排序方式: 共有30条查询结果,搜索用时 31 毫秒
1.
Chen M Kohar I Southwell-Keely PT 《Redox report : communications in free radical research》2001,6(3):194-196
The 5-alkoxymethyl-2,2,7,8-tetramethyl-6-chromanols (II) are excellent antioxidants against autoxidising safflower oil (ASO), although not as good as 2,2,5,7,8-pentamethyl-6-chromanol (I), the model compound of alpha-tocopherol. The aim of this work was to determine whether the rate of reaction of (II) with the radicals diphenylpicrylhydrazyl (DPP*) and galvinoxyl (ArO*) was directly proportional to their antioxidant activity against ASO. Compounds (II) reacted faster with DPP* than with ArO* but, in each case, slower than compound (I). The rates of reaction of I and II with both radicals followed the order I > II (R = H) > II (R = CH3) > II (R = other alkyls) and were directly proportional to their antioxidant activity against ASO. 相似文献
2.
3.
M Sumarno E Atkinson C Suarna J K Saunders E R Cole P T Southwell-Keely 《Biochimica et biophysica acta》1987,920(3):247-250
(+/-)-alpha-Tocopherol has been oxidised with t-butyl hydroperoxide in chloroform in order to simulate in vivo oxidations due to lipid hydroperoxides. t-Butyl hydroperoxide proved to be a weak oxidant and failed to oxidise alpha-tocopherol in 3 h at 60 degrees C. Inclusion of a small amount of ethanol in the reaction mixture brought about immediate oxidation and the formation of a new product, 5-ethoxymethyl-7,8-dimethyltocol in addition to the spiro dimer and spiro trimer of alpha-tocopherol, alpha-tocopherylquinone and 5-formyl-7,8-dimethyltocol. Formation of 5-ethoxymethyl-7,8-dimethyltocol increased with increasing concentrations of ethanol, up to a maximum of 59% at 20% ethanol. Further increase in ethanol concentration brought about a decrease in the oxidation of alpha-tocopherol and in the formation of 5-ethoxymethyl-7,8-dimethyltocol. Oxidation of the tocopherol model compound 2,2,5,7,8-pentamethyl-6-hydroxychroman under similar conditions produced the analogous product, 5-ethoxymethyl-2,2,7,8-tetramethyl-6-hydroxychroman together with 5-formyl-2,2,7,8-tetramethyl-6-hydroxychroman and 2-(3'-hydroxy-3'-methylbutyl)-3,5,6-trimethylbenzo-1,4-quinone. 相似文献
4.
5.
Yamauchi R Southwell-Keely P Suarna C Ray S Raftery M Cynshi O Stocker R 《Free radical biology & medicine》2005,38(1):32-40
4,6-Di-tert-butyl-2,3-dihydro-2,2-dipentyl-5-benzofuranol (BO-653) is a novel antioxidant synthesized by theoretical findings and considerations. Here we report on the aqueous peroxyl radical-induced oxidation of human plasma in the presence of BO-653. When BO-653 was given to healthy human subjects at 400 mg twice daily for 28 days, lipids in the resulting plasma were protected from oxidation compared with lipids present in plasma from subjects receiving placebo. Similarly, BO-653 added in vitro at 50 muM inhibited the peroxyl radical-induced accumulation of cholesteryl ester hydroperoxides that occurred in the presence of alpha-tocopherol, although BO-653 did not decrease the rate of consumption of ascorbate, albumin-bound bilirubin, and uric acid. The antioxidant action of in vivo and in vitro added BO-653 was associated with the formation of two major reaction products of BO-653, the structures of which were elucidated by mass spectrometry and nuclear magnetic resonance analyses. The products were identified as stereoisomers of dioxybis(4,6-di-tert.-butyl-2,3,5,7a-tetrahydro-2,2-dipentylbenzofuran-5-one). These dialkylperoxides of BO-653 might be useful markers to assess the antioxidant function of BO-653 in biological systems in vivo. 相似文献
6.
Witting PK Wu BJ Raftery M Southwell-Keely P Stocker R 《The Journal of biological chemistry》2005,280(16):15612-15618
Atherosclerosis is associated with endothelial dysfunction and a heightened state of inflammation characterized, in part, by an increase in vascular myeloperoxidase and proteins modified by its principal oxidant, hypochlorous acid (HOCl). Here we examined whether probucol could protect against endothelial dysfunction induced by the two-electron oxidant HOCl. Hypochlorous acid eliminated endothelium-dependent relaxation of rabbit aorta, whereas endothelial function and tissue cGMP was preserved and elevated, respectively, in animals pretreated with probucol. Exogenously added probucol also protected against HOCl-induced endothelial dysfunction. In vitro, HOCl oxidized probucol in a two-phase process with rate constants k(1) = 2.7 +/- 0.3 x 10(2) and k(2) = 0.7 +/- 0.2 x 10(2) m(-1) s(-1) that resulted in a dose- and time-dependent accumulation of probucol-derived disulfoxide, 4,4'-dithiobis(2,6-di-tert-butyl-phenol) (DTBP), DTBP-derived thiosulfonate, disulfone, and sulfonic acid, together with 3,3',5,5'-tetra-tert-butyl-4,4'-diphenoquinone (DPQ) as determined by high performance liquid chromatography and mass spectrometry. Like HOCl, selected one-electron oxidants converted probucol into DTBP and DPQ. Also, dietary and in vitro added DTBP protected aortic rings from HOCl-induced endothelial dysfunction and in vitro oxidation by HOCl gave rise to the thiosulfonate, disulfone, and sulfonic acid intermediates and DPQ. However, the product profiles of the in vitro oxidation systems were different from those in aortas of rabbits receiving dietary probucol or DTBP +/- HOCl treatment. Together, the results show that both probucol and DTBP react with HOCl and protect against HOCl-induced endothelial dysfunction, although direct scavenging of HOCl is unlikely to be responsible for the vascular protection by the two compounds. 相似文献
7.
Paul REL Lafond T Müller-Graf CDM Nithiuthai S Brey PT Koella JC 《BMC evolutionary biology》2004,4(1):1-13
Background
Theoretical studies suggest that direct and indirect selection have the potential to cause substantial evolutionary change in female mate choice. Similarly, sexual selection is considered a strong force in the evolution of male attractiveness and the exaggeration of secondary sexual traits. Few studies have, however, directly tested how female mate choice and male attractiveness respond to selection. Here we report the results of a selection experiment in which we selected directly on female mating preference for attractive males and, independently, on male attractiveness in the guppy, Poecilia reticulata. We measured the direct and correlated responses of female mate choice and male attractiveness to selection and the correlated responses of male ornamental traits, female fecundity and adult male and female survival.Results
Surprisingly, neither female mate choice nor male attractiveness responded significantly to direct or to indirect selection. Fecundity did differ significantly among lines in a way that suggests a possible sexually-antagonistic cost to male attractiveness.Conclusions
The opportunity for evolutionary change in female mate choice and male attractiveness may be much smaller than predicted by current theory, and may thus have important consequences for how we understand the evolution of female mate choice and male attractiveness. We discuss a number of factors that may have constrained the response of female choice and male attractiveness to selection, including low heritabilities, low levels of genetic (co)variation in the multivariate direction of selection, sexually-antagonistic constraint on sexual selection and the "environmental covariance hypothesis".8.
Alexis Llewellyn Craig Whittington Gavin Stewart Julian PT Higgins Nick Meader 《PloS one》2015,10(12)
Background
The grades of recommendation, assessment, development and evaluation (GRADE) approach is widely implemented in systematic reviews, health technology assessment and guideline development organisations throughout the world. We have previously reported on the development of the Semi-Automated Quality Assessment Tool (SAQAT), which enables a semi-automated validity assessment based on GRADE criteria. The main advantage to our approach is the potential to improve inter-rater agreement of GRADE assessments particularly when used by less experienced researchers, because such judgements can be complex and challenging to apply without training. This is the first study examining the inter-rater agreement of the SAQAT.Methods
We conducted two studies to compare: a) the inter-rater agreement of two researchers using the SAQAT independently on 28 meta-analyses and b) the inter-rater agreement between a researcher using the SAQAT (who had no experience of using GRADE) and an experienced member of the GRADE working group conducting a standard GRADE assessment on 15 meta-analyses.Results
There was substantial agreement between independent researchers using the Quality Assessment Tool for all domains (for example, overall GRADE rating: weighted kappa 0.79; 95% CI 0.65 to 0.93). Comparison between the SAQAT and a standard GRADE assessment suggested that inconsistency was parameterised too conservatively by the SAQAT. Therefore the tool was amended. Following amendment we found fair-to-moderate agreement between the standard GRADE assessment and the SAQAT (for example, overall GRADE rating: weighted kappa 0.35; 95% CI 0.09 to 0.87).Conclusions
Despite a need for further research, the SAQAT may aid consistent application of GRADE, particularly by less experienced researchers. 相似文献9.
Suzanne Arends Marianne Hofman Yvo PT Kamsma Eveline van der Veer Pieternella M Houtman Cees GM Kallenberg Anneke Spoorenberg Elisabeth Brouwer 《Arthritis research & therapy》2013,15(4):R99
Introduction
The aim of this study was to investigate the construct validity and test-retest reliability of the International Physical Activity Questionnaire (IPAQ; long form) and the Short QUestionnaire to Assess Health-enhancing physical activity (SQUASH) and to investigate the relation between daily physical activity and clinical assessments in patients with ankylosing spondylitis (AS).Methods
For validity, the self-report questionnaires IPAQ and SQUASH were compared with daily physical activity assessed with the ActiGraph accelerometer during 7 consecutive days in 63 AS outpatients. For reliability, the IPAQ and SQUASH were administered twice approximately 1 week apart in 52 AS outpatients. In all 115 patients, clinical assessments were performed at the outpatient clinic.Results
IPAQ and SQUASH total scores correlated significantly with accelerometer outcome: ρ = 0.38 and r = 0.35, respectively. Intraclass correlation coefficients between first and second assessments of the IPAQ and SQUASH were 0.83 and 0.89, respectively. Bland-Altman analyses showed no systemic bias, but in particular for the IPAQ the 95% limits of agreement were wide. Daily physical activity assessed by accelerometer, IPAQ, and SQUASH correlated significantly with disease activity, physical activity, and quality of life. A relation with spinal mobility was found only for the accelerometer and SQUASH. The direction of these correlations indicates that higher daily physical activity is related to lower disease activity and better physical function, spinal mobility and quality of life.Conclusions
Both physical activity questionnaires showed modest construct validity. The SQUASH showed good test-retest reliability, superior to the IPAQ. These results indicate that the SQUASH is more suitable than the IPAQ to assess daily physical activity in AS population studies. However, it is desirable to add questions on AS-specific physical activity. Further studies are needed to investigate the causality of the relation between daily physical activity and clinical assessments. 相似文献10.
Steven PT Hooton Andrew R Timms Joanna Rowsell Ray Wilson Ian F Connerton 《Virology journal》2011,8(1):1-14