Biomedical subjects
Publications and source records attributed to T Kakiuchi.
The synthesis of a mg amount of pure argon containing fullerene allowed the synthesis of the first endohedral superconductors with critical temperatures lower than expected, an indication of the strong influence of the argon atom on the C60 cage.
PET-imaging of the sigma receptors is very helpful to understand processes, e.g., several central nervous system (CNS)-diseases in which the sigma receptors are involved. The [(18)F]fluoroethylated analogs of SA4503 and SA5845 ([(18)F]FE-SA4503 and [(18)F]FE-SA5845) were evaluated in conscious monkeys to estimate its suitability for human application for PET. Conscious monkeys (Macaca Mulatta) were either scanned with [(18)F]FE-SA4503 or [(18)F]FE-SA5845 (n = 3 for both groups, 220-802 MBq). After a dynamic study of 120 min, radioactivity was displaced by intravenous (i.v.) injection of haloperidol (1 mg/kg). One month later the same set of three monkeys were scanned with [(18)F]FE-SA4503 for 120 min and "cold" SA4503 (1 mg/kg) was infused to displace the radioactivity, and the other three monkeys were pretreated with haloperidol (1 mg/kg) before the 120-min PET-scan with [(18)F]FE-SA5845. Cortical areas (cingulate, frontal, occipital, parietal, temporal), striatum, and thalamus showed high radioactivity uptake. Infusion of haloperidol displaced the radioactivity levels of the two radioligands. The same effect was found for [(18)F]FE-SA4503 after SA4503 displacement. Pretreatment with haloperidol blocked the [(18)F]FE-SA5845 binding to give PET-images with low and uniform uptake in the brain. The findings demonstrated the reversible binding of the two radioligands. Metabolite analysis showed that 14% and 23% parent compound of [(18)F]FE-SA5845 and [(18)F]FE-SA4503, respectively, at 120 min postinjection was present in plasma. Kinetic analysis showed that the binding potential of [(18)F]FE-SA5845 was higher in all brain regions than that of [(18)F]FE-SA4503 (4.75-8.79 vs. 1.65-4.04). The highest binding potential was found in the hippocampus, followed by the cortical regions, thalamus, cerebellar hemisphere, striatum and vermis. Both [(18)F]FE-SA compounds bound specifically to cerebral sigma receptors of the monkey and have potential for mapping sigma receptors in the human brain.
Age-related changes in the serotonin 5-HT(1A) receptors in the living brains of conscious young (5.9 +/- 1.8 years old) and aged (19.0 +/- 3.3 years old) monkeys (Macaca mulatta) were evaluated by [carbonyl-(11)C]WAY-100635 and high-resolution positron emission tomography (PET). The regional distribution pattern of [carbonyl-(11)C]WAY-100635 at 60-91 min postinjection was the highest in the cingulate gyrus and hippocampus, high in the frontal and temporal cortices, lower in the occipital cortex, striatum, thalamus, and raphe nuclei, and lowest in the cerebellum in both young and aged monkeys. Graphical Logan plot analysis with metabolite-corrected plasma radioactivity as an input function into the brain was applied to evaluate 5-HT(1A) receptor binding in vivo. Significant age-related decreases in 5-HT(1A) receptor binding were observed only in the frontal and temporal cortices. In the hippocampus, although 5-HT(1A) receptor binding indicated no significant age-related changes, it showed an inverse correlation with individual cortisol levels in plasma. When the 5-HT(1A) receptor agonist 8-OH-DPAT was administered intravenously at a dose of 0.1, 0.3, or 1 mg/kg 30 min after tracer injection, binding of [carbonyl-(11)C]WAY-100635 was displaced in both age groups in a dose-dependent manner. However, the degree of displacement was more marked in young than in aged monkeys. These observations demonstrated the usefulness of [carbonyl-(11)C]WAY-100635 as an indicator of the age-related changes in cortical 5-HT(1A) receptors measured noninvasively by PET. In addition, these observations suggested that the age-related impairment of 5-HT(1A) receptor responses to 8-OH-DPAT might be related to the reduced efficacy of antidepressant therapy in elderly patients with depression.
The effects of ketamine anesthesia on the binding of [(11)C]-labeled cocaine analogs, [(11)C]beta-CFT (2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane) and [(11)C]beta-CIT-FE (N-(2-fluoroethyl)-2beta-carbomethoxy-3beta-(4-iodophenyl)tropane), to the striatal dopamine transporter (DAT) were evaluated in the monkey brain using positron emission tomography (PET). We sequentially measured the kinetics of these labeled compounds in the brains of five young-adult male rhesus monkeys (Macaca mulatta) in the conscious state, followed by those under ketamine anesthesia with continuous infusion (3 and 10 mg/kg/h). After intravenous injection, [(11)C]beta-CFT and [(11)C]beta-CIT-FE were predominantly accumulated in the striatum in both conscious and ketamine-anesthetized states. In the conscious state, the striatal uptake of [(11)C]beta-CFT and [(11)C]beta-CIT-FE continuously increased with time up to 91 min after injection. Continuous infusion of ketamine-induced higher levels of uptake of [(11)C]beta-CFT and [(11)C]beta-CIT-FE into the brain in a dose-dependent manner as compared with conscious state, and kinetic analysis with metabolite-corrected arterial input function indicated that the binding potentials (BP = k(3)/k(4)) of both compounds were elevated by ketamine. Not only [(11)C]beta-CIT-FE but also [(11)C]beta-CFT reached the equilibrium state of specific binding in the striatum within 40-50 min after injection. The present results demonstrated that ketamine significantly alters the DAT availability as measured with [(11)C]beta-CFT and [(11)C]beta-CIT-FE in the brain.
The present study evaluated the effects of methamphetamine and scopolamine on the striatal dopamine D(1) receptor binding, measured by [(11)C]SCH23390, and D(1) receptor-coupled cAMP messenger system, determined as phosphodiesterase type-IV (PDE-IV) activity, were evaluated in the brains of conscious monkeys using positron emission tomography (PET) with microdialysis. When methamphetamine (0.1, 0.3, and 1 mg/kg) or scopolamine (0.01, 0.03, and 0.1 mg/kg) was systemically administered, [(11)C]SCH23390 binding to D(1) receptors was not affected. With administration of methamphetamine, the striatal PDE-IV activity, as measured with R-[(11)C]rolipram (active form) and S-[(11)C]rolipram (inactive form), was dose-dependently facilitated with enhanced dopamine level in the striatal ECF. Administration of scopolamine also induced facilitated PDE-IV activity without any apparent changes in the ECF dopamine. These facilitations of PDE-IV activity were abolished by preadministration of SCH23390, but not by raclopride. These results demonstrate that, as evaluated by PDE-IV activity, the inhibition of muscarinic cholinergic receptors actually facilitated dopamine neuronal signal transduction through D(1) receptors, as observed previously on D(2) receptors with no apparent increase in the striatal ECF dopamine level, but the enhanced dopamine transmission could not detected by [(11)C]SCH23390.
Explore the source record for details and available documents.
The effects of changes in regional cerebral blood flow (rCBF) with aging on muscarinic cholinergic receptor binding were evaluated with [15O]H(2)O and N-[11C]methyl-4-piperidyl benzilate (4-MPB) in the living brains of young (5.9+/-1.8 years old) and aged (19.0+/-3.3 years old) monkeys (Macaca mulatta) in the conscious state using high-resolution positron emission tomography (PET). For quantitative analysis of receptor binding in vivo with [11C]4-MPB, metabolite-corrected arterial plasma radioactivity curves were obtained as an input function into the brain, and graphical Patlak plot analysis was applied. In addition, two-compartment model analysis using the radioactivity curve in the cerebellum as an input function (reference analysis) was also applied to determine the distribution volume (DV=K(1)/k(2)') for [11C]4-MPB. With metabolite-corrected arterial input, Patlak plot analysis of [11C]4-MPB indicated a regionally specific decrease in muscarinic cholinergic receptor binding in vivo in the frontal and temporal cortices as well as the striatum in aged compared with young animals, showing no correlation with the degree of reduced rCBF. In contrast, on the reference analysis with cerebellar input of [11C]4-MPB, all regions assayed except the pons showed a significant age-related decrease of DV, and the degree of reduction of DV was correlated with that of rCBF. These results demonstrated the usefulness of kinetic analysis of [11C]4-MPB with metabolite-corrected arterial input, not with reference region's input, as an indicator of the aging process of cortical muscarinic cholinergic receptors in vivo measured by PET with less blood flow dependency.
Age-related changes in muscarinic cholinergic receptors were evaluated with the novel ligand (+)N-[(11)C]methyl-3-piperidyl benzilate ((+)3-MPB) in the living brains of young (5.9 +/- 1.8 years old) and aged (19.0 +/- 3.3 years old) monkeys (Macaca mulatta) in the conscious state using high-resolution positron emission tomography (PET). For quantitative analysis of receptor binding in vivo, metabolite-corrected arterial plasma radioactivity curves were obtained as an input function into the brain, and kinetic analyses using the three-compartment model and graphical Logan plot analysis were applied. Kinetic analyses of [(11)C](+)3-MPB indicated a regionally specific decrease in the receptor binding in vivo determined as binding potential (BP) = k(3)/k(4) in aged animals compared with young animals. Thus, the frontal and temporal cortices as well as the striatum showed age-related reduction of muscarinic cholinergic receptors in vivo, reflecting the reduced receptor density (B(max)) determined by Scatchard plot analysis in vivo. In the hippocampus, although BP of [(11)C](+)3-MPB indicated no significant age-related changes, it showed an inverse correlation with individual cortisol levels in plasma. When the graphical Logan plot analysis was applied, all regions assayed showed significant age-related decrease of [(11)C](+)3-MPB binding. These results demonstrate the usefulness of kinetic three-compartment model analysis of [(11)C](+)3-MPB with metabolite-corrected arterial plasma input as an indicator for the aging process of the cortical muscarinic cholinergic receptors in vivo as measured by PET.
We developed PET ligands (+)N-[(11)C]ethyl-3-piperidyl benzilate ([(11)C](+)3-EPB) and (+)N-[(11)C]propyl-3-piperidyl benzilate ([(11)C](+)3-PPB) for cerebral muscarinic cholinergic receptors. The distribution and kinetics of the novel ligands were evaluated for comparison with the previously reported ligand (+)N-[(11)C]methyl-3-piperidyl benzilate ([(11)C](+)3-MPB) in the monkey brain (Macaca mulatta) in the conscious state using high-resolution positron emission tomography (PET). At 60-91 min postinjection, regional distribution patterns of these three ligands were almost identical, and were consistent with the muscarinic receptor density in the brain as previously reported in vitro. However, the time-activity curves of [(11)C](+)3-EPB and [(11)C](+)3-PPB showed earlier peak times of radioactivity and a faster clearance rate than [(11)C](+)3-MPB in cortical regions rich in the receptors. Kinetic analysis using the three-compartment model with time-activity curves of radioactivity in metabolite-corrected arterial plasma as input functions revealed that labeling with longer [(11)C]alkyl chain length induced lower binding potential (BP = k(3)/k(4)), consistent with the rank order of affinity of these ligands obtained by an in vitro assay using rat brain slices and [(3)H]QNB. The cholinesterase inhibitor Aricept administered at doses of 50 and 250 microg/kg increased acetylcholine level in extracellular fluid of the frontal cortex and the binding of [(11)C](+)3-PPB with the lowest affinity to the receptors was displaced by the endogenous acetylcholine induced by cholinesterase inhibition, while [(11)C](+)3-MPB with the highest affinity was not significantly affected. Taken together, these observations indicate that the increase in [(11)C]alkyl chain length could alter the kinetic properties of conventional receptor ligands for PET by reducing the affinity to receptors, which might make it possible to assess the interaction between endogenous neurotransmitters and ligand-receptor binding in vivo as measured by PET.
Age-related changes in the serotonin transporter (SERT) in the living brains of conscious young (5.9 +/- 1.8 years old) and aged (19.0 +/- 3.3 years old) monkeys (Macaca mulatta) were evaluated in combination with [(11)C](+)McN5652 and its inactive enantiomer [(11)C](-)McN5652 by high-resolution positron emission tomography (PET). For the quantitative analysis of SERT binding in vivo, two serial PET scans with [(11)C](+)McN5652 and [(11)C](-)McN5652 were performed in the same animals in a day and the differences in radioactivities of [(11)C](+)McN5652 vs. [(11)C](-)McN5652 measured from 41-91 min postinjection were calculated as an estimate of specific ligand binding. Higher specific binding of SERT was observed in the thalamus and striatum, regions known to contain high densities of SERT by in vitro assay, with intermediate levels in the pons, hippocampus, cingulate gyrus, and cortical regions and lower levels in the cerebellum in both young and aged monkeys. Almost all regions assayed except the cerebellum showed significant age-related decreases in the specific binding of SERT, which showed reverse correlation with cortisol level in plasma. When the SERT blocker fluvoxamine (1 mg/kg) was administered intravenously 30 min after tracer injection, specific binding of SERT was displaced in both age groups. However, the degree of displacement was more marked in young than in aged monkeys. Cortisol level in plasma was significantly higher in aged than in young animals. These observations demonstrate the usefulness of the combined use of [(11)C](+)McN5652 and [(11)C](-)McN5652 as an indicator for the age-related changes in cortical SERT measured noninvasively by PET. In addition, these observations suggest that the age-related impairment of SERT sensitivity for fluvoxamine might be related to the reduced efficacy of antidepressant therapy in elderly patients with depression.
Phytochrome B (PhyB), one of the major photosensory chromoproteins in plants, mediates a variety of light-responsive developmental processes in a photoreversible manner. To analyze the structural requirements of the chromophore for the spectral properties of PhyB, we have designed and chemically synthesized 20 analogs of the linear tetrapyrrole (bilin) chromophore and reconstituted them with PhyB apoprotein (PHYB). The A-ring acts mainly as the anchor for ligation to PHYB, because the modification of the side chains at the C2 and C3 positions did not significantly influence the formation or difference spectra of adducts. In contrast, the side chains of the B- and C-rings are crucial to position the chromophore properly in the chromophore pocket of PHYB and for photoreversible spectral changes. The side-chain structure of the D-ring is required for the photoreversible spectral change of the adducts. When methyl and ethyl groups at the C17 and C18 positions are replaced with an n-propyl, n-pentyl, or n-octyl group, respectively, the photoreversible spectral change of the adducts depends on the length of the side chains. From these studies, we conclude that each pyrrole ring of the linear tetrapyrrole chromophore plays a different role in chromophore assembly and the photochromic properties of PhyB.
The paucity of lymph node T cells (plt) mutation leads to a loss of CCL21 and CCL19 expression in secondary lymphoid organs. plt mice have defects in the migration of naive T cells and activated dendritic cells into the T cell zones of lymphoid organs, suggesting that they would have defects in T cell immune responses. We now demonstrate T cell responses in plt mice are delayed but ultimately enhanced. Responses to contact sensitization are decreased at day 2 after priming but increased at day 6. After subcutaneous immunization, antigen-specific T cell proliferation and cytokine production in plt mice are increased and remain markedly elevated for at least 8 wk. Compared with wild-type mice, a proportion of T cell response in plt mice are shifted to the spleen, and prior splenectomy reduces the T cell response in draining lymph nodes. After immunization of plt mice, T cells and dendritic cells colocalize in the superficial cortex of lymph nodes and in splenic bridging channels, but not in T cell zones. These results demonstrate that plt mice mount robust T cell responses despite the failure of naive T cells and activated dendritic cells to enter the thymus dependent areas of secondary lymphoid organs.
2'-C-cyano-2'-deoxy-1-beta-D-arabino-pentofuranosylcytosine (CNDAC) is a potent anti-cancer agent, and we previously observed that liposomal formulation of 5'-O-dipalmitoylphosphatidyl derivative of CNDAC (DPP-CNDAC) is desirable for targeting. For targeting to pulmonary cancer, we investigated the in vivo behavior of liposomes containing DPP-CNDAC by a non-invasive method using positron emission tomography. Liposomes composed of DPP-CNDAC and cholesterol (DPP-CNDAC/CH liposomes) were markedly accumulated in mice lung bearing B16BL6 melanoma. In metastatic pulmonary cancer model, DPP-CNDAC/CH liposomes significantly reduced the lung colonization in a dose-dependent manner. The activity was significantly superior to conventional liposomal formulation or soluble CNDAC. These results suggest that DPP-CNDAC/CH liposomes are useful for metastatic pulmonary cancer.
The novel muscarinic cholinergic ligands (+)N-[11C]methyl-3-piperidyl benzilate ([11C](+)3-MPB) and its stereoisomer [11C](-)3-MPB were evaluated in comparison with [11C]4-MPB in the brains of conscious monkeys (Macaca mulatta) using high-resolution positron emission tomography (PET). The regional distribution patterns of [11C](+)3-MPB and [11C]4-MPB at 60-91 min postinjection were almost identical: highest in the striatum and occipital cortex; intermediate in the temporal and frontal cortices, cingulate gyrus, hippocampus, and thalamus; lower in the pons; and lowest in the cerebellum. The uptake of [11C](+)3-MPB in all regions was higher and the dynamic range of regional uptake differences of [11C](+)3-MPB was better than those of [11C]4-MPB. The levels of [11C](-)3-MPB were much lower in all regions of the brain than [11C](+)3-MPB and [11C]4-MPB. Administration of scopolamine, a muscarinic cholinergic antagonist, at a dose of 50 microg/kg reduced the radioactivity of [11C](+)3-MPB and [11C]4-MPB in all regions except the cerebellum. Time-activity curves of [11C](+)3-MPB peaked in all regions, while those of [11C]4-MPB showed gradual increases with time in all regions except the thalamus, pons, and cerebellum. Two graphical analyses (Logan plot and Patlak plot) with plasma radioactivity as an input function into the brain were applied to evaluate receptor binding in vivo. [11C](+)3-MPB showed linear regression curves on Logan plot analysis and nonlinear curves on Patlak plot in all regions, suggesting that [11C](+)3-MPB bound reversibly to the muscarinic receptors. The in vivo binding parameters as well as uptake at 60-91 min postinjection of [11C](+)3-MPB were consistent with muscarinic receptor density in the brain as reported in vitro.
BACKGROUND: Postoperative infection of intestine with methicillin-resistant Staphylococcus aureus (MRSA) is fatal in some cases. The object of this study was to establish a mouse model for the infection, providing a useful tool for investigating mechanisms in the progression of infection. METHODS: Mice were pretreated with cyclophosphamide, injected orally or directly into jejunum with MRSA prepared from a postoperative patient, and then given 5 daily doses of antibiotics. Forty-eight hours after the injection, bacterial translocation and serum endotoxin levels were examined. Macrophage depletion was carried out by the administration of liposome-encapsulated dichloromethylene diphosphate (Cl(2)MDP), 4 days before MRSA injection. RESULTS: Injection into the jejunum but not oral administration of MRSA induced enteritis with diarrhea and resulted in death in most cyclophosphamide-treated mice. Translocation of MRSA in mesenteric lymph nodes and liver was observed, concomitantly with E. coli infection. Endotoxin-resistant C3H/HeJ mice infected with MRSA survived longer than endotoxin-sensitive C3H/He mice, but also died within a week after MRSA injection. Selective depletion of macrophages induced infection in mice that were not pretreated with cyclophosphamide. CONCLUSION: We established a mouse model for the fatal MRSA infection which induced enteritis with diarrhea, that will be a useful tool for investigating the mechanisms for sometimes fatal MRSA infection of the intestine in postoperative patients. The presence of E. coli or endotoxin seemed to play a major role in the mortality of mice in the early days of MRSA-induced enteritis, but other factors, probably from MRSA, in the later days. Phagocytes were quite important for protection against the MRSA infection.
We evaluated the impact of yohimbine administration on benzodiazepine (BDZ) receptor binding in the central nervous system of non-human primates (rhesus monkeys). Estimates of the binding potential (Bmax/Kd) of BDZ receptors were made following intravenous administration of yohimbine, an alpha2-adrenoceptor antagonist. Positron emission tomography was used in conjunction with [11C]flumazenil (Ro 15-1788), a tracer for central BDZ receptor binding activity. The effects of yohimbine were compared with a control condition in which saline was administered. Yohimbine significantly increased the binding potential in the hippocampus, as assessed using a Student's t-test with Bonferroni correction. The result that the administration of yohimbine readily induces an increase in the binding potential for BDZ receptors in the primate brain suggests that the presence of an anxiety state potentiates the effect of anxiolytics.
The in vitro response of peripheral blood mononuclear cells or enriched CD4+ T cells from patients with ossification of the posterior longitudinal ligament to anti-CD3 monoclonal antibody has been studied. The response in both was significantly lower in patients with the continuous-type ossification than in patients with the segmental-type ossification and in healthy volunteers, and was inversely correlated with the number of vertebral bodies with ossified ligament. In patients with the segmental-type ossification, the response of peripheral blood mononuclear cells was significantly lower than that in healthy volunteers, but that of the enriched T cells was not. B cell proliferation in response to fixed Staphylococcus aureus cells was significantly lower in patients with the continuous-type ossification than in healthy volunteers but was not correlated with the number of vertebral bodies with ossified ligament. The B cell response in patients with the segmental-type ossification was not lower than that in healthy volunteers. Serum concentrations of transforming growth factor-beta1 and basic fibroblast growth factor also were higher in patients with the continuous-type ossification than in patients with the segmental-type ossification and in healthy volunteers. The findings raise the possibility that continuous-type ossification of posterior longitudinal ligament might develop differently from segmental-type ossification.
UNLABELLED: FK506 is an immunosuppressive agent that has been reported to have neuroprotective effects in several kinds of rodent models of stroke. The purpose of this study was to evaluate the neuroprotective effects of FK506 in a monkey model of stroke. METHODS: Cynomolgus monkeys underwent 3 h of occlusion followed by 5 h of reperfusion of the right middle cerebral artery (MCA) through a transorbital approach. A single bolus dose of FK506 (0.1 mg/kg) was injected intravenously 5 or 175 min after MCA occlusion. Eight hours after ischemia, a neuropathologic study was performed and the volume of ischemic damage was determined. To measure local cerebral blood flow (CBF), the cerebral metabolic rate of oxygen (CMRO(2)), and the oxygen extraction fraction during the experiments, PET scans were obtained using a steady-state (15)O continuous-inhalation method. Four consecutive PET scans (before and 2 h after ischemia and immediately and 3 h after reperfusion) were obtained on each monkey. RESULTS: Treatment with FK506 (0.1 mg/kg) 5 or 175 min after ischemia significantly reduced cortical damage 8 h after ischemia by 82% (P < 0.05) and 73% (P < 0.05), respectively. In PET studies, FK506 did not affect CBF or physiologic parameters in any treatments. In the FK506-treated group, a volume of >40% CMRO(2) reduction 3 h after reperfusion decreased significantly (P < 0.05). CONCLUSION: This study showed that FK506 showed a powerful neuroprotective effect in a nonhuman primate model of stroke. The therapeutic time window of FK506 was at least 3 h after onset. PET studies detected neuroprotective effects only in areas with >40% CMRO(2) reduction 3 h after reperfusion.