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101.
邻二氮菲-Fe2+氧化法检测H2O2/Fe2+产生的羟自由基 总被引:122,自引:0,他引:122
报告检测H2O2/Fe2+所产生羟自由基的新方法. 羟自由基氧化反应后, 邻二氮菲-Fe2+的A536明显下降, 且△A536与邻二氮菲, FeSO4及H2O2呈量效关系, 随反应时间延长, △A536依幂函数规律上升. 此法试验结果表明, 甘露醇, 抗坏血酸及硫肥清除羟自由基作用呈明显的量效关系. 相似文献
102.
动物细胞在鼓泡式生物反应器中的死亡速率 总被引:1,自引:1,他引:0
通过实验测定,证明生物反应器中细胞死亡速率与气体鼓泡速率成正比而与反应器体积成反比。实验发现气泡大小对细胞死亡速率具有两种作用,一种作用在于影响气泡表面积生成速率;另一种作用则在于影响细胞在气泡表面的吸附程度,其最佳直径为5mm左右。血清和Pluronic F68能显著降低细胞死亡速率,当Pluronic F68浓度达到0.1%时,kd趋于零。所有这些实验结果均与前文提出的生物反应器设计模型具有很好的一致性。 相似文献
103.
癫痫对大鼠学习记忆的影响及与生长抑素的相关性研究 总被引:5,自引:1,他引:4
对听源性癫痫大鼠进行迷宫训练,观察癫痫发作对大鼠光分辨学习作业的成绩以及用放射免疫分析法测定的大鼠部分脑区中生长抑素含量的影响。结果表明:(1)癫痫发作对大鼠记忆阶段有明显的抑制作用(P<0.01);(2)癫痫发作后,在大鼠信息提取明显障碍的同时,其颞叶皮层、下丘脑、垂体及海马中生长抑素的含量明显增加(P<0.05-0.01)。结果提示:癫痫发作影响大鼠学习记忆过程,在该过程中生长抑素含量发生改变。 相似文献
104.
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106.
应用二维电泳技术,分析了经水分胁迫(PEG)、盐分胁迫(NaCl)和热激(40℃)处理后林生山黧豆(LathyrussylvestrisL.)体内蛋白质多肽及其含量的变化。有些蛋白质经PEG、NaCl和热激处理后可以产生相同的变化。两种不同的胁迫因子对某些蛋白质的影响有一定的共同性。特定的胁迫条件可以造成特定的影响。不同胁迫因子对同一蛋白质多肽可以造成不同的影响。胁迫下蛋白质的变化可能与林生山黧豆抵抗和适应胁迫条件的能力以及体内非蛋白质氨基酸的代谢有关 相似文献
107.
Chang WC Shyu WJ Shi GY Lin MT Jen CJ Wing LY Tang MJ Wu HL 《Journal of biomedical science》1996,3(1):59-66
Treatment of cultured bovine carotid artery endothelial cells with 0.1 µM human plasmin has been reported to induce a receptor-mediated short burst of arachidonate release, which is a pertussis toxin-sensitive and extracellular calcium-dependent reaction. Plasmin-induced calcium influx in cells was significantly inhibited by pretreatment with pertussis toxin, indicating that the former was coupled with a pertussis toxin-sensitive guanosine 5-triphosphate (GTP)-binding protein. Plasmin significantly induced the formation of lysophosphatidylcholine but not lysophosphatidylethanolamine. A cellular phospholipase A2 with an arachidonyl specificity at the sn-2 position of phosphatidylcholine, which required submicromolar calcium, was identified as a cytosolic phospholipase A2 by immunoblot analysis. By a cell-free enzyme activity assay and immunoblot analysis, plasmin was found to induce a translocation of the cytosolic phospholipase A2 from the cytosol to the membrane. Taken together, the results suggest that plasmin bound to its putative receptor and activated a GTP-binding protein coupled to calcium influx channel, followed by translocation and activation of cytosolic phospholipase A2 in endothelial cells. 相似文献
108.
C4 Photosynthesis (The Effects of Leaf Development on the CO2-Concentrating Mechanism and Photorespiration in Maize) 总被引:1,自引:1,他引:0 下载免费PDF全文
The effect of O2 on photosynthesis was determined in maize (Zea mays) leaves at different developmental stages. The optimum level of O2 for maximum photosynthetic rates was lower in young and senescing tissues (2-5 kPa) than in mature tissue (9 kPa). Inhibition of photosynthesis by suboptimal levels of O2 may be due to a requirement for functional mitochondria or to cyclic/pseudocyclic photophosphorylation in chloroplasts; inhibition by supraoptimal levels of O2 is considered to be due to photorespiration. Analysis of a range of developmental stages (along the leaf blade and at different leaf ages and positions) showed that the degree of inhibition of photosynthesis by supraoptimal levels of O2 increased rapidly once the ribulose-1,5-bisphosphate carboxylase/oxygenase and chlorophyll contents were below a critical level and was similar to that of C3 plants. Tissue having a high sensitivity of photosynthesis to O2 may be less effective in concentrating CO2 in the bundle sheath cells due either to limited function of the C4 cycle or to higher bundle sheath conductance to CO2. An analysis based on the kinetic properties of ribulose-1,5-bisphosphate carboxylase/oxygenase was used to predict the maximum CO2 level concentrated in bundle sheath cells at a given degree of inhibition of photosynthesis by supraoptimal levels of O2. 相似文献
109.
A procedure is described, based on a spline-function representation of ab initio peptide conformational geometry maps, that allows one to predict backbone bond distances and angles of proteins as functions of the peptide ?(N-Cα)/Ψ(Cα-C′) torsions with an accuracy comparable to that of high-resolution protein crystallography. For example, for the more than 40 residues of crambin, the rms deviation between predicted and crystallographic values of N-Cα-C′ is 1.9° for the 1.5 Å resolution structure and 1.9° for the 0.83 Å resolution structure, compared with angle variations of < 10°. Accurate information on protein backbone geometries is important for establishing dictionaries of flexible geometry functions for use in empirical peptide and protein modeling. © 1995 John Wiley & Sons, Inc. 相似文献
110.
Mechanical properties of neuronal growth cone membranes studied by tether formation with laser optical tweezers. 总被引:6,自引:2,他引:4
Many cell phenomena involve major morphological changes, particularly in mitosis and the process of cell migration. For cells or neuronal growth cones to migrate, they must extend the leading edge of the plasma membrane as a lamellipodium or filopodium. During extension of filopodia, membrane must move across the surface creating shear and flow. Intracellular biochemical processes driving extension must work against the membrane mechanical properties, but the forces required to extend growth cones have not been measured. In this paper, laser optical tweezers and a nanometer-level analysis system were used to measure the neuronal growth cone membrane mechanical properties through the extension of filopodia-like tethers with IgG-coated beads. Although the probability of a bead attaching to the membrane was constant irrespective of treatment; the probability of forming a tether with a constant force increased dramatically with cytochalasin B or D and dimethylsulfoxide (DMSO). These are treatments that alter the organization of the actin cytoskeleton. The force required to hold a tether at zero velocity (F0) was greater than forces generated by single molecular motors, kinesin and myosin; and F0 decreased with cytochalasin B or D and DMSO in correlation with the changes in the probability of tether formation. The force of the tether on the bead increased linearly with the velocity of tether elongation. From the dependency of tether force on velocity of tether formation, we calculated a parameter related to membrane viscosity, which decreased with cytochalasin B or D, ATP depletion, nocodazole, and DMSO.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献