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PubMed1975

Studies of the metabolism of asialotransferrins: the metabolic heterogeneity of human asialotransferrin.

Catabolism of human transferrin and human asialotransferrin was simultaneously studied in guinea pigs by means of total body radioactivity measurements. Total body activity representing transferrin decreased at a constant rate with an average half-life of 88 h. Decrease of the total body activity representing asialotransferrin exhibited at least two rates; the half-life of the fast initial component averaged at 25 h, whereas the half-life of the slower component averaged at 55 h. Transition occurred between the 50th and 80th hours of the experiments. The complex character of the elimination curves could not be explained by differences in the iron content of asialotransferrin, by the presence of transferrin variants or of denatured protein in the injected material, by residual sialic acid in the preparations, by accumulation of radioactive terminal catabolic products in the body, by an association of asialotransferrin with any other macromolecular plasma constituent, by changing conditions for mass action, or by a continuing return of labeled protein from the extravascular space. Injection of bovine asialotransferrin into guinea pigs did not result in complex total body curves. Analyses of guinea pig tissues demonstrated that human asialotransferrin had marked affinity for the liver and none for the kidney, lung, or spleen. These observations are consistent with the hypothesis that the glycopeptides in human transferrin are heterogeneous in that removal of the sialyl residues exposes structures with different affinities for the hepatic asialoglycoprotein receptor. The precise chemical basis for the metabolic heterogeneity is unknown.

Animals↗
PubMedDate not supplied

[Use of metal salts for radioprotection of plants during radioactive pollution of the territory].

The applying salts of some metals to radionuclide contaminated soddy-podzolic soil in the zone of Chernobyl nuclear power station or the spraying of plants by its solutions are showing the radioprotective effect (salts of iron, zinc, cobalt and manganese) and decreasing the uptake of 90Sr and 137Cs through roots (salts of zinc, manganese, boron, lithium, cobalt and copper).

Chlorides↗
PubMed1985

Investigation of mine and industry dumps in the FRG in relation to a possible release of natural radioactive elements.

More than 350 dumps of mines and industries in two federal states of the FRG were recorded, measured radiometrically, evaluated, and some of them sampled. Most of the mine dumps belonged to old and smaller residues from lead/zinc and iron ore mining, while the largest depositions contain tailings of modern ore beneficiation or flyash disposal. All mine dumps from uranium exploration in Baden-Württemberg and Bavaria were investigated. The highest doses, up to 100 mSv/a, were found on the piles of the uranium exploration. These depositions, which are supervised and licensed, are followed, in terms of surface dose, by the old uncontrolled mine dumps of silver/cobalt mining with doses up to 20 mSv/a. The numerous porphyry and granite quarries show doses between 1 and 2 mSv/a, as do flyash and slag dumps. The lowest doses were found on the dumps of the hydrothermal Pb/Zn and iron ore deposits, while the slag piles of iron ore processing showed higher thorium values. Assays for Ra-226 and Pb-210 of the materials deposited confirmed the radiometric results. Analyses of seepage waters and gallery waters showed only very few values exceeding the derived drinking water concentrations.

Environmental Pollution↗
PubMed1995

Iron and erythropoiesis in normal subjects and in pregnancy.

Erythropoiesis is a highly dynamic process which may be monitored by quantitative reticulocyte counting. In chronic renal failure erythropoietin therapy can restore erythropoiesis to normal level. Occult infection and malignancy can limit this response and quantitative reticulocate counting can be used to identify this at an early stage. Iron supply may also be limiting and the measurement of percentage hypochromia is an effective means of detecting this. In pregnancy erythropoiesis is stimulated at a very early stage, direct measurement of red cell mass using a non-radioactive method has shown that half of the increase may occur within the first trimester. Recent studies suggest that erythropoiesis is stimulated very soon after conception.

Erythropoiesis↗
PubMed1983

Cyanide production by Pseudomonas fluorescens and Pseudomonas aeruginosa.

Of 200 water isolates screened, five strains of Pseudomonas fluorescens and one strain of Pseudomonas aeruginosa were cyanogenic. Maximum cyanogenesis by two strains of P. fluorescens in a defined growth medium occurred at 25 to 30 degrees C over a pH range of 6.6 to 8.9. Cyanide production per cell was optimum at 300 mM phosphate. A linear relationship was observed between cyanogenesis and the log of iron concentration over a range of 3 to 300 microM. The maximum rate of cyanide production occurred during the transition from exponential to stationary growth phase. Radioactive tracer experiments with [1-14C]glycine and [2-14C]glycine demonstrated that the cyanide carbon originates from the number 2 carbon of glycine for both P. fluorescens and P. aeruginosa. Cyanide production was not observed in raw industrial wastewater or in sterile wastewater inoculated with pure cultures of cyanogenic Pseudomonas strains. Cyanide was produced when wastewater was amended by the addition of components of the defined growth medium.

Cyanides↗
PubMed1987

Fate of haem after parenteral administration of haem arginate to rabbits.

Rabbits were injected either intravenously or intramuscularly with [14C]haem arginate and [59Fe]haem arginate (haem 5 mg kg-1). The main part (80%) of AUCINF of labelled haem was associated with the beta-phase, T1/2 being about 6 h. Only 1% of the haem dose had been taken up by the red blood cells. In contrast, the iron moiety from the haem molecule was effectively utilized. Thirty days post-injection of [59Fe]haem arginate, 40% of the dose after intravenous injection and 60% after intramuscular injection was circulating with the red cells. Radioactivity was shown to concentrate in the liver, where haem is mainly metabolized and eliminated. An accumulation of haem in the adrenals was also evident. Haem itself did not concentrate in the bone marrow, and a negligible amount of radioactivity was recovered from brain, implying a poor penetration of the blood brain barrier.

Adrenal Glands↗
PubMed1984

Guanylate cyclase from bovine lung. Evidence that enzyme activation by phenylhydrazine is mediated by iron-phenyl hemoprotein complexes.

The mechanism of activation of soluble guanylate cyclase purified from bovine lung by phenylhydrazine is reported. Heme-deficient and heme-containing forms of guanylate cyclase were studied. Heme-deficient enzyme was activated 10-fold by NO but was not activated by phenylhydrazine. Catalase or methemoglobin enabled phenylhydrazine to activate guanylate cyclase 10-fold and enhanced activation by NO to over 100-fold. Heme-containing enzyme was activated only 3-fold by phenylhydrazine but over 100-fold by NO. Added hemoproteins enhanced enzyme activation by phenylhydrazine to 12-fold without enhancing activation by NO. Reducing or anaerobic conditions inhibited, whereas oxidants enhanced enzyme activation by phenylhydrazine plus catalase, and KCN had no effect. In contrast, enzyme activation by NO and NaN3 was inhibited by oxidants or KCN. NaN3 required native catalase, whereas phenylhydrazine also utilized heat-denatured catalase for enzyme activation. Thus, the mechanism of guanylate cyclase activation by phenylhydrazine differed from that by NO or NaN3. Guanylate cyclase activation by phenylhydrazine resulted from an O2-dependent reaction between phenylhydrazine and hemoproteins to generate stable iron-phenyl hemoprotein complexes. These complexes activated guanylate cyclase in the absence of O2, but lost activity after acidification, basification, or heating. Gel filtration of prereacted mixtures of [U-14C]phenylhydrazine plus hemoproteins resulted in co-chromatography of radioactivity, protein, and guanylate cyclase stimulating activity, and yielded a phenyl-hemoprotein binding stoichiometry of four under specified conditions (one phenyl/heme). [14C]Phenyl bound to heme-containing but not heme-deficient guanylate cyclase and binding correlated with enzyme activation. Moreover, reactions between enzyme and iron-[14C] phenyl hemoprotein complexes resulted in the exchange or transfer of iron-phenyl heme to guanylate cyclase and this correlated with enzyme activation.

Animals↗
PubMed1998

Iron deficiency reduces the hydrolysis of cell membrane phosphatidyl inositol-4,5-bisphosphate during splenic lymphocyte activation in C57BL/6 mice.

Iron deficiency impairs lymphocyte proliferation in humans and laboratory animals by unknown mechanisms. In this study, we investigated whether this alteration can be attributed in part to impaired hydrolysis of cell membrane phosphatidyl inositol-4, 5-bisphosphate (PIP2), a required early event of T-lymphocyte activation. The study involved 46 iron-deficient (ID), 26 control (C) and 23 pair-fed (PF) mice, and ID mice that were repleted for 3 (n = 16), 7 (n = 17) or 14 d (n = 18). Mice were killed after 40-63 d (mean, 48 d) of consuming the test diet (0.09 mmol/kg iron) or the control diet (0.9 mmol/kg). The mean (+/-SEM) hemoglobin concentrations were 57 +/- 16.7, 176 +/- 2.6 and 181 +/- 9.7 g/L for ID, C and PF groups, respectively. After splenic lymphocytes were labeled in vitro with 3H-myoinositol for 3 h, PIP2 hydrolysis was estimated by measuring the radioactivity recovered as a mixture of inositol mono-, di- and triphosphate (IP) from concanavalin A (0, 1, 2.5, 5 and 10 mg/L) activated cells. Although cells from ID mice and those from mice repleted for 3 d incorporated slightly more radioactivity in cellular phospholipids than did cells from C or PF mice, less (P < 0.005) was recovered as IP than in controls, suggesting impaired conversion of the precursor to PIP2. At almost all incubation periods (10-120 min) and mitogen concentrations, the rate of PIP2 hydrolysis expressed as the ratio of radioactivity obtained in Con A-treated to untreated cells was significantly (P < 0.05) reduced in cells from ID mice compared with those obtained from C and PF mice. For cells that were activated for 60 min or less, iron repletion for 14 d significantly (P < 0.05) improved the rate of PIP2 hydrolysis. PIP2 hydrolysis positively and significantly (P < 0.05) correlated (r = 0.27-0.56) with indicators of iron status. Mitogenic response was also significantly (P < 0.05) reduced in ID but not PF mice, and it was corrected by iron repletion for 3, 7 or 14 d. Lymphocyte proliferation positively (r = 0.27-0.37, P < 0.01) correlated with indices of iron status and IP ratios. The data suggest that reduced PIP2 hydrolysis contributes to impaired blastogenesis in iron deficiency.

Animals↗
PubMed2003

Evaluation of natural radionuclides at Um-Greifat area, eastern desert of Egypt.

Air borne radiometric maps and remote sensing techniques were used to explore for the occurrence of radioactive materials. The previous techniques recorded radioactive mineralization for the first time along the NW-SE trending fault zones within the Miocene clastic-carbonate sediments. In the present study, gamma-ray spectrometry was used to confirm the presence of this mineralization. Concentrations of radionuclides, associated within the iron ochre at Um-Greifat area, have been measured, using a hyper-pure germanium spectrometer. The variation in concentration of radionuclides for the area under investigation can be classified into A, B and C regions of high, medium and low natural radioactivity. In region A, average concentration in Bqkg(-1) has been observed to range from 1858 to 4062 for 238U, between 29 and 151 for 232Th, from 60 to 136 for 235U and between 46 and 409 Bqkg(-1) for 40K. Radium equivalent activities (Ra(eq)) in addition to external and internal hazard indices (H(ex), H(in)) have also been determined. Ra(eq) varies between 1901 and 4307Bqkg(-1), which exceeds the permitted value (370Bqkg(-1)) and H(ex) and H(in) are higher than 1. The high activity concentration within region A points to an environmental hazard, while regions B and C have less exposure effect on human beings.

Calibration↗
PubMed2001

Kinetics of the adsorption and desorption of radionuclides of Co, Mn, Cs, Fe, Ag and Cd in freshwater systems: experimental and modelling approaches.

The sorption and release kinetics of 54Mn, 58Co, 59Fe, 109Cd, 110mAg and 134Cs by freshwater suspended particles were investigated to better identify the biogeochemical processes involved and to obtain suitable data for improving models describing radionuclide migration in freshwater streams. In order to observe any seasonal variability in the interaction of radionuclides with natural particles, experiments were performed both in winter and in summer during a phytoplanktonic bloom. Two kinetic models are compared in this paper: the "one-step reversible" model, based on the hypothesis that the transfer of radionuclides between water and suspended solids is governed by a reversible reaction, and the "two-successive-step reversible" model, which assumes two distinct types of sites or reactions on the solid phase. The "one-step reversible" model is generally unable to describe properly the exchange kinetics; this result shows that at least two processes are generally involved in radionuclide exchange between water and suspended particles. On the contrary, a model involving the existence of two successive reversible reactions properly simultes both the sorption and release kinetics. The determination of the kinetic coefficients allows quantitative assessment of the relative importance and kinetics of the processes. In particular, it has been shown that, except for Cs and Cd, major fractions of the radionuclides are associated at equilibrium with particulate sites involving strong interactions. The kinetics to reach this equilibrium depend on seasonal conditions, especially for Co and Mn: the transfer of Co and Mn to particulate sites involving strong interactions is much slower in winter. The distribution of the radionuclides between water and particulate sites involving weak interactions also shows seasonal variations for Co, Mn, Fe and Ag: the capacity to associate radionuclides is much higher in summer for Co and Mn, while the inverse tendency is observed for Fe and Ag. For Cs and Cd, no significant seasonal differences were observed.

Adsorption↗
PubMed2006

Affinity labeling of the rabbit 12/15-lipoxygenase using azido derivatives of arachidonic acid.

Lipoxygenases are lipid-peroxidizing enzymes, which have been implicated in the pathogenesis of important diseases. They consist of a single polypeptide chain, which is folded into a two-domain structure. The large catalytic domain contains the putative substrate-binding pocket and the catalytic non-heme iron. To identify structural elements of the rabbit 12/15-lipoxygenase that are involved in enzyme/substrate and/or enzyme/product interaction, we synthesized a set of radioactively labeled lipoxygenase substrates carrying a photoreactive azido group (17-azido-ETE, 18-azido-ETE, 19-azido-ETE) and used these compounds as affinity probes. After photoaffinity labeling, the enzyme was digested proteolytically and modified tryptic cleavage peptides were identified by a combination of radio-HPLC and mass spectral analysis. Following this strategy, we observed covalent linkage of a cleavage peptide that contained Ile593, which has previously been identified as the sequence determinant for the positional specificity. These data are consistent with the previous suggestion that this peptide lines the substrate-binding pocket. Surprisingly, we also observed strong labeling of cleavage peptides originating from the N-terminal beta-barrel domain, and our mass spectral data suggested covalent linkage of oxidized affinity probes. Taken together, these results confirm the previous conclusion that Ile593 and surrounding amino acids are constituents of the active site, but they also implicate the N-terminal beta-barrel in enzyme/substrate and/or enzyme/product interaction.

Affinity Labels↗
PubMed2004

Role of surface alteration in determining the mobility of U(VI) in the presence of citrate: implications for extraction of U(VI) from soils.

In the present study, the adsorption of U(VI) by a natural iron-rich sand in the presence of citrate was studied over a range of citrate concentrations and pH values. Adsorption of U(VI) on the iron-rich sand decreased in the presence of increasing concentrations of citrate. Adsorption of citrate to the sand was weak under most conditions studied. Several explanations for the adsorption behavior of U(VI) and citrate were investigated, including aqueous complexation of U(VI) by citrate, competition of U(VI) and citrate for adsorption sites, and extraction of Fe and Al from the sorbent surface by citrate (surface alteration). Although aqueous complexation of U(VI) by citrate may still play a significant role, both competitive adsorption and aqueous complexation proved to be inadequate explanations of the adsorption behavior. Both physical surface alteration (i.e., loss of surface area) and chemical surface alteration (i.e., change in the chemical composition of the sand surface) were investigated, with chemical surface alteration controlling the bulk of U(VI) adsorption. Considering these results, remediation schemes that involve organic complexing agents should address the possibility of surface alteration affecting radionuclide adsorption and mobility.

Adsorption↗
PubMedDate not supplied

Effect of iron on the absorption and distribution of clodronate after oral administration in rats.

The effect of iron on the absorption and distribution of disodium clodronate in rats after oral administration was studied. Disodium clodronate (300 mg/25 microCi/kg) was given both alone and with an equivalent amount of ferrous sulphate. The radioactivity in plasma and various tissue was measured. Concentration of clodronate in plasma was also determined with the GC-mass-selective detection method and the values compared with those measured with the isotope method. After administration, clodronate was rapidly cleared from plasma. Most of the dose was taken up by bone and only small amounts were found in non-calcified tissues. Concurrent ingestion of iron caused a marked decrease in the absorption of clodronate.

Absorption↗
PubMed1997

Secretion of ferritin by rat hepatoma cells and its regulation by inflammatory cytokines and iron.

The possibility that serum ferritin is a secreted protein and an acute phase reactant regulated by inflammatory hormones and iron was examined in a hepatic cell line that secretes plasma proteins. Differentiated rat hepatoma cells released albumin and ferritin into the medium, as determined by rocket immunoelectrophoresis and isolation of ferritin by standard procedures plus immunoaffinity chromatography, following labeling with radioactive amino acid. Administration of interleukin-1-beta (IL-1) or tumor necrosis factor-alpha (TNF) doubled the amounts of ferritin released into the medium over 24 and 48 hours. Together, the cytokines had more than an additive effect. Albumin secretion was diminished by IL-1, but not TNF. Iron, administered as an iron dextran complex or as a 1:1 chelate with nitrilotriacetate (Fe-NTA), also enhanced ferritin release, but had no effect on albumin. Intracellular ferritin concentrations did not change significantly with cytokine treatment, but increased in response to iron. With or without treatments, release of ferritin and albumin from cells into the medium was inhibited by brefeldin A, an inhibitor of Golgi function. The effect of each of the cytokines and of iron on ferritin and albumin was also blocked by dichlorofuranosylbenzimidazole (DRB), an inhibitor of transcription. The stimulatory effect of Fe-NTA on ferritin secretion was diminished by TNF, and this was partially counteracted by IL-1, indicating additional regulatory complexity. These results show for the first time that hepatic cells secrete ferritin, that this ferritin secretion is regulated by iron and inflammatory cytokines, and that the mechanisms of regulation differ from those for intracellular ferritin. The results would explain why serum ferritin increases in inflammation or when iron flux is enhanced.

Animals↗