We have adjusted the ICRP model of alkaline earth metabolism to fit data on the *"Ra content of 87 samples of soft tissue from 17 persons who received radium by injection or ingestion 5 days to 53 yr before measurement. The fitted functions indicate that soft tissue retention rises to 58% of the whole body retention at 18 days after single intake, and then falls steadily reaching 33% at 100 days and 6% at 1000 days. The adjusted model was also found to fit data on bone retention in 5 persons 8-467 days after injection. For both types of tissue, the new functions differ substantially from those originally published. The adjustments improve or do not significantly reduce the model's ability to fit other radium data.The fits to soft tissue and bone data were achieved by changing the quantity 8 in the ICRP model from its original value for radium I0.06236 ( l-RBODy)}-2.410 to {0.1247( 1 -RBODy)}-2'410, where R B o D y is the whole body retention function. This forced new values for five model parameters for radium: / 3 = 0.6254, w = 1.436, fc = 5.629, v = 1.521, r = 0.9953. Also changed are the empirical values for the percentages of the body's natural alkaline earth contents which lie in soft tissue: Ca(0.28%), Sr(0.98%), Ba(4.7%), ZZ6Ra(S.5%).For use in dosimetry, effective retention integrals are given for 224226.228 Ra and for '=Th in soft tissue, on bone surfaces, in bone volume, and in the whole body. Integration times of 1 yr, 50yr and infinity are used. For 226.228Ra, the soft tissue integrals are reduced by factors of 1.5-2.5 below the values originally published; for Z24Ra, the reduction factor is about 1.1. The bone volume integrals increase for all isotopes; the percentage increase, about loo%, is greatest for 224Ra.A reanalysis of the autoradiographic data on 226Ra in bone has been carried out using the adjusted functions. The best fit results with dc = 1.5 rather than with the previous value, 10, indicating that the so-called modified version of the ICRP model may be unnecessary. An examination was made of the ability of the ICRP model to predict the outcomes of experiments to which the model functions had not been previously fitted. Results were positive.
We analyzed six different tissue DNA samples from a leukemic individual who received an injection of Thorotrast for alterations in proto-oncogene or tumor-suppressor gene structure. Our examination of the DNA indicated an alteration of the c-fms gene in the blood sample from this individual. This locus showed a deletion in which the 3' end of the deleted region maps between exons 11 and 12. In this particular case, the type of leukemia is unknown but myeloid leukemia is a neoplasm associated with individuals injected with Thorotrast. It is possible that the alteration in the c-fms gene of this individual is a consequence of the radiation exposure. No apparent alterations in the c-mos gene were observed in any of the tissues from the individual. This is in contrast to previous studies that described alterations in methylation patterns associated with the c-mos locus in radium-exposed individuals. A number of the individuals exposed to radium also had alterations of the retinoblastoma gene while no such alterations were observed in any tissue DNA samples from this Thorotrast case. It is possible that our inability to detect alterations of the c-mos and retinoblastoma gene may be attributable to the nature of alpha-emitting radionuclides or their distribution, or to the limited set of tissues available for analysis.
A novel system for Rn gas exposure of mammalian cells in culture has been designed, constructed, and used to directly assess both the magnitude and the nature of chronic, low-dose Rn/Rn daughter toxicity of exposed vital lung cells isolated from normal pulmonary tissue, propagated and exposed in vitro. Direct correlations between atmospheric Rn concentrations, alpha-particle fluences, and macro- and microdoses of absorbed radiation doses by lung cells provide for a heretofore unavailable assessment of critical doses to vital cells.
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