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961.
Schneider K Kuznetzov VK Sanzharova NI Kanter U Telikh KM Khlopuk MS 《Radiation and environmental biophysics》2008,47(2):241-252
Field-grown maize hybrids were assessed for variability in 137Cs accumulation in vegetative parts of young and mature maize shoots and grains during 2 years with contrasting climatic conditions.
Trials were carried out at different sites in the Tula region of Russia, which is characterized by a highly homogenous soil
classified as Luvic Chernozem according to FAO/UNESCO, and average contamination levels of about 509–564 Bq 137Cs kg−1 soil. In the first year, 19 hybrids were tested. The two hybrids with the highest and the two with the lowest 137Cs concentration ratios (C
r) were also tested in the second year, together with another 11 hybrids. All samples were additionally assessed for their
potassium content. In both investigation periods 137Cs accumulation in vegetative shoots and grains was found to vary up to more than twofold between hybrids. However, C
r values of those hybrids that showed a relatively low 137Cs accumulation in the first year were not necessarily low in the second year, and the ratio between the 137Cs C
r of low- and high-accumulating hybrids was much smaller than in the year before. In both vegetative shoots and grains the
variance caused by the different years was larger than the genotypic variance, thus indicating the limits of genotype selection
for this trait. Significant correlations were determined between the 40K and 137Cs C
r values in the same tissue, but for one hybrid indications for uncoupling of the two traits were found. Average Cs/K ratios
in young shoots, mature shoots and grains were 0.06, 0.05 and 0.02, respectively, indicating tissue- and stage-specific regulation
of accumulation within each plant. The findings are discussed with respect to new approaches towards a better understanding
of 137Cs accumulation and its potential reduction in plants.
Katharina Schneider was deceased. 相似文献
962.
One of the main problems in phylogenetics is to develop systematic methods for constructing evolutionary or phylogenetic trees. For a set of species X, an edge-weighted phylogenetic X-tree or phylogenetic tree is a (graph theoretical) tree with leaf set X and no degree 2 vertices, together with a map assigning a non-negative length to each edge of the tree. Within phylogenetics, several methods have been proposed for constructing such trees that work by trying to piece together quartet trees on X, i.e. phylogenetic trees each having four leaves in X. Hence, it is of interest to characterise when a collection of quartet trees corresponds to a (unique) phylogenetic tree. Recently, Dress and Erdös provided such a characterisation for binary phylogenetic trees, that is, phylogenetic trees all of whose internal vertices have degree 3. Here we provide a new characterisation for arbitrary phylogenetic trees. 相似文献
963.
964.
Grikscheit K Thomas N Bruce AF Rothery S Chan J Severs NJ Dupont E 《Cell communication & adhesion》2008,15(1):185-193
In the human heart, ventricular myocytes express connexin 43 (Cx43) and traces of Cx45. In congestive heart failure, Cx43 levels decrease, Cx45 levels increase and gap junction size decreases. To determine whether alterations of connexin coexpression ratio influence gap junction size, we engineered a rat liver epithelial cell line that endogenously expresses Cx43 to coexpress inducible levels of Cx45 under stimulation of the insect hormone, ponasterone A. In cells induced to express Cx45, gap junction sizes are significantly reduced (by 15% to 20%; p < 0.001), an effect that occurs despite increased levels of junctional connexons made from both connexins. In contrast, coexpression of Cx40 with Cx43 does not lead to any change in gap junction size. These results are consistent with the idea that increased Cx45 expression in the failing ventricle contributes to decreased gap junction size. 相似文献
965.
Urs Lewandrowski Katharina Lohrig René P. Zahedi Dirk Wolters Albert Sickmann 《Clinical proteomics》2008,4(1-2):25-36
Introduction
Glycosylations range among the most common posttranslational modifications with an estimated 50% of all proteins supposed to be glycosylated. These modifications are required for essential cellular processes including cell–cell recognition, protein structure and activity, e.g., of surface receptors, as well as subcellular localization of proteins. Beside the elucidation of the carbohydrate structures, the annotation of glycosylation sites is of primary interest as a basis for subsequent functional characterization. Although mass spectrometry is the method of choice for large-scale analysis of glycosylation sites, it requires initial enrichment of glycopeptides prior mass spectrometric detection in most cases.Materials and Methods
In this paper, we present a novel approach for glycopeptide enrichment by electrostatic repulsion hydrophilic interaction chromatography (ERLIC). Glycopeptides were separated from the bulk of non-modified peptides and gradually eluted from the stationary phase with potential for isoform resolution. Applied to human platelets, 125 glycosylation sites on 66 proteins were identified including major platelet glycoproteins responsible for cellular function.Conclusion
These sites add a major contribution to the now more than 250 glycosylation sites annotated for platelets, which enable the clinically relevant design of quantification assays for platelet glycoproteins. 相似文献966.
Nitrogen-fixing root nodule symbioses (RNS) occur in two major forms—Actinorhiza and legume-rhizobium symbiosis—which differ in bacterial partner, intracellular infection pattern, and morphogenesis. The phylogenetic restriction of nodulation to eurosid angiosperms indicates a common and recent evolutionary invention, but the molecular steps involved are still obscure. In legumes, at least seven genes—including the symbiosis receptor-kinase gene SYMRK —are essential for the interaction with rhizobia bacteria and for the Arbuscular Mycorrhiza (AM) symbiosis with phosphate-acquiring fungi, which is widespread in occurrence and believed to date back to the earliest land plants. We show that SYMRK is also required for Actinorhiza symbiosis of the cucurbit Datisca glomerata with actinobacteria of the genus Frankia , revealing a common genetic basis for both forms of RNS. We found that SYMRK exists in at least three different structural versions, of which the shorter forms from rice and tomato are sufficient for AM, but not for functional endosymbiosis with bacteria in the legume Lotus japonicus . Our data support the idea that SYMRK sequence evolution was involved in the recruitment of a pre-existing signalling network from AM, paving the way for the evolution of intracellular root symbioses with nitrogen-fixing bacteria. 相似文献
967.
Brattig NW Kowalsky K Liu X Burchard GD Kamena F Seeberger PH 《Microbes and infection / Institut Pasteur》2008,10(8):885-891
Following exposure to synthetic Plasmodium falciparum glycosylphosphatidylinositol (P.f.-GPI), red blood cells (RBCs) reacted with antibodies in the serum of a patient with severe acute P. falciparum malaria. Carbohydrate microarray analysis of the patient's serum confirmed the presence of both, IgM and IgG antibodies against P.f.-GPI. The antibodies failed to bind to RBCs when P.f.-GPI lacking the lipid portion was applied. Addition of the detergent Triton X-100 during preincubation with P.f.-GPI resulted in increased recognition. Recognition of P.f.-GPI was dependent on the concentrations of synthetic P.f.-GPI, the serum and the numbers of RBCs. IgM antibodies dominated P.f.-GPI-sensitized RBCs recognition. Recognition by IgM antibodies proved highest during the 1stweek of acute malaria and decreased during the following 2weeks as assessed by flow cytometry and carbohydrate microarray analysis. These results strongly support the notion that released P.f.-GPI can insert into non-parasitized RBC membranes and results in recognition by circulating anti-GPI antibodies and possibly subsequent elimination. This process may contribute to malaria-associated anemia. 相似文献
968.
Since there is no upper age limit for general organ donation, unlike heart valve donation, and since a quarter of all organ
donors are 65 years and older, we examined whether the heart valves from these donors are suitable as allografts. In the period
1999–2004 the aortic valve and pulmonary valve of 100 organ donors above 65 years of age were examined to establish whether
they would have been suitable as valve grafts. To compare the valve grafts above and below the age limit of 65 years, we used
data on the aortic and pulmonary valves of 380 organ donors below the age limit in the same time period. Examination of the
200 heart valves showed that – just like valves from donors below the age limit – 100 of them would have met the medical quality
standards for transplantation, which discriminate among optimal, suitable and unsuitable tissue morphology. The morphological
suitability of the aortic valves decreases rapidly during the 4th decade of life and near to the age limit only 6% of them
are accepted as grafts. The rate of potentially acceptable aortic valve grafts from organ donors aged over 65 years of 15%
is also small. By contrast, the pulmonary valves are not affected by age-related tissue changes that might reduce their transplantability.
The predominant majority (85%) of potential pulmonary valve grafts from organ donors over 65 years of age fulfilled the acceptance
criteria, half of them (48%) even showing good tissue quality. In light of these results the age limit was raised to 70 years
in 2005. 相似文献
969.
Questions: Does the increased atmospheric deposition of nitrogen, which can have major effects on the established vegetation of nutrient‐poor habitats, also impact germination from the soil seed bank? Location: Coastal dune slacks at Newborough Warren, Wales, UK. Methods: The effects of nitrogen addition (15 kg.ha‐1.a‐1) on seed germination from the soil seed bank were investigated using the seedling emergence method between September 2004 and February 2005. Results: More seedlings emerged from fertilised samples than unfertilised controls. Most species showed enhanced germination after fertilisation with nitrogen, with seedling numbers statistically significantly greater in nitrogen addition samples in a quarter of species abundant enough for analysis. Species that responded positively to fertilisation were species with low Ellenberg indicator values indicative of infertile sites. Conclusions: Most species showed increased germination after fertilisation with nitrogen, including early successional species normally growing in nutrient‐poor conditions. This suggests that the increased atmospheric deposition of nitrogen probably not only impacts on established vegetation, but also has the potential to alter seed bank dynamics. 相似文献
970.
At the rocky island of Helgoland (North Sea), the distribution and abundances of intertidal communities were assessed and
the effects of wave exposure and tidal height on the spatial distribution patterns of the communities were evaluated. Macroalgae
and invertebrates were sampled quantitatively along line transects in three intertidal locations, a semi-exposed, an exposed
and a sheltered one. The semi-exposed location was characterised by (1) Ulva spp. at the high intertidal (Ulva-community), (2) mussels and periwinkles at the mid intertidal (Mytilus-community) and (3) Corallina officinalis and mainly the large brown alga Fucus serratus at the low intertidal (Fucus-community). The exposed location encompassed the mid and low intertidal; at both zones the Fucus-community occurred. The sheltered location was characterised by (1) barnacles (Balanus-community) and (2) bryozoans, hydrozoans and mainly the large brown alga Ascophyllum nodosum (Ascophyllum-community). At the semi-exposed, but not at the exposed location the communities changed with the intertidal position. A
relationship between wave exposure and the occurrence of specific communities was shown for the sheltered location; in contrast,
communities of the semi-exposed and the exposed location appear to be little influenced by wave exposure directly. The community
concept and the potential causes of distribution patterns of the defined communities are discussed and suggestions for a future
monitoring are given. Variations in the communities at different spatial scales speak in favour of a multiple scale sampling
design to monitor changes in the intertidal communities at Helgoland.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献