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1.
Sustained dendritic gradients of Ca2+ induced by excitatory amino acids in CA1 hippocampal neurons 总被引：8，自引：0，他引：8
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. 相似文献
2.
N-methyl-D-aspartate (NMDA) activates a class of excitatory amino acid receptor involved in a variety of plastic and pathological processes in the brain. Quantitative study of the NMDA receptor has been difficult in mammalian neurons, because it usually exists with other excitatory amino acid receptors of overlapping pharmacological specificities. Xenopus oocytes injected with messenger RNA isolated from primary cultures of rat brain have now been used to study NMDA receptors. The distinguishing properties of neuronal NMDA receptors have been reproduced in this amphibian cell, including voltage-dependent block by magnesium, block by the NMDA receptor antagonist D-2-amino-5-phosphonovaleric acid, and potentiation by glycine. This preparation should facilitate the quantitative study of the regulation of NMDA receptor activation and serve as a tool for purification of the encoding messenger RNA. 相似文献
3.
Hypoglycemia-induced neuronal damage prevented by an N-methyl-D-aspartate antagonist 总被引：20，自引：0，他引：20
T Wieloch 《Science (New York, N.Y.)》1985,230(4726):681-683
The possibility that neuronal damage due to hypoglycemia is induced by agonists acting on the N-methyl-D-aspartate (NMDA) receptor was investigated in the rat caudate nucleus. Local injections of an NMDA receptor antagonist, 2-amino-7-phosphonoheptanoic acid, were performed before induction of 30 minutes of reversible, insulin-induced, hypoglycemic coma. Neuronal necrosis in these animals after 1 week of recovery was reduced 90 percent compared to that in saline-injected animals. The results suggest that hypoglycemic neuronal damage is induced by NMDA receptor agonists, such as the excitatory amino acids or related compounds. 相似文献
4.
Indole-2-carboxylic acid: a competitive antagonist of potentiation by glycine at the NMDA receptor 总被引：6，自引：0，他引：6
J E Huettner 《Science (New York, N.Y.)》1989,243(4898):1611-1613
The N-methyl-D-aspartate (NMDA) class of excitatory amino acid receptors regulates the strength and stability of excitatory synapses and appears to play a major role in excitotoxic neuronal death associated with stroke and epilepsy. The conductance increase gated by NMDA is potentiated by the amino acid glycine, which acts at an allosteric site tightly coupled to the NMDA receptor. Indole-2-carboxylic acid (I2CA) specifically and competitively inhibits the potentiation by glycine of NMDA-gated current. In solutions containing low levels of glycine, I2CA completely blocks the response to NMDA, suggesting that NMDA alone is not sufficient for channel activation. I2CA will be useful for defining the interaction of glycine with NMDA receptors and for determining the in vivo role of glycine in excitotoxicity and synapse stabilization. 相似文献
5.
A. S. Timoshchenko V. F. Semikhov P. N. Kharchenko L. O. Nurminskaya 《Russian Agricultural Sciences》2011,37(6):441-446
The state of overwintering cereals during their transition into anabiosis is studied. It is shown that by the time growth
processes associated with a decrease of temperature below physiological zero ceases, free amino acids are utilized, the quantitative
ratio of protein amino acids changes, and raffinose, sucrose, and phenylalanine accumulate in the aboveground part of the
plants. It is concluded that the transition of cereals to a state of anabiosis occurs upon maximum binding of intracellular
water by the protein-carbohydrateamino acid complex after stabilization of negative ambient temperatures. The results of this
work and a number of previous publications permitted formulating an idea about the structure of the physiological and biochemical
mechanism of adaptation to negative temperatures acquired by perennial cereals during evolution. 相似文献
6.
Pharmacological induction of use-dependent receptive field modifications in the visual cortex 总被引：6，自引：0，他引：6
Lasting modifications of the receptive fields of neurons in the visual cortex can be induced by pairing visual stimuli with iontophoretic application of the neuromodulators acetylcholine and noradrenaline or the excitatory amino acids N-methyl-D-aspartate (NMDA) and L-glutamate. The modifications are obtained in less than 1 hour and persist for more than 40 minutes. Thus, acetylcholine and norepinephrine have a permissive role in use-dependent neuronal plasticity. These results support the notion of a postsynaptic threshold for neuronal malleability that differs from that of sodium-dependent action potentials. 相似文献
7.
Glutamate has been found to play an unexpectedly important role in neuroendocrine regulation in the hypothalamus, as revealed in converging experiments with ultrastructural immunocytochemistry, optical physiology with a calcium-sensitive dye, and intracellular electrical recording. There were large amounts of glutamate in boutons making synaptic contact with neuroendocrine neurons in the arcuate, paraventricular, and supraoptic nuclei. Almost all medial hypothalamic neurons responded to glutamate and to the glutamate agonists quisqualate and kainate with a consistent increase in intracellular calcium. In all magnocellular and parvocellular neurons of the paraventricular and arcuate nuclei tested, the non-NMDA (non-N-methyl-D-aspartate) glutamate antagonist CNQX (cyano-2,3-dihydroxy-7-nitroquinoxaline) reduced electrically stimulated and spontaneous excitatory postsynaptic potentials, suggesting that the endogenous neurotransmitter is an excitatory amino acid acting primarily on non-NMDA receptors. These results indicate that glutamate plays a major, widespread role in the control of neuroendocrine neurons. 相似文献
8.
Contributions of quisqualate and NMDA receptors to the induction and expression of LTP 总被引：18，自引：0，他引：18
The contributions of two subclasses of excitatory amino acid transmitter receptors to the induction and expression of long-term potentiation (LTP) were analyzed in hippocampal slices. The quisqualate/kainate receptor antagonist DNQX (6,7-dinitro-quinoxaline-2,3-dione) blocked 85% of the evoked field potential, leaving a small response that was sensitive to D-AP5 (D-2-amino-5-phosphonopentanoate), an N-methyl-D-aspartate (NMDA) receptor blocker. This residual D-AP5-sensitive response was of comparable size in control and previously potentiated inputs. High-frequency stimulation in the presence of DNQX did not result in the development of robust LTP. Washout of the drug, however, revealed the potentiation effect. Thus NMDA-mediated responses can induce, but are not greatly affected by, LTP; non-NMDA receptors, conversely, mediate responses that are not needed to elicit LTP but that are required for its expression. 相似文献
9.
洋葱种子种质超干保存的效果及其对膜系统的影响 总被引：13，自引：0，他引：13
洋葱超干种子室温下抗老化能力增强,耐储性提高。能明显延缓衰老。超干种子直接吸胀会引 起胚根断裂和种子活力下降。但吸胀前回水处理可以减轻吸胀过程中造成的损伤;超干处理大大增加了 苏氨酸（Ｔｈｒ）的渗漏,回水处理可恢复到原来水平。经回水处理的老化超干种子较未超干的对照老化种 子氨基酸和无机离子泄漏量减少,洋葱种子漏失的氨基酸以组氨酸（Ｈｉｓ）和苏氨酸（Ｔｈｒ）为多,外渗离子 以钾最多,超干还增加Ｃａ２＋和Ｍｇ２＋的渗漏,但回水后恢复到超干前的水平。 相似文献
10.
越冬暂养对雌性中华绒螯蟹的营养品质及风味的影响 总被引：1，自引：1，他引：0
为探究越冬暂养后雌性中华绒螯蟹(Eriocheir sinensis,以下简称河蟹)是否存在营养流失或风味品质下降现象,该研究利用嵌入在池塘循环水养殖系统中的网箱对雌性河蟹进行105天暂养,分析了暂养前后河蟹一般生物学指数、营养成分、脂肪酸、游离氨基酸、呈味核苷酸及挥发性风味物质的变化差异。结果显示,河蟹在越冬暂养期间处于稳定的生长状态,未出现“掉膏”。暂养后的河蟹,肌肉中必需氨基酸含量(E)显著上升(P<0.05),必需氨基酸与游离氨基酸总含量比值(E/T)显著上升(P<0.05);可食组织中腺苷酸(AMP)和肌苷酸(IMP)显著增加(P<0.05),次黄嘌呤(Hx)和肌苷(HxR)显著下降(P<0.05);虽然可食组织及卵巢中粗脂肪、C22:1和C22:4含量显著下降,但C20:2、C20：4和C20：5等多不饱和脂肪酸含量显著升高(P<0.05),同时PUFA/SFA比值显著上升;河蟹暂养105天后,1-辛烯-3-醇,己醛,壬醛和2-戊基呋喃为主要的挥发性物质,这些具有良好气味的物质占主导地位,表明河蟹的风味整体优于暂养前。以上结果表明,越冬暂养后河蟹的营养有一定的流失,品质和食用风味有所改善。 相似文献
11.
为研究鲫鱼(Carassius auratus)冰温无水保活技术,通过冰点测定确定了鲫鱼的生理冰温,采用僵硬指数作为离水后鲫鱼的活力指数,并通过比较冰温及冷藏(4℃)保鲜鲫鱼的氨基酸变化分析了冰温技术对鲫鱼营养吸收及口感的影响。结果表明,-0.3℃为鲫鱼生理冰点,在水中经过1℃/h由室温18℃降至冰温,离水后僵硬指数上升缓慢,可以在无水冰温状态下存活32h;并且水解及游离氨基酸中部分氨基酸含量得到提高。降温处理可能提高了鱼体的抗冻能力,显示经过冰温储藏后蛋白质易于消化吸收,并提高了风味口感。 相似文献
12.
Newly identified 'glutamate interneurons' and their role in locomotion in the lamprey spinal cord 总被引：3，自引：0，他引：3
A new class of excitatory premotor interneurons that are important in the generation of locomotion in the lamprey has now been described. In the isolated spinal cord, these neurons act simultaneously with their postsynaptic motoneurons during fictive swimming. They are small and numerous, and they monosynaptically excite both motoneurons and inhibitory premotor interneurons. The excitatory postsynaptic potentials are depressed by an antagonist of excitatory amino acids. These interneurons receive reticulospinal input from the brain stem and polysynaptic input form skin afferents. A model of the network underlying locomotion based on the synaptic interactions of these neurons can now be proposed for the lamprey. 相似文献
13.
【目的】球孢白僵菌(Beauveria bassiana)是一种重要的昆虫病原真菌,在毁灭性害虫葱蝇(Delia antiqua)的防治上具有重大潜力。研究旨在明确球孢白僵菌侵染葱蝇成虫后,血淋巴中蛋白质和游离氨基酸的变化及其致病的关系,揭示球孢白僵菌对葱蝇的生理调控机制。【方法】基于球孢白僵菌对葱蝇成虫的室内生物测定的研究基础,使用菌株GZGY-1-3,采用点滴法,用浓度为1×10~8个孢子/mL的孢子悬浮液处理葱蝇初羽化成虫,采用BCA法及高效液相色谱——串联质谱法(HPLC-MS/MS)测定球孢白僵菌侵染不同时间(12、24、36、48、60和72 h)后,侵染组与对照组葱蝇成虫血淋巴中蛋白质总量及20种游离氨基酸含量;分析不同处理时间蛋白质和游离氨基酸总量和重要氨基酸的含量变化。【结果】球孢白僵菌侵染12—36 h,侵染组与对照组血淋巴蛋白浓度变化趋势相近,均呈先下降后小幅度上升趋势。但侵染组血淋巴中蛋白含量高于对照组,侵染24 h后,侵染组血淋巴内蛋白质是对照组的1.20倍;侵染48 h后,侵染组中蛋白含量下降到最低,仅为对照组的0.83倍。侵染60—72 h,血淋巴蛋白含量升高。葱蝇成虫血淋巴中共检测出20种游离氨基酸。侵染12—36 h,葱蝇成虫血淋巴中游离氨基酸总量下降;侵染36 h,游离氨基酸总量下降到最低,仅为对照组的0.63倍;侵染48—60 h,游离氨基酸总量持续上升;侵染60 h后,游离氨基酸总量上升到最高,为对照组的2.01倍;感染72 h,游离氨基酸总量下降。侵染后,血淋巴内游离氨基酸种类没有变化,各种游离氨基酸的含量波动差异较大。球孢白僵菌对血淋巴重要氨基酸的含量变化有显著影响。【结论】球孢白僵菌的侵染引起葱蝇成虫血淋巴中蛋白质和游离氨基酸的一系列变化,严重阻碍了葱蝇成虫的正常生理活动,在葱蝇生物防治中具有应用潜力。 相似文献
14.
Role for excitatory amino acids in methamphetamine-induced nigrostriatal dopaminergic toxicity 总被引：23，自引：0，他引：23
The systemic administration of either methamphetamine or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to experimental animals produces degenerative changes in nigrostriatal dopaminergic neurons or their axon terminals. This study was conducted to determine if excitatory amino acids, which appear to be involved in various neurodegenerative disorders, might also contribute to the dopaminergic neurotoxicity produced in mice by either methamphetamine or MPTP. MK-801, phencyclidine, and ketamine, noncompetitive antagonists of one subtype of excitatory amino acid receptor, the N-methyl-D-aspartate receptor, provided substantial protection against neurotoxicity produced by methamphetamine but not that produced by MPTP. These findings indicate that excitatory amino acids play an important role in the nigrostriatal dopaminergic damage induced by methamphetamine. 相似文献
15.
目的：为提高刺参性腺利用率,制备风味较佳的海鲜风味调味料。方法：以刺参性腺酶解物为研究对象,加入D-木糖和L-半胱氨酸进行美拉德反应,结合低分子质量香味中间体、褐变程度、游离氨基酸、呈味核苷酸和挥发性物质等指标分析刺参性腺酶解物滋味和气味的变化。结果表明：美拉德反应后,鲜味、甜味游离氨基酸含量显著增加(P<0.05),苦味游离氨基酸占比减少；AMP为刺参性腺酶解物中主要的呈味核苷酸,且反应后含量显著下降(P<0.05)；关键风味化合物种类和数量均增加,醛类为主要的挥发性风味成分,苯甲醛是反应前后的最主要差异物质,吡嗪、噻吩和2-乙基呋喃是美拉德反应形成的特征性风味物质。结论：刺参肠酶解物/D-木糖/L-半胱氨酸美拉德反应产物具有良好的风味,为高品质调味基料和功能性食品的开发提供应用参考。 相似文献
16.
对甘蔗组培绿苗分化过程中的游离氨基酸组分和含量进行的主分量分析表明,不同培养基或不同品种供体下的第一主分量均为中性氨基酸,贡献率达40％—66％,并且中性氨基酸处于转化状态比处于积累状态对绿苗分化更为有利。而第一、二主分量共同表明丙氨酸—丝氨酸族、天冬氨酸族和谷氨酸族的效应较为重要,但在不同培养基中所起的效应有所差异。通径分析表明各类氨基酸对于不同培养基和不同供体对绿苗分化所起的直接和间接作用不尽相同。而同一品种在同一培养基分化过程中对绿苗分化率、核酸及蛋白质含量起主要直接作用的氨基酸种类和排列顺序是很相似的,相似程度越大,绿苗分化率越高。本试验在MS培养基分化过程起主要直接作用的是甘氨酸和蛋氮酸,而在N_6培养基中的是赖氨酸,苏氨酸和亮氨酸。 相似文献
17.
不同菌种发酵对藜麦蛋白质特性及脂质构成的影响 总被引：1，自引：0，他引：1
【目的】 比较不同菌种发酵对藜麦蛋白质水解及脂质变化的影响,为藜麦发酵食品的开发提供理论参考。【方法】 以藜麦为原料,加入不同菌种（酵母菌、植物乳杆菌及其混合菌）进行发酵,通过测定蛋白水解指数、蛋白质各组分、游离氨基酸、游离脂肪酸及脂质构成来判定发酵效果,确认哪种微生物更有利于藜麦营养成分的转化。【结果】 经酵母、植物乳杆菌、酵母和植物乳杆菌混合菌发酵后,藜麦蛋白质水解指数均有所升高,且主要是清蛋白和球蛋白发生了水解。发酵后藜麦中的游离氨基酸含量增加显著,尤其是必需氨基酸。酵母发酵藜麦更有利于蛋白质、多肽等水解成氨基酸。通过发酵处理,藜麦中的游离脂肪酸含量显著增加,且饱和脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸的比例更为接近1﹕1﹕1;甘油三酯、甘油二酯含量降低,但磷脂等功能脂的含量有所提高,且有酵母菌参与更有利于上述转化。【结论】 酵母菌、植物乳杆菌发酵过程中主要水解藜麦清蛋白和球蛋白成氨基酸等小分子化合物,且游离必需氨基酸含量显著升高;两种菌发酵后都有利于增加游离脂肪酸含量,降低甘油三酯、甘油二酯含量,且提高磷脂的含量。经酵母发酵,更有利于改善藜麦营养。 相似文献
18.
Coat protein gp120 from the human immunodeficiency virus type-1 (HIV-1) increased intracellular free calcium and injured rodent retinal ganglion cells and hippocampal neurons in culture. Highly purified recombinant gp120 envelope protein produced these effects in a dose-dependent fashion at picomolar concentrations. Immunoprecipitation with antibody to gp120, but not with control immunoglobulin-containing serum, depleted solutions of the viral envelope protein and also prevented both the rise in intracellular calcium and neuronal toxicity. The gp120-induced increase in intracellular calcium was abrogated by transiently lowering extracellular calcium or by adding the dihydropyridine calcium channel antagonist nimodipine (100 nM). Calcium channel antagonists also prevented gp120-induced neuronal injury. In addition, intracellular stores appeared to contribute substantially to the increase in calcium elicited by gp120. Since increases in intracellular calcium have been associated with neurotoxicity, it is possible that an injurious effect of gp120 on neurons might be related to this mechanism and that treatment with calcium channel antagonists may prove useful in mitigating HIV-1-related neuronal injury. 相似文献
19.
用HPLC法分析了苦丁茶游离氨基酸的组成及其含量,并与茶叶游离氨基酸组成和含量作了比较,结果表明,苦丁茶鲜叶检出16种游离氨基酸,苦丁绿细茶和苦丁红细茶分别检出14种游离氨基酸,其中以组氨酸为主,它在鲜叶中占氨基酸总量的55.92％,在苦丁绿细茶和苦丁红细茶中分别占85.4％和71.0％;其次为天门冬氨酸、苏氨酸、丝氨酸和谷氨酸,而茶叶最主要的游离氨基酸为茶氨酸;其次为谷氨酸、精氨酸和组氨酸,苦丁茶游离氨基酸总量约为茶叶的1/5～1/50,两种植物分别属于不同的氮代谢类型。 相似文献
20.
An excitatory amino acid antagonist blocks cone input to sign-conserving second-order retinal neurons 总被引：8，自引：0，他引：8
cis-2,3-Piperidinedicarboxylic acid (PDA), an excitatory amino acid antagonist, reversibly blocked cone input to OFF bipolars and horizontal cells, whereas ON bipolars were relatively unaffected. Kainic acid effects were also blocked, indicating a postsynaptic mechanism of action. The use of PDA helps to characterize one of two classes of excitatory amino acid synaptic receptors that mediate cone influence in the outer retina. 相似文献