Microglia activation in a model of retinal degeneration and TUDCA neuroprotective effects

Background: Retinitis pigmentosa is a heterogeneous group of inherited neurodegenerative retinal disorders characterized by a progressive peripheral vision loss and night vision difficulties, subsequently leading to central vision impairment. Chronic microglia activation is associated with various neurodegenerative diseases including retinitis pigmentosa. The objective of this study was to quantify microglia activation in the retina of P23H rats, an animal model of retinitis pigmentosa, and to evaluate the therapeutic effects of TUDCA (tauroursodeoxycholic acid), which has been described as a neuroprotective compound. Methods: For this study, homozygous P23H line 3 and Sprague-Dawley (SD) rats were injected weekly with TUDCA (500 mg/kg, ip) or vehicle (saline) from 20 days to 4 months old. Vertical retinal sections and whole-mount retinas were immunostained for specific markers of microglial cells (anti-CD11b, anti-Iba1 and anti-MHC-II). Microglial cell morphology was analyzed and the number of retinal microglial was quantified. Results: Microglial cells in the SD rat retinas were arranged in regular mosaics homogenously distributed within the plexiform and ganglion cell layers. In the P23H rat retina, microglial cells increased in number in all layers compared with control SD rat retinas, preserving the regular mosaic distribution. In addition, a large number of amoeboid CD11b-positive cells were observed in the P23H rat retina, even in the subretinal space. Retinas of TUDCA-treated P23H animals exhibited lower microglial cell number in all layers and absence of microglial cells in the subretinal space. Conclusions: These results report novel TUDCA anti-inflammatory actions, with potential therapeutic implications for neurodegenerative diseases, including retinitis pigmentosa.This research was supported by grants from the Spanish Ministry of Economy and Competitiveness-FEDER (BFU2012-36845), Instituto de Salud Carlos III (RETICS RD12/0034/0010), Organización Nacional de Ciegos Españoles (ONCE), FUNDALUCE, Asociación Retina Asturias and Fundación Jesús de Gangoiti

Reversible Alteration of Morphology in an Invertebrate Erythrocyte: Properties of the Natural Inducer and the Cellular Response

Volume: 197Start Page: 395End Page: 40

Ulva armoricana (Ulvales, Chlorophyta) from the coasts of Brittany (France). II. Nuclear rDNA ITS sequence analysis

International audienc

Enhancement of the magnetoresistence at the Curie temperature of the ferromagnetic insulator La_1.5Sr_0.5MnRhO₆

We report a study of the magnetic and electrical properties of the ferromagnetic insulator La1.5Sr0.5MnRhO6. A significant magnetoresistance is found in this system which is largest at the Curie temperature (Tc) even though there is no metal-insulator transition. The electrical transport is found to be activated above Tc and described by a variable range hopping law below Tc. Above Tc the carriers are magnetic polarons with a size which increases as the temperature approaches the magnetic transition. Rh substitution preserves ferromagnetic ordering, in contrast with the effect of other dopants on the B sites, but modifies the electrostatic potential leading to carrier localization. We attribute the peak in the magnetoresistance at Tc to the field-induced suppression of critical spin fluctuations which modulate the energetic barriers seen by the carriers

Spin, charge and orbital ordering in the B-site diluted manganates La_2-xSr_xGaMnO₆

Oxidation of the ferromagnetic B-site diluted manganese(III) perovskite La2GaMnO6 is investigated by synthesis of the La2-xSrxGaMnO6 series. At the x = 0.3 composition, which corresponds to diamagnetic element substitution at the B-site of metallic LaO.7SrO.3MnO3, the MnIII and MnIV valences order in real space at low temperature with an unusual lamellar motif. Orbital ordering at the MnIII centers in this array maintains ferromagnetism and enhances the static coherent Jahn-Teller distortion over that found for the pure MnIII end-member, facilitating eg electron hopping in the insulating state. Further oxidation to x = 0.5 completely suppresses the charge and orbital ordering, leading to glassy rather than long-range ordered magnetism

Evolution of the magnetic and magnetotransport properties of the Ga-substituted manganite compounds La_2-xSr_xMnGaO₆

We report a series of magnetic and magnetotransport studies performed on Ga-substituted manganite compounds La2-xSrxMnGaO6 (x≤0.7). We replace half of the Mn ions in LaMnO3 with diamagnetic ions Ga3+ and find that the system transforms into a ferromagnet as the result of local coherent and incoherent distortions. Following additional doping with Sr ions we find that the La2-xSrxMnGaO6 compounds remain ferromagnetic up to x∼0.3 but for higher concentrations the competition between the ferromagnetic and antiferromagnetic superexchange interactions, together with the randomness in distribution of the magnetic ions, lead to magnetic frustration, cluster-glass and spin-glass behavior. All compounds are insulating and the activation energy decreases almost linearly with x. μSR measurements suggest the existence of short-range magnetic correlations in the high-temperature region. We measure a significant increase in the muon-spin relaxation rate at low temperatures due to fluctuations of random internal magnetic fields. The observed magnetoresistance in the high-temperature region is mainly a consequence of the reduction of the spin disorder on a local scale, and is as high as 50% in 14 T and T>100 K for samples with x=0.3 and x=0.5