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Biomedical subjects

T Ido

Publications and source records attributed to T Ido.

At least 127 records · Page 7Linked to original sources
PubMed1991

Labeling of histamine H1-receptors in vivo: a compartment model analysis and positron emission tomographic imaging.

Binding of [3H]-pyrilamine to guinea-pig brain in vivo was studied and analyzed kinetically on the basis of a four-compartment model to establish the method of analysis for the in vivo binding. The pharmacological properties of the [3H]-pyrilamine binding in vivo were similar to those of the in vitro binding to brain homogenate. The distribution of histamine H1-receptors in dog brain, which was obtained by positron emission tomography (PET) with [11C]-pyrilamine or doxepin as a tracer, was in good correlation to that obtained by the in vitro binding method. We finally applied this in vivo binding method to a living healthy human to reveal the distribution of H1-receptor in the brain.

Animals↗
PubMed1991

Measurement of L-[methyl-11C]methionine in human plasma.

The routine measurement of L-[methyl-11C]methionine in human plasma after i.v. injection of the tracer is described. The protein-free plasma metabolites of the tracer were analyzed using a cation-exchange column (Aminex A-6) eluted with a pH 4.25 citrate buffer. The ratios of L-[methyl-11C]methionine for the total radioactivity decreased gradually, and the standard deviations among 19 humans were relatively small for 30 min: 97.2 +/- 1.4%, 5 min; 92.6 +/- 2.1%, 10 min; 89.4 +/- 4.0%, 15 min; 84.1 +/- 3.1%, 20 min; 73.1 +/- 9.8%, 30 min; 45.0 +/- 16.8%, 60 min. A convenient analysis using a Bond elute SCX cartridge showed slightly larger ratios than those measured by liquid chromatography.

Adolescent↗
PubMed1991

Synthesis and radiation dosimetry of 4-borono-2-[18F]fluoro-D,L-phenylalanine: a target compound for PET and boron neutron capture therapy.

The 18F-labeling of 4-borono-D-L-phenylalanine (BPA), a potential target compound for cancer treatment with boron neutron capture therapy, is described. By direct fluorination of BPA with [18F]AcOF or [18F]F2 followed by HPLC separation, 4-borono-2-[18F]fluoro-D,L-phenylalanine was prepared with radiochemical yields of 25-35% and with a radiochemical purity of over 99%. The tissue distribution study showed that the compound has potential as a tracer for pancreas imaging with positron emission tomography. Radiation dosimetry is also described.

Animals↗
PubMed1991

Potential radiopharmaceuticals labeled with titanium-45.

The potential of some compounds labeled with cyclotron-produced titanium-45 (45Ti) as radiopharmaceuticals was studied. Properties of colloid formation of 45TiOCl2 or 45TiO-phytate in vivo resulted in the highest radioactivity uptake in the rat liver, followed by the spleen, suggesting potential for imaging the reticuloendothelial system. Three 45TiO-complexes with diethylenetriaminepentaacetic acid, citric acid and human serum albumin showed the highest radioactivity levels in the blood over 6 h. The binding of the 45Ti with plasma transferrin in vitro and in vivo suggested that these compounds can be used for estimating the blood volume. Also, potential as an indicator representing the breakdown of the blood-brain barrier in the rat was demonstrated by autoradiography.

Animals↗
PubMed1991

4-Borono-2-[18F]fluoro-D,L-phenylalanine as a target compound for boron neutron capture therapy: tumor imaging potential with positron emission tomography.

We studied the tumor uptake and metabolism of 4-borono-2-[18F]fluoro-D,L-phenylalanine ([18F]FBPA), an 18F-labeled target compound for boron neutron capture therapy. In mice bearing FM3A mammary carcinoma, the accumulation of [18F]FBPA in the FM3A for the first 2 h, and its decrease in all other tissues, resulted in high FM3A-to-tissue uptake ratios. In the FM3A, the tracer was stable for metabolic alteration, which was in contrast to the gradual increase of protein-bound radioactivity in plasma. Imaging of FM3A was demonstrated by whole body autoradiography. [18F]FBPA has potential for use as a PET tracer for tumor imaging with high contrast, even in the pancreas.

Animals↗
PubMed1991

Possibility for tumor detection with fatty acid analogs.

Newly synthesized 17-[18F]fluoro-3-methylheptadecanoic acid ([18F]BMHDA), 16-[18F]fluoropalmitic acid ([18F]PA) and 15-(p-[125I]iodophenyl)-3-R,S-methylpentadecanoic acid ([125I]BMIPP), fatty acid tracers, were examined for the possibility of tumor imaging using 10 tumor models in rats and mice. The highest tumor/muscle ratios with [18F]BMHDA were 2.3 using rat tumor AH109A and 1.9 using mouse tumor B16F1 (tumor accumulation 0.41 +/- 0.05, 4.29 +/- 0.77% ID/g, respectively). Tumor/muscle ratios with [125I]BMIPP and [18F]PA were lower than those with [18F]BMHDA. Labeled fatty acids seem to have a lower potential for tumor detection.

Animals↗
PubMed1991

Metabolic fates of 2'-deoxy-5-[18F]fluorouridine in tumor-bearing mice and human plasma.

The metabolic fate of 2'-deoxy-5-[18F]fluorouridine ([18F]FdUrd), a useful positron emission tomography (PET) tracer of nucleic acid metabolism in tumors, was investigated in mice and humans. A rapid increase in labeled catabolites was found in mouse and human plasma. In mouse FM3A mammary carcinoma, the corresponding catabolites were also detected in addition to metabolites which were activated by the nucleic acid metabolism. From a biodistribution study of beta-[3H]alanine, alpha-[18F]fluoro-beta-alanine, a major catabolite, was assumed to be taken up twice as much by tumor than by the brain. Nucleic acid metabolism in brain tumors by [18F]FdUrd-PET may be assessed using normal brain regions as a reference.

Animals↗
PubMed1991

Diurnal variation of intraocular pressure of normal-tension glaucoma. Influence of sleep and arousal.

The measurement of the diurnal variation of intraocular pressure (IOP) is indispensable for the diagnosis of normal-tension glaucoma (NTG). To determine the diurnal variation of IOP, its measurement has to be made repeatedly for 24 hours, which interferes with patients's sleep at night and may influence the physiologic IOP variation. The authors studied the IOP variation in 82 NTG suspects, whose IOP was first measured every 2 hours for 24 hours. The following night they were suddenly aroused without any notice and IOP was measured. The diurnal IOP variation of NTG patients was found to be similar to that of the normal population and there was no significant difference in the IOP values at the same time points on the two successive nights. Sleep may have little, if any, influence on diurnal IOP variation in NTG patients.

Adult↗
PubMed1991

Absorbed dose estimates in positron emission tomography studies based on the administration of 18F-labeled radiopharmaceuticals.

Absorbed doses were estimated after intravenous administration of 18F-labeled radiopharmaceuticals in Positron Emission Tomography (PET) studies. These radiopharmaceuticals, [18F]-2-Fluoro-2-Deoxy-D-Glucose (FDG), 6-[18F]Fluoro-L-Dopa (FDOPA) and 18F-5-Fluorodeoxyuridine (FdUR), are used in clinical research at the Cyclotron and Radioisotope Center of Tohoku University. Radiopharmaceutical biokinetic values were measured in humans or extrapolated from animal experiments. Selective organ uptake and rapid clearance of activity from the blood were observed. High activity in the bladder contents of humans was found. Calculations were made by the MIRD method, modified to account for the differences in physique and organ mass between the Caucasian Reference Man and the Japanese one. The bladder wall receives the highest dose (more than 1.23 x 10(-1) mGy/MBq) when any of these compounds are administered. Other organs receiving high doses are the heart, brain and kidneys from FDG; the kidneys and pancreas from FDOPA, and the kidneys and small intestine from FdUR. These organs received absorbed doses of more than 2.7 x 10(-2) mGy/MBq. Effective dose equivalents of 2.4 x 10(-2), 2.6 x 10(-2) and 3.3 x 10(-2) mSv/MBq were estimated in the intravenous administration of 18F-FDG, 18F-FDOPA and 18F-FdUR, respectively.

Adult↗
PubMed1991

Measurement of D2 dopamine receptor-specific carbon-11-YM-09151-2 binding in the canine brain by PET: importance of partial volume correction.

Carbon-11-YM-09151-2 binds highly selectively to D2 dopamine receptors in the brain. Using this ligand, D2 dopamine receptor density (Bmax) and affinity (Kd) in canine striatum were measured. After administering various doses of the ligand in nine experiments, regional uptake was followed by repeated PET scanning for up to 80 min. D2 dopamine receptor specific binding at equilibrium was defined as striatal minus occipital activity after partial volume correction. Bmax and Kd were estimated by Scatchard analysis to be 40.3 pmole/ml of tissue and 22.9 nM, respectively. When a low mass dose of the ligand was administered, the bound-to-free ligand ratio in the striatum at equilibrium was consistent with the Bmax/Kd value obtained from the Scatchard analysis. The present study demonstrates the importance of partial volume correction and the Bmax/Kd measurement in a single PET study with carbon-11-YM-09151-2.

Animals↗