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- Gilbert, M. Thomas P., et al.
(författare)
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Intraspecific phylogenetic analysis of Siberian woolly mammoths using complete mitochondrial genomes
- 2008
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 105:24, s. 8327-8332
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Tidskriftsartikel (refereegranskat)abstract
- We report five new complete mitochondrial DNA (mtDNA) genomes of Siberian woolly mammoth (Mammuthus primigenius), sequenced with up to 73-fold coverage from DNA extracted from hair shaft material. Three of the sequences present the first complete mtDNA genomes of mammoth clade II. Analysis of these and 13 recently published mtDNA genomes demonstrates the existence of two apparently sympatric mtDNA clades that exhibit high interclade divergence. The analytical power afforded by the analysis of the complete mtDNA genomes reveals a surprisingly ancient coalescence age of the two clades, approximate to 1-2 million years, depending on the calibration technique. Furthermore, statistical analysis of the temporal distribution of the C-14 ages of these and previously identified members of the two mammoth clades suggests that clade II went extinct before clade I. Modeling of protein structures failed to indicate any important functional difference between genomes belonging to the two clades, suggesting that the loss of clade II more likely is due to genetic drift than a selective sweep.
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- Keita, Åsa V, et al.
(författare)
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Characterization of antigen and bacterial transport in the follicle-associated epithelium of human ileum
- 2006
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Ingår i: Laboratory investigation. - : Elsevier BV. - 0023-6837 .- 1530-0307. ; 86:5, s. 504-516
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Tidskriftsartikel (refereegranskat)abstract
- The follicle-associated epithelium (FAE), covering Peyer's patches, provides a route of entry for antigens and microorganisms. Animal studies showed enhanced antigen and bacterial uptake in FAE, but no study on barrier function of human FAE has been reported. Our aim was to characterize the normal barrier properties of human FAE. Specimens of normal ileum were taken from 30 patients with noninflammatory colonic disease. Villus epithelium (VE) and FAE were identified and mounted in Ussing chambers. Permeability to 51Cr-EDTA, transmucosal flux of the protein antigen, horseradish peroxidase (HRP), and transport of fluorescent Escherichia coli (chemically killed K-12 and live HB101) were measured. Uptake mechanisms were studied by confocal- and transmission electron microscopy, and by using pharmacological inhibitors in an in vitro coculture model of FAE and in human ileal FAE. HRP flux was substantially higher in FAE than in VE, and was reduced by an amiloride analog. Electron microscopy showed HRP-containing endosomes. Transport of E. coli K-12 and HB101 was also augmented in FAE and was confirmed by confocal microscopy. In vitro coculture experiments and electron microscopy revealed actin-dependent, mainly transcellular, uptake of E. coli K-12 into FAE. 51Cr-EDTA permeability was equal in FAE and VE. Augmented HRP flux and bacterial uptake but similar paracellular permeability, suggest functional variations of transcellular transport in the FAE. We show for the first time that FAE of human ileum is functionally distinct from regular VE, rendering the FAE more prone to bacterial–epithelial cell interactions and delivery of antigens to the mucosal immune system.
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- Ohlson, Jan I., 1966-
(författare)
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Molecular phylogeny of tyrant flycatchers, cotingas, manakins and their allies (Aves: Tyrannida)
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tyrannida is a monophyletic clade that together with Furnariida constitutes the New World suboscines. The ca 560 species in Tyrannida are traditionally divided between three families: Tyrannidae (tyrant flycatchers), Cotingidae (cotingas) and Pipridae (manakins). They are most diverse in South America, where they make up roughly one third of the passerine diversity in most habitats. Constituting such a substantial part of South America’s avian diversity, they are of great importance for the understanding of South American biogeography, but also for studies of more general issues in evolutionary biology, e.g. patterns of adaptive radiation. However, their usefulness in such studies has been limited by the lack of a robust and well-resolved phylogeny for the group. Although three or four main lineages are universally recognized, phylogenetic relationships in the group are generally poorly understood and the affinities of a large number of genera are uncertain.The principal aim of this thesis is to reconstruct a well-resolved phylogenetic hypothesis for Tyrannida, which can serve as a platform for further studies of suboscine systematics and of broader issues in evolutionary biology. This has been achieved by employing comprehensive taxon sampling, DNA sequence data from multiple genes and model-based phylogenetic methods. The resulting phylogenies are generally well resolved and lend support to several earlier hypotheses of relationships in Tyrannida, but further clarify the basal divergences and show that all insectivorous groups form a monophyletic clade. Several novel relationships are revealed, most importantly that nearly all of the genera of debated affinities represent deep lineages in the insectivorous clade. Early evolution of Tyrannida took place in humid forest, and nearly all species tied to open habitats belong in a monophyletic clade that radiated in response to the cooling and drying climatic trend from the Mid Miocene and onwards.
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- Sodhi, Navjot S., et al.
(författare)
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Barcoding Indo-Malayan birds
- 2007
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Ingår i: The Raffles bulletin of zoology. - 0217-2445. ; 55:2, s. 397-398
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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