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PubMed2000

Comparisons between radioactive and non-radioactive gas lantern mantles.

Gas lantern mantles containing radioactive thorium have been used for more than 100 years. Although thorium was once believed to be indispensable for giving a bright light, non-radioactive mantles are now available. From the radioactivities of the daughter nuclides, we estimated the levels of radioactivity of 232Th and 228Th in 11 mantles. The mantles contained various levels of radioactivity from background levels to 1410 +/- 140 Bq. Our finding that radioactive and non-radioactive mantles are equally bright suggests that there is no advantage in using radioactive mantles. A remaining problem is that gas lantern mantles are sold without any information about radioactivity.

Camping↗
PubMed1979

Ultrastructure of Bacteroides species: Bacteroides asaccharolyticus, Bacteroides fragilis, Bacteroides melaninogenicus subspecies melaninogenicus, and B. melaninogenicus subspecies intermedius.

Representative strains of two subspecies of Bacteroides melaninogenicus (subspecies melaninogenicus and subspecies intermedius) and Bacteroides asaccharolyticus as well as B. asaccharolyticus strain 536B isolated from a human perirectal abscess and Bacteroides fragilis ATCC 25285 were examined by glutaraldehyde-osmium fixation, ruthenium red fixation and staining, and thorium hydroxyde staining as well as by the physical preparative techniques of critical point drying--transmission electron microscopy (CPD--TEM) and scanning electron microscopy (SEM). All strains, with the exception of B. fragilis 25285, possessed an electron-dense material external to their outer membranes. Ruthenium red staining further revealed a layer, external to the surface of the outer membrane, that was distinct for each species examined. Thorium hydroxide, as well as CPD--TEM and SEM, showed the cells to be interconnected by thin fibers that not only connected adjacent cells but also traversed several microns to connect cell aggregates.

Bacteroides↗
PubMed2003

NORM workers: a challenge for internal dosimetry programmes.

The mining, milling and processing of uranium and thorium bearing minerals may result in radiation doses to workers. The control of occupational exposures from these natural sources of radiation imposes a challenge to regulators and radiation protection advisers. A survey pilot programme, which included six mines in Brazil and a monazite plant, was established, consisting of the collection and analysis of concentrations of uranium, thorium and polonium in urine, faeces and air samples. Results from workers were compared to background data from their families living in the same area and from residents from the population of Rio de Janeiro. Positive exposure results were identified among the coal miners, the niobium miners and the monazite sand workers. Difficulties in the application of internal dosimetry programmes are discussed in relation to the control of NORM workers.

Administration, Inhalation↗
PubMed1985

Cutaneous Thorotrast granulomas and chronic lymphocytic leukemia following Thorotrast angiography.

A patient underwent cerebral angiography with thorium dioxide (Thorotrast). Six years later, an acne-like eruption of the face and scalp occurred which persisted despite aggressive treatment. Twenty-six years after the angiography he developed chronic lymphocytic leukemia with massive lymphadenopathy. Review of three facial biopsies revealed collections of Thorotrast-laden histiocytes and free thorium dioxide within a background of chronic inflammation and dermal fibrosis. These changes are of the same type described in Thorotrast granulomas of the subcutaneous tissues. There is an increased incidence of myelogenous leukemia in Thorotrast-treated patients; lymphoproliferative disorders, however, are only rarely observed.

Cerebral Angiography↗
PubMed1998

Thorotrast distribution in monkey bone marrow at early and late times after injection.

Thorotrast, a 25% colloidal suspension of 232ThO2, was formerly used as a radiographic contrast medium. Although epidemiological studies have shown that alpha particles emitted from 232Th and its decay products incorporated in the bone marrow cause leukemia, the use of these data for alpha particle induced leukemogenesis risk estimation has been criticized mainly for inhomogeneity of Thorotrast distribution. Four monkeys were injected with Thorotrast to investigate the degree of inhomogeneity in the thorium content of different bone marrow sites and the cellular localization of Thorotrast. Two were injected via an artery and two via a vein and sacrificed either at 1 wk or 3 to 4 y after injection. Microscopic, solid state autoradiography and back scatter electron imaging methods were applied to several bone sites to determine the degree of inhomogeneity. Quantification was performed using x-ray fluorescence for trabecular bone and bone marrow and neutron activation analysis for compact bones. At 1 wk Thorotrast was found to be distributed evenly in the red marrow; by 3 and 4 y conglomerates were seen which were restricted to macrophages. The monkey was found to be a good model for humans. The choice of injection route did not noticeably affect the Thorotrast distribution in bones of the skeletal system. Considering the even distribution of Thorotrast within the red bone marrow at early times after its injection, the inevitable diffusion of thorium progeny from the particles, the mobility of bone marrow macrophages, and the well established correction factor of self-absorption within conglomerates, these results suggest that data derived from Thorotrast patients are useful for risk estimation of alpha particle induced leukemia.

Animals↗
PubMed2001

Determination of 232Th in urine by ICP-MS for individual monitoring purposes.

Thorium is naturally occurring in various ores used for industrial purposes and has numerous applications. This paper sets out to investigate urine analysis as a suitable monitoring approach for workers potentially exposed to thorium. Due to its biokinetic behavior and its low solubility, urinary concentrations are generally very low, requiring therefore high sensitivity analytical methods. An analytical procedure has been developed for detecting 232Th concentrations of below 1 mBq L(-1) quickly and easily. Due to the long half-life (1.41 x 10(10) y) of 232Th, the potential of a procedure based on urine sample dilution and ICP-MS (inductively coupled plasma-mass spectrometry) measurement was investigated first. Two dilution factors were chosen: 100, which is more suitable for long-term measurement trials, and 20, which increases sensitivity. It has been shown that a 100-fold dilution can be used to measure concentrations of below 1 mBq L(-1), whereas a 20-fold one can be used to reach concentrations of below 0.06 mBq L(-1). Then, on the basis of the limitation of the procedure based on urine dilution, the suitable field of application for the different procedures (100-fold and 20-fold dilution and also a chemical purification followed by an ICP-MS measurement) was determined in relation to monitoring objectives.

Humans↗
PubMed2002

Atmospheric aerosol measurements of 238U and 232Th at Fernald, Ohio, and implications on inhalation dose calculations.

Measurements of the aerosol size distribution of 238U and 232Th at the U.S. Department of Energy's Fernald Environmental Management Project site were made to improve the inhalation dose calculations to off-site individuals. For approximately 1 y an 8-stage cascade impactor was co-located with a high volume sampler and operated at the Fernald Environmental Management Project site to collect aerosol samples. During most of the year, the site was dominated by giant particles with more than 70% of the mass of 238U above 15 microm. The seasonal average of the activity median aerodynamic diameter, based on the impactor samples, which excluded particles >15 microm, for both uranium and thorium was approximately 6.5 microm. These numbers reflect the activities at the site and the domination of the resuspension processes. During most sampling periods the size distribution was bimodal. Thorium concentrations were comparable to the uranium concentrations during the late spring and summer period and decreased to approximately 25% of the 238U concentration in the late summer. Fernald Environmental Management Project is required to calculate the maximum allowable dose from airborne emissions, excluding radon, to meet NESHAP compliance. These calculations assume an AMAD of 1 microm. We found that if you combine size distribution information with the latest ICRP 66 lung model you reduce the estimated dose by a factor of 7. Inclusion of the size distribution of radionuclides at any sampling site would substantially improve the dose estimates to the population.

Aerosols↗
PubMed2006

Characterization of local Egyptian iron ores for use in radiation shielding concrete.

Petrographic, physical, chemical, mechanical, and radioactive characteristics tests were performed on magnetite, limonite, and hematite found in abundance in Egypt to determine their suitability for producing radiation shielding concrete. The contents of uranium and thorium were determined using instrumental neutron activation analysis and gamma spectroscopy. The results obtained using the two methods have shown satisfactory correlation. The tests confirm that magnetite and limonite are suitable as concrete aggregate while hematite is not because of its friable nature and high contents of uranium, thorium, and cobalt.

Ferric Compounds↗
PubMed1998

Global elemental maps of the moon: the Lunar Prospector gamma-Ray spectrometer.

Lunar Prospector gamma-ray spectrometer spectra along with counting rate maps of thorium, potassium, and iron delineate large compositional variations over the lunar surface. Thorium and potassium are highly concentrated in and around the nearside western maria and less so in the South Pole-Aitken basin. Counting rate maps of iron gamma-rays show a surface iron distribution that is in general agreement with other measurements from Clementine and the Lunar Prospector neutron detectors.

Elements↗
PubMed1992

Cell membrane polarity of the epithelial cells in the endolymphatic sac of the guinea pig.

The epithelial cells of the endolymphatic sac (ES) were studied in order to characterize their glycocalyx composition. Colloidal thorium and cationized ferritin were used as electron-dense markers to visualize the glycocalyx as well as the basement membrane. In addition, enzymatic digestions were performed to identify the reactive components of the glycocalyx responsible for colloidal thorium labeling. The results indicate that the glycocalyx of the ES epithelial lining is very rich in sialic acid. Furthermore, a marked polarity in glycocalyx reactivity is present between the apical and basolateral membranes, whereas difference in glycocalyx reactivity between the light and the dark cells are not obvious. We speculate that the specific composition and the apparent polarity of the ES epithelial cell glycocalyx are of importance to the equilibrium of electrolytes in the ES lumen.

Animals↗
PubMed1975

The coating of mouse myocardial cells. A cytochemical electron microscopical study.

The coating of mouse myocardial cells has been investigated with a variety of cytochemical methods. The coating of the surface membrane gives a positive reaction with ruthenium red, colloidal thorium, phosphotungstic acid (PTA) at low pH, silver methenamine after periodic oxidation (PA-silver technique) and with silver proteinate after periodic oxidation and thiocarbohydrazide treatment (PA-TCH-silver technique). The coating of the T system gives almost similar results. The nexuses do not react with PTA nor with the PA-silver and PA-TCH-silver techniques, but they are strongly stained with ruthenium red which reveals periodic structures in their gaps. The specificities of the colloidal thorium technique and PAT staining have been tested by chemical treatments (methylation, acetylation, saponification), enzymatic digestions (pronase, trypsin, hyaluronidase, neuraminidase) and carbohydrate extractions (with 0.1 N NaOH and 0.05 M H2SO4). These cytochemical data indicate, considering the specificity of the reactions, that the coating of the membrane surface and the T system contains polyanionic groups. A part of them, at least, would belong to a carbohydrate-containing material (glycoproteins), whereas at the level of nexuses the sugar residues would probably be absent.

Animals↗
PubMed1976

Electron histochemistry and ultrastructural localization of carbohydrate-containing substances in the sheath of Volvox.

The location and characteristics of carbohydrate-containing structures within the intact sheath of Volvox were studied by 3,3'-diaminobenzidine tetrahydrochloride-osmium, colloidal iron, colloidal thorium, ruthenium red and periodic acid-silver methenamine staining. The sheath consists of external and internal fibrillar layers separated by a tripartite structure. The external layer reacts positively with 3,3'-diaminobenzidine tetrahydrochloride, colloidal iron, colloidal thorium and ruthenium red, indicating that it contains acid mucosaccharides. Staining in the external layer is abolished by Ba(OH)2 treatment. The tripartite structure and internal fibrillar layer contain periodic acid reactive groups which do not occur in the external layer. Under certain conditions, reactions between the cationic dyes and the internal material were also observed. It is postulated that the internal matrix of the sheath contains glycoproteins or a mixture of acid mucosaccharides and glycoproteins. Possible functions of the sheath material are discussed.

Animals↗
PubMedDate not supplied

Effect of 50-Hz electromagnetic field on the retention of toxic radionuclides in rat tissues.

The effect of electromagnetic field (EMF) 50 Hz, 10 mT, on the tissue retention of radiotoxic polonium-210 and thorium-234 was studied in a rat model. Regarding 210Po in the ionic state, small but significant effects were obtained by exposure of rats to EMF either before the intravenous injection of 210Po (pre-exposure) or after the rats had already been injected with 210Po (post-exposure). When compared with control values, pre-exposure to EMF caused a significant 28% decrease in the retention of 210Po in the skin and a 10% decrease in total 210Po retention in the investigated tissues. Relative to controls, post-exposure resulted in a 131% increase in 210Po retention only in the thymus. Regarding carrier-free 234Th in the ionic state, both types of EMF exposure caused a substantial increase in 234Th retention in the liver and spleen and a decrease of 234Th in the bones. A different effect of EMF on the retention of 234Th in the body was obtained when the mass of thorium was increased by adding as carrier 232Th (50 micrograms kg-1 body mass). With pre-exposure, a significant 10% decrease in the high retention of 234Th in the liver (77% of injected radioactivity) was observed. On the other hand, with post-exposure no significant changes in retention of 234Th were found in the tissues.

Animals↗
PubMed1980

Thorotrast-induced meningioma. Case report.

The authors report an adult patient with a symptomatic intracranial meningioma that was demonstrated by computerized tomography, angiography, and at surgery. The meningioma had occurred at a site where 19 years previously thorium dioxide had been injected into an abscess cavity. Pathological examination revealed the presence of thorium granules within the meningioma.

Brain Abscess↗
PubMed1983

Thorotrast granuloma of the neck with local complications.

A case of cervical granuloma with involvement of the right vocal cord is reported. The cause of the granuloma was traced to thorium dioxide contrast medium which had escaped into the surrounding tissues during arteriography performed 40 years before. The long-term toxic effects of thorium-232 irradiation and the local complications which may follow an injection of this medium are discussed.

Angiography↗
PubMed2002

Validating the analytical methodologies for determining some important trace elements in food consumed in India.

This paper reports on the development, standardization, and application of instrumental as well as radiochemical neutron activation analysis (INAA and RNAA) techniques for determining the concentrations of iron, zinc, cobalt, cesium, strontium, selenium, thorium, and calcium in food consumed in India. Based on the analysis of 20 diet samples, prepared as per the data on dietary intake patterns of an adult in four provinces of India and that of an average adult Indian, the geometric mean (GM) intake of various elements for the reference Indian man was estimated to be 15.9 (10.7-34.4) mg for iron, 8.6 (5.1-15.6) mg for zinc, 17.0 (8.3-31.4) micrograms for cobalt, 4.76 (2.8-11.8) micrograms for cesium, 1.46 (0.79-2.96) mg for strontium, 52.4 (35.0-130.8) micrograms for selenium, 0.75 (0.44-1.75) micrograms for thorium, and 0.35 (0.17-0.67) mg for calcium. A comparison of the daily dietary intakes of these trace elements by the reference Indian man was made with that of the International Commission on Radiological Protection (ICRP) reference man and also with the world average compiled by the International Atomic Energy Agency (IAEA). When compared with the ICRP reference man data, the daily dietary intakes of all the eight elements by the reference Indian man were considerably lower by factors ranging from 1.4 for strontium to as much as 18.0 for cobalt. However, when compared with the world average, daily dietary intakes by the reference Indian man were comparable for iron and lower by factors 1.2 to 1.9 for zinc, selenium, and calcium.

Diet↗