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- Petroff, E., et al.
(författare)
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A polarized fast radio burst at low Galactic latitude
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford Academic. - 0035-8711 .- 1365-2966. ; 469:4, s. 4465-4482
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Tidskriftsartikel (refereegranskat)abstract
- We report on the discovery of a new fast radio burst (FRB), FRB 150215, with the Parkes radio telescope on 2015 February 15. The burst was detected in real time with a dispersion measure (DM) of 1105.6 +/- 0.8 pc cm(-3), a pulse duration of 2.8(-0.5)(+1.2) ms, and a measured peak flux density assuming that the burst was at beam centre of 0.7(-0.1)(+0.2) Jy. The FRB originated at a Galactic longitude and latitude of 24.66 degrees, 5.28 degrees and 25 degrees away from the Galactic Center. The burst was found to be 43 +/- 5 per cent linearly polarized with a rotation measure (RM) in the range -9 < RM < 12 rad m(-2) (95 per cent confidence level), consistent with zero. The burst was followed up with 11 telescopes to search for radio, optical, X-ray, gamma-ray and neutrino emission. Neither transient nor variable emission was found to be associated with the burst and no repeat pulses have been observed in 17.25 h of observing. The sightline to the burst is close to the Galactic plane and the observed physical properties of FRB 150215 demonstrate the existence of sight lines of anomalously low RM for a given electron column density. The Galactic RM foreground may approach a null value due to magnetic field reversals along the line of sight, a decreased total electron column density from the Milky Way, or some combination of these effects. A lower Galactic DM contribution might explain why this burst was detectable whereas previous searches at low latitude have had lower detection rates than those out of the plane.
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| 2. |
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| 3. |
- Costa, João T., et al.
(författare)
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Gephyrin Cleavage in In Vitro Brain Ischemia Decreases GABAA Receptor Clustering and Contributes to Neuronal Death
- 2016
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Ingår i: Molecular Neurobiology. - : Springer Science and Business Media LLC. - 0893-7648 .- 1559-1182. ; 53:6, s. 3513-3527
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Tidskriftsartikel (refereegranskat)abstract
- GABA (γ-aminobutyric acid) is the major inhibitory neurotransmitter in the central nervous system, and changes in GABAergic neurotransmission modulate the activity of neuronal networks. Gephyrin is a scaffold protein responsible for the traffic and synaptic anchoring of GABAA receptors (GABAAR); therefore, changes in gephyrin expression and oligomerization may affect the activity of GABAergic synapses. In this work, we investigated the changes in gephyrin protein levels during brain ischemia and in excitotoxic conditions, which may affect synaptic clustering of GABAAR. We found that gephyrin is cleaved by calpains following excitotoxic stimulation of hippocampal neurons with glutamate, as well as after intrahippocampal injection of kainate, giving rise to a stable cleavage product. Gephyrin cleavage was also observed in cultured hippocampal neurons subjected to transient oxygen-glucose deprivation (OGD), an in vitro model of brain ischemia, and after transient middle cerebral artery occlusion (MCAO) in mice, a model of focal brain ischemia. Furthermore, a truncated form of gephyrin decreased the synaptic clustering of the protein, reduced the synaptic pool of GABAAR containing γ2 subunits and upregulated OGD-induced cell death in hippocampal cultures. Our results show that excitotoxicity and brain ischemia downregulate full-length gephyrin with a concomitant generation of truncated products, which affect synaptic clustering of GABAAR and cell death.
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