Strontium-/Y- are major radionuclides observed in the water samples tested recently at the site of the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company. A simple method of evaluating Sr- concentration in these water samples by measuring β rays from Y- with a GM-detector setup was developed. By applying the precipitation method, Sr- and Y- were separated and quantitatively collected with a filter. β rays from Y- in the filter were measured two times at appropriate intervals by inserting a polyethylene plate of 2 mm thickness as a β-ray absorber. The contribution of γ rays from Cs-134 and Cs-137 to the Y- count rates was quantitatively evaluated using a 10-mm-thick acrylic resin plate. From the parent-daughter relationship between Sr- and Y-, the Sr- concentration was evaluated using the conversion coefficient of Y- count rate (cps) to Sr- concentration (Bq/cm³). It was verified that Sr- concentration of below 0.01 Bq/cm³ in water samples can be correctly measured by this simple method.

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Bacillus laterosporus ATP-dependent deoxyribonuclease has been found to be inhibited by pyridoxal 5'-phosphate. The inhibition is specific for pyridoxal 5'-phosphate and pyridoxal which are required in relatively high concentrations. Pyridoxamine 5'-phosphate, pyridoxamine, and pyridoxine are ineffective. The inhibition is reversed by dilution or dialysis but can be changed to an irreversible inactivation by reduction of the enzyme. pyridoxal 5'-phosphate complex with sodium borohydride. The compound is a competitive inhibitor with respect to DNA but not ATP. Moreover, the presence of DNA substrate protects the enzyme against this inactivation but the presence of ATP shows no effect. The reduced enzyme pyridoxal 5'-phosphate complex displays a new absorption maximum at 325 nm and a fluorescence emission at 390-400 nm when excited at 325 nm which are characteristic for ε-N-(phosphopyridoxyl)lysine. Thus, B. laterosporus DNase appears to have an essential lysine residue at the DNA binding site of the enzyme, and the enzyme possesses two different active sites, a DNA binding site and an ATP binding site.

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To construct a non-clinical database for drug-induced QT interval prolongation, the electrophysiological effects of 11 positive and 10 negative compounds on action potentials (AP) in guinea-pig papillary muscles were investigated in a multi-site study according to a standard protocol. Compounds with a selective inhibitory effect on the rapidly activated delayed rectifier potassium current (I_Kr) prolonged action potential duration at % repolarization () in a concentration-dependent manner, those showing Ca²⁺ current (I_Ca) inhibition shortened APD₃₀, and those showing Na⁺ current (I_Na) inhibition decreased action potential amplitude (APA) and V_max. Some of the mixed ion-channel blockers showed a bell-shaped concentration-response curve for , probably due to their blockade of I_Na and/or I_Ca, sometimes leading to a false-negative result in the assay. In contrast, all positive compounds except for terfenadine and all negative compounds with I_Kr-blocking activity prolonged APD30–

90

regardless of their I_Na- and/or I_Ca-blocking activities, suggesting that APD30–

90

is a useful parameter for evaluating the I_Kr-blocking activity of test compounds. Furthermore, the assay is highly informative regarding the modulation of cardiac ion channels by test compounds. Therefore, when

APD₉₀

and APD30–

90

are both measured, the action potential assay can be considered a useful method for assessing the risk of QT interval prolongation in humans in non-clinical safety pharmacology studies.
Supplementary material (Appendix): available only at http://dx.doi.org/10.1254/jphs.QT-A1

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Activity on the international standardization of the test methods for industrial superconductors is introduced, which is authorized by IEC/TC (Superconductivity). A brief history and strategy of the organization are explained. The substantial work involved to discuss and prepare the draft for each item is left to the respective international working group. At present, 8 working groups cover the field of superconductivity and related properties; terminology, critical current, residual resistance ratio, copper ratio, mechanical property and surface resistance. One of them, the test method of critical current for Cu/Nb-Ti composite superconductors, will soon be published as an international standard. The domestic activity in Japan supporting international standardization is supervised by the Japanese National Committee of IEC/TC. The mission of the JNC is the following three activities; support of the international activity as a secretary country, translation of international standards to JIS and supervision of domestic activities. The actual test methods are proposed and carried out by the New Materials Center and Japanese Fine Ceramics Association. It is emphasized that establishing good liaison with groups such as VAMAS concerning the fundamental aspects of standardization is crucial to promote effective international collaboration.

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　腫瘍治療法の一つである放射線治療は、他の治療法と比較して患者への負担が少ないことが利点である。しかしながらX線を使用した従来の治療法の場合、放射線単独での固形腫瘍の治療は困難であるのが現状である。放射線医学総合研究所にある重粒子加速器HIMAC (heavy ion medical accelerator in Chiba)では、炭素イオン線による腫瘍治療が行われている。腫瘍以外の臓器への影響が小さく、腫瘍に対して効率的に照射が可能なこと、従来のX線等と比較して治療効果が高いことからその有用性が期待されている。その一方で、従来のX線による放射線治療に加えて、薬剤を併用することにより腫瘍をより効果的に治療するための研究もすすめられている。その中で、野口らは放射線応答で重要な役割を持つシグナル分子に着目した。Hsp (heat shock protein )はそのような分子の一つであり、ストレスによって発現が増加することが知られている。Hspを阻害することにより、下流にある癌化関連タンパク質の発現も抑えられることが考えられる。このことから野口らは、Hspの分子治療標的薬剤である17 – allylamino – 17 - demethoxygeldanamycin (17AAG)を用いて、X線との併用による放射線増感効果を検討した (Noguchi et al., Biochem Biophys Res Commun, 2006)。その結果、腫瘍細胞に対してのX線との併用による有意な治療効果をみることができた。これを踏まえて、炭素イオン線を用いて17AAGとの併用による治療効果をマウスのin vivoモデルで検討し、X線でのin vivoモデルの実験結果、in vitroでの実験結果と比較して発表する。

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