480 research outputs found
Control of primordial follicle recruitment by anti-Mullerian hormone in the mouse ovary
The dimeric glycoprotein anti-Mullerian hormone (AMH) is a member of the
transforming growth factor-beta superfamily of growth and differentiation
factors. During male fetal sex differentiation, AMH is produced by Sertoli
cells and induces degeneration of the Mullerian ducts, which form the
anlagen of part of the internal female genital system. In females, AMH is
produced by the ovary, but only postnatally. The function of AMH in the
ovary is, however, still unknown. Female AMH null mice were reported to be
fertile, with normal litter size, but this does not exclude a more subtle
function for ovarian AMH. To investigate the function of AMH in the ovary,
the complete follicle population was determined in AMH null mice, in mice
heterozygous for the AMH null mutation, and in wild-type mice of different
ages: 25 days, 4 months, and 13 months. In the present study we found that
ovaries of 25-day- and 4-month-old AMH null females, compared to those of
wild-type females, contain more preantral and small antral follicles. In
addition, in 4- and 13-month-old AMH null females, smaller numbers of
primordial follicles were found. Actually, in 13-month-old AMH null
females, almost no primordial follicles could be detected, coinciding with
a reduced number of preantral and small antral follicles in these females.
In almost all females heterozygous for the AMH null mutation the number of
follicles fell in between the numbers found in wild-type and AMH null
females. In 4-month-old AMH null females serum inhibin levels were higher
and FSH levels were lower compared to those in wild-type females. In
contrast, inhibin levels were lower in 13-month-old AMH null females, and
FSH levels were unchanged compared to those in wild-type females.
Furthermore, the weight of the ovaries was twice as high in the
4-month-old AMH null females as in age-matched wild-type females. We
conclude that AMH plays an important role in primordial follicle
recruitment, such that more primordial follicles are recruited in AMH null
mice than in wild-type mice; the mice heterozygous for the AMH null
mutation take an in-between position. Consequently, the ovaries of AMH
null females and those of females heterozygous for the AMH null mutation
will show a relatively early depletion of their stock of primordial
follicles. The female AMH null mouse may thus provide a useful model to
study regulation of primordial follicle recruitment and the relation
between follicular dynamics and ovarian aging
Anti-Mullerian hormone attenuates the effects of FSH on follicle development in the mouse ovary
Although ovarian follicle growth is under the influence of many growth
factors and hormones of which FSH remains one of the most prominent
regulators. Therefore, factors affecting the sensitivity of ovarian
follicles to FSH are also important for follicle growth. The aim of the
present study was to investigate whether anti-Mullerian hormone (AMH) has
an inhibitory effect on follicle growth by decreasing the sensitivity of
ovarian follicles to FSH. Furthermore, the combined action of AMH and FSH
on ovarian follicle development was examined. Three different experiments
were performed. Using an in vitro follicle culture system it was shown
that FSH-stimulated preantral follicle growth is attenuated in the
presence of AMH. This observation was confirmed by an in vivo experiment
showing that in immature AMH-deficient females, more follicles start to
grow under the influence of exogenous FSH than in their wild-type
littermates. In a third experiment, examination of the follicle population
of 4-month-old wild-type, FSH beta-, AMH-, and AMH-/FSH beta-deficient
females revealed that loss of FSH expression has no impact on the number
of primordial and preantral follicles, but the loss of inhibitory action
of AMH on the recruitment of primordial follicles in AMH-deficient mice is
increased in the absence of FSH. In conclusion, these studies show that
AMH inhibits FSH-stimulated follicle growth in the mouse, suggesting that
AMH is one of the factors determining the sensitivity of ovarian follicles
for FSH and that AMH is a dominant regulator of early follicle growth
WFPC2 Observations of the Cooling Flow Elliptical in Abell 1795
We present WFPC2 images of the core of the cooling flow cD galaxy in Abell
1795. An irregular, asymmetric dust lane extends 7 \h75 kpc in projection to
the north-northwest. The dust shares the morphology observed in the H
and excess UV emission. We see both diffuse and knotty blue emission around the
dust lane, especially at the ends. The dust and emission features lie on the
edge of the radio lobes, suggesting star formation induced by the radio source
or the deflection of the radio jets off of pre-existing dust and gas. We
measure an apparent R significantly less than 3.1, implying that the
extinction law is not Galactic in the dust lane, or the presence of line
emission which is proportional to the extinction. The dust mass is at least
2 M\solar\ and is more likely to be 6.5 M\solar.Comment: 14 pages, LaTeX, Figure 4 included, Postscript Figs. 1-3 available at
ftp://astro.nmsu.edu/pub/JASON/A1795/, accepted for publication in ApJ
Letter
Deep ATLAS radio observations of the CDFS-SWIRE field
We present the first results from the Australia Telescope Large Area Survey
(ATLAS), which consist of deep radio observations of a 3.7 square degree field
surrounding the Chandra Deep Field South, largely coincident with the infrared
Spitzer Wide-Area Extragalactic (SWIRE) Survey. We also list
cross-identifications to infrared and optical photometry data from SWIRE, and
ground-based optical spectroscopy. A total of 784 radio components are
identified, corresponding to 726 distinct radio sources, nearly all of which
are identified with SWIRE sources. Of the radio sources with measured
redshifts, most lie in the redshift range 0.5-2, and include both star-forming
galaxies and active galactic nuclei (AGN). We identify a rare population of
infrared-faint radio sources which are bright at radio wavelengths but are not
seen in the available optical, infrared, or X-ray data. Such rare classes of
sources can only be discovered in wide, deep surveys such as this.Comment: Accepted by A
Reduced Vitamin K Status as a Potentially Modifiable Risk Factor of Severe Coronavirus Disease 2019
BACKGROUND: Respiratory failure and thromboembolism are frequent in SARS-CoV-2-infected patients. Vitamin K activates both hepatic coagulation factors and extrahepatic endothelial anticoagulant protein S, required for thrombosis prevention. In times of vitamin K insufficiency, hepatic procoagulant factors are preferentially activated over extrahepatic proteins. Vitamin K also activates matrix Gla protein (MGP), which protects against pulmonary and vascular elastic fiber damage. We hypothesized that vitamin K may be implicated in coronavirus disease 2019 (COVID-19), linking pulmonary and thromboembolic disease. METHODS: 135 hospitalized COVID-19 patients were compared with 184 historical controls. Poor outcome was defined as invasive ventilation and/or death. Inactive vitamin K-dependent MGP (dp-ucMGP) and prothrombin (PIVKA-II) were measured, inversely related to extrahepatic and hepatic vitamin K status, respectively. Desmosine was measured to quantify the rate of elastic fiber degradation. Arterial calcification severity was assessed by computed tomography. RESULTS: Dp-ucMGP was elevated in COVID-19 patients compared to controls (p<0.001), with even higher dp-ucMGP in patients with poor outcomes (p<0.001). PIVKA-II was normal in 82.1% of patients. Dp-ucMGP was correlated with desmosine (p<0.001), and coronary artery (p=0.002) and thoracic aortic (p<0.001) calcification scores. CONCLUSIONS: Dp-ucMGP was severely increased in COVID-19 patients, indicating extrahepatic vitamin K insufficiency, which was related to poor outcome while hepatic procoagulant factor II remained unaffected. These data suggest a mechanism of pneumonia-induced extrahepatic vitamin K depletion leading to accelerated elastic fiber damage and thrombosis in severe COVID-19 due to impaired activation of MGP and endothelial protein S, respectively. A clinical trial could assess whether vitamin K administration improves COVID-19 outcomes
The ANTARES Optical Beacon System
ANTARES is a neutrino telescope being deployed in the Mediterranean Sea. It
consists of a three dimensional array of photomultiplier tubes that can detect
the Cherenkov light induced by charged particles produced in the interactions
of neutrinos with the surrounding medium. High angular resolution can be
achieved, in particular when a muon is produced, provided that the Cherenkov
photons are detected with sufficient timing precision. Considerations of the
intrinsic time uncertainties stemming from the transit time spread in the
photomultiplier tubes and the mechanism of transmission of light in sea water
lead to the conclusion that a relative time accuracy of the order of 0.5 ns is
desirable. Accordingly, different time calibration systems have been developed
for the ANTARES telescope. In this article, a system based on Optical Beacons,
a set of external and well-controlled pulsed light sources located throughout
the detector, is described. This calibration system takes into account the
optical properties of sea water, which is used as the detection volume of the
ANTARES telescope. The design, tests, construction and first results of the two
types of beacons, LED and laser-based, are presented.Comment: 21 pages, 18 figures, submitted to Nucl. Instr. and Meth. Phys. Res.
Performance of the First ANTARES Detector Line
In this paper we report on the data recorded with the first Antares detector
line. The line was deployed on the 14th of February 2006 and was connected to
the readout two weeks later. Environmental data for one and a half years of
running are shown. Measurements of atmospheric muons from data taken from
selected runs during the first six months of operation are presented.
Performance figures in terms of time residuals and angular resolution are
given. Finally the angular distribution of atmospheric muons is presented and
from this the depth profile of the muon intensity is derived.Comment: 14 pages, 9 figure
Status and Recent Results of the Acoustic Neutrino Detection Test System AMADEUS
The AMADEUS system is an integral part of the ANTARES neutrino telescope in
the Mediterranean Sea. The project aims at the investigation of techniques for
acoustic neutrino detection in the deep sea. Installed at a depth of more than
2000m, the acoustic sensors of AMADEUS are based on piezo-ceramics elements for
the broad-band recording of signals with frequencies ranging up to 125kHz.
AMADEUS was completed in May 2008 and comprises six "acoustic clusters", each
one holding six acoustic sensors that are arranged at distances of roughly 1m
from each other. The clusters are installed with inter-spacings ranging from
15m to 340m. Acoustic data are continuously acquired and processed at a
computer cluster where online filter algorithms are applied to select a
high-purity sample of neutrino-like signals. 1.6 TB of data were recorded in
2008 and 3.2 TB in 2009. In order to assess the background of neutrino-like
signals in the deep sea, the characteristics of ambient noise and transient
signals have been investigated. In this article, the AMADEUS system will be
described and recent results will be presented.Comment: 7 pages, 8 figures. Proceedings of ARENA 2010, the 4th International
Workshop on Acoustic and Radio EeV Neutrino Detection Activitie
The Antares Collaboration : Contributions to the 34th International Cosmic Ray Conference (ICRC 2015, The Hague)
The ANTARES detector, completed in 2008, is the largest neutrino telescope in the Northern hemisphere. Located at a depth of 2.5 km in the Mediterranean Sea, 40 km off the Toulon shore, its main goal is the search for astrophysical high energy neutrinos. In this paper we collect the 21 contributions of the ANTARES collaboration to the 34th International Cosmic Ray Conference (ICRC 2015). The scientific output is very rich and the contributions included in these proceedings cover the main physics results, ranging from steady point sources, diffuse searches, multi-messenger analyses to exotic physics
Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope
The ANTARES telescope is well-suited for detecting astrophysical transient
neutrino sources as it can observe a full hemisphere of the sky at all times
with a high duty cycle. The background due to atmospheric particles can be
drastically reduced, and the point-source sensitivity improved, by selecting a
narrow time window around possible neutrino production periods. Blazars, being
radio-loud active galactic nuclei with their jets pointing almost directly
towards the observer, are particularly attractive potential neutrino point
sources, since they are among the most likely sources of the very high-energy
cosmic rays. Neutrinos and gamma rays may be produced in hadronic interactions
with the surrounding medium. Moreover, blazars generally show high time
variability in their light curves at different wavelengths and on various time
scales. This paper presents a time-dependent analysis applied to a selection of
flaring gamma-ray blazars observed by the FERMI/LAT experiment and by TeV
Cherenkov telescopes using five years of ANTARES data taken from 2008 to 2012.
The results are compatible with fluctuations of the background. Upper limits on
the neutrino fluence have been produced and compared to the measured gamma-ray
spectral energy distribution.Comment: 27 pages, 16 figure
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