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1.
目的:观察咪达唑仑对人胚肾上皮细胞(HEK-293)中异源表达的人类相关基因(h ERG)钾电流作用及其机制。方法:利用全细胞膜片钳技术,观察咪达唑仑对h ERG钾通道的抑制作用,分析其对通道激活、失活动力学过程的影响以及咪达唑仑对Y652A和F656C突变型h ERG钾通道的作用。结果:咪达唑仑浓度依赖性地抑制h ERG钾电流,其IC50值为(1.31±0.32)μmol/L。1.0μmol/L的咪达唑仑加药前后半数激活电压V1/2由(2.32±0.38)m V变为(-1.96±0.83)m V;加药前后半数失活电压V1/2由(-49.25±0.69)m V变为(-57.53±0.53)m V(P0.05),失活曲线左移;与野生型(WT)比较,Y652A和F656C突变型可显著减弱咪达唑仑对h ERG通道的阻断作用。结论:咪达唑仑能阻断h ERG钾通道,失活速度加快,Y652和F656可能是咪达唑仑与h ERG钾通道结合的关键位点。  相似文献   

2.
目的:SK通道存在于心肌细胞上,其中SK2亚型主要表达在心房。SK2通道对胞内游离钙离子高度敏感,可快速将钙离子浓度的变化转换成细胞膜电位变化。本实验应用穿孔膜片钳技术记录人心肌细胞SK2电流,观察心房肌细胞SK2电流在窦性患者和心房颤动患者之间的差别,以及电极液中不同的钙浓度对两组细胞SK2电流的影响。方法:将接受体外循环手术的患者分为两组:心房颤动组和窦性心律组。以心房肌细胞为研究对象,用穿孔膜片钳技术记录人心肌细胞电流,观察窦性组与房颤组SK2通道电流的差异以及两组细胞SK2电流对电极液中钙敏感性的不同。结果:在全细胞穿孔膜片钳模式下,电极液中游离钙离子浓度为5×10-7mol/L时,记录到房颤组SK2通道电流明显大于窦性组,尤其是在超极化水平。膜电位在-130 mV时,窦性组与房颤组的SK2通道电流密度分别为(-2.92±0.35)pA/pF(n=6),(-6.83±0.19)pA/pF(n=3,P〈0.05)。在电极液游离钙离子浓度分别为0 mol/L、5×10-7mol/L、10-6mol/L,膜电位为-130 mV时,窦性组SK2通道电流密度分别为(-1.43±0.33)pA/pF(n=7),(-2.92±0.35)pA/pF(n=6),(-10.11±2.15)pA/pF(n=8,P〈0.05);房颤组SK2通道电流密度分别为(-2.17±0.40)pA/pF(n=4)(-6.83±0.19)pA/pF(n=3)(-14.47±2.89)pA/pF(n=4)(P〈0.05)。结论:人心房肌细胞SK2通道具有电压不敏感、内向整流、apamin敏感的特性。电极液中钙浓度相同的情况下,房颤组的SK2电流密度明显大于窦性组,SK2通道电流对钙离子的敏感性高于窦性组,提示SK2通道钙敏感性增加可能与心房颤动的发生发展密切相关。  相似文献   

3.
弱激光对大鼠海马神经元钠通道特性的影响   总被引:6,自引:0,他引:6  
利用波长670nm、功率5mW的半导体激光器照射急性分离的大鼠海马CA3区锥体神经元,应用全细胞膜片钳技术研究其电压门控Na 通道的特性.实验发现:弱激光作用5min时,Na 通道激活电位和峰值电位开始向负电位方向移动,7min激光作用达稳定;激光照射对Na 通道电流峰值无影响,对照组和激光照射组峰值电流密度分别为(-383.51±26.93)pA/pF和(-368.36±33.14)pA/pF(n=8,P>0.05);激光作用降低了Na 通道的激活阈值电位和峰值电位,对照组通道电流在-40mV激活,-30mV达峰值,激光照射组通道电流在-60mV激活,-40mV达峰值;激光照射改变了Na 通道半数激活电压和斜率因子,对照组和激光照射组的半数激活电压分别为(-42.091±1.537)mV和(-54.971±1.846)mV(n=8,P<0.01),斜率因子分别为(1.529±0.667)mV和(2.634±0.519)mV(n=8,P<0.05).结果表明,弱激光照射海马神经元可改变Na 通道的激活特性,从而影响动作电位的去激化过程,进而会引起神经元细胞生理功能发生变化.  相似文献   

4.
西洛他唑对人心房肌细胞瞬间外向钾电流的影响   总被引:2,自引:0,他引:2  
目的:观察西洛他唑对人心房肌细胞瞬间外向钾电流(Ito1)的影响,探讨该药抗心律失常作用的机制.方法:二步酶解法分离人单个右心房肌细胞,应用全细胞膜片钳技术记录人心房肌细胞Ito1.结果:在保持电位-50 mV和去极化脉冲为 50 mV条件下,30 μmol/L西洛他唑显著降低Ito1,使Ito1幅值由加药前(8.16±0.70)pA/pF降至(4.84±0.60)pA/pF(P<0.01).西洛他唑在1~50 μmol/L范围内呈浓度依赖性的抑制Ito1,1 μmol/L时即产生作用,50 μmol/L时达最大效应(降低51.09%±3.00%),IC50为(13.18±2.60)μmol/L.此外,该药对Ito1的电压依赖性激活和失活曲线以及恢复曲线均无显著影响.结论:本实验结果表明西洛他唑浓度依赖性地阻滞人心房肌细胞的Ito1.  相似文献   

5.
Lu JY  Wu DM  Wu BW  Chai WX  Kang CS  Li TL 《生理学报》1999,51(5):588-592
本文观察了心肌肥厚对大鼠心肌细胞Na /Ca2 交换电流的影响。我们采用Goldblatt两肾一夹方法诱发大鼠心肌肥厚,应用全细胞膜片钳技术记录电流。结果表明:肥厚心肌细胞的Ni2 -敏感Na /Ca2 交换电流密度大于正常细胞。在钳制电压为+50mV时,正常细胞的外向交换电流密度为1.53±0.31pA/pF,而肥厚细胞则为2.62±0.53pA/pF(P<0.01);钳制电压为-100mV时,正常细胞的内向交换电流密度为0.42±0.14pA/pF,肥厚细胞达1.12±0.33pA/pF(P<0.001)。这些结果提示,肥厚心肌细胞的Na /Ca2 交换电流发生了改变,其意义有待进一步探讨。  相似文献   

6.
目的:比较右美托咪啶与咪达唑仑用于重症破伤风患者镇静中效果。方法:选取2012年1月~2015年12月间在我院治疗的重症破伤风患者72例,通过随机数表法分为右美托咪啶组与咪达唑仑组,各36例,给予右美托咪啶组静脉泵入右美托咪啶1μg/kg持续时间为10 min,之后以0.3~0.6μg/kg进行维持,咪达唑仑组静脉泵入咪达唑仑0.05 mg/kg,持续时间为1 min,之后以0.02~0.1/kg·h进行维持。监测两组患者用药前及用药12 h后平均动脉压(MAP)、呼吸频率(RR)、血氧饱和度(SpO_2)和心率(HR)深用Ramasy评分法评估镇静程度。结果:两组患者治疗后HR、RR、MAP水平明显降低而SpO_2明显上升且右美托咪啶组HR、RR、及SpO_2改善更显著差异均有统计学意义(P0.05);两组用药后4 h、8 h、12 h时Ramasy评分在组间、组内比较差异均无统计学意义(P0.05);右美托咪啶组不良反应发生率为5.56%,低于咪达唑仑组的16.67%,差异有统计学意义(P0.05)。结论右美托咪啶有助于维持患者血流动力学的稳定减少重症破伤风患者心动过速、心率增快、呼吸抑制等不良反应情况的发生。  相似文献   

7.
Lin YY  Wu DM  Liu L  Liu QH  Yan ZY  Wu BW 《生理学报》2008,60(1):38-42
本研究采用全细胞膜片钳技术观察了SNCl62(一种选择性δ阿片受体激动剂)对人鼠心室肌细胞L型钙电流(L-type Ca2 current,ICa-L)和瞬时外向钾电流(transient outward K current,Ito)的影响.结果显示,SNCl62明显抑制大鼠心室肌细胞,Ica L和Ica L,对Ica L.和k的最大抑制率分别为(46.13±4.12)%和(36.53±10.57)%.1x10-4mol/L SNCl62使,Ica L的甲均电流密度从(8.98±0.40)pA/pF下降到(4.84±0.44)pA/pF(P<0.01,n=5),Ito的平均电流密度从(18.69±2.42)pA/pF降低到(11.73±1.67)pA/pF(P<0.01,n=5).单独应用naltrindole(一种选择性δ阿片受体拮抗剂)对大鼠心室肌细胞Ica L和Ito无显著作用,但预先应用naltrindole可以消除SNCl62对Ica L和Ito的抑制作用.结果表明,通过δ阿片受体,SNCl62(1x10-6~1x10-4mol/L)浓度依赖性地抑制人鼠心室肌细胞Ica L和Ito这可能是激动δ阿片受体产生抗心律失常效应的重要机制.  相似文献   

8.
Cui XL  Chen HZ  Wu DM  Wu BW 《生理学报》2004,56(6):713-716
本文旨在研究氨甲酰胆碱(carbachol, CCh)对豚鼠心肌的正性变力性机制。用Axon200A膜片钳放大器观察CCh 对电压钳制下的豚鼠心肌细胞L-型钙电流(ICa)和钠钙交换电流(INa/Ca)的效应。结果表明, CCh(100 μmol/L)分别使正向INa/Ca从对照组的(1.2 ± 0.1) pA/pF 增加到(2.0 ± 0.3) pA/pF,使反向 INa/Ca 从对照组的(1.3 ± 0.5) pA/pF 增加到(2.1 ± 0.8) pA/pF (P<0.01)。CCh对ICa无影响。CCh 对INa/Ca的激动作用可被阿托品和methoctramine所阻断。以上结果提示, CCh 对豚鼠心脏的正性变力作用是通过激动了钠钙交换,而且是 M2 毒蕈碱受体所介导的。  相似文献   

9.
目的:比较婴幼儿在机械通气镇静时使用右旋美托咪定和咪达唑仑效果。方法:收集我院2009年2月至2011年10月入住ICU需要机械通气且镇静时间大于24h的患儿60例,随机分为3组,每组20例,右旋美托咪啶1组(输注剂量为0.25μg.kg-1.h-1,D1组)、2组(输注剂量为0.5μg.kg-1.h-1,D2组)维持镇静,咪达唑仑组(输注剂量为0.05 mg.kg-1.h-1,M组)维持镇静。同时根据病情需要间断给予吗啡镇痛。镇静的疗效评估采用Ramsay镇静评分以及脑电双屏指数(BIS)评价。结果:60例患儿分为3组,每组20例,咪达唑仑组(M组)的输注持续时间(h)为22±8 h,0.25μg(D1组)和0.5μg(D2组)右旋美托咪啶组输注持续时间分别为21±10 h和22±9 h;M组的平均输注速率为0.22±0.05 mg.kg-1.h-1,D1组和D2组平均输注速率分别为0.28±0.07μg.kg-1.h-1和0.21±0.05μg.kg-1.h-1;三组差异无统计学意义。其中M组、D1组、D2组使用吗啡的剂量是分别为36 mg.kg-1.24h-1、29 mg.kg-1.24h-1和20mg.kg-.124h-1。D1组与M组使用吗啡的剂量差异无统计学意义。D2组与M组使用吗啡的剂量差异有统计学意义(P<0.05)。三组患儿BIS值和Ramsay评分监测差异无统计学意义。结论:右旋美托咪啶应用于婴幼儿是安全有效的,0.5μg.kg-1.h-1右旋美托咪啶组镇静更加有效,24小时吗啡的使用剂量显著减少。  相似文献   

10.
为了明确大鼠背根节(DRG)神经元中存在慢的Ca2 激活K 电流成分,本实验在新鲜分散的DRG神经元胞体上,采用全细胞电压箝技术,给予DRG神经元一定强度的去极化刺激,记录刺激结束后30ms时的尾电流幅度。结果发现:(1)随着去极化时间从1ms延长至180ms时,尾电流幅度由9.3±2.8pA逐渐增大至64.1±3.4pA(P<0.001);(2)当去极化结束后的复极化电位降低时,尾电流幅度先逐渐下降到零,然后改变方向,逆转电位约为-63mV;(3)细胞外施加500μmol/LCd2 或细胞内液中施加11mmol/LEGTA时尾电流明显减小甚至完全消失;(4)尾电流中慢成分的幅度在细胞外给与200nmol/L蜂毒明肽后,减小了约26.32±3。9%(P<0。01);(5)细胞外施加10mmol/LTEA,可明显降低尾电流中的快成分。结果提示,在DRG神经元启超极化中存在Ca2 激活K 电流的蜂毒明肽敏感成分──IAHP。  相似文献   

11.
To study how conserved fundamental concepts of the heat stress response (HSR) are in photosynthetic eukaryotes, we applied pharmaceutical and antisense/amiRNA approaches to the unicellular green alga Chlamydomonas reinhardtii. The Chlamydomonas HSR appears to be triggered by the accumulation of unfolded proteins, as it was induced at ambient temperatures by feeding cells with the arginine analog canavanine. The protein kinase inhibitor staurosporine strongly retarded the HSR, demonstrating the importance of phosphorylation during activation of the HSR also in Chlamydomonas. While the removal of extracellular calcium by the application of EGTA and BAPTA inhibited the HSR in moss and higher plants, only the addition of BAPTA, but not of EGTA, retarded the HSR and impaired thermotoler- ance in Chlamydomonas. The addition of cycloheximide, an inhibitor of cytosolic protein synthesis, abolished the attenu- ation of the HSR, indicating that protein synthesis is necessary to restore proteostasis. HSP90 inhibitors induced a stress response when added at ambient conditions and retarded attenuation of the HSR at elevated temperatures. In addition, we detected a direct physical interaction between cytosolic HSP90A/HSP70A and heat shock factor 1, but surprisingly this interaction persisted after the onset of stress. Finally, the expression of antisense constructs targeting chloroplast HSP70B resulted in a delay of the cell's entire HSR, thus suggesting the existence of a retrograde stress signaling cascade that is desensitized in HSP7OB-antisense strains.  相似文献   

12.
To accommodate two seemingly contradictory biological roles in plant physiology, providing both the rigid structural support of plant cells and the adjustable elasticity needed for cell expansion, the composition of the plant cell wall has evolved to become an intricate network of cellulosic, hemicellulosic, and pectic polysaccharides and protein. Due to its complexity, many aspects of the cell wall influence plant cell expansion, and many new and insightful observations and technologies are forthcoming. The biosynthesis of cell wall polymers and the roles of the variety of proteins involved in polysaccharide synthesis continue to be characterized. The interactions within the cell wall polymer network and the modification of these interactions provide insight into how the plant cell wall provides its dual function. The complex cell wall architecture is controlled and organized in part by the dynamic intracellular cytoskeleton and by diverse trafficking pathways of the cell wall polymers and cell wall-related machinery. Meanwhile, the cell wall is continually influenced by hormonal and integrity sensing stimuli that are perceived by the cell. These many processes cooperate to construct, maintain, and manipulate the intricate plant cell wall--an essential structure for the sustaining of the plant stature, growth, and life.  相似文献   

13.
Citrate synthase has a key role in the tricarboxylic (TCA) cycle of mitochondria of all organisms, as it cata- lyzes the first committed step which is the fusion of a carbon-carbon bond between oxaloacetate and acetyl CoA. The regulation of TCA cycle function is especially important in plants, since mitochondrial activities have to be coordinated with photosynthesis. The posttranslational regulation of TCA cycle activity in plants is thus far almost entirely unexplored. Although several TCA cycle enzymes have been identified as thioredoxin targets in vitro, the existence of any thioredoxin-dependent regulation as known for the Calvin cycle, yet remains to be demonstrated. Here we have investigated the redox regulation of the Arabidopsis citrate synthase enzyme by site-directed mutagenesis of its six cysteine residues. Our results indicate that oxidation inhibits the enzyme activity by the formation of mixed disulfides, as the partially oxidized citrate synthase enzyme forms large redox-dependent aggregates. Furthermore, we were able to demonstrate that thioredoxin can cleave diverse intraas well as intermolecular disulfide bridges, which strongly enhances the activity of the enzyme. Activity measurements with the cysteine variants of the enzyme revealed important cysteine residues affecting total enzyme activity as well as the redox sensitivity of the enzyme.  相似文献   

14.
Proper vesicle tethering and membrane fusion at the cell plate are essential for cytokinesis. Both the vesicle tethering complex exocyst and membrane fusion regulator KEULE were shown to function in cell plate formation, but the exact mechanisms still remain to be explored. In this study, using yeast two-hybrid (Y-2-H) assay, we found that SEC6 interacted with KEULE, and that a small portion of C-terminal region of KEULE was required for the interaction. The direct SEC6-KEULE interaction was supported by further studies using in vitro pull-down assay, immunoprecipitation, and in vivo bimolecular florescence complementation (BIFC) microscopy, sec6 mutants were male gametophytic lethal as reported; however, pollen-rescued sec6 mutants (PRsec6) displayed cytokinesis defects in the embryonic cells and later in the leaf pavement cells and the guard cells. SEC6 and KEULE proteins were co-localized to the cell plate during cytokine- sis in transgenic Arabidopsis. Furthermore, only SEC6 but not other exocyst subunits located in the cell plate interacted with KEULE in vitro. These results demonstrated that, like KEULE, SEC6 plays a physiological role in cytokinesis, and the SEC6-KEULE interaction may serve as a novel molecular linkage between arriving vesicles and membrane fusion machin- ery or directly regulate membrane fusion during cell plate formation in plants.  相似文献   

15.
The pH of intracellular compartments is essential for the viability of cells. Despite its relevance, little is known about the pH of these compartments. To measure pH in vivo, we have first generated two pH sensors by combining the improved-solubility feature of solubility-modified green fluorescent protein (GFP) (smGFP) with the pH-sensing capabil- ity of the pHluorins and codon optimized for expression in Arabidopsis. PEpHluorin (plant-solubility-modified ecliptic pHluorin) gradually loses fluorescence as pH is lowered with fluorescence vanishing at pH 6.2 and PRpHluorin (plant- solubility-modified ratiomatric pHluorin), a dual-excitation sensor, allowing for precise measurements. Compartment- specific sensors were generated by further fusing specific sorting signals to PEpHluorin and PRpHluorin. Our results show that the pH of cytosol and nucleus is similar (pH 7.3 and 7.2), while peroxisomes, mitochondrial matrix, and plastidial stroma have alkaline pH. Compartments of the secretory pathway reveal a gradual acidification, spanning from pH 7.1 in the endoplasmic reticulum (ER) to pH 5.2 in the vacuole. Surprisingly, pH in the trans-Golgi network (TGN) and mul- tivesicular body (MVB) is, with pH 6.3 and 6.2, quite similar. The inhibition of vacuolar-type H+-ATPase (V-ATPase) with concanamycin A (ConcA) caused drastic increase in pH in TGN and vacuole. Overall, the PEpHluorin and PRpHluorin are excellent pH sensors for visualization and quantification of pH in vivo, respectively.  相似文献   

16.
Reactive oxygen species and auxin play important roles in the networks that regulate plant development and morphogenetic changes, However, the molecular mechanisms underlying the interactions between them are poorly understood. This study isolated a mas (More Axillary Shoots) mutant, which was identified as an allele of the mitochondrial AAA-protease AtFtSH4, and characterized the function of the FtSH4 gene in regulating plant development by medi- ating the peroxidase-dependent interplay between hydrogen peroxide (H2Oz) and auxin homeostasis. The phenotypes of dwarfism and increased axillary branches observed in the mas (renamed as ftsh4-4) mutant result from a decrease in the IAA concentration. The expression levels of several auxin signaling genes, including IAA1, IAA2, and IAA3, as well as several auxin binding and transport genes, decreased significantly in ftsh4-4 plants. However, the H202 and peroxidases levels, which also have IAA oxidase activity, were significantly elevated in ftsh4-4 plants. The ftsh4-4 phenotypes could be reversed by expressing the iaaM gene or by knocking down the peroxidase genes PRX34 and PRX33. Both approaches can increase auxin levels in the ftsh4-4 mutant. Taken together, these results provided direct molecular and genetic evidence for the interaction between mitochondrial ATP-dependent protease, H2O2, and auxin homeostasis to regulate plant growth and development.  相似文献   

17.
18.
Aphis gossypii Glover shows obvious host specialization, with cucurbit- and cotton-specialized biotypes or host races in many regions. Because its annual natal hostcrops senesce earlier the cucurbit-specialized biotype may suffer food deficiency. The method this biotype uses to overcome this challenge is still poorly understood. In orderto understand the potential of the cucurbit-specialized biotype aphids in host shift and usage, the performance of this biotype on cotton (Gossypium hirsutum), a common butpoor quality host plant, was explored in this study. The cucurbit-specialized aphids could establish populations on cotton only when these plants had at least nine leaves, and subsequent populations developed rather slowly. The presence of whitefly populations on cotton improved the success rate of cucurbit-specialized aphids. The cucurbit-specialized aphidswere mainly distributed on the older leaves of cotton, with only a few settling on the upper leaves. The cucurbit-specialized aphids reared on cotton for 40, 54 and 61 days stillmaintained strong preference for their natal host plant, cucumber (Cucumis sativus), rather than cotton, and their net reproductive rates and intrinsic rates of natural increase weredramatically lower when they were transferred onto new six-leaf cotton plants or detached leaves. Therefore, we concluded that the cucurbit-specialized aphids have the potentialto utilize mature or whitefly-stressed cotton plants, but that this feeding experience on cotton did not alter their specialization for cucurbits. Some cotton plants could act as atemporary host for the cucurbit-specialized aphids to overcome food deficiency arising from senescing cucurbits.  相似文献   

19.
The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmentation between veins and interveinal regions due to specific aberrations in the development of mesophyll cells. Thus, the reticulate mutants offer a potent tool to investigate cell-type-specific developmental processes. The discovery that most mutants are affected in plastid-localized, metabolic pathways that are strongly expressed in vasculature-associated tis- sues implicates a crucial role for the bundle sheath and their chloroplasts in proper development of the mesophyll cells. Here, we review the reticulate mutants and their phenotypic characteristics, with a focus on those in Arabidopsis thali- ana. Two alternative models have been put forward to explain the relationship between plastid metabolism and meso- phyll cell development, which we call here the supply and the signaling hypotheses. We critically assess these proposed models and discuss their implications for leaf development and bundle sheath function in C3 species. The characteriza- tion of the reticulate mutants supports the significance of plastid retrograde signaling in cell development and highlights the significance of the bundle sheath in C3 photosynthesis.  相似文献   

20.
The Receptor-Like Kinase (RLK) is a vast protein family with over 600 genes in Arabidopsis and 1100 in rice. The Lectin RLK (LecRLK) family is believed to play crucial roles in saccharide signaling as well as stress perception. All the LecRLKs possess three domains: an N-terminal lectin domain, an intermediate transmembrane domain, and a C-terminal kinase domain. On the basis of lectin domain variability, LecRLKs have been subgrouped into three subclasses: L-, G-, and C-type LecRLKs. While the previous studies on LecRLKs were dedicated to classification, comparative structural analysis and expression analysis by promoter-based studies, most of the recent studies on LecRLKs have laid special emphasis on the potential of this gene family in regulating biotic/abiotic stress and developmental pathways in plants, thus mak- ing the prospects of studying the LecRLK-mediated regulatory mechanism exceptionally promising. In this review, we have described in detail the LecRLK gene family with respect to a historical, evolutionary, and structural point of view. Furthermore, we have laid emphasis on the LecRLKs roles in development, stress conditions, and hormonal response. We have also discussed the exciting research prospects offered by the current knowledge on the LecRLK gene family. The multitude of the LecRLK gene family members and their functional diversity mark these genes as both interesting and worthy candidates for further analysis, especially in the field of crop improvement.  相似文献   

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