Kinetic analysis of [(11)C]MP4A using a high-radioactivity brain region that represents an integrated input function for measurement of cerebral acetylcholinesterase activity without arterial blood sampling

N -[(11)C]methylpiperidin-4-yl acetate ([(11)C]MP4A) is an acetylcholine analog. It has been used successfully for the quantitative measurement of acetylcholinesterase (AChE) activity in the human brain with positron emission tomography (PET). [(11)C]MP4A is specifically hydrolyzed by AChE in the brain to a hydrophilic metabolite, which is irreversibly trapped locally in the brain. The authors propose a new method of kinetic analysis of brain AChE activity by PET without arterial blood sampling, that is, reference tissue-based linear least squares (RLS) analysis. In this method, cerebellum or striatum is used as a reference tissue. These regions, because of their high AChE activity, act as a biologic integrator of plasma input function during PET scanning, when regional metabolic rates of [(11)C]MP4A through AChE (k(3); an AChE index) are calculated by using Blomqvist's linear least squares analysis. Computer simulation studies showed that RLS analysis yielded k(3) with almost the same accuracy as the standard nonlinear least squares (NLS) analysis in brain regions with low (such as neocortex and hippocampus) and moderately high (thalamus) k(3) values. The authors then applied these methods to [(11) C]MP4A PET data in 12 healthy subjects and 26 patients with Alzheimer disease (AD) using the cerebellum as the reference region. There was a highly significant linear correlation in regional k(3) estimates between RLS and NLS analyses (456 cerebral regions, [RLS k(3) ] = 0.98 x [NLS k(3) ], r = 0.92, P < 0.001). Significant reductions were observed in k(3) estimates of frontal, temporal, parietal, occipital, and sensorimotor cerebral neocortices (P < 0.001, single-tailed t-test), and hippocampus (P = 0.012) in patients with AD as compared with controls when using RLS analysis. Mean reductions (19.6%) in these 6 regions by RLS were almost the same as those by NLS analysis (20.5%). The sensitivity of RLS analysis for detecting cortical regions with abnormally low k 3 in the 26 patients with AD (138 of 312 regions, 44%) was somewhat less than NLS analysis (52%), but was greater than shape analysis (33%), another method of [(11)C]MP4A kinetic analysis without blood sampling. The authors conclude that RLS analysis is practical and useful for routine analysis of clinical [(11)C]MP4A studies.

High-throughput characterization for organic pollutants in environmental waters using a capillary electrophoresis chip

To evaluate organic pollution in water, we did preliminarily studies on high-throughput characterization of organic pollution in water using microchip-based capillary electrophoresis (CE) with laseer-induced fluorescence (LIF) detection. The applied voltage was investigated to control the gated valve injection and CE separation for conventional cross type microchips using a self-made personal computer (PC)-based controller as the voltage supply. We obtained high-throughput data for the reproducible separation of fluorescein isothiocyanate (FITC)-labeled river-water samples using a zwitter-ion based buffer solution to avoid adsorption of the labeled sample onto the channel of a microchip made from quartz glass. We used real samples from the Hino River that flows into Lake Biwa, from ten sampling points and obtained several reproducible peaks in different separation patterns for each sample within 2 min. We successfully demonstrated high-throughput characterization of dissolved organic carbon (DOC) in environmental water using the microchip.

Positron emission tomographic measurement of brain acetylcholinesterase activity using N-[(11)C]methylpiperidin-4-yl acetate without arterial blood sampling: methodology of shape analysis and its diagnostic power for Alzheimer's disease

N-[11C]methylpiperidin-4-yl acetate ([11C]MP4A) is a radiotracer that has been used successfully for the quantitative measurement of acetylcholinesterase (AChE) activity in the human brain with positron emission tomography (PET) using a standard compartment model analysis and a metabolite-corrected arterial input function. In the current study, the authors evaluated the applicability of a simple kinetic analysis without blood sampling, namely shape analysis. First, the authors used computer simulations to analyze factors that affect the precision and bias of shape analysis, then optimized the shape analysis procedure for [11C]MP4A. Before shape analysis execution, the later part of dynamic PET data except for the initial 3 minutes were smoothed by fitting to a bi-exponential function followed by linear interpolation of 8 data points between each of adjacent scan frames. Simulations showed that shape analysis yielded estimates of regional metabolic rates of [11C]MP4A by AChE (k3) with acceptable precision and bias in brain regions with low k3 values such as neocortex. Estimates in regions with higher k3 values became progressively more inaccurate. The authors then applied the method to [11C]MP4A PET data in 10 healthy subjects and 20 patients with Alzheimer's disease (AD). There was a highly significant linear correlation in regional k3 estimates between shape and compartment analyses (300 neocortical regions, [shape k3] = 0.93 x [NLS k3], r = 0.89, P < 0.001). Significant reductions in k3 estimates of frontal, temporal, parietal, occipital, and sensorimotor cerebral cortices in patients with AD as compared with controls were observed when using shape analysis (P < 0.013, two-tailed t-test), although these reductions (17% to 20%) were somewhat less than those obtained by compartment analysis (22% to 27%). The sensitivity of shape analysis for detecting neocortical regions with abnormally low k3 in the 20 patients with AD (92 out of 200 regions, 46%) also was somewhat less than compartment analysis (136 out of 200 regions, 68%). However, taking its simplicity and noninvasiveness into account, the authors conclude that quantitative measurement of neocortical AChE activity with shape analysis and [11C]MP4A PET is practical and useful for clinical diagnosis of AD.

Effect of donepezil on brain acetylcholinesterase activity in patients with AD measured by PET

Acetylcholinesterase (AChE) activities in the brain of three patients with AD were measured once before and once during donepezil treatment (5 mg/d in two patients, 3 mg/d in one patient) using PET and N-[11C]methylpiperidin-4-yl acetate. Donepezil reduced k(3) values, an index of AChE activity, in the cerebral cortex by 39 +/- 5%. All patients showed some degree of symptomatic improvement, and it was concluded that this improvement was likely caused by improved cholinergic activity by inhibition of AChE in the brain.

Ecological co-inhabitance index (ECI) as a management tool for ecosystem preservation in rivers

The number of novel man-made hazardous substances produced by industries is increasing year after year, resulting in conventional discharge standards ineffective to preserve the natural ecological environment. A novel index, ecological co-inhabitance index (ECI), was proposed in order to evaluate the river ecosystem sensitively. The river benthic community with a high value of ECI is formed in the healthy ecosystem where benthic animals can share resources in the river environment efficiently, keep the ecosystem functioning, and give the least adverse effect to lower reaches of the river. In order to clarify the characteristic of ECI, the relationship between ECI and water quality in the river was investigated using the data on benthic animals obtained from 17 various rivers. Results of this investigation indicated that ECI could synthetically evaluate the river environment without a bias toward a specific water quality. Moreover, ECI had the significant correlation coefficients with diversity index, biotic index and pollution index at significance level 0.05, respectively. Therefore, ECI is a promising index for managing the river ecosystem.

Isolation of copper-binding proteins from activated sludge culture

Six copper-binding microbial proteins were isolated from activated sludge cultures grown on media containing copper at various concentrations. Molecular weights among isolated proteins were ranged from 1.3k to 1 74k dalton. Isolated proteins were compared for their copper binding capabilities. Proteins isolated from cultures grown in the presence of copper in the growth media exhibited higher copper binding capabilities than those isolated from the culture grown in the absence of copper. The highest metal uptake of 61.23 (mol copper/mol protein) was observed by a protein isolated from a culture grown with copper at a concentration of 0.25 mM. This isolated protein (CBP2) had a molecular weight of 24k dalton. Other protein exhibited copper binding capability of 4.8-32.5 (mol copper/mol protein).

Enhanced virus recovery from municipal sewage sludge with a combination of enzyme and cation exchange resin

There is a great difficulty in virus enumeration in sewage sludge because viruses in sludge are firmly captured by sludge solids. In order to determine the precise number of viruses in sludge, an enhanced virus recovery method with a combination of an enzyme and a cation exchange resin (CER) was developed. Test viruses were seeded to a sample sludge obtained from a municipal wastewater treatment plant, and the sludge were incubated with various eluents. The quantity of eluted viruses in the liquid phase was then measured by the plaque assay technique. Using the eluent containing only water, CER, and CER with enzyme exhibited 0%, 19% and 39% of virus recovery, respectively. While the conventional USEPA method exhibited a virus recovery of 21%. Furthermore, viruses eluted by the eluent containing the CER and the lysozyme included not only surface-attached viruses but also solids-embedded viruses.

Brain acetylcholinesterase activity in Alzheimer disease measured by positron emission tomography

Brain acetylcholinesterase activity was measured in 14 patients with Alzheimer disease and 14 age-matched control subjects by positron emission tomography with a radioactive acetylcholine analogue. Kinetic analysis was performed to calculate k3, an index of acetylcholinesterase activity. The k3 values were significantly reduced in the neocortex, hippocampus, and amygdala of all patients with Alzheimer disease, suggesting a loss of cholinergic innervation from the basal forebrain. Most profound reductions of k3 values were observed in the temporal (-30%) and parietal cortices (-31%), although reductions of k3 values were relatively uniform in the cerebral neocortex. This technique may be a powerful tool for early diagnosis of Alzheimer disease and also for therapeutic monitoring of acetylcholinesterase inhibitors in Alzheimer disease.

Separation of bisphenol A and three alkylphenols by micellar electrokinetic chromatography

Analytical conditions of pH, surfactants, and additives were investigated for the simultaneous separation of bisphenol A and alkylphenols by micellar electrokinetic chromatography. Reproducibility of migration time was improved at higher pH (pH 8.0). When five surfactants having linear alkyl chains or four bile salts were used, the separation of hydrophobic phenols and 4-nonylphenol isomers was not achieved. In order to improve the separation, the use of additives with sodium dodecyl sulfate solution was investigated. The separation of hydrophobic phenols was improved by the addition of organic solvents, however, isomers were not separated. Their separation was achieved by the addition of beta- or gamma-cyclodextrin.

Soluble Fas ligand and soluble Fas in ocular fluid of patients with uveitis

AIMS

To investigate the presence of soluble Fas ligand (sFasL) and soluble Fas (sFas) in ocular fluid of patients with uveitis.

METHODS

Samples of aqueous humour (AH, n=17), vitreous fluid (n=9), and serum (n=60) were collected from patients with uveitis which included Behçet's disease, Vogt-Koyanagi-Harada disease, sarcoidosis, human T lymphotropic virus type 1 (HTLV-I) uveitis, sympathetic ophthalmia, HLA-B27 associated acute anterior uveitis, and ocular toxoplasmosis. The AH of patients with age related cataract without uveitis obtained during cataract surgery was used as controls (n=20). The amounts of sFasL and sFas were measured by enzyme linked immunosorbent assay.

RESULTS

Significant amounts of sFasL were detected in AH of patients with age related cataract (non-uveitis group). sFasL was also detected in AH of patients with uveitis, though the amounts were slightly lower than those in the non-uveitis group. On the other hand, the levels of sFas in AH of patients with uveitis were significantly higher than those in controls. As for the disease activity, the levels of sFasL and sFas in the vitreous fluid of patients with active uveitis were significantly higher than those in inactive uveitis. sFasL in the serum of healthy donors and patients with uveitis was below detectable levels, except for patients with HTLV-I uveitis who had significant amounts of sFasL in the serum. The levels of sFas in the serum of patients with Behçet's disease, sarcoidosis, and HTLV-I uveitis were significantly higher than those of healthy donors.

CONCLUSIONS

sFasL is present in the AH of non-uveitic eyes with age related cataract. Intraocular levels of sFasL and sFas are significantly increased in uveitis, particularly in active uveitis. These data suggest that intraocular sFasL and sFas may have a regulatory role in uveitis.

Analysis of highly saline samples by capillary zone electrophoresis: enhanced direct UV detection of inorganic anions using on-capillary preconcentration and clean-up techniques

The ability to analyze samples with disparate levels of analyte and matrix ions is among the important benefits defining the practical utility of modern capillary electrophoresis. To compensate for the sensitivity limitations regarding trace-level inorganic anions, a number of on-line approaches that should offer an improved S/N ratio in direct UV detection were examined. The novel use of reversed pre-electrophoresis (at the applied voltage opposite to the separation voltage) made it possible to efficiently remove the most part of high chloride levels from the sample and hence to lower the background signal and to inject increased quantities of fast analyte anions. Specifically, by taking these advantages the sensitivity response of iodide was improved by a factor of 5 over normal CE mode. Using isotachophoretic sample stacking, a two-fold increase in detectability was obtained for moderately mobile anions, nitrate and nitrite, that corresponds to the minimum detectable concentrations close to their natural occurrences in seawater. Furthermore, field-amplified sample injection at increased electrolyte-to-sample matrix concentration ratios enabled the maximum S/N enhancement, with detection limits at the level of 10(-6) M and lower in the presence of > or = 5 x 10(4)-fold molar excess of chloride.

Improvement of capillary zone electrophoresis sensitivity with artificial seawater as the background electrolyte utilizing transient isotachophoresis for the determination of nitrate and nitrate ions in seawater

We describe capillary zone electrophoresis (CZE) with transient isotachophoresis (ITP) for the determination of low concentrations of nitrite and nitrate ions in seawater. Bromide-free artificial seawater was adopted as background electrolyte (BGE) to eliminate the interference of high concentrations of salts in seawater. To reverse the electroosmotic flow (EOF), 3 mM cetyltrimethylammonium chloride (CTAC) was added to the BGE. High concentrations of chlorate were added to sample solutions as the terminating ion to generate the ITP process before the CZE separation. In general, the stacking effect increased with increasing amounts of chlorate injected into the capillary. The limits of detection (LODs) for nitrite and nitrate were 0.063 and 0.033 mg/L when the chlorate concentration was 600 and 200 mM, respectively; these were half of those obtained by CZE without the transient ITP. The LODs were obtained at a signal to noise ratio (S/N) of 3. The relative standard deviations (RSD, n = 10) of the peak areas for these ions were 3.2 and 2.9%. The RSDs of peak heights for these ions were 1.6 and 2.1%. The RSDs of migration times for these ions were 0.67 and 0.46%.

Progressive loss of cortical acetylcholinesterase activity in association with cognitive decline in Alzheimer's disease: a positron emission tomography study

We measured brain acetylcholinesterase activity in 30 patients with Alzheimer's disease (AD) and 14 age-matched controls by positron emission tomography (PET) and using a carbon 11-labeled acetylcholine analogue. Seven AD patients had repeat PET scans. The k3 values were calculated as an index of acetylcholinesterase activity in a three-compartment analysis using the metabolite corrected arterial input function. Twenty-eight of the 30 AD patients (14 each in the early and late onset subgroups) were retained in the study so as to equalize the range and average severity of cognitive impairment within the early and late onset subgroups. The k3 values were significantly reduced in the neocortex, hippocampus, and amygdala in the early onset AD patients, although the k3 values were significantly reduced only in the temporoparietal cortex and amygdala in the late onset AD patients. In the longitudinal study, all 7 repeat AD patients showed further reduction of cortical k3 values in the second PET scans, with a mean interval of 2 years, suggesting a progressive loss of the ascending cholinergic system from the nucleus basalis of Meynert in AD. In 37 AD patients, there was a highly significant correlation between the cortical k3 values and Mini-Mental State Examination scores, supporting the cholinergic hypothesis in AD.

Simultaneous determination of bromide, nitrite and nitrate ions in seawater by capillary zone electrophoresis using artificial seawater as the carrier solution

We describe capillary zone electrophoresis (CZE) for the simultaneous determination of bromide, nitrite and nitrate ions in seawater. Artificial seawater was adopted as the carrier solution to eliminate the interference of high concentrations of salts in seawater. The artificial seawater was free from bromide ion to enable the determination of bromide ion in a sample solution. For the purpose of reversing the electroosmotic flow (EOF), 3 mM cetyltrimethylammonium chloride (CTAC) was added to the carrier solution. A 100 microm ID (inside diameter) capillary was used to extend the optical path length. The limits of detection (LODs) for bromide, nitrite, and nitrate ions were 0.46, 0.072, and 0.042 mg/L (as nitrogen), respectively. The LODs were obtained at a signal to noise ratio (S/N) of 3. The values of the relative standard deviation (RSD) of peak area for these ions were 1.1, 1.5, and 0.97%. The RSDs of migration time for these ions were 0.61, 0.69, and 0.66%. Artificial seawater samples containing various concentrations of bromide, nitrite, and nitrate ions were analyzed by the method. The error was less than +/-12% even if the concentration ratio of bromide ion to nitrite or nitrate ion was 20-240. The proposed method was applied to the determination of bromide, nitrite, and nitrate ions in seawater samples taken from the surface and the seabed. These ions in other environmental waters such as river water and rainwater samples were also determined by ion chromatography (IC) as well as this method.

Positron emission tomographic measurement of acetylcholinesterase activity reveals differential loss of ascending cholinergic systems in Parkinson's disease and progressive supranuclear palsy

We measured brain acetylcholinesterase activity in 16 patients with Parkinson's disease (PD), 12 patients with progressive supranuclear palsy (PSP), and 13 age-matched controls, using N-methyl-4-[11C]piperidyl acetate and positron emission tomography. Kinetic analysis was performed to calculate k3, an index of acetylcholinesterase activity. In PD patients, there was a significant reduction (-17%) of cerebral cortical k3 compared with normal controls, whereas there was only a nonsignificant reduction (-10%) of cortical k3 in PSP patients. However, there was a prominent reduction (-38%) of thalamic k3 in PSP patients compared with normal controls, whereas there was only a nonsignificant reduction (-13%) of thalamic k3 in PD patients. The results suggest that there is a loss of cholinergic innervation to the cerebral cortex in association with cholinergic innervation to the thalamus in PD, whereas there is a preferential loss of cholinergic innervation to the thalamus in PSP. When the thalamic to cerebral cortical k3 ratio was taken for each subject, PD and PSP were separated, suggesting that positron emission tomography measurement of acetylcholinesterase activity may be useful for differentiating the two similar disorders.

Application of capillary electrophoresis to the analysis of inorganic ions in environmental samples

A comprehensive review is presented of the state-of-the-art of capillary electrophoresis for application to the analysis of inorganic species, mainly ions, in environmental samples. This brief review covers the developments principally in sensitivity and matrix interference for the determination of inorganic ions in the following samples: drinking, mineral, surface, and ground waters, rainwater, snow, seawater, brine and waste waters, aerosol, and others. References published mainly from 1995 to 1997 were summarized in this review.

Human cerebral acetylcholinesterase activity measured with positron emission tomography: procedure, normal values and effect of age

The regional cerebral metabolic rate of [11C]N-methyl-4-piperidyl acetate, which is nearly proportional to regional cerebral acetylcholinesterase (AChE) activity, was measured by dynamic positron emission tomography in 20 healthy subjects with a wide age range (24-89 years). Quantitative measurement was achieved using a kinetic model which consisted of arterial plasma and cerebral tissue compartments. The plasma input function was obtained using thin-layer chromatography and an imaging phosphor plate system at frequent sampling intervals to catch the rapid metabolism of the tracer in the blood. The distribution of the rate constant k3, an index of AChE activity, agreed well with reported post-mortem AChE distribution in the cerebral cortex (0.067-0.097 min-1) and thalamus (0.268 min-1), where AChE activity was low to moderate. The k3 values in the striatum and cerebellum, where AChE activity was very high, did not respond linearly to AChE activity because of increased flow dependency. No significant effect of age was found on AChE activity of the cerebral cortex, suggesting that the ascending central cholinergic system is preserved in normal aging. This study has shown that quantitative measurement of enzyme activity in the living brain is possible through appropriate modelling of tracer kinetics and accurate measurement of the input function. The method should be applicable to patients with Alzheimer's disease and those with other kinds of dementia whose central cholinergic system has been reported to be disturbed.

A mutation in plasma platelet-activating factor acetylhydrolase (Val279Phe) is a genetic risk factor for cerebral hemorrhage but not for hypertension

Platelet-activating factor (PAF) acetylhydrolase is an enzyme that inactivates PAF. Deficiency of this enzyme is caused by a missense mutation in the gene. We previously found a higher prevalence of this mutation in patients with ischemic stroke. This fact suggests that the mutation might enhance the risk for stroke through its association with hypertension. We have addressed this hypothesis by analyzing the prevalence of the mutation in hypertension. We studied 138 patients with essential hypertension, 99 patients with brain hemorrhage, and 270 healthy controls. Genomic DNA was analyzed for the mutant allele by the polymerase-chain reaction. The prevalence of the mutation was 29.3% (27.4% heterozygotes and 1.9% homozygotes) in controls and 36.2% in hypertensives and the difference was not significant. The prevalence in patients with brain hemorrhage was significantly higher than the control: 32.6% heterozygotes and 6.1% homozygotes (p <0.05). PAF acetylhydrolase deficiency may be a genetic risk factor for vascular diseases.

Glucose and methionine uptake by rat brain tumor treated with prodrug-activated gene therapy

The effect of acyclovir (ACV) on the metabolism of rat 9L-gliosarcoma cells expressing the herpes simplex virus-thymidine kinase gene was studied using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) and L-[methyl-11C]methionine. Though the average weight of the tumors treated with ACV was significantly lower than that of the saline-injected control group, FDG and methionine uptake per weight of tumor tissue was not different between the two groups. This result exhibits a striking contrast to the metabolic pattern observed after radiation therapy, suggesting the different pathways regarding tumor cell death between the therapies.

Measurement of acetylcholinesterase by positron emission tomography in the brains of healthy controls and patients with Alzheimer's disease

BACKGROUND

Acetylcholinesterase activity, a marker for degeneration of the central cholinergic system, has consistently been reported, in necropsy brain studies, to be reduced in the cerebral cortex of patients with Alzheimer's disease. We have shown regional acetylcholinesterase activity in vivo in rodent and primate brains with radioactive acetylcholine analogues. In the present study, we used one of the analogues to map acetylcholinesterase activity in the brains of living people.

METHODS

Positron emission tomography (PET) and a radiolabelled acetylcholine analogue with high hydrolytic specificity to acetylcholinesterase [11C]N-methyl-4-piperidyl acetate (MP4A), was used in eight elderly healthy controls and five patients with Alzheimer's disease who had mild dementia. All participants were given an intravenous injection of [11C]MP4A and then sequential patterns of radioactivity in various brain regions were obtained by PET. Time courses of [11C]MP4A concentration in arterial blood were also measured to obtain an input function. A three-compartment model was used to estimate regional acetylcholinesterase activity in the brain.

FINDINGS

The estimated acetylcholinesterase distribution in the brain of the control participants agreed with the acetylcholinesterase distribution at necropsy. All patients with Alzheimer's disease had multiple cortical regions with a reduced estimated acetylcholinesterase activity in comparison with control participants. The reduction was more pronounced in the parietotemporal cortex, with an average reduction rate of 31% in temporal and 38% in parietal cortex, and less pronounced in other cortical lesions (19% in frontal, 24% in occipital, and 20% in sensorimotor cortex). Each patient was found to have at least two cortical regions with significantly reduced acetylcholinesterase activity.

INTERPRETATION

The method we describe for non-invasive in-vivo detection of regional acetylcholinesterase changes in the living human brain that is feasible for biochemical assessment of Alzheimer's disease.