Evidence Of Structural Reorganization Research Articles

Brain Plasticity in Charcot-Marie-Tooth Type 1A Patients? A Combined Structural and Diffusion MRI Study.

Central nervous system involvement has been described in peripheral neuropathies, including different forms of Charcot-Marie-Tooth (CMT) disease. The aim of our study was to systematically investigate possible brain structural modifications in CMT1A patients, using volumetric MRI, and diffusion tensor imaging (DTI). In this prospective cross-sectional study, from May 2017 to May 2019, we acquired 3T MRI brain scans of genetically confirmed CMT1A patients and age- and sex-comparable healthy controls. Patients also underwent clinical and electrophysiological examinations assessing motor and sensory domains. Voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS) analyses were performed using a non-parametric approach based on permutations, including age and sex (and total intracranial volume for VBM) as nuisance covariates. When between-group differences emerged at VBM or TBSS analyses, the first eigenvariate was extracted from the cluster and its age- and sex-adjusted standardized residuals tested for correlation with clinical and electrophysiological variables. Twenty CMT1A patients (34.5 ± 11.1 years; M/F:11/9) were enrolled, along with 20 healthy controls (30.1 ± 10.2 years; M/F:11/9). The VBM analysis revealed clusters of significantly increased GM volume in CMT1A patients compared to healthy controls, encompassing the bilateral cerebellar lobules III-VI and the left hippocampus (all ps = 0.04), with no differences in terms of DTI metrics at the TBSS analysis. A negative correlation (r = −0.502, p = 0.03) emerged between ulnar compound motor action potential and the z-scores corresponding to the right cerebellar cluster of augmented GM volume. Our data show evidence of structural reorganization in the brain of CMT1A patients, possibly reflecting neural plasticity mechanisms in response to peripheral nerve pathology and modulating the effect of axonal degeneration on functional impairment.

129 Chronic Pain and Advanced MRI Techniques

Abstract INTRODUCTION Chronic Pain is a difficult entity to define and treat. The usual definition is that of pain that persists beyond expected healing period of 3–6 months. The pathophysiology, in particular changing neural connections, are still not widely agreed on. In recent years neuroimaging has shown evidence of structural reorganization and change. These new developments can further improve understanding of the brains plasticity and potentially new strategies to either help identify those experiencing acute pain at risk of transition to chronic pain, but also as a potential target for therapy. METHODS The study population of 67 patients includes: a group of 26 selected from a pain management service and a group of 41 normal controls. The participants were matched on age, gender and ethnicity. Each patient has undergone structural and diffusion-weighted MRI scans. Voxel based morphometry was used to investigate differences in grey matter volumes between the groups, as well as to investigate correlations with neurocognitive outcomes. Cortical thickness was also calculated. Tract-based spatial statistics (TBSS) were used to investigate differences and correlation with neurocognitive outcomes between diffusion metrics (fractional anisotropy, mean diffusivity). RESULTS >The chronic pain group showed smaller cerebellar grey matter volume relative to healthy controls. There was no difference in cortical thickness observed. Furthermore, those experiencing chronic pain exhibited significantly decreased FA and increased MD in multiple white matter tracts, relative to controls. CONCLUSION These findings suggest that cerebellar atrophy maybe involved in chronic pain.

Evidence of structural reorganization during aggregation of silica nanoparticles

Silica nanoparticles have been produced by neutralization of sodium silicate. The obtained suspension was unstable because of the high value of the ionic strength of the medium. Aggregation of the particles has been monitored thanks to a combination of in situ turbidity and dynamic light scattering (DLS) measurements. An optical model has been developed to extract both fractal dimension Df and primary particle radius rpp of the formed aggregates from these data. The obtained results clearly indicate a densification of the clusters as aggregation proceeds. A correlation between our experimental turbidity values and hydrodynamic radii was found. Comparison with calculated dimensionless numbers showed that a constant Df could not explain the observed trend. A fractal dimension dependent on the number of particles inside the aggregate Npp is thus suggested.

Ultrastructural evidence for the presence of "fibroclasts" and "myofibroclasts" in wound healing tissues.

We have observed, by light and electron microscopy, fibroblast-like cells which appear to be involved in collagen fiber and filament degradation. These cells are most prominent in the dermis of mature hypertrophic scars which were clinically observed to be in the remodeling phase of wound repair. Total incorporation of collagen filaments within cellular vacuoles, as seen by TEM, appears to precede the enzymatic degradation of the collagen. Cytoplasmic contractile bundles and/or collagen filament remnants found within residual lysosomes were also seen in many of these cells. Evidence of structural reorganization within the tissue was observed by means of SEM. These cells appear to be similar to osteoclasts in function: thus we propose to name them "fibroclasts" and "myofibroclasts."

Structural changes in glassy polymers

AbstractIt has previously been shown that glassy poly(ethylene terephthalate) gives rise to endothermal peaks in DTA when annealed at temperatures near to the glass temperature. The present work describes results obtained from DTA and DSC on annealing a number of glassy polymers which have been rapidly cooled from above the glass temperature and on slowly cooled samples of the same polymers. The polymers which have been studied are: poly(ethylene terephthalate), poly(methyl methacrylate), atactic and isotactic polystyrene, bisphenol‐A polycarbonate, poly(ethyl methacrylate) and poly(vinyl acetate). In every case, evidence of structural reorganization is observed, and the rate at which this takes place is reported. Separate studies on poly(ethylene terephthalate) reflect density changes which also take place upon annealing. These results are discussed in the context of the calorimetric observations.