bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conditional deletion of β1‐integrin in astroglia causes partial reactive gliosis
Authors: Robel Stefanie , Mori Tetsuji , Zoubaa Saida , Schlegel Jürgen , Sirko Svetlana , Faissner Andreas , Goebbels Sandra , Dimou Leda , Götz Magdalena 
Published: April 2009

AbstractAstrocytes play many pivotal roles in the adult brain, including their reaction to injury. A hallmark of astrocytes is the contact of their endfeet with the basement membrane surrounding blood vessels, but still relatively little is known about the signaling mediated at the contact site. Here, we examine the role of β1‐integrin at this interface by its conditional deletion using different Cre lines. Thereby, the protein was reduced only at postnatal stages either in both glia and neurons or specifically only in neurons. Strikingly, only the former resulted in reactive gliosis, with the hallmarks of reactive astrocytes comprising astrocyte hypertrophy and up‐regulation of the intermediate filaments GFAP and vimentin as well as pericellular components, such as Tenascin‐C and the DSD‐1 proteoglycan. In addition, we also observed to a certain degree a non‐cell autonomous activation of microglial cells after conditional β1‐integrin deletion. However, these reactive astrocytes did not divide, suggesting that the loss of β1‐integrin‐mediated signaling is not sufficient to elicit proliferation of these cells as observed after brain injury. Interestingly, this partial reactive gliosis appeared in the absence of cell death and blood brain barrier disturbances. As these effects did not appear after neuron‐specific deletion of β1‐integrin, we conclude that β1‐integrin‐mediated signaling in astrocytes is required to promote their acquisition of a mature, nonreactive state. Alterations in β1‐integrin‐mediated signaling may hence be implicated in eliciting specific aspects of reactive gliosis after injury. © 2009 Wiley‐Liss, Inc.
Epigenetic mechanisms facilitating oligodendrocyte development, maturation, and aging
Authors: Copray Sjef , Huynh Jimmy Long , Sher Falak , Casaccia‐Bonnefil Patrizia , Boddeke Erik 
Published: April 2009

AbstractThe process of oligodendrocyte differentiation is regulated by a dynamic interaction between a genetic and an epigenetic program. Recent studies, addressing nucleosomal histone modifications have considerably increased our knowledge regarding epigenetic regulation of gene expression during oligodendrocyte development and aging. These results have generated new hypotheses regarding the mechanisms underlying the decreased efficiency of endogenous remyelination in response to demyelinating injuries with increasing age. In this review, we present an overview of the epigenetic mechanisms regulating gene expression at specific stages of oligodendrocyte differentiation and maturation as well as the changes that occur with aging. © 2009 Wiley‐Liss, Inc.
Expression and function of P2Y receptors on Müller cells of the postnatal rat retina
Authors: Wurm Antje , Erdmann Ines , Bringmann Andreas , Reichenbach Andreas , Pannicke Thomas 
Published: April 2009

AbstractIn the postnatal and mature retina, many processes are controlled by the action of nucleotides. Their effects are partly mediated via activation of metabotropic P2Y receptors. However, little is known about the developmental regulation and cellular localization of P2Y receptor subtypes. Combining immunohistochemical and neurophysiological methods, we investigated the developmental expression of P2Y receptors on Müller cells, the principal macroglial cells of the retina. The P2Y1 and the P2Y4 receptors, but no other subtypes, were unequivocally localized on Müller cells. P2Y1 was expressed from postnatal day 5 (P5) on and mediated a calcium response to ATP in Müller cells as well as a volume regulatory signaling cascade preventing Müller cells from swelling under hypotonic conditions. Differentiation of Müller cells was accompanied by a change of the calcium response pattern; the calcium responses in Müller cell endfeet persisted, but ATP responsiveness of Müller cell somata disappeared. P2Y4 immunoreactivity was observed in Müller cell endfeet and synaptic terminals of rod bipolar cells from P20 on. Activated protein kinases were detected by immunohistochemistry; p‐ERK occurred in Müller cells and amacrine cells, whereas p‐Akt was detected in bipolar cells. Our data indicate that purinergic signaling via P2Y1 and P2Y4 receptors might contribute to differentiation processes in the postnatal retina. © 2009 Wiley‐Liss, Inc.
Elastin‐derived peptides: Matrikines critical for glioblastoma cell aggressiveness in a 3‐D system
Authors: Coquerel Bérénice , Poyer Florent , Torossian Frédéric , Dulong Virginie , Bellon Georges , Dubus Isabelle , Reber Annie , Vannier Jean‐Pierre 
Published: April 2009

AbstractIn the most common primary brain tumors, malignant glioma cells invade the extracellular matrix (ECM) and proliferate rapidly in the cerebral tissue, which is mainly composed of hyaluronan (HA) along with the elastin present in the basement membrane of blood vessels. To determine the role of ECM components in the invasive capacity of glioma cell lines, we developed a 3‐D cell‐culture system, based on a hydrogel in which HA can be coreticulated with kappa‐elastin (HA‐κE). Using this system, the invasiveness of cells from four glioma cell lines was dramatically increased by the presence of κE and a related, specific peptide (VGVAPG)3. In addition, MMP‐2 secretion increased and MMP‐12 synthesis occurred. Extracellular injections of κE or (VGVAPG)3 provoked a pronounced and dose‐dependent increase in [Ca2+]i. κE significantly enhanced the expression of the genes encoding elastin‐receptor and tropoelastin. We propose the existence of a positive feedback loop in which degradation of elastin generates fragments that stimulate synthesis of tropoelastin followed by further degradation as well as migration and proliferation of the very cells responsible for degradation. All steps in this ECM‐based loop could be blocked by the addition of either of the EBP antagonists, lactose, and V‐14 peptide, suggesting that the loop itself should be considered as a new therapeutic target. © 2009 Wiley‐Liss, Inc.
Post‐traumatic stress disorder and prediction of aggression in persons with dementia
Authors: Ball Valdesha L. , Hudson Sonora , Davila Jessica , Morgan Robert , Walder Annette , Graham David P. , Snow Andrea L. , Kunik Mark E. 
Published: April 2009

AbstractObjectiveThis prospective cohort study evaluated the potential of increased aggression in patients with dementia who had a preexisting diagnosis of post‐traumatic stress disorder (PTSD) compared with those without a diagnosis of PTSD.MethodsPatients more than 60 years of age with newly diagnosed dementia between 2001 and 2004 were identified from the Michael E. DeBakey Veterans Affairs (VA) Medical Center in Houston, TX. Among these patients, we identified patients with a preexisting diagnosis of PTSD. The proportions of patients who became aggressive within 2 years of enrollment were compared in patients with and without PTSD. Fisher's exact tests were used to compare differences in the number of PTSD patients with and without aggression.ResultsA total of 215 patients were identified with newly diagnosed dementia. Ten were found to have a diagnosis of PTSD, and 205 did not. Eighty‐four (41%) of the 205 were found to be aggressive. Among the 10 patients with a diagnosis of PTSD, 4 (40%) were aggressive.ConclusionThere was no evidence to support an increased risk of aggression in patients with a coexisting diagnosis of dementia and PTSD. Copyright © 2009 John Wiley & Sons, Ltd.
Detection of event‐related modulations of oscillatory brain activity with multivariate statistical analysis of MEG data
Authors: Soto Juan L.P. , Pantazis Dimitrios , Jerbi Karim , Lachaux Jean‐Phillipe , Garnero Line , Leahy Richard M. 
Published: April 2009

AbstractWe describe a method to detect brain activation in cortically constrained maps of current density computed from magnetoencephalography (MEG) data using multivariate statistical inference. We apply time–frequency (wavelet) analysis to individual epochs to produce dynamic images of brain signal power on the cerebral cortex in multiple time–frequency bands. We form vector observations by concatenating the power in each frequency band, and fit them into separate multivariate linear models for each time band and cortical location with experimental conditions as predictor variables. The resulting Roy's maximum root statistic maps are thresholded for significance using permutation tests and the maximum statistic approach. A source is considered significant if it exceeds a statistical threshold, which is chosen to control the familywise error rate, or the probability of at least one false positive, across the cortical surface. We compare and evaluate the multivariate approach with existing univariate approaches to time–frequency MEG signal analysis, both on simulated data and experimental data from an MEG visuomotor task study. Our results indicate that the multivariate method is more powerful than the univariate approach in detecting experimental effects when correlations exist between power across frequency bands. We further describe protectedF‐tests and linear discriminant analysis to identify individual frequencies that contribute significantly to experimental effects. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
The fMRI success rate of children and adolescents: Typical development, epilepsy, attention deficit/hyperactivity disorder, and autism spectrum disorders
Authors: Yerys Benjamin E. , Jankowski Kathryn F. , Shook Devon , Rosenberger Lisa R. , Barnes Kelly Anne , Berl Madison M. , Ritzl Eva K. , VanMeter John , Vaidya Chandan J. , Gaillard William D. 
Published: April 2009

AbstractFunctional magnetic resonance imaging (fMRI) in children is increasingly used in clinical application and in developmental research; however, little is known how pediatric patient and typically developing populations successfully complete studies. We examined pediatric success rates with epilepsy, attention deficit/hyperactivity disorder (ADHD), autism spectrum disorders (ASD), and typically developing children (TYP). We also examined the affect of age, and, for ADHD populations, medication status on success rates. We defined a successful fMRI individual run when the data were interpretable and included in group statistics. For unsuccessful runs, datasets with excessive motion or floor task performance were categorized when possible. All clinical groups scanned less successfully than controls; medication status did not affect ADHD success (epilepsy, 80%; ADHD (off methylphenidate), 77%; ADHD (on methylphenidate), 81%; ASD, 70%; TYP, 87%). Ten to 18‐year‐old had a significantly greater scan success rate than 4‐ to 6‐year‐old; adolescents (13‐ to 18‐year‐old) demonstrated greater scan success rates than 7‐ to 9‐year‐old. Success rate for completing an entire battery of experimental runs (n = 2–6), varied between 50–59% for patient populations and 69% for TYP (79% when excluding 4‐ to 6‐year‐old). Success rate for completing one run from a battery was greater than 90% for all groups, except for ASD (81%). These data suggest 20–30% more children should be recruited in these patient groups, but only 10–20% for TYP for research studies. Studies with 4‐ to 6‐year‐olds may require 20–40% additional participants; studies with 10‐ to 18‐year‐olds may require 10–15% additional participants. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Dynamic Granger–Geweke causality modeling with application to interictal spike propagation
Authors: Lin Fa‐Hsuan , Hara Keiko , Solo Victor , Vangel Mark , Belliveau John W. , Stufflebeam Steven M. , Hämäläinen Matti S. 
Published: April 2009

AbstractA persistent problem in developing plausible neurophysiological models of perception, cognition, and action is the difficulty of characterizing the interactions between different neural systems. Previous studies have approached this problem by estimating causal influences across brain areas activated during cognitive processing using structural equation modeling (SEM) and, more recently, with Granger–Geweke causality. While SEM is complicated by the need for a priori directional connectivity information, the temporal resolution of dynamic Granger–Geweke estimates is limited because the underlying autoregressive (AR) models assume stationarity over the period of analysis. We have developed a novel optimal method for obtaining data‐driven directional causality estimates with high temporal resolution in both time and frequency domains. This is achieved by simultaneously optimizing the length of the analysis window and the chosen AR model order using the SURE criterion. Dynamic Granger–Geweke causality in time and frequency domains is subsequently calculated within a moving analysis window. We tested our algorithm by calculating the Granger–Geweke causality of epileptic spike propagation from the right frontal lobe to the left frontal lobe. The results quantitatively suggested that the epileptic activity at the left frontal lobe was propagated from the right frontal lobe, in agreement with the clinical diagnosis. Our novel computational tool can be used to help elucidate complex directional interactions in the human brain. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Optical flow approaches to the identification of brain dynamics
Authors: Lefèvre Julien , Baillet Sylvain 
Published: April 2009

AbstractThe superior temporal resolution of magneto‐ and electroencephalography (MEEG) provides unique insight into the dynamics of brain function. The analysis of the spatial dimensions of MEEG recordings can take a multiplicity of approaches: from the original scalp recordings to the identification of their generators through localizing or imaging techniques. Overall, both MEEG native or imaging data may be considered as multidimensional structures with potentially dense information contents. Quantitative analysis of the spatiotemporal flow of information conveyed by MEEG begins with a feature‐extraction problem, thereby leading to improved insight in the multidimensional structure of brain dynamics. In this contribution, we approach this endeavor by suggesting that brain dynamic features from local through global spatial scales may be identified using the previously‐introduced technique of surface‐based optical flow. We illustrate this assertion by the quantitative analysis of time‐resolved sequences of brain activity through the identification of episodes of relative topographical stability. In that respect, we revisit the concept of brain microstates with a new approach and distinct operational hypotheses. Local dynamic features from a variety of brain systems may also be explored through this methodology, as illustrated by experimental data on fast responses in the visual system as revealed by MEEG source imaging. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
EEG source imaging with spatio‐temporal tomographic nonnegative independent component analysis
Authors: Valdés‐Sosa Pedro A. , Vega‐Hernández Mayrim , Sánchez‐Bornot José Miguel , Martínez‐Montes Eduardo , Bobes María Antonieta 
Published: April 2009

AbstractThis article describes a spatio‐temporal EEG/MEG source imaging (ESI) that extracts a parsimonious set of “atoms” or components, each the outer product of both a spatial and a temporal signature. The sources estimated are localized as smooth, minimally overlapping patches of cortical activation that are obtained by constraining spatial signatures to be nonnegative (NN), orthogonal, sparse, and smooth‐in effect integrating ESI with NN‐ICA. This constitutes a generalization of work by this group on the use of multiple penalties for ESI. A multiplicative update algorithm is derived being stable, fast and converging within seconds near the optimal solution. This procedure, spatio‐temporal tomographic NN ICA (STTONNICA), is equally able to recover superficial or deep sources without additional weighting constraints as tested with simulations. STTONNICA analysis of ERPs to familiar and unfamiliar faces yields an occipital‐fusiform atom activated by all faces and a more frontal atom that only is active with familiar faces. The temporal signatures are at present unconstrained but can be required to be smooth, complex, or following a multivariate autoregressive model. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Comparing MEG and fMRI views to naming actions and objects
Authors: Liljeström Mia , Hultén Annika , Parkkonen Lauri , Salmelin Riitta 
Published: April 2009

AbstractMost neuroimaging studies are performed using one imaging method only, either functional magnetic resonance imaging (fMRI), electroencephalography (EEG), or magnetoencephalography (MEG). Information on both location and timing has been sought by recording fMRI and EEG, simultaneously, or MEG and fMRI in separate sessions. Such approaches assume similar active areas whether detected via hemodynamic or electrophysiological signatures. Direct comparisons, after independent analysis of data from each imaging modality, have been conducted primarily on low‐level sensory processing. Here, we report MEG (timing and location) and fMRI (location) results in 11 subjects when they named pictures that depicted an action or an object. The experimental design was exactly the same for the two imaging modalities. The MEG data were analyzed with two standard approaches: a set of equivalent current dipoles and a distributed minimum norm estimate. The fMRI blood‐oxygen‐level dependent (BOLD) data were subjected to the usual random‐effect contrast analysis. At the group level, MEG and fMRI data showed fairly good convergence, with both overall activation patterns and task effects localizing to comparable cortical regions. There were some systematic discrepancies, however, and the correspondence was less compelling in the individual subjects. The present analysis should be helpful in reconciling results of fMRI and MEG studies on high‐level cognitive functions. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Dynamical MEG source modeling with multi‐target Bayesian filtering
Authors: Sorrentino Alberto , Parkkonen Lauri , Pascarella Annalisa , Campi Cristina , Piana Michele 
Published: April 2009

AbstractWe present a Bayesian filtering approach for automatic estimation of dynamical source models from magnetoencephalographic data. We apply multi‐target Bayesian filtering and the theory of Random Finite Sets in an algorithm that recovers the life times, locations and strengths of a set of dipolar sources. The reconstructed dipoles are clustered in time and space to associate them with sources. We applied this new method to synthetic data sets and show here that it is able to automatically estimate the source structure in most cases more accurately than either traditional multi‐dipole modeling or minimum current estimation performed by uninformed human operators. We also show that from real somatosensory evoked fields the method reconstructs a source constellation comparable to that obtained by multi‐dipole modeling. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Predicting stimulus‐rate sensitivity of human somatosensory fMRI signals with MEG
Authors: Nangini Cathy , Hlushchuk Yevhen , Hari Riitta 
Published: April 2009

AbstractWith increasing stimulus rate (SR), cortical EEG and MEG responses typically decrease in amplitude whereas BOLD fMRI signals increase. To address this discrepancy, we predicted BOLD responses with squared MEG waveforms using a recently proposed energy‐density model. Tactile stimuli were delivered to finger tips at SRs of 1, 4, or 10 Hz in successive 25‐s blocks, and brain signals were detected from area 3b of the primary somatosensory cortex of nine healthy adults using a 306‐channel whole‐scalp neuromagnetometer and a 3‐T fMRI magnet. The main MEG deflections decreased in amplitude as a function of SR, whereas the BOLD signals increased from 1‐ to 4‐Hz SR, with no further change at 10 Hz. MEG energy densities, obtained over the whole stimulus train and convolved with different hemodynamic response functions, predicted both the shape and amplitude of the BOLD signals well, and incorporation of nonlinear terms into the model did not offer any further advantage. Thus, squared MEG waveforms obtained over the entire stimulus train provided an appropriate estimate of area 3b neuronal activity associated with the BOLD signal. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Sources of auditory brainstem responses revisited: Contribution by magnetoencephalography
Authors: Parkkonen Lauri , Fujiki Nobuya , Mäkelä Jyrki P. 
Published: April 2009

AbstractAuditory brainstem responses provide diagnostic value in pathologies involving the early parts of the auditory pathway. Despite that, the neural generators underlying the various components of these responses have remained unclear. Direct electrical recordings in humans are possible only in limited time periods during surgery and from small regions of the diseased brains. The evidence of the generator sites is therefore fragmented and indirect, based strongly on lesion studies and animal models. Source modeling of EEG has been limited to grand averages across multiple subjects. Here, we employed magnetoencephalography (MEG) to shed more light on the neural origins of the auditory brainstem responses (ABR) and to test whether such deep brain structures are accessible by MEG. We show that the magnetic counterparts of the electric ABRs can be measured in 30 min and that they allow localization of some of the underlying neural sources in individual subjects. Many of the electric ABR components were present in our MEG data; however, the morphologies of the magnetic and electric responses were different, indicating that the MEG signals carry information complementary to the EEG data. The locations of the neural sources corresponding to the magnetic ABR deflections ranged from the auditory nerve to the inferior colliculus. The earliest cortical responses were detectable at the latency of 13 ms. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Clinical applications of magnetoencephalography
Authors: Stufflebeam Steven M. , Tanaka Naoaki , Ahlfors Seppo P. 
Published: April 2009

AbstractMagnetoencephalography (MEG), in which magnetic fields generated by brain activity are recorded outside of the head, is now in routine clinical practice throughout the world. MEG has become a recognized and vital part of the presurgical evaluation of patients with epilepsy and patients with brain tumors. We review investigations that show an improvement in the postsurgical outcomes of patients with epilepsy by localizing epileptic discharges. We also describe the most common clinical MEG applications that affect the management of patients, and discuss some applications that are close to having a clinical impact on patients. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Synthetic approach for novel bis(α‐aminophosphonic acid) derivatives of chromone containing 1,2,4,3‐triazaphosphole moieties
Authors: Ali Tarik E. , Halacheva Silvia S. 
Published: April 2009

AbstractTerephthalic acid hydrazide (1) was reacted with phenylphosphonic dichloride to yield bis(1,3,4,2‐oxadiazaphosphole) derivative 3, which was condensed with α‐aminophosphonic acid derivative 4 to afford bis[(1,2,4,3‐triazaphospholyl)(chromonyl)methylphosphonic acid] derivative 5. The addition of diethyl phosphite to Schiff bases 9 and 10 derived from the condensation of bis(4‐amino‐1,2,4,3‐triazaphosphole) derivative 6 or bis(4‐phosphorylamino‐1,2,4,3‐triazaphosphole) derivative 7 with 3‐formyl‐6‐methylchromone (8) yielded bis[(1,2,4,3‐triazaphospholyl)(chromonyl)aminomethylphosphonate] derivative 11 and bis[(1,2,4,3‐triazaphospholyl)(chromonyl)phosphorylamino‐methylphosphonate] derivative 12, respectively. The structures of all products were established by elemental analysis and spectral data. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:117–122, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20520