Tracer studies with the B12 vitamins. II. Biosynthesis of vitamin B12 labelled with 60Co and 32P.
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Vitamin D increases intestinal calcium and phosphate absorption. Not so well known, however, is that vitamin D stimulates the co-absorption of other essential minerals like magnesium, iron, and zinc; toxic metals including lead, cadmium, aluminum, and cobalt; and radioactive isotopes such as strontium and cesium. Vitamin D may contribute to the pathologies induced by toxic metals by increasing their absorption and retention. Reciprocally, lead, cadmium, aluminum, and strontium interfere with normal vitamin D metabolism by blocking renal synthesis of 1,25-dihydroxyvitamin D. This is the first review of the role of the vitamin D endocrine system in metal toxicology.
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For isotropic point photon sources above an air-ground interface, the spectral energy fluences at the ground have been calculated by the Monte Carlo method for source energies in the range 50 keV-10 MeV. The source heights and the horizontal source-detector distances varied from 0.05 to 5 mean free paths in air. Air-ground interface correction factors have been calculated and then analytically approximated. The greatest deviations from unity were found for 100-keV sources located on the ground. Near the source, kerma free in air is enhanced by 30%, and far from the source it is reduced by a factor of 3.
Previously, we have reconstructed cohort dependent individual doses for residents living in rebar buildings of high 60Co contamination. These reconstructions were carried out using intensively collected TLD data on exposure rates at locations of 1 m height and 1 m x 1 m intersections. The present work deals with dose reconstructions for residents living in rebar buildings of moderate and minor 60Co contamination. Since only limited data on exposure rates from survey meters were available, dose reconstructions were based on these data using interpolations. To utilize such data, we examined them with respect to all factors that influenced the dose uncertainties. The interpolated results were given in terms of contour plots (isodose curves) and compared with corresponding results derived from TLD data and Monte Carlo simulations. The comparison revealed that survey meter data could be used to provide reasonable and conservative estimates of residential doses. By applying the cohort-dependent room occupancy factor and the site-dependent area occupancy factor, we reconstructed cohort dependent individual doses and associated uncertainties. Results of dose reconstructions for all residents living in contaminated rebar buildings were provided to the Atomic Energy Council and health authorities for epidemiologic and medical uses.
Radioactive chromium, cobalt, gold and mercury, all of which may occur as corrosion products from dental restorations, were injected in single doses via the tail vein of mice and an in vivo analysis of their distribution was performed using whole-body autoradiography. Gold seemed to be inert and went mainly to the liver and bones. The other elements studied were distributed widely in the body and remained for a long period of time in specific target organs and tissues.
A pilot study on the effect of localised irradiation applied to the site of a standard perforating injury in the rabbit eye, showed that gamma rays limited the formation of post-traumatic vitreoretinal membranes. A controlled study was therefore undertaken to confirm this observation. Twenty-four pairs of rabbits underwent a standard perforating injury in the right eye. One rabbit of each pair received a radioactive ophthalmic Cobalt applicator and the other a dummy applicator. Nineteen of 24 non-irradiated eyes developed vitreoretinal membranes, with associated traction retinal detachment. Only four of 24 irradiated eyes developed traction retinal detachment.
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