6,918 research outputs found
Host-Specific Enzyme-Substrate Interactions in SPM-1 Metallo-beta-Lactamase are Modulated by Second Sphere Residues
Pseudomonas aeruginosa is one of the most virulent and resistant non-fermenting Gram-negative pathogens in the clinic. Unfortunately, P. aeruginosa has acquired genes encoding metallo-beta-lactamases (MBLs), enzymes able to hydrolyze most beta-lactam antibiotics. SPM-1 is an MBL produced only by P. aeruginosa, while other MBLs are found in different bacteria. Despite similar active sites, the resistance profile of MBLs towards beta-lactams changes from one enzyme to the other. SPM-1 is unique among pathogen-associated MBLs in that in that it contains "atypical" second sphere residues (S84, G121). Codon randomization on these positions and further selection of resistance-conferring mutants was performed. MICs, periplasmic enzymatic activity, Zn(II) requirements, and protein stability was assessed. Our results indicated that identity of second sphere residues modulates the substrate preferences and the resistance profile of SPM-1 expressed in P. aeruginosa. The second sphere residues found in wild type SPM-1 give rise to a substrate selectivity that is observed only in the periplasmic environment. These residues also allow SPM-1 to confer resistance in P. aeruginosa under Zn(II)-limiting conditions, such as those expected under infection. By optimizing the catalytic efficiency towards beta-lactam antibiotics, the enzyme stability and the Zn(II) binding features, molecular evolution meets the specific needs of a pathogenic bacterial host by means of substitutions outside the active site.Fil: Gonzalez, Lisandro Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Moreno, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; ArgentinaFil: Bonomo, Robert A.. Case Western Reserve University; Estados UnidosFil: Vila, Alejandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; Argentin
TLR4 and NLRP3 Caspase 1- IL-1β- Axis are not Involved in Colon Ascendens Stent Peritonitis (Casp)-Associated Heart Disease
Hemodynamic collapse and myocardial dysfunction are among the major causes ofdeath in severe sepsis. The purpose of this study was to assess the role played by TLR4and by the NLRP3 inflammasome in the cardiac dysfunction that occurs after highgradepolymicrobial sepsis. We performed the colon ascendens stent peritonitis (CASP)surgery in Tlr4-/-, Nlrp3-/- and caspase-1-/- mice. We also assessed for the first time theelectrical heart function in the CASP model. The QJ interval was increased in wild-typeC57BL/6J mice after CASP when compared to sham controls, a result paralleled by anincrease in the cardiac action potential duration (APD). The decreases in ejectionfraction (EF), left-ventricle end diastolic volume (LVEDV), stroke volume, and cardiacoutput found after CASP were similar among all groups of mice. Similar heart responsewas found when Nlrp3-/- mice were submitted to high-grade CLP. Despite developingcardiac dysfunction similar to wild-types after CASP, Nlrp3-/- mice had reducedcirculating levels of IL-1β, IL-6 and TNF-α. Our results demonstrate that the geneticablation of Tlr4, Nlrp3, and caspase-1 does not prevent the cardiac dysfunction, despitepreventing the increase in pro-inflammatory cytokines, indicating that these are notfeasible targets to therapy in high-grade sepsis.Fil: López Alarcón, Maria Micaela. Universidade Federal do Rio de Janeiro; BrasilFil: Fernandez Ruocco, Maria Julieta. Universidade Federal do Rio de Janeiro; BrasilFil: Ferreira, Fabiano. Universidade Federal do Rio de Janeiro; BrasilFil: Paula Neto, Heitor A.. Universidade Federal do Rio de Janeiro; BrasilFil: Sepúlveda, Marisa Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Investigaciones Cardiovasculares ; ArgentinaFil: Vila Petroff, Martin Gerarde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Investigaciones Cardiovasculares ; ArgentinaFil: Carvalho, Adriana Bastos. Universidade Federal do Rio de Janeiro; BrasilFil: Peroba Ramos, Isalira. Universidade Federal do Rio de Janeiro; BrasilFil: Branda, Hugo Justino. Universidade Federal do Rio de Janeiro; BrasilFil: Neto Paiva, Claudia. Universidade Federal do Rio de Janeiro; BrasilFil: Medei, Emiliano. Universidade Federal do Rio de Janeiro; Brasi
Herbicide-resistant weeds : from research and knowledge to future needs
Synthetic herbicides have been used globally to control weeds in major field crops. This has imposed a strong selection for any trait that enables plant populations to survive and reproduce in the presence of the herbicide. Herbicide resistance in weeds must be minimized because it is a major limiting factor to food security in global agriculture. This represents a huge challenge that will require great research efforts to develop control strategies as alternatives to the dominant and almost exclusive practice of weed control by herbicides. Weed scientists, plant ecologists and evolutionary biologists should join forces and work towards an improved and more integrated understanding of resistance across all scales. This approach will likely facilitate the design of innovative solutions to the global herbicide resistance challenge
Investigating the origins and evolution of a glyphosate-resistant weed invasion in South America
The global invasion, and subsequent spread and evolution of weeds provides unique opportunities to address fundamental questions in evolutionary and invasion ecology. Amaranthus palmeri is a widespread glyphosate-resistant (GR) weed in the USA. Since 2015, GR populations of A. palmeri have been confirmed in South America, raising questions about introduction pathways and the importance of pre- vs. post-invasion evolution of GR traits. We used RAD-sequencing genotyping to characterize genetic structure of populations from Brazil, Argentina, Uruguay and the USA. We also quantified gene copy number of the glyphosate target, 5-enolpyruvyl-3-shikimate phosphate synthase (EPSPS), and the presence of an extrachromosomal circular DNA (eccDNA) replicon known to confer glyphosate resistance in USA populations. Populations in Brazil, Argentina and Uruguay were only weakly differentiated (pairwise FST ≤0.043) in comparison to USA populations (mean pairwise FST =0.161, range =0.068–0.258), suggesting a single major invasion event. However, elevated EPSPS copy number and the EPSPS replicon were identified in all populations from Brazil and Uruguay, but only in a single Argentinean population. These observations are consistent with independent in situ evolution of glyphosate resistance in Argentina, followed by some limited recent migration of the eccDNA-based mechanism from Brazil to Argentina. Taken together, our results are consistent with an initial introduction of A. palmeri into South America sometime before the 1980s, and local evolution of GR in Argentina, followed by a secondary invasion of GR A. palmeri with the unique eccDNA-based mechanism from the USA into Brazil and Uruguay during the 2010s.Fil: Gaines, Todd A. State University of Colorado - Fort Collins; Estados UnidosFil: Slavov, Gancho. No especifíca;Fil: Hughes, David. No especifíca;Fil: Kupper, Anita. State University of Colorado - Fort Collins; Estados UnidosFil: Sparks, Crystal. State University of Colorado - Fort Collins; Estados UnidosFil: Oliva, Julian. Universidad Católica de Córdoba; ArgentinaFil: Vila Aiub, Martin Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: García, Alejandro Marcelo. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Merotto, Aldo. Universidade Federal do Rio Grande do Sul; BrasilFil: Neve, Paul. No especifíca
Examining the Seyfert - Starburst Connection with Arcsecond Resolution Radio Continuum Observations
We compare the arcsecond-scale circumnuclear radio continuum properties
between five Seyfert and five starburst galaxies, concentrating on the search
for any structures that could imply a spatial or causal connection between the
nuclear activity and a circumnuclear starburst ring. No evidence is found in
the radio emission for a link between the triggering or feeding of nuclear
activity and the properties of circumnuclear star formation. Conversely, there
is no clear evidence of nuclear outflows or jets triggering activity in the
circumnuclear rings of star formation. Interestingly, the difference in the
angle between the apparent orientation of the most elongated radio emission and
the orientation of the major axis of the galaxy is on average larger in
Seyferts than in starburst galaxies, and Seyferts appear to have a larger
physical size scale of the circumnuclear radio continuum emission. The
concentration, asymmetry, and clumpiness parameters of radio continuum emission
in Seyferts and starbursts are comparable, as are the radial profiles of radio
continuum and near-infrared line emission. The circumnuclear star formation and
supernova rates do not depend on the level of nuclear activity. The radio
emission usually traces the near-infrared Br-gamma and H2 1-0 S(1) line
emission on large spatial scales, but locally their distributions are
different, most likely because of the effects of varying local magnetic fields
and dust absorption and scattering.Comment: 21 pages, 10 figures. Accepted for publication in the Astronomical
Journa
An updated checklist of the European Butterflies (Lepidoptera, Papilionoidea)
This paper presents an updated checklist of the butterflies of Europe, together with their original name combinations, and their occurrence status in each European country. According to this checklist, 496 species of the superfamily Papilionoidea occur in Europe. Changes in comparison with the last version (2.6.2) of Fauna Europaea are discussed. Compared to that version, 16 species are new additions, either due to cryptic species most of which have been discovered by molecular methods (13 cases) or due to discoveries of Asian species on the eastern border of the European territory in the Ural mountains (three cases). On the other hand, nine species had to be removed from the list, because they either do not occur in Europe or lost their species status due to new evidence. In addition, three species names had to be changed and 30 species changed their combination due to new evidence on phylogenetic relationships. Furthermore, minor corrections were applied to some authors¿ names and years of publication. Finally, the name Polyommatus ottomanus Lefèbvre, 1831, which is threatened by its senior synonym Lycaena legeri Freyer, 1830, is declared a nomen protectum, thereby conserving its name in the current combination Lycaena ottomana.VL was supported by grant N 14-14-00541 from the Russian Science Foundation
to the Zoological Institute of the Russian Academy of Sciences and ZF by grant 14-
36098G from the Czech Science Foundation
Integrated Nebular Abundances of Disk Galaxies
We study whether integrated optical spectroscopy of a disk galaxy can be used
to infer the mean, or characteristic gas-phase oxygen abundance in the presence
of systematic effects such as spatial abundance variations, contributions to
the integrated emission-line spectrum from diffuse-ionized gas, and dust
attenuation. Our sample consists of 14 nearby disk galaxies with integrated
spectrophotometry, and observations of more than 250 individual HII regions
culled from the literature. We consider both theoretical and empirical
strong-line abundance calibrations based on the R23=([OII]+[OIII])/H-beta
parameter. We find that the integrated oxygen abundance correlates well with
the gas-phase abundance measured at a fixed galactocentric radius, as
determined by the HII-region abundance gradient. The typical scatter in the
correlation is +/-0.1 dex, independent of the abundance calibration, or whether
the observed integrated emission-line fluxes, the reddening-corrected fluxes,
or the emission-line equivalent widths are used. Integrated abundances based on
the observed fluxes or equivalent widths, however, are susceptible to
additional systematic effects of order 0.05-0.1 dex, at least for the range of
reddenings and stellar populations spanned by our sample. Unlike the integrated
R23 parameter, we find that the integrated [NII]/H-alpha and [SII]/H-alpha
ratios are enhanced with respect to line-ratios typical of HII regions,
consistent with a modest contribution from diffuse-ionized gas emission. We
conclude that the R23 parameter can be used to reliably measure the gas-phase
abundances of distant star-forming galaxies.Comment: 12 pages, 7 figures, 4 tables, emulateapj style; ApJ, in press;
replaced with accepted version (expanded analysis/discussion, main
conclusions unchanged
PINGS: the PPAK IFS Nearby Galaxies Survey
We present the PPAK Integral Field Spectroscopy (IFS) Nearby Galaxies Survey:
PINGS, a 2-dimensional spectroscopic mosaicking of 17 nearby disk galaxies in
the optical wavelength range. This project represents the first attempt to
obtain continuous coverage spectra of the whole surface of a galaxy in the
nearby universe. The final data set comprises more than 50000 individual
spectra, covering in total an observed area of nearly 80 arcmin^2. In this
paper we describe the main astrophysical issues to be addressed by the PINGS
project, we present the galaxy sample and explain the observing strategy, the
data reduction process and all uncertainties involved. Additionally, we give
some scientific highlights extracted from the first analysis of the PINGS
sample.Comment: Accepted for publication in MNRAS, 26 pages, 14 figures (some in low
resolution), 3 table
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