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排序方式: 共有215条查询结果,搜索用时 602 毫秒
31.
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Franco Klingberg Melissa L. Chow Anne Koehler Stellar Boo Lara Buscemi Thomas M. Quinn Mercedes Costell Benjamin A. Alman Elisabeth Genot Boris Hinz 《The Journal of cell biology》2014,207(2):283-297
Integrin-mediated force application induces a conformational change in latent TGF-β1 that leads to the release of the active form of the growth factor from the extracellular matrix (ECM). Mechanical activation of TGF-β1 is currently understood as an acute process that depends on the contractile force of cells. However, we show that ECM remodeling, preceding the activation step, mechanically primes latent TGF-β1 akin to loading a mechanical spring. Cell-based assays and unique strain devices were used to produce a cell-derived ECM of controlled organization and prestrain. Mechanically conditioned ECM served as a substrate to measure the efficacy of TGF-β1 activation after cell contraction or direct force application using magnetic microbeads. The release of active TGF-β1 was always higher from prestrained ECM as compared with unorganized and/or relaxed ECM. The finding that ECM prestrain regulates the bioavailability of TGF-β1 is important to understand the context of diseases that involve excessive ECM remodeling, such as fibrosis or cancer. 相似文献
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Suraj B. Baloda Gunnar Fröman Johan E. Peeters Torkel Wadström 《FEMS microbiology letters》1986,34(2):225-229
Abstract 32 different strains of Escherichia coli isolated from rabbits with diarrhoea were studied for cell-surface properties which may be involved in intestinal colonisation. Strains isolated from diarrhoeic suckling (6 strains) and weaning (26 strains) rabbits which were shown to attach to brush borders in vivo, showed high relative cell-surface hydrophobicity as determined by the Salt Aggregation Test (SAT) when grown on Colonisation Factor Antigen (CFA) agar at 33°C. Cells of these strains grown to express surface hydrophobicity were also defined as high, moderate or low binders of 125 I-fibronectin or its 125 I-29-kDa fragment in a standard binding assay. Based on these findings, we propose that binding to intestinal cell surface (mucus)-associated fibronectin may be an early important step in intestinal colonisation of the small bowel in enteropathogenic E. coli (EPEC) diarrhoea in rabbits and other animal species. 相似文献
35.
Francesca Munari Szabolcs Soeroes Hans Michael Zenn Adrian Schomburg Nils Kost Sabrina Schr?der Rebecca Klingberg Nasrollah Rezaei-Ghaleh Alexandra Stützer Kathy Ann Gelato Peter Jomo Walla Stefan Becker Dirk Schwarzer Bastian Zimmermann Wolfgang Fischle Markus Zweckstetter 《The Journal of biological chemistry》2012,287(40):33756-33765
Binding of heterochromatin protein 1 (HP1) to the histone H3 lysine 9 trimethylation (H3K9me3) mark is a hallmark of establishment and maintenance of heterochromatin. Although genetic and cell biological aspects have been elucidated, the molecular details of HP1 binding to H3K9me3 nucleosomes are unknown. Using a combination of NMR spectroscopy and biophysical measurements on fully defined recombinant experimental systems, we demonstrate that H3K9me3 works as an on/off switch regulating distinct binding modes of hHP1β to the nucleosome. The methyl-mark determines a highly flexible and very dynamic interaction of the chromodomain of hHP1β with the H3-tail. There are no other constraints of interaction or additional multimerization interfaces. In contrast, in the absence of methylation, the hinge region and the N-terminal tail form weak nucleosome contacts mainly with DNA. In agreement with the high flexibility within the hHP1β-H3K9me3 nucleosome complex, the chromoshadow domain does not provide a direct binding interface. Our results report the first detailed structural analysis of a dynamic protein-nucleosome complex directed by a histone modification and provide a conceptual framework for understanding similar interactions in the context of chromatin. 相似文献
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Midstream urine samples from 37 patients with urinary tract infections were studied by electron microscopy, hemagglutination, and the salt aggregation test (SAT) to measure the hydrophobicity of the bacterial surface.Escherichia coli subcultured from these urine samples were tested in the same way. Fimbriae were visualized onE. coli in the urine of 31 specimens, and all these urines containedE. coli that expressed pronounced surface hydrophobicity and aggregated in ammonium sulfate of 0.1–1.6 M final concentration. Hemagglutination of human and/or guinea pig erythrocytes was expressed by 21E. coli in the urine. TheE. coli strains subcultured from these 31 urine samples were also fimbriated, but the number of fimbriae per bacterium as well as the percentage of fimbriated bacteria varied compared with the directly collected strains. The surface hydrophobicity and hemagglutination were similar to the results with the directly collected bacteria. However, after serial transfer in CFA-broth under static conditions, all non-hemagglutinating strains expressed mannose-sensitive hemagglutination of guinea pig erythrocytes, and three strains also expressed weak mannose-resistant hemagglutination of human erythrocytes. Following serial transfer, fimbriae were also visualized on the sixE. coli strains that appeared non-fimbriate in the urine. It is thus concluded thatE. coli causing urinary tract infection are often fimbriated and express surface hydrophobicity in the urine. Based on these findings, a rapid method to isolate hydrophobic, possibly fimbriated bacteria was tried in which the urine was mixed with a hydrophobic gel. Hydrophobic bacteria bound to the gel and could be eluted from the sedimented gel. 相似文献
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The production of heat-stable and heat-labile enterotoxins byYersinia enterocolitica was studied in 69 strains from healthy swine and in 24 strains from humans with acute diarrhea. All of the human strains
were of serotype O3, and 20 (83%) of them produced heat-stable enterotoxin detectable in the infant mouse assay. All were
negative in the Chinese Hamster Ovary (CHO) cell test for detection of heat-labile enterotoxin. Of the 69 porcine strains,
which were of twelve serotypes plus 9 nontypable strains, 26 (38%) gave a positive infant mouse test. Of the porcine isolates
of serotype O3, 42% were enterotoxigenic. A high incidence of enterotoxigenicity was also apparent among six other serotypes
(53%). All porcine strains were negative in the CHO cell test. However, of seven culture supernatants from these porcine strains,
three gave positive reactions in rabbit skin permeability tests, two of which were also positive in rabbit loop tests. Heat
treatment of the supernatants abolished the reactivity in both tests. It is concluded that production of a heatstable enterotoxin
is fairly common in porcine and human strains ofY. enterocolitica of serotype O3 in Sweden. 相似文献
39.
Effects of a storm event on the structure of the pelagic food web with special emphasis on planktonic ciliates 总被引:1,自引:0,他引:1
Storm-induced changes in the water column structure and thepelagic food web were investigated by daily sampling duringa 3 week period (October 24 to November 10, 1988) at a permanentstation in the southern Kattegat (Denmark) Subsequent to a stormthe primary production increased and the size-distribution ofthe phytoplankton changed towards larger cells. Some componentsof the zooplankton community responded to the increase in potentialfood, either in terms of a functional response (copepods) orin terms of a numerical response (cladocera), whereas no changesin the populations of mixo- and heterotrophic aliates were evident.The dilates were not food limited since growth rates determinedin situ were comparable to maximum growth rates measured inthe laboratory. Calculations suggest that the total clearancecapacity of planktonic copepods (as fraction of water columncleared per unit time) was of the same magnitude as the measuredinstantaneous growth rates of the ciliates (0.550 85day1). Ciliate populations were therefore probably limitedby copepod predation. Ciliates, however, contributed only insignificantlyto the diets of copepods. Although the total zooplankton productionincreased by at least 30% subsequent to the storm (and thatof the copepods by 50%), the zooplankton community was unableto assimilate the entire increase in primary production. Therelative zooplankton (copepods, cladoceran and ciliates) grazingrate on the primary production decreased 30%, and the flow ofcarbon to biomass accumulation, other grazers and in particularsedimentation is predicted to have increased by 100% followingthe storm. 相似文献
40.