Effects of histamine on bronchial artery blood flow and bronchomotor tone

The effects of aerosolized 5% histamine (10 breaths) on bronchial artery blood flow (Qbr), airflow resistance (RL), and pulmonary and systemic hemodynamics were studied in mechanically ventilated sheep anesthetized with pentobarbital sodium. Histamine increased mean Qbr and RL to 252 +/- 45 and 337 +/- 53% of base line, respectively. This effect was significantly different from base line for 30 min after challenge. The histamine-induced increase in RL was blocked by pretreatment with the histamine H1 receptor antagonist, chlorpheniramine, whereas the histamine-induced elevation in Qbr was prevented by the H2 antagonist, metiamide. Both responses were blocked only when both antagonists were present. Changes in Qbr were not directly associated with alterations in systemic and pulmonary hemodynamics or arterial blood gas composition. In vitro histamine caused a dose-dependent contraction of ovine bronchial artery strips that was prevented by H1 antagonist. The H2 agonist, impromidine, caused relaxation of precontracted arterial strips and was more potent and efficacious than histamine, whereas H1 agonists failed to elicit a relaxant response. Thus these findings indicate that histamine aerosol induces a vasodilation in the bronchial vascular bed; histamine has a direct effect on Qbr that is independent of alterations in RL, systemic and pulmonary hemodynamics, or arterial blood gas composition; and, histamine-induced bronchoconstriction is mediated predominantly by H1-receptors, whereas increased Qbr is controlled predominantly by H2-receptors, probably located in resistance vessels. This local effect of histamine on Qbr may have important implications in the pathophysiology of bronchial asthma and pulmonary edema.     

柱孢鱼腥藻的铁蛋白与棕色固氮菌的钼铁蛋白的交叉互补作用

纯化的柱孢鱼腥藻铁蛋白能够与棕色固氮菌的钼铁蛋白有效地交叉反应,展现较高的活性。此异源交叉反应的乙炔还原比活及放氢比活,分别是蓝藻同源互补比活的83.8及66.7％。比较藻铁蛋白与菌钼铁蛋白异源交叉反应及藻固氮酶组分之间的同源反应的动力学特点时发现,铁蛋白对钼铁蛋白的最佳克分子比数前者(异源交叉反应)较后者(藻同源反应)为高,前者为5,后者为1;但反应的时间进程两者差别不大。     

DNA启动子的计算机识别

本文介绍了两种预测DNA顺序上的启动子位置的计算机识别方法,方法1是基于启动子部位单核苷酸的分布不均一性,方法2是基于启动子部位二核苷酸的分布不均一性。分别用这两种方法推测了质粒pBR322DNA上启动子的位置,从而验证了化学实验的结果。     

Generalized transduction in Rhizobium meliloti.

Generalized transduction of Rhizobium meliloti 1021 was carried out by bacteriophage N3. Genetic markers on the chromosome and the pSym megaplasmid were transduced, along with markers on several IncP plasmids. Cotransduction between transposon Tn5 insertions and integrated recombinant plasmid markers permitted correlation of cotransductional frequencies and known physical distances. Bacteriophage N3 was capable of infecting several commonly used strains of R. meliloti.     

Inhibition of the DNA catenation activity of type II topoisomerase by VP16-213 and VM26

Studies suggest that the anticancer drugs VP16-213 and VM26 produce cytotoxicity by inducing protein-associated DNA breakage in vivo through interaction with a yet unknown nuclear component. The effects of these drugs and their congeners on topoisomerase activities was investigated. VP16-213, VM26, and congeners active toward inducing DNA breaks also inhibited the catenation activity of eukaryote type II topoisomerase in vitro at very low drug concentrations. A structure-activity relationship was obtained for inhibition of catenation that parallels in vivo DNA breakage and cytotoxic activities. Type I topoisomerase activity was totally unaffected by these drugs.     

一次密度梯度超速离心分离人血清四种主要脂蛋白的某些理化性质的研究

 本文对一次密度梯度超速离心获得的四种脂蛋白(VLDL、LDL、HDL_2、HDL_3)进行了理化性质的研究。超速离心分析LDL、HDL_2,HDL_3均呈现一个单一尖锐的上浮峰,上浮速率分别为S_1 6.9和F~0_(1.21) 5.7及2.6。等电点聚焦电泳显示,VLDL主要含载脂蛋白C族,E族和少量A-I,B。HDL_2、HDL_3二者载脂蛋白的种类很相似,但量上略有差异,均以载脂蛋白A-Ⅰ,A-Ⅱ为主,Apoc’s,E次之。VLDL、LDL、HDL_2和HDL_3的化学组分分析与文献报道相似。 作者用本法初步分析了不同性别的各脂蛋白分布图,获得有意义的结果。     

饲料硒和维生素E对大鼠机体抗氧化能力的影响

 用克山病病区粮配成基础低硒饲料,补充硒和/或维生素E组成四种不同水平的饲料,饲喂雄性断乳大鼠,观察其对机体抗氧化能力的影响。评价指标是用抗坏血酸诱发的红细胞溶血率、被O~-_2(超氧阴离子)氧化的血红蛋白量和组织中的TBA值。动物饲养13周后,自尾静脉取血,测定溶血率和血红蛋白被氧化的百分率,和全血SeGSHPx(含硒谷胱甘肽过氧化物酶)活力。15周后将动物断头杀死,立即取出心脏和肝脏测定SeGSHPx活力和TBA值。结果表明在克山病病区粮的饲料中补充硒或维生素E,或者二者同时补充均明显提高组织中的SeGSHPx活力和降低组织中的TBA值。不论在硒缺乏时或硒充足时,饲料中补充维生素E显著降低抗坏血酸诱发的红细胞溶血率,对O~-_2氧化血红蛋白无保护作用。在维生素E缺乏时,仅补充硒对溶血无作用。不论饲料中维生素E缺乏或者充足,补充硒对O~-_1氧化血红蛋白均有显著保护作用。     

Brain temperature measurements in rats: a comparison of microwave and ambient temperature exposures

In an effort to understand microwave heating better, regional brain and core temperatures of rats exposed to microwave radiation (2450 MHz) or elevated air temperatures were measured in two studies. In general, we have found no substantial evidence for temperature differentials, or "hot spots," in the brain of these animals. In the first study, after a 30-min exposure, no temperature differences between brain regions either after microwave or ambient air exposure were found. However, a highly significant correlation between brain and core temperatures was found and this correlation was the same for both microwave and ambient air heating. In the second study, time-temperature profiles were measured in rats exposed to either 30 mW/cm2 or 36.2 degrees C. In this study, the 30-min exposure period was divided into seven intervals and the change in temperature during each period was analyzed. Only the cortex showed significantly different heating rates between the air heating and microwave heating; however, this difference disappeared after the initial 5 min of exposure.