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PubMed2003

Stabilization of available arsenic in highly contaminated mine tailings using iron.

To evaluate the stabilization of available As in contaminated tailings from two abandoned metal mines of South Korea (the Myoungbong and Daduck Mines, 6670 and 56,600 mg/kg total As, respectively), characteristics of the tailings were investigated, and the tailings were treated through precipitation of amorphous iron compounds. Steep decreasing trends of extractable (5% NaOCl) As with increasing initial Fe(III) additions were observed in both treated tailings. In general, the treated tailings had the lowest extractable As concentration at pH 6. Available As, defined as the sum of As concentrations for the first four steps of a sequential extraction, was reduced from 2090 to 428 mg/kg (80% reduction) in the Myoungbong tailings and from 1320 to 395 mg/kg (70% reduction) in the Daduck tailings. As levels in the treated tailings decreased even more after a 1-month dormant period. Adsorption/coprecipitation tests performed with mixed As(III) and Fe(III) solutions demonstrated dramatically increased As sequestration via interaction with amorphous iron compounds with increasing pH. The bulk of the As appeared to be affiliated with stable Fe precipitates.

Arsenic↗
PubMed1988

Nuclear aberrations and micronuclei induction in the digestive tract of mice treated with different iron salts.

Toxic effects of ferrous sulfate and of ferric chloride were determined in the gastrointestinal tract by measuring the induction of nuclear aberrations and micronuclei. In fasting animals ferric chloride induced a dose-related increase of nuclear aberrations in the stomach, whereas ferrous sulfate was not active. In normally feeding animals no increase of nuclear aberrations was observed. The effects of the iron compounds on the duodenum were minimal. In fasting animals a dose-related increase of nuclear aberrations was observed at the level of the colon, with no clear difference between ferrous and ferric compounds. A modest increase of nuclear aberrations of the colon was seen in feeding animals only with ferrous sulphate. By intrarectal administration, nuclear aberrations were induced especially by ferric chloride. An increase of the frequency of micronuclei was not observed at the level of the stomach, duodenum and colon, with the exception of ferric chloride, that induces a significant, although small increase of colon micronuclei when administered intra-rectally. The data demonstrate that iron compounds have an intrinsic cellular toxicity when not administered with food, but do not seem to carry any genotoxic potential for the gastrointestinal tract.

Animals↗
PubMed2006

Iron-radiofrequency synergism in lymphomagenesis.

The parenteral iron administration effects on the acceleration of lymphomagenesis by radiofrequency exposure were investigated using an animal model that develops spontaneous lymphomas with ageing. Complementary studies of the in vivo uptake of 59Fe-labeled ferric gluconate and ferric-ATP complex showed differences ob absorption and excretion between both iron compounds. In vitro assays of their effects on calcium cellular uptake using a cell model and tissues homogenates showed a molecular structure-dependence. The current results (mortality, clinical and histopathological examinations) demonstrated a synergism between radiofrequency and ferric gluconate, and the increased risk of radiofrequency exposure when it is simultaneous to parenteral iron administration.

Adenosine Triphosphate↗
PubMed1991

[Evaluation of the fibrogenic effect of coke dust on the lungs and internal organs of experimental animals].

Based on the data collected by the Provincial Regional Administration Unit for Control of Epidemics and Hygiene in Katowice, dust concentration at the MAKOSZOWY Coking Plant in Zabrze at 18 work-places exceeded the TLV's. The purpose of this study was to determine changes within the respiratory systems of experimental animals exposed to intratracheal administration of MAKOSZOWY Coking Plant dust, sampled at the charging larry 3-4 operating stand and at the battery roof. After pulverization the dusts contained 98.1% and 99.6% respirable particles, and 6.5% and 6.0% of SiO2, respectively, determined with the Polezhajev method. They also contained aluminum and iron compounds. Hydroxyproline content in the lungs of the animals following the intratracheal administration of 50 mg of the dusts investigated 3-6 months after the experiment was determined. Determination of Hypro contend within the animals' lungs was pursued with the Stegemann method as modified by Hurych and Chvapil. The biochemical investigation results obtained were statistically analyzed with the t-Student's Test. Single intratracheal administration of dust from the battery roof work stand of the MAKOSZOWY Coking Plant caused within 6 months a statistically significant increase in the lung Hydroxyproline level in experimental animals (t = 13.10). An almost triole Hypro increase with respect to the control group was observed. No analogy between lung Hypro level increase (12.833 mg) and histological change was noted. Such a significant lung Hydroxyproline level increase could have been due to the SiO2 content of dust (6%), as well as to the presence of iron compounds in it (4.98%).(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants↗
PubMed2001

Micellar electrokinetic chromatography of tri aza aromatic ligand compounds of iron (II): influence of bile salt type on enantiomeric separation.

Micellar electrokinetic chromatography is used with a variety of bile salt micelles to separate the enantiomers of bis(8-((pyridine-2-methylene)amino)quinoline)iron(II) hexafluorophosphate, Fe(PMAQ)2(PF6)2; bis(8-((pyridine-2-methylene)amino)lepidine iron(II) hexafluorophosphate, Fe(PMAL)2(PF6)2; and bis(1-(2-pyridinyl)ethylidine)-8-aminoquinoline iron(II) hexafluorophosphate, Fe(PEAQ)2(PF6)2. The influence of ten different bile salts on the resolution of each pair of enantiomers is investigated. Significant changes in resolution are seen depending upon the bile salt used. The dihydroxy bile salts are superior to the trihydroxy bile salts in terms of resolution, and the taurine or glycine conjugated bile salts yield better results than the unconjugated bile salts. Resolution for most enantiomers is maximized in a buffer solution containing 10-15% acetone and employing either taurochenodeoxycholic or glycochenodeoxycholic acid as the bile salt. Evidence for the separation of the corresponding Fe(III) complexes is presented.

Aza Compounds↗
PubMed2006

Oxidative stress in hepatic ischemia-reperfusion injury: the role of antioxidants and iron chelating compounds.

Ischemia-reperfusion (IR) injury is a multifactorial process triggered when the liver or other organs are transiently subjected to reduced blood supply followed by reperfusion. It has been shown that "reactive oxygen species" (ROS) are generated during ischemia and reperfusion and may represent pivotal mediators of the ensuing pathological complications. In some cases, however, moderate production of ROS may exert protective effects, a phenomenon presumably related to "ischemic preconditioning". This review will focus mainly on: a) describing the sources and the biochemical mechanisms of ROS generation during ischemia and reperfusion, b) discussing current developments in understanding the biochemical pathways by which ROS may induce toxic or protective effects, c) critically evaluating the results of previous attempts to counteract the toxic effects of ROS by using a variety of antioxidant and transition metal-chelating agents, and d) if feasible, proposing potential new pharmaceutical agents aimed at ameliorating ROS-inducing deleterious effects during reperfusion. It is concluded that ROS are generated from different sources, at different periods during IR, and may act by a variety of not well understood biochemical mechanisms which ultimately lead to cell damage and tissue failure.

Animals↗
PubMed2002

Charge-transfer studies of iron cyano compounds bound to nanocrystalline TiO(2) surfaces.

Nanocrystalline (anatase) titanium dioxide films have been sensitized to visible light with K(4)[Fe(CN)(6)] and Na(2)[Fe(LL)(CN)(4)], where LL = bpy (2,2'-bipyridine), dmb (4,4'-dimethyl-2,2'-bipyridine), or dpb (4,4'-diphenyl-2,2'-bipyridine). Coordination of Fe(CN)(6)(4-) to the TiO(2) surface results in the appearance of a broad absorption band (fwhm approximately 8200 cm(-1)) centered at 23800 +/- 400 cm(-1) assigned to an Fe(II)-->TiO(2) metal-to-particle charge-transfer (MPCT) band. The absorption spectra of Fe(LL)(CN)(4)(2-) compounds anchored to TiO(2) are well modeled by a sum of metal-to-ligand charge-transfer (MLCT) bands and a MPCT band. Pulsed light excitation (417 or 532 nm, approximately 8 ns fwhm, approximately 2-15 mJ/pulse) results in the immediate appearance of absorption difference spectra assigned to an interfacial charge separated state [TiO(2)(e(-)), Fe(III)], k(inj) > 10(8) s(-1). Charge recombination is well described by a second-order equal concentration kinetic model and requires milliseconds for completion. A model is proposed wherein sensitization of Fe(LL)(CN)(4)(2-)/TiO(2) occurs by MPCT and MLCT pathways, the quantum yield for the latter being dependent on environment. The solvatochromism of the materials allows the reorganization energies associated with charge transfer to be quantified. The photocurrent efficiencies of the sensitized materials are also reported.

Journal Article↗
PubMed1996

Ferrimagnetic Mixed-Valency and Mixed-Metal Tris(oxalato)iron(III) Compounds: Synthesis, Structure, and Magnetism.

The synthesis and structural and magnetic characterization of 16 compounds AM(II)Fe(III)(C(2)O(4))(3) (A = N(n-C(3)H(7))(4), N(n-C(4)H(9))(4), N(n-C(5)H(11))(4), P(n-C(4)H(9))(4), P(C(6)H(5))(4), N(n-C(4)H(9))(3)(C(6)H(5)CH(2)), (C(6)H(5))(3)PNP(C(6)H(5))(3), As(C(6)H(5))(4); M(II) = Mn, Fe) are reported. X-ray powder diffraction profiles are indexed in R3c or its subgroup P6(5)22 or P6/mmm to derive unit cell constants. The structures of all the compounds consist of two-dimensional honeycomb networks [M(II)Fe(III)(C(2)O(4))(3)(-)](infinity). The M(II) = Fe compounds behave as ferrimagnets with T(c) between 33 and 48 K, but five exhibit a crossover from positive to negative magnetization near 30 K when cooled in a field of 10 mT. The compounds exhibiting this unusual magnetic behavior are those that have the highest T(c). Within the set N(n-C(n)()H(2)(n)()(+1))(4)Fe(II)Fe(III)(C(2)O(4))(3) (n = 3-5), T(c) increases with interlayer separation and the low-temperature magnetization changes from positive (n = 3) to negative (n = 4, 5). In the M = Mn(II) compounds, the in-plane cell parameter a(0) is approximately 0.03 Å greater than in the corresponding M = Fe(II) ones while the interlayer separation (c(0)/6) is on average 0.08 Å smaller. All members of the M(II) = Mn series have magnetic susceptibilities showing broad maxima at 55 K characteristic of two-dimensional antiferromagnetism, but the magnetization of several of the salts increases sharply below 27 K due to the onset of spin canting, the magnitude of which varies significantly with A.

Journal Article↗
PubMed1996

Model Compounds for Iron Proteins. Structures and Magnetic, Spectroscopic, and Redox Properties of Fe(III)M(II) and [Co(III)Fe(III)](2)O Complexes with (&mgr;-Carboxylato)bis(&mgr;-phenoxo)dimetalate and (&mgr;-Oxo)diiron(III) Cores.

A series of heterobimetallic complexes of the type [Fe(III)M(II)L(&mgr;-OAc)(OAc)(H(2)O)](ClO(4)).nH(2)O (2-5) and [{Fe(III)Co(III)L(&mgr;-OAc)(OAc)}(2)(&mgr;-O)](ClO(4))(2).3H(2)O (6) where H(2)L is a tetraaminodiphenol macrocyclic ligand and M(II) = Zn(2), Ni(3), Co(4), and Mn(5) have been synthesized and characterized. The (1)H NMR spectrum of 6 exhibits all the resonances between 1 and 12 ppm. The IR and UV-vis spectra of 2-5 indicate that in all the cases the metal ions have similar coordination environments. A disordered crystal structure determined for 3 reveals the presence of a (&mgr;-acetate)bis(&mgr;-phenoxide)-Ni(II)Fe(III) core, in which the two metal ions have 6-fold coordination geometry and each have two amino nitrogens and two phenolate oxygens as the in-plane donors; aside from the axial bridging acetate, the sixth coordination site of nickel(II) is occupied by the unidentate acetate and that of iron(III) by a water molecule. The crystal structure determination of 6 shows that the two heterobinuclear Co(III)Fe(III) units are bound by an Fe-O-Fe linkage. 6 crystallizes in the orthorhombic space group Ibca with a = 17.577(4) Å, b = 27.282(7) Å, c = 28.647(6) Å, and Z = 8. The two iron(III) centers in 6 are strongly antiferromagnetically coupled, J = -100 cm(-1) (H = -2JS(1).S(2)), whereas the other two S(1) = S(2) = (5)/(2) systems, viz. [Fe(2)(III)(HL)(2)(&mgr;-OH)(2)](ClO(4))(2) (1) and the Fe(III)Mn(II) complex (5), exhibit weak antiferromagnetic exchange coupling with J = -4.5 cm(-1) (1) and -1.8 cm(-1) (5). The Fe(III)Ni(II) (3) and Fe(III)Co(II) (4) systems, however, exhibit weak ferromagnetic behavior with J = 1.7 cm(-1) (3) and 4.2 cm(-1) (4). The iron(III) center in 2-5 exhibits quasi-reversible redox behavior between -0.44 and -0.48 V vs Ag/AgCl associated with reduction to iron(II). The oxidation of cobalt(II) in 4 occurs quasi-reversibly at 0.74 V, while both nickel(II) and manganese(II) in 3 and 5 undergo irreversible oxidation at 0.85 V. The electrochemical reduction of 6 leads to the generation of 4.

Journal Article↗
PubMed2004

An in vitro digestion/Caco-2 cell culture system accurately predicts the effects of ascorbic acid and polyphenolic compounds on iron bioavailability in humans.

We developed a rapid in vitro digestion/Caco-2 cell culture model for assessing relative bioavailabilities of iron in foods and meals. The objective of the present study was to determine how closely our Caco-2 model reflects the human response. Meals described in published reports of studies on effects of varying levels of ascorbic acid (AA) and tannic acid (TA) on iron absorption by human subjects were carefully replicated. Iron absorption ratios (iron absorption from meals containing AA or TA divided by iron absorption from identical meals without these enhancers or inhibitors) were determined using the Caco-2 model. Ferritin formation by the Caco-2 cells was used as an indicator of iron absorption. Response patterns of effects of AA and TA on absorption ratios (AR) calculated from Caco-2 and human data were very similar: AA increased ARs in a dose-response manner and TAs decreased AR. The natural logs of the ARs determined in Caco-2 and human studies were correlated: R = 0.935 (P = 0.012) and 0.927 (P = 0.007) for AA and TA, respectively. When results from meals with AA and TA were pooled, a linear relation between the natural logs of ARs from Caco-2 and human studies was observed (R = 0.968, P < 0.001). We conclude that our Caco-2 model accurately predicts the human response to AA and TA in the meals we tested. If future work reproduces the precision and accuracy shown in this paper for predicting iron bioavailability to humans, then the implications for saving time and resources in iron bioavailability measurements are considerable.

Ascorbic Acid↗