13C MAS NMR studies of crystalline cholesterol and lipid mixtures modeling atherosclerotic plaques.

Cholesterol and cholesteryl esters are the predominant lipids of atherosclerotic plaques. To provide fundamental data for the quantitative study of plaque lipids in situ, crystalline cholesterol (CHOL) and CHOL/cholesteryl ester (CE) mixtures with other lipids were studied by solid-state nuclear magnetic resonance with magic-angle-sample spinning. Highly distinctive spectra for three different crystalline structures of CHOL were obtained. When CHOL crystals were mixed with isotropic CE oil, solubilized CHOL (approximately 13 mol % CHOL) was detected by characteristic resonances such as C5, C6, and C3; the excess crystalline CHOL (either anhydrous or monohydrate) remained in its original crystalline structure, without being affected by the coexisting CE. By use of 13C-enriched CHOL, the solubility of CHOL in the CE liquid-crystalline phase (approximately 8 mol %) was measured. When phosphatidylcholine was hydrated in presence of CHOL and CE, magic-angle-sampling nuclear magnetic resonance revealed liquid-crystalline CHOL/phosphatidylcholine multilayers with approximately an equal molar ratio of CHOL/phosphatidylcholine. Excess CHOL existed in the monohydrate crystalline form, and CE in separate oil or crystalline phases, depending on the temperature. The magic-angle-sampling nuclear magnetic resonance protocol for identifying different lipid phases was applied to intact (ex vivo) atherosclerotic plaques of cholesterol-fed rabbits. Liquid, liquid-crystalline, and solid phases of CE were characterized.     

中药凌霄花的药理学考察

实验结果表明,凌霄花对离体猪冠状动脉条具有抑制收缩的作用;对大鼠血栓形成有抑制作用;能加快红细胞电泳,增加红细胞电泳率,使血液红细胞处于分散状态;对离体孕子宫能显著增强收缩活性,增加收缩频率及增强收缩强度。以上结果可初步说明,凌霄花行血去瘀的作用及其“孕妇慎用”的合理性。凌霄花的３种混淆品（白泡桐花,毛泡桐花,兰考泡桐花）的药理作用与凌霄花不同,故不能作凌霄花使用。     

羊草草地枯枝落叶中N,P,K变化动态

羊草草地枯枝落叶中Ｎ、Ｐ、Ｋ变化动态郭继勋,祝廷成（东北师范大学国家草地生态工程实验室,长春１３００２４）ＤｙｎａｍｉｃｓｏｆＮ,ＰａｎｄＫｉｎｌｉｔｔｅｒｓｏｎＡｎｅｕｒｏｌｏｐｉｄｉｕｍｃｈｉｎｅｎｓｅｇｒａｓｓｌａｎｄ．￥ＧｕｏＪｉｘｕｎａｎｄ...     

中药凌霄花的研究进展

本文对中药凌霄花的研究进展进行了综述,包括生药学研究、化学成分研究、药理学研究及临床应用。     

应用PCR技术检测细小病毒H－1DNA在人肝癌与裸鼠正常组织中复制的差异

应用ＰＣＲ技术检测细小病毒Ｈ－１ＤＮＡ在人肝癌与裸鼠正常组织中复制的差异黄青山,马承武,郭兰萍,陈献华,罗祖玉（上海复旦大学生理与生物物理学系,上海２００４３３）关键词：自主性细小病毒Ｈ－１及ＭＶＭ,聚合酶链式反应（ＰＣＲ）,人肝癌模型,抑瘤作用,肿...     

PCR法快速检测临床标本中结核杆菌DNA

应用聚合酶链反应（ＰＣＲ）快速检测临床标本（脑脊液、胸水、腹水、血、痰液）中的结核杆菌ＤＮＡ,特异性扩增片段１２３ｂｐ,为结核杆菌的特异性重复序列ＩＳ６１１０部分基因。ＰＣＲ检测人型结核杆菌的敏感性达１０ｆｇＤＮＡ。临床标本的ＰＣＲ检测阳性率（２３．３％）明显高于抗酸染色涂片（２．９％）和细菌培养（５．７％）的阳性率（Ｐ〈０．０５）。通过设立对照系统及对扩增产物酶切分析,表明该法无假阴性结果（特异     

混合氨基酸含量测定新方法

介绍用交流示波极谱滴定法测混合氨基酸的含量。在ＫＣｌ底液中,利用ＨＣＨＯ将－ＮＨ２封闭,用ＫＯＨ标准液滴定,ＨＣＨＯ同时做指示剂,以极谱图形的敏锐变化指示终点的到过,测定结果准确。     

Construction of a novel bifunctional biogenic amine receptor by two point mutations of the H2-histamine receptor.

BACKGROUND: H2-histamine receptors mediate a wide range of physiological functions extending from stimulation of gastric acid secretion to induction of human promyelocyte differentiation. We have previously cloned the H2-histamine receptor gene and noted that only three amino acids on the receptor were sufficient to define its specificity and selectivity. Despite only modest overall amino acid homology (34% amino acid identity and 57.5% similarity) between the H2-histamine receptor and the receptor for another monoamine, the beta 2-adrenergic receptor, there is remarkable similarity at their critical ligand binding sites. We hypothesized that, if the specificity and selectivity of both receptors are invested in just three amino acids, it should be possible to convert one of the receptors into one that recognizes the ligand of the other by simple mutations at only one or two sites. MATERIAL AND METHODS: We explored the effect of two single mutations in the fifth transmembrane domain of the H2-histamine receptor, which encompasses the sites that determine H2 selectivity. The canine H2 receptor gene was mutated at Asp186 and Gly187 (Asp186 to Ala186 and Gly187 to Ser187) by oligonuceotide directed mutagenesis. The coding region of both the wild-type and mutated H2 receptors was subcloned into the eukaryotic expression vector, CMVneo, and stably transfected into Hepa cells and L cells. The biological activity of histamine and epinephrine on the expressed receptor was examined by measurement of cellular cAMP production and inositol trisphosphate formation. RESULTS: Hepa cells transfected with the Ala186-Ser187 mutant H2 receptor demonstrated a biphasic rise in cAMP in response to epinephrine with an early phase (ED50 approximately 10(-11) M) that could be inhibited by both propranolol and cimetidine. Epinephrine also induced IP3 generation in the same cells, a biological response that is characteristic of activation of the wild-type H2 but not of the beta-adrenergic receptor. L cells transfected with the Ala186-Ser187 mutant H2 receptor also responded to epinephrine in a cimetidine and propranolol inhibitable manner. CONCLUSIONS: We converted the H2-histamine receptor into a bifunctional one that has characteristics of both histamine and adrenergic receptors by two simple mutations. These results support the hypothesis that ligand specificity is determined by only a few key points on a receptor regardless of the structure of the remainder of the molecule. Our studies have important implications on the design of pharmacological agents targeted for action at physiological receptors.