Cellular and Behavioral Effects of Cranial Irradiation of the Subventricular Zone in Adult Mice

Background: In mammals, new neurons are added to the olfactory bulb (OB) throughout life. Most of these new neurons, granule and periglomerular cells originate from the subventricular zone (SVZ) lining the lateral ventricles and migrate via the rostral migratory stream toward the OB. Thousands of new neurons appear each day, but the function of this ongoing neurogenesis remains unclear. Methodology/Principal Findings: In this study, we irradiated adult mice to impair constitutive OB neurogenesis, and explored the functional impacts of this irradiation on the sense of smell. We found that focal irradiation of the SVZ greatly decreased the rate of production of new OB neurons, leaving other brain areas intact. This effect persisted for up to seven months after exposure to 15 Gray. Despite this robust impairment, the thresholds for detecting pure odorant molecules and short-term olfactory memory were not affected by irradiation. Similarly, the ability to distinguish between odorant molecules and the odorant-guided social behavior of irradiated mice were not affected by the decrease in the number of new neurons. Only long-term olfactory memory was found to be sensitive to SVZ irradiation. Conclusion/Significance: These findings suggest that the continuous production of adult-generated neurons is involved i

Long-Term Alterations of Cytokines and Growth Factors Expression in Irradiated Tissues and Relation with Histological Severity Scoring

PURPOSE: Beside its efficacy in cancer treatment, radiotherapy induces degeneration of healthy tissues within the irradiated area. The aim of this study was to analyze the variations of proinflammatory (IL-1α, IL-2, IL-6, TNF-α, IFN-γ), profibrotic (TGF-β1), proangiogneic (VEGF) and stem cell mobilizing (GM-CSF) cytokines and growth factors in an animal model of radiation-induced tissue degeneration. MATERIALS AND METHODS: 24 rats were irradiated unilaterally on the hindlimb at a monodose of 30 Gy. Six weeks (n=8), 6 months (n=8) and 1 year (n=8) after irradiation the mediators expression in skin and muscle were analyzed using Western blot and the Bio-Plex® protein array (BPA) technology. Additional histological severity for fibrosis, inflammation, vascularity and cellularity alterations scoring was defined from histology and immnunohistochemistry analyses. RESULTS: A significant increase of histological severity scoring was found in irradiated tissue. Skin tissues were more radio-sensitive than muscle. A high level of TGF-β1 expression was found throughout the study and a significant relation was evidenced between TGF-β1 expression and fibrosis scoring. Irradiated tissue showed a chronic inflammation (IL-2 and TNF-α significantly increased). Moreover a persistent expression of GM-CSF and VEGF was found in all irradiated tissues. The vascular score was related to TGF-β1 expression and the cellular alterations score was significantly related with the level of IL-2, VEGF and GM-CSF. CONCLUSION: The results achieved in the present study underline the complexity and multiplicity of radio-induced alterations of cytokine network. It offers many perspectives of development, for the comprehension of the mechanisms of late injuries or for the histological and molecular evaluation of the mode of action and the efficacy of rehabilitation techniques

Neurogenèse dans le cerveau adulte. Conséquences fonctionnelles

Dans le cerveau adulte des Mammifères, des neuroblastes sont produits en permanence dans la zone subgranulaire de l’hippocampe et la zone subventriculaire (ZSV) du cerveau antérieur. Dans cette revue, nous décrivons le rôle déterminant d’un certain nombre de facteurs physiologiques et environnementaux dans la régulation de la neurogenèse hippocampique. Les neuroblastes issus de la SVZ migrent en direction du bulbe olfactif à l’intérieur duquel ils se différencient en interneurones. Les données présentées ont pour objectif de préciser les processus de production, de survie et les conséquences fonctionnelles de ces neurones nouvellement générés. Nous montrons qu’un environnement olfactif enrichi augmente dans le bulbe olfactif adulte la densité des neurones nouvellement générés. Ces effets ne sont pas la conséquence d’une augmentation du taux de prolifération des neuroblastes mais d’une augmentation de la probabilité de survie des nouveaux interneurones. Parallèlement, ces conditions d’élevage sont à l’origine de plus grandes facultés de mémoire olfactive des animaux. Ainsi la régulation par l’activité bulbaire d’un remplacement constitutif permanent des interneurones semble jouer un rôle majeur dans les processus de mémoire olfactive

The Exploitation of Wetland Ecosystems by Herbivores on Bylot Island

We examine the interactions between herbivores, plants and climatic factors in arctic wetlands using, as a case study, results of our research on grazing by snow geese on Bylot Island. During the summer, geese are the most important herbivore on the island and consume a high proportion of the annual graminoid production (grasses and sedges). Herbivores can sometimes enhance plant production by increasing the turnover rate of nitrogen, a nutrient which commonly limits growth of arctic plants. However, we found no evidence of positive feedback of grazing on plant growth and, on the contrary, chronic goose grazing tended to decrease production of these ecosystems in the long term. Geese need large quantities of high-quality plants to breed successfully, and negative effects on goose reproduction as a result of lack of food were detected. Herbivore populations are also influenced by climatic factors, either directly or indirectly through effects on plant growth. It is likely that tundra plant-herbivore systems will be strongly affected by future climatic changes. Résumé Nous examinons les interactions entre les herbivores, les plantes et les facteurs climatiques dans les terres humides arctiques en utilisant nos recherches sur le broutement par les oies des neiges à l'île Bylot comme étude de cas. Durant l'été, les oies sont les herbivores les plus importants de l'île et elles consomment une forte proportion de la production annuelle de graminoides. Les herbivores peuvent parfois stimuler la production végétale en augmentant le taux de recyclage de l'azote, un nutriment qui limite fréquemment la croissance des plantes arctiques. Cependant, nous n'avons pas trouvé d'évidence de rétroaction positive du broutement sur la croissance des plantes et, au contraire, le broutement chronique par les oies semblait diminuer la production de ces écosystèmes. Les oies ont besoin d'une grande quantité de plantes de haute qualité pour se reproduire avec succès, et des effets dépendants de la densité sur leur succès reproducteur suite à un manque de nourriture ont été détectés. Les populations d'herbivores sont aussi influencées par des facteurs climatiques, soit directement ou indirectement par les effets surla croissance des plantes. Il est probable que les systèmes plantes/herbivores de la toundra seront fortement affectés par les changements climatiques futurs

An Evolutionary Approach For Blind Deconvolution Of Barcode Images With Nonuniform Illumination

International audience—This paper deals with a joint nonuniform illumination estimation and blind deconvolution for barcode signals by using evolutionary algorithms. Indeed, such optimization problems are highly non convex and a robust method is needed in case of noisy and/or blurred signals and nonuniform illumination. Here, we present the construction of a genetic algorithm combining discrete and continuous optimization which is successfully applied to decode real images with very strong noise and blur

Radiocarbon ages and diatom abundance in samples obtained from Qarlikturvik Valley, Bylot Island

The formation of many arctic wetlands is associated with the occurrence of polygon-patterned permafrost. Existing scenarios to describe and explain surface landforms in arctic wetlands (low-center and high-center polygons and polygon ponds) invoke competing hypotheses: a cyclic succession (the thaw-lake hypothesis) or a linear succession (terrestrialization). Both hypotheses infer the predictable development of polygon-patterned wetlands over millennia. However, very few studies have applied paleoecological techniques to reconstruct long-term succession in tundra wetlands and thereby test the validity of existing hypotheses. This paper uses the paleoecological record of diatoms to investigate long-term development of individual polygons in a High Arctic wetland. Two landform processes were examined: (1) the millennial-scale development of a polygon-pond, and (2) the transition from low-center to erosive high-center polygons. Diatom assemblages were quantified from habitats associated with contrasting landforms in the present-day landscape, and used as an analog to reconstruct past transitions between polygon types. On the basis of this evidence, the paleoecological record does not support either of the existing models describing the predictable succession of polygon landforms in an arctic wetland. Our results indicate a need for greater paleoecological understanding, in combination with in situ observations in present-day geomorphology, in order to identify patterns of polygon wetland development and elucidate the long-term drivers of these landform transitions

Enriched odor exposure increases the number of newborn neurons in the adult olfactory bulb and improves odor memory

In the mammalian forebrain, most neurons originate from proliferating cells in the ventricular zone lining the lateral ventricles, including a discrete area of the subventricular zone (SVZ). In this region, neurogenesis continues into adulthood. Most of the cells generated in the SVZ are neuronal precursors with progeny that migrate rostrally along a pathway known as the rostral migratory stream before they reach the main olfactory bulb (MOB) where they differentiate into local interneurons. The olfactory system thus provides an attractive model to investigate neuronal production and survival, processes involving interplay between genetic and epigenetic influences. The present study was conducted to investigate whether exposure to an odorenriched environment affects neurogenesis and learning in adult mice. Animals housed in either a standard or an odorenriched environment for 40 d were injected intraperitoneall