The effect of hypoxia on hepatic cytochromes and heme turnover in rats in vivo

Summary We evaluated the effect of hypoxia (7% v/v) on hepatic heme turnover in vivo and microsomal heme protein content in male Sprague-Dawley rats. Hepatic heme protein turnover, measured as¹⁴CO-production during continuous infusion of 5-¹⁴C-aminolevulinic acid, a precursor of nonerythrogenic heme, was decreased 60% during hypoxia and returned to control levels promptly after reoxygenation. Hepatic cytochrome P-450 content was decreased in hypoxic and 24-h reoxygenated animals. We conclude that normobaric hypoxia decreases hepatic cytochrome P-450 which could contribute to decreased drug metabolism in hypoxia. This decrease is probably due to heme oxygenase-independent breakdown of hepatic heme.     

Mo（Ⅵ）还原产物催化NO2^—的极谱研究

Mo(Ⅵ)在pH 2～3,0.1mol/L KCl溶液中能被还原,其电位为-0.45V(对Ag/AgCl)。还原产物能沉积在滴汞上,它能催化N0_2~-的还原。NO_2~-的还原电位从-0.95V(对Ag/AgCl)正移到-0.81V。NO_2~-还原峰电流的大小正比于它的浓度,NO_3~-在很宽的浓度范围内不干扰。本文对NO_2~-和NO_3~-在Mo存在时的极谱行为作了探讨。     

离子选择电极应用研究——乙醇-水混合溶剂中硝酸根对铅离子的配合平衡

本文用铅离子选择电极测定了乙醇-水混合溶剂中Pb-NO_3配合物的稳定常数.实验证明,铅和硝酸根可以形成PbNO_3~+和Pb(NO_3)_2两种配合物。所计算的热力学稳定常数表明溶剂中乙醇含量直到76%(w/w)lgβ_i°-1/ε都呈直线关系.     

Development and hormonal control of thioredoxin and the thioredoxin-reductase system in the rat liver during the perinatal period

Summary The development and hormonal regulation of thioredoxin and of the thioredoxin-reductase system were investigated during the perinatal period in rat liver. An immunological procedure was developed in order to quantify thioredoxin in fetal and neonatal hepatocytes. Both immunoreactive thioredoxin and thioredoxin-reductase activity appeared on day 16.5 of pregnancy. The level of immunoreactive thioredoxin increased during the late fetal period, and its level was the same 24 h after birth. Moreover, its development was not subjected to hormonal regulation by corticosteroids and glucagon. In contrast, thioredoxin-reductase activity increased 3 times during the late fetal period and presented a marked increase 24 h after birth. In the absence of glucocorticoids there was no increase in the level of thioredoxin reductase, while administration of hydrocortisone acetate and glucagon to fetuses prematurely evoked its activity. This study suggests that if thioredoxin acts physiologically, this activity is related to the state of reduction of the molecule rather than to the total concentration in the liver.     

Site-directed mutagenesis reveals new and essential elements for iron-coordination of the sulfur oxygenase reductase from the acidothermophilic Acidianus tengchongensis

Previous study on refolding of sulfur oxygenase reductase (SOR) inclusion bodies from recombinant Escherichia coli showed that iron was critical to the activity of the SOR from Acidianus ambivalens. In this study, enzymatic assays showed that 2,2′-Dipyridyl, Tiron and 8-hydroxyquinoline, which are specific for chelating ferrous or ferric ions, strongly inhibited the activity of SOR from A. tengchongensis, suggesting that iron atom is essential for SOR activity. Alignment of several functionally identified S...     

3-酮基嘌呤还原酶(TSC10)表达载体的构建及其在毕赤酵母中的表达

目的：Tsc10基因所编码的3-酮基嘌呤还原酶是酵母中神经酰胺合成的重要因子,本文研究从酵母中提取神经酰胺经济、便捷、高效的方法。方法：1.利用构建含有tsc10基因的毕赤酵母GS115表达载体pPIC3.5K-tsc10。2.电转化法将该表达质粒转化到GS115感受态细胞中。3.用G418筛选以及PCR鉴定。4.使用qRT-PCR和SDS-PAGE进行检测。结果：经过G418筛选以及PCR鉴定后确定获得了包含tsc10基因的毕赤酵母转化子,经过qRT-PCR和SDS-PAGE进行检测后发现tsc10基因在20个阳性菌株中均可以稳定、高效表达。结论：本方法成功构建了3-酮基嘌呤还原酶高表达的毕赤酵母菌株,并为后续获得高收率神经酰胺奠定了基础。     

5—苯亚甲基—3—羧甲基若丹宁的合成

本文报导一种新型抗糖尿病药物—5-苯亚甲基—3-羧甲基若丹宁的合成方法。本法具有原料易得,操作简单,产率高,易纯化等优点。经熔点,IR谱、~1HNMR谐和元素分析,证明其结构是正确的。并经初步试验,有明显的降血糖作用。     

Biochemical approaches to the study of plant-fungal interactions in arbuscular mycorrhiza

This communication compares some biochemical methods for quantifying colonization by arbuscular mycorrhizal (AM) fungi. The degree of mycorrhizal colonization can conveniently be measured by determining fungal specific sterols. AM-colonized plants show a specific synthesis of 24-methylene cholesterol and an enhanced level of campesterol (=24-methyl cholesterol). A gene probe for nitrate reductase, the key enzyme for nitrogen assimilation, has been developed, which allows the monitoring of the distribution of this enzyme in fungi. Among the phytohormones tested, only abscisic acid (ABA) is found at a considerably higher level in AM-colonized plants than in controls. The concentration of ABA is about twenty times higher in spores and hyphae of the AM fungusGlomus than in maize roots. Other phytohormones (auxins, cytokinins) do not show such alterations after mycorrhizal colonization. The roots of gramineous plants become yellow as a result of mycorrhizal colonization. The yellow pigment(s) formed is (are) deposited in larger quantities in the vacuole(s) of the root parenchyma and endodermis cells during the development of the gramineous plants. A substance isolated from such roots has now been identified as a C-14 carotenoid with two carboxylic groups, and named mycorradicin.