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991.
Jeremy Goodall Ed T. F. Witkowski Sigrun Ammann Carl Reinhardt 《Biological invasions》2010,12(10):3497-3512
Campuloclinium macrocephalum is an Asteraceous alien weed that invades roadside vegetation and grassland in South Africa. The role of allelopathy and
competition in its invasiveness was investigated using Eragrostis curvula (weeping lovegrass, an indigenous grass), E. tef and Lactuca sativa (lettuce) as test species. Trials were conducted in Petri-dishes, pots and in the field. Root and shoot extracts of adult
C. macrocephalum plants did not inhibit seed germination in any test species. The greatest effect was radicle stunting produced by leaf extracts
at 10 and 25% w/v. Eragrostis curvula was less tolerant of the extracts than E. tef. Allelopathic effects could however not be confirmed in pot trials evaluating the interference potential of the weed or weed
residue effects against E. curvula. E. curvula growth and biomass was not affected by plant densities of one or five C. macrocephalum per pot, whereas C. macrocephalum suffered a 17% mortality and density-dependant trade-offs of size and biomass for survival. Under field conditions C. macrocephalum had a broader ecological niche than E. curvula, invading hygrophilous and undisturbed grasslands not amenable for E. curvula establishment, this included well drained disturbed soils on which the latter proliferated. Evidence of competitive exclusion
of E. curvula by C. macrocephalum or vice versa was not detected. The coexistence of both species irrespective of relative density suggested these species
have different resource requirements. Allelopathy was not an adequate causal mechanism to explain invasiveness in Campuloclinium macrocephalum. A more traditional hypothesis such as the absence of natural enemies, at this stage, better justifies the weed’s invasion
success. 相似文献
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995.
Omega-3 Fatty Acids and Inflammation: Novel Interactions Reveal a New Step in Neutrophil Recruitment
Samantha P. Tull Clara M. Yates Benjamin H. Maskrey Valerie B. O'Donnell Jackie Madden Robert F. Grimble Philip C. Calder Gerard B. Nash G. Ed. Rainger 《PLoS biology》2009,7(8)
Inflammation is a physiological response to tissue trauma or infection, but leukocytes, which are the effector cells of the inflammatory process, have powerful tissue remodelling capabilities. Thus, to ensure their precise localisation, passage of leukocytes from the blood into inflamed tissue is tightly regulated. Recruitment of blood borne neutrophils to the tissue stroma occurs during early inflammation. In this process, peptide agonists of the chemokine family are assumed to provide a chemotactic stimulus capable of supporting the migration of neutrophils across vascular endothelial cells, through the basement membrane of the vessel wall, and out into the tissue stroma. Here, we show that, although an initial chemokine stimulus is essential for the recruitment of flowing neutrophils by endothelial cells stimulated with the inflammatory cytokine tumour necrosis factor-α, transit of the endothelial monolayer is regulated by an additional and downstream stimulus. This signal is supplied by the metabolism of the omega-6-polyunsaturated fatty acid (n-6-PUFA), arachidonic acid, into the eicosanoid prostaglandin-D2 (PGD2) by cyclooxygenase (COX) enzymes. This new step in the neutrophil recruitment process was revealed when the dietary n-3-PUFA, eicosapentaenoic acid (EPA), was utilised as an alternative substrate for COX enzymes, leading to the generation of PGD3. This alternative series eicosanoid inhibited the migration of neutrophils across endothelial cells by antagonising the PGD2 receptor. Here, we describe a new step in the neutrophil recruitment process that relies upon a lipid-mediated signal to regulate the migration of neutrophils across endothelial cells. PGD2 signalling is subordinate to the chemokine-mediated activation of neutrophils, but without the sequential delivery of this signal, neutrophils fail to penetrate the endothelial cell monolayer. Importantly, the ability of the dietary n-3-PUFA, EPA, to inhibit this process not only revealed an unsuspected level of regulation in the migration of inflammatory leukocytes, it also contributes to our understanding of the interactions of this bioactive lipid with the inflammatory system. Moreover, it indicates the potential for novel therapeutics that target the inflammatory system with greater affinity and/or specificity than supplementing the diet with n-3-PUFAs. 相似文献
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Dr. Ed. Formánek 《Plant Systematics and Evolution》1887,37(8):280-282
Ohne Zusammenfassung 相似文献
998.
Raphael Ed. Liesegang 《Development genes and evolution》1911,33(1-2):328-338
Ohne Zusammenfassung 相似文献
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Dr. Ed. Formánek 《Plant Systematics and Evolution》1885,35(9):316-321
Ohne Zusammenfassung 相似文献
1000.
Ohne Zusammenfassung 相似文献