University of Bordeaux

About: University of Bordeaux is a education organization based out in Bordeaux, France. It is known for research contribution in the topics: Population & Laser. The organization has 28811 authors who have published 55536 publications receiving 1619635 citations. The organization is also known as: UB.

Almost Ring Theory

Abstract: 3.1 Flat, unramified and etale morphisms 3.2 Nilpotent deformations of almost algebras and modules 3.3 Nilpotent deformations of torsors 3.4 Descent 3.5 Behaviour of etale morphisms under Frobenius

Hippocampal LTP and contextual learning require surface diffusion of AMPA receptors

Abstract: Surface diffusion of AMPA receptors, from extra-synaptic to synaptic sites at the plasma membrane, is essential for full long-term potentiation in hippocampal neurons and for fear conditioning in living mice. Learning and memory are thought to rely on the long-term potentiation (LTP) of excitatory synaptic transmission, as a result of either an increase in presynaptic release of the neurotransmitter (glutamate) or recruitment of its postsynaptic receptor (AMPAR) in greater numbers. Now, using molecular techniques for immobilizing AMPARs, Daniel Choquet and colleagues demonstrate that surface diffusion of the receptor, from extra-synaptic to synaptic sites at the plasma membrane, is essential for full LTP in hippocampal neurons, and for fear conditioning in living mice. The results suggest new targets for the deliberate modulation of synaptic plasticity, learning and memory. Long-term potentiation (LTP) of excitatory synaptic transmission has long been considered a cellular correlate for learning and memory1,2. Early LTP (less than 1 h) had initially been explained either by presynaptic increases in glutamate release3,4,5 or by direct modification of postsynaptic AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor function6,7. Compelling models have more recently proposed that synaptic potentiation can occur by the recruitment of additional postsynaptic AMPA receptors (AMPARs)8, sourced either from an intracellular reserve pool by exocytosis or from nearby extra-synaptic receptors pre-existing on the neuronal surface9,10,11,12. However, the exact mechanism through which synapses can rapidly recruit new AMPARs during early LTP remains unknown. In particular, direct evidence for a pivotal role of AMPAR surface diffusion as a trafficking mechanism in synaptic plasticity is still lacking. Here, using AMPAR immobilization approaches, we show that interfering with AMPAR surface diffusion markedly impairs synaptic potentiation of Schaffer collaterals and commissural inputs to the CA1 area of the mouse hippocampus in cultured slices, acute slices and in vivo. Our data also identify distinct contributions of various AMPAR trafficking routes to the temporal profile of synaptic potentiation. In addition, AMPAR immobilization in vivo in the dorsal hippocampus inhibited fear conditioning, indicating that AMPAR diffusion is important for the early phase of contextual learning. Therefore, our results provide a direct demonstration that the recruitment of new receptors to synapses by surface diffusion is a critical mechanism for the expression of LTP and hippocampal learning. Since AMPAR surface diffusion is dictated by weak Brownian forces that are readily perturbed by protein–protein interactions, we anticipate that this fundamental trafficking mechanism will be a key target for modulating synaptic potentiation and learning.

Covalent modification of iron surfaces by electrochemical reduction of aryldiazonium salts.

Abstract: Electrochemical reduction of aryldiazonium salts (in acetonitrile or acidic aqueous medium) on an iron or mild steel surface permits the strong bonding (which resists an ultrasonic cleaning) of aryl groups on these surfaces. Attachment of aryl groups was demonstrated by the combined used of electrochemistry, infrared spectroscopy and polarization modulation infrared reflection spectroscopy (PMIRRAS), Rutherford backscattering, X-ray photoelectron spectroscopy, and capacity measurements. The substituents of aryl groups, which can be widely varied, include NO2, I, COOH, and long alkyl chains. It is shown that the attachment of the aryl groups is to an iron and not to an oxygen atom and that the bond is covalent.