3,062 research outputs found

    Using blubber explants to investigate adipose function in grey seals:glycolytic, lipolytic and gene expression responses to glucose and hydrocortisone

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    Adipose tissue is fundamental to energy balance, which underpins fitness and survival. Knowledge of adipose regulation in animals that undergo rapid fat deposition and mobilisation aids understanding of their energetic responses to rapid environmental change. Tissue explants can be used to investigate adipose regulation in wildlife species with large fat reserves, when opportunities for organismal experimental work are limited. We investigated glucose removal, lactate, glycerol and NEFA accumulation in media, and metabolic gene expression in blubber explants from wild grey seals. Glycolysis was higher in explants incubated in 25 mM glucose (HG) for 24 h compared to controls (C: 5.5 mM glucose). Adipose-derived lactate likely contributes to high endogenous glucose production in seals. Lipolysis was not stimulated by HG or high hydrocortisone (HC: 500 nM hydrocortisone) and was lower in heavier animals. HC caused NEFA accumulation in media to decrease by ~30% relative to C in females, indicative of increased lipogenesis. Lipolysis was higher in males than females in C and HG conditions. Lower relative abundance of 11-β-hydroxysteroid dehydrogenase 1 mRNA in HG explants suggests glucose involvement in blubber cortisol sensitivity. Our findings can help predict energy balance responses to stress and nutritional state in seals, and highlight the use of explants to study fat tissue function in wildlife

    Extra- and intra-cellular accumulation of platinum group elements by the marine microalga, Chlorella stigmatophora.

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    To better understand the marine biogeochemistry of the platinum group elements (PGE), Rh(III), Pd(II) and Pt(IV) were added in combination and at ppb concentrations to cultures of the marine microalga, Chlorella stigmatophora, maintained in sea water at 15 °C and under 60 μmol m(-2) s(-1) PAR. The accumulation of PGE was established in short-term (24-h) exposures, and under varying conditions of algal biomass and PGE concentration, and in a longer-term exposure (156-h) by ICP-MS analysis of sea water and nitric acid digests and EDTA washes of the alga. In short-term exposures, and under all conditions, the extent of accumulation by C. stigmatophora was in the order: Rh > Pd >> Pt; and Pd was internalised (or resistant to EDTA extraction) to a considerably greater extent than Rh and Pt. Accumulation isotherms were quasi-linear up to added PGE concentrations of 30 μg L(-1) and all metals displayed a significant reduction in accumulation on a weight-normalised basis with increasing density (biomass) of C. stigmatophora, an effect attributed to the production of exudates able to stabilise metals in sea water through complexation. In the longer-term exposure, kinetic constraints on the reactivities of Rh and, in particular, Pt, resulted in final degrees of accumulation and internalisation by C. stigmatophora that were greatest for Rh and similar between Pd and Pt. Among the PGE, therefore, Rh is predicted to participate in biological removal and transport processes in the marine environment to the greatest extent while decoupling in the biogeochemistries of Pd and Pt is predicted in shorter-term or more transient processes

    SO(n + 1) Symmetric Solutions of the Einstein Equations in Higher Dimensions

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    A method of solving the Einstein equations with a scalar field is presented. It is applied to find higher dimensional vacuum metrics invariant under the group SO(n + 1) acting on n-dimensional spheres.Comment: 11 page

    Metal accumulation kinetics by the estuarine macroalga, Fucusceranoides

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    The kinetics of Cu, Cd and Pb accumulation by the macroalga, Fucus ceranoides, was studied under simulated estuarine conditions. Accumulation of Cu and Pb proceeded via a pseudo-first-order reaction that was reversible, suggesting desorption or efflux of accumulated metal, with forward rate constants on the order of 0.1h-1. For both metals, reaction reversibility increased and the equilibrium constant decreased with increasing salinity (from 1 to 33.5) and system response times were <10h throughout. Accumulation of Cd proceeded via a first-order reaction that was irreversible, suggesting little desorption or efflux of metal, with rate constants that decreased with increasing salinity (from 0.023 to 0.015h-1) and reaction half-lives ranging from approximately 30-50h. Inorganic equilibrium speciation calculations suggest that interactions of Cu, Cd and Pb principally involve the respective free ions, but that additional ions (e.g. CdCl+) and biotic processes may also be significant. •Accumulation of Cu, Cd and Pb by the estuarine macroalga, Fucus ceranoides, decreases along a salinity gradient.•Accumulation of Cu and Pb proceeds via a reversible pseudo-first-order reaction.•In contrast, accumulation of Cd proceeds via an irreversible first-order reaction.•Differences in reaction mechanisms are attributed to differences in the ability of metals to be internalised. © 2013 Elsevier Ltd

    Low Carbon Cities: Is Ambitious Action Affordable?

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    Research has begun to uncover the extent that greenhouse gas emissions can be attributed to cities, as well as the scope for cities to contribute to emissions reduction. But assessments of the economics of urban climate mitigation are lacking, and are currently based on selective case studies or specific sectors. Further analysis is crucial to enable action at the urban level. Here we consider the investment needs associated with 11 clusters of low carbon measures that could be deployed across the world’s urban areas in a way that is consistent with a broader 2°C target. Economic assessment of these low carbon measures finds that they could be deployed around the world with investments of c1trillionperyearbetween2015and2050(equivalentto1.31 trillion per year between 2015 and 2050 (equivalent to 1.3% of global GDP in 2014). When the direct savings that emerge from these measures due to avoided energy costs are considered, under the central scenario these investments have a net present value of c16.6 trillion USD in the period to 2050. However, discount rates, energy prices and rates of technological learning are key to the economic feasibility of climate action, with the NPV of these measures ranging from -1.1trillionUSDto1.1 trillion USD to 65.2 trillion USD under different conditions

    Iterative in Situ Click Chemistry Assembles a Branched Capture Agent and Allosteric Inhibitor for Akt1

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    We describe the use of iterative in situ click chemistry to design an Akt-specific branched peptide triligand that is a drop-in replacement for monoclonal antibodies in multiple biochemical assays. Each peptide module in the branched structure makes unique contributions to affinity and/or specificity resulting in a 200 nM affinity ligand that efficiently immunoprecipitates Akt from cancer cell lysates and labels Akt in fixed cells. Our use of a small molecule to preinhibit Akt prior to screening resulted in low micromolar inhibitory potency and an allosteric mode of inhibition, which is evidenced through a series of competitive enzyme kinetic assays. To demonstrate the efficiency and selectivity of the protein-templated in situ click reaction, we developed a novel QPCR-based methodology that enabled a quantitative assessment of its yield. These results point to the potential for iterative in situ click chemistry to generate potent, synthetically accessible antibody replacements with novel inhibitory properties

    Producer Cities and Consumer Cities: Using Production- and Consumption-Based Carbon Accounts to Guide Climate Action in China, the UK, and the US

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    Meeting the commitments made in the Paris Agreement on climate change will require different approaches in different countries. However, a common feature in many contexts relates to the continued and sometimes increasing significance of the carbon footprints of urban centres. These footprints consider both production or territorial (i.e. Scope 1 and 2) emissions, and consumption or extra-territorial (i.e. Scope 3) emissions. Although a growing number of cities have adopted targets for their production-based emissions, very few have even started to analyse or address their consumption-based emissions. This presents a potential challenge for urban policymaking if consumption emissions rise while production emissions fall, and for climate mitigation more broadly if emissions are effectively migrating to areas without carbon reduction targets or capabilities. To explore these issues, in this paper we analyse and compare production- and consumption-based emissions accounts for urban centres in China, the UK and the US. Results show that per-capita income and population density are strong predictors of consumption-based emissions levels, and consumption-based emissions appear to diminish but not decouple with higher per-capita incomes. In addition, results show that per-capita income is a predictor of net emissions - or the difference between production- and consumption-based accounts - suggesting that continuing increases in per capita income levels may drive the ‘leakage’ of urban emissions. These findings highlight a risk in placing too much faith in city-level climate strategies focused only on production-based emissions, and stress the importance of new city-level initiatives that focus on consumption-based emissions, especially in cities that are shifting from producer to consumer city status

    Uncovering Blind Spots in Urban Carbon Management: The Role of Consumption-Based Carbon Accounting in Bristol, UK

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    The rapid urbanisation of the twentieth century, along with the spread of high-consumption urban lifestyles, has led to cities becoming the dominant drivers of global anthropogenic greenhouse gas emissions. Reducing these impacts is crucial, but production-based frameworks of carbon measurement and mitigation—which encompass only a limited part of cities’ carbon footprints—are much more developed and widely applied than consumption-based approaches that consider the embedded carbon effectively imported into a city. Frequently, therefore, cities are left blind to the importance of their wider consumption-related climate impacts, while at the same time left lacking effective tools to reduce them. To explore the relevance of these issues, we implement methodologies for assessing production- and consumption-based emissions at the city-level and estimate the associated emissions trajectories for Bristol, a major UK city, from 2000 to 2035. We develop mitigation scenarios targeted at reducing the former, considering potential energy, carbon and financial savings in each case. We then compare these mitigation potentials with local government ambitions and Bristol’s consumption-based emissions trajectory. Our results suggest that the city’s consumption-based emissions are three times the production-based emissions, largely due to the impacts of imported food and drink. We find that low-carbon investments of circa £3 billion could reduce production-based emissions by 25% in 2035. However, we also find that this represents <10% of Bristol’s forecast consumption-based emissions for 2035 and is approximately equal to the mitigation achievable by eliminating the city’s current levels of food waste. Such observations suggest that incorporating consumption-based emission statistics into cities’ accounting and decision-making processes could uncover largely unrecognised opportunities for mitigation that are likely to be essential for achieving deep decarbonisation
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