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151.
Large‐scale disturbance legacies and the climate sensitivity of primary Picea abies forests 下载免费PDF全文
Jonathan S. Schurman Radek Bače Vojtěch Čada Shawn Fraver Pavel Janda Dominik Kulakowski Jana Labusova Martin Mikoláš Thomas A. Nagel Rupert Seidl Michal Synek Kristýna Svobodová Oleh Chaskovskyy Marius Teodosiu Miroslav Svoboda 《Global Change Biology》2018,24(5):2169-2181
Determining the drivers of shifting forest disturbance rates remains a pressing global change issue. Large‐scale forest dynamics are commonly assumed to be climate driven, but appropriately scaled disturbance histories are rarely available to assess how disturbance legacies alter subsequent disturbance rates and the climate sensitivity of disturbance. We compiled multiple tree ring‐based disturbance histories from primary Picea abies forest fragments distributed throughout five European landscapes spanning the Bohemian Forest and the Carpathian Mountains. The regional chronology includes 11,595 tree cores, with ring dates spanning the years 1750–2000, collected from 560 inventory plots in 37 stands distributed across a 1,000 km geographic gradient, amounting to the largest disturbance chronology yet constructed in Europe. Decadal disturbance rates varied significantly through time and declined after 1920, resulting in widespread increases in canopy tree age. Approximately 75% of current canopy area recruited prior to 1900. Long‐term disturbance patterns were compared to an historical drought reconstruction, and further linked to spatial variation in stand structure and contemporary disturbance patterns derived from LANDSAT imagery. Historically, decadal Palmer drought severity index minima corresponded to higher rates of canopy removal. The severity of contemporary disturbances increased with each stand's estimated time since last major disturbance, increased with mean diameter, and declined with increasing within‐stand structural variability. Reconstructed spatial patterns suggest that high small‐scale structural variability has historically acted to reduce large‐scale susceptibility and climate sensitivity of disturbance. Reduced disturbance rates since 1920, a potential legacy of high 19th century disturbance rates, have contributed to a recent region‐wide increase in disturbance susceptibility. Increasingly common high‐severity disturbances throughout primary Picea forests of Central Europe should be reinterpreted in light of both legacy effects (resulting in increased susceptibility) and climate change (resulting in increased exposure to extreme events). 相似文献
152.
153.
Heyue Zhou Bin Zhou Sabine Pellett Eric A. Johnson Kim D. Janda 《Bioorganic & medicinal chemistry letters》2009,19(3):662-664
Botulinum neurotoxins (BoNTs) are causative agents for botulism and are identified as a category A bioterror agents by the Centers for Disease Control and Prevention (CDC). Current antitoxins against BoNTs intoxication have some limitations including side effects or limited supply. As an alternative, neutralizing monoclonal antibodies will play an increasing role as BoNTs therapeutics. To date, no human anti-BoNT/B neutralizing monoclonal antibodies have yet to be reported. Herein, we describe an improved selection approach and characterization of a human monoclonal antibody, F2, which is capable of binding BoNT/B with high specificity and displays neutralizing activity in an in vitro cell-based assay. Through surface plasmon resonance studies, we have determined its association and dissociation rate constants. In sum, our data demonstrate that monoclonal antibody F2 is a promising BoNT/B therapeutic lead for further development. 相似文献
154.
Summary The Gladenbach Formation is an approximately 30 m thick, well-segregated calciturbidite sequence, restricted to the H?rre
belt of the eastern Rheinisches Schiefergebirge. It is middle Tournaisian in age (lowerPericyclus Stage, lower cd II of the German Culm zonation) and is an equivalent of the Liegende Alaunschiefer. The sequence is composed
predominantly of minor turbiditic fining-upward cycles.
Cycles start with massive calciturbidite beds. They are composed of fine-grained intraclastic-bioclastic grainstone/packstone,
more or less ooid-bearing in the top of the formation, and/or radiolarian-rich packstone. Cycles continue with platy, dense
limestones consisting of radiolarian-rich wackestone/packstone and microlithoclastic-microbioclastic wackestone/packstone.
Different types of shales finish the fining-upward development. Minor cycles can be grouped into several 4th order cycles,
composing a single 3rd order cycle. Towards the top, abundance of resedimented platform components, like ooids, calcareous
smaller foraminifers, echinoderms, brachiopods, bryozoans and critical conodont genera, increases. Simultaneously, the thickness
of the minor cycles decreases. This indicates a transgressive phase, characterized by increasing over-production of carbonate
on platform realms and a correlated increase in the frequency of resedimentation events in the basin. The transgression corresponds
to the well-documented global eustatic transgression of the Lowercrenulata andisosticha-uppercrenulata Zone of the conodont chronology. Thus, the Gladenbach Formation is interpreted as a transgressive systems tract/highstand
systems tract. The Liegende Alaunschiefer is the time-equivalent, starved basin facies.
Predominating hemipelagic calciturbidites of the lower Gladenbach Formation derive from the deeper shelf slope or from an
intrabasinal swell, which might constitute a flexural bulge in front of the shelf slope. Turbidite sediments from the upper
part of the formation derive from shelf-edge sands and the upper shelf slope. The source might be related to the ancient Devonian
reef complex of Langenaubach-Breitscheid in the southwest. 相似文献
155.
Anti-adhesive glycosylation of fibronectin-like molecules in human placental matrix-type fibrinoid 总被引:1,自引:1,他引:0
Hans-Georg Frank Berthold Huppertz Sonja Kertschanska Dominique Blanchard Dieter Roelcke Peter Kaufmann 《Histochemistry and cell biology》1995,104(4):317-329
Recently, fibrinoid of the human placenta has been described as being composed of two main types differing in origin and chemical composition. Fibrin-type fibrinoid is mostly a blood clot product. Matrix-type fibrinoid was defined as the extracellular matrix secreted by extravillous trophoblast cells. The structure and composition of matrix-type fibrinoid was addressed in this study, focusing on fibronectins as one major constituent. A panel of antibodies directed against different fibronectin isoforms generated by different mRNA splicing, as well as antibodies recognizing oncofetal carbohydrate epitopes, were used on cryostat, paraffin and Lowicryl sections of placental tissue from different stages of pregnancy. The oncofetal carbohydrate epitopes studied comprised the blood group precursor antigens i and I. We identified the blood group-related antigen i as an additional marker for matrix-type fibrinoid. The antigen was detected on a glycoprotein that was also recognized by the fibronectin antibodies in western blots. Immunohistochemically this i-glycosylated oncofetal fibronectin-like molecule of about 55 kDa is expressed only by the invasive phenotype of extravillous trophoblast. Long chain carbohydrate moieties with a structure fulfilling the criteria for i reactivity on human placental fibronectin are known to have anti-adhesive properties and to enhance resistance of the protein chain to proteolysis. These properties underline the functional relevance of glycosylation of fibronectins in matrix-type fibrinoid and suggest matrix-type fibrinoid is a typical matrix of invasive cells. In contrast, the more mature blood group precursor I could be detected after sialidase pretreatment of sections. This antigen was expressed by villous, non-invasive trophoblast. 相似文献
156.
Cloning, sequencing and production of the lantibiotic mersacidin 总被引:5,自引:0,他引:5
Gabriele Bierbaum Heike Brötz Klaus-Peter Koller Hans-Georg Sahl 《FEMS microbiology letters》1995,127(1-2):121-126
Abstract Mersacidin is a lanthionine-containing peptide antibiotic that shows a good in vivo efficiency against methicillin-resistant Staphylococcus aureus . It is excreted during early stationary phase and could be purified from culture supernatant in a one-step procedure by reversed phase HPLC. Its structural gene was cloned from chromosomal DNA of the producer strain Bacillus subtilis HIL Y-85,54728. Sequencing revealed that pre-mersacidin consists of an unusually long 48 amino acid leader sequence and a 20 amino acid propeptide part which is modified during biosynthesis to the mature lantibiotic. The comparison of the mersacidin prepeptide with those of hitherto known lantibiotics demonstrates that mersacidin is more closely related to type B lantibiotic cinnamycin than to type A lantibiotics. 相似文献
157.
158.
Klaus Geider Gholamreza Darai Seong-Lyul Rhim Hans-Georg Simon Marion Moos Günter Harth 《Molecular and cellular biochemistry》1989,85(1):19-28
Summary The large Ti-plasmid from Agrobacterium tumefaciens strain C58 has been used for transfection experiments with mammalian cells. In DNA from Tupaia baby fibroblasts Ti-plasmid sequences could be identified by filter hybridization as long as four weeks after transfection including two cell passages. The hybridization signals decreased rapidly after addition of the Ti-plasmid DNA-coprecipitate to the cells. The signals were often not detected any more after the first day, but were visible one week after transfection. Nuclei prepared from Ti-plasmid-transfected cells hybridized to pTi-specific RNA. With the chloramphenicol acetyl transferase-gene as marker no discrimination in DNA uptake was found between the Ti-plasmid and much smaller plasmids. According to the number of nuclei with homology to pTi-sequences it is assumed that about 0.2% of the cells carry Ti-plasmid DNA in the nucleus. Analysis of RNA isolated from cells transfected with cloned segments of the Ti-plasmid revealed that the TDNA region of the Ti-plasmid was predominantly transcribed.Abbreviations CAT
Chloramphenicol Acetyl Transferase
- NPT
Neomycin Phosphotransferase
- SDS
Sodium Dodecylsulfate
- TK
Thymidine Kinase 相似文献
159.
A colorimetric estimation of lipopolysaccharides 总被引:27,自引:0,他引:27
160.
Summary The effects of theophylline on insulin receptors and insulin action in isolated rat adipocytes were studied. Theophylline reduced insulin binding by a decrease of receptor affinity. As concentration-response curves revealed, the effect was paralleled by a reduction of the cellular ATP content. Basal as well as insulin-stimulated glucose transport (2-deoxyglucose and 3-O-methylglucose uptake) were inhibited by much smaller theophylline concentrations (0.15–0.6 mM ) than those necessary to reduce insulin binding and to lower ATP levels (1–4.8 mM), or to stimulate lipolysis (0.3-2.4 mM). Insulin fully antagonized the effect of theophylline on lipolysis but failed to reverse the inhibition of glucose transport completely. The results suggest that (a) theophylline impairs insulin action at a post-receptor level and, at higher concentrations, by a decrease of receptor binding, (b) the reduction of insulin receptor affinity probably reflects ATP depletion of the adipocyte, and (c) the xanthine inhibits glucose transport independently from its effects on lipolysis. 相似文献