2,333 research outputs found
Temperature Affects Hatching Success of Cocoons in the Invasive Asian Earthworm Amynthas agrestis from the Southern Appalachians
Invasive Asian earthworms are increasingly common in the eastern USA where they are a major cause of terrestrial ecosystem disturbance. Among these, Amynthas agrestis (Crazy Worm, Alabama Jumper, and other common names) has been shown to alter above- and belowground food webs. Life-history traits of these earthworms are largely unknown, particularly in their invaded range. Here, we sought to answer questions about temperature effects on hatching success for cocoons of this species, using specimens collected from the southern Appalachian Mountains. We conducted 2 experiments investigating the effects of incubation temperature and the effect of varying the duration of cold temperature on hatching success. Of the temperatures tested, we found that cocoons hatched with greatest success at 10 °C, but our tests indicate a long duration at that temperature may be needed to result in an increase in hatching success. These results indicate that temperature and the duration of temperature exposure affect hatching success in this species. While our results contribute to the growing body of knowledge about the life-history traits of invasive Asian earthworms in the eastern US, more research is needed to provide a finer-resolution understanding of the optimum level and duration of temperatures for hatching success of A. agrestis
Gibberellin A1 Metabolism Contributes to the Control of Photoperiod-Mediated Tuberization in Potato
Some potato species require a short-day (SD) photoperiod for tuberization, a process that is negatively affected by gibberellins (GAs). Here we report the isolation of StGA3ox2, a gene encoding a GA 3-oxidase, whose expression is increased in the aerial parts and is repressed in the stolons after transfer of photoperiod-dependent potato plants to SD conditions. Over-expression of StGA3ox2 under control of constitutive or leaf-specific promoters results in taller plants which, in contrast to StGA20ox1 over-expressers previously reported, tuberize earlier under SD conditions than the controls. By contrast, StGA3ox2 tuber-specific over-expression results in non-elongated plants with slightly delayed tuber induction. Together, our experiments support that StGA3ox2 expression and gibberellin metabolism significantly contribute to the tuberization time in strictly photoperiod-dependent potato plants
SPROUTY-2 represses the epithelial phenotype of colon carcinoma cells via upregulation of ZEB1 mediated by ETS1 and miR-200/miR-150
SPROUTY-2 (SPRY2) is a modulator of tyrosine kinase receptor signaling with
receptor- and cell type-dependent inhibitory or enhancing effects. Studies on the action
of SPRY2 in major cancers are conflicting and its role remains unclear. Here we have
dissected SPRY2 action in human colon cancer. Global transcriptomic analyses show
that SPRY2 downregulates genes encoding tight junction proteins such as claudin-7 and
occludin and other cell-to-cell and cell-to-matrix adhesion molecules in human SW480-
ADH colon carcinoma cells. Moreover, SPRY2 represses LLGLL2/HUGL2,
PATJ1/INADL and ST14, main regulators of the polarized epithelial phenotype, and
ESRP1, an epithelial-to-mesenchymal transition (EMT) inhibitor. A key action of
SPRY2 is the upregulation of the major EMT inducer ZEB1, as these effects are
reversed by ZEB1 knock-down by means of RNA interference. Consistently, we found
an inverse correlation between the expression level of claudin-7 and those of SPRY2
and ZEB1 in human colon tumors. Mechanistically, ZEB1 upregulation by SPRY2
results from the combined induction of ETS1 transcription factor and the repression of
microRNAs (miR-200 family, miR-150) that target ZEB1 RNA. Moreover, SPRY2
increased AKT activation by epidermal growth factor (EGF) whereas AKT and also Src
inhibition reduced the induction of ZEB1. Altogether, these data suggest that AKT and
Src are implicated in SPRY2 action. Collectively, these results show a tumorigenic role
of SPRY2 in colon cancer that is based on the dysregulation of tight junction and
epithelial polarity master genes via upregulation of ZEB1. The dissection of the
mechanism of action of SPRY2 in colon cancer cells is important to understand the
upregulation of this gene in a subset of patients with this neoplasia that have poor
prognosis.This study was supported by the Ministerio de
Economía y Competitividad of Spain and Fondo Europeo de Desarrollo Regional
(FEDER) (grant SAF2013-43468-R to A.M., SAF2011-29530 to F.X.R.); FEDERInstituto
de Salud Carlos III (RD12/0036/0021 to A.M. and J.M.R., RD12/0036/0034 to
F.X.R., RD12/0036/0016 to M.S., RD12/0036/0012 to H.G.P., RD06/0020/0003,
PS09/00562 and PI13/00703 to J.M.R.); Comunidad de Madrid (S2010/BMD-2344
Colomics2 to A.M.); Fundación Científica de la Asociación Española contra el Cáncer
(to J.M.R.); U.S. Department of Defense (CA093471 and CA110602 to E.H.); National
Institutes of Health/National Cancer Institute (1R01CA155234-01 to E.H.); National
Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin
Diseases (1R21AR062239-01 to E.H.); and the Melanoma Research Alliance (to E. H.)
Short-term variability in the activity and composition of the diazotroph community in a coastal upwelling system
Today we know that diazotrophs are common and active in nitrogen (N) replete regions, however the factors controlling their distribution remain elusive. Previous studies in upwelling regions revealed that the composition of diazotrophs responded to changes in hydrodynamic forcing over seasonal scales. Here we used high-frequency observations collected during a 3-week cruise in the upwelling region off NW Iberia to describe changes in the activity and composition of diazotrophs over shorter temporal scales. The cruise started after a strong upwelling event followed by a few days of relaxation-downwelling, and soon after another upwelling pulse. Higher N2 fixation rates (2.2 ± 0.7 µmol m-3 d-1) were measured during relaxation-downwelling, when surface nitrate concentration was low. During the fertilization associated with the upwelling, N2 fixation dramatically decreased to 0.10 ± 0.09 µmol m-3 d-1. The comparison with nitrate consumption and diffusion confirmed the minor role of N2 fixation (<1%) as a source of new N for primary production. The unicellular cyanobacterium UCYN-A2 was the dominant diazotroph during the cruise. UCYN-A2 abundance was four times higher during relaxation-downwelling (4x104 copies L-1) compared to upwelling conditions (0.2x104 copies L-1), when the unusual Epsilonproteobacteria increased their relative abundance. These results indicate that diazotrophs can respond rapidly to changes in the environment, and point out to the availability of N as a key factor controlling the activity, composition and distribution of diazotrophs in eutrophic regions
AINUR: Atlas of Images of NUclear Rings
We present the most complete atlas of nuclear rings to date. We include 113
rings found in 107 galaxies, six of which are elliptical galaxies, five are
highly inclined disc galaxies, 18 are unbarred disc galaxies, and 78 are barred
disc galaxies. Star-forming nuclear rings occur in 20% of disc galaxies with
types between T=-3 and T=7. We aim to explore possible relationships between
the size and morphology of the rings and various galactic parameters. We
produce colour index and structure maps, as well as Halpha and Paalpha
continuum-subtracted images from HST archival data. We derive ellipticity
profiles from H-band 2MASS images in order to detect bars and find their metric
parameters. We measure the non-axisymmetric torque parameter, Qg, and search
for correlations between bar, ring metric parameters, and Qg.
Our atlas of nuclear rings includes star-forming and dust rings. Nuclear
rings span a range from a few tens of parsecs to a few kiloparsecs in radius.
Star-forming nuclear rings can be found in a wide range of morphological types,
from S0 to Sd, with a peak in the distribution between Sab and Sb, and without
strong preference for barred galaxies. Dust nuclear rings are found in
elliptical and S0 galaxies. For barred galaxies, the maximum radius that a
nuclear ring can reach is a quarter of the bar radius. We found a nearly random
distribution of PA offsets between nuclear rings and bars. There is some
evidence that nuclear ring ellipticity is limited by bar ellipticity. We
confirm that the maximum relative size of a star-forming nuclear ring is
inversely proportional to the non-axisymmetric torque parameter, Qg, and that
the origin of nuclear rings, even the ones in non-barred hosts, are closely
linked to the existence of dynamical resonances.Comment: Accepted for publication in MNRAS. A full resolution version of the
manuscript with high resolution figures can be found at
http://www.iac.es/folleto/research/preprints
Multi-Element Abundance Measurements from Medium-Resolution Spectra. IV. Alpha Element Distributions in Milky Way Dwarf Satellite Galaxies
We derive the star formation histories of eight dwarf spheroidal (dSph) Milky
Way satellite galaxies from their alpha element abundance patterns. Nearly 3000
stars from our previously published catalog (Paper II) comprise our data set.
The average [alpha/Fe] ratios for all dSphs follow roughly the same path with
increasing [Fe/H]. We do not observe the predicted knees in the [alpha/Fe] vs.
[Fe/H] diagram, corresponding to the metallicity at which Type Ia supernovae
begin to explode. Instead, we find that Type Ia supernova ejecta contribute to
the abundances of all but the most metal-poor ([Fe/H] < -2.5) stars. We have
also developed a chemical evolution model that tracks the star formation rate,
Types II and Ia supernova explosions, and supernova feedback. Without metal
enhancement in the supernova blowout, massive amounts of gas loss define the
history of all dSphs except Fornax, the most luminous in our sample. All six of
the best-fit model parameters correlate with dSph luminosity but not with
velocity dispersion, half-light radius, or Galactocentric distance.Comment: 28 pages, 14 figures; accepted for publication in ApJ; very minor
editorial corrections in v
Search for new fermions ("quirks") at the Fermilab Tevatron Collider
We report results of a search for particles with anomalously high ionization
in events with a high transverse energy jet and large missing transverse energy
in fb of integrated luminosity collected by the D0 experiment at
the Fermilab Tevatron collider. Production of such particles
(quirks) is expected in scenarios with extra QCD-like {\it SU(N)} sectors, and
this study is the first dedicated search for such signatures. We find no
evidence of a signal and set a lower mass limit of 107 ~GeV for the mass of a
charged quirk with strong dynamics scale in the range from 10 keV to
1 MeV.Comment: submitted to Phys. Rev. Letter
Evidence for an anomalous like-sign dimuon charge asymmetry
We measure the charge asymmetry A of like-sign dimuon events in 6.1 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy root s = 1.96 TeV at the Fermilab Tevatron collider. From A, we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.00957 +/- 0.00251 (stat) +/- 0.00146 (syst). This result differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(0.6)(+0.5)) x 10(-4) and provides first evidence of anomalous CP violation in the mixing of neutral B mesons
Search for sneutrino production in emu final states in 5.3 fb^-1 of ppbar collisions at sqrt(s) =1.96 TeV
We report the results of a search for R parity violating (RPV) interactions
leading to the production of supersymmetric sneutrinos decaying into emu final
states using 5.3 fb^-1 of integrated luminosity collected by the D0 experiment
at the Fermilab Tevatron Collider. Having observed no evidence for production
of emu resonances, we set direct bounds on the RPV couplings lambda^'_311 and
lambda_312 as a function of sneutrino mass.Comment: 7 pages, 6 figures. To be submitted to Phys. Rev. Let
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