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Results for “THORIUM DIOXIDE”

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At least 577 records · Page 32Linked to original sources
PubMed1992

Frequency of mutant T lymphocytes defective in the expression of the T-cell antigen receptor gene among radiation-exposed people.

The frequency of mutant T lymphocytes defective in T-cell receptor gene (alpha or beta) expression was measured using the 2-color flow cytometric technique. Results for a total of 203 atomic bomb survivors, 78 of whom were proximally exposed (DS86 doses of greater than or equal to 1.5 Gy) and 125 of whom were distally exposed (DS86 dose of less than 0.005 Gy), showed that the mutant frequency was significantly higher in males than in females. No significant dose effects were observed. In contrast, a significant increase of mutant frequency was observed for 6 patients treated with Thorotrast, a contrast medium containing thorium-232 formerly used for radioligands. In addition, thyroid disease patients treated with 131I showed a dose-related increase of mutant frequency. It was suggested that the present T-cell receptor mutation assay has a unique characteristic as a biological dosimeter for measurement of recent exposures to genotoxic agents.

Adult↗
PubMed1987

Computed tomography of thorotrastosis.

Two cases of thorotrastosis examined by computed tomography are reported. The appearance of the liver, spleen, and lymph nodes is diagnostic. This technique is probably the procedure of choice for detection of Thorotrast-induced liver neoplasm.

Aged↗
PubMed1990

Radiation exposure and chromosome abnormalities. Human cytogenetic studies at the National Institute of Radiological Sciences, Japan, 1963-1988.

The results of human cytogenetic studies performed at the National Institute of Radiological Sciences (NIRS), Chiba, Japan for about 25 years are described. The studies were pursued primarily under two major projects: one involving people exposed to radiation under various conditions and the other involving patients with malignant diseases, especially leukemias. Whereas chromosome abnormalities in radiation-exposed people are excellent indicators of radiation exposure, their behavior in bone marrow provide useful information for a better understanding of chromosome abnormalities in leukemias and related disorders. The role of chromosome abnormalities in the genesis and development of leukemia and related disorders is considered, suggesting a view for future studies in this field.

Animals↗
PubMed1994

Preneoplastic foci of altered hepatocytes induced in rats by irradiation with alpha-particles of Thorotrast and neutrons.

Prestages of hepatocellular neoplasms induced in rats by continuous internal alpha-radiation of Thorotrast or by fractionated external radiation with neutrons were studied by cytomorphological, cytochemical and morphometric methods. Irradiation with both Thorotrast and neutrons resulted in a significant increase in the number and volume fraction of foci of altered hepatocytes (FAH), the occurrence of which at 14 months correlated well with the previously reported increased incidence of hepatocellular neoplasms appearing after long lag periods. The morphological and biochemical phenotypes of radiation-induced FAH were similar to those of preneoplastic lesions described earlier in hepatocarcinogenesis elicited by chemicals or viruses.

Alpha Particles↗
PubMed1988

Early effects of gentamicin on inner ear glycocalyx cytochemistry.

The early effects of gentamicin treatment on the inner ear glycocalyx were investigated using two cationic probes, colloidal thorium and cationized ferritin. Gentamicin treatment resulted in a diminished thorium reactivity of both the endolymphatic and perilymphatic glycocalyx of the hair cells after 1 day and complete abolishment of reactivity after 5 days. Cationized ferritin reactivity of the perilymphatic and endolymphatic glycocalyx was not significantly influenced. The cytochemistry of the inner ear glycocalyx and the possible biochemical changes induced by gentamicin are discussed.

Animals↗
PubMed1993

Pattern of mortality among Danish thorotrast patients.

The mortality pattern among 999 Danish patients who had been subjected to angiography of the carotid artery with the alpha-ray emitting X-ray contrast media Thorotrast during the period 1935-47 was assessed by record linkage with the National Death Registry through 1989. Standardized mortality ratios (SMR) were calculated relative to the general population. The overall SMR was increased by 18 times during the first 3 years after Thorotrast injection. This rate reflects the often serious, underlying neurological conditions for which angiography was performed, however, mortality was increased by 3-4 fold even for the follow up period after the first 3 years. The increase in mortality was evident for all categories of cause of death, the SMR being 11.1 (95% confidence interval (CI) 7.1-16.4) for cirrhosis of the liver, 4.7 (4.1-5.3) for cancer, 1.6 (1.3-1.9) for cardiac disease, 3.3 (2.6-4.2) for cerebrovascular diseases, 3.9 (3.3-4.5) for other natural causes, and 4.4 (3.4-5.6) for violent causes (including suicides). The SMR was generally related positively to young age at injection, to time since injection, and to the amount injected. The excess mortality can be explained only partially by underlying neurological conditions and by diseases known to be induced by Thorotrast (cirrhosis and cancer of the liver, leukaemia and other haematological diseases), and it is suggested that unspecific effects induced by the alpha-radiation of Thorotrast may have contributed.

Cause of Death↗
PubMedDate not supplied

MRI in thorotrastosis.

Magnetic resonance imaging (MRI) and computed tomography (CT) were performed in four patients with thorotrastosis. On CT scan, Thorotrast (thorium oxide) deposition was shown as high-density areas in the liver and spleen and the abdominal lymph nodes. These deposits were not found on MRIs. Splenic volume was significantly small due to atrophy. The contrast-noise ratio in the spleen on T1-weighted images was significantly lower. Thorotrast deposition does not affect MRI appearance; therefore it may be useful for the early detection of malignant tumors as a complication of thorotrastosis.

Aged↗
PubMed2004

Gamma dose rates and distribution of natural radionuclides in sand beaches--Ilha Grande, Southeastern Brazil.

In order to study the process of dispersion and the activity concentration of 232Th and 238U series and 40K radionuclides in two island beaches in southeastern Brazil, analyses was made of sand samples of 0-10 cm profile, during a 12-month period. Moreover, the monthly variations of gamma dose rates were studied to determine the local environment absorbed dose rate. The average activity concentration of primordial radionuclides 232Th, 238U and 40K at Preta beach, they were 239, 121 and 110 Bq kg(-1), while at Dois Rios beach they were 48, 39 and 412 Bq kg(-1), respectively. The absorbed dose rate in air, observed at 1 m above the ground, ranged from 54 to 228 nGy h(-1) at Preta beach and from 39 to 110 nGy h(-1) at Dois Rios beach. The annual effective dose equivalent corresponding to Preta beach is 0.15 mSv a(-1) and to Dois Rios 0.08 mSv a(-1).

Background Radiation↗
PubMed2004

Specific activity and hazards of granite samples collected from the Eastern Desert of Egypt.

Fifty granitic rock samples were collected from different plutons in the central part of the Eastern Desert of Egypt and were analyzed for specific concentrations of (238)U, (232)Th and (40)K radionuclei. The measurements were carried out using a high performance and stability Nomad Plus spectroscopy system attached to a 1.7 keV (FWHM) HPGe detector. The spectra were analyzed using the direct gamma counting comparison method as well as the traditional absolute efficiency curve method. The highest average value of (238)U concentration (1184 Bq kg(-1)) was observed at EI Misikat region whereas the highest average values of (40)K and (232)Th concentration (2301.8 and 162.5 Bq kg(-1) respectively), were detected at Gabal Homret Waggat area. The radium equivalent activity (Ra(eq)), the absorbed dose rate (D), the external hazard index (H(ex)) and the annual gonadal dose equivalent were also calculated and compared to the international recommended values. Radon exhalation rate from the rock samples were measured using the activated charcoal canister method. The average value of radon exhalation varies from 0.052 to 0.69 Bq m(-2) h(-1) and depends on the specific concentration of uranium.

Desert Climate↗