Hiromitsu Matsuoka

Uptake and transport of positron-emitting tracer (18F) in plants☆

Abstract The transport of a positron-emitting isotope introduced into a plant was dynamically followed by a special observation apparatus called ‘Positron-Emitting Tracer Imaging System’ to observe the damage and recovery functions of plants in vivo. In the system, annihilation γ-rays from the positron emitter are detected with two planar detectors (5 × 6 cm2). The water containing ca. 5 MBq/ml of 18F was fed to the cut stem of soybean for 2 min and then the images of tracer activity were recorded for 30–50 min. When the midrib of a leaf near the petiole was cut just before measurement, the activity in the injured leaf was decreased but detected even at the apex. This result suggests that the damaged leaf recovered the uptake of water through the lamina. Maximum tracer activities in leaves of unirradiated plant were observed within 10 min, whereas those of irradiated plant at 100 Gy were observed after over 25 min. The final activity of irradiated plant after 30 min was lower than that of unirradiated plant. In case of beans, there was a difference in the absorption behavior of the 18F-labeled water between unirradiated and irradiated samples. These results show that the system is effective to observe the uptake and transportation of water containing positron emitting tracer for the study of damage and recovery functions of plants.

Production method of no-carrier-added186Re

No-Carrier-Added186Re was produced using the186W(p,n)186Re nuclear reaction with 13.6 MeV protons on thick targets of 99.79% isotopically enriched186WO3. The theoretical excitation functions for producing186Re, and possible radionuclidic impurities of182Re,183Re, and184Re were calculated using the ALICE code. Cross-sections of the186W(p,n)186Re reaction were measured up to 20 MeV using the stacked target method with thin foils of natural composition tungsten metal. The experimental and theoretical excitation functions were in good agreement. Targetry used at the TIARA cyclotron, and a radiochemical separation scheme for186Re are described.

Production of no-carrier-added 177Lu via the 176Yb(n, &;#947;)177Yb &;#8594; 177Lu process

No-carrier-added 177Lu was produced by the 176Yb(n,γ)177Yb→177Lu process using enriched 176Yb2O3. The radiochemical separation of the nca 177Lu from the macroscopic ytterbium target was investigated by reversed-phase ion-pair HPLC. Effects of the concentrations of 2-hydroxyisobutyric acid and 1-octanesulfonate in the eluent, the amount of Yb2O3, the type and length of the C18 column on the separation efficiency were examined. Under optimum conditions, the nca 177Lu was obtained in radiochemically pure form from 5 mg of Yb2O3 with a separation yield of 84%.

Production of positron emitters and application of their labeled compounds to plant studies

The positron emitters11C,13N and18F and their labeled compounds have been produced for studies on plants using a newly developed positron emitting tracer imaging system. Although this system covers, at present, a limited area in a plant, the distribution of the positron emitter fed into the plant can be visualized dynamically. Further development of positron-emitter-labeled compounds is expected to elucidate the physiological function of plants in vivo.

Excitation Functions of Rhenium Isotopes on the natW(d, xn) Reactions and Production of No-carrier-added 186Re

Experimental cross sections for the reactions 186W(d, 2n)186Re, natW(d, xn)181-184Re and 186W(d, p)187W are measured up to 34 MeV using the stacked target method. The values obtained are compared with cross sections calculated using the ALICE code. The experimental and theoretical excitation functions are in reasonable agreement except for the l86W(d, p)187W reaction.

Uptake and transport of positron-emitting tracer in irradiated plants

The transport of l8F-water introduced into irradiated plants was followed dynamically by the detection of annihilation γ -rays from a positron emitter using a “Positron-Emitting Tracer Imaging System”. Tracer activities at the vein of top leaf of unirradiated soybean (Glysine max) were observed in a short time, whereas those in plants irradiated with a doses up to 100 Gy were delayed with increase in dose. In the case of rose (Rosa sp. Rote Rose), radiation using a dose of 800 Gy for disinfestation as a quarantine procedure inhibited flowering. Uptake and transport of 18F-water through the cut stem was changed significantly by irradiation. These results show that the system is effective in observing the damage of irradiated plants and is useful for the study of physiological functions of plants.

Analysis of 188Re-EDTMP complexes by HPLC and ultrafiltration

Abstract High performance liquid chromatography (anion-exchange, reversed-phase ion-pair and gel permeation chromatography) and ultrafiltration have been employed to analyze 188Re-ethylenediamine-N,N,N´,N´-tetrakis(methylenephosphonic acid) complexes ( 188Re-EDTMP), prepared from the tin chloride reduction or sodium borohydride reduction in the presence or absence of rhenium carrier. The HPLC analysis showed that the 188Re-EDTMP complexes were mixtures of components and the distribution of the components was dependent upon the total amount of rhenium present and the reducing agents (SnCl2, NaBH4). The ultrafiltration analysis showed that the distribution of nominal molecular weight of 188Re-EDTMP was dependent upon the presence of rhenium carrier and the reducing agents. In addition, it was found that the proportion of chemical species with bigger molecular weight in no-carrier-added 188Re(SnCl2)-EDTMP was larger than that in carrier-added 188Re(SnCl2)-EDTMP.

TANTALUM-183 : CYCLOTRON PRODUCTION OF A NEUTRON-RICH BIOMEDICAL TRACER

Abstract No-carrier-added tantalum-183 was produced free of radiotantalum impurities by the 186 W(p,α) 183 Ta nuclear reaction using 13.6 MeV protons on thick targets of isotopically enriched 186 WO 3 . The proton energy was optimum for the simultaneous production of 186 Re and 183 Ta. The ALICE code was used to theoretically determine the optimum irradiation conditions for the production of 183 Ta with proton and deuteron nuclear reactions. A Bio-imaging analyser was used to illustrate the migration of 183 Ta species into a grass plant ( Cyperus microiria steud). 183 Ta has potential applications as a tracer for ecotoxicity studies, and for developmental studies for radiotantalum pharmaceuticals.