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991.
The major side-effect of treatment with α-glucosidase inhibitors, flatulence, occurs when undigested carbohydrates are fermented by colonic bacteria, resulting in gas formation. We propose that the cardiovascular benefits of α-glucosidase inhibitors are partly attributable to their ability to neutralise oxidative stress via increased production of H2 in the gastrointestinal tract. Acarbose, which is an α-glucosidase inhibitor, markedly increased H2 production, with a weaker effect on methane production. Our hypothesis is based on our recent discovery that H2 acts as a unique antioxidant, and that when inhaled or taken orally as H2-dissolved water it ameliorates ischaemia-reperfusion injury and atherosclerosis development. 相似文献
992.
993.
Intracellular content of hydrogen peroxide and of the product of lipid peroxidation malonic dialdehyde as well as activity of antioxidant enzymes catalase, ascorbate peroxidase, and superoxide dismutase were studied in cells of morphogenic and derived from them non-morphogenic calluses of tatar buckwheat Fagopyrum tataricum L. Non-morphogenic calluses were characterized by significantly higher content of hydrogen peroxide and malonic dialdehyde, low catalase activity, and high activity of superoxide dismutase compared to morphogenic cultures. The results may indicate that cells of non-morphogenic calluses are in the state of continuous oxidative stress. Nevertheless, proliferative activity of non-morphogenic cultures and the biomass increase significantly exceeded these parameters in morphogenic calluses. An analogy is drawn between animal cancer cells and non-morphogenic plant calluses. 相似文献
994.
Xuejuan Feng Jing Zhao Zhisheng Jiang Bin Geng 《Biochemical and biophysical research communications》2009,380(1):153-38
Recent data suggested that endogenous hydrogen sulfide (H2S) contributes to the pathogenesis of diabetes. Here, we identified that cystathionine gamma lyase (CSE) was expressed in adipose tissue in rats and endogenously generated H2S. The CSE/H2S system exists in both rat adipocytes and pre-adipocytes. This system was up-regulated with aging, although a high level of glucose down-regulated the system in a concentration- and time-dependent manner. H2S inhibited the basal and insulin-stimulated glucose uptake of mature adipocytes, whereas administration of CSE inhibitors enhanced the glucose uptake of adipocytes. The PI3K but not KATP channel pathway is involved in the inhibitory effect of H2S on glucose uptake. Finally, in fructose-induced diabetes in rats, we confirmed the up-regulated CSE/H2S system in adipose tissue, which was negatively correlated with glucose uptake in this tissue. Our findings suggest that H2S might be a novel insulin resistance regulator. 相似文献
995.
Tomihiko Higuchi Hiroyuki Fujimura Hirotsugu Ikota Takemitsu Arakaki Tamotsu Oomori 《Journal of experimental marine biology and ecology》2009,370(1-2):48-55
Coral metabolism reflects the physiological condition of a coral colony. We studied coral metabolism using a continuous-flow, complete mixing (CFCM) experimental system. Small-size Goniastrea aspera coral colonies were incubated in the CFCM system with and without hydrogen peroxide (H2O2) added to the supplied seawater (0 µM H2O2 for 12 days; 0, 0.3, 3.0, and 30 µM H2O2 for 3 days, for each treatment) Without addition of H2O2, coral metabolism, including photosynthesis (gross primary productivity) and calcification, was relatively stable and there were no significant metabolic changes, suggesting that, without H2O2 added to the CFCM system, the corals did not suffer significant stress from the experimental system over a 12-day incubation period. When H2O2 was added, large decreases in photosynthesis and calcification were observed. The non-parametric Mann–Whitney U-test showed that there were statistically significant differences in photosynthesis after addition of 3.0 µM and 30 µM H2O2, compared with the control. We also found statistically significant differences in net calcification after addition of 30 µM H2O2. Thus, the incubation experiments suggest that higher H2O2 concentrations in seawater clearly influence coral metabolism. However, the results also suggest that the current seawater H2O2 level in Okinawa is not likely to pose significant acute effects on the metabolic activities of corals. 相似文献
996.
Hai-Tuong Le Emmanuelle Demey-Thomas Bertrand Friguet Jean Mary 《Journal of molecular biology》2009,393(1):58-164
The oxidized protein repair methionine sulfoxide reductase (Msr) system has been implicated in aging, in longevity, and in the protection against oxidative stress. This system is made of two different enzymes (MsrA and MsrB) that catalyze the reduction of the two diastereoisomers S- and R-methionine sulfoxide back to methionine within proteins, respectively. Due to its role in cellular protection against oxidative stress that is believed to originate from its reactive oxygen species scavenging ability in combination with exposed methionine at the surface of proteins, the susceptibility of MsrA to hydrogen-peroxide-mediated oxidative inactivation has been analyzed. This study is particularly relevant to the oxidized protein repair function of MsrA in both fighting against oxidized protein formation and being exposed to oxidative stress situations. The enzymatic properties of MsrA indeed rely on the activation of the catalytic cysteine to the thiolate anion form that is potentially susceptible to oxidation by hydrogen peroxide. The residual activity and the redox status of the catalytic cysteine were monitored before and after treatment. These experiments showed that the enzyme is only inactivated by high doses of hydrogen peroxide. Although no significant structural modification was detected by near- and far-UV circular dichroism, the conformational stability of oxidized MsrA was decreased as compared to that of native MsrA, making it more prone to degradation by the 20S proteasome. Decreased conformational stability of oxidized MsrA may therefore be considered as a key factor for determining its increased susceptibility to degradation by the proteasome, hence avoiding its intracellular accumulation upon oxidative stress. 相似文献
997.
ANTONIO JESÚS SERRATO ELENA MARÍA YUBERO-SERRANO LUISA MARÍA SANDALIO JUAN MUÑOZ-BLANCO ANA CHUECA JOSÉ LUIS CABALLERO & MARIAM SAHRAWY 《Plant, cell & environment》2009,32(7):811-827
A full-length FBPase cDNA has been isolated from Fragaria × ananassa (strawberry) corresponding to a novel putative chloroplastic FBPase but lacking the regulatory redox domain, a characteristic of the plastidial isoenzyme (cpFBPaseI). Another outstanding feature of this novel isoform, called cpFBPaseII, is the absence of the canonical active site. Enzymatic assays with cpFBPaseII evidenced clear Mg2+ -dependent FBPase activity and a K m for fructose-1,6-bisphosphate (FBP) of 1.3 m m . Immunolocalization experiments and chloroplast isolation confirmed that the new isoenzyme is located in the stroma. Nevertheless, unlike cpFBPaseI, which is redox activated, cpFBPaseII did not increase its activity in the presence of either DTT or thioredoxin f (TRX f ) and is resistant to H2 O2 inactivation. Additionally, the novel isoform was able to complement the growth deficiency of the yeast FBP1 deletion fed with a non-fermentable carbon source. Furthermore, orthologues are restricted to land plants, suggesting that cpFBPaseII is a novel and an intriguing chloroplastic FBPase that emerged late in the evolution of photosynthetic organisms, possibly because of a pressing need of land plants. 相似文献
998.
In the last few years, the role of reactive oxygen species as signaling molecules has emerged, and not only as damage-related
roles. Here, we analyzed how root hydraulic properties were modified by different hydrogen peroxide (H2O2) concentrations applied exogenously to the root medium. Two different experimental setups were employed: Phaseolus vulgaris plants growing in hydroponic or in potted soils. In both experimental setups, we found an increase of root hydraulic conductance
(L) in response to H2O2 application for the first time. Twenty millimolar was the threshold concentration of H2O2 for observing an effect on L in the soil experiment, while in the hydroponic experiment, a positive effect on L was observed at 0.25 mM H2O2. In the hydroponic experiment, a correlation between increased L and plasma membrane aquaporin amount and their root localization was observed. These findings provide new insights to study
how several environmental factors modify L. 相似文献
999.
叶片衰老是一个复杂的过程.多年来人们对叶片衰老的机制开展了大量的研究。许多研究证明叶片中H2O2的迅速积累与叶片的衰老密切相关^[1-3],然而,H2O2的积累是衰老的结果还是作为信号启动衰老?H2O2作为植物细胞的信号分子,调控一系列重要的生理生化过程,如系统获得抗性(SAR)、细胞衰老与程序化死亡(PCD)、气孔关闭、根的生长、细胞壁的发育等^[4]。H2O2参与脱落酸(A—BA)、甲基茉莉酸(MJ)诱导的水稻叶片衰老,且H2O2产生早于叶片衰老^[2,5]。 相似文献
1000.
Enzymatic hydrolysis of hybrid poplar treated by ammonia recycle percolation (ARP) was studied applying cellulase enzyme supplemented with additional xylanase or pectinase. The effect of xylanase addition was much more significant than pectinase addition. Conversion of ARP‐treated hybrid poplar to ethanol was carried out by simultaneous saccharification and fermentation (SSF) and SS and cofermentation (SSCF). The maximum ethanol yield observed from the SSCF experiment was 78% of theoretical maximum based on the total carbohydrate (glucan + xylan). The same feedstock was also treated by soaking in aqueous ammonia (SAA), a batch pretreatment process with lower severity than ARP. The test results indicated that relatively high severity is required to attain acceptable level of digestibility of hybrid poplar. In order to lower the severity of the pretreatment, addition of H2O2 was attempted in the SAA. Addition of H2O2 significantly enhanced delignification of hybrid poplar due to its oxidative degradation of lignin. Several different H2O2 feeding schemes and different temperature profiles were attempted in operation of the SAA to investigate the effects of H2O2 on degradation of lignin and carbohydrates in hybrid poplar. More than 60% of lignin in hybrid poplar was removed with stepwise‐increase of temperature (60–120°C after 4h of reaction). Increase of carbohydrate degradation was also observed under this condition. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 相似文献