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PubMed1987

Ultrastructural pathology of iron-loaded rat myocardial cells in culture.

The pathological changes induced by in-vitro iron-loading or cultured rat myocardial cells were studied. Cells were exposed to 59Fe-labelled ferric ammonium citrate for up to 24 h followed by 24-72 h chase experiment. After 24 h exposure 29% of the total cellular radioactivity was found in ferritin, 10% in non-ferritin heat supernatant and 61% in an insoluble heat-precipitable form. Mössbauer spectroscopy showed a gradual shift from intracellular iron particles less than 1.8 nm in diameter, through particles of intermediate size, to ferritin-like aggregates over 3.0 nm in diameter, reaching about 20% of total iron by 24 h. Ultrastructural studies showed premature damage such as mitochondrial abnormalities and excessive autophagocytosis. Small, 2.0-5.0 nm electron-dense cytosolic particles were noticed at 3 h of iron loading and reached maximal concentrations at 6 h. This was followed by accumulation of the small particles and of typical iron-rich ferritin cores within siderosomes. Because of the limited duration of iron loading and the high concentrations of non-transferrin inorganic iron employed, the present model is more relevant to acute than chronic iron overload. The efficient incorporation of large amounts of iron within ferritin molecules and its subsequent segregation, together with other smaller particles, within membrane-bound bodies, may represent a defence mechanism limiting iron toxicity in the face of advanced cytosiderosis.

Animals↗
PubMed1996

In situ measurement of iron overload in liver tissue by dual-energy methods.

The errors for determining liver iron content by dual-energy computed tomography (dual-energy CT) are calculated for the ideal case where only monochromatic x-ray beams are used. Because of the strong influence of spatial resolution on the radiation dose needed to reduce the error to a given level, we have also calculated the error in dual-energy transmission measurements alone, where the spatial information along the beam path is lost. The prediction of error was tested by simulations and measurements using x-rays emitted by radioactive isotopes and synchrotron radiation. Good agreement between calculation, simulation and measurement was found. It is shown that concentrations of liver iron content (disregarding variation of tissue composition) can be studied with a skin dose of about 30 mGy using dual-energy CT and even with much lower dose using dual-energy transmission measurements. However, there are sources of error besides photon noise, especially errors caused by variation of tissue composition. For example dual-energy CT, although suggested to avoid artifacts caused by fat in the case of a fatty liver, still is affected by fat. The magnitude of these errors is discussed qualitatively, and possibilities for their reduction are suggested. For a definitive estimate of errors of iron content measurements with optimized apparatus more experimental data for well defined variations of body tissue, especially in the case of haemochromatosis, are needed.

Artifacts↗
PubMed2003

Surface reactions kinetics between nanocrystalline magnetite and uranyl.

Magnetite is the most important end member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Nanocrystalline magnetite was synthesized in the laboratory and its physicochemical properties were analyzed in detail. The kinetics of the adsorption of U(VI) and the kinetics of the actinide reduction to a lower oxidation state, in presence of the oxide, were studied by means of batch sorption techniques and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the uranium sorption and reduction processes on the magnetite surface have very fast kinetics (hours), the reduction process being triggered by sorption. XPS measurements showed that the speciation of uranium at the surface does not show significant changes with time (from 1 day to 3 months), as well as the quantity of uranium detected at the surface. The surface speciation depended on the initial pH of the contact solution. Considering that the Eh of equilibrium between magnetite and the solution, under our experimental conditions, is slightly positive (50-100 mV), the uranium reduction would also be thermodynamically possible within the liquid phase. However, the kinetics of reduction in the liquid occur at a much slower rate which, in turn, has to depend on the attainment of the magnetite/solution equilibrium. The decrease of uranium in solution, observed after the uranyl adsorption stage, and particularly at acidic pH, is most probably due to the precipitation of U(IV) formed in the solution.

Journal Article↗
PubMed1980

Use of negative chemical ionization mass spectrometry for the trace analysis of metals.

The synthesis of various volatile and thermally stable derivatives of metals ions has permitted the use of conventional mass spectrometry for trace metal analysis. This paper reviews the development of the field using electron impact and chemical ionization mass spectrometry. This latter methodology produces simple mass spectra that enable complex mixtures to be analyzed. In addition the use of negative ion detection has produced selective ionization since many metal chelates contain heteroatoms which are electronegative. A discussion of the use of this general methodology for trace metal analysis is included, together with its applications to the analysis of ruthenium in automobile exhaust emissions and iron in red blood cells from laboratory rats. The future use of this methodology is expected to be for the monitoring of stable metal isotopes. This procedure could be used to follow these tracers in clinical and environmental studies and it is expected that their use will replace radioactive isotopes in most studies.

Animals↗
PubMed2004

Iron uptake by Escherichia coli cultured with antibodies from cows immunized with high-affinity ferric receptors.

The synergistic effects of immunoglobulin G (IgG) from cows vaccinated with ferric citrate receptor (FecA) and IgG from cows vaccinated with ferric enterobactin receptor (FepA) were measured in an in vitro iron uptake assay. Serum was isolated and pooled within treatment from five cows each vaccinated with FepA or FecA or not vaccinated. Immunoglobulin G was isolated by ammonium sulfate precipitation and protein G affinity chromatography. Six Escherichia coli isolates from bovine intramammary infections were cultured in an iron-depleted medium to induce high-affinity iron acquisition systems and, in iron-depleted conditions, to specifically induce the expression of FecA. The bacterial cells were mixed with either 3 or 6 mg/mL of purified IgG and 55Fe. The radioactivity of 55Fe taken up by the bacterial cells was measured by a liquid scintillation counter after 5-, 10-, and 15-min incubations at 37 degrees C. The combination of anti-FecA IgG and anti-FepA IgG reduced 55Fe uptake compared with either anti-FecA or anti-FepA alone. Iron uptake was reduced more by anti-FecA IgG than by anti-FepA IgG when the ferric citrate system was induced. Reduction of iron uptake did not differ between anti-FepA alone and anti-FecA alone when citrate was absent from the medium.

Animals↗
PubMed2002

Model investigations on the effect of Si transport on the nanocrystallization of amorphous FeSiB-(Cu,Nb).

Amorphous material of the class FeSiB-(Cu,Nb) has been investigated with a background of soft-magnetic application of the corresponding nanocrystalline material. Thin-film analytical methods (SIMS, AES, TEM) have been used to study the diffusion of Si in such materials prepared as layer systems by magnetron sputter deposition. Significant interdiffusion occurs even at low temperatures - approximately 400 degrees C. Quantitative description failed, however, because formation of new iron monosilicide phases begins above this temperature. It is concluded that only high-mass-resolution SIMS or radioactive tracer analysis can be used for successful acquisition of information at this material system.

Journal Article↗
PubMed2005

Mechanism of uranium removal from the aqueous solution by elemental iron.

The effectiveness of elemental iron (Fe(0)) to remove uranium (U) from the aqueous phase has been demonstrated. While the mitigation effect is sure, discrepancies in the removal mechanism have been reported. The objective of this study was to investigate the mechanism of U(VI) removal from aqueous phases by Fe(0). For this purpose, a systematic sequence of bulk experiments was conducted to characterize the effects of the availability and the abundance of corrosion products on U(VI) removal. Results indicated that U(VI) removal reactions did not primary occur at the surface of the metallic iron. It is determined that U(VI) co-precipitation with aging corrosion products is a plausible explanation for the irreversible fixation under experimental conditions. Results of XRD analyses did no show any U phases, whereas SEM-EDX analyses showed that U tended to associate with rusted areas on the surface of Fe(0). Recovering U with different leaching solutions varied upon the dissolution capacity of the individual solutions for corrosion products, showing that the irreversibility of the removal depends on the stability of the corrosion products. U(VI) co-precipitation as removal mechanism enables a better discussion of reported discrepancies.

Adsorption↗
PubMed2003

Mitigating uranium in groundwater: prospects and limitations.

Removal of uranium(VI) by zerovalent iron has been suggested as a feasible pathway to control uranium contaminations in seepage waters. Available information in the literature however presents discrepant evidence on the process responsible for the mitigation effect. On basis of an EH-pH diagram of uranium and iron, it is outlined that these discrepancies may be explained by the aqueous chemistry of uranium and iron. Additional effects contributing to the complexity of the system are given. Solubilization experiments using scrap iron together with water works sludge, MnO2, and pyrite indicate that U(VI) is immobilized by iron corrosion products after about 50 days.

Iron↗
PubMed2005

Reoxidation of bioreduced uranium under reducing conditions.

Nuclear weapons and fuel production have left many soils and sediments contaminated with toxic levels of uranium (U). Although previous short-term experiments on microbially mediated U(VI) reduction have supported the prospect of immobilizing the toxic metal through formation of insoluble U(IV) minerals, our longer-term (17 months) laboratory study showed that microbial reduction of U can be transient, even under sustained reducing conditions. Uranium was reduced during the first 80 days, but later (100-500 days) reoxidized and solubilized, even though a microbial community capable of reducing U(VI) was sustained. Microbial respiration caused increases in (bi)-carbonate concentrations and formation of very stable uranyl carbonate complexes, thereby increasing the thermodynamic favorability of U(IV) oxidation. We propose that kinetic limitations including restricted mass transfer allowed Fe-(III) and possibly Mn(IV) to persist as terminal electron acceptors (TEAs) for U reoxidation. These results show that in-situ U remediation by organic carbon-based reductive precipitation can be problematic in sediments and groundwaters with neutral to alkaline pH, where uranyl carbonates are most stable.

Biodegradation, Environmental↗
PubMed1991

Effects of hydroxyethyl starch conjugated deferoxamine on myocardial functional recovery following coronary occlusion and reperfusion in dogs.

The effect of hydroxyethyl starch-conjugated deferoxamine (HES-DFO) on the recovery of regional myocardial function after 15 min of coronary artery occlusion followed by 3 h of reperfusion of the left anterior descending coronary artery (stunned myocardium) was investigated in anesthetized dogs. Regional myocardial blood flow was measured by radioactive microspheres and regional myocardial segment shortening (%SS) by sonomicrometry. HES-DFO (equivalent of 50 mg/kg DFO), iron saturated HES-DFO (HES-FO), deferoxamine (DFO, 50 mg/kg), or saline were administered by intravenous infusion starting 30 min before occlusion and throughout occlusion. Ischemic bed size and collateral blood flow were similar in all four groups. HES-DFO significantly improved %SS in the ischemic-reperfused region during reperfusion; however, HES-FO and DFO had no effect on %SS as compared to the saline-treated group. HES-DFO and HES-FO had no effect on hemodynamics; however, DFO produced a marked reduction in systemic blood pressure. Since HES-FO had no effect on the recovery of %SS, the beneficial effect of HES-DFO is thought to be due to its iron chelating characteristics. Plasma concentrations of HES-DFO not only reached a higher peak level but also had a longer half life (3 h) than that of regular DFO (20 min). Thus, high-molecular-weight HES-DFO is effective in enhancing the recovery of regional wall motion in stunned myocardium. The reason for the lack of efficacy of DFO compared to HES-DFO at this high dose may be related to the formation of a toxic deferoxamine free radical species.

Animals↗
PubMed1975

[The functional state of the thyroid gland following partial pancreatectomy].

In Wistar rats a study was made of a functional condition of the thyroid gland 1, 6 and 24 hours after partial pancreatectomy. The following signs-served as criteria of a functional condition of the gland: the amount of neutrone-activated iodine in iron, iodine-absorptive capacity of the gland by I131, the amount of protein-bound stable and radioactive iodine in the blood, a morphological condition of the gland structures. It was demonstrated that, despite the initial intensification of the process of synthesis and secretion in the thyroid gland, its secretory activity fell by the end of the experiment. This reduction is regarded as an adaptive response to partial insulin deficiency.

Animals↗
PubMed1975

Multinuclide evaluation of hepatic mass lesions.

Radionuclide imaging with labeled colloids is widely used to evaluate and localize primary and metastatic tumors of the liver. The method is fairly sensitive, but the nonspecificity of focal defects remains a significant limitation. Lesions such as cysts and abscesses appear as space occupying areas that are indistinguishable from neoplastic masses. Utilizing a variety of radiopharmaceuticals, one may obtain additional information concerning such lesions. Hepatic blood flow scintiphotography is performed with the Anger camera following the intravenous injection of a high activity, small volume bolus of 99m-Tc pertechnetate. Vascular lesions such as hepatomas or hemangiomas will show increased activity in the lesion which should easily differentiate them from avascular processes such as abscesses, cirrhotic pseudomasses and most metastatic lesions, all of which remain "cold" on these flow studies. If one does not posses a camera, useful blood pool rectilinear scans of these lesions may be obtained with 131-I or 99m-Tc human serum albumin or ionic 113m-In. Additional information concerning the metabolic activity of focal defects on the colloid study is obtained using 75-Se-selenomethionine or 67-Ga. The former is an indicator of active protein metabolism while the latter attaches to lysozymes of metabolically active cells. With either agent, hepatomas show avid uptake, metastatic lesions show variable uptake, and cysts or chronic pseudotumors of cirrhosis show poor uptake. The two agents differ in abscess detection where 75-Se-selenomethionine uptake is poor while 67-Ga concentration generally is intense. 131-I-Rose Bengal occasionally may prove useful in demonstrating impression by an atypically positioned gallbladder or focal dilatation of the biliary tract as a cause of a defect on the colloid scan. Ultrasound examination may complement the radionuclide studies. It is useful for corroborating the presence of lesions and for evaluating their consistency (cystic vs. solid). The information obtained from this multinuclide approach has made scintigraphy examination of the livermore specific. After the completion of this non-invasive series of studies, one generally may venture an intelligent opinion concerning the etiology of the space occupying disease.

Aneurysm↗