蔬菜中的硝酸盐、亚硝酸盐的气相色谱法测定

目的：利用选择性强的电子捕获检测器测定蔬菜中的硝酸盐和亚硝酸盐。方法：样品中硝酸根用硫酸作催化剂,温度控制在90℃以下时可与苯发生反应生成硝基苯,萃取,然后利用选择性强的电子捕获检测器检测。结果：样品加标回收率硝酸盐的回收率在79.72%～101.79%之间,亚硝酸盐的回收率在88.06%～105.81%;变异系数3.22～5.93,硝酸盐最低检出浓度为0.75 mg/kg）;亚硝酸盐的最低检测浓度为0.609 mg/kg。结论：该法的样品处理与经典的国标法比较取样量少、简单快速,避免了其他离子的干扰,提高了灵敏度和准确度,操作简便易性行。一机多用。     

离子色谱法测定瓶(桶)装水中痕量亚硝酸盐

[目的]采用离子色谱法测定水中痕量亚硝酸盐的含量.[方法]色谱柱为DIONEX Ionpac AS19-2mm, KOH为淋洗液,梯度淋洗,流速为0.3ml/min,抑制电流:34mA,电导检测.[结果]瓶(桶)装饮用水中的痕量亚硝酸盐测定,最低检测浓度(定量下限)为1.00μg/L,回收率在98.5%-112.0%之间.[结论]本法能满足μg/L级的定量分析要求,测定方法简便、准确、实用性强.     

新鲜果蔬保健作用的探讨

对24种新鲜水果蔬菜的主要营养成分、氧化还原特性、对亚硝酸盐的消除作用及抗氧化活性的测定及统计分析结果表明,果蔬对NO_2~-的消除率与其抗氧化活性之间存在显著的相关(P<0.05)。NO_2~-消除量和自由基综合消除活性均与果蔬的氧化还原当量之间存在极显著的回归相关(P<0.01),与糖、蛋白质含量间有显著的回归关系,而与果蔬的电动势值、VC及B族维生素含量等无相关性(P>0.05)。说明新鲜果蔬所含营养成分的综合还原特性是其具有防衰保健作用的重要原因之一。     

大蒜与胃癌Ⅱ——大蒜对胃液硝酸盐还原菌生长及产生亚硝酸盐的抑制作用

本文报导常吃大蒜的胃癌低发区苍山县居民胃液中活菌总数、硝酸盐还原菌检出率和胃液pH值均显著低于少吃大蒜的胃癌高发区栖霞县。体外实验进一步证实大蒜匀浆、乙基硫代磺酸乙酯和二烯丙三硫对从受检人胃液中分离出的硝酸盐还原菌的生长及产生亚硝酸盐均有明显的抑制作用。由此可提示前文报导常吃大蒜居民胃液中亚硝酸盐含量显著低于少食大蒜者,其原因可能是由于大蒜对胃液中细菌,特别是对硝酸盐还原菌的抑杀作用。     

胃癌危险性不同人群膳食硝酸盐、亚硝酸盐及维生素C摄入量

本文研究福建省长乐县胃癌危险性不同的人群膳食硝酸盐(NO_3~-)、亚硝酸盐(NO_2~-)及维生素C摄入量。胃癌死亡率较高的漳港乡居民NO_3~-摄入量(132.75mg/日)明显高于死亡率居中的首占乡(84.65mg/日)(P<0.05),但与死亡率较低的梅花乡(113.12mg/日)无显著性差异。NO_2~-摄入量漳港乡显著高于首占乡和梅花乡(3.36mg/日对0.21和0.73mg/日)(P<0.01)。首占乡居民维生素C摄入量(56.13mg/日)明显低于漳港乡(123.09mg/日)和梅花乡(105.90mg/日)(P<0.01)。维生素C摄入量与NO_2~-摄入量的摩尔比值三个乡分别为3.22、3.30和4.33,与胃癌死亡率呈相反平行关系。结果提示:NO_3~-和NO_2~-可能是该地区胃癌高发的因素之一。     

A short history of nitroglycerine and nitric oxide in pharmacology and physiology

1. Nitroglycerine (NG) was discovered in 1847 by Ascanio Sobrero in Turin, following work with Theophile-Jules Pelouze. Sobrero first noted the 'violent headache' produced by minute quantities of NG on the tongue. 2. Constantin Hering, in 1849, tested NG in healthy volunteers, observing that headache was caused with 'such precision'. Hering pursued NG ('glonoine') as a homeopathic remedy for headache, believing that its use fell within the doctrine of 'like cures like'. 3. Alfred Nobel joined Pelouze in 1851 and recognized the potential of NG. He began manufacturing NG in Sweden, overcoming handling problems with his patent detonator. Nobel suffered acutely from angina and was later to refuse NG as a treatment. 4. During the mid-19th century, scientists in Britain took an interest in the newly discovered amyl nitrite, recognized as a powerful vasodilator. Lauder Brunton, the father of modern pharmacology, used the compound to relieve angina in 1867, noting the pharmacological resistance to repeated doses. 5. William Murrell first used NG for angina in 1876, although NG entered the British Pharmacopoeia as a remedy for hypertension. William Martindale, the pharmaceutical chemist, prepared '...a more stable and portable preparation': 1/100th of a grain in chocolate. 6. In the early 20th century, scientists worked on in vitro actions of nitrate-containing compounds although little progress was made towards understanding the cellular mode of action. 7. The NG industry flourished from 1900, exposing workers to high levels of organic nitrites; the phenomena of nitrate tolerance was recognized by the onset of 'Monday disease' and of nitrate-withdrawal/overcompensation by 'Sunday Heart Attacks'. 8. Ferid Murad discovered the release of nitric oxide (NO) from NG and its action on vascular smooth muscle (in 1977). Robert Furchgott and John Zawadski recognized the importance of the endothelium in acetylcholine-induced vasorelaxation (in 1980) and Louis Ignarro and Salvador Moncada identified endothelial-derived relaxing factor (EDRF) as NO (in 1987). 9. Glycerol trinitrate remains the treatment of choice for relieving angina; other organic esters and inorganic nitrates are also used, but the rapid action of NG and its established efficacy make it the mainstay of angina pectoris relief.     

瓜蒌皮抗缺氧作用的研究

实验结果显示，瓜蒌皮提取液（ＥＰＴ）腹腔注射４０ ｇ·ｋｇ－１能明显延长常压缺氧、组织缺氧、特异性心肌缺氧小鼠的存活时间，延长率分别为 １４５％， ２．７９％， １１０．７％，使减压缺氧小鼠的存活率达８５％．表明瓜蒌皮确能增强整体动物的抗缺氧能力．     

Effects of 4-dimethylaminophenol,Co2EDTA,or NaNO2 on cerebral blood flow and sinus blood homeostasis of dogs in connection with acute cyanide poisoning

The effects of the cyanide antidotes DMAP, Co₂EDTA, and NaNO₂ on cerebral blood flow (CBF) and cerebral blood gases were investigated in connection with acute poisoning of dogs by cyanide. The substances were injected intravenously. Local CBF as measured with thermocouples in the cingulum increased by 100–200% after a non-lethal dose of KCN (1 mg/kg) and by 50% after injection of NaNO₂ (15 mg/kg), that oxidized some 20% of the total hemoglobin to ferrihemoglobin. Co₂EDTA (10 mg/kg) induced a decrease in local CBF of 30% and in brain temperature of 0.5°C. The temperature diminished also after poisoning by KCN, but it rose by 0.15°C after the administration of NaNO₂. Local CBF and sinus sagittalis blood flow increased by 60–160% for about 15 min, and the brain temperature decreased by 0.4–0.5°C when DMAP (3.25 mg/kg) or Co₂EDTA (15 mg/kg) was injected 1 min after poisoning by cyanide (4 mg/kg), a dose that always caused respiratory arrest. Immediately after injection of DMAP the brain temperature rose transiently by 0.1–0.2°C. Co₂EDTA did not exert such an effect. In the sinus sagittalis blood of artificially ventilated animals pCO₂ decreased rapidly by 10–20 mmHg after poisoning and approached the initial level after treatment with DMAP or Co₂EDTA. The highest value of pO₂ was about 80 mmHg and 50 mmHg after injection of DMAP and Co₂EDTA, respectively; thereafter pO₂ declined to 20 mmHg or 40 mmHg at 20 min. The lactate concentration increased by 60–70% without tendency to return to normal.     

The action of different coronary active drugs on intraand extravascular components of local myocardial perfusion

Summary In isolated guinea pig hearts epicardial perfusion was estimated by analysis of the transit profile of different fluorescence indicators. Several coronary dilating agents were tested with regard to their influence on local perfusion kinetics revealing distinct patterns of microcirculatory drug action.Supported by the Deutsche Forschungsgemeinschaft (SFB 68 A 18)     

The effect of quercetin on topotecan cytotoxicity in MCF-7 and MDA-MB 231 human breast cancer cells

BACKGROUND: Topotecan, which is a Camptothecin derivative, shows a large spectrum in anti-tumor activity. Topotecan exerts its cytotoxic effect on tumor cells mainly by inhibition of topoisomerase I activity resulting in double-strand DNA breaks. In our study, we investigated the combined cytotoxic action of Topotecan and Quercetin in MCF-7 and MDA-MB 231 human breast cancer cells. To examine the possible relation between the cytotoxic activity of Topotecan and oxidative stress, we measured ROS and nitrite levels in both human breast cell lines. MATERIALS AND METHODS: MCF-7 and MDA-MB 231 cells were exposed to Topotecan, Quercetin, or a combination of both agents for 24 h at 37 degrees C. The viability of the cells was measured using the colorimetric MTT (3-(4,5)-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. We determined reactive oxygen species and nitrite levels as indicators of oxidative stress in both cell lines with and without Topotecan and/or Quercetin incubations using fluorometric dichlorofluorescin diacetate (DCFH-DA) and diaminonaphtalene (DAN) assay. RESULTS: The IC(50) concentration of Topotecan was 100 ng/ml in MCF-7 cell line and 160 ng/ml in MDA-MB231 cell line. Treatment with Quercetin enhanced cytotoxicity of Topotecan as 1.4-fold in MCF-7 and 1.3-fold in MDA-MB-231 cell line. A significant increment on ROS and nitrite levels was found in MCF-7 and MDA-MB-231 cells following Topotecan incubation. CONCLUSIONS: Our results suggest that Topotecan has cytotoxic activity against both of the breast cancer cell lines in vitro. A combination with Quercetin increases efficacy of Topotecan in the treatment of breast cancers. Our results indicate that increased oxidative stress plays a role in the cytotoxic action of Topotecan.