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Search Results: 1 - 10 of 404901 matches for " Nick J. B. Isaac "
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Phylogenetically-Informed Priorities for Amphibian Conservation
Nick J. B. Isaac, David W. Redding, Helen M. Meredith, Kamran Safi
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043912
Abstract: The amphibian decline and extinction crisis demands urgent action to prevent further large numbers of species extinctions. Lists of priority species for conservation, based on a combination of species’ threat status and unique contribution to phylogenetic diversity, are one tool for the direction and catalyzation of conservation action. We describe the construction of a near-complete species-level phylogeny of 5713 amphibian species, which we use to create a list of evolutionarily distinct and globally endangered species (EDGE list) for the entire class Amphibia. We present sensitivity analyses to test the robustness of our priority list to uncertainty in species’ phylogenetic position and threat status. We find that both sources of uncertainty have only minor impacts on our ‘top 100‘ list of priority species, indicating the robustness of the approach. By contrast, our analyses suggest that a large number of Data Deficient species are likely to be high priorities for conservation action from the perspective of their contribution to the evolutionary history.
Global Patterns of Evolutionary Distinct and Globally Endangered Amphibians and Mammals
Kamran Safi, Katrina Armour-Marshall, Jonathan E. M. Baillie, Nick J. B. Isaac
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063582
Abstract: Background Conservation of phylogenetic diversity allows maximising evolutionary information preserved within fauna and flora. The “EDGE of Existence” programme is the first institutional conservation initiative that prioritises species based on phylogenetic information. Species are ranked in two ways: one according to their evolutionary distinctiveness (ED) and second, by including IUCN extinction status, their evolutionary distinctiveness and global endangerment (EDGE). Here, we describe the global patterns in the spatial distribution of priority ED and EDGE species, in order to identify conservation areas for mammalian and amphibian communities. In addition, we investigate whether environmental conditions can predict the observed spatial pattern in ED and EDGE globally. Methods and Principal Findings Priority zones with high concentrations of ED and EDGE scores were defined using two different methods. The overlap between mammal and amphibian zones was very small, reflecting the different phylo-biogeographic histories. Mammal ED zones were predominantly found on the African continent and the neotropical forests, whereas in amphibians, ED zones were concentrated in North America. Mammal EDGE zones were mainly in South-East Asia, southern Africa and Madagascar; for amphibians they were in central and south America. The spatial pattern of ED and EDGE was poorly described by a suite of environmental variables. Conclusions Mapping the spatial distribution of ED and EDGE provides an important step towards identifying priority areas for the conservation of mammalian and amphibian phylogenetic diversity in the EDGE of existence programme.
Trait correlates of distribution trends in the Odonata of Britain and Ireland: Southern species benefit from climate warming
Gary D Powney,Steve SA Cham,Dave Smallshire,Nick J B Isaac
PeerJ , 2015, DOI: 10.7287/peerj.preprints.648v1
Abstract: A major challenge in ecology is understanding what enables certain species to persist, while others decline, in response to environmental change. Trait-based comparative analyses are useful in this regard as they can help identify the key drivers of decline, and highlight traits that promote resistance to change. Despite their popularity trait-based comparative analyses tend to focus on explaining variation in range shift and extinction risk, seldom being applied to actual measures of species decline. Furthermore they have tended to be taxonomically restricted to birds, mammals, plants and butterflies. Here we utilise a novel approach to estimate trends for the Odonata in Britain and Ireland, and examine trait correlates of these trends using a recently available trait dataset. We found the dragonfly fauna in Britain and Ireland has undergone considerable change between 1980 and 2012, with 33 and 39% of species showing significant declines and increases respectively. Distribution type was the key trait associated with these trends, where southern species showed significantly higher trends than widespread and northern species. We believe this reflects the impact of climate change as the increased ambient temperature in Britain and Ireland better suits species that are adapted to warmer conditions. We conclude that northern species are particularly vulnerable to climate change due to the combined pressures of a decline in climate suitability, and competition from species that were previously limited by lower thermal tolerance.
Mammals on the EDGE: Conservation Priorities Based on Threat and Phylogeny
Nick J.B. Isaac, Samuel T. Turvey, Ben Collen, Carly Waterman, Jonathan E.M. Baillie
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0000296
Abstract: Conservation priority setting based on phylogenetic diversity has frequently been proposed but rarely implemented. Here, we define a simple index that measures the contribution made by different species to phylogenetic diversity and show how the index might contribute towards species-based conservation priorities. We describe procedures to control for missing species, incomplete phylogenetic resolution and uncertainty in node ages that make it possible to apply the method in poorly known clades. We also show that the index is independent of clade size in phylogenies of more than 100 species, indicating that scores from unrelated taxonomic groups are likely to be comparable. Similar scores are returned under two different species concepts, suggesting that the index is robust to taxonomic changes. The approach is applied to a near-complete species-level phylogeny of the Mammalia to generate a global priority list incorporating both phylogenetic diversity and extinction risk. The 100 highest-ranking species represent a high proportion of total mammalian diversity and include many species not usually recognised as conservation priorities. Many species that are both evolutionarily distinct and globally endangered (EDGE species) do not benefit from existing conservation projects or protected areas. The results suggest that global conservation priorities may have to be reassessed in order to prevent a disproportionately large amount of mammalian evolutionary history becoming extinct in the near future.
Heat and Mass Transfer of Upper Convected Maxwell Fluid Flow with Variable Thermo-Physical Properties over a Horizontal Melting Surface  [PDF]
Kolawole S. Adegbie, Adeola J. Omowaye, Akeem B. Disu, Isaac L. Animasaun
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.68129
Abstract: The objective of this article is to present the dynamics of an Upper Convected Maxwell (UCM) fluid flow with heat and mass transfer over a melting surface. The influence of melting heat transfer, thermal and solutal stratification are properly accounted for by modifying the classical boundary conditions of temperature and concentration respectively. It is assumed that the ratio of inertia forces to viscous forces is high enough for boundary layer approximation to be valid. The corresponding influence of exponential space dependent internal heat source on viscosity and thermal conductivity of UCM is properly considered. The dynamic viscosity and thermal conductivity of UCM are temperature dependent. Classical temperature dependent viscosity and thermal conductivity models were modified to suit the case of both melting heat transfer and thermal stratification. The governing non-linear partial differential equations describing the problem are reduced to a system of nonlinear ordinary differential equations using similarity transformations and completed the solution numerically using the Runge-Kutta method along with shooting technique. For accurate and correct analysis of the effect of variable viscosity on fluid flow in which (Tw or Tm) < T , the mathematical models of variable viscosity and thermal conductivity must be modified.
Beta Diversity of Demersal Fish Assemblages in the North-Eastern Pacific: Interactions of Latitude and Depth
Marti J. Anderson, Nick Tolimieri, Russell B. Millar
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0057918
Abstract: Knowledge of broad-scale global patterns in beta diversity (i.e., variation or turnover in identities of species) for marine systems is in its infancy. We analysed the beta diversity of groundfish communities along the North American Pacific coast, from trawl data spanning 32.57°N to 48.52°N and 51 m to 1200 m depth. Analyses were based on both the Jaccard measure and the probabilistic Raup-Crick measure, which accounts for variation in alpha diversity. Overall, beta diversity decreased with depth, and this effect was strongest at lower latitudes. Superimposed on this trend were peaks in beta diversity at around 400–600 m and also around 1000–1200 m, which may indicate high turnover around the edges of the oxygen minimum zone. Beta diversity was also observed to decrease with latitude, but this effect was only observed in shallower waters (<200 m); latitudinal turnover began to disappear at depths >800 m. At shallower depths (<200 m), peaks in latitudinal turnover were observed at ~43°N, 39°N, 35°N and 31°N, which corresponded well with several classically observed oceanographic boundaries. Turnover with depth was stronger than latitudinal turnover, and is likely to reflect strong environmental filtering over relatively short distances. Patterns in beta diversity, including latitude-by-depth interactions, should be integrated with other biodiversity measures in ecosystem-based management and conservation of groundfish communities.
Kinetic Characterization of Na,K-ATPase Inhibition by the Acetaminophen Metabolite N-Acetylbenzoquinoneimine  [PDF]
Jeff B. Helms, Lauren P. Saunders, Jamie Meyer, Charles J. Costa, Eric Plowman, Nick Williford, Matthew Corbitt, Jeremy P. Holden, Craig Gatto
Open Journal of Molecular and Integrative Physiology (OJMIP) , 2015, DOI: 10.4236/ojmip.2015.51001
Abstract: N-acetylbenzoquinoneimine (NABQI) is a toxic metabolite of the common analgesic acetaminophen (APAP). NABQI is an electrophilic intermediate formed via the oxidation of APAP within the cytochrome P450 system. Within the normally recommended low-dose use of APAP, NABQI is a minor metabolite which is either quickly reduced back to APAP or conjugated to Glutathione (GSH) producing an innocuous by-product. However, with overdose or prolonged high-dose usage of acetaminophen, GSH levels can become depleted and the bioactive NABQI is thought to form adducts with proteins and oxidize protein sulfhydryls producing intra- and intermolecular disulfide bridges in proteins. In this work we investigated the effect of NABQI on purified kidney Na,K-ATPase to see if the clinical renal insufficiencies seen in APAP overdose may be linked to inhibition of the Na,K-ATPase. Our work has shown that NABQI does indeed inhibit the Na,K-ATPase in a dose dependent (IC50 = 19.8 ± 2.9 μM) and irreversible manner. Interestingly, brief storage of NABQI at -20°C eliminates the irreversible effects of the compound, and leads to a product that remains a potent reversible inhibitor of the Na,K-ATPase (IC50 = 58.7 ± 19.5 μM). Further, the reversible inhibition produced by stored NABQI competes with para-nitrop.
Preparation of atomically-flat SrTiO3 surfaces using a deionized-water etching and thermal annealing procedure
J. G. Connell,B. J. Isaac,D. R. Strachan,S. S. A. Seo
Physics , 2012, DOI: 10.1063/1.4773052
Abstract: We report that a deionized water etching and thermal annealing technique can be effective for preparing atomically-flat and singly-terminated surfaces of single crystalline SrTiO3 substrates. After a two-step thermal-annealing and deionized-water etching procedure, topography measured by atomic force microscopy shows the evolution of substrates from a rough to step-terraced surface structure. Lateral force microscopy confirms that the atomically-flat surfaces are singly-terminated. Moreover, this technique can be used to remove excessive strontium oxide or hydroxide composites segregated on the SrTiO3 surface. This acid-etchant-free technique facilitates the preparation of atomically-aligned SrTiO3 substrates, which promotes studies on two-dimensional physics of complex oxide interfaces.
Effects of strontium-doped bioactive glass on the differentiation of cultured osteogenic cells
J Isaac
European Cells and Materials (ECM) , 2011,
Abstract: There is accumulating evidence that strontium-containing biomaterials have positive effects on bone tissue repair. We investigated the in vitro effect of a new Sr-doped bioactive glass manufactured by the sol-gel method on osteoblast viability and differentiation. Osteoblasts isolated from foetal mouse calvaria were cultured in the presence of bioactive glass particles; particles were undoped (B75) or Sr-doped with 1 wt.% (B75-Sr1) and 5 wt.% (B75-Sr5). Morphological analysis was carried out by contrast-phase microscopy and scanning electron microscopy (SEM). Cell viability was evaluated by the MTS assay at 24 h, 48 h and 72 h. At 24 h, day 6 and day 12, osteoblast differentiation was evaluated by assaying alkaline phosphatase (ALP) activity, osteocalcin (OC) secretion and gene expression of various bone markers, using Real-Time-PCR. Alizarin Red staining and ALP histoenzymatic localisation were performed on day 12. Microscopic observations and MTS showed an absence of cytotoxicity in the three investigated bioactive glasses. B75-Sr5 particles in cell cultures, in comparison with those of B75 and B75-Sr1, resulted in a significant up-regulation of Runx2, Osterix, Dlx5, collagen I, ALP, bone sialoprotein (BSP) and OC mRNA levels on day 12, which was associated with an increase of ALP activity on day 6 and OC secretion on day 12. In conclusion, osteoblast differentiation of foetal mouse calvarial cells was enhanced in the presence of bioactive glass particles containing 5 wt.% strontium. Thus, B75-Sr5 may represent a promising bone-grafting material for bone regeneration procedures.
Behavioral Characterization of GCLM-Knockout Mice, a Model for Enhanced Susceptibility to Oxidative Stress
Toby B. Cole,Gennaro Giordano,Aila L. Co,Isaac Mohar,Terrance J. Kavanagh,Lucio G. Costa
Journal of Toxicology , 2011, DOI: 10.1155/2011/157687
Abstract: Glutathione (GSH) is a major player in cellular defense against oxidative stress. Deletion of the modifier subunit of glutamate cysteine ligase (GCLM), the first and the rate-limiting enzyme in the synthesis of GSH, leads to significantly lower GSH levels in all tissues including the brain. GCLM-knockout (Gclm?/?) mice may thus represent a model for compromised response to oxidative stress amenable to in vitro and in vivo investigations. In order to determine whether the diminished GSH content would by itself cause behavioral alterations, a series of behavioral tests were carried out comparing young adult Gclm?/? with wild-type mice. Tests included the rotarod, acoustic startle reflex and prepulse inhibition of the startle reflex, open field behavior, and the platform reversal variant of the Morris Water Maze. Results showed no differences between Gclm?/? and wild-type mice in any of the neurobehavioral tests. However, more subtle alterations, or changes which may appear as animals age, cannot be excluded. 1. Introduction Oxidative stress refers to the cytotoxic consequences of reactive oxygen species (ROS), which are generated as byproducts of normal and aberrant metabolic processes that use molecular oxygen. The tripeptide glutathione (GSH; γ-glutamyl-cysteinyl-glycine) is one of the most abundant cellular thiols. GSH is a major player in cellular defense against ROS, because it nonenzymatically scavenges both singlet oxygen and hydroxyl radicals, and is used by glutathione peroxidases and glutathione transferases to limit the levels of certain reactive aldehydes and peroxides within the cell [1, 2]. When ROS production exceeds the antioxidant defense capacity of the cell, oxidative stress ensues, leading to the damage of DNA, proteins, and membrane lipids. The first and the rate-limiting step in the synthesis of GSH is carried out by glutamate-cysteine ligase (GCL; [1]). The enzyme consists of two subunits, a larger (73?kD) catalytic subunit (GCLC) and a smaller (31?kD) modifier, or regulatory, subunit (GCLM), which are coded by separate genes [3]. GCLC alone provides catalytic activity and is the site of GSH feedback inhibition. By lowering the of GCL for glutamate and raising the for GSH, GCLM, although enzymatically inactive, plays an important regulatory function, as the holoenzyme (GCLholo) has higher catalytic efficiency than GCLC [3, 4]. While disruption of the Gclc gene in mice is embryolethal [5], no overt phenotype is observed upon disruption of the Gclm gene in mice [4, 6, 7]. In the absence of GCLM, the ability of GCLC to synthesize GSH
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