Localization and mobility of omega-conotoxin-sensitive Ca2+ channels in hippocampal CA1 neurons

Voltage-dependent Ca2+ channels (VDCCs) are modulators of synaptic plasticity, oscillatory behavior, and rhythmic firing in brain regions such as the hippocampus. The distribution and lateral mobility of VDCCs on CA1 hippocampal neurons have been determined with biologically active fluorescent and biotinylated derivatives of the selective probe omega-conotoxin in conjunction with circular dityndallism, digital fluorescence imaging, and photobleach recovery microscopy. On noninnervated cell bodies, VDCCs were found to be organized in multiple clusters, whereas after innervation the VDCCs were concentrated and immobilized at synaptic contact sites. On dendrites, VDCC distribution was punctate and was interrupted by extensive bare regions or abruptly terminated. More than 85% of the dendritic VDCCs were found to be immobile by fluorescence photobleach recovery. Thus, before synaptic contact, specific mechanisms target, segregate, and immobilize VDCCs to neuronal cell bodies and to specialized dendritic sites. Regulation of this distribution may be critical in determining the firing activity and integrative properties of hippocampal CA1 neurons.     

Sustained dendritic gradients of Ca2+ induced by excitatory amino acids in CA1 hippocampal neurons

Spatially resolved measurements of intracellular free calcium and of the changes produced by excitatory amino acids were made in neurons isolated from adult mammalian brain. Extremely long-lasting (minutes) Ca2+ gradients were induced in the apical dendrites of hippocampal CA1 neurons after brief (1 to 3 seconds), local application of either glutamate or N-methyl-D-aspartate (NMDA). These gradients reflect the continuous flux of Ca2+ into the dendrite. The sustained gradients, but not the immediate transient response to the agonists, were prevented by prior treatment with the protein kinase C inhibitor sphingosine. Expression of the long-lasting Ca2+ gradients generally required a priming or conditioning stimulus with the excitatory agonist. The findings demonstrate a coupling between NMDA receptor activation and long-lasting intracellular Ca2+ elevation that could contribute to certain use-dependent modifications of synaptic responses in hippocampal CA1 neurons.     

Interaction of brain synaptic vesicles induced by endogenous Ca2+ -dependent phospholipase A2

Endogenous phospholipase A2 activity of brain synaptic vesicles was Ca2+ -dependent and was increased by prostaglandin F2 alpha, calmodulin, adenosine 3', 5' -monophosphate, and adenosine triphosphate, whereas the activity was inhibited by prostaglandin E2 in the absence or presence of calmodulin. Light-scattering measurements demonstrated that stimulation of the enzyme's activity correlated with the induction of vesicle-vesicle aggregation. The effects of these compounds on endogenous synaptic vesicle phospholipase A2 activity may imply a common end point of their purported neuromodulatory actions, and indicate that synaptic vesicle phospholipase A2 may play a central role in presynaptic neurotransmission.     

Restoration by calmodulin of a Ca2+-dependent K+ current missing in a mutant of Paramecium

A combination of genetics, biochemistry, and biophysics was used to show that calmodulin is involved in the regulation of an ion channel. Calmodulin restored the Ca2+-dependent K+ current in pantophobiac, a mutant in Paramecium that lacks this current. The restoration of the current occurred within 2 hours after the injection of 1 picogram of wild-type calmodulin into the mutant. The current remained for approximately 30 hours before the mutant phenotype returned. The injection of calmodulin isolated from pantophobiac had no effect. These results imply that calmodulin is required for the function or regulation of the Ca2+-dependent K+ current in Paramecium.     

青霉素和Ca2+对花生老化种子发芽的影响

使用不同浓度的青霉素和Ca2 处理老化的花生种子,结果表明:适宜浓度的青霉素和Ca2 能显著提高老化花生种子的发芽率、发芽指数、活力指数、电导率,增强根系活力.青霉素的适宜浓度为200 mg/L,Ca2 的适宜浓度为0.15%,青霉素和Ca2 的互作效应以青霉素100 mg/L,Ca2 0.15%为最好.     

Ca2+ and Ca2+-activated K+ currents in mammalian gastric smooth muscle cells

Inward movement of calcium through voltage-dependent channels in muscle is thought to initiate the action potential and trigger contraction. Calcium-activated potassium channels carry large outward potassium currents that may be responsible for membrane repolarization. Calcium and calcium-activated potassium currents were identified in enzymatically isolated mammalian gastric myocytes. These currents were blocked by cadmium and nifedipine but were not substantially affected by diltiazem or D600. No evidence for a tetrodotoxin-sensitive sodium current or an inwardly rectifying potassium current was found.     

Dominant role of N-type Ca2+ channels in evoked release of norepinephrine from sympathetic neurons

Multiple types of calcium channels have been found in neurons, but uncertainty remains about which ones are involved in stimulus-secretion coupling. Two types of calcium channels in rat sympathetic neurons were described, and their relative importance in controlling norepinephrine release was analyzed. N-type and L-type calcium channels differed in voltage dependence, unitary barium conductance, and pharmacology. Nitrendipine inhibited activity of L-type channels but not N-type channels. Potassium-evoked norepinephrine release was markedly reduced by cadmium and the conesnail peptide toxin omega-Conus geographus toxin VIA, agents that block both N- and L-type channels, but was little affected by nitrendipine at concentrations that strongly reduce calcium influx, as measured by fura-2. Thus N-type calcium channels play a dominant role in the depolarization-evoked release of norepinephrine.     

Inactivation and block of calcium channels by photo-released Ca2+ in dorsal root ganglion neurons

Calcium channels are inactivated by voltage and intracellular calcium. To study the kinetics and the mechanism of calcium-induced inactivation of calcium channels, a "caged" calcium compound, dimethoxy-nitrophen was used to photo-release about 50 microM calcium ion within 0.2 millisecond in dorsal root ganglion neurons. When divalent cations were the charge carriers, intracellular photo-release of calcium inactivated the calcium channel with an invariant rate [time constant (tau) approximately equal to 7 milliseconds]. When the monovalent cation sodium was the charge carrier, photorelease of calcium inside or outside of the cell blocked the channel rapidly (tau approximately equal to 0.4 millisecond), but the block was greater from the external side. Thus the kinetics of calcium-induced calcium channel inactivation depends on the valency of the permeant cation. The data imply that calcium channels exist in either of two conformational states, the calcium- and sodium-permeant forms, or, alternatively, calcium-induced inactivation occurs at a site closely associated with the internal permeating site.     

A potential second messenger role for unsaturated fatty acids: activation of Ca2+-dependent protein kinase

Arachidonate and other unsaturated long-chain fatty acids were found to activate protein kinase C from human neutrophils. Kinase activation by arachidonate required calcium and was enhanced by diolein but did not require exogenous phosphatidylserine. Submaximal levels of arachidonate also enhanced the affinity of the kinase for calcium during activation by phosphatidylserine. Thus the release of arachidonate, which is triggered in many cell types by ligand-receptor interactions, could play a second messenger role in the regulation of cellular function by activation of protein kinase C.     

The Role of Extracellular Ca2+Influx, Intracellular Ca2+ Release and Calmodulin in Mouse Egg Fertilization

The effects of various Ca^2 -modifying drugs on moue egg fertilization were studied.Ca^2 chelator,ethylen glycol-bis-(2-aminoethyl)-tetracetic acid(EGTA),and calmodulin(CaM) antagonist,trifluoperzaine (TFP),inhibited fertilization in a dose-dependent manner,whild Ca^2 channel bolcker,verspamil,did not have any effect.When intracellular Ca^2 release was blocked by 8-(N,N-diethylamino) octy 1-3,4,5-trimethoxy-benzonate(TME-8) or the Ca^2 oscillations were inhibited by an inhibitor of endoplasmic reticulum Ca^2 -At-Pase,thapsigargin,the second polar body emission and pronuclear formation were significantly decreased.In contrast,inhibition of intracellular Ca^2 release via bolckage of inositol 1,4,5-triphosphate (IP3) production by neomycin or lithium did not affect fertilization.The results sugest that both extracellular influx,intracellular Ca^2 release and CaM activation are required for mormal fertilization.However,extracellular influx through voltage-gated Ca^2 channel and intracellular release induced by IP3 and not the only pathways for producing Ca^2 transients in moue eggs.     

肉鸡腹水综合征患鸡肺脏组织钙沉积和Ca2＋-ATPase活性变化

肺动脉收缩和重塑在肉鸡AS发生过程中起着重要作用.本实验经采用右心导管法研究发现AS患鸡PASP 、PADP和mPAP极显著高于对照组(P <0.01).同时,采用焦锑酸钾沉淀法、电镜酶细胞化学法研究AS患鸡肺脏组织Ca2+和Ca2+-ATPase活性变化,发现AS患鸡肺脏组织中钙沉积量显著增多,且Ca2+-ATPase的电子密度颗粒显著减少或缺失.表明AS患鸡具有明显的肺动脉高压,其可能与肺脏组织,特别是肺动脉平滑肌细胞钙处理能力异常导致的钙离子浓度升高和肌浆网Ca2+-ATPase酶活性降低有关.     

高糖培养对乳鼠海马神经元存活及c-fos蛋白表达影响

目的探讨高糖培养对乳鼠海马神经元存活及c-fos蛋白表达影响。方法无血清体外培养方法获得新生SD乳鼠海马神经元,分为正常组和高糖6、12、18、24h共5组。分别用PI/Hoechest33342染色法、免疫荧光细胞化学法检测检测海马神经元存活率及c-fos蛋白表达。结果高糖24h组海马神经元存活率明显低于正常组及高糖6、12、18h组(P<0.01)。高糖处理后,c-fos蛋白表达在6h开始出现,12h达高峰,此后逐渐下降(P<0.01)。结论高糖培养导致的乳鼠海马神经元存活率下降与c-fos蛋白表达有关。     

Somatostatin augments the M-current in hippocampal neurons

Immunocytochemical and electrophysiological evidence suggests that somatostatin may be a transmitter in the hippocampus. To characterize the ionic mechanisms underlying somatostatin effects, voltage-clamp and current-clamp studies on single CA1 pyramidal neurons in the hippocampal slice preparation were performed. Both somatostatin-28 and somatostatin-14 elicited a steady outward current and selectively augmented the noninactivating, voltage-dependent outward potassium current known as the M-current. Since the muscarinic cholinergic agonists carbachol and muscarine antagonized this current, these results suggest a reciprocal regulation of the M-current by somatostatin and acetylcholine.     

植物Ca2+信号的研究进展

在植物的生长发育过程中,为了适应环境,调节自身代谢和生长,需要对各种外界环境刺激以及植物内部生理信息做出反应,因此,植物产生了自己的信号系统。Ca2 作为一种信号分子在植物细胞信号系统中起着举足轻重的作用。针对国内外对植物Ca2 信号的研究情况,综述了Ca2 信号的产生、Ca2 信号参与的各种植物生理过程、Ca2 信号的检测以及其研究的最新进展。     

大鼠全脑缺血前注射灯盏花素对再灌后海马神经元内钙离子浓度的影响

目的观察灯盏花素对大鼠脑缺血再灌后海马CA1区神经元内游离钙离子浓度的影响。方法采用钙离子成像系统检测海马CA1区神经元内钙离子浓度。实验分为(1)正常组:大鼠不做任何处理,直接断头取脑分离出神经元,观察神经元内钙离子浓度;(2)再灌注组:制作大鼠的全脑缺血模型,并以再灌后分1.5、3.0、4.5、6.0 h 4个时间点进行观察;(3)灯盏花素组:在制作全脑缺血模型前15 min腹腔注射灯盏花素50 mg/kg,并以再灌后分1.5、3.0、4.5、6.0 h 4个时间点进行观察。每组(时间点)均检测11个神经元。结果再灌注组再灌后1.5、3.0、4.5 h时间点与正常组比较,Ca2 浓度升高(P<0.05或P<0.01);再灌后6.0 h神经元内游离Ca2 浓度与正常组比较,差异无统计学意义。灯盏花素组再灌后1.5、4.5 h时间点Ca2 浓度比再灌组相同时间点低(P<0.01);而再灌后3.0、6.0 h Ca2 浓度与再灌组相应时间点比较,差异无统计学意义。结论全脑缺血前给予灯盏花素可降低全脑缺血再灌后大鼠海马CA1区神经元内游离Ca2 浓度。     

Ca2+ Fe2+ Mg2+ Zn2+ Na+ K+对哺乳仔猪乳糖酶活力的影响

乳糖和矿质元素是哺乳仔猪十分重要的营养素,对7日龄的哺乳仔猪乳糖酶研究结果表明:哺乳仔猪乳糖酶的酶活力常数是65.825μg(ONP)/mL.m in,矿质元素钠、铁和钙能促进乳糖酶的酶活力。     

Immunocyte Ca2+ influx system mediated by LTRPC2

We characterized an activation mechanism of the human LTRPC2 protein, a member of the transient receptor potential family of ion channels, and demonstrated that LTRPC2 mediates Ca2+ influx into immunocytes. Intracellular pyrimidine nucleotides, adenosine 5'-diphosphoribose (ADPR), and nicotinamide adenine dinucleotide (NAD), directly activated LTRPC2, which functioned as a Ca2+-permeable nonselective cation channel and enabled Ca2+ influx into cells. This activation was suppressed by intracellular adenosine triphosphate. These results reveal that ADPR and NAD act as intracellular messengers and may have an important role in Ca2+ influx by activating LTRPC2 in immunocytes.     

Ca2+ Fe2+ Mg2+ Zn2+ Na+ K+对哺乳仔猪乳糖酶活力的影响

乳糖和矿质元素是哺乳仔猪十分重要的营养素,对7日龄的哺乳仔猪乳糖酶研究结果表明:哺乳仔猪乳糖酶的酶活力常数是65.825μg(ONP)/mL·min,矿质元素钠、铁和钙能促进乳糖酶的酶活力.     

Ethanol inhibits NMDA-activated ion current in hippocampal neurons

The ion current induced by the glutamate receptor agonist N-methyl-D-aspartate (NMDA) in voltage-clamped hippocampal neurons was inhibited by ethanol (EtOH). Inhibition increased in a concentration-dependent manner over the range 5 to 50 mM, a range that also produces intoxication. The amplitude of the NMDA-activated current was reduced 61 percent by 50 mM EtOH; in contrast, this concentration of EtOH reduced the amplitude of current activated by the glutamate receptor agonists kainate and quisqualate by only 18 and 15 percent, respectively. The potency for inhibition of the NMDA-activated current by several alcohols is linearly related to their intoxicating potency, suggesting that alcohol-induced inhibition of responses to NMDA receptor activation may contribute to the neural and cognitive impairments associated with intoxication.     

Cu2+、Mn2+、Mg2+胁迫对小麦种子发芽状况的影响

采用不同浓度Cu^2 、Mn^2 、Mg^2 胁迫，研究其对小麦种子发芽状况的影响。结果表明：≥0．1％浓度的Cu^2 胁迫对小麦种子发芽影响最大，导致小麦叶片呈黄绿色，苗矮小，根系衰退，发芽势和发芽率大幅度降低，不正常幼苗和未发芽种子数增加。≥0．1％浓度的Mn^2 胁迫对小麦种子发芽产生负面影响，幼苗新生叶尖全部枯黄，叶片相对较短，根系生长受抑制。≥0．5％浓度的Mn^2 胁迫对小麦种子发芽产生较明显影响。≤0．5％浓度的Mg^2 胁迫对小麦种子发芽的影响较小，与对照差异不明显。