氧应力在产朊假丝酵母发酵生产谷胱甘肽过程中的作用

为了提高产朊假丝酵母合成GSH的能力,采用外界氧应力刺激的方式对细胞进行处理。稳定期之前添加H2O2对细胞生长有抑制作用,但稳定期添加H2O2对GSH的合成有促进作用,当H2O2添加总浓度为30 mmol.L-1时,无论采用一次性添加还是补加策略,都可以提高GSH的合成能力,胞内GSH质量分数提高幅度最大接近于20%,GSH产量最多提高17%。GSH分批发酵结果表明,稳定期补加H2O2对于产朊假丝酵母细胞来说,要比一次性添加H2O2对提高胞内GSH含量并最终增加GSH产量更为有效,该结果为实现氧应力刺激下GSH的过量合成提供了条件。     

Neuroprotection of Insulin against Oxidative Stress-induced Apoptosis in Cultured Retinal Neurons： Involvement of Phosphoinositide 3-kinase/Akt Signal Pathway

In order to investigate the neuroprotection of insulin in retinal neurons,we used retinal neuronalculture as a model system to study the protective effects of insulin against H_2O_2-induced cytotoxicity andapoptotic death.Primary retinal neuronal cultures were grown from retinas of 0-2-day old Sprague-Dawleyrats.Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay.Apoptotic cell death was evaluated by the TdT-mediated digoxigenin-dUTP nick-end labeling assay,and byDNA laddering analysis.Phosphoinositide 3-kinase (PI3K) activity was measured using phosphoinositide4,5-bisphophate and [γ-~(32)P]ATP as substrate.Western blot analysis with anti-phospho-Akt (pS473) antibodywas performed to examine the level of phosphorylated Akt.We observed that treatment with 100μM H_2O_2for 24 h significantly decreased cell viability and induced apoptotic death of retinal neurons,and that pretreatmentwith 10 nM insulin significantly inhibited or attenuated H_2O_2-induced cytotoxicity and apoptosis.Pretreatmentwith LY294002,a specific PI3K inhibitor,abolished the cytoprotective effect of insulin.Insulin also stronglyactivated both PI3K and the downstream effector Akt.These results suggest that insulin protects retinalneurons from oxidative stress-induced apoptosis and that the PI3K/Akt signal pathway is involved in insulin-mediated retinal neuroprotection.     

Effect of Osmotic Stress in Early Stages of Ontogenesis on Root Respiration, Growth, Sugar Content, and Cell Injury in Maize Seedlings Differing in Drought Sensitivity

Cultivars of maize （Zea mays L.） with different sensitivity to drought were exposed to 0.3 mol/L sorbitol （-1.4 MPa water potential） for 24 h. Exposure to water deficiency significantly reduced the growth of both shoots （coleoptile and hypocotyl） and roots. Shoot growth was inhibited more than the growth of roots. Osmotic stress enhanced accumulation of soluble sugars. Electrolyte leakage, a cell injury index, was slightly increased after 0.3 mol/L sorbitoh Respiration was measured in the presence and absence of 2,6-dlchloro-phenol indophenoh 2,6-Dichloro-phenol indophenol did not influence respiration rates, because statistically equal results were observed under both conditions. Total respiration （VT） decreased after osmoticum treatment. There were no significant differences in the VT among the cultlvars analysed. The decrease In VT was caused by a decline In the activities and capacities of both cytochrome （Vcyt, Vcyt） and alternative pathway （Valt, Valt） of respiration. A high residual respiration （Vres） was observed, up to 27% of total uninhibited respiration. The result of uncoupler use clearly indicated that coupling was maintained after 24 h of osmotic stress. The recovery of the respiration rate was comparable with that of non-stressed control rates. According to these observations, no possible mltochondrial damage is expected. Water deficiency did not induce a stimulation of the alternative oxidase, so we assume that the stimulation of the alternative pathway is not related to drought stress resistance; rather, the function of the alternative pathway is to balance carbon metabolism and electron transport in a response to a changing environment.     

桩蛋白与肾脏

桩蛋白(paxillin,Pax)作为细胞骨架蛋白的关键调节蛋白之一,具有对细胞外刺激发应的潜能,在多种信号转导途径中起到结构和信号转导的承接作用.近年来有关Pax在细胞黏附与迁移中的作用备受关注,同时与肾脏发育及肾脏疾病发生的关系也日渐受到重视,现将目前相关研究作简单综述.     

完全固定桥修复前后基牙和牙槽骨表面的电测应力分析(二)

本文采用电阻应变片电测技术,在具有模拟双侧颞肌、嚼肌和颞下颌关节盘,牙列完整,(牙合)关系正常的头颅综合力学模型上,对完整牙列及局部缺牙区用完全固定桥修复后,不同(牙合)位上模拟产生正中(牙合)位下的早接触,测试分析基牙和牙槽骨受力后的应力分布。     

恐龙蛋壳的生物力学性质(Ⅰ)──在外力作用下恐龙蛋壳的应力分析

本文研究恐龙蛋在外压力作用下蛋壳内部的内力和应力变化规律,计算出蛋壳内部不同方位和不同方向上内力和应力的变化值。对四种不同类型恐龙蛋的蛋壳应力值进行了比较。得出了影响应力大小的因素和蛋壳在外压力作用下的破坏规律。     

Xyloglucan for Generating Tensile Stress to Bend Tree Stem

In response to environmental variation, angiosperm trees bend their stems by forming tension wood, which consists of a cellulose-rich G （gelatinous）-Iayer in the walls of fiber cells and generates abnormal tensile stress in the secondary xylem. We produced transgenic poplar plants overexpressing several endoglycanases to reduce each specific polysaccharide in the cell wall, as the secondary xylem consists of primary and secondary wall layers. When placed horizontally, the basal regions of stems of transgenic poplars overexpressing xyloglucanase alone could not bend upward due to low strain in the tension side of the xylem. In the wild-type plants, xyloglucan was found in the inner surface of G-layers during multiple layering. In situ xyloglucan endotransglucosylase （XET） activity showed that the incorporation of whole xyloglucan, potentially for wall tightening, began at the inner surface layers S1 and S2 and was retained throughout G-layer development, while the incorporation of xyloglucan heptasaccharide （XXXG） for wall loosening occurred in the primary wall of the expanding zone. We propose that the xyloglucan network is reinforced by XET to form a further connection between wall-bound and secreted xyloglucans in order to withstand the tensile stress created within the cellulose G-layer micro fibrils.     

VASP在切应力诱导的内皮细胞骨架重排中的变化

目的:探讨不同强度的稳定层流切应力对内皮细胞骨架肌动蛋白相关蛋白VASP表达、磷酸化和分布影响规律及其机制.方法:采用平行板流动腔模型,刺激培养HUVECs.免疫荧光双标显示层流下细胞中肌动蛋白重排与VASP分布变化之间的规律.RT-PCR检测VASP mRNA表达;Western blot监测VASP表达及磷酸化水平.结果:10 dyn/cm2剪切24 h后,细胞延长、长轴重排、形成顺流场排列的粗大肌动蛋白纤维丝;VASP沿肌动蛋白纤维分布,在其末端汇聚成明显的点状;10 dyn/cm2剪切1 h诱导VASPmRNA表达增加;24 h内VASP反复磷酸化、总表达量增加2 h达高峰后恢复,8 h后再次升高;cAMP抑制剂H89显著抑制切应力诱导VASP表达增加及磷酸化.结论:切应力通过cAMP/cAK途径磷酸化VASP,发挥骨架调节蛋白作用,介导血液流动引起的内皮细胞骨架重组、形态改变.     

血清反应因子参与RhoA诱导的人血管内皮细胞肌动蛋白骨架重构

为进一步阐明RhoA调控人脐静脉内皮细胞(human umbilical vein endothelial cell,HUVEC)肌动蛋白骨架重构的分子机制,用逆转录病毒感染并筛选出稳定表达持续活化型RhoA(Q63LRhoA)和主导抑制型RhoA(T19NRhoA)的HUVECs。应用免疫组化和Western blot方法分析去血清前后HUVECs血清反应因子(serum response factor,SRF)的表达及定位,Rhodamine-Phalloidine染色观察F-actin动态变化。结果显示,Q63LRhoA组细胞核中SRF表达增加,F-actin重排形成大量应力纤维;T19NRhoA组中SRF表达较弱,F-actin无明显改变,无应力纤维形成。去血清后,正常HUVECs(对照组)和感染细胞中SRF的表达均显著增加,但其亚细胞定位明显不同。对照组去血清培养3d,SRF主要定位在细胞核,去血清培养5d,SRF出核转位入细胞浆。Q63LRhoA组SRF发生核滞留,不随去血清培养时间延长发生出核转位现象。T19NRhoA组SRF的表达主要定位于细胞核周。对照组去血清培养3d,F-actin表达增加,同时形成大量应力纤维,去血清培养5d,细胞F-actin表达下调,应力纤维解聚。Q63LRhoA组F-actin重构持续发生并形成大量应力纤维,但不随去血清培养时间延长发生明显解聚。而T19NRhoA组F-actin表达不随去血清时间延长而增加。上述结果提示,RhoA介导HUVECs F-actin的重构与SRF的核转位现象密切相关。     

生姜精油对黑腹果蝇的急性毒性分析

在蔗糖水溶液中加入不同浓度的生姜精油饲喂野生型黑腹果蝇成虫,用时间-剂量-死亡率模型对96h内各处理果蝇成虫累计死亡率随时间、剂量的变化进行拟合.结果表明:较高浓度的生姜精油对果蝇成虫具有较强的急性毒性.0.5%生姜精油作用72h,果蝇成虫的累计死亡率分别为雌88%、雄79%;1%和10%生姜精油作用72h,雌雄成虫的累计死亡率均达100%.随着处理时间的延长,达到50%致死水平所需生姜精油浓度(即LC50)逐渐降低.Tween-20对果蝇成虫(尤其是雄虫)也有较强的毒性,高浓度时作用尤为明显.