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2.
Friederike Anton-Erxleben 《Helgoland Marine Research》1981,34(4):439-450
Energy dispersive X-ray analysis of elements with Z>11 in a SEM (scanning electron microscope) was used to investigate the elytra ofLagisca extenuata, Lepidonotus clava, andHarmothoe areolata from Naples (Italy) and Banyuls (France). High concentrations of halogens and a few other elements were found in certain papillae in samples from both locations. Additional TEM-examinations and X-ray analysis of thin sections revealed that the halogen concentration is inversely related to the collagen content of the matrix. The halogens are presumably bound to tyrosines, which occur in these structures. In addition, accumulation of Mn2+ and possibly Fe3+ in the papillae might depend on environmental conditions. The results show that valuable information about the chemical composition of biological structures can be obtained by energy dispersive X-ray analysis. Moreover, the results indicate that this method may be useful for environmental investigations.This work is part of a doctoral thesis, written at the Zoological Institute of the University at Hamburg. 相似文献
3.
Friederike A. Schulte Floor M. Lambers Thomas L. Mueller Martin Stauber 《Computer methods in biomechanics and biomedical engineering》2014,17(5):539-548
Time-lapsed in vivo micro-computed tomography is a powerful tool to analyse longitudinal changes in the bone micro-architecture. Registration can overcome problems associated with spatial misalignment between scans; however, it requires image interpolation which might affect the outcome of a subsequent bone morphometric analysis. The impact of the interpolation error itself, though, has not been quantified to date. Therefore, the purpose of this ex vivo study was to elaborate the effect of different interpolator schemes [nearest neighbour, tri-linear and B-spline (BSP)] on bone morphometric indices. None of the interpolator schemes led to significant differences between interpolated and non-interpolated images, with the lowest interpolation error found for BSPs (1.4%). Furthermore, depending on the interpolator, the processing order of registration, Gaussian filtration and binarisation played a role. Independent from the interpolator, the present findings suggest that the evaluation of bone morphometry should be done with images registered using greyscale information. 相似文献
4.
Andreas Koeberle Eva-Maria Haberl Antonietta Rossi Carlo Pergola Friederike Dehm Hinnak Northoff Reinhard Troschuetz Lidia Sautebin Oliver Werz 《Bioorganic & medicinal chemistry》2009,17(23):7924-7932
Selective inhibition of pro-inflammatory prostaglandin (PG)E2 formation via microsomal PGE2 synthase-1 (mPGES-1) might be superior over inhibition of all cyclooxygenase (COX)-derived products by non-steroidal anti-inflammatory drugs (NSAIDs) and coxibs. We recently showed that benzo[g]indol-3-carboxylates potently suppress leukotriene biosynthesis by inhibiting 5-lipoxygenase. Here, we describe the discovery of benzo[g]indol-3-carboxylates as a novel class of potent mPGES-1 inhibitors (IC50 ? 0.1 μM). Ethyl 2-(3-chlorobenzyl)-5-hydroxy-1H-benzo[g]indole-3-carboxylate (compound 7a) inhibits human mPGES-1 in a cell-free assay (IC50 = 0.6 μM) as well as in intact A549 cells (IC50 = 2 μM), and suppressed PGE2 pleural levels in rat carrageenan-induced pleurisy. Inhibition of cellular COX-1/2 activity was significantly less pronounced. Compound 7a significantly reduced inflammatory reactions in the carrageenan-induced mouse paw edema and rat pleurisy. Together, based on the select and potent inhibition of mPGES-1 and 5-lipoxygenase, benzo[g]indol-3-carboxylates possess potential as novel anti-inflammatory drugs with a valuable pharmacological profile. 相似文献
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Friederike Fleischer 《Ethnos》2013,78(3):300-325
In this article, I explore the growing popularity of volunteering in China. I delineate several factors that play into the phenomenon, including students' desire to break out of strict routines, to engage in meaningful activities, to meet people, and to contribute to China's development. Linking these issues to the socio-political, economic, and ideological transformations in China, I show that we cannot meaningfully distinguish between altruistic and self-interested motivations to volunteer. For the students volunteering is a means to transform themselves into modern, entrepreneurial, and responsible selves, necessary to meet the challenges of urban life in China today. Yet, volunteering, encouraged and framed by the government, is also a ‘technology of power’, a means to nurture self-reliant and socially responsible individuals. I show that volunteerism is not simply the reflection of a new ‘governmentality’ but an encounter in which the very relationship between state and society is constantly negotiated. 相似文献
7.
Ralf Salzer Martin Herzberg Dietrich H. Nies Friederike Joos Barbara Rathmann Yvonne Thielmann Beate Averhoff 《The Journal of biological chemistry》2014,289(44):30343-30354
The traffic AAA-ATPase PilF is essential for pilus biogenesis and natural transformation of Thermus thermophilus HB27. Recently, we showed that PilF forms hexameric complexes containing six zinc atoms coordinated by conserved tetracysteine motifs. Here we report that zinc binding is essential for complex stability. However, zinc binding is neither required for pilus biogenesis nor natural transformation. A number of the mutants did not exhibit any pili during growth at 64 °C but still were transformable. This leads to the conclusion that type 4 pili and the DNA translocator are distinct systems. At lower growth temperatures (55 °C) the zinc-depleted multiple cysteine mutants were hyperpiliated but defective in pilus-mediated twitching motility. This provides evidence that zinc binding is essential for the role of PilF in pilus dynamics. Moreover, we found that zinc binding is essential for complex stability but dispensable for ATPase activity. In contrast to many polymerization ATPases from mesophilic bacteria, ATP binding is not required for PilF complex formation; however, it significantly increases complex stability. These data suggest that zinc and ATP binding increase complex stability that is important for functionality of PilF under extreme environmental conditions. 相似文献
8.
Friederike Thor Matthias Gautschi Roger Geiger Ari Helenius 《Traffic (Copenhagen, Denmark)》2009,10(12):1819-1830
The C-terminal domain, Cp, of the Semliki Forest virus capsid protein, known for its rapid, efficient and chaperone-independent folding, was used to measure bulk fluid flow in the secretory pathway of Chinese hamster ovary cells. Being small, nonglycosylated, soluble and cytoplasmic in origin, Cp was not likely to interact with lectins, cargo receptors and retention factors. Using pulse-chase analysis, we observed that translocation into the endoplasmic reticulum resulted in rapid and efficient folding and transport of the newly synthesized Cp protein to the extracellular medium. The first Cp molecules were secreted 15 min after synthesis, which is the fastest transport of a protein so far recorded in mammalian cells. The rate constant of secretion was 1.2% per min, which amounts to an estimated bulk flow rate of about 155 coat protein II (COPII) vesicles per second. Transport was independent of expression level, and blocked by CI-976, brefeldin A and ATP depletion indicating that it depended on COPII vesicle formation, and followed the classical secretory pathway. In polarized Madin-Darby canine kidney cells, the secretion rate was similar but occurred mainly apically. The results demonstrated that fluid flow in the secretory pathway is fast, and can therefore play a significant role in the secretion of soluble secretory products. 相似文献
9.
The ultrastructure of astrocytes in an organotypic slice culture of the rat visual cortex was investigated using ultrathin sections and freeze-fracture replicas. After a culture period of 9–15 days, a glial scaffold formed that separated the bulk of the slice neuropil from the medium and the underlying plasma clot. However, the glial cells and processes did not build a dense barrier but allowed the outgrowth of neurites. A basal lamina covering the medium-oriented surface of the astrocytes was not found. In freeze-fracture replicas, orthogonal arrays of particles (OAP) were characteristic components of astrocytic membranes. The OAP density in membranes bordering the medium was 35±13 OAP/m2, corresponding to 2.5% of this membrane area; the OAP density in membranes within the slice neuropil was 22±12 OAP/2, corresponding to 1.4% of this membrane area. Although the difference was significant, it was greatly reduced when comparing OAP densities in endfoot and non-endfoot membranes in vivo. Another mode of polarity was recognized in astrocytes of the organotypic slice culture. In membranes of astrocytes bordering upon the medium, the density of non-OAP intramembranous particles (IMP) was clearly higher (1130±136 IMP/ m2) than in membranes of astrocytes in the center of the slice (700±172 IMP/m2). This pronounced IMP-related polarity was observed neither in vivo nor in cultured astrocytes. The present study suggests, together with data from the literature, that the distribution of astrocytic OAP across the cell surface is influenced by the existence of a basal lamina and neuronal activity, and that astrocytes possess a more remarkable plasticity of membrane structure than previously suspected. 相似文献
10.
Sonya C. Bardswell Friederike Cuello Alexandra J. Rowland Sakthivel Sadayappan Jeffrey Robbins Mathias Gautel Jeffery W. Walker Jonathan C. Kentish Metin Avkiran 《The Journal of biological chemistry》2010,285(8):5674-5682
Protein kinase D (PKD), a serine/threonine kinase with emerging cardiovascular functions, phosphorylates cardiac troponin I (cTnI) at Ser22/Ser23, reduces myofilament Ca2+ sensitivity, and accelerates cross-bridge cycle kinetics. Whether PKD regulates cardiac myofilament function entirely through cTnI phosphorylation at Ser22/Ser23 remains to be established. To determine the role of cTnI phosphorylation at Ser22/Ser23 in PKD-mediated regulation of cardiac myofilament function, we used transgenic mice that express cTnI in which Ser22/Ser23 are substituted by nonphosphorylatable Ala (cTnI-Ala2). In skinned myocardium from wild-type (WT) mice, PKD increased cTnI phosphorylation at Ser22/Ser23 and decreased the Ca2+ sensitivity of force. In contrast, PKD had no effect on the Ca2+ sensitivity of force in myocardium from cTnI-Ala2 mice, in which Ser22/Ser23 were unavailable for phosphorylation. Surprisingly, PKD accelerated cross-bridge cycle kinetics similarly in myocardium from WT and cTnI-Ala2 mice. Because cardiac myosin-binding protein C (cMyBP-C) phosphorylation underlies cAMP-dependent protein kinase (PKA)-mediated acceleration of cross-bridge cycle kinetics, we explored whether PKD phosphorylates cMyBP-C at its PKA sites, using recombinant C1C2 fragments with or without site-specific Ser/Ala substitutions. Kinase assays confirmed that PKA phosphorylates Ser273, Ser282, and Ser302, and revealed that PKD phosphorylates only Ser302. Furthermore, PKD phosphorylated Ser302 selectively and to a similar extent in native cMyBP-C of skinned myocardium from WT and cTnI-Ala2 mice, and this phosphorylation occurred throughout the C-zones of sarcomeric A-bands. In conclusion, PKD reduces myofilament Ca2+ sensitivity through cTnI phosphorylation at Ser22/Ser23 but accelerates cross-bridge cycle kinetics by a distinct mechanism. PKD phosphorylates cMyBP-C at Ser302, which may mediate the latter effect. 相似文献