249 research outputs found
Hydrogen peroxide is a neuronal alarmin that triggers specific RNAs, local translation of Annexin A2, and cytoskeletal remodeling in Schwann cells
Schwann cells are key players in neuro-regeneration: They sense "alarm" signals released by degenerating nerve terminals and differentiate toward a proregenerative phenotype, with phagocytosis of nerve debris and nerve guidance. At the murine neuromuscular junction, hydrogen peroxide (H2O2) is a key signal of Schwann cells' activation in response to a variety of nerve injuries. Here we report that Schwann cells exposed to low doses of H2O2 rewire the expression of several RNAs at both transcriptional and translational levels. Among the genes positively regulated at both levels, we identified an enriched cluster involved in cytoskeleton remodeling and cell migration, with the Annexin (Anxa) proteins being the most represented family. We show that both Annexin A2 (Anxa2) transcript and protein accumulate at the tips of long pseudopods that Schwann cells extend upon H2O2 exposure. Interestingly, Schwann cells reply to this signal and to nerve injury by locally translating Anxa2 in pseudopods, and undergo an extensive cytoskeleton remodeling. Our results show that, similarly to neurons, Schwann cells take advantage of local protein synthesis to change shape and move toward damaged axonal terminals to facilitate axonal regeneration
MIRELLA: a mathematical model explains the effect of microRNA-mediated synthetic genes regulation on intracellular resource allocation
Competition for intracellular resources, also known as gene expression burden, induces coupling between independently co-expressed genes, a detrimental effect on predictability and reliability of gene circuits in mammalian cells. We recently showed that microRNA (miRNA)-mediated target downregulation correlates with the upregulation of a co-expressed gene, and by exploiting miRNAs-based incoherent-feed-forward loops (iFFLs) we stabilise a gene of interest against burden. Considering these findings, we speculate that miRNA-mediated gene downregulation causes cellular resource redistribution. Despite the extensive use of miRNA in synthetic circuits regulation, this indirect effect was never reported before. Here we developed a synthetic genetic system that embeds miRNA regulation, and a mathematical model, MIRELLA, to unravel the miRNA (MI) RolE on intracellular resource aLLocAtion. We report that the link between miRNA-gene downregulation and independent genes upregulation is a result of the concerted action of ribosome redistribution and ‘queueing-effect’ on the RNA degradation pathway. Taken together, our results provide for the first time insights into the hidden regulatory interaction of miRNA-based synthetic networks, potentially relevant also in endogenous gene regulation. Our observations allow to define rules for complexity- and context-aware design of genetic circuits, in which transgenes co-expression can be modulated by tuning resource availability via number and location of miRNA target sites
The Herschel Stripe 82 Survey (HerS): maps and early catalog
We present the first set of maps and band-merged catalog from the Herschel Stripe 82 Survey (HerS). Observations at 250, 350, and 500μm were taken with the Spectral and Photometric Imaging Receiver instrument aboard the Herschel Space Observatory. HerS covers 79deg 2 along the SDSS Stripe 82 to an average depth of 13.0, 12.9, and 14.8mJybeam −1 (including confusion) at 250, 350, and 500μm, respectively. HerS was designed to measure correlations with external tracers of the dark matter density field—either point-like (i.e., galaxies selected from radio to X-ray) or extended (i.e., clusters and gravitational lensing)—in order to measure the bias and redshift distribution of intensities of infrared-emitting dusty star-forming galaxies and active galactic nuclei. By locating HerS in Stripe 82, we maximize the overlap with available and upcoming cosmological surveys. The band-merged catalog contains 3.3 × 10 4 sources detected at a significance of ?3σ (including confusion noise). The maps and catalog are available at http://www.astro.caltech.edu/hers/
HerMES: point source catalogues from Herschel-SPIRE observations II
Key Programme on the Herschel Space Observatory. With a wedding cake survey strategy, it consists of nested fields with varying depth and area totalling ∼380 deg2. In this paper, we present deep point source catalogues extracted from Herschel-Spectral and Photometric Imaging Receiver (SPIRE) observations of all HerMES fields, except for the later addition of the 270 deg2 HerMES Large-Mode Survey (HeLMS) field. These catalogues constitute the second Data Release (DR2) made in 2013 October. A sub-set of these catalogues, which consists of bright sources extracted from Herschel-SPIRE observations completed by 2010 May 1 (covering ∼74 deg2) were released earlier in the first extensive data release in 2012 March. Two different methods are used to generate the point source catalogues, the SUSSEXTRACTOR point source extractor used in two earlier data releases (EDR and EDR2) and a new source detection and photometry method. The latter combines an iterative source detection algorithm, STARFINDER, and a De-blended SPIRE Photometry algorithm. We use end-to-end Herschel-SPIRE simulations with realistic number counts and clustering properties to characterize basic properties of the point source catalogues, such as the completeness, reliability, photometric and positional accuracy. Over 500 000 catalogue entries in HerMES fields (except HeLMS) are released to the public through the HeDAM (Herschel Database in Marseille) website (http://hedam.lam.fr/HerMES)
BLAST Observations of the South Ecliptic Pole field: Number Counts and Source Catalogs
We present results from a survey carried out by the Balloon-borne Large
Aperture Submillimeter Telescope (BLAST) on a 9 deg^2 field near the South
Ecliptic Pole at 250, 350 and 500 {\mu}m. The median 1{\sigma} depths of the
maps are 36.0, 26.4 and 18.4 mJy, respectively. We apply a statistical method
to estimate submillimeter galaxy number counts and find that they are in
agreement with other measurements made with the same instrument and with the
more recent results from Herschel/SPIRE. Thanks to the large field observed,
the new measurements give additional constraints on the bright end of the
counts. We identify 132, 89 and 61 sources with S/N>4 at 250, 350, 500 {\mu}m,
respectively and provide a multi-wavelength combined catalog of 232 sources
with a significance >4{\sigma} in at least one BLAST band. The new BLAST maps
and catalogs are available publicly at http://blastexperiment.info.Comment: 25 pages, 6 figures, 4 tables, Accepted by ApJS. Maps and catalogs
available at http://blastexperiment.info
Submillimeter Number Counts From Statistical Analysis of BLAST Maps
We describe the application of a statistical method to estimate submillimeter
galaxy number counts from confusion limited observations by the Balloon-borne
Large Aperture Submillimeter Telescope (BLAST). Our method is based on a
maximum likelihood fit to the pixel histogram, sometimes called 'P(D)', an
approach which has been used before to probe faint counts, the difference being
that here we advocate its use even for sources with relatively high
signal-to-noise ratios. This method has an advantage over standard techniques
of source extraction in providing an unbiased estimate of the counts from the
bright end down to flux densities well below the confusion limit. We
specifically analyse BLAST observations of a roughly 10 sq. deg. map centered
on the Great Observatories Origins Deep Survey South (GOODS-S) field. We
provide estimates of number counts at the three BLAST wavelengths, 250, 350,
and 500 microns; instead of counting sources in flux bins we estimate the
counts at several flux density nodes connected with power-laws. We observe a
generally very steep slope for the counts of about -3.7 at 250 microns and -4.5
at 350 and 500 microns, over the range ~0.02-0.5 Jy, breaking to a shallower
slope below about 0.015 Jy at all three wavelengths. We also describe how to
estimate the uncertainties and correlations in this method so that the results
can be used for model-fitting. This method should be well-suited for analysis
of data from the Herschel satellite.Comment: Accepted for publication in the Astrophysical Journal; see associated
data and other papers at http://blastexperiment.info
A panchromatic study of BLAST counterparts: total star-formation rate, morphology, AGN fraction and stellar mass
We carry out a multi-wavelength study of individual galaxies detected by the
Balloon-borne Large Aperture Submillimeter Telescope (BLAST) and identified at
other wavelengths, using data spanning the radio to the ultraviolet (UV). We
develop a Monte Carlo method to account for flux boosting, source blending, and
correlations among bands, which we use to derive deboosted far-infrared (FIR)
luminosities for our sample. We estimate total star-formation rates for BLAST
counterparts with z < 0.9 by combining their FIR and UV luminosities. Star
formation is heavily obscured at L_FIR > 10^11 L_sun, z > 0.5, but the
contribution from unobscured starlight cannot be neglected at L_FIR < 10^11
L_sun, z < 0.25. We assess that about 20% of the galaxies in our sample show
indication of a type-1 active galactic nucleus (AGN), but their submillimeter
emission is mainly due to star formation in the host galaxy. We compute stellar
masses for a subset of 92 BLAST counterparts; these are relatively massive
objects, with a median mass of ~10^11 M_sun, which seem to link the 24um and
SCUBA populations, in terms of both stellar mass and star-formation activity.
The bulk of the BLAST counterparts at z<1 appear to be run-of-the-mill
star-forming galaxies, typically spiral in shape, with intermediate stellar
masses and practically constant specific star-formation rates. On the other
hand, the high-z tail of the BLAST counterparts significantly overlaps with the
SCUBA population, in terms of both star-formation rates and stellar masses,
with observed trends of specific star-formation rate that support strong
evolution and downsizing.Comment: Accepted for publication in the Astrophysical Journal. 44 pages, 11
figures. The SED template for the derivation of L_FIR has changed (added new
figure) and the discussion on the stellar masses has been improved. The
complete set of full-color postage-stamps can be found at
http://blastexperiment.info/results_images/moncelsi
Environment of MAMBO galaxies in the COSMOS field
Submillimeter galaxies (SMG) represent a dust-obscured high-redshift
population undergoing massive star formation activity. Their properties and
space density have suggested that they may evolve into spheroidal galaxies
residing in galaxy clusters. In this paper, we report the discovery of compact
(~10"-20") galaxy overdensities centered at the position of three SMGs detected
with the Max-Planck Millimeter Bolometer camera (MAMBO) in the COSMOS field.
These associations are statistically significant. The photometric redshifts of
galaxies in these structures are consistent with their associated SMGs; all of
them are between z=1.4-2.5, implying projected physical sizes of ~170 kpc for
the overdensities. Our results suggest that about 30% of the radio-identified
bright SMGs in that redshift range form in galaxy density peaks in the crucial
epoch when most stars formed.Comment: Accepted for publication in ApJ Letter
HELP: star formation as function of galaxy environment with Herschel
The Herschel Extragalactic Legacy Project (HELP) brings together a vast range of data from many astronomical observatories. Its main focus is on the Herschel data, which maps dust obscured star formation over 1300 deg2. With this unprecedented combination of data sets, it is possible to investigate how the star formation vs stellar mass relation (main-sequence) of star-forming galaxies depends on environment. In this pilot study we explore this question between 0:1 2. We also estimate the evolution of the star formation rate density in the COSMOS field and our results are consistent with previous measurements at z 2 but we find a 1:4 (superscript) +0:3 (subscript) 0:2 times higher peak value of the star formation rate density at z about 1:9
A Bright Submillimeter Source in the Bullet Cluster (1E0657--56) Field Detected with BLAST
We present the 250, 350, and 500 micron detection of bright submillimeter
emission in the direction of the Bullet Cluster measured by the Balloon-borne
Large Aperture Submillimeter Telescope (BLAST). The 500 micron centroid is
coincident with an AzTEC 1.1 mm point-source detection at a position close to
the peak lensing magnification produced by the cluster. However, the 250 micron
and 350 micron centroids are elongated and shifted toward the south with a
differential shift between bands that cannot be explained by pointing
uncertainties. We therefore conclude that the BLAST detection is likely
contaminated by emission from foreground galaxies associated with the Bullet
Cluster. The submillimeter redshift estimate based on 250-1100 micron
photometry at the position of the AzTEC source is z_phot = 2.9 (+0.6 -0.3),
consistent with the infrared color redshift estimation of the most likely IRAC
counterpart. These flux densities indicate an apparent far-infrared luminosity
of L_FIR = 2E13 Lsun. When the amplification due to the gravitational lensing
of the cluster is removed, the intrinsic far-infrared luminosity of the source
is found to be L_FIR <= 10^12 Lsun, consistent with typical luminous infrared
galaxies.Comment: Accepted for publication in the Astrophysical Journal. Maps are
available at http://blastexperiment.info
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