This paper describes a differential ionization chamber system which measures a wide-range concentration of tritium gas without being affected by the tritium contamination of the chamber wall. Since tritium is easily adsorbed to or into the wall, the detection level of tritium gas is raised. The differential ionization chamber system consists of a spherical and a cylindrical chamber. The inner walls of the two chambers are made of the same material and have identical surface areas. With this pair of chambers, it is possible to cancel currents, which are produced by β-rays from the accumulated tritium gas on the chamber wall. Experiments show that gas-borne tritium can be measured over a range of concentration from 3.7 × 10-2to 3.7 × 104Bq/cm3in real time.
Measurement of autoradiographic grains produced by the decay of incorporated radioisotopes is often used for a quantitative assay of the rate of DNA replication and DNA repair in cells or tissues. However, visual grain counting by microscopic observation is time-consuming and tedious process. Recently, Kraemer et al. reported that automated measurement of grains in cultured human cells may be facilitated by using appropriate grain counting instruments. Under their experimental conditions using Kodak NTB-3 emulsion, instrument-determined grain number per nucleus was proportional to visual counts up to 30 grains, and then leveled off at much larger visual counts. The saturation phenomenon was due to counting-loss by the instrument caused by overlapping of neighboring grains. To prevent the counting-loss, we have used in the present study Japanese Sakura NR-M2emulsion which is less sensitive to radiation exposure than Kodak NTB-3, thereby yielding smaller size of grains per radioactive decay. Samples were prepared from cultured skin fibroblasts derived from normal individuals and xeroderma pigmentosum (XP) patients defective in DNA repair. These cells were irradiated with 254 nm UV incubated for 3h with culture medium containing3H-thymidine, and autoradiograms were made by dipping in Sakura NR-M2emulsion. The number of grains as well as grain surface area per nucleus was measured by using ARTEK CYTO TALLY MODEL 900 counting instrument, and compared with visual counts. The results showed that, under our optimum condition, the instrument-determined number of grains was directly proportional to visual counts, at least up to 150 grains per nucleus, with a correlation coefficient of 0.971. The instrument-determined grain surface area was also linear in comparison to visual counts with the same correlation coefficient, 0.971. Automated analysis of grain numbers enabled us to estimate the rates of ultraviolet-induced unscheduled DNA synthesis (UDS) in XP cells; the instrument-determined UDS in a XP cell strain relative to that in normal cells was 10.0%, which was very close to the value obtained by visual counts (11.1%) . The time required for the instrumental counting was about one-sixth of that of visual counting.
Metabolic studies of ipriflavone (TC-80) in rats by gas-liquid chromatography-mass spectrometry led to the characterization of the following metabolites: the parent compound, 7-hydroxy-3-phenyl-4H-1-benzopyran-4-one, 7-hydroxy-3- (4-hydroxyphenyl) -4H-1-benzopyran-4-one, 3- (4-hydroxyphenyl) -7-isopropoxy-4H-1-benzopyran-4-one, 2- (3-phenyl-4-oxo-4H-1-benzo-pyran-7-yl) oxypropionic acid, 2- [3- (4-hydroxyphenyl) -4-oxo-4H-1-benzopyran-7-yl] oxypropionic acid and 2- [3- (3-hydroxyphenyl) -4-oxo-4H-1-benzopyran-7-yl] oxypropionic acid. From the metabolites identified, TC-80 was shown to be metabolized primarily by oxidation. In vitro study using tissue slices of rats indicated that the above metabolic changes occurred exclusively in the liver. It was also demonstrated that the compound did not undergo metabolic conversion by gut flora of rats.
Oral14C-ipriflavone was absorbed by rats to give a maximum plasma14C level at 1.5h and a half-life of 5.8h. In dogs, after po dosing, the plasma14C peaked at 0.5h, followed by gradual decline. The plasma of both animals contained mostly metabolites, with small amounts of unchanged ipriflavone. In rats, 14C was distributed widely in tissues, with relatively high concns. in the liver, kidney and gut. Distribution in rat thigh bone of unmetabolized ipriflavone was also demonstrated. 14C-Ipriflavone was eliminated mostly as metabolites within 48 and 72h, respectively, in rats and dogs. Rats excreted more14C in urine than in feces, whereas the reverse was noted in dogs. Biliary excretion and reabsorption of14C were also obvious in both animals.
Full-energy peak efficiencies of Ge (Li) detectors in the gamma-ray energy range of 120 to 2800 keV were experimentally measured by using calibrated standard sources. Five kinds of analytical function were fitted to the experimental points by leastsquares method. Fittabilities of these functions to the points in the different gamma-ray energy range were compared. As a result, the most successful of these functions was the polynomial, 1n ε (E) =NΣi=0 ai (1nE) i, where ε is the efficiency and E is the corresponding gamma-ray energy.
Antimony-121 Mössbauer spectra of antimony compounds, with large absorption intensity of ca. 30% were obtained by cooling both a Ca121mSnO3source and an absorber at 20 K using a cryostat incorporating a closed cycle refrigerator and counting the 7.4keV escape peak generated by the 37.1keV γ-rays in a Xe-CO2proportional counter. The121Sb Mössbauer spectroscopy was found to be very useful in characterizing various substances containing antimony atoms.