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At least 757 records · Page 42Linked to original sources
PubMed1981

Precision and accuracy of serum ferritin measurements.

For the epidemiological evaluation of iron stores the precision of serum ferritin measurement in the low range are important for the accurate determination of the prevalence of iron deficiency and the detection of subtle changes in serum ferritin levels after food iron manipulation. In addition the recognition of iron overload and the evaluation of its severity are important. In this study samples with low serum ferritin values were repetitively measured in a classic radioimmunoassay (RIA) and in two "2-site" immunoradiometric assays (IRMA), one of which used a polystyrene bead and the other a polystyrene tube fas the solid phase. Variability was significantly less with the IRMA using a bead than that using a tube. Optimum precision was noted when samples were run at the lowest possible dilution (1:10) with relatively long reaction times. The bead IRMA was also more precise that the RIA which had a standard curve with 50% radioactive binding (maximum precision) of 40 ng/ml. Within the normal serum ferritin range (12 to 300 ng/ml) extremely similar results were obtained with an RIA and IRMA. However, when iron overload samples (serum ferritin values greater than 2000 ng/ml) were examined the RIA gave values significantly lower than those obtained by IRMA. The lower values by RIA may be related to the immunological heterogeneity of serum ferritin which is maximized by an assay performed in antigen excess (RIA) and minimized by one performed in antibody excess (IRMA). These observations indicate a need for the development of specific serum ferritin assays for epidemiological studies. By manipulating the components of the standard curve the RIA and IRMA can be optimized to provide maximum precision when low serum ferritin values are being measured. in choosing an assay the ability of the method to determine the severity of iron overload must also be taken into consideration.

Ferritins↗
PubMed2002

Sampling and analyses of colloids at the Drigg low level radioactive waste disposal site.

Water samples have been extracted from inside (from standpipes) and from outside (from boreholes) of the trenches at the low level radioactive waste disposal site at Drigg in Cumbria, UK. The samples were taken anaerobically from between 8.5 and 10.0 m below the surface using a submersible pump at low flow rates to ensure that the waters in the standpipes and boreholes were maintained at constant levels. To ensure representative samples, the Eh, pH. conductivity, temperature, iron and dissolved oxygen concentrations of the waters were taken during initial purging and during sampling. The gross tritium, gross non-tritium beta, gross alpha and gamma activities of each sample were determined using suitable sample preparation and counting techniques. Samples were then anaerobically, sequentially filtered through 12 microm, 1 microm, 30 kDa and 500 Da filter membranes. The filtrates were analysed for gross alpha, gross non-tritium beta and gamma activities. SEM and STEM analyses were used to determine the colloid population. An energy dispersive analyser on the SEM was used to determine the major elements present in the colloids. UV-visible spectrophotometry, fluorescence spectrophotometry and high performance size exclusion liquid chromatography were used to analyse the waters before and after treatment with ion exchange materials to determine whether natural organic matter was present in the waters. Results showed that two major types of colloids (iron containing colloids and silicon containing colloids) were present in the waters. There were also a small number of other colloids that contain, as major elements, aluminium, calcium and chromium. Organic colloids were also present. The majority of the radioactivity in the waters was due to tritium. Waters taken from outside the trenches contained low levels of non-tritium beta activities and alpha activities which were lower than the minimum detectable amount. Waters taken from the trenches contained non-tritium beta activities and low levels of alpha emitters. Filtration of the trench waters showed that some of the alpha activity was retained by the 30 kDa and 500 Da membranes suggesting that this activity was associated with small colloids. Radioactivity was not found to be associated with colloids present in the waters taken from outside the trenches. Possible reasons for this observation could be that radionuclide bearing colloids have not yet reached the far-field or that the radionuclide concentration is diluted to below the minimum detectable amount. After concentrating two of the samples by factors of x20 and x 16 respectively, 2.4+/-0.1 and 0.6+/-0.1 Bq dm(-3) of 137Cs were measured.

Colloids↗
PubMed1978

Studies of the lymphatic drainage of dog lungs.

The lymphatic system of the lungs has proved difficult to study and characterize because it is technically complex to investigate, its properties are difficult to quantitate, and anatomically it is extraordinarily variable. This study was part of a more comprehensive effort to understand the nature of lymphatic permeation by extrinsic materials (e.g., dusts) arising from alveolar deposition, and had three main objectives; (1) to develop a reliable surgical approach for the collection of lymph from the right duct; (2) to investigate some of the inconsistencies in lymphatic structure and function, especially the relationship of the right lymph duct (RLD) and thoracic lymph duct (TLD) outflows to the pulmonic lymph; and (3) to begin a systematic investigation of lymphatic uptake of administered materials by varying their physicochemical parameters. Ultimately, we utilized a modification of the surgical approach of Meyer, which we believe is less prone to blood contamination than the venous-sac procedure of Leeds and Uhley and provides purer pulmonic lymph. By this means we obtained average RLD flow rates of 4.5 ml/h or 0.35 ml/h . kg body weight in 24 dogs, which are comparable to those in the recent literature. For demarcation of the pulmonic drainage in relation to the RLD and TLD, we found in 13 dogs that 75% or more of the lung lymph returned to the venous circulation through the RLD, wheras less than 3% of the thoracic lymph entered the RLD. Radioactive tracers were administered by intralymphatic, intrabronchial, inhalation, and intravenous routes to obtain these findings and the uptake data. Lymphatic uptake values for iron, cadmium, and lead were obtained principally after intrabronchial administration. The uptake data, while preliminary, indicate that both the chemical species and their physical states are important in affecting alveolar permeation into the pulmonic lymph. Evidence for varying lymphatic roles in the alveolar retention of these heavy metals is also presented.

Animals↗
PubMed1953

New therapy for leukemia, polycythemia, and lymphoma.

X-radiation remains the treatment of choice in most cases of leukemia and lymphoma, but new agents are playing an increasing role in therapy. Radioactive phosphorus does not produce radiation sickness and results with it are comparable to those of x-ray therapy in chronic leukemia. Urethane and nitrogen mustard may produce remissions in patients with chronic leukemia who have become resistant to radiation. Triethylene melamine may be administered orally with nitrogen mustard-like effects and is undergoing further trial. Aminopterin, ACTH and cortisone often cause short remissions in acute leukemia. Urethane is the best treatment available for multiple myeloma. Polycythemia vera is well controlled by radioactive phosphorus combined with venesection. Nitrogen mustard is often effective and triethylene melamine shows promise in Hodgkin's disease. Antianemic substances such as iron and liver extract are of no value in the treatment of anemia caused by leukemia, lymphoma and myeloma.

Aminopterin↗
PubMed1988

Syncatalytic inactivation of prolyl 4-hydroxylase by anthracyclines.

The anthracyclines doxorubicin and daunorubicin were found to act as irreversible inhibitors of prolyl 4-hydroxylase. The reaction rate for enzyme from both chick and human origin was first order, the concentration of inhibitor giving 50% inhibition being 60 microM for both compounds after 1 h. The effect was dependent on the presence of iron ions in the reaction mixture. Inactivation could be prevented by addition of high concentrations of ascorbate, but not 2-oxoglutarate, before the inactivation period. The same results were obtained with competitive analogues of these cosubstrates. Lysyl hydroxylase from chick embryos was also susceptible to inactivation. Its activity was decreased by 50% after incubation for 1 h with a 150 microM concentration of the inhibitors. When chick-embryo prolyl 4-hydroxylase was incubated with [14-14C]doxorubicin, both enzyme subunits were radioactively labelled, about 70% of the total radioactivity being found in the alpha-subunit. Since the anthracyclines are known to undergo a redox reaction generating semiquinone radicals with Fe3+ only, the results suggest that the enzyme-bound iron ion is oxidized to a tervalent intermediate in uncoupled reaction cycles. The data also suggest that both enzyme subunits contribute to the catalytic site of prolyl 4-hydroxylase.

Animals↗
PubMed1975

Changes in the fluorescence and absorbance of lipoxygenase-1 induced by 13-Ls-hydroperoxylinoleic acid and linoleic acid.

1. The addition of 13-Ls-hydroperoxylinoleic acid to lipoxygenase-1 (linoleate: oxygen oxidoreductase EC 1.13.11.12) from soybeans at pH 9 and 25 degrees C causes a quenching of the fluorescence of the enzyme at 328 nm when exciited at 280 nm and gives rise to an increase of the absorbance of the enzyme in the 300 nm to 450 nm region. 2. In the absence of 02, addition of linoleic acid to enzyme treated with 13-Ls-hydroperoxylinoleic acid, causes an increase of the fluorescence at 328 nm and a decrease of the absorbance in the 300 nm to 450 nm region. 3. The fluorescence changes are suggested to be directly coupled to the absorbance changes via a non-radioactive energy transfer process. 4. It is proposed that the observed fluorescence and absorbance changes are related to changes in the formal change of iron in the protein.

Hydrogen Peroxide↗
PubMed2004

Effects of phosphate on uranium(VI) adsorption to goethite-coated sand.

U(VI)-phosphate interactions are important in governing the subsurface mobility of U(VI) in both natural and contaminated environments. We studied U(VI) adsorption on goethite-coated sand (to mimic natural Fe-coated subsurface materials) as a function of pH in systems closed to the atmosphere, in both the presence and the absence of phosphate. Our results indicate that phosphate strongly affects U(VI) adsorption. The effect of phosphate on U(VI) adsorption was dependent on solution pH. At low pH, the adsorption of U(VI) increased in the presence of phosphate, and higher phosphate concentration caused a larger extent of increase in U(VI) adsorption. Phosphate was strongly bound by the goethite surface in the low pH range, and the increased adsorption of U(VI) at low pH was attributed to the formation of ternary surface complexes involving both U(VI) and phosphate. In the high pH range, the adsorption of U(VI) decreased in the presence of phosphate at low total Fe concentration, and higher phosphate concentration caused a larger extent of decrease in U(VI) adsorption. This decrease in U(VI) adsorption was attributed to the formation of soluble uranium-phosphate complexes. A surface complexation model (SCM) was proposed to describe the effect of phosphate on U(VI) adsorption to goethite. This proposed model was based on previous models that predict U(VI) adsorption to iron oxides in the absence of phosphate and previous models developed to predict phosphate adsorption on goethite. A postulated ternary surface complex of the form of (>FePO4UO2) was included in our model to account for the interactions between U(VI) and phosphate. The model we established can successfully predict U(VI) adsorption in the presence of phosphate under a range of conditions (i.e., pH, total phosphate concentration, and total Fe concentration).

Adsorption↗
PubMed2001

Iron prevents ferritin turnover in hepatic cells.

It has long been assumed that iron regulates the turnover of ferritin, but evidence for or against this idea has been lacking. This issue was addressed using rat hepatoma cells with characteristics of hepatocytes subjected to a continuous influx of iron. Iron-pretreated cells were pulsed with [(35)S]Met for 60 min or with (59)Fe overnight and harvested up to 30 h thereafter, during which they were/were not cultured with ferric ammonium citrate (FAC; 180 microm). Radioactivity in ferritin/ferritin subunits of cell heat supernatants was determined by autoradiography of rockets obtained by immunoelectrophoresis or after precipitation with ferritin antibody and SDS-PAGE. Both methods gave similar results. During the +FAC chase, the concentration of ferritin in the cells increased linearly with time. Without FAC, the half-life of (35)S-ferritin was 19-20 h; with FAC there was no turnover. Without FAC, the iron in ferritin had an apparent half-life of 20 h; in the presence of FAC there was no loss of (59)Fe. Without FAC, concentrations of ferritin iron and protein also decreased in parallel. We conclude that a continuous influx of excess iron can completely inhibit the degradation of ferritin protein and that the iron and protein portions of ferritin molecules may be coordinately degraded.

Animals↗
PubMed1987

Factors influencing the absorption of iron from soya-bean protein products.

The absorption of iron from soya-bean (Glycine hispida)-based and milk-based infant formulas was assessed in 138 multiparous Indian women, using the erythrocyte utilization of radioactive Fe method. Fe absorption was significantly greater from the basal milk formula (1.5 g protein) than it was from the basal soya-bean formula (2.3 g protein), with geometric mean values of 0.083 and 0.044 respectively. Ascorbic acid markedly increased Fe absorption from the milk-based formula in a dose-dependent fashion. The increase was fivefold when the ascorbic acid:Fe ratio on a weight-for-weight basis was 6:1 and over tenfold when it was 20:1. In contrast, ascorbic acid had a less-marked effect on the absorption of Fe from the soya-bean-based formula, with only a two- to threefold increase at an ascorbic acid:Fe ratio of 20:1. The geometric mean Fe absorption from the soya-bean formula (1.27 mg Fe, 2.3 g isolated soya-bean protein (ISP] was somewhat less than that from the same amounts of ISP and ascorbic acid made up in milk (0.075 and 0.113 respectively). However, a direct comparison between the soya-bean formula in milk and in water showed no significant difference (0.043 and 0.060 respectively). Fe absorption from a drink containing 10 g ISP and 30 mg ascorbic acid was significantly better than that from a similar drink containing the soya-bean flour from which ISP is extracted (0.044 and 0.027 respectively). Heating ISP to 200 degrees for 2 h before its use had no effect on Fe availability.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1980

Cytosol intermediates in the transport of iron.

Three 59Fe-labeled nonheme components of the cytosol were identified when rabbit reticuloyctes were incubated with 59Fe-labeled plasma under conditions in which the iron supply was not limiting. Two of these components were identified as ferritin and transferrin. The latter was characterized by gel filtration as having apparent molecular weight higher than transferrin, indicating that the transferrin may be complexed to another moiety. The third component, referred to as iron-binding protein-I (IBP-I), is as yet uncharacterized. When the reticulocytes were incubated with unlabeled plasma after pulse-labeling with 59Fe-labeled plasma, 59Fe radioactivity in these cytosol components decreased; after 15 min of chase, the 59Fe in ferritin, transferrin, and IBP-I fell to 64.6%, 26.5%, and 65.8% of the initial values, respectively. A good correlation existed between the decrease of 59Fe in these three nonheme compartments and the associated increase in 59Fe-heme. The data presented suggest that cytosol ferritin, transferrin, and IBP-I are intermediates in the transport of 59Fe from the plasma membrane to the mitochondria.

Animals↗
PubMed1986

Requirement for reduced, unliganded hemoprotein for the hemoglobin- and myoglobin-mediated biotransformation of glyceryl trinitrate.

The biotransformation of glyceryl trinitrate (GTN) by hemoglobin (Hb) and myoglobin (Mb) was assessed using solutions of various forms of the hemoproteins, viz., the oxy-, deoxy-, carbonmonoxy- and met-forms. After incubation with these, GTN loss was observed only with the deoxy-forms of Hb and Mb. The stoichiometry and products of [14C]GTN biotransformation by deoxy-Hb and deoxy-Mb were determined by measuring the formation of [14C]glyceryl dinitrate [14C]GDN), met-Hb (or met-Mb) and inorganic nitrite anion. Biotransformation of GTN involved the oxidation of 2 mol of heme iron (II) per mol of GTN biotransformed to GDN and inorganic nitrite anion. In addition to the formation of GDN, 1 to 2.5% of the radioactivity could not be extracted from the incubation samples. The ratio of 1,2-GDN/1,3-GDN formed during incubation of deoxy-Hb with GTN was 11:1, which indicated a high degree of regioselectivity for the denitration of the nitrate ester group in position 1 or position 3 of GTN. The metabolite ratio obtained for deoxy-Mb incubation with GTN (1,2-GDN/1,3-GDN,3:1) was less than that for deoxy-Hb, which indicated less regioselectivity for the deoxy-Mb-mediated denitration reaction. This could reflect differences in the topography of the heme pocket of the two hemoproteins and steric differences in the GTN-hemoprotein interaction.

Biotransformation↗
PubMed1990

[Effect of mercuric chloride poisoning on iron distribution in rats].

The aim of our work was to establish the influence of the HgCl2 poisoning (various doses) on the Fe distribution in the rat organism. 175 Wistar rats were divided into 5 groups: I--control group, II--intoxicated with HgCl2 in the dose of 1 mg/kg of body weight, in the III group the HgCl2 dose was 6 mg/kg, in the IV group--12 mg/kg, in the V--12 mg/kg but rats of this group were given afterwards BAL (2.3-dimercaptopropanol). All rats were given 0.2 ml of 59FeCl3, radioactivity 3.7 kBq. The animals were put to sleep with chloroform after 3 and 6 hours, and 1, 2, 4, 8, 14 days after the isotope administration. For the radiometric assays the following organs or tissues were taken: stomach, small and large intestine, liver, kidneys, lungs, heart, muscles, spleen, blood, brain, testicles. The results are given in the percent of Fe dose in 1 g of wet tissue. The statistical analysis (Students' t test) was performed. The results indicate that in poisoned animals the Fe distribution was different than in controls. Increased concentration of 59Fe was noted after 3 and 6 hours in stomach and after 1 day in large intestine, whereas in other organs the Fe concentration was lower, correlating usually with the Hg dose. One interesting thing was noted: the Fe concentration in almost all organs was higher in rats intoxicated with the 12 mg/kg dose of HgCl2 and given afterwards BAL (IV group), than in rats that were not given BAL. Present results can have some practical significance in therapeutic procedure in mercury poisoning and during the convalescence.

Animals↗