THE BINDING OF BOTULINUM TOXIN TO MEMBRANE LIPIDS: SPHINGOLIPIDS, STEROIDS AND FATTY ACIDS

A number of lipids known to be constituents of nerve-ending membranes were tested for their ability to inactivate botulinum toxin. Inactivation of the toxin by a lipid was taken as presumptive evidence that the lipid might be the in vivo receptor for the toxin. Several sphingolipids (sphingosine, galactosylceramide, glucosylceramide, lactosylceramide, cytolipin K and cytolipin R), steroids (cholesterol and deoxycholic acid) and fatty acids (palmitic acid, stearic acid, prostaglandin E₁) did not affect the potency of botulinum toxin, and thus were discounted as potential toxin receptors. However, the gangliosides did inactivate botulinum toxin rapidly (in less than 5 min), within a temperature range of 2°-40°C, and at ionic strengths of 0.05-0.40. Inactivation diminished as pH fell below 6. The activity of gangliosides in suppressing the potency of botulinum toxin was a function of the number of sialic acid residues in the lipid. Thus, the data suggest that a molecule containing sialic acid may be the receptor for the toxin.     

多重扫描伏安法在平面双分子脂膜(BLM)研究中的应用

本文阐明了伏安技术对重组膜的各种电性质测量原理和方法,并用多重扫描技术着重研究了膜电导的可逆跃迁变化,以及扫描速度和电压的影响,结果指出,伏安法可能发展成一种研究重组膜离子通道现象的新手段.     

川棟素在小鼠神经肌肉标本上的抗肉毒作用

本文用小白鼠离体膈神经膈肌标本,研究了川棟素的抗肉素作用。在我们所用的试验条件下,川棟素均显著地延长肉毒中毒标本对间接刺激收缩反应的麻痹时间,表明川楝素能在神经肌肉接头处对抗肉毒的阻遏作用。文中对川棟素的抗毒机理进行了讨论。     

天然胶乳脂质的磷脂组成与分布

本文采用单向硅胶薄层色谱对“红星1号”（抗风品系）和“9－110”（抗寒品系）两种无性系天然橡胶胶乳脂质的磷脂组成进行定性分析,分离出8种磷脂组分,已检出6种,发现两种是从来没检出过的磷脂组分,此外用薄层色谱扫描和“吸光度比例系数校正法”对两种品系天然胶乳总脂,橡胶相和底层脂质中各种磷脂组分的分布进行了快速定量分析。     

THE SYNTHESIS OF PHOSPHOLIPIDS IN THE NUCLEUS AND NUCLEAR MEMBRANE OF SYNCHRONIZED HeLa CELLS

HeLa cells were synchronized by a double thymidine block and pulse labeled at different stages of the cell cycle with ³H-choline. The specific activity of phospholipids extracted from the cell, the nucleus and the nuclear membrane showed a progressive increase from S to G₁; the incorporation of choline into phospholipids of asynchronous cells showed a specific activity intermediate between the values of S and G₁ cells. Similar results were obtained when ³²phosphorus was used as a precursor instead of choline. Thin layer chromatographic analysis of phospholipids extracted from cells in S and from cells in G₁ failed to show any difference in the distribution of radioactivity among the various phospholipid classes. Choline uptake by HeLa cells in different phases of the cell cycle did not show significant variations. However, during the synchronization process, shortly after the addition of excess thymidine, an increased uptake of choline by cells and an increased incorporation of choline into phospholipids were found. The results indicate that some of the changes occurring in phospholipids synthesis may not be cell cycle dependent, but may be the effect of the synchronizing process.     

山莨菪碱对紫膜中菌紫质结构的影响及其与膜脂的关系

本文用吸收光谱和可见圆二色谱研究了不同浓度的山莨菪碱对紫膜中菌紫质结构的影响,并设计了用不同浓度的去垢剂Triton X-100作为脂环境的扰动剂,研究山莨菪碱对菌紫质的影响与膜脂关系的实验.结果表明山莨菪碱不仅影响菌紫质分子本身的构象变化而且扰动了菌紫质分子之间的激子偶联作用.通过吸收差光谱技术表明山莨菪碱对菌紫质结构的影响与膜脂密切相关并指出紫膜中菌紫质的三体结构对膜功能的贡献是不容忽视的.     

THE EFFECTS OF BOTULINUM TOXIN ON ACETYLCHOLINE METABOLISM IN MOUSE BRAIN SLICES AND SYNAPTOSOMES

The effects of Type A botulinum toxin on acetylcholine metabolism were studied using mouse brain slice and synaptosome preparations. Brain slices that had been incubated with the toxin for 2h exhibited a decreased release of acetylcholine into high K⁺ media. Botulinum toxin did not affect acetylcholine efflux from slices in normal K⁺ media. When labeled choline was present during the release incubation, a‘newly-synthesized’pool of acetylcholine was formed in the tissue. In toxin-treated slices exposed to high K⁺, both the production and the release of this‘newly-synthesized’acetylcholine were depressed. A possible explanation for these actions of botulinum toxin would be via an inhibition of the high affinity uptake of choline. This hypothesis was tested by measuring the high affinity uptake of [³H]choline into synaptosomes prepared from brain slices. Previous exposure of slices to botulinum toxin caused a significant reduction in the accumulation of label by the synaptosomes. These data are discussed in terms of our current understanding of the mechanism of action of botulinum toxin and the toxin's interaction with the mechanisms regulating acetylcholine turnover.     

羟基自由基对兔脑微粒体膜脂及膜蛋白的损伤

本文研究了过氧化氢与亚铁离子体系产生的羟基自由基对兔脑微粒体脂质过氧化作用及对膜上(Na~++K~+)-ATP酶活性的影响.结果表明,羟基自由基导致兔脑微粒体脂质过氧化,增加丙二醛的含量.羟基自由基还使微粒体膜巯基数下降,(Na~++K~+)-ATP酶活力受到抑制.阿魏酸钠对抑制微粒体脂质过氧化及对膜巯基和(Na~++K~+)-ATP酶均有保护作用.自旋捕集实验结果进一步证明药物对羟基自由基的猝灭作用.     

NEUTRAL LIPIDS AND PHOSPHOLIPIDS FROM CULTURED ASTROBLASTS

—A study of the neutral lipid and phospholipid compositions of two clones of glial cells in culture is reported. These clones are normal astroblasts (NN clone) and chemically-induced astrocytoma cells (C6 clone). The lipid composition of the NN cells is similar to that obtained with glial enriched fractions from mammalian brains; however, the fatty acid patterns of the phospholipids from NN cells show an important increase in saturation. Slight differences are observed between NN and C6 cells; these differences are similar to those found during the oncogenic transformation of some other clonal cell lines.     

BINDING OF 5-HYDROXYTRYPTAMINE TO ACIDIC LIPIDS IN AN AQUEOUS MEDIUM

The affinities of 5-hydroxy-[³H]tryptamine (5-HT) for cerebroside sulfate, 1-phosphatidylinositol, 1-phosphatidylinositol 4-phosphate, 1-phosphatidylinositol 4,5-bisphosphate, phosphatidic acid, and phosphatidyl serine were determined in an aqueous medium. They were observed to be, in general, much lower than and poorly correlated with the values previously reported by Johnson et al (1977a), measured in isobutanol. This suggested that these lipids probably are not 5-HT receptors and that drug affinities measured in organic media must be evaluated with caution.     

急性热应激对大鼠肺细胞膜磷脂代谢及膜流动性的影响

使用高效液相色谱法测定了正常健康雄性大鼠经急性热应激致肛温达42℃后,肺细胞膜中磷脂酰丝氨酸(PS),磷脂酰胆碱(PC)的变化,同时用荧光探剂标记红细胞和肺组织细胞膜制剂,采用偏振荧光法测定了膜流动性的改变。结果表明,正常大鼠的PS和PC分别为425.1±68.1μg/g湿重和53.5±9.7mg/g湿重,肛温达42℃持续15min时,两者明显减低,分别为224.3±51.3μg/g湿重和26.5±5.5mg/g湿重。热应激大鼠置于室温下恢复4h后,两者又都回到正常水平。热应激后,大鼠红细胞膜及肺组织细胞膜的流动性明显降低。表明膜磷脂含量的改变对膜流动性有明显的影响。     

低温下黄瓜幼苗子叶硫氢基（SH）含量变化与膜脂过氧化

随着温度的降低,黄瓜(Cucumis sativus)幼苗子叶中的 SH 基含量逐渐减少;子叶电解质泄漏逐渐提高;SH 基含量的减少与丙二醛(MDA)的增加呈负相关。在黄瓜幼苗子叶中由低温引起的 SH 含量降低和 MDA 增加可因苯甲酸钠和 Vit E 预处理而抑制,因甲基紫精(MV)预处理而加剧。随着对黄瓜幼苗预处理的 MDA 浓度的增大,幼苗子叶中 SH 基含量的降低和电解质泄漏的增加越来越剧,显示出 MDA 对 SH 基具有一定的破坏作用。     

THE COMPLEX BINDING OF γ-AMINOBUTYRIC ACID TO A RAT BRAIN SYNAPTIC MEMBRANE PREPARATION

The association of γ-aminobutyric acid (GABA) with rat brain synaptic membranes is complex and involves more than one set of binding sites. This fact is suggested by the form of experimentally determined binding curves and confirmed by the destruction of one set of homogenous sites by covalent modifications with iodine. The difference in binding of GABA by two sets of membranes which have been exhaustively iodinated in the presence and absence of an excess of GABA corresponds to 1/6 of the binding expressed by uniodinated membranes after equilibration with 0.25 μm -GABA. This difference appears to be the result of the expression of a homogeneous set of independent sites, each of which contains an iodinatable'residue that is protected by bound GABA. Examination of the factors leading to the retention of radioactive ligand by a synaptic membrane preparation is suggestive of a method for determining the maximum number of binding sites for a given ligand and for evaluating solution space without displacing the bound species or adding a presumably inert tracer. Three additional measurements of retention of high ligand concentration are shown to be sufficient for the determination. Employment of the method facilitates the investigation of the interaction of the membrane preparations with individual agonists and antagonists.     

血红蛋白对人红细胞膜脂质分子侧向运动的影响

用荧光漂白恢复法测定了血红蛋白对红细胞膜脂质分子侧向扩散的限制作用.血红蛋白主要是通过和内侧膜脂质的结合而产生影响的,pH6及PH7.7时都显示出效应的存在.和膜结合较强的高铁血红蛋白,表现出对膜脂质侧向扩散亦有较大的限制作用.