Tube Research and Development

Contains reports on two research projects

Axons Amplify Somatic Incomplete Spikes into Uniform Amplitudes in Mouse Cortical Pyramidal Neurons

BACKGROUND: Action potentials are the essential unit of neuronal encoding. Somatic sequential spikes in the central nervous system appear various in amplitudes. To be effective neuronal codes, these spikes should be propagated to axonal terminals where they activate the synapses and drive postsynaptic neurons. It remains unclear whether these effective neuronal codes are based on spike timing orders and/or amplitudes. METHODOLOGY/PRINCIPAL FINDINGS: We investigated this fundamental issue by simultaneously recording the axon versus soma of identical neurons and presynaptic vs. postsynaptic neurons in the cortical slices. The axons enable somatic spikes in low amplitude be enlarged, which activate synaptic transmission in consistent patterns. This facilitation in the propagation of sequential spikes through the axons is mechanistically founded by the short refractory periods, large currents and high opening probability of axonal voltage-gated sodium channels. CONCLUSION/SIGNIFICANCE: An amplification of somatic incomplete spikes into axonal complete ones makes sequential spikes to activate consistent synaptic transmission. Therefore, neuronal encoding is likely based on spike timing order, instead of graded analogues

NMDA Receptors Mediate Synaptic Competition in Culture

Background: Activity through NMDA type glutamate receptors sculpts connectivity in the developing nervous system. This topic is typically studied in the visual system in vivo, where activity of inputs can be differentially regulated, but in which individual synapses are difficult to visualize and mechanisms governing synaptic competition can be difficult to ascertain. Here, we develop a model of NMDA-receptor dependent synaptic competition in dissociated cultured hippocampal neurons. Methodology/Principal Findings: GluN1-/- (KO) mouse hippocampal neurons lacking the essential NMDA receptor subunit were cultured alone or cultured in defined ratios with wild type (WT) neurons. The absence of functional NMDA receptors did not alter neuron survival. Synapse development was assessed by immunofluorescence for postsynaptic PSD-95 family scaffold and apposed presynaptic vesicular glutamate transporter VGlut1. Synapse density was specifically enhanced onto minority wild type neurons co-cultured with a majority of GluN1-/- neighbour neurons, both relative to the GluN1-/neighbours and relative to sister pure wild type cultures. This form of synaptic competition was dependent on NMDA receptor activity and not conferred by the mere physical presence of GluN1. In contrast to these results in 10 % WT and 90

Le macrotron : accélérateur de 100 kW en régime permanent

Le macrotron est un accélérateur d'électrons où le faisceau traverse plusieurs dizaines de fois une cavité alimentée en régime permanent en ondes métriques. Il délivre un faisceau de très bonne qualité et de très grande puissance

Le macrotron : accélérateur de 100 kW en régime permanent

The macrotron is an electron accelerator in which the beam crosses a large number of times the accelerating gap of an RF cavity fed by CW power at metre wavelengths. It delivers a beam of high average power and very good optical quality.Le macrotron est un accélérateur d'électrons où le faisceau traverse plusieurs dizaines de fois une cavité alimentée en régime permanent en ondes métriques. Il délivre un faisceau de très bonne qualité et de très grande puissance

Structure tripériodique

It is well known that the accelerating structure using travelling waves operates with better efficiency at a 2π/3 mode than at a π/2 mode. It is the same, in standing wave operation, it can be shown that the triperiodic structure should be more efficient than the biperiodic one. We present performances obtained from experimental structures of both kinds.Il est connu que les structures accélératrices en ondes progressives fonctionnent avantageusement au mode 2π/3 plutôt qu'au mode π/2. Il en est de même en ondes stationnaires pour la structure tripériodique par rapport à la structure bipériodique. Nous présentons dans cet article les performances respectives obtenues sur différentes structures expérimentales

Structure tripériodique

Il est connu que les structures accélératrices en ondes progressives fonctionnent avantageusement au mode 2π/3 plutôt qu'au mode π/2. Il en est de même en ondes stationnaires pour la structure tripériodique par rapport à la structure bipériodique. Nous présentons dans cet article les performances respectives obtenues sur différentes structures expérimentales