334 research outputs found
P-057. Computation of sperm motion for the prediction of fertilization in vitro of cumulus-enclosed human oocytes
Species-specific differences in follicular antral sizes result from diffusion-based limitations on the thickness of the granulosa cell layer
The size of mature oocytes is similar across mammalian species, yet the size
of ovarian follicles increases with species size, with some ovarian follicles
reaching diameters more than 1000-fold the size of the enclosed oocyte. Here we
show that the different follicular sizes can be explained with diffusion-based
limitations on the thickness of the hormone-secreting granulosa layer. By
analysing published data on human follicular growth and granulosa cell
expansion during follicular maturation we find that the 4-fold increase of the
antral follicle diameter is entirely driven by an increase in the follicular
fluid volume, while the thickness of the surrounding granulosa layer remains
constant at about 45+/-10 mkm. Based on the measured kinetic constants, the
model reveals that the observed fall in the gonadotropin concentration from
peripheral blood circulation to the follicular antrum is a result of
sequestration in the granulosa. The model further shows that as a result of
sequestration, an increased granulosa thickness cannot substantially increase
estradiol production but rather deprives the oocyte from gonadotropins. Larger
animals (with a larger blood volume) require more estradiol as produced by the
ovaries to downregulate FSH-secretion in the pituitary. Larger follicle
diameters result in larger follicle surface areas for constant granulosa layer
thickness. The reported increase in follicular surface area in larger species
indeed correlates linearly both with species mass and with the predicted
increase in estradiol output. In summary, we propose a structural role for the
antrum in that it determines the volume of the granulosa layer and thus the
level of estrogen production.Comment: Mol Hum Repr 201
P-259. Characterization of an immortalized human granulosa cell line (COV434) for the study of the development of ovarian follicles in vitro
Comparative birth weights of singletons born after assisted reproduction and natural conception in previously infertile women
BACKGROUND: The possible interference of assisted reproduction techniques (ART) with epigenetic reprogramming during early embryo development has recently sparked renewed interest about the reported lower birth weight among infants born as a consequence of infertility treatments. However, the latter finding so far has relied on the comparison of the birth weight of infants conceived with ART to general population data. A more appropriate comparison group should involve pregnancies in infertile women after natural conception. Therefore, we compared neonatal birth weight data of infants born after various ART treatments, including intrauterine insemination (IUI), with those of previously infertile women achieving pregnancy after sexual intercourse. METHODS: Between August 1996 and March 2004 the data of all infertile women presenting in the infertility unit of the University Women's Hospital of Basel, Switzerland, were collected prospectively, adding up to 995 intact pregnancies and deliveries. The birth weight of all infants resulting from 741 singleton pregnancies were analysed with regard to the patients' characteristics, the occurrence of complications during pregnancy and the type of infertility treatment with which the pregnancies were achieved. RESULTS: Comparison of duration of pregnancy and birth weight of infants born after infertility treatment confirms a shorter pregnancy span and a lower mean birth weight in infants born after IVF and ICSI. If women with pregnancies after ART deliver before term, neonatal birth weight is significantly lower. CONCLUSIONS: There is a specific effect of ART, mainly IVF and ICSI, on both shortening the duration of pregnancy and lowering neonatal birth weight. Both these parameters seem to be interrelated consequences of some modification in the gestational process induced by the infertility treatment. Freezing and thawing of oocytes in the pronucleate stage had a lesser impact on pregnancy span and on neonatal birth weigh
Chromatin condensation, fragmentation of DNA and differences in the epigenetic signature of infertile men
Large and small-scale structures and the dust energy balance problem in spiral galaxies
The interstellar dust content in galaxies can be traced in extinction at
optical wavelengths, or in emission in the far-infrared. Several studies have
found that radiative transfer models that successfully explain the optical
extinction in edge-on spiral galaxies generally underestimate the observed
FIR/submm fluxes by a factor of about three. In order to investigate this
so-called dust energy balance problem, we use two Milky Way-like galaxies
produced by high-resolution hydrodynamical simulations. We create mock optical
edge-on views of these simulated galaxies (using the radiative transfer code
SKIRT), and we then fit the parameters of a basic spiral galaxy model to these
images (using the fitting code FitSKIRT). The basic model includes smooth
axisymmetric distributions along a S\'ersic bulge and exponential disc for the
stars, and a second exponential disc for the dust. We find that the dust mass
recovered by the fitted models is about three times smaller than the known dust
mass of the hydrodynamical input models. This factor is in agreement with
previous energy balance studies of real edge-on spiral galaxies. On the other
hand, fitting the same basic model to less complex input models (e.g. a smooth
exponential disc with a spiral perturbation or with random clumps), does
recover the dust mass of the input model almost perfectly. Thus it seems that
the complex asymmetries and the inhomogeneous structure of real and
hydrodynamically simulated galaxies are a lot more efficient at hiding dust
than the rather contrived geometries in typical quasi-analytical models. This
effect may help explain the discrepancy between the dust emission predicted by
radiative transfer models and the observed emission in energy balance studies
for edge-on spiral galaxies.Comment: 9 pages, 5 figures, accepted for publication in A&
REVIEW OF WINDOW AND DOOR TYPE DETECTION APPROACHES
The use of as-built Building Information Models (BIM) has become increasingly commonplace. This process of creating a BIM model from point cloud data, also referred to as Scan-to-BIM, is a mostly manual task. Due to the large amount of manual work, the entire Scan-to-BIM process is time-consuming and error prone. Current research focuses on the automation of the Scan-to-BIM pipeline by applying state-of-the-art techniques on its consecutive steps including the data acquisition, data processing, data interpretation and modelling. By automating the matching and modelling of window and door objects, a considerable amount of time can be saved in the Scan-to-BIM process. This is so because each window and door instance needs to be examined by the modeller and must be adapted to the actual on-site situation. Large object libraries containing predefined window and door objects exists but the matching to the best-fit predefined object remains time consuming. The aim of this research is to examine the possibilities to speed up the modelling of window and door objects. First, a literature review discussing existing methods for window and door detection and matching is presented. Second, the acquired data is examined to explore the capabilities of capturing window and door information for different remote sensing devices. Followed by tests of some commonplace features in the use for window and door occurrence matching and clustering
The distribution of interstellar dust in CALIFA edge-on galaxies via oligochromatic radiative transfer fitting
We investigate the amount and spatial distribution of interstellar dust in
edge-on spiral galaxies, using detailed radiative transfer modeling of a
homogeneous sample of 12 galaxies selected from the CALIFA survey. Our
automated fitting routine, FitSKIRT, was first validated against artificial
data. This is done by simultaneously reproducing the SDSS -, -, - and
-band observations of a toy model in order to combine the information
present in the different bands. We show that this combined, oligochromatic
fitting, has clear advantages over standard monochromatic fitting especially
regarding constraints on the dust properties. We model all galaxies in our
sample using a three-component model, consisting of a double exponential disc
to describe the stellar and dust discs and using a S\'ersic profile to describe
the central bulge. The full model contains 19 free parameters, and we are able
to constrain all these parameters to a satisfactory level of accuracy without
human intervention or strong boundary conditions. Apart from two galaxies, the
entire sample can be accurately reproduced by our model. We find that the dust
disc is about 75% more extended but only half as high as the stellar disc. The
average face-on optical depth in the V-band is and the spread of
within our sample is quite substantial, which indicates that some spiral
galaxies are relatively opaque even when seen face-on.Comment: 18 pages, 6 figures, 4 tables, Accepted for publication in MNRA
Species-specific differences in follicular antral sizes result from diffusion-based limitations on the thickness of the granulosa cell layer
The size of mature oocytes is similar across mammalian species, yet the size of ovarian follicles increases with species size, with some ovarian follicles reaching diameters >1000-fold the size of the enclosed oocyte. Here we show that the different follicular sizes can be explained with diffusion-based limitations on the thickness of the hormone-secreting granulosa layer. By analysing published data on human follicular growth and granulosa cell expansion during follicular maturation we find that the 4-fold increase of the antral follicle diameter is entirely driven by an increase in the follicular fluid volume, while the thickness of the surrounding granulosa layer remains constant at âŒ45 ± 10 ”m. Based on the measured kinetic constants, the model reveals that the observed fall in the gonadotrophin concentration from peripheral blood circulation to the follicular antrum is a result of sequestration in the granulosa. The model further shows that as a result of sequestration, an increased granulosa thickness cannot substantially increase estradiol production but rather deprives the oocyte from gonadotrophins. Larger animals (with a larger blood volume) require more estradiol as produced by the ovaries to down-regulate follicle-stimulating hormone-secretion in the pituitary. Larger follicle diameters result in larger follicle surface areas for constant granulosa layer thickness. The reported increase in the follicular surface area in larger species indeed correlates linearly both with species mass and with the predicted increase in estradiol output. In summary, we propose a structural role for the antrum in that it determines the volume of the granulosa layer and thus the level of estrogen productio
R-189. An integrated psychosocial service in an infertility clinic: functions, objectives and skills
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