A cytogenetic characterization comparing a rat 6TG-resistant strain and 6TG-sensitive clones

Summary A 8.3 /ml 6-thioguanine (6TG)-resistant strain was isolated from a rat tetraploid cell line by step-by-step selection in 6TG-medium. In the 6TG-resistant cell population 51% of the cells were tetraploid and 35% of the cells were hypertetraploid, i.e., one chromosome more than a tetraploid. The 6TG-resistant strain grew very well in RPMI 1640 medium with intervals of three days between subcultures. The 6TG-resistant cells all have a homogeneously staining region (HSRs) in one of the X chromosomes which do not stain after chromosome C-banding. They also possess a higher NORs activity and much lower frequency of sister chromatid exchanges (SCE). When the 6TG-resistant RCT cells were subcultured in 6TG-free medium for three days, their SCE frequency did not change. 5-bromodeoxyuridine (BrdU) significantly suppressed the NORs activity for both 6TG-resistant cells and 6TG-sensitive cells (P<0.001).Abbreviations 6TG 6-thioguanine - HSRs homogeneously staining region - NORs nucleolar organizer region - SCE sister chromatid exchange - BrdU 5-bromodeoxyuridine - HPRT Hypoxanthine phosphoribosyl transferase     

中药马蓝叶及其混乱品的比较鉴别

马蓝叶是加工传统中药青黛的主要原料。为了确保药材质量,作者对中药马蓝叶及其混乱品种球花马蓝、疏花马蓝、广西马蓝的原植物、药材性状、叶组织显微特征和薄层层析鉴别等进行了研究。指出其混乱品种虽与马蓝叶是同属植物,但不含马蓝叶的有效成分靛玉红,应仔细鉴别,不宜混用。     

猪肺炎支原体膜上ATP酶生化性质的研究

猪肺炎支原体膜上ATP酶为Mg~(2+)激活,乌巴因不抑制。DCCD和寡霉素对该酶也无抑制作用,只有NBD与Quercetin才有一定的抑制效果。用梯度凝胶电泳可获均一的具有活性的酶蛋白带。     

Comparative analysis of glycoprotein and glycolipid composition of virulent and avirulent strain membranes ofMycoplasma hyopneumoniae

The glycoproteins and glycolipids from membranes of virulent strain Z and avirulent strain M ofMycoplasma hyopneumoniae have been compared. The proteins and the glycoproteins were identified by SDS-polyacrylamide gel electrophoresis and concanavalin A-biotin labeling, respectively. The membrane preparation contained approximately 34 protein bands with molecular weights between 20 KD and 100 KD. The concanavalin A-biotin system reacted with a glycoprotein of a molecular weight of approximately 28,000 from avirulent strain M and did not react with the correspondent band from virulent strain Z. The membrane glycolipids of both strains consisted of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and the percentages of 160, 180, and 181 fatty acids comprised more than 80% of the total fatty acids of membrane glycolipids. The 180 fatty acid of MGDG in avirulent strain M was twofold higher than that of virulent strain Z.     

脂质过氧化对人红细胞膜脂流动性的影响

研究枯稀过氧化氢/高铁血红素体系所产生的烷基过氧自由基对红细胞的损伤。测定了脂质过氧化的产物——丙二脂的生成,并证明阿魏酸钠对脂质过氧化的抑制。荧光偏振的结果指出,膜脂过氧化以后降低了膜脂的流动性。人红细胞用5DSA和16DSA标记并用ESR检测膜脂流动性,结果表明,序参数S几乎没有发生变化,旋转相关时间τ值的增加证明膜脂过氧化以后,疏水尾部的物理状态发生了改变。经脂质过氧化以后,红细胞膜中的不饱和脂防酸的减少,可能是降低膜脂流动性的原因之一。     

小量个体人血清中补体成分C_4的纯化

 <正> 补体成分的多态现象,特别是对人C4多态现象的研究,是近年来补体研究进展的一个重要方面。1969年Roseufeld等报告了人补体C4的多态现象以后,Teisberg等(1976)率先应用免疫固定电泳研究C4多态现象。这是当前研究补体多态现象的通用方法。1978年O’Neill等报告人的C4F和C4S分别由C4A和C4B两个基因座位控制,并分别与Rodgers和Chido血型抗原相应。现已发现C4A共有13个别型,C4B共有22个别型。     

Main Immunogenic Region of Torpedo Electroplax and Human Muscle Acetylcholine Receptor: Localization and Microheterogeneity Revealed by the Use of Synthetic Peptides

Most anti-nicotinic acetylcholine receptor (AChR) antibodies in myasthenia gravis are directed against an immunodominant epitope or epitopes [main immunogenic region (MIR)] on the AChR alpha-subunit. Thirty-two synthetic peptides, corresponding to the complete Torpedo alpha-subunit sequence and to a segment of human muscle alpha-subunit, were used to map the epitopes for 11 monoclonal antibodies (mAbs) directed against the Torpedo and/or the human MIR and for a panel of anti-AChR mAbs directed against epitopes on the alpha-subunit other than the MIR. A main constituent loop of the MIR was localized within residues alpha 67-76. Residues 70 and 75, which are different in the Torpedo and human alpha-subunits, seem to be crucial in determining the binding profile for several mAbs whose binding to the peptides correlated very well with their binding pattern to native Torpedo and human AChRs. This strongly supports the identification of the peptide loop alpha 67-76 as the actual location of the MIR on the intact AChR molecule. Residues 75 and 76 were necessary for binding of some mAbs and irrelevant for others, in agreement with earlier suggestions that the MIR comprises overlapping epitopes. Structural predictions for the sequence segment alpha 67-76 indicate that this segment has a relatively high segmental mobility and a very strong turning potential centered around residues 68-71. The most stable structure predicted for this segment, in both the Torpedo and human alpha-subunits, is a hairpin loop, whose apex is a type I beta-turn and whose arms are beta-strands. This loop is highly hydrophilic, and its apex is negatively charged. All these structural properties have been proposed as characteristic of antibody binding sites. We also localized the epitopes for mAbs against non-MIR regions. Among these, the epitope for a monoclonal antibody (mAb 13) that noncompetitively inhibits channel function was localized within residues alpha 331-351.     

山莨菪碱对经有限蛋白水解后的脑突触膜Ca~(2+)-ATPase的影响

 从猪脑中提取钙调蛋白和突触质膜,我们研究了山莨菪碱对经有限蛋白水解和磷脂酶A_2处理后的突触膜Ca~(2+)-ATPase活性影响。发现药物对不同预处理后的Ca~(2+)-ATPase表现出不同影响并调节钙调蛋白对它的激活作用。     

外源脂肪酸及胆固醇对莱氏衣原体膜糖脂含量的影响

 <正> 单葡萄糖甘油二酯(MGDG)和双葡萄糖甘油二酯(DGDG)是莱氏衣原体膜上主要的极性脂。糖脂的生理功能过去很少研究,至今仍不清楚。近年来实验结果表明,MGDG在膜上容易形成六角形Ⅱ结构,而DGDG则形成脂双层结构。六角形Ⅱ结构的出现与生物膜的生理功能的关系是当前瞩目的研究内容。本文首次研究了外源脂肪酸和胆固酵对莱氏衣原体AIH089菌株膜上糖脂含量的影响。     

不同磷脂和糖脂对莱氏衣原体膜上Mg~（2＋）－ATPase活性的影响

莱氏衣原体膜上Ｍｇ~（２＋）－ＡＴＰａｓｅ用ＤＯＣ溶解后,经Ｓｅｐｈａｒｏｓｅ－６Ｂ和ＤＥＡＥ－ＣｅｌｌｕｌｏｓｅＤＥ－５２离子交换柱,得到了部分纯化的Ｍｇ~（２＋）ＡＴＰａｓｅ,并将此ＡＴＰａｓｅ与不同极性头部的磷脂和膜糖脂重组,研究了不同的极性头部的磷脂和膜糖脂对ＡＴＰａｓｅ活性的影响。此酶的活性不依赖酸性磷脂,ＰＧ、ＤＰＧ、大豆磷脂等明显抑制酶活性,中性磷脂ＤＭＰＣ、ＰＥ、ＰＣ则能增加酶活性,其中尤以非双层脂ＰＥ的作用最为明显。从莱氏衣原体膜上提取的糖脂（ＭＧＤＧ,ＤＧＤＧ）单独和ＡＴＰａｓｅ重组时,酶活性增加并不明显,当ＭＧＤＧ和ＤＧＤＧ以等比例混合时,能大大地增加酶活性。这表明Ｍｇ~（２＋）－ＡＴＰａｓｅ的活性很大程度上与磷脂的表面电荷及磷脂的组成相关。