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Results for “Selenium Radioisotopes”

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At least 19 recordsLinked to original sources
PubMed2001

Considerations on the behavior of long-lived radionuclides in the soil.

The migration of radionuclides from waste repositories to the biosphere potentially leads to a contamination of soil. Due to the importance of food production, the mobilisation and accumulation behaviour of long-lived radionuclides in the soil plays a key role in performance assessment studies. In this paper, the main features and processes that control radionuclide behaviour in soil, such as pH, redox potential and sorption to organic and inorganic soil components, are discussed for the radionuclides 36Cl, 79Se, 129I, 99Tc, 237Np and 238U, that are usually most relevant in long-term safety assessments of nuclear waste. The interaction of radionuclide behaviour in soil with environmental factors, such as temperature and humidity as well as farming practices are discussed. The possible impact of future soil development on long-term behaviour in soil are taken into consideration. Due to the physiological constraints of plant growth, appropriate soil conditions for growth will probably not be substantially different from current requirements, bearing in mind that sustainable agriculture strives for optimal plant growth. Against this background, present-day parameters may in general be considered appropriate for roughly estimating the behaviour of radionuclides in the soil-plant system.

Chlorine↗
PubMed2004

Methanococcus vannielii selenium metabolism: purification and N-terminal amino acid sequences of a novel selenium-binding protein and selenocysteine lyase.

Selenium is an essential component of several enzymes and proteins in a number of methane-producing archae. Information concerning accessory proteins that function in selenium transport processes, however, is limited. A novel selenium-binding protein with a potential transport role and a selenocysteine lyase that serves as a selenium delivery protein are present in Methanococcus vannielii. The selenium-binding protein was purified from extracts of 75Se-labeled cells. Although there was gradual loss of 75Se during purification, the isolated protein still could be detected as a radioactive 42 kDa species on native PAGE gels and as a 33 kDa species on SDS PAGE gels. The N-terminal amino acid sequence of residues 1 - 63 of the protein was determined by automated Edman degradative analysis. The only homologous sequence detected in the recorded data base was that of a gene encoding an unknown protein located in the genomic sequence of Methanococcus maripaludis. Cloning and expression of the corresponding gene from M. vannielii are described in a manuscript in press (Self et al.). A 47 kDa selenocysteine lyase isolated from M. vannielii extracts exhibited sequence homology to the NIFS family of proteins that transport sulfur. The purified selenocysteine lyase catalyzed the elimination of an elemental form of selenium from free selenocysteine and delivered this selenium directly to selenophosphate synthetase. The synthetase converted the selenium to selenophosphate in an ATP-dependent reaction.

Amino Acid Sequence↗
PubMed1980

Transfer coefficients of radionuclides secreted in milk of dairy cows.

This study simulated experimentally the transfer of radionuclides to milk of dairy cows on a worst-case situation using various radionuclides known to emanate from nuclear power stations and which have been detected on particulates. Two lactating Holstein cows were administered orally one gelatin capsule containing 10 radionuclides in water-soluble form per day for 14 consecutive days. Milk samples were collected and aliquots analyzed in a germanium lithium-drifted detector coupled to a 2048-multichannel gamma-ray analyzer to measure small amounts of complex mixtures of radionuclides. The transfer coefficients of the radionuclides were calculated when their secretion in milk reached or approached a plateau of concentration. The radionuclides and their transfer coefficients to milk were: chromium51 less than .01%; manganese54 .033 +/- .005%; cobalt60 .01 +/- .002%; iron59 .0048 +/- .002%; zinc65 .31 +/- .07%; selenium75 .29 +/- .1%; antimony125 .011 +/- .003%; iodine131 .88 +/- .05%; and cesium137 .79 +/- .08%.

Animals↗
PubMed1989

A 14-kilodalton selenium-binding protein in mouse liver is fatty acid-binding protein.

In a previous study, we purified three selenium-binding proteins (molecular masses 56, 14, and 12 kDa) from mouse liver using column chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The aim of the present study was to determine the amino acid sequence of the 14-kDa protein thereby establishing any relationship with known proteins. Although the amino terminus of the 14-kDa protein was blocked, separate in situ digestions of the protein with endoproteinases Glu-c and Lys-c gave overlapping peptides that provided a continuous sequence of 93 amino acids. This sequence exhibited a 92.5% sequence homology with rat liver fatty acid-binding protein. In situ enzymatic digestion and partial sequencing of a 12-kDa selenium-binding protein revealed identical homology to the 14-kDa protein. The 14-kDa protein bound specifically to an oleate-affinity column from which the protein and 75Se coeluted. Delipidation or sodium dodecyl sulfate treatment failed to remove 75Se from the protein, indicating that the selenium moiety was tightly bound to the protein. These observations confirm that the mouse liver selenium-binding 14-kDa protein is a fatty acid-binding protein. The nature of the selenium linkage to the protein still needs to be explored.

Amino Acid Sequence↗
PubMed1977

Choice of monitoring isotope in double label radioimmunoassays with nonimmunological separation techniques.

We discuss the suitability of some radioactive isotopes as volume markers in radioimmunoassays, from a radiochemical point of view. For three eligible isotopes (22Na, 60Co, and 75Se) we studied the concentration of the marker in the precipitate formed in the separation phase of radioimmunoassays. For all those kinds of separations tested (charcoal, ammonium sulfate, polyethylene glycol, and ethanol), binding or coprecipitation was virtually absent or negligible with 22Na but 75Se was strongly concentrated in the precipitate. Concentration of 60Co occurred only with charcoal and ethanol precipitation. Because heavy metals tend to bind to serum proteins, we conclude that of all radioactive isotopes commercially available only 22Na should be used in radioimmunoassays with nonimmunological separation methods.

Charcoal↗
PubMed1996

Isolation of 75Se binding protein from hepatic tissues of chick embryos.

Distribution study using 75Se shows that maximum accumulation was in liver tissues after 24h of 75Se administration. Induction of selenium binding protein (Se-P) in hepatic tissues of chick embryo was observed. Chick embryo hepatic Se-P was isolated after 24h of 75Se treatment using Sephadex G-75 column chromatography. Fractions of induced protein shows the presence of maximum concentration of 75Se. This induced protein was found to have an approximate molecular weight of 56 KD on molecular sieve. It also showed an absorbance maxima at 254 nm, which indicates the presence of high concentrations of sulphydryl groups.

Animals↗
PubMed1994

Application of short-lived radionuclides in neutron activation analysis of biological and environmental samples.

The application of short-lived nuclides, especially in connection with the 6LiD-converter, in biological and environmental samples is demonstrated on I and Br determination in human urine, on I in pet food, and on the analysis of all the halogens in volcanic gases in a single activation. Trace element determination in lichens indicates polluted and unpolluted areas. The use of the .74-s 38mCl enables the rapid screening of great number of samples.

Animal Feed↗
PubMed1992

Use of radiochemical methods as tools for speciation purposes in environmental and biological sciences.

Chemical speciation for a few elements can be facilitated to a great extent by incorporating a suitable radioisotope into the system and measuring the radiation of the isolated species. This radiospiking can be applied to in vitro and in vivo labelled experiments. Radionuclides are, however, also present as an anthropogenic contaminant from various nuclear fission activities. The radiotracer should be added under such conditions that it behaves in exactly the same way as the isotopes it represents. It should possess an adequate radioactive half-life, and preferably be a gamma-emitter because of the ease of detection. Radiotracer labelling is now widely used to study speciation problems of many essential and toxic elements in body fluids and tissues. It can be used to trace the different locations where the element is metabolized and stored, and subsequently to detect the element in the isolated biocomponents. The determination of the location of a radiotracer in a cell by autoradiography proved to be impractical because of the lack of resolution. Radiochemistry is similarly very useful for investigating particular aspects of the speciation of heavy metals as they occur in the ecosystem, and to follow the fate and effects of fission nuclides in the environment as they are carried around by the water and air masses. However, in certain circumstances the behaviour of fission products appears to be different from that of their stable analogues. For the actinides they simply do not exist. Radiochemical methods are a major tool for identifying and quantifying the nuclides in the different species.

Animals↗
PubMed1974

Thrombopoietin.

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Animals↗