ICRF wave field measurements in the presence of scrape off layer turbulence on the ASDEX Upgrade tokamak (invited).

A new array of B-dot probes was installed on ASDEX Upgrade. The purpose of the new diagnostic is to study Ion Cyclotron Range-off Frequencies (ICRF) wave field distributions in the evanescent scrape-off layer (SOL) plasma region on the low field side of ASDEX Upgrade. The vacuum measurements (no gas, BT = 0 T) reveal ICRF wave field measurements consistent with the profiles expected from the newly installed 3-strap ICRF antennas outside the antenna box: the shape of the toroidal distribution of both the amplitude and the phase is the same for the case of only the central straps being active, as for the case of only the side straps being active. These profiles become strongly modified during plasma operations. The modifications can be separated into two types: "Inter-edge localized mode (ELM)" and "During-ELM" periods. The phase distribution of the ICRF wave fields remains well-defined during the Inter-ELM period; however, it becomes more spread out over the entire 360° range during ELMs. The observed modulations cannot be explained by the observed changes in the ICRF power, as monitored in the transmission line. However, they are consistent with ICRF coupling changes introduced by plasma filaments: the plasma density perturbations due to the filaments are high enough to change the nature of the fast ICRF wave field from evanescent to propagating. The coverage of the present diagnostic is being expanded to include both the low field side and the high field side probes. Additionally, a manipulator probe head is being developed to measure ICRF wave field radial profiles across the SOL region.

Bone disease in cystic fibrosis: new pathogenic insights opening novel therapies.

Mutations within the gene encoding for the chloride ion channel cystic fibrosis transmembrane conductance regulator (CFTR) results in cystic fibrosis (CF), the most common lethal autosomal recessive genetic disease that causes a number of long-term health problems, as the bone disease. Osteoporosis and increased vertebral fracture risk associated with CF disease are becoming more important as the life expectancy of patients continues to improve. The etiology of low bone density is multifactorial, most probably a combination of inadequate peak bone mass during puberty and increased bone losses in adults. Body mass index, male sex, advanced pulmonary disease, malnutrition and chronic therapies are established additional risk factors for CF-related bone disease (CFBD). Consistently, recent evidence has confirmed that CFTR plays a major role in the osteoprotegerin (OPG) and COX-2 metabolite prostaglandin E2 (PGE2) production, two key regulators in the bone formation and regeneration. Several others mechanisms were also recognized from animal and cell models contributing to malfunctions of osteoblast (cell that form bone) and indirectly of bone-resorpting osteoclasts. Understanding such mechanisms is crucial for the development of therapies in CFBD. Innovative therapeutic approaches using CFTR modulators such as C18 have recently shown in vitro capacity to enhance PGE2 production and normalized the RANKL-to-OPG ratio in human osteoblasts bearing the mutation F508del-CFTR and therefore potential clinical utility in CFBD. This review focuses on the recently identified pathogenic mechanisms leading to CFBD and potential future therapies for treating CFBD.

Magnetic reversal in Mn5Ge3 thin films: an extensive study.

We present a comprehensive study of magnetization reversal process in thin films of Mn5Ge3. For this investigation, we have studied the magnetic anisotropy of Mn5Ge3 layers as a function of the film thickness using VSM and SQUID magnetometers. The samples grown by molecular beam epitaxy exhibit a reorientational transition of the easy axis of magnetization from in-plane to out-of-plane as the film thickness increases. We provide evidence that above a critical thickness estimated as 20 nm, the magnetic structure is most probably constituted of stripes with out-of-plane magnetization pointing alternately up and down. We have analyzed our results using different phenomenological models and all the calculations converge towards values for magnetocrystalline anisotropy constant and saturation magnetization that are in excellent agreement with the reported values for bulk Mn5Ge3. This study has also led to the first estimation in Mn5Ge3 of the exchange constant, the surface energy of domain walls as well as their width. These parameters are essential for determining whether this material can be used in the next generation of spintronic devices.

Pushing NMR sensitivity limits using dynamic nuclear polarization with closed-loop cryogenic helium sample spinning.

We report a strategy to push the limits of solid-state NMR sensitivity far beyond its current state-of-the-art. The approach relies on the use of dynamic nuclear polarization and demonstrates unprecedented DNP enhancement factors for experiments performed at sample temperatures much lower than 100 K, and can translate into 6 orders of magnitude of experimental time-savings. This leap-forward was made possible thanks to the employment of cryogenic helium as the gas to power magic angle sample spinning (MAS) for dynamic nuclear polarization (DNP) enhanced NMR experiments. These experimental conditions far exceed what is currently possible and allows currently reaching sample temperatures down to 30 K while conducting experiments with improved resolution (thanks to faster spinning frequencies, up to 25 kHz) and highly polarized nuclear spins. The impressive associated gains were used to hyperpolarize the surface of an industrial catalyst as well as to hyperpolarize organic nano-assemblies (self-assembling peptides in our case), for whom structures cannot be solved using diffraction techniques. Sustainable cryogenic helium sample spinning significantly enlarges the realm and possibilities of the MAS-DNP technique and is the route to transform NMR into a versatile but also sensitive atomic-level characterization tool.

Probing the plasma near high power wave launchers in fusion devices for static and dynamic electric fields (invited).

An exploratory study was carried out in the long-pulse tokamak Tore Supra, to determine if electric fields in the plasma around high-power, RF wave launchers could be measured with non-intrusive, passive, optical emission spectroscopy. The focus was in particular on the use of the external electric field Stark effect. The feasibility was found to be strongly dependent on the spatial extent of the electric fields and overlap between regions of strong (>∼1 kV/cm) electric fields and regions of plasma particle recycling and plasma-induced, spectral line emission. Most amenable to the measurement was the RF electric field in edge plasma, in front of a lower hybrid heating and current drive launcher. Electric field strengths and direction, derived from fitting the acquired spectra to a model including time-dependent Stark effect and the tokamak-range magnetic field Zeeman-effect, were found to be in good agreement with full-wave modeling of the observed launcher.

Magnetic field dependence of the magnetic susceptibility and the specific heat of the doped plasticized polyaniline (PANI-DB3EPSA)0.5.

Specific heat, magnetization and electron spin resonance (ESR) data obtained from a self-standing film of the doped plasticized polyaniline (PANI-DB3EPSA)(0.5) are shown. No long range magnetic order has been observed at zero magnetic field, above 2 K. For a magnetic field of 3.3 kOe applied perpendicular to the plane of the film, a clear signature of an induced ordered state can be seen in the specific heat data and ESR also reveals this antiferromagnetic order. An electronic contribution is detected from ESR, magnetization and specific heat; however, for T ≤ 5 K, the specific heat data show the existence of a gap. Magnetization data also show a low temperature dominant Curie behaviour which cannot be seen from ESR, probably due to a very large linewidth, suggesting short range correlations among spin 1/2 polarons.

The plant thioredoxin system.

Thioredoxins are small proteins catalyzing thiol-disulfide interchange and are involved in the regulation of the redox environment of the cell. In plants, the thioredoxin system is particularly complex since at least 20 thioredoxin isoforms are found in the plant model Arabidopsis thaliana. Based upon primary sequence analysis and subcellular localization, thioredoxins can be classified into different groups and subgroups. Different pathways allowing thioredoxin reduction also coexist in the plant involving ferredoxin-thioredoxin reductase, thioredoxin reductases and the glutathione/glutaredoxin system. This review discusses the literature of plant thioredoxins with emphasis on recent findings in the field.

Plant glutaredoxins: still mysterious reducing systems.

Glutaredoxins are ubiquitous oxidoreductases which are similar to thioredoxins and possess a typical glutathione-reducible CxxC or CxxS active site. We present here the current knowledge about these proteins in plants. At least 31 glutaredoxin genes are present in Arabidopsis thaliana, a value close to the thioredoxin gene number. Based essentially on active site sequences, a classification of these multiple genes is proposed. The specificity of the various apparently redundant forms within the glutaredoxin group or between glutaredoxin and thioredoxin can be analysed in terms of differential spatiotemporal expression of the genes, specificity vs. target proteins and mode of catalysis (glutathiolation/ deglutathiolation processes appear to be a specific function of glutaredoxin). Additional putative functions are proposed for plant glutaredoxins based on their targets in other organisms and in the light of the existence of hybrid proteins containing glutaredoxin modules in their N- or C-terminal part.

Fluticasone reduces IL-6 and IL-8 production of cystic fibrosis bronchial epithelial cells via IKK-beta kinase pathway.

Inhaled fluticasone propionate (FP) is widely used to reduce pulmonary inflammation in chronic obstructive pulmonary disease, but the potential effects of FP on airway epithelial cells from patients with cystic fibrosis (CF) are unknown. In CF disease, a nonregulated inflammatory lung response occurs through exaggerated nuclear factor (NF)-kappaB activation and elevated pro-inflammatory cytokines production by airway epithelial cells. To determine whether FP reduces cytokine production in bronchial epithelial cells via NF-kappaB, the authors investigated the nonstimulated and the Pseudomonas aeruginosa lipopolysaccharide (LPS) stimulated production of NF-kappaB-dependent interleukin (IL)-6, IL-8 and RANTES (regulated on activation, T-cell expressed and secreted) along with the activation of NF-kappaB in non-CF and CF human bronchial gland epithelial cells. It was demonstrated that a relevant concentration of FP (10(-8) M) inhibited constitutive and P. aeruginosa LPS-induced IL-6 and IL-8 production of non-CF and CF bronchial epithelial cells. Interestingly, the expression of two IkappaB kinases (IKK)-alpha/beta, the degradation of cytosolic IkappaB-beta inhibitor and the NF-kappaB deoxyribonucleic acid binding activity were markedly reduced after FP treatment in both CF and non-CF bronchial epithelial cells. It was shown by the authors that fluticasone propionate exerts an anti-inflammatory effect by blocking a signal transduction leading to a reduced level of IkappaB-alpha/beta kinases in bronchial epithelial cells. In particular the strong effect on the IkappaB-beta kinase, which is known to be elevated in bronchial epithelial cells in cystic fibrosis patients, was observed.

Influence of tropolone on Poria placenta wood degradation.

Fenton reactions are believed to play important roles in wood degradation by brown rot fungi. In this context, the effect of tropolone (2-hydroxycyclohepta-2,4,6-trienone), a metal chelator, on wood degradation by Poria placenta was investigated. Tropolone (50 micro M) strongly inhibits fungal growth on malt agar, but this inhibition could be relieved by adding iron salts. With an experimental system containing two separate parts, one supplemented with tropolone (100 micro M) and the other not, it was shown that the fungus is able to reallocate essential minerals from the area where they are available and also to grow in these conditions on malt-agar in the presence of tropolone. Nevertheless, even in the presence of an external source of metals, P. placenta is not able to attack pine blocks impregnated with tropolone (5 mM). This wood degradation inhibition is related to the presence of the tropolone hydroxyl group, as shown by the use of analogs (cyclohepta-2,4,6-trienone and 2-methoxycyclohepta-2,4,6-trienone). Furthermore, tropolone possesses both weak antioxidative and weak radical-scavenging properties and a strong affinity for ferric ion and is able to inhibit ferric iron reduction by catecholates, lowering the redox potential of the iron couple. These data are consistent with the hypothesis that tropolone inhibits wood degradation by P. placenta by chelating iron present in wood, thus avoiding initiation of the Fenton reaction. This study demonstrates that iron chelators such as tropolone could be also involved in novel and more environmentally benign preservative systems.

Oxidation-reduction and activation properties of chloroplast fructose 1,6-bisphosphatase with mutated regulatory site.

The concentration of Mg(2+) required for optimal activity of chloroplast fructose 1,6-bisphosphatase (FBPase) decreases when a disulfide, located on a flexible loop containing three conserved cysteines, is reduced by the ferredoxin/thioredoxin system. Mutation of either one of two regulatory cysteines in this loop (Cys155 and Cys174 in spinach FBPase) produces an enzyme with a S(0.5) for Mg(2+) (0.6 mM) identical to that observed for the reduced WT enzyme and significantly lower than the S(0.5) of 12.2 mM of oxidized WT enzyme. E(m) for the regulatory disulfide in WT spinach FBPase is -305 mV at pH 7.0, with an E(m) vs pH dependence of -59 mV/pH unit, from pH 5.5 to 8.5. Aerobic storage of the C174S mutant produces a nonphysiological Cys155/Cys179 disulfide, rendering the enzyme partially dependent on activation by thioredoxin. Circular dichroism spectra and thiol titrations provide supporting evidence for the formation of nonphysiological disulfide bonds. Mutation of Cys179, the third conserved cysteine, produces FBPase that behaves very much like WT enzyme but which is more rapidly activated by thioredoxin f, perhaps because the E(m) of the regulatory disulfide in the mutant has been increased to -290 mV (isopotential with thioredoxin f). Structural changes in the regulatory loop lower S(0.5) for Mg(2+) to 3.2 mM for the oxidized C179S mutant. These results indicate that opening the regulatory disulfide bridge, either through reduction or mutation, produces structural changes that greatly decrease S(0.5) for Mg(2+) and that only two of the conserved cysteines play a physiological role in regulation of FBPase.

Isolation and characterization of a new peroxiredoxin from poplar sieve tubes that uses either glutaredoxin or thioredoxin as a proton donor.

A sequence coding for a peroxiredoxin (Prx) was isolated from a xylem/phloem cDNA library from Populus trichocarpa and subsequently inserted into an expression plasmid yielding the construction pET-Prx. The recombinant protein was produced in Escherichia coli cells and purified to homogeneity with a high yield. The poplar Prx is composed of 162 residues, a property that makes it the shortest plant Prx sequence isolated so far. It was shown that the protein is monomeric and possesses two conserved cysteines (Cys). The Prx degrades hydrogen peroxide and alkyl hydroperoxides in the presence of an exogenous proton donor that can be either thioredoxin or glutaredoxin (Grx). Based on this finding, we propose that the poplar protein represents a new type of Prx that differs from the so-called 2-Cys and 1-Cys Prx, a suggestion supported by the existence of natural fusion sequences constituted of a Prx motif coupled to a Grx motif. The protein was shown to be highly expressed in sieve tubes where thioredoxin h and Grx are also major proteins.

Physiomer reduces the chemokine interleukin-8 production by activated human respiratory epithelial cells.

The authors have recently shown that the transcription factor nuclear factor-kappaB (NF-kappaB) is a central mediator in the NaCl-mediated interleukin (IL)-8 production by human airway epithelial cells. In this study, it was investigated whether Physiomer, an isotonic sea water-derived solution commercialized for cleaning the nasal mucosa, impaired the chemokine IL-8 expression and secretion by human respiratory epithelial cells compared with that obtained with an isotonic 9% NaCl solution. Primary human bronchial gland (HBG) epithelial cells were incubated either in Physiomer or in a NaCl 9% solution and activated either with 20 ng x mL(-1) tumour necrosis factor-alpha, or IL-1beta, respectively. Physiomer significantly reduced the IL-8 protein release in basal and activated HBG cells in comparison with that obtained with the 9% NaCl solution. In contrast to the effects of Physiomer observed on resting HBG cells, Physiomer did not significantly reduce the level of phosphorylation of the NF-kappaB inhibitor protein IkappaBalpha or the steady-state IL-8 messenger ribonucleic acid levels in activated HBG cells, suggesting that Physiomer would have a post-transcriptional effect on IL-8 expression in activated HBG cells. The authors conclude that Physiomer is potentially useful in the reduction of airway mucosal inflammation.

[Dementia and falls]. / Démence et chutes.

INTRODUCTION: Dementia is now a frequent disease in elderly and may be a major risk of falling. Usually these falls are multiple and serious, but their consequences are not specific. All types of dementia (Alzheimer's disease, dementia with Lewy bodies, dementia in Parkinson's disease, fronto-temporal dementia, vascular dementiaellipsis) and all stages of evolution are concerned. DISCUSSION: These falls result from cognitive and behavioural disorders, visual and motor problems, gait and balance disturbances, malnutrition, adverse effects of medication and fear of falling. CONCLUSION: Prevention is possible. Attention must be given on the patient himself (keeping in good health, limitation in sedative treatment and mechanical restraintsellipsis) and on his environment (lighting, obstacles on the ground, stress levelellipsis). After a fall, especially after a complicated fall, rehabilitation modalities and aims must be adapted but caring must not be defeatist. Randomized studies need to be realized.

Crystal structure of the wild-type and D30A mutant thioredoxin h of Chlamydomonas reinhardtii and implications for the catalytic mechanism.

Thioredoxins are ubiquitous proteins which catalyse the reduction of disulphide bridges on target proteins. The catalytic mechanism proceeds via a mixed disulphide intermediate whose breakdown should be enhanced by the involvement of a conserved buried residue, Asp-30, as a base catalyst towards residue Cys-39. We report here the crystal structure of wild-type and D30A mutant thioredoxin h from Chlamydomonas reinhardtii, which constitutes the first crystal structure of a cytosolic thioredoxin isolated from a eukaryotic plant organism. The role of residue Asp-30 in catalysis has been revisited since the distance between the carboxylate OD1 of Asp-30 and the sulphur SG of Cys-39 is too great to support the hypothesis of direct proton transfer. A careful analysis of all available crystal structures reveals that the relative positioning of residues Asp-30 and Cys-39 as well as hydrophobic contacts in the vicinity of residue Asp-30 do not allow a conformational change sufficient to bring the two residues close enough for a direct proton transfer. This suggests that protonation/deprotonation of Cys-39 should be mediated by a water molecule. Molecular-dynamics simulations, carried out either in vacuo or in water, as well as proton-inventory experiments, support this hypothesis. The results are discussed with respect to biochemical and structural data.

Molecular cloning, characterization and regulation by cadmium of a superoxide dismutase from the ectomycorrhizal fungus Paxillus involutus.

The gene encoding a superoxide dismutase (PiSOD) was cloned by suppressive subtractive hybridization from cDNA library of the ectomycorrhizal fungus, Paxillus involutus, grown under cadmium-stress conditions. The encoded protein was presumed to be localized in the peroxisomes because it contained a C-terminal peroxisomal localization peptide (SKL) and lacked an N-terminal mitochondrial transit peptide. Complementation of an Escherichia coli SOD null strain that is unable to grow in the presence of paraquat or cadmium indicated that cloned Pisod encoded a functional superoxide dismutase. Sensitivity of PiSOD activity to H2O2 but not KCN, and sequence homologies to other SODs strongly suggest that it is a manganese-containing superoxide dismutase. Monitoring PiSOD transcript, immunoreactive polypeptide and superoxide dismutase activity following cadmium stress suggests that the principal level of control is post-translational. This is, to our knowledge, the first insight in the characterization of molecular events that take place in an ectomycorrhizal fungus during exposure to heavy metals.

Conformational change of Arabidopsis thaliana thioredoxin reductase after binding of pyridine nucleotide and thioredoxin.

We have found that the binding of NADP+ (Kd = 0.86+/-0.11 microM) enhanced the FAD fluorescence of Arabidopsis thaliana NADPH:thioredoxin reductase (TR, EC 1.6.4.5) by 2 times, whereas the binding of 3-aminopyridine adenine dinucleotide phosphate (AADP+) (Kd < 0.1 microM) quenched the fluorescence by 20%. Thioredoxin (TRX) also enhanced the FAD fluorescence by 35%. The Kd of TR-NADP+ and TR-AADP+ complexes did not change in the presence of 45 microM TRX. Our findings imply that the binding of NADP+ and AADP+ at the NADP(H)-binding site of A. thaliana TR, and/or the binding of TRX in the vicinity of the catalytic disulfide increase the content of fluorescent FR conformer (NADP(H)-binding site adjacent to flavin). The different effects of NADP+ and AADP+ on FAD fluorescence intensity may be explained by the superposition of two opposite factors: i) increased content of fluorescent FR conformer upon binding of NADP+ or AADP+; ii) quenching of FAD fluorescence by electron-donating 3-aminopyridinium ring of AADP+.

[Deglutition disorders in the elderly. Epidemiological aspects]. / Les troubles de la déglutition du sujet âgé. Aspects épidémiologiques.

THE PREVALENCE: The exact prevalence of deglutition disorders in the elderly is not known. It appears frequent in very old patients and in those suffering from polypathological symptoms, affecting 50% of the populations in long-term care units. THE EFFECTS OF AGING: Physiological aging alters various parameters of swallowing, however it seems that these modifications related to age have little effect on healthy subjects. However, they may increase vulnerability in those presenting with intercurrent pathologies. CONCOMITANT DISORDERS: Other than the decrease in efficient mastication and the existence of xerostomia, frequently observed contributing factors, many diseases may be responsible for dysphagia in the elderly. Neurological disorders, particularly cerebral vascular diseases, central nervous system degenerative disorders and neuro-motor diseases predominate. In the aging, muscular disorders and after effects of various diseases can set-in. Modifications in oropharyngeal anatomy generally results from cancerous lesions of the aero-digestive junction, but also, occasionally from extrinsic compression that does not necessarily reflect a neoplastic etiology. Zenker's diverticulitis represents a cause of dysphagia specific to the elderly. Problems in swallowing of iatrogenic origin are also frequent, following cervical radiotherapy or after oropharyngeal surgery, during tracheal intubation or when using feeding tubes and also during various medical treatments. UNDERRATED CONSEQUENCES: Dysphagia leads to multiple morbid after effects, primarily alteration in quality of life, dehydration, undernutrition, asphyxia and congestion and recurrent infections of the respiratory tract. The responsibility of deglutition disorders in the occurrence of these complications is difficult to assess in weak elderly subjects because of the frequent concomitance with multiple deficiencies and incapacities.

[Deglutition disorders in the elderly. Evaluation methods]. / Les troubles de la déglutition du sujet âgé. Procédés d'évaluation.

FROM DISCOVERY TO CLINICAL DIAGNOSIS: Dysphagia is easy to diagnose in its acute stage and when complicating a known neurological disease. However diagnosis may be greatly delayed when expressed by respiratory or nutritional symptoms, or when the patient presents cognitive disorders, as is frequent in the elderly. In such instances, simple tests such as the water test are clearly indicated. However, although they are reliable for diagnosing dysphagia, they are not precise in diagnosis of inhalation. Clinical examination is essential for diagnosing the etiology of the disorder. In the absence of clinical orientation, a nasofibroscopy is mandatory and digestive endoscopy debatable. SPECIALIZED EXAMINATIONS: The first-line supplementary examination is a videoradiography. It consists in the patient swallowing a liquid or solid barium sulfate bolus. This detects any anatomical or functional abnormalities. It is the examination of choice for the diagnosis of inhalation and its mechanism. Videoendoscopy is complementary to videoradiography. It can be conducted in first intention in patients who cannot be transported to the radiology unit. It provides precise information on glottal closing and pharyngeal contraction. IMPACT ON MANAGEMENT: In a restricted number of patients, the precise knowledge of the mechanism of dysphagia can help to orientate specific treatment. In others, such examinations will orient re-education, postural adaptation and the modification of food texture. In many patients, precise diagnosis of the mechanism at the origin of dysphagia has no impact on the management of dysphagia.