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  • 1
    ISSN: 1420-9071
    Keywords: Bird feeding preferences ; digestion ; intestinal enzymes ; sucrase ; fruit ; nectar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Plants pollinated and dispersed by different groups of birds offer different kinds of sugars in nectar and fruit pulp. The preferences and physiological traits of avian pollinators and seed dispersers are broadly correlated with the sugar composition of the nectar and fruit that they feed on and appear to have influenced the evolution of the sugar composition of the rewards that plants offer. Hummingbirds prefer sucrose whereas many nectar- and fruit-eating passerines prefer glucose and fructose. Preference for hexoses in passerines seems to be associated with poor sucrose assimilation resulting from two physiological mechanisms: lack of intestinal sucrase activity and fast passage rates. Sucrase activity absence appears to be restricted to a single phylogenetic group (the sturnid-muscicapid lineage). Fast passage rates seem to be characteristic of many small frugivores and to hinder the assimilation of complex nutrients that require hydrolysis before absorption. Hummingbirds have extremely specialized digestive traits that allow them to assimilate sucrose at high rates and with extremely high efficiency. These specialized digestive traits appear not to be present in many nectar-feeding passerines.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0460
    Keywords: Dysphagia, postsurgical ; Dysphagia long term ; Deglutition disorders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Dysphagia commonly results from surgical resection of various structures within the oral, pharyngeal, and esophageal areas. The type and severity of swallowing dysfunction are based largely on the number and quantity of structures removed as well as the reconstructive procedure. Short term-recovery has been addressed in many studies [1–10]. However, follow-up studies of longterm functional results and continuing swallowing problems following oral/pharyngeal surgery are unavailable. In this study, perception of swallowing dysfunction was compared with actual videofluoroscopic findings in subjects at least 1 year after oral/pharyngeal surgery. The comparative results of a questionnaire developed to evaluate patients' perception of continuing swallowing difficulty and an analysis of actual videofluoroscopic tapes indicated that the degree or type of dysphagia could not be determined from patients' subjective descriptions of the swallowing problem.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 302-316 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The three-dimensional structure of human dicupric monooxalate lactoferrin, Cu2oxLf, has been determined to 2.0 Å resolution, using X-ray diffraction data collected by diffractometry to 2.5 Å resolution, and oscillation photography on a synchrotron source to 2.0 Å resolution. Difference electron-density maps calculated between Cu2oxLf and both dicupric lactoferrin, Cu2Lf, and diferric lactoferrin, Fe2Lf, showed that the oxalate had replaced a carbonate in the C-terminal binding site, and that, relative to Cu2Lf, there were no significant differences in the N-terminal site. The structure was then refined crystallographically by restrained least-squares methods. The final model, in which the r.m.s. deviation in bond distances is 0.017 Å, contains 5314 protein atoms (691 residues), two Cu2+ ions, one bicarbonate ion, one oxalate ion, 325 solvent molecules and one sugar residue. The crystallographic R factor of 0.193 is for 46 134 reflections in the range 8.0 to 2.0 Å resolution. The oxalate ion is coordinated to copper in a 1,2-bidentate fashion, and the added bulk of the anion results in the rearrangement of the side chains of nearby arginine and tyrosine residues. No other major alterations in the molecule can be observed, the overall protein structure being the same as that for Cu2Lf and Fe2Lf.
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 429-440 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: In protein crystallography, the initial experimental problem is the identification of physical and chemical conditions that will support nucleation and crystal growth. Ideally, experiments to search for such conditions would be based on a full-factorial structure, with variation in the temperature and solution composition. However, consideration of even a moderate number of possibilities for the composition of the system will result in factorial experiments which may be prohibitively large. In this paper it is proposed that search experiments for protein crystallization might be based on orthogonal arrays. These are subsets of full-factorial experiments which possess a great deal of symmetry, such that a uniform distribution of points throughout the experimental region is preserved. Such experiments have reasonable size, explore the proposed experimental region in a systematic fashion, and form a logical basis for a sequential approach to the search for crystallization conditions. Examples of such initial search experiments are given, and their application to some recent protein crystallization problems in this laboratory is described briefly. The relationship of this approach to other protein crystallization search procedures is also discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 380-384 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Enzymatic deglycosylation has been used in attempts to crystallize several glycoproteins with the aim of overcoming the problems resulting from heterogeneity and flexibility of the attached glycan chains. An endoglycosidase preparation from Flavobacterium meningosepticum, comprising the enzymes endo F and PNGase-F, was used in experiments on the mammalian binding proteins lactoferrin and haemopexin. Significant differences were found in the susceptibility of different proteins to deglycosylation. For human lactoferrin (Lf) and its recombinant N-terminal half-molecule (LfN), deglycosylation was rapid and complete, and was essential for obtaining high-quality crystals of both apo-Lf and LfN; for bovine Lf, however, complete deglycosylation did not occur. Similarly, for rabbit haemopexin the carbohydrate chain on the C-terminal domain was easily removed, but the three chains on the N-terminal domain proved more resistant and their removal led to some fragmentation of the protein. Nevertheless, this approach provided the only means of crystallizing the C-terminal domain and is likely to be useful for other glycoproteins.
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  • 7
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Digestive diseases and sciences 38 (1993), S. 2273-2280 
    ISSN: 1573-2568
    Keywords: Caco-2 cells ; oxidant injury ; superoxide ; hydrogen peroxide ; glutathione cycle ; hexose monophosphate shunt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Reactive oxygen metabolites have been associated with gastrointestinal injury and may play a role as mediators of inflammation. The effect of oxygen metabolites on Caco-2 cell viability (trypan blue exclusion and51Cr release), hexose monophosphate shunt activity, and glutathione was assessed. Caco-2 cells were incubated with amino acid oxidase, xanthine oxidase, menadione, andt-butylhydroperoxide in the presence and absence of superoxide dismutase, catalase, mannitol, and butylated hydroxytoluene. With amino acid oxidase, trypan blue exclusion decreased (P〈0.01) and51Cr release, oxidized glutathione, and shunt activity increased (P〈0.05). The addition of catalase attenuated these changes. Trypan blue exclusion decreased (P〈0.005) and51Cr release, oxidized glutathione, and shunt activity increased (P〈0.01) with xanthine oxidase. The addition of superoxide dismutase caused a further increase in51Cr release, oxidized glutathione, and shunt activity (P〈0.01), which was prevented by the addition of catalase or mannitol.t-Butylhydroperoxide did not effect51Cr release or trypan blue exclusion, but oxidized glutathione and shunt activity increased (P〈0.01). The increase in shunt activity was prevented by preincubation with butylated hydroxytoluene (P〈0.01). Menadione did not alter trypan blue exclusion or51Cr release, but caused an increase in oxidized glutathione and shunt activity (P〈0.001). The increase in shunt activity was attenuated by preincubation with butylated hydroxytoluene (P〈0.001). Menadione also caused a depletion of total glutathione. Thus, Caco-2 cells are sensitive to oxidant injury and in all four systems increase in shunt activity and oxidized glutathione occurred at concentrations lower than those that caused cell injury, suggesting the shunt via the glutathione cycle is important in Caco-2 cell metabolism of oxidant species.
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  • 10
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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