Visible spectroscopy diagnostics for tungsten source assessment in the WEST tokamak: First measurements.

The present work concerns the measurements obtained with the Tungsten (W) Environment in Steady-state Tokamak (WEST) visible spectroscopy system during the first experimental campaign. This system has been developed in the framework of the WEST project that equipped the existing Tore Supra device with a tungsten divertor in order to test actively cooled tungsten Plasma Facing Components (PFC) in view of preparing for ITER operation. The goal of this diagnostic is to measure the PFC sources and the deuterium recycling with spectral, spatial, and temporal resolution adapted to the predicted power deposition profiles on the objects observed. Three kinds of PFCs are monitored: the Ion Cyclotron Resonance Heating (ICRH) antenna and Low Hybrid Current Drive (LHCD) launcher W limiters; one of the 6 W inner bumpers; and the upper and lower W divertors. Large-aperture in-vessel actively cooled optical systems (f-number ∼ 3) were installed for each view and connected to optical fibres. A total of 240 optical fibers can be distributed on various detection systems including a fast response-time, multi-channel, filtered photodetector-based "Filterscope" system, developed by Oak Ridge National Laboratory (USA) as well as grating spectrometers optimized for multi-sightline analysis. The first WEST experimental campaign conducted in 2017 has been dedicated to plasma start-up development during which the visible spectroscopy system has provided crucial information related to the impurity content first and then impurity sources. The diagnostic setup for that first experimental campaign was limited to the inner bumper and outer limiters but was sufficient to demonstrate that the optical setup was in accordance with the specifications. The radiance calibration procedure allowed us to estimate fluxes from the main limiter of about 8 × 1018 atoms/(s m2) and to show a first W source radial profile along the outboard limiter.

Residents in tutored practice exchange groups have better medical reasoning as measured by script concordance test: a controlled, nonrandomized study.

STUDY OBJECTIVE: Clinical reasoning by anesthesiology residents in emergency situations where optimal management is uncertain could be improved by setting up a tutored practice exchange group. This study attempted to evaluate the impact of a practice exchange group (PEG), tutored by a senior anesthesiologist, on anesthesiology residents in emergency situations. Changes in clinical reasoning were measured by script concordance tests (SCT). DESIGN: We conducted a controlled, non-randomized study. SETTING AND PARTICIPANTS: Participants are residents in anesthesiology in Rouen, Caen and Amiens University Hospitals. INTERVENTIONS: Two resident groups were made up without randomization. The first group was the control group and consisted of residents from Amiens University Hospital and Caen University Hospital. The second study group (PEG group) consisted of residents from Rouen University Hospital, who followed weekly PEG sessions. Two groups had the same learning objectives except the PEG. MEASUREMENTS: In both the control group and the study group, each resident's clinical reasoning was assessed in the same formal manner by SCT. The primary outcome measurement of this study was to compare SCT results in the study group with PEG training (PEG group) with those without (control group). MAIN RESULTS: Performance in the SCT, expressed as degree of concordance with the expert panel (95% CI), was better in the PEG group (64% [62.1%-66%]) than in control group (60% [57.5%-62.8%])) (P= .004). CONCLUSION: Our study strongly suggests that an expert-directed, peer-conducted educational training program may improve the clinical reasoning of anesthesiology residents as measured by SCT.

Whole-genome re-sequencing of non-model organisms: lessons from unmapped reads.

Unmapped reads are often discarded from the analysis of whole-genome re-sequencing, but new biological information and insights can be uncovered through their analysis. In this paper, we investigate unmapped reads from the re-sequencing data of 33 pea aphid genomes from individuals specialized on different host plants. The unmapped reads for each individual were retrieved following mapping to the Acyrthosiphon pisum reference genome and its mitochondrial and symbiont genomes. These sets of unmapped reads were then cross-compared, revealing that a significant number of these unmapped sequences were conserved across individuals. Interestingly, sequences were most commonly shared between individuals adapted to the same host plant, suggesting that these sequences may contribute to the divergence between host plant specialized biotypes. Analysis of the contigs obtained from assembling the unmapped reads pooled by biotype allowed us to recover some divergent genomic regions previously excluded from analysis and to discover putative novel sequences of A. pisum and its symbionts. In conclusion, this study emphasizes the interest of the unmapped component of re-sequencing data sets and the potential loss of important information. We here propose strategies to aid the capture and interpretation of this information.

Transforming growth factor-beta 3, glial cell line-derived neurotrophic factor, and fibroblast growth factor-2, act in different manners to promote motoneuron survival in vitro.

Developing chick motoneurons depend on as yet unidentified factors from the periphery and the central nervous system for their survival. Using cultures of purified embryonic motoneurons, we show that basic fibroblast growth factor (FGF-2) or transforming growth factor-beta 3 (TGF beta 3) each have only low survival-promoting activity when tested alone, but act synergistically to keep motoneurons alive for at least 3 days. Glial cell line-derived neurotrophic factor (GDNF), another member of the TGF beta family, was itself sufficient to maintain a population of motoneurons. However, its effect was not significantly increased by the addition of FGF-2. These results suggest that FGF-2, TGF beta 3, and GDNF, which are all present in the environment of developing motoneurons, may act different mechanisms as physiological survival factors for this population of central neurons.

Survival of newly postmitotic motoneurons is transiently independent of exogenous trophic support.

We compared the survival requirements of early- and late-born motoneurons from E5 chicken spinal cord. Density gradient centrifugation followed by immunopanning using SC1 antibody allowed us to purify two size classes of motoneuron. Large motoneurons retained by 6.8% metrizamide were shown by BrdU labeling in ovo to be born on average 1.5 d earlier than the small motoneurons recovered from the metrizamide pellet. Large motoneurons were both biochemically and functionally more mature: they expressed higher levels of choline acetyltransferase and low-affinity neurotrophin receptor, and had an acute requirement for trophic support from muscle-derived factors. After 24 hr in culture in basal medium, all early-born motoneurons died, whereas 60% of late-born motoneurons survived. Small motoneurons can develop into large motoneurons in ovo, suggesting that they represent a general transitional stage in motoneuron development. Our results suggest that a defined period elapses between birth of a motoneuron and its acquisition of trophic dependence, possibly corresponding to the time required for target innervation. This property may have important consequences for the timing and regulation of developmental motoneuron death.

Motoneuron survival factors: biological roles and therapeutic potential.

The existence of factors that promote motoneuron survival in the spinal cord at critical stages of development was first deduced 50 yr ago. The large amount of work that has been put into characterizing such factors reflects both their biological importance and the hope that such molecules may be used therapeutically to slow motoneuron death in pathologies such as the spinal muscular atrophies and amyotrophic lateral sclerosis. Since 1990, several factors have been shown to have in vitro and/or in vivo activities that suggest they play a role in regulating motoneuron survival. Their physiological functions during motoneuron development are probably different and complementary. Several of them seem reasonable candidates for preclinical development, but many crucial experiments remain to be done.

Neurotrophins promote motor neuron survival and are present in embryonic limb bud.

Embryonic spinal motor neurons are thought to depend for survival on unidentified factors secreted both by their peripheral targets and by cells within the central nervous system. The neurotrophins are a family of polypeptides required for survival of discrete central and peripheral neuronal populations in vivo and in vitro. In spite of their ability to reduce motor neuron death in vivo, the known neurotrophins have been thought to be without direct effect on motor neurons. Here we show that picomolar concentrations of three of them, brain-derived neurotrophic factor, neurotrophin-3 and neurotrophin-5, can prevent the death of cultured embryonic rat spinal motor neurons. Furthermore, messenger RNA coding for neurotrophins is present at appropriate stages in spinal cord and limb bud, and mRNA for their receptors is found in motor neurons. These neurotrophins may therefore be physiological motor neuron growth factors.

[Growth and survival factors of spinal motoneurons]. / Facteurs de croissance et de survie des motoneurones spinaux.

The development of motoneurons in the spinal cord is strongly dependent on their interactions with their target tissue, skeletal muscle, and with other cells of the central nervous system. The molecular nature of these interactions has remained obscure for many years. However, over the last few years, known growth factors have been shown to have biological activity on the survival of motoneurons, at least in culture. The factors that have been studied are members of the FGF family (fibroblast growth factors), the TGF-beta family (transforming growth factor-beta), CNTF (ciliary neurotrophic factor) and CDF-LIF (cholinergic development factor-leukaemia inhibitory factor). There are also strong reasons to suppose that at least one member of the neurotrophin family (the family that contains Nerve Growth Factor) is involved in motoneuron development. A more detailed analysis of the biological role of each of these factors should not only enlighten us as to the importance of cell-cell interactions in development of the motoneuron, but also open the way to attempts to slow motoneuron death in pathological situations, either in animals or in man.

Neurotrophic factors in development and plasticity of spinal neurons.

Factors affecting neuronal growth may be considered to fall into two major categories: those required for neuronal survival during development or following a lesion, and those which enhance growth or regeneration of axonal or dendritic processes. We briefly review here some recent studies on the former in spinal cord development and plasticity as an introduction to other papers in the session on Factors controlling Neural Growth, and then present in more detail work on factors affecting motoneuron development in vitro. The neurotrophins are a closely-related family of basic neurotrophic factors including nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) and neurotrophins -3, -4 and -5 that enhance neuronal survival by binding to surface receptors whose major components are the trk tyrosine kinases and p75NGF-R. Only the latter has been studied in the context of spinal cord neuroplasticity: its levels on motoneurons are up-regulated following central or peripheral trauma, although its function there remains unknown. Much evidence exists for the existence of 'motoneuron growth factors' involved in regulation of survival and development of spinal motoneurons. Following a critical comparison of techniques for their purification, we review results obtained in vitro and in vivo using known growth factors such as ciliary neurotrophic factor (CNTF), basic fibroblast growth factor (bFGF) and transforming growth factor (TGF/ß1). Although none of them satisfies all the criteria for the embryonic 'motoneuron growth factor', CNTF is of potential interest for reducing motoneuron loss in pathological situations.

K+ channel expression in primary cell cultures mediated by vaccinia virus.

A recombinant vaccinia virus (VV) was used to express functional Drosophila Shaker H4 K+ channels in primary cell cultures from rat heart (atrial and ventricular myocytes, fibroblasts), autonomic ganglia (SCG neurons) and CNS (hippocampal neurons, cerebral astroglia). In most cells the expressed currents possessed the typical characteristics of the native Drosophila muscle A currents; a few cells showed evidence of hetero-oligomers with new properties. The maximum current density corresponded to a channel density of 2-3/microns 2. Voltage recordings in heart cells showed altered action potential waveforms after successful infection. VV vectors thus are useful for studying altered excitability and cell-specific processing of ion channel proteins.

Reverse pharmacology of the nicotinic acetylcholine receptor. Mapping the local anesthetic binding site.

We have been examining the interaction of a local anesthetic derivative, QX-222, with the ion channel pore of the muscle AChR, using a combination of mutagenesis, oocyte expression, and electrophysiology. Single channel recording, together with macroscopic voltage-jump relaxations, provides a measure of the residence time of the open channel blocker within the pore. We have found systematic changes in the apparent affinity of the open channel for QX-222 following amino acid substitutions in the proposed M2 transmembrane helix of each of the four subunits of the AChR. Assigning the number 1' to the residue at the cytoplasmic end of the M2 helix, positions 2',6',10',14', and 18' are modeled as forming the lining of the pore. Polar to nonpolar substitutions at 6' decrease QX-222 residence time, while the opposite effect is seen at position 10'. Nonpolar to polar substitutions have the converse effect. The distance between the aromatic and quaternary amine moieties of QX-222 corresponds almost exactly to the repeat distance of an alpha helix. This structural feature is common to many local anesthetic drugs. We propose a model for the binding of QX-222 within the ion channel of the AChR that is consistent with these observations.

An open-channel blocker interacts with adjacent turns of alpha-helices in the nicotinic acetylcholine receptor.

The binding site for an open-channel blocker, QX-222, at mouse muscle nicotinic acetylcholine receptors was probed using site-directed mutagenesis, oocyte expression, and electrophysiological analysis. The proposed cytoplasmic end of the M2 transmembrane helix is termed position 1'. At position 10' (alpha S252, beta T263, gamma A261, delta A266), Ala residues yield stronger and longer binding of QX-222 than Ser or Thr residues. These effects are opposite and roughly equal (30%-50% per mutation) to previously reported effects at position 6'. The polar end of an anesthetic molecule seems to bind to the position 6' OH groups, which provide a water-like region; the nonpolar moiety is near position 10' and binds more strongly in a nonpolar environment. Interactions with adjacent OH-rich turns of an amphiphilic helix may explain the widespread blocking effects of local anesthetics at the conduction pore of ion channels.