Secretory autophagy of lysozyme in Paneth cells

Secretion of antimicrobial proteins is an important host defense mechanism against bacteria, yet how secretory cells maintain function during bacterial invasion has been unclear. We discovered that Paneth cells, specialized secretory cells in the small intestine, react to bacterial invasion by rerouting a critical secreted antibacterial protein through a macroautophagy/autophagy-based secretion system termed secretory autophagy. Mice harboring a mutation in an essential autophagy gene, a mutation which is common in Crohn disease patients, cannot reroute their antimicrobial cargo during bacterial invasion and thus have compromised innate immunity. We showed that this alternative secretion system is triggered by both a cell-intrinsic mechanism, involving the ER stress response, and a cell-extrinsic mechanism, involving subepithelial innate immune cells. Our findings uncover a new role for secretory autophagy in host defense and suggest how a mutation in an autophagy gene can predispose individuals to Crohn disease.     

An updated global data set for diet preferences in terrestrial mammals: testing the validity of extrapolation

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Biogeography of body size in terrestrial isopods (Crustacea: Oniscidea)

This study tries to unveil the contribution of climatic shift in shaping the extreme body size diversity in terrestrial isopods (Oniscidea). Trying to explain size variation at an interspecific level, we test five hypotheses: (1) Bergmann's Rule and the temperature‐size rule postulate large size in cold areas; (2) The metabolic cold adaptation theory postulates small animal sizes in cold environments; (3) The primary productivity hypothesis predicts size increase in resource‐rich areas; (4) The aridity resistance hypothesis predicts large size in arid regions; and (5). The acidosis hypothesis predicts smaller size with decreasing soil pH. Globally, Bergmann's rule and the aridity hypothesis are weakly supported. Among families and genera, results are variable and idiosyncratic. Conglobating species sizes provide weak support for the acidosis hypothesis. Overall, size is strongly affected by familial affiliation. Isopod size evolution seems to be mainly affected by phylogenetically constrained life‐history traits.     

Evolution and ecology of lizard body sizes

Aim Body size is instrumental in influencing animal physiology, morphology, ecology and evolution, as well as extinction risk. I examine several hypotheses regarding the influence of body size on lizard evolution and extinction risk, assessing whether body size influences, or is influenced by, species richness, herbivory, island dwelling and extinction risk. Location World‐wide. Methods I used literature data and measurements of museum and live specimens to estimate lizard body size distributions. Results I obtained body size data for 99% of the world's lizard species. The body size–frequency distribution is highly modal and right skewed and similar distributions characterize most lizard families and lizard assemblages across biogeographical realms. There is a strong negative correlation between mean body size within families and species richness. Herbivorous lizards are larger than omnivorous and carnivorous ones, and aquatic lizards are larger than non‐aquatic species. Diurnal activity is associated with small body size. Insular lizards tend towards both extremes of the size spectrum. Extinction risk increases with body size of species for which risk has been assessed. Main conclusions Small size seems to promote fast diversification of disparate body plans. The absence of mammalian predators allows insular lizards to attain larger body sizes by means of release from predation and allows them to evolve into the top predator niche. Island living also promotes a high frequency of herbivory, which is also associated with large size. Aquatic and nocturnal lizards probably evolve large size because of thermal constraints. The association between large size and high extinction risk, however, probably reflects a bias in the species in which risk has been studied.     

Apoptosis as a mechanism of T-regulatory cell homeostasis and suppression

Activation-induced cell death is a general mechanism of immune homeostasis through negative regulation of clonal expansion of activated immune cells. This mechanism is involved in the maintenance of self- and transplant tolerance through polarization of the immune responses. The Fas/Fas-ligand interaction is a major common executioner of apoptosis in lymphocytes, with a dual role in regulatory T cell (Treg) function: Treg cell homeostasis and Treg cell-mediated suppression. Sensitivity to apoptosis and the patterns of Treg-cell death are of outmost importance in immune homeostasis that affects the equilibrium between cytolytic and suppressor forces in activation and termination of immune activity. Naive innate (naturally occurring) Treg cells present variable sensitivities to apoptosis, related to their turnover rates in tissue under steady state conditions. Following activation, Treg cells are less sensitive to apoptosis than cytotoxic effector subsets. Their susceptibility to apoptosis is influenced by cytokines within the inflammatory environment (primarily interleukin-2), the mode of antigenic stimulation and the proliferation rates. Here, we attempt to resolve some controversies surrounding the sensitivity of Treg cells to apoptosis under various experimental conditions, to delineate the function of cell death in regulation of immunity.     

Life on the edge: carnivore body size variation is all over the place

Evolutionary biologists have long been fascinated by both the ways in which species respond to ecological conditions at the edges of their geographic ranges and the way that species'' body sizes evolve across their ranges. Surprisingly, though, the relationship between these two phenomena is rarely studied. Here, we examine whether carnivore body size changes from the interior of their geographic range towards the range edges. We find that within species, body size often varies strongly with distance from the range edge. However, there is no general tendency across species for size to be either larger or smaller towards the edge. There is some evidence that the smallest guild members increase in size towards their range edges, but results for the largest guild members are equivocal. Whether individuals vary in relation to the distance from the range edges often depends on the way edge and interior are defined. Neither geographic range size nor absolute body size influences the tendency of size to vary with distance from the range edge. Therefore, we suggest that the frequent significant association between body size and the position of individuals along the edge-core continuum reflects the prevalence of geographic size variation and that the distance to range edge per se does not influence size evolution in a consistent way.