4,889 research outputs found

    Discovery of faint double-peak Halpha emission in the halo of low redshift galaxies

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    Aiming at the detection of cosmological gas being accreted onto galaxies of the local Universe, we examined the Halpha emission in the halo of 164 galaxies in the field of view of the Multi-Unit Spectroscopic Explorer Wide survey (\musew ) with observable Halpha (redshift < 0.42). An exhaustive screening of the corresponding Halpha images led us to select 118 reliable Halpha emitting gas clouds. The signals are faint, with a surface brightness of 10**(-17.3 pm 0.3) erg/s/cm2/arcsec2. Through statistical tests and other arguments, we ruled out that they are created by instrumental artifacts, telluric line residuals, or high redshift interlopers. Around 38% of the time, the Halpha line profile shows a double peak with the drop in intensity at the rest-frame of the central galaxy, and with a typical peak-to-peak separation of the order of pm 200 km/s. Most line emission clumps are spatially unresolved. The mass of emitting gas is estimated to be between one and 10**(-3) times the stellar mass of the central galaxy. The signals are not isotropically distributed; their azimuth tends to be aligned with the major axis of the corresponding galaxy. The distances to the central galaxies are not random either. The counts drop at a distance > 50 galaxy radii, which roughly corresponds to the virial radius of the central galaxy. We explore several physical scenarios to explain this Halpha emission, among which accretion disks around rogue intermediate mass black holes fit the observations best.Comment: pay attention to the last sentence of the abstract! Accepted for publication in Ap

    Fracture energy of coarse recycled aggregate concrete using the wedge splitting test method: influence of water-reducing admixtures

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    The aim of this study is to evaluate the effect of the replacement levels of coarse natural aggregates with recycled aggregates and water-reducing admixtures on the fracture energy of concrete. Four mixes with 0, 20, 50 and 100% replacement ratios are produced per concrete family: without admixture, with plasticizer and with superplasticizer. The experimental fracture energy is tested using the wedge splitting test method on notched specimens at 28 days. The results prove that the incorporation of up to 20% coarse recycled aggregates led to improved energy absorption capacity of concrete mixes with water-reducing admixtures, reaching 1.5% for concrete with normal plasticizer and 7.0% for concrete with superplasticizer. Furthermore, the compressive strength, slump, and fresh density are tested in order to evaluate the effect of water-reducing admixtures on recycled aggregate concrete with different ratios of coarse natural aggregate replacement, allowing to conclude that the use of plasticizers and superplasticizers improves the behaviour of recycled aggregate concrete for all these properties

    The Right to Code and Share Arms

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    Glycerol is, to date, the most widely used cryoprotectant to freeze stallion spermatozoa at concentrations between 2% and 5%. Cryoprotectant toxicity has been claimed to be the single most limiting factor for the success of cryopreservation. In order to evaluate the toxic effects of the concentrations of glycerol used in practice, stallion spermatozoa were incubated in Biggers Whitten and Whittingham (BWW) media supplemented with 0%, 0.5%, 1.5%, 2.5%, 3.5%, and 5% glycerol. In two additional experiments, a hyposmotic (75 mOsm/kg) and a hyperosmotic (900 mOsm/kg) control media were included. Sperm parameters evaluated included cell volume, membrane integrity, lipid peroxidation, caspase 3, 7, and 8 activation, mitochondrial membrane potential, and integrity of the cytoskeleton. Glycerol exerted toxicity at concentrations 3.5% and the maximal toxicity was observed at 5%. The actin cytoskeleton was especially sensitive to glycerol presence, inducing rapid F actin depolymerization at concentrations over 1.5%. The sperm membrane and the mitochondria were other structures affected. The toxicity of glycerol is apparently related to osmotic and nonosmotic effects. In view of our results the concentration of glycerol in the freezing media for stallion spermatozoa should not surpass 2.5%.Funding Agencies|Ministerio de Ciencia e Innovacion-FEDER Madrid, Spain|AGL 2010 20758 (GAN)|Inia|RZ2008-00018-00-00|Junta de Extremadura FEDER GR|10010

    Age- and Gender-Related Changes in Contractile Properties of Non-Atrophied EDL Muscle

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    Background: In humans, ageing causes skeletal muscles to become atrophied, weak, and easily fatigued. In rodent studies, ageing has been associated with significant muscle atrophy and changes in the contractile properties of the muscles. However, it is not entirely clear whether these changes in contractile properties can occur before there is significant atrophy, and whether males and females are affected differently. Methods and Results: We investigated various contractile properties of whole isolated fast-twitch EDL muscles from adult (2–6 months-old) and aged (12–22 months-old) male and female mice. Atrophy was not present in the aged mice. Compared with adult mice, EDL muscles of aged mice had significantly lower specific force, longer tetanus relaxation times, and lower fatiguability. In the properties of absolute force and muscle relaxation times, females were affected by ageing to a greater extent than males. Additionally, EDL muscles from a separate group of male mice were subjected to eccentric contractions of 15 % strain, and larger force deficits were found in aged than in adult mice. Conclusion: Our findings provide further insight into the muscle atrophy, weakness and fatiguability experienced by the elderly. We have shown that even in the absence of muscle atrophy, there are definite alterations in the physiological properties of whole fast-twitch muscle from ageing mice, and for some of these properties the alterations are mor

    Evolution of the Early-Type Galaxy Fraction in Clusters since z = 0.8

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    We study the morphological content of a large sample of high-redshift clusters to determine its dependence on cluster mass and redshift. Quantitative morphologies are based on bulge+disk decompositions of cluster and field galaxies on deep VLT/FORS2 images of 18 optically-selected clusters at 0.45 < z < 0.80 from the ESO Distant Cluster Survey (EDisCS). Morphological content is given by the early-type galaxy fraction f_et, and early-type galaxies are selected based on their bulge fraction and image smoothness. A set of 158 SDSS clusters is analyzed exactly as the EDisCS sample to provide a robust local comparison. Our main results are: (1) f_et values for the SDSS and EDisCS clusters exhibit no clear trend as a function of sigma. (2) Mid-z EDisCS clusters around sigma = 500 km/s have f_et ~= 0.5 whereas high-z EDisCS clusters have f_et ~= 0.4 (~25% increase over 2 Gyrs). (3) There is a marked difference in the morphological content of EDisCS and SDSS clusters. None of the EDisCS clusters have f_et greater than 0.6 whereas half of the SDSS clusters lie above this value. This difference is seen in clusters of all velocity dispersions. (4) There is a strong correlation between morphology and star formation in SDSS and EDisCS clusters. This correlation holds independent of sigma and z even though the fraction of [OII] emitters decreases from z~0.8 to z~0.06 in all environments. Our results pose an interesting challenge to structural transformation and star formation quenching processes that strongly depend on the global cluster environment and suggest that cluster membership may be of lesser importance than other variables in determining galaxy properties. (ABRIDGED)Comment: 22 pages, 10 figures, accepted for publication in A&

    The abundant marine bacterium Pelagibacter simultaneously catabolizes dimethylsulfoniopropionate to the gases dimethyl sulfide and methanethiol

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    Marine phytoplankton produce ~109 tons of dimethylsulfoniopropionate (DMSP) per year1,2, an estimated 10% of which is catabolized by bacteria through the DMSP cleavage pathway to the climatically active gas dimethyl sulfide (DMS)3,4. SAR11 Alphaproteobacteria (order Pelagibacterales), the most abundant chemoorganotrophic bacteria in the oceans, have been shown to assimilate DMSP into biomass, thereby supplying this cell’s unusual requirement for reduced sulfur5,6. Here we report that Pelagibacter HTCC1062 produces the gas methanethiol (MeSH) and that simultaneously a second DMSP catabolic pathway, mediated by a cupin-like DMSP lyase, DddK, shunts as much as 59% of DMSP uptake to DMS production. We propose a model in which the allocation of DMSP between these pathways is kinetically controlled to release increasing amounts of DMS as the supply of DMSP exceeds cellular sulfur demands for biosynthesis

    Chance and necessity in the genome evolution of endosymbiotic bacteria of insects

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    [EN] An open question in evolutionary biology is how does the selection¿drift balance determine the fates of biological interactions. We searched for signatures of selection and drift in genomes of five endosymbiotic bacterial groups known to evolve under strong genetic drift. Although most genes in endosymbiotic bacteria showed evidence of relaxed purifying selection, many genes in these bacteria exhibited stronger selective constraints than their orthologs in free-living bacterial relatives. Remarkably, most of these highly constrained genes had no role in the host¿symbiont interactions but were involved in either buffering the deleterious consequences of drift or other host-unrelated functions, suggesting that they have either acquired new roles or their role became more central in endosymbiotic bacteria. Experimental evolution of Escherichia coli under strong genetic drift revealed remarkable similarities in the mutational spectrum, genome reduction patterns and gene losses to endosymbiotic bacteria of insects. Interestingly, the transcriptome of the experimentally evolved lines showed a generalized deregulation of the genome that affected genes encoding proteins involved in mutational buffering, regulation and amino acid biosynthesis, patterns identical to those found in endosymbiotic bacteria. Our results indicate that drift has shaped endosymbiotic associations through a change in the functional landscape of bacterial genes and that the host had only a small role in such a shiftThis work was supported by Science Foundation Ireland (12/IP/1637) and grants from the Spanish Ministerio de Economia y Competitividad (MINECO-FEDER; BFU2012-36346 and BFU2015-66073-P) to MAF. DAP and CT were supported by Juan de la Cierva fellowships from MINECO (references: JCI-2011-11089 and JCA-2012-14056, respectively). DAP is supported by funds from the University of Nevada, Reno, NV, USA.Sabater-Muñoz, B.; Toft, C.; Alvarez-Ponce, D.; Fares Riaño, MA. (2017). Chance and necessity in the genome evolution of endosymbiotic bacteria of insects. The ISME Journal. 11(6):1291-1304. https://doi.org/10.1038/ismej.2017.18S12911304116Aguilar-Rodriguez J, Sabater-Munoz B, Montagud-Martinez R, Berlanga V, Alvarez-Ponce D, Wagner A et al. (2016). The molecular chaperone DnaK is a source of mutational robustness. Genome Biol Evol 8: 2979–2991.Alvarez-Ponce D, Sabater-Munoz B, Toft C, Ruiz-Gonzalez MX, Fares MA . (2016). Essentiality is a strong determinant of protein rates of evolution during mutation accumulation experiments in Escherichia coli. Genome Biol Evol 8: 2914–2927.Anders S, Huber W . (2010). Differential expression analysis for sequence count data. Genome Biol 11: R106.Archibald J . (2014) One Plus One Equals One: Symbiosis and the Evolution of Complex Life. Oxford University Press: Oxford, UK.Aussel L, Loiseau L, Hajj Chehade M, Pocachard B, Fontecave M, Pierrel F et al. (2014). ubiJ, a new gene required for aerobic growth and proliferation in macrophage, is involved in coenzyme Q biosynthesis in Escherichia coli and Salmonella enterica serovar Typhimurium. J Bacteriol 196: 70–79.Baumann P, Baumann L, Clark MA . (1996). Levels of Buchnera aphidicola chaperonin groEL during growth of the aphid Schizaphis graminum. Curr Microbiol 32: 7.Benjamini Y, Yekutieli Y . (2005). False discovery rate controlling confidence intervals for selected parameters. J Am Stat Assoc 100: 10.Bennett GM, Moran NA . (2015). Heritable symbiosis: the advantages and perils of an evolutionary rabbit hole. Proc Natl Acad Sci USA 112: 10169–10176.Bermingham J, Rabatel A, Calevro F, Vinuelas J, Febvay G, Charles H et al. (2009). Impact of host developmental age on the transcriptome of the symbiotic bacterium Buchnera aphidicola in the pea aphid (Acyrthosiphon pisum. Appl Environ Microbiol 75: 7294–7297.Bogumil D, Dagan T . (2010). Chaperonin-dependent accelerated substitution rates in prokaryotes. Genome Biol Evol 2: 602–608.Carbon S, Ireland A, Mungall CJ, Shu S, Marshall B, Lewis S et al. (2009). AmiGO: online access to ontology and annotation data. Bioinformatics 25: 288–289.Chen Z, Wang Y, Li Y, Li Y, Fu N, Ye J et al. (2012). Esre: a novel essential non-coding RNA in Escherichia coli. FEBS Lett 586: 1195–1200.Clark JW, Hossain S, Burnside CA, Kambhampati S . (2001). Coevolution between a cockroach and its bacterial endosymbiont: a biogeographical perspective. Proc Biol Sci 268: 393–398.Dale C, Wang B, Moran N, Ochman H . (2003). Loss of DNA recombinational repair enzymes in the initial stages of genome degeneration. Mol Biol Evol 20: 1188–1194.Deatherage DE, Barrick JE . (2014). Identification of mutations in laboratory-evolved microbes from next-generation sequencing data using breseq. Methods Mol Biol 1151: 165–188.Douglas AE . (2003). The nutritional physiology of aphids. Adv Insect Physiol 31: 68.Fares MA, Barrio E, Sabater-Munoz B, Moya A . (2002a). The evolution of the heat-shock protein GroEL from Buchnera, the primary endosymbiont of aphids, is governed by positive selection. Mol Biol Evol 19: 1162–1170.Fares MA, Ruiz-Gonzalez MX, Moya A, Elena SF, Barrio E . (2002b). Endosymbiotic bacteria: groEL buffers against deleterious mutations. Nature 417: 398.Gancedo C, Flores CL, Gancedo JM . (2016). The expanding landscape of moonlighting proteins in yeasts. Microbiol Mol Biol Rev 80: 765–777.Gerardo NM, Altincicek B, Anselme C, Atamian H, Barribeau SM, de Vos M et al. (2010). Immunity and other defenses in pea aphids, Acyrthosiphon pisum. Genome Biol 11: R21.Gomez-Valero L, Latorre A, Silva FJ . (2004). The evolutionary fate of nonfunctional DNA in the bacterial endosymbiont Buchnera aphidicola. Mol Biol Evol 21: 2172–2181.Gomez-Valero L, Silva FJ, Christophe Simon J, Latorre A . (2007). Genome reduction of the aphid endosymbiont Buchnera aphidicola in a recent evolutionary time scale. Gene 389: 87–95.Gonzalez-Domenech CM, Belda E, Patino-Navarrete R, Moya A, Pereto J, Latorre A . (2012). Metabolic stasis in an ancient symbiosis: genome-scale metabolic networks from two Blattabacterium cuenoti strains, primary endosymbionts of cockroaches. BMC Microbiol 12 (Suppl 1): S5.Hansen AK, Moran NA . (2011). Aphid genome expression reveals host-symbiont cooperation in the production of amino acids. Proc Natl Acad Sci USA 108: 2849–2854.Hansen AK, Moran NA . (2014). The impact of microbial symbionts on host plant utilization by herbivorous insects. Mol Ecol 23: 1473–1496.Henderson B, Fares MA, Lund PA . (2013). Chaperonin 60: a paradoxical, evolutionarily conserved protein family with multiple moonlighting functions. Biol Rev Camb Philos Soc 88: 955–987.Humphreys NJ, Douglas AE . (1997). Partitioning of symbiotic bacteria between generations of an insect: a quantitative study of a Buchnera sp. in the pea aphid (Acyrthosiphon pisum reared at different temperatures. Appl Environ Microbiol 63: 3294–3296.International Aphid Genomics Consortium. (2010). Genome sequence of the pea aphid Acyrthosiphon pisum. PLoS Biol 8: e1000313.Kadibalban AS, Bogumil D, Landan G, Dagan T . (2016). DnaK-dependent accelerated evolutionary rate in prokaryotes. Genome Biol Evol 8: 1590–1599.Katoh K, Standley DM . (2013). MAFFT multiple sequence alignment software version 7: improvements in performance and usability. Mol Biol Evol 30: 772–780.Kelkar YD, Ochman H . (2013). Genome reduction promotes increase in protein functional complexity in bacteria. Genetics 193: 303–307.Koga R, Meng XY, Tsuchida T, Fukatsu T . (2012). Cellular mechanism for selective vertical transmission of an obligate insect symbiont at the bacteriocyte-embryo interface. Proc Natl Acad Sci USA 109: E1230–E1237.Kuo CH, Moran NA, Ochman H . (2009). The consequences of genetic drift for bacterial genome complexity. Genome Res 19: 1450–1454.Kuo CH, Ochman H . (2009). Deletional bias across the three domains of life. Genome Biol Evol 1: 145–152.Law R, Lewis DH . (1983). Biotic environments and the maintenance of sex-some evidence from mutualistic symbioses. Biol J Linnean Soc 20: 28.Liu XD, Xie L, Wei Y, Zhou X, Jia B, Liu J et al. (2014). Abiotic stress resistance, a novel moonlighting function of ribosomal protein RPL44 in the halophilic fungus Aspergillus glaucus. Appl Environ Microbiol 80: 4294–4300.Lohse M, Bolger AM, Nagel A, Fernie AR, Lunn JE, Stitt M et al. (2012). RobiNA: a user-friendly, integrated software solution for RNA-Seq-based transcriptomics. Nucleic Acids Res 40: W622–W627.Macdonald SJ, Lin GG, Russell CW, Thomas GH, Douglas AE . (2012). The central role of the host cell in symbiotic nitrogen metabolism. Proc Biol Sci 279: 2965–2973.McClure R, Balasubramanian D, Sun Y, Bobrovskyy M, Sumby P, Genco CA et al. (2013). Computational analysis of bacterial RNA-Seq data. Nucleic Acids Res 41: e140.McCutcheon JP, Moran NA . (2012). Extreme genome reduction in symbiotic bacteria. Nat Rev Microbiol 10: 13–26.McFall-Ngai M, Hadfield MG, Bosch TC, Carey HV, Domazet-Loso T, Douglas AE et al. (2013). Animals in a bacterial world, a new imperative for the life sciences. Proc Natl Acad Sci USA 110: 3229–3236.Mira A, Ochman H, Moran NA . (2001). Deletional bias and the evolution of bacterial genomes. Trends Genet 17: 589–596.Moran NA . (1996). Accelerated evolution and Muller's rachet in endosymbiotic bacteria. Proc Natl Acad Sci USA 93: 2873–2878.Moran NA, Dunbar HE, Wilcox JL . (2005). Regulation of transcription in a reduced bacterial genome: nutrient-provisioning genes of the obligate symbiont Buchnera aphidicola. J Bacteriol 187: 4229–4237.Moran NA, McCutcheon JP, Nakabachi A . (2008). Genomics and evolution of heritable bacterial symbionts. Annu Rev Genet 42: 165–190.Moran NA, McLaughlin HJ, Sorek R . (2009). The dynamics and time scale of ongoing genomic erosion in symbiotic bacteria. Science 323: 379–382.Nakabachi A, Ishida K, Hongoh Y, Ohkuma M, Miyagishima SY . (2014). Aphid gene of bacterial origin encodes a protein transported to an obligate endosymbiont. Curr Biol 24: R640–R641.Nilsson AI, Koskiniemi S, Eriksson S, Kugelberg E, Hinton JC, Andersson DI . (2005). Bacterial genome size reduction by experimental evolution. Proc Natl Acad Sci USA 102: 12112–12116.Patino-Navarrete R, Moya A, Latorre A, Pereto J . (2013). Comparative genomics of Blattabacterium cuenoti: the frozen legacy of an ancient endosymbiont genome. Genome Biol Evol 5: 351–361.Pettersson ME, Berg OG . (2007). Muller's ratchet in symbiont populations. Genetica 130: 199–211.Price DR, Feng H, Baker JD, Bavan S, Luetje CW, Wilson AC . (2014). Aphid amino acid transporter regulates glutamine supply to intracellular bacterial symbionts. Proc Natl Acad Sci USA 111: 320–325.Reyes-Prieto M, Vargas-Chavez C, Latorre A, Moya A . (2015). SymbioGenomesDB: a database for the integration and access to knowledge on host-symbiont relationships. Database 2015: bav109 (1–8).Robinson MD, McCarthy DJ, Smyth GK . (2010). edgeR: a Bioconductor package for differential expression analysis of digital gene expression data. Bioinformatics 26: 139–140.Sabater-Muñoz B, Prats-Escriche M, Montagud-Martinez R, Lopez-Cerdan A, Toft C, Aguilar-Rodriguez J et al. (2015). Fitness trade-offs determine the role of the molecular chaperonin groel in buffering mutations. Mol Biol Evol 32: 2681–2693.Schlicker A, Domingues FS, Rahnenfuhrer J, Lengauer T . (2006). A new measure for functional similarity of gene products based on Gene Ontology. BMC Bioinformatics 7: 302.Shigenobu S, Watanabe H, Hattori M, Sakaki Y, Ishikawa H . (2000). Genome sequence of the endocellular bacterial symbiont of aphids Buchnera sp. APS. Nature 407: 81–86.Supek F, Bosnjak M, Skunca N, Smuc T . (2011). REVIGO summarizes and visualizes long lists of gene ontology terms. PLoS ONE 6: e21800.Tamas I, Klasson L, Canback B, Naslund AK, Eriksson AS, Wernegreen JJ et al. (2002). 50 million years of genomic stasis in endosymbiotic bacteria. Science 296: 2376–2379.Toft C, Fares MA . (2008). The evolution of the flagellar assembly pathway in endosymbiotic bacterial genomes. Mol Biol Evol 25: 2069–2076.van Ham RC, Kamerbeek J, Palacios C, Rausell C, Abascal F, Bastolla U et al. (2003). Reductive genome evolution in Buchnera aphidicola. Proc Natl Acad Sci USA 100: 581–586.Wernegreen JJ . (2002). Genome evolution in bacterial endosymbionts of insects. Nat Rev Genet 3: 850–861.Wernegreen JJ . (2011). Reduced selective constraint in endosymbionts: elevation in radical amino acid replacements occurs genome-wide. PLoS One 6: e28905.Williams TA, Fares MA . (2010). The effect of chaperonin buffering on protein evolution. Genome Biol Evol 2: 609–619.Yang Z . (2007). PAML 4: phylogenetic analysis by maximum likelihood. Mol Biol Evol 24: 1586–1591
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