1000 resultados para Passagem celular


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The objective of this work was to make a comparative analysis of germ cell organization at different stages of cellular differentiation in adult males of Dendropsophus nanus (Boulenger, 1889), Pseudis limellum (Cope, 1862), P. paradoxa (Linnaeus, 1758), and Scinax acuminatus (Cope, 1862), belonging to the family Hylidae; and Leptodactylus chaquensis (Cei, 1950) and L. podicipinus (Cope, 1862), belonging to the family Leptodactylidae, collected in the Pantanal and in Serra da Bodoquena, Mato Grosso do Sul State, Brazil. The testes were removed and fixed, dehydrated in a graded series of ethanol and embedded in methacrylate glycol resin (Historesin Leica®). The sections were stained by 1% toluidine blue and observed under light microscope. It was detected that all individual of the Hylidae family show, throughout the year, the presence of all germ cell types of spermatogenesis. However, all Leptodactylidae family individuals only show the presence of all germ cell types during the rainy season. The variations of characteristics in seminiferous epithelium organization, as well as the evident difference in the amount of spermatozoa inside the tubules, are evidence that the anurans in this work show different forms of spermatogenesis development throughout the year: the cycle is continuous for the Hylidae family, and discontinuous with explosive release of spermatozoa for the Leptodactylidae family.

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The transit time of seeds ingested by frugivorous animals has important implications for the spatial distribution of seeds and their dispersal distance. Nevertheless, this parameter is rarely included in seed dispersal studies. In this paper, we provide information about the transit time of seeds of nine species of plants ingested by individuals of six species of captive birds (Turdus albicollis, T. amaurochalinus, T. leucomelas, T. rufiventris, Stephanophorus diadematus and Saltator similis). We found that (1) seeds are regurgitated quickly through the digestive tract of birds than defecated seeds, and (2) large seeds (e.g., > 5 mm in diameter for Turdus spp.) are regurgitated rather than defecated. These results corroborate other studies, but the relationship between seed size and transit time seems to be quite complex and variable, requiring more detailed studies on this important aspect of the ecology of seed dispersal and digestive physiology of frugivorous birds.

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Pós-graduação em Biociências e Biotecnologia Aplicadas à Farmácia - FCFAR

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Pós-graduação em Ciências Biológicas (Microbiologia Aplicada) - IBRC

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Pesquisa e Desenvolvimento (Biotecnologia Médica) - FMB

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)