25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Reverse saturable absorption in aluminophthalocyanines doped xerogels

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Assessment of genetic variation explained by markers for wool traits in sheep via a segment mapping approach

"Chantier qualité spécifique "Auteurs Externes" département de Génétique animale : uniquement liaison auteur au référentiel HR-Access "International audienc

Allyloxy ketones as efficient photoinitiators with high migration stability in free radical polymerization and 3D printing

Five ketone derivatives (ketone-1~ketone-5) never synthesized in the literature and containing the same peripheral 1,3-bis(allyloxy)benzene substituting group but different central cyclohexanone cores were designed and proposed as high-performance photoinitiators for the free radical polymerization of acrylates under mild conditions. In combination with an amine and an iodonium salt (Iod), these ketones could initiate the photopolymerization of di(trimethylolpropane) tetraacrylate (TA), a tetrafunctional acrylates monomer, upon visible LED irradiation at room temperature in both thick films (1.4 mm) and thin films (25 μm) conditions. The distinct photopolymerization profiles of acrylates were studied by real time Fourier transform infrared spectroscopy, which indicated that the ketone-2/amine/Iod system could induce the highest final conversion of acrylates in thick films condition, while ketone-5/amine/Iod system could induce the highest final conversion of acrylates in thin films condition. Photoreactivity of ketone-2 and ketone-5 was systematically investigated by steady state photolysis and fluorescence quenching experiments in the presence of an amine and an iodonium salt, respectively. Moreover, eminent migration stability of ketones in photocured TA was observed. Finally, the ketone-2 and ketone-5-based three-component photoinitiating systems were applied for the laser writing experiments of TA, and macroscopically tridimensional patterns were fabricated with an excellent spatial resolution

Novel Push–Pull Dyes Derived from 1H-cyclopenta[b]naphthalene-1,3(2H)-dione as Versatile Photoinitiators for Photopolymerization and Their Related Applications: 3D Printing and Fabrication of Photocomposites

A series of eleven push–pull chromophores with specific structures have been designed for the free radical polymerization of acrylates, but also for the fabrication of photocomposites and 3D-printed structures. New photoinitiating systems comprising the different push–pull dyes showed excellent photochemical reactivities at 405 nm. Notably, polymerization reactions could be initiated with light-emitting diodes (LEDs) which constitute a unique opportunity to promote the free radical polymerization under mild conditions, i.e., low light intensity (e.g., sunlight) and under air. Photopolymerization is an active research field, and push–pull dyes have already been investigated for this purpose. Besides, it remains of crucial interest to investigate new reactive structures capable of efficiently initiating photopolymerization reactions. The plausible potential of these structures to act as efficient photoinitiators in vat photopolymerization (or 3D printing) and fabrication of photocomposites prompts us to select eleven new push–pull dyes to design multi-component photoinitiating systems activable with LEDs emitting at 405 nm. Precisely, a tertiary amine, i.e., ethyl dimethylaminobenzoate (EDB) used as an electron/hydrogen donor and an iodonium salt used as an electron acceptor were selected to behave as powerful co-initiators to construct three-component photoinitiating systems (PISs) with the different push–pull dyes. Among these new PISs, dye 8 and 9-based PISs could efficiently promote the free radical photopolymerization of acrylates upon exposure to a LED emitting at 405 nm also upon sunlight irradiation, highlighting their huge performance. Photoinitiating abilities could be explained on the basis of steady state photolysis experiments. Fluorescence measurements and electron spin resonance (ESR) spin-trapping experiments were also performed to obtain a deeper insight into the chemical mechanisms supporting the polymerization reaction and determine the way the initiating species, i.e., the radicals, are observed. Finally, two investigated dye-based PISs were applied to the fabrications of photocomposites. Three-dimensional patterns with excellent spatial resolutions were generated by the laser writing technique to identify the effects of photopolymerization of acrylates both in the absence and presence of fillers (silica). Interestingly, comparison between the 3D objects fabricated by the PISs/monomer systems and the PISs/monomer/filler photocomposites indicates that the newly designed photocomposites are suitable for practical applications. View Full-TextThis article belongs to the Special Issue Progression in Photocatalytic Materials for Efficient Performanc

Molecular basis for temperature sensing by an RNA thermometer

Regulatory RNA elements, like riboswitches, respond to intracellular signals by three-dimensional (3D) conformational changes. RNA thermometers employ a similar strategy to sense temperature changes in the cell and regulate the translational machinery. We present here the first 3D NMR structure of the functional domain of a highly conserved bacterial RNA thermometer containing the ribosome binding site that remains occluded at normal temperatures (30°C). We identified a region adjacent to the Shine–Dalgarno sequence that has a network of weak hydrogen bonds within the RNA helix. With the onset of heat shock at 42°C, destabilisation of the RNA structure initiates at this region and favours the release of the ribosome binding site and of the start codon. Deletion of a highly conserved G residue leads to the formation of a stable regular RNA helix that loses thermosensing ability. Our results indicate that RNA thermometers are able to sense temperature changes without the aid of accessory factors