Four hundred seventy ddN female mice of 10 weeks old were divided into five groups : (1) whole body exposure, (2) head exposure, (3) trunk exposure (chest and abdomen), (4) lower body exposure (pelvis, legs and tail), and (5) non-irradiated control. All the exposure groups received a single x-ray dose of 40O R under anaesthesia. The mean survival times of five groups were 46.0±2.3 weeks for whole body exposure, 63.5±2.3 weeks for head exposure, 51.5±2.3 weeks for trunk exposure, 68.1±2.4 weeks for lower body exposure and 73.8±2.8 weeks for non-irradiated control. The exposure of 400 R to whole body, head, and trunk resulted in significant lifeshortening from that of non-irradiated group, while the exposure to lower body did not produce any significant life-shortening. The life shortening per volume dose for head exposure group was the highest among all the exposure groups. This suggests that head (brain included) may play an important role in the radiation-induced life-shortening.

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The protective effect of AET against pulsed radiations and the distributions of AET-³⁵S in mouse tissue were studied. AET afforded protection against mortality after exposure to pulsed as well as sustained radiations. Its effectiveness was of the same extent when AET was administered during 2 to 30 minutes pre-irradiation. Administration less than one second before or after irradiation afforded no protection. The maximum content of AET-³⁵S in tissue occured 10 to 20 minutes after the administration of ³⁵S-AET. In general, a good correlation was observed between the AET contents of tissues and the protection afforded.

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The effect of radiation on kininogen (a precursor of physiologically active peptides, kinins) levels in plasma and liver was investigated. Male rats were exposed to 70O R of X-rays. The kininogen level showed 10-fold elevation in four hours after irradiation and then rapidly returned to the normal value. Effects of liver-protecting compounds, such as PKI (Potato Kallikrein Inhibitor) and MET (S-methyl-L-cysteine sulfoxide), on radiation-induced elevation of kininogen levels in plasma and liver were then investigated. The elevation was strongly suppressed when the animals were treated with these compounds. When tested in mice, these compounds were effective in extending survival time after X-irradiation of 700 R.

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The effects of fractionated X-irradiation on the spontaneous electrical activity in the visual cortex were studied in four adult male rabbits with permanently implanted electrodes. Two of the rabbits received a dose of 300 R and two a dose of 1500 R, fractionated into 50 and 150R per day administered at semi-weekly intervals. The head, except for the region of brain, was shielded with a lead plate. The electrical activity was averaged with a CAT 400B. The obtained averaged electrocorticograms were classified into seven waves: δ₂, δ₁, θ, α, β₁, β₂ and β₃ by means of an EEG frequency analyzer. The amplitude of the δ₂, δ₁, θ, α and β₁ waves of the two animals irradiated with 1, 500 R gradually decreased with increasing doses during fractionated X-irradiation. The decreased value remained relatively constant throughout the observation period after the end of exposure. The two animals irradiated with 30O R did not show any definite changes in amplitude during and after fractionated irradiation. The results are discussed in reference to the findings of the previous study using photic stimulation.

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The time variation in the mobility spectrum of radioactive charged particles, stored in a closed vessel, and the concentration ratio of positive to negative particles were studied by using a mobility spectrometer of parallel plates type.
A remarkable variation in the mobility spectrum with the mobility ranging from 3 × 10^-2 cm²/V·sec. to 3 × 10^-4 cm²/V·sec. was observed during four hours. A small hump appeared in the spectrum of mobility ranging from 1 × 10^-2 cm²/V·sec. to 1 × 10^-1 cm²/V·sec. under the condition that the radioactive equilibrium state was held in the vessel. The concentration ratio in each fine range of mobility was distributed from 1 to 1.5.

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The exposure experiment of experimental animals was carried at a level of about 0.01 μCi radon/ml of chamber air. The concentration of radon was measured by a double screen ionization chamber. The concentration of dust free daughters in the chamber is decreased by radioactive decay, attachment to dust particles and deposition to the chamber wall. To express the rate of decrease, the attachment constant k_p and the deposition constant k_w were introduced in addition to the radioactive decay constant. The values of k_p and k_w were experimentally obtained by using a semiconductor detector installed on the chamber wall. The diffusion constant of daughter atoms estimated from the deposition constant k_w was in good agreement with those obtained by other methods. The absorbed lung doses given to rat and mouse were 8.0 and 18.9 rads respectively, when radon was introduced into the test chamber at a level of 0.01 μCi/ml. The retention efficiency of the lung was approximately 2%9 for rat and mouse.

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The retention of ⁸⁵Sr administered intraveneously or orally to 14 Japanese was studied for the period of less than one month. The whole body retention curve, as determined from excreta, could be fitted well by a sum of two component exponential functions when the amount of ⁸⁵Sr exogenously excreted into the feces was excluded. However, the sizes and the rate constants of the respective components varied with individuals. The absorption coefficient of ⁸⁵Sr was calculated for four subjects and found to be about 50 percent for normal cases and 30 percent for subjects with osteoporosis. Cumulative urinary excretion of ⁸⁵Sr was not less than cumulative fecal excretion for absorbed ⁸⁵Sr. The fractions (f_u) of the element excreted in 24 hr urine over that in 24 hr total excreta of both stable Sr and Ca, which included exogenous origins, were higher for the subjects in this study than those to be reported for the normal male adults.
The fraction varied greatly day to day when the amount of stable Sr exogenously excreted into the feces was included in this calculation. Higher content of stable Sr in the excreta of the subjects in this study was generally observed in comparison with those of the normal male adults, but the amount of Ca in excreta of the subjects in this study was comparable to that of the normal male adults.

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The whole-body retention of ⁶⁵Zn in the young and adult mice after single and daily oral administration was investigated. The retention values for ⁶⁵Zn in young mice were significantly higher than those of the old ones. Since significant differences were noted in the presence or absence of the fast declining component of the retention curves and since the final slopes of ⁶⁵Zn retention curves were similar among all the age groups, the higher retention of ⁶⁵Zn in the 7- and 14-day-old mice was probably attributed to its near-complete absorption from the G. I. tract, while the 21-day-old and adult mice absorbed 45 and 12 percent of the administered dose, respectively. It is also noted that the 7-day-old mice contained significantly higher ⁶⁵Zn in the pelt and lower ⁶⁵Zn in pancreas, liver and G. I. tract than those of the adult mice.
When ⁶⁵Zn was administered orally everyday over a period of two weeks, the young animals retained 50 percent of the administered dose at the termination of administration, while the adult retained 8 percent. Again, its difference could be attributed to an efficient intestinal absorption of young animals.

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A chelating agent, trisodium calcium salt of diethylenetriaminepentaacetic acid (DTPA), was administered intraperitoneally with a single dose of 1.5 mM (750 mg)/kg body weight to rats 1 hr after subcutaneous, intramuscular or intravenous injection of ¹⁴⁴CeCl₃. Daily urinary and fecal excretion of ¹⁴⁴Ce was determined for 15 days postinjection. Tissue distribution of ¹⁴⁴Ce 15 days postinjection was also determined. The DTPA markedly increased the urinary excretion of subcutaneously and intramuscularly injected ¹⁴⁴Ce as well as of intravenously injected one, and decreased the contents of ¹⁴⁴Ce in all the tissues observed. It was suggested that a prompt DTPA treatment followed by intermittent therapy might be effective for the removal of ¹⁴⁴Ce transferred from the contaminated wounds and that in the wounds.

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Deoxyribonucleohistone (DNH) from calf-thymus was studied by E. S. R. spectroscopy following gamma-irradiation. Free radicals formed in gamma-irradiated deoxyribonucleohistone were mainly localized in DNA moeity. The G-value for radical production in DNH was 1.6, while the G-values in DNA and histone were 1.1 and 2.1, respectively. Thus the spectrum obtained in deoxyribonucleohistone could be explained as a consequence of an electron transfer from histone to DNA. This observation was also confirmed from E. S. R. spectrum of the reconstituted deoxyribonucleohistone.

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An alkaline sucrose gradient centrifugation method applicable for non-dividing and slowlydividing cells was developed through modification of a fluorometric method of Kissane and Robins.

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