176 research outputs found
Immunohistochemical characteristics of porcine intrahepatic nerves under physiological conditions and after bisphenol A administration
Background: The neurochemistry of hepatic nerve fibres was investigated in large animal models after dietary exposure to the endocrine disrupting compound known as bisphenol A (BPA).
Materials and methods: Antibodies against neuronal peptides were used to study changes in hepatic nerve fibres after exposure to BPA at varying concentrations using standard immunofluorescence techniques. The neuropeptides investigated were substance P (SP), galanin (GAL), pituitary adenylate cyclase activating polypeptide (PACAP), calcitonin gene regulated peptide (CGRP) and cocaine and amphetamine regulated transcript (CART). Immunoreactive nerve fibres were counted in multiple sections of the liver and among multiple animals at varying exposure levels. The data was pooled and presented as mean ± standard error of the mean.
Results: It was found that all of the nerve fibres investigated showed upregulation of these neural markers after BPA exposure, even at exposure levels currently considered to be safe. These results show very dramatic increases in nerve fibres containing the above-mentioned neuropeptides and the altered neurochemical levels may be causing a range of pathophysiological states if the trend of over-expression is extrapolated to developing humans.
Conclusions: This may have serious implications for children and young adults who are exposed to this very common plastic polymer, if the same trends are occurring in humans
The obscured hyper-energetic GRB 120624B hosted by a luminous compact galaxy at z = 2.20
Gamma-ray bursts are the most luminous explosions that we can witness in the
Universe. Studying the most extreme cases of these phenomena allows us to
constrain the limits for the progenitor models. In this Letter, we study the
prompt emission, afterglow, and host galaxy of GRB 120624B, one of the
brightest GRBs detected by Fermi, to derive the energetics of the event and
characterise the host galaxy in which it was produced. Following the
high-energy detection we conducted a multi-wavelength follow-up campaign,
including near-infrared imaging from HAWKI/VLT, optical from OSIRIS/GTC, X-ray
observations from the Chandra X-ray Observatory and at
sub-millimetre/millimetre wavelengths from SMA. Optical/nIR spectroscopy was
performed with X-shooter/VLT. We detect the X-ray and nIR afterglow of the
burst and determine a redshift of z = 2.1974 +/- 0.0002 through the
identification of emission lines of [OII], [OIII] and H-alpha from the host
galaxy of the GRB. This implies an energy release of Eiso = (3.0+/-0.2)x10^54
erg, amongst the most luminous ever detected. The observations of the afterglow
indicate high obscuration with AV > 1.5. The host galaxy is compact, with R1/2
< 1.6 kpc, but luminous, at L ~ 1.5 L* and has a star formation rate of 91 +/-
6 Msol/yr as derived from H-alpha. As other highly obscured GRBs, GRB 120624B
is hosted by a luminous galaxy, which we also proof to be compact, with a very
intense star formation. It is one of the most luminous host galaxies associated
with a GRB, showing that the host galaxies of long GRBs are not always blue
dwarf galaxies, as previously thought.Comment: 6 pages, 4 figures, 4 tables; accepted for publication in A&
Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies
Superluminous supernovae (SLSNe) are very bright explosions that were only
discovered recently and that show a preference for occurring in faint dwarf
galaxies. Understanding why stellar evolution yields different types of stellar
explosions in these environments is fundamental in order to both uncover the
elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In
this paper, we present the first results of our project to study SUperluminous
Supernova Host galaxIES, focusing on the sample for which we have obtained
spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen-poor) often (~50% in
our sample) occur in a class of galaxies that is known as Extreme Emission Line
Galaxies (EELGs). The probability of this happening by chance is negligible and
we therefore conclude that the extreme environmental conditions and the SLSN
phenomenon are related. In contrast, SLSNe-II (hydrogen-rich) occur in more
massive, more metal-rich galaxies with softer radiation fields. Therefore, if
SLSNe-II constitute a uniform class, their progenitor systems are likely
different from those of H-poor SLSNe. Gamma-ray bursts (GRBs) are, on average,
not found in as extreme environments as H-poor SLSNe. We propose that H-poor
SLSNe result from the very first stars exploding in a starburst, even earlier
than GRBs. This might indicate a bottom-light initial mass function in these
systems. SLSNe present a novel method of selecting candidate EELGs independent
of their luminosity.Comment: Published version, matches proofs. Accepted 2015 February 13. 23
pages, 8 figures, 4 tables. Minor changes with respect to previous versio
Discovery of the broad-lined Type Ic SN 2013cq associated with the very energetic GRB 130427A
Long-duration gamma-ray bursts (GRBs) at z < 1 are in most cases found to be
accompanied by bright, broad-lined Type Ic supernovae (SNe Ic-BL). The
highest-energy GRBs are mostly located at higher redshifts, where the
associated SNe are hard to detect observationally. Here we present early and
late observations of the optical counterpart of the very energetic GRB 130427A.
Despite its moderate redshift z = 0.3399+/-0.0002, GRB 130427A is at the high
end of the GRB energy distribution, with an isotropic-equivalent energy release
of Eiso ~ 9.6x10^53 erg, more than an order of magnitude more energetic than
other GRBs with spectroscopically confirmed SNe. In our dense photometric
monitoring, we detect excess flux in the host-subtracted r-band light curve,
consistent with what expected from an emerging SN, ~0.2 mag fainter than the
prototypical SN 1998bw. A spectrum obtained around the time of the SN peak
(16.7 days after the GRB) reveals broad undulations typical of SNe Ic-BL,
confirming the presence of a SN, designated SN 2013cq. The spectral shape and
early peak time are similar to those of the high expansion velocity SN 2010bh
associated with GRB 100316D. Our findings demonstrate that high-energy
long-duration GRBs, commonly detected at high redshift, can also be associated
with SNe Ic-BL, pointing to a common progenitor mechanism.Comment: 12 pages, 4 figures, 1 table, accepted for publication in Ap
Looking Into the Fireball: ROTSE-III and Swift Observations of Early GRB Afterglows
We report on a complete set of early optical afterglows of gamma-ray bursts
(GRBs) obtained with the ROTSE-III telescope network from March 2005 through
June 2007. This set is comprised of 12 afterglows with early optical and
Swift/XRT observations, with a median ROTSE-III response time of 45 s after the
start of gamma-ray emission (8 s after the GCN notice time). These afterglows
span four orders of magnitude in optical luminosity, and the contemporaneous
X-ray detections allow multi-wavelength spectral analysis. Excluding X-ray
flares, the broadband synchrotron spectra show that the optical and X-ray
emission originate in a common region, consistent with predictions of the
external forward shock in the fireball model. However, the fireball model is
inadequate to predict the temporal decay indices of the early afterglows, even
after accounting for possible long-duration continuous energy injection. We
find that the optical afterglow is a clean tracer of the forward shock, and we
use the peak time of the forward shock to estimate the initial bulk Lorentz
factor of the GRB outflow, and find 100<Gamma_0<1000, consistent with
expectations.Comment: 31 pages, 5 figures, submitted to Ap
Stress hormones or general well-being are not altered in immune-deficient mice lacking either T- and B- lymphocytes or Interferon gamma signaling if kept under specific pathogen free housing conditions
It is controversially discussed whether immune-deficient mice experience severity in the absence of infection. Because a comprehensive analysis of the well-being of immune-deficient mice under specific pathogen free conditions is missing, we used a multi-parametric test analyzing, corticosterone, weight, nest building and facial expression over a period of 9 month to determine the well-being of two immune-deficient mouse lines (recombination activating gene 2- and interferon gamma receptor-deficient mice). We do not find evidence for severity when comparing immune-deficient mice to their heterozygous immune-competent littermates. Our data challenge the assumption that immune-deficiency per se regardless of housing conditions causes severity. Based on our study we propose to use objective non-invasive parameters determined by laboratory animal science for decisions concerning severity of immune-deficient mice
Long-term X-ray variability of Swift J1644+57
We studied the X-ray timing and spectral variability of the X-ray source Sw
J1644+57, a candidate for a tidal disruption event. We have separated the
long-term trend (an initial decline followed by a plateau) from the short-term
dips in the Swift light-curve. Power spectra and Lomb-Scargle periodograms hint
at possible periodic modulation. By using structure function analysis, we have
shown that the dips were not random but occurred preferentially at time
intervals ~ [2.3, 4.5, 9] x 10^5 s and their higher-order multiples. After the
plateau epoch, dipping resumed at ~ [0.7, 1.4] x 10^6 s and their multiples. We
have also found that the X-ray spectrum became much softer during each of the
early dip, while the spectrum outside the dips became mildly harder in its
long-term evolution. We propose that the jet in the system undergoes precession
and nutation, which causes the collimated core of the jet briefly to go out of
our line of sight. The combined effects of precession and nutation provide a
natural explanation for the peculiar patterns of the dips. We interpret the
slow hardening of the baseline flux as a transition from an extended, optically
thin emission region to a compact, more opaque emission core at the base of the
jet.Comment: 16 pages, 12 figures. Accepted by MNRAS on 2012 Feb 11; minor
improvements in the introduction and discussion from the previous arXiv
versio
A redshift - observation-time relation for gamma-ray bursts: evidence of a distinct sub-luminous population
We show how the redshift and peak-flux distributions of gamma-ray bursts
(GRBs) have an observation time dependence that can be used to discriminate
between different burst populations. We demonstrate how observation time
relations can be derived from the standard integral distributions and that they
can differentiate between GRB populations detected by both the BATSE and
\emph{Swift} satellites. Using \emph{Swift} data we show that a
redshift--observation-time relation (log\,\,--\,log\,) is consistent with
both a peak-flux\,--\,observation time relation (log\,\,--\,log\,) and a
standard log\,\,--\,log\, brightness distribution. As the method depends
only on rarer small- events, it is invariant to high- selection effects.
We use the log\,\,--\,log\, relation to show that sub-luminous GRBs are a
distinct population occurring at a higher rate of order . Our analysis suggests that GRB 060505 -- a
relatively nearby GRB observed without any associated supernova -- is
consistent with a sub-luminous population of bursts. Finally, we suggest that
our relations can be used as a consistency test for some of the proposed GRB
spectral energy correlations.Comment: Accepted by MNRA
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