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91.
Membrane Transport in Isolated Vesicles from Sugarbeet Taproot : II. Evidence for a Sucrose/H-Antiport 总被引:6,自引:6,他引:0 下载免费PDF全文
The process of sucrose transport was investigated in sealed putative tonoplast vesicles isolated from sugarbeet (Beta vulgaris L.) taproot. If the vesicles were allowed to develop a steady state pH gradient by the associated transport ATPase and 10 millimolar sucrose was added, a transient flux of protons out of the vesicles was observed. The presence of an ATPase produced pH gradient allowed [14C]sucrose transport into the vesicles to occur at a rate 10-fold higher than the rate observed in the absence of an imposed pH gradient. Labeled sucrose accumulated into the sealed vesicles could be released back to the external medium if the pH gradient was dissipated with carbonylcyanide-m-chlorophenyl hydrazone (CCCP). When the kinetics of ATP dependent [14C]sucrose uptake were examined, the kinetic profile followed the simple Michaelis-Menten relationship and a Michaelis constant of 12.1 millimolar was found. When a transient, inwardly directed sucrose gradient was imposed on the vesicles in the absence of charge compensating ions, a transient interior negative membrane potential was observed. This membrane potential could be prevented by the addition of CCCP prior to sucrose or dissipated by the addition of CCCP after sucrose was added. These results suggest that an electrogenic H+/sucrose antiport may be operating on the vesicle membrane. 相似文献
92.
Inhibition of plant acetyl-coenzyme A carboxylase by the herbicides sethoxydim and haloxyfop 总被引:14,自引:0,他引:14
J D Burton J W Gronwald D A Somers J A Connelly B G Gengenbach D L Wyse 《Biochemical and biophysical research communications》1987,148(3):1039-1044
Incorporation of [14C]acetate or [14C]pyruvate into fatty acids in isolated corn seedling chloroplasts was inhibited 90% or greater by 10 microM sethoxydim or 1 microM haloxyfop. At these concentrations, neither sethoxydim nor haloxyfop inhibited [14C]acetate incorporation into fatty acids in isolated pea chloroplasts. Sethoxydim (10 microM) and haloxyfop (1 microM) did not inhibit incorporation of [14C]malonyl-CoA into fatty acids in cell free extracts from corn tissue cultures. Acetyl coenzyme A carboxylase (EC 6.4.1.2) from corn seedling chloroplasts was inhibited by both sethoxydim and haloxyfop, with I50 values of 2.9 and 0.5 microM, respectively. This enzyme in pea was not inhibited by 10 microM sethoxydim or 1 microM haloxyfop. 相似文献
93.
Albert Y. Chang Beatrice M. Wyse 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,672(3):239-247
An epithelial cell line, designated CHK-ACE, was established from the kidney of a spontaneously diabetic Chinese hamster from the highly inbred AC line. CHK-ACE was separated into two sublines, CHK-ACE-100 and CHK-ACE-400, by successive passages in 100 and 400 mg/dl glucose respectively. Extra- and intracellular activities of and β-D-galactosidase were measured in these cultures after exposure to varying concentrations of glucose (100, 200, 300 and 400 mg/dl) for one passage and 10% heated fetal calf serum for 6.5 h before enzyme measurements were taken; no apparent dependence on medium-glucose concentration was found. In serum-free medium, the time-dependent release of both and β-D-galactosidase was sustained for up to 24 h; no significant difference in their activities was found between CHK-ACE-100 cultures grown in 100 and 400 mg/dl glucose for one passage. 相似文献
94.
Typifications and new nomenclatural combinations in Nordic Cerastium fontanum taxa (Caryophyllaceae)
Michael B. Wyse Jackson 《Nordic Journal of Botany》2000,20(5):531-535
Nomenclatural types for Cerastium fontanum Baumg. and infra-specific taxa occurring in the Nordic region are designated. Five new combinations (comb. nov. or stat. nov.) are made. — Flora Nordica Notes No. 29. 相似文献
95.
96.
The conifer Agathis australis (New Zealand kauri; Araucariaceae) has a significant influence on soil processes beneath its canopies, reducing soil pH, stalling nitrogen cycling processes, and sometimes forming podzols. Distinctive plant species assemblages have been anecdotally observed to occur in association with A. australis stands; however, the authenticity of these proposed associations has not been formally assessed. Owing to the effects of A. australis on its soil environment and the recorded vegetation patterns, we hypothesized that this species may act as a foundation species, playing a significant role in structuring plant community composition in its vicinity. To test this, we investigated the influence of proximity to A. australis on plant community composition at stand and individual tree scales. We also investigated compositional variation with distance from the conifer Dacrydium cupressinum (rimu, Podocarpaceae) within the same forests to directly compare A. australis effects to those of another large conifer. We examined changes in stand composition relative to the abundance of each of these conifers at two forests, and measured changes in environmental conditions and plant composition with increasing distance from mature individuals at one of the same and one other study site. The organic soil formed beneath A. australis individuals was highly acidic, with high levels of NH4‐N, carbon and total nitrogen, but low levels of NO3‐N. We recorded a difference in species composition in the vicinity of A. australis compared to forest without this species in the same environment, describing three groups of species: stress‐tolerant species dependent on the presence of A. australis within mature forest; those dependent on areas with A. australis absent; and those with distributions unaffected by A. australis presence. Such effects on the abiotic and biotic environments were not recorded in the vicinity of individuals of D. cupressinum. These results highlight the substantial effect that A. australis has in enhancing landscape‐scale habitat heterogeneity and influencing overall forest diversity. 相似文献
97.
98.
Sean R Landman Tae Hyun Hwang Kevin AT Silverstein Yingming Li Scott M Dehm Michael Steinbach Vipin Kumar 《BMC genomics》2014,15(1)
Background
Personal genome assembly is a critical process when studying tumor genomes and other highly divergent sequences. The accuracy of downstream analyses, such as RNA-seq and ChIP-seq, can be greatly enhanced by using personal genomic sequences rather than standard references. Unfortunately, reads sequenced from these types of samples often have a heterogeneous mix of various subpopulations with different variants, making assembly extremely difficult using existing assembly tools. To address these challenges, we developed SHEAR (Sample Heterogeneity Estimation and Assembly by Reference; http://vk.cs.umn.edu/SHEAR), a tool that predicts SVs, accounts for heterogeneous variants by estimating their representative percentages, and generates personal genomic sequences to be used for downstream analysis.Results
By making use of structural variant detection algorithms, SHEAR offers improved performance in the form of a stronger ability to handle difficult structural variant types and better computational efficiency. We compare against the lead competing approach using a variety of simulated scenarios as well as real tumor cell line data with known heterogeneous variants. SHEAR is shown to successfully estimate heterogeneity percentages in both cases, and demonstrates an improved efficiency and better ability to handle tandem duplications.Conclusion
SHEAR allows for accurate and efficient SV detection and personal genomic sequence generation. It is also able to account for heterogeneous sequencing samples, such as from tumor tissue, by estimating the subpopulation percentage for each heterogeneous variant.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-84) contains supplementary material, which is available to authorized users. 相似文献99.
Feksa LR Latini A Rech VC Wajner M Dutra-Filho CS de Souza Wyse AT Wannmacher CM 《Neurochemistry international》2006,49(1):87-93
Despite the significant brain abnormalities, the neurotoxic mechanisms of brain injury in hypertryptophanemia are virtually unknown. In this work, it was investigated the in vitro effect of l-tryptophan on various parameters of oxidative stress, namely spontaneous chemiluminescence, thiobarbituric acid-reactive substances (TBA-RS), total radical-trapping antioxidant potential (TRAP), total antioxidant reactivity (TAR) and glutathione (GSH) levels in cerebral cortex from 30-day-old rats. Tryptophan significantly increased chemiluminescence and TBA-RS measurements indicating that this amino acid induced lipid peroxidation in vitro. We also observed that tryptophan significantly decreased the brain antioxidant defenses by reducing the values of TRAP, TAR and GSH, reflecting that the overall content of antioxidants was reduced by tryptophan. Furthermore, the tryptophan-induced increase of TBA-RS was fully prevented by GSH and by combination of catalase plus superoxide dismutase, but not by the inhibitor of nitric oxide synthase N(omega)-nitro-L-arginine methyl ester (L-NAME). In case these findings also occur in human hypertryptophanemia or in other neurodegenerative diseases in which tryptophan accumulates, it is feasible that oxidative stress may be involved in the mechanism leading to the brain injury observed in patients affected by these disorders. 相似文献
100.
Taneli Tirkkonen Jaakko Pakarinen Elina Rintala Terhi Ali-Vehmas Harri Marttila Olli AT Peltoniemi Johanna M?kinen 《Acta veterinaria Scandinavica》2010,52(1):21