Des syncinésies aux mécanismes d'inhibition motrice chez l'enfant

Certaines manifestations motrices involontaires représentent une caractéristique développementale ou pathologique connue sous le terme de syncinésie. Cet article traite de la question des syncinésies en trois temps. Une première partie fait un point sur la diversité de leurs manifestations selon les populations et dresse un bilan sur les multiples épreuves psychomotrices qui mesurent leurs intensités et leurs évolutions dans le temps. Une seconde partie s'intéresse à une catégorie de ces syncinésies, les syncinésies d'imitation, et fait la description dedeux modèles d'organisation neuro-motrices qui pourraient expliquer leur survenue. Enfin dans un troisième temps, nous montrons que les déterminants neurobiologiques du couplage neuro-moteur à l'origine des syncinésies d'imitation sont également une source d'intérêt pour les travaux de recherche qui s'intéressent à l'évolution avec l'âge des coordinations bimanuelles et plus particulièrement au développement des mécanismes d'inhibition motrice. Nous faisons l'hypothèse de mécanismes de contrôle en commun (et probablement de nature inhibitrice) qui, d'une part, participent à la diminution des syncinésies d'imitation et d'autre part favorisent la production des performances bimanuelles plus complexes chez l'enfant. Une approche interdisciplinaire intégrant des mesures classiques des manifestations syncinétiques et l'analyse de l'inhibition motrice inter-hémisphérique pourrait, dans une perspective développementale, permettre de mettre en évidence les liens entre ces deux phénomènes fondamentaux de la motricité humaine.

Advanced MRI unravels the nature of tissue alterations in early multiple sclerosis.

INTRODUCTION: In patients with multiple sclerosis (MS), conventional magnetic resonance imaging (MRI) provides only limited insights into the nature of brain damage with modest clinic-radiological correlation. In this study, we applied recent advances in MRI techniques to study brain microstructural alterations in early relapsing-remitting MS (RRMS) patients with minor deficits. Further, we investigated the potential use of advanced MRI to predict functional performances in these patients. METHODS: Brain relaxometry (T1, T2, T2*) and magnetization transfer MRI were performed at 3T in 36 RRMS patients and 18 healthy controls (HC). Multicontrast analysis was used to assess for microstructural alterations in normal-appearing (NA) tissue and lesions. A generalized linear model was computed to predict clinical performance in patients using multicontrast MRI data, conventional MRI measures as well as demographic and behavioral data as covariates. RESULTS: Quantitative T2 and T2* relaxometry were significantly increased in temporal normal-appearing white matter (NAWM) of patients compared to HC, indicating subtle microedema (P = 0.03 and 0.004). Furthermore, significant T1 and magnetization transfer ratio (MTR) variations in lesions (mean T1 z-score: 4.42 and mean MTR z-score: -4.09) suggested substantial tissue loss. Combinations of multicontrast and conventional MRI data significantly predicted cognitive fatigue (P = 0.01, Adj-R (2) = 0.4), attention (P = 0.0005, Adj-R (2) = 0.6), and disability (P = 0.03, Adj-R (2) = 0.4). CONCLUSION: Advanced MRI techniques at 3T, unraveled the nature of brain tissue damage in early MS and substantially improved clinical-radiological correlations in patients with minor deficits, as compared to conventional measures of disease.

Nature conservation efforts by forest owners : intentions and practice in a Swedish case study

Abstract

Chemical nature of soil humified fractions and their bioactivity

The aim of this work was to evaluate the humus composition from an Ultisol from Campos dos Goytacazes, RJ, Brazil. Soil samples of four depths (0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m) and its chemical nature were analysed by elemental composition, E4/E6 ratios and Fourier transformed infrared spectroscopy. The bioactivity of these humified substances was evaluated through their action on maize root growth and H+-ATPase activity of roots microsomes. In topsoil, the content of high condensed alkaline soluble humic substances is greater than that found in the subsuperficial layers. The chemical nature of humic and fulvic acids also varied with the soil depth. The humic acids isolated from the soil samples exhibited higher bioactivity compared with the fulvic acids. Moreover, the results suggest that more condensed humic substances can promote highest stimulation of the microsomal H+-ATPases from maize roots. These data reinforce the concept that the activity of the H+ pumps can be used as a biochemical marker for evaluation of humic substances bioactivity.

Learning form Nature to improve the heat generation of iron-oxide nanoparticles for magnetic hyperthermia applications.

The performance of magnetic nanoparticles is intimately entwined with their structure, mean size and magnetic anisotropy. Besides, ensembles offer a unique way of engineering the magnetic response by modifying the strength of the dipolar interactions between particles. Here we report on an experimental and theoretical analysis of magnetic hyperthermia, a rapidly developing technique in medical research and oncology. Experimentally, we demonstrate that single-domain cubic iron oxide particles resembling bacterial magnetosomes have superior magnetic heating efficiency compared to spherical particles of similar sizes. Monte Carlo simulations at the atomic level corroborate the larger anisotropy of the cubic particles in comparison with the spherical ones, thus evidencing the beneficial role of surface anisotropy in the improved heating power. Moreover we establish a quantitative link between the particle assembling, the interactions and the heating properties. This knowledge opens new perspectives for improved hyperthermia, an alternative to conventional cancer therapies.