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排序方式: 共有195条查询结果,搜索用时 15 毫秒
101.
Margery L Evans Jens C Schmidt Marianne Ilbert Shannon M Doyle Shu Quan James CA Bardwell Ursula Jakob Sue Wickner Matthew R Chapman 《朊病毒》2011,5(4):323-334
Amyloid formation is an ordered aggregation process, where β-sheet rich polymers are assembled from unstructured or partially folded monomers. We examined how two Escherichia coli cytosolic chaperones, DnaK and Hsp33, and a more recently characterized periplasmic chaperone, Spy, modulate the aggregation of a functional amyloid protein, CsgA. We found that DnaK, the Hsp70 homolog in E. coli, and Hsp33, a redox-regulated holdase, potently inhibited CsgA amyloidogenesis. The Hsp33 anti-amyloidogenesis activity was oxidation dependent, as oxidized Hsp33 was significantly more efficient than reduced Hsp33 at preventing CsgA aggregation. When soluble CsgA was seeded with preformed amyloid fibers, neither Hsp33 nor DnaK were able to efficiently prevent soluble CsgA from adopting the amyloid conformation. Moreover, both DnaK and Hsp33 increased the time that CsgA was reactive with the amyloid oligomer conformation-specific A11 antibody. Since CsgA must also pass through the periplasm during secretion, we assessed the ability of the periplasmic chaperone Spy to inhibit CsgA polymerization. Like DnaK and Hsp33, Spy also inhibited CsgA polymerization in vitro. Overexpression of Spy resulted in increased chaperone activity in periplasmic extracts and in reduced curli biogenesis in vivo. We propose that DnaK, Hsp33 and Spy exert their effects during the nucleation stages of CsgA fibrillation. Thus, both housekeeping and stress induced cytosolic and periplasmic chaperones may be involved in discouraging premature CsgA interactions during curli biogenesis.Key words: chaperone, curli, functional amyloid, CsgA, DnaK, Hsp33, Spy 相似文献
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104.
CA Lei- CHEN Run-Zheng- YIN Zhi-Jian- ZHANG Guo-Xue- CHEN Wen-Hong- SHUI Yu-Min 《Plant Diversity》2015,37(6):733-736
A new species of Gesneriaceae from Honghe County, Southeastern Yunnan, China, Tremacron hongheense WH. Chen & YM. Shui, is described and illustrated. The new species is similar to Tremacron forrestii Craib, but differs by its leaf blade adaxially sparsely long setose (vs. densely white appressed pubescent and sparsely rusty brown villous), corolla tube outside short white glandular (vs. nearly glabrous), corolla lobes red and thickening at apex, especially adaxial lip (vs. yellow and not thickening), stamens 16-18cm long (vs. 04-12cm long), staminode 05-14cm long (vs. 02-04cm long). 相似文献
105.
Grasslands are one of the most widespread landscapes worldwide, covering approximately one-fifth of the world’s land surface, where grazing is a common practice. How carbon storage responds to grazing in steppes remains poorly understood. We quantified the effects of grazing on community composition and species diversity, and carbon storage in two typical grasslands of northeastern China, one in Horqin and the other one in Hulunbeier. In both grasslands, grazing did not influence plant species diversity. However, it substantially decreased aboveground carbon by 31% and 54% in Horqin and Hulunbeier, respectively. Fenced and grazing treatments showed a similar belowground carbon at both locations. The predominant carbon pool in the study grassland ecosystem was found in the upper 100 cm soil depth, from 98.2 to 99.1% of the total carbon storage. There were no significant effects of grazing on soil carbon neither in the whole profile nor in the uppermost 20 cm soil depth in the two study grasslands. Studies on the effects of varying rangeland management, such as region disparity and grazing systems, may have important consequences on species diversity and carbon partitioning, and thus on rangeland stability and ecosystem functioning. 相似文献
106.
Tree range expansion in eastern North America fails to keep pace with climate warming at northern range limits 下载免费PDF全文
Fabian Sittaro Alain Paquette Christian Messier Charles A. Nock 《Global Change Biology》2017,23(8):3292-3301
Rising global temperatures are suggested to be drivers of shifts in tree species ranges. The resulting changes in community composition may negatively impact forest ecosystem function. However, long‐term shifts in tree species ranges remain poorly documented. We test for shifts in the northern range limits of 16 temperate tree species in Quebec, Canada, using forest inventory data spanning three decades, 15° of longitude and 7° of latitude. Range shifts were correlated with climate warming and dispersal traits to understand potential mechanisms underlying changes. Shifts were calculated as the change in the 95th percentile of latitudinal occurrence between two inventory periods (1970–1978, 2000–2012) and for two life stages: saplings and adults. We also examined sapling and adult range offsets within each inventory, and changes in the offset through time. Tree species ranges shifted predominantly northward, although species responses varied. As expected shifts were greater for tree saplings, 0.34 km yr?1, than for adults, 0.13 km yr?1. Range limits were generally further north for adults compared to saplings, but the difference diminished through time, consistent with patterns observed for range shifts within each life stage. This suggests caution should be exercised when interpreting geographic range offsets between life stages as evidence of range shifts in the absence of temporal data. Species latitudinal velocities were on average <50% of the velocity required to equal the spatial velocity of climate change and were mostly unrelated to dispersal traits. Finally, our results add to the body of evidence suggesting tree species are mostly limited in their capacity to track climate warming, supporting concerns that warming will negatively impact the functioning of forest ecosystems. 相似文献
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Craig J Smith Hedley CA Emsley Carole M Gavin Rachel F Georgiou Andy Vail Elisa M Barberan Gregory J del Zoppo John M Hallenbeck Nancy J Rothwell Stephen J Hopkins Pippa J Tyrrell 《BMC neurology》2004,4(1):1-8
Background
Cerebral ischaemia initiates an inflammatory response in the brain and periphery. We assessed the relationship between peak values of plasma interleukin-6 (IL-6) in the first week after ischaemic stroke, with measures of stroke severity and outcome.Methods
Thirty-seven patients with ischaemic stroke were prospectively recruited. Plasma IL-6, and other markers of peripheral inflammation, were measured at pre-determined timepoints in the first week after stroke onset. Primary analyses were the association between peak plasma IL-6 concentration with both modified Rankin score (mRS) at 3 months and computed tomography (CT) brain infarct volume.Results
Peak plasma IL-6 concentration correlated significantly (p < 0.001) with CT brain infarct volume (r = 0.75) and mRS at 3 months (r = 0.72). It correlated similarly with clinical outcome at 12 months or stroke severity. Strong associations were also noted between either peak plasma C-reactive protein (CRP) concentration or white blood cell (WBC) count, and all outcome measures.Conclusions
These data provide evidence that the magnitude of the peripheral inflammatory response is related to the severity of acute ischaemic stroke, and clinical outcome. 相似文献109.
Aikaterini A. Zompra Vassiliki Magafa Dimitra G. Chryssanthi Fotini N. Lamari Georgios A. Spyroulias Theodosia Maina Berthold A. Nock Nikos K. Karamanos Paul Cordopatis 《International journal of peptide research and therapeutics》2007,13(1-2):143-149
GnRH analogues have been extensively used in oncology to induce reversible chemical castration due to their hypophysiotropic
action. In addition to that, it has recently been shown that many malignant cells, such as breast cancer cells, locally produce
GnRH and express the GnRH receptor/s. In order to investigate the structure-activity relationships in both pituitary and extrapituitary
biological systems, we synthesized eight new GnRH analogues with modifications in the N-terminal part and/or in position 6
and studied their pituitary binding affinity (in αT3-1 cell membranes) and effect on breast cancer (MCF-7) cell proliferation.
2-Amino-4-pyrrolidinothieno[2,3-d]pyrimidine-6-carboxylic acid (ATPC) was incorporated instead of pGlu1-His2- and/or Gly6 was substituted by α-aminoisobutyric acid, D-Leu and D-Lys (alone or covalently linked to Gly, Ala, Sar, ATPC). Most GnRH
analogues lacked the carboxy-terminal Gly10-amide of GnRH and an ethylamide residue was added to Pro9, a modification common in many potent GnRH agonists, such as leuprolide ([D-Leu6, des-Gly10]-GnRH-NHEt. Results show differential impact of these modifications on the binding affinity to the GnRH receptor in mouse
pituitary cells and on the inhibition of human breast cancer cell proliferation. ATPC in the N-terminus resulted in analogues
with low binding affinity but high antiproliferative effect. Substitutions in position 6 always resulted in high binding affinities.
In particular, [D-Lys6(Gly), desGly10]-GnRH-NHEt and [D-Lys6(Sar), desGly10]-GnRH-NHEt have higher pituitary binding affinity than leuprolide, but only the latter had significant antiproliferative
effect on both MCF-7 and MDA-MB-231 cells. These results contribute to the on-going research for more potent GnRH analogues.
Abbreviations of common amino acids are in accordance with the recommendations of IUPAC-IUB Joint Commission on Biochemical
Nomenclature: Arch. Biochem. Biophys. 206, pp.v-xxii (1988), J. Biol. Chem. 264, 668–673 (1989) or J. Peptide Sci. 9, 1–8
(2003). 相似文献
110.
Germana B Rona Natalia P Almeida Gilson C Santos Jr Tatiana KS Fidalgo Fabio CL Almeida Elis CA Eleutherio Anderson S Pinheiro 《Journal of cellular biochemistry》2019,120(4):5377-5385
NSD3s, the proline-tryptophan-tryptophan-proline (PWWP) domain-containing, short isoform of the human oncoprotein NSD3, displays high transforming properties. Overexpression of human NSD3s or the yeast protein Pdp3 in Saccharomyces cerevisiae induces similar metabolic changes, including increased growth rate and sensitivity to oxidative stress, accompanied by decreased oxygen consumption. Here, we set out to elucidate the biochemical pathways leading to the observed metabolic phenotype by analyzing the alterations in yeast metabolome in response to NSD3s or Pdp3 overexpression using 1H nuclear magnetic resonance (NMR) metabolomics. We observed an increase in aspartate and alanine, together with a decrease in arginine levels, on overexpression of NSD3s or Pdp3, suggesting an increase in the rate of glutaminolysis. In addition, certain metabolites, including glutamate, valine, and phosphocholine were either NSD3s or Pdp3 specific, indicating that additional metabolic pathways are adapted in a protein-dependent manner. The observation that certain metabolic pathways are differentially regulated by NSD3s and Pdp3 suggests that, despite the structural similarity between their PWWP domains, the two proteins act by unique mechanisms and may recruit different downstream signaling complexes. This study establishes for the first time a functional link between the human oncoprotein NSD3s and cancer metabolic reprogramming. 相似文献