Consistent and variable leaf anatomical characters in Carex (Cyperaceae)

The anatomy and morphology of leaves in Carex have the potential to be taxonomically useful. However, studies on the variability of leaf characteristics in the genus are sparse. Researchers therefore risk using leaf anatomical characters without the knowledge of whether they are consistent in a species. We examined 22 qualitative and seven quantitative leaf anatomy characters from transverse leaf sections to test their consistency across 11 Carex spp. The characters were clearly described and primarily microscopic. Some characters were found to exhibit high levels of intraspecific variation, whereas other characters exhibited high levels of consistency in a species, including the shape of the leaf section, the density of papillae and the size of epidermal cells. Caution must be applied when choosing leaf anatomy to delimit taxa because of the intraspecific variability found in some characters, but sufficient numbers of invariant characters exist to provide useful taxonomic separation. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172 , 371–384.     

Predictors of Parasitism in Wild White-Faced Capuchins (Cebus capucinus)

Parasite infections in wildlife are influenced by many factors including host demography, behavior and physiology, climate, habitat characteristics, and parasite biology and ecology. White-faced capuchins (Cebus capucinus) host a suite of gastrointestinal and pulmonary parasites, yet the mechanisms affecting host susceptibility and parasite transmissibility have not been examined in this host species. We used the information-theoretic approach (Akaike’s information criterion) and traditional null-hypothesis testing to determine which host characteristics, behaviors, or environmental factors affected the presence of two prevalent capuchin parasites (Filariopsis barretoi and Strongyloides sp.) as well as parasite species richness in four groups of wild capuchins from September 2007 to January 2008 and January to August 2009. Older capuchins were more likely to be infected with Filariopsis barretoi and had higher parasite species richness. Age-biased nematode infections may stem from age differences in capuchin behavior and physiology while high species richness likely results from long- term exposure to numerous parasite species. Infections with Strongyloides sp. were more likely to occur in the dry season when capuchins often descend to the forest floor to drink from terrestrial water sources, potentially increasing their risk of infection from soil-borne larvae. Capuchin behaviors were poor predictors of parasitism, as were female rank, host sex, home range size, and habitat quality. Many of our results were atypical for primate parasitology, suggesting that host–parasite interactions, and subsequently infection risk, may differ in highly seasonal habitats such as tropical dry forests where these monkeys occur.     

Can temperate insects take the heat? A case study of the physiological and behavioural responses in a common ant, Iridomyrmex purpureus (Formicidae), with potential climate change

Insects in temperate regions are predicted to be at low risk of climate change relative to tropical species. However, these assumptions have generally been poorly examined in all regions, and such forecasting fails to account for microclimatic variation and behavioural optimisation. Here, we test how a population of the dominant ant species, Iridomyrmex purpureus, from temperate Australia responds to thermal stress. We show that ants regularly forage for short periods (minutes) at soil temperatures well above their upper thermal limits (upper lethal temperature = 45.8 ± 1.3 °C; CT_max = 46.1 °C) determined over slightly longer periods (hours) and do not show any signs of a classic thermal performance curve in voluntary locomotion across soil surface temperatures of 18.6–57°C (equating to a body temperature of 24.5–43.1 °C). Although ants were present all year round, and dynamically altered several aspects of their thermal biology to cope with low temperatures and seasonal variation, temperature-dependence of running speed remained invariant and ants were unable to elevate high temperature tolerance using plastic responses. Measurements of microclimate temperature were higher than ant body temperatures during the hottest part of the day, but exhibited a stronger relationship with each other than air temperatures from the closest weather station. Generally close associations of ant activity and performance with microclimatic conditions, possibly to maximise foraging times, suggest I. purpureus displays highly opportunistic thermal responses and readily adjusts behaviour to cope with high trail temperatures. Increasing frequency or duration of high temperatures is therefore likely to result in an immediate reduction in foraging efficiency. In summary, these results suggest that (1) soil-dwelling temperate insect populations may be at higher risks of thermal stress with increased frequency or duration of high temperatures resulting from climate change than previously thought, however, behavioural cues may be able to compensate to some extent; and (2) indices of climate change-related thermal stress, warming tolerance and thermal safety margin, are strongly influenced by the scale of climate metrics employed.     

The Bile Acid Receptor TGR5 Does Not Interact with β-Arrestins or Traffic to Endosomes but Transmits Sustained Signals from Plasma Membrane Rafts

TGR5 is a G protein-coupled receptor that mediates bile acid (BA) effects on energy balance, inflammation, digestion, and sensation. The mechanisms and spatiotemporal control of TGR5 signaling are poorly understood. We investigated TGR5 signaling and trafficking in transfected HEK293 cells and colonocytes (NCM460) that endogenously express TGR5. BAs (deoxycholic acid (DCA), taurolithocholic acid) and the selective agonists oleanolic acid and 3-(2-chlorophenyl)-N-(4-chlorophenyl)-N, 5-dimethylisoxazole-4-carboxamide stimulated cAMP formation but did not induce TGR5 endocytosis or recruitment of β-arrestins, as assessed by confocal microscopy. DCA, taurolithocholic acid, and oleanolic acid did not stimulate TGR5 association with β-arrestin 1/2 or G protein-coupled receptor kinase (GRK) 2/5/6, as determined by bioluminescence resonance energy transfer. 3-(2-chlorophenyl)-N-(4-chlorophenyl)-N, 5-dimethylisoxazole-4-carboxamide stimulated a low level of TGR5 interaction with β-arrestin 2 and GRK2. DCA induced cAMP formation at the plasma membrane and cytosol, as determined using exchange factor directly regulated by cAMP (Epac2)-based reporters, but cAMP signals did not desensitize. AG1478, an inhibitor of epidermal growth factor receptor tyrosine kinase, the metalloprotease inhibitor batimastat, and methyl-β-cyclodextrin and filipin, which block lipid raft formation, prevented DCA stimulation of ERK1/2. Bioluminescence resonance energy transfer analysis revealed TGR5 and EGFR interactions that were blocked by disruption of lipid rafts. DCA stimulated TGR5 redistribution to plasma membrane microdomains, as localized by immunogold electron microscopy. Thus, TGR5 does not interact with β-arrestins, desensitize, or traffic to endosomes. TGR5 signals from plasma membrane rafts that facilitate EGFR interaction and transactivation. An understanding of the spatiotemporal control of TGR5 signaling provides insights into the actions of BAs and therapeutic TGR5 agonists/antagonists.     

Overground versus underground: a genetic insight into dispersal and abundance of the Cape dune mole‐rat

Molecular methods are commonly used to investigate cryptic populations that are difficult to locate or observe directly. The population dynamics of many subterranean organisms have been overlooked, at least in part, as a result of the absence of appropriate molecular markers. Recent studies in African mole‐rats have raised questions about the modes of dispersal and mate acquisition. In the present study, we apply a suite of 25 microsatellite markers to test the overground/underground dispersal hypotheses. Using these data, we also apply an approach to estimate population size and look for signal of demographic expansion or contraction. The genetic data suggest that the same breeding population extends between locations (approximately 50 km), with elevated inbreeding coefficients suggestive of some degree of isolation of the urban location. Low genetic differentiation between study sites supports the proposed high levels of vagility of dispersing individuals overground. We find a signal of long‐term population decline of Bathyergus suillus in this region. Their adherence to mesic conditions potentially recommends B. suillus to be of utility in monitoring the proposed climate‐induced desiccation of the Western Cape. Of potential interest is the discovery of a second divergent population at the rural location, with microsatellite data suggesting contemporary reproductive isolation and a mitochondrial divergence putatively dated at approximately 0.6 Mya. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 890–897.     

PATTERNS OF OSSIFICATION IN SOUTHERN VERSUS NORTHERN PLACENTAL MAMMALS

Consensus on placental mammal phylogeny is fairly recent compared to that for vertebrates as a whole. A stable phylogenetic hypothesis enables investigation into the possibility that placental clades differ from one another in terms of their development. Here, we focus on the sequence of skeletal ossification as a possible source of developmental distinctiveness in “northern” (Laurasiatheria and Euarchontoglires) versus “southern” (Afrotheria and Xenarthra) placental clades. We contribute data on cranial and postcranial ossification events during growth in Afrotheria, including elephants, hyraxes, golden moles, tenrecs, sengis, and aardvarks. We use three different techniques to quantify sequence heterochrony: continuous method, sequence‐ANOVA (analysis of variance) and event‐paring/Parsimov. We show that afrotherians significantly differ from other placentals by an early ossification of the orbitosphenoid and caudal vertebrae. Our analysis also suggests that both southern placental groups show a greater degree of developmental variability; however, they rarely seem to vary in the same direction, especially regarding the shifts that differ statistically. The latter observation is inconsistent with the Atlantogenata hypothesis in which afrotherians are considered as the sister clade of xenarthrans. Interestingly, ancestral nodes for Laurasiatheria and Euarchontoglires show very similar trends and our results suggest that developmental homogeneity in some ossification sequences may be restricted to northern placental mammals (Boreoeutheria).     

Reducing infectivity of HIV upon exposure to surfaces coated with N,N‐dodecyl,methyl‐polyethylenimine

The infectivity of high‐titer, cell‐free HIV in culture media and human milk is rapidly reduced upon exposure to polyethylene slides painted with the linear hydrophobic polycation N,N‐dodecyl,methyl‐polyethylenimine (DMPEI). Accompanying viral p24 protein and free viral RNA analysis of solutions exposed to DMPEI‐coated surfaces suggests that virion attachment to the polycationic surface and its subsequent inactivation are the likely mechanism of this phenomenon. Biotechnol. Bioeng. 2013; 110: 2058–2062. © 2013 Wiley Periodicals, Inc.     

The discovery of the benzazepine class of histamine H3 receptor antagonists

This Letter describes the discovery of a novel series of H₃ receptor antagonists. The initial medicinal chemistry strategy focused on deconstructing and simplifying an early screening hit which rapidly led to the discovery of a novel series of H₃ receptor antagonists based on the benzazepine core. Employing an H₃ driven pharmacodynamic model, the series was then further optimised through to a lead compound that showed robust in vivo functional activity and possessed overall excellent developability properties.