A novel protein family mediates Casparian strip formation in the endodermis

Polarized epithelia are fundamental to multicellular life. In animal epithelia, conserved junctional complexes establish membrane diffusion barriers, cellular adherence and sealing of the extracellular space. Plant cellular barriers are of independent evolutionary origin. The root endodermis strongly resembles a polarized epithelium and functions in nutrient uptake and stress resistance. Its defining features are the Casparian strips, belts of specialized cell wall material that generate an extracellular diffusion barrier. The mechanisms localizing Casparian strips are unknown. Here we identify and characterize a family of transmembrane proteins of previously unknown function. These 'CASPs' (Casparian strip membrane domain proteins) specifically mark a membrane domain that predicts the formation of Casparian strips. CASP1 displays numerous features required for a constituent of a plant junctional complex: it forms complexes with other CASPs; it becomes immobile upon localization; and it sediments like a large polymer. CASP double mutants display disorganized Casparian strips, demonstrating a role for CASPs in structuring and localizing this cell wall modification. To our knowledge, CASPs are the first molecular factors that are shown to establish a plasma membrane and extracellular diffusion barrier in plants, and represent a novel way of epithelial barrier formation in eukaryotes.     

Lipoxygenase metabolites of arachidonic acid as second messengers for presynaptic inhibition of Aplysia sensory cells

Biochemical and biophysical studies on Aplysia sensory neurons indicate that inhibitory responses to the molluscan peptide FMRFamide are mediated by lipoxygenase metabolites of arachidonic acid. These compounds are a new class of second messengers in neurons.     

40Ar retention in the terrestrial planets

The solid Earth is widely believed to have lost its original gases through a combination of early catastrophic release and regulated output over geologic time. In principle, the abundance of 40Ar in the atmosphere represents the time-integrated loss of gases from the interior, thought to occur through partial melting in the mantle followed by melt ascent to the surface and gas exsolution. Here we present data that reveal two major difficulties with this simple magmatic degassing scenario--argon seems to be compatible in the major phases of the terrestrial planets, and argon diffusion in these phases is slow at upper-mantle conditions. These results challenge the common belief that the upper mantle is nearly degassed of 40Ar, and they call into question the suitability of 40Ar as a monitor of planetary degassing. An alternative to magmatism is needed to release argon to the atmosphere, with one possibility being hydration of oceanic lithosphere consisting of relatively argon-rich olivine and orthopyroxene.     

Evidence for a novel cytoplasmic processing event in ribosome maturation in the sea urchin Paracentrotus lividus

In this paper we demonstrate the existence of a cytoplasmic processing step, never before described, involving both the pre-ribosomal subunits in the sea urchin Paracentrotus lividus. Northern-blot hybridization, primer extension, S1 mapping experiments and in situ hybridizations allowed us to demonstrate that cytoplasmic processed particles are successively re-imported into the nucleus where maturation of their RNAs is completed prior to being exported to the cytoplasm. Our findings lead to the proposal of a new model of ribosome maturation and shuttling.     

Bond-controlled configurational entropy reduction in chemical vitrification

Glass formation is usually viewed in terms of physical vitrification: a liquid in a metastable state is cooled or compressed so as to avoid crystallization. However, glasses may also be formed by chemical vitrification, a process involving progressive polymerization of the constituent molecules via the formation of irreversible chemical bonds. The formation of most of the materials used in engineering plastics and the hardening of natural and synthetic resins are based on chemical vitrification. Despite the differences in the molecular processes involved in chemical and physical vitrification, surprising similarities are observed in the slowing down of the dynamics and in the thermodynamical properties of the resulting glasses. Explaining such similarities would improve general understanding of the glass transition and may disclose its universal nature. Here we report dielectric and photon-correlation measurements that reveal the origin of the similarity in the dynamical behaviour of physical and chemical glass formers. We find that the evolution of their configurational restrictions proceeds in a similar manner. In particular, we make a connection between the reduction in configurational entropy and the number of chemical bonds, a quantity that can be controlled in experiments.     

Predicting the Distribution of Stock Returns: Model Formulation,Statistical Evaluation,VaR Analysis and Economic Significance

A large literature has investigated predictability of the conditional mean of low‐frequency stock returns by macroeconomic and financial variables; however, little is known about predictability of the conditional distribution. We look at one‐step‐ahead out‐of‐sample predictability of the conditional distribution of monthly US stock returns in relation to the macroeconomic and financial environment. Our methodological approach is innovative: we consider several specifications for the conditional density and combinations schemes. Our results are as follows: the entire density is predicted under combination schemes as applied to univariate GARCH models with Gaussian innovations; the Bayesian winner in relation to GARCH‐skewed‐t models is informative about the 5% value at risk; the average realised utility of a mean–variance investor is maximised under the Bayesian winner as applied to GARCH models with symmetric Student t innovations. Our results have two implications: the best prediction model depends on the evaluation criterion; and combination schemes outperform individual models. Copyright © 2015 John Wiley & Sons, Ltd.     

An anorexic lipid mediator regulated by feeding.

Oleylethanolamide (OEA) is a natural analogue of the endogenous cannabinoid anandamide. Like anandamide, OEA is produced in cells in a stimulus-dependent manner and is rapidly eliminated by enzymatic hydrolysis, suggesting a function in cellular signalling. However, OEA does not activate cannabinoid receptors and its biological functions are still unknown. Here we show that, in rats, food deprivation markedly reduces OEA biosynthesis in the small intestine. Administration of OEA causes a potent and persistent decrease in food intake and gain in body mass. This anorexic effect is behaviourally selective and is associated with the discrete activation of brain regions (the paraventricular hypothalamic nucleus and the nucleus of the solitary tract) involved in the control of satiety. OEA does not affect food intake when injected into the brain ventricles, and its anorexic actions are prevented when peripheral sensory fibres are removed by treatment with capsaicin. These results indicate that OEA is a lipid mediator involved in the peripheral regulation of feeding.