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排序方式: 共有980条查询结果,搜索用时 15 毫秒
71.
Kenneth Hensley Quentin N. Pye Michael L. Maidt Charles A. Stewart Kent A. Robinson Fatima Jaffrey Robert A. Floyd 《Journal of neurochemistry》1998,71(6):2549-2557
Abstract: Mitochondrial complexes I, II, and III were studied in isolated brain mitochondrial preparations with the goal of determining their relative abilities to reduce O2 to hydrogen peroxide (H2 O2 ) or to reduce the alternative electron acceptors nitroblue tetrazolium (NBT) and diphenyliodonium (DPI). Complex I and II stimulation caused H2 O2 formation and reduced NBT and DPI as indicated by dichlorodihydrofluorescein oxidation, nitroformazan precipitation, and DPI-mediated enzyme inactivation. The O2 consumption rate was more rapid under complex II (succinate) stimulation than under complex I (NADH) stimulation. In contrast, H2 O2 generation and NBT and DPI reduction kinetics were favored by NADH addition but were virtually unobservable during succinate-linked respiration. NADH oxidation was strongly suppressed by rotenone, but NADH-coupled H2 O2 flux was accelerated by rotenone. α-Phenyl- N-tert -butyl nitrone (PBN), a compound documented to inhibit oxidative stress in models of stroke, sepsis, and parkinsonism, partially inhibited complex I-stimulated H2 O2 flux and NBT reduction and also protected complex I from DPI-mediated inactivation while trapping the phenyl radical product of DPI reduction. The results suggest that complex I may be the principal source of brain mitochondrial H2 O2 synthesis, possessing an "electron leak" site upstream from the rotenone binding site (i.e., on the NADH side of the enzyme). The inhibition of H2 O2 production by PBN suggests a novel explanation for the broad-spectrum antioxidant and antiinflammatory activity of this nitrone spin trap. 相似文献
72.
Markus K Muellner Barbara Mair Yasir Ibrahim Claudia Kerzendorfer Hannelore Lechtermann Claudia Trefzer Freya Klepsch André C Müller Ernestine Leitner Sabine Macho‐Maschler Giulio Superti‐Furga Keiryn L Bennett José Baselga Uwe Rix Stefan Kubicek Jacques Colinge Violeta Serra Sebastian MB Nijman 《Molecular systems biology》2015,11(2)
73.
Melanie Brügger Thomas Dmoulins G. Tuba Barut Beatrice Zumkehr Blandina I. Oliveira Esteves Kemal Mehinagic Quentin Haas Aline Schgler Marie-Anne Rameix-Welti Jean-Franois Elouët Ueli Moehrlen Thomas M. Marti Ralph A. Schmid Artur Summerfield Horst Posthaus Nicolas Ruggli Sean R. R. Hall Marco P. Alves 《PLoS pathogens》2021,17(7)
74.
Biochemical reaction networks are subjected to large fluctuations attributable to small molecule numbers, yet underlie reliable biological functions. Thus, it is important to understand how regularity can emerge from noise. Here, we study the stochastic dynamics of a self-repressing gene with arbitrarily long or short response time. We find that when the mRNA and protein half-lives are approximately equal to the gene response time, fluctuations can induce relatively regular oscillations in the protein concentration. To gain insight into this phenomenon at the crossroads of determinism and stochasticity, we use an intermediate theoretical approach, based on a moment-closure approximation of the master equation, which allows us to take into account the binary character of gene activity. We thereby obtain differential equations that describe how nonlinearity can feed-back fluctuations into the mean-field equations to trigger oscillations. Finally, our results suggest that the self-repressing Hes1 gene circuit exploits this phenomenon to generate robust oscillations, inasmuch as its time constants satisfy precisely the conditions we have identified. 相似文献
75.
Sandra Namoff Quentin Luke Francisco Jiménez Alberto Veloz Carl E. Lewis Victoria Sosa Mike Maunder Javier Francisco-Ortega 《Journal of plant research》2010,123(1):57-65
Phylogenetic analyses of nucleotide sequences of the internal transcribed spacers and 5.8 regions of the nuclear ribosomal
DNA and of the trnH-psbA spacer of the chloroplast genome confirm that the three taxa of the Jacquemontia ovalifolia (Choicy) Hallier f. complex (Convolvulaceae) form a monophyletic group. Levels of nucleotide divergence and morphological
differentiation among these taxa support the view that each should be recognized as distinct species. These three species
display unique intercontinental disjunction, with one species endemic to Hawaii (Jacquemontia sandwicensis A. Gray.), another restricted to eastern Mexico and the Antilles [Jacquemontia obcordata (Millspaugh) House], and the third confined to East and West Africa (J. ovalifolia). The Caribbean and Hawaiian species are sister taxa and are another example of a biogeographical link between the Caribbean
Basin and Polynesia. We provide a brief conservation review of the three taxa based on our collective field work and investigations;
it is apparent that J. obcordata is highly threatened and declining in the Caribbean. 相似文献
76.
Dempewolf H Kane NC Ostevik KL Geleta M Barker MS Lai Z Stewart ML Bekele E Engels JM Cronk QC Rieseberg LH 《Molecular ecology resources》2010,10(6):1048-1058
We present an EST library, chloroplast genome sequence, and nuclear microsatellite markers that were developed for the semi-domesticated oilseed crop noug (Guizotia abyssinica) from Ethiopia. The EST library consists of 25 711 Sanger reads, assembled into 17 538 contigs and singletons, of which 4781 were functionally annotated using the Arabidopsis Information Resource (TAIR). The age distribution of duplicated genes in the EST library shows evidence of two paleopolyploidizations—a pattern that noug shares with several other species in the Heliantheae tribe (Compositae family). From the EST library, we selected 43 microsatellites and then designed and tested primers for their amplification. The number of microsatellite alleles varied between 2 and 10 (average 4.67), and the average observed and expected heterozygosities were 0.49 and 0.54, respectively. The chloroplast genome was sequenced de novo using Illumina’s sequencing technology and completed with traditional Sanger sequencing. No large re-arrangements were found between the noug and sunflower chloroplast genomes, but 1.4% of sites have indels and 1.8% show sequence divergence between the two species. We identified 34 tRNAs, 4 rRNA sequences, and 80 coding sequences, including one region (trnH-psbA) with 15% sequence divergence between noug and sunflower that may be particularly useful for phylogeographic studies in noug and its wild relatives. 相似文献
77.
78.
Schlaitz AL Srayko M Dammermann A Quintin S Wielsch N MacLeod I de Robillard Q Zinke A Yates JR Müller-Reichert T Shevchenko A Oegema K Hyman AA 《Cell》2007,128(1):115-127
Microtubule behavior changes during the cell cycle and during spindle assembly. However, it remains unclear how these changes are regulated and coordinated. We describe a complex that targets the Protein Phosphatase 2A holoenzyme (PP2A) to centrosomes in C. elegans embryos. This complex includes Regulator of Spindle Assembly 1 (RSA-1), a targeting subunit for PP2A, and RSA-2, a protein that binds and recruits RSA-1 to centrosomes. In contrast to the multiple functions of the PP2A catalytic subunit, RSA-1 and RSA-2 are specifically required for microtubule outgrowth from centrosomes and for spindle assembly. The centrosomally localized RSA-PP2A complex mediates these functions in part by regulating two critical mitotic effectors: the microtubule destabilizer KLP-7 and the C. elegans regulator of spindle assembly TPXL-1. By regulating a subset of PP2A functions at the centrosome, the RSA complex could therefore provide a means of coordinating microtubule outgrowth from centrosomes and kinetochore microtubule stability during mitotic spindle assembly. 相似文献
79.
Marcelo R. de Carvalho Flávio A. Bockmann Dalton S. Amorim Carlos Roberto F. Brandão Mário de Vivo José L. de Figueiredo Heraldo A. Britski Mário C. C. de Pinna Naércio A. Menezes Fernando P. L. Marques Nelson Papavero Eliana M. Cancello Jorge V. Crisci John D. McEachran Robert C. Schelly John G. Lundberg Anthony C. Gill Ralf Britz Quentin D. Wheeler Melanie L. J. Stiassny Lynne R. Parenti Larry M. Page Ward C. Wheeler Julián Faivovich Richard P. Vari Lance Grande Chris J. Humphries Rob DeSalle Malte C. Ebach Gareth J. Nelson 《Evolutionary biology》2007,34(3-4):140-143
80.
Human immunodeficiency virus type 1 assembly, budding, and cell-cell spread in T cells take place in tetraspanin-enriched plasma membrane domains 总被引:8,自引:4,他引:4 下载免费PDF全文
Human immunodeficiency virus type-1 (HIV-1) egress from infected CD4+ T cells is thought to be via assembly and budding at the plasma membrane and may involve components of the T-cell secretory apparatus, including tetraspanins. However, many studies on HIV-1 assembly have examined the trafficking of viral proteins in isolation, and most have used immortalized epithelial, fibroblastic, or hematopoietic cell lines that may not necessarily reflect natural infection of susceptible T cells. Here we have used immunofluorescence and cryoimmunoelectron microscopy (CEM) to examine protein transport during HIV-1 assembly in productively infected Jurkat CD4+ T cells and primary CD4+ T cells. The HIV-1 envelope glycoprotein (Env) and the core protein (Gag) colocalize strongly with CD63 and CD81 and less strongly with CD9, whereas no colocalization was seen between Env or Gag and the late endosome/lysosomal marker Lamp2. CEM revealed incorporation of CD63 and CD81 but not Lamp2 into virions budding at the plasma membrane, and this was supported by immunoprecipitation studies, confirming that HIV-1 egress in T cells is trafficked via tetraspanin-enriched membrane domains (TEMs) that are distinct from lysosomal compartments. CD63, CD81, and, to a lesser extent, CD9 were recruited to the virological synapse (VS), and antibodies against these tetraspanins reduced VS formation. We propose that HIV-1 promotes virus assembly and cell-cell transfer in T cells by targeting plasma membrane TEMs. 相似文献