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Find video protocols related to scientific articles indexed in Pubmed.
TOMM40 Alterations in Alzheimer's Disease Over a 2-Year Follow-Up Period.
J. Alzheimers Dis.
PUBLISHED: 09-10-2014
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We previously reported TOMM40 to be significantly down-regulated in whole blood of Alzheimer's disease (AD) subjects at baseline and after one-year. In this longitudinal follow-up study of TOMM40 expression up to 2 years, we performed 6-monthly assessments for the first year and 2nd year blood sampling on 27 probable AD subjects compared with age- and gender-matched controls. TOMM40 gene expression remained significantly lower in AD patients at all time-points compared to controls, supported by confirmatory RT-PCR results. Our findings of consistently lower TOMM40 expression on longitudinal 2-year sampling support its potential role as a diagnostic blood AD biomarker.
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Unconditional and Conditional Standards Using Cognitive Function Curves for the Modified Mini-Mental State Exam: Cross-Sectional and Longitudinal Analyses in Older Chinese Adults in Singapore.
Am J Geriatr Psychiatry
PUBLISHED: 05-01-2014
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The conventional practice of assessing cognitive status and monitoring change over time in older adults using normative values of the Mini-Mental State Exam (MMSE) based on age bands is imprecise. Moreover, population-based normative data on changes in MMSE score over time are scarce and crude because they do not include age- and education-specific norms. This study aims to develop unconditional standards for assessing current cognitive status and conditional standards that take prior MMSE score into account for assessing longitudinal change, with percentile curves as smooth functions of age.
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Long-term metformin usage and cognitive function among older adults with diabetes.
J. Alzheimers Dis.
PUBLISHED: 03-01-2014
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Evidence strongly supports the important role of insulin resistance in cognitive decline and dementia and suggests that insulin sensitizers may protect against cognitive decline in diabetic and pre-diabetic individuals. Inconclusive results have been reported in clinical trials of rosiglitazone, an insulin sensitizer that also increases cardiovascular mortality risks. No study has yet reported a protective cognitive effect of metformin, an insulin-sensitizing biguanide widely used in diabetic patients. We studied 365 older persons aged 55 and over in the population-based Singapore Longitudinal Aging Study with diabetes who were followed up over 4 years. The odds ratios (OR) of association of metformin use (n = 204) versus non-use (n = 161) with cognitive impairment (Mini-Mental State Exam ? 23), and by duration: up to 6 years (n = 114) and more than 6 years (n = 90) were evaluated in cross-sectional and longitudinal multivariate analyses. Controlling for age, education, diabetes duration, fasting blood glucose, vascular and non-vascular risk factors, metformin use showed a significant inverse association with cognitive impairment in longitudinal analysis (OR = 0.49, 95% CI 0.25-0.95). Metformin use showed significant linear trends of association across duration of use in cross-sectional and longitudinal analyses (p = 0.018 and p = 0.002, respectively), with use for more than 6 years significantly associated with lowest risk of cognitive impairment in both cross-sectional analysis (OR = 0.30, 95% CI 0.11-0.80) and in longitudinal analysis (OR = 0.27, 95% CI 0.12-0.60). No significant interactive effects of metformin use with APOE-?4, depression, or fasting glucose level were observed. Among individuals with diabetes, long-term treatment with metformin may reduce the risk of cognitive decline. Further studies should establish the role of hyperglycemia and insulin resistance, and the protective role of metformin in the risk of cognitive decline and dementia.
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The Longitudinal Youth at Risk Study (LYRIKS) - An Asian UHR perspective.
Schizophr. Res.
PUBLISHED: 05-31-2013
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Numerous studies have been published on the psychosis prodrome and have explored a wide array of its many aspects. However, the set of risk factors identified by these various efforts is not homogenous across studies. This could be due to unique population factors or relatively small sample sizes. Only few studies were conducted on Asian populations, whose socio-cultural characteristics differ - in some cases remarkably - from those in western populations. Singapore is a highly dense city-state in South-east Asia, with low rates of substance abuse. The Longitudinal Youth at Risk Study (LYRIKS) commenced in Singapore in 2008, designed to comprehensively assess a group of ultra high risk (UHR) individuals and identify clinical, social, neuropsychological and biological risk factors unique to the local population. 173 UHR individuals were recruited from this single-site study over 4years. Here, we detail aspects of the study methodology and report on the baseline social and clinical characteristics of the sample population. 78% of the UHR sample suffered from a psychiatric disorder, with Major Depressive Disorder present in more than half of the sample. The mean Global Assessment of Functioning (GAF) score was 57.4, which indicated a moderate level of impairment. Although the recruited sample did not differ significantly by social and clinical characteristics when compared to previously published reports, the conversion rate to psychosis was 3.5% (n=6) at 6months. Follow-up measures are currently underway to assess longitudinal incidence of psychosis and impact of risk factors on cognition, functioning and remission.
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Regulation of astrocyte glutamine synthetase in epilepsy.
Neurochem. Int.
PUBLISHED: 05-28-2013
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Astrocytes play a crucial role in regulating and maintaining the extracellular chemical milieu of the central nervous system under physiological conditions. Moreover, proliferation of phenotypically altered astrocytes (a.k.a. reactive astrogliosis) has been associated with many neurologic and psychiatric disorders, including mesial temporal lobe epilepsy (MTLE). Glutamine synthetase (GS), which is found in astrocytes, is the only enzyme known to date that is capable of converting glutamate and ammonia to glutamine in the mammalian brain. This reaction is important, because a continuous supply of glutamine is necessary for the synthesis of glutamate and GABA in neurons. The known stoichiometry of glutamate transport across the astrocyte plasma membrane also suggests that rapid metabolism of intracellular glutamate via GS is a prerequisite for efficient glutamate clearance from the extracellular space. Several studies have indicated that the activity of GS in astrocytes is diminished in several brain disorders, including MTLE. It has been hypothesized that the loss of GS activity in MTLE leads to increased extracellular glutamate concentrations and epileptic seizures. Understanding the mechanisms by which GS is regulated may lead to novel therapeutic approaches to MTLE, which is frequently refractory to antiepileptic drugs. This review discusses several known mechanisms by which GS expression and function are influenced, from transcriptional control to enzyme modification.
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Autism spectrum disorder in Chinese populations: a brief review.
Asia Pac Psychiatry
PUBLISHED: 03-12-2013
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This review summarizes the published work on the prevalence and incidence rates of autism spectrum disorder (ASD) in Chinese populations. The authors searched MEDLINE, Web of Science and the PsycINFO database and identified seven studies that were published in the English language. In mainland China, Li and colleagues reported an autism prevalence rate of 2.38/10,000 but admitted the possibility of underestimation. A higher prevalence of 11/10,000 was reported by Zhang and Ji based on a survey that was conducted in Tianjin, China. In Taiwan, Chien and colleagues reported that the cumulative prevalence of ASD increased from 1.79 to 28.72/10,000 from 1996 to 2005 and the annual incidence rate increased from 0.91 to 4.41/10,000 per year from 1997 to 2005. Another study based on the Taiwan national health insurance database reported a high prevalence rate of 122.8/10,000 for the year 2007. Two studies based on the Taiwan national disability registry data reported an increasing trend of ASD for the period 2000-2007 and 2004-2010, respectively. In Hong Kong, Wong and colleagues estimated that the incidence of ASD was 5.49/10,000 and the average prevalence over the 1986-2005 period was 16.1/10,000. We identified 12 studies through the searching of Chinese databases. The prevalences among these studies varied from 2.8 to 29.5/10,000. While existing data appear to suggest, it remains unclear whether there is a true rise in the prevalence of ASD in ethnic Chinese population across geographic sites. More collaborative research on this topic should be conducted in the future.
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Absence of A673T amyloid-? precursor protein variant in Alzheimers disease and other neurological diseases.
Neurobiol. Aging
PUBLISHED: 03-11-2013
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The rare variant A673T in the amyloid-? precursor protein (APP) gene has been shown to reduce the risk of cognitive impairment. We genotyped the variant in 8721 Asian individuals comprising 552 with Alzheimers disease and vascular dementia, 790 with Parkinsons disease, and 7379 controls. The A673T variant was absent in all of the subjects. Our finding suggests that the A673T protective variant is not relevant in our Asian population. Studies in other ethnic populations would clarify whether this variant is specific to specific races/ethnicities.
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Reliability and Validity of the Clinical Dementia Rating for Community-Living Elderly Subjects without an Informant.
Dement Geriatr Cogn Dis Extra
PUBLISHED: 01-01-2013
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The Clinical Dementia Rating (CDR) scale is widely used to assess cognitive impairment in Alzheimers disease. It requires collateral information from a reliable informant who is not available in many instances. We adapted the original CDR scale for use with elderly subjects without an informant (CDR-NI) and evaluated its reliability and validity for assessing mild cognitive impairment (MCI) and dementia among community-dwelling elderly subjects.
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A brain-computer interface based cognitive training system for healthy elderly: a randomized control pilot study for usability and preliminary efficacy.
PLoS ONE
PUBLISHED: 01-01-2013
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Cognitive decline in aging is a pressing issue associated with significant healthcare costs and deterioration in quality of life. Previously, we reported the successful use of a novel brain-computer interface (BCI) training system in improving symptoms of attention deficit hyperactivity disorder. Here, we examine the feasibility of the BCI system with a new game that incorporates memory training in improving memory and attention in a pilot sample of healthy elderly. This study investigates the safety, usability and acceptability of our BCI system to elderly, and obtains an efficacy estimate to warrant a phase III trial. Thirty-one healthy elderly were randomized into intervention (n?=?15) and waitlist control arms (n?=?16). Intervention consisted of an 8-week training comprising 24 half-hour sessions. A usability and acceptability questionnaire was administered at the end of training. Safety was investigated by querying users about adverse events after every session. Efficacy of the system was measured by the change of total score from the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) before and after training. Feedback on the usability and acceptability questionnaire was positive. No adverse events were reported for all participants across all sessions. Though the median difference in the RBANS change scores between arms was not statistically significant, an effect size of 0.6SD was obtained, which reflects potential clinical utility according to Simons randomized phase II trial design. Pooled data from both arms also showed that the median change in total scores pre and post-training was statistically significant (Mdn?=?4.0; p<0.001). Specifically, there were significant improvements in immediate memory (p?=?0.038), visuospatial/constructional (p?=?0.014), attention (p?=?0.039), and delayed memory (p<0.001) scores. Our BCI-based system shows promise in improving memory and attention in healthy elderly, and appears to be safe, user-friendly and acceptable to senior users. Given the efficacy signal, a phase III trial is warranted.
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Integrated genetic and genomic approach in the SingaporeTranslational and Clinical Research in Psychosis Study: an overview.
Early Interv Psychiatry
PUBLISHED: 05-04-2011
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Schizophrenia is a severe mental disorder with onset frequently in adolescence and followed by a chronic and disabling course. Although the exact pathophysiology of this devastating disorder has not been clearly elucidated, a large part of it has been attributed to genetic influences. This article seeks to provide an overview on what our group has embarked on--to elucidate genetic risk factors for schizophrenia within the Chinese ethnic group.
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Altered expression of brain monocarboxylate transporter 1 in models of temporal lobe epilepsy.
Neurobiol. Dis.
PUBLISHED: 02-28-2011
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Monocarboxylate transporter 1 (MCT1) facilitates the transport of monocarboxylate fuels (lactate, pyruvate and ketone bodies) and acidic drugs, such as valproic acid, across cell membranes. We recently reported that MCT1 is deficient on microvessels in the epileptogenic hippocampal formation in patients with medication-refractory temporal lobe epilepsy (TLE). To further define the role of MCT1 in the pathophysiology of TLE, we used immunohistochemistry and stereological analysis to localize and quantify the transporter in the hippocampal formation in three novel and highly relevant rat models of TLE and in nonepileptic control animals. One model utilizes methionine sulfoximine to induce brain glutamine synthetase deficiency and recurrent limbic seizures, while two models employ an episode of perforant pathway stimulation to cause epilepsy. MCT1 was lost on microvessels and upregulated on astrocytes in the hippocampal formation in all models of TLE. Notably, the loss of MCT1 on microvessels was not due to a reduction in microvessel density. The similarities in MCT1 expression among human subjects with TLE and several animal models of the disease strongly suggest a critical role of this molecule in the pathogenesis of TLE. We hypothesize that the downregulation of MCT1 may promote seizures via impaired uptake of ketone bodies and antiepileptic drugs by the epileptogenic brain. We also propose that the overexpression of MCT1 on astrocytes may lead to increased uptake or release of monocarboxylates by these cells, with important implications for brain metabolism and excitability. These hypotheses can now be rigorously tested in several animal models that replicate key features of human TLE.
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White matter abnormalities in major depression: evidence from post-mortem, neuroimaging and genetic studies.
J Affect Disord
PUBLISHED: 07-17-2010
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Until more recently, most studies have examined the changes in brain gray matter in major depressive disorder (MDD) with less studies focusing on understanding white matter pathology in MDD. Studies of brain white matter volume changes, connectivity disruptions, as well as genetic factors affecting myelination can throw light on the nature of white matter abnormalities underpinning MDD.
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Effectiveness of a brain-computer interface based programme for the treatment of ADHD: a pilot study.
Psychopharmacol Bull
PUBLISHED: 06-29-2010
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Majority of children with attention deficit hyperactivity disorder (ADHD) have significant inattentive symptoms. We developed a progressive series of activities involving brain-computer interface-based games which could train users to improve their concentration. This pilot study investigated if the intervention could be utilized in children and if it could improve inattentive symptoms of ADHD. Ten medication-naive children aged 7 to 12 diagnosed with ADHD (combined or inattentive subtypes) received 20 sessions of therapy over a 10-week period. They were compared with age- and gendermatched controls. Both parent and teacher-rated inattentive score on the ADHD Rating Scale-IV improved more in the intervention group. A larger scale trial is warranted to further investigate the efficacy of our treatment programme in treating ADHD.
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Electroconvulsive therapy for catatonia in neuropsychiatric systemic lupus erythematosus.
J ECT
PUBLISHED: 06-02-2010
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Neuropsychiatric systemic lupus erythematosus encompasses neurological syndromes of the central, peripheral, and autonomic nervous system and a variety of psychiatric syndromes. Neuropsychiatric systemic lupus erythematosus presenting as catatonia is uncommon, and treatment of this condition is not well defined. Here we describe a case of neuropsychiatric systemic lupus erythematosus with catatonia and our treatment approach focusing on electroconvulsive therapy in conjunction with cyclophosphamide. We also discuss the pathophysiological underpinnings of the condition and the basis for treatment.
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Monocarboxylate transporter 1 is deficient on microvessels in the human epileptogenic hippocampus.
Neurobiol. Dis.
PUBLISHED: 05-27-2010
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Monocarboxylate transporter 1 (MCT1) facilitates the transport of important metabolic fuels (lactate, pyruvate and ketone bodies) and possibly also acidic drugs such as valproic acid across the blood-brain barrier. Because an impaired brain energy metabolism and resistance to antiepileptic drugs are common features of temporal lobe epilepsy (TLE), we sought to study the expression of MCT1 in the brain of patients with this disease. Immunohistochemistry and immunogold electron microscopy were used to assess the distribution of MCT1 in brain specimens from patients with TLE and concomitant hippocampal sclerosis (referred to as mesial TLE or MTLE (n=15)), patients with TLE and no hippocampal sclerosis (non-MTLE, n=13) and neurologically normal autopsy subjects (n=8). MCT1 was present on an extensive network of microvessels throughout the hippocampal formation in autopsy controls and to a lesser degree in non-MTLE. Patients with MTLE were markedly deficient in MCT1 on microvessels in several areas of the hippocampal formation, especially CA1, which exhibited a 37% to 48% loss of MCT1 on the plasma membrane of endothelial cells when compared with non-MTLE. These findings suggest that the uptake of blood-derived monocarboxylate fuels and possibly also acidic drugs, such as valproic acid, is perturbed in the epileptogenic hippocampus, particularly in MTLE. We hypothesize that the loss of MCT1 on brain microvessels is mechanistically involved in the pathophysiology of drug-resistant TLE, and propose that re-expression of MCT1 may represent a novel therapeutic approach for this disease.
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Astrocytes and epilepsy.
Neurotherapeutics
PUBLISHED: 05-23-2010
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Astrocytes form a significant constituent of seizure foci in the human brain. For a long time it was believed that astrocytes play a significant role in the causation of seizures. With the increase in our understanding of the unique biology of these cells, their precise role in seizure foci is receiving renewed attention. This article reviews the information now available on the role of astrocytes in the hippocampal seizure focus in patients with temporal lobe epilepsy with hippocampal sclerosis. Our intent is to try to integrate the available data. Astrocytes at seizure foci seem to not be a homogeneous population of cells, and in addition to typical glial fibrillary acidic protein, positive reactive astrocytes also include a population of neuron glia-2-like cells The astrocytes in sclerotic hippocampi differ from those in nonsclerotic hippocampi in their membrane physiology, having elevated Na+ channels and reduced inwardly rectifying potassium ion channels, and some having the capacity to generate action potentials. They also have reduced glutamine synthetase and increased glutamate dehydrogenase activity. The molecular interface between the astrocyte and microvasculature is also changed. The astrocytes are also associated with increased expression of many molecules normally concerned with immune and inflammatory functions. A speculative mechanism postulates that neuron glia-2-like cells may be involved in creating a high glutamate environment, whereas the function of more typical reactive astrocytes contribute to maintain high extracellular K+ levels; both factors contributing to the hyperexcitability of subicular neurons to generate epileptiform activity. The functions of the astrocyte vascular interface may be more critical to the processes involved in epileptogenesis.
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Transient and spontaneously-remitting complex hallucinations in a patient with melanoma and brain metastases.
Psychosomatics
PUBLISHED: 05-21-2010
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Neuropsychiatric sequelae are common in primary and secondary brain tumors, with symptoms varying as a function of tumor type, location, and size.
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The development of recurrent seizures after continuous intrahippocampal infusion of methionine sulfoximine in rats: a video-intracranial electroencephalographic study.
Exp. Neurol.
PUBLISHED: 06-23-2009
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Glutamine synthetase is deficient in astrocytes in the epileptogenic hippocampus in human mesial temporal lobe epilepsy (MTLE). To explore the role of this deficiency in the pathophysiology of MTLE, rats were continuously infused with the glutamine synthetase inhibitor methionine sulfoximine (MSO, 0.625 microg/h) or 0.9% NaCl (saline control) unilaterally into the hippocampus. The seizures caused by MSO were assessed by video-intracranial electroencephalogram (EEG) monitoring. All (28 of 28) of the MSO-treated animals and none (0 of 12) of the saline-treated animals developed recurrent seizures. Most recurrent seizures appeared in clusters of 2 days duration (median; range, 1 to 12 days). The first cluster was characterized by frequent, predominantly stage I seizures, which presented after the first 9.5 h of infusion (median; range, 5.5 to 31.7 h). Subsequent clusters of less-frequent, mainly partial seizures occurred after a clinically silent interval of 7.1 days (median; range, 1.8 to 16.2 days). The ictal intracranial EEGs shared several characteristics with recordings of partial seizures in humans, such as a distinct evolution of the amplitude and frequency of the EEG signal. The neuropathology caused by MSO had similarities to hippocampal sclerosis in 23.1% of cases, whereas 26.9% of the animals had minimal neuronal loss in the hippocampus. Moderate to severe diffuse neuronal loss was observed in 50% of the animals. In conclusion, the model of intrahippocampal MSO infusion replicates key features of human MTLE and may represent a useful tool for further studies of the cellular, molecular and electrophysiological mechanisms of this disorder.
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Diffusion tensor imaging findings of white matter changes in first episode schizophrenia: a systematic review.
Clin Psychopharmacol Neurosci
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Earlier structural magnetic resonance imaging in schizophrenia have noted smaller white matter volumes in diverse brain regions and recent diffusion tensor imaging (DTI) studies have allowed better elucidation of changes in brain white matter integrity within the illness. As white matter abnormalities have been reported to occur early in the course of schizophrenia, we systematically review extant DTI studies of anomalies of white matter integrity in first episode schizophrenia (FES) up till October 2011. Overall, disruptions of white matter integrity were found in the cortical, subcortical brain regions and white matter associative and commissural tracts, suggesting that changes of cortical-subcortical white matter integrity were found at an early stage of the disorder. These changes in white matter integrity were correlated with specific cognitive deficits (verbal and spatial working memory) as well as psychopathology (positive more than negative symptoms) in patients with FES. The correlation of these white matter integrity changes with cognitive and phenomenological factors may shed light on neurobiological substrates underlying these clinical manifestations. Future studies need to validate these findings in larger samples of subjects and in different populations as well as chart the progress of these cerebral white matter changes over time so as to better appreciate their trajectory with illness course, treatment and chronicity.
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Gene expression of glutamate metabolizing enzymes in the hippocampal formation in human temporal lobe epilepsy.
Epilepsia
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Increased interictal concentrations of extracellular hippocampal glutamate have been implicated in the pathophysiology of temporal lobe epilepsy (TLE). Recent studies suggest that perturbations of the glutamate metabolizing enzymes glutamine synthetase (GS) and phosphate activated glutaminase (PAG) may underlie the glutamate excess in TLE. However, the molecular mechanism of the enzyme perturbations remains unclear. A better understanding of the regulatory mechanisms of GS and PAG could facilitate the discovery of novel therapeutics for TLE.
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A brain-computer interface based attention training program for treating attention deficit hyperactivity disorder.
PLoS ONE
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Attention deficit hyperactivity disorder (ADHD) symptoms can be difficult to treat. We previously reported that a 20-session brain-computer interface (BCI) attention training programme improved ADHD symptoms. Here, we investigated a new more intensive BCI-based attention training game system on 20 unmedicated ADHD children (16 males, 4 females) with significant inattentive symptoms (combined and inattentive ADHD subtypes). This new system monitored attention through a head band with dry EEG sensors, which was used to drive a feed forward game. The system was calibrated for each user by measuring the EEG parameters during a Stroop task. Treatment consisted of an 8-week training comprising 24 sessions followed by 3 once-monthly booster training sessions. Following intervention, both parent-rated inattentive and hyperactive-impulsive symptoms on the ADHD Rating Scale showed significant improvement. At week 8, the mean improvement was -4.6 (5.9) and -4.7 (5.6) respectively for inattentive symptoms and hyperactive-impulsive symptoms (both p<0.01). Cohens d effect size for inattentive symptoms was large at 0.78 at week 8 and 0.84 at week 24 (post-boosters). Further analysis showed that the change in the EEG based BCI ADHD severity measure correlated with the change ADHD Rating Scale scores. The BCI-based attention training game system is a potential new treatment for ADHD.
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Bipolar disorder, brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and brain morphology.
PLoS ONE
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In this study of the effect of bipolar status and presence of BDNF Val66Met polymorphism on differences in regional brain volumes, we hypothesized based on previous studies that 1) bipolar subjects will have smaller regional brain volumes than healthy controls; 2) BDNF Met66 allele carriers within the same population are likely to have smaller regional brain volumes as compared to Val66 homozygyotes. In our Caucasian sample of 166 bipolar subjects and 64 gender-matched healthy controls, we found significant decreases in total (p = 0.005) and regional gray matter volumes in bipolar patients compared to healthy controls, more pronounced in the inferior and posterior parts of the brain, together with a concomitant increase in total CSF (p = 0.012) particularly in the lateral ventricles (p = 0.023). However, there was no difference in white matter volumes noted by other studies. Furthermore we did not find significant differences in other brain regions that have been reported by other authors. Nor did we find a significant effect of BDNF on these measurements.
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Evidence for astrocytes as a potential source of the glutamate excess in temporal lobe epilepsy.
Neurobiol. Dis.
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Increased extracellular brain glutamate has been implicated in the pathophysiology of human refractory temporal lobe epilepsy (TLE), but the cause of the excessive glutamate is unknown. Prior studies by us and others have shown that the glutamate degrading enzyme glutamine synthetase (GS) is deficient in astrocytes in the epileptogenic hippocampal formation in a subset of patients with TLE. We have postulated that the loss of GS in TLE leads to increased glutamate in astrocytes with elevated concentrations of extracellular glutamate and recurrent seizures as the ultimate end-points. Here we test the hypothesis that the deficiency in GS leads to increased glutamate in astrocytes. Rats were chronically infused with methionine sulfoximine (MSO, n=4) into the hippocampal formation to induce GS deficiency and recurrent seizures. A separate group of rats was infused with 0.9% NaCl (saline) as a control (n=6). At least 10days after the start of infusion, once recurrent seizures were established in the MSO-treated rats, the concentration of glutamate was assessed in CA1 of the hippocampal formation by immunogold electron microscopy. The concentration of glutamate was 47% higher in astrocytes in the MSO-treated vs. saline-treated rats (p=0.02), and the ratio of glutamate in astrocytes relative to axon terminals was increased by 74% in the MSO-treated rats (p=0.003). These data support our hypothesis that a deficiency in GS leads to increased glutamate in astrocytes. We additionally propose that the GS-deficient astrocytes in the hippocampal formation in TLE lead to elevated extracellular brain glutamate either through decreased clearance of extracellular glutamate or excessive release of glutamate into the extracellular space from these cells, or a combination of the two.
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Redistribution of monocarboxylate transporter 2 on the surface of astrocytes in the human epileptogenic hippocampus.
Glia
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Emerging evidence points to monocarboxylates as key players in the pathophysiology of temporal lobe epilepsy (TLE) with hippocampal sclerosis (mesial temporal lobe epilepsy, MTLE). Monocarboxylate transporters (MCTs) 1 and 2, which are abundantly present on brain endothelial cells and perivascular astrocyte endfeet, respectively, facilitate the transport of monocarboxylates and protons across cell membranes. Recently, we reported that the density of MCT1 protein is reduced on endothelial cells and increased on astrocyte plasma membranes in the hippocampal formation in patients with MTLE and in several animal models of the disorder. Because the perivascular astrocyte endfeet comprise an important part of the neurovascular unit, we now assessed the distribution of the MCT2 in hippocampal formations in TLE patients with (MTLE) or without hippocampal sclerosis (non-MTLE). Light microscopic immunohistochemistry revealed significantly less perivascular MCT2 immunoreactivity in the hippocampal formation in MTLE (n = 6) than in non-MTLE (n = 6) patients, and to a lesser degree in non-MTLE than in nonepilepsy patients (n = 4). Immunogold electron microscopy indicated that the loss of MCT2 protein occurred on perivascular astrocyte endfeet. Interestingly, the loss of MCT2 on astrocyte endfeet in MTLE (n = 3) was accompanied by an upregulation of the protein on astrocyte membranes facing synapses in the neuropil, when compared with non-MTLE (n = 3). We propose that the altered distribution of MCT1 and MCT2 in TLE (especially MTLE) limits the flux of monocarboxylates across the blood-brain barrier and enhances the exchange of monocarboxylates within the brain parenchyma.
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Analysis of blood-based gene expression signature in first-episode psychosis.
Psychiatry Res
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Blood-based transcriptomic signature in psychosis is an alternative to a brain-based signature. In this study, we profiled whole-blood RNA from 26 patients with first-episode psychosis, and 26 matching controls. We identified a 400-gene signature that classified patients from controls accurately and tested the robustness using other modelling methods.
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Roles of glutamine synthetase inhibition in epilepsy.
Neurochem. Res.
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Glutamine synthetase (GS, E.C. 6.3.1.2) is a ubiquitous and highly compartmentalized enzyme that is critically involved in several metabolic pathways in the brain, including the glutamine-glutamate-GABA cycle and detoxification of ammonia. GS is normally localized to the cytoplasm of most astrocytes, with elevated concentrations of the enzyme being present in perivascular endfeet and in processes close to excitatory synapses. Interestingly, an increasing number of studies have indicated that the expression, distribution, or activity of brain GS is altered in several brain disorders, including Alzheimers disease, schizophrenia, depression, suicidality, and mesial temporal lobe epilepsy (MTLE). Although the metabolic and functional sequelae of brain GS perturbations are not fully understood, it is likely that a deficiency in brain GS will have a significant biological impact due to the critical metabolic role of the enzyme. Furthermore, it is possible that restoration of GS in astrocytes lacking the enzyme could constitute a novel and highly specific therapy for these disorders. The goals of this review are to summarize key features of mammalian GS under normal conditions, and discuss the consequences of GS deficiency in brain disorders, specifically MTLE.
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Downregulation of TOMM40 expression in the blood of Alzheimer disease subjects compared with matched controls.
J Psychiatr Res
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Translocase of outer mitochondrial membrane 40 homolog (TOMM40) gene has been reported in several GWAS to be associated with Alzheimer disease (AD). Gene expression studies thus far only showed TOMM40 differential expression in one study on brain cortex and not in peripheral blood. We studied the gene expression profiles of AD blood versus controls in an Asian population in Singapore. In this first analysis we focused on genes that have been previously reported on GWAS. We found TOMM40 to be significantly down-regulated in blood samples of AD in one discovery and two validation sets, totalling 45 subjects (mean age 76.90, SD 6.46) and 45 controls (mean age 76.23, SD 5.09), matched for ethnicity and gender. The function of TOMM40 is not yet fully characterized but is believed to be involved in import and trafficking of protein into mitochondria. Therefore TOMM40 downregulation, found in the brain in severe AD and in our blood profile, may be a potential marker for AD, disease severity or progression and merit further investigation.
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