Role of catalase and hydroxyl radicals in the oxidation of methanol by rat liver microsomes

In view of the presence of adventitious catalase in isolated microsomes, and the requirement for H2O2, it has been suggested that NADPH-dependent oxidation of methanol by rat liver microsomes was mediated exclusively by the peroxidatic activity of catalase. However, H2O2 may also serve as a precursor of the hydroxyl radical, and methanol reacts with hydroxyl radicals to produce formaldehyde. Inhibition of H2O2 production should therefore decrease methanol oxidation by either a hydroxyl radical-dependent pathway or a catalase-dependent pathway. To attempt to clarify some of the controversies concerning the roles of H2O2 and catalase in the microsomal pathway of oxidation of short chain alcohols, studies were carried out to determine the nature of the pathway responsible for methanol oxidation by isolated microsomes. In the absence of the catalase inhibitor azide, methanol may be oxidized primarily by the peroxidatic activity of catalase since there was little effect on methanol oxidation by competing hydroxyl radical scavengers. Azide, which inhibited catalase activity greater than 95%, inhibited NADPH-dependent oxidation of methanol by 30-50%. The azide-insensitive (catalase-independent) pathway of methanol oxidation was inhibited by scavengers of hydroxyl radicals. The inhibition of the scavengers reflected the rate constant for interaction with hydroxyl radicals and was greater at lower concentrations of methanol than at higher concentrations, suggesting competition between the scavengers and methanol. The addition of H2O2 stimulated the oxidation of methanol in the presence of azide; H2O2 may serve as a precursor of the hydroxyl radical. Iron-EDTA, which is known to increase hydroxyl radical production, stimulated the oxidation of methanol in the absence and presence of azide. The stimulation by iron-EDTA was blocked by the competing hydroxyl radical scavengers even in the absence of azide, suggesting that the added iron-EDTA favorably with microsomal catalase for H2O2 to produce hydroxyl radicals (or a species with the oxidizing power of the hydroxyl radical). These results suggest that in microsomes, depending on the absence or presence of azide, methanol may be oxidized by two primary pathways, one involving the peroxidatic activity of catalase, and the other in which hydroxyl radicals, generated from microsomal electron transfer, play a role. In view of the crucial role played by H2O2 in both pathways, inhibition of H2O2 formation should not be interpreted solely as evidence for a role for catalase in the microsomal oxidation of alcohols.     

A study of erythrocyte fatty acids, adenosinetriphosphatase and acetylcholinesterase in cystic fibrosis.

1. The proportions of both saturated and polyunsaturated fatty acids were measured in the erythrocytes in Cystic Fibrosis (CF) patients along with two membrane bound enzymes ATPase and acetylcholinesterase. Linoleic acid was found to be significantly decreased and arachidonic acid increased in CF patients. The proportion of saturated fatty acids were not significantly different from the controls. Only adenosinetriphosphatase activity was found to be reduced and not acetylcholinesterase in CF patients.     

Changes in the respiratory activity of different tissues of rat and mouse embryos during development

Summary Whole naked mouse and rat embryos have identical respiratory rates during organogenesis when judging from the dry weight basis. This way of plotting enables to distinguish between a developmental retardation for hours and days and a significant developmental reduction on the basis of the two parameters. This allows to draw conclusions in experimental tetratology at this very early state which cannot be drawn from an age-dependent plot.The respiratory capacity of mouse embryos on day 9 and rat embryos on day 10+16 h is significantly lower than on the following day. Since whole rat embryos exceed the limiting thickness on day 13 of gestation, it is suggested to perform measurements of the on day 14 and 15 with isolated organs (hearts and livers) and from day 16 to term with liver slices of rat embryos applying the Warburg method. The of isolated hearts and livers on day 14 to 16 and of liver slices from day 16 to term is at least 10, which is comparable to adult liver slices.The succinate-dependent respiratory activity can be measured with these embryonic tissue preparations on day 14 and later on, it increases considerably on day 19 in liver slices and reaches the values of adult liver tissue at term. This developmental change was confirmed by measurements in the presence of the uncoupler 2,4-dinitrophenol and the inhibitor rotenone.This work was supported by grants from the Deutsche Forschungsgemeinschaft given to the Sonderforschungsbereich 29, Embryonale Entwicklung und Differenzierung (Embryonal-Pharmakologie).     

肾脏疾病的生化学诊断及进展

目的:分析肾脏疾病的生化诊断及进展.方法:全自动生化分析仪(美国Bckman-CX4),竞争ELISA法测透明质酸(HA).结果:肾脏疾病的诊断和治疗效果观察可使用组合指标检测.结论:血尿素氮(BUN),血肌酐(Cr),血透明质酸(HA)可作肾衰、肾移植后的检测组合;尿中乙酰β氨基葡萄糖苷酶(NAG)及尿微量白蛋白(malb)的检测组合可反映早期肾损伤.     

多媒体技术在生物化学教学中的运用

多媒体教学方法的设计，包括教学目标的分析、课件脚本的编写、课件制作和课件实施等方面。计算机多媒体教学的开展可使生物化学课更加形象生动。     

医学生化教学中创新素质培养的探讨与实践

文章阐述了培养医学生创新素质的重要性，就生物化学教学中如何培养医学生的创新素质进行了探讨。     

综合运用多种教学方法提高生物化学教学效果

生物化学是一门重要的医学基础课,由于内容繁多,理论抽象,代谢反应复杂,学生难以掌握。文章介绍了在生物化学教学过程中,根据教材内容和学生实际水平综合运用多种教学方法激发学生的学习兴趣,活跃课堂气氛,提高生化教学质量。     

Inhibition of calcium influx in rabbit aorta by nicardipine hydrochloride (YC-93)

The Ca²⁺ antagonistic effects of a potent vasodilator, nicardipine hydrochloride [2-(N-benzyl-N-methylamino)ethyl methyl 2,6-dimethyl-4-(m-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate hydrochloride], were investigated. Both nicardipine and verapamil, neither of which exhibited a significant effect on cellular ⁴⁵Ca²⁺ uptake by the rabbit aorta in normal buffer containing 2.68 mM KCl as measured by the “lanthanum method”, inhibited the enhancement of ⁴⁵Ca²⁺ uptake induced by equimolar replacement of 120 mM NaCl by KCl. Nicardipine with an ic₅₀ (the concentration required for 50 per cent inhibition) of 10^?9 M was sixty-eight times more potent than verapamil in the inhibition of KCl-induced ⁴⁵Ca²⁺ uptake. Nicardipine also repressed KCl-induced contraction of the aorta and its ic₅₀ was about 2 × 10^?9M, eighty-five times smaller than that of verapamil. These comparative studies on the relation between cellular ⁴⁵Ca²⁺ uptake and KCl-induced contraction of the rabbit aorta suggest that nicardipine causes relaxation of smooth muscle mainly by interfering with Ca²⁺ influx.     

噬血细胞综合征患儿生化及免疫指标分析

目的 探讨噬血细胞综合征生化免疫指标的改变及临床意义.方法 分别应用免疫荧光法和酶联免疫法,对噬血细胞综合征患儿及同期普通呼吸道感染患儿静脉血进行生化及免疫指标检测.结果 实验组患儿转氨酶、乳酸脱氢酶、胆红素、甘油三酯、血清铁蛋白、β2微球蛋白明显增高,纤维蛋白原、白蛋白明显降低等较对照组差异有统计学意义(P<0.05).结论 噬血细胞综合征患儿部分生化及免疫指标有明显变化,对明确诊断及进一步采取针对性治疗有很大意义.