豚鼠心肌α-肾上腺素受体反应的可能机制——增强细胞外钙离子内流

同时记录豚鼠心室肌细胞动作电位、零期最大去极化速率和心肌条的收缩幅度,观察了α-肾上腺素受体激动剂或增加细胞外钙离子浓度([Ca~(2 )]_0)的作用,以及在肾上腺素受体或钙通道阻断剂存在下这些作用的变化,试图分析α-受体与钙通道的可能关系。我们看到甲氧胺与增加[Ca~(2 )]_0都可使动作电位峰值增加、平台期电位高抬、收缩幅度增高,甲氧胺的效应可被戊脉胺阻断,而增加[Ca~(2 )]_0的效应可被酚妥拉明阻断。酚妥拉明同戊脉安两者的效应有近似之处,心得安对甲氧胺和增加[Ca~(2 )]_0效应无显著影响。由此认为:心肌α-肾上腺素受体的电生理效应与缓慢正性变力作用很可能是通过激活钙通道,增加细胞外钙离子的慢内流来实现的。     

心肌d_1-肾上腺素受体激动对豚鼠心室乳头肌的影响

用α-受体激动剂新福林(5.0×10~(-6)mol/L)激动豚鼠心室乳头肌α-受体,观察乳头肌跨膜动作电位和收缩力的变化,并用α_1-受体阻断剂哌唑嗪(5.0×10~(-7)mol/L)和α_2-受体阻断剂育亨宾(5.0×10~(-7)mol/L)来判别何种α-受体亚型参与。实验中,β-受体阻断剂心得安(1.0×10~(-6)mol/L)始终存在。实验结果表明心肌α_1-受体激动使(1) 豚鼠心室乳头肌收缩力增强;(2) 收缩峰时间延长;舒张期不变;(3) 快反应动作电位时程延长;(4) 慢反应动作电位零相最大除极速率增加。提示,心肌α_1-受体激动的电生理和正性变力效应的离子机制可能是促进慢内向离子流,使Ca~(2 )内流增加。     

雨蛙肽中枢促胃酸分泌作用机制的初步分析

利用特异的受体阻断剂能够拮抗相应的受体激动剂的效应的原理,分析雨蛙肽中枢促胃酸分泌作用的受体机制。向大鼠侧脑室内注射微量雨蛙肽(67ng/鼠),可引起急性灌流大鼠胃酸分泌明显增加。预先向大鼠侧脑室内注射肾上腺素受体阻断剂酚妥拉明或心得安,20min后再向侧脑室内注射雨蛙肽,预处理对雨蛙肽的促胃酸分泌作用影响不大。但事先向侧脑室内注射乙酰胆碱受体阻断剂阿托品或胆囊收缩素(CCK)受体阻断剂二丁酰环化-磷酸鸟苷(Bt_2 cGMP)则可有效地阻断雨蛙肽的作用。以上结果提示,脑内雨蛙肽促胃酸分泌机制中,可能有 CCK 受体和胆碱能受体参与,而与肾上腺素能系统关系不大。     

κ阿片肽受体激活对培养心肌细胞生长抑制的影响

目的 :通过体外培养乳鼠心肌细胞 ,观测κ阿片肽受体激活对心肌细胞生长的影响。方法 :对培养乳鼠心肌细胞分组给药 4 8h后 ,用结晶紫染色法测心肌细胞的增殖程度 ,用Lowry’s法测心肌细胞的蛋白质含量。 结果 :κ阿片肽受体激动剂U5 0 ,4 88H(0 .1μmol/L～ 10 μmol/L)对培养心肌细胞的增殖程度和蛋白质含量均有抑制作用并呈剂量依赖性 ;κ阿片肽受体拮抗剂nor binaltorphimine (nor BNI) (1μmol/L)对U5 0 ,4 88H(1μmol/L)的这些抑制效应具有相应的拮抗作用。结论 :阿片肽对心肌细胞生长具有负性调节作用 ,这种作用是通过激活κ阿片肽受体发挥的     

大豆甙元磺酸钠对胃运动的影响及其机制

目的:研究大豆甙元磺酸钠对胃运动的影响及其作用机制。方法:采用SD大鼠腹腔和侧脑室给药,记录胃运动收缩的幅度和频率。结果:①腹腔注射不同剂量的大豆甙元磺酸钠,均引起胃收缩幅度下降,但未呈现剂量效应关系;胃收缩频率无明显变化。②腹腔注射纳洛酮可反转大豆甙元磺酸钠的作用。③腹腔注射心得安,可使大豆甙元磺酸钠抑制胃运动的作用增强,注射酚妥拉明可反转大豆甙元磺酸钠的作用。④腹腔注射阿托品对大豆甙元磺酸钠的作用无明显的影响。⑤侧脑室注射不同剂量的大豆甙元磺酸钠,其中小剂量组出现胃收缩幅度下降,但胃收缩频率亦无明显变化。结论:腹腔和侧脑室注射大豆甙元磺酸钠对胃运动均有抑制作用,且腹腔注射大豆甙元磺酸钠的效应至少部分是与内源性阿片肽及其受体和去甲肾上腺素能神经元及其α受体有关,肾上腺素能神经元及β肾上腺素能受体也参与了大豆甙元磺酸钠抑制胃运动的作用。     

阿托品能阻断α-受体降低大鼠血压

众所周知,阿托品是M—胆碱受体阻断剂,但大剂量阿托品的扩张血管和降压作用却很难用抗胆碱作用来解释。最近S.Abraham等在研究胆碱能神经系统在高血压中的作用时发现,大于阻断M—受体剂量的阿托品可降低大鼠血压。此作用随剂量增大而增强。他们用几种受体阻断剂预先处理动物,然后再观察阿托品的作用,发现预先用心得安(20mg/kg)或六烃季铵(20mg/kg)处理,不能阻断阿托品的降压作用。而用α-受体阻断剂育亨宾(2.5mg/kg)或酚妥拉明(5mg/kg)处理,阿托品的降压作用可完全被阻断。为了进一步弄清阿托品的作用方式,他们还观察了阿托品对几种激动剂引起的血压变化的影响。实验     

P物质对大鼠胃窦肌条收缩活动的影响及其机制探讨

本文利用器官浴槽孵育离体大鼠胃窦肌条,观察Ｐ物质（ｓｕｂｓｔａｎｃｅＰ,ＳＰ）对肌条收缩的效应及多种拮抗剂或抑制剂对ＳＰ效应的影响。结果：（１）ＳＰ明显增强肌条收缩幅度,在剂量为８×１０－１１－８×１０－７ｍｏｌ范围内里剂量－效应关系。ＳＰ４×１０－８ｍｏｌ,使肌条收缩幅度增强１６０．９±２３．０％．与生理盐水组比较Ｐ＜０．００１。（２）神经节阻断剂六烃季胺、５－ＨＴ２受体阻断剂赛庚啶、Ｈ１受体阻断剂苯海拉明、磷酸二酯酶抑制剂氨茶碱使ＳＰ肌条收缩幅度增强效应明显减弱（Ｐ＜０．０５）。（３）阿托品、心得安、酚妥拉明、氟哌啶醇和纳洛酮预孵育后,ＳＰ增强收缩幅度的效应与单独ＳＰ组相比差异无显著性。结果提示ＳＰ可能是肠神经系统中的非胆碱能兴奋性递质,可能通过激活５－ＨＴ神经元、促使组织胺释放等途径而增强肌条的收缩幅度。     

Ca~(2+)信号在肿瘤坏死因子-α诱导心肌肥大PI3-K信号途径中的作用

目的:研究Ca2+信号在肿瘤坏死因子-α(TNF-α)诱导心肌细胞肥大PI3-K信号途径中的作用。方法:Lowry法测心肌细胞蛋白含量;计算机图像分析系统测心肌细胞体积;[3H]-亮氨酸掺入法测心肌细胞蛋白合成;Till阳离子测定系统观察胞内[Ca2+]i瞬变。结果:①TNF-α(100μg/L)明显诱导心肌细胞蛋白含量、蛋白合成及体积的增加,PI3-K特异性抑制剂LY294002(50μmol/L)明显抑制TNF-α诱导的心肌肥大,但对正常心肌细胞生长无影响。L型Ca2+通道阻断剂verapamil(1μmol/L)对TNF-α诱导的心肌肥大无明显影响。②TNF-α引起心肌细胞内钙离子浓度([Ca2+]i)瞬间变化幅度增高,LY294002明显降低TNF-α诱导的上述改变,L型Ca2+通道阻断剂verapamil(1μmol/L)对TNF-α引起的变化无明显影响。结论:PI3-K可能通过引起心肌细胞[Ca2+]i升高参与TNF-α诱导的心肌细胞肥大,但与L型Ca2+通道无关。     

氨甲酰胆碱增加大鼠心室肌细胞收缩机制的初步研究

目的:本文研究非选择性M受体激动剂氨甲酰胆碱(Cch)对心肌细胞收缩的作用,并同时观察L-型钙流,探讨其机制.方法:以分离大鼠的单个心室肌细胞为对象,采用膜片钳和单细胞收缩测量技术,在35℃恒温,细胞外钙离子浓度1.8 mmol/L,0.2 Hz,1.0 Hz刺激下测量细胞收缩幅度和ICa(L)、INa/Ca.结果:①大鼠心肌细胞收缩与刺激频率呈负相关;②选择△L0.2 Hz/△L1.0 Hz≥1.25(n=6)的细胞给予1.0 Hz的刺激,100 μmol/L Cch增加大鼠心室肌细胞收缩28%.③ Cch作用能被非选择性M受体阻滞剂阿托品阻滞,选择性M1受体激动剂MCN-A-343 100 μmol/L对细胞收缩无影响.④ 100 μmol/L Cch对ICa(L)无影响,但增加从 10 mV复极到-40 mV所产生的晚期尾电流,提示INa/Ca加大.结论:Cch能加强大鼠心室肌细胞收缩,它的作用由M2受体介导,其机制可能是通过加强INa/Ca,增加肌质网(SR)内的钙内容和钙释放,导致细胞收缩加强,而非通过L-型钙流.     

电压激活的钾通道阻断剂抑制山莨菪碱松弛去甲肾上腺素预收缩的兔主动脉平滑肌

研究显示,山莨菪碱预处理不改变高钾引起的兔主动脉环收缩,但可明显减弱去甲肾上腺素(noradrenaline,NA)、组织胺或5-羟色胺引起的收缩,且其减弱作用不受去除血管内皮影响。本实验观察了几种钾通道阻断剂对山良菪碱松弛：NA预收缩的兔主动脉环的影响。结果表明,1、3、10μmol／L山莨菪碱作用8min,可使0．01μmol／L NA预收缩的兔主动脉环松弛(P＜O．01)。10mmol／L,CsCl、1mmol／L 4-氨基吡啶、10μmol／L BaCl2、10μmol/L格列本脲、3μmol／L charybdotoxin和3μmol／L蜂毒明从分别与0．0lμmol／L NA同时加入,可增强后者收缩兔主动脉环的作用(P＜0．01)。10、30mmol／L CsCl或10、30mmol／L 4-氨基吡啶存在时,10μmol／L山茛菪碱对NA预收缩的兔主动脉环的松弛作用减弱,松弛率与对照组比较分别有极显著差异(P＜0．01);10、30μmol／L BaCl2,10、30μmol/L格列本脲,3μmol/L charybdotoxin或3μmol／L蜂毒明肽存在时,山莨菪碱对NA预收缩的兔主动脉环的松弛作用不受影响(P＞O．05)。本研究表明,电压激活的钾通道阻断剂抑制山莨菪碱松弛NA预收缩的兔主动脉平滑肌,初步提示血管平滑肌细胞膜上电压激活的钾通道参与山莨菪碱扩血管作用。     

六种藓类植物茎的比较解剖学研究

通过对6种藓类植物,即褶叶青藓(Brachythecium salebrosum(Web.et Mohr.)B.S.G.)、湿地匐灯藓(Plagiomnium acutum(Lindb.)Kop.)、侧枝匐灯藓(Plagiomnium maximoviczii(Lindb.)Kop.)、大凤尾藓(Fissidensnobilis Griff.)、大羽藓(Thuidium cymbifolium(Doz.et Molk.)B.S.G.)和大灰藓(Hypnum plumaeforme Wils.)嫩茎和老茎的石蜡切片和显微观察发现,同一藓类植株的嫩茎和老茎,茎结构稳定,不同种藓类植物茎横切面具有不同特征.植物体茎横切面形状、表层细胞的层数、细胞大小和细胞壁厚薄、皮层细胞大小和形状、中轴的有无以及比例等特征可以作为藓类植物的分科分类依据之一.     

Photoregulation of seed germination of wild-type and of an aurea-mutant of tomato

Seed germination of an aurea mutant of tomato ( Lycopersicon esculentum Mill.) is promoted by continuous irradiation with red, far-red or long-wavelength far-red (758 nm) light as well as by cyclic irradiations (5 min red or 5 min far-red/25 min darkness). Far-red light applied immediately after each red does not change the germination behaviour. Seed germination of the isogenic wild-type, cv. UC-105, is promoted by continuous and cyclic red light while it is inhibited by continuous and cyclic far-red light and by continious 758 nm irradiation. Far-red irradiation reverses almost completely the promoting effect of red light. The promoting effect (in the aurea mutant) and the inhibitory effect (in the wild-type) of continuous far-red light do not show photon fluence rate dependency above 20 nmol m⁻² s⁻¹. It is concluded that phytochrome controls tomato seed germination throgh low energy responses in both the wild type and the au mutant. The promoting effect of continuous and cyclic far-red light in the au mutant can be attributed to a greater sensitivity to P_fr.     

Cause of Senescence of Nine Sorts of Flowers

The levels of endogenous phytohormones and respiratory rate in nine sorts of flowers such as Cymbidium faberi Rolfe, Nopalxochia ackermannii Kunth and others were investigated both at full bloom and senescence and meanwhile the effect of exogenous phytohormones on prolonging the blossoms and promoting ethylene production were tested. There is a high content of endogenous ethylene in all the long-lived flowere, about 3–16 folds higer than the short-lived ones. There is a high level of ABA at full blooming flowers of short-lived flowers, in which there is no or only some cytokinins in it, but the ratio of CTK (6BA+zeatin)/ABA is smaller(l.7). The endogenous ABA reached a much higher level at senescence in all nine sorts of flowers, so it is reasonable to consider that it is ABA which plays an important role of regulation in controlling flower's senescence. There is a much higher level of GA3 and zeatin in the long-lived flowers which is not demonstrated in the shortlived ones. The respiratory rate is one of the factors controtling the longevity of flowers, but it does not play a decided role. Application of 6BA and zeatin prolongs distinctly orchid’s longevity, however exogenous IAA through the promotive action on ethylene production, evidently extends the longevity of the flowers of the Nopalxochia ackermannii Kunth.     

龙胆科药用植物化学成分的研究现状

龙胆科植物在我国的分布范围很广,且多数为药用植物,其多数种属的药用植物,至今其化学成分尚未被系统研究。综述了目前龙胆科药用植物的化学成分的研究现状及一般提取方法,对近年来发现的环烯醚萜及裂环烯醚萜类化合物进行了总结,为本科药用植物的更深入研究提供了参考。     

Interconnection of parameters of regulation system of lipid peroxidation and of morphophysiological parameters of mouse liver

A complex analysis of seasonal fluctuations of the mean group parameters of the system of regulation of lipid peroxidation has been performed in liver of Balb/c mice. Association of lipid characteristics and morphophysiological parameters is studied in the Balb/c mouse liver. An inter-connection is revealed between the liver index and the amount of lysoforms of phospholipids, the scale and character of the interconnection differing essentially depending on proportion of phos-phatidylcholine in mouse liver phospholipids.     

The effects of glutamine of the maintenance of embryogenic cultures of Cryptomeria japonica

Summary Embryogenic tissues of sugi (Cryptomeria japonica) were induced on a modified Campbell and Durzan (CD) medium containing 1 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 600 mg l⁻¹ glutamine, and subcultured in the medium of the same composition for over 1 yr. This resulted in a mixed culture of embryogenic and non-embryogenic cells. When embryogenic cells were isolated and cultured independently, their capacity to form embryogenic aggregates was lost. Thus, the non-embryogenic cells present within a mixed culture system were essential to the formation of embryogenic aggregates. When embryogenic tissues were isolated and cultured independently on a high glutamine-containing (2400 mg l⁻¹) medium, dry weights and endogenous levels of glutamine increased, and the tissue could generate a large number of embryogenic aggregates. Amino acid analysis of embryogenic and non-embryogenic cells from the maintenance culture indicated a higher level of glutamine was present in the latter. The high endogenous level of glutamine in the non-embryogenic portion of mixed cell masses may be the supplier of glutamine for maintaining the embryogenic property of the tissues.     

Specificity of action of piperidylcholine derivatives as substrates of cholinesterases of various origin

The review deals with study of enzymologic properties of a novel highly specific acetylcholinesterase substrate, N-(β-acetoxyethyl) piperidinium iodomethylate (“piperidylcholine”), and its 30 derivatives that were tested as effectors of cholinesterases of mammals and various species of Pacific squids. It was proven for the first time that responsible for specificity of action was structure of cyclic ammonium grouping of the alcohol part of molecule of the ester substrate. Analysis of specificity is performed based on enzymatic hydrolysis parameters—activity of catalytic center of cholinesterases and bimolecular constant of the reaction rate that are determined at optimal and low substrate concentrations. Among the specially synthesized group of thioester compounds there is revealed one more highly specific acetylcholinesterase substrate—N-(β-acetoxyethyl) piperidinium.     

Physiological characteristics of various species of strains of carboxydobacteria

Seven strains of aerobic carbon monoxide-oxidizing bacteria (carboxydebacteria) when growing on CO as sole source of carbon and energy had doubling times which ranged from 12–42 h. The activity profiles obtained after discontinuous sucrose density gradient centrifugation indicated that the CO-oxidizing enzymes are soluble and the hydrogenases are membrane-bound in all strains examined. The CO-oxidizing enzymes of Pseudomonas carboxydohydrogena, Pseudomonas carboxydoflava, Comamonas compransoris, and the so far unidentified strains OM2, OM3, and OM4 had a molecular weight of 230,000; that of Achromobacter carboxydus amounted to 170,000. The molecular weights of the CO-oxidizing and H₂-oxidizing enzymes turned out to be identical. The cell sonicates were shown to catalyze the oxidation of both CO and H₂ with methylene blue, thionine, phenazine methosulfate, toluylene blue, dichlorophenolindophenol, cytochrome c or ferricyanide as electron acceptors. Methyl viologen, benzyl viologen, FAD⁺, FMN⁺, and NAD(P)⁺ were not reduced. The spectrum of electron acceptors was identical for all strains tested. Neither free formate, hydrogen nor oxygen gas were involved in the CO-oxidation reaction. Methylene blue was reduced by CO at a 1:1 molar ratio. The results indicate that CO-oxidation by carboxydobacteria is catalyzed by identical or similar enzymes and that the reaction obeys the equation CO+H₂OCO₂+2H⁺+2e^- as previously shown for Pseudomonas carboxydovorans.Dedicated to Otto Kandler remembering almost three decades of enjoyable cooperation     

Modulation of allostery of pyruvate kinase by shifting of an ensemble of microstates

Since the introduction of the concepts of allostery about four decades ago, much advancement has been made in elucidating the structure-function correlation in allostery. However, there are still a number of issues that remain unresolved. In this review we used mammalian pyruvate kinase (PK) as a model system to understand the role of protein dynamics in modulating cooperativity. PK has a triosephosphate isomerase (TIM)(α/β)₈ barrel structural motif. PK is an ideal system to address basic questions regarding regulatory mechanisms about this common (α/β)₈ structural motif. The simplest model accounting for all of the solution thermodynamic and kinetic data on ligand-enzyme interactions involves two conformational states, inactive E^T and active E^R. These conformational states are represented by domain movements. Further studies provide the first evidence for a differential effect of ligand binding on the dynamics of the structural elements, not major secondary structural changes. These data are consistent with our model that allosteric regulation of PK is the consequence of perturbation of the distribution of an ensemble of states in which the inactive E^T and active E^R represent the two extreme end states. Sequence differences and ligands can modulate the distribution of states leading to alterations of functions. The future work includes: defining the network of functionally connected residues; elucidating the chemical principles governing the sequence differences which affect functions; and probing the nature of mutations on the stability of the secondary structural elements, which in turn modulate allostery.