A Trade-Off between Reproduction and Feather Growth in the Barn Swallow (Hirundo rustica)

Physiological trade-offs mediated by limiting energy, resources or time constrain the simultaneous expression of major functions and can lead to the evolution of temporal separation between demanding activities. In birds, plumage renewal is a demanding activity, which accomplishes fundamental functions, such as allowing thermal insulation, aerodynamics and socio-sexual signaling. Feather renewal is a very expensive and disabling process, and molt is often partitioned from breeding and migration. However, trade-offs between feather renewal and breeding have been only sparsely studied. In barn swallows (Hirundo rustica) breeding in Italy and undergoing molt during wintering in sub-Saharan Africa, we studied this trade-off by removing a tail feather from a large sample of individuals and analyzing growth bar width, reflecting feather growth rate, and length of the growing replacement feather in relation to the stage in the breeding cycle at removal and clutch size. Growth bar width of females and length of the growing replacement feather of both sexes were smaller when the original feather had been removed after clutch initiation. Importantly, in females both growth bar width and replacement feather length were negatively predicted by clutch size, and more strongly so for large clutches and when feather removal occurred immediately after clutch completion. Hence, we found strong, coherent evidence for a trade-off between reproduction, and laying effort in particular, and the ability to generate new feathers. These results support the hypothesis that the derived condition of molting during wintering in long-distance migrants is maintained by the costs of overlapping breeding and molt.     

Errors Affect Hypothetical Intertemporal Food Choice in Women

Growing evidence suggests that the ability to control behavior is enhanced in contexts in which errors are more frequent. Here we investigated whether pairing desirable food with errors could decrease impulsive choice during hypothetical temporal decisions about food. To this end, healthy women performed a Stop-signal task in which one food cue predicted high-error rate, and another food cue predicted low-error rate. Afterwards, we measured participants’ intertemporal preferences during decisions between smaller-immediate and larger-delayed amounts of food. We expected reduced sensitivity to smaller-immediate amounts of food associated with high-error rate. Moreover, taking into account that deprivational states affect sensitivity for food, we controlled for participants’ hunger. Results showed that pairing food with high-error likelihood decreased temporal discounting. This effect was modulated by hunger, indicating that, the lower the hunger level, the more participants showed reduced impulsive preference for the food previously associated with a high number of errors as compared with the other food. These findings reveal that errors, which are motivationally salient events that recruit cognitive control and drive avoidance learning against error-prone behavior, are effective in reducing impulsive choice for edible outcomes.     

Classifying behavior from short‐interval biologging data: An example with GPS tracking of birds

1. Recent advances in digital data collection have spurred accumulation of immense quantities of data that have potential to lead to remarkable ecological insight, but that also present analytic challenges. In the case of biologging data from birds, common analytical approaches to classifying movement behaviors are largely inappropriate for these massive data sets.
2. We apply a framework for using K‐means clustering to classify bird behavior using points from short time interval GPS tracks. K‐means clustering is a well‐known and computationally efficient statistical tool that has been used in animal movement studies primarily for clustering segments of consecutive points. To illustrate the utility of our approach, we apply K‐means clustering to six focal variables derived from GPS data collected at 1–11 s intervals from free‐flying bald eagles (Haliaeetus leucocephalus) throughout the state of Iowa, USA. We illustrate how these data can be used to identify behaviors and life‐stage‐ and age‐related variation in behavior.
3. After filtering for data quality, the K‐means algorithm identified four clusters in >2 million GPS telemetry data points. These four clusters corresponded to three movement states: ascending, flapping, and gliding flight; and one non‐moving state: perching. Mapping these states illustrated how they corresponded tightly to expectations derived from natural history observations; for example, long periods of ascending flight were often followed by long gliding descents, birds alternated between flapping and gliding flight.
4. The K‐means clustering approach we applied is both an efficient and effective mechanism to classify and interpret short‐interval biologging data to understand movement behaviors. Furthermore, because it can apply to an abundance of very short, irregular, and high‐dimensional movement data, it provides insight into small‐scale variation in behavior that would not be possible with many other analytical approaches.

     

A spectrofluorometric analysis to evaluate transcutaneous biodistribution of fluorescent nanoparticulate gel formulations

The investigation of the absorption of drug delivery systems, designed for the transport of therapeutic molecules inside the body, could be relatively simplified by the fluorophore association and tracking by means of bio-imaging techniques (i.e., optical in vivo imaging or confocal and multiphoton microscopy). However, when a fluorescence signal comes out from the skin, its specific detection can be problematic. Skin high autofluorescence can hinder the observation of administered exogenous fluorophores conjugated to drug delivery systems, making it more challenging to detect their biodistribution. In the present study, we have developed a method based on the spectrofluorometric analysis of skin samples to discriminate the fluorescent signal coming from administered fluorescent molecules from the background. Moreover, we gave a semi-quantitative evaluation of the signal intensity. Thus, we distinguished two gel formulations loading the fluorophore rhodamine B (called GEL RHO and GEL SLN-RHO). The two formulations of gels, one of which containing solid lipid nanoparticles (GEL RHO-SLN), were administered on skin explants incubated in a bioreactor, and the penetration was evaluated at different time points (2 and 6 hours). Cryostatic sections of skin samples were observed with confocal laser scanning microscopy, and a spectrofluorometric analysis was performed. Significantly higher signal intensity in the samples administered with SLN-RHO GEL, with a preferential accumulation in the hair bulbs, was found. Reaching also the deeper layers of the hair shaft after 6 hours, the solid lipid nanoparticles thickened with polymer represent a suitable drug delivery system for transcutaneous administration.Key words: Organ culture, bioreactor, transcutaneous biodistribution, spectrofluorimetric analysis     

Polyploidisation and Geographic Differentiation Drive Diversification in a European High Mountain Plant Group (Doronicum clusii Aggregate,Asteraceae)

Range shifts (especially during the Pleistocene), polyploidisation and hybridization are major factors affecting high-mountain biodiversity. A good system to study their role in the European high mountains is the Doronicum clusii aggregate (Asteraceae), whose four taxa (D. clusii s.s., D. stiriacum, D. glaciale subsp. glaciale and D. glaciale subsp. calcareum) are differentiated geographically, ecologically (basiphilous versus silicicolous) and/or via their ploidy levels (diploid versus tetraploid). Here, we use DNA sequences (three plastid and one nuclear spacer) and AFLP fingerprinting data generated for 58 populations to infer phylogenetic relationships, origin of polyploids—whose ploidy level was confirmed by chromosomally calibrated DNA ploidy level estimates—and phylogeographic history. Taxonomic conclusions were informed, among others, by a Gaussian clustering method for species delimitation using dominant multilocus data. Based on molecular data we identified three lineages: (i) silicicolous diploid D. clusii s.s. in the Alps, (ii) silicicolous tetraploid D. stiriacum in the eastern Alps (outside the range of D. clusii s.s.) and the Carpathians and (iii) the basiphilous diploids D. glaciale subsp. glaciale (eastern Alps) and D. glaciale subsp. calcareum (northeastern Alps); each taxon was identified as distinct by the Gaussian clustering, but the separation of D. glaciale subsp. calcareum and D. glaciale subsp. glaciale was not stable, supporting their taxonomic treatment as subspecies. Carpathian and Alpine populations of D. stiriacum were genetically differentiated suggesting phases of vicariance, probably during the Pleistocene. The origin (autopolyploid versus allopolyploid) of D. stiriacum remained unclear. Doronicum glaciale subsp. calcareum was genetically and morphologically weakly separated from D. glaciale subsp. glaciale but exhibited significantly higher genetic diversity and rarity. This suggests that the more widespread D. glaciale subsp. glaciale originated from D. glaciale subsp. calcareum, which is restricted to a prominent Pleistocene refugium previously identified in other alpine plant species.     

Laboratory evolution of copper tolerant yeast strains

Background  

Yeast strains endowed with robustness towards copper and/or enriched in intracellular Cu might find application in biotechnology processes, among others in the production of functional foods. Moreover, they can contribute to the study of human diseases related to impairments of copper metabolism. In this study, we investigated the molecular and physiological factors that confer copper tolerance to strains of baker's yeasts.     

Potentiation of NMDA Receptor-Dependent Cell Responses by Extracellular High Mobility Group Box 1 Protein

Background

Extracellular high mobility group box 1 (HMGB1) protein can operate in a synergistic fashion with different signal molecules promoting an increase of cell Ca²⁺ influx. However, the mechanisms responsible for this effect of HMGB1 are still unknown.

Principal Findings

Here we demonstrate that, at concentrations of agonist per se ineffective, HMGB1 potentiates the activation of the ionotropic glutamate N-methyl-D-aspartate receptor (NMDAR) in isolated hippocampal nerve terminals and in a neuroblastoma cell line. This effect was abolished by the NMDA channel blocker MK-801. The HMGB1-facilitated NMDAR opening was followed by activation of the Ca²⁺-dependent enzymes calpain and nitric oxide synthase in neuroblastoma cells, resulting in an increased production of NO, a consequent enhanced cell motility, and onset of morphological differentiation. We have also identified NMDAR as the mediator of HMGB1-stimulated murine erythroleukemia cell differentiation, induced by hexamethylenebisacetamide. The potentiation of NMDAR activation involved a peptide of HMGB1 located in the B box at the amino acids 130–139. This HMGB1 fragment did not overlap with binding sites for other cell surface receptors of HMGB1, such as the advanced glycation end products or the Toll-like receptor 4. Moreover, in a competition assay, the HMGB1_(130–139) peptide displaced the NMDAR/HMGB1 interaction, suggesting that it comprised the molecular and functional site of HMGB1 regulating the NMDA receptor complex.

Conclusion

We propose that the multifunctional cytokine-like molecule HMGB1 released by activated, stressed, and damaged or necrotic cells can facilitate NMDAR-mediated cell responses, both in the central nervous system and in peripheral tissues, independently of other known cell surface receptors for HMGB1.     

Spectral Properties of Single Gold Nanoparticles in Close Proximity to Biological Fluorophores Excited by 2-Photon Excitation

Metallic nanoparticles (NPs) are able to modify the excitation and emission rates (plasmonic enhancement) of fluorescent molecules in their close proximity. In this work, we measured the emission spectra of 20 nm Gold Nanoparticles (AuNPs) fixed on a glass surface submerged in a solution of different fluorophores using a spectral camera and 2-photon excitation. While on the glass surface, we observed the presence in the emission at least 3 components: i) second harmonic signal (SHG), ii) a broad emission from AuNPS and iii) fluorescence arising from fluorophores nearby. When on the glass surface, we found that the 3 spectral components have different relative intensities when the incident direction of linear polarization was changed indicating different physical origins for these components. Then we measured by fluctuation correlation spectroscopy (FCS) the scattering and fluorescence signal of the particles alone and in a solution of 100 nM EGFP using the spectral camera or measuring the scattering and fluorescence from the particles. We observed occasional fluorescence bursts when in the suspension we added fluorescent proteins. The spectrum of these burst was devoid of the SHG and of the broad emission in contrast to the signal collected from the gold nanoparticles on the glass surface. Instead we found that the spectrum during the burst corresponded closely to the spectrum of the fluorescent protein. An additional control was obtained by measuring the cross-correlation between the reflection from the particles and the fluorescence arising from EGFP both excited at 488 nm. We found a very weak cross-correlation between the AuNPs and the fluorescence confirming that the burst originate from a few particles with a fluorescence signal.