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1-13 of 13

Masanori Otake

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Journal Articles

Journal:
Radiation Research

*Radiation Research*(1996) 146 (3): 339–348.

Published: 01 September 1996

Abstract

This report re-examines the relationship of radiation dose to the occurrence of cataracts among 1742 atomic bomb survivors seen in the years 1963-1964 for whom the degree of epilation and Dosimetry System 1986 (DS86) doses are known. Of these individuals, 67 had cataracts. A relative risk model with two thresholds, one for the epilation group and the other for the noepilation group, has been fitted to the data using a binomial odds regression approach and a constant relative biological effectiveness (RBE) for neutrons of 10. Among these models, a linear-linear (L-L) dose-response relationship with two thresholds presents the best fit. Under the L-L threshold model based on DS86 eye organ dose estimates for the epilation and no-epilation groups, the slope estimate for the epilation group was 1.6-2.0 times greater than that for the no-epilation group, but no statistical difference between the two slope estimates was noted. The estimated threshold for the epilation group was 0.86 Sv and 1.54 Sv for the no-epilation group, but again the difference between the two threshold estimates is not statistically significant. When an L-L relative risk model with two thresholds was fitted to the data assuming the dose estimates to be in error by 35%, or when the data were restricted to the 1105 individuals exposed in Japanese houses at distances of less than 2500 m, where the DS86 doses are thought to be most reliable, the results were almost the same as those for the individuals for whom unadjusted DS86 eye organ dose estimates were used.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1995) 144 (1): 107–113.

Published: 01 October 1995

Abstract

Among 1713 atomic bomb survivors who underwent ophthalmological examinations from 1963-1964, the risk of cataract formation per unit dose of radiation was significantly greater for those who reported hair loss of 67% or more after exposure (the epilation group) than for those who reported less or no hair loss (the no-epilation group) (P < 0.01). Such an epilation effect has also been associated with leukemia mortality and the frequency of chromosome aberrations. Although this might be interpreted as indicating differential sensitivity to radiation between the epilation group and the no-epilation group, it could also be explained by imprecision in dose estimates. We have calculated that a 48% random error in DS86 dose estimates could be in accordance with the dose-response relationship for the prevalence of cataracts in the epilation group or the no-epilation group. Possible mechanisms for variation in radiosensitivity are discussed.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1994) 140 (1): 112–122.

Published: 01 October 1994

Abstract

Reduction of growth from exposure to atomic bomb radiation has been examined using individuals under 10 years old at the time of the bombing (ATB) and a growth curve analysis based on measurements of height and weight made in the course of the 4th-7th cycles of the Adult Health Study examinations (1964-1972). As expected, the largest difference in growth to emerge is between males and females. However, a highly significant reduction of growth associated with dose (DS86) was observed among those survivors for whom four repeated measurements of height and weight were available. Longitudinal analysis of a more extended data set (n = 821), using expected values based on simple linear regression models fitted to the three available sets of measurements of height and weight on the 254 individuals with a missing measurement, also indicates a significant radiation-related growth reduction. The possible contribution of such factors as poor nutrition and disruption of normal family life in the years immediately after the war is difficult to evaluate, but the effects of socioeconomic factors on the analysis of these data are discussed.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1993) 134 (1): 94–101.

Published: 01 April 1993

Abstract

Growth retardation due to exposure to the atomic bomb has been evaluated using repeated measurements of stature from 10 to 18 years of age. A highly significant growth retardation due to the DS86 uterine dose was observed in all trimesters combined and in the first and second trimesters of pregnancy. In the first trimester, all parameter estimates based on a linear (L) or linear-quadratic (L-Q) dose-response relationship were negative in relation to the DS86 uterine dose. The positive dose estimate in the second trimester is small and close to the control level. Statistically significant difference was determined by a multivariate test statistic examining whether or not a set of two- or three-parameter estimates including a constant term related to an L or L-Q dose-response relationship was different from zero. A radiation-related growth retardation was demonstrable as a longitudinal result of the repeated measurements of stature. The dose effect in the third trimester was not significant under either the L or the L-Q model. The relationship between birth weights and repeated measurements of stature in adolescence is discussed based on the results obtained by a growth curve analysis.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1992) 131 (3): 315–324.

Published: 01 September 1992

Abstract

The relationship of ionizing radiation to the age-related ophthalmological findings of the 1978-1980 ophthalmological examination of A-bomb survivors of Hiroshima and Nagasaki has been reanalyzed using DS86 eye organ dose estimates. The main purpose of this reevaluation was to determine whether age and radiation exposure, as measured using the recently revised dosimetry information (DS86), have an additive, synergistic, or antagonistic effect. The data in this study are limited to axial opacities and posterior subcapsular changes, for which a definite radiation-induced effect has been observed in Hiroshima and Nagasaki A-bomb survivors. The best model fitting for axial opacities gives a significant positive effect for both linear dose and linear age-related regression coefficients and a significant negative effect for an interaction between radiation dose and age. Such a negative interaction implies an antagonistic effect in that the relative risks in relation to radiation exposure doses become smaller with an increase in age. On the other hand, the best-fitting relationship for posterior subcapsular changes suggested a linear-quadratic dose and linear age-related effect. The estimate of the quadratic dose coefficient shows a highly negative correlation with age, but the negative quadratic dose term is extremely small and is of little biological significance.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1990) 122 (1): 1–11.

Published: 01 April 1990

Abstract

Of all the data sets pertinent to the estimation of the genetic risks to humans following exposure to ionizing radiation, potentially the most informative is that composed of the cohort of children born to atomic bomb survivors. We present here an analysis of the relationship between parental exposure history and untoward pregnancy outcomes within this cohort, using to the fullest extent possible the recently revised estimates of the doses received by their parents, the so-called DS86 doses. Available for study are 70,073 terminations, but DS86 doses have not been or presently cannot be computed on the parents of 14,770. The frequency of untoward pregnancy outcomes, defined as a pregnancy terminating in a child with a major congenital malformation, and/or stillborn, and/or dying in the first 14 days of life, increases with combined (summed) parental dose, albeit not significantly so. Under a standard linear model, when the sample of observations is restricted to those children whose parents have been assigned the newly established DS86 doses (n = 55,303), ignoring concomitant sources of variation and assuming a neutron RBE of 20, the estimated increase per sievert in the predicted frequency of untoward outcomes is 0.00354 (±0.00343). After adjustment for concomitant sources of variation, the estimated increase per sievert in the proportion of such births is 0.00422 (±0.00342) if the neutron RBE is assumed to be 20. A "one-hit" model with appropriate adjustments for extraneous sources of variation results in an almost identical value, namely, 0.00412 (±0.00364). When the sample is extended to include parents lacking the full array of dose parameters necessary to calculate the DS86 dose, but sufficient for an empirical conversion of the previously employed T65DR dose system to its DS86 equivalent, we find under the linear model that the estimated increase per sievert in untoward pregnancy outcomes is some 31% higher than that published previously, 0.00264 (±0.00277), assuming an RBE of 20, after adjustment for extraneous sources of variation. (Since a dose could not be calculated in 367 of the 70,073 outcomes, the n = 69,706.) The corresponding value with the one-hit model is 0.00262 (±0.00294).

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1990) 121 (1): 3–13.

Published: 01 January 1990

Abstract

This paper investigates the quantitative relationship of ionizing radiation to the occurrence of posterior lenticular opacities among the survivors of the atomic bombings of Hiroshima and Nagasaki suggested by the DS86 dosimetry system. DS86 doses are available for 1983 (93.4%) of the 2124 atomic bomb survivors analyzed in 1982. The DS86 kerma neutron component for Hiroshima survivors is much smaller than its comparable T65DR component, but still 4.2-fold higher (0.38 Gy at 6 Gy) than that in Nagasaki (0.09 Gy at 6 Gy). Thus, if the eye is especially sensitive to neutrons, there may yet be some useful information on their effects, particularly in Hiroshima. The dose-response relationship has been evaluated as a function of the separately estimated γ-ray and neutron doses. Among several different dose-response models without and with two thresholds, we have selected as the best model the one with the smallest χ 2 or the largest log likelihood value associated with the goodness of fit. The best fit is a linear γ-linear neutron relationship which assumes different thresholds for the two types of radiation. Both γ and neutron regression coefficients for the best fitting model are positive and highly significant for the estimated DS86 eye organ dose.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1984) 98 (3): 456–470.

Published: 01 June 1984

Abstract

Analysis carried out here generalized on earlier studies of chromosomal aberrations in the populations of Hiroshima and Nagasaki, by allowing extrabinomial variation in aberrant cell counts corresponding to within-subject correlations in cell aberrations. Strong within-subject correlations were detected with corresponding standard errors for the average number of aberrant cells that were often substantially larger than was previously assumed. The extrabinomial variation is accommodated in the analysis in the present report, as described in the section on dose-response models, by using a beta-binomial (β-B) variance structure. It is emphasized that we have generally satisfactory agreement between the observed and the β-B fitted frequencies by city-dose category. The chromosomal aberration data considered here are not extensive enough to allow a precise discrimination between competing dose-response models.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1983) 96 (3): 560–579.

Published: 01 December 1983

Abstract

A 2-year ophthalmologic study of age and radiation-related ophthalmologic lesions among the atomic bomb survivors in Hiroshima and Nagasaki was conducted in 1978-80. The study sample in both cities was composed of all persons exposed to 100+ rad, their controls, and all other persons with a previous record of axial opacities or posterior subcapsular changes. Most of the losses were due to persons who refused to participate or for whom it was not possible to arrange for an ophthalmologic examination at the time of the regularly scheduled medical examination. It should be emphasized, however, that the loss of persons in both the control and the 100+ rad groups did not change systematically with increasing age by city. Increased lenticular opacities, other lens changes, and loss of visual acuity and accommodation occurred with increasing age in both exposed and control subjects as manifestations of the normal aging process. A highly significant excess risk for all age categories in the 300+ rad group in comparison to those in the control group was observed for both axial opacities and posterior subcapsular changes in Hiroshima, but not in Nagasaki. A stronger radiosensitive aging effect for persons who were under 15 years old at the time of the bombing (ATB) was observed for both axial opacities and posterior subcapsular changes in Hiroshima.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1982) 92 (3): 574–595.

Published: 01 December 1982

Abstract

The occurrence of lenticular opacities among atomic bomb survivors in Hiroshima and Nagasaki detected in 1963-1964 has been examined in reference to their γ and neutron doses. A lenticular opacity in this context implies an ophthalmoscopic and slit lamp biomicroscopic defect in the axial posterior aspect of the lens which may or may not interfere measurably with visual acuity. Several different dose-response models were fitted to the data after the effects of age at time of bombing (ATB) were examined. Some postulate the existence of a threshold(s), others do not. All models assume a "background" exists, that is, that some number of posterior lenticular opacities are ascribable to events other than radiation exposure. Among these alternatives we can show that a simple linear γ-neutron relationship which assumes no threshold does not fit the data adequately under the T65 dosimetry, but does fit the recent Oak Ridge and Lawrence Livermore estimates. Other models which envisage quadratic terms in gamma and which may or may not assume a threshold are compatible with the data. The "best" fit, that is, the one with the smallest χ 2 and largest tail probability, is with a "linear gamma:linear neutron" model which postulates a γ threshold but no threshold for neutrons. It should be noted that the greatest difference in the dose-response models associated with the three different sets of doses involves the neutron component, as is, of course, to be expected. No effect of neutrons on the occurrence of lenticular opacities is demonstrable with either the Lawrence Livermore or Oak Ridge estimates. This presumably is ascribable to the smallness of the exposures since other data clearly establish the cataractogenic effect of this form of radiation.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1979) 77 (2): 377–394.

Published: 01 February 1979

Abstract

The incidence of leukemia during 1950-1971 in a fixed mortality sample of atomic bomb survivors in Hiroshima and Nagasaki was analyzed as a function of neutron and γ kerma and marrow doses. Two dose-response models were tested for acute leukemia, chronic granulocytic leukemia, and all types of leukemia, respectively. Each model postulates that the leukemia incidence depends upon the sum of separate risks imposed by γ and neutron doses. In Model I the risk from both types of radiation is assumed to be directly proportional to the respective doses, while Model II assumes that whereas the risk from neutrons is directly proportional to the dose, the risk from γ rays is proportional to dose-squared. The analysis demonstrated that the dose-response of the two types of leukemia differed by type of radiation. The data suggested that the response of acute leukemia was best explained by Model II, while the response of chronic granulocytic leukemia depended almost linearly upon neutron dose alone, because the regression coefficients associated with γ radiation for both Models I and II were not significant. The relative biological effectiveness (RBE) of neutrons in relation to γ rays for incidence of acute leukemia was estimated to be approximately <tex-math>$30/({\rm Dn})^{{\textstyle\frac{1}{2}}}$</tex-math> [95% confidence limits; <tex-math>$17/(D{\rm n})^{{\textstyle\frac{1}{2}}}\sim 54/(D{\rm n})^{{\textstyle\frac{1}{2}}}]$</tex-math> for kerma and <tex-math>$32/(D{\rm n})^{{\textstyle\frac{1}{2}}}$</tex-math> [95% confidence limits; <tex-math>$18/(D{\rm n})^{{\textstyle\frac{1}{2}}}\sim 58/(D{\rm n})^{{\textstyle\frac{1}{2}}}]$</tex-math> for marrow dose (Dn = neutron dose). If acute and chronic granulocytic leukemias are considered together as all types of leukemia, Model II appears to fit the data slightly better than Model I, but neither model is statistically rejected by the data.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1977) 72 (2): 353–363.

Published: 01 November 1977

Abstract

Microscopic and photographic studies were conducted in 1972-1973 at the Atomic Bomb Casualty Commission (ABCC) in Hiroshima on the morphology of superficial blood vessels of A-bomb survivors to determine whether the somatic effects of radiation still existed 30 yr after the A-bomb. Control curves representing the relationship between age and score values assigned to morphological changes of the minute blood vessels of the fingernail fold, labial mucosa, and lingual mucosa, which could be regarded as an index of aging, were obtained. These were compared with similar curves obtained from A-bomb survivors with the aim of evaluating the effect of radiation on the aging process of these vessels. 1. The late somatic effects of irradiation which were demonstrated 10 yr after the A-bomb in a previous study (1956-1957) were found to persist in the current study (1972-1973) conducted 30 yr after the A-bomb, though not as pronounced as in the earlier study. A significant effect was observed only in the nail fold of those exposed to 100 rad or more under the age of 10 at the time of bomb (ATB). A statistically significant difference was not observed with labial and lingual mucosae because the number of cases available for score evaluation was small, but a trend was observed for abnormalities of these two sites to be higher in frequency in the group exposed to 100 rad or more under the age of 10 ATB than that of the control group. 2. No significant difference was observed between the control and exposed with regard to radiation effect on the aging process using the relationship of score values to age as an index of aging.

Journal Articles

Journal:
Radiation Research

*Radiation Research*(1971) 46 (1): 199–216.

Published: 01 April 1971

Abstract

Capillary morphological studies were conducted in 1956-1957 at the Atomic Bomb Casualty Commission (ABCC) on superficial blood vessels to determine late somatic effects of irradiation on 435 subjects composed of A-bomb survivors and their controls. Significant differences were observed in the score assigned to morphological changes, being marked in proximally exposed group and those exposed to 100 rad or more under the age of 10 at the time of bomb. The level of significance was higher for labial and lingual mucosa than fingernail fold and bulbar conjunctiva.