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排序方式: 共有640条查询结果,搜索用时 359 毫秒
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Barbara Zerega Aldo Pagano Ada Pianezzi Valentina Ulivi Laura Camardella Ranieri Cancedda Fiorella Descalzi Cancedda 《Matrix biology》2004,23(1):35-46
Serum amyloid A (SAA) is synthesized by the liver during the acute phase. Local expression of SAA mRNA has been reported also in non-liver cells, a potential local source of SAA protein not related to the systemic acute phase response. SAA function has not been established yet. In the present study, we identified SAA as a protein expressed by chondrocytes and myoblasts in response to inflammatory stimula. In both cell systems, SAA mRNA and protein expression is strongly stimulated by bacterial lipopolysaccharide treatment. SAA mRNA expression is also enhanced during terminal differentiation of cells of the chondrogenic and myogenic lineage; mRNA is barely detectable in prechondrogenic cells and is highly expressed in differentiated hyperthrophic chondrocytes. An increased level of SAA mRNA was also observed in vivo when we compared mRNA extracted from tibiae of 10 day embryos, still fully cartilaginous, with tibiae from 18 day embryos, a stage when the endochondral ossification process has already started. p38 activation, a well-known event of the chondrogenesis signaling cascade, controls expression of SAA in cartilage following inflammatory stimuli. SAA secreted by stimulated chondrocytes is associated with cholesterol. Cholesterol is synthesized by the same chondrocytes and is also increased in inflammatory conditions. A role of SAA in cholesterol homeostasis in chondrocytes is proposed. 相似文献
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Séveno M Cabrera G Triguero A Burel C Leprince J Rihouey C Vézina LP D'Aoust MA Rudd PM Royle L Dwek RA Harvey DJ Lerouge P Cremata JA Bardor M 《Analytical biochemistry》2008,379(1):66-72
Development of convenient strategies for identification of plant N-glycan profiles has been driven by the emergence of plants as an expression system for therapeutic proteins. In this article, we reinvestigated qualitative and quantitative aspects of plant N-glycan profiling. The extraction of plant proteins through a phenol/ammonium acetate procedure followed by deglycosylation with peptide N-glycosidase A (PNGase A) and coupling to 2-aminobenzamide provides an oligosaccharide preparation containing reduced amounts of contaminants from plant cell wall polysaccharides. Such a preparation was also suitable for accurate qualitative and quantitative evaluation of the N-glycan content by mass spectrometry. Combining these approaches allows the profiling to be carried out from as low as 500 mg of fresh leaf material. We also demonstrated that collision-induced dissociation (CID) mass spectrometry in negative mode of N-glycans harboring α(1,3)- or α(1,6)-fucose residue on the proximal GlcNAc leads to specific fragmentation patterns, thereby allowing the discrimination of plant N-glycans from those arising from mammalian contamination. 相似文献
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Alfredo Téllez-Valencia Ada A. Sandoval Mario Pedraza-Reyes 《Current microbiology》2003,46(4):0307-0310
The modular endocellulase Cel9 of the bicistronic operon cel9-cel48 of Myxobacter sp. AL-1 shares not only amino acid sequence similarity but also biochemical properties similar to those of Thermobifida fusca endo/exocellulase E4. Amino acid alignments of a T. fusca E4 cellulase subfamily of family 9 cellulases revealed that Asp446 of Myxobacter sp. AL-1 Cel9, a putatively noncatalytic residue, is highly conserved in one of the catalytic domains of this subfamily.
Directed mutagenesis of residue aspartate (Asp446) to alanine generated a Cel9 mutant that lost more than 99% of its activity, suggesting that Asp446 plays an essential structural role in Cel9 during cellulose degradation. Owing to its high degree of conservation and essential
role, we propose that Asp446 of Myxobacter sp. AL-1 Cel9 is a good landmark that distinguishes members of the E4 subfamily of family 9 cellulases.
Received: 4 May 2002 / Accepted: 5 July 2002 相似文献
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Katrin B?ttger Haralambos Hatzikirou Anja Voss-B?hme Elisabetta Ada Cavalcanti-Adam Miguel A. Herrero Andreas Deutsch 《PLoS computational biology》2015,11(9)
Tumor cells develop different strategies to cope with changing microenvironmental conditions. A prominent example is the adaptive phenotypic switching between cell migration and proliferation. While it has been shown that the migration-proliferation plasticity influences tumor spread, it remains unclear how this particular phenotypic plasticity affects overall tumor growth, in particular initiation and persistence. To address this problem, we formulate and study a mathematical model of spatio-temporal tumor dynamics which incorporates the microenvironmental influence through a local cell density dependence. Our analysis reveals that two dynamic regimes can be distinguished. If cell motility is allowed to increase with local cell density, any tumor cell population will persist in time, irrespective of its initial size. On the contrary, if cell motility is assumed to decrease with respect to local cell density, any tumor population below a certain size threshold will eventually extinguish, a fact usually termed as Allee effect in ecology. These results suggest that strategies aimed at modulating migration are worth to be explored as alternatives to those mainly focused at keeping tumor proliferation under control. 相似文献
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How to deal with ground truthing affected by human‐induced habitat change?: Identifying high‐quality habitats for the Critically Endangered Red Siskin 下载免费PDF全文
Ada Sánchez‐Mercado Kathryn M. Rodríguez‐Clark Jhonathan Miranda José Rafael Ferrer‐Paris Brian Coyle Samuel Toro Arlene Cardozo‐Urdaneta Michael J. Braun 《Ecology and evolution》2018,8(2):841-851
Species distribution models (SDM) can be valuable for identifying key habitats for conservation management of threatened taxa, but anthropogenic habitat change can undermine SDM accuracy. We used data for the Red Siskin (Spinus cucullatus), a critically endangered bird and ground truthing to examine anthropogenic habitat change as a source of SDM inaccuracy. We aimed to estimate: (1) the Red Siskin's historic distribution in Venezuela; (2) the portion of this historic distribution lost to vegetation degradation; and (3) the location of key habitats or areas with both, a high probability of historic occurrence and a low probability of vegetation degradation. We ground‐truthed 191 locations and used expert opinion as well as landscape characteristics to classify species' habitat suitability as excellent, good, acceptable, or poor. We fit a Random Forest model (RF) and Enhanced Vegetation Index (EVI) time series to evaluate the accuracy and precision of the expert categorization of habitat suitability. We estimated the probability of historic occurrence by fitting a MaxLike model using 88 presence records (1960–2013) and data on forest cover and aridity index. Of the entire study area, 23% (20,696 km2) had a historic probability of Red Siskin occurrence over 0.743. Furthermore, 85% of ground‐truthed locations had substantial reductions in mean EVI, resulting in key habitats totaling just 976 km2, in small blocks in the western and central regions. Decline in Area of Occupancy over 15 years was between 40% and 95%, corresponding to an extinction risk category between Vulnerable and Critically Endangered. Relating key habitats with other landscape features revealed significant risks and opportunities for proposed conservation interventions, including the fact that ongoing vegetation degradation could limit the establishment of reintroduced populations in eastern areas, while the conservation of remaining key habitats on private lands could be improved with biodiversity‐friendly agri‐ and silviculture programs. 相似文献