PepT1 mRNA expression levels in sea bream (Sparus aurata) fed different plant protein sources

The expression and regulation of intestinal oligopeptide transporter (PepT)-1 when vegetable sources are used as a substitute for fish meal in the diet of marine fish has not yet been explored. In the present study, as part of our ongoing work on elucidating PepT1 gene expression in relation to different dietary treatments, we have now isolated and deposited in Genbank database (accession no. GU733710) a cDNA sequence representing the PepT1 in the sea bream (Sparus aurata). The \u201cde novo\u201d prediction of the three-dimensional structure of PepT1 protein is presented. We also analyzed diet-induced changes in the expression of PepT1 mRNA via real-time RTPCR using the standard curve method. Sea bream were fed for 140 days with one of the following four diet formulations (43% protein/21% lipid): a control fast growth-promoting diet (C), and three diets with the same formulation but in which 15% of the fish meal was substituted by protein concentrates either from lupine (LPC), chick pea (CPC), or green pea (PPC). Fish fed PPC had significantly (p < 0.05) lower levels of PepT1 transcripts in the proximal intestine than the controls, whereas PepT1 transcript levels in fish fed LPC or CPC were not significantly different from the controls. Although growth was similar between fish fed with different diets during the first 72 days of feeding, growth of the fish fed with PPC was reduced during the second part of the trial and was significantly (p < 0.05) lower than fish fed LPC and CPC diets by the end of the experiment. Correlation between these results and fish growth performances highlights that the intestinal PepT1 mRNA level may serve as a useful marker of the dietary protein quality and absorption efficiency

Caracterización de cepas de Bacillus thuringiensis berliner y actividad biológica hacia Spodoptera frugiperda (J. E. Smith) (Lepidoptera: noctuidae) y Anticarsia gemmatalis hübner (Lepidoptera: noctuidae).

RESUMEN: Se realizó la caracterización de nueve cepas cubanas de Bacillus thuringiensis según la morfología del cristal, la determinación del patrón de proteínas Cry y la actividad biológica frente a los insectos lepidópteros Spodoptera frugiperda y Anticarsia gemmatalis. Se observó la típica morfología bipiramidal en todas las cepas, y además la presencia de inclusiones cúbicas. El patrón de proteínas Cry obtenido correspondió con el de la cepa estándar internacional de B. thuringiensis var. kurstaki cepa HD1, en el que se observan dos bandas bien definidas correspondientes a la proteína Cry 1 (130 kDa) y Cry 2 (70 kDa). En la evaluación de la actividad biológica las cepas LBT 4 y LBT 7 causaron el 100% de mortalidad frente a S. frugiperda, mientras que las LBT 4, LBT 7, LBT 13 y LBT 47 provocaron el 100% de mortalidad para A. gemmatalis. abstract: This study describes the characterization of nine Cuban Bacillus thuringiensis strains based on crystal morphology, SDS polyacrylamide electrophoresis (PAGE) and insecticidal activity against Spodoptera frugiperda and Anticarsia gemmatalis. Ultrastructural analysis of parasporal bodies of the nine strains showed the typical bipyramidal crystal and cubic inclusion partially embedded in the middle of the bipyramidal crystal. The PAGE analysis showed two bands of 130 kDa and 70 kDa belongs to Cry 1 and Cry 2 protein present to HD1 standard strains B. thuringiensis var. kurstaki. The strains LBT 4 and LBT 7 analyzed in this report showed potential as biological insecticide against S. frugiperda and LBT 4, LBT 7, LBT13 and LBT47 strains showed 100% of mortality to Anticarsia gemmatalis

Stellar Mass and Velocity Functions of Galaxies: Backward evolution and the fate of Milky Way siblings

We attempt in this paper to check the consistency of the observed Stellar Mass Function (SMF), SFR functions and the cosmic star formation rate density with simple backward evolutionary models. Starting from observed SMF for star-forming galaxies, we use backwards models to predict the evolution of a number of quantities, such as the SFR function, the cosmic SFR density and the Velocity Function. The velocity being a parameter attached to a galaxy during its history (contrary to the stellar mass), this approach allows us to quantify the number density evolution of galaxies of a given velocity, e.g. of the Milky Way siblings. Observations suggest that the SMF of star forming galaxies is constant between redshift 0 and 1. In order to reproduce this result, we must quench star formation in a number of star forming galaxies. The SMF of these quenched galaxies is consistent with available data concerning the increase in the population of quiescent galaxies in the same redshift interval. The SMF of quiescent galaxies is then mainly determined by the distribution of active galaxies that must stop star formation, with a modest mass redistribution during mergers. The cosmic SFR density, and the evolution of the SFR functions are relatively well recovered, although they provide some clue for a small evolution of the SMF of star forming galaxies at the lowest redshifts. We thus consider that we have obtained in a simple way a relatively consistent picture of the evolution of galaxies at intermediate redshifts. We note that if this picture is correct, 50 percent of the Milky-Way sisters (galaxies with the same velocity as our Galaxy, i.e. 220 km/s) have quenched their star formation since redshift 1 (and an even larger fraction for larger velocities). We discuss the processes that might be responsible for this transformation.Comment: 12 pages, 14 figures, accepted in Astronomy and Astrophysic

Galaxy interactions II: High density environments

With the aim to assess the role of dense environments in galaxy interactions, properties we present an analysis of close galaxy pairs in groups and clusters, obtained from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). We identified pairs that reside in groups by cross-correlating the total galaxy pair catalogue with the SDSS-DR7 group catalogue from Zapata et al. (2009). We classify pair galaxies according to the intensity of interaction. We analysed the effect of high density environments on different classes of galaxy-galaxy interactions and we have also studied the impact of the group global environment on pair galaxies. We find that galaxy pairs are more concentrated towards the group centres with respect to the other group galaxy members, and disturbed pairs show a preference to contain the brightest galaxy in the groups. The color-magnitude relation exhibits significant differences between pair galaxies and the control sample, consisting in color tails with a clear excess of extremely blue and red galaxies for merging systems. In addition, pair galaxies show a significant excess of young stellar populations with respect to galaxies in the control sample; this finding suggests that, in dense environments, strong interactions produce an important effect in modifying galaxy properties. We find that the fraction of star forming galaxies decreases toward the group centre; however, galaxy pairs show a more efficient star formation activity than galaxies without a close companion. We have also found that pair galaxies prefer groups with low density global environments with respect to galaxies of the corresponding control sample. Blue, young stellar population galaxies prefer groups within low density global environments.Comment: 10 pages, 11 figures, accepted for publication in A&

Galaxy and Mass Assembly (GAMA): merging galaxies and their properties

We derive the close pair fractions and volume merger rates for galaxies in the Galaxy and Mass Assembly (GAMA) survey with −23 < Mr < −17 (ΩM = 0.27, ΩΛ = 0.73, H0 = 100 km s−1 Mpc−1) at 0.01 < z < 0.22 (look-back time of <2 Gyr). The merger fraction is approximately 1.5 per cent Gyr−1 at all luminosities (assuming 50 per cent of pairs merge) and the volume merger rate is ≈3.5 × 10−4 Mpc−3 Gyr−1. We examine how the merger rate varies by luminosity and morphology. Dry mergers (between red/spheroidal galaxies) are found to be uncommon and to decrease with decreasing luminosity. Fainter mergers are wet, between blue/discy galaxies. Damp mergers (one of each type) follow the average of dry and wet mergers. In the brighter luminosity bin (−23 < Mr < −20), the merger rate evolution is flat, irrespective of colour or morphology, out to z ∼ 0.2. The makeup of the merging population does not appear to change over this redshift range. Galaxy growth by major mergers appears comparatively unimportant and dry mergers are unlikely to be significant in the buildup of the red sequence over the past 2 Gyr. We compare the colour, morphology, environmental density and degree of activity (BPT class, Baldwin, Phillips & Terlevich) of galaxies in pairs to those of more isolated objects in the same volume. Galaxies in close pairs tend to be both redder and slightly more spheroid dominated than the comparison sample. We suggest that this may be due to ‘harassment’ in multiple previous passes prior to the current close interaction. Galaxy pairs do not appear to prefer significantly denser environments. There is no evidence of an enhancement in the AGN fraction in pairs, compared to other galaxies in the same volume

What turns galaxies off? The different morphologies of star-forming and quiescent galaxies since z~2 from CANDELS

We use HST/WFC3 imaging from the CANDELS Multicycle Treasury Survey, in conjunction with the Sloan Digital Sky Survey, to explore the evolution of galactic structure for galaxies with stellar masses >3e10M_sun from z=2.2 to the present epoch, a time span of 10Gyr. We explore the relationship between rest-frame optical color, stellar mass, star formation activity and galaxy structure. We confirm the dramatic increase from z=2.2 to the present day in the number density of non-star-forming galaxies above 3e10M_sun reported by others. We further find that the vast majority of these quiescent systems have concentrated light profiles, as parametrized by the Sersic index, and the population of concentrated galaxies grows similarly rapidly. We examine the joint distribution of star formation activity, Sersic index, stellar mass, inferred velocity dispersion, and stellar surface density. Quiescence correlates poorly with stellar mass at all z<2.2. Quiescence correlates well with Sersic index at all redshifts. Quiescence correlates well with `velocity dispersion' and stellar surface density at z>1.3, and somewhat less well at lower redshifts. Yet, there is significant scatter between quiescence and galaxy structure: while the vast majority of quiescent galaxies have prominent bulges, many of them have significant disks, and a number of bulge-dominated galaxies have significant star formation. Noting the rarity of quiescent galaxies without prominent bulges, we argue that a prominent bulge (and perhaps, by association, a supermassive black hole) is an important condition for quenching star formation on galactic scales over the last 10Gyr, in qualitative agreement with the AGN feedback paradigm.Comment: The Astrophysical Journal, in press; 20 pages with 13 figure

An empirical prediction for stellar metallicity distributions in nearby galaxies

We combine star-formation histories derived from observations of high redshift galaxies with measurements of the z~0 relation between gas-phase metallicity, stellar mass, and star formation rate to make an explicit and completely empirical connection between near-field and distant galaxy observations. Our approach relies on two basic assumptions: 1) galaxies' average paths through time in stellar mass vs. star formation rate space are represented by a family of smooth functions that are determined by the galaxies' final stellar mass, and 2) galaxies grow and become enriched with heavy elements such that they always evolve along the mass--metallicity--star formation rate relation. By integrating over these paths, we can track the chemical evolution of stars in galaxies in a model independent way, without the need for explicit assumptions about gas inflow, outflow, or star formation efficiency. Using this approach, we present predictions of stellar metallicity (i.e., O/H) distribution functions for present day star-forming galaxies of different stellar masses and the evolution of the alpha-element stellar metallicity-mass relation since z~1. The metallicity distribution functions are fairly well described as Gaussians, truncated at high metallicity, with power-law tails to low metallicity. We find that the stellar metallicity distribution for Milky Way mass galaxies is in reasonable agreement with observations for our Galaxy, and that the predicted stellar mass vs. mean stellar metallicity relation at z=0 agrees quite well with results derived from galaxy surveys. This validates the assumptions that are implicit in our simple approach. Upcoming observations will further test these assumptions and their range of validity, by measuring the mean stellar mass-metallicity relation up to z~1, and by measuring the stellar metallicity distributions over a range of galaxy masses.Comment: 8 pages, 2 figures, 2 tables. MNRAS, in pres

Newborn spheroids at high redshift: when and how did the dominant, old stars in today's massive galaxies form?

We study ~330 massive (M* > 10^9.5 MSun), newborn spheroidal galaxies (SGs) around the epoch of peak star formation (1<z<3), to explore the high-redshift origin of SGs and gain insight into when and how the old stellar populations that dominate today's Universe formed. The sample is drawn from the HST/WFC3 Early-Release Science programme, which provides deep 10-filter (0.2 - 1.7 micron) HST imaging over a third of the GOODS-South field. We find that the star formation episodes that built the SGs likely peaked in the redshift range 2<z<5 (with a median of z~3) and have decay timescales shorter than ~1.5 Gyr. Starburst timescales and ages show no trend with stellar mass in the range 10^9.5 < M* < 10^10.5 MSun. However, the timescales show increased scatter towards lower values ( 10^10.5 MSun, and an age trend becomes evident in this mass regime: SGs with M* > 10^11.5 MSun are ~2 Gyrs older than their counterparts with M* < 10^10.5 MSun. Nevertheless, a smooth downsizing trend with galaxy mass is not observed, and the large scatter in starburst ages indicate that SGs are not a particularly coeval population. Around half of the blue SGs appear not to drive their star formation via major mergers, and those that have experienced a recent major merger, show only modest enhancements (~40%) in their specific star formation rates. Our empirical study indicates that processes other than major mergers (e.g. violent disk instability driven by cold streams and/or minor mergers) likely play a dominant role in building SGs, and creating a significant fraction of the old stellar populations that dominate today's Universe.Comment: MNRAS in pres