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Purpose: Our study aimed to elucidate the intracellular processes associated with quinolinic acid (QA)-induced brain injury by acquiring semiquantitative fluorescent images of reactive oxygen species (ROS) generation and positron emission tomography (PET) images of mitochondrial complex I (MC-I) activity. Methods: Ex vivo fluorescent imaging with dihydroethidium (DHE) and PET scans with 18F-BCPP-EF were conducted at 3 h and 24 h after QA injection into the rat striatum. Immunohistochemical studies were performed 24 h after QA injection into the rat brain using monoclonal antibodies against neuronal nuclei (NeuN) and CD11b. Results: A strong DHE-derived fluorescent signal was detected in a focal area within the QA-injected striatum 3 h after QA injection, and increased fluorescent signal spread throughout the striatum and parts of the cerebral cortex after 24 h. By contrast, 18F-BCPP-EF uptake in the QA-injected rat brain was unchanged after 3 h and markedly decreased after 24 h, not only in the striatum but also in the cerebral hemisphere. The fluorescent signal in the striatum 24 h after QA injection colocalised with microglial marker expression. Conclusions: We successfully obtained functional images of focal ROS generation during the early period of excitotoxic injury, and microglial ROS generation and mitochondrial dysfunction were observed during the progression of the inflammatory response. Both ex vivo DHE imaging and in vivo 18F-BCPP-EF-PET were sufficiently sensitive to detect the respective processes of QA-induced brain damage. Our study contributes to the functional imaging of multiple events during the pathological process. [ABSTRACT FROM AUTHOR]

Soluble forms of platelet membrane proteins are released upon platelet activation. We previously reported that soluble C-type lectin-like receptor 2 (sCLEC-2) is released as a shed fragment (Shed CLEC-2) or as a whole molecule associated with platelet microparticles (MP-CLEC-2). In contrast, soluble glycoprotein VI (sGPVI) is released as a shed fragment (Shed GPVI), but not as a microparticle-associated form (MP-GPVI). However, mechanism of sCLEC-2 generation or plasma sCLEC-2 has not been fully elucidated. Experiments using metalloproteinase inhibitors/stimulators revealed that ADAM10/17 induce GPVI shedding, but not CLEC-2 shedding, and that shed CLEC-2 was partially generated by MMP-2. Although MP-GPVI was not generated, it was generated in the presence of the ADAM10 inhibitor. Moreover, antibodies against the cytoplasmic or extracellular domain of GPVI revealed the presence of the GPVI cytoplasmic domain, but not the extracellular domain, in the microparticles. These findings suggest that most of the GPVI on microparticles are induced to shed by ADAM10; MP-GPVI is thus undetected. Plasma sCLEC-2 level was 1/32 of plasma sGPVI level in normal subjects, but both soluble proteins significantly increased in plasma of patients with acute coronary syndrome. Thus, sCLEC-2 and sGPVI are released by different mechanisms and released in vivo upon platelet activation. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective method for determination of histamine in rat plasma and tissue extracts by liquid chromatography with fluorescence detection is described. The method is based on precolumn derivatization of amino groups of histamine with two molecules of 4-(1-pyrene)butyric acid N-hydroxysuccinimide ester that allows generation of intramolecular excimer fluorescence. The detection limit for histamine was 0.183 nM. This sensitivity allowed determination of histamine in 10 μL of rat plasma or in the extracts from less than 1 mg of tissue. [ABSTRACT FROM AUTHOR]

Glutamate plays an essential role in neuronal cell death in many neurological disorders. In this study, we examined both glucose metabolism and cerebral blood flow in the same rat following infusion of glutamate or ibotenic acid using the dual-tracer technique. The effects of MK-801, an NMDA receptor antagonist, and NBQX, an AMPA-kainate receptor antagonist, on the changes in the glucose metabolism and cerebral blood flow induced by glutamate were also examined. The rats were microinjected with glutamate (1 μmol/μl, 2 μl) or ibotenic acid (10 μg/μl, 1 μl) into the right striatum, and dual-tracer autoradiograms of [18F]FDG and [14C]IMP were obtained. MK-801 and NBQX were injected intravenously about 45 and 30 min, respectively, after the infusion of glutamate. De-coupling of blood flow and metabolism was noted in the glutamate-infused hemisphere (as assessed by no alteration of [18F]FDG uptake and significant decrease of [14C]IMP uptake). Pretreatments with MK-801, NBQX, or combined use of MK-801 and NBQX did not affect the de-coupling of the blood flow and metabolism induced by glutamate. A histochemical study revealed that about 20% neuronal cell death had occurred in the striatum at 105 min after the infusion of glutamate. In addition, a significant increase of the [18F]FDG uptake and decrease of [14C]IMP uptake were also seen in the rat brain infused with ibotenic acid. These results indicate that glutamate and ibotenic acid caused a significant de-coupling of blood flow and glucose metabolism in the intact rat brain during the early phase of neurodegeneration. It is necessary to evaluate the relation between metabotropic glutamate receptors and de-coupling of blood flow and metabolism. [ABSTRACT FROM AUTHOR]

Objective: To clarify the role of N-methyl-D: -aspartate (NMDA) receptors upon [(14)C]acetate uptake in the rodent central nervous system (CNS), ibotenic acid (IBO) was infused into the right striatum of the rat brain. Methods: Autoradiograms of [(14)C]acetate uptake in the brain for 2 h following the infusion of IBO (10 microg/microl) were obtained in both non-treated and MK-801 (1 mg/kg, i.v.) pretreated rats. The effect of MK-801 on [(14)C]acetate uptake in the normal rat brain was also studied. Results: Infusion of IBO significantly decreased [(14)C]acetate uptake in the infused side of the striatum. The expression of monocarboxylate transporter-1 was not altered, suggesting that the activity of tricarboxylic acid (TCA) cycle in glial cells might be depressed. Pretreatment with MK-801 completely blocked the decreasing effect of IBO on [(14)C]acetate uptake. MK-801 also increased [(14)C]acetate uptake in the whole brain of normal rats. Conclusions: These results indicate the important roles of NMDA receptors on [(14)C]acetate uptake in the intact rat brain. [ABSTRACT FROM AUTHOR]

To clarify the role of N-methyl- d-aspartate (NMDA) receptors upon [14C]acetate uptake in the rodent central nervous system (CNS), ibotenic acid (IBO) was infused into the right striatum of the rat brain. Autoradiograms of [14C]acetate uptake in the brain for 2 h following the infusion of IBO (10 μg/μl) were obtained in both non-treated and MK-801 (1 mg/kg, i.v.) pretreated rats. The effect of MK-801 on [14C]acetate uptake in the normal rat brain was also studied. Infusion of IBO significantly decreased [14C]acetate uptake in the infused side of the striatum. The expression of monocarboxylate transporter-1 was not altered, suggesting that the activity of tricarboxylic acid (TCA) cycle in glial cells might be depressed. Pretreatment with MK-801 completely blocked the decreasing effect of IBO on [14C]acetate uptake. MK-801 also increased [14C]acetate uptake in the whole brain of normal rats. These results indicate the important roles of NMDA receptors on [14C]acetate uptake in the intact rat brain. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to compare validity of various biomarkers of occupational exposure to toluene (Tol) at low levels. The focus was placed on the comparison of un-metabolized toluene in urine (Tol-U) and peripheral blood (Tol-B) with hippuric acid in urine (HA-U). Surveys were conducted in 16 workplaces on the second half of working weeks, with participation of male solvent workers. Urine and peripheral blood samples were collected at the end of the shifts. After exclusion of cases with dense or diluted urine samples, 473 valid sets of samples were obtained for statistical evaluation. Time-weighted average exposure (for about 8-h) were monitored by diffusive sampling for toluene and other four solvents. Blood samples were subjected to the analyses for Tol-B, whereas urine samples were analyzed for HA-U and Tol-U. The solvent exposures were low, i.e., a grand geometric mean (GM) Tol concentration was 1.6 ppm, and the GM for the SUM in the additiveness equation was 0.12. The correlation analyses of the biomarkers in urine and blood with Tol exposure showed that Tol-U and Tol-B were more closely [correlation coefficients ( r) being 0.67 and 0.60, respectively] related than HA-U ( r = 0.27). Results of receiver operator characteristic analyses were in agreement with the correlation analysis results. Taking the non-invasive nature of sampling together, Tol in the end-of-shift spot urine sample appears to be the marker of choice for biological monitoring of occupational exposure to Tol at low levels such as <2 ppm as a geometric mean. [ABSTRACT FROM AUTHOR]

This study was initiated to make comparative evaluation of five proposed urinary markers of occupational exposure to toluene, i.e., benzyl alcohol, benzylmercapturic acid, o-cresol, hippuric acid and un-metabolized toluene. In practice, six plants in Japan were surveyed, and 122 Japanese workers (mostly printers; all men) together with 12 occupationally nonexposed control subjects (to be called controls; all men) agreed to participate in the study. Surveys were conducted in the second half of working weeks. Time-weighted average exposure (about 8 h) to toluene and other solvents were monitored by diffusive sampling. End-of-shift urine samples were collected and analyzed for the five markers by the methods previously described; simultaneous determination of o-cresol was possible by the method originally developed for benzyl alcohol analysis. The toluene concentration in the six plants was such that the grand geometric mean (GM) for the 122 cases was 10.4 ppm with the maximum of 121 ppm. Other solvents coexposed included ethyl acetate (26 ppm as GM), methyl ethyl ketone (26 ppm), butyl acetate (1 ppm) and xylenes (1 ppm). By simple regression analysis, hippuric acid correlated most closely with toluene in air ( r = 0.85 for non-corrected observed values) followed by un-metabolized toluene ( r = 0.83) and o-cresol ( r = 0.81). In a plant where toluene in air was low (i.e., 2 ppm as GM), however, un-metabolized toluene and benzylmercapturic acid in urine showed better correlation with air-borne toluene ( r = 0.79 and 0.61, respectively) than hippuric acid ( r = 0.12) or o-cresol ( r = 0.17). Benzyl alcohol tended to increase only when toluene exposure was intense. Correction for creatinine concentration or specific gravity of urine did not improve the correlation in any case. Multiple regression analysis showed that solvents other than toluene did not affect the levels of o-cresol, hippuric acid or un-metabolized toluene. Levels of benzylmercapturic acid and un-metabolized toluene were below the limits of detection [limit of detections (LODs); 0.2 and 2 μg/l, respectively] in the urine from the control subjects. In over-all evaluation, hippuric acid, followed by un-metabolized toluene and o-cresol, is the marker of choice for occupational toluene exposure. When toluene exposure level is low (e.g., 2 ppm), un-metabolized toluene and benzylmercapturic acid in urine may be better indicators. Detection of un-metabolized toluene or benzylmercapturic acid in urine at the levels in excess of the LODs may be taken as a positive evidence of toluene exposure, because their levels in urine from the controls are below the LODs. The value of benzyl alcohol as an exposure marker should be limited. [ABSTRACT FROM AUTHOR]

Although several pieces of evidence have indicated that glial cells support neuronal cells in the ischemia-reperfusion brain, the direct contribution of glial cells to cell damage is not well known. The present study was designed to determine whether there are any changes in cell damage after a short-term middle cerebral artery occlusion (MCAO) when glial metabolism is suppressed. Injection of fluorocitrate (FC) or 10 minutes MCAO alone did not produce cell damage. However, 10 minutes MCAO in rats pretreated with FC caused significant cell damage. These data directly demonstrated that inhibition of glial metabolism might increase neuronal vulnerability to even a short-term transient ischemia. [ABSTRACT FROM AUTHOR]

An early image of intra-tumor distribution of 14C-labeled fluorodeoxy glucose (14C-FDG) was compared with a late image of 18F-labeled FDG (18F-FDG) using mouse fibrosarcoma. Heterogeneous intra-tumor distribution of 14C-FDG was observed 1 minute post injection of the tracer, whereas relatively homogeneous distribution of 18F-FDG was seen 30 minutes later. 14C-FDG was particularly taken up in the peripheral part of the tumor immediately after the tracer injection. A gradual and significant increase in 18F-FDG accumulation with time was seen in the central part of tumor, which indicated an enhancement of anaerobic glycolysis. An initial uptake of 18F-FDG was also compared with distribution of 14C-iodoantipyrine and 14C-thymidine uptake. Intratumoral distribution of initial uptake of 18F-FDG showed almost the same regional distribution of 14C-iodoantipyrine. A similar distribution of 14C-thymidine as the initial uptake of 18F-FDG was also observed. These results indicated that a high initial FDG uptake area seemed to be highly proliferative. A significant difference in the intratumoral distribution of FDG between early phase and late phase seemed to be related to heterogeneous biological characteristics of tumor cells. [ABSTRACT FROM AUTHOR]

The binding kinetics of 11C-N-methyl piperidyl benzilate (11C-NMPB) in rhesus monkey brain were studied using animal positron emission tomography (PET) (SHR2000). This study is intended to assess the validity of the method using the cerebellum as a reference region, and to evaluate the effects of anesthesia on 11C-NMPB binding. Two monkeys, anesthetized with ketamine, received intravenous 11C-NMPB alone (370-760 MBq, < 1 microg/kg) or mixed with varying doses of nonradioactive NMPB (3 microg/kg, 10 microg/kg, 30 microg/kg) and were subjected to PET scans for 60 minutes. Regions of interest (ROI) were drawn on reconstructed PET images and a time-activity curve was obtained for each region. 11C-NMPB accumulated densely in the striatum and cerebral cortex with time. In contrast, the tracer accumulation significantly decreased with increased doses of nonradioactive NMPB. In the cerebellum, on the other hand, the accumulation of 11C-NMPB remained low and the tracer was slowly eliminated from the brain following the injection. 11C-NMPB binding in the cerebellum was barely affected by the increased dose of nonradioactive NMPB. We thus concluded that the specific 11C-NMPB binding was negligible in the cerebellum, and performed simplified evaluation of 11C-NMPB binding in each brain region by a graphical method using the cerebellum as a reference region. PET was conducted 26 times, in total both in ketamine-anesthetized and awake monkeys (n = 3 each). Measurements of 11C-NMPB binding showed good run-to-run reproducibility within individual animals. When 11C-NMPB binding was compared between ketamine-treated and awake animals, a significant increase in 11C-NMPB binding was observed in the striatum but not in other brain regions of ketamine-treated animals. [ABSTRACT FROM AUTHOR]

The binding kinetics of11C-N-methyl piperidyl benzilate (11C-NMPB) in rhesus monkey brain were studied using animal positron emission tomography (PET) (SHR2000). This study is intended to assess the validity of the method using the cerebellum as a reference region, and to evaluate the effects of anesthesia on11C -NMPB binding. Two monkeys, anesthetized with ketamine, received intravenous11C-NMPB alone (370–760 MBq, <1 μg/kg) or mixed with varying doses of nonradioactive NMPB (3 μg/kg, 10 μg/kg, 30 μg/kg) and were subjected to PET scans for 60 minutes. Regions of interest (ROI) were drawn on reconstructed PET images and a time-activity curve was obtained for each region.11C-NMPB accumulated densely in the striatum and cerebral cortex with time. In contrast, the tracer accumulation significantly decreased with increased doses of nonradio-active NMPB. In the cerebellum, on the other hand, the accumulation of11C-NMPB remained low and the tracer was slowly eliminated from the brain following the injection.11C-NMPB binding in the cerebellum was barely affected by the increased dose of nonradioactive NMPB. We thus concluded that the specific11C-NMPB binding was negligible in the cerebellum, and performed simplified evaluation of11C-NMPB binding in each brain region by a graphical method using the cerebellum as a reference region. PET was conducted 26 times, in total both in ketamine-anesthetized and awake monkeys (n = 3 each). Measurements of11C-NMPB binding showed good run-to-run reproducibility within individual animals. When11C-NMPB binding was compared between ketamine-treated and awake animals, a significant increase in11C-NMPB binding was observed in the striatum but not in other brain regions of ketamine-treated animals. [ABSTRACT FROM AUTHOR]

The kinetics of18F-fluorodeoxyglucose (18F-FDG) in the monkey brain were monitored, and comparisons were made between the conscious state and when under ketamine and pentobarbital anesthesia. Rhesus monkeys were intravenously injected with18F-FDG and followed by 60 min of PET scanning. In the conscious state, the18F-FDG concentration reached a plateau 5 min after intravenous injection. Under ketamine anesthesia, the18F-FDG concentration gradually increased with time in all monitored regions. At 60 min after injection, the concentration in the striatum was about 3.2 times greater than that in the conscious state, and about 4.5 times greater in the cerebral cortex. Under pentobarbital anesthesia, the18F-FDG concentration in the occipital cortex was slightly lower. These findings demonstrate that18F-FDG concentration in the monkey brain is significantly affected by anesthesia. The results also imply the existence of a short-term regulation mechanism for hexokinase activity in intact monkey brain. [ABSTRACT FROM AUTHOR]

Purpose: 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has become a useful imaging tool for inflammatory diseases. In this study we investigated the effects of rolipram, a selective phosphodiesterase type 4 inhibitor, on 14C-deoxyglucose (DG) uptake in inflammatory lesions and other normal tissues, and attempted to improve the inflammation/muscle ratio. Methods: To induce inflammation, mice were inoculated with turpentine oil. Inflammation-bearing mice were pretreated with rolipram (3 mg/kg i.p. or i.v.), and the effect on 18C-DG uptake was measured using a tissue dissection method and autoradiography. The inflammatory tissue samples were stained with haematoxylin and eosin. Results: Rolipram (3 mg/kg i.p.) significantly decreased 14C-DG uptake in normal tissues like brain, heart and skeletal muscle (brain 31%, heart 60%, skeletal muscle 61%). On the other hand, 14C-DG uptake in inflammatory lesions was not significantly altered by pretreatment with rolipram. The inflammation/muscle ratio of 14C-DG uptake (30 min after tracer injection) was enhanced from 1.1 to 2.8 by rolipram. An autoradiographic study revealed heterogeneous distributions of 14C-DG in the inflammatory lesions and skeletal muscle of animals that were not treated with rolipram. Pretreatment with rolipram significantly attenuated the intramuscular distribution of 14C-DG, producing a relatively homogeneous distribution of radioactivity. Conclusion: These results indicate that rolipram decreased 14C-DG uptake in skeletal muscle by activation of the adenosine 3',5'-cyclic monophosphate system, whereas 14C-DG uptake in inflammatory lesions was not significantly altered. Therefore, rolipram may be a valuable tool for improving the visualisation of inflammatory lesions in clinical PET studies employing FDG. [ABSTRACT FROM AUTHOR]

The [S] enantiomer of [11C]-N,alpha-dimethylbenzylamine (DMBA) was synthesized by N-methylation of [S]-alpha-methylbenzylamine, and its biodistribution in mice was measured. [11C]-[S]-DMBA was rapidly distributed into the brain, heart and lungs, and considerable long-term retention in the brain was observed. The radioactive metabolites in the plasma were analyzed by liquid chromatography. Kinetic analysis using unmetabolized [11C]DMBA in the plasma as the input function was performed employing a simplified two-compartment model. The estimated distribution volumes (DV) of [11C]DMBA in the brain and heart were 6.05 and 3.95, respectively. The right striatum of the rat brain was lesioned with ibotenic acid 2 weeks before the tracer experiment. Both in vitro and in vivo autoragiographic studies were performed, and revealed significant reduction of the radioactivity levels in the lesioned striatum. On the other hand, the regional cerebral blood flow, as measured by [14C]iodoantipyrine, was not significantly altered in the lesioned striatum. These results indicate that the ionic binding component for DMBA exists mainly in neural cells rather than in glial cells. [11C]DMBA might be a useful radiotracer for detection of neural cell loss in the brain. [ABSTRACT FROM AUTHOR]

The [S] enantiomer of [11C]- N,α-dimethylbenzylamine (DMBA) was synthesized by N-methylation of [S]-α-methylbenzylamine, and its biodistribution in mice was measured. [11C]-[S]-DMBA was rapidly distributed into the brain, heart and lungs, and considerable long-term retention in the brain was observed. The radioactive metabolites in the plasma were analyzed by liquid chromatography. Kinetic analysis using unmetabolized [11C]DMBA in the plasma as the input function was performed employing a simplified two-compartment model. The estimated distribution volumes (DV) of [11C]DMBA in the brain and heart were 6.05 and 3.95, respectively. The right striatum of the rat brain was lesioned with ibotenic acid 2 weeks before the tracer experiment. Both in vitro and in vivo autoragiographic studies were performed, and revealed significant reduction of the radioactivity levels in the lesioned striatum. On the other hand, the regional cerebral blood flow, as measured by [14C]iodoantipyrine, was not significantly altered in the lesioned striatum. These results indicate that the ionic binding component for DMBA exists mainly in neural cells rather than in glial cells. [11C]DMBA might be a useful radiotracer for detection of neural cell loss in the brain. [ABSTRACT FROM AUTHOR]

Sabcomeline [(R-(Z)-(+)-alpha-(methoxyiamino)-1-azabicyclo[2.2.2]octane-3-acetonitrile)] is a potent and functionally selective muscarinic M1 receptor partial agonist. However, little is known of the binding properties of sabcomeline under in vivo conditions. In this study, muscarinic receptor occupancy by sabcomeline in mouse brain regions and heart was estimated using [3H]quinuclidinyl benzilate (QNB) and [3H]N-methylpiperidyl benzilate (NMPB) as radioligands. In the cerebral cortex, hippocampus, and striatum, the estimated IC50 value of sabcomeline for [3H]NMPB binding was almost 0.2 mg/kg. Sabcomeline was not a selective ligand to M1 receptors as compared with biperiden in vivo. In the cerebral cortex, maximum receptor occupancy was observed about 1 hr after intravenous injection of sabcomeline (0.3 mg/kg), and the binding availability of mACh receptors had almost returned to the control level by 3-4 hr. These findings indicated that the binding kinetics of sabcomeline is rather rapid in mouse brain. Examination of dopamine D2 receptor binding revealed that sabcomeline affected the kinetics of both [3H]raclopride and [3H]N-methylspiperone (NMSP) binding in the striatum. It significantly decreased the k3 and k4 of [3H]raclopride binding resulting in an increase in binding potential (BP = k3/k4 = Bmax/Kd) in sabcomeline-treated mice, and an approximately 15% decrease in k3 of [3H]NMSP binding was also observed. Although the mechanism is still unclear, sabcomeline altered dopamine D2 receptor affinity or availability by modulations via neural networks. [ABSTRACT FROM AUTHOR]

The effect of rolipram, a selective phosphodiesterase type 4 inhibitor, on the uptake of 18F-fluorodeoxyglucose (18F-FDG) in tumor tissue was examined in mice transplanted with NFSa fibrosarcoma. The uptake indexes of 18F-FDG in the heart, skeletal muscle and brain remarkably decreased after treatment with 3 mg/kg of rolipram (heart: 13%, skeletal muscle: 14%, brain: 31%), but fibrosarcoma tissue showed only a 50% reduction in the uptake index of 18F-FDG. The tumor/muscle ratio of radioactivity 30 min after 18F-FDG injection was consequently enhanced from 1.9 to 6.5 by rolipram. This indicates the possible use of rolipram to enhance the sensitivity of tumor detection, as well as characterization of tumors in 18F-FDG PET. [ABSTRACT FROM AUTHOR]

The effect of rolipram, a selective phosphodiesterase type 4 inhibitor, on the uptake of18F-fluorodeoxyglucose (18F-FDG) in tumor tissue was examined in mice transplanted with NFSa fibrosarcoma. The uptake indexes of18F-FDG in the heart, skeletal muscle and brain remarkably decreased after treatment with 3 mg/kg of rolipram (heart: 13%, skeletal muscle: 14%, brain: 31%), but fibrosarcoma tissue showed only a 50% reduction in the uptake index of18F-FDG. The tumor/muscle ratio of radioactivity 30 min after18F-FDG injection was consequently enhanced from 1.9 to 6.5 by rolipram. This indicates the possible use of rolipram to enhance the sensitivity of tumor detection, as well as characterization of tumors in18F-FDG PET. [ABSTRACT FROM AUTHOR]

The effects of systemic administration of rolipram, a selective phosphodiesterase type 4 inhibitor, on [³H]2-deoxyglucose (DG) uptake in brain and peripheral tissues were examined. Rolipram significantly and dosedependently decreased [³H]DG uptake in brain, heart and skeletal muscle. In contrast, the radioactivity concentrations in the plasma of rolipram-treated mice were significantly higher than those of control mice at all times after injection of the tracer. In the kinetic study, the initial uptake of [³H]DG in brain was decreased by rolipram, whereas no significant differences were observed in the uptake in heart and skeletal muscle. However, radioactivity concentrations in the brain, heart and skeletal muscle 30 min after the injection of [³H]DG were significantly lowered by rolipram to about 60%, 10% and 10% of control values, respectively. The uptake of [[sup 13]N]ammonia in brain and heart of rolipram-treated mice was slightly decreased, which indicated that rolipram diminished both cerebral and cardiac blood flow. These results indicate that the phosphorylation process via hexokinase rather than the transport of [³H]DG might be depressed by rolipram. Together with the previous observations that inhibition of protein kinase A (PKA) markedly enhanced [[sup 14]C]DG uptake in rat brain, these results indicate an important role of the cAMP/PKA systems in the regulation of glucose metabolism in the living brain as well as in peripheral tissues such as the heart and skeletal muscle. [ABSTRACT FROM AUTHOR]

Objective: To examine if benzylmercapturic acid (or N-acetyl-S-benzyl cysteine) in urine can be used as a marker of occupational exposure to toluene. Methods: A factory survey was conducted in the latter half of a working week. A group of 46 men, who volunteered for the study, was engaged in ink preparation, surface coating or printing work. Diffusive samplers were used to measure average solvent exposure in an 8-h shift. End-of-shift urine samples were analyzed for benzylmercapturic acid (BMA) by a modification of an HPLC method originally developed for phenylmercapturic acid determination. Results: The workers were exposed primarily to toluene [TOL; 13 ppm as the geometric mean (GM) and 86 ppm at the maximum] together with isopropyl alcohol (<1 and 4 ppm), ethyl acetate (2 and 127 ppm) and methyl ethyl ketone (2 and 142 ppm). BMA in urine correlated closely [correlation coefficient (r) =0.7] with TOL in air, irrespective of correction for urine density. The lowest TOL concentration at which urinary BMA increased to a measurable level was approximately 10 ppm, and urinary BMA could separate the exposed from the non-exposed when TOL exposure was 15 ppm or higher. Conclusions: BMA in end-of-shift urine samples is a good marker of occupational TOL exposure. Urinalysis for BMA is sensitive enough to detect TOL exposure at 15 ppm, and therefore BMA appears to be more sensitive than hippuric acid and possibly o-cresol as a urinary marker of TOL exposure. [ABSTRACT FROM AUTHOR]

In order to investigate possible effects of smoking and drinking on the metabolism of toluence in occupational settings, 206 toluene-exposed men (mean age: 31.4 years) in shoemaking, painting, or surface-coating workshops together with 246 nonexposed control men (36.8 years) were studied for the time-weighted average intensities of exposure to toluene, hippuric acid concentration in shift-end urine samples, and the two social habits of smoking and drinking. The mean daily consumptions of cigarettes and ethanol were about 20 pieces and 10 g among smokers and drinkers, respectively. The geometric mean toluene concentration among the exposed subjects was about 20 ppm, with a maximum of 521 ppm. Regression analysis after classification of the subjects by smoking and drinking clearly demonstrated that the two social habits, when combined, markedly reduce the hippuric acid level in the urine of workers exposed to was a significant association between smoking and drinking habits, which hindered separate evaluation of the effects of the two habits on toluene metabolism. Comparison of the present results with the findings reported in the literature, however, suggested that the observed effects may be attributable to smoking rather than to drinking habits. [ABSTRACT FROM AUTHOR]

The relationship of the intensity of occupational vapor exposure to isopropyl alcohol (IPA) with urinary excretion of acetone and unmetabolized IPA was studied in 99 printers of both sexes, who were exposed to up to 66 ppm IPA (as time-weighted average), together with toluene, xylenes, methyl ethyl ketone and/or ethyl acetate. Acetone and IPA concentrations in urine were studied also in 34 non-exposed subjects. Acetone was detectable in the urine of most of the non-exposed, and the urinary acetone concentration increased in proportion to the IPA exposure intensity ( r = 0.84 for observed, non-corrected values), whereas the correction for creatinine concentration or specific gravity of urine did not give a larger correlation coefficient. IPA itself was not found in the urine of the non-exposed, and was detectable in urine of only those who were exposed to IPA above a certain level, e.g. 5 ppm. The present study results suggest that urinary acetone is a valuable index for biological monitoring of occupational exposure to IPA as low as 70 ppm. [ABSTRACT FROM AUTHOR]

The exposure intensity during a shift and the metabolite levels in the shift-end urine were examined in male workers exposed to either benzene (65 subjects; the benzene group), toluene (35 subjects; the toluene group), or a mixture of both (55 subjects; the mixture group). In addition, 35 non-exposed male workers (the control group) were similarly examined for urinary metabolites to define background levels. A linear relationship was established between the intensity of solvent exposure and the corresponding urinary metabolite levels (i.e. phenol, catechol and quinol from benzene, and hippuric acid and o-cresol from toluene) in each case when one of the three exposed groups was combined with the control group for calculation. Comparison of regression lines in combination with regression analysis disclosed that urinary levels of phenol and quinol (but not catechol) were lower in the mixture group than in the benzene group when the intensities of exposure to benzene were comparable, indicating that the biotransformation of benzene to phenolic compounds (excluding catechol) in man is suppressed by co-exposure to toluene. Conversely, metabolism of toluene to hippuric acid was suppressed by benzene co-exposure. Conversion of toluene to o-cresol was also reduced by benzene, but to a lesser extent. The significance of the present findings on the mutual suppression of metabolism between benzene and toluene is discussed in relation to solvent toxicology and biological monitoring of exposure to the solvents. [ABSTRACT FROM AUTHOR]

The article presents a study which determines the presence of six metabolites including hippuric acid (HA), phenylglyoxylic acid (PhGA), and mandelic acid (MA) in urine by high-performance liquid chromatography (HPLC). The study uses urine samples from non-exposed and exposed to industrial xylenes, and statistical method of geometric standard deviation and geometric mean. It states that p-xylene and ethylbenzene are minor components, and m-xylene is a major components in xylene preparations.

The article presents a study which investigates the pathways for 1,2-4 benzenetriol and catechol in rabbits. The study conducted high performance liquid chromatography (HPLC) analyses of urine for t, t-muconic acid, catechol, and quinol. The result of the study shows that a significant increase in the urinary level of quinol was recorded when phenol was administered but not that of t,t-muconic acid nor catechol.

The article focuses on a study which analyses the strain difference in free p-cresol excretion in rats urine exposure to toluene at sub-narcotic concentrations. The study used female rats of Donryu, Sprague-Dawley, and Wistar strains, analyzed the urine samples using acid hydrolysis and gas-chromatography, and employed analysis of variance (ANOVA). The study found that there was no significant difference in free p-cresol levels among the rats at 45 and 500 parts per million (ppm) toluene level.

Objective: To establish a convenient method by high-pressure liquid chromatography (HPLC) to measure toluene in urine as a marker of occupational exposure to toluene. Methods: As soon after sampling as possible, 1 ml of urine was mixed with an equal volume of acetonitrile in a 2.2-ml HPLC glass bottle, and the bottle was tightly sealed and stored at 4 °C. Immediately before HPLC determination, 100 μl methanol was added to the mixture to prevent confounding effects of glycosuria, and the bottle was spun to remove any suspended matter. An aliquot of the supernate was introduced into the HPLC system and analyzed on a PRODIGY column, with an acetonitrile – perchloric acid – phosphoric acid – water mixture serving as the mobile phase. The effluent was monitored at 191 nm. Results: The method can measure toluene in urine every 20 min; the detection limit was 2 μg/l, the coefficient of variation was less than 5%, and the recovery rate was 100%. No significant reduction in toluene concentration was observed for 1 week after storage at 4 °C. When the method was applied to end-of-shift urine samples from 13 male workers exposed to toluene at 18–140 ppm and also to urine samples from 10 nonexposed male controls, toluene in urine was linearly related to toluene exposure concentration, with a regression line passing close to the origin. The correlation coefficient was as high as 0.97 ( n = 23). No toluene was detected in control urine samples. Calculations suggest that urinary toluene accounts for as little as less than 0.01% of the toluene absorbed via inhalation and that the absorbed toluene is converted almost quantitatively to hippuric acid and, by less than 0.1%, to o-cresol. [ABSTRACT FROM AUTHOR]

Peripheral leukocyte counts were examined in venous blood of more than 800 male workers exposed to toluene, xylenes, a combination of the two, or neither. Information on the social habits of smoking and drinking was obtained in an occupational health interview. The analysis showed that smoking (15 cigarettes/day on average) induced a significant increase (by 7%) in leukocyte counts, and that an additional increase was induced when the drinking habit was coupled with smoking. Drinking alone tended to increase the leukocyte counts but the effect was statistically nonsignificant, possibly because the number of nondrinking smokers was limited. The study stresses the importance of paying attention to smoking and drinking habits when evaluating hematological parameters such as peripheral leukocyte counts in solvent-exposed workers. [ABSTRACT FROM AUTHOR]

The correlation between exposure to three xylene isomers and resulting urinary excretion of corresponding methylhippuric acid (MHA) isomers was studied among 175 Chinese workers of both sexes who had been predominantly exposed to xylenes (exposure to xylenes accounting for 70% or more of the total exposure on a ppm basis). Nonexposed controls (281 men and women) were also studied to define the background level of MHAs in urine. The solvent exposure of xylene-exposed workers during their workshift was monitored by diffusive sampling of breathing zone air, and MHAs in shift-end urine were determined by high-performance liquid chromatography. Regression analysis showed that the concentration of each MHA isomer correlated significantly with the time-weighted average intensity of exposure to the corresponding xylene isomer, and therefore the correlation between the sum of three xylene isomers in air and that of three MHA isomers in urine was also significant; the slope of the regression line was essentially the same among the three isomers. The calculated regression line suggested that the urinary MHA level after hypothetical exposure to xylenes at 100 ppm will be somewhat less than the proposed biological exposure index and biological tolerance value. Two social habits of smoking and drinking in combination suppressed the conversion of xylenes to MHAs in male workers. [ABSTRACT FROM AUTHOR]

Many reports support the concept of serotonergic-dopaminergic interaction in the brain. However, at present, there are few methods to study this relationship in vivo. The purpose of this study was to investigate the effect of serotonin (5-HT) uptake inhibitor, clomipramine, on a dopamine (DA) transporter ligand, [[sup 123]I]βCIT (RTI-55), in rat brain. Dose-dependent changes in [[sup 123]I]β-CIT specific binding induced by clomipramine were studied in the striatum (rich in DA transporter) and the hypothalamus (rich in 5-HT transporter). The changes in the time-activity curves of [[sup 123]I]β-CIT specific binding after clomipramine injection were also examined in these two regions. Using the cerebellum as the reference region, k[sub 3] and k[sub 4] values with and without clomipramine administration were estimated by a two-compartment kinetic analysis. Clomipramine inhibited [[sup 123]I]β-CIT specific binding in the hypothalamus, but enhanced its specific binding in the striatum in a dose-dependent manner. Kinetic analysis showed that k[sub 3] in the striatum was increased by 55%. In conclusion, enhancement of [[sup 123]I]β-CIT binding in the striatum after clomipramine administration indicated the possibility of 5-HTDA interaction. [ABSTRACT FROM AUTHOR]

Iodine-123-labelled 3β-(4-iodophenyl)tropane-2β-carboxylic acid ([I]β-CIT) labels both the dopamine transporter (DAT) and the serotonin transporter (5-HTT) and this ligand is able to clarify pathological changes in both dopaminergic and serotonergic systems. However, the differential kinetics of β-CIT binding to DAT and 5-HTT has not been clarified fully. In this study we examined time-activity curves of [I]β-CIT in individual regions in the rat brain. Using cerebellum as the reference region, k and k values were estimated by a two-compartment kinetic analysis. In the striatum, the kinetics was slowest among all brain areas. In this area specific binding reached its peak 4 h after the injection. In the hypothalamus, specific binding reached its peak 1 h after the injection and its amount did not change until 4 h after the injection. In the occipital cortex, the binding and washout of the ligand were fastest among all brain regions. Estimated k values were 0.040±0.003 in the striatum, 0.019±0.002 in the hypothalamus and 0.082±0.011 in the occipital cortex (min, mean ±SD). Estimated k values were 0.0034±0.0005 in the striatum, 0.0071±0.0009 in the hypothalamus and 0.083±0.013 in the occipital cortex (min, mean ±SD). Therefore binding kinetics of [I]β-CIT in the region rich in DAT is apparently different from that in the region rich in 5-HTT. These results will provide fundamental data to image both DAT and 5-HTT in one series of examinations with [I]β-CIT. [ABSTRACT FROM AUTHOR]

The biodistribution ofH-PK 11195, an antagonist of the peripheral-type benzodiazepine receptors, was studied in mice. High accumulations of radioactivity in the heart, lung, spleen, kidney and adrenal were observed after intravenous injection of tracer amounts ofH-PK 11195 into the mice. The radioactivity in the heart, lung, spleen, kidney and adrenal was significantly decreased by the coadministration of carrier PK 11195, which indicated that PK 11195 specifically binds to the receptors. No radioactive metabolites were observed in the heart, lung and brain 20 min after intravenous administration ofH-PK 11195. The accumulation ofH-PK 11195 in the lung was not affected by pretreatment with either α-methyl benzylamine or imipramine, suggesting thatH-PK 11195 specifically binds to the receptors. The ratios of radioactivity of the kidney, adrenal and spleen to blood increased as a function of time, whereas that of the lung and heart rapidly reached to a steady state.C-PK 11195 was synthesized by the N-methylation of desmethyl precursor yielding more than 100 mCi with high specific activity (more than 1.4 Ci/μmol). The labeling and purification procedure was completed within 23 min after the end of bombardment (EOB). TheC-PK 11195 solution for injection seems to have a high potential for the in vivo study of the peripheral-type benzodiazepine receptors in the living human by means of positron emission tomography (PET). [ABSTRACT FROM AUTHOR]

An acute effect of triazolam, a potent benzodiazepine agonist, on cholinergic receptor binding in the human brain was measured by PET (positron emission tomography) using [C] N-methyl-4-piperidylbenzilate ([C]NMPB), a potent muscarinic cholinergic receptor antagonist. Two PET scans were performed in each subject: (1) control scan; (2) after oral administration of 0.5 mg triazolam or placebo. The previously discussed amnestic effect of triazolam was measured by immediate and delayed recall of meaningful and meaningless syllables. A compartment model employing the radioactivity in the cerebellum as an input function was used for the quantification of receptor binding. The binding parameter, k, was decreased after triazolam administration in all measured regions, whereas no change was observed after placebo treatment. The reduction compared to the control study varied from 8.6±3.7% in the temporal cortex to 16.3±6.3% in the thalamus. Triazolam administration impaired both immediate and delayed recall of syllables, whereas placebo administration had no effects. Benzodiazepine agonists are reported to decrease the cortical acetylcholine release. The decrease of acetylcholine release in the synaptic cleft might be the explanation for the decreased binding of [C]NMPB. [ABSTRACT FROM AUTHOR]

D dopamine receptor binding in mood disorders was studied by positron emission tomography (PET) usingC-SCH23390. Ten patients with bipolar mood disorders and 21 normal controls were studied in the drug-free state. The patients were in euthymic ( N=6), depressed ( N=3) and manic ( N=1) states. Regional radioactivity in the brain was followed for 40 min by PET. A two-compartment model was used to obtain the binding potential (k/k) for the striatum and frontal cortex. The binding potentials for the frontal cortex for the patients were significantly lower than those for normal controls, whereas those for striatum were not significantly different. These findings suggest that D dopamine receptors in the frontal cortex may be in a different state in patients with bipolar mood disorders. [ABSTRACT FROM AUTHOR]

Benzodiazepine receptor occupancy in the brain following oral administration of clonazepam (CZP) with a dose of 30 μg/kg in six healthy young men and a further dose of 50 μg/kg in one of the subjects was estimated by carbon-11 labeled Ro15-1788 and positron emission tomography (PET). The effects of CZP on the latency of auditory event-related potentials (P300) were also studied. Overall brain C uptake was depressed and the % inhibition of C uptake in the gray matter of the brain at 30 min after [C]Ro15-1788 injection was 15.3-23.5% (mean, n=6) following 30 μg/kg CZP when compared with that in the control experiment without any previous treatment. The C uptake in the cerebral cortex in the subject who received both doses decreased in a dose-related manner after 30 μg/kg and 50 μg/kg CZP. The P300 latency was prolonged significantly by 30 μg/kg CZP [31.6±16.3 ms (mean±SD, n=6), P<0.05]. The P300 latency in the same subject was prolonged in a dose-related manner by 30 μg/kg and 50 μg/kg CZP. The technique using [C]Ro15-1788 and PET permits comparison of the pharmacological effects with the percentage of receptor sites which benzodiazepines occupy in the human brain. P300 also seems to be useful to investigate the pharmacological effects of benzodiazepines. [ABSTRACT FROM AUTHOR]

The in vivo binding kinetics of 11C-iomazenil were compared with those of 11C-flumazenil binding in rhesus monkey brain. The monkey was anesthetized with ketamine and intravenously injected with either 11C-iomazenil or 11C-flumazenil in combination with the coadministration of different doses of non-radioactive flumazenil (0, 5 and 20 microg/kg). The regional distribution of 11C-iomazenil in the brain was similar to that of 11C-flumazenil, but the sensitivity of 11C-iomazenil binding to competitive inhibition by non-radioactive flumazenil was much less than that of 11C-flumazenil binding. A significant reduction in 11C-flumazenil binding in the cerebral cortex was observed with 20 microg/kg of flumazenil, whereas a relatively smaller inhibition of 11C-iomazenil binding in the same region was observed with the same dose of flumazenil. These results suggest that 11C-flumazenil may be a superior radiotracer for estimating benzodiazepine receptor occupancy in the intact brain. [ABSTRACT FROM AUTHOR]

The effects of occupational exposure to N,N-dimethylformamide (DMF) on sister chromatid exchange (SCE) rates were studied in peripheral lymphocytes from 22 DMF-exposed women (aged 22-52 years) in comparison with 22 sex-, age-, and residence-matched controls. All subjects were nonsmokers and nondrinkers as confirmed by medical interview. The 22 pairs were divided by the intensity of exposure to DMF into 3 subgroups of high-exposed (8 pairs with mean DMF exposure at 5.8ppm), middle-exposed (5 pairs with DMF at 0.7 ppm in combination with toluene at 0.9 ppm), and low-exposed (9 pairs with DMF at 0.3 ppm). The SCE rates were significantly higher in the high ( P < 0.005) and middle ( P < 0.01) exposed than in their matched pairs, and the increase was related to the intensity of DMF exposure. [ABSTRACT FROM AUTHOR]

Background: Nonalcoholic fatty liver disease is a common disorder that progresses from simple fatty liver (steatosis) to nonalcoholic steatohepatitis (NASH). It is thought that mitochondrial dysfunction plays a critical role in the progression of NASH. In this study, we developed a non-invasive method for early diagnosis and staging of NASH that directly measures mitochondrial complex-I (MC-I) activity in the liver of NASH model mice by positron emission tomography (PET) imaging using the novel tracer 2-tert-butyl-4-chloro-5-[6-(4-[18F]fluorobutoxy)-pyridin-3-ylmethoxy]-2H-pyridazin-3-one (18F-BCPP-BF). Liver uptake of 18F-BCPP-BF in NASH and age-matched control mice was measured as a standard uptake value over a period of 1 to 12 weeks. Histopathological evaluation of the liver tissue was performed by haematoxylin and eosin staining, and fibrosis was assessed by Masson’s trichrome staining.Results: Significant mitochondrial dysfunction was detected as early as 1 week after commencing the diet, and MC-I activity in the liver measured by PET was reduced by > 50% relative to that in age-matched control mice after 6 weeks. Liver uptake of 18F-BCPP-BF was low throughout the 12-week experimental period. Histopathological examination revealed that steatosis, inflammation, and ballooning progressed from 1 to 6 weeks, with fibrosis observed from 6 to 12 weeks.Conclusions: PET scans and histopathological analysis revealed that mitochondrial dysfunction in the liver contributed to the progression of NASH. PET imaging with 18F-BCPP-BF is a useful tool for detecting NASH at early stages and for monitoring therapeutic response. [ABSTRACT FROM AUTHOR]