Acceleration Data Reveal Highly Individually Structured Energetic Landscapes in Free-Ranging Fishers (Pekania pennanti)

Investigating animal energy expenditure across space and time may provide more detailed insight into how animals interact with their environment. This insight should improve our understanding of how changes in the environment affect animal energy budgets and is particularly relevant for animals living near or within human altered environments where habitat change can occur rapidly. We modeled fisher (Pekania pennanti) energy expenditure within their home ranges and investigated the potential environmental and spatial drivers of the predicted spatial patterns. As a proxy for energy expenditure we used overall dynamic body acceleration (ODBA) that we quantified from tri-axial accelerometer data during the active phases of 12 individuals. We used a generalized additive model (GAM) to investigate the spatial distribution of ODBA by associating the acceleration data to the animals'' GPS-recorded locations. We related the spatial patterns of ODBA to the utilization distributions and habitat suitability estimates across individuals. The ODBA of fishers appears highly structured in space and was related to individual utilization distribution and habitat suitability estimates. However, we were not able to predict ODBA using the environmental data we selected. Our results suggest an unexpected complexity in the space use of animals that was only captured partially by re-location data-based concepts of home range and habitat suitability. We suggest future studies recognize the limits of ODBA that arise from the fact that acceleration is often collected at much finer spatio-temporal scales than the environmental data and that ODBA lacks a behavioral correspondence. Overcoming these limits would improve the interpretation of energy expenditure in relation to the environment.     

Accounting for phenology in the analysis of animal movement

The analysis of animal tracking data provides important scientific understanding and discovery in ecology. Observations of animal trajectories using telemetry devices provide researchers with information about the way animals interact with their environment and each other. For many species, specific geographical features in the landscape can have a strong effect on behavior. Such features may correspond to a single point (eg, dens or kill sites), or to higher dimensional subspaces (eg, rivers or lakes). Features may be relatively static in time (eg, coastlines or home‐range centers), or may be dynamic (eg, sea ice extent or areas of high‐quality forage for herbivores). We introduce a novel model for animal movement that incorporates active selection for dynamic features in a landscape. Our approach is motivated by the study of polar bear (Ursus maritimus) movement. During the sea ice melt season, polar bears spend much of their time on sea ice above shallow, biologically productive water where they hunt seals. The changing distribution and characteristics of sea ice throughout the year mean that the location of valuable habitat is constantly shifting. We develop a model for the movement of polar bears that accounts for the effect of this important landscape feature. We introduce a two‐stage procedure for approximate Bayesian inference that allows us to analyze over 300 000 observed locations of 186 polar bears from 2012 to 2016. We use our model to estimate a spatial boundary of interest to wildlife managers that separates two subpopulations of polar bears from the Beaufort and Chukchi seas.     

Membrane structural perturbations caused by anesthetics and nonimmobilizers: a molecular dynamics investigation.

The structural perturbations of the fully hydrated dimyristoyl-phosphatidylcholine bilayer induced by the presence of hexafluoroethane C(2F6), a "nonimmobilizer," have been examined by molecular dynamics simulations and compared with the effects produced by halothane CF3CHBrCl, an "anesthetic," on a similar bilayer (DPPC) (Koubi et al., Biophys. J. 2000. 78:800). We find that the overall structure of the lipid bilayer and the zwitterionic head-group dipole orientation undergo only a slight modification compared with the pure lipid bilayer, with virtually no change in the potential across the interface. This is in contrast to the anesthetic case in which the presence of the molecule led to a large perturbation of the electrostatic potential across to the membrane interface. Similarly, the analysis of the structural and dynamical properties of the lipid core are unchanged in the presence of the nonimmobilizer although there is a substantial increase in the microscopic viscosity for the system containing the anesthetic. These contrasting perturbations of the lipid membrane caused by those quite similarly sized molecules may explain the difference in their physiological effects as anesthetics and nonimmobilizers, respectively.     

Solution structure of the human Grb14-SH2 domain and comparison with the structures of the human Grb7-SH2/erbB2 peptide complex and human Grb10-SH2 domain

Grb14 is an adapter protein that is known to be overexpressed in estrogen receptor positive breast cancers, and in a number of prostate cancer cell lines. Grb14 has been demonstrated to bind to a number of activated receptor tyrosine kinases (RTKs) and to modulate signals transduced through these receptors. The RTKs to which Grb14 binds include the insulin receptor (IR), the fibroblast growth factor receptor (FGFR), the platelet-derived growth factor receptor (PDGFR), and the tunica endothelial kinase (Tek/Tie2) receptor. Grb14 has been shown to bind to these activated RTKs through its Src homology 2 (SH2) domain, with the exception of the insulin receptor, where the primary binding interaction is via a small domain adjacent to the SH2 domain (the BPS or PIR domain). Grb14 is a member of the Grb7 family of proteins, which also includes Grb7 and Grb10. We have solved the solution structure of the human Grb14-SH2 domain and compared it with the recently determined Grb7-SH2 and Grb10-SH2 domain structures.