Biomedical subjects

Tatsuo Ido

Publications and source records attributed to Tatsuo Ido.

10 recordsLinked to original sources

PubMed2005

Increased [18F]fluorodeoxyglucose accumulation in right ventricular free wall in patients with pulmonary hypertension and the effect of epoprostenol.

OBJECTIVES: We examined whether right ventricular (RV) [(18)F]fluorodeoxyglucose (FDG) accumulation is increased in patients with pulmonary hypertension using gated positron emission tomography (PET) and whether RV FDG accumulation changes after therapy with epoprostenol. BACKGROUND: Myocardial glucose utilization is increased in animal models with ventricular pressure overload. METHODS: We performed gated FDG-PET in 24 patients with pulmonary hypertension. The RV standardized uptake value (SUV) of FDG was corrected for the partial volume effect based on the wall thickness measured by electron-beam computed tomography or magnetic resonance imaging. RESULTS: The corrected RV SUV of FDG was significantly correlated with the pulmonary vascular resistance, mean pulmonary artery pressure, right atrial pressure, RV wall stress, and plasma brain natriuretic peptide levels, but not with the RV wall thickness and mass. After pulmonary vasodilator therapy with epoprostenol for three months, the corrected RV SUV of FDG significantly decreased in the responders, but not in the non-responders, and the percentage change of the corrected RV SUV of FDG was significantly correlated with the percentage change of the pulmonary vascular resistance (r = 0.78; p < 0.01) and RV systolic wall stress (r = 0.76; p < 0.05). CONCLUSIONS: The RV FDG accumulation corrected for the partial volume effect was significantly increased in accordance with the severity of the RV pressure overload (i.e., the RV peak-systolic wall stress) in patients with pulmonary hypertension. Furthermore, the corrected RV FDG accumulation was decreased after the treatment with epoprostenol in accordance with the degree of reduction in the pulmonary vascular resistance and RV peak-systolic wall stress.

Antihypertensive Agents↗

PubMed2005

Reliability of one-point blood sampling method for calculating input function in Na18F PET.

OBJECTIVE: Conventional methods of quantitative Na18F positron emission tomography require multiple arterial blood sampling in order to obtain the input function, and the procedures are invasive and complicated. This study aims to establish a simplified and reliable technique for obtaining the input function. METHODS: Multiple arterial blood sampling was performed on 12 persons. The time point for one-point sampling was determined as the time when (1) the plasma radioactivity obtained showed the highest correlation to the real integrated value, which was calculated from the input function, and (2) the coefficient of variation of the real integrated value divided by plasma radioactivity obtained at each time point became the minimum. Scaling factors were obtained in order to estimate the plasma radioactivity at each time point, and a reference table was produced in order to estimate the input function. RESULTS: The optimal timing for one-point sampling was 12 min after intravenous injection of Na18F. The estimated integrated value obtained from arterial blood sampling at 12 min and the reference table was highly correlated with the real integrated value (P<0.001). Levels of plasma radioactivity of arterial blood and venous blood were almost the same at 12 and 40 min after Na18F injection. Percentage errors in the estimation of the integrated value were 2.63% (n=12) for the arterial blood collected at 12 min and 4.14% (n=12) for the venous blood collected at 30 min. CONCLUSIONS: This simplified method is clinically applicable and would replace traditional methods that require multiple blood sampling.

Adult↗

PubMed2005

Myocardial 11C-diacylglycerol accumulation and left ventricular remodeling in patients after myocardial infarction.

UNLABELLED: Left ventricular (LV) remodeling after myocardial infarction (MI) is a maladaptive process that increases the risk of heart failure and death. The myocardial phosphoinositide cycle, which is located downstream from several neurohumoral factors, plays a crucial role in LV remodeling. Our animal studies demonstrated that 1-[1-11C]butyryl-2-palmitoyl-rac-glycerol (11C-DAG) can be used to visualize regions with an activated phosphoinositide cycle. Therefore, we examined whether myocardial 11C-DAG accumulation assessed by PET is relevant to LV enlargement and systolic dysfunction in post-MI patients. METHODS: We performed PET with 11C-DAG in 13 post-anteroseptal MI patients and 4 healthy volunteers. We placed regions of interest on the noninfarcted myocardium and calculated the myocardium-to-left atrial (LA) chamber ratio of 11C-DAG accumulation. RESULTS: The myocardium-to-LA chamber ratio of 11C-DAG was significantly higher in the post-MI patients (mean +/- SD, 1.73 +/- 0.35) compared with that of the healthy volunteers (mean +/- SD, 1.25 +/- 0.13; P < 0.05). In the post-MI patients, the myocardium-to-LA chamber ratio of (11)C-DAG was significantly correlated with the LV end-diastolic volume index (r = 0.79, P < 0.01) and the plasma concentration of brain natriuretic peptide (r = 0.85, P < 0.001) and negatively correlated with the LV ejection fraction (r = -0.69, P < 0.01). CONCLUSION: These findings suggest that the myocardial 11C-DAG accumulation assessed by PET is relevant to LV enlargement, LV systolic dysfunction, and humoral activation in post-MI patients. This new imaging strategy based on intracellular signaling may contribute to the assessment and treatment of post-MI patients.

Adult↗

PubMed2003

Improved synthesis of pure [18F]fluoro-compounds for PET studies from bromo-compounds.

For preparing [18F]labeled compounds free from bromo-compounds for PET (positron emission tomography) studies, we propose the following two processes in which no separation is needed between the fluoro-compound and bromo-compound : (1). the bromo-compound is first converted into O-tosylate, which is then [18F]fluorinated; and (2). after [18F]fluorination of the bromo-compound, its excess is converted into an easily separable compound, e.g., phthalimide-compound. Direct tosylation with silver tosylate was effected in 65-85% yield for most commercial bromo-compounds, and with potassium phthalimide, the bromo-compounds in cold run were converted easily into phthalimide-compounds in 84-90% yield.

Chemistry, Organic↗

PubMed2003

Tumor detection using 18F-labeled matrix metalloproteinase-2 inhibitor.

Matrix metalloproteinase-2 (MMP-2) is a key enzyme involved in tumor invasiveness. (2R)-2- [4-(6-[(18)F]Fluorohex-1-ynyl)-benzenesulfonylamino]-3-methylbutyric acid ([(18)F]SAV03), a new fluorine-18 labeled MMP-2 inhibitor developed for tumor imaging with PET, was biologically evaluated using in vivo tumor model. Enzymatic MMP-2 assay of SAV03 yielded an IC(50) value of 1.9 microM. Biodistribution study of [(18)F]SAV03 using Ehrlich tumor bearing mice showed that the uptake in tumor was higher than in other organs, except for the liver, small intestine, and bone. When [(18)F]SAV03M, a methyl ester of [(18)F]SAV03, was used as a prodrug, the uptake in liver at 30 min after injection decreased by half and that in tumor increased by 2.4 times, compared with [(18)F]SAV03. Radio-thin-layer chromatographic analysis of [(18)F]SAV03M metabolites revealed that administered [(18)F]SAV03M was easily converted to the parent drug in vivo and accumulated in tumor tissue. Thus, [(18)F]SAV03M is suitable as the prodrug of [(18)F]SAV03 with potent efficacy. Whole body autoradiography using [(18)F]SAV03M also indicated tumor-specific accumulation of radioactivity, while higher accumulations in bone and intestinal contents were observed. Our results suggest that [(18)F]SAV03M could be potentially suitable for tumor imaging with PET.

Animals↗

PubMed2003

Brain and heart specific alteration of methamphetamine (MAP) distribution in MAP-sensitized rat.

The repeated administration of methamphetamine (MAP) causes behavioral sensitization in animals. We previously reported that the high accumulation of MAP was observed in the MAP-sensitized animal brain, which suggested that this phenomenon is an important factor in the development or expression of behavioral sensitization. The purpose of the present study is to elucidate the MAP distribution in the MAP-sensitized rat using gas chromatography/mass spectrometry (GC/MS). As a result, the MAP distribution in the heart at 10 min when showing a high accumulation of MAP in the MAP-sensitized rat brain was significantly higher than that of the control rat, whereas no significant differences in the liver, kidney, abdominal muscle, femoral muscle and blood were observed. In the brain and heart, there was no different distribution at 1 min, reflecting only the influx process from blood to brain and heart. On the contrary, there was the significant difference at 10 min, reflecting both the influx and efflux process, suggesting that the efflux process of MAP from brain or heart to blood may be slow due to MAP sensitization. In conclusion, it was clear that the brain and heart specific alteration of the MAP distribution occurred in the MAP sensitization. It was considered that the high accumulation of MAP in the MAP-sensitized rat brain may be related to the expression of behavioral sensitization and that the delayed efflux of MAP in the MAP-sensitized rat heart may be connected with the cardiac toxicity.

Animals↗

PubMed2003

Evaluation of the binding characteristics of [5-(11)C-methoxy]Donepezil in the rat brain for in vivo visualization of acetylcholinesterase.

Donepezil, an acetylcholinesterase (AChE) inhibitor, has not been evaluated for its binding characteristics using a radioactive tracer, although its inhibitory action on AChE has been studied. The aim of this research is to examine whether AChE can be visualized in vivo and in vitro with [(11)C]donepezil. [5-(11)C-methoxy]Donepezil was synthesized by O-methylation using [(11)C]methyl triflate. The binding of [(11)C]donepezil to brain homogenates was higher in the brain stem and striatum, and it was lowest in the cerebellum. The in vitro autoradiographic study successfully demonstrated the specific binding of [(11)C]donepezil to AChE in the rat brain. The IC(50) value of binding was approximately 10 nM, which is comparable to the reported value for inhibiting enzyme activity (6 nM). Saturation experiments revealed that the B(max) and K(d) of [(11)C]donepezil binding in vitro are 65 fmol/mg tissue and 39.8 nM, respectively. In accordance with the in vitro bindings, the in vivo distribution of [(11)C]donepezil was heterogeneous in the rat brain. In the blocking experiments, the heterogeneous distribution disappeared in the presence of a large amount of unlabeled donepezil. These data suggest that [5-(11)C-methoxy]donepezil can be potentially useful to image AChE non-invasively in the human brain by positron emission tomography.

Acetylcholinesterase↗

PubMed2002

Effect of angiotensin converting enzyme inhibition on myocardial phosphoinositide metabolism visualised with 1-[1-11C]-butyryl-2-palmitoyl-rac-glycerol in myocardial infarction in the rat.

We recently reported that myocardial phosphoinositide (PI) metabolism can be visualised by 1-[1-11C]-butyryl-2-palmitoyl-rac-glycerol (11C-DAG) in rats with myocardial infarction (MI). Angiotensin II, the receptors for which are expressed predominantly in infarcted areas with active fibrogenesis rather than in non-infarcted regions, is involved in the upstream signalling systems of PI metabolism and plays an important role in the process of left ventricular (LV) remodelling after MI. We therefore hypothesised that the distribution of 11C-DAG after MI may be affected by the inhibition of angiotensin converting enzyme, which is one of the most important factors in the development of LV remodelling after MI. Rats were injected with 11C-DAG after 3 or 10 weeks of treatment with captopril or no treatment following coronary artery ligation, and quantitative autoradiography was performed. Cells occupying the infarcted region were identified by immunohistochemistry. Compared with untreated rats, treatment with captopril for 3 weeks after MI elicited a reduction in the 11C-DAG uptake in the infarcted region (P<0.05) but not in the non-infarcted region, and was associated with a 22% decrease in the heart weight/body weight ratio. The thallium-201 distribution in the infarcted area was similarly low in the rats with and rats without the 3-week captopril treatment after MI. Abundant macrophages and myofibroblasts occupied the infarcted area in both rats with and rats without the captopril treatment for 3 weeks after MI. The 11C-DAG radioactivity in the infarcted region in the untreated rats was lower 10 weeks after MI than 3 weeks after MI (P<0.01). This finding was in agreement with the results of immunohistochemistry demonstrating that the number and size of macrophages and myofibroblasts were remarkably reduced in rats 10 weeks after MI compared with 3 weeks after MI. Captopril treatment for 10 weeks after MI did not decrease the 11C-DAG radioactivity in the infarcted area further. These data suggest that 11C-DAG is useful for visually detecting regions with activated PI metabolism after MI, and that captopril reduces PI metabolism in the infarcted region in the relatively early phase of MI, which might contribute to the attenuation of ventricular remodelling.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2002

Initial and subsequent approach for the synthesis of 18FDG.

2-deoxy-2-[18F] fluoro-D-glucose (18FDG) was developed in 1976 in a collaboration between scientists at the National Institutes of Health, the University of Pennsylvania, and Brookhaven National Laboratory. It was developed for the specific purpose of mapping brain glucose metabolism in living humans, thereby serving as a tool in the basic human neurosciences. With 18FDG it was possible for the first time to measure regional glucose metabolism in the living human brain. Around the same time, the use of 18FDG for studies of myocardial metabolism and as a tracer for tumor metabolism were reported. After the first synthesis of 18FDG via an electrophilic fluorination with 18F gas (produced via the 20Ne(d,alpha)18F reaction), small volume enriched water targets were developed that made it possible to produce large quantities of [18F]fluoride ion via the high-yield 18(p,n)18F reaction. This was followed by a major milestone, the development of a nucleophilic fluorination method that produced 18FDG in very high yield. These advances and the remarkable properties of 18FDG have largely overcome the limitations of the 110-minute half-life of 18F so that 18FDG is now available to most regions of the United States from a number of central production sites. This avoids the need for an on-site cyclotron and chemistry laboratory and has opened up the use of 18FDG to institutions that have a positron emission tomography (PET) scanner (or other imaging device) but no cyclotron or chemistry infrastructure. Currently, 18FDG is used by many hospitals as an off the shelf radiopharmaceutical for clinical diagnosis in heart disease, seizure disorders, and oncology, the area of most rapid growth. However, it remains an important tool in human neuroscience and in drug research and development.

Animals↗

PubMed2002

[Short time bacterial endotoxins test for positron emission tomography by means of positively charged filters].

Positron emission tomography (PET) radiotracers have very short physical half-lives. It is hard to complete a bacterial endotoxins test prior to release from medical institutes. For endotoxin quantitative determination, limulus amebocyte lysate (LAL) reagent and kinetic-turbidimetry system were previously developed. We investigated the possibility of a short time test by means of positively charged filters. As a result of this study, the effects of positively charged filters on endotoin removal were over 99.5% for [18F]FDG and [18F]NaF, which were contaminated with the indicated concentration of endotoxin. Combining this filter and the kinetic-turbidimetric method, it was possible to complete a bacterial endotoxins test in 5 min prior to the patient's administration. This test should be required prior to release for PET radiopharmaceutical quality control. It has been suggested that this combination is a good method for this purpose.

Drug Contamination↗