53 research outputs found
Cytochalasin D restores nuclear size acting on F-actin and IZUMO1 localization in low-quality spermatozoa
In spermatozoa, the nuclear F-actin supports the acroplaxome, a subacrosomal structure involved in the correct exposure of several acrosomal membrane proteins; among them, the glycoprotein IZUMO1 is the major protein involved in sperm-oocyte fusion. Nuclear F-actin is also involved in sperm head shaping and chromosome compartmentalization. To date, few notions regarding the bivalent role of F-actin on sperm chromatin organization and IZUMO1 positioning have been reported. In our work, we characterized subcellular organization of F-actin in human high- and low-quality spermatozoa (A- and B-SPZ), respectively, showing that F-actin over-expression in sperm head of B-SPZ affected IZUMO1 localization. A correct IZUMO1 repositioning following in vitro induction of F-actin depolymerization, by cytochalasin D treatment, occurred. Interestingly, F-actin depolymerization was also associated with a correct acrosome repositioning, thus to favor a proper acrosome reaction onset, with changes in sperm nuclear size parameters and histone acetylation rate reaching high-quality conditions. In conclusion, the current work shows a key role of F-actin in the control of IZUMO1 localization as well as chromatin remodeling and acetylation events
Asteroids' physical models from combined dense and sparse photometry and scaling of the YORP effect by the observed obliquity distribution
The larger number of models of asteroid shapes and their rotational states
derived by the lightcurve inversion give us better insight into both the nature
of individual objects and the whole asteroid population. With a larger
statistical sample we can study the physical properties of asteroid
populations, such as main-belt asteroids or individual asteroid families, in
more detail. Shape models can also be used in combination with other types of
observational data (IR, adaptive optics images, stellar occultations), e.g., to
determine sizes and thermal properties. We use all available photometric data
of asteroids to derive their physical models by the lightcurve inversion method
and compare the observed pole latitude distributions of all asteroids with
known convex shape models with the simulated pole latitude distributions. We
used classical dense photometric lightcurves from several sources and
sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff,
Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the
lightcurve inversion method to determine asteroid convex models and their
rotational states. We also extended a simple dynamical model for the spin
evolution of asteroids used in our previous paper. We present 119 new asteroid
models derived from combined dense and sparse-in-time photometry. We discuss
the reliability of asteroid shape models derived only from Catalina Sky Survey
data (IAU code 703) and present 20 such models. By using different values for a
scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in
the dynamical model for the spin evolution and by comparing synthetics and
observed pole-latitude distributions, we were able to constrain the typical
values of the cYORP parameter as between 0.05 and 0.6.Comment: Accepted for publication in A&A, January 15, 201
The small binary asteroid (939) Isberga
In understanding the composition and internal structure of asteroids, their
density is perhaps the most diagnostic quantity. We aim here to characterize
the surface composition, mutual orbit, size, mass, and density of the small
main-belt binary asteroid (939) Isberga. For that, we conduct a suite of
multi-technique observations, including optical lightcurves over many epochs,
near-infrared spectroscopy, and interferometry in the thermal infrared. We
develop a simple geometric model of binary systems to analyze the
interferometric data in combination with the results of the lightcurve
modeling. From spectroscopy, we classify Ibserga as a Sq-type asteroid,
consistent with the albedo of 0.14 (all uncertainties are
reported as 3- range) we determine (average albedo of S-types is 0.197
0.153, Pravec et al., 2012, Icarus 221, 365-387). Lightcurve analysis
reveals that the mutual orbit has a period of 26.6304 0.0001 h, is close
to circular, and has pole coordinates within 7 deg. of (225, +86) in ECJ2000,
implying a low obliquity of 1.5 deg. The combined analysis of lightcurves and
interferometric data allows us to determine the dimension of the system and we
find volume-equivalent diameters of 12.4 km and
3.6 km for Isberga and its satellite, circling each other on a
33 km wide orbit. Their density is assumed equal and found to be
g.cm, lower than that of the associated ordinary
chondrite meteorites, suggesting the presence of some macroporosity, but
typical of S-types of the same size range (Carry, 2012, P\&SS 73, 98-118). The
present study is the first direct measurement of the size of a small main-belt
binary. Although the interferometric observations of Isberga are at the edge of
MIDI capabilities, the method described here is applicable to others suites of
instruments (e.g, LBT, ALMA).Comment: 12 pages, 6 figures, 4 table
Emerging roles of anti-Müllerian hormone in hypothalamic-pituitary function
Since its initial discovery in the 1940s, research into the physiological actions of anti-Müllerian hormone (AMH), from its eponymous role in male developmental biology to its routine clinical use in female reproductive health, has undergone a paradigm shifting change. With several exciting studies recently reporting hitherto unforeseen AMH actions at all levels in the hypogonadal-pituitary-gonadal axis, the importance of this hormone for both hypothalamic and pituitary reproductive control is finding increasing support and significance. In this review, we will briefly summarize what is known about the traditional roles and biology of AMH and how this could be integrated with new findings of AMH actions at the level of the hypothalamic-pituitary axis. We also synthesize the important findings from these new studies and discuss their potential impact and significance to our understanding of one of the most common reproductive disorders currently affecting women, polycystic ovary syndrome
Conséquences de l’âge du père sur la fertilité, les résultats de l’AMP et la santé des enfants
International audienceMany studies exist on the impact of female age on fertility, success of assisted reproductive technologies and on obstetric, fetal and neonatal adverse outcomes. Late paternity seems commonplace especially in the media… But there are reliable scientific data which confirm decline of fertility related to male age but also an increased risk of genetic diseases for the offspring. The objective of this article is to make a synthesis of the literature on this subject
Exopolysaccharide production by the Rhizobium meliloti M5N1 CS strain. Location and quatitation of the site of O-acetylation
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A(1→4)-β-D-glucuronan excreted by a mutant of the <i>Rhizobium meliloti</i> M5N1 strain
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Influence of acetyl substituent on oligoglucuronans separation by anion exchange chromatography
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