猪卵丘细胞对卵母细胞膜电位影响的研究

本文应用细胞内微电极技术,测试分析了猪卵丘细胞对卵母细胞膜电位的影响。结果表明,卵母细胞周围卵丘细胞的数量和形态特点的差异对卵母细胞膜电位有显著影响,Ａ、Ｂ、Ｃ三类卵母细胞的膜电位有极显著差异。Ａ类和部分Ｂ类母细胞的膜电位为负值,Ｃ类和另一部分Ｂ类卵母细胞的膜电位为正值。     

丙氨酸对卵母细胞膜电位去极化作用及其影响因素

本文通过微电极细胞内记录方法对丙氨酸促进卵母细胞成熟,导致卵母细胞膜电位法去极化及与时间和剂量依赖关系进行了研究。丙氨酸不能使裸化的卵母细胞民位去极化;孕酮,丙氨酸及丙氨酸加孕酮对卵母细胞膜电位影响与对照组相比皆有极显著性差异;孕烯醇酮能使膜电位去极化;丙氨酸能明显加强孕燃醇酮的去极化效应。     

胰岛素对蟾蜍卵母细胞膜电位及电解质的影响

应用普通玻璃微电极和离子选择性微电极,对正常及经过胰岛素处理的中华大蟾蜍卵母细胞膜电位、细胞内Na~+、K~+、Cl~-、H~+等活度及膜对Na~+、K~+的转运系数进行了测定。结果表明,胰岛素在促进蟾蜍卵母细胞发育成熟同时,具有使膜电位降低、细胞内Na~+、Cl~-活度增加、K~+、H~+活度减少及K~+转运系数降低等作用。胰岛素的上述作用可能与膜的通透性改变及膜上钠泵活性和Na~+/H~+交换的改变有关。     

酪氨酸、hCG对蟾蜍卵母细胞膜电位的影响

作者用微电极记录了蟾蜍卵母细胞的膜电位。当用含hCG的溶液培灌时,蟾蜍卵母细胞膜电位呈去极化变化;当用含酪氨酸溶液培灌时膜电位呈超极化变化,并能抑制hCG的去极化作用。超微结构的变化与膜电位变化相一致。因此我们认为,酪氨酸可能在蟾蜍卵母细胞有对抗hCG的作用。     

乙酰胆碱对蟾蜍背根神经节神经元膜电位的影响及离子机制

在离体灌流的蟾蜍背根神经节(DRG)标本上,用微电极进行胞内记录。在73个神经元中,依神经纤维的传导速度将神经元分为 A 型及 C 型,其中 A 型细胞67个,C 型6个,静息膜电位为-67.5±1.3mV((?)±SE)。当加4×10~(-4)—6×10~(-4)mol/L 乙酰胆碱(ACh),可观察到如下四种膜电位变化:1.超极化:幅值9.1±3.0mV((?)±SE,n=23);(2)去极化:幅值12.9±2.2mV((?)+SE,n=20);(3)双相反应(n=24):先超极化,后去极化,超极化幅值8.0±2.4mV((?)+SE),去极化幅值10.9±3.1mV((?)±SE);(4)无反应(n=6)。用阿托品(1.3×10~(-5)mol/L,n=23),或同时应用筒箭毒与六甲双铵(浓度均为1.4×10~(-5)mol/L,n=8)灌流,能分别阻断 ACh 引起的膜的超极化或去极化。ACh 引起超极化反应时膜电导平均增加13.8%,翻转电位值大约-96mV。四乙铵(TEA,20mmol/L)能使 ACh 的去极化幅值增加48.2±3.2%((?)±SE,n=6),超极化幅值减小79.4±4.3%((?)±SE,n=8)。MnCl_2(4mmol/L)使 ACh 的去极化及超极化幅值分别减小54.2±7.2%((?)±SE,n=5)及69.2±6.4%((?)±SE,n=14)。以上结果提示:ACh 引起的 DRG 神经细胞膜去极化反应由 N 型乙酰胆碱受体介导,而超极化反应由 Μ 型乙酰胆碱受体介导,前者可能包含了多种离子电导的改变,后者则可能与钾电导增加有关。     

钩藤对蟾蜍心脏的作用机制研究

目的：探讨钩藤对蟾蜍心脏的作用。方法：用钩藤灌流蟾蜍心脏,观察灌流前后心肌收缩力,心输出量和心率的变化,结果心肌收缩幅度减小,心输出量减少和心率变慢。结论：钩藤对蟾蜍心脏的抑制作用,从而降低血压。     

低氧对大鼠颈动脉体培养细胞膜电位及输入阻抗的影响

本文采用离体培养的大鼠颈动脉体主细胞(glomus cell)的细胞群体和单细胞的标本,观察了不同程度的低氧对细胞膜电位(MP)和输入阻抗(Ri)的影响。在常氧(20％O_2,5％CO_2,75％N_2)条件下培养的细胞(常氧细胞)暴露在常氧中测得的MP和Ri值为对照值。当常氧细胞暴露在低氧(10％O_2,5％CO_2,85％N_2)时,MP幅度有的增加(超极化),有的减少(去极化),MP值增加和减少的细胞数各占细胞总数的百分比大体相同,当暴露在100％N_2中时,MP增加的细胞百分数明显高于MP减少的细胞百分数。在低氧条件下培养的细胞(低氧细胞),暴露在常氧中测得的MP和Ri值与对照值比较无显著性差别,但是,当低氧细胞暴露在低氧中时MP和Ri的值均明显增加(MP:P<0.01,Ri:P<0.05)。结果提示:颈动脉体的glomus细胞可能在感受pO_2变化中起重要作用。     

七叶莲对蟾蜍坐骨神经动作电位的影响

目的：观察七叶莲水煎液对蟾蜍离体坐骨神经复合动作电位的幅度及传导速度的影响,研究其对坐骨神经电生理特性的作用。方法：将制备的蟾蜍坐骨神经干分为4组,分别在任氏液和浓度为10％,20％,40％的七叶莲水煎液中浸泡,用MedLab生物信号采集处理系统引导神经干复合双相动作电位,并分别测定各组不同浸泡时间的坐骨神经干动作电位的幅度和传导速度两项电生理指标。记录不同浓度的七叶莲水煎液对蟾蜍离体坐骨神经复合动作电位的幅度和传导速度的影响。结果：10％,20％,40％3种浓度的七叶莲水煎液均使坐骨神经复合动作电位的幅度变小（P〈0．01）,传导速度变慢（P〈0．01）并最终使坐骨神经动作电位消失,且经过一段时间后动作电位的幅度和传导速度均能恢复。结论：七叶莲能可逆地阻滞神经动作电位的传导。     

Reconstitution of Neutral Amino Acid Transport Systems from Ehrlich Ascites Tumor Cells

Amino acid transport systems for alanine and leucine were reconstituted into artificial lipid vesicles. Purified plasma membrane vesicles from Ehrlich ascites cells were dissolved in 2% sodium cholate, 1mM dithiothreitol, and 0.5 mM EDTA a mixture that solubilized approximately 50% of the membrane protein. This solubilized protein fraction was further purified by a combination of ammonium sulfate precipitations, gel filtration, and DEAE-cellulose chromatography. A fraction containing approximately 15 Coomassie blue-staining bands on sodium dodecyl sulfate gels was obtained. This material was reconstituted into liposomes, and preliminary results demonstrated transport of alanine and leucine dependent on a sodium gradient. In addition, an electrogenic gradient mediated by valino-mycin-induced potassium diffusion seemed to stimulate alanine uptake further.     

Reconstitution of Neutral Amino Acid Transport System from Ehrlich Ascites Tumor Cells

Amino acid transport systems for alanine and leucine have been reconstituted into artificial lipid vesicles. Purified plasma membrane vesicles from Ehrlich ascites cells were dissolved in 2% sodium cholate, 1 mM dithiothreitol, 0.5 mM EDTA, a mixture which solubilized approximately 50% of the membrane protein. This solubilized protein fraction was further purified by a combination of ammonium sulfate precipitations, gel filtration, and DEAE-cellulose chromatography. A fraction containing approximately 15 Coomassie blue staining bands on sodium dodecyl sulfate gels was obtained. This material was reconstituted into liposomes, and preliminary results demonstrated transport of alanine and leucine dependent on a sodium gradient. In addition, an electrogenic gradient mediated by valinomycin-induced potassium diffusion seemed to stimulate alanine uptake further.     

Side reactions in the preparation of 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid

Summary During a study on the preparation of the conformationally restricted analogue of tryptophan into 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid1 by a Pictet-Spengler condensation with formaldehyde, two site products were detected:N-hydroxymethyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid2 and a dimer3 of two 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid units linked by a methylene group. Their structures were determined by HPLC-MS and 2D NMR spectroscopy. By changing the isolation procedure, theN-hydroxymethyl compound was removed. Treatment of the mixture with TFA in water converted the dimer into 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid1.     

AMINO ACID AND UREA UPTAKE IN TEN SPECIES OF CHLOROPHYTA1

The Uptake of radioartively-labelled mixed amino acids, arginine, lysine, leucine, glutamic acid and urea was examined in six species of Volvocales and four species of Chlarococcales grown in nitrate-containing medium. Nonradioactive amino acids in excess were used to estimate specificity of amino and carriers in selected cases. All ten species possess salurable (hence, carrier-mediated) systems for uptake of both arginine and urea. In all Volvacales and one Chlorococcales, the arginine-speciftc carrier (which also transported lysine with lower efficiency) was the only amino acid carrier detected. Three species of Chlororoccales appear to possess a separate carrier for lysine and two of these appear to possess at least one additional carrier that is involved in uptake of non-basic amino acids.     

Dose–response evaluation of the standardized ileal digestible tryptophan : lysine ratio to maximize growth performance of growing-finishing gilts under commercial conditions

Environmental regulations as well as economic incentives have resulted in greater use of synthetic amino acids in swine diets. Tryptophan is typically the second limiting amino acid in corn-soybean meal-based diets. However, using corn-based co-products emphasizes the need to evaluate the pig’s response to increasing Trp concentrations. Therefore, the objective of these studies was to evaluate the dose–response to increasing standardized ileal digestible (SID) Trp : Lys on growth performance of growing-finishing gilts housed under large-scale commercial conditions. Dietary treatments consisted of SID Trp : Lys of 14.5%, 16.5%, 18.0%, 19.5%, 21.0%, 22.5% and 24.5%. The study was conducted in four experiments of 21 days of duration each, and used corn-soybean meal-based diets with 30% distillers dried grains with solubles. A total of 1166, 1099, 1132 and 975 gilts (PIC 337×1050, initially 29.9±2.0 kg, 55.5±4.8 kg, 71.2±3.4 kg and 106.2±3.1 kg BW, mean±SD) were used. Within each experiment, pens of gilts were blocked by BW and assigned to one of the seven dietary treatments and six pens per treatment with 20 to 28 gilts/pen. First, generalized linear mixed models were fit to data from each experiment to characterize performance. Next, data were modeled across experiments and fit competing dose–response linear and non-linear models and estimate SID Trp : Lys break points or maximums for performance. Competing models included broken-line linear (BLL), broken-line quadratic and quadratic polynomial (QP). For average daily gain (ADG), increasing the SID Trp : Lys increased growth rate in a quadratic manner (P<0.02) in all experiments except for Exp 2, for which the increase was linear (P<0.001). Increasing SID Trp : Lys increased (P<0.05) feed efficiency (G : F) quadratically in Exp 1, 3 and 4. For, ADG the QP was the best fitting dose–response model and the estimated maximum mean ADG was obtained at a 23.5% (95% confidence interval (CI): [22.7, 24.3%]) SID Trp : Lys. For maximum G : F, the BLL dose–response models had the best fit and estimated the SID Trp : Lys minimum to maximize G : F at 16.9 (95% CI: [16.0, 17.8%]). Thus, the estimated SID Trp : Lys for 30 to 125 kg gilts ranged from a minimum of 16.9% for maximum G : F to 23.5% for maximum ADG.     

An enzymatic fluorometric assay for L-lysine in plasma and tissue

A simple, specific, and reliable method has been developed for the determination of L-lysine in blood plasma and tissue. The L-lysine in the sample is decarboxylated enzymatically, and fluorescamine is added to a pentan-1-ol extract of the cadaverine formed. This produces a stable product which is measured fluorometrically.