592 research outputs found
Increased adrenal steroid secretion in response to CRF in women with hypothalamic amenorrhea
Objectie: To evaluate adrenal steroid hormone secretion in response to corticotropin-releasing factor (CRF) or to adrenocorticotropin
hormone in women with hypothalamic amenorrhea. Design: Controlled clinical study. Setting: Department of
Reproductive Medicine and Child Development, Section of Gynecology and Obstetrics, University of Pisa, Italy. Patient(s):
Fifteen women with hypothalamic amenorrhea were enrolled in the study. Eight normal cycling women were used as control
group. Interention(s): Blood samples were collected before and after an injection of ovine CRF (0.1 g/kg iv bolus) or after
synthetic ACTH (0.25 mg iv). Main outcome measure(s): Plasma levels of ACTH, 17-hydroxypregnenolone (17OHPe), progesterone
(P), dehydroepiandrosterone (DHEA), 17-hydroxyprogesterone (17OHP), cortisol (F), 11-deoxycortisol (S) and androstenedione
(A). Result(s): Basal plasma concentrations of ACTH, cortisol, 11-deoxycortisol, DHEA and 17OHPe were significantly
higher in patients than in controls, whereas plasma levels of progesterone and 17-OHP were significantly lower in patients than
in controls. In amenorrheic women the ratio of 17-OHPe/DHEA, of 17-OHPe/17-OHP and of 11-deoxycortisol/cortisol were
significantly higher than in controls, while a significant reduction in the ratio of 17-OHP/androstenedione, of 17-OHP/11-deoxycortisol
was obtained. In response to corticotropin-releasing factor test, plasma levels of ACTH, cortisol, 17-OHP, 11-deoxycortisol,
DHEA and androstenedione were significantly lower in patients than in controls. In response to adrenocorticotropin
hormone, plasma levels of 17-OHP, androstenedione and androstenedione/cortisol were significantly higher in patients than in
controls. Conclusions: Patients suffering for hypothalamic amenorrhea showed an increased activation of hypothalamus-pituitaryadrenal
(HPA) axis, as shown by the higher basal levels and by augmented adrenal hormone response to corticotropin-releasing
factor administration. These data suggest a possible derangement of adrenal androgen enzymatic pathway
A spatial model of autocatalytic reactions
Biological cells with all of their surface structure and complex interior
stripped away are essentially vesicles - membranes composed of lipid bilayers
which form closed sacs. Vesicles are thought to be relevant as models of
primitive protocells, and they could have provided the ideal environment for
pre-biotic reactions to occur. In this paper, we investigate the stochastic
dynamics of a set of autocatalytic reactions, within a spatially bounded
domain, so as to mimic a primordial cell. The discreteness of the constituents
of the autocatalytic reactions gives rise to large sustained oscillations, even
when the number of constituents is quite large. These oscillations are
spatio-temporal in nature, unlike those found in previous studies, which
consisted only of temporal oscillations. We speculate that these oscillations
may have a role in seeding membrane instabilities which lead to vesicle
division. In this way synchronization could be achieved between protocell
growth and the reproduction rate of the constituents (the protogenetic
material) in simple protocells.Comment: Submitted to Phys. Rev.
Differential protein folding and chemical changes in lung tissues exposed to asbestos or particulates
Environmental and occupational inhalants may induce a large number of pulmonary diseases, with asbestos exposure being the most risky. The mechanisms are clearly related to chemical composition and physical and surface properties of materials. A combination of X-ray fluorescence (\u3bcXRF) and Fourier Transform InfraRed (\u3bcFTIR) microscopy was used to chemically characterize and compare asbestos bodies versus environmental particulates (anthracosis) in lung tissues from asbestos exposed and control patients. \u3bcXRF analyses revealed heterogeneously aggregated particles in the anthracotic structures, containing mainly Si, K, Al and Fe. Both asbestos and particulates alter lung iron homeostasis, with a more marked effect in asbestos exposure. \u3bcFTIR analyses revealed abundant proteins on asbestos bodies but not on anthracotic particles. Most importantly, the analyses demonstrated that the asbestos coating proteins contain high levels of \u3b2-sheet structures. The occurrence of conformational changes in the proteic component of the asbestos coating provides new insights into long-term asbestos effects
On RAF Sets and Autocatalytic Cycles in Random Reaction Networks
The emergence of autocatalytic sets of molecules seems to have played an
important role in the origin of life context. Although the possibility to
reproduce this emergence in laboratory has received considerable attention,
this is still far from being achieved. In order to unravel some key properties
enabling the emergence of structures potentially able to sustain their own
existence and growth, in this work we investigate the probability to observe
them in ensembles of random catalytic reaction networks characterized by
different structural properties. From the point of view of network topology, an
autocatalytic set have been defined either in term of strongly connected
components (SCCs) or as reflexively autocatalytic and food-generated sets
(RAFs). We observe that the average level of catalysis differently affects the
probability to observe a SCC or a RAF, highlighting the existence of a region
where the former can be observed, whereas the latter cannot. This parameter
also affects the composition of the RAF, which can be further characterized
into linear structures, autocatalysis or SCCs. Interestingly, we show that the
different network topology (uniform as opposed to power-law catalysis systems)
does not have a significantly divergent impact on SCCs and RAFs appearance,
whereas the proportion between cleavages and condensations seems instead to
play a role. A major factor that limits the probability of RAF appearance and
that may explain some of the difficulties encountered in laboratory seems to be
the presence of molecules which can accumulate without being substrate or
catalyst of any reaction.Comment: pp 113-12
Study of the Decay phi --> eta pi0 gamma with the KLOE detector
In a sample of 5.3x10^7 phi-decays observed with the KLOE detector at the
Frascati phi-factory Dafne we find 605 eta pi0 gamma events with eta -->
gamma\gamma and 197 eta pi0 gamma events with eta --> pi+ pi- pi0. The decay
phi --> eta pi0 gamma is dominated by the process phi --> a0 gamma. From a fit
to the eta pi0 mass spectrum we find BR(phi --> ao(980) gamma)= (7.4 +-
0.7)x10^-5.Comment: 12 pages, 6 figures, submitted to Phys.Lett.
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