The solid polymer electrolysis apparatus for tritium enrichment requires the enrichment factor to calculate the tritium concentration in sample water measured. Standard tritium water, with the initial concentration of approximately 10Bq kg-1, was thus used twice a year to determine the enrichment factor. We found a tritium memory effect of 50-80mBq, which was much than the detection limit (20mBq), after enrichment of the standard water. The observed memory effect corresponded to the level explained by the residue of enriched standard water restrained in the polymer electrolyte membrane. We found that the restrained tritium water is diluted by filling the apparatus with distilled water (<1 Bq kg-1) and electrolyzing it over 2 days with low electrolysis current (0.5-1 A), and memory effect problem can be solved. This method is recommended since it is effective not only to memory effect problem but also in protecting cathode.
We have developed a new type of glycoprotein-liposome conjugates and examined their potential utilities as drug-targeting carriers which exploit cellular functions. of carbohydrate-binding proteins, i.e. animal lectins. An extremely low labeling efficiency, however, has been often a big problem in biodistribution study by using radiolabeled glycoprotein-liposome conjugates. In this study, improvement of the labeling efficiency was conducted by using Bolton-Hunter Reagent (BHR) . First, tyrosyl groups were introduced into liposome membrane through amines of a constitutive phospholipid, dipalmitoylphosphatidlethanolamine (DPPE) . Then, glycoprotein-tyrosyl group introduced liposomes were iodinated with125I according to Chloramine-T methods. Labeling efficiency was markedly elevated in comparison with the BHR-untreated liposome conjugates. There was no significant changes in binding activity of BHR-treated glycoprotein-liposome conjugates with lectin. However biodistribution of glycoprotein-tyrosyl group introduced liposomes in mice was significantly different from the mother conjugates. Thus, another suitable method for radioiodination of the glycoprotein-liposome conjugates should be developed.
Determination of uranium in sixty-one species of marine organisms was carried out by inductively coupled plasma mass spectrometry to obtain concentration factors and to estimate the internal radiation dose. The concentrations of uranium in soft tissues of marine animals were ranged from 0.077 to 5040 ng/g wet wt. Especially, the branchial heart of cephalopod molluscs showed the specific accumulation of uranium. The concentration factor of the branchial heart of Octopus vulgaris, which indicated the highest value, was calculated to be about 1.6×103, comparing with that (3.1 ng/ml) in coastal seawaters of Japan. The concentrations of uranium in hard tissues of marine invertebrates such as clam and sea urchin were similar to those in soft tissues. In contrast, hard tissues like bone, scale, fin, etc. of fishes showed much higher concentrations of uranium than soft tissues like muscle. The concentrations of uranium of twenty-two species of algae were ranged from 2 to 310 ng/g wet wt. Particularly, the brown alga Undaria pinnatifida showed the highest value of the uranium content in the algae and its concentration factor was calculated to be 102.
Hydrogen gas evolution induced by60Co gammaray irradiation of nnoparticles dispersed in water was investigated. Nanoparticles of TiO2and Al2O3, whose average sizes were within the range of 14-33 nm, were employed. Hydrogen-gas yield from a sample dispersion in a closed vial was measured by gas chromatography after the irradiation. The sample exhibited much larger hydrogen yields than that in the pure water radiolysis. The hydrogen yield increased with the absorbed dose and the amount of particles dispersed in water. These results support the fact that the reaction is activated by both the γ-ray irradiation and the dispersed particles. In conjunction with results of TEM observation, it was implied that these enhancement effects should depend on the size and/or shape of the particles rather than their chemical species. We calculated the G-values for the hydrogen-gas evolution. They will be useful for the discussion about the reaction.
Radiation hormesis was studied at an X-ray photography room. Seed of radish (Kaiwaredaikon) was irradiated by X-ray, from 10 to 3000mGy. Since the growth of plant was the highest around 500mGy, 100 seeds were irradiated at a dose of 500mGy. Fifty seeds were selected and the growth rate was measured after 1 and 2 weeks. After 2 weeks, the growth of the seeds irradiated (129±5mm) was found to be higher than those without irradiation (115±5mm) .