Peptide Derived from HIV-1 TAT Protein Destabilizes a Monolayer of Endothelial Cells in an in Vitro Model of the Blood-Brain Barrier and Allows Permeation of High Molecular Weight Proteins

Most chemotherapeutic agents are blood-brain barrier (BBB) impermeants. HIV-1-derived TAT protein variants contain a transmembrane domain, which may enable them to cross the BBB and reach the brain. Here we synthesized CAYGRKKRRQRRR, a peptide containing a cysteine moiety attached to the N terminus of the transmembrane domain (C-TAT peptide), and studied its effects in an in vitro BBB model, which we found to reflect penetration by a receptor-independent pathway. Incubation of the brain capillary endothelial cell monolayer with 0.3–0.6 μmol/ml of this C-TAT peptide, for a period of 1–2 h, destabilizes brain capillary endothelial cell monolayer and introduces the ability of impermeant therapeutic agents including high molecular weight proteins to penetrate it substantially. The cysteinyl moiety at position 1 of the C-TAT peptide contributes largely to the destabilizing potency and the penetration efficacy of impermeant substances. The destabilizing effect was reversed using heparin. In summary, experimental conditions allowing a significant increase in entry of impermeant low and high molecular weight substances from the luminal (blood) to the abluminal side (brain) were found in an in vitro BBB model reflecting in vivo protein penetrability by a receptor-independent pathway.     

Intraspecific directed deterrence by the mustard oil bomb in a desert plant

Plant secondary metabolites (SMs) acting as defensive chemicals in reproductive organs such as fruit tissues play roles in both mutualistic and antagonistic interactions between plants and seed dispersers/predators. The directed-deterrence hypothesis states that SMs in ripe fruits deter seed predators but have little or no effect on seed dispersers. Indeed, studies have demonstrated that birds are able to cope with fruit SMs whereas rodents are deterred by them. However, this mechanism was only demonstrated at the class level, i.e., between birds and mammals, based on differences in the vanilloid receptors. Here we present experimental and behavioral data demonstrating the use of the broad-range, class-independent "mustard oil bomb" mechanism in Ochradenus baccatus fruits to force a behavioral change at an ecological timescale, converting rodents from seed predators to seed dispersers. This is achieved by a unique compartmentalization of the mustard oil bomb, causing activation of the system only upon seed and pulp coconsumption, encouraging seed dispersal via seed spitting by rodents. Our findings demonstrate the power of SMs to shift the animal-plant relationship from predation to mutualism and provide support for the directed-deterrence hypothesis at the intraspecific level, in addition to the interspecific level.     

Genomic variation in the vomeronasal receptor gene repertoires of inbred mice

ABSTRACT: BACKGROUND: Vomeronasal receptors (VRs), expressed in sensory neurons of the vomeronasal organ, are thought to bind pheromones and mediate innate behaviours. The mouse reference genome has over 360 functional VRs arranged in highly homologous clusters, but the vast majority are of unknown function. Differences in these receptors within and between closely related species of mice are likely to underpin a range of behavioural responses. To investigate these differences, we interrogated the VR gene repertoire from 17 inbred strains of mice using massively parallel sequencing. RESULTS: Approximately half of the 6222 VR genes that we investigated could be successfully resolved, and those that were unambiguously mapped resulted in an extremely accurate dataset. Collectively VRs have over twice the coding sequence variation of the genome average; but we identify striking non-random distribution of these variants within and between genes, clusters, clades and functional classes of VRs. We show that functional VR gene repertoires differ considerably between different Mus subspecies and species, suggesting these receptors may play a role in mediating behavioural adaptations. Finally, we provide evidence that widely-used, highly inbred laboratory-derived strains have a greatly reduced, but not entirely redundant capacity for differential pheromone-mediated behaviours. CONCLUSIONS: Together our results suggest that the unusually variable VR repertoires of mice have a significant role in encoding differences in olfactory-mediated responses and behaviours. Our dataset has expanded over nine fold the known number of mouse VR alleles, and will enable mechanistic analyses into the genetics of innate behavioural differences in mice.     

Care for kin: within-group relatedness and allomaternal care are positively correlated and conserved throughout the mammalian phylogeny

With an increasing amount of data becoming available, comparative analyses have called attention to the associations between cooperative breeding, monogamy and relatedness. We focus here upon the association between allomaternal care and relatedness among females within a social unit. Previous studies found a positive association, but such results date back to before molecular tools were in common use, they considered only a few mammalian orders, neglected phylogenetic clustering and/or did not correct for group sizes. Here, we use molecular data on relatedness from 44 species of mammals to investigate the phylogenetic clustering of, and the association between, allomaternal care and relatedness among females within a social unit. We find (i) a strong phylogenetic signal for allomaternal care and a moderate one for relatedness and group size, and (ii) a positive association between relatedness and allomaternal care, even when correcting for the smaller than average group sizes in species with allomaternal care. We also find that, in species without allomaternal care, adult females often live with unrelated females even when groups are small. We discuss these results in the light of recent evidence for the role of kin selection and the monogamy hypothesis in cooperative breeding.     

A p38 MAPK-CREB pathway functions to pattern mesoderm in Xenopus

Dorsal-ventral patterning is specified by signaling centers secreting antagonizing morphogens that form a signaling gradient. Yet, how morphogen gradient is translated intracellularly into fate decisions remains largely unknown. Here, we report that p38 MAPK and CREB function along the dorsal-ventral axis in mesoderm patterning. We find that the phosphorylated form of CREB (S133) is distributed in a gradient along the dorsal-ventral mesoderm axis and that the p38 MAPK pathway mediates the phosphorylation of CREB. Knockdown of CREB prevents chordin expression and mesoderm dorsalization by the Spemann organizer, whereas ectopic expression of activated CREB-VP16 chimera induces chordin expression and dorsalizes mesoderm. Expression of high levels of p38 activator, MKK6E or CREB-VP16 in embryos converts ventral mesoderm into a dorsal organizing center. p38 MAPK and CREB function downstream of maternal Wnt/β-catenin and the organizer-specific genes siamois and goosecoid. At low expression levels, MKK6E induces expression of lateral genes without inducing the expression of dorsal genes. Loss of CREB or p38 MAPK activity enables the expansion of the ventral homeobox gene vent1 into the dorsal marginal region, preventing the lateral expression of Xmyf5. Overall, these data indicate that dorsal-ventral mesoderm patterning is regulated by differential p38/CREB activities along the axis.     

Dab2 inhibits the cholesterol-dependent activation of JNK by TGF-β

Transforming growth factor-β (TGF-β) ligands activate Smad-mediated and noncanonical signaling pathways in a cell context–dependent manner. Localization of signaling receptors to distinct membrane domains is a potential source of signaling output diversity. The tumor suppressor/endocytic adaptor protein disabled-2 (Dab2) was proposed as a modulator of TGF-β signaling. However, the molecular mechanism(s) involved in the regulation of TGF-β signaling by Dab2 were not known. Here we investigate these issues by combining biophysical studies of the lateral mobility and endocytosis of the type I TGF-β receptor (TβRI) with TGF-β phosphoprotein signaling assays. Our findings demonstrate that Dab2 interacts with TβRI to restrict its lateral diffusion at the plasma membrane and enhance its clathrin-mediated endocytosis. Small interfering RNA–mediated knockdown of Dab2 or Dab2 overexpression shows that Dab2 negatively regulates TGF-β–induced c-Jun N-terminal kinase (JNK) activation, whereas activation of the Smad pathway is unaffected. Moreover, activation of JNK by TGF-β in the absence of Dab2 is disrupted by cholesterol depletion. These data support a model in which Dab2 regulates the domain localization of TβRI in the membrane, balancing TGF-β signaling via the Smad and JNK pathways.     

Biodegradation of BTEX by bacteria on powdered activated carbon

Aerobic degradation of a mixture of benzene, toluene, ethylbenzene and the mixed xylenes (BTEX) by a mixed bacterial population was studied in a continuously fed, completely mixed bioreactor in the presence of powdered activated carbon (PAC). Adsorption was characterized in the presence and in the absence of bacteria on PAC, and the affinity of virgin PAC to individual BTEX components was shown to be inversely correlated to their solubility in water. Bacteria colonizing the PAC particles are essential for simultaneous adsorption–biodegradation processes. In order to restrict biofilm formation and thereby mass transfer resistance of pollutants from the bulk to the PAC, the slurry was recirculated in the reactor system using a high shear pump. The bacteria on the PAC surface were constantly in a flux between the adsorbed and free phase, a phenomenon that prevented the formation of a biofilm on the PAC surface and thereby extended the life of the PAC.     

An experimental design and a statistical analysis separating interference from exploitation competition

Previous experimental studies of competition among foragers rarely distinguished between exploitation and interference competition. In many systems this separation is experimentally impossible without interfering with the natural behavior of the animals. Consequently, these studies can only demonstrate the combined effect of interference and exploitation on the forager’s feeding rate, namely, it usually decreases in a decelerating rate as a function of density. We suggest here a simple experimental and statistical procedure that facilitates the separation of the effects of interference from those of exploitation. This procedure includes manipulation of both predator density and the foraging experiment duration. The statistical analysis is based on multiple linear regression. The working assumption is that exploitation can be neglected at the beginning of the foraging experiment because, initially, predators do not experience diminishing returns in prey capture rates. Using both the results of an individual-based simulation and a field experiment dataset of gerbils foraging for seeds in an artificial food patch located in the field, we demonstrate that our procedure can successfully detect and separate the effect of interference from the combined overall effect of competition (i.e., interference plus exploitation). Inon Scharf and Ido Filin contributed equally to this paper.