Rate constants for the reactions of OH radicals with commonly occuring amino acids and several enzyme proteins were determined by the competition kinetics using p-nitrosodimethylaniline. From the assumption that the reaction of OH radicals with an amino acid residue is restricted to the surface region of enzyme molecule, an estimation of rate constant for the reaction of OH radicals with enzyme was attempted. The calculated values for cytochrome c and lysozyme were in good agreement with those obtained experimentally.

View full abstract

The absorbed dose in the head of human fetus exposed in utero to gamma-rays and neutrons from the 1945 atomic bombs in Hiroshima and Nagasaki has been estimated as a function of distance from the hypocenter. The ratios of the absorbed dose in the fetal head to the inair tissue absorbed dose was determined using a depth-dose curve and a dose build-up factor experimentally determined with simulated radiation sources of the atomic bombs. The ratio was corrected for the angular distribution of the atomic bomb radiations.
The results showed that the ratios varied depending on a distance from the hypocenter, a posture of mother and her stage of pregnancy at the time of exposure, and ranged from the minimum value of 0.56 to the maximum value of 0.70 for initial gamma-rays; 0.072 to 0.16 for recoil protons ; 0.075 to 0.11 for gamma-rays from ¹H (n, γ) ²D reaction ; 0.0030 to 0.0082 for protons from ¹⁴N (n, p) ¹⁴C reaction. The absorbed dose in the fetal head at the end of first month of gestation and at 1, 000m from the Hiroshima hypocenter was 194 rads for initial gamma-rays; 22.2 rads for recoil protons ; 15.8 rads for gamma-rays from the ¹H (n, γ) ²D reaction, and 1.22 rads for proton from the ¹⁴N (n, p) ¹⁴C reaction.

View full abstract

This report presents the result on the measurement of plutonium in Japanese human bone samples collected in four cities. Those measurement was done in connection with the nuclear explosion tests conducted since 1962.
The results show that the concentration of plutonium in human bone has increased yearly from 1962 through 1971, and the average concentration in 1971 was 4 × 10^-15Ci per one gram of bone. Any difference due to the sampling place, sex or age has not been detected in the plutonium concentration in bone. It is of significance to note that the transfer of plutonium to fetus was recognized. The amount of plutonium deposited in bone showed a closer relation to the concentration of plutonium in air than in diet. It is estimated by using the equation of ICRP (1959) that the radiation dose delivered to bone is 16.3 mrem/year at the radioactivity level in 1971.

View full abstract

Coprecipitation behavior of ruthenium in sea water with ferric hydroxide and cobalt sulfide was studied. It was found that the coprecipitation yield was considerably affected by chemical forms of ruthenium (chloro, nitrosyl nitrato and nitrosyl nitro complexes). With ferric hydroxide formed at pH 9 by adding sodium hydroxide or ammonia water, chloro complex was coprecipitated quantitatively, while nitrosyl nitrato and nitrosyl nitro complexes were coprecipitated as few as about 50 and 10%, respectively. When cobalt sulfide was formed at pH 9 by adding thioacetamide, all the three species were coprecipitated quantitatively. In the case of using ammonium sulfide as the reactant instead of thioacetamide, the coprecipitation yield for chloro complex was quantitative, but those for nitrosyl nitrato and nitro complexes were considerably reduced. The yields for the latter two species were increased with elapsed time after the addition of radioruthenium to sea water.

View full abstract

A transfer of radioactive substance through a food chain in an aquatic ecosystem was analyzed through application of modified three compartment model of Aten's. The modification of the original model is an introduction of two processes, an excretion of radioactivity from Fish-1 (preys) to sea water and an direct uptake of radioactivity by Fish-2 (predator) from sea water. In the model, a following ration rate coefficient (k₁₂) was defined as a mass transfer coefficient of a radioactive nuclide from preys to a predator:
k₁₂ = θ(M₁ ÷ M₂)
where θ is an assimilation rate of a radioactive nuclide, M₁ is a daily average ration taken by a predator, and M₂ is a weight of the predator.
In the experimental system, pike cichlids and minows were used as predators and preys. And ¹³⁷Cs was used as a radionuclide in the system. The accumulation of a ¹³⁷Cs in pike was explained by application of the above modified three compartment model and various parameters in the model were determined. This shows that the transfer of a radionuclide through a food chain can be estimated by knowing the uptake rate and the turnover rate of Fish-2 (predator). They in ecological term are a daily average ration and an assimilation rate respectively.

View full abstract

The uptake and accumulation of cesium-137 by fishes from sea water was studied through the field studies for eight years (1963-1970). The concentrations of cesium-137 in marine fish muscles have decreased with time since 1963, and the concentration factors ranged from 11 to 81. On the other hand, the concentration factors of stable cesium remained in a narrow range between 34 and 52. The mean value of the observed ratio (OR) calculated by cesium-137 and potassium was 5.7 during the period from 1964 to 1970, and the OR value based on stable cesium was 5.9. The ratios between annual mean values of the specific activities of fish muscles and of sea water were found to be from 0.6 to 1.5.
From these data, if the concentration of cesium-137 in the environmental sea water is known, it is possible to estimate the approximate concentrations of cesium-137 in marine fishes by using the concentration factor or observed ratio without any analytical procedures.

View full abstract

The distribution of fallout ⁹⁰Sr in the skin, juice and residue part of the mature fruit of Satsuma orange trees grown on soils under clean, mulch and sod systems of soil management was investigated for the years from 1961 through 1971.
The level of this nuclide in the skin showed a high concentration during the period of heavy fallout deposition followed by a slow exponential decrease with almost the same halftime as that of the replaceable ⁹⁰Sr content in soil. On the contrary, the level of ⁹⁰Sr in the juice part was not influenced by the heavy fallout deposition, and the ⁹⁰Sr content showed almost the same pattern as that of the replaceable ⁹⁰Sr content in soil between 1961 and 1971. The ratio of the ⁹⁰Sr content due to direct (surface) absorption including floral absorption to that due to indirect (root) absorption was 7: 1 for the skin and 1: 6 for the residue in 1963 when heavy fallout deposition was observed. The ratio of ⁹⁰Sr/Ca in plant tissues to replaceable ⁹⁰Sr/Ca in soil was also discussed.

View full abstract

Upon gradual removal of Mg⁺⁺, 81 S ribosomes of silkglands were dissociated into 61 S and 44S subunits. Irradiation of partially-dissociated ribosomes in a low Mg⁺⁺ buffer (0.05 mM—0.02 mM) resulted in enhancing the unfolding of 61S and 44S ribosomal subunits further into 39 S and 25 S. This result indicates that ribosomes become more radiosensitive in the unstable structure than in the stable one.

View full abstract

Ghosts of rabbit red blood cells were prepared by hemolysis of red blood cells with distilled water, followed by restoration to an iso-osmotic plasma at the time of incubation. X-irradiation stimulated the leakage of ³²P from ³²P-loaded ghosts. The effect was observed even at a dose of 500 R. X-irradiation induced immediately an increase in cellular acid-soluble ³²P, which was partly responsible for the increase of leakage. The concomitant decrease in the level of acid-insoluble ³²P in irradiated ghosts recovered slightly within the first several minutes of incubation at 37°C.

View full abstract

Lethal effects of thermal neutrons were compared with those of ⁶⁰Co-γ-rays on the two types of Amoeba proteus. D₃₇ doses against γ-rays were 2.5 × 10⁵ (M-type) and 7.2 × 10⁵ rads (P-type), and those for thermal neutrons were 9.1 and 11.7 × 10¹³ n. cm^-2 (total flux) respectively. Additions of AET, D₂O or boron failed to increase or decrease the lethal effects of thermal neutrons. The lethal actions by thermal neutrons must arise by the nuclear reaction, namely, ³¹P (n, γ) ³²P on DNA strands. When amoebae were irradiated by thermal neutrons on pre-γ-irradiated status, the lethal actions were markedly enhanced (γ-n effect).

View full abstract

The restorative effects of post-irradiation treatment with some nucleic acid precursors were studied in mouse L cells in culture and in mice irradiated with X-rays. Deoxyribonucleosides increased the survival of L cells as well as mice while adenosine increased the survival of mice but not of L cells. The results suggest two different types of restoration in mammals.

View full abstract

The reaction between thymine glycol and hydrated electron was studied by the flash photolysis technique with a time resolution of 10 μsec. Hydrated electron was formed from ferrocyanide ion in the aqueous solution of thymine glycol. Though its lifetime was shorter than the time resolution of measurements, the rate constant was estimated to be>-2.6 × 10⁹ M^-1 sec^-1 at 19°C from the yield of hydrated electron as a function of the concentration of thymine glycol present. The high rate constant explains the results from a conventional scavenger method.

View full abstract