Astrocyte swelling is observed in different types of brain injury. We studied a potential contribution of swelling to protein tyrosine nitration (PTN) by using cultured rat astrocytes exposed to hypoosmotic (205 mosmol/L) medium. Hypoosmolarity (2 h) increases total PTN by about 2-fold in 2 h. The hypoosmotic PTN is significantly inhibited by the NMDA receptor antagonist MK-801, the nitric oxide synthase (NOS) inhibitor L-NMMA, the extracellular Ca2+ chelator EGTA and the calmodulin antagonist W13, suggesting the involvement of NMDA receptor activation, influx of extracellular Ca2+ and Ca2+/calmodulin-dependent NO synthesis. Further, superoxide dismutase plus catalase and uric acid strongly inhibit hypoosmotic PTN, suggesting the involvement of the toxic metabolite peroxynitrite (ONOO-) as a nitrating agent. Hypoosmotic astrocyte swelling rapidly stimulates generation of reactive oxygen intermediates; this process is prevented by MK-801 and EGTA. In addition, MK-801 inhibits the hypoosmotic elevation of [Ca2+]i. The findings support the view that astrocyte swelling as induced, for example, by toxins relevant for hepatic encephalopathy is sufficient to produce oxidative stress and PTN and thus contributes to altered astroglial and neuronal function.

The structures of one synthetic and two natural melanins are examined by solid-state NMR using cross polarization, magic angle sample spinning, and high-power proton decoupling. The structural features of synthetic dopa melanin are compared to those of melanin from malignant melanoma cells grown in culture and sepia melanin from squid ink. Natural abundance 13C and 15N spectra show resonances consistent with known pyrrolic and indolic structures within the heterogeneous biopolymer; 13C spectra indicate the presence of aliphatic residues in all three materials. These solid-phase experiments illustrate the promise of solid-phase NMR for elucidating structural information from insoluble biomaterials.

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This paper explores the impacts of migration both on the small island community of Grand Manan, New Brunswick, and on the group of Newfoundland families who have moved there from their homes 1500 km away. Based upon personal interviews with individuals and families, impacts and meanings are examined in terms of social networks, community cleavages, and intergenerational differences. The complexity of patterns and the ambiguities experienced by both groups are related to Bourdieu's concept of ‘habitus’, and its relevance for changing meanings of ‘place’ and ‘community’. In exploring the changing patterns of social relationships and meanings of community, this paper highlights issues of social cohesion and tensions associated with forging new identities, and examines the particular impacts upon youth whose sense of belonging is explicitly between homes. The experience of migration for those who decide to stay permanently is shown to be different than for the majority who come as seasonal migrants. In the decision to stay through the winter or not, crucial factors are both the sense of belonging back in Newfoundland and whether or not families have children, whose abilities to forge new relationships are the everyday concerns for parents. While the importance of jobs provides the main incentive to migrate, the difficulties associated with integrating into new social groups, negotiating new identities, and adjusting to different educational requirements pose almost insurmountable challenges for many families. It is in the details of family lives, values and perceptions, told through their narratives of experience, that we begin to discern the ambiguities and fluidity of evolving habitus for both groups. Cet article analyse les effets de la migration à la fois sur la petite communauté insulaire de Grand Manan au Nouveau‐Brunswick et sur les families qui s'y sont déplacées, depuis Terre‐Neuve, à plus de 1500 km de distance. Basé sur des entrevues auprès d'individus et de families, il examine le sens et l'effet de la migration en accordant une attention particulière aux réseaux sociaux, aux disparités communautaires et au fossé intergénérationnel. On y fait appel au concept d'habitus de Bourdieu pour rendre compte de la complexité des pratiques propres à chacun des deux groupes et de l'ambiguité du sens qu'ils confèrent à leur expérience. L'analyse contextualisée de la dynamique des relations sociales et du sens de la communauté met en lumière des questions liées à la cohésion sociale et aux inévitables tensions liées à ces dynamiques. Plus particulièrement, l'article examine les effets de la migration sur les jeunes dont le sentiment d'appartenance se définit précisément entre deux ‘chez soi’. L'éxpérience de la migration chez ceux qui ont décidé de s'établir de façon permanente est bien différente de celle vécue par la majorité qui se déplace de façon saisonnière. Le sentiment d'appartenance à Terre‐Neuve et le fait d'avoir ou non des enfants (leur capacité de tisser de nouvelles relations sociales étant un souci perm...

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