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1.
The phylogeny of the fungus gnat family Mycetophilidae (Diptera) is reconstructed with a focus on the species‐rich and taxonomically difficult subfamilies Gnoristinae and Mycomyinae. The multigene phylogenetic analyses are based on five nuclear (18S, 28S, CAD, MCS, ITS2) and four mitochondrial (12S, 16S, COI, CytB) gene markers. The analyses strongly support the monophyly of Mycetophilidae and the subfamilies Manotinae, Sciophilinae, Leiinae, and Mycomyinae, although Gnoristinae is paraphyletic with respect to Mycetophilinae. All the genera and groups of genera included are supported as monophyletic, except for Acomoptera Vockeroth, Boletina Staeger, Dziedzickia Johannsen, Ectrepesthoneura Enderlein, and Neoempheria Osten Sacken. Ancestral character state reconstructions were applied to two morphological features present in Gnoristinae and Mycomyinae (i.e. presence of setae on wing membrane and wing vein R4) in order to assess their evolution. The wing vein R4 appears as an unstable character, spread throughout different clades. A dated phylogeny of the family Mycetophilidae showed that most of the subfamilies of Mycetophilidae originated and diversified during the Cretaceous. The youngest subfamilies, originated in the Paleogene, appear to be Mycomyinae and Mycetophilinae. 相似文献
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This paper is concerned with gene survival in a population which may increase without density dependence according to a generalization of the Moran model for haploid individuals. A selective advantage to one allele and the possibility of differential reproductive rates are allowed. Simple conditions are given for ultimate homozygosity to be certain and for the possibility of ultimate polymorphism. The results complement and extend those of Heyde (1981, 1982). 相似文献
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Peter Buchwald 《Theoretical biology & medical modelling》2009,6(1):5-13
Background
The function and viability of cultured, transplanted, or encapsulated pancreatic islets is often limited by hypoxia because these islets have lost their vasculature during the isolation process and have to rely on gradient-driven passive diffusion, which cannot provide adequate oxygen transport. Pancreatic islets (islets of Langerhans) are particularly susceptible due to their relatively large size, large metabolic demand, and increased sensitivity to hypoxia. Here, finite element method (FEM) based multiphysics models are explored to describe oxygen transport and cell viability in avascular islets both in static and in moving culture media. 相似文献9.
The action of trypsin at 55 degree C and pH 8.3 on pig IgM anti-Salmonella has been compared with the action of pepsin at 37 degree C and pH 4.6. Both processes cause the gradual removal of Fab arms and Cmu2 domains to produce eventually an (Fc)5 fragment. However, during tryptic digestion Fab arms are preferentially removed from the same subunit, whereas peptic digestion causes random removal from any subunit. At intermediate stages of digestion both processes produce partially fragmented molecules which consist of an (Fc)5 portion still attached to limited numbers of Fab arms. Both processes cause a gradual decrease in the ability of molecules to agglutinate Salmonella, but complement fixation by the complexes declines much more rapidly. A stage is reached where molecules having four Fab arms can still agglutinate but there is no complement fixation. However, the remaining arms on the tryptic molecules are distributed in pairs on the same subunit, whereas those on the peptic molecules are distributed randomly. Hence the number of remaining Fab arms, rather than their distribution, appears to be the critical factor which influences biological activity. A possible explanation for this is discussed. 相似文献
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