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  • 1
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Tracer experiments with two diatoms labelled with 13C (Nitzschia palea) and 15N (Fragilaria crotonensis), were conducted to investigate feeding selectivity and interspecific competition between the grazers Asellus aquaticus (Isopoda, Crustacea) and Potamopyrgus antipodarum (Hydrobiidae, Gastropoda). Conventional methods, such as cell counts and estimated biovolume, were used first to detect feeding preferences within the different grazer treatments.2. The results revealed a significant decline in algal biovolume in all grazer treatments and no indications of active selectivity were observed. In contrast to conventional methods, measurements based on isotope signatures showed strong differences in tracer uptake, thus indicating different degrees of assimilation and digestion by the two grazers.3. The selectivity index Q, which provides information on the uptake ratio of 13C to 15N, showed a significant time effect for both grazer species and a significant difference between single- and mixed-grazer treatments for P. antipodarum. Thus, this technique enabled the direct quantification of the uptake by grazers and, therefore, served as an ideal tool for the detection of passive selectivity.4. Our results indicate a shift in feeding preferences related to between-species competition and a potential divergence of trophic niches when species coexist.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 34 (2004), S. 0 
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Cysteinyl leukotrienes are potent pro-inflammatory mediators that contribute to the pathophysiologic features observed in allergic asthma. Inhibitors of leukotriene receptors represent novel therapy in asthma treatment. In addition to the protection from early asthmatic responses, these drugs have recently been shown to protect from late airway responses too.Methods We studied the effect of treatment with an oral antagonist of cysteinyl leukotriene receptors on the increased expression of the low-affinity IgE receptor, CD23, on B cells, and of its ligands, CD11b and CD11c, on CD4+ T cells and monocytes in peripheral blood of patients with allergic asthma. In this uncontrolled open-label study, 14 children with allergic asthma received montelukast, a cysteinyl leukotrine receptor antagonist, for a period of 6 weeks after demonstrating forced expiratory volume in 1 s (FEV1) of less than 80% of the predicted value. Samples of peripheral heparinized blood and sera were obtained before and after therapy completion. Three-colour immunofluorescence analysis was performed, and expression of CD11b and CD11c on CD4+ T lymphocytes and monocytes as well as the expression of CD21 and CD23 on B cells were determined (n=12). Peripheral blood eosinophil count, changes in FEV1 and peak expiratory flow rate (PEFR), asthma exacerbations, and as-needed use of β-agonist were also monitored.Results Montelukast improved FEV1 and PEFR, and decreased peripheral eosinophil counts in all study patients. There was no significant change in the expression of CD21 and CD23 on B cells. The expression of CD11c on CD4+ T cells and of both CD11b and CD11c on monocytes remained similar to the pretreatment expression. However, the percentage of CD11b+CD4+ T lymphocytes significantly decreased after treatment with montelukast. This was accompanied by a significant decrease in the levels of total IgE.Conclusion The capacity of 6-week montelukast therapy to reduce the percentage of CD11b CD4+ T cells might be a mechanism leading to the immune response modulation on this T cell subset interaction with CD23-expressing B cells and subsequent down-regulation of IgE synthesis.
    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
    Notes: [Auszug] More than 50% of the Earth' s surface is sea floor below 3,000 m of water. Most of this major reservoir in the global carbon cycle and final repository for anthropogenic wastes is characterized by severe food limitation. Phytodetritus is the major food source for abyssal benthic ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Allergy 52 (1997), S. 0 
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The role of the low-affinity IgE receptor CD23 in immune reactions has been further emphasized by recent discoveries of novel surface ligands for CD23: CD21, CD11b, and CD11c. We previously observed the difference between the expression of CD23 and CD21 antigens in children suffering from extrinsic asthma when compared to healthy controls. In the present study, we investigated the expression of CD23 and its ligand CD21 on CD20+B cells in 44 asthmatic children (23 allergic and 21 nonallergic) using three-color immunofluorescence analysis. In addition, the expression of two other ligands for CD23, CD11b, and CD11c, on T cells (CD3+), a subpopulation of T cells (CD4+ and CD8+), natural killer cells (CD56+), and monocytes (CD14+) was tested by two-color immunofluorescence analysis in 12 allergic and 14 nonallergic children. We found that children with extrinsic asthma had higher levels of CD23+ B cells than those with intrinsic asthma. No difference was observed in the percentage of either CD23+CD21+ or CD23- CD21+ B cells. The CD11b antigen was expressed on each tested population, but only on CD4+ T cells was CD11b significantly increased in children with extrinsic asthma. CD11c was expressed mainly on monocytes, and no difference was observed between tested groups. The increased percentage of CD11b antigen on CD4+ T cells and the increased percentage of CD23 antigen on B cells in children with extrinsic asthma provide further evidence of the immunologic differences between intrinsic and extrinsic asthma.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2016-02-27
    Description: Global warming and ocean acidification are among the most important stressors for aquatic ecosystems in the future. To investigate their direct and indirect effects on a near-natural plankton community, a multiple-stressor approach is needed. Hence, we set up mesocosms in a full-factorial design to study the effects of both warming and high CO 2 on a Baltic Sea autumn plankton community, concentrating on the impacts on microzooplankton (MZP). MZP abundance, biomass, and species composition were analysed over the course of the experiment. We observed that warming led to a reduced time-lag between the phytoplankton bloom and an MZP biomass maximum. MZP showed a significantly higher growth rate and an earlier biomass peak in the warm treatments while the biomass maximum was not affected. Increased p CO 2 did not result in any significant effects on MZP biomass, growth rate, or species composition irrespective of the temperature, nor did we observe any significant interactions between CO 2 and temperature. We attribute this to the high tolerance of this estuarine plankton community to fluctuations in p CO 2 , often resulting in CO 2 concentrations higher than the predicted end-of-century concentration for open oceans. In contrast, warming can be expected to directly affect MZP and strengthen its coupling with phytoplankton by enhancing its grazing pressure.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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  • 6
    Publication Date: 2019-08-19
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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