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Search Results: 1 - 10 of 721434 matches for " Claudia A. M. Wheeler-Kingshott "
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A comprehensive assessment of resting state networks: bidirectional modification of functional integrity in cerebro-cerebellar networks in dementia
Gloria Castellazzi,Fulvia Palesi,Stefano Casali,Paolo Vitali,Claudia A. M. Wheeler-Kingshott,Egidio D'Angelo
Frontiers in Neuroscience , 2014, DOI: 10.3389/fnins.2014.00223
Abstract: In resting state fMRI (rs-fMRI), only functional connectivity (FC) reductions in the default mode network (DMN) are normally reported as a biomarker for Alzheimer's disease (AD). In this investigation we have developed a comprehensive strategy to characterize the FC changes occurring in multiple networks and applied it in a pilot study of subjects with AD and Mild Cognitive Impairment (MCI), compared to healthy controls (HC). Resting state networks (RSNs) were studied in 14 AD (70 ± 6 years), 12 MCI (74 ± 6 years), and 16 HC (69 ± 5 years). RSN alterations were present in almost all the 15 recognized RSNs; overall, 474 voxels presented a reduced FC in MCI and 1244 in AD while 1627 voxels showed an increased FC in MCI and 1711 in AD. The RSNs were then ranked according to the magnitude and extension of FC changes (gFC), putting in evidence 6 RSNs with prominent changes: DMN, frontal cortical network (FCN), lateral visual network (LVN), basal ganglia network (BGN), cerebellar network (CBLN), and the anterior insula network (AIN). Nodes, or hubs, showing alterations common to more than one RSN were mostly localized within the prefrontal cortex and the mesial-temporal cortex. The cerebellum showed a unique behavior where voxels of decreased gFC were only found in AD while a significant gFC increase was only found in MCI. The gFC alterations showed strong correlations (p < 0.001) with psychological scores, in particular Mini-Mental State Examination (MMSE) and attention/memory tasks. In conclusion, this analysis revealed that the DMN was affected by remarkable FC increases, that FC alterations extended over several RSNs, that derangement of functional relationships between multiple areas occurred already in the early stages of dementia. These results warrant future work to verify whether these represent compensatory mechanisms that exploit a pre-existing neural reserve through plasticity, which evolve in a state of lack of connectivity between different networks with the worsening of the pathology.
Degeneration of the Injured Cervical Cord Is Associated with Remote Changes in Corticospinal Tract Integrity and Upper Limb Impairment
Patrick Freund, Torben Schneider, Zoltan Nagy, Chloe Hutton, Nikolaus Weiskopf, Karl Friston, Claudia A. Wheeler-Kingshott, Alan J. Thompson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0051729
Abstract: Background Traumatic spinal cord injury (SCI) leads to disruption of axons and macroscopic tissue loss. Using diffusion tensor imaging (DTI), we assessed degeneration of the corticospinal tract (CST) in the cervical cord above a traumatic lesion and explored its relationship with cervical atrophy, remote axonal changes within the cranial CST and upper limb function. Methods Nine cervical injured volunteers with bilateral motor and sensory impairment and ten controls were studied. DTI of the cervical cord and brain provided measurements of fractional anisotropy (FA), while anatomical MRI assessed cross-sectional spinal cord area (i.e. cord atrophy). Spinal and central regions of interest (ROI) included the bilateral CST in the cervical cord and brain. Regression analysis identified correlations between spinal FA and cranial FA in the CST and disability. Results In individuals with SCI, FA was significantly lower in both CSTs throughout the cervical cord and brain when compared with controls (p≤0.05). Reduced FA of the cervical cord in patients with SCI was associated with smaller cord area (p = 0.002) and a lower FA of the cranial CST at the internal capsule level (p = 0.001). Lower FA in the cervical CST also correlated with impaired upper limb function, independent of cord area (p = 0.03). Conclusion Axonal degeneration of the CST in the atrophic cervical cord, proximal to the site of injury, parallels cranial CST degeneration and is associated with disability. This DTI protocol can be used in longitudinal assessment of microstructural changes immediately following injury and may be utilised to predict progression and monitor interventions aimed at promoting spinal cord repair.
MS Cortical Lesions on DIR: Not Quite What They Seem?
Varun Sethi, Nils Muhlert, Maria Ron, Xavier Golay, Claudia A. Wheeler-Kingshott, David H. Miller, Declan T. Chard, Tarek A. Yousry
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078879
Abstract: Objective Accurate identification and localization of cortical gray matter (CGM) lesions in MS is important when determining their clinical relevance. Double inversion recovery (DIR) scans have been widely used to detect MS CGM lesions. Phase sensitive inversion recovery (PSIR) scans have a higher signal to noise, and can therefore be obtained at a higher resolution within clinically acceptable times. This enables detection of more CGM lesions depicting a clearer cortical and juxtacortical anatomy. In this study, we systematically investigated if the use of high resolution PSIR scans changes the classification of CGM lesions, when compared with standard resolution DIR scans. Methods 60 patients [30 RR(Relapsing remitting) and 15 each with PP(Primary progressive) and SP(Secondary progressive) MS] were scanned on a 3T Philips Achieva MRI scanner. Images acquired included DIR (1×1×3 mm resolution) and PSIR (0.5×0.5×2 mm). CGM lesions were detected and classified on DIR as intracortical (IC) or leucocortical (LC). We then examined these lesions on corresponding slices of the high resolution PSIR scans and categorized them as IC, LC, Juxtacortical white matter (JC-WM, abutting but not entering cortex) and other white matter (WM, not juxtacortical). Classifications using both scans were noted. Results 282 IC and 483 LC were identified on DIR. Of the IC lesions, 61% were confirmed as IC on PSIR, 35.5% were reclassified as LC and 3.5% as JC-WM or other WM only. Of the LC DIR lesions, 43.9% were confirmed at LC on PSIR, 16.1% were reclassified as IC and 40% as JC-WM or other WM only. Overall, 50% (381/765) of CGM lesions seen on DIR were reclassified, and 26.5% (203/765) affected WM only. Conclusions When compared with higher resolution PSIR, a significant proportion of lesions classified as involving CGM on DIR appear to either contain more white matter than expected or to not involve CGM at all.
The mesenchymal stem cells in multiple sclerosis (MSCIMS) trial protocol and baseline cohort characteristics: an open-label pre-test: post-test study with blinded outcome assessments
Peter Connick, Madhan Kolappan, Rickie Patani, Michael A Scott, Charles Crawley, Xiao-Ling He, Karen Richardson, Kelly Barber, Daniel J Webber, Claudia AM Wheeler-Kingshott, Daniel J Tozer, Rebecca S Samson, David L Thomas, Ming-Qing Du, Shi L Luan, Andrew W Michell, Daniel R Altmann, Alan J Thompson, David H Miller, Alastair Compston, Siddharthan Chandran
Trials , 2011, DOI: 10.1186/1745-6215-12-62
Abstract: MSCIMS is a phase IIA study of autologous mesenchymal stem cells (MSCs) in secondary progressive MS. A pre-test : post-test design is used with healthy controls providing normative data for inter-session variability. Complementary eligibility criteria and outcomes are used to select participants with disease affecting the anterior visual pathway.Ten participants with MS and eight healthy controls were recruited between October 2008 and March 2009. Mesenchymal stem cells were successfully isolated, expanded and characterised in vitro for all participants in the treatment arm.In addition to determining the safety and feasibility of the intervention and informing design of future studies to address efficacy, MSCIMS adopts a novel strategy for testing neuroprotective agents in MS - the sentinel lesion approach - serving as proof of principle for its future wider applicability.ClinicalTrials.gov (NCT00395200).Multiple sclerosis (MS) is the commonest neurological cause of disability in young adults, affecting over 1.3 million people worldwide. It is a chronic multifocal and multiphasic immune mediated disorder characterised pathologically by inflammatory demyelination, axonal injury and partial remyelination [1]. Although recent evidence suggests that conventional disease modifying approaches can mitigate demyelination and secondary axonal loss resulting from focal inflammation if given during a narrow therapeutic-window in nascent RR-MS,[2,3] there are currently no therapies that slow, stop, or reverse progressive axonal loss in established disease. Mesenchymal stem cells (MSCs) are recognised as a candidate in this respect due to evidence that they promote oligodendrogenesis both in vitro and in vivo,[4,5] result in functional improvement in animal models of MS,[6,7] and confer benefit in non-neurological T-cell driven autoimmune human disease [8].Trial design for the assessment of putative neuroprotective agents in MS presents a range of challenges including the need t
On the possibility of quasi small-world nanomaterials
Novotny, M.A.;Wheeler, Shannon M.;
Brazilian Journal of Physics , 2004, DOI: 10.1590/S0103-97332004000300011
Abstract: the possibility of materials that are governed by a fixed point related to small world networks is discussed. in particular, large-scale monte carlo simulations are performed on ising ferromagnetic models on two different small-world networks generated from a one-dimensional spin chain. one has the small-world bond strengths independent of the length, and exhibits a finite-temperature phase transition. the other has small-world bonds built from atoms, and although there is no finite-temperature phase transition the system shows a slow power-law change of the effective critical temperature of a finite system as a function of the system size. an outline of a possible synthesis route for quasi small-world nanomaterials is presented.
Abdominal Wall Endometriosis as Endometrioma-Cutaneous Fistula: A Case Report  [PDF]
Oluyemisi A. Adeyemi, Creighton L. Edwards, Thomas M. Wheeler, Shannon M. Hawkins
Open Journal of Obstetrics and Gynecology (OJOG) , 2014, DOI: 10.4236/ojog.2014.414116
Abstract: Endometriosis outside the pelvic cavity is rare, but its most common extra-pelvic location is the abdominal wall, occurring most frequently after cesarean delivery. Fistula tracks through these lesions in the abdominal wall to the uterus are rare. However, a fistula between abdominal wall endometriosis to an endometrioma has not been reported. A 46-year-old multigravid woman presented with complaint of cyclical pain and bleeding from her cesarean delivery scar and pelvic pressure. Computed tomography revealed a complex, 16-cm left adnexal mass. Intraoperatively, a fistulous tract connecting a large endometrioma in the abdominal-pelvic cavity to the skin was noted and wide local excision of this track was performed in conjunction with aggressive surgical management of endometriosis throughout the pelvis. Pathologic analysis of the resected specimen confirmed the diagnosis. Although rare, endometrioma-cutaneous fistula should be included in the differential diagnosis of suspected abdominal wall endometriosis with concurrent adnexal mass for appropriate surgical planning.
On the Possibility of Quasi Small-World Nanomaterials
M. A. Novotny,Shannon M. Wheeler
Physics , 2003, DOI: 10.1103/PhysRevE.69.056110
Abstract: The possibility of materials that are governed by a fixed point related to small world networks is discussed. In particular, large-scale Monte Carlo simulations are performed on Ising ferromagnetic models on two different small-world networks generated from a one-dimensional spin chain. One has the small-world bond strengths independent of the length, and exhibits a finite-temperature phase transition. The other has small-world bonds built from atoms, and although there is no finite-temperature phase transition the system shows a slow power-law change of the effective critical temperature of a finite system as a function of the system size. An outline of a possible synthesis route for quasi small-world nanomaterials is presented.
MCAMC: An Advanced Algorithm for Kinetic Monte Carlo Simulations: from Magnetization Switching to Protein Folding
M. A. Novotny,Shannon M. Wheeler
Physics , 2002,
Abstract: We present the Monte Carlo with Absorbing Markov Chains (MCAMC) method for extremely long kinetic Monte Carlo simulations. The MCAMC algorithm does not modify the system dynamics. It is extremely useful for models with discrete state spaces when low-temperature simulations are desired. To illustrate the strengths and limitations of this algorithm we introduce a simple model involving random walkers on an energy landscape. This simple model has some of the characteristics of protein folding and could also be experimentally realizable in domain motion in nanoscale magnets. We find that even the simplest MCAMC algorithm can speed up calculations by many orders of magnitude. More complicated MCAMC simulations can gain further increases in speed by orders of magnitude.
Deposition nucleation on mineral dust particles: a case against classical nucleation theory with the assumption of a single contact angle
M. J. Wheeler ,A. K. Bertram
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: Deposition nucleation on two mineral species, kaolinite and illite, was studied using a flow cell coupled to an optical microscope. The results show that the Sice conditions when ice first nucleated, defined as the onset Sice (Sice,onset), is a strong function of the surface area available for nucleation, varying from 100% to 125% at temperatures between 242 and 239 K. The surface area dependent data could not be described accurately using classical nucleation theory and the assumption of a single contact angle (defined here as the single-α model). These results suggest that caution should be applied when using contact angles determined from Sice,onset data and the single-α model. In contrast to the single-α model, the active site model, the deterministic model, and a model with a distribution of contact angles fit the data within experimental uncertainties. Parameters from the fits to the data are presented.
Deposition nucleation on mineral dust particles: a case against classical nucleation theory with the assumption of a single contact angle
M. J. Wheeler,A. K. Bertram
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012, DOI: 10.5194/acp-12-1189-2012
Abstract: Deposition nucleation on two mineral species, kaolinite and illite, was studied using a flow cell coupled to an optical microscope. The results show that the Sice conditions when ice first nucleated, defined as the onset Sice (Sice,onset), is a strong function of the surface area available for nucleation, varying from 100% to 125% at temperatures between 242 and 239 K. The surface area dependent data could not be described accurately using classical nucleation theory and the assumption of a single contact angle (defined here as the single-α model). These results suggest that caution should be applied when using contact angles determined from Sice,onset data and the single-α model. In contrast to the single-α model, the active site model, the deterministic model, and a model with a distribution of contact angles fit the data within experimental uncertainties. Parameters from the fits to the data are presented.
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