Quantitative measurement of intracellular RNA genomes of Rauscher murine leukemia virus by competition hybridization in DNA excess.

The technique of competition hybridization in DNA excess was used to determine the intracellular distribution of RNA genomes of Rauscher murine leukemia virus. An examination of subcellular RNA fractions revealed that 59% of intracellular viral RNA genomes were associated with the nuclear-enriched fraction, 41% with the cytoplasmic fraction, and 18% with the polysomal-enriched fraction. Also, an analysis of total cellular RNA disclosed that 20% of intracellular viral RNA genomes were polyadenylated and 80% were not polyadenylated.     

Enalapril in the treatment of hypertension with renal artery stenosis.

The converting enzyme inhibitor enalapril, in single daily doses of 10-40 mg, was given to 20 hypertensive patients with renal artery stenosis. The blood pressure fall six hours after the first dose of enalapril was significantly related to the pretreatment plasma concentrations of active renin and angiotensin II and to the concurrent fall in angiotensin II. Blood pressure fell further with continued treatment; the long term fall was not significantly related to pretreatment plasma renin or angiotensin II concentrations. At three months, 24 hours after the last dose of enalapril, blood pressure, plasma angiotensin II, and converting enzyme activity remained low and active renin and angiotensin I high; six hours after dosing, angiotensin II had, however, fallen further. The rise in active renin during long term treatment was proportionally greater than the rise in angiotensin I; this probably reflects the fall in renin substrate that occurs with converting enzyme inhibition. Enalapril alone caused reduction in exchangeable sodium, with distinct increases in serum potassium, creatinine, and urea. Enalapril was well tolerated and controlled hypertension effectively long term; only two of the 20 patients required concomitant diuretic treatment.     

Lipid selectivity of the calcium and magnesium ion dependent adenosinetriphosphatase, studied with fluorescence quenching by a brominated phospholipid

1,2-Bis(9,10-dibromooleoyl)phosphatidylcholine (BRPC) has been prepared from dioleoylphosphatidylcholine (DOPC). It is shown that the gel to liquid-crystalline phase transition for BRPC occurs below ca. 5 degrees C and that the motional properties of bilayers of BRPC and DOPC as detected by spin-labeled fatty acids are similar. The ATPase activities of the (Ca2+-Mg2+)-ATPase from rabbit muscle sarcoplasmic reticulum reconstituted with BRPC and DOPC are similar. The brominated lipid quenches the fluorescence of the ATPase and can be used to determine selectivity of lipid binding to the ATPase. We show that there is little selectivity on the basis of fatty acyl chain length. Binding constants for phosphatidylcholines and phosphatidylserines are similar in the absence of calcium, although that for phosphatidylserine decreases in the presence of calcium. Phosphatidylethanolamines binds less strongly than phosphatidylcholines, although the difference is small. The largest difference in binding constants is seen between phosphatidylcholines in the gel and liquid-crystalline phases, with a distribution coefficient of 30 in favor of the liquid-crystalline phase. It is shown that the distribution of the ATPase in mixtures of dipalmitoylphosphatidylcholine and BRPC can be understood in terms of the phase diagram for this mixture of lipids. Activities of the ATPase in the presence of mixtures of lipids can be explained in terms of the relative binding constants obtained from the fluorescence experiments.     

The use of negative ion thermospray liquid chromatography/tandem mass spectrometry for the determination of bile acids and their glycine conjugates.

A study was carried out on the negative ion thermospray liquid chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry of a group of bile acids and their glycine conjugates. The liquid chromatographic/tandem mass spectrometric experiments were performed using low-energy collisions on a triple-quadrupole mass spectrometer. It was found that relatively high collision energies and collision gas pressures were required to produce fragmentation and that some unusual fragments were produced.     

Effects of phospholipids on the function of (Ca2(+)-Mg2+)-ATPase.

The ATPase activity for the (Ca2(+)-Mg2+)-ATPase purified from rabbit skeletal muscle sarcoplasmic reticulum is lower when reconstituted into bilayers of dimyristoleoylphosphatidylcholine [(C14:1)PC] than when it is reconstituted into dioleoylphosphatidylcholine [(C18:1)PC]. The rate of formation of phosphoenzyme on addition of ATP is slower for (C14:1)PC-ATPase than for the native ATPase or (C18:1)PC-ATPase. The reduction in rate of phosphoenzyme formation is attributed to a reduction in the rate of a conformational change on the ATPase following binding of ATP but before phosphorylation. The level of phosphoenzyme formed from Pi is also less for (C14:1)PC-ATPase than for (C18:1)PC-ATPase. At steady state at pH 6.0 in the presence of ATP Ca2+ is released from (C18:1)PC-ATPase into the medium, but not from (C14:1)PC-ATPase. These effects of (C14:1)PC on the ATPase are reversed by addition of androstenol to a 1:1 molar ratio with (C14:1)PC. The results are interpreted in terms of a kinetic model for the ATPase.     

小黑杨转双价抗虫基因的研究

用根癌农杆菌介导的叶盘法,将蜘蛛杀虫肽与Bt基因C肽序列的融合基因导入小黑杨(Populus simonii×P.nigra),所获得的3株卡那霉素抗性再生植株进行PCR和PCR-Southern杂交检测的结果均为阳性,Southern杂交检测的结果2株为阳性.抗虫试验结果显示,3个转基因株系均具有明显的抗虫效果,能显著抑制舞毒蛾幼虫的生长发育,表现出强烈的抗虫作用.     

假丝酵母Candida rugosa产脂肪酶条件的优化

对假丝酵母Candidarugosa产脂肪酶的条件进行了优化.比较实验证明,碳源是影响酶产量的主要因素.其中,糖类使细胞生长良好,但酶产量较低,而脂类是较为适合的碳源.本实验首次发现长链的不饱和脂肪酸酯,三油酸甘油酯是最好的碳源.氮源的影响较小.而添加物的使用是有效提高脂肪酶产量的另一种方法.PVA可促进碳源的乳化,从而提高脂肪酶产量.吐温虽没有促进细胞生长,但却大幅度提高了酶的产量.将以上优化的结果应用于发酵罐中,分批流加操作时,脂肪酶产量高达每毫升128.2单位,为目前报道的最高值.     

水稻转录因子OsBP-73靶基因的初步筛选

OsBP-73是用酵母单杂交系统,以水稻蜡质基因(Wx)的顺式作用元件为诱饵,从水稻cDNA表达文库中筛选获得的转录因子。本文以OsBP-73基因为例介绍了用"下拉"(pull-down)方法筛选转录因子靶基因的一般步骤。将含有该基因DNA结合功能域的cDNA片段构建到原核表达载体上,并在大肠杆菌中诱导表达获得其蛋白p73。用纯化后的p73蛋白通过"下拉"实验对OsBP-73靶基因进行初步筛选,获得了22个阳性克隆,为进一步研究转录因子OsBP-73参与的水稻转录调控网络提供依据。     

南丰蜜桔可溶性固形物近红外检测的多元线性回归变量筛选

文章采用反向区间偏最小二乘法结合连续投影算法,筛选南丰蜜桔近红外检测的多元线性回归变量。对南丰蜜桔近红外光谱进行多元散射校正后,利用反向间隔偏最小二乘法,从500～1750 nm中初选出7个光谱区间,用于多元线性回归变量筛选。利用通过遗传算法和连续投影算法筛选出的变量建立了多元线性回归模型。经比较发现,利用反向区间偏最小二乘法结合连续投影算法筛选出的变量建立的多元线性回归模型,预测结果最优,模型预测相关系数为0.937,模型预测均方根误差为0.613 oBrix。结果表明,反向区间偏最小二乘法结合连续投影算法,可以有效地筛选近红外光谱的多元线性回归变量,提高南丰蜜桔可溶性固形物模型的预测精度。