Ungulate community structure and ecological processes: body size,hoof area and trampling in African savannas

A wide range of bioenergetic, production, life history and ecological traits scale with body size in vertebrates. However, the consequences of differences in community body-size structure for ecological processes have not been explored. We studied the scaling relationships between body mass, shoulder height, hoof area, stride length and daily ranging distance in African ungulates ranging in size from the 5 kg dik-dik to the 5,000 kg African elephant, and the implications of these relationships on the area trampled by single and multispecies herbivore communities of differing structure. Hoof area, shoulder height and stride length were strongly correlated with body mass (Pearson's r >0.98, 0.95 and 0.90, respectively). Hoof area scaled linearly to body mass with a slope of unity, implying that the pressures exerted on the ground per unit area by a small antelope and an elephant are identical. Shoulder height and stride length scaled to body mass with similar slopes of 0.32 and 0.26, respectively; larger herbivores have relatively shorter legs and take relatively shorter steps than small herbivores, and so trample a greater area of ground per unit distance travelled. We compared several real and hypothetical single- and multi-species ungulate communities using exponents of between 0.1 and 0.5 for the body mass to daily ranging distance relationship and found that the estimated area trampled was greater in communities dominated by larger animals. The impacts of large herbivores are not limited to trampling. Questions about the ecological implications of community body-size structure for such variables as foraging and food intake, dung quality and deposition rates, methane production, and daily travelling distances remain clear research priorities.     

Detection of protease activity in the wetted surface of gelatin-coated electrodes in air by AC impedance spectroscopy

As a step towards developing a biosensor which can detect airborne protease droplets, a biosensor which had previously been developed to detect protease in solution is shown to be capable of detecting different concentrations of protease in liquid films on the sensor surface in air. The biosensor measured impedance change due to proteolytic digestion of its gelatin coating. In saturated air there was a rise in impedance, with a loss in weight of the gelatin, in proportion to collagenase concentration. The addition of glycerol to the gelatin caused a lower impedance response and smaller loss in weight. A critical thickness of the gelatin layer prior to a more rapid change in the rate of impedance was noted, with and without the addition of glycerol. In low air humidity (40%), with gelatin, all collagenase concentrations produced a very similar rapid increase in impedance. However, with glycerol-enhanced gelatin, there was a clear distinction between the extent of impedance change with different collagenase concentrations. The application of these findings for use in the field of bioaerosol sampling is discussed.     

Cross-Sectional Comparison of Small Animal [18F]-Florbetaben Amyloid-PET between Transgenic AD Mouse Models

We aimed to compare [¹⁸F]-florbetaben PET imaging in four transgenic mouse strains modelling Alzheimer’s disease (AD), with the main focus on APPswe/PS2 mice and C57Bl/6 mice serving as controls (WT). A consistent PET protocol (N = 82 PET scans) was used, with cortical standardized uptake value ratio (SUVR) relative to cerebellum as the endpoint. We correlated methoxy-X04 staining of β-amyloid with PET results, and undertook ex vivo autoradiography for further validation of a partial volume effect correction (PVEC) of PET data. The SUVR in APPswe/PS2 increased from 0.95±0.04 at five months (N = 5) and 1.04±0.03 (p<0.05) at eight months (N = 7) to 1.07±0.04 (p<0.005) at ten months (N = 6), 1.28±0.06 (p<0.001) at 16 months (N = 6) and 1.39±0.09 (p<0.001) at 19 months (N = 6). SUVR was 0.95±0.03 in WT mice of all ages (N = 22). In APPswe/PS1G384A mice, the SUVR was 0.93/0.98 at five months (N = 2) and 1.11 at 16 months (N = 1). In APPswe/PS1dE9 mice, the SUVR declined from 0.96/0.96 at 12 months (N = 2) to 0.91/0.92 at 24 months (N = 2), due to β-amyloid plaques in cerebellum. PVEC reduced the discrepancy between SUVR-PET and autoradiography from −22% to +2% and increased the differences between young and aged transgenic animals. SUVR and plaque load correlated highly between strains for uncorrected (R = 0.94, p<0.001) and PVE-corrected (R = 0.95, p<0.001) data. We find that APPswe/PS2 mice may be optimal for longitudinal amyloid-PET monitoring in planned interventions studies.     

Spatial and temporal variation in harvest probabilities for American black duck

Assessing spatial variation in waterfowl harvest probabilities from banding data is challenging because reporting and recovery probabilities have distinct spatial patterns that covary temporally with harvesting regulations, hunter effort, and reporting methods. We analyzed direct band recovery data from American black ducks banded on the Canadian breeding grounds from 1970 through 2010. Data were registered to a 1‐degree grid and analyzed using hierarchical logistic regression models with spatially correlated errors to estimate the annual probabilities of band recovery and the proportion of individuals recovered in Canada. Probability of harvest was estimated from these values, in combination with independent estimates of reporting probabilities in Canada and the USA. Model covariates included estimates of hunting effort and factors for harvest regulation and band reporting methods. Both the band recovery processes and the proportion of individuals recovered in Canada had significant spatial structure. Recovery probabilities were highest in southern Ontario, along the Saint Lawrence River in Quebec, and in Nova Scotia. Black ducks breeding in Nova Scotia and southern Quebec were harvested predominantly in Canada. Recovery probabilities for juveniles were correlated with hunter effort, while the adult recoveries were weakly correlated with the implementation of stricter harvest regulations in the early 1980s. Mean harvest probability decreased in the northern portion of the survey area but remained stable or even increased in the south. Harvest probabilities for juveniles in 2010 exceeded 20% in southern Quebec and the Atlantic provinces. Our results demonstrate fine‐scale variation in harvest probabilities for black duck on the Canadian breeding ground. In particular, harvest probabilities should be closely monitored along the Saint Lawrence River system and in the Atlantic provinces to avoid overexploitation.     

2-Phenyl-9H-purine-6-carbonitrile derivatives as selective cathepsin S inhibitors

Starting from previously disclosed equally potent cathepsin K and S inhibitor 4-propyl-6-(3-trifluoromethylphenyl)pyrimidine-2-carbonitrile 1, a novel 2-phenyl-9H-purine-6-carbonitrile scaffold was identified to provide potent and selective cathepsin S inhibitors.     

Piperazine sulfonamide BACE1 inhibitors: Design,synthesis, and in vivo characterization

With collaboration between chemistry, X-ray crystallography, and molecular modeling, we designed and synthesized a series of novel piperazine sulfonamide BACE1 inhibitors. Iterative exploration of the non-prime side and S2′ sub-pocket of the enzyme culminated in identification of an analog that potently lowers peripheral Aβ₄₀ in transgenic mice with a single subcutaneous dose.     

6-Phenyl-1H-imidazo[4,5-c]pyridine-4-carbonitrile as cathepsin S inhibitors

6-Phenyl-1H-imidazo[4,5-c]pyridine-4-carbonitrile analogues were identified as potent and selective cathepsin S inhibitor against both purified enzyme and in human JY cell based cellular assays. This core has a very stable thio-trapping nitrile war-head in comparison with the well reported pyrimidine-2-carbonitrile cysteine cathepsin inhibitors. Compound 47 is also very potent in in vivo mouse spleenic Lip10 accumulation assays.     

A novel series of positive modulators of the AMPA receptor: Structure-based lead optimization

Starting from lead compound 1, we demonstrate how X-ray structural data can be used to understand SAR and expediently optimize bioavailability in a novel series of AMPA receptor modulators, furnishing 5 with improved bioavailability and robust in vivo activity.     

Error bars in experimental biology

Error bars commonly appear in figures in publications, but experimental biologists are often unsure how they should be used and interpreted. In this article we illustrate some basic features of error bars and explain how they can help communicate data and assist correct interpretation. Error bars may show confidence intervals, standard errors, standard deviations, or other quantities. Different types of error bars give quite different information, and so figure legends must make clear what error bars represent. We suggest eight simple rules to assist with effective use and interpretation of error bars.