Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)

Context. Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3, which contains identical astrometric results). The reference frame is defined by the positions and proper motions at epoch 2016.0 for a specific set of extragalactic sources in the (E)DR3 catalogue. Aims. We describe the construction of Gaia-CRF3 and its properties in terms of the distributions in magnitude, colour, and astrometric quality. Methods. Compact extragalactic sources in Gaia DR3 were identified by positional cross-matching with 17 external catalogues of quasi-stellar objects (QSO) and active galactic nuclei (AGN), followed by astrometric filtering designed to remove stellar contaminants. Selecting a clean sample was favoured over including a higher number of extragalactic sources. For the final sample, the random and systematic errors in the proper motions are analysed, as well as the radio-optical offsets in position for sources in the third realisation of the International Celestial Reference Frame (ICRF3). Results. Gaia-CRF3 comprises about 1.6 million QSO-like sources, of which 1.2 million have five-parameter astrometric solutions in Gaia DR3 and 0.4 million have six-parameter solutions. The sources span the magnitude range G = 13-21 with a peak density at 20.6 mag, at which the typical positional uncertainty is about 1 mas. The proper motions show systematic errors on the level of 12 μas yr-1 on angular scales greater than 15 deg. For the 3142 optical counterparts of ICRF3 sources in the S/X frequency bands, the median offset from the radio positions is about 0.5 mas, but it exceeds 4 mas in either coordinate for 127 sources. We outline the future of Gaia-CRF in the next Gaia data releases. Appendices give further details on the external catalogues used, how to extract information about the Gaia-CRF3 sources, potential (Galactic) confusion sources, and the estimation of the spin and orientation of an astrometric solution

Inhibition of ataxia telangiectasia-p53-E2F-1 pathway in neurons as a target for the prevention of neuronal apoptosis

Over the last few decades, understanding of the mechanisms involved in the process of neuronal'cell death, has grown. Recent findings have established that DNA damage, and specifically ataxia telangiectasia mutated protein (ATM), is key to the castade of regulation of neuronal apoptosis. Another characteristic common to all neurodegenerative diseases is oxidative. stress. Likewise, a common feature in the brain of patients with neurodegenerative diseases such as Alzheimer's and Paskinson's diseases and other neurological disorders is the expression of proteins involved in cell-cycle control. In the process of re-entry in the cell cycle, an additional component, transcription factor E2F-1, also involved in the regulation of apoptosis, is expressed. Finally, in this complex puzzle, mitochondrial activation with the release of proteins and the activation of cystein proteases, specifically caspase-3, is prominent in the last step of neuronal apoptosis. This review focuses on the role of ATM activation and its re-entry into the cell cycle in neurons as a potential target for the prevention of neuronal apoptosis. We suggest the mechanisms by which ATM and E2F-1 orchestrate the apoptotic process. Among them, p53 could be a common point on this apoptotic route. Finally, we put forward drugs that are now being studied experimentally such as, p53 inhibitors, ATM inhibitors and cyclin-dependent kinase (CDKs) inhibitors, for the treatment of neurodegenerative diseases. © 2007 Bentham Science Publishers Ltd

Antiapoptotic drugs: A therapautic strategy for the prevention of neurodegenerative diseases

The purpose of this review is to discuss potential pathways involved in the pathogenesis of neurodegenerative diseases, highlighting current pharmacological drug targets in neuronal apoptosis prevention. The incidence of these disorders is expected to rise in the coming years and so finding effective treatments represents a significant challenge for medicine. Alzheimer's disease and Parkinson's disease were both described almost a century ago and are the most important neurodegenerative disorders in the developed world. However, the molecular mechanisms that lead to the development of the neuronal pathology in both diseases are unclear. For this reason, despite substantial research in the area, an effective treatment for these diseases does not yet exist. In the present study we discuss in depth the pathways involved in apoptosis and neuronal death in neurodegenerative diseases. We also examine drugs that may have a neuroprotective effect. Inhibition of apoptosis mediated by oxidative stress generation and mitochondrial alteration or by the blockade of NMDA receptors could constitute a suitable therapeutic strategy for Alzheimer's disease. A multiple therapy with antioxidants, cell cycle inhibitors, GSK3β inhibitors, and STATINS could, in the future, represent a suitable strategy for delaying the progression of neurodegenerative diseases. This research contributes to the development of new methods in the field of apoptosis inhibitors that could provide the future tools for the treatment of Alzheimer's and Parkinson's disease, as well as other neurodegenerative diseases. © 2011 Bentham Science Publishers Ltd

ESPGHAN’s 2008 recommendation for early introduction of complementary foods: how good is the evidence?

Epidemiology in Pediatrics and Child Healt

Authors' response to the letter from ESPGHAN CoN

Epidemiology in Pediatrics and Child Healt

Ophiovirus

Taxonomy lies at the uneasy interface between biology and logic. The processing of information follows somewhat different rules in these two systems and the role of taxonomy is to reconcile them as tidily as possible. To this end, the Virology Division of the International Union of Microbiological Societies (IUMS) charged the International Committee on Taxonomy of Viruses (ICTV) with the task of developing, refining, and maintaining a universal virus taxonomy. The goal of this undertaking is to categorize the multitude of known viruses into a single classification scheme that reflects their evolutionary relationships, i.e. their individual phylogenies. The most recent report of the ICTV: "Virus taxonomy: classification and nomenclature of viruses: Ninth Report of the International Committee on Taxonomy of Viruse