Seasonal pulses of migratory prey and annual variation in small mammal abundance affect abundance and reproduction by arctic foxes

We examined how large seasonal influxes of migratory prey influenced population dynamics of arctic foxes and how this varied with fluctuations in small mammal (lemming and vole) abundance—the main prey of arctic foxes throughout most of their range. Specifically, we compared how arctic fox abundance, breeding density and litter size varied inside and outside a large goose colony and in relation to annual variation in small mammal abundance. Information-theoretic model selection showed that (1) breeding density and fox abundance were 2–3 times higher inside the colony than they were outside the colony and (2) litter size, breeding density and annual variation in fox abundance in the colony tracked fluctuations in lemming abundance. The influence of lemming abundance on reproduction and abundance of arctic foxes outside the colony was inconclusive, largely because fox densities outside the colony were low, which made it difficult to detect such relationships. Lemming abundance was, thus, the main factor governing reproduction and abundance of arctic foxes in the colony, whereas seasonal influxes of geese and their eggs provided foxes with external subsidies that elevated breeding density and fox abundance above that which lemmings could support. This study highlights (1) the relative importance of migratory prey and other foods on the abundance and reproduction by local consumers and (2) how migratory animals function as vectors of nutrient transfer between distant ecosystems such as Arctic environments and wintering areas by geese thousands of kilometres to the south.     

Green chiral HPLC enantiomeric separations using high temperature liquid chromatography and subcritical water on Chiralcel OD and Chiralpak AD

We report here the application of subcritical water in chiral separations on two popular polysaccharide chiral stationary phases (CSPs): Chiralpak AD and Chiralcel OD. The behavior of these two CSPs was studied under reversed phase conditions at room temperature to discover the maximum percentage of water in the mobile phase, which provided the separation of enantiomers of flavanone and benzoin, respectively, in a reasonable time (i.e., less than 1 h). Then, the stability of Chiralpak AD and Chiralcel OD versus temperature was investigated and discussed. Chiralcel OD separation of flavanone racemate was obtained at 120 °C with water and 2-propanol (80/20) as the mobile phase, while benzoin racemate was separated in pure water at 160 °C. Separations of several racemates were also presented, and advantages and limitations of the technique were discussed.     

Difluoroethylamines as an amide isostere in inhibitors of cathepsin K

The trifluoroethylamine group found in cathepsin K inhibitors like odanacatib can be replaced by a difluoroethylamine group. This change increased the basicity of the nitrogen which positively impacted the log D. This translated into an improved oral bioavailability in pre-clinical species. Difluoroethylamine compounds exhibit a similar potency against cathepsin K and selectivity profile against other cathepsins when compared to trifluoroethylamine analogs.     

Abundance-variance and abundance-occupancy relationships in a marine host-parasite system: the importance of taxonomy and ecology of transmission

Abundance-occupancy and abundance-variance relationships are two of the most general macroecological patterns capturing essential fundamentals of the structuring of species distributions and are widely documented for free-living animal and plant species populations at different spatial scales. However, empirical data for parasites have been gathered using appropriate sampling designs only recently. We performed analyses across species of the variation in infection parameters and patterns of aggregation of the most widespread parasites in the marine sparid fish Boops boops across seven localities of two marine biogeographical regions, the North East Atlantic and the Mediterranean. We used a large dataset of multiple population samples replicated over time for 20 parasite species and carried out assessments both intraspecifically and interspecifically, across taxonomic and ecological groupings. This taxonomically diverse complex of species representing five major metazoan higher taxa with differing transmission ecologies allowed us to assess the effect of taxonomic and ecological determinants on the abundance-occupancy and abundance-variance relationships in the model marine host-parasite system. The results revealed that: (i) a power function, relating spatial variance to mean abundance, represents a suitable model for the spatial distribution of the species; (ii) prevalence, abundance and the degree of spatial heterogeneity are true species characteristics and differ consistently between higher level taxonomic groupings; (iii) infection parameters and abundance-variance relationship are dependent on host specificity and regional distribution patterns of the parasites; and (iv) the observed infection parameters agree well with predictions from the epidemiological negative binomial abundance-occupancy model built on parameters of Taylor's power law both within and across species.     

Genome sequence of Rhizobium etli CNPAF512, a nitrogen-fixing symbiont isolated from bean root nodules in Brazil

Rhizobium etli is a Gram-negative soil-dwelling alphaproteobacterium that carries out symbiotic biological nitrogen fixation in close association with legume hosts. R. etli strains exhibit high sequence divergence and are geographically structured, with a potentially dramatic influence on the outcome of symbiosis. Here, we present the genome sequence of R. etli CNPAF512, a Brazilian isolate from bean nodules. We anticipate that the availability of genome sequences of R. etli strains from distinctly different areas will provide valuable new insights into the geographic mosaic of the R. etli pangenome and the evolutionary dynamics that shape it.     

Correction method for null alleles in species with variable microsatellite flanking regions, a case study of the black-lipped pearl oyster Pinctada margaritifera

In bivalves, heterozygote deficiencies and departures from Hardy-Weinberg equilibrium (HWE) in microsatellite analysis are common and mainly attributed to inbreeding, genetic patchiness (Walhund effect), or null alleles. We checked for the occurrence of null alleles at 3 microsatellite loci in 3 populations of black-lipped pearl oyster, Pinctada margaritifera, using a step-by-step method to re-amplify homozygotes and null individuals with redesigned primer pair combinations. After amplification with original primer pairs, the 3 populations exhibited null alleles, absence of structure, and significant departure from HWE for all 3 loci due to heterozygote deficiencies. After 3 re-amplification steps, with modified primer sets, all loci were corrected for null alleles. Once corrected, all populations appeared at HWE, demonstrating that null alleles were responsible for the initial disequilibrium of the populations. Furthermore, analysis from corrected genotypes demonstrates significant genetic differentiation for one population from the other 2.     

Effect of sub-optimal neuromotor control on the hip joint load during level walking

Skeletal forces are fundamental information in predicting the risk of bone fracture. The neuromotor control system can drive muscle forces with various task- and health-dependent strategies but current modelling techniques provide a single optimal solution of the muscle load sharing problem. The aim of the present work was to study the variability of the hip load magnitude due to sub-optimal neuromotor control strategies using a subject-specific musculoskeletal model. The model was generated from computed tomography (CT) and dissection data from a single cadaver. Gait kinematics, ground forces and electromyographic (EMG) signals were recorded on a body-matched volunteer. Model results were validated by comparing the traditional optimisation solution with the published hip load measurements and the recorded EMG signals. The solution space of the instantaneous equilibrium problem during the first hip load peak resulted in 10(5) dynamically equivalent configurations of the neuromotor control. The hip load magnitude was computed and expressed in multiples of the body weight (BW). Sensitivity of the hip load boundaries to the uncertainty on the muscle tetanic stress (TMS) was also addressed. The optimal neuromotor control induced a hip load magnitude of 3.3 BW. Sub-optimal neuromotor controls induced a hip load magnitude up to 8.93 BW. Reducing TMS from the maximum to the minimum the lower boundary of the hip load magnitude varied moderately whereas the upper boundary varied considerably from 4.26 to 8.93 BW. Further studies are necessary to assess how far the neuromotor control can degrade from the optimal activation pattern and to understand which sub-optimal controls are clinically plausible. However we can consider the possibility that sub-optimal activations of the muscular system play a role in spontaneous fractures not associated with falls.