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101.
J?rg Müller Valentin H. Klaus Till Kleinebecker Daniel Prati Norbert H?lzel Markus Fischer 《PloS one》2012,7(12)
While bryophytes greatly contribute to plant diversity of semi-natural grasslands, little is known about the relationships between land-use intensity, productivity, and bryophyte diversity in these habitats. We recorded vascular plant and bryophyte vegetation in 85 agricultural used grasslands in two regions in northern and central Germany and gathered information on land-use intensity. To assess grassland productivity, we harvested aboveground vascular plant biomass and analyzed nutrient concentrations of N, P, K, Ca and Mg. Further we calculated mean Ellenberg indicator values of vascular plant vegetation. We tested for effects of land-use intensity and productivity on total bryophyte species richness and on the species richness of acrocarpous (small & erect) and pleurocarpous (creeping, including liverworts) growth forms separately. Bryophyte species were found in almost all studied grasslands, but species richness differed considerably between study regions in northern Germany (2.8 species per 16 m2) and central Germany (6.4 species per 16 m2) due environmental differences as well as land-use history. Increased fertilizer application, coinciding with high mowing frequency, reduced bryophyte species richness significantly. Accordingly, productivity estimates such as plant biomass and nitrogen concentration were strongly negatively related to bryophyte species richness, although productivity decreased only pleurocarpous species. Ellenberg indicator values for nutrients proved to be useful indicators of species richness and productivity. In conclusion, bryophyte composition was strongly dependent on productivity, with smaller bryophytes that were likely negatively affected by greater competition for light. Intensive land-use, however, can also indirectly decrease bryophyte species richness by promoting grassland productivity. Thus, increasing productivity is likely to cause a loss of bryophyte species and a decrease in species diversity. 相似文献
102.
PtdIns is an important precursor for inositol-containing lipids, including polyphosphoinositides, which have multiple essential functions in eukaryotic cells. It was previously proposed that different regulatory functions of inositol-containing lipids may be performed by independent lipid pools; however, it remains unclear how such subcellular pools are established and maintained. In the present paper, a previously uncharacterized Arabidopsis gene product with similarity to the known Arabidopsis PIS (PtdIns synthase), PIS1, is shown to be an active enzyme, PIS2, capable of producing PtdIns in vitro. PIS1 and PIS2 diverged slightly in substrate preferences for CDP-DAG [cytidinediphospho-DAG (diacylglycerol)] species differing in fatty acid composition, PIS2 preferring unsaturated substrates in vitro. Transient expression of fluorescently tagged PIS1 or PIS2 in onion epidermal cells indicates localization of both enzymes in the ER (endoplasmic reticulum) and, possibly, Golgi, as was reported previously for fungal and mammalian homologues. Constitutive ectopic overexpression of PIS1 or PIS2 in Arabidopsis plants resulted in elevated levels of PtdIns in leaves. PIS2-overexpressors additionally exhibited significantly elevated levels of PtdIns(4)P and PtdIns(4,5)P(2), whereas polyphosphoinositides were not elevated in plants overexpressing PIS1. In contrast, PIS1-overexpressors contained significantly elevated levels of DAG and PtdEtn (phosphatidylethanolamine), an effect not observed in plants overexpressing PIS2. Biochemical analysis of transgenic plants with regards to fatty acids associated with relevant lipids indicates that lipids increasing with PIS1 overexpression were enriched in saturated or monounsaturated fatty acids, whereas lipids increasing with PIS2 overexpression, including polyphosphoinositides, contained more unsaturated fatty acids. The results indicate that PtdIns populations originating from different PIS isoforms may enter alternative routes of metabolic conversion, possibly based on specificity and immediate metabolic context of the biosynthetic enzymes. 相似文献
103.
Birnbacher J Schüffler A Deininger F Opatz T Anke T 《Zeitschrift für Naturforschung. C, Journal of biosciences》2008,63(3-4):203-206
Five new norhirsutanes, named creolophins A-E, and complicatic acid were isolated from the culture broth of the rare tooth fungus Creolophus cirrhatus by solvent extraction, silica gel column chromatography and HPLC. In addition, neocreolophin, a complex dimerization product, was formed as an artefact during purification. The structures were elucidated by spectroscopic methods and are published in a separate paper. Two of the metabolites showed moderate antibacterial, antifungal and cytotoxic activities. 相似文献
104.
Riepl H Maurer T Kalbitzer HR Meier VM Haslbeck M Schmitt R Scharf B 《Molecular microbiology》2008,69(6):1373-1384
An unusual regulatory mechanism involving two response regulators, CheY1 and CheY2, but no CheZ phosphatase, operates in the chemotactic signalling chain of Sinorhizobium meliloti . Active CheY2-P, phosphorylated by the cognate histidine kinase, CheA, is responsible for flagellar motor control. In the absence of any CheZ phosphatase activity, the level of CheY2-P is quickly reset by a phospho-transfer from CheY2-P first back to CheA, and then to CheY1, which acts as a phosphate sink. In studying the mechanism of this phosphate shuttle, we have used GFP fusions to show that CheY2, but not CheY1, associates with CheA at a cell pole. Cross-linking experiments with the purified proteins revealed that both CheY2 and CheY2-P bind to an isolated P2 ligand-binding domain of CheA, but CheY1 does not. The dissociation constants of CheA–CheY2 and CheA–CheY2-P indicated that both ligands bind with similar affinity to CheA. Based on the NMR structures of CheY2 and CheY2-P, their interactions with the purified P2 domain were analysed. The interacting surface of CheY2 comprises its C-terminal β4-α4-β5-α5 structural elements, whereas the interacting surface of CheY2-P is shifted towards the loop connecting β5 and α5. We propose that the distinct CheY2 and CheY2-P surfaces interact with two overlapping sites in the P2 domain that selectively bind either CheY2 or CheY2-P, depending on whether CheA is active or inactive. 相似文献
105.
106.
Guinée Jeroen B. Koning Arjan de Pennington David W. Rosenbaum Ralph Hauschild Michael Olsen Stig I. Molander Sverker Bachmann Till M. Pant Rana 《The International Journal of Life Cycle Assessment》2004,9(5):320-326
Goal, Scope and Background The EU 5th framework project OMNIITOX will develop models calculating characterisation factors for assessing the potential toxic impacts
of chemicals within the framework of LCA. These models will become accessible through a web-based information system. The
key objective of the OMNIITOX project is to increase the coverage of substances by such models. In order to reach this objective,
simpler models which need less but available data, will have to be developed while maintaining scientific quality. Methods.
Experience within the OMNIITOX project has taught that data availability and quality are crucial issues for calculating characterisation
factors. Data availability determines whether calculating characterisation factors is possible at all, whereas data quality
determines to what extent the resulting characterisation factors are reliable. Today, there is insufficient knowledge and/or
resources to have high data availability as well as high data quality and high model quality at the same time.
Results The OMNIITOX project is developing two inter-related models in order to be able to provide LCA impact assessment characterisation
factors for toxic releases for as broad a range of chemicals as possible: 1) A base model representing a state-of-the-art
multimedia model and 2) a simple model derived from the base model using statistical tools. Discussion. A preliminary decision
tree for using the OMNIITOX information system (IS) is presented. The decision tree aims to illustrate how the OMNIITOX IS
can assist an LCA practitioner in finding or deriving characterisation factors for use in life cycle impact assessment of
toxic releases.
Conclusions and Outlook Data availability and quality are crucial issues when calculating characterisation factors for the toxicity impact categories.
The OMNIITOX project is developing a tiered model approach for this. It is foreseen that a first version of the base model
will be ready in late summer of 2004, whereas a first version of the simple base model is expected a few months later. 相似文献
107.
Biological systems possess the ability to adapt quickly andadequately to both environmental and internal changes. This vital ability cannot be explained in terms ofconventional stochastic processes because such processes arecharacterized by atrade-off between flexibility and accuracy, that is, they either show shorttransition times (large Kramers escape rates) to broad steady-statedistributions or long transition times to sharply peaked distributions. To develop a stochastic theory for systemsexhibiting both flexibility and accuracy, we study systems under the impact of white noise multiplied with anaccordant statistical measure, here the probability density. Thisresults in negative feedback and circular causality: the more probable a stable state the lessit will be affected by noise and, conversely, the less a stable state is affected by noisethe more probable it is. Using nonlinear Fokker-Planckequations, steady states are computed via transformations ofsolutions of the corresponding linear Fokker-Planck equations. Transients reveal rapidly evolving and sharply peaked probability densities and thus mimic systems characterized by both flexibility and accuracy. 相似文献
108.
Wolfram Krewitt Alfred Trukenmüller Till M. Bachmann Thomas Heck 《The International Journal of Life Cycle Assessment》2001,6(4):199-210
An integrated impact assessment model is used to calculate the impact per tonne of SO2, NOx, fine particles, and NMVOC emitted from different source countries on human health, acidification, eutrophication, and the
man-made environment (crop yield and building materials). Indicators on the endpoint level are used to measure the effects
resulting from a marginal change in emission levels. While the assessment of impacts on ecosystems and the man-made environment
is limited to Europe, damage factors for health effects are also derived for Asia and South America. For Europe, emission
scenarios for the years 1990 and 2010 are considered to analyse the influence of changing background conditions on the resulting
impacts. Results show that there is a significant variation in the damage resulting from a unit emission for some of the impact
categories, both between countries and between base years. Depending on the scope of the study and the information available
from the life cycle inventory, results from the paper can be used to consider site dependent conditions in life cycle impact
assessment as a complement to the current site-independent (or global) approach. 相似文献
109.
Maria D Mjaavatten Désirée van der Heijde Till Uhlig Anne J Haugen Halvor Nygaard Göran Sidenvall Knut Helgetveit Tore K Kvien 《Arthritis research & therapy》2010,12(3):R76
Introduction
We wanted to assess the importance of the levels of anti-citrullinated peptide antibody (anti-CCP) and immunoglobulin M (IgM) rheumatoid factor (RF) in predicting development of persistent arthritis from undifferentiated arthritis (UA), and to investigate whether there is an added predictive value for persistent arthritis in testing for both anti-CCP and IgM RF. 相似文献110.