共查询到20条相似文献，搜索用时 31 毫秒
1.
The traditional view that quantal release of neurotransmitter results from the fusion of transmitter-containing vesicles with the neuronal membrane has been recently challenged. Although various alternative mechanisms have been proposed, a common element among them is the release of cytoplasmic transmitter, which, in one view, could occur through large conductance channels on the presynaptic membrane. Six nerve-muscle cell pairs were examined with a whole-cell patch clamp for the presence of such channels that are associated with the production of miniature end-plate potentials. Examination of the neuronal membrane current during the occurrence of 822 miniature end-plate potentials produced no evidence of large channels. Thus it is unlikely that quantal release is mediated by such channels in the neuromuscular junction. 相似文献
2.
Electrical responses of insect central neurons: augmentation by nerve section or colchicine 总被引：3，自引：0，他引：3
Intracellular recording from the somata of central motor neurons in the cockroach Periplaneta americana normally shows little or no electrical response evoked by soma depolarization or by antidromic stimulation. Within 4 days after either cutting the axon or administration of colchicine, large action potentials can regularly be recorded from cell bodies of metathoracic motor neurons. Each experimental procedure evokes formation of a dense, perinuclear ribonucleic acid ring in the soma of neurons showing augmented electrical responses. 相似文献
3.
We examined dendritic protein synthesis after a prolonged blockade of action potentials alone and after a blockade of both action potentials and miniature excitatory synaptic events (minis). Relative to controls, dendrites exposed to a prolonged blockade of action potentials showed diminished protein synthesis. Dendrites in which both action potentials and minis were blocked showed enhanced protein synthesis, suggesting that minis inhibit dendritic translation. When minis were acutely blocked or stimulated, an immediate increase or decrease, respectively, in dendritic translation was observed. Taken together, these results reveal a role for miniature synaptic events in the acute regulation of dendritic protein synthesis in neurons. 相似文献
4.
5.
Calcium: is it required for transmitter secretion? 总被引：7，自引：0，他引：7
Ethanol multiplies miniature end-plate potential frequency independently of calcium ion concentrations and also multiplies calcium-dependent depolarization-evoked quantal release, to the same extent. This result implies a final common pathway, requiring little or no calcium, for both kinds of transmitter secretion. Chlorpromazine and hypertonicity act similarly to ethanol, but also depress depolarization-secretion coupling. 相似文献
6.
Xenopus oocytes injected with rat uterine RNA express very slowly activating potassium currents 总被引：3，自引：0，他引：3
M B Boyle E M Azhderian N J MacLusky F Naftolin L K Kaczmarek 《Science (New York, N.Y.)》1987,235(4793):1221-1224
Under the influence of estrogen, uterine smooth muscle becomes highly excitable, generating spontaneous and prolonged bursts of action potentials. In a study of the mechanisms by which this transition in excitability occurs, polyadenylated RNA from the uteri of estrogen-treated rats was injected into Xenopus oocytes. The injected oocytes expressed a novel voltage-dependent potassium current. This current was not observed in oocytes injected with RNA from several other excitable tissues, including rat brain and uterine smooth muscle from ovariectomized rats not treated with estrogen. The activation of this current on depolarization was exceptionally slow, particularly for depolarizations from relatively negative membrane potentials. Such a slowly activating channel may play an important role in the slow, repetitive bursts of action potentials in the myometrium. 相似文献
7.
In a variety of vertebrates and invertebrates, long-lasting enhancement of synaptic transmission contributes to the storage of memory lasting one or more days. However, it has not been demonstrated directly whether this increase in synaptic transmission is caused by an enhancement of transmitter release or an increase in the sensitivity of the postsynaptic receptors. These possibilities can be distinguished by a quantal analysis in which the size of the miniature excitatory postsynaptic potential released spontaneously from the presynaptic terminal is used as a reference. By means of microcultures, in which single sensory and motor neurons of Aplysia were plated together, miniature excitatory postsynaptic potentials attributable to the spontaneous release of single transmitter quanta from individual presynaptic neurons were recorded and used to analyze long-term facilitation induced by repeated applications of 5-hydroxytryptamine. The results indicate that the facilitation is caused by an increase in the number of transmitter quanta released by the presynaptic neuron. 相似文献
8.
《Computers and Electronics in Agriculture》1987,2(1):57-66
A system is described which allows sheep electrocardiograms (ECG) to be recorded by a miniature 24-h tape recorder. Two types of electrode were used. Skin electrodes offered a more versatile system, but did not perform as well as subcutaneous electrodes. Subcutaneous electrodes remained functional for longer (90% in position after 49 weeks compared with a working life of less than 24 h), they worked reliably when in position (100% vs. 55%), and they were less affected by electrical noise resulting from electrode movement or muscle potential (16 vs. 23%).An experiment to investigate the effects of placing the recording equipment on the sheep showed that, 5 min after handling, heart rate had returned to its pre-handling level. This is a much briefer effect than the effects reported by other workers, but there are breed and species differences in responses to handling, and the animals in the present study were handled regularly. 相似文献
9.
瓜实蝇(Bactrocera cucurbitae)是苦瓜(Momordica charantia)的一种重要入侵性害虫,评估其在不同生长期苦瓜上的产卵偏好,旨在摸清该虫的防治适期。本研究选取了不同生长期的苦瓜,通过设定选择性和非选择性测试,在室内研究了不同生长期损伤和未损伤的苦瓜对瓜实蝇产卵偏好的影响。结果表明:不同生长期的苦瓜显著影响了瓜实蝇的产卵偏好。针对无损伤的苦瓜,瓜实蝇偏好在谢花2~5和6~8 d后的苦瓜上产卵;针对损伤的苦瓜,除谢花1 d的苦瓜外,瓜实蝇在其它生长期苦瓜上的产卵偏好无显著性差异。基于本研究,对于无损伤的苦瓜,谢花2~8 d是预防和防治瓜实蝇的关键时期;而苦瓜一旦损伤,除谢花1 d外所有生长期均应提防瓜实蝇的为害。 相似文献
10.
Functional arteries grown in vitro 总被引：1，自引：0，他引：1
Niklason LE Gao J Abbott WM Hirschi KK Houser S Marini R Langer R 《Science (New York, N.Y.)》1999,284(5413):489-493
A tissue engineering approach was developed to produce arbitrary lengths of vascular graft material from smooth muscle and endothelial cells that were derived from a biopsy of vascular tissue. Bovine vessels cultured under pulsatile conditions had rupture strengths greater than 2000 millimeters of mercury, suture retention strengths of up to 90 grams, and collagen contents of up to 50 percent. Cultured vessels also showed contractile responses to pharmacological agents and contained smooth muscle cells that displayed markers of differentiation such as calponin and myosin heavy chains. Tissue-engineered arteries were implanted in miniature swine, with patency documented up to 24 days by digital angiography. 相似文献
11.
[目的]克隆五指山小型猪生长激素释放激素（GHRH）受体基因的cDNA,并对其进行序列分析。[方法]以五指山小型猪耳组织提取的基因纽RNA为模板,根据已报道的猪GHRHRcDNA序列设计3对引物,用RT—PCR方法进行cDNA扩增。PCR产物经回收纯化后,与pMD18-T连接并转化大肠杆菌DH5a,转化产物经PCR和双酶切鉴定后筛选出阳性克隆,阳性克隆经LB液体培养基培养鉴定后测序。[结果]成功获得了五指山小型猪GHRH受体基因的cDNA,该片段长1577bp,编码423个氨基酸。BLAST分析结果表明,该片段与猪GHRH受体基因仅有23个碱基的差异,同源性为98％;而两者GHRH受体基因均由423个氨基酸组成,序列同源性为96％。[结论]该研究为进一步揭示五指山小型猪的矮小机理提供了理论依据。 相似文献
12.
【目的】为探索新疆草原兔尾鼠(Lagurus lagurus)卵透明带3(lZP3)在精卵结合中的机理,有效的控制草原兔尾鼠的生育;【方法】将RNA干扰载体pGenesil-ZP31和真核表达质粒p-ACLC一起通过尾静脉大容量快速注射法(Hydrodynamics-based transfectionmethod,HD法)共注射小鼠。【结果】半定量RT-PCR和real-timePCR结果表明,2种质粒共注射时,pGenesil-ZP31的干涉作用至少发生在注射后的8h到10d之间;顺序性注射实验中,注射pGenesil-ZP31后间隔8h和1d再注射p-ACLC时,pGenesil-ZP31能在一定程度上干涉lZP3mRNA的表达,间隔3d以后lZP3mRNA的表达几乎不受影响,未出现干涉现象。而注射p-ACLC后间隔1h、2h、4h和8h再注射pGenesil-ZP31,lZP3mRNA的表达也受到了抑制,间隔24h时抑制现象则消失;【结论】以载体为基础的体内RNAi过程具有时间依赖性,为在卵母细胞水平进一步研究siRNA对lZP3的干涉机制提供借鉴。 相似文献
13.
Electrical sources in human somatosensory cortex: identification by combined magnetic and potential recordings 总被引：7，自引：0，他引：7
Magnetic fields and electrical potentials produced by neuronal activity have different properties that can be used for the identification of electrical sources in the human brain. Fields and potentials occurring 20 to 30 milliseconds after median nerve stimulation in human subjects were compared in order to investigate the sources of evoked potential components that have been attributed by different investigators to the thalamus or thalamocortical afferents, to separate radial sources in somatosensory cortex and motor cortex, or to a tangential source in somatosensory cortex. The magnetic and potential wave forms were highly similar in morphology, and their spatial distributions were centered over sensorimotor cortex, were dipolar in shape, and differed in orientation by approximately 90 degrees; distances between the minimum and maximum of the magnetic distributions were about 60 percent of those of the potential distributions. These results cannot be accounted for by thalamic sources or radial cortical sources alone, but are consistent with a tangential source in somatosensory cortex, with an additional smaller contribution from radial sources. 相似文献
14.
15.
The water potential of leaves in situ can be measured without temperature control with a miniature, single-junction psychrometer constructed from silver foil and attached to the leaf with a silver-impregnated, conductive coating. The temperature of the psychrometer has been found to stay within 0.025 degrees C of the temperature of a simulated leaf when the latter temperature was changing at a rate of 1 degrees C per minute. Leaf water potentials can be measured with a precision of +/- 1 bar, or better. 相似文献
16.
17.
报道了采用红外探测－计算机控制的超低温快速冷冻固定技术、Ｘ－射线能量色散谱微区定量分析及Ｃａ２＋细胞化学技术对骨骼肌收缩潜伏期时肌浆网内的Ｃａ２＋进行了分析,从超微结构形态学的角度对骨骼肌兴奋－收缩偶联发生时,肌浆网内Ｃａ２＋的作用进行了研究,这对揭示骨骼肌兴奋－收缩偶联时,肌浆网内Ｃａ２＋的释放机理研究有重要意义。 相似文献
18.
GRAFSTEIN B 《Science (New York, N.Y.)》1963,142(3594):973-975
After topical application of thiosemicarbazide, semicarbazide, or isoniazid to the surface of an isolated region of cortex, convulsive responses to electrical stimulation appeared only after a finite number of normal responses had been elicited, and disappeared again if stimulation was interrupted for about 10 minutes. With any of the other convulsant drugs tested, development of the convulsive pattern was independent of whether or not the cortex was stimulated. The two groups of drugs evidently have dijferent modes of action. 相似文献
19.
Amantadine: neuromuscular blockade by suppression of ionic conductance of the acetylcholine receptor 总被引：5，自引：0，他引：5
E X Albuquerque A T Eldefrawi M E Eldefrawi N A Mansour M C Tsai 《Science (New York, N.Y.)》1978,199(4330):788-790
Amantadine hydrochloride decreases the sensitivity of denervated mammalian muscle to iontophoretically applied acetylcholine. The drug depresses the amplitude of the end-plate current and reverses the slope of the relation between half-decay time and membrane potential suggesting that it alters the ionic conductance that is mediated by the acetylcholine receptor. Binding studies confirm that amantadine acts on the ion conductance modulator rather than the acetylcholine receptor. 相似文献
20.
Cross-striated muscle fibers of very large size have been found in the scutal-tergal adductor and depressor muscles of the large barnacle B. nubilus. Adductor muscle fibers are up to 2 mm thick. They are innervated by separate nerves, each supplying one end, but not the central region, with terminals; each fiber receives two or three excitor axons. Depressor muscle fibers are up to 1.4 mm thick and receive multiterminal innervation along their entire length; they are innervated by two excitor axons. Postsynaptic potentials are of small or large size and lead to small or large twitches; they do not show facilitation. The muscle fibers shorten to as little as one-sixth resting length. 相似文献