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.     

Paternal age and the occurrence of birth defects

The association between paternal age and the occurrence of birth defects was studied using data collected in Metropolitan Atlanta. Paternal-age information for babies born with defects was obtained from birth certificates, hospital records, and interviews with mothers; for babies born without defects, the information was obtained from birth certificates. Several statistical techniques were used to evaluate the paternal-age-birth-defects associations for 86 groups of defects. Logistic regression analysis that controlled for maternal age and race indicated that older fathers had a somewhat higher risk for having babies with defects, when all types of defects were combined; an equivalent association for older mothers was not found. Logistic regression analyses also indicated modestly higher risks for older fathers for having babies with ventricular septal defects and atrial septal defects and substantially higher risks for having babies with defects classified in the category chondrodystrophy (largely sporadic achondroplasia) and babies with situs inversus. An association between elevated paternal age and situs inversus has not been reported before; the magnitude of the estimated increased risk for situs inversus was about the same as that found in this study for chondrodystrophy.     

斯氏狸殖吸虫螺类宿主新记录:洪山拟钉螺新种记述

本文报道斯氏狸殖吸虫新的螺类宿主——洪山拟钉螺Tricula hongshanensis sp. nov.的特点:螺壳较宽而短,体螺层较高大,壳口上缘成锐角,触角伸展时较长,收缩吋有环状皱褶,雄性阴茎较粗短,末端钝圆,齿舌公式不同于其它拟钉螺。     

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     

Studies of hormonal regulation of osteocalcin synthesis in cultured fetal rat calvariae

The synthesis of osteocalcin, the major non-collagenous protein of adult bone, was examined in cultures of 21-day fetal rat calvariae. Osteocalcin was measured by a sensitive and specific radioimmunoassay. Osteocalcin concentration in unincubated calvariae was 14.5 +/- 0.5 ng/calvaria. After incubation, there was a continuous increase in bone and medium osteocalcin, and by 96 h the values were about 100% higher than in unincubated calvariae. 1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) at 10(-11) to 10(-8)M increased osteocalcin synthesis. The effect appeared as early as 6 h after treatment and was primarily observed in the culture medium, and 1,25-(OH)2D3 stimulated osteocalcin up to 9-fold by 96 h. Concomitant with the effect on osteocalcin synthesis, 1,25-(OH)2D3 inhibited collagen synthesis. Cycloheximide markedly decreased osteocalcin concentrations in control and 1,25-(OH)2D3-treated calvariae. The stimulatory effect on osteocalcin synthesis was specific to 1,25-(OH)2D3 since 24,25-dihydroxyvitamin D3, parathyroid hormone, epidermal growth factor, and prostaglandin E2 did not stimulate osteocalcin synthesis, and parathyroid hormone and epidermal growth factor opposed the 1,25-(OH)2D3 stimulatory effect. Insulin did not alter osteocalcin concentration by itself but enhanced the effect of 1,25-(OH)2D3. In conclusion, 1,25-(OH)2D3 stimulates osteocalcin synthesis in cultures of normal calvariae, but this effect is not shared by other hormones known to affect bone metabolism.