Concentrations of ^{239, 240}Pu in human autopsy tissue samples from the general population in Japan are reported for 1970. The mean plutonium concentration was determined to be 0.23±0.63, 0.57±0.37, and 1.10±0.63 pCi/kg for the lung, liver and vertebrae samples, respectively; no appreciable concentration of plutonium was found in the kidney samples. These results are being compared with the data obtained from autopsy cases from the general population in the United States for the same year.

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2-Mercaptopropionyl glycine (MPG) treatment has not improved leucocytopenia in laboratory mice after 760R or 1060R gamma exposure inspite of the fact that reduction in the total leucocyte count was slightly less in MPG treated group on the 10th day after 760R gamma exposure ; leucocytopenia was more marked in MPG treated group on the 14th day and 21st day after 760R gamma exposure as compared to that in control animals.
Two hundred mg/kg of 2-aminoethyl isothiuronium bromide hydrobromide (AET) treatment which is half the recommended dose for radioprotection has offered considerable protection to leucopenia after 760R and 1060R gamma exposure. It has also helped substantially in rapid recovery of lymphocytes after 760R exposure.
MPG combined with two hundred mg/kg AET has not offered any extra radioprotection to peripheral blood leucocytes after 760R gamma exposure, on the contrary the combination has been less effective than the respective AET dose given singly. Similar result has been noted with combination treatment of MPG and 40 mg/kg AET in 1060R gamma exposure.

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When spores of Bccillus subtilis were treated in a frozen state with tritiated glycerol of different concentrations (up to 160 μCi/ml), efficiencies of killing and mutation induction per absorption dose were higher in solutions of lower tritium concentrations where low dose-rate β-irradiations were performed. Similarly when transforming DNA of Bacillus subtilis was kept with tritiated glycerol solution of concentrations ranging 0.05-500 μCi/ml at 4°C, efficiency of inactivation of the arginine marker increased strikingly by lowering the tritium concentration. On the other hand, the RBE of DNA-strand scissions of colicin El plasmids exposed to tritiated glycerol of a relatively high concentration (680 μCi/ml) was found to be approximately 1, when compared at the same absorption dose of gamma-irradiation (36 kR/hr) from a ¹³⁷Cs source.

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Studies have been carried out on the amount of hydrogen chloride formed by the radiolysis of chloroform in a solid paraffin-chloroform-Methyl Yellow system, and the color changes from yellow to red and absorption energy observed. The amount of hydrogen chloride formed and the intensity of the red color were determined with a pH meter, a spectrophotometer, and a color/ color-difference meter. It was found that the color-difference meter had the most excellent spectral response and sensitivity for measurement of the irradiated sample, and that the color-difference, ΔE, obtained by reflectometry increased proportionally with the increase in the radiation dose throughout a region of 100 ?? 5000R.
When a solid sample composed of 1.0 kg paraffin (m. p. 62 ?? 64°C), 0.74 kg chloroform and 3.4 × 10^-3 mol Methyl Yellow was subjected to 1000R irradiation at 20°C, 2.5 × 10¹⁴ molecules of hydrogen chloride were formed in 1.0 g of the solid sample with the absorption energy of 5.9 × 10¹⁶ eV, 3.2 × 10¹⁶ eV of which contributed to chloroform as the absorption energy.

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The growth kinetics of haemopoietic cells after irradiation was compared between the normal (+/+) and the genetically anemic W/W^υ mice both in vivo and in vitro. The parameters studied were the total cellularity and the number of granulocyte/macrophage precursor cells (CFUc).
The onset of haemopoiesis in vivo after irradiation with 150R of X-rays was significantly delayed in W/W^υ mice compared to that in +/+ littermates. In the culture of W/W^υ marrow, haemopoietic cells could recover after 50R-irradiation but not after irradiation with more than 100R, whereas the +/+ marrow culture restored normal haemopoiesis soon after irradiation. The number and concentration of CFUc within the W/W^υ marrow culture showed a temporary ncrease after irradiation, followed by a gradual decrease which preceded the depletion of differentiated cells in suspension.
These results suggest that the differentiation potency of W/W^υ stem cell is normal but the capacity for self-renewal is defective.

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An alkaline separation technique originally established by Ahnstrom is modified to detect small amount of DNA damage in X-irradiated mouse leukemic L5178Y cells. It is made quantitative by calibration with an alkaline sucrose gradient centrifugation. The present method would make it possible to study DNA damage and its repair within a dose range of X-rays where cell survival and mutation are usually investigated. It is also useful for detecting DNA damage caused by chemicals.

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The hematopoietic activity in the bone marrow was investigated in male CF#1 mice at 28 and 56 days after intravenous injection of polymeric plutonium-239 at the dose level of 15 μCi/kg, 10 μCi/kg and 5 μCi/kg of body weight. The number of nucleated cells in the femoral marrow decreased in proportion to the amount of plutonium injected. The number of in vivo colony forming units per femoral marrow also decreased with the increase of the dose of plutonium. No significant change was observed in the blood clearance of 69Fe with the exception of the group at 56 days after injection of the heighest dose. In this group ⁵⁹Fe in the blood disappeared very rapidly within 2 minutes after injection of ⁵⁹Fe. With the injection of plutonium, ⁵⁹Fe incorporation into circulating erythrocytes was depressed even in the lowest dose group. Except for the group at 56 days after injection of the highest dose, ⁵⁹Fe in the femur increased. The possibility of ineffective erythropoiesis by polymeric plutonium was discussed. From the facts investigated in this study, we may conclude that the hematological activity in the bone marrow was disturbed by as low as 5 μCi/kg of polymeric plutonium, the dose with which clinically detectable anemia had not been induced.

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Wistar rats have continuously ingested tritiated food (48.1 kBq/g) or tritiated water (37.0 kBq/ml) from three weeks before mating of P₀ through delivery of the F₃ generation. An analysis of tissues at various ages during treatment shows that: (1) tritium incorporation into tissues of rats life-time exposed to tritiated food was on the average 3.53 ± 0.38 times higher than after similar exposure to tritiated water; (2) the highest organically bound tritium concentrations were found in ovaries and lungs of rats exposed to tritiated focd. Tritiated water exposure gave the highest concentrations of this isotope in testes and lungs; (3) exposure of females to tritiated water during 64 days, including pregnancy and lactation, is not sufficient to attain equilibrium concentrations of organically bound tritium in all the studied tissues, while in the tritiated food exposure group such equilibrium concentrations were attained in the majority of tissues; (4) the dose rate estimation on the basis of tritium in body water leads to underestimation of absorbed dese in the tissues of rats, especially after exposure to tritiated food.

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The effect of total body γ-irradiation with sub-lethal dose (400 rad) on acid phosphatase has been studied in spleen of pigeons. The specific activity of acid phosphatase increased significantly 48 hr and 72 hr after irradiation. This increase was accompanied by a substantial reduction in per cent ‘bound’ activity. The histochemical observation after irradiation confirmed the result obtained by quantitative biochemical study. This increase in acid phosphatase activity may be attributed to an increased permeability of lysosomal membrane caused by damaged lymphocytes (lymphocytolysis) after γ-irradiation.

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Effects of cell concentrations on the survival and repopulation of haemopoietic stem cells after irradiation were studied in the long-term culture of mouse bone marrow cells in vitro.
No difference was observed in the survival of the stem cells among cultures in which 0-10⁷ cells were re-inoculated on the adherent cell colonies in the culture flask. Stem cells showed a significant proliferation within 1 week and the number of the stem cells exceeded the control in 3 weeks after irradiation in the cultures with less than 10⁶ re-inoculated cells per flask. In contrast, there was a considerable delay in the onset of stem cell proliferation after irradiation in the culture with 107 cells per flask.
Based on these results, a possiblity that a stimulator of stem cell proliferation, released from irradiated stromal cells, is cancelled by an inhibitory factor produced by irradiated or unirradiated haemopoietic cells is postulated.

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In a comparative analysis of mortality among atomic bomb survivors versus the non-exposed, both resident in Hiroshima Prefecture, it was found that in addition to leukaemia, malignant lymphoma, multiple myeloma, and cancers of the thyroid gland, breast, lung, esophagus, stomach, urinary organs and salivary gland which have been reported from the past to be elevated in risk among atomic bomb survivors, cancers of the colon, larynx, accessory sinuses, uterus, ovary and testis, diseases of the blood, cirrhosis of liver, hypertensive disease and diabetes mellitus were elevated in risk, but the risk of cerebrovascular disease, heart disease, peptic ulcer, gastroenteritis, senility, and accidents was lower than the non-exposed. The relationship of atomic bomb exposure to the relative risk of cancers of the lung, breast, uterus, and testis could be readily explained, but the relationship between atomic bomb exposure and the relative risk of cancers of many other sites, diseases of the blood, and other causes of death was inconsistent. One of the reasons why the risk of senility was low and the risk of diseases of the blood, malignant neoplasms, diabetes mellitus, and hypertensive disease was high is considered to be the higher diagnostic accuracy in atomic bomb survivors.

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