Hydrophobic counter ion effects on the formation of mesh and reversed phases in the perfluorodecanoate/water system

The tetramethylammonium perfluorodecanoate (C10TMA)/water system forms both random, Mh1(0) and correlated mesh, Mh1(R[3 with combining macron]m) phases over a wide range of concentration and temperature. Whilst the random mesh phase is found in the ammonium homologue, the extensive correlated mesh phase seems to be a result of the hydrophobic nature of the tetramethylammonium (TMA) counter ion. In order to explore the reasons for the occurrence of these mesh phases and the effects of hydrophobic counter ions on phase structure the counter ion has been substituted by a series of increasing hydrophobicity namely butyltrimethylammonium (BTMA), dibutyldimethylammonium (DBDMA), and methyltributylphosphonium (MTBP). The phases and their structures were identified by small angle X-ray scattering. Increasing counter ion hydrophobicity causes a change from mesh, to lamellar, and finally to reversed phases. All the hydrophobic counter ions are strongly bound to the water/fluorocarbon interface and, in the case of those with butyl chains, there is penetration of between 50 and 60% of the total number of counter ion methyl groups into the fluorocarbon region of the lamellar phase. These bound counter ions reduce the accessibility of the head group region to solvent water. As the number of butyl chains on the counter ion increases the lamellar phase is progressively lost and is replaced by a reversed micelle phase either as a single phase or as part of an extensive two phase region

Multiple Cu-ATPase genes are differentially expressed and transcriptionally regulated by Cu exposure in sea bream, Sparus aurata

Copper (Cu) is an essential metal, although in excess is highly toxic due to its redox properties and, therefore intracellular Cu homeostasis is a highly regulated process. Cu-ATPases are pivotal regulatory, proteins of intracellular and bodily Cu homeostasis. Two Cu-ATPases, ATP7A and ATP7B with distinct, functions are found in mammals and herein we report the structure and expression under Cu stress of, homologues of ATP7A and ATP7B in gilthead sea bream (Sparus aurata), the first such report for any, fish. The deduced protein sequences of S. aurata ATP7A (saATP7A) and ATP7B (saATP7B), displayed 63% and 75% identity respectively to their human homologues. All characteristic structural, features of Cu-ATPases were conserved between fish and mammals, although the number of Cu-binding, domains was less in fish ATP7B than in mammalian ATP7B. The tissue expression of sea bream, Cu-ATPases was similar to that observed in mammals, saATP7A being ubiquitously expressed, although low in liver, whilst saATP7B was mainly expressed in the intestine and liver. By analysis of the sequenced genomes of other species we have confirmed the presence of ATP7A and ATP7B genes in fish and propose that the presence of two Cu-ATPase genes in vertebrates represents a retention and neo-functionalization of a duplicated ancestral gene coincident with the development of a closed circulatory system and discrete hepato-biliary system. Expression of Cu-ATPase mRNA was changed after exposure to excess Cu in a manner dependent on exposure route and tissue type. Excess dietary Cu (130mgkg−1 Cu dry diet) reduced saATP7A mRNA levels in intestine, gill, kidney and liver, and increased hepatic saATP7B mRNA consistent with increased biliary excretion. Whilst after waterborne Cu exposure (0.3mgL−1 Cu), expression of ATP7A mRNA was increased in intestine and liver and toxic responses were observed in gill and liver. Our results indicate that Cu-ATPases in both fish and mammals have similar functions in maintenance of Cu homeostasis and are consistent with previous physiological evidence from various fish species for the involvement of multiple Cu-ATPases in Cu transport. Furthermore, our evidence suggests that fish can detoxify excess dietary Cu relatively efficiently but are unable to cope with excess dissolved Cu in the water, demonstrating that the exposure route is critical to toxicity

Tributyltin is a potent inhibitor of piscine peroxisome proliferator-activated receptor α and β

Increasing evidence suggests that common environmental contaminants can act as endocrine disrupters in fish. However, current data are biased towards environmental estrogens, highlighting the need to elucidate potential pollutant impact on other endocrine axes. Here, we report a highthroughput assay to identify chemicals interacting with piscine peroxisome proliferator-activated receptors (PPARs). Our transactivation assay employs a fish cell line and uses recombinant proteins combining the yeast Gal4 DNA-binding domain with the ligand-binding domain of PPARs from plaice. Compared to assays with full-length PPARs, this approach circumvents interaction of chemicals binding to retinoid X receptors, which form heterodimers with PPAR and many other nuclear receptors. Plaice PPARa and PPARb are activated by fibrate drugs and by phthalate monoesters at concentrations similar to those activating the homologous mammalian receptors. In line with their assumed role as central transcriptional regulators of energy homostasis, a number of fatty acids activate plaice PPARa and PPARb. In contrast, tributyl tin oxide (TBTO) is a potent antagonist of PPARa and PPARb, showing activity at environmentally relevant concentrations of TBTO (1-50 nM). Given the ubiquitous and persistent nature of TBTO, the possibility that chronic environmental effects are occurring via disruption of PPAR signalling in fish should be further investigated. Keywords: tributyltin, TBTO, PPAR, pollutant, fib

Transcriptional control mechanisms of genes of lipid and fatty acid metabolism in the Atlantic salmon (Salmo salar L.) established cell line, SHK-1

The regulatory control mechanisms of lipid and fatty acid metabolism were investigated in Atlantic salmon. We identified sterol regulatory element binding protein (SREBP) genes in salmon and characterised their response, and the response of potential target and other regulatory genes including liver X receptor (LXR), to cholesterol and long-chain polyunsaturated fatty acids (LC-PUFA) in the salmon established cell line, SHK-1. Two cDNAs for SREBPs homologous to mammalian SREBP-1 and SREBP-2 were characterised. We identified three groups of genes whose expression responded differently to the treatments. One group of genes, including cholesterol biosynthetic genes, showed increased expression in response to lipid depletion but supplementary cholesterol or LC-PUFA had no further effect. The expression of a second group of genes belonging to fatty acid biosynthetic pathways, included fatty acid synthase, Δ6 and Δ5 fatty acyl desaturases, also increased after lipid depletion but this was negated by cholesterol or by LC-PUFA supplementation. The expression of a third group of genes including acyl-CoA oxidase, HMG-CoA reductase and Elovl5 elongase was increased by cholesterol treatment but was not affected by lipid depletion or by LC-PUFA. This same pattern of expression was also shown by liver X receptor (LXR), indicating that acyl-CoA oxidase, HMG-CoA reductase and Elovl5 are possible direct targets of LXR. This suggests that salmon Elovl5 may be regulated differently from mammalian Elovl5, which is an indirect target of LXR, responding to LXR-dependent increases in SREBP-1

Copper transporter 1, metallothionein and glutathione reductase genes are differentially expressed in tissues of sea bream (Sparus aurata) after exposure to dietary or waterborne copper

The high affinity copper transporter 1 (Ctr1), metallothionein (MT) and glutathione reductase (GR) are essential for copper uptake, sequestration and defense respectively. Following rearing on a normal commercial diet (12.6±0.2 mgKg-1Cu), sea bream were fed an experimental control diet lacking mineral mix (7.7±0.3 mgKg-1Cu), an experimental diet enhanced with Cu (135±4 mgKg-1 Cu) or an experimental diet (7.7±0.3 mgKg-1Cu) while exposed to Cu in water (0.294±0.013mgL-1). Fish were sampled at 0, 15 and 30 d after exposures. Fish fed the Cu-enhanced experimental diet showed lower levels of expression of Ctr1 in the intestine and liver compared to fish fed control experimental diets, whilst Ctr1 expression in the gill and kidney was unaffected by excess dietary Cu exposure. Waterborne Cu-exposure increased Ctr1 mRNA levels in the intestine and the kidney compared to experimental controls. Excess dietary Cu exposure had no effect on levels of metallothionein (MT) mRNA, and the only effect of dietary excess Cu on glutathione reductase (GR) mRNA was a decrease in the intestine. Both MT mRNA and GR were increased in the liver and gill after waterborne Cu exposure, compared to levels in fish fed experimental control low Cu diets. Thus, Ctr1, MT and GR mRNA expression in response to excess Cu is dependent on the route of exposure. Furthermore, the tissue expression profile of sea bream Ctr1 is consistent with the known physiology of copper exposure in fish and indicates a role both in essential copper uptake and in avoidance of excess dietary and waterborne copper influx

Binary black hole merger dynamics and waveforms

We study dynamics and radiation generation in the last few orbits and merger of a binary black hole system, applying recently developed techniques for simulations of moving black holes. Our analysis of the gravitational radiation waveforms and dynamical black hole trajectories produces a consistent picture for a set of simulations with black holes beginning on circular-orbit trajectories at a variety of initial separations. We find profound agreement at the level of one percent among the simulations for the last orbit, merger and ringdown. We are confident that this part of our waveform result accurately represents the predictions from Einstein's General Relativity for the final burst of gravitational radiation resulting from the merger of an astrophysical system of equal-mass non-spinning black holes. The simulations result in a final black hole with spin parameter a/m=0.69. We also find good agreement at a level of roughly 10 percent for the radiation generated in the preceding few orbits.Comment: 11 pages, 11 figures, submitted to PRD, update citations, minor change

Playing Three-Level Games in the Global Economy. Case Studies from the EU. College of Europe EU Diplomacy Paper 4/2008, May 2008

The case studies in this paper are a selection of essays that have been written in the framework of the compulsory first-semester course The EU in a Global Political Economy Context, taught by Professor Sieglinde Gstöhl, in the academic year 2007-2008 in the EU International Relations and Diplomacy Studies programme at the College of Europe. They all address recent cases of two- or three-level games played by the European Union in different policy fields of the global economy (reflecting the state of affairs at the end of 2007)

An evolutionary perspective on Elovl5 fatty acid elongase: comparison of Northern pike and duplicated paralogs from Atlantic salmon

BACKGROUND The ability to produce physiologically critical LC-PUFA from dietary fatty acids differs greatly among teleost species, and is dependent on the possession and expression of fatty acyl desaturase and elongase genes. Atlantic salmon, as a result of a recently duplicated genome, have more of these enzymes than other fish. Recent phylogenetic studies show that Northern pike represents the closest extant relative of the preduplicated ancestral salmonid. Here we characterise a pike fatty acyl elongase, elovl5, and compare it to Atlantic salmon elovl5a and elovl5b duplicates. RESULTS Phylogenetic analyses show that Atlantic salmon paralogs are evolving symmetrically, and they have been retained in the genome by purifying selection. Heterologous expression in yeast showed that Northern pike Elovl5 activity is indistinguishable from that of the salmon paralogs, efficiently elongating C18 and C20 substrates. However, in contrast to salmon, pike elovl5 was predominantly expressed in brain with negligible expression in liver and intestine. CONCLUSIONS We suggest that the predominant expression of Elovl5b in salmon liver and Elovl5a in salmon intestine is an adaptation, enabled by genome duplication, to a diet rich in terrestrial invertebrates which are relatively poor in LC-PUFA. Pike have retained an ancestral expression profile which supports the maintenance of PUFA in the brain but, due to a highly piscivorous LC-PUFA-rich diet, is not required in liver and intestine. Thus, the characterisation of elovl5 in Northern pike provides insights into the evolutionary divergence of duplicated genes, and the ecological adaptations of salmonids which have enabled colonisation of nutrient poor freshwaters

Regulatory divergence of homeologous Atlantic salmon elovl5 genes following the salmonid-specific whole genome duplication

Fatty acyl elongase 5 (elovl5) is a critical enzyme in the vertebrate biosynthetic pathway which produces the physiologically essential long chain polyunsaturated fatty acids (LC-PUFA), docosahexenoic acid (DHA) and eicosapentenoic acid (EPA) from 18 carbon fatty acids precursors. In contrast to most other vertebrates, Atlantic salmon possess two copies of elovl5 (elovl5a and elovl5b) as a result of a whole genome duplication (WGD) which occurred at the base of the salmonid lineage. WGDs have had a major influence on vertebrate evolution, providing extra genetic material, enabling neofunctionalization to accelerate adaptation and speciation. However, little is known about the mechanisms by which such duplicated homeologous genes diverge. Here we show that homeologous Atlantic salmon elovl5a and elovl5b genes have been asymmetrically colonised by transposon-like elements. Identical locations and identities of insertions are also present in the rainbow trout duplicate elovl5 genes, but not in the nearest extant representative preduplicated teleost, the northern pike. Both elovl5 salmon duplicates possessed conserved regulatory elements that promoted Srebp1- and Srebp2-dependent transcription, and differences in the magnitude of Srebp response between promoters could be attributed to a tandem duplication of SRE and NF-Y cofactor binding sites in elovl5b. Furthermore, an insertion in the promoter region of elovl5a confers responsiveness to Lxr/Rxr transcriptional activation. Our results indicate that most, but not all transposon mobilisation into elovl5 genes occurred after the split from the common ancestor of pike and salmon, but before more recent salmonid speciations, and that divergence of elovl5 regulatory regions have enabled neofuntionalization by promoting differential expression of these homeologous genes

Key Biofouling Organisms in Tidal Habitats Targeted by the Offshore Renewable Energy Sector in the North Atlantic Include the Massive Barnacle Chirona hameri

Marine habitats are being targeted for the extraction of offshore renewable energy (ORE) as part of the drive to decarbonise electricity generation. Unmanaged biofouling impacts ORE devices and infrastructure by elevating drag forces, increasing weight, and accelerating corrosion, leading to decreased performance and survivability, and extending costly periods of maintenance. ORE deployments in high tidal flow locations are providing opportunities to study the biofouling unique to these habitats. In this study, surveys of numerous devices and associated infrastructure deployed at the European Marine Energy Centre in Scotland identified high tidal flow fouling assemblages. Substrate orientation relative to tidal flow appears to affect the abundance of key fouling species, including the massive barnacle Chirona hameri. This species is shown to recruit to a wide range of artificial substrates, over a prolonged period from mid-spring to mid-summer, and in maximum current speeds from 0.4–4.0 m/s. For the first time, C. hameri is reported in near-surface depths, on uncoated components of a floating tidal device. The highly gregarious settlement behaviour and rapid growth exhibited by this species may have important implications for managing fouling in the ORE industry, especially in ‘niche’ areas. Anti-fouling strategies and maintenance scheduling applicable to ORE and other marine industries are discussed