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PubMed1983

Rapid identification of correctly located intracerebroventricular cannula in the rat.

We describe a radiographic technique to identify a correctly located cannula in the ventricular system of the rat brain during life. A suspension of thorium dioxide was infused into the left lateral ventricle through a cannula placed in the brain under stereotaxic guidance. Correctly located injections were identified by the presence of a distinct thorium shadow on lateral X-ray of the in situ brain. When 6-hydroxydopamine was co-injected with thorium the resultant depletion of striatal dopamine and the changes in a conditioned avoidance responses were correlated with the degree of spreading of thorium through the ventricular system.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2006

Direct determination of lanthanides in simulated irradiated thoria fuels using reversed-phase high-performance liquid chromatography.

Studies were carried out to develop an HPLC method for the determination of lanthanides, in presence of Th and U, without involving any pre-separation procedure for the matrix elements (Th, U). The effect of concentration of the ion interaction reagent on the retention pattern of lanthanides, thorium and uranium was studied using a reversed-phase C18 column. The chromatographic parameters were optimized for maximizing the capacity of the column to hold thorium. Dual gradient elution was used for the separation of lanthanides from a mixture of thorium and uranium present in large proportion. The method facilitates the use of a minor fission product as an internal standard for the accurate and precise quantification of lanthanides by HPLC. The developed methodology was validated by using synthetically prepared samples with different proportions of lanthanides. Studies were also carried out for the separation and determination of U and Th on a reversed-phase column. A gradient of methanol and alpha-hydroxy isobutyric acid was employed for the separation and determination of uranium in presence of large amounts of thorium.

Butyrates↗
PubMed2001

Determination of 232Th by neutron activation analysis using isotope-related ki factors.

Neutron activation analysis was applied to determine the 232Th activity in different matrices. Since in nature thorium consists of almost 100% of the long-lived 232Th, the instrumental trace element analysis method of neutron activation analysis can be applied to determine the thorium content in a sample. which can then be converted into the corresponding specitic activity. For the analysis about 100 mg of the sample was irradiated at a thermal neutron flux of phi(th) = 8 x 10(13) n.cm(-2) x s(-1). After irradiation the activity of the indicator nuclid 232Pa--produced by the (n,gamma) reaction--was measured by gamma spectrometry. The content of thorium was calculated using the activation equation and the isotope-related ki constant. Finally, the concentration of thorium in the sample was converted into the specific activity. The activities of 232Th measured by applying neutron activation analysis in different samples were compared with the results found by a spectrometry and gamma spectrometry for the daughter nuclides 228Ac and 224Ra.

Health Physics↗
PubMed1996

Natural radionuclide and plutonium content in Black Sea bottom sediments.

The content of uranium, thorium, radium, lead, polonium, and plutonium in bottom sediments and algae from two locations at the Bulgarian Black Sea coast have been determined. Some parent:progeny ratios for evaluation of the geochemical behavior of the nuclides have been estimated as well. The extractable and total uranium and thorium are determined by two separate radiochemical procedures to differentiate the more soluble chemical forms of the elements and to estimate the potential hazard for the biosphere and for humans. No distinct seasonal variation as well as no significant change in total and extractable uranium (also for 226Ra) content is observed. The same is valid for extractable thorium while the total thorium content in the first two seasons is slightly higher. Our data show that 210Po content is accumulated more in the sediments than 210Pb, and the evaluated disequilibria suggest that the two radionuclides belong to more recent sediment layers deposited in the slime samples compared to the silt ones for the different seasons. The obtained values for plutonium are in the lower limits of the data cited in literature, which is quite clear as there are no plutonium discharge facilities at the Bulgarian Black Sea coast. The obtained values for the activity ratio 238Pu:239 + 240Pu are higher for Bjala sediments compared to those of Kaliakra. The ratio values are out of the variation range for the global contamination with weapon tests fallout plutonium which is probably due to Chernobyl accident contribution. The dependence of natural radionuclide content on the sediment type as well as the variation of nuclide accumulation for two types of algae in two sampling locations for five consecutive seasons is evaluated. No serious contamination with natural radionuclides in the algae is observed.

Eukaryota↗
PubMed2004

Dietary intakes of seven elements of importance in radiological protection by asian population: comparison with ICRP data.

Within the framework of a Coordinated Research Project (CRP) organized by the International Atomic Energy Agency, Vienna, the daily dietary intakes of seven elements by adult populations living in nine Asian countries were estimated. The countries that participated in the study were Bangladesh, China, India, Indonesia, Japan, Pakistan, Philippines, South Korea (Republic of Korea, ROK), and Vietnam and together they represented more than half of the world population. The seven elements studied were calcium, cesium, iodine, potassium, strontium, thorium, and uranium. These elements have chemical and biological similarity to some of the radionuclides abundantly encountered during nuclear power production and therefore data on these elements could provide important information on their biokinetic behavior. Analyses of diet samples for these seven elements were carried out using highly sensitive and reliable analytical techniques. One thousand one hundred and sixty analytical determinations were made on two hundred and twenty samples of typical diets consumed in these countries to estimate the daily intakes of these elements by the adult Asian population. The median daily dietary intakes for the adult Asian population were found to be 0.45 g calcium, 7 microg cesium, 90 microg iodine, 1.75 g potassium, 1.65 mg strontium, 1 microg thorium, and 1 microg uranium. When compared with the intakes proposed for ICRP Reference Man by International Commission for Radiological Protection, these intakes were lower by factors of 0.41 for calcium, 0.7 for cesium, 0.45 for iodine, 0.53 for potassium, 0.87 for strontium, 0.33 for thorium, and 0.52 for uranium. The lower daily intakes of calcium, cesium, and iodine by Asian population could be due to significantly lower consumption of milk and milk products, which are rich in these elements. The significantly lower intake of calcium in most of the Asian countries may lead to higher uptake of fission nuclide 90Sr and could result in perhaps higher internal radiation dose. The use of highly sensitive and reliable analytical methods resulted in accurate and lower intake values obtained for thorium and uranium, which suggest that radiation dose from their ingestion at natural background levels is likely to be lower than what may be concluded from ICRP data.

Asia↗
PubMed1992

Glycocalyx heterogeneity in normal and hydropic cochleas of the guinea pig.

The endo- and perilymphatic glycocalyx of the cochlear epithelia were investigated ultrastructurally in normal and hydropic cochleas using the electron-dense markers cationized ferritin and colloidal thorium. In the normal cochleas all epithelial surfaces showed reactivity with both markers. Using cationized ferritin, no regional differences in reactivity could be demonstrated. With colloidal thorium, however, the apical membranes of the outer hair cells reacted more intensely than either the basolateral membranes or the membranes of the supporting cells of the organ of Corti. Cationized ferritin reactivity was not affected by digestion with either neuraminidase or hyaluronidase. In contrast, colloidal thorium reactivity of the endolymphatic surfaces was greatly reduced after neuraminidase digestion. Reactivity of the cell membranes lining the perilymphatic compartments of the cochlea was less affected by neuraminidase digestion, except for the basolateral membranes of the sensory and supporting cells of the organ of Corti, which demonstrated a greatly reduced reactivity. These findings indicate that the glycocalyx of the epithelial surfaces lining the endolymphatic compartment has a high content of sialic acid. The differences that are observed in normal cochleas in regard to colloidal thorium reactivity between the apical membranes of the outer hair cells and the membranes of the Deiters' cells, could not be demonstrated in hydropic cochleas. This probably contributes to the early functional changes in outer hair cells observed in experimental hydrops.

Animals↗
PubMed2002

Enhanced selectivity for actinides over lanthanides with CMPO ligands secured to a C(3)-symmetric triphenoxymethane platform.

A ligand system containing three preorganized carbamoylmethylphosphine oxide (CMPO) moieties anchored onto a rigid C(3)-symmetric triphenoxymethane platform has been developed for facile metal complexation and subsequent extraction from aqueous acidic nuclear waste streams. Intended to mimic the 3:1 CMPO-actinide stoichiometry of the extracted species in the TRUEX nuclear waste treatment process, the CMPO arms on this ligand are oriented such that all three CMPO moieties can cooperatively bind a metal ion. Extractions of simulated nuclear waste streams (10(-4) M metal in 1 M nitric acid) with solutions of this ligand in methylene chloride (10(-3) M) reveal a high affinity for the actinide thorium and a very low, but constant, affinity for the lanthanides across the series. Thorium and five lanthanide (lanthanum, cerium, neodymium, europium, and ytterbium) nitrate complexes of this ligand have been synthesized and fully characterized by X-ray crystallography, (1)H and (31)P NMR spectra, and FT-ICR-MS to elucidate the mechanism of this unique actinide selectivity. All six oxygen donors from the three CMPO arms of the ligand and one or two nitrate counterions coordinate these metals to afford 2+ cationic complexes in every case. Because of the large size of the ligand, both the thorium and lanthanide complexes present similarly charged and sized surfaces to the extraction solvents, but the thorium complex is extracted quantitatively over the lanthanide complexes. A possible rationale for this extraction behavior difference is presented and further illustrated by the extraction properties of this ligand system for the alkali metals (lithium, sodium, potassium, rubidium, and cesium) as picrate salts and by the solid- and solution-state structures of its lithium picrate complex.

Journal Article↗
PubMed1997

U-Th Isotopes in Arc Magmas: Implications for Element Transfer from the Subducted Crust

Uranium-thorium isotope results from island arc volcanic rocks were used to investigate the rates of transfer of fluids and sediments from the downgoing slab. Uranium, but not thorium, is readily mobilized in the fluid. A negative array between thorium/cerium and neodymium-143/neodymium-144 indicates that significant amounts of the thorium in arc rocks are derived from subducted sediments, although perhaps only about 30 percent of the thorium in subducted sediments is returned to the crust in this way. The transfer times for fluid through the mantle wedge are about 30,000 to 120,000 years, whereas those for sediment melts may be several million years. The low average uranium/thorium ratios of bulk crust primarily reflect different crustal generation processes in the Archaean.

Journal Article↗
PubMed1984

Radioactivity released from burning gas lantern mantles.

Gas lantern mantles contain thorium to produce incandescence when lantern fuel is burned on the mantle. Although only thorium is initially present on the mantle, the thorium daughters build up, some over a period of weeks and some over a period of years, and significant quantities of these daughters are present when the mantle is used. Some of these daughters are released when the lantern fuel is burned on the mantle. The amounts of radioactivity released during burning is studied by measuring the gamma radiation emitted by the daughters. Results of this study show that some of the radium (224Ra and 228Ra) and more than half the 212Pb and 212Bi is released during the first hour of a burn. The actual amounts release depend on the age of the mantle.

Environmental Exposure↗
PubMed1996

Radiation risk estimation based on activity measurements of zirconium oxide implants.

Implants made form zirconium dioxide exhibit higher specific radionuclide activities of the uranium-radium and thorium series than metallic and aluminum implants. This study presents data on activity measurements performed on different samples of ZrO2 raw material (powder) and on the ceramic joint heads belonging to it to formulate a correlation between the specific radionuclide activities of the uranium-radium and thorium series in the raw material, the flux density of the alpha particle leaving the implant surface, and the annual dose of the tissue surrounding the implant. Based on this experimental study, an equation for defining the limits of the specific activities in raw material is proposed, taking into account the long-lived radionuclides (key nuclides) of the uranium-radium and thorium series weighted with their relative dose contributions from alpha emitters.

Alpha Particles↗
PubMed1993

Structure and composition of stereocilia cross-links in normal and hydropic cochleas of the guinea pig.

Structure and composition of stereocilia cross-links were investigated cytochemically in normal and hydropic cochleas of the guinea pig. The electron-dense markers colloidal thorium and cationized ferritin were used for visualization. Side links as well as tip links were visualized using both markers. Cationized ferritin allowed a better visualization of the delicate cross-link substructure than did colloidal thorium. Following digestion with neuraminidase, cross-link reactivity for colloidal thorium was virtually abolished. However, the basic structure of the cross-links could still be observed as a result of routine post-fixation and contrast staining. In both 3- and 6-month hydropic cochleas glycocalyx reactivity of the stereocilia appeared to be unaltered, provided that stereocilia were still present. However, loss of cross-links of the outer hair cells - resulting in disarrangement of the stereociliary bundles - was observed in hydropic cochleas. Our results suggest that cross-links are a separate morphological and cytochemical entity, which is different from the glycocalyx. Furthermore, loss of stereocilia cross-links, with concomitant disarrangement of the outer hair cell stereociliary bundle, appears to be one of the early pathological features of surgically induced endolymphatic hydrops, which might be responsible for permanent sensorineural hearing loss.

Animals↗
PubMed1975

Electron microscopic studies on the uptake of exogenous marker particles by different cell types in the guinea pig metaphysis.

Guinea pig metaphyseal bone was exposed to horse spleen ferritin in vitro and to colloidal thorium dioxide in vivo. The cellular uptake and intracellular accumulation of these marker particles were studied ultrastructurally. In vitro, the ferritin molecules were found to spread evely throughout the tissue. After 1-2 hours ferritin was mainly found in plasma membrane invaginations and in endocytic vesicles of varying size. At 4-6 hours a successive accumulation of the marker in secondary lysosomes could be observed. In addition to ferritin, the lysosomes and the large endocytic vesicles often contained other inclusions. In vivo, the pattern of intracellular accumulation of the marker particles was identical to that in vitro. Moreover, the presence within the cells of similar amounts of thorium dioxide after 1 and 4 days suggested that these indigestible molecules are stored intracellularly for a considerable time. In accordance therewith there were no definite signs of extrusion of labeled bodies or secretion of the exogenous marker by exocytosis. Ferritin and thorium dioxide were taken up by all cell types in the metaphysis. Both in vitro and in vivo perivascular cells type B ingested large amounts of marker particles, whereas chondroclasts, endothelial cells. perivascular cells type A and osteoblasts showed a more restricted endocytizing ability. On the basis of these observations, the functional significance of different cell types in the resorption of the epiphyseal cartilage and the formation of bone is discussed.

Animals↗
PubMed1993

Spurious dual-energy X-ray absorptiometry images in a patient exposed to the contrast agent Thorotrast.

A 69-year-old woman presented with a 20-year history of back pain and a 10 cm height loss. She had received an injection of the contrast agent, Thorotrast, at age 23. There was no history of fluoride exposure. Multiple vertebral compression fractures were seen on radiographs. Dual-energy X-ray absorptiometry (DXA) scans revealed high normal bone mineral content on the spine and, on whole body scan, visualization of the liver and spleen regions. Given the attenuation coefficient of thorium and the thorium concentrations reported for liver, spleen and vertebral bodies, it is likely that thorium was visualized in the liver and spleen and that it caused spurious elevation in her DXA bone mineral content values.

Absorptiometry, Photon↗
PubMed2004

Cholangiocarcinoma in association with Thorotrast exposure.

Thorotrast is a colloidal suspension of thorium dioxide that was used as an intravascular contrast agent until the 1950's. It is retained by the reticuloendothelial system, and because it emits densely ionizing radioactivity thorium dioxide it is carcinogenic. Two patients with prior thorium dioxide exposure diagnosed with cholangiocarcinoma and recently treated at the Massachusetts General Hospital are presented. Radiology, treatment, pathologic findings, and relevant literature are discussed.

Aged↗
PubMed2004

Indoor gamma radiation and radon concentrations in a Norwegian carbonatite area.

Results of indoor gamma radiation and radon measurements in 95 wooden dwellings located in a Norwegian thorium-rich carbonatite area using thermoluminescent dosemeters and CR-39 alpha track detectors, respectively, are reported together with a thorough analysis of the indoor data with regard to geological factors. Slightly enhanced radium levels and thorium concentrations of several thousands Bq kg(-1) in the carbonatites were found to cause elevated indoor radon-222 levels and the highest indoor gamma dose rates ever reported from wooden houses in Norway. An arithmetic mean indoor gamma dose rate of 200 nGy h(-1) and a maximum of 620 nGy h(-1) were obtained for the group of dwellings located directly on the most thorium-rich bedrock.

Air Pollutants, Radioactive↗
PubMed2005

Uptake and distribution of natural radioactivity in wheat plants from soil.

The uptake of naturally occurring uranium, thorium, radium and potassium by wheat plant from two morphologically different soils of India was studied under natural field conditions. The soil to wheat grain transfer factors (TF) were calculated and observed to be in the range of 4.0 x 10(-4) to 2.1 x 10(-3) for 238U, 6.0 x 10(-3) to 2.4 x 10(-2) for 232Th, 9.0 x 10(-3) to 1.6 x 10(-2) for 226Ra and 0.14-3.1 for 40K. Observed ratios (OR) of radionuclides with respect to calcium have been calculated to explain nearly comparable TF values in spite of differences in soil concentration of the different fields. They also give an idea about the discrimination exhibited by the plant in uptake of essential and nonessential elements. The availability of calcium and potassium in soil for uptake affects the uranium, thorium and radium content of the plant. The other soil factors such as illite clays of alluvial soil which trap potassium in its crystal lattice and phosphates which form insoluble compounds with thorium are seen to reduce their availability to plants. A major percentage (54-75%) of total 238U, 232Th and 226Ra activity in the plant is concentrated in the roots and only about 1-2% was distributed in the grains, whereas about 57% of 40K activity accumulated in the shoots and 16% in the grains. The intake of radionuclides by consumption of wheat grains from the fields studied contributes a small fraction to the total annual ingestion dose received by man due to naturally existing radioactivity in the environment.

Aluminum Silicates↗
PubMed2001

Exposure of workers in mineral processing industries in Brazil.

The mining, milling and processing of uranium and thorium bearing minerals may result in radiation doses to workers. A preliminary survey pilot program, that included six mines in Brazil (two coal mines, one niobium mine, one nickel mine, one gold mine and one phosphate mine), was launched in order to determine the need to control the radioactive exposure of the mine-workers. Our survey consisted of the collection and analysis of urine samples, complemented by feces and air samples. The concentrations of uranium, thorium and polonium were measured in these samples and compared to background data from family members of the workers living in the same dwelling and from residents from the general population of Rio de Janeiro. The results from the coal mines indicated that the inhalation of radon progeny may be a source of occupational exposure. The workers from the nickel, gold and phosphate mines that were visited do not require a program to control internal radiological doses. The niobium mine results showed that in some areas of the industry exposure to thorium and uranium might occur.

Brazil↗
PubMed1998

Disposal options and case-study pathway analyses.

This paper presents an overview of alternatives that currently are employed for the disposal of wastes containing enhanced concentrations of naturally occurring radioactive materials (NORM). The application of pathway assessment methodology to the derivation of acceptable cleanup criteria for residual NORM is described. A specific example is provided drawing on experience with a site containing above-background levels of natural uranium-series and thorium-series nuclides. The options for safe, permanent disposal of U and Th bearing NORM waste are discussed and the application of pathway analysis to performance assessment of a typical engineered disposal cell is illustrated. Typical methods for disposal of other NORM waste forms also are described. This includes radium-contaminated wastes from petroleum sludges, uranium milling, and geothermal power plant operation as well as thorium wastes from production of thorium-magnesium alloys.

Background Radiation↗