龙葵碱对HepG2细胞内[Ca2+]i的影响

探讨龙葵碱对HepG2细胞形态及细胞内[Ca~(2 )]i的影响,揭示龙葵碱诱导细胞凋亡的机制.以人肝癌细胞HepG2为研究对象,采用AO/EB双染HepG2细胞,激光共聚焦扫描显微镜观察细胞形态学改变,Fluo-3/AM单染HepG2细胞,激光共聚焦扫描显微镜观察细胞内[Ca~(2 )]i的改变.结果发现龙葵碱作用于HepG2 48h后,细胞形态出现典型的细胞凋亡形态;细胞内[Ca~(2 )]i浓度明显升高.表明龙葵碱升高细胞内Ca~(2 )浓度启动细胞凋亡机制.     

Mechanisms of peroxynitrite-induced [Ca2+]i increase in single neuronal cell

The mechanism of peroxynitrite (ONOO⁻)-induced [ca²⁺]_i increase in single MN9D cell (Dopaminergic neuroblastoma cell line) was studied by using Fura-2 microfluorometric technique. The results show that ONOO⁻ caused a rapid increase of [Ca²⁺]_i when ONOO₋ was puffed to the cell. Removing Ca²⁺ from the bath or using calcium channel antagonist (CdCl₂, Nifedipine) greatly inhibited the [Ca²⁺]_i increase induced by ONOO⁻¹, suggesting that the opening of L-Ca²⁺ channel makes a great contribution to the [Ca²⁺]_i increase. The effect of sulfhydryl reductive agent (DTT) on ONOO⁻-induced [Ca²⁺]_i increase suggests that ONOO⁻-activating L-Ca²⁺ channel is partly related to its oxidative speciality.     

Heat and hyposmotic stimulation increase in [Ca^2＋]i by Ca^2＋ influx in rat synoviocytes

Rheumatoid arthritis （RA）, which is marked by inflammatory synovitis, is a common, chronic autoimmune-disease, whose pathogenesis is complex and still unclear. In order to explore the effects of heat and hyposmotic stimuli on synoviocytes in rheumatoid arthritis, the changes of [Ca^2＋]i induced by heat, hyposmotic and 4α-PDD stimuli were observed in synoviocytes. [Ca^2＋]i elevation induced by heat 28℃, hyposmotic and 4α-PDD stimuli is found to be positively relative to increasing temperature, decreasing osmolality and rising concentration of 4α-PDD. Results show that there is reciprocity among these stimuli and desensitization, and that [Ca^2＋]i elevation depends on Ca^2＋ influx, but not necessarily links to Ca^2＋ release from intracellular stores and voltage-dependent Ca^2＋ channel in synoviocytes. The above characteristics of Ca^2＋ influx are similar to those of TRPV4. A probable mechanism has been suggested that heat and hyposmotic stimulation might increase the level of [Ca^2＋]i by activating the TRPV4-like channel and Ca^2＋ influx in the synoviocytes.     

α-LTX and α-LTXN4C induce [Ca2+]i elevation through different mechanisms in pancreatic β cells

α-latrotoxin (α-LTX) is the only neurotoxin from black-widow spider which has secretagogue effects in the vertebrates. It causes massive neurotransmitter and hormone release via two instinct mechanisms after binding with its high-affinity membrane recep…     

不同浓度ET-1引起心肌细胞[Ca2+]i 升高作用的量效关系

目的：探讨内皮素－１（ＥＴ－１）对心肌细胞内游离钙浓度（［Ｃａ２＋］ｉ）的作用以及不同浓度ＥＴ－１引起［Ｃａ２＋］ｉ升高作用的量效关系。方法：采用分离的Ｓｐｒａｇｕｅ－Ｄａｗｌｅｙ大鼠心室肌细胞,以Ｆｕｒａ－２／ＡＭ荧光指示剂负载,检测不同浓度ＥＴ－１引起［Ｃａ２＋］ｉ变化。结果：ＥＴ－１引起［Ｃａ２＋］ｉ升高呈双相反应,即起始的短暂快速相和随后的持续相。在１×１０－９～５×１０７ｍｏｌ／Ｌ范围内,随着ＥＴ－１浓度的增加,其升高［Ｃａ２＋］ｉ的作用亦增强;并且这种作用可被ＥＴＡ的特异性受体阻断剂ＢＱ１２３（２×１０６ｍｏｌ／Ｌ）所阻断。结论：ＥＴ－１升高［Ｃａ２＋］ｉ呈剂量依赖关系,其作用具有特异性,并且是通过ＥＴＡ受体介导的。     

不同浓度ET—1引起心肌细胞[Ca^2＋]i升高作用的？…

目的:探讨内皮素-1(ET-1)对心肌细胞内游离钙浓度([Ca2+]i)的作用以及不同浓度ET-1引起[Ca2+]i升高作用的量效关系.方法:采用分离的Sprague-Dawley大鼠心室肌细胞,以Fura-2/AM荧光指示剂负载,检测不同浓度ET-1引起[Ca2+]i变化.结果:ET-1引起[Ca2+]i升高呈双相反应,即起始的短暂快速相和随后的持续相.在1×10-9～5×10-7mol/L范围内,随着ET-1浓度的增加,其升高[Ca2+]i的作用亦增强;并且这种作用可被ETA的特异性受体阻断剂BQ123(2×10-6mol/L)所阻断.结论:ET-1升高[Ca2+]i呈剂量依赖关系,其作用具有特异性,并且是通过ETA受体介导的.     

大黄酸抑制脂多糖刺激巨噬细胞升高[Ca2+]i和释放TNFα的作用特征

以正常腹腔巨噬细胞(PMφ)和脂多糖(Lipopolysacharide，LPS)刺激的PM垂为对象，用MTT法和激光共焦扫描显微术检测肿瘤坏死因子α(TNFα)释放量和单细胞[Ca^2 ]i的动态变化，研究了大黄酸(Rhein)的作用特征和机理．结果显示，大黄酸对正常PMφ释放TNFα没有明确的影响，但对LPS刺激的PMφ释放TNFα有显的抑制作用，其抑制作用随浓度增加而增强，10^-4mol／L大黄酸抑制了10μg／mL LPS效应的72％．值得注意的是，大黄酸不但抑制了LPS引发的PMφ[Ca^2 ]i的升高，而且使LPS引发的[Ca^2 ]i由宽平台峰状转变为振荡动力学模式，胞外介质无钙时又转变为更低幅值的峰．以上结果表明，大黄酸降低LPS引发的PM垂的[Ca^2 ]i升高是其抑制TNFα释放的信号传导通路的重要环节，并提示大黄酸在降低胞内钙释放和胞外钙内流的同时又对其动力学进行了类周期性的调制．     

知柏地黄丸浸液对大鼠嗜铬细胞内钙的作用

运用Fura-2显微荧光测量技术,在单个大鼠肾上腺嗜铬细胞上,测量中药知柏地黄丸浸液对胞内游离钙浓度([Ca     

ATP刺激巨噬细胞[Ca2+]i升高和氧自由基增加及大黄酸的抑制作用研究

研究了ATP刺激的大鼠腹腔巨噬细胞[Ca2 ]i升高与氧自由基(ROS)产生的关系和大黄酸抑制作用特征.提取大鼠腹腔巨噬细胞,利用Ca2 探针Fura-2检测单细胞胞内自由Ca2 浓度([Ca2 ]i)变化,同时利用NBT还原反应强度检测同一细胞ROS产生能力.结果发现无ATP刺激的巨噬细胞的ROS产生量较低;1mmol/L ATP刺激巨噬细胞单细胞后诱发[Ca2 ]i显著升高由胞内Ca2 释放和胞外Ca2 内流组成,同时ROS产生增强2倍;胞外无Ca2 条件下ROS产生随着[Ca2 ]i下降而减少.10-5和10-4mol/L浓度大黄酸对1mmol/L ATP刺激巨噬细胞单细胞的[Ca2 ]i升高和ROS产生有剂量依赖性的抑制作用;多细胞的统计分析表明10-5和10-4mol/L浓度大黄酸分别抑制了[Ca2 ]i峰值的49%和84%,同时抑制了ROS产生的59%和81%.因此认为ATP刺激大鼠腹腔巨噬细胞诱发的[Ca2 ]i升高介导了ROS的产生,大黄酸剂量依赖性的抑制ATP刺激的细胞[Ca2 ]i升高和ROS产生能力,并提示大黄酸抑制细胞[Ca2 ]i升高是其抑制ROS产生的重要机制.     

Progressive inhibition of the Ca pump and Ca:Ca exchange in sickle red cells

Sickle cell anaemia red cells (SS) were reported to have a high Ca content and an increased Ca uptake on deoxygenation, but their Ca-pump activity was described as normal. This seemed puzzling because the saturated Ca-extrusion rate of the normal, high Ca-affinity Ca pump is about 10 mmol per 1 cells per h (refs 3, 4) and the highest sickling-induced Ca influx reported in SS cells and observed in ATP-depleted sickle-trait (SA) red cells never exceeded 0.2 mmol per 1 cells per h. Normal pump performance is, therefore, incompatible with Ca accumulation unless SS cells have abnormally high Ca-binding capacity. We provide here evidence which suggests that SS cells have normal Ca-buffering capacity and probably genetically normal Ca pumps, but that the sickling process causes progressive Ca-pump failure and a marked reduction in Ca:Ca exchange.     

Ebselen 抑制 ONOO~- 对神经元[Ca~(2+)]_i 的影响

Ｆｕｒａ－２显微荧光测钙技术研究发现,过氧亚硝基阴离子（ＯＮＯＯ－）作用于ＭＮ９Ｄ细胞,数ｓ内即可导致其胞内游离钙离子浓度（［Ｃａ２＋］ｉ）的急剧升高．胞外液换为无钙液或向胞外液中加入硝苯吡啶（Ｎｉｆｅｄｉｐ－ｉｎｅ）、二硫苏糖醇（ＤＴＴ）均可抑制ＯＮＯＯ－对［Ｃａ２＋］ｉ的影响,提示Ｌ－型钙通道的激活是ＯＮＯＯ－引起［Ｃａ２＋］ｉ升高的主要原因,ＯＮＯＯ－的这种作用可能与其氧化特性有关．Ｅｂｓｅｌｅｎ（２－苯基－１,２－苯并异硒唑－３（２Ｈ）酮）明显抑制ＯＮＯＯ－对［Ｃａ２＋］ｉ的影响,并且存在一定的剂量效应关系．     

H_2SO_4溶液中[H~+]的计算

本文根据质子等衡和物料平衡原则推导出了H2SO4溶液中[H+]的三个计算公式,并把计算结果与实验结果进行了比较分析。     

Point mutation of an FGF receptor abolishes phosphatidylinositol turnover and Ca2+ flux but not mitogenesis.

Stimulation of certain receptor tyrosine kinases results in the tyrosine phosphorylation and activation of phospholipase C gamma (PLC gamma), an enzyme that catalyses the hydrolysis of phosphatidylinositol (PtdIns). This hydrolysis generates diacylglycerol and free inositol phosphate, which in turn activate protein kinase C and increase intracellular Ca2+, respectively. PLC gamma physically associates with activated receptor tyrosine kinases, suggesting that it is a substrate for direct phosphorylation by these kinases. Here we report that a fibroblast growth factor (FGF) receptor with a single point mutation at residue 766 replacing tyrosine with phenylalanine fails to associate with PLC gamma in response to FGF. This mutant receptor also failed to mediate PtdIns hydrolysis and Ca2+ mobilization after FGF stimulation. However, the mutant receptor phosphorylated itself and several other cellular proteins, and it mediated mitogenesis in response to FGF. These findings show that a point mutation in the FGF receptor selectively eliminates activation of PLC gamma and that neither Ca2+ mobilization nor PtdIns hydrolysis are required for FGF-induced mitogenesis.     

Ca2+ signalling between single L-type Ca2+ channels and ryanodine receptors in heart cells

Ca2+-induced Ca2+ release is a general mechanism that most cells use to amplify Ca2+ signals. In heart cells, this mechanism is operated between voltage-gated L-type Ca2+ channels (LCCs) in the plasma membrane and Ca2+ release channels, commonly known as ryanodine receptors, in the sarcoplasmic reticulum. The Ca2+ influx through LCCs traverses a cleft of roughly 12 nm formed by the cell surface and the sarcoplasmic reticulum membrane, and activates adjacent ryanodine receptors to release Ca2+ in the form of Ca2+ sparks. Here we determine the kinetics, fidelity and stoichiometry of coupling between LCCs and ryanodine receptors. We show that the local Ca2+ signal produced by a single opening of an LCC, named a 'Ca2+ sparklet', can trigger about 4-6 ryanodine receptors to generate a Ca2+ spark. The coupling between LCCs and ryanodine receptors is stochastic, as judged by the exponential distribution of the coupling latency. The fraction of sparklets that successfully triggers a spark is less than unity and declines in a use-dependent manner. This optical analysis of single-channel communication affords a powerful means for elucidating Ca2+-signalling mechanisms at the molecular level.     

SA和Ca2+配合对月季切花的保鲜效果及其生理机制

研究了含水杨酸(salicylic acid,SA)和Ca2+的保鲜剂对月季切花的保鲜效果及其生理作用.结果表明,SA和Ca2+相配合可明显改善月季切花的水分代谢,增加花枝鲜重,显著延长月季切花的瓶插寿命.另外,SA和Ca2+相配合的处理还可明显延缓花青素的降解速度,降低细胞膜相对透性,显著增加SOD和CAT的活性.因...