284 research outputs found
Impact of photometric variability on age and mass determination of Young Stellar Objects: A case study on Orion Nebula Cluster
In case of pre-main sequence objects, the only way to determine age and mass
is by fitting theoretical isochrones on color-magnitude (alternatively
luminosity-temperature) diagrams. Since young stellar objects exhibit
photometric variability over wide range in magnitude and colors, the age and
mass determined by fitting isochrones is expected to be inaccurate, if not
erroneous. These in turn will badly affect any study carried out on age spread
and process of star formation. Since we have carried out very extensive
photometric observations of the Orion Nebula Cluster (ONC), we decided to use
our multi-band data to explore the influence of variability in determining mass
and age of cluster members. In this study, we get the amplitudes of the
photometric variability in V, R, and I optical bands of a sample of 346 ONC
members and use it to investigate how the variability affects the inferred
masses and ages and if it alone can take account for the age spread among the
ONC members reported by earlier studies. We find that members that show
periodic and smooth photometric rotational modulation have their masses and
ages unaffected by variability. On other hand, we found that members with
periodic but very scattered photometric rotational modulation and members with
irregular variability have their masses and ages significantly affected.
Moreover, using Hertzsprung-Russell (HR) diagrams we find that the observed I
band photometric variability can take account of only a fraction (about 50%) of
the inferred age spread, whereas the V band photometric variability is large
enough to mask any age spread.Comment: Accepted by MNRAS; 17 pages, 4 Tables, 15 Figure
Analysis of pregnancy-associated plasma protein a production in human adult cardiac progenitor cells
IGF-binding proteins (IGFBPs) and their proteases regulate IGFs bioavailability in multiple tissues. Pregnancy-associated plasma protein A (PAPP-A) is a protease acting by cleaving IGFBP2, 4, and 5, regulating local bioavailability of IGFs. We have previously shown that IGFs and IGFBPs are produced by human adult cardiac progenitor cells (haCPCs) and that IGF-1 exerts paracrine therapeutic effects in cardiac cell therapy with CPCs. Using immunofluorescence and enzyme immunoassays, we firstly report that PAPP-A is produced and secreted in surprisingly high amounts by haCPCs. In particular, the homodimeric, enzymatically active, PAPP-A is secreted in relevant concentrations in haCPC-conditioned media, while the enzymatically inactive PAPPA/proMBP complex is not detectable in the same media. Furthermore, we show that both homodimeric PAPP-A and proMBP can be detected as cell associated, suggesting that the previously described complex formation at the cell surface does not occur easily, thus positively affecting IGF signalling. Therefore, our results strongly support the importance of PAPP-A for the IGFs/IGFBPs/PAPP-A axis in CPCs biology
EMT/MET at the crossroad of stemness, regeneration and oncogenesis. The Ying-Yang equilibrium recapitulated in cell spheroids
The epithelial-to-mesenchymal transition (EMT) is an essential trans-differentiation process, which plays a critical role in embryonic development, wound healing, tissue regeneration, organ fibrosis, and cancer progression. It is the fundamental mechanism by which epithelial cells lose many of their characteristics while acquiring features typical of mesenchymal cells, such as migratory capacity and invasiveness. Depending on the contest, EMT is complemented and balanced by the reverse process, the mesenchymal-to-epithelial transition (MET). In the saving economy of the living organisms, the same (Ying-Yang) tool is integrated as a physiological strategy in embryonic development, as well as in the course of reparative or disease processes, prominently fibrosis, tumor invasion and metastasis. These mechanisms and their related signaling (e.g., TGF-β and BMPs) have been effectively studied in vitro by tissue-derived cell spheroids models. These three-dimensional (3D) cell culture systems, whose phenotype has been shown to be strongly dependent on TGF-β-regulated EMT/MET processes, present the advantage of recapitulating in vitro the hypoxic in vivo micro-environment of tissue stem cell niches and their formation. These spheroids, therefore, nicely reproduce the finely regulated Ying-Yang equilibrium, which, together with other mechanisms, can be determinant in cell fate decisions in many pathophysiological scenarios, such as differentiation, fibrosis, regeneration, and oncogenesis. In this review, current progress in the knowledge of signaling pathways affecting EMT/MET and stemness regulation will be outlined by comparing data obtained from cellular spheroids systems, as ex vivo niches of stem cells derived from normal and tumoral tissues. The mechanistic correspondence in vivo and the possible pharmacological perspective will be also explored, focusing especially on the TGF-β-related networks, as well as others, such as SNAI1, PTEN, and EGR1. This latter, in particular, for its ability to convey multiple types of stimuli into relevant changes of the cell transcriptional program, can be regarded as a heterogeneous "stress-sensor" for EMT-related inducers (growth factor, hypoxia, mechano-stress), and thus as a therapeutic target
New perspectives to repair a broken heart
The aim of cardiac cell therapy is to restore at least in part the functionality of the diseased or injured myocardium by the use of stem/ progenitor cells. Recent clinical trials have shown the safety of cardiac cell therapy and encouraging efficacy results. A surprisingly wide range of non-myogenic cell types improves ventricular function, suggesting that benefits may result in part from mechanisms that are distinct from true myocardial regeneration. While clinical trials explore cells derived from skeletal muscle and bone marrow, basic researchers are investigating sources of new cardiomyogenic cells, such as resident myocardial progenitors and embryonic stem cells. In this commentary we briefly review the evolution of cell-based cardiac repair, some progress that has been made toward this goal, and future perspectives in the regeneration of cardiac tissue. © 2009 Bentham Science Publishers Ltd
Split-appendix technique: Alternative urinary diversion for pediatric complete incontinence
We report our series of selected patients with complete incontinence in whom the appendix was
divided and utilized for creating two continent catheterizable stomas. All patients were treated for
urinary and fecal incontinence by split appendix technique. The appendix was divided into two
different parts preserving adequate perfusion and used for creating an appendicocecostomy (ACE)
and an appendicovesicostomy at the same time. After a clinical and radiological follow up, our
patients referred a good acceptance and an easily management of the stomas in order to stay dry for
all day from urine and feces with improving of their quality of life. The combination of ACE and
Mitrofanoff principle have revolutionized the management of urinary and fecal incontinence in
patients who are unable to utilize their urethra to keep themselves dry
Chromosome 18q-Syndrome and 1p terminal duplication in a patient with bilateral vesicoureteral reflux: case report and literature revision
Background: Vesico-ureteral reflux (VUR) is a dynamic event in which a retrograde flow of urine is present into the
upper tracts. VUR may occur isolated or in association with other congenital abnormalities or as part of syndromic
entities. We present a patient with a bilateral primary VUR, syndromic disease caused by a large deletion of 18q
(18q21.3-qter) and terminal duplication of 1p (1p36.32-p36.33).
Case report: The patient was 8 years old female with a disease including moderate growth retardation,
psychomotor retardation, facial dysmorphism, single umbilical artery, umbilical hernia, urachal remnant, bilateral
congenital clubfeet and renal-urinary disease. Chromosomal analysis and Array-CGH revealed two heterozygous
chromosomal rearrangements: 1p terminal duplication and de novo 18q terminal deletion. She referred to our clinic
to evaluation of bilateral hydronephrosis and right renal cortex thinning. Voiding cystourethrography demonstrated
bilateral grade IV VUR and dimercaptosuccinic acid renal scintigraphy confirmed right renal cortex thinning and
showed a cortical uptake of 75% of the left kidney and 25% of the right kidney. The patient underwent
ureterovesical reimplantation after failure of 3 endoscopic submeatal Deflux injections with VUR resolution.
Conclusions: This is the first report involving a patient with 18q-syndrome and contemporary presence of 1p
chromosomal terminal duplication. The coexistence of two chromosomal rearrangements complicates the clinical
picture and creates a chimeric disorder (marked by characteristics of both chromosomal anomalies). Kidney
problems, primarily VUR is reported in 15% of patients affected by 18-q syndrome and no cases is reported in the
literature regarding a correlation between VUR and 1p36 chromosomal duplication
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