Spatio-temporal activity patterns of mammals in an agro-ecological mosaic with seasonal recreation activities

Recreation activities in developed landscapes may add additional stressors that affect wildlife spatial and temporal activity patterns. We assessed medium to large mammal species response to a tourist scenic route in an agro-ecological mosaic landscape of the Shikma region, Israel. We placed 60 camera traps in an agro-ecological matrix and recorded mammals during three seasons between 2015 and 2017. We used N-mixture models to estimate mammal activity in relation with proximity to the scenic route and additional anthropogenic related factors such as traffic volume and land use. Anthropogenic development and activities had negative effects on large, endangered species, and none or positive on smaller, commensal species. Our results suggest an expansion of human recreation activity may have adverse outcomes on apex predators, which can cause a chain reaction and lead to meso-predator release, ultimately affecting prey species. The results emphasize the need for land managers to be extra cautious when attempting to add additional stressors (i.e., recreation activity) to developed landscapes such as the study area. Such landscapes can function as healthy ecosystems and provide suitable habitats for wildlife given that land managers are aware and account for wildlife-limiting factors in future development plans.     

Learning in the fast lane: new insights into neuroplasticity

The timescale of structural remodeling that accompanies functional neuroplasticity is largely unknown. Although structural remodeling of human brain tissue is known to occur following long-term (weeks) acquisition of a new skill, little is known as to what happens structurally when the brain needs to adopt new sequences of procedural rules or memorize?a cascade of events within minutes or hours. Using diffusion tensor imaging (DTI), an MRI-based framework, we examined subjects before and after a spatial learning and memory task. Microstructural changes (as reflected by DTI measures) of limbic system structures (hippocampus and parahippocampus) were significant after only 2?hr of training. This observation was also found in a supporting rat study. We conclude that cellular rearrangement of neural tissue can be detected by DTI, and that this modality may allow neuroplasticity to be localized over short timescales.     

Community structure of stony and soft corals on vertical unplanned artificial reefs in Eilat (Red Sea): comparison to natural reefs

In many reef ecosystems, artificial reefs (AR) have become permanent additions to the area, sustaining well-developed benthic communities. Long-term studies on the development of AR coral communities are scarce, and comparisons with their natural surroundings are limited. The present study describes the stony and soft coral community structure of unplanned vertical AR in Eilat (Red Sea) that have progressed beyond the initial successional phases, and compares these to the adjacent natural reefs (NR). Coral communities were characterized using belt transects, conducted on 34- and 14-year-old unplanned AR, and on two proximate NR. Stony corals were the major component in the NR, while soft corals, mainly Nephtheidae, accounted for up to 90% of the total living coverage in the AR. This was attributed to physical and biological features associated with the ARs vertical orientation, which was absent in the NR, and to the life history traits of these soft corals. Community differences between the two AR were related to structural stability and age. The results suggest that AR may increase local heterogeneity and space availability by adding novel habitats, increasing production and elevating species diversity in the surroundings.Communicated by Biological Editor H.R. Lasker     

Hepatic mechanisms of the Walnut antidiabetic effect in mice

The present study was designed to explore the mechanism of action of walnut (the seed of Juglans regia) leaf and ridge on hepatic glucose metabolism in diabetic mice. Experimental diabetes was induced by intravenous administration of streptozotocin (60 mg/kg)and confirmed with an increase of blood glucose, 90–100% of the control, 72 hours later. Isolated extracts from walnut leaf and ridges were administered in a single effective dose of 400 mg/kg orally. Firstly, blood glucose was determined every 1 hour until 5 hours post administration of extracts. In the second experiment, the liver was surgically removed, 2 hours post treatment of diabetic animals with extracts, homogenized and used for measurement of key enzymes of glycogenolysis (glycogen phosphorylase, GP) and gluconeogenesis (phosphoenolpyruvate carboxykinase, PEPCK). Treatment by both leaf and ridge extracts decreased blood glucose and liver PEPCK activity and increased blood insulin and liver GP activity. It is concluded that walnut is able to lower blood glucose through inhibition of hepatic gluconeogenesis and secretion of pancreatic insulin.     

Membrane-anchored beta 2-microglobulin stabilizes a highly receptive state of MHC class I molecules

The magnitude of response elicited by CTL-inducing vaccines correlates with the density of MHC class I (MHC-I)-peptide complexes formed on the APC membrane. The MHC-I L chain, beta2-microglobulin (beta2m), governs complex stability. We reasoned that genetically converting beta2m into an integral membrane protein should exert a marked stabilizing effect on the resulting MHC-I molecules and enhance vaccine efficacy. In the present study, we show that expression of membranal human beta2m (hbeta2m) in mouse RMA-S cells elevates MHC-I thermal stability. RMA-S transfectants bind an exogenous peptide at concentrations 10(4)- to 10(6)-fold lower than parental RMA-S, as detected by complex-specific Abs and by T cell activation. Moreover, saturation of the transfectants' MHC-I by exogenous peptide occurs within 1 min, as compared with approximately 1 h required for parental cells. At saturation, however, level of peptide bound by modified cells is only 3- to 5-fold higher. Expression of native hbeta2m only results in marginal effect on the binding profile. Soluble beta2m has no effect on the accelerated kinetics, but the kinetics of transfectants parallel that of parental cells in the presence of Abs to hbeta2m. Ab inhibition and coimmunoprecipitation analyses suggest that both prolonged persistence of peptide-receptive H chain/beta2m heterodimers and fast heterodimer formation via lateral diffusion may contribute to stabilization. In vivo, peptide-loaded transfectants are considerably superior to parental cells in suppressing tumor growth. Our findings support the role of an allosteric mechanism in determining ternary MHC-I complex stability and propose membranal beta2m as a novel scaffold for CTL induction.     

Reciprocal Interactions between Membrane Bilayers and S. aureus PSMα3 Cross-α Amyloid Fibrils Account for Species-Specific Cytotoxicity

Phenol-soluble modulin α3 (PSMα3) is a functional amyloid secreted by the pathogenic bacterium Staphylococcus aureus. This 22-residue peptide serves as a key virulence determinant, toxic to human cells via the formation of unique cross-α amyloid-like fibrils. We demonstrate that bilayer vesicles accelerated PSMα3 fibril formation, and the fibrils, in turn, inserted deeply into bilayers mimicking mammalian cell membranes, accounting for PSMα3 cellular toxicity. Importantly, a mere amphipathic helical conformation was not a sufficient determinant for membrane-activity of PSMα3, pointing to the functional role of cross-α fibrils. In contrast to deep insertion of PSMα3 into mammalian membrane bilayers, the peptide only interacted with the surface of bilayers mimicking bacterial membranes, which might be related to its lack of antibacterial activity. Together, our data provide mechanistic insight into species-specific toxicity of a key bacterial amyloid virulence factor via reciprocal interactions with membranes, and open new perspectives into amyloid-related cytotoxicity mediated by helical fibril structures.     

The role of differential survival patterns in shaping coral communities on neighboring artificial and natural reefs

Understanding the processes that shape artificial reef (AR) communities is critical if these are to be implemented for reef restoration or enhancement purposes. A study of the post-recruitment survival of coral colonies transplanted onto a 19-year-old AR and its adjacent natural reef (NR) was carried out at Eilat (Red Sea) in order to test the hypothesis that differences in benthic communities between the two reefs are derived from differential survival processes. Transplanted miniature coral colonies were monitored in situ on both reef types. It was found that the survival of those of the soft coral Dendronephthya hemprichi on the AR was nearly double that of those transplanted onto the NR. Similarly, survival of nubbins of the stony coral Pocillopora damicornis on the AR was over three-fold greater than on the NR. We suggest that the observed differential survival resulted from the unique suites of environmental conditions at the two habitats, mainly in terms of sedimentation load and current velocities, yet not from differences in substratum type (artificial vs. natural). The results demonstrate the role played by survival processes in shaping coral assemblages on ARs and NRs, and indicate that post-recruitment survival must be considered when designing ARs for restoration or enhancement purposes.     

Reproductive timing as a constraint on invasion success in the Ring-necked parakeet (<Emphasis Type="Italic">Psittacula krameri</Emphasis>)

Climate similarity favors biological invasion, but a match between seasonality in the novel range and the timing of life cycle events of the invader also influences the outcome of species introduction. Yet, phenology effects on invasion success have generally been neglected. Here we study whether a phenological mismatch limits the non-native range of a globally successful invader, the Ring-necked parakeet, in Europe. Given the latitudes at which parakeets have established across Europe, they breed earlier than expected based on breeding dates from the native Asian range. Moreover, comparing the breeding dates of European populations to those of parakeets in the native Asian range, to five native breeding bird species in Europe and to the start of the growing season of four native European trees shows that the discrepancy between expected and actual breeding phenology is greater in northern Europe. In northern European populations, this temporal mismatch appears to have negative effects on hatching success, and on population growth rates in years that are colder than average in the first six months. Phenological mismatch also can explain why parakeets from African populations (that are more likely to breed in autumn) have been poor invaders compared to parakeets from Asia. These lines of evidence support the hypothesis that the reproductive phenology of the Ring-necked parakeet can be a limiting factor for establishment and range expansion in colder climates. Our results provide growing support for the hypothesis that the match between climate seasonality and timing of reproduction (or other important life cycle events) can affect the establishment success, invasive potential and distribution range of introduced non-native species, beyond the mere effect of climate similarity.