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971.
We have studied pH regulation in both intracellular and extracellular compartments of mouse colonic crypts, using distal colonic mucosa with intact epithelial architecture. In this work, we question how transepithelial SCFA gradients affect intracellular pH (pHi) and examine interactions between extracellular pH (pHo) and pHi regulation in crypts of distal colonic epithelium from mouse. We studied pH regulation in three adjacent compartments of distal colonic epithelium (crypt lumen, crypt epithelial cell cytosol, and lamina propria) with SNARF-1 (a pH sensitive fluorescent dye), digital imaging microscopy (for pHi), and confocal microscopy (for pHo). Combining results from the three compartments allows us to find how pHi and pHo are regulated and related under the influence of physiological transepithelial SCFA gradients, and develop a better understanding of pH regulation mechanisms in colonic crypts. Results suggest a complex interdependency between SCFA fluxes and pHo values, which can directly affect how strongly SCFAs acidify colonocytes. 相似文献
972.
Based on the solutions of through-cracked strip, the constitutive relations of line-springs for embedded crack and slightly emergent surface crack are formulated for the first time. The line-spring model has been improved with the aid of a three-dimensional solution of embedded elliptical crack in an infinite body to include the curvature effects of surface crack front, i.e. the interaction between springs. The calculated results from the improved model are very consistent with those from the alternative iteration reported previously (Shah, R. C. & Kobayashi, A. S. J. Pres. Vessel Technol., 1 (1974) 47–54); the improved model has higher precision and a larger effective range than the unimproved model. 相似文献
973.
974.
Comparative studies of polymer electrolyte membrane fuel cell stack and single cell 总被引:10,自引:0,他引:10
The polymer electrolyte membrane fuel cell (PEMFC) was investigated comparatively as a single cell and a 30-cell stack. Various types of Nafion membranes, such as Nafion 117, 115, 112 and 105, were tested as electrolyte within the single cell and at different temperatures, among which Nafion 112 gave the optimal result. The 30-cell stack was evaluated at different humidities and temperatures. The potential–current and power–current curves, both for single cell and the stack, were analyzed by computer simulation, whereby the kinetic and mass-transfer parameters were calculated. The long-term performance of the stack and the water production during long-term operation were also measured. 相似文献
975.
再生热塑性聚氨酯/聚氯乙烯共混材料性能的研究 总被引:4,自引:0,他引:4
通过对再生热塑性聚氨酯与聚氯乙烯共混材料力学性能等的研究,发现当TPUR含量在40%时具有较好综合性能。 相似文献
976.
Hydrogen-induced cracking of an alumina ceramic 总被引:1,自引:0,他引:1
977.
进行不同的钢板厚度、锚固措施和结构胶种类对粘贴钢板加固钢筋混凝土梁承载能力、变形特性和破坏形式的试验研究,选取合适的钢板厚度和锚固措施,可使粘贴钢板加固梁的效果达到最佳。 相似文献
978.
Hui Mei Yu Bor-Sen Wang Heuy Ling Chu Lee-Wen Chang Wen-Jye Yen Chia-Jung Lin Pin-Der Duh 《Food chemistry》2007,105(4):1364-1374
The effects of water extract of napiergrass (Pennisetum purpureum S.) (WEN) on oxidative damage of biomolecules and modulation of antioxidant enzyme activity were investigated. The results showed that WEN displayed marked free radical scavenging, reducing power, as well as ferrous ions chelating effects. WEN has a dose-dependent response for protective action on oxidation of phospholipid, deoxyribose and low-density lipoprotein (LDL) in the range of 0–0.5 mg/ml, indicating that WEN had in vitro protective action on oxidative damage of biomolecules. Oxidative stress induced by H2O2 significantly decreased the viability of BNL cells. However, addition of WEN in the medium protected cells from H2O2-induced cytotoxicity. Furthermore, treatment of cells with WEN in the range of 0–0.2 mg/ml displayed protective effect from H2O2 induced oxidation in a concentration dependent manner. With respect to the effect of WEN on antioxidant enzymes, the results showed the WEN at 0.2 mg/ml enhanced activities of glutathione peroxidase (GPX), glutathione reductase (GR), glutathione transferase (GST) and catalase (CAT) in BNL cells by 2.93-, 35.8-, 4.23-, and 2.78-fold, respectively, compared to the control; WEN increased the GSH content by 3.2-fold, implying that WEN may up-regulate the levels of GSH and antioxidant enzymes in BNL cells. WEN scavenged NO generated by a NO donor, sodium nitroprusside (SNP) and suppressed NO production in lipopolysaccharide (LPS)-activated macrophage RAW 264.7 cells. The determination of ascorbic acid and total anthocyanins as well as HPLC analysis revealed that ascorbic acid, rutin, epicatechin, anthocyanins, p-coumaric acid, quercetin and catechin were present in WEN, which function as in vitro antioxidants by virtue of their ability to scavenge ROS and RNS. Overall, the results obtained showed that WEN is rich in antioxidant components and they can serve as an excellent potential for use as a natural phytochemicals source. 相似文献
979.
980.