Hyperactivations frontales en mémoire de travail dans le trouble cognitif léger

Des études récentes ont rapporté que les individus âgés avec un trouble cognitif léger (TCL) ont de plus grandes activations en lien avec la réalisation d’une tâche cognitive que des personnes âgées saines. Des auteurs ont proposé que ces hyperactivations pourraient refléter des processus de plasticité cérébrale compensatoires ayant lieu pendant la phase précoce de la maladie d’Alzheimer. Des processus de compensations fonctionnelles pourraient émerger en réponse à une perte d’intégrité structurelle dans les régions du cerveau normalement requises pour compléter une tâche. Dans ce mémoire, j’ai évalué cette hypothèse chez des personnes avec TCL en faisant appel à une tâche de mémoire de travail comportant plusieurs niveaux de difficulté ainsi qu’aux techniques d’imagerie par résonnance magnétique (IRM) structurelle et fonctionnelle. Des analyses de régression multiples ont été utilisées afin d’identifier les régions cérébrales dont l’activité variait en fonction de l’intégrité neuronale telle que définie par le volume de l’hippocampe. Les valeurs estimées des paramètres du signal de ces régions furent ensuite extraites afin de procéder à des analyses corrélationnelles sur la performance ainsi que sur le volume de différentes structures cérébrales. Les résultats indiquent des hyperactivations dans les régions frontales droites chez les participants TCL souffrant d’une plus grande atteinte neuronale. De plus, le niveau d’activation est négativement corrélé au volume de structures frontales et pariétales. Ces résultats indique la présence d’une hyperactivation compensatoire dans la phase du TCL associée à la réalisation d’une tâche de mémoire de travail.

Hyperactivations frontales en mémoire de travail dans le trouble cognitif léger

Des études récentes ont rapporté que les individus âgés avec un trouble cognitif léger (TCL) ont de plus grandes activations en lien avec la réalisation d’une tâche cognitive que des personnes âgées saines. Des auteurs ont proposé que ces hyperactivations pourraient refléter des processus de plasticité cérébrale compensatoires ayant lieu pendant la phase précoce de la maladie d’Alzheimer. Des processus de compensations fonctionnelles pourraient émerger en réponse à une perte d’intégrité structurelle dans les régions du cerveau normalement requises pour compléter une tâche. Dans ce mémoire, j’ai évalué cette hypothèse chez des personnes avec TCL en faisant appel à une tâche de mémoire de travail comportant plusieurs niveaux de difficulté ainsi qu’aux techniques d’imagerie par résonnance magnétique (IRM) structurelle et fonctionnelle. Des analyses de régression multiples ont été utilisées afin d’identifier les régions cérébrales dont l’activité variait en fonction de l’intégrité neuronale telle que définie par le volume de l’hippocampe. Les valeurs estimées des paramètres du signal de ces régions furent ensuite extraites afin de procéder à des analyses corrélationnelles sur la performance ainsi que sur le volume de différentes structures cérébrales. Les résultats indiquent des hyperactivations dans les régions frontales droites chez les participants TCL souffrant d’une plus grande atteinte neuronale. De plus, le niveau d’activation est négativement corrélé au volume de structures frontales et pariétales. Ces résultats indique la présence d’une hyperactivation compensatoire dans la phase du TCL associée à la réalisation d’une tâche de mémoire de travail.

Multimodal Mri-based Study In Patients With Spg4 Mutations.

Mutations in the SPG4 gene (SPG4-HSP) are the most frequent cause of hereditary spastic paraplegia, but the extent of the neurodegeneration related to the disease is not yet known. Therefore, our objective is to identify regions of the central nervous system damaged in patients with SPG4-HSP using a multi-modal neuroimaging approach. In addition, we aimed to identify possible clinical correlates of such damage. Eleven patients (mean age 46.0 ± 15.0 years, 8 men) with molecular confirmation of hereditary spastic paraplegia, and 23 matched healthy controls (mean age 51.4 ± 14.1years, 17 men) underwent MRI scans in a 3T scanner. We used 3D T1 images to perform volumetric measurements of the brain and spinal cord. We then performed tract-based spatial statistics and tractography analyses of diffusion tensor images to assess microstructural integrity of white matter tracts. Disease severity was quantified with the Spastic Paraplegia Rating Scale. Correlations were then carried out between MRI metrics and clinical data. Volumetric analyses did not identify macroscopic abnormalities in the brain of hereditary spastic paraplegia patients. In contrast, we found extensive fractional anisotropy reduction in the corticospinal tracts, cingulate gyri and splenium of the corpus callosum. Spinal cord morphometry identified atrophy without flattening in the group of patients with hereditary spastic paraplegia. Fractional anisotropy of the corpus callosum and pyramidal tracts did correlate with disease severity. Hereditary spastic paraplegia is characterized by relative sparing of the cortical mantle and remarkable damage to the distal portions of the corticospinal tracts, extending into the spinal cord.

Baseline Results of an Acute Ischemic Stroke Registry Including Acute Multimodal Imaging (ASTRAL)

Background: The DEFUSE (n_74) and EPITHET (n_101) studies have in common that a baseline MRI was obtained prior to treatment (tPA in DEFUSE; tPA or placebo in EPITHET) in the 3-6 hour time-window. There were however important methodological differences between the studies. A standardized reanalysis of pooled data was undertaken to determine the effect of these differences on baseline characteristics and study outcomes. Methods: To standardize the studies 1) the DWI and PWI source images were reprocessed and segmented using automated image processing software (RAPID); 2) patients were categorized according to their baseline MRI profile as either Target Mismatch (PWITmax_6/DWI ratio_ 1.8 and an absolute mismatch _15mL), Malignant (DWI or PWITmax_10 lesion _ 100 mL), or No Mismatch. 3) favorable clinical response was defined as NIHSS score of 0-1 or a _8 points improvement on the NIHSSS at day 90. Results: Prior to standardization there was no difference in the proportion of Target Mismatch patients between EPITHET and DEFUSE (54% vs 49%, p_0.6), but the EPITHET study had more patients with the Malignant profile than DEFUSE (35% vs 9%, p_0.01) and fewer patients that had No Mismatch (11% vs 42%, p_0.01). These differences in baseline MRI profiles between EPITHET and DEFUSE were largely eliminated by standardized processing of PWI and DWI images with RAPID software (Target Mismatch 49% vs 48%; Malignant 15% vs 8%; No Mismatch 36% vs 25%; p_NS for all comparisons) Reperfusion was strongly associated with a favorable clinical response in mismatch patients (figure). This relationship was not affected by the standardization procedures (pooled odds ratio of 8.8 based on original data and 6.6 based on standardized data). Conclusion: Standardization of image analyses procedures in acute stroke is important as non-standardized techniques introduce significant variability in DWI and PWI imaging characteristics. Despite methodological differences, the DEFUSE and EPITHET studies show a consistent and robust association between reperfusion and favorable clinical response in Target Mismatch patients regardless of standardization. These data support an RCT of iv tPA in the 3-6 hour time-window for Target Mismatch patients identified using RAPID.

Peripheral Nerve Repair: Multimodal Comparison of the Long-Term Regenerative Potential of Adipose Tissue-Derived Cells in a Biodegradable Conduit.

Tissue engineering is a popular topic in peripheral nerve repair. Combining a nerve conduit with supporting adipose-derived cells could offer an opportunity to prevent time-consuming Schwann cell culture or the use of an autograft with its donor site morbidity and eventually improve clinical outcome. The aim of this study was to provide a broad overview over promising transplantable cells under equal experimental conditions over a long-term period. A 10-mm gap in the sciatic nerve of female Sprague-Dawley rats (7 groups of 7 animals, 8 weeks old) was bridged through a biodegradable fibrin conduit filled with rat adipose-derived stem cells (rASCs), differentiated rASCs (drASCs), human (h)ASCs from the superficial and deep abdominal layer, human stromal vascular fraction (SVF), or rat Schwann cells, respectively. As a control, we resutured a nerve segment as an autograft. Long-term evaluation was carried out after 12 weeks comprising walking track, morphometric, and MRI analyses. The sciatic functional index was calculated. Cross sections of the nerve, proximal, distal, and in between the two sutures, were analyzed for re-/myelination and axon count. Gastrocnemius muscle weights were compared. MRI proved biodegradation of the conduit. Differentiated rat ASCs performed significantly better than undifferentiated rASCs with less muscle atrophy and superior functional results. Superficial hASCs supported regeneration better than deep hASCs, in line with published in vitro data. The best regeneration potential was achieved by the drASC group when compared with other adipose tissue-derived cells. Considering the ease of procedure from harvesting to transplanting, we conclude that comparison of promising cells for nerve regeneration revealed that particularly differentiated ASCs could be a clinically translatable route toward new methods to enhance peripheral nerve repair.

Desenvolvimento de modelo matemático de otimização logística para o transporte multimodal de safras agrícolas pelo corredor centro-oeste

Este artigo apresenta um modelo matemático de otimização logística para o transporte multimodal de safras agrícolas pelo corredor Centro-Oeste. Tal ferramenta foi desenvolvida no contexto de três amplos projetos de pesquisa financiados pela FINEP e executados por um grupo de universidades. O modelo, conhecido genericamente como Modelo de fluxo de Custo Mínimo Multiproduto, considera a otimização de fluxos em rede, para os produtos açúcar, álcool, milho, soja, óleo de soja, farelo de soja e trigo. O modelo proposto para estimativa dos fluxos inter-regionais mostrou-se uma ferramenta factível para fins de avaliação do potencial de utilização da multimodalidade. A análise destes resultados gera importantes subsídios para a seleção dos locais com potencial para instalação de mecanismos e equipamentos de transferência de cargas, além de auxiliar no dimensionamento dessas infraestruturas. Também é um resultado importante do ferramental desenvolvido a identificação das zonas de cargas que apresentam potencial captável pelas ferrovias, hidrovias e dutovias, ou seja, possibilita a identificação das regiões que revelam potencial para uso da multimodalidade.

The importance of promoting multimodal teaching in the foreign language classroom for the acquisition of social competences: practical examples

This article analyses the way in which the subject English Language V of the degree English Studies (English Language and Literature) combines the development of the five skills (listening, speaking, reading, writing and interacting) with the use of multimodal activities and resources in the teaching-learning process so that students increase their motivation and acquire different social competences that will be useful for the labour market such as communication, cooperation, leadership or conflict management. This study highlights the use of multimodal materials (texts, videos, etc.) on social topics to introduce cultural aspects in a language subject and to deepen into the different social competences university students can acquire when they work with them. The study was guided by the following research questions: how can multimodal texts and resources contribute to the development of the five skills in a foreign language classroom? What are the main social competences that students acquire when the teaching-learning process is multimodal? The results of a survey prepared at the end of the academic year 2015-2016 point out the main competences that university students develop thanks to multimodal teaching. For its framework of analysis, the study draws on the main principles of visual grammar (Kress & van Leeuwen, 2006) where students learn how to analyse the main aspects in multimodal texts. The analysis of the different multimodal activities described in the article and the survey reveal that multimodality is useful for developing critical thinking, for bringing cultural aspects into the classroom and for working on social competences. This article will explain the successes and challenges of using multimodal texts with social content so that students can acquire social competences while learning content. Moreover, the implications of using multimodal resources in a language classroom to develop multiliteracies will be observed.

Photoelastic And Finite Element Analyses Of Occlusal Loads In Mandibular Body.

This study proposed to evaluate the mandibular biomechanics in the posterior dentition based on experimental and computational analyses. The analyses were performed on a model of human mandible, which was modeled by epoxy resin for photoelastic analysis and by computer-aided design for finite element analysis. To standardize the evaluation, specific areas were determined at the lateral surface of mandibular body. The photoelastic analysis was configured through a vertical load on the first upper molar and fixed support at the ramus of mandible. The same configuration was used in the computer simulation. Force magnitudes of 50, 100, 150, and 200 N were applied to evaluate the bone stress. The stress results presented similar distribution in both analyses, with the more intense stress being at retromolar area and oblique line and alveolar process at molar level. This study presented the similarity of results in the experimental and computational analyses and, thus, showed the high importance of morphology biomechanical characterization at posterior dentition.

Chemical And Structural Analyses Of Titanium Plates Retrieved From Patients.

The aim of this study was to evaluate the microscopic structure and chemical composition of titanium bone plates and screws retrieved from patients with a clinical indication and to relate the results to the clinical conditions associated with the removal of these devices. Osteosynthesis plates and screws retrieved from 30 patients between January 2010 and September 2013 were studied by metallographic, gas, and energy dispersive X-ray (EDX) analyses and the medical records of these patients were reviewed. Forty-eight plates and 238 screws were retrieved. The time elapsed between plate and screw insertion and removal ranged between 11 days and 10 years. Metallographic analysis revealed that all the plates were manufactured from commercially pure titanium (CP-Ti). The screw samples analyzed consisted of Ti-6Al-4V alloy, except four samples, which consisted of CP-Ti. Titanium plates studied by EDX analysis presented greater than 99.7% titanium by mass. On gas analysis of Ti-6Al-4V screws, three samples were outside the standard values. One CP-Ti screw sample and one plate sample also presented an oxygen analysis value above the standard. The results indicated that the physical properties and chemical compositions of the plates and screws did not correspond with the need to remove these devices or the time of retention.

Comparative Study Of Transgenic And Non-transgenic Maize (zea Mays) Flours Commercialized In Brazil, Focussing On Proteomic Analyses.

Genetically modified foods are a major concern around the world due to the lack of information concerning their safety and health effects. This work evaluates differences, at the proteomic level, between two types of crop samples: transgenic (MON810 event with the Cry1Ab gene, which confers resistance to insects) and non-transgenic maize flour commercialized in Brazil. The 2-D DIGE technique revealed 99 differentially expressed spots, which were collected in 2-D PAGE gels and identified via mass spectrometry (nESI-QTOF MS/MS). The abundance of protein differences between the transgenic and non-transgenic samples could arise from genetic modification or as a result of an environmental influence pertaining to the commercial sample. The major functional category of proteins identified was related to disease/defense and, although differences were observed between samples, no toxins or allergenic proteins were found.

Micromorphological and hardness analyses of human and bovine sclerotic dentin: a comparative study

The purpose of this study was to test the hypothesis that both human and bovine sclerotic dentin have similar hardness properties, in addition to similar micromorphological characteristics. Sixteen teeth (8 human and 8 bovine) exhibiting exposed dentin in the incisal edge and showing characteristics typical of sclerosis were used. Vickers surface microhardness testing was conducted. Three areas of the dentin surface of each specimen were selected. All teeth were processed for scanning electron microscopy in order to estimate the amount (in percentage) of solid dentin on the sclerotic dentin surface. The data were compared by Student's t test (α = 0.05). The micromorphological and microhardness data were compared by Pearson's linear correlation test (α = 0.05). The mean percentages of solid dentin of human and bovine sclerotic dentin were similar (human 90.71 ± 0.83 and bovine 89.08 ± 0.81, p = 0.18). The mean microhardness value (VHN) of human sclerotic dentin was significantly higher than that of bovine sclerotic dentin (human 45.26 ± 2.92 and bovine 29.93 ± 3.83, p = 0.006). No correlation was found between the microhardness values and the amount of solid dentin in the sclerotic dentin, irrespective of the species considered (human R² = 0.0240, p = 0.714; bovine R² = 0.0017, p = 0.923; and combined R² = 0.038, p = 0.46). We concluded that although both bovine and human sclerotic dentin present a similar amount of solid tissue, human sclerotic dentin presents higher microhardness than bovine sclerotic dentin.

Phylogenetic analyses of Cladophora vagabunda (L.) C. Hoek (Cladophorales, Chlorophyta) from Brazil based on SSU rDNA sequences

The complete SSU rDNA was sequenced for 10 individuals of Cladophora vagabunda collected along the coast of Brazil. For C. rupestris (L.) Kütz. a partial SSU rDNA sequence (1634 bp) was obtained. Phylogenetic trees indicate that Cladophora is paraphyletic, but the section Glomeratae sensu lato including C. vagabunda from Brazil, Japan and France, C. albida (Nees) Kütz., C. sericea (Hudson) Kütz., and C. glomerata (L.) Kütz. is monophyletic. Within this group C. vagabunda is paraphyletic. The sequence identity for the SSU rDNA varied from 98.9% to 100% for the Brazilian C. vagabunda, and from 98.3% to 99.7% comparing the Brazilian individuals to the ones from France and Japan. Sequence identity of the Brazilian C. vagabunda to C. albida and C. sericea vary from 98.0% to 98.6%. The SSU rDNA phylogeny support partially the morphological characteristics presented by Brazilian populations of C. vagabunda. On the other hand, C. rupestris from Brazil does not group with C. rupestris from France, both sequences presenting only 96.9% of identity. The inclusion of sequences of individuals from Brazil reinforces the need of taxonomical revision for the genus Cladophora and for the complex C. vagabunda.

Karyotypic analyses and morphological comments on the endemic and endangered Brazilian painted tree rat Callistomys pictus (Rodentia, Echimyidae)

The genus Callistomys belongs to the rodent family Echimyidae, subfamily Echimyinae, and its only living representative is Callistomys pictus, a rare and vulnerable endemic species of the state of Bahia, Brazil. Callistomys has been previously classified as Nelomys, Loncheres, Isothrix and Echimys. In this paper we present the karyotype of Callistomys pictus, including CBG and GTG-banding patterns and silver staining of the nucleolus organizer regions (Ag-NORs). Comments on Callistomys pictus morphological traits and a compilation of Echimyinae chromosomal data are also included. Our analyses revealed that Callistomys can be recognized both by its distintinctive morphology and by its karyotype.

Molecular and geographic analyses of vampire bat-transmitted cattle rabies in central Brazil

Background: Vampire bats are important rabies virus vectors, causing critical problems in both the livestock industry and public health sector in Latin America. In order to assess the epidemiological characteristics of vampire bat-transmitted rabies, the authors conducted phylogenetic and geographical analyses using sequence data of a large number of cattle rabies isolates collected from a wide geographical area in Brazil. Methods: Partial nucleoprotein genes of rabies viruses isolated from 666 cattle and 18 vampire bats between 1987 and 2006 were sequenced and used for phylogenetic analysis. The genetic variants were plotted on topographical maps of Brazil. Results: In this study, 593 samples consisting of 24 genetic variants were analyzed. Regional localization of variants was observed, with the distribution of several variants found to be delimited by mountain ranges which served as geographic boundaries. The geographical distributions of vampire-bat and cattle isolates that were classified as the identical phylogenetic group were found to overlap with high certainty. Most of the samples analyzed in this study were isolated from adjacent areas linked by rivers. Conclusion: This study revealed the existence of several dozen regional variants associated with vampire bats in Brazil, with the distribution patterns of these variants found to be affected by mountain ranges and rivers. These results suggest that epidemiological characteristics of vampire bat-related rabies appear to be associated with the topographical and geographical characteristics of areas where cattle are maintained, and the factors affecting vampire bat ecology.

Chemical analyses confirm a rare case of seed dispersal by bees

It has been suggested that dispersal of seeds of Coussapoa asperifolia magnifolia could have endozoochoric dispersal by frugivorous birds and monkeys because the fruits are red when ripe, or exozoochoric dispersal, because the exocarp is mucilaginous and sticky. However, our field observations showed only stingless bees collecting the exocarp with seeds of C. asperifolia magnifolia, which are used for building and repairing their nests, from which the plants sprout. This paper aimed to determine the fruit chemical composition, since we postulated that C. asperifolia magnifolia is neither consumed by birds nor monkeys due to being very sticky and apparently resinous. Apolar extract analyses revealed the fruits are not resinous but extremely rich in waxes ( mainly esterified triglycerides), and polar extract analyses revealed the sugar content to be close to the sensorial minimum level. This probably accounts for why only stingless bees are seen visiting fruits and dispersing seeds.