Reversal or no reversal: the evolution of the star formation rate–density relation up to z ∼ 1.6

We investigate the evolution of the star formation rate (SFR)–density relation in the Extended Chandra Deep Field South and the Great Observatories Origin Deep Survey fields up to z ∼ 1.6. In addition to the ‘traditional method’, in which the environment is defined according to a statistical measurement of the local galaxy density, we use a ‘dynamical’ approach, where galaxies are classified according to three different environment regimes: group, ‘filament-like’ and field. Both methods show no evidence of an SFR–density reversal. Moreover, group galaxies show a mean SFR lower than other environments up to z ∼ 1, while at earlier epochs group and field galaxies exhibit consistent levels of star formation (SF) activity. We find that processes related to a massive dark matter halo must be dominant in the suppression of the SF below z ∼ 1, with respect to purely density-related processes. We confirm this finding by studying the distribution of galaxies in different environments with respect to the so-called main sequence (MS) of star-forming galaxies. Galaxies in both group and ‘filament-like’ environments preferentially lie below the MS up to z ∼ 1, with group galaxies exhibiting lower levels of star-forming activity at a given mass. At z > 1, the star-forming galaxies in groups reside on the MS. Groups exhibit the highest fraction of quiescent galaxies up to z ∼ 1, after which group, ‘filament-like’ and field environments have a similar mix of galaxy types. We conclude that groups are the most efficient locus for SF quenching. Thus, a fundamental difference exists between bound and unbound objects, or between dark matter haloes of different masses

Primordial Black Holes as Near Infrared Background sources

The near infrared background (NIRB) is the collective light from unresolved sources observed in the band 1-10 $\mu$m. The measured NIRB angular power spectrum on angular scales $\theta \gtrsim 1$ arcmin exceeds by roughly two order of magnitudes predictions from known galaxy populations. The nature of the sources producing these fluctuations is still unknown. Here we test primordial black holes (PBHs) as sources of the NIRB excess. Considering PBHs as a cold dark matter (DM) component, we model the emission of gas accreting onto PBHs in a cosmological framework. We account for both accretion in the intergalactic medium (IGM) and in DM haloes. We self consistently derive the IGM temperature evolution, considering ionization and heating due to X-ray emission from PBHs. Besides $\Lambda$CDM, we consider a model that accounts for the modification of the linear matter power spectrum due to the presence of PBHs; we also explore two PBH mass distributions, i.e. a $\delta$-function and a lognormal distribution. For each model, we compute the mean intensity and the angular power spectrum of the NIRB produced by PBHs with mass 1-$10^3~\mathrm{M}_{\odot}$. In the limiting case in which the entirety of DM is made of PBHs, the PBH emission contributes $<1$ per cent to the observed NIRB fluctuations. This value decreases to $<0.1$ per cent if current constraints on the abundance of PBHs are taken into account. We conclude that PBHs are ruled out as substantial contributors to the NIRB.Comment: Accepted for publication in MNRA

Lipid storage and autophagy in melanoma cancer cells

Cancer stem cells (CSC) represent a key cellular subpopulation controlling biological features such as cancer progression in all cancer types. By using melanospheres established from human melanoma patients, we compared less differentiated melanosphere-derived CSC to differentiating melanosphere-derived cells. Increased lipid uptake was found in melanosphere-derived CSC vs. differentiating melanosphere-derived cells, paralleled by strong expression of lipogenic factors Sterol Regulatory Element-Binding Protein-1 (SREBP-1) and Peroxisome Proliferator-Activated Receptor-γ (PPAR-γ). An inverse relation between lipid-storing phenotype and autophagy was also found, since microtubule-associated protein 1A/1B-Light Chain 3 (LC3) lipidation is reduced in melanosphere-derived CSC. To investigate upstream autophagy regulators, Phospho-AMP activated Protein Kinase (P-AMPK) and Phospho-mammalian Target of Rapamycin (P-mTOR) were analyzed; lower P-AMPK and higher P-mTOR expression in melanosphere-derived CSC were found, thus explaining, at least in part, their lower autophagic activity. In addition, co-localization of LC3-stained autophagosome spots and perilipin-stained lipid droplets was demonstrated mainly in differentiating melanosphere-derived cells, further supporting the role of autophagy in lipid droplets clearance. The present manuscript demonstrates an inverse relationship between lipid-storing phenotype and melanoma stem cells differentiation, providing novel indications involving autophagy in melanoma stem cells biology

Interference coloration as an anti-predator defence

Interference coloration, in which the perceived colour varies predictably with the angle of illumination or observation, is extremely widespread across animal groups. However, despite considerable advances in our understanding of the mechanistic basis of interference coloration in animals, we still have a poor understanding of its function. Here, I show, using avian predators hunting dynamic virtual prey, that the presence of interference coloration can significantly reduce a predator's attack success. Predators required more pecks to successfully catch interference-coloured prey compared with otherwise identical prey items that lacked interference coloration, and attacks against prey with interference colours were less accurate, suggesting that changes in colour or brightness caused by prey movement hindered a predator's ability to pinpoint their exact location. The pronounced antipredator benefits of interference coloration may explain why it has evolved independently so many times. © 2015 The Author(s) Published by the Royal Society. All rights reserved

Toll-iike receptor-3 activation enhances malignant traits in human breast cancer cells through hypoxia-inducible factor-1α

Background/Aim: Hypoxia-inducible factor 1 (HIF1) inhibitors have been proposed as therapeutic agents for several tumor types. HIF1α is induced by hypoxia and by pathogens in normoxia through toll-like receptors (TLRs). The TLR3 activator polyinosinic:polycytidylic acid [poly(I:C)] induces apoptosis in various types of cancer but not in the most aggressive breast cancer cell lines. We hypothesized that the failure of TLR3 stimulation to induce apoptosis in these cells might be due to an elevated HIF1α level and this link might be exploited. Materials and Methods: Poly(I:C)-induced signaling pathway and expression of HIF1α and HIF1α targets were studied in MDA MB-231 and MCF-7 breast cancer cell lines by western blot. Flow cytometry was used for apoptotic responses and vasculogenic mimicry as bioassay. Results: Poly(I:C) increased expression of HIF1α and its targets BCL2 apoptosis regulator and c-MYC. Moreover, using pharmacological or genetic HIF1 inhibition, reduction of poly(I:C)-induced expression of HIF1α was paralleled by lowering of c-MYC and increased sensitivity to poly(I:C)-induced apoptosis, demonstrating the crucial role of this factor. We provide the first evidence in breast cancer cells that TLR3 stimulation induces HIF1αdependent vasculogenic mimicry. By using specific inhibitors, we identified a signaling cascade upstream of HIF1α induction. Conclusion: Combined treatment with poly(I:C) and HIF1 inhibitors deserves consideration as an effective strategy in breast cancer therapy

Stem-like and highly invasive prostate cancer cells expressing CD44v8-10 marker originate from CD44-negative cells

In human prostate cancer (PCa), the neuroendocrine cells, expressing the prostate cancer stem cell (CSC) marker CD44, may be resistant to androgen ablation and promote tumor recurrence. During the study of heterogeneity of the highly aggressive neuroendocrine PCa cell lines PC3 and DU-145, we isolated and expanded in vitro a minor subpopulation of very small cells lacking CD44 (CD44neg). Unexpectedly, these sorted CD44neg cells rapidly and spontaneously converted to a stable CD44high phenotype specifically expressing the CD44v8-10 isoform which the sorted CD44high subpopulation failed to express. Surprisingly and potentially interesting, in these cells expression of CD44v8-10 was found to be induced in stem cell medium. CD44 variant isoforms are known to be more expressed in CSC and metastatic cells than CD44 standard isoform. In agreement, functional analysis of the two sorted and cultured subpopulations has shown that the CD44v8-10pos PC3 cells, resulting from the conversion of the CD44neg subpopulation, were more invasive in vitro and had a higher clonogenic potential than the sorted CD44high cells, in that they produced mainly holoclones, known to be enriched in stem-like cells. Of interest, the CD44v8-10 is more expressed in human PCa biopsies than in normal gland. The discovery of CD44v8-10pos cells with stem-like and invasive features, derived from a minoritarian CD44neg cell population in PCa, alerts on the high plasticity of stem-like markers and urges for prudency on the approaches to targeting the putative CSC

The XXL Survey X: K-band luminosity - weak-lensing mass relation for groups and clusters of galaxies

We present the K-band luminosity-halo mass relation, $L_{K,500}-M_{500,WL}$, for a subsample of 20 of the 100 brightest clusters in the XXL Survey observed with WIRCam at the Canada-France-Hawaii Telescope (CFHT). For the first time, we have measured this relation via weak-lensing analysis down to $M_{500,WL} =3.5 \times 10^{13}\,M_\odot$. This allows us to investigate whether the slope of the $L_K-M$ relation is different for groups and clusters, as seen in other works. The clusters in our sample span a wide range in mass, $M_{500,WL} =0.35-12.10 \times 10^{14}\,M_\odot$, at $0<z<0.6$. The K-band luminosity scales as $\log_{10}(L_{K,500}/10^{12}L_\odot) \propto \beta log_{10}(M_{500,WL}/10^{14}M_\odot)$ with $\beta = 0.85^{+0.35}_{-0.27}$ and an intrinsic scatter of $\sigma_{lnL_K|M} =0.37^{+0.19}_{-0.17}$. Combining our sample with some clusters in the Local Cluster Substructure Survey (LoCuSS) present in the literature, we obtain a slope of $1.05^{+0.16}_{-0.14}$ and an intrinsic scatter of $0.14^{+0.09}_{-0.07}$. The flattening in the $L_K-M$ seen in previous works is not seen here and might be a result of a bias in the mass measurement due to assumptions on the dynamical state of the systems. We also study the richness-mass relation and find that group-sized halos have more galaxies per unit halo mass than massive clusters. However, the brightest cluster galaxy (BCG) in low-mass systems contributes a greater fraction to the total cluster light than BCGs do in massive clusters; the luminosity gap between the two brightest galaxies is more prominent for group-sized halos. This result is a natural outcome of the hierarchical growth of structures, where massive galaxies form and gain mass within low-mass groups and are ultimately accreted into more massive clusters to become either part of the BCG or one of the brighter galaxies. [Abridged]Comment: A&A, in pres

Salivary cortisol and α-amylase production at awakening is associated with positivity (POS) levels in healthy young subjects

A large variety of positive outcomes including social adjustment, psychological well-being and health, have been recently closely associated with positivity (POS). On the assumption that differences in the POS degree might be associated with different individual neuroendocrine assets that enables people to cope effectively with stress, the present study examined the association between POS, salivary cortisol and α-Amylase (α-Amy) production in a group of healthy male volunteers university students, respectively scoring high (POS-H, N = 10) and low (POS-L, N = 10) in POS. Participants were selected from a larger sample of 300 students of the Medical School at Sapienza University of Rome on the basis of their positivity level: POS was analysed and the upper and lower 25% were invited to participate in this new study. The findings report a distinct salivary cortisol and α-Amy production in the study population: in comparison to the POS-H group, the POS-L subjects presented a lower salivary cortisol awake response (CAR) and a flattened α-Amy production at 30 and 60&nbsp;min after awakening. In addition, salivary cortisol and α-Amy areas under the curve (AUCs), which were calculated as indicators of the two subclinical biomarkers production during the first hour after awakening, resulted significantly lower in the POS-L group in comparison to the POS-H group. Further studies on larger and different populations are needed to definitively confirm that the different cortisol and α-Amy secretion patterns between POS-H and POS-L individuals is associated with a potentially better capacity to preserving an adequate quality of life in individuals being equipped with a system apparently able to better respond to external and/or internal stimuli. Lastly, a better understanding of the biological correlates of POS is crucial to design psychological interventions able to take advantage of individuals’ assets and thus to integrate and strengthen the efficacy of traditional medications