Shoji Motoishi

In vivo recognition of cyclopentadienyltricarbonylrhenium (CpTR) derivatives

In vivo metabolism of [(188)Re]tricarbonyl(carboxycyclopentadienyl)rhenium ([(188)Re]CpTR-COOH) and its glycine conjugate ([(188)Re]CpTR-Gly) was investigated to estimate the applicability of cyclopentadienyltricarbonylrhenium (CpTR) compounds to (186/188)Re-labeling reagents for polypeptides and peptides. Both [(188)Re]CpTR derivatives were stable after incubation in a buffered-solution and in murine plasma at 37 degrees C for 6 h. Plasma protein binding was hardly observed with the two derivatives. However, different biodistribution and metabolic fates were observed with the two CpTR derivatives. While more lipophilic [(188)Re]CpTR-COOH was excreted by both hepatobiliary and urinary excretion, the majority of less lipophilic [(188)Re]CpTR-Gly was excreted by urinary excretion. In addition, while [(188)Re]CpTR-Gly was rapidly excreted into urine as its intact structure, [(188)Re]CpTR-COOH was metabolized to more hydrophilic compounds including its glycine conjugate, [(188)Re]CpTR-Gly. Renal excretion of [(188)Re]CpTR-Gly was significantly reduced in probenecid retreated mice. The present studies reinforced that CpTR core remained stable under biological environment. CpTR-COOH was partially recognized as an aromatic acid and was metabolized as such. However, glycine conjugation rendered CpTR-COOH hydrophilic enough to be excreted into urine without further metabolism. These findings suggested that radiolabeling reagents that liberate [(186/188)Re]CpTR-Gly from covalently conjugated (186/188)Re-labeled polypeptides and peptides by the action of renal brush border enzymes would be useful to reduce renal radioactivity levels.

Test Production of Tritium in 3 TBq Level from Neutron-Irradiated 6Li-AL Alloy Targets

Equipments were constructed for the development of tritium production technology. Gaseous tritium in a level of 3 TBq (∼80 Ci) was extracted from neutron-irradiated 6Li-Al alloy by heating at 1,073 K under vacuum and collected in an activated-uranium getter. The recovery of the tritium was 90% or more and the isotopic purity of the product was about 50%. Throughout the production experiment, no release of tritium out of the equipments to the environment was observed.

High Thermo-Separation Efficiency of 99mTc from Molten 100MoO3 Samples by Repeated Milking Tests

High thermo-separation efficiencies of about 90 and 70% have been obtained for the first time for 99mTc from molten MoO3 samples containing 99Mo with thicknesses of 4.0 and 8.5 mm, respectively, by repeated milking tests. 99Mo was produced with 100Mo(n,2n)99Mo by using neutrons from 3H(d,n)4He. The thermo-separation efficiency was determined by measuring the 141 keV γ-ray yield of 99mTc within the molten MoO3 samples with a radiation detector as a function of the furnace temperature and time. The diffusion coefficients of 99mTc in the molten MoO3 samples were estimated in order to help understand the high thermo-separation efficiency. The present result solves a long-standing problem of decreasing the separation efficiency of 99mTc from MoO3 while increasing the sample mass or repeating sublimation in thermo-separation, and will bring a major breakthrough to obtain high-quality 99mTc from MoO3 irradiated by accelerator-neutrons (protons) or reactor-neutrons.

Experimental radioimmunotherapy with 186Re-MAG3-A7 anti-colorectal cancer monoclonal antibody: comparison with 131I-counterpart.

A murine IgG1 against aMr 45 kD tumor-associated glycoprotein in human colorectal cancer, A7, was radiolabeled with186Re by a chelating method with a mercaptoacetyltriglycine (MAG3). Its specific activity was 119 MBq/mg, which would be high enough for a therapeutic purpose, and its immunoreactivity was preserved well as was131I-A7 labeled by the chloramine-T method. Growth of human colon cancer xenografts, 9.14±0.44 mm in diameter, in nude mice was significantly suppressed by an intravenous dose of 4.48 MBq of186Re-A7. The therapeutic outcome with186Re-A7 was better than that with 4.63 MBq of131I-A7. Toxicity of treatments assessed by body weight change was similar with both conjugates. These results are likely caused by the tumor size and more favorable physical properties of186Re than those of131I.

Measurement of the Effective Neutron Capture Cross Section of Cesium-134 by Triple Neutron Capture Reaction Method

The measurement of effective neutron capture cross section( ) of 134Cs was carried out with a method using a triple neutron capture reaction,133Cs(n, γ)134Cs(n,γ)135Cs(n, γ)136Cs. The target used for the experiment was natural cesium(133Cs), and was irradiated for 23 days and 17 hours in the reactor JRR-3 at Japan Atomic Energy Research fnstitute(JAERI). The neutron field of the reactor was monitored by Au/Al and Co/Al alloy wires. A high purity Ge detector was employed for the measurement of γ-rays from the irradiated target and monitor wires. Gamma-rays emitted in the decay of 134Cs and 136Cs nuclides induced by single and triple neutron capture reactions of 133Cs were seen at the energies of 563, 569. 605, 796, 802, 819, 1,039, 1,048, 1,168 and 1,235 keV. Decays of the 819 and the 1,048 keV γ-ray intensities were followed; it was confirmed that these γ-rays originated in the 136Ba, the decay product of 136Cs. Data obtained were analyzed with values of neutron capture cross sections of 133Cs and 135Cs. ...

SPECT Imaging of Mice with 99mTc-Radiopharmaceuticals Obtained from 99Mo Produced by 100Mo(n,2n)99Mo and Fission of 235U

The distribution of 99mTc-radiopharmaceutical in mouse was determined by single photon emission computed tomography (SPECT) for the first time using 99mTc, which was separated by thermochromatograp...

Quality of99mTcO4−from99Mo Produced by100Mo(n,2n)99Mo

The pharmaceutical quality of 99mTc pertechnetate solution obtained from 99Mo, the 100Mo(n,2n) reaction product, was investigated for the first time with an emphasis on the nonradioactive Mo conten...

Thermal neutron cross section and resonance integral of the reaction of135Cs(n,γ)136Cs: Fundamental data for the transmutation of nuclear waste

To determine the cross sections of the135Cs(n,γ)136Cs reaction, a sample of135Cs included in a “standardized solution” of137Cs was used as a target and irradiated in a reactor. The ratio of the atom number of135Cs to that of137Cs was determined to be 0.89±0.03 with a quadrupole mass spectrometer. The thermal cross section and the resonance integral measured in this study were determined to be 8.3±0.3 and 38.1±2.6 b respectively.

99Mo Yield Using Large Sample Mass of MoO3 for Sustainable Production of 99Mo

A neutron source from the C(d,n) reaction has the unique capability of producing medical radioisotopes such as 99Mo with a minimum level of radioactive waste. Precise data on the neutron flux are crucial to determine the best conditions for obtaining the maximum yield of 99Mo. The measured yield of 99Mo produced by the 100Mo(n,2n)99Mo reaction from a large sample mass of MoO3 agrees well with the numerical result estimated with the latest neutron data, which are a factor of two larger than the other existing data. This result establishes an important finding for the domestic production of 99Mo: approximately 50% of the demand for 99Mo in Japan could be met using a 100 g 100MoO3 sample mass with a single accelerator of 40 MeV, 2 mA deuteron beams.

Quality of 99m TcO 4 − from 99 Mo Produced by 100 Mo( n ,2 n ) 99 Mo

The pharmaceutical quality of 99mTc pertechnetate solution obtained from 99Mo, the 100Mo(n,2n) reaction product, was investigated for the first time with an emphasis on the nonradioactive Mo conten...