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PubMed2002

Low-background gamma spectrometry for environmental radioactivity.

Development and performance of a low-background gamma-ray spectrometer are described. The spectrometer consists of a 131% efficient Ge detector in U-type configuration. The passive shielding consists of ultrapure lead of 6" thickness. A top muon guard is used as an active shielding. The spectrometer and shielding are positioned inside a steel room made of 6"-thick pre-World War II iron. The steel room is located underground with 33 m of water-equivalent overburden. The total integrated background rate in the energy range 50-2,700 keV was measured at 0.068 counts per second per 100 cm3 Ge volume. The spectrometer serves as a reference instrument for low-level and highly accurate environmental radioactivity measurements. One specific application of 228Ra determination in drinking water is described. With a 1 l water sample, 1-step chemical procedure, and 1,000 min counting time, a detection limit Ld = 20 mBq/l (0.55 pCi/l) was reached, which meets the EPA mandated limit of 1 pCi/l. Methods of upgrading the spectrometer as well as the predicted improvements in 228Ra detection, including direct counting of water without chemical processing, are discussed.

Journal Article↗
PubMed1997

Histochemical localization of heme oxygenase-2 protein and mRNA expression in rat brain.

Heme oxygenase (HO) proteins are members of the HSP30 family and consist of 2 isozymes identified to date, termed HO-1 and HO-2. Separate genes encode the isozymes and protein products which are immunochemically distinct, share less than 50% similarity at the amino acid sequence level. Each form, however, shows greater than 90% similarity among species, including human and the rat (reviewed in ref.). Furthermore, these isozymes function in a well-defined role to carry out oxidation of the heme molecule (Fe-protoporphyrin IX) in concert with NADPH-cytochrome P450 reductase. The oxidation of heme is isomer specific and results in the formation of bile pigments, carbon monoxide, and iron. The heme molecule constitutes the prosthetic moiety of hemoproteins, such as hemoglobin, myoglobin, catalase, soluble guanylate cyclase, cytochrome b5, cytochromes P450 and NO synthase. HO-1 also known as heat shock protein (HSP) 32 is encoded by a gene which is exquisitely stress-responsive and a host of stimuli that mediate oxidative stress cause induction of the protein both in vivo and in vitro. The HO-2 form shows a unique pattern of regulation from that of HO-1. HO-2 is a constitutive protein and its expression is not affected by the inducers of HO-1 tested to date; rather, the only known regulator of HO-2 yet identified is adrenal glucocorticoids. The two isozymes display vast differences in tissue distribution and under normal conditions HO-1 is present in the whole brain at the limit of immunodetection and is discreetly localized in select neuronal populations. HO-1 protein (approximately 32 kDa) and its approximately 1.8 kb transcript are increased, however, in response to stressful stimuli primarily in non-neuronal cell populations. The heme oxygenase system serves in both a catabolic and anabolic capacity in the cell. In the former capacity, it down-regulates cellular heme and hemoprotein levels. And, as such it inactivates the most effective catalyst for formation of free radicals, the heme molecule. In its anabolic role, as noted above, heme oxygenase produces bile pigments, carbon monoxide, and iron, all of which are biologically active: bile pigments function as antioxidants; the carbon monoxide generated by HO activity has been correlated with the generation of cGMP; and iron regulates expression of various genes, including that of HO-1 itself, as well as transferrin receptors, ferritin, and NO synthase. We used rabbit anti-rat HO-2 polyclonal antibody and HO-2 cDNA to localize HO-2 immunoreactive protein and the 1.3- and 1.9 kb homologous transcripts, respectively, in rodent brain as visualized by histochemical staining procedures. These protocols provide the first detailed description of methodologies successfully used to define the pattern of HO-2 expression at the transcriptional and translational levels in the adult rat brain and glucocorticoid-treated newborn rats. The procedures described herein have the virtue of being non-radioactive, as well as applicability to the systemic organs, such as the cardiovascular system and the male reproductive organs. Visualization of cellular HO-2 expression aids in assessment of potential sites of carbon monoxide, iron, and bilirubin production within the nervous system.

Animals↗
PubMed1987

The fate of intravenously administered hepatic ferritin in normal, phenylhydrazine-treated and scorbutic guinea-pigs.

When highly purified hepatic 59Fe-ferritin was injected intravenously into normal guinea-pigs more than half of it was taken up by red cell precursors and the iron was used for haem formation. This was studied in more detail in animals in which a reticulocytosis had been induced either by phenylhydrazine or by repeated venescetions. 55% of the injected ferritin iron was found in reticulocytes at 1 h. Experiments using ferritin doubly labelled with 59Fe and 125I indicated that the whole molecule was taken up, with two-thirds of the radioactivity being associated with the membrane at 1 h and one third being already within the cell. There was a progressive loss of 125I activity over the ensuing hours, while most of the 59Fe was slowly internalized and incorporated into haem between 1 and 24 h. In contrast, 90% of the activity taken up by red cell precursors from 59Fe-transferrin was present as haem at all times. The liver and spleen were the two other major sites of 59Fe-ferritin uptake in phenylhydrazine treated animals. While there was an early uptake of 59Fe into haem in these organs, some redistribution occurred with time, since most of the 59Fe was in a non-haem fraction by 24 h. In a final experiment the distribution and fate of 59Fe-ferritin was studied in scorbutic animals treated with phenylhydrazine. The findings were similar to those in normals similarly treated, which suggests that ferritin iron was being effectively mobilized for haem formation despite the ascorbic acid depletion.

Animals↗
PubMed1987

Dithiothreitol-induced oxidative damage to thymine and DNA in solution.

Studies on dithiothreitol-induced oxidative damage to thymine and DNA in solution are reported. The major thymine products, cis- and trans-5,6-dihydroxy-5,6-dihydrothymine (thymine glycols), are produced rapidly in 37 degrees C neutral solutions of 10mM thymine and 10mM dithiothreitol. Iron-EDTA enhances while the iron chelator, diethylenetriaminepentaacetic acid, inhibits the reaction. In experiments using 3H-TdR-labeled Escherichia coli DNA, DNA damage was measured as increased ethanol-soluble radioactivity after treatment of the DNA with 5mM dithiothreitol at 45 degrees C. The findings are important with respect to current research interest in thiol radioprotection and thiol-plus-heat toxicity.

DNA Damage↗
PubMed2003

Fe(O)/lignitic coal: an efficient and mechanically stable reactive material for purification of water containing heavy metals, radionuclides, and nitroaromatics.

Mine water in the former uranium mine of Königstein (Saxony, Germany) contains high concentrations of acid, sulfate, iron, aluminum, various heavy metals, radionuclides, and nitroaromatics. Research has been conducted for several years to establish the extent to which reduction of pollutant concentrations can be positively influenced and accelerated by storage of reactive materials in mine cavities. Investigations were made at different scales to test and select materials with respect to maximum fixation of contaminants (underground column tests) to examine hydraulic effects (underground large-scale column tests) and to optimize material properties (laboratory tests). The investigations have shown that a mixture of Fe chips and lignitic coal is capable of efficiently cleaning acid and contaminant-containing mine water. The examined material is easily available and compatible with the environment. A large-scale application of such a reactive barrier is being considered for mine water treatment in the future and is deemed to be a reasonable conception for a safety component after conclusion of the flooding.

Coal↗
PubMed1999

Resolved splenic accumulation of Tc-99m HMDP after recovery of disseminated intravascular coagulation in a patient with rhabdomyosarcoma.

Unusual, intense splenic radioactivity was seen on bone scintigraphy with Tc-99m HMDP in a 14-year-old boy with alveolar rhabdomyosarcoma complicated by disseminated intravascular coagulation. Abnormal splenic radioactivity was resolved after recovery from the disseminated intravascular coagulation. During treatment of disseminated intravascular coagulation and tumors, the patient received repeated blood transfusions, resulting in iron overload, but this did not prevent the abnormal splenic uptake from resolving. This case indicates that disseminated intravascular coagulation may be a cause of splenic accumulation of bone-seeking agents, and that abnormal splenic uptake can be resolved.

Adolescent↗
PubMed1982

Ingestion of iron in sow's faeces by piglets reared in farrowing crates with slotted floors.

1. Two sows were housed in farrowing crates with slotted floors and fed daily with approximately 200 microCi 198Au from 3 d before farrowing until their piglets were 21 d old. 2. Th sows' faeces became radioactive but their milk remained free of radioactivity. The piglets' mean (+/- SE) whole-body radioactivity was equivalent to 8.5 +/- 0.9 g (range 3.8-15.5 g) of faeces. This is probably a measure of their daily intake of faeces. 3. The possibility of using this natural coprophagia to prevent piglet anaemia has been demonstrated on two commercial piggeries by feeding the sows a diet containing 2000 mg Fe/kg.

Anemia, Hypochromic↗
PubMed1981

Relations between iron and vanadium metabolism: in vivo incorporation of vanadium into iron proteins of the rat.

In vivo experiments with 48V and 59Fe radiotracers were performed to study the association of V with Fe proteins. Each male rat was injected ip with 10 micrograms 48VO2+ and then with 1 microgram 59Fe3+ to label Fe-containing proteins. The radioactivities incorporated were measured in plasma transferrin, red blood cell hemoglobin, liver ferritin, partially purified heart myoglobin, and liver mitochondrial and microsomal cytochromes b and c and ferriporphyrin. Liver ferritin can bind V in vivo similarly to plasma transferrin, as shown by gel filtration and immunoprecipitation. Negligible amounts of 48 V were incorporated into hemoglobin, partially purified myoglobin, and cytochromes b and c. These findings suggest that the nonenzymatic Fe-containing proteins may be involved in the V metabolism.

Animals↗
PubMed1986

Hematopoiesis in the rat: quantitation of hematopoietic progenitors and the response to iron deficiency anemia.

To determine the quantitative effects of iron deficiency on erythropoiesis and to assess the response of erythroid progenitors to sustained anemia, we developed quantitative assays for various hematopoietic progenitors in the adult, Sprague-Dawley rat including erythroid colony- and burst-forming cells (CFU-E and BFU-E), granulocyte/macrophage colony-forming cells (CFU-GM), and megakaryocytic colony-forming cells (CFU-Meg). CFU-E were cultured in methylcellulose and grew best in the presence of fetal calf serum. CFU-GM, BFU-E, and CFU-Meg grew better in normal rat plasma and required the presence of pokeweed mitogen-stimulated rat spleen cell conditioned medium. The numbers of progenitors and nucleated erythroblasts in total marrow were estimated by the ratios of radioactivity in the humerus to the total skeleton as determined by radioiron dilution. The numbers of progenitors and erythroblasts in the spleen were measured by simple dilution. Sustained anemia was brought about through chronic iron deficiency. The response to iron deficiency anemia (IDA) was monitored by the numbers of the various progenitors and their cell cycle characteristics as measured by the tritiated thymidine suicide technique. With IDA, the number of CFU-F in the body (marrow plus spleen) was increased to 3.5 times control, whereas the numbers of BFU-E and CFU-GM were unchanged. There was no difference in the percentage of CFU-E, BFU-E, and CFU-GM in DNA synthesis (68%, 19.4%, and 18.8%, respectively). With iron therapy of IDA, CFU-E numbers in marrow began to decrease by day 1 and fell in a manner reciprocal to changes in the hematocrit. Marrow and spleen erythroblasts, 1.7 times control in IDA, increased further to 3.9 times control by the fourth day after iron administration. There was no change in BFU-E or CFU-GM numbers in response to iron repletion, although the fraction of progenitors increased in the spleen. Thus, IDA does not limit the increase in CFU-E seen with anemia, but does restrict erythroid maturation. Furthermore, the increase in CFU-E and the state of chronic anemia occur without detectable changes in the number of cell cycle state of the more primitive BFU-E.

Anemia, Hypochromic↗
PubMed1997

Uptake and processing of 59Fe-labelled and 125I-labelled rat transferrin by early organogenesis rat conceptuses in vitro.

The delivery of iron to the early organogenesis rat embryo has been studied, using 59Fe- and 125I-labelled rat transferrin. Rat conceptuses at 9.5 days postconception were cultured for 27 or 51 h in whole rat serum. Rat transferrin labelled with 59Fe was added for the final 0.1, 0.5, 6, 24 or 48 h of culture. Radioactivity accumulated progressively in both the embryo and the visceral yolk sac. Similar results were obtained when unconjugated 59Fe3+ was added to the rat serum used as culture medium. Both acid-soluble and acid-insoluble 59Fe were substantially present in the embryo and yolk sac after all exposure periods. When conceptuses were cultured in the presence of 125I-labelled rat transferrin, acid-soluble radioactivity was progressively released into the culture medium, but accumulation into the embryo and visceral yolk sac was slight and did not change with duration of exposure to the labelled protein. Similar findings were obtained using 125I-labelled bovine serum albumin. In these experiments, there was a close correspondence between the amount of iron accumulated by the embryo and visceral yolk sac in the final 24 h of a 51-h culture and the amount of transferrin converted into acid-soluble products in the same period. Visceral yolk sacs from 17.5-day pregnant rats were explanted and cultured in the presence of 59Fe-labelled rat transferrin, 125I-labelled rat transferrin or 125I-labelled bovine serum albumin, for periods up to 3 h. Again uptake of 59Fe increased with time of incubation, and the 125I-labelled proteins were digested to acid-soluble products which were released into the culture medium. The results indicate that transferrin delivers iron for incorporation into both the embryo and the visceral yolk sac, and are consistent with a mechanism involving receptor-mediated endocytosis of iron-laden transferrin by the cells of the visceral yolk sac. The transferrin itself appears to be quantitatively degraded, following delivery of iron to the yolk sac cells, a result that differs from findings in other cell types, in which the protein is not degraded but returns to the plasma membrane to participate in further cycles of iron acquisition and delivery.

Animals↗
PubMed2000

Sorption and desorption of radiocesium on red earth and its solid components: relative contribution and hysteresis.

The relative contributions of organic matter and iron oxides to the Cs+ sorption on red earth were investigated by using the batch technique and selective extraction methods. The sorption and desorption isotherms and the distribution coefficients of Cs+ on the untreated red earth and the three treated soils to remove organic matter, iron oxides and organic matter plus iron oxides were determined at 20 degrees C, pH 6.3+/-0.2, in the presence of 0.01 mol/l CaCl2. It was found that all the isotherms are linear in the Cs+ concentration range used here, that the sorption desorption hysteresis on the red earth actually occurs, and besides the clay minerals, the organic matter present in the red earth is a significant trap of Cs+ and is responsible for the hysteresis instead of the iron oxides.

Adsorption↗
PubMed1975

Molybdenum and iron as functional consitituents of the enzymes of the nitrate-reducing system of Azotobacter chroococcum.

The roles of molybdenum and iron in the enzymes of the assimilatory nitrate-reducing system from Azotobacter chroococcum have been investigated. 1. By adding 99 Mo-molybdate to a cell culture of A. chrocococcum with nitrate as the nitrogen source, it has been possible to incroporate the radioactive metal into a purified preparation of the enzyme nitrate reductase. 2. When 185 W-tungstate was supplied to a culture medium lacking added molybdate, a 185 W-labelled nitrate reductase preparation with negligible activity could be obtained. This in vivo incorporation of tungsten was competitively hindered by molybdenum. 3. The cellular level of nitrite reductase activity gradually increased in response to the addition of increasing amounts of iron to the culture medium. Under the same conditions, of the level of nitrate reductase activity was not affected.

Azotobacter↗
PubMed1982

Microvillar iron-binding glycoproteins isolated from the rabbit small intestine.

Rabbit intestinal microvillus membranes possess high-affinity receptors for iron whose activity reflects homeostatic changes in mucosal iron transport. To isolate and characterize these membrane components, purified microvilli were radiolabelled with 59Fe(II) and solubilized in Triton X-100. 59Fe in 105000g supernatants co-eluted with a major broad protein peak (Mr approx. 100000) on gel-permeation chromatography and was rendered diffusible by Pronase digestion but not mild periodate degradation. Fluorescence studies with castor-bean lectin conjugates showed specific binding of this affinity probe exclusively to brush-border membranes in the intestinal epithelium. Affinity chromatography of solubilized membrane proteins showed binding to columns of immobilized lectin. Elution with D(+)-galactose released glycoprotein-bound 59Fe purified up to sevenfold over initial membrane extracts. The lectin bound up to 82% of protein-bound 59Fe. In contrast polyspecific antisera raised against rabbit microvilli in guinea-pigs precipitated less than 10% of solubilized radioactivity. Significantly more protein-bound 59Fe in detergent extracts of microvilli purified from bled animals interacted specifically with the lectin, suggesting that membrane glycoprotein receptors are involved in the homeostatic control of intestinal iron transport.

Animals↗