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61.
Vos J. van der Putten P.E.L. Hassan Hussein Muktar van Dam A.M. Leffelaar P.A. 《Plant and Soil》1998,201(1):149-155
Nitrogen catch crops help to reduce the loss of nitrogen from arable cropping systems during autumn and winter. The ability of catch crops to absorb nitrogen from the soil profile is affected by rate and depth of colonization of the soil by roots. The aim of the current work was to analyze total root length and root length density of catch crops in relation to above ground growth, nitrogen supply and crop species. In two field experiments roots were sampled with an auger. Experimental factors included crop species (winter rye, Secale cereale and forage rape, Brassica napus ssp. oleifera (Metzg.) Sinsk., or oil radish, Raphanus sativus spp. oleiferus (DC.) Metzg.), two sowing dates S1 and S2 (end of August and three weeks later) and two nitrogen treatments: N0, no nitrogen applied, and N1, nitrogen applied at non-limiting rate.The natural logarithm of the total root length, measured in the top 40 cm, L0–40 (km m-2), was linearly related to natural logarithm of the dry weight of the shoot, W (g m-2). There was no effect of species or sowing date on this relation. For a given W, N1 treatments showed lower values of L0–40 than N0 treatments. The decline in root length density, D (cm cm-3), with depth, X (cm), was described with the function ln D = ln D0 – qX, where D0 is the value of D at zero depth and q the linear coefficient. D0 was linearly related to L0–40, without effect of species, time of observation or N supply. The ratio D0/q, an estimate of the absolute root length, was 1.24 × L0–40.Together the relations enable estimates to be made of total root length and of root length distribution with depth using shoot dry weight of catch crops and its change with time as input. The generation of such estimates of root distribution is necessary for model studies in which the efficacy of catch crops to prevent N losses is evaluated in relation to sowing dates, distribution of N in the soil profile and the distribution of rainfall in the season. 相似文献
62.
The disappearance of spawned copepod eggs can, at times, approach100% day1 and may be a bottleneck to population recruitmentof marine copepods. We examined the egg production rate andegg hatching success of Centropages hamatus and Temora longicomis(Copepoda: Calanoida) on natural diets, and the role of delayedhatching combined with high sinking rates in removing theireggs from the water column. Cumulative hatching success withinIS days was consistently high from March to June 1996: 相似文献
63.
Recommendations for the routine sampling of diatoms for water quality assessments in Europe 总被引:15,自引:0,他引:15
M. G. Kelly A. Cazaubon E. Coring A. Dell'Uomo L. Ector B. Goldsmith H. Guasch J. Hürlimann A. Jarlman B. Kawecka J. Kwandrans R. Laugaste E.-A. Lindstrøm M. Leitao P. Marvan J. Padisák E. Pipp J. Prygiel E. Rott S. Sabater H. van Dam J. Vizinet 《Journal of applied phycology》1998,10(2):215-224
Many methods for using diatoms for routine monitoring of water quality have been developed in Europe and, in some countries,
these are being used to enforce environmental legislation. In order to facilitate their wider use, particularly with respect
to European Union legislation, steps are being taken to harmonize methodology. In this paper, the principles and practice
of sampling are described in relation to the main habitat types encountered in Europe. Although details of methods and sampling
programmes have to be tailored to particular circumstances and the overall objectives of the monitoring, a number of generalizations
can be made. Where available, rocks and other hard surfaces are the preferred substrates and methods for sampling these are
described. If such substrata are not available, then introduced ('artificial') substrata have many applications. Various types
of introduced substrata can be used successfully, so long as some basic precautions are described. Other types of substrata
such as macrophytes and macroalgae may also be useful under certain circumstances, although there is less consensus in the
literature on the most appropriate methods, and of the validity of comparisons between indices computed from epiphytic and
epilithic communities. When designing surveys, it is recommended that as far as possible, extremes of non-water quality factors
(e.g. shade, current speed, etc) are avoided, unless these are characteristic of the system under investigation. Detailed
guidelines for sampling epilithon are described. Along with the recommendations for sampling other substrata, it is hoped
that these provide a framework that can be adapted to most river types in Europe.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
64.
We present a design to quantify fitness consequences of jasmonate-induced responses in plants that are competing for limited resources with a conspecific. Under both high and low nitrogen supply rates, uninduced (control) Nicotiana attenuata plants growing next to a plant induced with 250 μg methyl jasmonate (MJ) yielded more seed capsules than control plants competing with another control plant. We conclude that there is a opportunity benefit for control plants growing next to an induced plant. Initially, MJ-induced plants grew more slowly, but by senescence they had produced the same number of seed capsules as control plants that had competed with another control plant. Replacement series showed that the fitness of MJ-induced plants is not influenced by the competitive status of their neighbour plant. We argue that competitive designs are useful tools for evaluating the phenotypic costs of ecologically important traits. 相似文献
65.
Anouk A. J. Hamers Laura van Dam José M. Teixeira Duarte Mariska Vos Goran Marinkovi? Claudia M. van Tiel Sybren L. Meijer Anne-Marieke van Stalborch Stephan Huveneers Anje A. te Velde Wouter J. de Jonge Carlie J. M. de Vries 《PloS one》2015,10(8)
Nuclear receptor Nur77, also referred to as NR4A1 or TR3, plays an important role in innate and adaptive immunity. Nur77 is crucial in regulating the T helper 1/regulatory T-cell balance, is expressed in macrophages and drives M2 macrophage polarization. In this study we aimed to define the function of Nur77 in inflammatory bowel disease. In wild-type and Nur77-/- mice, colitis development was studied in dextran sodium sulphate (DSS)- and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced models. To understand the underlying mechanism, Nur77 was overexpressed in macrophages and gut epithelial cells. Nur77 protein is expressed in colon tissues from Crohn’s disease and Ulcerative colitis patients and colons from colitic mice in inflammatory cells and epithelium. In both mouse colitis models inflammation was increased in Nur77-/- mice. A higher neutrophil influx and enhanced IL-6, MCP-1 and KC production was observed in Nur77-deficient colons after DSS-treatment. TNBS-induced influx of T-cells and inflammatory monocytes into the colon was higher in Nur77-/- mice, along with increased expression of MCP-1, TNFα and IL-6, and decreased Foxp3 RNA expression, compared to wild-type mice. Overexpression of Nur77 in lipopolysaccharide activated RAW macrophages resulted in up-regulated IL-10 and downregulated TNFα, MIF-1 and MCP-1 mRNA expression through NFκB repression. Nur77 also strongly decreased expression of MCP-1, CXCL1, IL-8, MIP-1α and TNFα in gut epithelial Caco-2 cells. Nur77 overexpression suppresses the inflammatory status of both macrophages and gut epithelial cells and together with the in vivo mouse data this supports that Nur77 has a protective function in experimental colitis. These findings may have implications for development of novel targeted treatment strategies regarding inflammatory bowel disease and other inflammatory diseases. 相似文献
66.
Nicole Hartwig Trier Catharina Essendrup Dam Dorthe Tange Olsen Paul Robert Hansen Gunnar Houen 《PloS one》2015,10(12)
Rheumatoid arthritis (RA) is one of the most common autoimmune diseases, affecting approximately 1–2% of the world population. One of the characteristic features of RA is the presence of autoantibodies. Especially the highly specific anti-citrullinated peptide antibodies (ACPAs), which have been found in up to 70% of RA patients’ sera, have received much attention. Several citrullinated proteins are associated with RA, suggesting that ACPAs may react with different sequence patterns, separating them from traditional antibodies, whose reactivity usually is specific towards a single target. As ACPAs have been suggested to be involved in the development of RA, knowledge about these antibodies may be crucial. In this study, we examined the influence of peptide backbone for ACPA reactivity in immunoassays. The antibodies were found to be reactive with a central Cit-Gly motif being essential for ACPA reactivity and to be cross-reactive between the selected citrullinated peptides. The remaining amino acids within the citrullinated peptides were found to be of less importance for antibody reactivity. Moreover, these findings indicated that the Cit-Gly motif in combination with peptide backbone is essential for antibody reactivity. Based on these findings it was speculated that any amino acid sequence, which brings the peptide into a properly folded structure for antibody recognition is sufficient for antibody reactivity. These findings are in accordance with the current hypothesis that structural homology rather than sequence homology are favored between citrullinated epitopes. These findings are important in relation to clarifying the etiology of RA and to determine the nature of ACPAs, e.g. why some Cit-Gly-containing sequences are not targeted by ACPAs. 相似文献
67.
Erling Mellerup Ole A. Andreassen Bente Bennike Henrik Dam Srdjan Djurovic Thomas Hansen Martin Balslev Jorgensen Lars Vedel Kessing Pernille Koefoed Ingrid Melle Ole Mors Thomas Werge Gert Lykke Moeller 《PloS one》2015,10(11)
The main objective of the study was to find combinations of genetic variants significantly associated with bipolar disorder. In a previous study of bipolar disorder, combinations of three single nucleotide polymorphism (SNP) genotypes taken from 803 SNPs were analyzed, and four clusters of combinations were found to be significantly associated with bipolar disorder. In the present study, combinations of four SNP genotypes taken from the same 803 SNPs were analyzed, and one cluster of combinations was found to be significantly associated with bipolar disorder. Combinations from the new cluster and from the four previous clusters were identified in the genomes of 209 of the 607 patients in the study whereas none of the 1355 control participants had any of these combinations in their genome. 相似文献
68.
69.
Fusarium venenatum A3/5 was transformed using the Aspergillus niger expression plasmid, pIGF, in which the coding sequence for the F. solani f. sp. pisi cutinase gene had been inserted in frame, with a KEX2 cleavage site, with the truncated A. niger glucoamylase gene under control of the A. niger glucoamylase promoter. The transformant produced up to 21 U cutinase l−1 in minimal medium containing glucose or starch as the primary carbon source. Glucoamylase (165 U l−1 or 8 mg l−1) was also produced. Both the transformant and the parent strain produced cutinase in medium containing cutin. 相似文献
70.