120 research outputs found
The mystery of the 'Kite' radio source in Abell 2626: insights from new Chandra observations
We present the results of a new Chandra study of the galaxy cluster A2626.
The radio emission of the cluster shows a complex system of four symmetric arcs
without known correlations with the X-ray emission. The mirror symmetry of the
radio arcs toward the center and the presence of two optical cores in the
central galaxy suggested that they may be created by pairs of precessing radio
jets powered by dual AGNs inside the cD galaxy. However, previous observations
failed to observe the second jetted AGN and the spectral trend due to radiative
age along the radio arcs, thus challenging this interpretation. The new Chandra
observation had several scientific objectives, including the search for the
second AGN that would support the jet precession model. We focus here on the
detailed study of the local properties of the thermal and non-thermal emission
in the proximity of the radio arcs, in order to get more insights into their
origin. We performed a standard data reduction of the Chandra dataset deriving
the radial profiles of temperature, density, pressure and cooling time of the
intra-cluster medium. We further analyzed the 2D distribution of the gas
temperature, discovering that the south-western junction of the radio arcs
surrounds the cool core of the cluster. We studied the X-ray SB and spectral
profiles across the junction, finding a cold front spatially coincident with
the radio arcs. This may suggest a connection between the sloshing of the
thermal gas and the nature of the radio filaments, raising new scenarios for
their origin. A possibility is that the radio arcs trace the projection of a
complex surface connecting the sites where electrons are most efficiently
reaccelerated by the turbulence that is generated by the gas sloshing. In this
case, diffuse emission embedded by the arcs and with extremely steep spectrum
should be most visible at very low radio frequencies.Comment: 7 pages, 7 figures. Accepted for publication on A&
Vps28 is involved in the intracellular trafficking of AWD, the Drosophila homolog of NMe1/2
The Awd (abnormal wing discs) gene is the Drosophila homolog of human NME1 and NME2 metastasis suppressor genes. These genes play a key role in tumor progression. Extensive studies revealed that intracellular NME1/2 protein levels could be related to either favorable or poor prognosis depending on tissue context. More recently, extracellular activities of NME1/2 proteins have also been reported, including a tumor- promoting function. We used Drosophila as a genetic model to investigate the mechanism controlling intra- and extracellular levels of NME1/2. We examined the role of several components of the ESCRT (endosomal sorting complex required for transport) complex in controlling Awd trafficking. We show that the Vps28 component of the ESCRT 12I complex is required for maintenance of normal intracellular level of Awd in larval adipocytes. We already showed that blocking of Shibire (Shi)/Dynamin function strongly- lowers Awd intracellular level. To further investigate this down regulative effect, we analyzed the distribution of endosomal markers in wild type and Shi-defective adipocytes. Our results suggest that Awd does not enter CD63-positive endosomes. Interestingly, we found that in fat body cells, Awd partly- colocalizes with the ESCRT accessory component ALiX, the ALG-2 (apoptosis-linked gene 2)-interacting protein X. Moreover, we show that the intracellular levels of both proteins are downregulated by blocking the function of the Dynamin encoded by the shibire gene
Comparative expression profiling of wild type Drosophila Malpighian tubules and von Hippel-Lindau haploinsufficient mutant
The von-Hippel Lindau (VHL) disease is a hereditary genetic disorder that predisposes to the onset of several highly vascularized benign and malignant tumors, developing with elevate frequency in the central nervous system and kidneys. The most-aggressive VHL tumor is ccRCC, the clear-cell renal cell carcinoma, affecting the kidney. VHL disease etiology can be attributed to the inheritance of a VHL loss-of-function allele, typically a deletion (Gnarra et al., 1994; Herman et al., 1994); this facilitates the somatic inactivation of the other allele (through amorphic mutations or gene silencing through promoter methylation), leading to the onset of the tumorous phenotype (Latif et al., 1993). This reveals the haploinsufficient behavior of the VHL gene.
The high vascularization of VHL tumors can be explained considering that human VHL protein is the substrate-binding subunit of an E3 ubiquitin ligase (Lonergan et al., 1998; Iwai et al., 1999; Kamura et al., 1999) involved in the poly-ubiquitination of HIF-1α transcription factor. This post-translational modification leads HIF-1α to proteosomal degradation (Maxwell et al., 1999). Loss of VHL function causes the stabilization of HIF-1α, triggering cellular response and adaptation to hypoxic conditions (expression of genes involved in glycolysis, angiogenesis and erythropoiesis) (Bader and Hsu, 2012). While this represents the canonical function of VHL, other HIF-1α-independent function of VHL have been identified, thanks to the contribution of model organisms (Hsu, 2012). Indeed, VHL gene function is conserved and also Drosophila has a VHL homolog, the dVHL gene (Adryan et al., 2000; Aso et al., 2000). dVHL is involved in the development of Drosophila vascular system (Adryan et al., 2000; Hsouna et al., 2010) and in morphogenesis of follicular epithelium of the egg chamber (Duchi et al., 2010). Interestingly, some VHL functions are mediated by Awd, an endocytic mediator whose human orthologs are NME1/2 metastasis suppressors (Rosengard et al., 1989). Awd is broadly required during Drosophila development since it is involved in epithelial morphogenesis (Nallamothu et al., 2008; Woolworth et al., 2009; Ignesti et al., 2014) and required for maintaining genomic stability (Romani et al., 2017). Moreover, Awd is also present into the extracellular fluids of Drosophila larvae (Romani et al., 2016, 2018).
In Drosophila, two pairs of monolayered epithelial Malpighian tubules, each composed of 100-150 cells, absolve to osmoregulation and excretion functions (Denholm and Skaer, 2009). Transcriptomic analysis of Malpighian tubules revealed that among genes that are here enriched there are homologs of human genes implicated into renal pathologies (Wang et al., 2004). This justifies the use of Drosophila Malpighian tubules as model system to gain insights into pathophysiology of human kidneys (Dow and Romero, 2010; Miller et al., 2013).
The dVHL1.1 allele is a loss of function mutation of the dVHL locus (Duchi et al., 2010; Hsouna et al., 2010). dVHL1.1/+ flies mimic the genetic condition of VHL patients. We carried out a genome-wide gene expression profiling of whole Malpighian tubules dissected from Drosophila females both heterozygous for the dVHL1.1 mutation and with two wild type copies of the dVHL gene. The comparison of differentially expressed genes in the two genetic backgrounds potentially allows to identify genes that are sensible to dVHL functional copy number. Quality control assessments of the data were performed and results obtained from the differential expression analysis were confirmed by qRT-PCR. With this approach we aimed to provide a well-controlled dataset for a better understanding of the VHL disease. Indeed, even if further molecular and functional characterization are needed, human homologs of the differentially expressed genes, if existing, could have a role in the somatic inactivation of the wild type copy of VHL and/or into the very first phase of cancer onset
The freezing process helps to preserve the quality of extra virgin olive oil over time: A case study up to 18 months
Radio continuum tails in ram pressure-stripped spiral galaxies: experimenting with a semi-empirical model in Abell 2255
Wide-field radio continuum observations of galaxy clusters are revealing an
increasing number of spiral galaxies hosting tens of kpc-long radio tails
produced by the nonthermal interstellar medium being displaced by the ram
pressure. We present a semi-empirical model for the multi-frequency radio
continuum emission from ram pressure stripped tails based on the pure
synchrotron cooling of a radio plasma moving along the stripping direction with
a uniform velocity. We combine LOFAR and uGMRT observations at 144 and 400 MHz
to study the flux density and spectral index profiles of the radio tails of 7
galaxies in Abell 2255, and use the model to reproduce the flux density and
spectral index profiles, and infer the stripped radio plasma velocity. For 5
out of 7 galaxies we observe monotonic decrease in both flux density and
spectral index up to kpc from their stellar disk. Our model reproduces
the observed trends with a radio plasma bulk projected velocity between 160 and
430 km s. This result represents the first indirect measure of the
stripped, nonthermal interstellar medium velocity. The observed spectral index
trends indicate that the synchrotron cooling is faster than the adiabatic
expansion losses, thus suggesting that the stripped radio plasma can survive
for a few tens of Myr outside of the stellar disk. This provides a lower limit
for the lifetime of the stripped ISM outside of the disk. As a proof of
concept, we use the best-fit velocities to constrain the galaxies' 3D velocity
in the cluster to be in the 300-1300 km s. We estimate the ram pressure
affecting these galaxies to be between 0.1 and 2.9 erg
cm, and measure the inclination between their stellar disk and the ram
pressure wind.Comment: 15 pages, 9 figures, 5 tables. Accepted for publication on A&A on May
31st 202
The LOFAR and JVLA view of the distant steep spectrum radio halo in MACS J1149.5+2223
Radio halos and relics are Mpc-scale diffuse radio sources in galaxy
clusters, with a steep spectral index (). It
has been proposed that they arise from particle acceleration induced by
turbulence and weak shocks, injected in the intracluster medium (ICM) during
mergers. MACS J1149.5+2223 (MACS J1149) is a high redshift () galaxy
cluster possibly hosting a radio halo and a relic. We analysed LOFAR, GMRT, and
JVLA radio data at 144, 323, 1500 MHz, and Chandra X-ray data to characterise
the thermal and non-thermal properties of the cluster. We obtained radio images
at different frequencies to investigate the spectral properties of the radio
halo. We used Chandra X-ray images to constrain the thermal properties of the
cluster. We measured a steep spectrum of the halo, with
between 144 and 1500 MHz. The radio surface brightness distribution across the
halo is found to correlate with the X-ray brightness of the ICM, with a
sub-linear slope in the range 0.4 to 0.6. We also report two possible cold
fronts in north-east and north-west, but deeper X-ray observations are required
to firmly constrain the properties of the upstream emission. We show that the
combination of high redshift, steep radio spectrum, and sub-linear radio-X
scaling of the halo rules out hadronic models. An old ( Gyr ago) major
merger likely induced the formation of the halo through stochastic
re-acceleration of relativistic electrons. We suggest that the two possible
X-ray discontinuities may actually be part of the same cold front. In this
case, the coolest gas pushed towards the north-west might be associated with
the cool core of a sub-cluster involved in the major merger. The peculiar
orientation of the south-east relic might indicate a different nature of this
source and requires further investigation.Comment: 15 pages, accepted for publication in A&
Results of the DAMA experiment at LNGS
DAMA is searching for rare processes by developing and using several kinds of radiopure scintillators: in particular, NaI(Tl), liquid Xenon and CaF2(Eu). Here more recent results are summarized with particular attention to the investigation of the WIMP annual modulation signature
- …