Depletion of SMN by RNA interference in HeLa cells induces defects in Cajal body formation

Neuronal degeneration in spinal muscular atrophy (SMA) is caused by reduced expression of the survival of motor neuron (SMN) protein. The SMN protein is ubiquitously expressed and is present both in the cytoplasm and in the nucleus where it localizes in Cajal bodies. The SMN complex plays an essential role for the biogenesis of spliceosomal U-snRNPs. In this article, we have used an RNA interference approach in order to analyse the effects of SMN depletion on snRNP assembly in HeLa cells. Although snRNP profiles are not perturbed in SMN-depleted cells, we found that SMN depletion gives rise to cytoplasmic accumulation of a GFP-SmB reporter protein. We also demonstrate that the SMN protein depletion induces defects in Cajal body formation with coilin being localized in multiple nuclear foci and in nucleolus instead of canonical Cajal bodies. Interestingly, the coilin containing foci do not contain snRNPs but appear to co-localize with U85 scaRNA. Because Cajal bodies represent the location in which snRNPs undergo 2′-O-methylation and pseudouridylation, our results raise the possibility that SMN depletion might give rise to a defect in the snRNA modification process

Estimating underwater light regime under spatially heterogeneous sea ice in the Arctic

Abstract: The vertical diffuse attenuation coefficient for downward plane irradiance (Kd ) is an apparent optical property commonly used in primary production models to propagate incident solar radiation in the water column. In open water, estimating Kd is relatively straightforward when a vertical profile of measurements of downward irradiance, Ed, is available. In the Arctic, the ice pack is characterized by a complex mosaic composed of sea ice with snow, ridges, melt ponds, and leads. Due to the resulting spatially heterogeneous light field in the top meters of the water column, it is difficult to measure at single-point locations meaningful Kd values that allow predicting average irradiance at any depth. The main objective of this work is to propose a new method to estimate average irradiance over large spatially heterogeneous area as it would be seen by drifting phytoplankton. Using both in situ data and 3D Monte Carlo numerical simulations of radiative transfer, we show that (1) the large-area average vertical profile of downward irradiance, Ed(z), under heterogeneous sea ice cover can be represented by a single-term exponential function and (2) the vertical attenuation coefficient for upward radiance (KLu), which is up to two times less influenced by a heterogeneous incident light field than Kd in the vicinity of a melt pond, can be used as a proxy to estimate Ed(z) in the water column

Enhancement of an Optical Fiber Sensor: Source Separation Based on Brillouin Spectrum

International audienceDistributed optical fiber sensors have gained an increasingly prominent role in structural-health monitoring. These are composed of an optical fiber cable in which a light impulse is launched by an opto-electronic device. The scattered light is of interest in the spectral domain: the spontaneous Brillouin spectrum is centered on the Brillouin frequency, which is related to the local strain and temperature changes in the optical fiber. When coupled with an industrial Brillouin optical time-domain analyzer (B-OTDA), an optical fiber cable can provide distributed measurements of strain and/or temperature, with a spatial resolution over kilometers of 40 cm. This paper focuses on the functioning of a B-OTDA device, where we address the problem of the improvement of spatial resolution. We model a Brillouin spectrum measured within an integration base of 1 m as the superposition of the elementary spectra contained in the base. Then, the spectral distortion phenomenon can be mathematically explained: if the strain is not constant within the integration base, the Brillouin spectrum is composed of several elementary spectra that are centered on different local Brillouin frequencies. We propose a source separation methodology approach to decompose a measured Brillouin spectrum into its spectral components. The local Brillouin frequencies and amplitudes are related to a portion of the integration base where the strain is constant. A layout algorithm allows the estimation of a strain profile with new spatial resolution chosen by the user. Numerical tests enable the finding of the optimal parameters, which provides a reduction to 1 cm of the 40-cm spatial resolution of the B-OTDA device. These parameters are highlighted during a comparison with a reference strain profile acquired by a 5-cm-resolution Rayleigh scatter analyzer under controlled conditions. In comparison with the B-OTDA strain profile, our estimated strain profile has better accuracy, with centimeter spatial resolut ion

Séparation de sources non négatives parcimonieuses appliquée aux spectres Brillouin acquis par capteur à fibre optique

National audienceStructure Health Monitoring (SHM) is an important issue in EDF. An optical fiber senor enables to acquire distributed strain measurements with a spatial sampling of 40cm over several kilometers. For every sensing point, a Brillouin spectrum is acquired centered on the Brillouin frequency sensitive to temperature and strain into the optical fiber. If the strain is non uniform within the integration base, then the spectrum will be distorted. A method of Non negative Matrix Factorization (NMF) enables to decompose it into several spectral components, centered on local Brillouin frequencies. A method enables to link their amplitudes to their positions within the integration base. Thus, the presented methodology enables to estimate a centimeter strain profile. It is successfully tested on experimental controlled data set. The comparison with a reference measurement enables to validate the presented methodology which permits a better sampling resolution and strain sensitivity.La surveillance d'ouvrage de grande ampleur est une problématique importante au sein d'EDF (Electricité de France). Un capteur à fibre optique permet de mesurer la déformation de manière répartie avec un pas de mesure de 40cm sur plusieurs kilomètres. A chaque distance interrogée, un spectre Brillouin est acquis. Ce spectre est centré sur une fréquence Brillouin sensible à la température et à la déformation imposée par l'ouvrage à la fibre optique. Si la déformation est non uniforme, alors le spectre est distordu. Nous proposons une méthode de Factorisation de Matrices Non négatives (FMN) afin de décomposer le spectre sur une base de spectres Brillouin élémentaires. Un algorithme basé sur leurs amplitudes relatives permet d'estimer la déformation avec une nouvelle résolution spatiale de l'ordre d'un centimètre. Cette méthodologie est testée sur des données expérimentales acquises en milieu contrôlé. La comparaison avec une mesure de référence montre la validité de cette approche

Nonnegative unmixing methodology applied on Brillouin Optical Fiber Sensor

International audienceAs a complement to conventional sensors, Distributed Optical Fiber Sensors (DOFS) have gradually played a prominent role in Structural Health Monitoring (SHM) for the last decade. The distributed Brillouin sensor enables to measure strain along kilometers of cable with a spatial resolution of 1 meter. The challenge is to have a centimeter spatial resolution to improve structure defaults detection and localization. A numerical model, based on the sensor physic, is first proposed in order to study Brillouin spectra distortion depending on strain distribution within spatial resolution. Then, based on nonnegative least squares (NNLS) problem, Brillouin spectra are decomposed into several elementary spectra. The estimated central frequencies and maxima permit to estimate a centimeter frequency distribution within the spatial resolution. It has been verified with numerical and experimental data: that method enables to enhance the accuracy and spatial resolution of the sensor from meter to centimeter

Quantification of sub-millimeter displacements caused by sinkholes, using distributed optical fiber sensors

International audience—The estimation of sinkhole-induced ground displacement is an important issue for monitoring soil structures. Distributed optical fiber sensors composed of an interrogator based on scattering effects in an optical fiber cable sensing element can be used to assess ground displacement. These sensors provide longitudinal strain measurements of the soil structure. This article proposes a methodology that enables estimation of displacement fields in the soil structure when a sinkhole appears. It also exposes an experiment which was carried out to create an artificial sinkhole instrumented by optical fiber sensors. This is the first time that those sensors are used to provide sub-millimeter vertical displacements. The first step of the methodology is to model the ground displacement under two-dimensional conditions. The longitudinal strain measured by a distributed optical fiber sensor can thus be linked to the displacement of the structure. This model is described by those parameters: the spatial extent of the displacement signature; a coefficient that depends on the interface between the optical fiber cable and the soil; the depth of the sinkhole; and the maximal vertical displacement. The second step consists of the estimation of each parameter independently. The spatial extension is given by fitting the measured strain signature with the empirical model. The depth of the sinkhole can be determined by measurement of the spatial extension of the ground-displacement profile at several observation depths in the structure. Finally, the vertical maximal displacement is furnished with high precision

Parametric Inversion of Brillouin Spectra to Enhance the Accuracy of Distributed Strain Measurement

International audienceTo ensure stability and durability of engineering structure in natural soil, optical fiber sensors have gained interest over last decade. In addition to conventional geophysical sensors, Brillouin spectra based sensor enables to perform distributed strain measurement. Its algorithm performs a strain measurement with a 40cm spatial sampling over several kilometers. The monitoring of engineering installations needs a centimeter spatial sampling and a better strain accuracy. Previous works highlighted that the industrialized algorithm has great limitation for the exploitation of the local information contained into Brillouin spectra. Indeed, based on its asymmetry and broadening, it is possible to estimate local Brillouin frequencies with a better strain accuracy. We propose here to apply a parametric inverse method using L-curve criterion to estimate the strain with a 5cm spatial sampling. To validate this method, a one-to-one scale experiment has been implemented by optical fiber cable at several depths. Comparing the distributed strain provided by the Brillouin based sensor and our algorithm with a reference strain sensor, the proposed algorithm successfully fulfills the combination of a 5cm spatial sampling over kilometers and a high strain accuracy

Biomechanical behaviour of human bile duct wall and impact of cadaveric preservation processes.

International audienceBiliary diseases are the third most common cause of surgical digestive disease. There is a close relationship between the mechanical performance of the bile duct and its physiological function. Data of biomechanical properties of human main bile duct are scarce in literature. Furthermore, mechanical properties of soft tissues are affected by these preservation procedures. The aim of the present work was, on the one hand, to observe the microstructure of the human bile duct by means of histological analysis, on the other hand, to characterize the mechanical behavior and describe the impact of different preservation processes. A mechanical study in a controlled environment consisting of cyclic tests was made. The results of the mechanical tests are discussed and explained using the micro-structural observations. The results show an influence of the loading direction, which is representative of an anisotropic behavior. A strong hysteresis due to the viscoelastic properties of soft tissues was also observed. Embalming and freezing preservation methods had an impact on the biomechanical properties of human main bile duct, with fiber network deterioration. That may further provide a useful quantitative baseline for anatomical and surgical training using embalming and freezing

Séparation de sources pour l'estimation de la déformation mesurée par capteur à fibre optique

National audience– La surveillance d'un ouvrage est une problématique importante pour augmenter sa durée de vie tout en garantissant sa stabilité. Un moyen efficace pour la surveillance de grands ouvrages linéaires est le capteur à fibre optique par effet Brillouin qui fournit une mesure de la déformation sur plusieurs dizaines de kilomètres de manière répartie avec un pas de mesure de 40 cm. Cette mesure est sensible à la déformation de la fibre optique mais également aux variations de température. Pour interpréter le signal fourni par un tel capteur il est alors nécessaire de séparer l'influence de l'effet de la température de la mesure de déformation. Sachant que dans une structure géotechnique des déformations thermiques apparaissent à cause de la dilatation du matériau, l'objectif est d'estimer les variations de la déformation athermique. Nous proposons alors une méthodologie de séparation de source basée sur le filtre de Wiener. En prenant en compte des informations a priori liées à la température dans la fibre optique mais également à la température extérieure à l'ouvrage, elle permet d'estimer la déformation irréversible dans l'ouvrage. Elle a été testée sur des données acquises sur une digue en terre, et l'influence de la mesure des sources est discutée. Abstract – Structural Health Monitoring is an important issue to increase the exploitation age of a structure as well as its structure. An efficient sensor to measure the strain is the optical fiber sensor, which provides a measure into the optical fiber with a 40cm spatial resolution. This measurement is sensitive to the strain but also to the temperature into the optical fiber. To interpret the strain signal, the influence of the variations of temperature has to be corrected from the given measurement. Knowing that in a geotechnical structure some reversible strain variations appear because of the dilatation of the material, the goal is the estimation of the irreversible strain into a geotechnical structure. We propose a separation source methodology based on the Wiener filter. Taking into account prior temperature measurements, this methodology enables to estimate the irreversible strain into the structure. It has been tested on data acquired into a dyke, and the influence on the sources measurement is discussed

Treatment of mycotic superior mesenteric vein pseudoaneurysm via placement of covered endovascular stent

Vascular pseudoaneurysms are a rare yet life-threatening complication of untreated pancreatic pseudocysts related to their high risk of rupture and bleeding. Several studies and reports have established endovascular approaches as a successful first-line therapy in the management of arterial pancreatic pseudoaneurysms. However, no reports have been published describing endovascular repair of a venous pseudoaneurysm that developed after infection of a chronically stable pancreatic pseudocyst, most likely due to its rare occurrence. We report in this technical note the treatment of a superior mesenteric vein pseudoaneurysm that developed as a result of an infected small pancreatic pseudocyst, by radiologic placement of a covered endovascular stent