Histopathological studies in Alzheimer's disease (AD) suggest severe and region-specific neurodegeneration of the basal forebrain cholinergic system (BFCS). Here, we studied the between-center reliability and diagnostic accuracy of MRI-based BFCS volumetry in a large multicenter data set, including participants with prodromal (n = 41) or clinically manifest AD (n = 134) and 148 cognitively healthy controls. Atrophy was determined using voxel-based and region-of-interest based analyses of high-dimensionally normalized MRI scans using a newly created map of the BFCS based on postmortem in cranio MRI and histology. The AD group showed significant volume reductions of all subregions of the BFCS, which were most pronounced in the posterior nucleus basalis Meynert (NbM). The mild cognitive impairment-AD group showed pronounced volume reductions in the posterior NbM, but preserved volumes of anterior-medial regions. Diagnostic accuracy of posterior NbM volume was superior to hippocampus volume in both groups, despite higher multicenter variability of the BFCS measurements. The data of our study suggest that BFCS morphometry may provide an emerging biomarker in AD.
Atrophy; biomarker; cholinergic system; dementia; European DTI Study on Dementia
Horizontal gene transfer (HGT) is a main driving force of bacterial evolution and innovation. This phenomenon was long thought to be marginal in mycoplasmas, a large group of self-replicating bacteria characterized by minute genomes as a result of successive gene losses during evolution. Recent comparative genomic analyses challenged this paradigm, but the occurrence of chromosomal exchanges had never been formally addressed in mycoplasmas. Here, we demonstrated the conjugal transfer of large chromosomal regions within and among ruminant mycoplasma species, with the incorporation of the incoming DNA occurring by homologous recombination into the recipient chromosome. By combining classical mating experiments with high-throughput next-generation sequencing, we documented the transfer of almost every position of the mycoplasma chromosome. Mycoplasma conjugation relies on the occurrence of an integrative conjugative element (ICE) in at least one parent cell. While ICE propagates horizontally from ICE-positive to ICE-negative cells, chromosomal transfers (CTs) occurred in the opposite direction, from ICE-negative to ICE-positive cells, independently of ICE movement. These findings challenged the classical mechanisms proposed for other bacteria in which conjugative CTs are driven by conjugative elements, bringing into the spotlight a new means for rapid mycoplasma innovation. Overall, they radically change our current views concerning the evolution of mycoplasmas, with particularly far-reaching implications given that over 50 species are human or animal pathogens.
Horizontal gene transfers (HGT) shape bacterial genomes and are key contributors to microbial diversity and innovation. One main mechanism involves conjugation, a process that allows the simultaneous transfer of significant amounts of DNA upon cell-to-cell contact. Recognizing and deciphering conjugal mechanisms are thus essential in understanding the impact of gene flux on bacterial evolution. We addressed this issue in mycoplasmas, the smallest and simplest self-replicating bacteria. In these organisms, HGT was long thought to be marginal. We showed here that nearly every position of the Mycoplasma agalactiae chromosome could be transferred via conjugation, using an unconventional mechanism. The transfer involved DNA blocks containing up to 80 genes that were incorporated into the host chromosome by homologous recombination. These findings radically change our views concerning mycoplasma evolution and adaptation with particularly far-reaching implications given that over 50 species are human or animal pathogens.
An emerging issue in neuroimaging is to assess the diagnostic reliability of PET and its application in clinical practice. We aimed at assessing the accuracy of brain FDG-PET in discriminating patients with MCI due to Alzheimer's disease and healthy controls. Sixty-two patients with amnestic MCI and 109 healthy subjects recruited in five centers of the European AD Consortium were enrolled. Group analysis was performed by SPM8 to confirm metabolic differences. Discriminant analyses were then carried out using the mean FDG uptake values normalized to the cerebellum computed in 45 anatomical volumes of interest (VOIs) in each hemisphere (90 VOIs) as defined in the Automated Anatomical Labeling (AAL) Atlas and on 12 meta-VOIs, bilaterally, obtained merging VOIs with similar anatomo-functional characteristics. Further, asymmetry indexes were calculated for both datasets. Accuracy of discrimination by a Support Vector Machine and the AAL VOIs was tested against a validated method (PALZ). At the voxel level SMP8 showed a relative hypometabolism in the bilateral precuneus, and posterior cingulate, temporo-parietal and frontal cortices. Discriminant analysis classified subjects with an accuracy ranging between .91 and .83 as a function of data organization. The best values were obtained from a subset of 6 meta-VOIs plus 6 asymmetry values reaching an area under the ROC curve of .947, significantly larger than the one obtained by the PALZ score. High accuracy in discriminating MCI converters from healthy controls was reached by a non-linear classifier based on SVM applied on predefined anatomo-functional regions and inter-hemispheric asymmetries. Data pre-processing was automated and simplified by an in-house created Matlab-based script encouraging its routine clinical use. Further validation toward nonconverter MCI patients with adequately long follow-up is needed.
•18F-FDG-PET/CT analysis of metabolic differences between MCI converting to AD and HC•Large and very well controlled cohorts from EADC-Consortium were investigated.•Data were analyzed by a friendly-to-use Matlab-based script and Support Vector Machine.•Excellent discrimination between MCI and HC (sensitivity 92%; specificity 91%)•Highest accuracy reported so far in MCI and promising implementation in clinical routine
MCI; FDG-PET; Volume of interest; Discriminant analysis; EADC
Different biomarkers could help to diagnose Alzheimer’s dementia (AD) since the earliest stages. We capitalized on data from different clinical series to compare sensitivity and specificity of individual biomarkers for predicting mild cognitive impairment (MCI) progression to AD
Medial temporal atrophy, cortical hypometabolism, and cerebrospinal fluid (CSF) biomarkers were assessed in 18 MCI patients with prodromal AD (pAD, conversion time = 26±12 months) and 18 stable MCI patients (sMCI) from TOMC cohort, as well as in 24 pAD patients (conversion time = 36±12 months) and 33 sMCI patients from ADNI cohort. Medial temporal atrophy was measured by manual, semi automated and automated hippocampal volumetry, cortical hypometabolism was measured using several indices of AD-related hypometabolism pattern, and CSF markers were Aβ42 and total tau protein concentrations. For each biomarker, sensitivity for prodromal AD, specificity for sMCI, and diagnostic accuracy were computed.
Sensitivity to predict MCI conversion to AD in ADNI and TOMC cohorts was 79% and 94% based on Aβ42, 46% and 28% based on hippocampal volumes, 33 to 66% and 56 to 78% based on different hypometabolism indices, and 46% and 61% based on total tau levels, respectively. Specificity to exclude sMCI was 27% and 50% based on Aβ42, 76% and 94% based on hippocampal volumes, 58 to 67% and 55 to 83% based on different hypometabolism indices, and 61% and 83% based on total tau levels.
Current findings suggest that Aβ42 concentrations and hippocampal volumes may be used in combination to best identify prodromal AD.
Alzheimer’s disease; MCI; MRI; PET; Diagnostic test assessment; Diagnostic accuracy
Effective therapies for the so-called atypical parkinsonian syndrome (APS) such as multiple system atrophy (MSA), progressive supranuclear palsy (PSP), or corticobasal syndrome (CBS) are not available. Dopamine agonists (DA) are not often used in APS because of inefficacy and in a minority of case, their side effects, like dyskinesias, impairment of extrapyramidal symptoms or the appearance of psychosis, and REM sleep behavioral disorders (RBD). Transdermal rotigotine (RTG) is a non-ergot dopamine agonist indicated for use in early and advanced Parkinson’s disease with a good tolerability and safety. Moreover, its action on a wide range of dopamine receptors, D1, D2, D3, unlike other DA, could make it a good option in APS, where a massive dopamine cell loss is documented. In this pilot, observational open-label study we evaluate the efficacy and tolerability of RTG in patients affected by APS. Thirty-two subjects with diagnosis of APS were treated with transdermal RTG. APS diagnosis was: MSA parkinsonian type (MSA-P), MSA cerebellar type (MSA-C), PSP, and CBS. Patients were evaluated by UPDRS-III, neuropsychiatric inventory, mini mental state examination at baseline, and after 6, 12, and 18 months. The titration schedule was maintained very flexible, searching the major clinical effect and the minor possible adverse events (AEs) at each visit. AEs were recorded. APS patients treated with RTG show an overall decrease of UPDRS-III scores without increasing behavioral disturbances. Only three patients were dropped out of the study. Main AEs were hypotension, nausea, vomiting, drowsiness, and tachycardia. The electroencephalographic recording power spectra analysis shows a decrease of theta and an increase of low alpha power. In conclusion, transdermal RTG seems to be effective and well tolerated in APS patients.
rotigotine; atypical parkinsonism; open-label study; safety; efficacy
Transdermal rotigotine (RTG) is a non-ergot dopamine agonist (D3>D2>D1), and is indicated for use in early and advanced Parkinson’s disease (PD). RTG patch has many potential advantages due to the immediacy of onset of the therapeutic effect. Of note, intestinal absorption is not necessary and drug delivery is constant, thereby avoiding drug peaks and helping patient compliance. In turn, transdermal RTG seems a suitable candidate in the treatment of atypical Parkinsonian disorders (APS).
Fifty-one subjects with a diagnosis of APS were treated with transdermal RTG. The diagnoses were: Parkinson’s disease with dementia, multiple system atrophy Parkinsonian type, multiple system atrophy cerebellar type, progressive supranuclear palsy, corticobasal degeneration, Lewy body dementia, and frontotemporal dementia with Parkinsonism. Patients were evaluated by the Unified Parkinson’s Disease Rating Scale (UPDRS; part III), Neuropsychiatric Inventory (NPI), and mini–mental state examination (MMSE) and all adverse events (AEs) were recorded. Patients treated with RTG showed an overall decrease of UPDRS III scores without increasing behavioral disturbances. Main AEs were hypotension, nausea, vomiting, drowsiness, tachycardia, and dystonia. On the whole, 15 patients were affected by AEs and seven patients suspended RTG treatment due to AEs.
The results show that transdermal RTG is effective with a good tolerability profile. RTG patch could be a good therapeutic tool in patients with APS.
transdermal dopamine agonist; open label study; Parkinson plus
Mutations in the gene coding for Sequestosome 1 (SQSTM1) have been genetically associated with amyotrophic lateral sclerosis (ALS) and Paget disease of bone. In the present study, we analyzed the SQSTM1 coding sequence for mutations in an extended cohort of 1,808 patients with frontotemporal lobar degeneration (FTLD), ascertained within the European Early-Onset Dementia consortium. As control dataset, we sequenced 1,625 European control individuals and analyzed whole-exome sequence data of 2,274 German individuals (total n = 3,899). Association of rare SQSTM1 mutations was calculated in a meta-analysis of 4,332 FTLD and 10,240 control alleles. We identified 25 coding variants in FTLD patients of which 10 have not been described. Fifteen mutations were absent in the control individuals (carrier frequency <0.00026) whilst the others were rare in both patients and control individuals. When pooling all variants with a minor allele frequency <0.01, an overall frequency of 3.2 % was calculated in patients. Rare variant association analysis between patients and controls showed no difference over the whole protein, but suggested that rare mutations clustering in the UBA domain of SQSTM1 may influence disease susceptibility by doubling the risk for FTLD (RR = 2.18 [95 % CI 1.24–3.85]; corrected p value = 0.042). Detailed histopathology demonstrated that mutations in SQSTM1 associate with widespread neuronal and glial phospho-TDP-43 pathology. With this study, we provide further evidence for a putative role of rare mutations in SQSTM1 in the genetic etiology of FTLD and showed that, comparable to other FTLD/ALS genes, SQSTM1 mutations are associated with TDP-43 pathology.
Electronic supplementary material
The online version of this article (doi:10.1007/s00401-014-1298-7) contains supplementary material, which is available to authorized users.
Sequestosome 1; SQSTM1; p62; FTLD; ALS; Rare variants
PET based tools can improve the early diagnosis of Alzheimer's disease (AD) and differential diagnosis of dementia. The importance of identifying individuals at risk of developing dementia among people with subjective cognitive complaints or mild cognitive impairment has clinical, social, and therapeutic implications. Within the two major classes of AD biomarkers currently identified, that is, markers of pathology and neurodegeneration, amyloid- and FDG-PET imaging represent decisive tools for their measurement. As a consequence, the PET tools have been recognized to be of crucial value in the recent guidelines for the early diagnosis of AD and other dementia conditions. The references based recommendations, however, include large PET imaging literature based on visual methods that greatly reduces sensitivity and specificity and lacks a clear cut-off between normal and pathological findings. PET imaging can be assessed using parametric or voxel-wise analyses by comparing the subject's scan with a normative data set, significantly increasing the diagnostic accuracy. This paper is a survey of the relevant literature on FDG and amyloid-PET imaging aimed at providing the value of quantification for the early and differential diagnosis of AD. This allowed a meta-analysis and GRADE analysis revealing high values for PET imaging that might be useful in considering recommendations.
Psychopathy has been associated with increased putamen and striatum volumes. The nucleus accumbens –a key structure in reversal learning, less effective in psychopathy –has not yet received specific attention. Moreover, basal ganglia morphology has never been explored. We examined the morphology of the caudate, putamen and accumbens, manually segmented from magnetic resonance images of 26 offenders (age: 32.5±8.4) with medium-high psychopathy (mean PCL-R=30±5) and 25 healthy controls (age: 34.6±10.8). Local differences were statistically modeled using a surface-based radial distance mapping method (p<0.05; multiple comparisons correction through permutation tests). In psychopathy, the caudate and putamen had normal global volume, but different morphology, significant after correction for multiple comparisons, for the right dorsal putamen (permutation test: p=0.02). The volume of the nucleus accumbens was 13% smaller in psychopathy (p corrected for multiple comparisons <0.006). The atypical morphology consisted of predominant anterior hypotrophy bilaterally (10–30%). Caudate and putamen local morphology displayed negative correlation with the lifestyle factor of the PCL-R (permutation test: p=0.05 and 0.03). From these data, psychopathy appears to be associated with an atypical striatal morphology, with highly significant global and local differences of the accumbens. This is, consistent with the clinical syndrome and with theories of limbic involvement.
psychopathy; neuroimaging; basal ganglia; nucleus accumbens; MRI; ASPD
Revised diagnostic criteria for Alzheimer disease (AD) acknowledge a key role of imaging biomarkers for early diagnosis. Diagnostic accuracy depends on which marker (i.e., amyloid imaging, 18F-fluorodeoxyglucose [FDG]-PET, SPECT, MRI) as well as how it is measured (“metric”: visual, manual, semiautomated, or automated segmentation/computation). We evaluated diagnostic accuracy of marker vs metric in separating AD from healthy and prognostic accuracy to predict progression in mild cognitive impairment. The outcome measure was positive (negative) likelihood ratio, LR+ (LR−), defined as the ratio between the probability of positive (negative) test outcome in patients and the probability of positive (negative) test outcome in healthy controls. Diagnostic LR+ of markers was between 4.4 and 9.4 and LR− between 0.25 and 0.08, whereas prognostic LR+ and LR− were between 1.7 and 7.5, and 0.50 and 0.11, respectively. Within metrics, LRs varied up to 100-fold: LR+ from approximately 1 to 100; LR− from approximately 1.00 to 0.01. Markers accounted for 11% and 18% of diagnostic and prognostic variance of LR+ and 16% and 24% of LR−. Across all markers, metrics accounted for an equal or larger amount of variance than markers: 13% and 62% of diagnostic and prognostic variance of LR+, and 29% and 18% of LR−. Within markers, the largest proportion of diagnostic LR+ and LR− variability was within 18F-FDG-PET and MRI metrics, respectively. Diagnostic and prognostic accuracy of imaging AD biomarkers is at least as dependent on how the biomarker is measured as on the biomarker itself. Standard operating procedures are key to biomarker use in the clinical routine and drug trials.
New criteria for the diagnosis of Alzheimer’s disease (AD) based on biomarker results have recently been developed and are currently undergoing extensive validation. The next few years may represent a time window where the diagnostic validity of biomarkers will be studied in highly specialized research settings. Biomarkers results will be used to direct clinical diagnosis and, whenever appropriate, therapy and management. This piece aims to stimulate discussion by identifying the ethical challenges involved in the use of biomarkers to make a diagnosis of mild cognitive impairment due to AD and disclose it to patients. At the individual level, these challenges are related to (i) the ethical appropriateness of implementing an ecological diagnostic research protocol, (ii) the related informed consent process, and (iii) the diagnostic disclosure. We justify the ethical legitimacy of implementing a research diagnostic protocol by referring to the respect of patients’ subjectivity and autonomy, and we suggest guidelines for informed consent development and diagnostic disclosure. All of the above points are discussed in light of the unique features of AD, currently scanty treatment options, and knowledge and uncertainties regarding the diagnostic value of biomarkers.
prodromal Alzheimer’s disease; informed consent; diagnosis disclosure; translational research; bioethics guideline
Background: Alzheimer’s disease (AD) is the most common cause of dementia in older patients. Rivastigmine (RV, Exelon, Novartis), a reversible cholinesterase inhibitor, improves clinical manifestations of AD and may enhance ACh-modulated electroencephalogram (EEG) alpha frequency. This pilot study aimed to determine the effects of two formulations of RV [transdermal patch (RV-TDP) and oral capsules (TV-CP)] on alpha frequency, in particular the posterior dominant rhythm, and cognitive function [assessed by the Mini-Mental State Examination (MMSE)] in patients with AD.
Methods: Subjects with AD were assigned to receive either RV-TDP 10 cm2 or RV-CP 12 mg/day. All patients underwent EEG recordings at the beginning and end of the 18-month study period using P3, P4, O1, and O2 electrodes, each at high (10.5–13.0 Hz) and low (8.0–10.5 Hz) frequency. MMSE scores were determined at the start of the study (T0) and at three successive 6-month intervals (T1, T2, and T3).
Results: RV-TDP administration (n = 10) maintained cognitive function as evidenced by stable MMSE scores from baseline to 18 months (21.07 ± 2.4–21.2 ± 3.1) compared with a decrease in MMSE score with RV-CP (n = 10) over 18 months [18.3 ± 3.6–13.6 ± 5.06 (adjusted for covariates p = 0.006)]. MMSE scores were significantly different between treatment groups from 6 months (p = 0.04). RV-TDP also increased the spectral power of alpha waves in the posterior region measured with electrode P3 in a significantly great percentage of patients than TV-CP from baseline to 18 months; 80% vs 30%, respectively [p = 0.025 (χ2 test)].
Conclusions: RV-TDP was associated with a greater proportion of patients with increased posterior region alpha wave spectral power and significantly higher cognitive function at 18 months, compared with RV-CP treatment. Our findings suggest that RV-TDP provides an effective long-term management option in patients with AD compared with oral RV-CP. This study is a pilot, open-label study with a clear explorative purpose and with a small number of patients. Further randomized, double-blind, placebo-controlled trial studies with a bigger sample size as well as healthy controls are needed to support these initial results.
transdermal rivastigmine oral rivastigmine; Alzheimer’s disease; dementia; cognitive function; EEG
Manual segmentation from magnetic resonance imaging (MR) is the gold standard for evaluating hippocampal atrophy in Alzheimer’s disease (AD). Nonetheless, different segmentation protocols provide up to 2.5-fold volume differences. Here we surveyed the most frequently used segmentation protocols in the AD literature as a preliminary step for international harmonization. The anatomical landmarks (anteriormost and posteriormost slices, superior, inferior, medial, and lateral borders) were identified from 12 published protocols for hippocampal manual segmentation ([Abbreviation] first author, publication year: [B] Bartzokis, 1998; [C] Convit, 1997; [dTM] deToledo-Morrell, 2004; [H] Haller, 1997; [J] Jack, 1994; [K] Killiany, 1993; [L] Lehericy, 1994; [M] Malykhin, 2007; [Pa] Pantel, 2000; [Pr] Pruessner, 2000; [S] Soininen, 1994; [W] Watson, 1992). The hippocampi of one healthy control and one AD patient taken from the 1.5T MR ADNI database were segmented by a single rater according to each protocol. The accuracy of the protocols’ interpretation and translation into practice was checked with lead authors of protocols through individual interactive web conferences. Semantically harmonized landmarks and differences were then extracted, regarding: (a) the posteriormost slice, protocol [B] being the most restrictive, and [H, M, Pa, Pr, S] the most inclusive; (b) inclusion [C, dTM, J, L, M, Pr, W] or exclusion [B, H, K, Pa, S] of alveus/fimbria; (c) separation from the parahippocampal gyrus, [C] being the most restrictive, [B, dTM, H, J, Pa, S] the most inclusive. There were no substantial differences in the definition of the anteriormost slice. This survey will allow us to operationalize differences among protocols into tracing units, measure their impact on the repeatability and diagnostic accuracy of manual hippocampal segmentation, and finally develop a harmonized protocol.
Hippocampus; manual segmentation protocol; harmonization; anatomical landmark; Alzheimer’s disease; manual tracing; medial temporal lobes; atrophy; degeneration; MRI
The brain of a patient with Alzheimer’s disease (AD) undergoes changes starting many years before the development of the first clinical symptoms. The recent availability of large prospective datasets makes it possible to create sophisticated brain models of healthy subjects and patients with AD, showing pathophysiological changes occurring over time. However, these models are still inadequate; representations are mainly single-scale and they do not account for the complexity and interdependence of brain changes. Brain changes in AD patients occur at different levels and for different reasons: at the molecular level, changes are due to amyloid deposition; at cellular level, to loss of neuron synapses, and at tissue level, to connectivity disruption. All cause extensive atrophy of the whole brain organ. Initiatives aiming to model the whole human brain have been launched in Europe and the US with the goal of reducing the burden of brain diseases. In this work, we describe a new approach to earlier diagnosis based on a multimodal and multiscale brain concept, built upon existing and well-characterized single modalities.
This supplement to the Journal of Alzheimer's Disease contains more than half of the chapters from The Handbook of Imaging the Alzheimer Brain, which was first presented at the International Conference on Alzheimer's Disease in Paris, in July, 2011.
While the Handbook contains 27 chapters that are modified articles from 2009, 2010, and 2011 issues of the Journal of Alzheimer's Disease, this supplement contains the 31 new chapters of that book and an introductory article drawn from the introductions to each section of the book.
The Handbook was designed to provide a multilevel overview of the full field of brain imaging related to Alzheimer's disease (AD). The Handbook, as well as this supplement, contains both reviews of the basic concepts of imaging, the latest developments in imaging, and various discussions and perspectives of the problems of the field and promising directions.
The Handbook was designed to be useful for students and clinicians interested in AD as well as scientists studying the brain and pathology related to AD.
The cerebrospinal fluid (CSF) biomarkers amyloid β (Aβ)-42, total-tau (T-tau), and phosphorylated-tau (P-tau) demonstrate good diagnostic accuracy for Alzheimer’s disease (AD). However, there are large variations in biomarker measurements between studies, and between and within laboratories. The Alzheimer’s Association has initiated a global quality control program to estimate and monitor variability of measurements, quantify batch-to-batch assay variations, and identify sources of variability. In this article, we present the results from the first two rounds of the program.
The program is open for laboratories using commercially available kits for Aβ, T-tau, or P-tau. CSF samples (aliquots of pooled CSF) are sent for analysis several times a year from the Clinical Neurochemistry Laboratory at the Molndal campus of the University of Gothenburg, Sweden. Each round consists of three quality control samples.
Forty laboratories participated. Twenty-six used INNOTESTenzyme-linked immunosorbent assay kits, 14 used Luminex xMAP with the INNO-BIA AlzBio3 kit (both measure Aβ-(1-42), P-tau(181P), and T-tau), and 5 used Meso Scale Discovery with the Aβ triplex (AβN-42, AβN-40, and AβN-38) or T-tau kits. The total coefficients of variation between the laboratories were 13% to 36%. Five laboratories analyzed the samples six times on different occasions. Within-laboratory precisions differed considerably between biomarkers within individual laboratories.
Measurements of CSF AD biomarkers show large between-laboratory variability, likely caused by factors related to analytical procedures and the analytical kits. Standardization of laboratory procedures and efforts by kit vendors to increase kit performance might lower variability, and will likely increase the usefulness of CSF AD biomarkers.
Alzheimer’s disease; Cerebrospinal fluid; Biomarkers; External assurance; External control; Proficiency testing
We report here the draft genome sequences of Mycoplasma auris and Mycoplasma yeatsii, two species commonly isolated from the external ear canal of Caprinae.
We report here the draft genome sequences of Mycoplasma alkalescens, Mycoplasma arginini, and Mycoplasma bovigenitalium. These three species are regularly isolated from bovine clinical specimens, although their role in disease is unclear.
Mycoplasma putrefaciens is one of the etiologic agents of contagious agalactia in goats. We report herein the complete genome sequence of Mycoplasma putrefaciens strain 9231.
Caspase Activated DNase (CAD) is an endonuclease that is activated by active caspase 3 during apoptosis and is responsible for degradation of chromatin into nucleosomal units. These nucleosomal units are then included in apoptotic bodies. The presence of apoptotic bodies is considered important for the generation of auto-antigens in autoimmune diseases such as lupus, which are characterized by the presence of anti-nuclear antibodies.
The present study was carried out to determine the role of CAD in Sle1, Sle123 and 3H9 spontaneous models of lupus, where autoimmunity is genetically pre-determined. We also determined the ability of lupus auto-antibodies to bind to CAD deficient or sufficient apoptotic cells.
The deficiency of CAD resulted in higher anti-dsDNA antibody titers in lupus-prone mice. Surprisingly, the absence of CAD only exacerbated genetically pre-determined autoimmune responses. To further determine whether nuclear modifications are required to maintain tolerance to nuclear auto-antigens, we used the 3H9 mouse, an anti-DNA heavy chain knock-in. In this model, the autoreactive B cells are tolerized by anergy. In line with the Sle1 and Sle123 CAD mutant mice, CAD deficient 3H9 mice spontaneously generated anti-DNA antibodies. We finally show that auto-antibodies with specificities towards histone/DNA complexes bind more to CAD deficient apoptotic cells compared to CAD sufficient apoptotic cells.
We propose that in mice genetically predisposed to lupus, nuclear apoptotic modifications are required to maintain tolerance. In the absence of these modifications, apoptotic chromatin is abnormally exposed, facilitating the autoimmune response.
Objective: Temporo-parietal cortex thinning is associated to mild cognitive impairment (MCI) due to Alzheimer disease (AD). The increase of EEG upper/low alpha power ratio has been associated with AD-converter MCI subjects. We investigated the association of alpha3/alpha2 ratio with patterns of cortical thickness in MCI.
Materials and Methods: Seventy-four adult subjects with MCI underwent clinical and neuropsychological evaluation, electroencephalogram (EEG) recording and high resolution 3D magnetic resonance imaging. Alpha3/alpha2 power ratio as well as cortical thickness was computed for each subject. Three MCI groups were detected according to increasing tertile values of upper/low alpha power ratio. Difference of cortical thickness among the groups was estimated. Pearson’s r was used to assess the topography of the correlation between cortical thinning and memory impairment.
Results: High upper/low alpha power ratio group had total cortical gray matter volume reduction of 471 mm2 than low upper/low alpha power ratio group (p < 0.001). Upper/low alpha group showed a similar but less marked pattern (160 mm2) of cortical thinning when compared to middle upper/low alpha power ratio group (p < 0.001). Moreover, high upper/low alpha group had wider cortical thinning than other groups, mapped to the Supramarginal and Precuneus bilaterally. Finally, in high upper/low alpha group temporo-parietal cortical thickness was correlated to memory performance. No significant cortical thickness differences was found between middle and low alpha3/alpha2 power ratio groups.
Conclusion: High EEG upper/low alpha power ratio was associated with temporo-parietal cortical thinning and memory impairment in MCI subjects. The combination of EEG upper/low alpha ratio and cortical thickness measure could be useful for identifying individuals at risk for progression to AD dementia and may be of value in clinical context.
EEG; brain rhythms; cortical atrophy; MRI; MCI-diagnosis
Background: Several biomarkers have been proposed for detecting Alzheimer's disease (AD) in its earliest stages, that is, in the predementia stage. In an attempt to find noninvasive biomarkers, researchers have investigated the feasibility of neuroimaging tools, such as MRI, SPECT as well as neurophysiological measurements using EEG. Moreover, the increase of EEG alpha3/alpha2 frequency power ratio has been associated with AD-converters subjects with mild cognitive impairment (MCI).
Objective: To study the association of alpha3/alpha2 frequency power ratio with regional cerebral blood flow (rCBF) changes in subjects with MCI.
Methods: Twenty-seven adult subjects with MCI underwent EEG recording and perfusion single-photon emission computed tomography (SPECT) evaluation. The alpha3/alpha2 frequency power ratio was computed for each subject. Two groups were obtained according to the median values of alpha3/alpha2, at a cut-off of 1.17. Correlation between brain perfusion and EEG markers were detected.
Results: Subjects with higher alpha3/alpha2 frequency power ratio showed a constant trend to a lower perfusion than low alpha3/alpha2 group. The two groups were significantly different as about the hippocampal volume and correlation with the theta frequency activity.
Conclusion: There is a complex interplay between cerebral blood flow, theta frequency activity, and hippocampal volume in MCI patients with prodromal Alzheimer's disease, characterized by higher EEG alpha3/alpha2 frequency power ratio.
EEG; alpha3/alpha2 frequency ratio; SPECT; mild cognitive impairment; Alzheimer's disease
GM (grey matter) changes of thalamus and basal ganglia have been demonstrated to be involved in AD (Alzheimer's disease). Moreover, the increase of a specific EEG (electroencephalogram) marker, α3/α2, have been associated with AD-converters subjects with MCI (mild cognitive impairment). To study the association of prognostic EEG markers with specific GM changes of thalamus and basal ganglia in subjects with MCI to detect biomarkers (morpho-physiological) early predictive of AD and non-AD dementia. Seventy-four adult subjects with MCI underwent EEG recording and high-resolution 3D MRI (three-dimensional magnetic resonance imaging). The α3/α2 ratio was computed for each subject. Three groups were obtained according to increasing tertile values of α3/α2 ratio. GM density differences between groups were investigated using a VBM (voxel-based morphometry) technique. Subjects with higher α3/α2 ratios when compared with subjects with lower and middle α3/α2 ratios showed minor atrophy in the ventral stream of basal ganglia (head of caudate nuclei and accumbens nuclei bilaterally) and of the pulvinar nuclei in the thalamus; The integrated analysis of EEG and morpho-structural markers could be useful in the comprehension of anatomo-physiological underpinning of the MCI entity.
Alzheimer's disease; basal ganglia; electroencephalogram (EEG); mild cognitive impairment; thalamus; voxel-based morphometry (VBM); AD, Alzheimer's disease; DARTEL, Diffeomorphic Anatomical Registration using Exponentiated Lie; EEG, electroencephalogram; fMRI, functional magnetic resonance imaging; GM, grey matter; IAF, individual α frequency; MCI, mild cognitive impairment; MMSE, Mini-Mental State Examination; PET, positron-emission tomography; TF, transition frequency; TIV, total intracranial volume; VBM, voxel-based morphometry