The knock-out of ARP3a gene affects F-actin cytoskeleton organization altering cellular tip growth, morphology and development in moss Physcomitrella patens.

The seven subunit Arp2/3 complex is a highly conserved nucleation factor of actin microfilaments. We have isolated the genomic sequence encoding a putative Arp3a protein of the moss Physcomitrella patens. The disruption of this ARP3A gene by allele replacement has generated loss-of-function mutants displaying a complex developmental phenotype. The loss-of function of ARP3A gene results in shortened, almost cubic chloronemal cells displaying affected tip growth and lacking differentiation to caulonemal cells. In moss arp3a mutants, buds differentiate directly from chloronemata to form stunted leafy shoots having differentiated leaves similar to wild type. Yet, rhizoids never differentiate from stem epidermal cells. To characterize the F-actin organization in the arp3a-mutated cells, we disrupted ARP3A gene in the previously described HGT1 strain expressing conditionally the GFP-talin marker. In vivo observation of the F-actin cytoskeleton during P. patens development demonstrated that loss-of-function of Arp3a is associated with the disappearance of specific F-actin cortical structures associated with the establishment of localized cellular growth domains. Finally, we show that constitutive expression of the P. patens Arp3a and its Arabidopsis thaliana orthologs efficiently complement the mutated phenotype indicating a high degree of evolutionary conservation of the Arp3 function in land plants.

Two-dimensional probabilistic inversion of plane-wave electromagnetic data: Methodology, model constraints and joint inversion with electrical resistivity data

Probabilistic inversion methods based on Markov chain Monte Carlo (MCMC) simulation are well suited to quantify parameter and model uncertainty of nonlinear inverse problems. Yet, application of such methods to CPU-intensive forward models can be a daunting task, particularly if the parameter space is high dimensional. Here, we present a 2-D pixel-based MCMC inversion of plane-wave electromagnetic (EM) data. Using synthetic data, we investigate how model parameter uncertainty depends on model structure constraints using different norms of the likelihood function and the model constraints, and study the added benefits of joint inversion of EM and electrical resistivity tomography (ERT) data. Our results demonstrate that model structure constraints are necessary to stabilize the MCMC inversion results of a highly discretized model. These constraints decrease model parameter uncertainty and facilitate model interpretation. A drawback is that these constraints may lead to posterior distributions that do not fully include the true underlying model, because some of its features exhibit a low sensitivity to the EM data, and hence are difficult to resolve. This problem can be partly mitigated if the plane-wave EM data is augmented with ERT observations. The hierarchical Bayesian inverse formulation introduced and used herein is able to successfully recover the probabilistic properties of the measurement data errors and a model regularization weight. Application of the proposed inversion methodology to field data from an aquifer demonstrates that the posterior mean model realization is very similar to that derived from a deterministic inversion with similar model constraints.

Aetiologies of pulseless electrical activity in out-of-hospital cardiac arrests:A retrospective study and analysis of specific causes

Background: Pulseless electrical activity (PEA) cardiac arrest is defined as a cardiac arrest (CA) presenting with a residual organized electrical activity on the electrocardiogram. In the last decades, the incidence of PEA has regularly increased, compared to other types of CA like ventricular fibrillation or pulseless ventricular tachycardia. PEA is frequently induced by reversible conditions. The "4 (or 5) H" & "4 (or 5) T" are proposed as a mnemonic to asses for Hypoxia, Hypovolemia, Hypo- /Hyperkalaemia, Hypothermia, Thrombosis (cardiac or pulmonary), cardiac Tamponade, Toxins, and Tension pneumothorax. Other pathologies (intracranial haemorrhage, severe sepsis, myocardial contraction dysfunction) have been identified as potential causes for PEA, but their respective probability and frequencies are unclear and they are not yet included into the resuscitation guidelines. The aim of this study was to analyse the aetiologies of PEA out-of-hospital CA, in order to evaluate the relative frequencies of each cause and therefore to improve the management of patients suffering a PEA cardiac arrest. Method: This retrospective study was based on data routinely and prospectively collected for each PEMS intervention. All adult patients treated from January 1st 2002 to December 2012 31st by the PEMS for out-of-hospital cardiac arrest, with PEA as the first recorded rhythm, and admitted to the emergency department (ED) of the Lausanne University Hospital were included. The aetiologies of PEA cardiac arrest were classified into subgroups, based on the classical H&T's classification, supplemented by four other subgroups analysis: trauma, intra-cranial haemorrhage (ICH), non-ischemic cardiomyopathy (NIC) and undetermined cause. Results: 1866 OHCA were treated by the PEMS. PEA was the first recorded rhythm in 240 adult patients (13.8 %). After exclusion of 96 patients, 144 patients with a PEA cardiac arrest admitted to the ED were included in the analysis. The mean age was 63.8 ± 20.0 years, 58.3% were men and the survival rate at 48 hours was 29%. 32 different causes of OHCA PEA were established for 119 patients. For 25 patients (17.4 %), we were unable to attribute a specific cause for the PEA cardiac arrest. Hypoxia (23.6 %), acute coronary syndrome (12.5%) and trauma (12.5 %) were the three most frequent causes. Pulmonary embolism, Hypovolemia, Intoxication and Hyperkaliemia occurs in less than 10% of the cases (7.6 %, 5.6 %, 3.5%, respectively 2.1 %). Non ischemic cardiomyopathy and intra-cranial haemorrhage occur in 8.3 % and 6.9 %, respectively. Conclusions: According to our results, intra-cranial haemorrhage and non-ischemic cardiomyopathy represent noticeable causes of PEA in OHCA, with a prevalence equalling or exceeding the frequency of classical 4 H's and 4 T's aetiologies. These two pathologies are potentially accessible to simple diagnostic procedures (native CT-scan or echocardiography) and should be included into the 4 H's and 4 T's mnemonic.

Direct three-dimensional myocardial strain tensor quantification and tracking using zHARP.

Images of myocardial strain can be used to diagnose heart disease, plan and monitor treatment, and to learn about cardiac structure and function. Three-dimensional (3D) strain is typically quantified using many magnetic resonance (MR) images obtained in two or three orthogonal planes. Problems with this approach include long scan times, image misregistration, and through-plane motion. This article presents a novel method for calculating cardiac 3D strain using a stack of two or more images acquired in only one orientation. The zHARP pulse sequence encodes in-plane motion using MR tagging and out-of-plane motion using phase encoding, and has been previously shown to be capable of computing 3D displacement within a single image plane. Here, data from two adjacent image planes are combined to yield a 3D strain tensor at each pixel; stacks of zHARP images can be used to derive stacked arrays of 3D strain tensors without imaging multiple orientations and without numerical interpolation. The performance and accuracy of the method is demonstrated in vitro on a phantom and in vivo in four healthy adult human subjects.

Post-Plutonic Magmatism: from the Source to the Emplacement of an Upper Crustal Dyke Swarm, Adamello Massif, Italy

Magmas of the arc-tholeiitic and calc-alkaline differentiation suites contribute substantially to the formation of continental crust in subduction zones. Different geochemical-petrological models have been put forward to achieve evolved magmas forming large volumes of tonalitic to granitic plutons, building an important part of the continental crust. Primary magmas produced in the mantle wedge overlying the subducted slab migrate through the mantle and the crust. During the transfer, magma can accumulate in intermediate reservoirs at different levels where crystallization leads to differentiation and the heat transfer from the magma, together with gained heat from solidification, lead to partial melting of the crust. Partial melts can be assimilated and mix with more primitive magma. Moreover, already formed crystal cumulates or crystal mushes can be recycled and reactivated to transfer to higher crustal levels. Magma transport in the crust involves fow through fractures within a brittle elastic rock. The solidified magma filled crack, a dyke, can crosscut previously formed geological structures and thus serves as a relative or absolute time marker. The study area is situated in the Adamello massif. The Adamello massif is a composite of plutons that were emplaced between 42 and 29 million years. A later dyke swarm intruded into the southern part of the Adamello Batholith. A fractionation model covering dyke compositions from picrobasalts to dacites results in the cummulative crystallization of 17% olivine, 2% Cr-rich spinel, 18% clinopyroxene, 41% amphibole, 4% plagioclase and 0.1% magnetite to achieve an andesitic composition out of a hydrous primitive picrobasalt. These rocks show a similar geochemical evolution as experimental data simulating fractional crystallization and associated magma differentiation at lower crustal depth (7-10 kbar). The peraluminous, corundum normative composition is one characteristic of more evolved dacitic magmas, which has been explained in a long lasting debate with two di_erent models. Melting of mafic crust or politic material provides one model, whereas an alternative is fractionation from primary mantle derived melts. Amphibole occurring in basaltic-andesitic and andesitic dyke rocks as fractionating cumulate phase extracted from lower crustal depth (6-7.5 kbar) is driving the magmas to peraluminous, corundum normative compositions, which are represented by tonalites forming most of the Adamello Batholith. Most primitive picrobasaltic dykes have a slightly steepened chondrite normalized rare earth elements (REE) pattern and the increased enrichment of light-REE (LREE) for andesites and dacites can be explained by the fractional crystallization model originating from a picrobasalt, taking the changing fractionating phase assemblage and temperature into account. The injection of hot basaltic magma (~1050°C) in a closely spaced dyke swarm increases the surface of the contact to the mainly tonalitic wallrock. Such a setting induces partial melting of the wall rock and selective assimilation. Partial melting of the tonalite host is further expressed through intrusion breccias from basaltic dykes. Heat conduction models with instantaneous magma injection for such a dyke swarm geometry can explain features of partial melting observed in the field. Geochemical data of minerals and bulk rock further underline the selective or bulk assimilation of the tonalite host rock at upper crustal levels (~2-3 kbar), in particular with regard to light ion lithophile elements (LILE) such as Sr, Ba and Rb. Primitive picrobasalts carry an immiscible felsic assimilant as enclaves that bring along refractory rutile and zircon with textures typically found in oceanic plagiogranites or high pressure/low-temperature metamorphic rocks in general. U-Pb data implies a lower Cretaceous age for zircon not yet described as assimilant in Eocene to Oligocene magmatic rocks of the Central Southern Alps. The distribution of post-plutonic dykes in large batholiths such as the Adamello is one of the key features for understanding the regional stress field during the post-batholith emplacement cooling history. The emplacement of the regional dyke swarm covering the southern part of the Adamello massif was associated with consistent left lateral strike-slip movement along magma dilatation planes, leading to en echelon segmentation of dykes. Through the dilation by magma of pre-existing weaknesses and cracks in an otherwise uniform host rock, the dyke propagation and according orientation in the horizontal plane adjusted continuously perpendicular to least compressive remote stress σ3, resulting in an inferred rotation of the remote principal stress field. Les magmas issus des zones de subduction contribuent substantiellement à la formation de la croûte continentale. Les plutons tonalitiques et granitiques représentent, en effet, une partie importante de la croûte continentale. Des magmas primaires produits dans le 'mantle wedge ', partie du manteau se trouvant au-dessus de la plaque plongeante dans des zones de subduction, migrent à travers le manteau puis la croûte. Pendant ce transfert, le magma peut s'accumuler dans des réservoirs intermédiaires à différentes profondeurs. Le stockage de magma dans ces réservoirs engendre, d'une part, la différentiation des magmas par cristallisation fractionnée et, d'autre part, une fusion partielle la croûte continentale préexistante associée au transfert de la chaleur des magmas vers l'encaissant. Ces liquides magmatiques issus de la croûte peuvent, ensuite, se mélanger avec des magmas primaires. Le transport du magma dans la croûte implique notamment un flux de magma à travers différentes fractures recoupant les roches encaissantes élastiques. Au cours de ce processus de migration, des cumulats de cristaux ou des agrégats de cristaux encore non-solidifiés, peuvent être recyclés et réactivés pour être transportés à des niveaux supérieures de la croûte. Le terrain d'étude est situé dans le massif d'Adamello. Celui-ci est composé de plusieurs plutons mis en place entre 42 et 29 millions d'années. Dans une phase tardive de l'activité magmatique liée à ce batholite, une série de filons de composition variable allant de picrobasalte à des compositions dacitiques s'est mise en place la partie sud du massif. Deux modèles sont proposés dans la littérature, pour expliquer la formation des magmas dacitiques caractérisés par des compositions peralumineux (i.e. à corindon normatif). Le premier modèle propose que ces magmas soient issus de la fusion de matériel mafique et pélitique présent dans la partie inférieur de la croûte, alors que le deuxième modèle suggère une évolution par cristallisation fractionnée à partir de liquides primaires issus du manteau. Un modèle de cristallisation fractionnée a pu être développé pour expliquer l'évolution des filons de l'Adamello. Ce modèle explique la formation des filons dacitiques par la cristallisation fractionnée de 17% olivine, 2% spinelle riche en Cr, 18% clinopyroxène, 41% amphibole, 4% plagioclase et 0.1% magnetite à partir de liquide de compositions picrobasaltiques. Ce modèle prend en considération les contraintes pétrologiques déduites de l'observation des différents filons ainsi que du champ de stabilité des différentes phases en fonction de la température. Ces roches montrent une évolution géochimique similaire aux données expérimentales simulant la cristallisation fractionnée de magmas évoluant à des niveaux inférieurs de la croûte (7-10 kbar). Le modèle montre, en particulier, le rôle prépondérant de l'amphibole, une phase qui contrôle en particulier le caractère peralumineux des magmas différentiés ainsi que leurs compositions en éléments en traces. Des phénomènes de fusion partielle de l'encaissant tonalitique lors de la mise en place de _lons mafiques sont observée sur le terrain. L'injection du magma basaltique chaud (~1050°C) sous forme de filons rapprochés augmente la surface du contact avec l'encaissante tonalitique. Une telle situation produit la fusion partielle des roches encaissantes nécessaire à l'incorporation d'enclaves mafiques observés au sein des tonalites. Pour comprendre les conditions nécessaires pour la fusion partielle des roches encaissantes, des modèles de conduction thermique pour une injection simultanée d'une série de filons ont été développées. Des données géochimiques sur les minéraux et sur les roches totales soulignent qu'au niveau supérieur de la croûte, l'assimilation sélective ou totale de l'encaissante tonalitique modifie la composition du liquide primaire pour les éléments lithophiles tel que le Sr, Ba et Rb. Un autre aspect important concernant la pétrologie des filons de l'Adamello est la présence d'enclaves felsiques dans les filons les plus primitifs. Ces enclaves montrent, en particulier, des textures proches de celles rencontrées dans des plagiogranites océaniques ou dans des roches métamorphiques de haute pression/basse température. Ces enclaves contiennent du zircon et du rutile. La datations de ces zircons à l'aide du géochronomètre U-Pb indique un âge Crétacé inférieur. Cet âge est important, car aucune roche de cet âge n'a été considérée comme un assimilant potentiel pour des roches magmatiques d'âge Eocène à Oligocène dans les Alpes Sud Centrales. La réparation spatiale des filons post-plutoniques dans des grands batholites tel que l'Adamello, est une caractéristique clé pour la compréhension des champs de contraintes lors du refroidissement du batholite. L'orientation des filons va, en particulier, indiqué la contrainte minimal au sein des roches encaissante. La mise en place de la série de filon recoupant la partie Sud du massif de l'Adamello est associée à un décrochement senestre, un décrochement que l'on peut lié aux contraintes tectoniques régionales auxquelles s'ajoutent l'effet de la dilatation produite par la mise en place du batholite lui-même. Ce décrochement senestre produit une segmentation en échelon des filons.