L-ascorbate, or L-cysteine produced single and double strand breaks as a function of reductant concentration. A combination of 0.1 microM Fe(III)-NTA and 100 microM L-ascorbate induced detectable DNA strand breaks after 30 min at 24 degrees C. Whereas superoxide dismutase was inhibitory only in systems containing H2O2 as reductant, catalase inhibited DNA breakage in all the iron-mediated systems studied. The effect of scavengers and enzymes indicates that H2O2 and .OH are involved in the DNA damaging process. These reactions may account for the toxicity and carcinogenicity associated with iron overload.

Ascorbic Acid↗

PubMed1993

Reversal of copper(II)-induced methemoglobin formation by thiols.

Oxyhemoglobin is oxidized to methemoglobin by copper(II) in a two-stage reaction that results in conversion of Fe(II) to Fe(III) in heme of the beta subunits, but not the alpha subunits. Glutathione and other thiols, which are slowly oxidized by Cu(II), protect oxyhemoglobin from Cu(II)-induced oxidation. In the present studies, when oxyhemoglobin was first oxidized to methemoglobin by Cu(II) and thiols such as glutathione added to the sample, methemoglobin was reduced to oxyhemoglobin. Once reduction of methemoglobin stopped, as the thiol was oxidized, the oxyhemoglobin formed was reoxidized by Cu(II). The addition of the same thiols to methemoglobin formed by autoxidation did not reduce it to oxyhemoglobin. The addition of thiols such as cysteine, which are rapidly oxidized by Cu(II), to methemoglobin formed by incubation with Cu(II) also resulted in reduction of methemoglobin, but the period of reversal was much shorter than that seen with glutathione and other less reactive thiols. When cysteine and glutathione were added together to Cu(II)-induced methemoglobin, the rate of reduction and reoxidation was intermediate to that seen when either was added separately. When EDTA was added to a system in which oxyhemoglobin was undergoing Cu(II)-induced oxidation, oxidation of oxyhemoglobin ceased and there was no reduction of the methemoglobin to oxyhemoglobin. When both glutathione and EDTA were added to this system, the response was the same as with EDTA alone, suggesting that Cu(I) or (II) may be required for the reduction of copper-induced methemoglobin by thiols. These studies show that thiols that are slowly oxidized by Cu(II) both protect oxyhemoglobin from Cu(II)-induced oxidation, and reduce the methemoglobin formed to oxyhemoglobin.

Copper↗

PubMed1985

Nanosecond transient resonance Raman spectra of the FeII-CO and FeIII-NO photolysis products of horseradish peroxidase.

Resonance Raman spectra, obtained with 7 ns pulsed laser excitation, are reported for the photoproducts of the FeII-CO and FeIII-NO adducts of horseradish peroxidase. The porphyrin skeletal frequencies are the same as those observed for unligated FeII and FeIII (native) horseradish peroxidase, respectively. The absence of unrelaxed spectra is discussed in relation to the photoproduct frequency shifts and relaxations observed previously for hemoglobin. It is proposed that protein conformational changes which are likely to be associated with the hydrogen-bonding interactions in the horseradish peroxidase heme pocket may not produce detectable changes in the porphyrin skeletal mode frequencies.

Carbon Monoxide↗

PubMed1992

Investigation of a role for reduction in ferric iron uptake by mouse duodenum.

59Fe uptake rates by mouse duodenal fragments incubated in vitro were markedly reduced by non-permeable reagents, ferricyanide (oxidising agent) and ferrozine (Fe2+ chelator), in the medium; ferrocyanide had no effect. Reduction of Fe3+, as reflected by an increase in ferrozine-(Fe2+)-chelatable iron, was observed in the presence of the tissue fragments. The generation of Fe2+ occurred linearly with time, was independent of the medium ferrozine concentration, and was not due to release of reducing factors from the duodenal fragments. Fe(3+)-reducing activity was mainly present on the mucosal surface and was localised primarily to the proximal region of the small intestine. Changes in Fe3+ reduction rates closely parallelled the changes in duodenal 59Fe uptake, when metabolic inhibitors or modulators of membrane potential were included in the medium. The enhancement in duodenal mucosal 59Fe uptake in chronic hypoxic and iron-deficient mice parallelled the changes in the tissue reduction of medium Fe3+. Moreover, the rates of reduction were quantitatively similar to rates of uptake. These observations indicate that a sequential reduction and uptake process operates for Fe3+ uptake in mouse duodenum.

Animals↗

PubMed1993

Serotonin binding proteins in bovine retina: binding of serotonin and catecholamines.

Serotonin binding proteins (SBP) are present in the soluble fraction of bovine retina homogenates. These proteins can be precipitated with 30% ammonium sulphate and their binding and physicochemical characteristics are very similar to those of SBP in bovine and rat brain. Binding of [3H]serotonin to bovine retina SBP requires Fe2+ but not Fe3+. In the presence of an optimal concentration of Fe2+ (0.1 mM), these proteins behave as a single class of non-cooperative sites for [3H]serotonin (Bmax = 242 +/- 10 pmol/mg protein, KD = 0.22 +/- 0.44 microM). Competition binding studies reveal that serotonin analogs possessing an hydroxyl group on the indole ring and catecholamine analogs possessing an intact catechol moiety are potent competitors (K1 from 0.12 to 0.3 microM). In both cases, the affinity is strongly decreased if aromatic hydroxyl groups are methoxylated. Catecholamine SBP interactions can also be demonstrated directly by binding experiments with [3H]dopamine. Binding of this catecholamine is greatly enhanced by Fe2+, to a lesser extent by Cu2+ and Mn2+, but not by Fe3+. The Fe(2+)-dependent binding component is saturable (Bmax = 505 +/- 30 pmol/mg protein. KD = 0.34 +/- 0.04 microM). The SBP from bovine retina show the same physicochemical properties as SBP from bovine and rat brain: they elute immediately after the void volume on a Sephacryl S100 HR (1.6 x 140 cm) gel filtration column (reflecting aggregation) and they migrate with apparent molecular weights of respectively 43 kDa and 57 kDa on native polyacrylamide gel electrophoresis. The serotonin-storing role of SBP in serotonergic neurones has already been well documented.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonium Sulfate↗

PubMed1993

The thiobarbituric acid assay reflects susceptibility to oxygen induced lipid peroxidation in vitro rather than levels of lipid hydroperoxides in vivo: a methodological approach.

Although the hypothesis of oxidative stress as a pathogenetic factor of neurodegenerative diseases became a matter of interest recently, direct evidence supporting this hypothesis is rare. The most prominent assay being currently used as an index for lipid peroxidation products in vivo is the thiobarbituric acid assay. Thiobarbituric acid reactive substances are mainly formed during the decomposition of lipid hydroperoxides in vitro. It is questionable however, that all species detectable with thiobarbituric acid are derived from in vivo preformed lipid hydroperoxides. These studies were undertaken to investigate the influence of autoxidation reactions on colour production during the acid heating stage of the assay. If driven aerobically, more than 90% of thiobarbituric acid reactive substances are newly generated in vitro during incubation at 95 degrees C for 75 min. This process can be enhanced by addition of ferric iron. Chain breaking antioxidants like butylated hydroxytoluene decrease colour formation in the absence or in the presence of iron. If driven anaerobically under argon, colour formation was only 10% of aerobically heated homogenates or lipid extracts of human brain tissue. These results may indicate that measurement of thiobarbituric acid reactive substances under the aerobic conditions described here reflects to a great extent the susceptibility of brain tissue or lipids to oxygen-induced formation of lipid hydroperoxides in vitro rather than degradation products of in vivo performed lipid hydroperoxides.

Aged↗

PubMed1995

Dermatography as an adjunctive treatment for cleft lip and palate patients.

PURPOSE: To investigate dermatography as a treatment for cleft lip and palate. METHODS: The results of the treatment of 19 cleft lip patients with discoloration of scars and the vermillion border after secondary cleft lip and palate surgery by dermatography and intracicatricial keloidectomy are described. RESULTS: This group of patients has gained self-confidence after treatments, to the extent that their articulation has improved. CONCLUSION: Dermatography can be applied as an adjuvant treatment with good cosmetic and esthetic results.

Carbon↗

PubMed1990

Effect of lipid peroxidation on Na+,K(+)-ATPase, 5'-nucleotidase and CNPase in mouse brain myelin.

In the presence of H2O2, solutions of Fe2+ were applied to brain homogenate and isolated myelin from adult SWV control mice and the shiverer dysmyelinating mutant mouse as a source of a reactive oxygen species (Fenton reaction). Under these conditions, lipid peroxidation was initiated and measured as thiobarbituric acid-reactive oxidation products (TBAR). This was accompanied by 85% inhibition of myelin-associated Na+,K(+)-ATPase and 25% inhibition of 5'-nucleotidase. In contrast, CNPase activity was not altered. Studies on the shiverer mutant brain revealed that in spite of hypomyelination and prevalence of premature, myelin-like membranes in the homogenate, the myelin-related enzymes reacted as normal enzymes to peroxidation. Differences in the resistance of Na+,K(+)-ATPase to peroxidation in the brain homogenate and myelin suggest that the myelin enzyme is extremely sensitive to reactive oxygen toxicity.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗

PubMed1995

Mixed valence state in ironporphyrin aggregates.

In biological systems, metalloporphyrins play a central role in energy and electron transfer process. Our aim is to understand the influence of ligands and iron coordination of ironporphyrin on the electron transfer. The lyophilized ironporphyrin, enriched in 57Fe up to 90% has been studied by Mössbauer spectroscopy between 2.8 and 313 K. Above room temperature the bounded diffusion of the ferric iron was observed. Below 293 K a part of iron appears in mixed Fe+3<==>Fe+2 valence state with 10 meV activation energy for the electron trapping. Below 4 K a part of iron shows magnetic ordering with a broad distribution of the hyperfine field. The results are discussed in terms of metalloporphyrin aggregation process.

Electrochemistry↗

PubMed1979

Intracellular hyperthermia. A biophysical approach to cancer treatment via intracellular temperature and biophysical alterations.

This paper introduces a new multi-disciplinary "intracellular" biophysical treatment of cancer. The basic concept uses locally induced heat energy after tumor phagocytosis of submicron particles whose composition permits magnetic excitation. The key to this process is the utilization of the cancer cell membrane to contain the energy within the cancer cell. Any magnetic or electric dipole contained within or introduced into the cell, or that is capable of being produced by an external field, can be used. Submicron particles are colloidally suspended, injected intravenously and are phagocytized by cancer cells. Application of an external high frequency or pulsed electromagnetic field then raises the particles' temperature thus generating intracellular heat in precise increments. This results in selective thermal destruction of cancer cells with little effect on normal cells. Experimental evidence is presented showing tumor cell destruction in spontaneous mammary tumors in Sprague Dawley rats. In addition, we suggest that certain biophysical properties are altered within the cancer cells and could be used to enhance this effect. Specific radioisotopes or tumor specific antibodies bound to particles or chemotherapeutic microspheres increase cancer cell sensitivity and affinity for these particles. This "intracellular" treatment of cancer has a wide potential range of applications.

Animals↗

PubMed1992

The role of Eh, pH and iron in the bactericidal power of human plasma.

The bactericidal power of fresh human plasma against Klebsiella pneumoniae and Escherichia coli was extremely sensitive to changes in Eh and pH. At a high Eh (approx. +200 mV) the bacteria were destroyed, but rapid regrowth occurred when the Eh was lowered to approx. -400 mV. Abolition of the bactericidal effect was also produced by adding ferric iron at a high Eh (approx. +200 mV). Lowering the pH to 6.50 reduced or prevented the bactericidal effect. These results are probably related to the availability of iron for bacterial growth, and could be important for understanding the development of infection in injured or diseased tissue.

Blood Bactericidal Activity↗

PubMed1993

Hydroxyl radical generation by a light-dependent Fenton reaction.

Illumination of Fe3+, with light of a wavelength varying from 250 to 450 nm, in the presence of the iron chelators ethylenediamine N,N,N',N'-tetraacetic acid (EDTA), ethyleneglycol-bis-(beta-aminoethylether)N,N,N',N'-tetraacet ic acid (EGTA), diethylenetriamine-N,N,N',N',N'-pentaacetic acid (DTPA), or citrate resulted in the reduction of Fe3+ to Fe2+. Fe2+ formation was measured by the formation of its complex with bathophenanthroline disulfonic acid. In all cases Fe2+ formation was completely dependent on the presence of the iron chelator and on the wavelength used for illumination. A correlation was found between the absorption spectrum of the iron-chelator complex and the amount of Fe3+ reduced, suggesting that the absorption of light induced an electron transfer from the chelator to the iron ion. Exposure to oxygen, either during or after illumination, resulted in degradation of the chelator molecule. Illumination of the Fe(3+)-chelator complexes in the presence of H2O2 resulted in the formation of hydroxyl radicals, which could be determined by the formation of the 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-hydroxyl radical adduct, using electron spin resonance spectroscopy. Formation of the spin adduct was inhibited by addition of catalase, mannitol, ethanol, or formate, whereas superoxide dismutase had no effect.

Citrates↗

PubMed1993

Fe(2+)-induced lipid peroxidation kinetics in liposomes: the role of surface Fe2+ concentration in switching the reaction from acceleration to decay.

Kinetics of malonyldialdehyde (MDA) accumulation, Fe2+ oxidation, and chemiluminescence (CL) at different initial iron ([Fe2+]) and liposome ([L]) concentrations were measured in liposome suspension. Above certain critical Fe2+ concentrations ([Fe2+]*) the latent period (LP) of LPO development was observed. The method of [Fe2+]* estimation by the dependence of LP value (tau) on [Fe2+] was elaborated. The increase of [L] resulted in decrease of tau and increase of delta MDA as well as SF CL amplitude. [Fe2+]* value changed from 10 to 50 microM with change of [L] from 1 to 4 mg/ml, so that the ratio [Fe2+]*/[L] was kept constant. This may be explained under the assumption that the major part of Fe2+ is bound by the membranes. At concentrations of Fe2+ higher than the critical one, iron chelators (desferrioxamine, o-phenanthroline, and EDTA) and cations (Eu3+, Ca2+, and Fe3+) decreased tau without any essential influence on the CL "slow flash" amplitude (h). Apparently, the only result of iron complexones and cations on LPO is the decrease of Fe2+ ion concentration on the membrane surface. Thus, [Fe2+]* value and surface concentration of Fe2+ are the main parameters determining both kinetics and efficiency of Fe(2+)-induced LPO in membrane systems.

Calcium↗

PubMed1994

Spectral characterization of lipid peroxidation in rabbit lens membranes induced by hydrogen peroxide in the presence of Fe2+/Fe3+ cations: a site-specific catalyzed oxidation.

The role of free-radical-induced lipid peroxidation (LPO) in relation to lens opacity is investigated using Fourier transform infrared spectroscopy. Phospholipids extracted from nuclear and cortical regions of the rabbit lens membranes are subjected to oxidative-damage induced by hydrogen peroxide and Fe2+/Fe3+ cations. Vibrational data suggest a homolytic decomposition of the unsaturated membrane hydrocarbon chains at cis-double bonds, as well as structural modifications at the carbonyl and phosphate-oxygen sites of the fiber cell membranes upon metal oxidation. This is also evident from a substantial induction of the carbonyl groups and a significant dephosphorylation of the phosphate groups in lens phospholipids. These covalent modifications and/or alterations of the carbonyl and phosphate groups, and specificity of certain vibrational modes only to iron oxidation, may serve as a diagnostic probe of the metal-catalyzed LPO in lens membranes. Despite covalent modifications of the hydrophilic part of the lens membranes, hydrocarbon chain region remains largely intact at physiological concentrations of hydrogen peroxide. However, at elevated concentrations of hydrogen peroxide, a substantial breakdown of the acyl chains occurs. Striking similarities observed between the spectral features of the oxidized rabbit lens phospholipids and those of the cataractous human lenses suggest that the mechanism and pathways of lipid oxidation in model animal membranes and in human lenses are similar. Differences in the nuclear or cortical regions are also evident upon metal oxidation. Nuclear lipids experience increased effects of the metal oxidation compared to cortical lipids. Both the nuclear or the cortical lipids indicate effective penetration of the bilayer water creating segregated membrane domains, possibly through breakdown of headgroup-specific lipid-water interactions. This could effectively alter the lens membrane permeability and fluidity, rendering it susceptible to a host of toxic oxidants present in the eye. These findings also demonstrate that LPO can lead to acyl chain degradation that may effectively derange the lens membrane function, which could be a contributing factor in cataractogenesis.

Animals↗

PubMed1995

Effects of intra- and intermolecular crosslinking on the free radical reactions of bovine hemoglobins.

Chemical modifications of human or bovine hemoglobins are designed to produce proteins that can act as oxygen-carrying blood substitutes. Concerns about the redox reactivity of cell-free hemoglobin and its contribution to tissue-damaging oxygen free radicals has not been fully established. We determined that bovine hemoglobins intra- or intermolecularly crosslinked differ in their ability to generate or interact with reactive oxygen species. These differences do not correlate with their oxygen affinities. We compared HbBv-FMDA, produced by the reaction of bovine hemoglobin with fumaryl-monodiaspirin and Poly HbBv, a glutaraldehyde polymerized bovine hemoglobin, with unmodified bovine hemoglobin (HbBv). Superoxide radicals are produced during the spontaneous oxidation of hemoglobin. Relative to the other two proteins. Poly HbBv was found to be more susceptible to autoxidation. Spectral changes indicative of protein modification and ferrylhemoglobin formation during the enzymatic peroxidation of these hemoglobins differ qualitatively and occur at an increasing order, poly HbBv > HbBv > HbBv-FMDA. The proteins also differ in the rate of hemoglobin catalyzed NADPH oxidation and aniline hydroxylation, reactions mediated by reactive oxygen species. Taken together, our results and those reported previously on modified human hemoglobins, suggest that redox and oxygen-carrying functions of hemoglobin can be experimentally manipulated as independently selectable parameters that may ultimately aid in the design of a safer reperfusion agent.

Aniline Compounds↗

PubMed1995

N-methyl(R)salsolinol produces hydroxyl radicals: involvement to neurotoxicity.

Recently, (R)-1,2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [N-methyl-(R)salsolinol, NM(R)Sal] and 1,2-dimethyl-6,7-dihydroxyisoquinolinium ion [DiMeDHIQ+] were found to cause a syndrome similar to parkinsonism in rodents. NM(R)Sal is produced in the brain by N-methylation of a naturally occurring catechol isoquinoline, 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [(R)salsolinol, (R)Sal], which is formed from dopamine. The mechanism of NM(R)Sal cytotoxicity to dopamine neurons was examined using in vitro experiments. NM(R)Sal was found to be nonenzymatically oxidized into DiMeDHIQ+, with concomitant formation of hydroxyl radicals. The oxidation and the radical production were completely inhibited by the antioxidants, ascorbic acid and reduced glutathione, and the radical formation was enhanced by Fe(II) and, to a less extent, by Fe(III). The oxidation of NM(R)Sal into DiMeDHIQ+ and the production of hydroxyl radicals may be essential for neurotoxicity to develop in dopamine neurons. The possible involvement of this catechol isoquinoline in the pathogenesis of Parkinson's disease is discussed.

Animals↗

PubMed1995

Quantification of lipid peroxidation in tissue extracts based on Fe(III)xylenol orange complex formation.

Commonly used spectrophotometric methods for determining the extent of lipid peroxidation in animal tissue extracts, such as measurements of diene conjugation and thiobarbituric acid reactive substances (TBARS), have been criticized for their lack of specificity. This study shows that lipid hydroperoxides can be effectively quantified in animal tissue extracts using an assay based on the formation of a Fe(III)xylenol orange complex. Addition of H2O2, cumene hydroperoxides, or methanolic tissue extracts to an acidic reaction mixture containing 0.25 mM Fe(II) and 0.1 mM xylenol orange caused the formation of a broad Fe(III)xylenol orange complex absorbance peak at 560-580 nm with a corresponding decrease in the xylenol orange peak at 440 nm. Complex formation measured at 580 nm was saturable with both xylenol orange and Fe (II) concentration. Addition of ascorbic acid, GSH, and cysteine (0.3-5 mM) caused a saturable reduction of the Fe(III)xylenol orange complex. Formation of the Fe(III)xylenol orange complex was linear with the amount of tissue extract added. A significant correlation (r = 0.88, p < 0.005) existed between the xylenol orange method of estimating lipid peroxidation and the conventional TBARS assay in a series of animal tissues tested. The time course of increase in A580nm in tests using tissue extracts was typical of a free radical reaction; a lag phase was followed by a log phase. No increase in A580nm was observed up to 24 h when highly peroxidizable arachidonic acid was assayed. These results indicate that the formation of the Fe(III)xylenol orange complex reflects a chemical amplification of the original level of lipid hydroperoxides present in tissue extracts and that peroxidizable lipids do not influence the assay. The potential usefulness of the xylenol orange assay for comparative biochemical and toxicological studies of oxidative stress is discussed.

Animals↗