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At least 73 records · Page 4Linked to original sources
PubMed1982

Comparative study of G2 delay and survival after 241 Americium-alpha and 60cobalt-gamma irradiation.

Survival and G2 dalay following exposure to either 60Cobalt-gamma-rays or 241Americium-alpha-particles were studied in eight mammalian cell lines of human and animal origin including human fibroblasts from normal individuals and from patients with Ataxia telangiectasia or Fanconi's anemia. For both endpoints the effectiveness of alpha particles was greater as compared to gamma-rays. RBE values for G2 delay (4.6-9.2) were in general comparable to RBE values derived from initial slopes of survival curves (RBE alpha) but higher compared to the ratio of mean inactivation doses (RB-DML). Ataxia cells were particularly sensitive to cell killing by gamma-irradiation (D37 = 0.57 Gy), however, showed average sensitivity to alpha-particles of high LET (D37 = 0.30 Gy). With the exception of Ataxia cells, cell killing and G2 delay seem to be related processes if individual cell cycle parameters are taken into account.

Alpha Particles↗
PubMed1984

Influence of the antimicrotubular agents, colchicine and vinblastin, on the uptake of americium by rat liver, kidneys, and skeleton.

The influence of pretreatment with colchicine and vinblastin sulfate, administered ip at dosages of 2.5 mumol/kg on the uptake of im or iv injected 241Am by rat liver, kidneys, and skeleton was investigated. Both agents reduced the nuclide uptake by liver and increased the 241Am contents in kidneys and skeleton. The effect was dependent on the time interval between pretreatment and nuclide injection as well as on the dose of the agents. The minimum effective dose was approximately 0.5 mumol/kg. A thousand times higher po dose of carbon tetrachloride was less effective than the highest colchicine dose. Lumicolchicine (2.5 mumol/kg) did not increase the 241Am skeleton and kidney contents and was less effective in reducing the hepatic content than colchicine or vinblastin. At the light microscopy level, livers of the rats appeared normal after the standard colchicine dose (1 mg/kg), but concentrations of four enzymes, which may indicate damage to the liver, were significantly raised.

Alanine Transaminase↗
PubMed1984

Studies on transformations of plutonium-239 and americium-241 in three major Indian soils.

These studies were carried out to elucidate the behaviour of 239Pu and and 241Am in three major soil groups of India, namely oxisol, vertisol-pellustert and entisol-haplaquent, over extended periods up to 400 days. The influences of soil characteristics, addition of organic matter and the chemical form of the radionuclides added to soils were investigated. A large fraction, ranging from 60 to 90% of the soluble radionuclides added as nitrates, underwent rapid conversion to precipitated hydrous oxides and hydroxides (0.3 M sodium citrate-dithionite extracts). At 3 h after contamination, ion-exchangeable forms (0.1 M MgCl2 extracts) contained low levels of total added Pu (0.7 to 19.1%) and from 0.1 to 2.8% of total Am. These levels decreased further with increasing periods of incubation of up to 400 days. In contrast, on addition of chelated forms of radionuclides (as DTPA and EDTA complexes) up to 85% of total Pu, and about 50% of total Am were associated with 0.1 M MgCl2 extracts 3 h post-contamination and significant amounts were extractable when maintained over extended periods of incubation of up to 400 days. The levels of Pu and Am associated with organic-bound forms (0.1 M NaOH extracts) did not show consistent trends, although in all three soil types the contents of these radionuclides in the insoluble residue fraction (including refractory compounds) generally increased with time of incubation.

Americium↗
PubMed1993

Speciation of plutonium in potato and the gastrointestinal transfer of plutonium and americium from potato.

Complexation of Pu(IV) and Am(III) by naturally occurring agents such as citrate and phytate might enhance their uptake from the digestive tract. However, the extent to which they enhance the gastrointestinal uptake of actinides from foodstuffs is far from resolved, as this study shows. Investigations of the chemical forms of Pu(IV) and Am(III), by gel permeation chromatography, in simulated digests of potato tubers naturally radiolabelled with 239Pu(IV) and 241Am(III) have shown that neither citrate nor phytate appear to determine their chemical forms. Therefore, it is possible that these are not the complexing anions which determine the gastrointestinal transfer of these radioelements from potato meal. Isotachophoretic analyses of the juices pressed from tubers and solutions prepared by simulated digestion of potato tubers have demonstrated the presence of several low molecular weight anions. These anions might be complexing agents because they possess an isotachophoretic mobility similar to that of citrate; some of these anions remain unidentified. Whereas 239Pu and 241Am were used in the foregoing studies, 238Pu and 241Am were used to produce either in vitro or naturally radiolabelled potatoes for gastrointestinal transfer measurements using rats and hamsters. Gastrointestinal transfer values of 0.13 +/- 0.05% (mean +/- standard error of mean) and 0.16 +/- 0.06% were determined with rats for the uptake of 238Pu and 241Am, respectively, from naturally labelled potato meal. Higher gastrointestinal transfer values were obtained for hamsters: for 238Pu and 241Am the transfer values from naturally labelled meal were 0.25 +/- 0.08% and 0.33 +/- 0.07%, respectively. Similar values were observed for uptake from in vitro labelled potato meal. On the basis of the similarity of the values for the naturally labelled potato meal and for the 'spiked' potato meal it would appear that biological incorporation is not necessary for the binding of the actinides to the ligands which will determine gastrointestinal transfer.

Americium↗
PubMed1994

The gastrointestinal absorption of neptunium, plutonium and americium in a primate (C. jacchus).

Mixtures of Np, Pu and Am were administered to primates (C. jacchus) by gastric intubation to measure their fractional gastrointestinal absorption (f1 values). The values obtained were about 2 x 10(-3) and 1 x 10(-3), respectively, for Np and Pu administered as the citrate, and 2 x 10(-3) and 6 x 10(-4), respectively, for Pu and Am in potato. The significance of these values in terms of absorption in humans is discussed.

Americium↗
PubMed2004

Biosorption of americium-241 by immobilized Rhizopus arrihizus.

Rhizopus arrihizus (R. arrihizus), a fungus, which in previous experiments had shown encouraging ability to remove 241Am from solutions, was immobilized by calcium alginate and other reagents. The various factors affecting 241Am biosorption by the immobilized R. arrihizus were investigated. The results showed that not only can immobilized R. arrihizus adsorb 241Am as efficiently as free R. arrihizus, but that also can be used repeatedly or continuously. The biosorption equilibrium was achieved within 2 h, and more than 94% of 241Am was removed from 241Am solutions of 1.08 MBq/l by immobilized R. arrihizu in the pH range 1-7. Temperature did not affect the adsorption on immobilized R. arrihizus in the range 15-45 degrees C. After repeated adsorption for 8 times, the immobilized R. arrihizus still adsorbed more than 97% of 241Am. At this time, the total adsorption of 241Am was more than 88.6 KBq/g, and had not yet reached saturation. Ninety-five percent of the adsorbed 241Am was desorbed by saturated EDTA solution and 98% by 2 mol/l HNO(3).

Adsorption↗