(1) Adsorption properties of14C-alanine, 14C-ATP (adenosine triphosphate) and14C-aspartic acid on the metal-chelating resins were determined and found that the Cu (II) -Chelex 100 and Fe (III) -Unicel-lex UR10, Fe (III) -Chelex 100 chelating resins were highly effective for the adsorption of14C-alanine and14C-ATP, respectively. (2) Desorption rate of14C-ATP from the Fe (III) -Unieellex UR10 and Fe (III) -Chelex 100 resins was somewhat higher than the case of14C-alanine, probably because the coordination bonds of Cu-alanine might be stronger than those of Fe-ATP.Thus, 14C-labeled organic compounds such as14C-alanine and14C-ATP of a low activity concentration (3.7 mBq/ml) (1 × 10-7μCi/ml) in aqueous solution may be measured with liquid scintillation counter after pre-concentration by use of the Fe (III) -and Cu (II) -chelating resin columns.
“Dead water”, low level tritiated water is indispensable to measure tritium concentration in environmental waters using a low background liquid scintillation counter. Water produced by combustion of natural gas, or deep sea water etc. are usually used for the above purpose. A new method of reducing tritium concentration in natural water has been introduced for preparation of“dead water”. This method is to combine hydrogen-oxygen mixture produced by water electrolysis with hop calite catalyzer at 700°C. Deep well water was electrolized up to 2/3 volume, and tritium concentration of recombined water was reduced to be about one third of that of the original one.
The highest60Co γ-ray field available in Radiation Center of Osaka Prefecture was determined employing a cylindrical cavity chamber which has been calibrated with the national standard up to 7.7 (C kg-1) /h (30 kR/h) . For higher exposure rate regionn four stage of calibrations were carried out up to 3.7 (kC kg-1) /h (14 MR/h), which is higher than ever reported, based on the additivity of gamma intensity in terms of the source activity. The errors accompanied with the resultant values were estimated as 6% at most. Axial dose rate distributions in the irradiation cans used in the irradiation pool were measured with PMMA dosimeters.
Clinical utility of determination of serum deoxythymidine kinase (TK) activity is described. It is well known that elevated TK level is observed in leukemia and other malignant diseases, or some viral infectious diseases. The TK activity was assayed on normal subjects, hepatitis B virus (HBV) positive liver diseases and various cancer by a newly developed high sensitive method, radio enzyme assay (REA) utilizing125I-iododeoxyuridine as the substrate. Measurement of TK activity by the REA is revealed to be useful for“the marker of DNA metabolism anomaly”in leukemia, etc.