Adult male house sparrows were exposed to Co-60 external irradiation at doses of 475, 712 and 950R. The dose rate was 100 R/hr at a distance of one foot. The birds were autopsied at intervals of 1, 3, 5, 7 and 15 days after irradiation. Testes were studied for histopathological damage produced. There was a significant loss of the testicular weight 3 days after irradiation. The seminiferous tubules showed pyknosis, karyolysis and depletion of spermatogonial cells. Maximum damage was observed in the testis exposed to 950R. However, there was no change in the Sertoli and Leydig cells.

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The International Commission on Radiological Protection (ICRP) has proposed the concept of effective dose equivalent for the purpose of radiation protection programs in occupational exposures. Dose equivalent of radiation workers has been popularly evaluated from the readings of film badges worn mostly on the chest region of the workers. At the present time, the effective dose equivalents must be estimated from the film-badge readings. In order to simplify the determinations of the effective dose equivalents, ratios of organ or tissue doses to unit film-badge reading were calculated with the aid of the Snyder''s mathematical phantom constructed so as to simulate the Japanese body. The dose calculations were carried out on the organs or tissues related to stochastic effects of radiations. The energy and angular dependencies of organ or tissue doses were calculated using depth-dose curves experimentally determined with a phantom measurement. The effective dose equivalents were determined with the weighting factor recommended by the ICRP.
The effective dose with respect to fatal malignant diseases was calculated using a modified weighting factor estimated from the excess mortalities of cancers caused by the atomic bomb radiations in Nagasaki. The effective dose is somewhat different from the effective dose equivalent and is used for the determination of malignancy significant dose which will be defined as one of the population doses in Part 2 of a series of paper.
The organ or tissue doses were calculated for gamma-rays from ⁶⁰Co and ¹³⁷Cs sources and X-rays of 30, 80 and 140 keV. These doses are tabulated as a function of gamma and X-ray energies for various incident angles of radiations on workers. On the basis of these data, the effective dose equivalents and the effective doses were determined for the estimation of population doses in Part 2.

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The population doses and risks of stochastic effects from occupational exposures in Japan in 1978 were estimated on the basis of a nationwide survey. The survey was conducted on annual collective dose equivalents by sex, age group and type of radiation work for about 82, 500 workers other than the workers in nuclear power stations. The data on the workers in nuclear power stations were obtained from the offitial publication of the Japan Nuclear Safety Commission. The total number of workers except for nuclear power stations was estimated to be about 170, 000 persons. Radiation works were subdivided as follows: medical works including dental; nondestructive inspectional ; non-atomic energy industrial; research and educational; atomic energy industrial and nuclear power industrial.
The annual collective dose equivalents were estimated to be about 6, 000 man rem for medical workers, 450 man rem for non-destructive inspectional, 450 man rem for non-atomic energy industrial and 13, 300 man rem for nuclear power industrial, respectively. The population doses from occuaptional exposures in Japan were calculated to be about 0.14 mrad person^-1 year^-1 for the genetically significant dose, 0.15 mrad person^-1 year^-1 for per Caput mean bone marrow dose, 0.14 mrad person^-1 year^-1 for the leukemia significant dose and 0.07 mrad person^-1 year^-1 for the malignancy significant dose, respectively. The risks of stochastic effects to individual and the Japanese population from occupational exposures were estimated using the data on the annual collective dose equivalent to individual and on the population doses, respectively. The total risk of population was estimated to be about 4 persons year^-1. The analyses of occupational exposures such as the dose equivalent per unit electrical power generated by nuclear energy or per radiological practice to patients were carried out.

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Accumulation of tritium in aquatic organisms was estimated through a model food chain such as;
tritiated water (THO) → diatoms → brine shrimps → Japanese killifish.
Tritium accumulations in each organism as organic bound form are expressed as the R value which is defined as the ratio of tritium specific activity in lyophilized organisms (μCi/gH) to that in water (μCi/gH). The maximum R values were 0.5 in diatoms, Chaetoceros gracilis, 0.5 in brine shrimps, Artamia salina, and 0.32 in Japanese killifish, Oryzias latipes under the growing condition where tritium accumulation took place from tritiated water without tritiated diets. Brine shrimps and Japanese killifish, which grew from larvae to adult in tritiated sea water with feeding on tritiated diets (model food chain), had the R value at 0.70 and 0.67 respectively, indicating that more tritium accumulation in consumer populations with tritiated diets than those without tritiated diets. In addition, the R values of each organ of Japanese killifish, of DNA and the nucleotides purified rfom brine shrimps growing under the condition with or without our model food chain were measured to estimate the tritium distribution in the body or various components of the organism. These results did not indicate the seeking characteristic of tritium to some specific organs of compounds.

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In order to investigate the cross placental transfer of particulate materials and their deposition in feto-placental unit, two kinds of ¹⁹⁸Au-colloid solutions, 5 and 30 nm in particle diameter, were injected into pregnant rats at 19th day of gestation. The transferred rate to the fetus was very small, being approximately 0.018 and 0.005% for ¹⁹⁸Au-colloid of 5 and 30 nm in diameter, respectively, of the administered dose per litter at 24 hours after injection. The concetration of colloidal gold in the fetus, fetal membranes and placenta was greater for ¹⁹⁸Au-colloids of 5 nm in diameter than those of 30 nm. This fact may be attributed not to the particle size but to the difference between the average concentrations of these particles in the maternal blood. In view of the fact that the radioactivity of fetal membranes was as high as placental tissues, it is speculated that these particles were transferred to the fetus not only across the chorioallantonic placeta but also via the yolk sac placenta.

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A commercial mixture of phenolic antioxidants containing BHA, BHT and PG, commonly used in the food industry, was found to protect Salmonella typhimurium against killing and induction of his⁺ mutations by γ radiation. The protective effect was apparent only when irradiotion was performed in the presence of oxygen and no protection could be detected in its absence. When each of the components of the antioxidant mixture was tested separately, only PG displayed a protective effect. The amount of protection provided by the mixture of antioxidants was close to the protection afforded by hypoxia. Also, protection against cell killing was very similar in magnitude to protection against induction of mutations. The protective effect could be detected only when antioxidants were added to the cells before irradiation. No protection was afforded upon addition immediately after irradiation.

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Mice were injected daily with a radioprotector WR-2721 after inoculation with Ehrlich''s ascites tumor cells. Increases in weight of mice, volume of ascitic fluid and number of ascitic cells per mouse were reduced by the daily administration of 5 mg/mouse of the drug, indicating a suppyessive effect of WR-2721 on growth of ascitic cells. But daily treatment with 5 mg/ mouse of WR-2721 caused earlier death of tumor-bearing mice.

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A non-perturbing and non-perturbed thermometer system in RF field was developed. The probe is composed of (1) C-A thermocouple, wrapped by (2) the conductor, which encircles the C-A thermocouple, and also (3) the insulator of a low dielectric constant in the most outer layer. Production of noises and “ hot spots ” was prevented by coiling both a part of the cable of the probe and C-A thermocouple at the one of the two ends connected to a temperature monitor.
It was pointed out that the RF current, which was rectified at the junction of the thermocouple, caused noises.

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An aqueous solution of calf thymus DNA was irradiated with 19.5 kHz ultrasound, and the template activity of the DNA for RNA synthesis in vitro was investigated. The template activity of the DNA was assayed by the incorporation of ¹⁴C-AMP into the synthesized RNA. The template activity of DNA decreased rapidly by sonication for the initial short period, and then further decreased exponentially with the increment of sonication period. The neutral sucrose gradient analysis of the sonicated DNA showed that the rapid reduction of the molecular weight was induced for the initial short period of sonication, and that the further sonication had little effect on it. This result indicated that the initial rapid decrease of the template activity was mainly due to the reduction of the molecular weight, i, e., due to the double strand breaks. The production of single strand breaks in the sonicated DNA was also investigated by alkaline sucrose gradient analysis. It was found that the number of single strand breaks increased with the increment of sonication period. The single strand breaks produced by sonication seem to participate in the above mentioned exponential decrease of the template activity.

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Lymphocytes isolated from bovine blood were irradiated at doses of 0.5, 1.0 and 1.5 Gy with dose-rates of 0.361 0.150, 0.062, and 0.006 Gy per min. The amount of trypan blue negative cells were counted directly after radiation and eight hours after the onset of the radiation, and compared with control cells. A considerable decrease of cells was found especially at the lowest dose-rate. At this low dose-rate, radiation induced cell loss already occurred during the irradiation period. These experiments suggest that the observed inverse dose-rate effects on lympocyte survival are caused by radiation induced damage to the plasma membrane of the cell. This phenomenon is especially pronounced at the lower range of dose-rates and is interpreted as a result of slowly progressing chain reactions occurring in the membranes, initiated by ionizing radiation.

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