Differential perturbation of erythrocyte membrane-associated transport and enzyme activities by structurally related lipophilic compounds

The alteration of two erythrocyte plasma membrane functions, acetylcholine hydrolysis and glucose exchange, by a series of structurally related small lipophilic compounds which exhibit similar antihemolytic behavior was studied. 2-Methyldimethylaminoazobenzene is a more potent inhibitor of acetylcholinesterase than the 3′-methyl analogue, while the unsubstituted compound fails to inhibit. Esterase inhibition by the 2-methyl compound is noncompetitive and dependent on the anion composition of the assay buffer. The temperature dependence of acetylcholinesterase activity in the presence of the 2-methyl compound suggests that interaction with inhibitor is influenced by the state of lipids tightly bound to the enzyme. Glucose exchange is inhibited to the same extent by both methyl derivatives but not by the unsubstituted dye, and the temperature dependence in the presence of inhibitor is not grossly altered. The lack of correlation between inhibition of membrane function and stabilization of erythrocytes against osmotic hemolysis is discussed.     

Ca2+-induced isotropic motion and phosphatidylcholine flip-flop in phosphatidylcholine-cardiolipin bilayers

Ca²⁺ induces a structural change in phosphatidylcholine-cardiolipin bilayers, which is visualised by freeze-fracturing as lipidic particles associated with the bilayer and is detected by ³¹P-NMR as isotropic motion of the phospholipids. In this structure a rapid transbilayer movement of phosphatidylcholine and a highly increased permeability towards Mn²⁺ are observed.     

Sister-chromatid exchange induction by indirect mutagens/carcinogens, aryl hydrocarbon hydroxylase activity and benzo[alpha]pyrene metabolism in cultured human hepatoma cells

2 human hepatoma cell lines (C-HC-4 and C-HC-20), in which aryl hydrocarbon hydroxylase activity was induced with benz[alpha]anthracene in vitro to about 140- and 64-fold of the respective basal levels, yielded an increased frequency of sister-chromatid exchanges (SCEs) when exposed to benzo[alpha]pyrene (BP), 7,12-dimethylbenz[alpha]anthracene and 3-methylcholanthrene in vitro. Analysis of the metabolism of BP by these cells by high-pressure liquid chromatography revealed that both cell lines produced various BP metabolites including the proximate form BP-7,8-dihydrodiol which has been reported to be the most potent inducer of SCEs among the metabolites of BP. In addition, aflatoxin B1 and cyclophosphamide also induced SCEs in these cell lines. The above findings suggest that these cells may be capable of metabolizing a range of indirect mutagens/carcinogens into DNA-active forms. These cells may therefore serve as a useful test system in vitro for the detection of genotoxic agents, without the use of an exogenous activating system.     

长江三峡库区蝶类群落的物种获得率、小生境占有率及相对多度

研究于 1998～ 2 0 0 3年在库区 10个区县 ,35个调查点进行。研究时 ,库区蝴蝶的生活环境被划分为 80个小生境 ,设置样带6 6 1条 ;调查期间获得 (Sampled)蝴蝶 331种 ,10 780只个体。报道三峡库区蝴蝶群落的部分参数 :2 5 3种蝴蝶的小生境占有率低于 10 % ,占有 4 0 %以上小生境的蝴蝶只有 7种 ;在 6 0条以上样带都获得的蝴蝶有 16种 ,而在 10条以下样带内获得的蝴蝶 2 19种 ,占总数的 6 6 .2 % ;优势种 2 1个 (6 .3% ) ,常见种 12 5个 (37.8% ) ,少见种 10 3个 (31.1% ) ,罕见种 82个 (2 4 .8% ) ;相对多度高于 1%的种类 2 2个 ,仅占总数的 6 .6 % ;个体数分布的规律接近对数级数法则。三峡库区蝶类现在的分布反映了库区生境破碎化的结果 ,意味着适宜的生境斑块周围分布不适宜生境 ,种群受到面积、隔离、边缘等多种效应的影响 ,形成了现有的物种多样性及其空间格局     

环青海湖地区天然草地时序光谱特征参量分析

获取了环青海湖地区4类主要天然草地2003年5~10月共16个时相的地面高分辨率光谱数据,并利用植被指数技术、导数光谱技术、植被光谱维特征提取模型及包络线归一化技术提取了多个光谱特征参量,通过对各参量在生育期内分布规律的分析,给出了能较好地表征草地生长发育规律时序特征参量的具体分布;最后计算了4类天然草地各时序特征参量的平均散度,结果表明黄边位置λY、红边位置λV、红边斜率SV、绿峰半高宽wλG、红谷半高宽wλR、去包络红谷净面积AR'和归一化植被指数NDV I对于天然草地分类更有效。     

以聚乙二醇为层析伴侣同时制备SOD、过氧化氢酶和血红蛋白

发展了一条从红细胞裂解液中同时制备超氧化物歧化酶(SOD)、过氧化氢酶和血红蛋白的新工艺。采用0 75 %的聚乙二醇600作为层析伴侣,使血红蛋白直接流过阴离子交换层析柱,同时吸附SOD和过氧化氢酶。经过梯度洗脱获得SOD和过氧化氢酶组分,再经过疏水性相互作用层析与凝胶过滤层析相串联,使SOD和过氧化氢酶得到纯化。纯化后的SOD和过氧化氢酶的比活力分别达到15932u/mg和65918u/mg ,血红蛋白的纯度达到99.9%以上。总回收率为:SOD ,47.4% ;过氧化氢酶,29.6% ;血红蛋白,88.7%。     

水动力条件下藻类动态模拟

藻类动态变化是其内部生理特征和外部驱动因素综合作用的结果。除了藻类自身生理因素及光、温度、营养盐等因素,水动力作用使底泥发生再悬浮所造成的营养盐的内源释放对藻类的影响也非常重要。1999年5月8日~6月24日在太湖湖泊生态系统研究站大型生态实验槽中进行了模拟水动力条件下的太湖藻类动态实验,并应用国外先进的PHREEQC软件从生物化学和生态动力学角度建立了藻类生态动力学模型。模型不仅考虑了氮循环及磷循环,还考虑了水动力条件引起的内源释放问题,根据2003年4月26~4月30日在河海大学环形水槽所做的底泥释放实验结果建立了水流和各形态氮磷营养盐释放的定量化关系。由于目前太湖的野外监测资料存在较明显的时空不一致性,模型参数率定的精度受到了较大影响。从室内模拟实验出发,通过对生态槽实验结果的模拟,确定和验证了模型的各参数值,计算结果显示模拟值能较好地拟合实验测量值,表明所建藻类生态动力学模型能较好地描述藻类及各种营养盐的动态变化,这对揭示藻类“水华”暴发机理有一定的意义。     

基于遗传算法的谷氨酸发酵动力学参数估计

把遗传算法应用于求解谷氨酸分批发酵动力学模型参数,取交叉概率Pc=0．8、变异概率Pm=0．06、初始种群为20、遗传世代数为200代,能进一步提高谷氨酸分批发酵过程状态变量的计算值与实验值的吻合程度。模拟值与实验值对比显示,该动力学模型能很好地反映谷氨酸分批发酵过程。     

Stabilized plasmid-lipid particles containing PEG-diacylglycerols exhibit extended circulation lifetimes and tumor selective gene expression

Stabilized plasmid lipid particles (SPLP) consist of a single copy of DNA surrounded by a lipid bilayer. The particles are small (∼100 nm), stable, monodisperse and have a low surface charge. A diffusible polyethylene glycol (PEG) coating attached to a lipid anchor is critical to the SPLP's functionality. The PEG-lipid exchanges out of the bilayer at a rate determined by the size of the lipid anchor. Here we show that SPLP can be prepared using a series of PEG-diacylglycerol lipids (PEG-S-DAGs). SPLP were prepared incorporating PEG-dimyristoylglycerol (C₁₄), PEG-dipalmitoylglycerol (C₁₆) or PEG-distearoylglycerol (C₁₈) and the rate of PEG-lipid diffusion from the bi-layer determined using a FRET assay. SPLP pharmacokinetics confirm a correlation between the stability of the PEG-lipid component and circulation lifetime. PEG-S-DAGs with longer lipid anchors yield more stable SPLP particles with longer circulation half-lives yielding an increase in tumor delivery and gene expression. PEG-distearoylglycerol (C₁₈) containing SPLP bypass so-called ‘first pass’ organs, including the lung, and elicit levels of gene expression in distal tumor tissue 100- to 1000-fold greater than that observed in any other tissue. The incorporation of PEG-S-DAG in SPLP confirms that small size, low surface charge and extended circulation lifetimes are prerequisite to the accumulation and tumor selective expression of plasmid DNA following systemic administration.