Impaired Spatial Reorientation in the 3xTg-AD Mouse Model of Alzheimer's Disease.

In early Alzheimer's disease (AD) spatial navigation is impaired; however, the precise cause of this impairment is unclear. Recent evidence suggests that getting lost is one of the first impairments to emerge in AD. It is possible that getting lost represents a failure to use distal cues to get oriented in space. Therefore, we set out to look for impaired use of distal cues for spatial orientation in a mouse model of amyloidosis (3xTg-AD). To do this, we trained mice to shuttle to the end of a track and back to an enclosed start box to receive a water reward. Then, mice were trained to stop in an unmarked reward zone to receive a brain stimulation reward. The time required to remain in the zone for a reward was increased across training, and the track was positioned in a random start location for each trial. We found that 6-month female, but not 3-month female, 6-month male, or 12-month male, 3xTg-AD mice were impaired. 6-month male and female mice had only intracellular pathology and male mice had less pathology, particularly in the dorsal hippocampus. Thus, AD may cause spatial disorientation as a result of impaired use of landmarks

Insertion of a Bulky Rhodium Complex into a DNA Cytosine−Cytosine Mismatch: An NMR Solution Study

The bulky octahedral complex Rh(bpy)_2chrysi^(3+) (chrysi = 5,6-chrysenequinonediimine) binds single-base mismatches in a DNA duplex with micromolar binding affinities and high selectivity. Here we present an NMR solution study to characterize the binding mode of this bulky metal complex with its target CC mismatch in the oligonucleotide duplex (5‘-CGGACTCCG-3‘)_2. Both NOESY and COSY studies indicate that Rh(bpy)_2chrysi^(3+) inserts deeply in the DNA at the mismatch site via the minor groove and with ejection of both destabilized cytosines into the opposite major groove. The insertion only minimally distorts the conformation of the oligonucleotide local to the binding site. Both flanking, well-matched base pairs remain tightly hydrogen-bonded to each other, and 2D DQF-COSY experiments indicate that all sugars maintain their original C_2‘-endo conformation. Remarkably, ^(31)P NMR reveals that opening of the phosphate angles from a B_I to a B_(II) conformation is sufficient for insertion of the bulky metal complex. These results corroborate those obtained crystallographically and, importantly, provide structural evidence for this specific insertion mode in solution

Magma sources involved in the 2002 Nyiragongo eruption, as inferred from an InSAR analysis

International audienceOn 17 January 2002, Nyiragongo volcano erupted along a 20 km-long fracture network extending from the volcano to the city of Goma. The event was captured by InSAR data from the ERS-2 and RADARSAT-1 satellites. A combination of 3D numerical modeling and inversions is used to analyze these displacements. Using Akaike Information Criteria, we determine that a model with two subvertical dikes is the most likely explanation for the 2002 InSAR deformation signal. A first, shallow dike, 2 km high, is associated with the eruptive fissure, and a second, deeper dike, 6 km high and 40 km long, lies about 3 km below the city of Goma. As the deep dike extends laterally for 20 km beneath the gas-rich Lake Kivu, the interaction of magma and dissolved gas should be considered as a significant hazard for future eruptions. A likely scenario for the eruption is that the magma supply to a deep reservoir started ten months before the eruption, as indicated by LP events and tremor. Stress analysis indicates that the deep dike could have triggered the injection of magma from the lake and shallow reservoir into the eruptive dike. The deep dike induced the opening of the southern part of this shallow dike, to which it transmitted magma though a narrow dike. This model is consistent with the geochemical analysis, the lava rheology and the pre- and post-eruptive seismicity. We infer low overpressures (1-10 MPa) for the dikes. These values are consistent with lithostatic crustal stresses close to the dikes and low magma pressure. As a consequence, the dike direction is probably not controlled by stresses but rather by a reduced tensile strength, inherited from previous rift intrusions. The lithostatic stresses indicate that magmatic activity is intense enough to relax tensional stresses associated with the rift extension

Meilleures techniques disponibles de lavage de sols contaminés par les HAP : Etude d'un procédé basé sur les cyclodextrines

http://www.ait.org.tn/gdsdd/International audienceLa pollution des sols par les Hydrocarbures Aromatiques Polycycliques (HAP) a été reconnue comme un problème majeur depuis de nombreuses années. L'impact environnemental de ces molécules hydrophobes, persistantes, aux effets toxiques (mutagènes et cancérigènes) rend nécessaire la décontamination des sites concernés. L'efficacité des techniques de bioremédiation ou d'extraction à l'eau pure est limitée par la faible solubilité aqueuse et donc la faible biodisponibilité des HAP. Les méthodes actuelles de lavage de sols augmentent cette solubilité par l'emploi de surfactants ou de solvants organiques, mais ont pour la plupart un impact écologique et/ou humain non négligeable

Le développement des comportements de timidité et d'agression physique au cours de la petite enfance

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal