The Structural Basis of the Farnesylated and Methylated KRas4B Interaction with Calmodulin

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Hepatic effects of long‐term tamoxifen administration to cycling female rats

The metabolic implications of tamoxifen (TAM) used as preventive therapy of young premenopausal women with high risk of breast cancer is unknown. To unravel this problem, an animal model of long‐term TAM administration to cycling young adult female rats was used to evaluate its effects in the liver. Body weight and food consumption were monitored, and at the end of the study, both parameters were lower in TAM‐treated rats. Biochemical measurements showed that the TAM administration induced alterations in serum levels of liver enzymes when compared with control rats at different stages of the estrous cycle. In TAM‐treated rats, lower glycogen storage was observed in hepatocytes close to the portal areas and pericentrolobular cells had a higher concentration of glycogen. Liver sections of TAM‐treated rats presented mild steatosis—a high percentage of area occupied by lipid droplets in the hepatocytes. These results point to metabolic changes upon long‐term TAM therapy.     

A homologue of the fungal tetraspanin Pls1 is required for Epichloë festucae expressorium formation and establishment of a mutualistic interaction with Lolium perenne

Epichloë festucae is an endophytic fungus that forms a mutualistic symbiotic association with the grass host Lolium perenne. Endophytic hyphae exit the host by an appressorium-like structure known as an expressorium. In plant-pathogenic fungi, the tetraspanin Pls1 and the NADPH oxidase component Nox2 are required for appressorium development. Previously we showed that the homologue of Nox2, NoxB, is required for E. festucae expressorium development and establishment of a mutualistic symbiotic interaction with the grass host. Here we used a reverse genetics approach to functionally characterize the role of the E. festucae homologue of Pls1, PlsA. The morphology and growth of ΔplsA in axenic culture was comparable to wild-type. The tiller length of plants infected with ΔplsA was significantly reduced. Hyphae of ΔplsA had a proliferative pattern of growth within the leaves of L. perenne with increased colonization of the intercellular spaces and the vascular bundles. The ΔplsA mutant was also defective in expressorium development although the phenotype was not as severe as for ΔnoxB, highlighting potentially distinct roles for PlsA and NoxB in signalling through the NoxB complex. Hyphae of ΔplsA proliferate below the cuticle surface but still occasionally form an expressorium-like structure that enables the mutant hyphae to exit the leaf to grow on the surface. These expressoria still form a septin ring-like structure at the point of cuticle exit as found in the wild-type strain. These results establish that E. festucae PlsA has an important, but distinct, role to NoxB in expressorium development and plant symbiosis.     

Drought‐response strategies of savanna herbivores

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Oribatid mites reveal that competition for resources and trophic structure combine to regulate the assembly of diverse soil animal communities

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Protein-induced surface structuring in myelin membrane monolayers

Monolayers prepared from myelin conserve all the compositional complexity of the natural membrane when spread at the air-water interface. They show a complex pressure-dependent surface pattern that, on compression, changes from the coexistence of two liquid phases to a viscous fractal phase embedded in a liquid phase. We dissected the role of major myelin protein components, myelin basic protein (MBP), and Folch-Lees proteolipid protein (PLP) as crucial factors determining the structural dynamics of the interface. By analyzing mixtures of a single protein with the myelin lipids we found that MBP and PLP have different surface pressure-dependent behaviors. MBP stabilizes the segregation of two liquid phases at low pressures and becomes excluded from the film under compression, remaining adjacent to the interface. PLP, on the contrary, organizes a fractal-like pattern at all surface pressures when included in a monolayer of the protein-free myelin lipids but it remains mixed in the MBP-induced liquid phase. The resultant surface topography and dynamics is regulated by combined near to equilibrium and out-of-equilibrium effects. PLP appears to act as a surface skeleton for the whole components whereas MBP couples the structuring to surface pressure-dependent extrusion and adsorption processes.     

The Influence of Large Tree Density on Howler Monkey (Alouatta palliata mexicana) Presence in Very Small Rain Forest Fragments

The populations of the Mexican mantled howler monkey ( Alouatta palliata mexicana ) in the Los Tuxtlas region, Mexico, have declined drastically due to habitat loss and fragmentation. Nevertheless, several troops still inhabit very small and isolated rain forest fragments. We identified the main vegetation attributes that can favor the presence of howlers within 18 small (< 10-ha) fragments that did not differ significantly in size, shape, and isolation (nine occupied and nine unoccupied by howlers). We found that habitat quality ( i.e. , food resources and vegetation structure) affected howler incidence in small fragments. Particularly, the occupied fragments showed greater density of big trees (dbh > 60 cm), greater total basal area, greater basal area of persistent tree species, and greater basal area of top food species than the unoccupied fragments; suggesting that even for small fragments the loss of big trees and particularly the decrease in size class of the top food species can negatively affect howler distribution in highly fragmented landscapes. These findings could be used to establish foreground conservation areas for this critically endangered subspecies in fragmented landscapes of Los Tuxtlas.     

Interleukin-13 interferes with CFTR and AQP5 expression and localization during human airway epithelial cell differentiation

Interleukin-13 (IL-13) is a central regulator of Th2-dominated respiratory disorders such as asthma. Lesions of the airway epithelial barrier frequently observed in chronic respiratory inflammatory diseases are repaired through proliferation, migration and differentiation of epithelial cells. Our work is focused on the effects of IL-13 in human cellular models of airway epithelial cell regeneration. We have previously shown that IL-13 altered epithelial cell polarity during mucociliary differentiation of human nasal epithelial cells. In particular, the cytokine inhibited ezrin expression and interfered with its apical localization during epithelial cell differentiation in vitro. Here we show that CFTR expression is enhanced in the presence of the cytokine, that two additional CFTR protein isoforms are expressed in IL-13-treated cells and that part of the protein is retained within the endoplasmic reticulum. We further show that aquaporin 5 expression, a water channel localized within the apical membrane of epithelial cells, is completely abolished in the presence of the cytokine. These results show that IL-13 interferes with ion and water channel expression and localization during epithelial regeneration and may thereby influence mucus composition and hydration.     

Trypanosoma cruzi: plasma corticosterone after repetitive stress during the acute phase of infection

An increased level of plasma corticosterone is one manifestation of severe environmental or physiologic stress. The stress response mediated by the hypothalamic-pituitary-adrenal axis is already known to suppress immunoglobulin production and to impair immune function, but there are few studies relating stress and plasma corticosterone to the outcome of Trypanosoma cruzi infection. In this study, male Wistar rats were infected with the Y strain of T. cruzi and then subjected to repetitive stress by exposure to ether vapor for 1min twice a day during the acute phase of infection. Stressed animals showed decreased lytic antibody activity and lowered levels of peritoneal macrophages. Despite an increase in the weight of the spleen, histological analyses demonstrated tissue alterations, the presence of amastigote nests, and a complete absence of activated lymphoid follicles. These results suggest that stress-induced increases in plasma corticosterone can suppress the immune response and worsen tissue injury during the acute phase of T. cruzi infection.