Substrate Deformation Predicts Neuronal Growth Cone Advance

AbstractAlthough pulling forces have been observed in axonal growth for several decades, their underlying mechanisms, absolute magnitudes, and exact roles are not well understood. In this study, using two different experimental approaches, we quantified retrograde traction force in Aplysia californica neuronal growth cones as they develop over time in response to a new adhesion substrate. In the first approach, we developed a novel method, to our knowledge, for measuring traction forces using an atomic force microscope (AFM) with a cantilever that was modified with an Aplysia cell adhesion molecule (apCAM)-coated microbead. In the second approach, we used force-calibrated glass microneedles coated with apCAM ligands to guide growth cone advance. The traction force exerted by the growth cone was measured by monitoring the microneedle deflection using an optical microscope. Both approaches showed that Aplysia growth cones can develop traction forces in the 100–102 nN range during adhesion-mediated advance. Moreover, our results suggest that the level of traction force is directly correlated to the stiffness of the microneedle, which is consistent with a reinforcement mechanism previously observed in other cell types. Interestingly, the absolute level of traction force did not correlate with growth cone advance toward the adhesion site, but the amount of microneedle deflection did. In cases of adhesion-mediated growth cone advance, the mean needle deflection was 1.05 ± 0.07 μm. By contrast, the mean deflection was significantly lower (0.48 ± 0.06 μm) when the growth cones did not advance. Our data support a hypothesis that adhesion complexes, which can undergo micron-scale elastic deformation, regulate the coupling between the retrogradely flowing actin cytoskeleton and apCAM substrates, stimulating growth cone advance if sufficiently abundant

Knockdown of zebrafish Nav1.6 sodium channel impairs embryonic locomotor activities

[[abstract]]Although multiple subtypes of sodium channels are expressed in most neurons, the specific contributions of the individual sodium channels remain to be studied. The role of zebrafish Nav1.6 sodium channels in the embryonic locomotor movements has been investigated by the antisense morpholino (MO) knockdown. MO1 and MO2 are targeted at the regions surrounding the translation start site of zebrafish Nav1.6 mRNA. MO3 is targeted at the RNA splicing donor site of exon 2. The correctly spliced Nav1.6 mRNA of MO3 morphants is 6% relative to that of the wild-type embryos. Nav1.6-targeted MO1, MO2 and MO3 attenuate the spontaneous contraction, tactile sensitivity, and swimming in comparison with a scrambled morpholino and mutated MO3 morpholino. No significant defect is observed in the development of slow muscles, the axonal projection of primary motoneurons, and neuromuscular junctions. The movement impairments caused by MO1, MO2, and MO3 suggest that the function of Nav1.6 sodium channels is essential on the normal early embryonic locomotor activities.[[notice]]補正完畢[[journaltype]]國

Cerebellar Nuclear Neurons Use Time and Rate Coding to Transmit Purkinje Neuron Pauses

Copyright: © 2015 Sudhakar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedNeurons of the cerebellar nuclei convey the final output of the cerebellum to their targets in various parts of the brain. Within the cerebellum their direct upstream connections originate from inhibitory Purkinje neurons. Purkinje neurons have a complex firing pattern of regular spikes interrupted by intermittent pauses of variable length. How can the cerebellar nucleus process this complex input pattern? In this modeling study, we investigate different forms of Purkinje neuron simple spike pause synchrony and its influence on candidate coding strategies in the cerebellar nuclei. That is, we investigate how different alignments of synchronous pauses in synthetic Purkinje neuron spike trains affect either time-locking or rate-changes in the downstream nuclei. We find that Purkinje neuron synchrony is mainly represented by changes in the firing rate of cerebellar nuclei neurons. Pause beginning synchronization produced a unique effect on nuclei neuron firing, while the effect of pause ending and pause overlapping synchronization could not be distinguished from each other. Pause beginning synchronization produced better time-locking of nuclear neurons for short length pauses. We also characterize the effect of pause length and spike jitter on the nuclear neuron firing. Additionally, we find that the rate of rebound responses in nuclear neurons after a synchronous pause is controlled by the firing rate of Purkinje neurons preceding it.Peer reviewedFinal Published versio

23rd IAEA Fusion Energy Conference: summary of sessions EX/C and ICC

An overview is given of recent experimental results in the areas of innovative confinement concepts, operational scenarios and confinement experiments as presented at the 2010 IAEA Fusion Energy Conference. Important new findings are presented from fusion devices worldwide, with a strong focus towards the scientific and technical issues associated with ITER and W7-X devices, presently under construction

Concentration-jump analysis of voltage-dependent conductances activated by glutamate and kainate in neurons of the avian cochlear nucleus

We have examined the mechanisms underlying the voltage sensitivity of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors in voltage-clamped outside-out patches and whole cells taken from the nucleus magnocellularis of the chick. Responses to either glutamate or kainate had outwardly rectifying current-voltage relations. The rate and extent of desensitization during prolonged exposure to agonist, and the rate of deactivation after brief exposure to agonist, decreased at positive potentials, suggesting that a kinetic transition was sensitive to membrane potential. Voltage dependence of the peak conductance and of the deactivation kinetics persisted when desensitization was reduced with aniracetam or blocked with cyclothiazide. Furthermore, the rate of recovery from desensitization to glutamate was not voltage dependent. Upon reduction of extracellular divalent cation concentration, kainate-evoked currents increased but preserved rectifying current-voltage relations. Rectification was strongest at lower kainate concentrations. Surprisingly, nonstationary variance analysis of desensitizing responses to glutamate or of the current deactivation after kainate removal revealed an increase in the mean single-channel conductance with more positive membrane potentials. These data indicate that the rectification of the peak response to a high agonist concentration reflects an increase in channel conductance, whereas rectification of steady-state current is dominated by voltage-sensitive channel kinetics

High quality biodiesel and its diesel engine application: a review

The continuous increasing demand for energy and the diminishing tendency of petroleum resources has led to the search for alternative renewable and sustainable fuel. Biodiesel is best substitute for petro-diesel and also most advantageous over petro-diesel for its environmental friendliness. The quality of biodiesel fuel was found to be significant for its successful use on compression ignition engines and subsequent replacement of non-renewable fossil fuels. Conventional biodiesel separation and purification technologies were noticed to yield lower quality biodiesel fuel with resultant excessive energy and water consumptions. Membrane technology showed more potential for effective and efficient separation and purification of biodiesel. This technology need be explored for the attainment of better quality biodiesel fuels. This paper reviews the technologies used for the biodiesel separation and purification, biodiesel quality, and its effects on diesel engines. Biodiesel biodegradability, lubricity, stability, economic importance, and gaseous emissions have been discussed. (C) 2010 Elsevier Ltd. All rights reserved

High quality biodiesel obtained through membrane technology

In this study, a ceramic membrane with a pore size of 0.02μm was used to purify crude biodiesel to achieve biodiesel product that meet both ASTM D6751 and EN 14241 standards specifications. The membrane system was successfully developed and used for the purification process. Process operating parameters such as transmembrane pressure, flow rate and temperature were investigated. Application of central composite design (CCD) coupled with Response Surface Methodology (RSM) was found to provide clear understanding of the interaction between various process parameters. Thus, the process operating parameters were then optimized. The optimum conditions obtained were transmembrane pressure, 2bar, temperature, 40°C and flow rate, 150L/min with corresponding permeate flux of 9.08 (kg/m 2h). At these optimum conditions, the values of free glycerol (0.007wt) and potassium (0.297mg/L) were all below ASTM standard specifications for biodiesel fuel. In addition the physical properties of biodiesel at the optimum conditions met both ASTM D6751 and EN 14214. This work showed that with ceramic membrane of pore size 0.02μm, biodiesel with high qualities that meet the stringent standards specifications more than those currently in application can be achieved. © 2012 Elsevier B.V

The effects of water on biodiesel production and refining technologies: A review

Presence of water during biodiesel production and purification processes, storage and use in compression ignition (diesel) engines causes problems that cannot be ignored. These problems include: difficulties in biodiesel processing especially during alkali-catalyzed transesterification process, deterioration of biodiesel quality, decrease in heat of combustion, corrosion of fuel system components, and acceleration of hydrolytic reaction. Beside use of water during biodiesel purification results in wastewater discharges which causes environmental effects, due to high contents of chemical oxygen demand, biological oxygen demand, and higher pH values. Thus, this study critically analyzed and examined the effects of water on biodiesel production and the refining of crude biodiesel. Furthermore the effects of water on the quality of biodiesel were also examined. © 2012 Elsevier Ltd. All rights reserved