Phase metastability and supercooled metastable state of diundecanoylphosphatidylethanolamine bilayers

Aqueous dispersons of L-alpha-phosphatidylethanolamine (PE) with identical saturated acyl chains are known to exhibit gel-state metastability. It is also known that the metastability in PE becomes more pronounced with decreasing acyl chain-length. In an attempt to study the metastable phase behavior of PE, we have synthesized diundecanoylphosphatidylethanolamine (diC11PE) and examined its polymorphic phase behavior. A single endothermic transition at 38 degrees C is detected between 10 and 55 degrees C by DSC for the nonheated sample of diC11PE in excess water. An immediate second heating scan done after cooling slowly of the same sample from the liquid-crystalline state shows a smaller endothermic transition at a lower temperature, 18 degrees C. However, the high-temperature transition at 38 degrees C can be detected, if the sample which has been heated above 38 degrees C is quench cooled from the liquid-crystalline to a temperature between 18 and 38 degrees C. Furthermore, two endothermic transitions at 18 and 38 degrees C and an exothermic transition at 19 degrees C are recorded for diC11PE after quench supercooling of the sample from the liquid-crystalline state to an appropriate temperature below 10 degrees C. The gel-state metastability of diC11PE can be most appropriately explained in terms of changes in interbilayer headgroup-headgroup interactions. It is suggested that the kinetically trapped supercooled metastable state may be a multilamellar structure with melted acyl chains but with strong interbilayer headgroup-headgroup interactions.     

青年昼间发汗调定点正常值探讨

以加热腿足诱发前臂屈侧初始发汗的口腔温度阈值,作为发汗调定点的参考值(ToSSP),检测健康青年93人夏冬两季昼间ToSSP134次。结果表明,季节、性别、民族、于室温24℃左右变异达30％的相对湿度对ToSSP均无显著影响。提示ToSSP为一间接反映体温调定点较发汗率为稳定的指标。ToSSP的频数分布属于正态,均值为37.34℃,95％正常值范围为36.97～37.71℃。经于本工作前,后年份检测的两组结果以及与正常体温夜间最低时相组和发热患者组的ToSSP相验证,证明此正常值范围可靠。检测ToSSP的潜伏期夏季均值为19′57″冬季为18′22″(P<0.05)。检测ToSSP时口温变化分别与皮肤温、心率变化紧密相关,因而心率,皮肤温可作为监测ToSSP的辅佐指标。     

一种新病毒——兔出血症病毒的鉴定初报

从我国新发生的一种家兔急性败血性传染病死兔内脏抽提物中,观察到典型的病毒粒子,回归兔可引起典型发病,再从病死兔内脏回收到同样病毒,证明该病系病毒性传染病,暂定名为“兔病毒性出血症”,病原暂定为“兔出血症病毒”。经初步鉴定,认为本病毒可能是一种首次发现的新病毒,属双股RNA病毒。但从病毒大小和核酸节段看,又不同于呼肠病毒科。最终归属正在进一步研究。     

激光、血卟啉对肿瘤细胞DNA单链断裂及其重接的影响

用简化的Kohn氏碱洗脱法,观察了光敏剂血卟啉衍生物(HPD)对小鼠S-180肿瘤细胞DNA单链断裂及其重接修复的影响。激光HPD能导致S-180细胞DNA单链断裂明显增加,而且这种断裂随着保温时间的延长,继续增多。在本实验条件下没有观察到HPD对X线的增敏作用,HPD不能增加X线所致的DNA单链断裂,也不能影响其重接。单链断裂重接动力学的实验进一步证明了这个论点。     

普通烟草和黄花烟草及体细胞杂种过氧化物酶同工酶等电聚焦电泳

日本学者长尾照义(1978)用原生质体融合获得普通烟草与黄花烟草的体细胞杂种植株。1980年陈家玉等在国内首先获得普通烟草(Copus Yeusuku No.4)和黄花烟草(Yellow Flower)的体细胞杂种植株。之后,中国农科院烟草所(1981)也得到相同的结果。陈家玉等(1983)对上述杂种进行了形态学、细胞学和同工酶的分析并取得一定的结果。Dlineee等(1975)分析比较了用等电聚焦技术分离的过氧     

Donnan potentials from striated muscle liquid crystals. Sarcomere length dependence.

Donnan potentials from A-bands and I-bands were measured as a function of sarcomere length in skinned long-tonic muscle fibers of the crayfish. These measurements were made using standard electrophysiological technique. Simultaneously, the relative cross-sectional area of the fibers was determined. Lattice plane spacings and hence unit-cell volumes were determined by low-angle x-ray diffraction. At a sarcomere length at which the myosin filaments and actin filaments nominally do not overlap, measurements of potential, relative cross-sectional area, and unit-cell volume were used in conjunction with Donnan equilibrium theory to calculate the effective linear charge densities along the myosin filament (6.6 X 10(4) e-/mu) and actin filament (6.8 X 10(3) e-/mu). Using these linear charge densities, unit-cell volumes and Donnan equilibrium theory, an algorithm was developed to predict A-band and I-band potentials at any sarcomere length. Over the range of sarcomere lengths investigated, the predicted values coincide with the experimental data. The ability of the model to predict the data demonstrates the applicability of Donnan equilibrium theory to measurements of electrochemical potential from liquid-crystalline systems.