912 research outputs found
Dynamics of glycine receptor insertion in the neuronal plasma membrane
The exocytosis site of newly synthesized glycine receptor was defined by means of a morphological assay to characterize its export from the trans-Golgi Network to the plasma membrane. This was achieved by expressing in transfected neurons an alpha1 subunit bearing an N-terminal tag selectively cleavable from outside the cell by thrombin. This was combined with a transient temperature-induced block of exocytic transport that creates a synchronized exocytic wave. Immunofluorescence microscopy analysis of the cell surface appearance of newly synthesized receptor revealed that exocytosis mainly occurred at nonsynaptic sites in the cell body and the initial portion of dendrites. At the time of cell surface insertion, the receptors existed as discrete clusters. Quantitative analysis showed that glycine receptor clusters are stable in size and subsequently appeared in more distal dendritic regions. This localization resulted from diffusion in the plasma membrane and not from exocytosis of transport vesicles directed to dendrites. Kinetic analysis established a direct substrate-product relationship between pools of somatic and dendritic receptors. This indicated that clusters represent intermediates between newly synthesized and synaptic receptors. These results support a diffusion-retention model for the formation of receptor-enriched postsynaptic domains and not that of a vectorial intracellular targeting to synapses
AMBER/VLTI high spectral resolution observations of the Br emitting region in HD 98922. A compact disc wind launched from the inner disc region
We analyse the main physical parameters and the circumstellar environment of
the young Herbig Be star HD 98922. We present AMBER/VLTI high spectral
resolution (R =12000) interferometric observations across the Br line,
accompanied by UVES high-resolution spectroscopy and SINFONI-AO assisted
near-infrared integral field spectroscopic data. To interpret our observations,
we develop a magneto-centrifugally driven disc-wind model. Our analysis of the
UVES spectrum shows that HD 98922 is a young (~5x10^5 yr) Herbig Be star
(SpT=B9V), located at a distance of 440(+60-50) pc, with a mass accretion rate
of ~9+/-3x10^(-7) M_sun yr^(-1). SINFONI K-band AO-assisted imaging shows a
spatially resolved circumstellar disc-like region (~140 AU in diameter) with
asymmetric brightness distribution. Our AMBER/VLTI UT observations indicate
that the Br emitting region (radius ~0.31+/-0.04 AU) is smaller than
the continuum emitting region (inner dust radius ~0.7+/-0.2 AU), showing
significant non-zero V-shaped differential phases (i.e. non S-shaped, as
expected for a rotating disc). The value of the continuum-corrected pure
Br line visibility at the longest baseline (89 m) is ~0.8+/-0.1, i.e.
the Br emitting region is partially resolved. Our modelling suggests
that the observed Br line-emitting region mainly originates from a disc
wind with a half opening angle of 30deg, and with a mass-loss rate of ~2x10(-7)
M_sun yr^(-1). The observed V-shaped differential phases are reliably
reproduced by combining a simple asymmetric continuum disc model with our
Br disc-wind model. The Br emission of HD 98922 can be modelled
with a disc wind that is able to approximately reproduce all interferometric
observations if we assume that the intensity distribution of the dust continuum
disc is asymmetric.Comment: Accepted for publication on Astronomy \& Astrophysics. High
resolution figures published on the main journal (see Astronomy &
Astrophysics: Forthcoming) or at
www.researchgate.net/profile/Alessio_Caratti_o_Garatti/publication
Opening the black box of outer space: the case of Jason-3
If you look at a rendering of planet Earth from a bird's eye view, you will see satellites orbiting the planet like electrons, each one a testament to humanity's expansion beyond Earth's atmosphere. It begs the question: what is this new humanized landscape? The dominant voice that has attempted to answer this question is the realist one, which has led the charge of academic inquiry into outer space since the fateful launch of the Sputnik in 1957. Though enlightening in some respects, the realist perspective oftentimes obscures the heterogeneous complexity of the actors, actions, limits and possibilities that have constructed this very humanized outer space. This paper looks at the humanization of outer space through the lens of JASON-3, an internationally collaborative satellite designed primarily to measure the topography of the Earth's oceans. A vast number of actors collaborated to enact the network that created JASON-3, including bureaucratic agencies, academics, private contractors, political bodies, other satellites, the sun and even gravity. This paper will focus on these actors and the work that they did to form the network, showing a glimpse of the entangled connections that eventually produced JASON-3. Through telling this story, I argue: (1) outer space is more complex than state-level relations and (2) critical geography -- with its insight into relational spaces and deconstructing power structures -- has a unique place to fill in outer space literature
Interés de las biopsias de útero como método diagnóstico de la infertilidad de origen inexplicado en la perra
Las lesiones uterinas están consideradas como una de las causas principales de la infertilidad canina. Sin embargo, hasta el momento, escasas publicaciones han evaluado su verdadero impacto en la perra. En este estudio se describen los resultados histológicos de 20 perras con infertilidad de origen indeterminado a las que se les practicó una biopsia uterina por laparotomía durante el periodo de diestro, en el 75% de los casos. Se definieron 3 grupos: perras cuya gestación nunca fue confirmada (GNC), perras con interrupción de la gestación (IG) y perras con subfertilidad. En total, el 89.5% de las biopsias fueron anormales. Las patologías más frecuentemente diagnosticadas fueron la endometritis (31.5%), la HGQ (Hiperplasia Glándulo-Quística) (31.5%) y la FDG (fibrosis asociada a la degeneración de las glándulas endometriales), (21%), que pudieron encontrarse aisladas o asociadas a otras anomalías. En ninguno de los casos se aisló un agente infeccioso. Mientras que la HGQ y la FDG probablemente jueguen un papel importante en la infertilidad, las endometritis podrían ser, en ciertos casos la causa primaria, y en otros, la consecuencia de la interrupción precoz de la gestación
First AMBER/VLTI observations of hot massive stars
AMBER is the first near infrared focal instrument of the VLTI. It combines
three telescopes and produces spectrally resolved interferometric measures.
This paper discusses some preliminary results of the first scientific
observations of AMBER with three Unit Telescopes at medium (1500) and high
(12000) spectral resolution. We derive a first set of constraints on the
structure of the circumstellar material around the Wolf Rayet Gamma2 Velorum
and the LBV Eta Carinae
Strong near-infrared emission in the sub-AU disk of the Herbig Ae star HD 163296: evidence of refractory dust?
This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.We present new long-baseline spectro-interferometric observations of the Herbig Ae star HD 163296 (MWC 275) obtained in the
H and K bands with the AMBER instrument at the VLTI. The observations cover a range of spatial resolutions between ∼3 and
∼12 milliarcseconds, with a spectral resolution of ∼30. With a total of 1481 visibilities and 432 closure phases, they represent the
most comprehensive (u, v) coverage achieved so far for a young star. The circumstellar material is resolved at the sub-AU spatial scale
and closure phase measurements indicate a small but significant deviation from point-symmetry. We discuss the results assuming that
the near-infrared excess in HD 163296 is dominated by the emission of a circumstellar disk. A successful fit to the spectral energy
distribution, near-infrared visibilities and closure phases is found with a model in which a dominant contribution to the H and K band
emission originates in an optically thin, smooth and point-symmetric region extending from about 0.1 to 0.45 AU. At a distance of
0.45 AU from the star, silicates condense, the disk becomes optically thick and develops a puffed-up rim, whose skewed emission can
account for the non-zero closure phases. We discuss the source of the inner disk emission and tentatively exclude dense molecular gas
as well as optically thin atomic or ionized gas as its possible origin. We propose instead that the smooth inner emission is produced by
very refractory grains in a partially cleared region, extending to at least ∼0.5 AU. If so, we may be observing the disk of HD 163296
just before it reaches the transition disk phase. However, we note that the nature of the refractory grains or, in fact, even the possibility
of any grain surviving at the very high temperatures we require (∼2100−2300 K at 0.1 AU from the star) is unclear and should be
investigated further.We acknowledge fundings from CNRS and INAF (grant
ASI-INAF I/016/07/0). This work was in part performed under contract with
the Jet Propulsion Laboratory (JPL) funded by NASA through the Michelson
Fellowship Progra
Tryptophan metabolism and bacterial commensals prevent fungal dysbiosis in Arabidopsis roots
In nature, roots of healthy plants are colonized by multikingdom microbial communities that include bacteria, fungi, and oomycetes. A key question is how plants control the assembly of these diverse microbes in roots to maintain host–microbe homeostasis and health. Using microbiota reconstitution experiments with a set of immunocompromised Arabidopsis thaliana mutants and a multikingdom synthetic microbial community (SynCom) representative of the natural A. thaliana root microbiota, we observed that microbiota-mediated plant growth promotion was abolished in most of the tested immunocompromised mutants. Notably, more than 40% of between-genotype variation in these microbiota-induced growth differences was explained by fungal but not bacterial or oomycete load in roots. Extensive fungal overgrowth in roots and altered plant growth was evident at both vegetative and reproductive stages for a mutant impaired in the production of tryptophan-derived, specialized metabolites (cyp79b2/b3). Microbiota manipulation experiments with single- and multikingdom microbial SynComs further demonstrated that 1) the presence of fungi in the multikingdom SynCom was the direct cause of the dysbiotic phenotype in the cyp79b2/b3 mutant and 2) bacterial commensals and host tryptophan metabolism are both necessary to control fungal load, thereby promoting A. thaliana growth and survival. Our results indicate that protective activities of bacterial root commensals are as critical as the host tryptophan metabolic pathway in preventing fungal dysbiosis in the A. thaliana root endosphere
Strong near-infrared emission in the sub-AU disk of the Herbig Ae star HD163296: evidence for refractory dust?
We present new long-baseline spectro-interferometric observations of the
HerbigAe star HD163296 obtained in the H and K bands with the AMBER instrument
at VLTI. The observations cover a range of spatial resolutions between 3 and 12
milli-arcseconds, with a spectral resolution of ~30. With a total of 1481
visibilities and 432 closure phases, they result in the best (u,v) coverage
achieved on a young star so far. The circumstellar material is resolved at the
sub-AU spatial scale and closure phase measurements indicate a small but
significant deviation from point-symmetry. We discuss the results assuming that
the near-infrared excess in HD163296 is dominated by the emission of a
circumstellar disk. A successful fit to the spectral energy distribution,
near-infrared visibilities and closure phases is found with a model where a
dominant contribution to the H and K band emissions arises from an optically
thin, smooth and point-symmetric region extending from about 0.1 to 0.45 AU. At
the latter distance from the star, silicates condense, the disk becomes
optically thick and develops a puffed-up rim, whose skewed emission can account
for the non-zero closure phases. We discuss the nature of the inner disk
emission and tentatively rule out dense molecular gas as well as optically thin
atomic or ionized gas as its possible origin. We propose instead that the inner
emission traces the presence of very refractory grains in a partially cleared
region, extending at least to 0.5 AU. If so, we may be observing the disk of
HD163296 just before it reaches the transition disk phase. However, we note
that the nature of the refractory grains or even the possibility for any grain
to survive at the very high temperatures we require (~2100-2300 K at 0.1 AU
from the star) is unclear and should be investigated further.Comment: 14 pages; 12 figures; accepted by A&
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