317 research outputs found
The prion or the related Shadoo protein is required for early mouse embryogenesis
AbstractThe prion protein PrP has a key role in transmissible spongiform encephalopathies but its biological function remains largely unknown. Recently, a related protein, Shadoo, was discovered. Its biological properties and brain distribution partially overlap that of PrP. We report that the Shadoo-encoding gene knockdown in PrP-knockout mouse embryos results in a lethal phenotype, occurring between E8 and E11, not observed on the wild-type genetic background. It reveals that these two proteins play a shared, crucial role in mammalian embryogenesis, explaining the lack of severe phenotype in PrP-knockout mammals, an appreciable step towards deciphering the biological role of this protein family
Cytogenetic mapping of 25 goat mammary gland Expressed Sequence Tags (ESTs)
Today, there is a shift towards a positional candidate approach in the molecular identification of genes. This study reports on an Expressed Sequence Tags (ESTs) mapping initiative in goats, based on sequence information gathered from a previous mammary gland cDNA systematic sequencing project. A total of 25 novel genes was localised cytogenetically on 16 goat chromosomes. Six of these ESTs were found to map to cattle milk QTL regions. These results made it possible to assess the use of ESTs as a shortcut to the molecular identification of some QTLs and as a valuable tool for comparative mapping
Carbon sequestration in the deep Atlantic enhanced by Saharan dust
sinking rates of particulate organicmatter. Here we present a two-year time series of sediment trap observations of particulate organic carbon flux to 3,000m depth, measured directly in two locations: the dust-rich central North Atlantic gyre and the dust-poor South Atlantic gyre. We find that carbon fluxes are twice as high and a higher proportion of primary production is exported to depth in the dust-rich North Atlantic gyre. Low stable nitrogen isotope ratios suggest that high fluxes result from the stimulation of nitrogen fixation and productivity following the deposition of dust-borne nutrients. Sediment traps in the northern gyre also collected intact colonies of nitrogen-fixing Trichodesmium species. Whereas ballast in Enhanced atmospheric input of dust-borne nutrients and minerals to the remote surface ocean can potentially increase carbon uptake and sequestration at depth. Nutrients can enhance primary productivity, and mineral particles act as ballast, increasing the southern gyre is predominantly biogenic, dust-derived mineral particles constitute the dominant ballast element during the enhanced carbon fluxes in the northern gyre. We conclude that dust deposition increases carbon sequestration in the North Atlantic gyre through the fertilization of the nitrogen-fixing community in surface waters and mineral ballasting of sinking particles
Plasticity of maritime pine (Pinus pinaster) wood-forming tissues during a growing season
Research• The seasonal effect is the most significant external source of variation affecting
vascular cambial activity and the development of newly divided cells, and hence
wood properties. Here, the effect of edapho-climatic conditions on the phenotypic
and molecular plasticity of differentiating secondary xylem during a growing season
was investigated.
• Wood-forming tissues of maritime pine (Pinus pinaster) were collected from the
beginning to the end of the growing season in 2003. Data from examination of fibre
morphology, Fourier-transform infrared spectroscopy (FTIR), analytical pyrolysis, and
gas chromatography/mass spectrometry (GC/MS) were combined to characterize the
samples. Strong variation was observed in response to changes in edapho-climatic
conditions.
• A genomic approach was used to identify genes differentially expressed during
this growing season. Out of 3512 studied genes, 19% showed a significant seasonal
effect. These genes were clustered into five distinct groups, the largest two representing
genes over-expressed in the early- or late-wood-forming tissues, respectively. The other
three clusters were characterized by responses to specific edapho-climatic conditions.
• This work provides new insights into the plasticity of the molecular machinery
involved in wood formation, and reveals candidate genes potentially responsible for
the phenotypic differences found between early- and late-wood
Background Light in Potential Sites for the ANTARES Undersea Neutrino Telescope
The ANTARES collaboration has performed a series of {\em in situ}
measurements to study the background light for a planned undersea neutrino
telescope. Such background can be caused by K decays or by biological
activity. We report on measurements at two sites in the Mediterranean Sea at
depths of 2400~m and 2700~m, respectively. Three photomultiplier tubes were
used to measure single counting rates and coincidence rates for pairs of tubes
at various distances. The background rate is seen to consist of three
components: a constant rate due to K decays, a continuum rate that
varies on a time scale of several hours simultaneously over distances up to at
least 40~m, and random bursts a few seconds long that are only correlated in
time over distances of the order of a meter. A trigger requiring coincidences
between nearby photomultiplier tubes should reduce the trigger rate for a
neutrino telescope to a manageable level with only a small loss in efficiency.Comment: 18 pages, 8 figures, accepted for publication in Astroparticle
Physic
Towards a standard typology of endogenous landslide seismic sources
The objective of this work is to propose a standard classification of seismic
signals generated by gravitational processes and detected at close distances
(<1 km). We review the studies where seismic instruments have been
installed on unstable slopes and discuss the choice of the seismic
instruments and the network geometries. Seismic observations acquired at 13
unstable slopes are analyzed in order to construct the proposed typology. The
selected slopes are affected by various landslide types (slide, fall, topple
and flow) triggered in various material (from unconsolidated soils to
consolidated rocks). We investigate high-frequency bands (>1 Hz) where
most of the seismic energy is recorded at the 1 km sensor to source
distances. Several signal properties (duration, spectral content and
spectrogram shape) are used to describe the sources. We observe that similar
gravitational processes generate similar signals at different slopes. Three
main classes can be differentiated mainly from the length of the signals, the
number of peaks and the duration of the autocorrelation. The classes are the
“slopequake” class, which corresponds to sources potentially occurring
within the landslide body; the “rockfall” class, which corresponds to
signals generated by rock block impacts; and the “granular flow” class,
which corresponds to signals generated by wet or dry debris/rock flows.
Subclasses are further proposed to differentiate specific signal properties
(frequency content, resonance, precursory signal). The signal properties of
each class and subclass are described and several signals of the same class
recorded at different slopes are presented. Their potential origins are
discussed. The typology aims to serve as a standard for further comparisons
of the endogenous microseismicity recorded on landslides.</p
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