Contribution of leaky modes in the modal analysis of unbounded problems with perfectly matched layers.

The modal analysis of wave problems of unbounded type involves a continuous sum of radiation modes. This continuum is difficult to handle mathematically and physically. It can be approximated by a discrete set of leaky modes, corresponding to improper modes growing to infinity.

p53 mRNA and p53 Protein Structures Have Evolved Independently to Interact with MDM2.

The p53 tumor suppressor and its key regulator MDM2 play essential roles in development, ageing, cancer, and cellular stress responses in mammals. Following DNA damage, MDM2 interacts with p53 mRNA in an ATM kinase-dependent fashion and stimulates p53 synthesis, whereas under normal conditions, MDM2 targets the p53 protein for degradation. The peptide- and RNA motifs that interact with MDM2 are encoded by the same conserved BOX-I sequence, but how these interactions have evolved is unknown.

The ancestral role of nodal signalling in breaking L/R symmetry in the vertebrate forebrain.

Left-right asymmetries in the epithalamic region of the brain are widespread across vertebrates, but their magnitude and laterality varies among species. Whether these differences reflect independent origins of forebrain asymmetries or taxa-specific diversifications of an ancient vertebrate feature remains unknown. Here we show that the catshark Scyliorhinus canicula and the lampreys Petromyzon marinus and Lampetra planeri exhibit conserved molecular asymmetries between the left and right developing habenulae.

Mechanisms of endoderm formation in a cartilaginous fish reveal ancestral and homoplastic traits in jawed vertebrates.

In order to gain insight into the impact of yolk increase on endoderm development, we have analyzed the mechanisms of endoderm formation in the catshark S. canicula, a species exhibiting telolecithal eggs and a distinct yolk sac. We show that in this species, endoderm markers are expressed in two distinct tissues, the deep mesenchyme, a mesenchymal population of deep blastomeres lying beneath the epithelial-like superficial layer, already specified at early blastula stages, and the involuting mesendoderm layer, which appears at the blastoderm posterior margin at the onset of gastrulation.

The chimerical and multifaceted marine acoel Symsagittifera roscoffensis: from photosymbiosis to brain regeneration.

A remarkable example of biological engineering is the capability of some marine animals to take advantage of photosynthesis by hosting symbiotic algae. This capacity, referred to as photosymbiosis, is based on structural and functional complexes that involve two distantly unrelated organisms. These stable photosymbiotic associations between metazoans and photosynthetic protists play fundamental roles in marine ecology as exemplified by reef communities and their vulnerability to global changes threats.

Numerical and analytical calculation of modal excitability for elastic wave generation in lossy waveguides.

In the analysis of elastic waveguides, the excitability of a given mode is an important feature defined by the displacement-force ratio. Useful analytical expressions have been provided in the literature for modes with real wavenumbers (propagating modes in lossless waveguides). The central result of this paper consists in deriving a generalized expression for the modal excitability valid for modes with complex wavenumbers (lossy waveguides or non-propagating modes).

Neuroglobins, pivotal proteins associated with emerging neural systems and precursors of metazoan globin diversity.

Neuroglobins, previously thought to be restricted to vertebrate neurons, were detected in the brain of a photosymbiotic acoel, Symsagittifera roscoffensis, and in neurosensory cells of the jellyfish Clytia hemisphaerica. For the neuroglobin of S. roscoffensis, a member of a lineage that originated either at the base of the bilateria or of the deuterostome clade, we report the ligand binding properties, crystal structure at 2.

Dephosphorylation of eIF2α is essential for protein synthesis increase and cell cycle progression after sea urchin fertilization.

The eukaryotic Initiation Factor 2 (eIF2) is a key regulator of protein synthesis in eukaryotic cells, implicated in the initiation step of translation. Fertilization of the sea urchin eggs triggers a rapid increase in protein synthesis activity, which is necessary for the progress into embryonic cell cycles. Here we demonstrate that fertilization triggers eIF2α dephosphorylation, concomitant with an increase in protein synthesis and that induction of the eIF2α phosphorylation is intimately linked with an inhibition of protein synthesis and cell cycle arrest.

Mitotic patterns in the migrating lateral line cells of zebrafish embryos.

The sense organs of the posterior lateral line system (neuromasts) are formed by a migrating primordium. In zebrafish, the primordium comprises approximately 100 cells at the onset of migration, and has deposited approximately 300 cells by the end of the process. Here, we report localized phases of mitotic activity and of mitotic quiescence within the migrating primordium.

Ultrasonic transient bounded-beam propagation in a solid cylinder waveguide embedded in a solid medium.

A semianalytical solution alternative and complementary to modal technique is presented to predict and interpret the ultrasonic pulsed-bounded-beam propagation in a solid cylinder embedded in a solid matrix. The spectral response to an inside axisymmetric velocity source of longitudinal and transversal cylindrical waves is derived from Debye series expansion of the embedded cylinder generalized cylindrical reflection/transmission coefficients. So, the transient guided wave response, synthesized by inverse double Fourier-Bessel transform, is expressed as a combination of the infinite medium contribution, longitudinal, transversal, and coupled longitudinal and transversal waveguide sidewall interactions.

Cell proliferation in the developing lateral line system of zebrafish embryos.

The sensory organs of the embryonic lateral line system are deposited by migrating primordia that originate in the otic region. Here, we examine the pattern of cell proliferation in the posterior lateral line system. We conclude that three phases of cell proliferation are involved in the generation of this system, separated by two phases of mitotic quiescence.