Navegando por Autor "OLIVEIRA, Marcus Augusto de"

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Em direção à costa brasileira fugindo do inverno: rotas migratórias contrastantes e plasticidade diferencial dos astrócitos hipocampais
(Universidade Federal do Pará, 2018-01-04) OLIVEIRA, Marcus Augusto de; DINIZ, Cristovam Wanderley Picanço; http://lattes.cnpq.br/2014918752636286
One of the largest seasonal events on the planet is the migration of birds from the Arctic to the southern hemisphere fleeing from winter and returning to the Arctic during the spring to the breeding season. Billions of individuals need to remember the routes learned during this epic journey and find the same places to rest and feeding. These birds can navigate thousands of miles with great accuracy, utilizing their spatial and temporal memories associated with the hippocampus, a key area for accomplishing this task. Recently, we have shown that the semipalmated sandpiper Calidris pusilla, after crossing the Atlantic towards the coast of South America, revealed significant changes in its hippocampal astrocytes. In fact, the hippocampal astrocytes of birds captured on the coast of Bragança in Brazil, compared with those of the hippocampus of individuals caught in the Bay of Fundy, Canada, were less numerous and exhibited shrunken branches. In the present work, we used another semipalmated shorebird, Charadrius semipalmatus, which, although having the same start and end points of C. pusilla migration, uses a different migratory strategy, performing a flight over the continent with stops for rest and feeding. Taking advantage of the opportunity offered by contrasting migratory flights, we tested the hypothesis that wintering bird species of the C. semipalmatus caught on the coast of Bragança (Brazil) would show greater morphological complexities than the hippocampal astrocytes of these migratory birds captured in the Bay of Fundy (Canada). Since the stands for food and rest, as well as the constant change in the landscape would constitute an enriched environment of multisensory stimuli, we expected to find in the individuals of C. semipalmatus captured in Bragança, an increase of the complexity, in opposition to the reduction in complexity previously found in C. pusilla. To test this hypothesis, we compared the three-dimensional (3-D) morphological characteristics of the adult C. semipalmatus astrocytes captured in the Bay of Fundy (n = 265 cells) with those of wintering birds captured in the coastal region of Bragança, Brazil, (n = 242 cells), and compared with the results obtained with C. pusilla. The Neurolucida program was used for three-dimensional reconstructions and the hierarchical cluster analysis (Ward’s method) was used to classify cells. This analysis showed two families of astrocytes, which we designated Type I and Type II, based on several morphological characteristics. Contrary to our expectations, Type I and Type II phenotypes showed, on average, independently of the species, lower morphological complexity after migration, and this reduction was significantly higher in Type I than in Type II. The magnitudes of these changes were significantly higher in C. pusilla than in C. semipalmatus. Taken together, these findings suggest that contrasting long-distance migratory flight strategies may differentially affect the astrocyte morphology and that distinct astrocyte morphologies may be associated with different functional roles during migration.
Acesso aberto (Open Access)
Influência do tamanho da ninhada sobre o declínio cognitivo e a morfologia microglial da camada molecular do giro denteado em rattus novergicus
(Universidade Federal do Pará, 2012-10-11) OLIVEIRA, Marcus Augusto de; DINIZ, Cristovam Wanderley Picanço; http://lattes.cnpq.br/2014918752636286; DINIZ JUNIOR, José Antônio Picanço; http://lattes.cnpq.br/3850460442622655
It has been proposed that aging is associated with neuroinflammation in the central nervous system but it is not known whether microglial changes induced by aging are affected by early in life effects of litter size. On the other hand the molecular layer of dentate gyrus has been recognized as the main target of the perforant pathway, whose synaptic integrity is essential for the recognition memories of identity and spatial location. In the present report we investigated if aging cognitive decline and microglial morphological changes in the molecular layer are influenced by litter size changes early in life and aging. To assess these questions Wistar rats suckled in litters of six or 12 pups/mother were raised sedentarily in groups of 2-3 from the 21st post-natal day onwards. At four (mature adult) or 23 (aged) months of age were submitted to spatial memory and object identity recognition tests, sacrificed, perfused with aldehyde fixatives and had their brains processed for selective microglia/macrophages immunolabeling with anti-IBA-1 antibodies. A representative sample of the immunolabeled cells in the molecular layer of dentate gyrus was analyzed after three-dimensional reconstruction with Neurolucida software (Microbright Field Inc.) and morphological features of each cell were quantified by Neuroexplorer (Microbright Field Inc.). It was found that Wistar rats maintained all life in standard laboratory cages showed spatial memory deficits in both mature and aged subjects no matter the litter size. On the other hand all aged subjects independent of the litter size had their object recognition identity memory impaired. Microglial morphological analysis revealed that cell soma area and perimeter and branches volume seem to be more intensely affected by aging and that these changes are mainly associated with animals from large litters. In addition it was observed important shrinkage and thickening of the microglial branches in aged individuals in higher proportion in the group from large litters. Taken together the results suggest that spatial memory seems to be more susceptible to the aging process than object recognition and that these changes are associated with distinct effects on the soma and branching patterns of microglia of molecular layer from young and aged subjects.
Acesso aberto (Open Access)
Microglia and neurons in the hippocampus of migratory sandpipers
(Universidade Federal do Pará, 2015-11) DINIZ, Cristovam Guerreiro; MAGALHÃES, Nara Gyzely de Morais; SOUSA, Aline Andrade de; SANTOS FILHO, Carlos; DINIZ, Daniel Guerreiro; LIMA, Camila Mendes de; OLIVEIRA, Marcus Augusto de; PAULO, Dario Carvalho; PEREIRA, Patrick Douglas Corrêa; SHERRY, David Francis
The semipalmated sandpiper Calidris pusilla and the spotted sandpiper Actitis macularia are long- and short-distance migrants, respectively. C. pusilla breeds in the sub-arctic and mid-arctic tundra of Canada and Alaska and winters on the north and east coasts of South America. A. macularia breeds in a broad distribution across most of North America from the treeline to the southern United States. It winters in the southern United States, and Central and South America. The autumn migration route of C. pusilla includes a non-stop flight over the Atlantic Ocean, whereas autumn route of A. macularia is largely over land. Because of this difference in their migratory paths and the visuo-spatial recognition tasks involved, we hypothesized that hippocampal volume and neuronal and glial numbers would differ between these two species. A. macularia did not differ from C. pusilla in the total number of hippocampal neurons, but the species had a larger hippocampal formation and more hippocampal microglia. It remains to be investigated whether these differences indicate interspecies differences or neural specializations associated with different strategies of orientation and navigation.