干旱胁迫下Ca2+·CaM信使系统对稻苗保护酶活性的影响

以氯丙嗪(CPZ)和LaCl3对水稻幼苗根际预处理,阻断其Ca2+·CaM信使系统传导后,研究了干旱胁迫下稻苗膜脂过氧化和保护酶活性的变化.结果表明干旱胁迫下,LaCl3和CPZ根际预处理显著加剧稻苗膜脂过氧化,加剧过氧化氢酶(CAT)活性和抗坏血酸过氧化物酶(APX)活性下降,对胁迫前期超氧化物岐化酶(SOD)和过氧化物酶(POD)活性无显著影响,且CPZ和LaCl3预处理加剧CAT和APX活性下降与加剧稻苗MDA含量积累分别呈极显著和显著正相关.这些结果暗示Ca2+·CaM信使系统可能主要通过调节或影响CAT和APX活性而调节稻苗的抗旱性.     

Ca2+对冷胁迫柑橘离体叶片的相关生理生化指标的影响

研究了不同浓度的外源Ca²⁺对柑橘离体叶片抗寒性的影响。结果表明:10~20 mmol/L Ca²⁺处理能够增加柑橘可溶性糖和可溶性蛋白质的含量,提高SOD和POD的活性,同时减少膜质过氧化物丙二醛(MDA)的积累,从而提高柑橘的抗寒性。     

低温胁迫对麻竹叶片和根系抗性生理指标的影响

采用室内人工低温处理,研究了麻竹(Dendrocalamus latiflorus)叶片及根部质膜透性、丙二醛、可溶性蛋白、可溶性糖含量,超氧化物歧化酶(SOD)、过氧化物酶(POD)活性和膜脂脂肪酸组成的变化,寻找与竹类植物耐寒性关系最密切的抗性生理指标。结果表明:低温预处理(8℃)15d后,麻竹叶片中可溶性糖、可溶性蛋白含量、POD活性显著提高,根部可溶性糖含量、POD活性显著升高;低温胁迫处理(-2℃)72h后,经低温预处理的麻竹叶片可溶性糖、可溶性蛋白质含量、SOD、POD活性显著高于未经低温预处理,而质膜透性显著低于未经低温预处理,但膜脂过氧化程度显著高于-2℃处理前;经低温预处理的麻竹根部SOD、POD活性及膜脂不饱和脂肪酸相对含量显著高于未经低温预处理,而质膜透性、膜脂过氧化程度较-2℃处理前无显著差异。说明剧烈降温对麻竹生理特征造成严重影响,叶片通过提高可溶性蛋白、可溶性糖含量,维持较高的POD活性以减轻低温伤害;根系则通过维持较高的SOD、POD活性以减轻低温下膜脂过氧化水平,并通过提高膜脂不饱和脂肪酸比例降低质膜透性来抵御低温对膜的伤害。     

SO2对采后葡萄某些生理生化特性的影响（简报）

以100μl·L(-1)SO2处理保鲜葡萄1h后,SOD、POD和CAT活性增高,膜脂的过氧化受抑制,MDA不积累,细胞膜电导率略有增加,细胞膜相对透性基本保持不变,有机酸、抗坏血酸及糖等营养成分损失率减小,葡萄呈新鲜状态。SO2剂量过高（达到300μl·L(-1)）,处理1h时,SOD、POD和CAT活性下降,MDA大量积累,细胞膜伤害率增大,葡萄呈漂白状伤害。     

美容杜鹃叶片再生及愈伤组织耐热生理研究

以美容杜鹃幼叶为外植体,通过三因素三水平的正交试验,探究不同培养基、激素对愈伤组织诱导、分化和植株再生的影响,并对愈伤组织进行38℃热胁迫,探讨热胁迫下其耐热生理指标随时间的变化规律。结果表明:(1)愈伤组织诱导和芽分化最佳培养基均为Read+0.1mg/L NAA+0.2mg/L TDZ;最佳壮苗培养基为改良MS+0.1mg/L KT+0.2mg/L NAA;最佳生根培养基为1/2改良MS+2.0mg/L GA3。(2)随着热胁迫时间的延长,愈伤组织中的可溶性糖和游离脯氨酸含量变化不明显,而MDA和可溶性蛋白质的含量呈上升趋势,超氧化物歧化酶(SOD)和过氧化物酶(POD)活性则表现为先升后降趋势;其中,MDA含量、可溶性蛋白质含量、SOD和POD活性随时间变化显著,可作为评价美容杜鹃耐热性的生理指标。     

茉莉酸甲酯对烟草愈伤组织一些活性氧生成和相关酶活性的影响

烟草愈伤组织用茉莉酸甲酯(MJ, 1mgml-1)处理;同时将愈伤组织在含AIP(0.1mmol/L,水杨酸合成抑制剂)和/或AOA(1mmol/L,乙烯合成抑制剂)的MS培养基上进行暗培养,测定在活性氧产生和脂质过氧化中起作用的相关酶活性及一些代谢物的含量。结果表明,茉莉酸甲酯能激活超氧阴离子的产生,提高脂氧合酶同工酶1(LOX1)的活性从而启动脂质过氧化,对脂氧合酶同工酶3(LOX3)没有明显影响;降低过氧化氢(H2O2)的含量、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)及抗坏血酸过氧化物酶(APX)等保护酶的活性,减少了膜脂过氧化中有毒物质丙二醛(MDA)的含量。AIP和AOA都对MJ的作用有不同程度的影响。MJ调节超氧阴离子和过氧化氢生成以及相关酶活性是通过不同的信号转导途径,MJ调节超氧阴离子和MDA生成、SOD和APX活性很可能是通过乙烯起作用,且对MDA生成和APX活性的调节可能通过水杨酸起作用;MJ直接调节LOX1活性,但对LOX3活性没有明显作用。     

垃圾填埋场渗滤液尾水灌溉下百慕大草抗氧化系统的反应

通过盆栽试验,研究了渗滤液尾水灌溉下百慕大草的膜脂过氧化及酶促、非酶促抗氧化系统的反应.结果表明,低稀释比的渗滤液尾水(<25%)灌溉下,随着稀释比增大,百慕大草叶绿素a/b提高,丙二醛(MDA)、H₂O₂含量及膜透性降低,膜脂过氧化水平较轻;但中、高稀释比(>25%)下,随稀释比的增大则显示出一定的负效应,表现为叶绿素a/b降低,MDA、H₂O₂含量及膜透性提高,从而导致膜脂过氧化水平提高.非酶抗氧化剂抗坏血酸(AsA)、还原型谷胱甘肽(GSH)、类胡萝卜素(Car)含量的变化趋势相同,即低稀释比下含量升高,中高稀释比胁迫下明显降低.抗氧化酶中,超氧化物岐化酶(SOD)和过氧化物酶(POD)的活性变化同抗氧化剂变化趋势相似,但POD对胁迫的反应更敏感;而过氧化氢酶(CAT)活性变化趋势则先减弱后增强;MDA含量和抗氧化剂含量、抗氧化酶SOD、POD活性间的显著负相关,表明3种抗氧化剂和SOD、POD在防止百慕大草膜脂过氧化上可能起到更重要的作用.     

Ca2+对冷胁迫柑橘离体叶片的相关生理生化指标的影响

研究了不同浓度的外源Ca^2＋对柑橘离体叶片抗寒性的影响。结果表明：10-20mmol／L Ca^2＋处理能够增加柑橘可溶性糖和可溶性蛋白质的含量,提高SOD和POD的活性,同时减少膜质过氧化物丙二醛（MDA）的积累,从而提高柑橘的抗寒性。     

NaCl胁迫和外源ABA对枸杞愈伤组织膜脂过氢化及抗氢化酶活性的影响

不同浓度NaCl胁迫下,枸杞愈伤组织生长量下降,质膜相对透性和丙二醛(MDA)含量增大,且二者呈正相关;过氧化酶(POD)和超氧化歧化酶(SOD)活性升高,但对POD同工酶酶带无影响,仅使酶带染色程度加深。加入ABA后,SOD、POD活性升高,说明盐胁迫下ABA可以延缓盐胁迫对膜的伤害,从而提高枸杞的耐盐性。     

木麻黄幼苗对模拟酸雨胁迫的响应和Ca2+的调节作用

随着酸雨pH值的下降,木麻黄幼苗中超氧化物歧化酶(SOD)活性、叶绿素含量和叶绿素a/b值逐渐下降,过氧化物酶(POD)活性、可溶性蛋白质含量、丙二醛(MDA)含量和超氧阴离子自由基(O2-·)含量逐渐增加,过氧化氢酶(CAT)活性和脯氨酸含量先升后降.在同一强度酸雨胁迫下,经0.1和1 mmol·L-1Ca(NO3)2处理的SOD活性、CAT活性、叶绿素含量和叶绿素a/b值相对较高,POD活性、蛋白质含量、MDA含量、O2-·含量和脯氨酸含量相对较低,Ca2 可缓解酸雨对木麻黄幼苗的伤害.     

抗寒剂CR-4 对冬小麦幼苗质膜钙泵（Ca2 +-ATPase） 的稳定作用

通过磷酸铈沉淀的细胞化学观察揭示,常温下生长的冬小麦幼苗的Ca2+ -ATP酶活性主要定位在质膜上,同时,水浸种和抗寒剂浸种的小麦质膜Ca2+ -ATP酶活性没有差异。然而,小麦幼苗经-7℃冰冻处理12小时和24小时后,则表现明显的区别：水浸种的小麦幼苗质膜Ca2+ -ATP酶活性明显下降,直至完全失活,细胞的精细结构也同时被破坏;而经抗寒剂浸种的小麦幼苗质膜Ca2+ -ATP酶仍维持较高的活性,细胞结构也保持完整,显示抗寒剂对质膜Ca2+ -ATPase酶起着明显的稳定作用。     

Influence of Low Temperature on Spatial-temporal Changes of Ca2+ in Winter or Spring Wheat

Stained with Fluo-3/AM and investigated under the laser scanning confocal microscope (LSCM), the spatial-temporal changes of ［Ca2+］cyt(the free Ca2+ concentration in the cytoplasm) in the protoplasts of mesophyll cells of wheat (Triticum aestivum L.) cultivars with different cold-hardiness under resting and temperature decreasing conditions were compared. The results showed that under the resting condition, the fluorescence intensities in the protoplasts of both cold-sensitive and cold-resistant wheat manifested no significant changes, implying that ［Ca2+］cyt could keep at a stable level under the resting condition although different wheat cultivars were different. However, different dynamics appeared with temperature decreasing from 15℃ to 2℃. In particular, for the cold-resistant wheat, ［Ca2+］cyt level at first increased, followed by drop to the resting level at 2℃, and then increased further when the temperature was below 2℃. On the contrary, the ［Ca2+］cyt level of the cold-sensitive spring wheat increased continuously to the maximal level within the whole range of temperature changes. Based on the above observations, it could be reasonably inferred that different dynamics of ［Ca2+］cyt determines decisively different cold acclimation abilities of plants. Furthermore, the results provide a new supporting evidence for the hypothesis that Ca2+ plays a key role as a primary physiological transducer upon chilling”.     

外源Ca2+对高温强光胁迫下滨梅幼苗的保护效应

以10 mmol/L CaCl2溶液处理滨梅幼苗叶片后,置于培养箱于(40±2)℃高温、光照强度(1 200±50)μmol·m-2·s-1下培养,定期测定有关生理生化指标,以探讨外源Ca2+对高温强光胁迫下滨梅幼苗的保护效应.结果显示:(1)与蒸馏水处理组相比,Ca2+处理使高温强光胁迫下滨梅幼苗叶片的脯氨酸含量显著升高,可溶性糖含量变化不明显,根系活力小幅降低;Ca2+处理有效抑制了高温强光下膜透性的加大,提高和保护了Ca2+-ATPase的活性.(2)采用Ca2+螯合剂EGTA或钙调素拮抗剂TFP对滨梅幼苗叶片同法处理并同条件胁迫时,与Ca2+处理相比,滨梅幼苗的脯氨酸、可溶性糖含量、Ca2+-ATPase活性和根系活力均明显下降,膜透性加大.研究表明,Ca2+处理能提高滨梅幼苗对高温强光的耐受性;Ca2+信号系统参与了胁迫过程中的渗透物质和Ca2+-ATPase活性等的调节.     

温度逆境交叉适应对葡萄叶片膜脂过氧化和细胞钙分布的影响

 研究了高温锻炼对低温胁迫下和低温锻炼对高温胁迫下葡萄(Vitis vinifera)叶片中丙二醛（MDA）、谷胱甘肽(GSH)和抗坏血酸(AsA)含量变化以及细胞中Ca2+分布的影响。结果表明: 高（低）温胁迫使正常生长的叶片丙二醛含量升高, GSH和AsA含量下降,低（高）温锻炼预处理能减少MDA含量,提高GSH和AsA含量,抑制了由于温度胁迫引起MDA含量升高和GSH和AsA下降趋势。常温下葡萄叶肉细胞的Ca2+主要分布于液泡、细胞间隙中;高温胁迫和低温胁迫后,细胞质中聚集大量Ca2+沉淀颗粒,液泡中和细胞间隙Ca2+沉淀颗粒减少,叶绿体超微结构被破坏,Ca2+稳态平衡遭到破坏。高温锻炼后细胞质出现大量的Ca2+沉淀颗粒,主要来源于细胞间隙,低温锻炼后细胞质也出现大量的Ca2+沉淀颗粒,主要来源于液泡,两者的叶绿体超微结构都完整;高温锻炼的叶片经过低温胁迫和低温锻炼的叶片经过高温胁迫后,细胞间隙和液泡内Ca2+沉淀颗粒增加,细胞质中Ca2+沉淀颗粒很少,叶绿体较完整,Ca2+稳态平衡得以维持。推测高低温锻炼能够通过Ca2+启动抗逆基因表达和维持细胞中Ca2+稳态平衡来交叉适应低高温的胁迫。     

Temperature-dependent inotropic action of A23187 on guinea-pig ventricular muscles

The effects of the Ca2+ ionophore, A23187, on the contraction and membrane action potential of the isolated guinea-pig papillary muscle were examined at various temperatures (30-16 degrees C) and compared to those of isoprenaline and a high calcium medium. A23187 caused a marked positive inotropic effect with a significant prolongation of the action potential duration at an early repolarization phase but not a late repolarization phase at normal temperature (30 degrees C). Such an inotropic effect was completely abolished at low temperature (16 degrees C) where a marked positive inotropic effect of isoprenaline (5 X 10(-8) M) and a high calcium medium (6.2 mM) still remained. These results suggest that the cardiac responsiveness to A23187 was sensitive to a low temperature at which a membrane lipid phase transition may occur.     

Effect of Mg2+ concentration on Ca2+ uptake kinetics and structure of the sarcoplasmic reticulum membrane.

Direct measurements of phosphorylation of the Ca2+ ATPase of the sarcoplasmic reticulum (SR) have shown that the lifetime of the first phosphorylated intermediate in the Ca2+ transport cycle, E1 approximately P, increases with decreasing [Mg2+] (Dupont, Y. 1980. Eur. J. Biochem. 109:231-238). Previous x-ray diffraction work (Pascolini, D., and J.K. Blasie. 1988. Biophys. J. 54:669-678) under high [Mg2+] conditions (25 mM) indicated that changes in the profile structure of the SR membrane could be responsible for the low-temperature transient trapping of E1 approximately P that occurs at temperatures below 2-3 degrees C, the upper characteristic temperature th for lipid lateral phase separation in the membrane. We now present results of our study of the Ca2+ uptake kinetics and of the structure of the SR membrane at low [Mg2+] (less than or equal to 100 microM). Our results show a slowing in the kinetics of both phases of the Ca2+ uptake process and an increase in the duration of the plateau of the fast phase before the onset of the slow phase, indicating an increase in the lifetime (transient trapping) of E1 approximately P. Calcium uptake kinetics at low [Mg2+] and moderately low temperature (approximately 0 degree C) are similar to those observed at much lower temperatures (approximately -10 degrees C) at high [Mg2+]. The temperature-induced structural changes that we observed at low [Mg2+] are much more pronounced than those found to occur at higher [Mg2+]. Also, at the lower [Mg2+] the upper characteristic temperature th for lipid lateral phase separation was found to be higher, at approximately 8-10 degrees C. Our studies indicate that both temperature and [Mg2+] affect the structure and the functionality (as measured by changes in the kinetics of Ca2+ uptake) of the SR membrane. Membrane lipid phase behavior and changes in the Ca2+ ATPase profile structure seem to be related, and we have found that structural changes are responsible for the slowing of the kinetics of the fast phase of Ca2+ uptake, and could also mediate the effect that [Mg2+] has on E1 approximately P lifetime.     

Macrophage activation by synthetic peptides. III. Changes in the membrane potential, Ca2+ content and the regulatory decrease of macrophage volume under the action of tuftsin and its antagonist

With the use of oxonol voltage-sensitive fluorescent dye it has been shown that the stimulation of macrophages (MP) with tuftsin results in a two-phase change in membrane potential: depolarization followed by hyperpolarization of plasma membrane. The pattern of changes in membrane potential depends on Na+ concentration in the medium and is disturbed with binding of cytoplasmic Ca2+. Fluorescent signal obtained from MP loaded with Ca(2+)-activated photoprotein obelin points to a significant increase in the concentration of cytoplasmic Ca2+ under the influence of tuftsin on cells: the source for Ca2+ being the medium. The rate of regulatory voltage decrease in MP increases under the influence of tuftsin: the effect of this peptide being similar to that of calcium ionophore. All these findings taken together enable us to suggest a phenomenological scheme of transmembrane ion signals arising during stimulation of MP with tuftsin: the receptor-mediated calcium channel provides a rise in cytoplasmic Ca2+ which opens non-selective cation channels for Na+ ions to activate eventually Ca(2+)-dependent K(+)-transport.     

The alteration of rabbit skeletal sarcoplasmic reticulum function by N-acylethanolamine, a lipid associated with myocardial infarction

The ability of N-acylethanolamines (pharmacologically active lipid metabolites which accumulate in canine myocardium during experimentally induced infarctions) to alter Ca2+ fluxes in a biological membrane system was studied using sarcoplasmic reticulum vesicles prepared from rabbit skeletal muscle. The effects of two N-acylethanolamines, the N-oleyl and N-lauryl derivatives, were compared to those of the lipophilic drugs, dibucaine and propranolol. The rate and extent of Ca2+ sequestration, Ca2+-Mg2+-ATPase activity and retention time of Ca2+ by the vesicles were all stimulated at low concentrations of the four compounds studied and inhibited at higher concentrations. The stoichiometry between Ca2+-pumping rates and ATPase activity was partially "uncoupled" indicating that both the calcium pump and the membrane permeability were affected by the drugs. However, although all four compounds exhibited the same qualitative behavior, the effects of the two N-acylethanolamines were more pronounced than dibucaine and propranolol and occurred at much lower concentrations. These results suggest that the N-acylethanolamines may have important physiological effects in the myocardium and, at least at lower concentrations, stimulate myocardial contractility by increasing the rate of calcium flux across the sarcoplasmic reticulum.     

Structure and dynamics of dimyristoylphosphatidic acid/calcium complexes by 2H NMR, infrared, spectroscopies and small-angle x-ray diffraction

The structural and dynamic properties of complexes of dimyristoylphosphatidic acid (DMPA) and calcium ions have been characterized by 2H NMR, Raman, and infrared spectroscopies and small-angle X-ray diffraction. All techniques used show that these complexes do not undergo a cooperative thermotropic phase transition. Small-angle X-ray diffraction unambiguously demonstrates that the structure of the lipid molecules of the DMPA/Ca2+ complexes remains lamellar even at a temperature as high as 85 degrees C. Raman results indicate that within this temperature range, only a few trans-gauche isomerizations of the C-C bonds of the phospholipid acyl chains arise in this system. The 2H NMR spectra indicate that the DMPA chains are highly motionally restricted up to 65 degrees C and that higher temperatures might activate some low-frequency overall motions of entire lamellar domains. Small-angle X-ray scattering and 2H NMR spectroscopy of 2H2O also show that the interaction of calcium with DMPA promotes an important dehydration of the lipid assembly, even though the latter technique clearly demonstrates that some water molecules remain strongly bond in the DMPA/Ca2+ complexes. The carbonyl stretching mode region of the infrared spectrum of DMPA/Ca2+ complexes suggests that these water molecules are trapped near the interfacial region of the lipid membrane and are hydrogen bonded with the carbonyl groups of the lipid. Finally, comparison of the phosphate stretching mode region of the infrared spectra of complexes of DMPA with calcium ions with those of model compounds provides strong evidence that calcium ions bind to both charges of the phosphate group of DMPA and form bridges between adjacent bilayers.     

Lipid vesicles which can bind to protein kinase C and activate the enzyme in the presence of EGTA.

Maximal protein kinase C activity with vesicles of phosphatidic acid and 1,2-dioleoyl-sn-glycerol is observed in the absence of added Ca2+. Addition of phosphatidylcholine to these vesicles restores some calcium dependence of enzyme activity. 1,2-Dioleoyl-sn-glycerol eliminates the Ca(2+)-dependence of protein kinase C activity found with phosphatidic acid alone. Phorbol esters do not mimic the action of 1,2-dioleoyl-sn-glycerol in this respect. This suggests that the 1,2-dioleoyl-sn-glycerol effect is a result of changes it causes in the physical properties of the membrane rather than to specific binding to the enzyme. The effect of 1,2-dioleoyl-sn-glycerol on the phosphatidic-acid-stimulated protein kinase C activity is dependent on the molar fraction of 1,2-dioleoyl-sn-glycerol used and results in a gradual shift from Ca2+ stimulation at low 1,2-dioleoyl-sn-glycerol concentrations to calcium inhibition at higher concentrations of 1,2-dioleoyl-sn-glycerol. Phosphatidylserine-stimulated activity is also shown to be largely independent of the calcium concentration at higher molar fractions of 1,2-dioleoyl-sn-glycerol. Thus, with certain lipid compositions, protein kinase C activity becomes independent of the calcium concentration or requires only very low, stoichiometric binding of Ca2+ to high affinity sites on the enzyme. Protein kinase C can bind to phosphatidic acid vesicles more readily than it can bind to phosphatidylserine vesicles in the absence of calcium. Addition of 1,2-dioleoyl-sn-glycerol to phosphatidylserine vesicles promotes the partitioning of protein kinase C into the membrane in the absence of added Ca2+. There is no isozyme specificity in this binding. These results suggest that a less-tightly packed headgroup region of the bilayer causes increased insertion of protein kinase C into the membrane. This is a necessary but not sufficient condition for activation of the enzyme in the presence of EGTA.