Becoming a face expert.

Young children do not form representations of newly encountered faces as efficiently as do adults. A first step in explaining this difference, like any age-related change, is locating its source. A major source of the improvement is acquisition of knowledge of faces per se, as opposed to age-related changes in general pattern encoding or memorial skills. Two consequences of expertise at individualizing members of classes that share a basic configuration are known: a large inversion effect and a caricature advantage. It is possible that both of these effects reflect increased reliance, with expertise, on configuration distinguishing features. Several phenomena that indicate that inversion interferes with the encoding of configural aspects of faces are reviewed. Finally, developmental data are presented that confirm the suspicion that there are at least two distinct sources of the vulnerability of face encoding to inversion, perhaps reflecting two distinct senses of 'configural encoding' of faces, only one of which is implicated in adult expertise at face encoding.     

The role of context, colour and location cues in socially learned novel food source preferences in starlings, Sternus vulgaris

Although the opportunity for errors in social learning is widely recognised, as yet little research has been directed towards understanding specific inaccuracies, biases and limitations in social learning and the mechanisms that give rise to them. In two experiments I ask how starlings, Sternus vulgaris, identify exemplars of novel feeders previously learned about socially. I find that starlings have a stronger response to feeders in the same context as that in which social learning took place, compared to identical and nonidentical feeders in a different context. Within a context that matches where social learning took place, starlings prefer feeders that show the same location and colour as the feeder demonstrated by the demonstrator starling, and show no preference when colour and location cues are dissociated. This suggests that starlings are relatively accurate social learners, since they show strong responses to novel foraging options only if they match the context, colour and location of options learned about socially, and they do so after very few trials. Furthermore, the responses of the subjects were compatible with conditioned learning-like mechanisms, which provide a useful basis for the further investigation of the origins and implications of errors in social learning.     

Intraspecific genetic variation of a Fagus sylvatica population in a temperate forest derived from airborne imaging spectroscopy time series

1. The growing pace of environmental change has increased the need for large‐scale monitoring of biodiversity. Declining intraspecific genetic variation is likely a critical factor in biodiversity loss, but is especially difficult to monitor: assessments of genetic variation are commonly based on measuring allele pools, which requires sampling of individuals and extensive sample processing, limiting spatial coverage. Alternatively, imaging spectroscopy data from remote platforms may hold the potential to reveal genetic structure of populations. In this study, we investigated how differences detected in an airborne imaging spectroscopy time series correspond to genetic variation within a population of Fagus sylvatica under natural conditions.
2. We used multi‐annual APEX (Airborne Prism Experiment) imaging spectrometer data from a temperate forest located in the Swiss midlands (Laegern, 47°28'N, 8°21'E), along with microsatellite data from F. sylvatica individuals collected at the site. We identified variation in foliar reflectance independent of annual and seasonal changes which we hypothesize is more likely to correspond to stable genetic differences. We established a direct connection between the spectroscopy and genetics data by using partial least squares (PLS) regression to predict the probability of belonging to a genetic cluster from spectral data.
3. We achieved the best genetic structure prediction by using derivatives of reflectance and a subset of wavebands rather than full‐analyzed spectra. Our model indicates that spectral regions related to leaf water content, phenols, pigments, and wax composition contribute most to the ability of this approach to predict genetic structure of F. sylvatica population in natural conditions.
4. This study advances the use of airborne imaging spectroscopy to assess tree genetic diversity at canopy level under natural conditions, which could overcome current spatiotemporal limitations on monitoring, understanding, and preventing genetic biodiversity loss imposed by requirements for extensive in situ sampling.

     

Mycobacterium tuberculosis ClpX Interacts with FtsZ and Interferes with FtsZ Assembly

FtsZ assembly at the midcell division site in the form of a Z-ring is crucial for initiation of the cell division process in eubacteria. It is largely unknown how this process is regulated in the human pathogen Mycobacterium tuberculosis. Here we show that the expression of clpX was upregulated upon macrophage infection and exposure to cephalexin antibiotic, the conditions where FtsZ-ring assembly is delayed. Independently, we show using pull-down, solid-phase binding, bacterial two-hybrid and mycobacterial protein fragment complementation assays, that M. tuberculosis FtsZ interacts with ClpX, the substrate recognition domain of the ClpXP protease. Incubation of FtsZ with ClpX increased the critical concentration of GTP-dependent polymerization of FtsZ. Immunoblotting revealed that the intracellular ratio of ClpX to FtsZ in wild type M. tuberculosis is approximately 1∶2. Overproduction of ClpX increased cell length and modulated the localization of FtsZ at midcell sites; however, intracellular FtsZ levels were unaffected. A ClpX-CFP fusion protein localized to the cell poles and midcell sites and colocalized with the FtsZ-YFP protein. ClpX also interacted with FtsZ mutant proteins defective for binding to and hydrolyzing GTP and possibly for interactions with other proteins. Taken together, our results suggest that M. tuberculosis ClpX interacts stoichiometrically with FtsZ protomers, independent of its nucleotide-bound state and negatively regulates FtsZ activities, hence cell division.     

In vivo regulation of hepatic LDL receptor mRNA in the baboon. Differential effects of saturated and unsaturated fat

The effects of diets enriched with cholesterol and different fats upon plasma lipoproteins and hepatic low density lipoprotein (LDL) receptor mRNA levels were studied in a group of 18 normal baboons. Animals were fed diets containing 1% cholesterol and 25% fat as either coconut oil, peanut oil, or olive oil for a period of 20 weeks. Plasma total cholesterol, high density lipoprotein (HDL) cholesterol, beta-lipoprotein (LDL + very low density lipoprotein) cholesterol, apolipoprotein B and apolipoprotein A-I were measured in samples obtained at 4-week intervals. All three diet groups demonstrated a statistically significant increase in plasma cholesterol as compared to base line throughout the experiment. Hepatic LDL receptor (LDL-R) mRNA levels were quantified by dot blot hybridization in serial liver biopsies. Animals fed saturated fat sustained a significant reduction in hepatic LDL-R mRNA as compared to those fed either monounsaturated or polyunsaturated fat. A strong negative correlation between LDL-R mRNA and plasma total cholesterol (r = -0.71), HDL cholesterol (r = -0.76), and plasma apo A-I (r = -0.77) was observed only in those animals fed coconut oil. Weak negative correlations between LDL-R mRNA and other plasma parameters did not achieve statistical significance. We conclude that saturated and unsaturated oils may influence plasma cholesterol levels in part through differential effects on LDL receptor biosynthesis in baboons.