Ferrous Iron Compounds Research Articles

Active Nitrogen Fixation by Iron-Reducing Bacteria in Rice Paddy Soil and Its Further Enhancement by Iron Application

In rice paddy soil, biological nitrogen fixation is important for sustaining soil nitrogen fertility and rice growth. Anaeromyxobacter and Geobacteriaceae, iron-reducing bacteria belonging to Deltaproteobacteria, are newly discovered nitrogen-fixing bacteria dominant in paddy soils. They utilize acetate, a straw-derived major carbon compound in paddy soil, as a carbon and energy source, and ferric iron compounds as electron acceptors for anaerobic respiration. In our previous paddy field experiments, a significant increase in soil nitrogen-fixing activity was observed after the application of iron powder to straw-returned paddy field soil. In addition, combining iron application with 60–80% of the conventional nitrogen fertilizer rate could maintain rice yields similar to those with the conventional nitrogen fertilization rate. It was thus suggested that iron application to paddy soil increased the amount of nitrogen fixed in the soil by enhancing nitrogen fixation by diazotrophic iron-reducing bacteria. The present study was conducted to directly verify this suggestion by 15N-IRMS analysis combined with 15N-DNA-stable isotope probing of iron-applied and no-iron-applied plot soils in an experimental paddy field. In no-iron-applied native paddy soil, atmospheric 15N2 was incorporated into the soil by biological nitrogen fixation, in which diazotrophic iron-reducing bacteria were the most active drivers of nitrogen fixation. In iron-applied paddy soil, the amount of 15N incorporated into the soil was significantly higher due to enhanced biological nitrogen fixation, especially via diazotrophic iron-reducing bacteria, the most active drivers of nitrogen fixation in the soil. Thus, our previous suggestion was verified. This study provided a novel picture of active nitrogen-fixing microorganisms dominated by diazotrophic iron-reducing bacteria in paddy soil, and directly proved the effectiveness of iron application to enhance their nitrogen fixation and increase the incorporation of atmospheric nitrogen into soil. The enhancement of biological nitrogen fixation in paddy fields by iron application may lead to novel and unique paddy soil management strategies to increase soil nitrogen fertility and ensure rice yields with reduced nitrogen fertilizer input and lower environmental nitrogen burdens.

The origin of gley colors in hydromorphic vertisols: the study case of the coastal plain of the Río de la Plata estuary

This work aims to contribute to the interpretation of soil colors; mainly to identify the pigments that generate the greenish colors in hydromorphic conditions (gley colors) in vertisols of the coastal plain of the Rio de la Plata estuary. These colors are of cold hues, generally greenish (olive-gray), and occur in poorly drained soils with prolonged water accumulation. For this purpose, samples of Bssg horizons of hydromorphic vertisols from the coastal plain of the Rio de la Plata estuary were analyzed using routine and chemical analyses, Mossbauer spectroscopy, determination of rocks magnetic parameters, X-ray diffraction, thermogravimetric and differential thermal analysis and petrographic-electronic microscopy. The pigments associated with the gley colors of these soils are mainly due to ferric iron content, corresponding to minerals such as ferric iron-rich smectites (nontronite/Fe-rich beidellite) and oxy-hydroxides like goethite, which colors range from green to yellow. These minerals, combined with gray or black components, e.g., manganese compounds and/or organic matter, contribute to the generation of the usual gley colors in the analyzed soils of the Pampean plain. The obtained data allows us to state that it is a mistake to assing the olive color in hydromorphic soils to the presence of ferrous iron compounds, as it is traditionally done. The oxidizing condition of iron is dominant in all the analyzed samples, integrating the composition of ferric iron-rich clay minerals and oxy-hydroxides (goethite).

Impact of methane occurrence on iron speciation in the sediments of the Gdansk Basin (Southern Baltic Sea)

Due to changing climate conditions, such inland seas as the Baltic are expected to become more eutrophicated and less saline (causing lower availability of sulphates). This may promote methanogenesis as the main process of organic matter (OM) degradation in marine sediments. Presence of methane, in turn, may affect biogeochemical cycling of many elements, including iron. Thus, in the present study we attempted to investigate the influence of CH4 on the Fe forms in marine sediments. Sediment cores were collected from three physico-chemically different stations within the Southern Baltic, taking into account such parameters as water depth, OM content, bottom zone oxygenation and distance from the Vistula River (main source of anthropogenic material). At two sampling stations methane was present in shallow sediments (P1, MET2) and at one station (W6) any traces of this gas were not determined. Iron species (FeCARB, FeOX1, FeOX2, FeMAG, FePRS, FeT, FeFeS2, FeFeS) in sediments were investigated using the sequential extraction. Pore water was analysed to obtain vertical profiles of hydrogen sulphide, sulphate and dissolved inorganic carbon (DIC). Additionally, such parameters as water and OM content, CH4 and Eh in sediments were determined. Results showed that methanogenesis affects the biogeochemical iron cycling in sediments of the Southern Baltic, leading to the increase of carbonates containing ferrous iron (as a result of DIC production during intensive OSR, AOM and methanogenesis) and decrease of ferric iron compounds used in the AOM. Moreover, in the areas of lower salinity, pyrite formation is limited by an insufficient amount of hydrogen sulphide, leading to the situation when a significant part of Fe is accumulated in the form of monosulphides. In turn, in the areas of higher salinity, where oxygen deficiencies occur more often, more hydrogen sulphide is present in pore water. Pyrite formation is then limited by iron, not by sulphur.

The iron-containing electric-furnace steelmaking waste: physical and chemical properties and acidic modification

The electric furnace steelmaking dust is formed at melting metalized pellets in electric-arc steel-making furnaces and is a largetonnage waste. It contains such elements as Fe, Mg, Al, C, Si, Zn, Mn, Na. The ferrous and ferric iron compounds in the EFS dust are mostly presented with oxides — the compounds, which are poorly soluble in aqueous media and can’t take part in exchange reactions under ordinary conditions. The acid treatment with HCl allows obtaining a coagulating suspension, which can be usedfor wastewater treatment. Besides, there was detected up to 14 % of CaO, both free and in calcium silicates such as CaSiO3 and Ca2SiO4. So, in the process of treatment with EFS dust the formation of polysilicic acids helps increasing the purification efficiency.

Native iron: Greenland's natural blast furnaces

We live in an oxidized world: oxygen makes up 22 percent of the atmosphere and by reacting with organic matter produces most of our energy, including the energy our bodies use to function: breathe, think, move, etc. It has not always been thus. Originally the Earth, in common with most of the Solar System, was reduced. The oxidized outer layers of the Earth have formed by two processes. Firstly, water is decomposed to oxygen and hydrogen by solar radiation in the upper parts of the atmosphere, the light hydrogen diffusing to space, leaving oxygen behind. Secondly, plants, over the course of geological time have utilized solar energy in the process of photosynthesis to produce carbon‐rich materials and release oxygen to the atmosphere. Of these, the second is by far the most important. It is a consequence of life and since about 2.4 billion years ago we have had an oxidizing atmosphere, a situation unique in the Solar System. In such a world, iron metal is unstable and, as we all know, oxidizes to the ferric iron compounds we call ‘rust’. If we require iron metal it must be produced at high temperatures by reacting iron ore, usually a mixture of ferrous (Fe2+) and ferric (Fe3+) oxides (Fe2O3, hematite, or FeO.Fe2O3, magnetite), with carbon in the form of coke. This is carried out in a blast furnace. Although the Earth's core consists of metallic iron, which may also be present in parts of the mantle, this is inaccessible to us, so we must make our own. In West Greenland, however, some almost unique examples of iron metal, otherwise called ‘native iron’ or ‘telluric iron’, occur naturally.

Wood: Diasters and Minewater (Book Review)

‘‘Disasters and Mine water’’ is a new book by Harvey Woodrecently published by IWA Publishing: Wood H (2012)Disasters and Mine Water—good practice and prevention.IWA Publishing, UK, ISBN 978-1-7804-0006-8, approxi-mately $142 (US). This hardbound book consists of 127pages and is divided into 19 chapters, some of which areonly two or three pages long. There are six figures in thetreatment chapter and one in the tailings dam chapter,though none of them are numbered or referred to in the text.I was excited when I first heard that a book aboutdisasters and mine water was to be published because Ithought it would nicely add to the existing papers andbooks about disasters published in Mine Water and theEnvironment and elsewhere. The subtitle, ‘‘Good Practiceand Prevention,’’ indicated that the book would be a usefulsource of information for colleagues involved in mineplanning and consulting. Yet—to say it upfront—none ofmy expectations and very few of the claims on the backcover of the book were met.Ofcourse,theauthorlistssomeminedisasters,butthereisno‘‘GoodPractice’’or‘‘Prevention’’guide.Infact,ifthereisany guidance in the book, it is very well hidden. There is arelatively long (20 page) chapter about ‘‘Mine WaterTreatment’’—butthebookthattheauthorpublishedtogetherwith Brown et al. (2002) is much more comprehensive.Besides the expectations that were not met, the book isfull of errors, missing or incorrect references, and incon-sistencies. Most of the ‘‘disasters’’ are described superfi-cially, and very few of them include citations, so that if youwant to know more about a specific disaster, you are out ofluck. The book does have about 130 references—but only avery small number of them are cited in the text. Moreover,many of the few references that are cited in the text can’tbe found in the reference list, such as the citations on pages15, 18, 19, 22, 34, 55, 63, 75, and 76.It appears that the author wrote many of the pagesmeaning to check his ‘‘facts’’ later and then forgot to do so.For example, on page 9, the author writes that ‘‘ferric ironcompounds’’ are the most common ‘‘elements’’ on theplanet. The author fails to discuss how ‘‘compounds’’ canbe ‘‘elements’’ or how ferric iron compounds can me moreabundant than silicon compounds. On the same page, theauthor lists some metals, and inappropriately includesarsenic. The new compound, ‘‘AQl

Ferric Iron and Cobalt (III) Compounds to Safely Decrease Hydrogen Sulfide in the Body?

To sort out the putative roles of endogenous hydrogen sulfide (H2S) in clinical conditions wherein systemic inflammation or hypoxia is present, it becomes crucial to develop approaches capable of affecting H2S concentration that can be safely applied in humans. We have investigated a paradigm, which could achieve such a goal, using vitamin B12 (vit.B12), at the dose recommended in cyanide poisoning, and very low levels of methemoglobin (MetHb). Hydroxocobalamin in the plasma, supernatant of kidney, and heart tissue homogenates of rats that had received vit.B12 (140 mg.kg(-1) intravenous) was found in the μM range. Exogenous H2S (100 μM) added to the plasma or supernatants of these rats decreased at a significantly higher rate than in control rats. In the latter however a spontaneous oxidation of exogenous H2S occurred. In vitro, hydroxocobalamin solution (100 μM) decreased, within <2 min, an equimolar concentration of H2S by 80%. Three to five percent MetHb prevented H2S induced hyperventilation in vivo and decreased exogenous H2S in vitro by 25-40 μM within 30 s. Our observations lead to the hypothesis that innocuous levels of MetHb and vit.B12 could be a used as an effective and safe way to test the role of endogenous H2S in vivo.

Parenteral iron formulations differentially affect MCP-1, HO-1, and NGAL gene expression and renal responses to injury

Despite their prooxidant effects, ferric iron compounds are routinely administered to patients with renal disease to correct Fe deficiency. This study assessed relative degrees to which three clinically employed Fe formulations [Fe sucrose (FeS); Fe gluconate (FeG); ferumoxytol (FMX)] impact renal redox- sensitive signaling, cytotoxicity, and responses to superimposed stress [endotoxin; glycerol-induced acute renal failure (ARF)]. Cultured human proximal tubule (HK-2) cells, isolated proximal tubule segments (PTS), or mice were exposed to variable, but equal, amounts of FeS, FeG, or FMX. Oxidant-stimulated signaling was assessed by heme oxygenase-1 (HO-1) or monocyte chemoattractant protein (MCP)-1 mRNA induction. Cell injury was gauged by MTT assay (HK-2 cells), %LDH release (PTS), or renal cortical neutrophil gelatinase-associated lipoprotein (NGAL) protein/mRNA levels. Endotoxin sensitivity and ARF severity were assessed by TNF-alpha and blood urea nitrogen concentrations, respectively. FeS and FeG induced lethal cell injury (in HK-2 cells, PTS), increased HO-1 and MCP-1 mRNAs (HK-2 cells; in vivo), and markedly raised plasma ( approximately 10 times), and renal cortical ( approximately 3 times) NGAL protein levels. Both renal and extrarenal (e.g., hepatic) NGAL production likely contributed to these results, based on assessments of tissue and HK-2 cell NGAL mRNA. FeS pretreatment exacerbated endotoxemia. However, it conferred marked protection against the glycerol model of ARF (halving azotemia). FMX appeared to be "bioneutral," as it exerted none of the above noted FeS/FeG effects. We conclude that 1) parenteral iron formulations that stimulate redox signaling can evoke cyto/nephrotoxicity; 2) secondary adaptive responses to this injury (e.g., HO-1/NGAL induction) can initiate a renal tubular cytoresistant state; this suggests a potential new clinical application for intravenous Fe therapy; and 3) FMX is bioneutral regarding these responses. The clinical implication(s) of the latter, vis a vis the treatment of Fe deficiency in renal disease patients, remains to be defined.

強磁性共鳴による磁性細菌より生合成された鉄化合物の研究

In order to analyze the magnetic behaviors of iron complexes biologically synthesized in magnetic bacteria MS-1, we performed FMR (Ferromagnetic Resonance) measurements for each fraction of the cell. We observed FMR spectra from the ferric iron (Fe3+) compounds distributed in each fraction of the MS-1 cell. In particular, the MS fraction yielded an anisotropic FMR signal, whereas other fractions were simple FMR spectra of Gaussian type. Upon counting the numbers of spins in various cell fractions, we compared them with the iron population as determined by the 1.10-phenanthroline method. We found a good correlation between the number of spins and the iron population in several cell fractions. We concluded that the cell fractions other than those fractions containing magnetite, consist mostly of ferric irons rather than ferrous irons.

A Ferromagnetic Resonance Study of Iron Complexes as Biologically Synthesized in Magnetic Bacteria

In order to analyze the magnetic behaviors of iron complexes biologically synthesized in magnetic bacteria MS-1, we performed FMR (Ferromagnetic Resonance) measurements for each fraction of the cell. We observed FMR spectra from the ferric iron (Fe 3þ ) compounds distributed in each fraction of the MS-1 cell. In particular, the magnetosome fraction yielded an anisotropic FMR signal, whereas other fractions were simple FMR spectra of a Gaussian type. Upon counting the numbers of spins in various cell fractions, we compared them with the iron population as determined by the 1.10phenanthroline method. We found a good correlation between the number of spins and the iron population in several cell fractions. We concluded that the cell fractions, other than those fractions containing magnetite, consist mostly of ferric irons rather than ferrous irons. [doi:10.2320/matertrans.M2009177]

Effect of temperature on the bioleaching of chalcopyrite concentrates containing different concentrations of silver

The primary copper sulfide mineral chalcopyrite (CuFeS 2) is recalcitrant to both chemical and biological leaching, due to the supposed passivation of the mineral surface by sulfur and/or ferric iron compounds. Previous work has shown that addition of soluble silver can enhance solubilisation of copper from chalcopyrite by acidophilic bacteria. Silver may also be present in the concentrate itself. Here we describe the bioleaching of chalcopyrite concentrates with silver contents varying from < 1 to 1500 g/t by consortia of thirteen species of mesophilic bacteria and eleven species of moderately thermophilic acidophiles in shake flask cultures incubated at between 30 °C and 45 °C. The compositions of the microbial consortia that established in each culture were determined using a combined cultivation-based and biomolecular approach. The most effective solubilisation of copper from the 1500 and 800 g/t Ag-concentrates occurred at 30 °C, while concentrates that contained < 1 and 26 g/t of silver displayed the opposite (and predicted) pattern of mineral dissolution increasing with incubation temperature. The type strain of Acidithiobacillus ferrooxidans was the sole dominant iron-oxidising autotroph in the 800 and 1500 g/t silver concentrates, and was present in similar numbers to Leptospirillum ferrooxidans in the < 1 and 26 g/t silver concentrates, leached at 30 °C. Obligate and facultatively heterotrophic acidophiles (e.g. Acidiphilium and Gram-positive acidophiles) were also usually present, but in much smaller numbers. In contrast, at 45 °C the dominant (or sole) bacterium present at day 30 was the iron/sulfur-oxidising mixotroph Sulfobacillus thermosulfidooxidans. Sulfobacillus spp. also tended to dominate cultures incubated at 37 °C, although other bacteria, including At. ferrooxidans, were present in some mineral leachates. Highly efficient dissolution of copper (76 to > 98% over 30 days) from the 1500 g/t chalcopyrite concentrate at 30 °C was achieved using pure and mixed cultures of At. ferrooxidans. The results indicated that chalcopyrite concentrates that contain significant concentrations of silver are highly amenable to bioleaching at relatively low temperatures, using well-known acidophilic micro-organisms.

Dialyzability of Minerals in Corn Masa Gruel (Atole) Fortified with Different Iron Compounds: Effects of Ascorbic Acid, Disodium EDTA, and Phytic Acid

Lime-treated corn gruel (atole) is a common weaning food in iron-deficient populations, especially in Mexico and Central America, and is a potential vehicle for fortification with iron. The objective of this study was to screen promising iron compounds for use in the fortification of atole, using in vitro enzymatic digestion-dialysis techniques, while also considering their response to known iron absorption enhancers and inhibitors. Atole, unaltered or preincubated with phytase, was fortified with iron (10 mg/L) from ferrous sulfate, ferrous bisglycinate, or ferrous fumarate, or with ferric chloride, ferric ammonium citrate, or ferric sodium ethylenediaminetetraacetic acid (NaFeEDTA), and submitted to in vitro digestion. Dialysis of calcium, copper, iron, phosphorus, and zinc (analyzed by inductively coupled plasma atomic emission spectrometry) was measured when atole was fortified with iron compounds alone or together with ascorbic acid or disodium ethylenediaminetetraacetic acid (Na2EDTA). Iron dialyzability was higher with NaFeEDTA (p < .05) than with all other iron compounds, which did not differ among themselves in iron dialyzability. Addition of ascorbic acid had no significant effect on iron dialysis, whereas Na2EDTA enhanced iron dialyzability by 7 to 10 times in unaltered atole and 15 to 20 times in phytase-preincubated atole (p < .05). Addition of Na2EDTA always increased intrinsic zinc dialyzability, and most of the time this increase was significant. Phytase pretreatment generally increased mineral dialysis. Adding EDTA (either as NaFeEDTA or as Na2EDTA) to atole can increase the dialyzability of ferrous and ferric iron compounds and enhance the dialyzability of intrinsic zinc without any negative effects on calcium, phosphorus, or copper dialysis.

Analysis of the iron state in ferric and ferrous iron containing pharmaceutical products by Mössbauer spectroscopy

An analysis of the iron state in commercial pharmaceuticals containing ferric and ferrous iron compounds, which are used for treatment of iron deficiency, was made by Mossbauer spectroscopy. Small variations of the FeOOH cores of injectable iron-dextran complexes were observed. The presence of ferrous impurity in iron-dextran complexes was found. Characterization of the iron state in vitamins and dietary supplements containing ferrous compounds was made. The presence of ferrous and ferric impurities and iron compounds that were in disagreement with compounds announced by the manufacturer was detected by Mossbauer spectroscopy.

The determination of ferric iron in plants by HPLC using the microbial iron chelator desferrioxamine E

Common methods for plant iron determination are based on atomic absorption spectroscopy, radioactive measurements or extraction with subsequent spectrophotometry. However, accuracy is often a problem due to background, contamination and interfering compounds. We here describe a novel method for the easy determination of ferric iron in plants by chelation with a highly effective microbial siderophore and separation by high performance liquid chromatography (HPLC). After addition of colourless desferrioxamine E (DFE) to plant fluids, the soluble iron is trapped as a brown-red ferrioxamine E (FoxE) complex which is subsequently separated by HPLC on a reversed phase column. The formed FoxE complex can be identified due to its ligand-to-metal charge transfer band at 435 nm. Alternatively, elution of both, DFE and FoxE can be followed as separate peaks at 220 nm wavelength with characteristic retention times. The extraordinarily high stability constant of DFE with ferric iron of K = 10(32) enables extraction of iron from a variety of ferrous and ferric iron compounds and allows quantitation after separation by HPLC without interference by coloured by-products. Thus, iron bound to protein, amino acids, citrate and other organic acid ligands and even insoluble ferric hydroxides and phosphates can be solubilized in the presence desferrioxamine E. The "Ferrioxamine E method" can be applied to all kinds of plant fluids (apoplasmic, xylem, phloem, intracellular) either at physiological pH or even at acid pH values. The FoxE complex is stable down to pH 1 allowing protein removal by perchloric acid treatment and HPLC separation in the presence of trifluoroacetic acid containing eluents.

Biogeochemistry of the compost bioreactor components of a composite acid mine drainage passive remediation system

The compost bioreactor (“anaerobic cell”) components of three composite passive remediation systems constructed to treat acid mine drainage (AMD) at the former Wheal Jane tin mine, Cornwall, UK were studied over a period of 16 months. While there was some amelioration of the preprocessed AMD in each of the three compost bioreactors, as evidenced by pH increase and decrease in metal concentrations, only one of the cells showed effective removal of the two dominant heavy metals (iron and zinc) present. With two of the compost bioreactors, concentrations of soluble (ferrous) iron draining the cells were significantly greater than those entering the reactors, indicating that there was net mobilisation (by reductive dissolution) of colloidal and/or solid-phase ferric iron compounds within the cells. Soluble sulfide was also detected in waters draining all three compost bioreactors which was rapidly oxidised, in contrast to ferrous iron. Oxidation and hydrolysis of iron, together with sulfide oxidation, resulted in reacidification of processed AMD downstream of the compost bioreactors in two of the passive treatment systems. The dominant cultivatable microorganism in waters draining the compost bioreactors was identified, via analysis of its 16S rRNA gene, as a Thiomonas sp. and was capable of accelerating the dissimilatory oxidation of both ferrous iron and reduced sulfur compounds. Sulfate-reducing bacteria (SRB) were also detected, although only in the bioreactor that was performing well were these present in significant numbers. This particular compost bioreactor had been shut down for 10 months prior to the monitoring period due to operational problems. This unforeseen event appears to have allowed more successful development of AMD-tolerant and other microbial populations with critical roles in AMD bioremediation, including neutrophilic SRB (nSRB), in this compost bioreactor than in the other two, where the throughput of AMD was not interrupted. This study has revealed new insights into the operation of compost bioreactors used to remediate mine waters and has shown that, when operated under appropriate conditions, they can be highly efficient at generating alkalinity and removing metals from extremely acidic, metal-rich AMD.

The Fermenting Bacterium Malonomonas rubra is Phylogenetically Related to Sulfur-Reducing Bacteria and Contains a c-Type Cytochrome similar to those of Sulfur and Sulfate Reducers

Malonomonas rubra is a microaerotolerant fermenting bacterium which can maintain its energy metabolism for growth by decarboxylation of malonate to acetate. 16S rRNA sequence analysis revealed that M. rubra is closely related to the cluster of mesophilic sulfur-reducing bacteria within the delta subclass of the Proteobacteria, with the fermenting bacterium Pelobacter acidigallici and the sulfur reducers Desulfuromusa kysingii, D. bakii and D. succinoxidans as closest relatives. The cells contain high amounts (up to 12% of the total cell protein content) of a c-type cytochrome which is present mainly (> 60%) in the cytoplasm and to minor parts in the periplasm (> 20%) and associated with the membrane fraction (> 10%), independent of the growth substrate. This cytochrome is a tetraheme cytochrome of 13,700 Da molecular mass with a midpoint redox potential of -0.210 V.M. rubra does not reduce sulfur or ferric iron compounds. Since this cytochrome appears not to be involved in the energy metabolism it is concluded that it is a remnant of sulfur-reducing ancestors of this bacterium, without a conceivable physiological function in its present energy metabolism.

Inhibition of adenylyl cyclase in rat striatal homogenates by combinations of dopamine and ferric iron compounds

The adenylyl cyclase activity of homogenates of striatal tissue from rat brain has been used as a model to test the hypothesis that the products of the reaction of polyphenols with ferric iron compounds are toxic. Dopamine (DA), at levels that stimulate adenylyl cyclase, inhibited the activity in the presence of 2 mol of potassium ferricyanide (FC), methemoglobin or ferricytochrome c per mol of DA. Combinations of potassium ferrocyanide and DA were not inhibitory. Neither pyrocatechol nor hydroquinone stimulated the activity, but these polyphenols were inhibitory in the presence of FC. Tyramine, phosphorylated DA or phosphorylated pyrocatechol had no effect on the activity of the enzyme in the presence or absence of FC. Forskolin was unable to stimulate the adenylyl cyclase once the latter was inhibited by DA plus FC, and dithiothreitol could not reverse inhibition by DA plus FC. Incubation of DA with FC, in the absence of the homogenate, resulted in substances that were not inhibitory. These findings suggest that the polyphenols plus FC react to yield substances that inhibit the adenylyl cyclase by affecting the catalytic unit of the enzyme complex.

The tissue-specific accumulation of hepatic zinc metallothionein following parenteral iron loading.

The synthesis in various tissues of the unique metal-binding protein, metallothionein, can be influenced by the administration of certain trace elements. Zinc and cadmium, both of which bind to metallothionein, are most widely recognized as potent inducers. Preliminary results in our laboratory suggested that iron loading causes a marked accumulation of hepatic zinc metallothionein. We present in this report the effects of parenteral iron administration on metallothionein concentration in various tissues. Male chicks (300-350 g) received (ip) either a single injection (+1 Fe) of iron (10 mg Fe/kg, as FeCl3), two injections (+2 Fe) given 24-hr apart, three injections (+3 Fe) each given 24-hr apart, or an equivalent volume of 0.9% saline (control). Twenty-four hours following the final injection, chicks were killed and tissues analyzed for cytoplasmic zinc and metallothionein (Zn-MT). The parenteral administration of ferric iron, FeCl3, resulted in a marked tissue-specific accumulation of zinc as metallothionein. In chicks given +2 Fe, hepatic Zn-MT increased more than 10-fold with a third injection (+3 Fe) causing no further change. The concentration of Zn-MT in renal and pancreatic tissue was unaffected by iron loading. An increase in hepatic Zn-MT was evident prior to detectable changes in total hepatic iron. The administration of other ferrous iron compounds at a similar rate produced comparable changes in hepatic Zn-MT. Feeding excess dietary iron, however, had no effect on liver Zn-MT levels even though similar hepatic iron concentrations were attained. Our results indicated that parenteral administration, but not feeding, of various iron compounds causes a marked increase in zinc metallothionein, specifically in liver tissue.

Effect of low-spin Fe2+on the composition of the lower mantle

The effects of low-spin Fe^(2+) in the earth's lower mantle are investigated in considerable detail. The existence of low-spin Fe^(2+) permits the formation of an extra phase, since Mg^(2+) and low-spin Fe^(2+) probably do not form solid solutions. The elastic behavior of phases containing low-spin iron is predicted from bulk modulus systematics and is compared with available shock wave data. It is likely that the high pressure phases of several ferrous iron compounds involve low-spin Fe^(2+). Iron will be spin-paired in the mantle below 1700 km and perhaps at higher levels as well. The observed density and bulk modulus in the lower mantle are inconsistent with any combination of phases in a pyrolite bulk composition but can be fit quite well by a model with all Fe^(2+) spin-paired below 650 km. The lower mantle is richer in FeO and SiO_2 than the upper mantle. The spin-pairing of Fe^(2+) provides an excellent mechanism for both iron and silicon enrichment in the lower mantle by partial melting. Thus spin-pairing in iron provides support for previous arguments for chemical inhomogeneity of the mantle and also provides a mechanism for generating the inhomogeneity. This removes the motivation for reducing FeO and SiO_2 in the mantle to supply Fe and Si for the core.

Enrichment of Pasteurized Whole Milk with Iron

Organoleptic evaluation of Iron-enriched whole milks showed that ferric iron compounds uniformly resulted in lipolytic rancidity when milk was pasteurized at minimum to moderate temperatures (below about 79C). This off-flavor was reduced acceptably, or completely eliminated simply by pasteurizing at 81C. Data consistently showed that milk lipase is made more heat resistant by ferrie forms of iron.Ferrous compounds normally caused definite oxidized flavor when added to raw whole milk before pasteurization. This off-flavor was markedly reduced by deacrating the milk before adding the iron. Ferrous compounds did not cause rancidity.Ferric ammonium citrate and ferrous sulfate were evaluated more extensively than other compounds. Addition of the citrate salt followed by pasteurization at 81C is the more feasible method, since it would be difficult to add the ferrous salt after deodorization and before pasteurization.