Microglial activation in Alzheimer's disease: an (R)-[C]PK11195 positron emission tomography study

Inflammatory mechanisms, like microglial activation, could be involved in the pathogenesis of Alzheimer's disease (AD). (R)-[¹¹C]PK11195 (1-(2-chlorophenyl)-N-methyl-N-1(1-methylpropyl)-3-isoquinolinecarboxamide), a positron emission tomography (PET) ligand, can be used to quantify microglial activation in vivo. The purpose of this study was to assess whether increased (R)-[¹¹C]PK11195 binding is present in AD and mild cognitive impairment (MCI), currently also known as “prodromal AD.”     

Determination of a novel calmodulin antagonist, 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1- (4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate, DY-9760e, in human plasma using solid-phase extraction and high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method for the determination of a novel calmodulin antagonist, 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-( 4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate, DY-9760e and its major metabolite, 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxyi ndazole, DY-9836 in human plasma has been developed. DY-9760e, DY-9836 and the internal standard (I.S.) were extracted from plasma by means of an Isolute C18 (EC) column. The extracts were chromatographed on a reversed-phase TSK-gel ODS-80Ts column using 0.1 M acetate buffer (pH 5)-CH3CN (65:35, v/v) as the mobile phase at a flow-rate of 1.0 ml/min. Fluorescence detection at an excitation wavelength of 303 nm and an emission wavelength of 347 nm resulted in a limit of quantitation of 1.000 ng/ml for plasma. The method showed satisfactory sensitivity, precision, accuracy, recovery and selectivity. Stability studies showed that DY-9760 and DY-9836 were stable in plasma up to at least eight weeks at -80 degrees C.     

Microglial activation in healthy aging

Healthy brain aging is characterized by neuronal loss and decline of cognitive function. Neuronal loss is closely associated with microglial activation and postmortem studies have indeed suggested that activated microglia may be present in the aging brain. Microglial activation can be quantified in vivo using (R)-[(11)C]PK11195 and positron emission tomography. The purpose of this study was to measure specific binding of (R)-[(11)C]PK11195 in healthy subjects over a wide age range. Thirty-five healthy subjects (age range 19-79 years) were included. In all subjects 60-minute dynamic (R)-[(11)C]PK11195 scans were acquired. Specific binding of (R)-[(11)C]PK11195 was calculated using receptor parametric mapping in combination with supervised cluster analysis to extract the reference tissue input function. Increased binding of (R)-[(11)C]PK11195 with aging was found in frontal lobe, anterior and posterior cingulate cortex, medial inferior temporal lobe, insula, hippocampus, entorhinal cortex, thalamus, parietal and occipital lobes, and cerebellum. This indicates that activated microglia appear in several cortical and subcortical areas during healthy aging, suggesting widespread neuronal loss.     

PET imaging with [11C]PBR28 can localize and quantify upregulated peripheral benzodiazepine receptors associated with cerebral ischemia in rat

Peripheral benzodiazepine receptors (PBRs) are upregulated on activated microglia. We recently developed a promising positron emission tomography (PET) ligand, [11C]PBR28, with high affinity and excellent ratio of specific to nonspecific binding. We assessed the ability of [11C]PBR28 PET to localize PBRs in a rat permanent middle cerebral artery occlusion (MCAO) model of neuroinflammation. [11C]PBR28 was intravenously administered to rats at 4 and 7 days after permanent MCAO. In all experiments, arterial blood was sampled for compartmental modeling of regional distribution volumes, and rat brains were sampled after imaging for in vitro [3H]PK 11195 autoradiography and histological evaluation. [11C]PBR28 PET and [3H]PK 11195 autoradiography showed similar areas of increased PBRs, especially in the peri-ischemic core. Results from these in vivo and in vitro methods were strongly correlated. In this first study to demonstrate neuroinflammation in vivo with small animal PET, [11C]PBR28 had adequate sensitivity to localize and quantify the associated increase in PBRs.     

In vivo receptor labeling of peripheral benzodiazepine receptor by ex vivo binding of [3H]PK11195

In vivo receptor labeling of the peripheral benzodiazepine receptor was investigated using ex vivo binding of [3H]-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carb ox-amide ([3H]PK11195). In autoradiographic studies, high level specific binding of [3H]PK11195 was observed in the olfactory bulb. Intravenous administration of PK11195 dose-dependently (0.03-3 mg/kg) inhibited ex vivo binding of [3H]PK11195 in the olfactory bulb. Likewise, N-(2,5-dimethoxybenzyl)-N-(5-fluoro-2-phenoxyphenyl)acetamide (DAA1106), a newly identified peripheral benzodiazepine receptor-specific ligand, dose-dependently (0.1-100 mg/kg) reduced ex vivo binding of [3H]PK11195, when administered intraperitoneally. In contrast, clonazepam, a central benzodiazepine receptor-specific agonist, had negligible effects on ex vivo binding of [3H]PK11195. We propose that the ex vivo receptor binding technique we used will facilitate determination of in vivo receptor occupancy of the peripheral benzodiazepine receptor.     

3H]PK 11195 and the localisation of secondary thalamic lesions following focal ischaemia in rat motor cortex.

The peripheral-type benzodiazepine binding site (PTBBS) ligand, PK 11195, is known to be a marker of damage in the central nervous system, the binding being predominantly to macrophages. Using photochemically induced focal cortical ischaemia as a lesion model in the rat, we have investigated the detection of secondary lesions using [3H]PK 11195 and ex vivo autoradiography. Secondary lesions in the thalamus became apparent during the second week post-lesioning, at a time when [3H]PK 11195 binding around the primary lesion was beginning to subside. Using Brain Browser software, the identity of the labelled thalamic nucleus was confirmed, objectively, as the ventrolateral nucleus, known to have reciprocal connections with the lesioned cortical area. As with the primary lesion, high densities of PTBBS correlated with infiltration of macrophages. Three-dimensional reconstruction of [3H]PK 11195 autoradiograph images showed binding along white matter tracts between the primary and secondary lesions. We conclude that radiolabelled PK 11195 given in vivo can be used in the visualisation of secondary lesions and their associated degenerating tracts.     

Development of a gradient elution high-performance liquid chromatography assay with ultraviolet detection for the determination in plasma of the anticancer peptide [Arg6, D-Trp7,9, mePhe8]-substance P (6-11) (antagonist G), its major metabolites and a C-terminal pyrene-labelled conjugate.

[Arg6, D-Trp7,9 mePhe8]-substance P (6-11), code-named antagonist G, is a novel peptide currently undergoing early clinical trials as an anticancer drug. A sensitive, high efficiency high-performance liquid chromatography (HPLC) method is described for the determination in human plasma of antagonist G and its three major metabolites, deamidated-G (M1), G-minus Met11 (M2) and G[Met11(O)] (M3). Gradient elution was employed using 40 mM ammonium acetate in 0.15% trifluoroacetic acid as buffer A and acetonitrile as solvent B, with a linear gradient increasing from 30 to 100% B over 15 min, together with a microbore analytical column (microBondapak C18, 30 cm X 2 mm I.D.). Detection was by UV at 280 nm and the column was maintained at 40 degrees C. Retention times varied by <1% throughout the day and were as follows: G, 13.0 min; M1, 12.2 min; M2, 11.2 min; M3, 10.8 min, and 18.1 min for a pyrene conjugate of G (G-P). The limit of detection on column (LOD) was 2.5 ng for antagonist G, M1-3 and G-P and the limit of quantitation (LOQ) was 20 ng/ml for G and 100 ng/ml for M1-3. Sample clean-up by solid-phase extraction using C2-bonded 40 microm silica particles (Bond Elut, 1 ml reservoirs) resulted in elimination of interference from plasma constituents. Within-day and between-day precision and accuracy over a broad range of concentrations (100 ng/ml-100 microg/ml) normally varied by < 10%, although at the highest concentrations of M1 and M2 studied (50 microg/ml), increased variability and reduced recovery were observed. The new assay will aid in the clinical development of antagonist G.     

Imaging microglial activation and glucose consumption in a mouse model of Alzheimer's disease

In Alzheimer's disease (AD), persistent microglial activation as sign of chronic neuroinflammation contributes to disease progression. Our study aimed to in vivo visualize and quantify microglial activation in 13- to 15-month-old AD mice using [¹¹C]-(R)-PK11195 and positron emission tomography (PET). We attempted to modulate neuroinflammation by subjecting the animals to an anti-inflammatory treatment with pioglitazone (5-weeks' treatment, 5-week wash-out period). [¹¹C]-(R)-PK11195 distribution volume values in AD mice were significantly higher compared with control mice after the wash-out period at 15 months, which was supported by immunohistochemistry data. However, [¹¹C]-(R)-PK11195 μPET could not demonstrate genotype- or treatment-dependent differences in the 13- to 14-month-old animals, suggesting that microglial activation in AD mice at this age and disease stage is too mild to be detected by this imaging method.     

PK11195 labels activated microglia in Alzheimer's disease and in vivo in a mouse model using PET

Activated microglia may promote neurodegeneration in Alzheimer's disease (AD) and may also help in amyloid clearance in immunization therapies. In vivo imaging of activated microglia using positron emission tomography (PET) could assist in defining the role of activated microglia during AD progression and therapeutics. We hypothesized that PK11195, a ligand that binds activated microglia, could label these cells in postmortem AD tissues and in vivo in an animal model of AD using PET. [(3)H](R)-PK11195 binding was significantly higher in AD frontal cortex compared to controls and correlated mainly with the abundance of immunohistochemically labeled activated microglia. With age, the brains of APP/PS1 transgenic mice showed progressive increase in [(3)H](R)-PK11195 binding and [(11)C](R)-PK11195 retention in vivo assessed using microPET, which correlated with the histopathological abundance of activated microglia. These results suggest that PK11195 binding in AD postmortem tissue and transgenic mice in vivo correlates with the extent of microglial activation and may help define the role of activated microglia in the pathogenesis and treatment of AD.     

Metabolism of D-[1-(13)C]fructose, D-[2-(13)C]fructose, and D-[6-(13)C]fructose in rat hepatocytes incubated in the presence of H(2)O or D(2)O

Isolated hepatocytes from fed rats were exposed for 120 min to D-[1-(13)C]fructose, D-[2-(13)C]fructose, or D-[6-(13)C]fructose in the presence of H(2)O or D(2)O. The identification and quantification of (13)C-enriched metabolites (D-glucose, L-lactate) in the incubation medium and the measurement of their deuterated isotopomers indicated that the ketohexose was phosphorylated predominantly at the intervention of fructokinase and that the majority of the D-glyceraldehyde molecules generated from d-fructose 1-phosphate were further metabolized, e.g., after phosphorylation to D-glyceraldehyde 3-phosphate. It is proposed that the present procedure may help to further characterize the regulation of D-fructose metabolism in both hepatocytes and other cell types.     

Determination of isotopic enrichments of [1-13C]homocysteine, [1-13C]methionine and [2H3-methyl-1-13C]methionine in human plasma by gas chromatography-negative chemical ionization mass spectrometry

We describe a reliable method for the simultaneous determination of isotopic enrichments of [1-13C]homocysteine, [1-13C]methionine and [2H3-methyl-1-13C]methionine in human plasma. Accurate [1-13C]homocysteine calibration standards were prepared by chemical conversion via thiolactonisation of [1-13C]methionine standards. Based upon anion-exchange chromatography, (di)acetyl-3,5-bis-trifluoromethylbenzyl derivatives, preparation of accurate calibration curves and gas chromatography-negative chemical ionization mass spectrometry, isotopic enrichments in human plasma could be determined with TTR (%) <+/-0.2% (N=3) for [1-13C]homocysteine (enrichment range 0-8%), [1-13C]methionine (enrichment range 0-3%) and [2H3-methyl-1-13C]methionine (enrichment range 0-12%). The method was applied in a [2H3-methyl-1-13C]methionine tracer infusion study in a biological model.     

[~(125)I]-(A14)单碘胰岛素在荷人肝癌裸鼠体内的趋瘤特性研究

目的 :观察放射性碘标记胰岛素在荷人肝癌裸鼠体内的趋瘤或亲肿瘤 (tumor-seeking)特性。方法 :采用荷人肝癌裸鼠模型。用 [12 5I]- (A14)单碘胰岛素进行荷人肝癌裸鼠体内分布实验和抑制实验。结果 :体内分布实验显示肝癌组织摄取 [12 5I]- (A14)单碘胰岛素明显高于本底组织 (肌肉 ) ,肿瘤与血和肿瘤与肌肉的放射性比值随时间延长而增高。体内抑制实验发现肿瘤组织于 30min的抑制率为 35 .0 %。结论 :[12 5I]- (A14)单碘胰岛素在荷人肝癌裸鼠体内 ,通过受体介导作用 ,能被肝细胞癌组织特异性摄取。     

Differential involvement of mu(1)-opioid receptors in endomorphin- and beta-endorphin-induced G-protein activation in the mouse pons/medulla

Several genetic mouse models of differential sensitivity to opioids have been used to investigate the mechanisms underlying individual variation in responses to opioids. The CXBK mice are inbred recombinant mice which have a lower level of mu(1)-opioid receptors than their parental strain. Endomorphin-1 and endomorphin-2 are endogenous opioid peptides that are highly selective for mu-opioid receptors, while beta-endorphin, which is also an endogenous opioid peptide, is non-selective for mu-, delta- and putative epsilon-opioid receptors. The present study was designed to investigate the effects of these endogenous opioid peptides on G-protein activation by monitoring guanosine-5'-o-(3-[35S]thio)triphosphate binding to pons/medulla membranes of CXBK mice and their parental strain C57BL/6 ByJ mice. Endomorphin-1 (0.1-10 microM), endomorphin-2 (0.1-10 microM) and beta-endorphin (0.1-10 microM) increased guanosine-5'-o-(3-[35S]thio)triphosphate binding to the pons/medulla membranes from C57BL/6 ByJ and CXBK mice in a concentration-dependent manner. However, the increases of guanosine-5'-o-(3-[35S]thio)triphosphate binding induced by either endomorphin-1 or endomorphin-2 in CXBK mice were significantly much lower than those in C57BL/6ByJ mice. However, no significant difference was found in the increases of the guanosine-5'-o-(3-[35S]thio)triphosphate binding induced by beta-endorphin in C57BL/6 ByJ and CXBK mice. Moreover, whereas the increase of guanosine-5'-o-(3-[35S]thio)triphosphate binding induced by 10 microM endomorphin-1 or endomorphin-2 were almost completely blocked by a mu-opioid receptor antagonist beta-funaltrexamine (10 microM) in both strains, the increase of guanosine-5'-o-(3-[35S]thio)triphosphate binding induced by 10 microM beta-endorphin was attenuated to approximately 70% of stimulation by co-incubation with 10 microM beta-funaltrexamine in both strains. The residual stimulation of [35S]guanosine-5'-o-(3-thio)triphosphate binding by 10 microM beta-endorphin in the presence of 10 microM beta-funaltrexamine was further attenuated by the addition of putative epsilon-opioid receptor partial agonist beta-endorphin (1-27) (1 microM) in both strains. Like the endomorphins, the synthetic mu-opioid receptor agonist [D-Ala(2),N-MePhe(4), Gly-ol(5)]enkephalin at 10 microM showed lower increases of guanosine-5'-o-(3-[35S]thio)triphosphate binding in CXBK mice than those in C57BL/6ByJ mice. However, there was no strain difference in the stimulation of guanosine-5'-o-(3-[35S]thio)triphosphate binding induced by 10 microM of the selective delta(1)-opioid receptor agonist [D-Pen(2,5)]enkephalin, delta(2)-opioid receptor agonist [D-Ala(2)]deltorphin II or kappa-opioid receptor agonist U50,488H. The results indicate that the G-protein activation by endomorphin-1 and endomorphin-2 in the mouse pons/medulla is mediated by both mu(1)- and mu(2)-opioid receptors. Moreover, beta-endorphin-induced G-protein activation in the mouse pons/medulla is, in part, mediated by mu(2)- and putative epsilon-, but not by mu(1)-opioid receptors.     

Topographical assessment of accumulated radioactivity from [14C]2-deoxyglucose and [6(-14C)]glucose in rat forebrain at different survival periods

The uptake and retention of radioactivity was measured in discrete areas of rat brain at different times after i.v. injection of [14C]2-deoxyglucose or [6(-14)C]glucose, in unrestrained rats. In most brain regions, the accumulation of radioactivity from the two compounds was similar when a 30-min survival period for [6(-14)C]glucose was compared to a 45-min survival period for [14C]2-deoxyglucose. However, at those times, autoradiographic images of the hippocampus and piriform cortex appeared distinctly different for [14C]2-deoxyglucose and [6(-14)C]glucose. Relatively more radioactivity accumulated from [14C]2-deoxyglucose, compared to [14C]glucose, in the stratum lacunosum-moleculare of the hippocampus and in layer 4 of the isocortex. In contrast, relatively more radioactivity accumulated from [6(-14)C]glucose, compared to [14C]2-deoxyglucose, in the molecular and granule cell layers of the dentate gyrus, the CA1 pyramidal cell layer of the hippocampus, and in layer 2 of the piriform cortex. When rats were killed 5 min after injection of [6(-14)C]glucose, the relative neuroanatomical distribution of radioactivity was similar to the 30-min survival period, except in layer 4 of the isocortex, where relatively more radioactivity was present at the early time. When rats were killed 5 min after injection of [14C]2-deoxyglucose, in 20 of 24 brain regions examined, the absolute and relative amounts of accumulated radioactivity were similar when compared to that of the 45-min survival period. In contrast, the absolute and relative amounts of radioactivity were significantly greater for the 5-min compared to the 45-min survival period, in the CA1 pyramidal cell field, dentate gyrus, and layer 2 of the piriform cortex. For those regions, the appearance of autoradiograms prepared from rats killed 5 min after administration of [14C]2-deoxyglucose is remarkably similar to the appearance of autoradiograms prepared from rats killed 5 or 30 min after injection of [6(-14)C]glucose. Possible mechanisms are discussed to explain the observed differences in the accumulation of radioactivity in discrete brain regions after injection of [6(-14)C]glucose and [14C]2-deoxyglucose at the different survival times examined.     

Quantitative analysis of Z-2-[4-(4-chloro-1,2-diphenyl-but-1-enyl)phenoxy]ethanol in human plasma using high-performance liquid chromatography

A highly sensitive and precise high-performance liquid chromatography (HPLC) assay was developed and validated for the quantitation of Z-2-[4-(4-chloro-1,2-diphenyl-but-1-enyl) phenoxy]ethanol (FC-1271a) in human plasma. Plasma samples (1.0 ml) containing FC-1271a and internal standard (toremifene citrate; Farestono) were extracted using a 2% 1-butanol, 98% hexane solution with an extraction efficiency of >97%. Samples were reconstituted in methanol, irradiated with high intensity ultraviolet light (254 nm) for 1 min, and injected onto a C18 reverse phase column. Samples were eluted isocratically at a flow-rate of 0.5 ml/min with a mobile phase consisting of 6.5% water and 0.5% triethylamine in methanol. The fluorescence of photochemically activated compounds was detected using a fluorometer set at an excitation wavelength of 266 nm and emission wavelength of 370 nm. Under these assay conditions, standard calibration curves were linear through a concentration range of 10-400 ng/ml. In summary, we have developed and validated an HPLC assay to quantitate FC-1271a in human plasma.     

Activated macrophages in HIV encephalitis and a macaque model show increased [H](R)-PK11195 binding in a PI3-kinase-dependent manner

HIV encephalitis (HIVE) is a neurodegenerative disease seen in approximately one in four terminally infected patients. Macaques infected with the simian immunodeficiency virus develop encephalitis (SIVE) very similar to the human disease. Neurodegeneration in both these conditions occurs from the effects of toxic viral proteins and neurotoxins derived from activated brain macrophages. Activated macrophages in the brain of macaques with SIVE can be labeled in vivo using positron emission tomography (PET) using PK11195, a ligand that binds the peripheral benzodiazepine receptor (PBR). However, the functional significance and mechanisms mediating increased PK11195 binding in activated brain macrophages are not known. Using post mortem tissues from macaques with SIVE and macrophages cell cultures activated with lipopolysaccharide (LPS), we show that [³H](R)-PK11195 binding is increased in activated macrophages. Increased [³H](R)-PK11195 binding in LPS-activated macrophages was reversed by pharmacologically inhibiting class III phosphatidylinositol-3 kinase (PI3-kinase), but was not altered by inhibiting the mitogen-activated protein kinase (MAP-kinase) pathway. Our results suggest that activated macrophages in lentiviral encephalitis show increased [³H](R)-PK11195 binding in a PI3-kinase-dependent fashion which may help elucidate the function of PBR in activated brain macrophages in HIVE and other neuroinflammatory diseases.     

Measurement of the novel antitumor agent 17-(allylamino)-17-demethoxygeldanamycin in human plasma by high-performance liquid chromatography

A sensitive HPLC assay has been developed to determine the concentration of 17-(allylamino)-17-demethoxygeldanamycin (AAG) in human plasma over the concentration range of 12.5 to 2,500 nM (7.33 to 1,465 ng/mL). After the addition of 1,000 nM geldanamycin as the internal standard, 1 mL samples of human plasma were subjected to solid-phase extraction, via Bond-Elut C18 cartridges, followed by analysis using an isocratic reversed-phase HPLC assay with UV detection. A Phenomenex Kingsorb, 3 micron, C18, 150x4.60 mm column and a Phenomenex Security Guard pre-column, C18 (ODS, Octadecyl), were used to achieve separation. AAG and GM were monitored at 334 and 308 nm, respectively, on a Hewlett-Packard 1050 Diode-Array Detector. The mobile phase, run at a flow-rate of 1 mL/min, was composed of 50% (v/v) 25 mM sodium phosphate (pH 3.00) with 10 mM triethylamine and 50% acetonitrile. HPLC effectively resolved AAG with retention times of 14.60 +/- 0.54 min and the internal standard geldanamycin at 10.72+/-0.38 min (n = 15). This assay was able to measure plasma concentrations of AAG, the lower limit of quantitation being 12.5 nM, at a starting dose of 10 mg/m2 infused intravenously over 1 h in a Phase I clinical trial in adult patients with solid tumors.     

Importance of post‐exercise hypotension in plasma volume restoration

The aim of this study was to test the hypothesis that post‐exercise hypotension was the mechanism for the plasma volume and albumin gain during recovery. Seven healthy young men completed two experiments (≥1 week apart) to exercise continuously at 65% of peak aerobic capacity for 60 min followed by the recovery without (experiment 1) or with phenylephrine infusion (experiment 2) to counteract post‐exercise hypotension. Heart rate, arterial pressure (Finapres), plasma volume (PV, Evans blue dye dilution), haematocrit, haemoglobin, plasma total solutes (refractometer), albumin, total proteins (colorimetric method), [Na⁺] and [K⁺] were not different prior to the experiments. Exercise decreased PV –13.7% (–521 mL) and –14.2% (–566 mL) at the end of 60 min in experiments 1 and 2, respectively, associated with increases in the concentrations of plasma albumin, total protein and solutes. These changes were similar between the two experiments. Following 30 min recovery in experiment 1 the decreased PV was not significantly different from the baseline. Although the volume restoration was complete at the end of 90 min recovery, the change in the albumin concentration was still above zero, indicating a gain of 11 g albumin (P < 0.05). When phenylephrine was infused during recovery, there was no gain in intravascular albumin associated with a sustained decrease in PV (–7% or –280 mL, P < 0.05) observed at the end of experiment 2. These data suggest that post‐exercise hypotension may be the mechanism for a gain of intravascular albumin via the lymph return, which enhances plasma water retention and PV restoration during recovery from exercise induced hypovolaemia, even without rehydration.     

Determination of a new oral iron chelator, ICL670, and its iron complex in plasma by high-performance liquid chromatography and ultraviolet detection

ICL670 is a representative of a new class of orally active tridentate selective iron chelators. Two molecules of ICL670 are required to form a complete hexacoordinate chelate Fe-[ICL670]2 with one ferric iron. A simple and rapid HPLC-UV method for the separate determination of ICL670 and Fe-[ICL670]2 in the plasma of iron-overloaded patients is described. Plasma samples were prepared as rapidly as possible, the tubes being kept at 4 degrees C. Plasma proteins were precipitated with methanol. The supernatant was diluted with water and placed on the refrigerated sample rack of an autosampler before injection. The chromatographic separations were achieved on an Alltima C18 column using 0.05 M Na2HPO4 and 0.01 M tetrabutylammonium hydrogen sulfate-acetonitrile-methanol (41:9:50, v/v/v) as mobile phase. The analytes were detected at 295 nm. Calibration and quality control samples were prepared in normal human plasma. The mean accuracy (n=6) over the entire investigated concentration range 0.25-20 microg/ml ranged from 91 to 109% with a coefficient of variation (C.V.) from 4 to 8% for ICL670, and from 95 to 105% with a C.V. from 2 to 20% for the iron complex. The dissociation of the complex during analysis was shown to be marginal. The iron removal from plasma of iron-overloaded patients by free ICL670 during analysis was low. The in vitro iron transfer from the iron pools of iron-overloaded plasma onto ICL670 was shown to be a slow process.     

Topography of basal glucose utilization in the hippocampus determined with [1-14C]glucose and [6-14C]glucose

The activity of the pentose phosphate shunt was assessed under basal conditions in subregions of the hippocampus by measuring the uptake and retention of [1-14C]glucose and [6-14C]glucose and their 14C-labelled metabolites. The relative and absolute retention of carbon-14 from each of the two compounds was nearly identical in all regions examined. For each compound, the highest accumulation of 14C occurred in the granule cell layer of the dentate gyrus and in the pyramidal cell layer. Relatively high retention of radioactivity was also found in the molecular layer of dentate gyrus and in the stratum lacunosum-molecular. The stratum radiatum and stratum oriens contained the lowest levels of radioactivity among hippocampal regions. The equal retention of radioactivity from [1-14C]glucose and [6-14C]glucose implies that pentose phosphate shunt activity is very low throughout the hippocampus under the conditions of this study. The uptake and retention of radioactivity was evaluated in different hippocampal regions 10 or 30 min following intravenous injection of [1-14C]glucose. Although there was significantly more radioactivity at 30 min than at 10 min, the same topographic pattern of radioactivity within the hippocampus was observed in rats after both survival periods, indicating that an equal fraction of the [1-14C]glucose utilized in different hippocampal regions is oxidized to 14CO2 under these conditions. Most regions of high glucose utilization in the hippocampus determined with [1-14C]glucose and [6-14C]glucose correspond to regions of intense histochemical staining for cytochrome oxidase reported in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)