Permeability of polydisperse solid foams.

The effect of polydispersity on foam permeability is investigated by numerical simulations. Foam structures are first generated by Laguerre tessellations via the Neper software and relaxed to minimize the surface energy via the Surface Evolver software. The fluid flow and permeability are then calculated by means of pore-network simulations, by considering either fully open-cell foams or foams with randomly selected closed windows. Different configurations of window aperture are used, including identical window aperture size, identical window aperture ratio, or random window aperture ratio. The main results are obtained for the case of foams having identical and uniform window aperture ratios. For such foams and at constant mean pore size, foam permeability is found to strongly increase with the polydispersity degree. The numerical results are employed to discuss the validity of the mean pressure field assumption used to calculate the foam permeability, the effect of small pores, and the definition of an equivalent Kelvin foam size. We show that as long as the fluctuations of the window aperture ratio remain low, foam permeability can be estimated by using the mean pressure field hypothesis. The weak effect of small pores on permeability is related to their small contribution to the overall fluid volume fraction. Finally, various estimations of the equivalent Kelvin foam size based on pore-size distribution are proposed.

Multiscale prediction of acoustic properties for glass wools: Computational study and experimental validation.

This work is concerned with the multiscale prediction of the transport and sound absorption properties associated with industrial glass wool samples. In the first step, an experimental characterization is performed on various products using optical granulometry and porosity measurements. A morphological analysis, based on scanning electron imaging, is further conducted to identify the probability density functions associated with the fiber angular orientation. The key morphological characterization parameters of the microstructure, which serve as input parameters of the model, include the porosity, the weighted volume diameter accounting for both lengths and diameters of the analyzed fibers (and therefore the specific surface area of the random fibrous material), and the preferred out-of-plane fiber orientation generated by the manufacturing process. A computational framework is subsequently proposed and allows for the reconstruction of an equivalent fibrous network. A fully stochastic microstructural model, parameterized by the probability laws inferred from the database, is also proposed herein. Multiscale simulations are carried out to estimate transport properties and sound absorption. With no adjustable parameter, the results accounting for ten different samples obtained with various processing parameters are finally compared with the experimental data and used to assess the relevance of the reconstruction procedures and the multiscale computations.

Five cases of acute Zika virus infection in French women of reproductive age returning from Central and South America.

INTRODUCTION: The favorable season for Aedes albopictus circulation has started in Europe and may lead to autochthonous transmission of Zika virus. Health care providers should be familiar with evocative clinical presentations and able to give updated information to women of reproductive age infected by Zika virus. OBSERVATIONS: We report five laboratory-confirmed Zika virus infections imported to metropolitan France from Central and South America between January and April, 2016. The five young women were not connected and not pregnant; common presentation combined a rash with persistent arthralgia. Zika virus was identified by RT-PCR from serum or urines, between two and eight days after the onset of the symptoms. CONCLUSION: As the duration of potential materno-foetal infectivity is still unknown, we were unable to answer with certitude to the patients' questions about the time interval to respect before attempting a pregnancy: one of them became pregnant one month after the diagnosis.

Stochastic hyperelastic constitutive laws and identification procedure for soft biological tissues with intrinsic variability.

In this work, we address the constitutive modeling, in a probabilistic framework, of the hyperelastic response of soft biological tissues. The aim is on the one hand to mimic the mean behavior and variability that are typically encountered in the experimental characterization of such materials, and on the other hand to derive mathematical models that are almost surely consistent with the theory of nonlinear elasticity. Towards this goal, we invoke information theory and discuss a stochastic model relying on a low-dimensional parametrization. We subsequently propose a two-step methodology allowing for the calibration of the model using standard data, such as mean and standard deviation values along a given loading path. The framework is finally applied and benchmarked on three experimental databases proposed elsewhere in the literature. It is shown that the stochastic model allows experiments to be accurately reproduced, regardless of the tissue under consideration.

AKRP and EMB506 are two ankyrin repeat proteins essential for plastid differentiation and plant development in Arabidopsis.

EMB506 is a chloroplast protein essential for embryo development, the function of which is unknown. A two-hybrid interaction screen was performed to provide insight into the role of EMB506. A single interacting partner, AKRP, was identified among a cDNA library from immature siliques. The AKR gene (Zhang et al., 1992, Plant Cell 4, 1575-1588) encodes a protein containing five ankyrin repeats, very similar to EMB506. Protein truncation series demonstrated that both proteins interact through their ankyrin domains. Using reverse genetics, we showed that loss of akr function resulted in an embryo-defective (emb) phenotype indistinguishable from the emb506 phenotype. Transient expression of the signal peptide of AKRP fused to green fluorescent protein demonstrated the chloroplast localization of AKRP. The ABI3 promoter was used to express AKR in a seed-specific manner in order to analyse the post-embryonic effect of AKR loss of function in akr/akr seedlings. Homozygous fertile and viable akr/akr plants were obtained. These plants exhibited mild to severe defects in chloroplast and leaf cellular organization. We conclude that EMB506 and AKRP are involved in crucial and tightly controlled events in plastid differentiation linked to cell differentiation, morphogenesis and organogenesis during the plant life cycle.

Differential expression of the Arabidopsis genes coding for Em-like proteins.

Late embryogenesis abundant (lea) genes are a large and diverse group of genes highly expressed during late stages of seed development. Five major groups of LEA proteins have been described. Two Em genes (group I lea genes) are present in the genome of Arabidopsis thaliana L., AtEm1 and AtEm6. Both genes encode for very similar proteins which differ basically in the number of repetitions of a highly hydrophilic amino acid motif. The spatial patterns of expression of the two Arabidopsis Em genes have been studied using in situ hybridization and transgenic plants transformed with the promoters of the genes fused to the beta-glucuronidase reporter gene (uidA). In the embryo, AtEm1 is preferentially expressed in the pro-vascular tissues and in meristems. In contrast, AtEm6 is expressed throughout the embryo. The activity of both promoters disappears rapidly after germination, but is ABA-inducible in roots of young seedlings, although in different cells: the AtEm1 promoter is active in the internal tissues (vasculature and pericycle) whereas the AtEm6 promoter is active in the external tissues (cortex, epidermis and root hairs). The AtEm1 promoter, but not AtEm6, is also active in mature pollen grains and collapsed nectaries of young siliques. These data indicate that the two Em proteins could carry out at least slightly different functions and that the expression of AtEm1 and AtEm6 is controlled at, at least, three different levels: temporal, spatial and hormonal (ABA).

The BANYULS gene encodes a DFR-like protein and is a marker of early seed coat development.

Mutations in the BANYULS (BAN) gene lead to precocious accumulation of anthocyanins in immature seed coat in Arabidopsis. The ban -1 allele has been isolated from a collection of T-DNA transformants and found to be tagged by the integrative molecule. The sequencing of wild-type and two independent mutant alleles confirmed the identity of the gene. Analysis of the full-length cDNA sequence revealed an open reading frame encoding a 342 amino acid protein which shared strong similarities with DFR and other enzymes of the phenylpropanoid biosynthesis pathway. BAN expression was restricted to the endothelium of immature seeds at the pre-globular to early globular stages of development as predicted from the maternal inheritance of the phenotype, and therefore represents a marker for early differentiation and development of the seed coat. BAN is probably involved in a metabolic channelling between the production of anthocyanins and pro-anthocyanidins in the seed coat.

Structure, organization and expression of two closely related novel Lea (late-embryogenesis-abundant) genes in Arabidopsis thaliana.

We have isolated and sequenced a 9.5 kb genomic region from A. thaliana, located on chromosome 2, which contains two tandemly arranged closely related genes (AtM10 and AtM17) coding for a new family of LEA proteins. The deduced proteins have a molecular mass of 11 and 29 kDa, respectively, are extremely hydrophilic except at their N-termini and share 70% amino acid (aa) identity. A 47 aa motif containing a 6-cysteine domain is present once in AtM10 and four times in AtM17. The short intergenic region, the identical position of the intron and the overall sequence homology suggest that these two genes evolved through a duplication event. This conclusion is supported by the presence of two homologous strictosidine synthase-like (pseudo)genes downstream from AtM17 and AtM10. Expression studies, using AtM10 and AtM17 cDNAs, revealed that both transcripts accumulate exclusively in seeds from late embryogenesis until two days after imbibition. Expression of both genes in young seedlings is repressed during ABA, salt or drought treatment, whereas a cold stress induces the expression of AtM17 only. In situ hybridization revealed that AtM10 transcripts are detected throughout the embryo while those of AtM17 are more localized to cotyledon cells.

The EMB 506 gene encodes a novel ankyrin repeat containing protein that is essential for the normal development of Arabidopsis embryos.

The EMB 506 gene of Arabidopsis, required for the normal development of the embryo beyond the globular stage, has been cloned. The gene encodes a protein of predicted size 35 kDa that contains five ankyrin (ANK) repeats within the C terminal moiety. ANK repeats are conserved domains of 33 amino acids involved in specific recognition of protein partners. The EMB 506 protein was detected at different stages of silique development but accumulated preferentially in the mature cauline leaves. The rescue of homozygous emb 506 embryos by complementation with the wild-type sequence cDNA demonstrated that the emb mutation is a consequence of the T-DNA insertion and that integration and expression of the transgene occurred during gametogenesis and/or early embryo development. In addition to the drastic effect of the emb 506 mutation during embryo development, complementation experiments revealed another effect of the gene: emb 506 plants transformed with the wild-type EMB 506 sequence were able to produce viable seeds but showed a reduction of apical dominance and the presence of adventitious buds or bracts along the stem. This result supports the idea that genes essential for embryogenesis may also be required at other stages of the plant life cycle.

Identification of a new exon of the brain microtubule-associated protein 2.

The 5'-region of the transcripts encoding the HMW-(MAP2b) and LMW-(MAP2c) microtubule associated proteins in the brain was amplified by RT-PCR. The sequencing of cloned PCR fragments allowed to identify a new variant of brain HMW-MAP2 which contained, compared to MAP2b, an insertion of 246 bp located downstream the 5'-junction between MAP2b and MAP2c and that does not alter the open reading frame of MAP2b. The number of amino acid residues encoded by this insertion increases the molecular weight by 8.5 kDa i.e. corresponds to the difference in apparent size between MAP2a and MAP2b. A LMW-MAP2 PCR amplification product containing this insertion has been also identified. Genomic Southern blot analysis confirmed that this region belongs to the MAP2 gene and is located on a single exon.

Tau and microtubule-associated protein 2c transfection and neurite outgrowth in ND 7/23 cells.

Neuronal hybrid ND 7/23 cells, which display sensorylike properties, develop neurites when cultured in the presence of either dibutyryl cyclic AMP plus nerve growth factor (DBcAMP + NGF) or retinoic acid or a phorbol ester derivative, although they express only trace amounts of the microtubule-associated tau proteins and low levels of microtubule-associated protein 2c (MAP2c). Nondifferentiated ND cells transfected with tau cDNAs did not develop neurites, whereas very short cell processes were formed in MAP2c-transfected cells. tau and MAP2 antibodies labeled microtubule bundles displayed in a ring array underneath the surface of the transfected cells and short microtubules starting from the cell center. After differentiation in the presence of DBcAMP + NGF, the same bundle organization was observed in the transfected cells. In addition, tau and MAP2 antibodies stained a short section of the formed neurites. These data demonstrate that the expression of tau protein is not sufficient to induce neurite extension and that other proteins induced by morphogens are more important to initiate morphological differentiation of this cell line.

Two novel HMW MAP2 variants with four microtubule-binding repeats and different projection domains.

The brain microtubule-associated protein MAP2 is composed of two high molecular (MAP2a and b) and one low molecular (MAP2c) weight isoforms. All these forms were thought to contain three repeated microtubule-binding domains in their C-terminal region but a MAP2c variant containing four repeats has recently been identified. We report here the existence of two high molecular weight MAP2 isoforms with four microtubule-binding domains in the sensory neuronal cell line ND 7/23. A stretch of 135 bp is missing in one of these forms suggesting that several HMW MAP2 variants can be produced by alternative splicing.

High molecular weight tau distribution and microtubule stability in neuroblastoma N115 cells.

The localization of high molecular weight (HMW) tau proteins in neuroblastoma N115 cells and of their transcripts was compared to that of non-tyrosinated and tyrosinated tubulin before and after treatment with depolymerizing drugs. Microtubules stained by tau antibodies were present both in a limited region of the cell center and in the cell processes, whereas tau transcripts were detected only in the cell body. The microtubules localized in the cell center and labeled by tau antibodies resisted colcemid treatment, whereas those in the neurites were completely depolymerized by the drug. Microtubules containing stable and unstable microtubule tracts were identified in the neurites after colcemid treatment. These composite microtubules were not labeled by tau antibodies. It is concluded that stable and unstable polymers--localized in the cell center and in the neurites, respectively--contain HMW tau proteins, whereas composite microtubules displayed in the cell processes do not. Microtubule stability in this cell line does not therefore seem to be related to the association of tau proteins to the polymers but, rather, to posttranslational modifications of the tubulin subunits.

Heterogeneity of the high molecular weight tau proteins in N115 neuroblastoma cells.

The sequence of a high molecular weight (HMW) tau cDNA cloned from a neuroblastoma N115 library contains, in addition to the C- and N-terminal and middle regions present in the low molecular weight mouse brain tau proteins, a 711-bp nonhomologous domain (exon 4a) and a region of 198 bp corresponding to exon 6 of the tau gene. Protein immunoblot analysis, performed with antibodies specific either for a sequence present in the N-terminal region of all the tau variants or for exon 4a revealed several bands suggesting that more than one tau form is expressed in this cell line. Northern blot experiments performed with a number of cDNA probes spanning domains common and uncommon to low molecular weight and HMW tau allowed the identification of four tau transcripts differing in the size of their coding and noncoding regions. All these transcripts contain the sequence encoded by exon 6, but two of them lack exon 4a. As shown by RNase protection assays, the N-terminal region of these transcripts is also variable and contains either exon 1, or exons 1 and 2, or exons 1-3. Yet all these HMW tau forms contain four homologous repeats in their C-terminal domain both in the differentiated and nondifferentiated cells, i.e., have adult characteristics. In conclusion, the data reported in this article demonstrate that several HMW tau variants are expressed in neuroblastoma N115 cells and that the transition between immature to mature tau forms occurring during brain development is not required for neurite outgrowth during morphological differentiation of this cell line.

[High molecular weight tau proteins and acquisition of neuronal polarity in peripheral nervous system]. / Protéines tau de haut poids moléculaire et acquisition de la polarité neuronale dans le système nerveux périphérique.

Several variants of the microtubule-associated tau proteins, are expressed during brain development and in adulthood. These entities are required to define the polarity of the neuron and the architecture of the axon but differ in sequence and in their microtubule polymerizing activity. Here, we describe a new group of high molecular weight tau proteins that contain one or two additional exons of 711 and 198 bp in their middle region and a variable N-terminal domain. These high molecular weight tau variants are preferentially expressed in the peripheral nervous system. Immunohistochemical studies showed that they are also present in the dorsal horn of the spinal cord where they are probably transported by sensory fibers arising in the periphery. However, a minor fraction of these proteins is present in the motor neurons of the ventral horn. Similar studies were performed with the neuroblastoma N115 cell line which can be differentiated in vitro and expresses only high molecular weight tau forms. In the non differentiated cells, tau antibodies label the domain of the cell body localized around the centrosome whereas, after differentiation, the cell process facing this structure is also stained. These data suggest that axonal polarity is predetermined by the localization of tau proteins in the domain of the cell body defined by the centrosome.

A tau-related protein of 130 kDa is present in Alzheimer brain.

Two abnormal entities of 69 and 130 kDa, immunologically related to the microtubule-associated tau proteins, are present in the hippocampus and the frontal cortex of the Alzheimer brain, which contain a large number of neurofibrillary tangles (NFTs), but are absent in the cerebellum, which does not contain these structures. Epitope mapping with antibodies spanning domains present in the N-terminal, middle, and C-terminal tau sequence demonstrated that the 69- and 130-kDa entities belong to the tau family. Both the 69- and the 130-kDa proteins were found in an insoluble form and were the major tau species present in purified NFTs. A procedure was devised that allowed us to prepare from Alzheimer hippocampi two NFT fractions differing in size (20 and 3 microns), both of which contained the tau entities of 130 and 69 kDa.

Protein TAU variants present in paired helical filaments (PHFs) of Alzheimer brains.

Polyclonal anti-TAU antisera directed against native Tau protein and the NH2-terminal side of the mouse TAU sequence were used to determine the nature of the TAU variants present in Alzheimer brains and in PHFs. These antibodies labelled specifically neurofibrillary tangles and plaque neurites in Alzheimer brains. On immunoblots of PHF extracts, two entities of 69 and 130 kDa were identified. These TAU-related species were absent from control brains. Protein immunoblot of total Alzheimer and control supernatants were shown to contain the same 4-5 TAU variants but none of the 69 and 130 TAU-related entities found in PHFs. These data suggest that specific TAU species are present in PHFs.

Expression of Tau protein and Tau mRNA in the cerebellum during axonal outgrowth.

UNLABELLED: "In situ" hybridization and immunohistochemical analysis of the expression of Tau mRNAs and Tau proteins in the developing cerebellum showed that: 1. At early postnatal stages Tau mRNAs are expressed in the deeper region of the external granular layer (EGL II) i.e. in the cells that begin to migrate from the proliferative zone. Little labeling was seen in the upper layer (EGL I) where the cerebellar interneurons actively proliferate during the first two postnatal weeks. Anti-Tau antibodies failed to detect Tau proteins both in EGL I and II. 2. Tau transcripts were also clearly detected in the migrating cells present in the molecular layer; no Tau immunoreactivity was seen in this layer. This suggests that Tau mRNAs remain very poorly translated in the migrating granule cells and in the other interneurons. 3. Tau proteins begin to be detected at postnatal day 8 in the molecular layer but only at the level of the parallel fibers that are present in the Purkinje cell dendritic field. This suggests that the Tau mRNAs transcribed in the migrating cells are not actively translated for several days and that Tau proteins accumulate only in the more mature sections of their axons, the parallel fibers. IN CONCLUSION: Tau mRNAs are transcribed in the migrating cells several days before Tau proteins are actively translated and transported to their axons. Tau proteins accumulation occurs only at the end of granule cell migration i.e. when the parallel fibers interact with their post-synaptic counterparts, the dendrites of the Purkinje cells. Thus, axonal outgrowth and differentiation seem to be a multistep process.

Dendritic and axonal distribution of the microtubule-associated proteins MAP2 and tau in the cerebellum of the nervous mutant mouse.

The fate of the different types of axons and dendrites in the nervous mutant mouse has been studied with antibodies raised against the two major microtubule-associated proteins, MAP2 and tau. These proteins are specific markers of dendrites and axons, respectively. (1) Immunoblot analysis of cerebellar extracts showed that MAP2 concentration is markedly reduced (by approximately 90%) in the adult mutant. A 60% decrease was already noticed at day 20 postnatal, i.e., when all the Purkinje cells are present in their normal location and in apparent normal number. (2) Immunohistochemical studies performed at an adult stage with anti MAP2 antibodies showed marked alterations in the shape of the dendrites of the rare surviving Purkinje cells present in the lateral sections of the cerebellum of the mutant. In the vermis, where 50% of the cells survive in adulthood, the MAP2 antibody revealed both clusters of cells with a normal density and an intricated and extensive pattern of dendritic arborization and isolated cells showing either an apparently normal or an altered dendritic tree. (3) At day 20 postnatal the same antibody revealed, in the lateral sections severe abnormalities of the dendrites of the Purkinje cells which were different from those seen in adulthood in the vermis. Thus, although few or any Purkinje cells are dead at this stage, a large proportion of them have already profound dendritic alterations. In contrast, in the vermis the Purkinje cells and their dendritic tree are undistinguishable at this stage from those of the unaffected normal mice. (4) Immunoblot and immunohistochemical studies performed with the anti Tau antibody suggested that the majority of the axonal fibers of the cerebellum were present both at day 20 postnatal and at later adult stages. This suggests that, although deprived of their postsynaptic targets these axons can survive for a long time after Purkinje cell death. However, an anti-neurofilament monoclonal antibody which stains specifically the axons of the basket cells, revealed an altered morphology of the basket cell nest in the regions devoid of Purkinje cells. (5) In conclusion the alterations in the morphology of dendrites seem to represent an early event of Purkinje cell degeneration and to be correlated with a marked decrease in expression of MAP2. It remains unclear, however, whether such changes in expression of MAP2 represent a primary effect of the mutation or if it is only a precocious result of Purkinje cell degeneration.

Both adult and juvenile tau microtubule-associated proteins are axon specific in the developing and adult rat cerebellum.

Several antibodies directed against the heterogeneous microtubule-associated protein group tau have been used to determine the immunocytochemical localization of these proteins in the developing rat cerebellum. Immunoblot analysis of brain extracts showed that both monoclonal and polyclonal anti-tau antibodies revealed not only the adult tau proteins (50,000-70,000 mol. wt) but also the immature (48,000 mol. wt) tau form. Immunocytochemical studies showed that, whatever the stage of development, anti-tau antibodies stained several types of axonal fibres. The Purkinje cell bodies and their dendrites were never significantly labelled. This means that immature tau is, as adult tau, localized essentially in axons. Axonal labelling seems to follow the cerebellar developmental pattern. For instance, the climbing fibres which reach the cerebellum during the embryonic life were stained soon after birth by the anti-tau antibodies. In contrast, the parallel fibres, that begin to develop perinatally, do not express tau at early (5 days) postnatal stages; a clear labelling of the deeper parallel fibres (which are more mature than the superficial ones) was seen at day 10 after birth in the vicinity of the developing dendrites of the Purkinje cells. This suggests that (1) the appearance of tau immunoreactivity reflects a certain stage of maturity of the parallel fibre; (2) both immature and mature tau microtubule-associated proteins seem to be axon specific in the developing rat cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)