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991.
In several fields of cell biology, correlative microscopy is applied to compare the structure of objects at high resolution under the electron microscope with low resolution light microscopy images of the same sample. It is, however, difficult to prepare samples and marker systems that are applicable for both microscopic techniques for the same specimen at the same time. In our studies, we used microbial mats from Cold Seep communities for a simple and rapid correlative microscopy method. The mats consist of bacterial and archaeal microorganisms, coupling reverse methanogenesis to the reduction of sulfate. The reverse methanogenic pathway also generates carbonates that precipitate inside the mat and may be the main reason for the formation of a microbial reef. The mat shows highly differentiated aggregates of various organisms, tightly interconnected by extracellular polysaccharides. In order to investigate the role of EPS as adhesive mucilage for the biofilm and as a precipitation matrix for carbonate minerals, samples were embedded in a hydrophilic resin (Lowicryl K4 M). Sections were suitable for light as well as electron microscopy in combination with lectins, either labeled with a fluorescent marker or with colloidal gold. This allows lectin mapping at low resolution for light microscopy in direct comparison with a highly resolved electron microscopic image. 相似文献
992.
Reinhard Huber Roswitha Baumung Maria Wurzinger Dan Semambo Okeyo Mwai Christoph Winckler 《Applied animal behaviour science》2008,112(3-4):223-234
The aim of this study was to assess the grazing, social and comfort behaviour of the indigenous purebred Ankole cattle breed and crossbred (Holstein × Ankole) animals under typical management conditions in south western Uganda. Twelve focal animals in each of four groups (two groups per genotype) were observed regarding their grazing, social and comfort behaviour on pasture.No significant differences in grazing behaviour patterns (eating, walking, standing) were found between the genotypes. Resting occurred only very rarely in both genotypes. Walking distances of Ankole and Ankole × Holstein crosses were also similar. There was no difference in the occurrence of agonistic interactions between the two genotypes. However, Ankole cattle engaged in more non-agonistic social interactions than their crossbred counterparts. Individual distances were lower in Ankole heifers and more herd mates were found within a radius of 5 m around the Ankole animals. The most important comfort behaviour pattern in both genotypes was self-licking, which occurred to similar frequency in Ankole and crossbred heifer groups. Crossbred animals scratched themselves and rubbed on objects more often than Ankole heifers.Although Ankole cattle and their Holstein crosses did not differ in grazing, distances walked and agonistic behaviours, the significant differences between the two genotypes in herd cohesion and comfort behaviour may pose challenges on the management of crossbred animals under extensive open grazing conditions as present in south western Uganda. Thus, apart from (re)productive performance traits, behavioural traits of both genotypes may also be taken into account for breeding decisions and management under current production conditions. 相似文献
993.
Petersen BO Sára M Mader C Mayer HF Sleytr UB Pabst M Puchberger M Krause E Hofinger A Duus JØ Kosma P 《Carbohydrate research》2008,343(8):1346-1358
The secondary cell wall polymer (SCWP) from Geobacillus stearothermophilus PV72/p2, which is involved in the anchoring of the surface-layer protein to the bacterial cell wall layer, is composed of 2-amino-2-deoxy- and 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-mannose, and 2-acetamido-2-deoxy-D-mannuronic acid. The primary structure of the acid-degraded polysaccharide--liberated by HF-treatment from the cell wall--was determined by high-field NMR spectroscopy and mass spectrometry using N-acetylated and hydrolyzed polysaccharide derivatives as well as Smith-degradation. The polysaccharide was shown to consist of a tetrasaccharide repeating unit containing a pyruvic acid acetal at a side-chain 2-acetamido-2-deoxy-alpha-D-mannopyranosyl residue. Substoichiometric substitutions of the repeating unit were observed concerning the degree of N-acetylation of glucosamine residues and the presence of side-chain linked 2-acetamido-2-deoxy-beta-D-glucopyranosyl units: [Formula: see text]. 相似文献
994.
Greubel C Hable V Drexler GA Hauptner A Dietzel S Strickfaden H Baur I Krücken R Cremer T Friedl AA Dollinger G 《Radiation and environmental biophysics》2008,47(4):415-422
Several proteins are known to form foci at DNA sites damaged by ionizing radiation. We study DNA damage response by immunofluorescence
microscopy after microirradiation of cells with energetic ions. By using microirradiation, it is possible to irradiate different
regions on a single dish at different time-points and to differentiate between cells irradiated earlier and later. This allows
to directly compare immunofluorescence intensities in both subsets of cells with little systematic error because both subsets
are cultivated and stained under identical conditions. In addition, by using irradiation patterns such as crossing lines,
it is possible to irradiate individual cells twice and to differentiate between immunofluorescence signals resulting from
the cellular response to the earlier and to the later irradiation event. Here, we describe the quantitative evaluation of
immunofluorescence intensities after sequential irradiation. 相似文献
995.
996.
Zuther K Mayser P Hettwer U Wu W Spiteller P Kindler BL Karlovsky P Basse CW Schirawski J 《Molecular microbiology》2008,68(1):152-172
Tryptophan is a precursor for many biologically active secondary metabolites. We have investigated the origin of indole pigments first described in the pityriasis versicolor-associated fungus Malassezia furfur . Some of the identified indole pigments have properties potentially explaining characteristics of the disease. As M. furfur is not amenable to genetic manipulation, we used Ustilago maydis to investigate the pathway leading to pigment production from tryptophan. We show by high-performance liquid chromatography, mass spectrometry and nuclear magnetic resonance analysis that the compounds produced by U. maydis include those putatively involved in the etiology of pityriasis versicolor. Using a reverse genetics approach, we demonstrate that the tryptophan aminotransferase Tam1 catalyses pigment biosynthesis by conversion of tryptophan into indolepyruvate. A forward genetics approach led to the identification of mutants incapable of producing the pigments. These mutants were affected in the sir1 gene, presumably encoding a sulphite reductase. In vitro experiments with purified Tam1 showed that 2-oxo 4-methylthio butanoate serves as a substrate linking tryptophan deamination to sulphur metabolism. We provide the first direct evidence that these indole pigments form spontaneously from indolepyruvate and tryptophan without any enzymatic activity. This suggests that compounds with a proposed function in M. furfur -associated disease consist of indolepyruvate-derived spontaneously generated metabolic by-products. 相似文献
997.
Nina Brenn Audrius Menkis Christoph R. Grünig Thomas N. Sieber Ottmar Holdenrieder 《Mycological Research》2008,112(6):650-662
Patterns of colonization of conifer roots by dark septate endopyhtes of the Phialocephala fortinii s. lat. species complex in nurseries in Switzerland and Lithuania were studied. The potential for man-mediated genotype flow was estimated for two Swiss nurseries based on customers' addresses and the number of delivered plants. Two hundred and forty-nine strains from three Swiss and five Lithuanian nurseries and an afforestation site were characterized using a combination of inter-simple sequence repeat-anchored PCR (ISSR-PCR), single-copy RFLP analysis, and sequence analysis. P. fortinii s. lat. was abundant in nursery seedlings, but the frequency of seedlings colonized varied considerably among and within nurseries. Ten cryptic species (CSP) of P. fortinii s. lat. were identified, including four hitherto undiscovered CSP. P. helvetica was the dominant species in Swiss nurseries, whereas P. fortinii s. str. was the most abundant species in Lithuanian nurseries and the afforestation site. Swiss nurseries deliver plants over distances of more than 200 km indicating the high potential for man-mediated genotype flow in P. fortinii s. lat. 相似文献
998.
Riethmüller C Oberleithner H Wilhelmi M Franz J Schlatter E Klokkers J Edemir B 《Biophysical journal》2008,94(2):671-678
Docking and fusion of vesicles to the plasma membrane is a fundamental process in living cells. An established model for the trafficking of vesicles is based on primary epithelial cells from the collecting duct of the nephron. Upon stimulation with the signaling peptide arginine-vasopressin (AVP), aquaporin-containing vesicles are directed to the plasma membrane. Since aquaporin selectively enhances the water permeability of plasma membranes, this process helps to balance the water content of the organism. A mechanism has been suggested involving local depolymerization of F-actin to facilitate the movement of vesicles to the membrane. Since F-actin is the major component of cytoskeletal restoring forces, AVP-stimulated cells can be expected to lose rigidity. Here, we used atomic force microscopy force mapping to test whether AVP alters cell stiffness. The Young's modulus of living epithelial cells at 37°C was continuously monitored, yielding a 51% decrease of Young's modulus after the addition of AVP. The data demonstrate that not the depolymerization of actin but a relaxation of actomyosin interaction facilitates vesicle translocation. 相似文献
999.
Münch C Zhu BG Mink A Seefried U Riepe MW Ludolph AC Meyer T 《Neurochemical research》2008,33(6):1005-1010
Hypoxia is one of the major common components of vascular risk factors for pathogenesis of Alzheimer’s disease. This study
investigated the possible relationship between hypoxia and alternative splicing of the excitatory amino acid transporter 2
(EAAT2) in a transgenic model for Alzheimer’s disease. We used an APP23 mouse model prior to amyloid deposition and subjected
it to chemical hypoxia treatment as induced by 3-nitropropionic acid. One hour after administration of 3-nitropropionic acid
changes in the expression of the 5′-splice forms mEAAT2/5UT3, mEAAT2/5UT4, and mEAAT2/5UT5 were found in the frontal cortex,
hippocampus and cerebellum of the APP23 model. In untreated APP23 animals the expression of EAAT2 splice variants was unchanged.
Our results demonstrate that hypoxia facilitates alternative splicing of EAAT2 in the APP23 model. This may be a molecular
mechanism linking vascular factors to early pathophysiology of Alzheimer’s disease. 相似文献
1000.