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- Bergfur, J., et al.
(author)
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Effects of nutrient enrichment on boreal streams : Invertebrates, fungi and leaf-litter breakdown
- 2007
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In: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 52:8, s. 1618-1633
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Journal article (peer-reviewed)abstract
- Summary 1. The effect of nutrient enrichment on structural (invertebrate indices) and functional (leaf-litter breakdown rates) characteristics of stream integrity was studied in nine boreal streams.2. The results showed predicted changes in biotic indices and leaf-litter breakdown along a complex (principal component) nutrient gradient. Biotic indices were better correlated with nutrient effects than leaf-litter breakdown.3. Fungal biomass and invertebrate densities in the litter bags were positively correlated with leaf-litter breakdown, and both were also positively related to the nutrient gradient.4. Invertebrate community composition influenced breakdown rate. High breakdown rates at one site were associated with the high abundance of the detritivore Asellus aquaticus. 5. This study lends support to the importance of invertebrate and fungi as mediators of leaf-litter decomposition. However, our study also shows that study design (length of incubation) can confound the interpretation of nutrient-induced effects on decomposition.
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- Gehring, U, et al.
(author)
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Asthma and allergic symptoms in relation to house dust endotoxin : Phase Two of the International Study on Asthma and Allergies in Childhood (ISAAC II)
- 2008
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In: Clinical and Experimental Allergy. - : Wiley. - 0954-7894 .- 1365-2222. ; 38:12, s. 1911-1920
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Journal article (peer-reviewed)abstract
- Background: Several studies have consistently reported inverse associations between exposure to endotoxin in house dust and atopy. With regard to the association between house dust endotoxin and asthma, the results are inconsistent. Objectives: To study the association between house dust endotoxin levels and respiratory symptoms and atopy in populations from largely different countries. Methods: Data were collected within the International Study on Asthma and Allergies in Childhood Phase Two, a multi-centre cross-sectional study of 840 children aged 9-12 years from six centres in the five countries of Albania, Italy, New Zealand, Sweden and the United Kingdom. Living room floor dust was collected and analysed for endotoxin. Health end-points and demographics were assessed by standardized questionnaires. Atopy was assessed by measurements of allergen-specific IgE against a panel of inhalant allergens. Associations between house dust endotoxin and health outcomes were analysed by logistic regression. Odds ratios (ORs) were presented for an overall interquartile range increase in exposure. Results: Many associations between house dust endotoxin in living room floor dust and health outcomes varied between countries. Combined across countries, endotoxin levels were inversely associated with asthma ever [adjusted OR (95% confidence interval (CI)) 0.53 (0.29-0.96) for endotoxin levels per m(2) of living room floor] and current wheeze [adjusted OR (95% CI) 0.77 (0.64-0.93) for endotoxin levels per gram of living room floor dust]. There were inverse associations between endotoxin concentrations and atopy, which were statistically significant in unadjusted analyses, but not after adjustment for gender, parental allergies, cat and house dust mite allergens. No associations were found with dust quantity and between endotoxin exposure and hayfever. Conclusion: These findings suggest an inverse association between endotoxin levels in living room floor dust and asthma in children.
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- Gherardi, E, et al.
(author)
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Structural basis of hepatocyte growth factor/scatter factor and MET signalling
- 2006
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 103:11, s. 4046-4051
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Journal article (peer-reviewed)abstract
- The polypeptide growth factor, hepatocyte growth factor/scatter factor (HGF/SF), shares the multidomain structure and proteolytic mechanism of activation of plasminogen and other complex serine proteinases. HGF/SF, however, has no enzymatic activity. Instead, it controls the growth, morphogenesis, or migration of epithelial, endothelial, and muscle progenitor cells through the receptor tyrosine kinase MET. Using small-angle x-ray scattering and cryo-electron microscopy, we show that conversion of pro(single-chain)HGF/SF into the active two-chain form is associated with a major structural transition from a compact, closed conformation to an elongated, open one. We also report the structure of a complex between two-chain HGF/SF and the MET ectodomain (MET928) with 1:1 stoichiometry in which the N-terminal and first kringle domain of HGF/SF contact the face of the seven-blade β-propeller domain of MET harboring the loops connecting the β-strands b–c and d–a, whereas the C-terminal serine proteinase homology domain binds the opposite “b” face. Finally, we describe a complex with 2:2 stoichiometry between two-chain HGF/SF and a truncated form of the MET ectodomain (MET567), which is assembled around the dimerization interface seen in the crystal structure of the NK1 fragment of HGF/SF and displays the features of a functional, signaling unit. The study shows how the proteolytic mechanism of activation of the complex proteinases has been adapted to cell signaling in vertebrate organisms, offers a description of monomeric and dimeric ligand-receptor complexes, and provides a foundation to the structural basis of HGF/SF-MET signaling.
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