162 research outputs found
Galactic Chemical Evolution of the s Process from AGB Stars
We follow the chemical evolution of the Galaxy for the s elements using a
Galactic chemical evolution (GCE) model, as already discussed by Travaglio et
al. (1999, 2001, 2004), with a full updated network and refined asymptotic
giant branch (AGB) models. Calculations of the s contribution to each isotope
at the epoch of the formation of the solar system is determined by following
the GCE contribution by AGB stars only. Then, using the r-process residual
method we determine for each isotope their solar system r-process fraction, and
recalculate the GCE contribution of heavy elements accounting for both the s
and r process. We compare our results with spectroscopic abundances at various
metallicities of [Sr,Y,Zr/Fe], of [Ba,La/Fe], of [Pb/Fe], typical of the three
s-process peaks, as well as of [Eu/Fe], which in turn is a typical r-process
element. Analysis of the various uncertainties involved in these calculations
are discussed.Comment: 8 pages, 6 figures, 1 tabl
MEOX2 Regulates the Growth and Survival of Glioblastoma Stem Cells by Modulating Genes of the Glycolytic Pathway and Response to Hypoxia
The most widely accepted hypothesis for the development of glioblastoma suggests that
glioblastoma stem-like cells (GSCs) are crucially involved in tumor initiation and recurrence as
well as in the occurrence of chemo- and radio-resistance. Mesenchyme homeobox 2 (MEOX2) is a
transcription factor overexpressed in glioblastoma, whose expression is negatively correlated with
patient survival. Starting from our observation that MEOX2 expression is strongly enhanced in six
GSC lines, we performed shRNA-mediated knock-down experiments in two different GSC lines and
found that MEOX2 depletion resulted in the inhibition of cell growth and sphere-forming ability
and an increase in apoptotic cell death. By a deep transcriptome analysis, we identified a core group
of genes modulated in response to MEOX2 knock-down. Among these genes, the repressed ones
are largely enriched in genes involved in the hypoxic response and glycolytic pathway, two strictly
related pathways that contribute to the resistance of high-grade gliomas to therapies. An in silico
study of the regulatory regions of genes differentially expressed by MEOX2 knock-down revealed
that they mainly consisted of GC-rich regions enriched for Sp1 and Klf4 binding motifs, two main
regulators of metabolism in glioblastoma. Our results show, for the first time, the involvement of
MEOX2 in the regulation of genes of GSC metabolism, which is essential for the survival and growth
of these cells
Cambios ecológicos en las fronteras urbano rurales : El caso de la región metropolitana de Buenos Aires
El caso de estudio revisó los vÃnculos entre la ciudad de Buenos Aires y la Pampa Ondulada, en la Ecoregión Pampa Argentina se describe la conocida pérdida de tierras agrÃcolas debido a la conversión a uso urbano, y las transferencias de suelo y subsuelo, como materia prima de especies invasoras, y desechos entre áreas urbanas y rurales. El trabajo también muestra la idea de que la pérdida de tierra rural valiosa es la principal amenaza a la producción potencial en un paÃs agroexportador como Argentina es sólo una faceta del proceso de pérdida de tierra de alta fertilidad. Nuestra hipótesis es que, en muchas áreas metropolitanas de América Latina, la demanda del suelo como materia prima es tan insaciable como la demanda de tierras agrÃcolas para crecimiento urbano, y ambos tipos de conversión de la tierra representan una seria amenaza para la producción de alimentos y la seguridad alimentaria a nivel regional, nacional e internacional.Evento también conocido bajo el nombre de "II Jornadas Platenses de GeografÃa"Facultad de Humanidades y Ciencias de la Educació
Gas embolization of the liver in a rat model of rapid decompression
Occurrence of liver gas embolism after rapid decompression was assessed in 31 female rats that were decompressed in 12 min after 42 min of compression at 7 ATA (protocol A). Sixteen rats died after decompression (group I). Of the surviving rats, seven were killed at 3 h (group II), and eight at 24 h (group III). In group I, bubbles were visible in the right heart, aortic arch, liver, and mesenteric veins and on the intestinal surface. Histology showed perilobular microcavities in sinusoids, interstitial spaces, and hepatocytes. In group II, liver gas was visible in two rats. Perilobular vacuolization and significant plasma aminotransferase increase were present. In group III, liver edema was evident at gross examination in all cases. Histology showed perilobular cell swelling, vacuolization, or hydropic degeneration. Compared with basal, enzymatic markers of liver damage increased significantly. An additional 14 rats were decompressed twice (protocol B). Overall mortality was 93%. In addition to diffuse hydropic degeneration, centrilobular necrosis was frequently observed after the second decompression. Additionally, 10 rats were exposed to three decompression sessions (protocol C) with doubled decompression time. Their mortality rate decreased to 20%, but enzymatic markers still increased in surviving rats compared with predecompression, and perilobular cell swelling and vacuolization were present in five rats. Study challenges were 1) liver is not part of the pathophysiology of decompression in the existing paradigm, and 2) although significant cellular necrosis was observed in few animals, zonal or diffuse hepatocellular damage associated with liver dysfunction was frequently demonstrated. Liver participation in human decompression sickness should be looked for and clinically evaluated
The epochs of early-type galaxy formation as a function of environment
The aim of this paper is to set constraints of the epochs of early-type
galaxy formation through the 'archaeology' of the stellar populations in local
galaxies. Using our models of absorption line indices that account for variable
abundance ratios, we derive the stellar population parameters of 124 early-type
galaxies in high and low density environments. We find that all three
parameters age, metallicity, and alpha/Fe ratio are correlated with velocity
dispersion. We further find evidence for an influence of the environment on the
stellar population properties. Massive early-type galaxies in low-density
environments appear on average ~2 Gyrs younger and slightly more metal-rich
than their counterparts in high density environments. No offsets in the
alpha/Fe ratios, instead, are detected. We translate the derived ages and
alpha/Fe ratios into star formation histories. We show that most star formation
activity in early-type galaxies is expected to have happened between redshifts
3 and 5 in high density and between redshifts 1 and 2 in low density
environments. We conclude that at least 50 per cent of the total stellar mass
density must have already formed at z 1, in good agreement with observational
estimates of the total stellar mass density as a function of redshift. Our
results suggest that significant mass growth in the early-type galaxy
population below z 1 must be restricted to less massive objects, and a
significant increase of the stellar mass density between redshifts 1 and 2
should be present caused mainly by the field galaxy population. The results of
this paper further imply vigorous star formation episodes in massive objects at
z 2-5 and the presence of evolved ellipticals around z 1, both observationally
identified as SCUBA galaxies and EROs.Comment: 20 pages, 10 figures, plus appendix, accepted by Ap
Human Endogenous Retroviruses in Autism Spectrum Disorders: Recent Advances and New Perspectives at the Gene-Environment Interface
Human endogenous retroviruses (HERVs) are genetic elements, derived from their exogenous retroviral counterpart by a process of germline infection and proliferation within the human genome, and their integration as proviruses led to the fixation and the vertical transmission, following Mendelian laws. HERVs currently make up ~8% of the genetic material, and some of them have been cooped for physiological functions. Otherwise, their activation in response to environmental factors has been associated with human pathological conditions. In the setting of neurodevelopmental disorders, HERVs have been proposed as contributing factors involved in Autism Spectrum Disorders (ASD), spanning the bridge between genetic susceptibility, environmental risk factors and immune response. We described a distinct expression profile of some HERV families and cytokines in lymphocytes from autistic children and in their mothers suggesting a close mother-child association in ASD. Moreover, in vitro treatment with an antiretroviral drug was able to restore the expression level of HERVs and cytokines providing new insights into the potential role of HERVs as biomarkers of ASD and raising the possibility of using HERVs expression as a therapeutic target for a tailored approach to patient care
Myocardial perfusion in chronic diabetic mice by the up-regulation of pLKB1 and AMPK signaling
Previous studies related impaired myocardial microcirculation in diabetes to oxidative stress and endothelial dysfunction. Thus, this study was aimed to determine the effect of up-regulating pAMPK-pAKT signaling on coronary microvascular reactivity in the isolated heart of diabetic mice. We measured coronary resistance in wild-type and streptozotocin (STZ)-treated mice, during perfusion pressure changes. Glucose, insulin, and adiponectin levels in plasma and superoxide formation, NOx levels and heme oxygenase (HO) activity in myocardial tissue were determined. In addition, the expression of HO-1, 3-nitrotyrosine, pLKB1, pAMPK, pAKT, and peNOS proteins in control and diabetic hearts were measured. Coronary response to changes in perfusion pressure diverged from control in a time-dependent manner following STZ administration. The responses observed at 28 weeks of diabetes (the maximum time examined) were mimicked by L-NAME administration to control animals and were associated with a decrease in serum adiponectin and myocardial pLKB1, pAMPK, pAKT, and pGSK-3 expression. Cobalt protoporphyrin treatment to induce HO-1 expression reversed the microvascular reactivity seen in diabetes towards that of controls. Up-regulation of HO-1 was associated with an increase in adiponectin, pLKB1, pAKT, pAMPK, pGSK-3, and peNOS levels and a decrease in myocardial superoxide and 3-nitrotyrosine levels. In the present study we describe the time course of microvascular functional changes during the development of diabetes and the existence of a unique relationship between the levels of serum adiponectin, pLKB1, pAKT, and pAMPK activation in diabetic hearts. The restoration of microvascular function suggests a new therapeutic approach to even advanced cardiac microvascular derangement in diabetes
Chemical abundance ratios of galactic globular clusters from modelling integrated light spectroscopy
We use our new, flux-calibrated stellar population model of absorption-line
indices to derive ages, metallicities, and various element abundance ratios
from integrated light spectroscopy of galactic globular clusters. The ages
agree well with the literature and are all consistent with the age of the
universe. There is a considerable scatter, though, and we obtain systematically
larger ages than CMD determinations mostly for metal-rich globular clusters.
The metallicities agree well with literature values on the Zinn & West scale,
if we adopt iron abundance [Fe/H] for those clusters whose ages agree with the
CMD ages. It turns out that the derivation of individual element abundance
ratios is not reliable at [Fe/H]<-1 dex, while the [alpha/Fe] ratio is robust
at all metallicities. We find general enhancement of light and alpha elements,
as expected, with significant variations for some elements. The elements O and
Mg follow the same general enhancement with almost identical distributions of
[O/Fe] and [Mg/Fe]. We obtain slightly lower [C/Fe] and very high [N/Fe]
ratios, instead. This chemical anomaly, commonly attributed to self-enrichment,
is well known in globular clusters from individual stellar spectroscopy. It is
the first time that this pattern is obtained also from the integrated light.
The alpha elements follow a pattern such that the heavier elements Ca and Ti
are less enhanced. More specifically, the [Ca/Fe] and [Ti/Fe] ratios are lower
than [O/Fe] and [Mg/Fe] by about 0.2 dex. This trend is also seen in recent
determinations of element abundances in globular cluster and field stars of the
Milky Way. This suggests that Type Ia supernovae contribute significantly to
the enrichment of the heavier alpha elements as predicted by nucleosynthesis
calculations and galactic chemical evolution models.Comment: MNRAS, re-submitted including referee's comments (minor revision),
update on CMD globular cluster age
Expression analysis of miRNA hsa-let7b-5p in naso-oropharyngeal swabs of COVID-19 patients supports its role in regulating ACE2 and DPP4 receptors
Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is the novel coronavirus responsible for worldwide coronavirus disease (COVID-19). We previously observed that Angiotensin-converting enzyme 2 (ACE2) and Dipeptidyl peptidase-4 (DPP4) are significantly overexpressed in naso-oropharyngeal swabs (NPS) of COVID-19 patients, suggesting their putative functional role in the disease progression. ACE2 and DPP4 overexpression in COVID-19 patients may be associated to epigenetic mechanism, such as miRNA differential expression. We investigated if hsa-let7b-5p, reported to target both ACE2 and DPP4 transcripts, could be involved in the regulation of these genes. We verified that the inhibition and overexpression of hsa-let7b-5p matched to a modulation of both ACE2 and DPP4 levels. Then, we observed a statistically significant downregulation (FC = -1.5; p < 0.05) of hsa-let7b-5p in the same COVID-19 and control samples of our previous study. This is the first study that shows hsa-let7b-5p low expression in naso-oropharyngeal swabs of COVID-19 patients and demonstrates a functional role of this miR in regulating ACE2 and DPP4 levels. These data suggest the involvement of hsa-let7b-5p in the regulation of genes necessary for SARS-CoV-2 infections and its putative role as a therapeutic target for COVID-19
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