咽喉部高频喷射通气调节各参数对狗肺通气效率的影响

用相关和回归处理方法,研究了8条正常狗咽喉部高频喷射通气时,调节驱动压、呼吸比和频率对喷气量、吸入气氧浓度、动脉血气及气道内压的作用。结果显示,驱动压和呼吸此对各观察指标几乎有同等重要的作用,频率的影响很小,喷气量与吸入气氧浓度、动脉血气、气道内压间存在显著的正相关关系。说明调节参数的意义主要在于改变了喷气量。     

互花米草人工植被生态效益和经济效益的初步研究

前言在我国海涂中被日潮淹没的中、低潮带,天然生长的高等植物种类比较贫乏,分布面积也较小,许多中低潮带海滩为光滩裸地。为了绿化海滩、保护海滩,提高海滩生态系统的初级生产力,我国在1963年和1978年分别从英国     

酸性水和投加铝、钙对鲢鱼早期发育和鳃超微结构的影响

在实验室条件下,研究了酸性水和投加铝、钙对鲢鱼胚胎孵化和鱼苗存活以及幼鱼鳃超微结构的影响。pH4.0引起所有胚胎在24小时内死亡,暴露于pH4.5—6.0的胚胎孵化率和暴露于pH4.0—6.0的5—15日龄鱼苗存活率随pH值上升而增高。投加0.5mg Al~(3+)/L使在酸性pH暴露条件下的胚胎孵化率和鱼苗存活率进一步降低。投加3.0mg Ca~(2+)/L可显著提高暴露于pH4.5和5.0的胚胎孵化率;投加2.0mg Ca~(2+)/L可在一定程度上提高暴露于pH4.5和5.0的鱼苗存活率。幼苗经pH4.5暴露8小时后出现严重的鳃超微结构损害;投加1.0mg Al~(3+)/L使鳃结构损害加剧;投加5.0mg Ca~(2+)/L可明显缓解酸性水对鳃的损害。     

云南羯布罗香树脂的化学成分

从云南产羯布罗香(Dipterocarpus tubinatus Gaertn. f.)树脂中分离得到6个三萜化合物,鉴定为羟基达玛烯酮—Ⅱ(hydroxydammarenone-Ⅱ,达玛烯二醇—Ⅱ(dammarenediol—Ⅱ),白桦脂酸(betulonk acid),亚细亚酸(asiatic acid),3,23-O-异丙叉亚细亚酸(3,23-O-isopropylidene asiatic acid)和崩大碗酸(madasiatic acid)。其中崩大碗酸系首次从龙脑香科树脂中分离得到。     

Potassium permanganate as an in situ probe for B-Z and Z-Z junctions.

The availability of DNA structural probes that can be applied to living cells is essential for the analysis of biological functions of unusual DNA structures adopted in vivo. We have developed a chemical probe assay to detect and quantitate left-handed Z-DNA structures in recombinant plasmids in growing E. coli cells. Potassium permanganate selectively reacts with B-Z or Z-Z junction regions in supercoiled plasmids harbored in the cells. Restriction enzyme recognition sites located at these junctions are not cleaved by the corresponding endonuclease after modification with KMnO4. This inhibition of cleavage allows the determination of the relative amounts of B- and Z-forms of the cloned inserts inside the cell. We have successfully applied this method to monitor the extent of Z-DNA formation in E. coli as a function of the growth phase and mutated topoisomerase or gyrase activities. The assay can in principle be used for any unusual DNA structure that contains a restriction recognition site inside or near the structural alteration. It can be a useful tool to analyze in vivo correlations between DNA structure and gene regulatory events.