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1.
Cardiac arrhythmia was induced in mice by the injection of ouabain, lidocaine, and diphenylhydantoin. Temporal spreading of ventricular electrocardiographic complexes is shown consistently to follow injection of a cardioactive drug and to precede rhythm disturbances. A computerized monitoring technique based on temporal spreading and waveform distortion should find wide clinical and experimental application. 相似文献
2.
The effects of pentobarbital (Nembutal) on synaptic transmission and postsynaptic potentials were studied by the use of several invertebrate preparations. Pentobarbital selectively and reversibly depressed both excitatory postsynaptic potentials and sodium-dependent postsynaptic responses to putative excitatory transmitters without affecting either inhibitory postsynaptic potentials or chloride- and potassium-dependent postsynaptic responses to putative transmitters. A selective depression of postsynaptic excitatory events was also observed with other central nervous system depressants (ethanol, chloroform, chloralose, diphenylhydantoin, and urethane). The results suggest that central and peripheral depression observed during general anesthesia is due to a selective depression of excitatory synaptic events. 相似文献
3.
The objective of this experiment is to evaluate the role of intracellular and extracellular Ca2＋ and calmodulin （CAM） in jasmonic acid （JA） signaling. The laser scanning microscopy was used to detect the changes of [Ca2＋]cyt of Arabidopsis thaliana leaf cells which pretreated with different types of calcium channel blocker. Moreover, the expression of VSP, one of JA response genes, was also investigated after pretreated with the above blocker and antagonist of CaM. The results showed that extracellular and intracellular calcium both involved in the JA-induced Ca2＋ mobilization, and then Ca2＋ exerted its functions through activating the CaM or CaM related proteins. The apoplast calcium influx and the calcium release from the calcium stores are both involved in the JA-induced calcium mobilization, then the JA-induced Ca2＋ transmited the JA signal through CaM or CaM related proteins, and regulated the JA responsive genes. 相似文献
4.
Puromycin effect on memory may be due to occult seizures 总被引：2，自引：0，他引：2
Intracerebral injections of puromycin, which have been shown to impair memory 3 hours after training, increase the susceptibility of mice to seizures after administration of normally subconvulsive doses of pentylenetetrazol. Cycloheximide, which antagonizes the puromycin-induced amnesia 3 hours after training, also antagonizes the puromycin effect on susceptibility to seizure. The anticonvulsant diphenylhydantoin antagonizes the puromycin effect on memory. The puromycin effect on memory may be due to occult seizures. 相似文献
5.
During activation of visceral smooth muscle there is an increase in cytosolic-free calcium, but the source (intracellular calcium release or calcium influx), kinetics, and stoichiometry of this increase have not been determined. Here, the fluorescent indicator, quin2-acetoxymethyl ester, was used to measure directly cytosolic-free calcium during contraction of isolated stomach muscle cells induced by the two neuropeptides cholecystokinin-octapeptide and Met-enkephalin as well as acetylcholine. An increase in cytosolic-free calcium was seen that was (i) dependent on the concentration of contractile agonist, (ii) derived from intracellular sources (that is, not significantly affected by removal of ambient calcium or addition of a calcium channel blocker), and (iii) kinetically and stoichiometrically related to net calcium efflux and contraction. In contrast, the increase in cytosolic-free calcium induced by depolarizing concentrations of potassium was caused by influx of calcium through voltage-dependent calcium channels. 相似文献
6.
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
7.
In thin bundles of dog ventricular myocardium, a slow inward current (distinct from the sodium inward current) could be recorded under voltageclamp conditions. This inward current was influenced by changes in external calcium concentration, but it was not dependent on external sodium concentration. Therefore, this current which contributes an appreciable amount of charge transfer during the plateau of the action potential, is carried by calcium ions. In sodium-free solution, the flow of calcium ions into the fiber is directly related to activation of contraction. In sodium-containing solution, however, calcium inward current serves primarily to fill up some intracellular stores from which calcium can be released by moderate depolarization. 相似文献
8.
在紫外辐射B胁迫下钙对大豆幼苗若干生物学特性的影响 总被引：4，自引：1，他引：3
采用室内水培的试验方法,初步探讨了钙离子(0、5、15mmo·lL-)1对紫外辐射B(UV-B,280～320nm)胁迫下大豆幼苗若干生物学特性的影响。结果表明,在UV-B胁迫下,15mmol·L-1钙离子处理的大豆幼苗叶鲜重的降幅低,且其株高有所增加,POD活性降幅低,可溶性蛋白含量和SOD活性增幅高。表明钙具有缓解紫外辐射伤害大豆幼苗的效应,这同钙离子对大豆幼苗部分生理生化指标的影响有关。 相似文献
9.
A "skinning%" procedure is described for irreversibly disrupting the sarcolemmal membrane of human skeletal muscle and allowing calcium and other diffusible solutes (such as adenosine triphosphate) access to the myofilament space. Single skinned fibers give isometric tensions of about 1.5 kilograms per square centimeter when exposed to ionized calcium event after 1 to 2 weeks of storage at 5 degrees C. For up to 5 days the preparation will sequester and, under appropriate conditions (anion substitution, caffeine addition, or magnesium withdrawal), release calciumn. The regulation of intracellular calcium distribution and the calcium-induced activation of the contractile proteins are discussed and related to the morphology of humnan fibers and to similar processes occurring on other muscle preparations. 相似文献
10.
Erythrocytes from patients with myotonic muscular dystrophy accumulate calcium at a significantly higher rate than normals do. This increased rate of net accumulation appears related to an enhanced permeability of the membrane to calcium, rather than to an impairment in its active outward transport. 相似文献
11.
Calcium antagonist receptors in cardiomyopathic hamster: selective increases in heart, muscle, brain 总被引：6，自引：0，他引：6
J A Wagner I J Reynolds H F Weisman P Dudeck M L Weisfeldt S H Snyder 《Science (New York, N.Y.)》1986,232(4749):515-518
The Syrian cardiomyopathic hamster has a hereditary disease in which a progressive myocardial necrosis mimics human forms of cardiac hypertrophy. Lesions are associated with calcium overload and can be prevented with the calcium antagonist verapamil. Numbers of receptor binding sites for calcium antagonists in heart, brain, skeletal muscle, and smooth muscle were markedly increased in cardiomyopathic hamsters. The uptake of calcium-45 into brain synaptosomes was also increased in cardiomyopathic hamsters. The increase in calcium antagonist receptors and related voltage-sensitive calcium channels may be involved in the pathogenesis of this cardiomyopathy. 相似文献
12.
The calcium ion is specifically required for the action of melanophorestimulating hormone on melanosome dispersion within lizard (Anolis carolinensis) melanophores in vitro. The response to this hormone is directly related to the concentration of the Ca(2+) ion. Lithium, choline, rubidium, and cesium will replace the sodium and potassium of Ringer solution if Ca(2+) is present. Calcium ions are not required for melanosome dispersion itself, since theophylline or dibutyryl cyclic adenosine monophosphate reversibly darkens lizard skins in the absence of calcium. 相似文献
13.
西南喀斯特石灰土中钙的形态与含量及其对土壤有机碳的影响 总被引：6，自引：0，他引：6
【目的】研究钙对喀斯特地区典型土壤有机碳积累与转化的影响。【方法】采取野外取样分析与室内培养相结合的方法,采集两种喀斯特典型土壤（棕色石灰土、黑色石灰土）和一种对照土壤（红壤）共54个样品,检测了土壤中钙的形态与含量及有机碳含量等理化指标。在此基础上,选取3种土壤类型具有代表性的样品,设置不添加外源物质（CK）、添加碳酸钙粉末（T2）和同时添加14C标记的稻草与碳酸钙粉末（T3）3个处理,通过室内培养试验,对培养过程中土壤CO2释放量和4种形态钙的含量进行了检测及分析。【结果】土壤中4种形态的钙以交换态和有机结合态与有机碳关系更为密切。添加碳酸钙显著影响土壤有机碳矿化,有机结合态钙含量的增量均值在红壤、棕色石灰土和黑色石灰土中依次为2.14%、4.66%、10.23%。土壤有机碳矿化对添加钙的激发效应在红壤中最强烈,其次为棕色石灰土,最后为黑色石灰土。【结论】西南喀斯特地区土壤有机碳的稳定性因土壤类型不同而存在差异。土壤有机碳的稳定性为黑色石灰土＞棕色石灰土＞红壤,因此,3种供试土壤中,黑色石灰土最有利于土壤有机碳的积累。 相似文献
14.
采后柑桔Gitrus reticulata Var.tankan果实经钙减压浸渍处理,提高了果实中的钙含量,使果实损耗率明显降低,糖酸比值高峰出现时间推迟,从而延缓了衰老。经钙处理后果肉中的可溶性蛋白质含量有所降低,但果实呼吸速率变化不大。同时,钙处理使果实纤维素酶活性降低并一直维持在较低水平,果胶甲酯酶和多聚半乳糖醛酸酶活性也受到明显抑制。用钙抑制剂EGTA处理,会使果实中钙含量降低,果实衰老加快;纤维素酶,果胶甲酯酶和多聚半乳糖醛酶的活性显著增加。 相似文献
15.
Shell aragonite from 96 specimens of the freshwater gastropod Limnaea stagnalis grown in laboratory tanks at different temperatures in water with variable strontium/calcium ratios have been analyzed for its strontium content in order to evaluate the mechanisms of strontium uptake in molluskan aragonite. Within the limits defined by natural freshwater environments, the strontium/calcium ratio in the aragonite was found to be linearly related to the strontium/calcium ratio in the water. A distribution coefficient k(A)(Sr) = 0.237 +/- 0.029, unaffected by variations in temperature and growth rate, has been found. This finding substantiates the existence of a strontium-discriminating effect in aragonite precipitated by mollusks as compared to the case for nonbiogenic aragonite which contains about five times as much strontium when precipitated under the same conditions. 相似文献
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17.
钙磷是营养学中的重要指标,是动物机体内含量最多的矿物元素。钙、磷为骨骼生长所必需,同时钙还参与神经传导、肌肉收缩、血液凝固等生理过程,而磷则与机体中各种类型的新陈代谢密切相关,研究宠物犬的钙磷营养十分必要,可为宠物饲养提供重要的理论基础,并具有现实的指导意义。 相似文献
18.
建立了EDTA滴定法测定饲料中钙含量不确定度评定的数学模型,分析了检测过程中不确定度的来源并计算了各不确定度分量,并得出合成标准不确定度和扩展不确定度。在产蛋鸡配合饲料钙含量的测定中,钙含量为4.00%,其扩展不确定度为0.040%,K=2。影响钙含量测量结果不确定度的最大因素是重复性实验的不确定度。 相似文献
19.
【背景】柑橘溃疡病是由柑橘黄单胞杆菌柑橘致病变种(Xanthomonas citri subsp. citri,Xcc)引起的细菌性病害,可侵染枝、叶、果,危害几乎所有的柑橘主栽品种。前期对湖南省39个柑橘园的调查结果显示柑橘果园土壤酸化和交换性钙缺乏严重,叶片中均存在钙缺乏现象。钙是植物所需大量元素之一,钙缺乏会造成植物营养失衡,生长势下降,植物免疫水平受影响。然而,钙元素对柑橘溃疡病抗性的影响尚不明确。【目的】分析对柑橘溃疡病敏感的枳(Poncirus trifoliata)在不同钙浓度处理下叶片注射接种Xcc后的致病差异,探讨钙在Xcc侵染枳叶片过程中的作用。【方法】采用沙培法对枳实生苗进行0、0.75、3、30 mmol·L-1钙浓度处理,分别测定枳生长期的生物量、叶绿素a和b浓度、根系和叶片钙元素含量、观察根系活性氧(ROS)的产生和胼胝质沉积,并分析枳叶片接种Xcc后细胞壁合成相关基因及免疫途径相关基因诱导表达变化特征。【结果】以3 mmol·L-1钙处理为对照,0、0.75和30 mmol·L-1钙处理后,... 相似文献
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