486 research outputs found
MGST1, a GSH transferase/peroxidase essential for development and hematopoietic stem cell differentiation.
We show for the first time that, in contrast to other glutathione transferases and peroxidases, deletion of microsomal glutathione transferase 1 (MGST1) in mice is embryonic lethal. To elucidate why, we used zebrafish development as a model system and found that knockdown of MGST1 produced impaired hematopoiesis. We show that MGST1 is expressed early during zebrafish development and plays an important role in hematopoiesis. High expression of MGST1 was detected in regions of active hematopoiesis and co-expressed with markers for hematopoietic stem cells. Further, morpholino-mediated knock-down of MGST1 led to a significant reduction of differentiated hematopoietic cells both from the myeloid and the lymphoid lineages. In fact, hemoglobin was virtually absent in the knock-down fish as revealed by diaminofluorene staining. The impact of MGST1 on hematopoiesis was also shown in hematopoietic stem/progenitor cells (HSPC) isolated from mice, where it was expressed at high levels. Upon promoting HSPC differentiation, lentiviral shRNA MGST1 knockdown significantly reduced differentiated, dedicated cells of the hematopoietic system. Further, MGST1 knockdown resulted in a significant lowering of mitochondrial metabolism and an induction of glycolytic enzymes, energetic states closely coupled to HSPC dynamics. Thus, the non-selenium, glutathione dependent redox regulatory enzyme MGST1 is crucial for embryonic development and for hematopoiesis in vertebrates
Gamma-ray emission from massive young stellar objects
Massive stars form in dense and massive molecular cores. The exact formation
mechanism is unclear, but it is possible that some massive stars are formed by
processes similar to those that produce the low-mass stars, with
accretion/ejection phenomena occurring at some point of the evolution of the
protostar. This picture seems to be supported by the detection of a collimated
stellar wind emanating from the massive protostar IRAS 16547-4247. A triple
radio source is associated with the protostar: a compact core and two radio
lobes. The emission of the southern lobe is clearly non-thermal. Such emission
is interpreted as synchrotron radiation produced by relativistic electrons
locally accelerated at the termination point of a thermal jet. Since the
ambient medium is determined by the properties of the molecular cloud in which
the whole system is embedded, we can expect high densities of particles and
infrared photons. Because of the confirmed presence of relativistic electrons,
inverse Compton and relativistic Bremsstrahlung interactions are unavoidable.
Proton-proton collision should also occur, producing an injection of neutral
pions. In this paper we aim at making quantitative predictions of the spectral
energy distribution of the non-thermal spots generated by massive young stellar
objects, with emphasis on the particular case of IRAS 16547-4247. We present
spectral energy distributions for the southern lobe of this source, for a
variety of conditions. We show that high-energy emission might be detectable
from this object in the gamma-ray domain (MeV to TeV). The source may also be
detectable at X-rays through long exposures with current X-ray instruments.Comment: 8 pages, 6 figures, accepted for publication in A&
Distributed Edge Connectivity in Sublinear Time
We present the first sublinear-time algorithm for a distributed
message-passing network sto compute its edge connectivity exactly in
the CONGEST model, as long as there are no parallel edges. Our algorithm takes
time to compute and a
cut of cardinality with high probability, where and are the
number of nodes and the diameter of the network, respectively, and
hides polylogarithmic factors. This running time is sublinear in (i.e.
) whenever is. Previous sublinear-time
distributed algorithms can solve this problem either (i) exactly only when
[Thurimella PODC'95; Pritchard, Thurimella, ACM
Trans. Algorithms'11; Nanongkai, Su, DISC'14] or (ii) approximately [Ghaffari,
Kuhn, DISC'13; Nanongkai, Su, DISC'14].
To achieve this we develop and combine several new techniques. First, we
design the first distributed algorithm that can compute a -edge connectivity
certificate for any in time .
Second, we show that by combining the recent distributed expander decomposition
technique of [Chang, Pettie, Zhang, SODA'19] with techniques from the
sequential deterministic edge connectivity algorithm of [Kawarabayashi, Thorup,
STOC'15], we can decompose the network into a sublinear number of clusters with
small average diameter and without any mincut separating a cluster (except the
`trivial' ones). Finally, by extending the tree packing technique from [Karger
STOC'96], we can find the minimum cut in time proportional to the number of
components. As a byproduct of this technique, we obtain an -time
algorithm for computing exact minimum cut for weighted graphs.Comment: Accepted at 51st ACM Symposium on Theory of Computing (STOC 2019
The Portrayal of Complementary and Alternative Medicine in Mass Print Magazines Since 1980
Objectives: The objectives of this study were to examine and describe the portrayal of complementary and alternative medicine (CAM) in mass print media magazines.
Design: The sample included all 37 articles found in magazines with circulation rates of greater than 1 million published in the United States and Canada from 1980 to 2005. The analysis was quantitative and qualitative and included investigation of both manifest and latent magazine story messages.
Results: Manifest analysis noted that CAM was largely represented as a treatment for a patient with a medically diagnosed illness or specific symptoms. Discussions used biomedical terms such as patient rather than consumer and disease rather than wellness. Latent analysis revealed three themes: (1) CAMs were described as good but not good enough; (2) individualism and consumerism were venerated; and (3) questions of costs were raised in the context of confusion and ambivalence
Massive protostars as gamma-ray sources
Massive protostars have associated bipolar outflows with velocities of
hundreds of km s. Such outflows can produce strong shocks when interact
with the ambient medium leading to regions of non-thermal radio emission. We
aim at exploring under which conditions relativistic particles are accelerated
at the terminal shocks of the protostellar jets and can produce significant
gamma-ray emission. We estimate the conditions necessary for particle
acceleration up to very high energies and gamma-ray production in the
non-thermal hot spots of jets associated with massive protostars embedded in
dense molecular clouds. We show that relativistic Bremsstrahlung and
proton-proton collisions can make molecular clouds with massive young stellar
objects detectable by the {\it Fermi}{} satellite at MeV-GeV energies and by
Cherenkov telescope arrays in the GeV-TeV range. Gamma-ray astronomy can be
used to probe the physical conditions in star forming regions and particle
acceleration processes in the complex environment of massive molecular clouds.Comment: 10 pages, 5 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
Radio continuum and near-infrared study of the MGRO J2019+37 region
(abridged) MGRO J2019+37 is an unidentified extended source of VHE gamma-rays
originally reported by the Milagro Collaboration as the brightest TeV source in
the Cygnus region. Its extended emission could be powered by either a single or
several sources. The GeV pulsar AGL J2020.5+3653, discovered by AGILE and
associated with PSR J2021+3651, could contribute to the emission from MGRO
J2019+37, although extrapolation of the GeV spectrum does not explain the
detected multi-TeV flux. Our aim is to identify radio and NIR sources in the
field of the extended TeV source MGRO J2019+37, and study potential
counterparts that could contribute to its emission. We surveyed a region of
about 6 square degrees with the Giant Metrewave Radio Telescope (GMRT) at the
frequency 610 MHz. We also observed the central square degree of this survey in
the NIR Ks-band using the 3.5 m telescope in Calar Alto. Archival X-ray
observations of some specific fields are included. VLBI observations of an
interesting radio source were performed. We explored possible scenarios to
produce the multi-TeV emission from MGRO J2019+37 and studied which of the
sources could be the main particle accelerator. We present a catalogue of 362
radio sources detected with the GMRT in the field of MGRO J2019+37, and the
results of a cross-correlation of this catalog with one obtained at NIR
wavelengths, as well as with available X-ray observations of the region. Some
peculiar sources inside the ~1 degree uncertainty region of the TeV emission
from MGRO J2019+37 are discussed in detail, including the pulsar PSR J2021+3651
and its pulsar wind nebula PWN G75.2+0.1, two new radio-jet sources, the HII
region Sh 2-104 containing two star clusters, and the radio source NVSS
J202032+363158.Comment: 10 pages, 6 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
Massive protostars as gamma-ray sources
Massive protostars have associated bipolar outflows with velocities of
hundreds of km s. Such outflows can produce strong shocks when interact
with the ambient medium leading to regions of non-thermal radio emission. We
aim at exploring under which conditions relativistic particles are accelerated
at the terminal shocks of the protostellar jets and can produce significant
gamma-ray emission. We estimate the conditions necessary for particle
acceleration up to very high energies and gamma-ray production in the
non-thermal hot spots of jets associated with massive protostars embedded in
dense molecular clouds. We show that relativistic Bremsstrahlung and
proton-proton collisions can make molecular clouds with massive young stellar
objects detectable by the {\it Fermi}{} satellite at MeV-GeV energies and by
Cherenkov telescope arrays in the GeV-TeV range. Gamma-ray astronomy can be
used to probe the physical conditions in star forming regions and particle
acceleration processes in the complex environment of massive molecular clouds.Comment: 10 pages, 5 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
Radio continuum and near-infrared study of the MGRO J2019+37 region
(abridged) MGRO J2019+37 is an unidentified extended source of VHE gamma-rays
originally reported by the Milagro Collaboration as the brightest TeV source in
the Cygnus region. Its extended emission could be powered by either a single or
several sources. The GeV pulsar AGL J2020.5+3653, discovered by AGILE and
associated with PSR J2021+3651, could contribute to the emission from MGRO
J2019+37, although extrapolation of the GeV spectrum does not explain the
detected multi-TeV flux. Our aim is to identify radio and NIR sources in the
field of the extended TeV source MGRO J2019+37, and study potential
counterparts that could contribute to its emission. We surveyed a region of
about 6 square degrees with the Giant Metrewave Radio Telescope (GMRT) at the
frequency 610 MHz. We also observed the central square degree of this survey in
the NIR Ks-band using the 3.5 m telescope in Calar Alto. Archival X-ray
observations of some specific fields are included. VLBI observations of an
interesting radio source were performed. We explored possible scenarios to
produce the multi-TeV emission from MGRO J2019+37 and studied which of the
sources could be the main particle accelerator. We present a catalogue of 362
radio sources detected with the GMRT in the field of MGRO J2019+37, and the
results of a cross-correlation of this catalog with one obtained at NIR
wavelengths, as well as with available X-ray observations of the region. Some
peculiar sources inside the ~1 degree uncertainty region of the TeV emission
from MGRO J2019+37 are discussed in detail, including the pulsar PSR J2021+3651
and its pulsar wind nebula PWN G75.2+0.1, two new radio-jet sources, the HII
region Sh 2-104 containing two star clusters, and the radio source NVSS
J202032+363158.Comment: 10 pages, 6 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
Analysis of transcripts differentially expressed between fruited and deflowered âGalaâ adult trees: a contribution to biennial bearing understanding in apple
Background
The transition from vegetative to floral state in shoot apical meristems (SAM) is a key event in plant development and is of crucial importance for reproductive success. In perennial plants, this event is recurrent during tree life and subject to both within-tree and between-years heterogeneity. In the present study, our goal was to identify candidate processes involved in the repression or induction of flowering in apical buds of adult apple trees.
Results
Genes differentially expressed (GDE) were examined between trees artificially set in either âONâ or âOFFâ situation, and in which floral induction (FI) was shown to be inhibited or induced in most buds, respectively, using qRT-PCR and microarray analysis. From the period of FI through to flower differentiation, GDE belonged to four main biological processes (i) response to stimuli, including response to oxidative stress; (ii) cellular processes, (iii) cell wall biogenesis, and (iv) metabolic processes including carbohydrate biosynthesis and lipid metabolic process. Several key regulator genes, especially TEMPRANILLO (TEM), FLORAL TRANSITION AT MERISTEM (FTM1) and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) were found differentially expressed. Moreover, homologs of SPL and Leucine-Rich Repeat proteins were present under QTL zones previously detected for biennial bearing.
Conclusions
This data set suggests that apical buds of âONâ and âOFFâ trees were in different physiological states, resulting from different metabolic, hormonal and redox status which are likely to contribute to FI control in adult apple trees. Investigations on carbohydrate and hormonal fluxes from sources to SAM and on cell detoxification process are expected to further contribute to the identification of the underlying physiological mechanisms of FI in adult apple trees
Complementary and alternative medicine use among older Australian women - a qualitative analysis
Background: The use of complementary and alternative medicines (CAM) among older adults is an emerging health issue, however little is known about older people's experiences of using CAM and the cultural, geographical and other determinants of CAM use in this population. This study used qualitative methods to explore older women's views of CAM and reasons for their use of CAM. Participants for the project were drawn from the Australian Longitudinal Study on Women's Health (ALSWH) 1921-1926 birth cohort. Women who responded positively to a question about CAM use in Survey 5 (2008) of the ALSWH were invited to participate in the study. A total of 13 rural and 12 urban women aged between 83 and 88 years agreed to be interviewed
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