血清亚硝酸盐的快速测定

目的：建立一种无需去蛋白的血清亚硝酸盐的快速测定方法。方法：加入蛋白活化剂后，直接用Ｇｒｉｅｓ试剂显色分光光度测定。结果：方法的检测下限为０．２μｍｏｌ／Ｌ，相对标准差为５．１３％～８．８６％，回收率为９４．５％～９９．８％（平均为９７．８％）。血清ＮＯ－２浓度为１４．３８±０．２５μｍｏｌ／Ｌ时，批内变异系数为１．７５％，ＮＯ－２浓度为５．６９±０．２５μｍｏｌ／Ｌ时，批间变异系数为４．４６％。测定５５例正常人血清，得到血清中ＮＯ－２浓度的平均值分别为５．３６±２．１６ｕｍｏｌ／Ｌ；对糖尿病病人血清测定结果表明，亚硝酸盐浓度明显高于正常人。与去蛋白的Ｇｒｉｅｓ试剂分光光度法比较，结果无统计学差异。结论：用蛋白活化剂替代蛋白沉淀剂，减少操作步骤和干扰，测定准确、简便、快速，适用于血清中ＮＯ－２的测定。     

Determination of N-nitrosodiethanolamine in urine by gas chromatography thermal energy analysis: application in workers exposed to aqueous metalworking fluids

 Objective: The aim of this study was to describe a detailed and validated methodology designed for the analysis of carcinogenic N-nitrosodiethanolamine (NDELA) down to sub-μg/l levels in urine and its application to a number of workers exposed to NDELA-contaminated aqueous metalworking fluids (MWF). Methods: Following a work-up procedure based on solid-phase extraction of NDELA, the urinary extracts were analysed without derivatization by gas chromatography on a polar wide-bore column with chemiluminescent detection using a thermal energy analyser (TEA). N-Nitroso-(2-hydroxypropyl)amine was used as an internal standard. The method was applied to 12 workers using “nitrite-free” or “nitrite-formulated” MWF and to 15 unexposed subjects. The NDELA content of the MWF was also determined using a similar, but simpler method able to easily quantify NDELA down to at least 0.1 mg/l. Results: Contamination by NDELA traces of some chemicals used for the sample preparation, particularly ethyl formate, must be carefully checked since it can give rise to false-positive results of up to 1 or 2 μg/l. The response was linear in the range of 0–500 μg/l. Between 0.5 and 10 μg/l, the recovery rate was close to 95%, while repeatability ranged from 12.5 to 6.4% (n = 5). The detection limit was 0.3 μg/l (Signal/noise = 3). No detectable NDELA could be observed in the control workers. There was no significant increase in NDELA levels at the end of shift spot samples from an exposed worker over 1 week. Higher NDELA concentrations were found in two workers (4.3 and 10.7 μg/l) exposed to “nitrite-formulated” fluids (contaminated with 65 and 18 mg NDELA per l, respectively) than in nine workers (range, 0.4–1.3 μg/l exposed to “nitrite-free” fluids with lower levels of NDELA (range, 0.5–6.6 mg/l). Conclusion: The detailed methodology described in this work and applied to a limited industrial situation was found to be suitable for monitoring NDELA in the urine of workers exposed to aqueous MWF. A much larger screening has been undertaken with the aim of obtaining better information on the real exposure of workers sometimes exposed to “nitrite-formulated” fluids that are still used. Received: 8 December 1998 / Accepted: 3 April 1999     

New method for quantitative measurement of N-nitrosodimethylamine formation in the whole mouse

A simple method for the quantitative estimation of the formation of N-nitrosodimethylamine (NDMA) in mice has been developed. Mice were frozen in liquid nitrogen and homogenized. NDMA was then extracted and analyzed by a gas chromatograph equipped with a thermal energy analyzer. In normal mice NDMA (100 nmole) administered orally was rapidly metabolized and recovery of NDMA was about 10% after 60 min. However, when pyrazole (300 mg/kg) was injected i.p. to mice 60 min before the administration of NDMA, more than 80% of the administered NDMA could be recovered within 60 min. This result suggested that in pyrazole pretreated mice the accurate amount of NDMA formed could be estimated. Therefore the NDMA formation was measured in the pyrazole pretreated mice. When 0.25 mole of aminopyrine and from 0.25 to 2.0 umole of sodium nitrite were simultaneously administered orally, the amount of the NDMA formation in 20 min was found to be from 8.2 to 60.3 nmole. These values are equal to about from 30 to 200 g/kg of body weight which are nearly daily doses expected to cause the carcinogenic effect on mice or rats. This method of measuring NDMA in pyrazole pretreated mice appears to be useful for investigating the in vivo formation of NDMA quantitatively.     

鼻咽癌患者唾液中亚硝酸根含量的研究

目的研究鼻咽癌患者唾液中亚硝酸根含量。方法选择成人鼻咽癌患者26例为实验组,健康人27例为对照组,测定实验组和对照组所有人员唾液中亚硝酸根的含量。结果对照组唾液中亚硝酸根含量为(37.16±2.55)μmol/L,男女间无显著性差异。实验组唾液中亚硝酸根含量为(61.36±7.26)μmol/L,明显高于对照组。结论鼻咽癌患者唾液中亚硝酸根含量显著高于健康人。     

A rapid method for simultaneous determination of nitrate,nitrite and thiocyanate in milk by CZE-UV using quaternary ammonium chitosan as electroosmotic flow inverter

This paper proposes a rapid method for the simultaneous determination of nitrate, nitrite and thiocyanate in different milk samples (cow, goat and soy) using capillary zone electrophoresis. The separations were conducted in a fused silica capillary dynamically coated with quaternary ammonium chitosan, with a total length of 48.5 cm (40 cm effective x 75 μm internal diameter) and direct detection in the UV region at 210 nm. The background electrolyte (BGE) was composed of 30 mmol L⁻¹ of aminocaproic acid and 24 mmol L¹ of perchloric acid (pH 3.85).A typical anodic electroosmotic flow of -31 × 10^-9 m² V⁻¹ s⁻¹ was observed at the pH of the separations. Bromate was used as the internal standard. The samples were injected by hydrodynamic pressure (50 mbar, 40 s) and the separation voltage was −30 kV. The proposed method was validated and presented good linearity (R²> 0.99) in the linear range of 0.1–4.0 mg L⁻¹. The ranges of the limit of detection (LOD) and limit of quantification (LOQ) were 0.03-0.04 and 0.05–0.07 mg L⁻¹, respectively. The intra-day and inter-day precision values were better than 4.2 and 8.7 %, respectively. Recovery values ranged from 85 to 104% for the different samples of milk. The proposed method was applied in 12 commercial samples with run times of less than 2 min. The good analytical performance indicates that the method proposed is a promising alternative for the determination of nitrate, thiocyanate and nitrite in milk samples.     

细菌硝酸盐还原中的关键酶影响细菌耐药性的研究进展

硝酸盐的还原是细菌氮代谢中最重要的生化反应之一.随着对细菌耐药机制的不断探索,氮代谢过程尤其是某些代谢酶对细菌耐药性的影响得以揭示.作为硝酸盐还原过程中的关键代谢酶,硝酸还原酶(nitrate reductase,NR)与亚硝酸还原酶(nitrite reductase,NiR)不仅催化着细菌体内硝酸盐的一系列还原反应,还从多方面影响了细菌的耐药性.本文综述了NR/NiR与细菌耐药性之间关系的最新研究进展,以期为新药物靶标的发现及提出新治疗措施提供依据.     

Nitrite-Induced Cross-Linking Alters Remodeling and Mechanical Properties of Collagenous Engineered Tissues

Cumulative damage to long-lived connective tissue proteins play a key role in the development of age-related human diseases such as cardiovascular stiffening and age-related macular degeneration. The processes that result in the accumulation of increasingly insoluble, undigestible damaged collagen are only partially known. Nonenzymatic glycation (NEG) is one such process and has been linked to the development of diabetic-related complications and aging. An additional novel mechanism particularly relevant to smoking- and inflammation-related diseases involves the nonenzymatic nitrite (NEN) modification of connective tissue proteins. The present study was undertaken to examine the effects of NEN of fibrillar type I collagen on cell-mediated remodeling and mechanical properties of collagenous tissues. Using a modification of an in vitro fibroblast-populated collagen gel model system developed in our laboratory, we tested two hypotheses: NEN reduces the ability of primary adult cardiac fibroblasts to remodel type I collagen gels; NEN reduces the deformability of type I collagen gels subjected to mechanical testing. The results show that NEN impairs both cell-mediated remodeling and mechanical deformability in collagenous engineered tissues. Furthermore, these mechanical changes correlate with the degree of cross-linking as determined by SDS-PAGE. Thus, we concluded that NEN reactions may contribute to alterations in the biomechanical properties of collagen-containing tissues consistent with the age-related functional decline observed in human disease.     

Histopathologic,biochemical and genotoxic investigations on chronic sodium nitrite toxicity in mice

The aim of this study was to investigate the effects of long term Sodium nitrite (NaNO₂) consumption. Swiss albino mice were given NaNO₂ (0, 10 and 20 mg/kg/day) as mixed in feed for 8 months. At the end of treatments, animals were sacrificed and selected organs were processed for histopathologic, imunohistochemical, biochemical and genotoxic investigations. Mild to moderate degenerative changes were observed in liver, kidney, intestine, lung and spleen of NaNO₂-given mice. Inducible nitric oxide synthase and nitrotyrosine activities increased in liver and kidney of NaNO₂-given mice. Proliferating cell nuclear antigen activity increased in liver. Apoptotic cell death was observed in livers of the treatment groups. Liver malondialdehyde level was higher in the treatment groups while no change was seen in kidney. Nitric oxide levels in both liver and kidney of the treatment groups were lower than those of the control group. In genotoxic investigations, the number of chromosome and chromatid breaks, chromatid association, and polyploidy increased while mitotic index decreased in NaNO₂-given mice. The results showed that NaNO₂ would cause histopathologic changes, nitrosative tissue damage, and lipid peroxidation in liver and kidney, as well as induce chromosomal aberrations even if it was given at low levels for long time.