Radiolabeling of protected tryptophan with [18F]fluoromethyl tosylate: Formation of [18F]fluoromethyl ester of tryptophan instead of 1-N-[18F]fluoromethyl tryptophan methylester.

The reaction of [18F]fluoromethyl tosylate with methyl(tert-butoxycarbonyl)-l-tryptophanate results in formation the O-alkylated ester of the tryptophan instead of alkylation of the indole nitrogen of tryptophan as initially anticipated. Treatment of protected tryptophan with NaH in dimethyl formamide (DMF) along with [18F]fluoromethyl tosylate at 130°C results in the formation of [18F]fluoromethyl(tert-butoxycarbonyl)-l-tryptophanate. Preferential formation of the O-alkylated product is postulated to be due to the hydrolysis of the ester. Confirmation of the O-alkylation was obtained by synthesizing the [19F]fluoromethyl(tert-butoxycarbonyl)-l-tryptophanate insitu and examining its NMR characteristics using multiple NMR techniques. Similar results were also obtained when reacting Boc-tryptophan-N-carboxyanhydride precursor with fluoromethyl tosylate.

Challenges in the automated synthesis of [18F]-1-fluoroethyl tryptophan: Formation of both O- and N-alkylated products.

[18F]Fluoroethyl tosylate was synthesized using an automated "Synthra" module using ethylene di-tosylate and [18F]fluoride/K222/K2CO3 in acetonitrile. [18F]Fluoroethyl tosylate was purified by semi-preparative HPLC followed by reformulation using a C18 Sep-Pak cartridge and eluted with DMF. Using this [18F]fluoroethyl tosylate, we attempted to alkylate protected tryptophan aiming to obtain the N-[18F]fluoroethyl-t-Boc-tryptophan methyl ester. Initial attempts resulted in the formation of the O-alkylated, rather than N-alkylated product. Manual removal of the cartridge from the automated module, followed by an extended drying of the cartridge under high flow nitrogen, was required to form the desired N-alkylated product. This demonstrates that the drying process in automated modules requires modification for sensitive N-alkylation of compounds and may be essential for compounds like tryptophan methyl ester that have multiple potential sites of alkylation in their chemical structure.

Management of radioactive waste gases from PET radiopharmaceutical synthesis using cost effective capture systems integrated with a cyclotron safety system.

The emphasis on the reduction of gaseous radioactive effluent associated with PET radiochemistry laboratories has increased. Various radioactive gas capture strategies have been employed historically including expensive automated compression systems. We have implemented a new cost-effective strategy employing gas capture bags with electronic feedback that are integrated with the cyclotron safety system. Our strategy is suitable for multiple automated 18F radiosynthesis modules and individual automated 11C radiosynthesis modules. We describe novel gas capture systems that minimize the risk of human error and are routinely used in our facility.

Executive functioning in schizophrenia: Unique and shared variance with measures of fluid intelligence.

OBJECTIVE: Patients with schizophrenia often display deficits on tasks thought to measure "executive" processes. Recently, it has been suggested that reductions in fluid intelligence test performance entirely explain deficits reported for patients with focal frontal lesions on classical executive tasks. For patients with schizophrenia, it is unclear whether deficits on executive tasks are entirely accountable by fluid intelligence and representative of a common general process or best accounted for by distinct contributions to the cognitive profile of schizophrenia. METHOD: In the current study, 50 patients with schizophrenia and 50 age, sex and premorbid intelligence matched controls were assessed using a broad neuropsychological battery, including tasks considered sensitive to executive abilities, namely the Hayling Sentence Completion Test (HSCT), word fluency, Stroop test, digit-span backwards, and spatial working memory. Fluid intelligence was measured using both the Matrix reasoning subtest from the Weschler Abbreviated Scale of Intelligence (WASI) and a composite score derived from a number of cognitive tests. RESULTS: Patients with schizophrenia were impaired on all cognitive measures compared with controls, except smell identification and the optimal betting and risk-taking measures from the Cambridge Gambling Task. After introducing fluid intelligence as a covariate, significant differences remained for HSCT suppression errors, and classical executive function tests such as the Stroop test and semantic/phonemic word fluency, regardless of which fluid intelligence measure was included. CONCLUSIONS: Fluid intelligence does not entirely explain impaired performance on all tests considered as reflecting "executive" processes. For schizophrenia, these measures should remain part of a comprehensive neuropsychological assessment alongside a measure of fluid intelligence.

Common genetic risk variants are associated with positive symptoms and decision-making ability in patients with schizophrenia.

Schizophrenia is a clinically heterogeneous disorder associated with broad deficits across cognitive domains. As large genomewide association studies uncover the genetic architecture of schizophrenia, the relationship between common genetic variants and clinical and cognitive characteristics will form part of an integrative approach to understanding genetic effects on the clinical phenotype. In the current study, association between common genetic risk variants and clinical and cognitive variables was investigated. Common risk variants were associated with positive symptoms and decision-making ability from the Cambridge Gambling Task with trends in other domains.

Heteronuclear NMR spectroscopic investigations of hydrogen bonding in 2-(benzo[d]thiazole-2'-yl)-N-alkylanilines.

The 2-(benzo[d]thiazole-2'-yl)-N-alkylanilines have previously revealed the presence of a strong intramolecular hydrogen bond. This in turn gives rise to a more complicated multiplet for the protons attached to the carbon adjacent to the amino group. This intramolecular hydrogen bond was investigated by a deuterium exchange experiment using heteronuclear NMR spectroscopy (1H, 13C, 15N and 2H). We observed changes in the multiplet structure and chemical shifts providing further evidence that the deuterium replaces the hydrogen in the intramolecular hydrogen bond. A time course study of the D2O exchange confirmed the presence of a strong hydrogen bond. The comparison of the structures obtained by X-ray crystallography showed a very small difference in planarity between the two-substituted and four-substituted amino compounds. In both the cases, the phenyl ring is not absolutely coplanar with the thiazole unit. The existence of this intramolecular hydrogen bond in 2-(benzo[d]thiazole-2'-yl)-N-alkylanilines was further confirmed by single crystal X-ray crystallography.

Copy number deletion burden is associated with cognitive, structural, and resting-state network differences in patients with schizophrenia.

Total burden of copy number deletions has been implicated in schizophrenia risk and has been associated with reduced cognitive functioning. The current study aims to replicate the cognitive findings and investigate regional grey and white matter volumes. Moreover, it will explore resting-state networks for correlations between functional connectivity and total deletion burden. All imaging differences will be investigated for correlations with cognitive differences. Seventy-eight patients with chronic schizophrenia, who formed a subset of a large genome-wide association study (GWAS), were assessed for intelligence, 34 had structural magnetic resonance imaging, 33 had resting-state functional magnetic resonance imaging, and 32 had diffusion tensor imaging (DTI). Total deletion burden was negatively associated with IQ performance and positively associated with regional volumes in the striatum bilaterally and in the right superior temporal gyrus and white-matter in the corpus callosum. Correlations were identified between deletion burden and both hyper and hypoconnectivity within the default-mode network and hypoconnectivity within the cognitive control network. The functional connectivity correlations with deletion burden were also correlated with the IQ differences identified. Total deletion burden affects regional volumes and resting-state functional connectivity in key brain networks in patients with schizophrenia. Moreover, effects of deletions on cognitive functioning in may be due to inefficiency of key brain networks as identified by dysconnectivity in resting-state networks.

Synthesis, characterization and (11) C-radiolabeling of aminophenyl benzothiazoles: structural effects on the alkylation of amino group.

Several aminophenyl benzothiazoles were prepared with a view to using them as amyloid binding agents for imaging ß-amyloid in Alzheimer's disease. These precursors were radiolabeled with (11) C-positron-emitting radioisotope using an automated synthesizer and selected radiolabeled compounds were further purified by HPLC. Our results demonstrate that changes in structure have a major influence on the radioactive yield and the ease with which the radiolabel can be introduced. Aminophenyl benzothiazoles with an attached isopropyl group resisted dialkylation perhaps due to steric hindrance caused by this group. Straight chain attachment of methyl, ethyl, butyl, and crotyl groups in the structure decreased the radiochemical yield. Notably, the o-aminophenyl benzothiazole derivatives were difficult to alkylate despite stringent experimental conditions. This reactivity difference is attributed to the hydrogen bonding characteristics of the o-amino group with the nitrogen atom of the thiazole ring.

A comparative study between para-aminophenyl and ortho-aminophenyl benzothiazoles using NMR and DFT calculations.

Ortho-substituted and para-substituted aminophenyl benzothiazoles were synthesised and characterised using NMR spectroscopy. A comparison of the proton chemical shift values reveals significant differences in the observed chemical shift values for the NH protons indicating the presence of a hydrogen bond in all ortho-substituted compounds as compared to the para compounds. The presence of intramolecular hydrogen bond in the ortho amino substituted aminophenyl benzothiazole forces the molecule to be planar which may be an additional advantage in developing these compounds as Alzheimer's imaging agent because the binding to amyloid fibrils prefers planar compounds. The splitting pattern of the methylene proton next to the amino group also showed significant coupling to the amino proton consistent with the notion of the existence of slow exchange and hydrogen bond in the ortho-substituted compounds. This is further verified by density functional theory calculations which yielded a near planar low energy conformer for all the o-aminophenyl benzothiazoles and displayed a hydrogen bond from the amine proton to the nitrogen of the thiazole ring. A detailed analysis of the (1)H, (13)C and (15)N NMR chemical shifts and density functional theory calculated structures of the compounds are described.

Theory of mind and the social brain: implications for understanding the genetic basis of schizophrenia.

Genome-wide association studies in schizophrenia have recently made significant progress in our understanding of the complex genetic architecture of this disorder. Many genetic loci have been identified and now require functional investigation. One approach involves studying their correlation with neuroimaging and neurocognitive endophenotypes. Theory of Mind (ToM) deficits are well established in schizophrenia and they appear to fulfill criteria for being considered an endophenotype. We aim to review the behavioral and neuroimaging-based studies of ToM in schizophrenia, assess its suitability as an endophenotype, discuss current findings, and propose future research directions. Suitable research articles were sourced from a comprehensive literature search and from references identified through other studies. ToM deficits are repeatable, stable, and heritable: First-episode patients, those in remission and unaffected relatives all show deficits. Activation and structural differences in brain regions believed important for ToM are also consistently reported in schizophrenia patients at all stages of illness, although no research to date has examined unaffected relatives. Studies using ToM as an endophenotype are providing interesting genetic associations with both single nucleotide polymorphisms (SNPs) and specific copy number variations (CNVs) such as the 22q11.2 deletion syndrome. We conclude that ToM is an important cognitive endophenotype for consideration in future studies addressing the complex genetic architecture of schizophrenia, and may help identify more homogeneous clinical sub-types for further study.

Size and shape of the corpus callosum in adult Niemann-Pick type C reflects state and trait illness variables.

BACKGROUND AND PURPOSE: Variable alterations to the structure of the corpus callosum have been described in adults with NPC, a neurometabolic disorder known to result in both white and gray matter pathology. This study sought to examine the structure of the callosum in a group of adult patients with NPC and compared callosal structure with a group of matched controls, and to relate callosal structure with state and trait illness variables. MATERIALS AND METHODS: Nine adult patients with NPC were matched to control subjects (n = 26) on age and sex. The corpus callosum was segmented from the midsagittal section of T1-weighted images on all subjects, and total area, length, bending angle, and mean thickness were calculated. In addition, 39 regional thickness measures were derived by using a previously published method. All measures were compared between groups, and analyzed alongside symptom measures, biochemical parameters, and ocular-motor measures. RESULTS: The callosal area and mean thickness were significantly reduced in the patient group, and regional thickness differences were greatest in the genu, posterior body, isthmus, and anterior splenium. Global callosal measures correlated significantly with duration of illness and symptom score, and at trend level with degree of filipin staining. Measures of reflexive saccadic peak velocity and gain, and self-paced saccades, correlated strongly with total callosal area. CONCLUSIONS: Callosal structure and size reflect both state and trait markers in adult NPC, and they may be useful biomarkers to index both white and gray matter changes that reflect illness severity and progression.

Language skills of school-aged children prenatally exposed to antiepileptic drugs.

OBJECTIVES: Fetal exposure to some antiepileptic drugs (AEDs) carries increased risk of major birth defects, and may be associated with reduced intellectual abilities. The impact on language remains unclear. This study aimed to investigate the impact of fetal AED exposure on language skills. METHODS: Women with epilepsy and their children were recruited to this observational study through the Australian Pregnancy Register for Women with Epilepsy and Allied Disorders. Language skills of 102 AED-exposed children were assessed using the Clinical Evaluation of Language Fundamentals, fourth edition (CELF-4). Assessments were conducted blind to drug. Maternal epilepsy, pregnancy, and medical histories were obtained from prospectively collected records. RESULTS: Mean CELF-4 Core Language scores of children exposed to sodium valproate in monotherapy (mean 91.5, SD 17.5) or polytherapy (mean 73.4, SD = 22.3) were significantly below the standardized test mean of 100 (p < 0.05). Mean language scores of children exposed to carbamazepine or lamotrigine monotherapy, or polytherapy without sodium valproate, were not significantly different from normal. First-trimester sodium valproate dose was negatively correlated with language scores, and significantly predicted language scores after controlling for other group differences. CONCLUSIONS: Fetal exposure to sodium valproate increases the risk of language impairment. This should be taken into account when making treatment decisions for women with epilepsy of childbearing age.

Synthesis and characterization of 1- and 2-cinnamoyloxyacetonaphthones.

The synthesis of 1- and 2-cinnamoyloxyacetonaphthones was achieved in one step using hydroxyl acetonaphthones and substituted cinnamic acids in the presence of a catalytic amount of phosphoroxychloride. Structural characterization was accomplished using high-resolution nuclear magnetic resonance (NMR) spectroscopy. Chemical shifts of the compounds were compared and the change in the chemical shifts relative to electron-donating and -withdrawing groups is presented. Introduction of a thiophene ring instead of phenyl-substituted analogs caused shielding of the olefinic proton.

Accuracy of clinical signs, SEP, and EEG in predicting outcome of hypoxic coma: a meta-analysis.

OBJECTIVE: Accurate prediction of neurologic outcome after hypoxic coma is important. Previous systematic reviews have not used summary statistics to summarize and formally compare the accuracy of different prognostic tests. We therefore used summary receiver operating characteristic curve (SROC) and cluster regression methods to compare motor and pupillary responses with sensory evoked potential (SEP) and EEG in predicting outcome after hypoxic coma. METHODS: We searched PubMed, MEDLINE, and Embase (1966-2007) for reports in English, German, and French and identified 25 suitable studies. An SROC was constructed for each marker (SEP, EEG, M1 and M < or = 3), and the area under the curve (AUC), a measure of diagnostic accuracy, was determined. For comparison, we calculated the differences between the AUC for each test and M1 reference standard. RESULTS: The AUC for absent SEP was larger than those for M1, M < or = 3, absent pupillary response, and EEG when the examinations were performed within the first 24 hours. The difference between the AUC for SEP (AUC 0.891) and that for M1 (AUC 0.786) was small (0.105, 95% confidence interval 0.023-0.187), only reaching significance on day 1 after coma onset. The use of M < or = 3 improved the diagnostic accuracy of motor signs. CONCLUSIONS: This study demonstrated that sensory evoked potential (SEP) is marginally better than M1 at predicting outcome after hypoxic coma. However, the superiority of SEP diminishes after day 1 and when M < or = 3 is used. The findings therefore caution against the tendency to generalize that SEP is a better marker than clinical signs.

Hippocampal volume and depression: insights from epilepsy surgery.

BACKGROUND: Major depression is common after epilepsy surgery. It has previously been suggested that surgical removal of limbic system structures such as the hippocampus may contribute to this comorbidity. Recent magnetic resonance imaging studies have found smaller hippocampal volumes in depressed patients in comparison with controls. AIMS: The current study examined whether preoperative hippocampal volumes were associated with depression experienced after epilepsy surgery. Patients undergoing mesial (n = 26) and non-mesial (n = 16) temporal lobe resections were assessed preoperatively, and for 1 year postoperatively. Assessment included a clinical interview and the Beck Depression Inventory. Hippocampal volumes were measured on the preoperative T1-weighted magnetic resonance imaging scans of the patients and 41 neurologically normal controls. RESULTS: A similar proportion of mesial and non-mesial temporal patients had a preoperative history of major depression. Postoperatively, 42% of mesial and 19% of non-mesial temporal patients were depressed. There was no relationship between hippocampal volume and preoperative depression in either group. Depression after surgery was associated with significantly smaller hippocampal volumes contralateral to the resection in the mesial temporal group (p = 0.005). This effect was seen in mesial temporal patients who developed de novo depression (p = 0.006). Hippocampal volume was unrelated to postoperative depression in the non-mesial group. CONCLUSION: This study highlights the role of neurobiological factors in the development of postoperative depression. These initial findings have implications for understanding depression following epilepsy surgery as well as the pathogenesis of depression more generally.

Reduced striatal D1 receptor binding in autosomal dominant nocturnal frontal lobe epilepsy.

BACKGROUND: Mutations of the neuronal nicotinic acetylcholine (nACh) receptor identified in patients with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) lead to increased sensitivity to ACh. As activation of presynaptic nicotinic receptors augments the release of dopamine in the striatum and the prefrontal regions, we tested the hypothesis that that the alpha4-Ser248Phe mutation affects dopaminergic transmission. METHODS: We measured D(1) receptor binding using [(11)C]-SCH23390 and PET in 12 subjects with the alpha4-Ser248Phe mutation (3 men, mean age 41 +/- 16 years) and 19 controls (8 men, mean age 36 +/- 13 years) matched for gender, smoking status, and age. Parametric images were produced using the simplified reference region method. Both MRI-based regions of interest and voxel based analyses were used. RESULTS: Reduced striatal [(11)C]-SCH23390 binding occurred with the mutation (controls 1.1 +/- 0.1; ADNFLE 0.97 +/- 0.2; p < 0.01). Statistical parametric mapping confirmed a region of reduced [(11)C]-SCH23390 binding in the right putamen in alpha4-Ser248Phe subjects compared to controls (309 voxels, local maxima 20 16 -2 mm; Z(score) 3.57, p < 0.05). CONCLUSIONS: Reduced D(1) receptor binding may represent increased extracellular dopamine levels or, more likely, receptor downregulation. Alterations in mesostriatal dopaminergic circuits may contribute to nocturnal paroxysmal motor activity in autosomal dominant nocturnal frontal lobe epilepsy.

Effect of levetiracetam on cortical excitability: a transcranial magnetic stimulation study.

BACKGROUND AND PURPOSE: We studied the effect of levetiracetam (LEV), an anticonvulsant with a novel mechanism of action, on cortical excitability, measured using transcranial magnetic stimulation (TMS). For this purpose, 38 healthy volunteers were assessed in two TMS sessions, before and after an oral dose of 3000 mg LEV. METHODS: Resting motor threshold (RMT), intracortical facilitation (ICF) and intracortical inhibition (ICI), cortical silent period (CSP) threshold and duration and motor-evoked potential (MEP) amplitude were calculated. RESULTS: After treatment with LEV, RMT was increased (mean +/- SD: 63 +/- 14% of the maximum stimulator output) compared with baseline (58 +/- 11%). CSP threshold was decreased after LEV (54 +/- 10%; baseline, 57 +/- 11%). CSP duration was increased after LEV (116 +/- 37 ms; baseline: 102 +/- 33 ms). LEV did not affect ICF or ICI or mean MEP amplitude significantly. CONCLUSIONS: Our results indicate that LEV modulates some aspects of cortical excitability. Whereas the increase in the RMT most probably reflects the effect of LEV on ion channel activity, effects on the CSP might represent a modulation of GABA receptors at cortical and spinal level.

An assessment of methods for aligning two-dimensional microscope sections to create image volumes.

This study assessed five different methods for aligning microscope images of Nissl-stained sections of mouse brain to form three-dimensional image volumes. Methods exploiting both image content and information from un-sectioned tissue were investigated. The accuracy of reconstruction was estimated using fiducials with known physical properties, demonstrating that methods exploiting tissue content produced distorted image volumes while a method using artificial fiducials produced the most accurate and unbiased alignment. Methodological issues relating to methods of volume reconstruction are discussed and it is recommended that methods using information from un-sectioned tissue be used wherever possible.

Asymmetry of language activation relates to regional callosal morphology following early cerebral injury.

The anatomical factors underlying reorganization of language representation are yet to be elucidated, although correlations between asymmetric structures and language lateralization have been identified. Previous research has implicated the corpus callosum in the development of language lateralization. This study examined the relationship between callosal morphology and language asymmetry, using letter fluency functional magnetic resonance imaging, in 13 patients with focal epilepsy and 8 healthy controls. Regional callosal thickness was determined without relying on a priori delineation of callosal segments. We predicted that language asymmetry measured by fMRI activation laterality scores would be correlated with regional callosal thickness in both groups. However, only the degree of language activation asymmetry was significantly correlated with callosal thickness in the isthmus and the midbody of patients, and there was a significant interaction between the groups with respect to callosal thickness and language activation asymmetry. These data suggest that callosal pathways may be important for language reorganization in the context of early cerebral injury.

Hypoxic tissue in ischaemic stroke: persistence and clinical consequences of spontaneous survival.

In ischaemic stroke, expansion of the infarct core occurs at the expense of surrounding hypoxic, metabolically compromised tissue over a period of 24 h or more in a considerable proportion of patients. It is uncertain whether hypoxic tissue observed at later times after stroke onset retains the potential for survival or whether such survival has an impact on functional outcome. These factors may determine the effectiveness of therapeutic strategies aimed at salvaging this tissue. We tested the hypotheses that metabolically compromised hypoxic tissue observed within 48 h after onset of ischaemic stroke retains the potential for spontaneous survival and that the impact of such survival on functional outcome is time dependent. Consecutive patients presenting within 48 h of ischaemic stroke were studied with [(18)F]fluoromisonidazole, a ligand binding to hypoxic but viable tissue, and PET. Subjects were grouped into two time epochs, 12 h, based on the interval from stroke onset to the time of tracer injection, and had infarct volumes measured on CT/MRI at 7 days (n = 60). The total ischaemic volume (TIV) and the proportion of the TIV that spontaneously survived (surviving hypoxic volume ratio, SHVR) were defined from the co-registered CT/MRI images. These volumetric measures were correlated with neurological outcome assessed at day 7-10 by percentage change in the National Institutes of Health Stroke Scale (DeltaNIHSS), and at 3 months by Barthel Index (BI) and modified Rankin Score (mRS). Of 66 patients investigated, hypoxic tissue occurred in 33 and outcome data was available in 27. Hypoxic tissue constituted >20% of the TIV in 60% of studies 12 h. The spontaneously surviving proportion of the TIV (median 6.9%) or hypoxic tissue (median 45.9%) was not significantly different in patient subgroups studied 12 h after stroke onset. Spontaneous survival of hypoxic tissue (surviving hypoxic volume ratio) was associated with improved neurological outcome in both time epochs: 12 h, DeltaNIHSS (r = 0.59, P < 0.01) and day 90 mRS (r = -0.46, P < 0.05). The finding that similar proportions of hypoxic tissue survived spontaneously within each time epoch suggests that its fate is not predetermined. The favourable neurological outcome associated with spontaneous survival of hypoxic tissue, even 12-48 h after stroke onset, suggests that the volume of hypoxic tissue that progressed to infarction may represent a valuable target for therapeutic intervention.