13 research outputs found
Testosterone insulin-like effects: an in vitro study on the short-term metabolic effects of testosterone in human skeletal muscle cells
Testosterone by promoting different metabolic pathways contributes to short-term homeostasis of skeletal muscle, the largest insulin-sensitive tissue and the primary site for insulin-stimulated glucose utilization. Despite evidences indicate a close relationship between testosterone and glucose metabolism, the molecular mechanisms responsible for a possible testosterone-mediated insulin-like effects on skeletal muscle are still unknown
An X-ray polarimeter for hard X-ray optics
Development of multi-layer optics makes feasible the use of X-ray telescope
at energy up to 60-80 keV: in this paper we discuss the extension of
photoelectric polarimeter based on Micro Pattern Gas Chamber to high energy
X-rays. We calculated the sensitivity with Neon and Argon based mixtures at
high pressure with thick absorption gap: placing the MPGC at focus of a next
generation multi-layer optics, galatic and extragalactic X-ray polarimetry can
be done up till 30 keV.Comment: 12 pages, 7 figure
A photoelectric polarimeter for XEUS: a new window in x-ray sky
XEUS is a large area telescope aiming to rise X-ray Astronomy to the level of
Optical Astronomy in terms of collecting areas. It will be based on two
satellites, locked on a formation flight, one with the optics, one with the
focal plane. The present design of the focal plane foresees, as an auxiliary
instrument, the inclusion of a Polarimeter based on a Micropattern Chamber. We
show how such a device is capable to solve open problems on many classes of
High Energy Astrophysics objects and to use X-ray sources as a laboratory for a
substantial progress on Fundamental Physics.Comment: 12 pages, 7 figure
POLARIX: a pathfinder mission of X-ray polarimetry
Since the birth of X-ray astronomy, spectral, spatial and timing observation
improved dramatically, procuring a wealth of information on the majority of the
classes of the celestial sources. Polarimetry, instead, remained basically
unprobed. X-ray polarimetry promises to provide additional information
procuring two new observable quantities, the degree and the angle of
polarization. POLARIX is a mission dedicated to X-ray polarimetry. It exploits
the polarimetric response of a Gas Pixel Detector, combined with position
sensitivity, that, at the focus of a telescope, results in a huge increase of
sensitivity. Three Gas Pixel Detectors are coupled with three X-ray optics
which are the heritage of JET-X mission. POLARIX will measure time resolved
X-ray polarization with an angular resolution of about 20 arcsec in a field of
view of 15 arcmin 15 arcmin and with an energy resolution of 20 % at 6
keV. The Minimum Detectable Polarization is 12 % for a source having a flux of
1 mCrab and 10^5 s of observing time. The satellite will be placed in an
equatorial orbit of 505 km of altitude by a Vega launcher.The telemetry
down-link station will be Malindi. The pointing of POLARIX satellite will be
gyroless and it will perform a double pointing during the earth occultation of
one source, so maximizing the scientific return. POLARIX data are for 75 % open
to the community while 25 % + SVP (Science Verification Phase, 1 month of
operation) is dedicated to a core program activity open to the contribution of
associated scientists. The planned duration of the mission is one year plus
three months of commissioning and SVP, suitable to perform most of the basic
science within the reach of this instrument.Comment: 42 pages, 28 figure
POLARIX: a small mission of x-ray polarimetry
X-Ray Polarimetry can be now performed by using a Micro Pattern Gas Chamber
in the focus of a telescope. It requires large area optics for most important
scientific targets. But since the technique is additive a dedicated mission
with a cluster of small telescopes can perform many important measurements and
bridge the 40 year gap between OSO-8 data and future big telescopes such as
XEUS. POLARIX has been conceived as such a pathfinder. It is a Small Satellite
based on the optics of JET-X. Two telescopes are available in flight
configuration and three more can be easily produced starting from the available
superpolished mandrels. We show the capabilities of such a cluster of
telescopes each equipped with a focal plane photoelectric polarimeter and
discuss a few alternative solutions.Comment: 9 pages, 5 figure
XIPE: the X-ray Imaging Polarimetry Explorer
X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and
temporal variability measurements and to imaging, allows a wealth of physical
phenomena in astrophysics to be studied. X-ray polarimetry investigates the
acceleration process, for example, including those typical of magnetic
reconnection in solar flares, but also emission in the strong magnetic fields
of neutron stars and white dwarfs. It detects scattering in asymmetric
structures such as accretion disks and columns, and in the so-called molecular
torus and ionization cones. In addition, it allows fundamental physics in
regimes of gravity and of magnetic field intensity not accessible to
experiments on the Earth to be probed. Finally, models that describe
fundamental interactions (e.g. quantum gravity and the extension of the
Standard Model) can be tested. We describe in this paper the X-ray Imaging
Polarimetry Explorer (XIPE), proposed in June 2012 to the first ESA call for a
small mission with a launch in 2017 but not selected. XIPE is composed of two
out of the three existing JET-X telescopes with two Gas Pixel Detectors (GPD)
filled with a He-DME mixture at their focus and two additional GPDs filled with
pressurized Ar-DME facing the sun. The Minimum Detectable Polarization is 14 %
at 1 mCrab in 10E5 s (2-10 keV) and 0.6 % for an X10 class flare. The Half
Energy Width, measured at PANTER X-ray test facility (MPE, Germany) with JET-X
optics is 24 arcsec. XIPE takes advantage of a low-earth equatorial orbit with
Malindi as down-link station and of a Mission Operation Center (MOC) at INPE
(Brazil).Comment: 49 pages, 14 figures, 6 tables. Paper published in Experimental
Astronomy http://link.springer.com/journal/1068
XIPE: the x-ray imaging polarimetry explorer
XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially- resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest Observer competitive program and it is organized as a consortium across Europe with main contributions from Italy, Germany, Spain, United Kingdom, Poland, Sweden
Use of carnitine therapy in selected cases of male factor infertility: a double-blind crossover trial
OBJECTIVE: To determine the efficacy of L-carnitine therapy in selected cases of male factor infertility. DESIGN: Placebo-controlled, double-blind, crossover trial. SETTING: University tertiary referral center. PATIENT(S): One hundred infertile patients (ages 20-40 years) with the following baseline sperm selection criteria: concentration, 10-20 x 10(6)/mL; total motility, 10%-30%; forward motility, <15%; atypical forms, <70%; velocity, 10-30 micro/s; linearity, <4. Eighty-six patients completed the study. INTERVENTION(S): Patients underwent L-carnitine therapy 2 g/day or placebo; the study design was 2 months of washout, 2 months of therapy/placebo, 2 months of washout, and 2 months placebo/therapy. MAIN OUTCOME MEASURE(S): Variation in sperm parameters used in the patients selection criteria, in particular, sperm motility. Excluding outliers, a statistically significant improvement in semen quality, greater than after the placebo cycle, was seen after the L-carnitine therapy for sperm concentration and total and forward sperm motility. The increase in forward sperm motility was more significant in those patients with lower initial values, i.e., <5 x 10(6) or <2 x 10(6) of forward motile sperm/ejaculate or sperm/mL. CONCLUSION(S): Based on a controlled study of efficacy, L-carnitine therapy was effective in increasing semen quality, especially in groups with lower baseline levels. However, these results need to be confirmed by larger clinical trials and in vitro studies. Comment in J Urol. 2003 Aug;170(2 Pt 1):677
Effect of chemo- or radiotherapy on sperm parameters of testicular cancer patients
BACKGROUND: The aims of our study were to investigate the short- and long-term effects of chemo- or radiotherapy on spermatogenesis in patients with testicular cancer and to establish any correlation between pre-therapy sperm parameters, histotype and treatment type/intensity and the progress of spermatogenesis during the post-therapy period. METHODS: We evaluated 166 patients affected by testicular cancer, who cryobanked about 1 month after the removal of the cancerous testis and before beginning chemo- (CH group; n = 71) or radiotherapy (RT group; n = 95). RESULTS: For the CH group, there was a statistically significant decrease in sperm parameters, which was most significant 3 months after the end of chemotherapy. For the RT group, this decrease was most relevant 6 months after the end of radiotherapy. Two years after therapy, 3% of the CH group and 6% of the RT group remained azoospermic. To evaluate whether spermatogenesis recovery is a function of baseline semen quality, we divided each group into two subgroups by pre-therapy total sperm count (A, = 40 x 10(6)/ejaculate). At t(24), subgroup A of both the CH and RT groups showed improved sperm parameters over the baseline, whereas subgroup B for both CH and RT groups showed a return of sperm parameters to those of baseline values. CONCLUSIONS: In conclusion, the recovery of spermatogenesis after chemo- or radiotherapy in our group of testicular cancer patients was not a function of pre-therapy sperm parameter quality. Cryopreservation of sperm before performing such therapy is therefore imperative
Androgens and fertility.
Androgens play a pivotal role in the development of the male reproductive tract. The spermatogenesis requires high levels of intratesticular testosterone secreted by the Leydig cells. Testosterone exerts its action through the androgen receptor (AR), which is located both in the cytoplasm and in the nucleus of cells in the target tissue. Severe defects of the AR may result in abnormal male sexual development, while more subtle modifications can be a potential cause of male infertility. Low circulating levels of testosterone can be found in 20-30% of infertile men, but administration of testosterone or gonadotropins does not result in improved sperm production. Abuse of anabolic steroids is a frequent cause of male infertility, and substances such as endocrine disruptors can alter male fertility through an anti androgenic action