Effects of acute and sub-chronic glucocorticoid treatments on hippocampal neurons of wild type and dystrophin-deficient DMDmdx mice: an in vitro and in vivo study

Duchenne muscular dystrophy (DMD) is a lethal X-linked disease characterized by progressive muscular wasting due to lack of full-length dystrophin (Dp427), a cytoskeletal protein expressed in muscle and selected brain regions (i.e. hippocampus). Dp427 binds to a large multi-proteic complex (Dystrophin Glycoprotein Complex, DGC), endowed with structural and functional properties, as the modulation of several intracellular signaling pathways. The presence of the dystrophin-DGC in areas involved in cognitive functions suggests that lack of Dp427 may be responsible for the neurological disturbances described in DMD patients. These could be further aggravated by the glucocorticoid (GC) therapeutic treatments of the muscular inflammation in DMD patients. As the hippocampus is one major GC target, in this study I analyzed whether in vitro (acute) and in vivo (acute and sub-chronic) treatments with either corticosterone (CORT) or dexamethasone (DEX) affected the already compromised hippocampal neuron physiology. Under any conditions we analyzed several parameters of the neuronal response to GCs: a) protein levels of the glucocorticoid receptor (GR) and of its phosphorylated (active) form pGR; b) mRNA levels of GR and GILZ; c) changes in the intensity of GR and pGR immunohistochemistry; d) protein levels of GR intracellular signaling effectors (i.e. caveolin 1, ERK 1/2); e) proliferation of hippocampal neural progenitor cells (NPC) (in vivo sub-chronic treatment only). In both in vitro and in vivo studies, mdx mouse hippocampal neurons respond differently than wild type to GC treatments. The general picture emerging is that they could be more sensitive to GCs and, therefore, more predisposed to be damaged. In fact, even acute GC administrations elicit a response similar to the more damaging chronic administration: i.e. reduction in GR levels, increase in the ration pGR/GR, possible reduction in GR gene expression, all aspects that are connotative of a chronic stress response. During high level of stress, which correspond to high and prolonged levels of secreted GCs, several physiological responses are altered, including those typical of hippocampal activity: i.e. synaptic plasticity, cognitive functions. These are accompanied by a reversal of the GC effects on hippocampal neurons: from the promotion of neuronal activity, and hence of its inhibitory control over the HPA axis, to its reduction, with consequent depression of HPA axis activity and increase in GC secretion. These are the basis for psychopathologies, as post-traumatic disorders. Therefore, the already compromised activity of the hippocampus in dystrophic subjects could be further damaged even by mild doses of GC, amplifying the risks for serious neural hilliness. Another crushing data is that sub-chronic treatments with DEX induce an increase in the proliferation of NPC in adult hippocampus, in contrast to what occurs in the wild type. This de-regulation of precursor cell cycle, responsible for of glia and neuronal self-renewal in adult brains, could further compromised hippocampal physiology. In conclusion, in the hope that new therapies could extend the life span of the young DMD patients, it is important to go deeper in the comprehension of how hippocampus and other brain areas affected by DMD, respond to anti-inflammatory (GCs) treatments

A micro-mechanical model of the elastic properties of a short fibre reinforced polyamide

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Evaluation of fibre lenght distribution in a short glass fibre reinforced PA-6

The aim of this work is to evaluate the fibre length distribution in a polyamide reinforced by short glass fibre. The fibre length and the fibre orientation distributions strongly influence the mechanical properties of short fibre reinforced composites. The sample investigated is a 30GFPA6 (polyamide-6 reinforced by 30 % by weight glass fibre), extracted from an injection-moulded plate. The digital reconstruction of the three-dimensional structure of the sample was obtained by synchrotron radiation micro-computed tomography (micro-CT), a high spatial resolution non-destructive technique. One global and one local method have been tested for the automatic evaluation of the fibre length distribution in our sample. The global method is based on the mean fibre length distribution computed from the Star Length Distribution (SLD), a morphological parameter. The local method is based on a 3D skeletonize function. The results are discussed in the light of the experimental data available in literature

Threshold Identification for Micro-Tomographic Damage Characterisation in a Short-Fibre-Reinforced Polymer

The micro-tomographic technique represents an important tool for the analysis of the internal structure in short-fibre-reinforced polymers samples. For the investigation of damage mechanisms, detection of the micro-voids within the matrix can be facilitated by applying a tensile load in-situ during the scan. The investigations here described started from two micro-CT acquisitions, at different strain levels, of the same PA6.6GF10 sample. An original procedure for micro-voids identification is proposed, based on the statistical elaboration of the matrix grey-tone range. In order to validate the suggested procedure beyond visual inspection, an independent method based on an optimisation approach, which puts to use the two available micro-tomographic sets, was developed and applied. The effect of the tensile load, which can induce a progression of the damage within the specimen, was investigated, and the relations among strain, fibre distribution and micro-voids volumetric fraction were studied. Our findings point out that the mechanisms of damage progression, even under static loading as in this case, appear to be more complex than those related to the fibre-density-induced stress concentrations alone and require further investigation

ELASTICITY of SHORT FIBRE REINFORCED POLYAMIDE: MORPHOLOGICAL AND NUMERICAl ANALYSIS OF FIBRE ORIENTATION EFFECTS

The fatigue behaviour of injection moulded short fibre reinforced polymers depends upon fibre orientation, as shown in experiments conducted with notched specimens injected through different injection gates. The different fatigue behaviour is mainly related to the different local elastic properties, as determined by the different fibre orientation patterns, resulting into different strain distributions. In order to quantify the relationship between fibre orientation and elastic constants, the Cell Method was applied to volumes extracted from the specimens, reconstructed by micro-tomography

PRELIMINARY DESIGN OF AN X-RAY IMAGING SYSTEM FOR THE BONE STRUCTURAL INDEX EVALUATION

Osteoporosis (OP) is a very common disease in which the bones become weak and are more likely to break. Despite the huge costs in the EU and worldwide, the majority of individuals who have sustained an osteoporosis-related fracture or who are at high risk of fracture are left untreated. In effect, OP is a silent disease, with bones deteriorating without warning until fracture, and the current screening modalities are not significantly better than age alone, also because they consider only the bone quantity (bone mineral density, BMD) and the clinical risk factors, but disregard the bone quality, that is the structural soundness of the trabecular arrangement, which can be evaluated by simulations on virtual models. While 3D models can only be used in research because of high costs, an alternative approach based on the acquisition of planar hand radiograms for bone behaviour simulations, and the use of a Structural Index, SI, for bone quality ranking, have been developed at the University of Trieste. In this work, we discuss the preliminary design of a portable low dose X-ray hand scanner to be used as a low cost, user-friendly device (Fig.1) for imaging the trabecular pattern in the proximal phalanges of the non-dominant hand and for providing a radiogram suitable for the SI evaluation

PRELIMINARY DESIGN OF AN X-RAY IMAGING SYSTEM FOR THE BONE STRUCTURAL INDEX EVALUATION

Osteoporosis (OP) is a very common disease in which the bones become weak and are more likely to break. Despite the huge costs in the EU and worldwide, the majority of individuals who have sustained an osteoporosis-related fracture or who are at high risk of fracture are left untreated. In effect, OP is a silent disease, with bones deteriorating without warning until fracture, and the current screening modalities are not significantly better than age alone, also because they consider only the bone quantity (bone mineral density, BMD) and the clinical risk factors, but disregard the bone quality, that is the structural soundness of the trabecular arrangement, which can be evaluated by simulations on virtual models. While 3D models can only be used in research because of high costs, an alternative approach based on the acquisition of planar hand radiograms for bone behaviour simulations, and the use of a Structural Index, SI, for bone quality ranking, have been developed at the University of Trieste. In this work, we discuss the preliminary design of a portable low dose X-ray hand scanner to be used as a low cost, user-friendly device (Fig.1) for imaging the trabecular pattern in the proximal phalanges of the non-dominant hand and for providing a radiogram suitable for the SI evaluation

ANALOGIE TRA I TENSORI UTILIZZATI PER DESCRIVERE L\u2019ORIENTAZIONE DELLE FIBRE NEI COMPOSITI

Nei polimeri rinforzati con fibre corte, le condizioni dinamiche del flusso che riempie lo stampo determinano la disposizione delle fibre di rinforzo e di conseguenza la capacit\ue0 del componente di resistere ai carichi applicati. I software che simulano il processo descrivono la configurazione delle fibre mediante il tensore di Advani-Tucker, del secondo ordine, i cui autovettori indicano le direzioni principali delle fibre e gli autovalori rappresentano la frazione di fibre nella direzione corrispondente. Per una verifica sperimentale, \ue8 necessario confrontare queste previsioni con le misure ottenute in una sezione opportunamente preparata o in una porzione ricostruita mediante micro-tomografia. La descrizione tensoriale basata sul concetto di Mean Intercept Length risulta essere in questo caso particolarmente semplice e veloce. In questo lavoro viene mostrato che \ue8 possibile confrontare i risultati ottenuti con i due approcci e che due tensori individuano le medesime direzioni principali delle fibre

A 3-year follow-up study on bone structure elastic quality

Osteoporosis is called a silent disease because bone fragility manifests itself to the patient only in an advanced state, through fracture and pain. Medical and industry leaders recognize that the current golden standard diagnostic method, densitometry, or Dual Energy X-ray Absorptiometry (DEXA), may not always be sufficient to assess the patient’s real risk of fragility fracture [1]. Indeed, pathological alterations affect not only the mineral content (quantity) of the bone, but also its “quality”, which can be measured from the elastic properties of the bone internal trabecular structure by means of the Bone Elastic Structure Test, BES TEST®. In this study, the incidence of fragility fractures was assessed after a 3-year follow-up period in the women enrolled for a population study in 2015. The BES TEST® resulted an effective estimator of bone health, and can improve the assessment of the patient’s fracture risk map