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Volume 16, Issue 2
Displaying 1-6 of 6 articles from this issue
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F. YATAGAI, T. TAKAHASHI, A. MATSUYAMA1975 Volume 16 Issue 2 Pages 99-112
Published: June 15, 1975
Released on J-STAGE: July 14, 2006
JOURNAL FREE ACCESSB. subtilis spores, E. coli BB-1 and E. coli B/r were bombarded with α-particles and heavy ions of carbon, nitrogen and oxygen accelerated in the IPCR Cyclotron. The RBE versus LET∞ curve for B. subtilis spores showed a maximum peak at ?? 120 keV/μm, while those for E. coli BB-1, and E. coli B/r declined without any maximum as LET∞ values increased. In the region of α-particles, the effective inactivation cross section (Seff) for these three strains increased with increasing LET∞ and the rates of increase in Seff in the LET region from ?? 30 to ?? 150 keV/μm were 15.0, 1.5 and 2.5 times for B. subtilis spores, E. coli BB-1, and E. coli B/r, respectively. In the case of B. subtilis spores, Seff values for heavy ions were almost independent of their energies, but the other two strains showed a considerable dependence upon beam energy. The charcteristic LET dependence of Seff observed in this study was fairly well explained by the target theory based on microdose concept.View full abstractDownload PDF (595K) -
H. FUJITA, K. MORITA1975 Volume 16 Issue 2 Pages 113-119
Published: June 15, 1975
Released on J-STAGE: July 14, 2006
JOURNAL FREE ACCESSStability of Escherichia coli ribosomes newly synthesized after γ-irradiation was compared with that of normal ribosomes. The ribosomal particles around 70-S synthesized in irradiated cells were more sensitive to digestion by pancreatic ribonuclease A. There existed a higher amount of the salt-unstable ‘50-S’ precursor particles in the extract from irradiated cells than in the extract from unirradiated cells. These facts suggest that ribosomal particles synthesized during an earlier stage in irradiated cells maintain an incomplete structure, even though they are not distinguishable from the normal ribosomes by means of sucrose density-gradient centrifugation.View full abstractDownload PDF (310K) -
H. KIMURA1975 Volume 16 Issue 2 Pages 120-124
Published: June 15, 1975
Released on J-STAGE: July 14, 2006
JOURNAL FREE ACCESSIntracellular levels of cyclic 3', 5'-adenosine monophosphate (c-AMP) seemed to be constant through the first cleavage cycle of sea urchin eggs. X-irradiation to the sperm, which induced the first cleavage delay, did not change this level. Although it was shown in the previous paper that X-ray-induced cleavage delay was reduced by caffeine but not by aminophylline, both caffeine and aminophylline caused an increase in c-AMP levels. These results indicated a possibility that c-AMP does not mediate this caffeine effect on cleavage delay.View full abstractDownload PDF (214K) -
H. KIMURA1975 Volume 16 Issue 2 Pages 125-131
Published: June 15, 1975
Released on J-STAGE: July 14, 2006
JOURNAL FREE ACCESSThe mitotic delay was induced when sea urchin eggs were treated with either ethidium bromide or puromycin, as observed with eggs fertilized with X or UV-irradiated sperm. Treatment of these eggs with caffeine during the period of early prophase block resulted in the reduction of the mitotic delay. Protein synthesis of these eggs was not affected by X-irradiation but inhibited by ethidium bromide or puromycin. Caffeine was almost ineffective in changing the protein synthesis of eggs inseminated with X-irradiated sperm or treated with ethidium bromide. These facts mean that additive synthesis of protein is not required for the reduction by caffeine of the mitotic delay. Some role of protein synthesis in the reduction by caffeine of the cleavage delay is not excluded for puromycin treated eggs, since caffeine counteracted the inhibitory effect of puromycin on protein synthesis.View full abstractDownload PDF (342K) -
L. AOYAWA, Y. INOUE1975 Volume 16 Issue 2 Pages 132-141
Published: June 15, 1975
Released on J-STAGE: July 14, 2006
JOURNAL FREE ACCESSIn order to estimate and evaluate the radioactivity concentration in an aquatic ecosystem, the transfer of radioactivity through a food web should be considered.
In this paper, systems analysis on the above problem was performed and a quantity of radioactivity in organisms concentrated through their diet was presented. It was found from numerical evaluation that whether the transfer of radioactivity through a diet is significant or not depended on such ecological factors as ration rates, assimilation rates, uptake rates and turnover rates, etc. The degree of the importance of these parameters on the concentration process of radioactivity was quantitatively evaluated by the mathematical technique of sensitivity analysis.View full abstractDownload PDF (391K) -
H. OKABAYASHI, M. SUZUKI-YASUMOTO, S. HONGO, S. WATANABE1975 Volume 16 Issue 2 Pages 142-151
Published: June 15, 1975
Released on J-STAGE: July 14, 2006
JOURNAL FREE ACCESSAs an indicator nuclide for inhalation exposure to Rn daughters of mine workers in a Japanese uranium mine, Po-210 urinalysis of the workers and surveys of some environmental factors were conducted.
An estimation study from the concentrations of Rn daughters in the mine indicated that about 800 ?? 50 pCi of Po-210 could have been accumlated in each miner's body. According to the results of the urinalysis for several times in 5 years, however, statistical difference was not clearly identified in the quantity of Po-210 in urine among miners and non-mining workers there.
Investigations on the concentrations of Po-210 in the mine's air, waters, foods of about 30 kinds, cigarets and on feces-urine ratios of Po-210 on human revealed that these factors would greatly affect the metabolism and excretion of Po-210 of the workers. In particular, some marine foods in Japan contained a great amount of Po-210 (several hundreds times of other foods) and cigarets showed 0.3 ?? 0.8 pCi of Po-210 per gramme.
Smokers excreted more Po-210 in urine definitely than non-smoker.
Feces-urine ratios changed between 5.2 ?? 42.9 on a human subject.
Therefore, it can be concluded that Po-210 would not be a good indicator for the personal exposure to Rn daughters, unless a great care were taken on the foods and smoking habits of mine workers, in addition to exposure conditions in the uranium mine.View full abstractDownload PDF (421K)
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