Characterization of the Aspergillus parasiticus niaD and niiA gene cluster

 The nitrate reductase gene (niaD) and nitrite reductase gene (niiA) of Aspergillus parasiticus are clustered and are divergently transcribed from a 1.6-kb intergenic region (niaD-niiA). The deduced aminoacid sequence of the A. parasiticus nitrate reductase demonstrated a high degree of homology to those of other Aspergillus species, as well as to Leptosphaeria maculans, Fusarium oxysporum, Gibberella fujikuroi and Neurospora crassa, particularly in the cofactor-binding domains for molybdenum, heme and FAD. A portion of the deduced nitrite reductase sequence was homologous to those of A. nidulans and N. crassa. The nucleotide sequences in niaD-niiA of A. parasiticus and of A. oryzae were 95% identical, indicating that these two species are closely related. Several GATA motifs, the recognition sites for the N. crassa positive-acting global regulatory protein NIT2 in nitrogen metabolism, were found in A. parasiticus niaD-niiA. Two copies of the palindrome TCCGCGGA and other partial palindromic sequences similar to the target sites for the pathway specific regulatory proteins, N. crassa NIT4 and A. nidulans NirA, in nitrate assimilation, were also identified. A recombinant protein containing the A. nidulans AreA (the NIT2 equivalent) zinc finger and an adjacent basic region was able to bind to segments of niaD-niiA encompassing the GATA motifs. These results suggest that the catalytic and regulatory mechanisms of nitrate assimilation are well conserved in Aspergillus. Received: 17 November 1995/16 January 1996     

Cured meat consumption and hypertension: an analysis from NHANES III (1988-94)

The in vitro reactions of nitrite (cured meat preservative) with collagen/elastin produce effects that could cause arterial stiffening, an early marker of essential hypertension. Because dietary cured meat ingestion can be a significant source of human nitrite exposure, the epidemiological association between cured meat consumption and hypertension was studied. We performed a cross-sectional analysis of the third National Health and Nutrition Examination Survey (1988-1994). Hypertension was defined using self-reported history, medication use, and measured blood pressures. A significant age interaction between hypertension and cured meat consumption was noted, and the age group 17 to 40 years was identified as the susceptible group. Cured meat consumption was an independent risk factor in a multivariate regression model that included a large number of covariates. This is the first epidemiological evidence that links cured meat consumption with hypertension. Further work with longitudinal data sets is necessary before recommendations can be considered regarding the proposed hypothesis.     

存放时间及存放温度对蔬菜亚硝酸盐含量的影响

目的研究不同存放时间及存放温度对生、熟蔬菜亚硝酸盐含量的影响,为减少亚硝酸盐危害提供依据。方法用格里斯试剂比色法测定生、熟蔬菜室温（25～29℃）和冰箱（4℃）存放温度下,随存放时间亚硝酸盐含量的变化。结果生大白菜存放时间超过24 h,亚硝酸盐含量显著性升高（P〈0.05）;冰箱存放比室温存放延缓亚硝酸盐升高（P〈0.05）;生空心菜存放24 h亚硝酸盐含量显著性下降（P〈0.05）,超过24 h逐渐升高;熟大白菜、熟包菜隔顿（6 h）亚硝酸盐含量下降,隔夜（12 h）亚硝酸盐含量升高。结论生蔬菜存放时间不超过24 h,熟蔬菜即熟即食有助于减轻亚硝酸盐危害。     

一起亚硝酸盐食物中毒的调查与思考

目的调查此次食物中毒的病因,防止类似食物中毒的发生。方法采用流行病学调查和对剩余食物及相关食物与添加剂进行实验室检验。结果吃剩的鸡肉(骨)和相关食物五香鸡腿、盐焗鸡腿的亚硝酸盐含量分别超过国家标准GB2760-1996的限量标准的8.3、51.8和30.1倍。结论食用亚硝酸盐含量超标的食物可引起食物中毒,要加强对肉制品加工业特别是熟肉制品加工摊店的卫生监督管理和食品从业人员的职业培训,严格食品添加剂的管理,防止亚硝酸盐食物中毒的再次发生。     

高效液相色谱法测定硝酸咪康唑栓的含量

目的建立测定硝酸咪康唑栓含量的高效液相色谱(HPLC)法。方法色谱柱为C18柱(150mm×4.6mm,5μm),流动相为甲醇-乙腈-0.5%乙酸铵(42.5∶42.5∶5),检测波长为230nm。结果硝酸咪康唑质量浓度在0.02～0.2mg/mL范围内与峰面积呈良好的线性关系(r=0.9999),平均回收率为101.3%,RSD为1.80%(n=9)。结论HPLC法准确、重现性好、简单,适用于硝酸咪康唑栓的含量测定。     

反相停留流动注射-催化光度法测定自来水及食品中微量亚硝酸盐含量

目的：测定自来水及食品中微量NO2ˉ的含量。方法：利用硫酸介质中NO2ˉ对溴酸钾氧化结晶紫的催化作用，建立室温下反相停留流动注射催化动力学光度法。结果：测得自来水中的N02含量为0．013μ／ml，相对标准偏差为3．8％（n=15），加标平均回收率为99．7％；测得火腿肠和榨菜中的NO2ˉ含量分别为7．5mg／kg和5．2mg／kg，测定值与产品的标称值基本相符。实验还考察了停留时间、硫酸和溴酸钾的浓度以及流速等条件对测量的影响并进行优化。方法的检出限为0．75μg／L，在0．01-0．1μ/ml范围内呈线性关系。结论：方法准确、可靠、简便，试剂消耗量少，适用于饮用水及其它食品中微量NO2ˉ含量的测定。     

核固红共振光散射法测痕量亚硝酸根

目的:建立测定痕量亚硝酸根的新方法。方法:在盐酸介质中痕量亚硝酸根与核固红发生重氮化反应,使得核固红溶液的共振散射光强度明显下降,从而建立了共振光散射法测定痕量亚硝酸根的新方法。结果:方法的线性范围为2.0×10-8~2.8×10-7g/ml,检出限为9.34×10-9g/ml,回收率为95.5%~98.6%。结论:该方法简便快速,用于环境水样中痕量亚硝酸根的测定,结果满意。     

Leucine aminopeptidase activity in plasma of rats,after combined carboxy- and methemoglobinemia

After combined treatment of rats with 0.8 mmol NaNO₂/kg intraperitoneally and 2.4 mmol CO/kg subcutaneously the leucine aminopeptidase activity in plasma increased significantly. Doses of 0.8 mmol NaNO₂/kg or 2.4mmol CO/kg alone did not change the enzyme activity. Single injection of 9.6 mmol CO/kg also produced an increase of the leucine aminopeptidase activity in the plasma of both normal and adrenalectomized rats. The results support the assumption that the enhancement of leucine aminopeptidase activity after carbon monoxide poisoning is an oxygen deficiency effect, and not an effect which is mediated by the adrenals.The authors wish to thank Miss Dagmar Liedtke for skilful technical assistance.     

口腔扁平苔藓患者唾液中亚硝酸根的测定及其意义

目的 :探讨口腔扁平苔藓 (OLP)患者唾液中一氧化氮 (NO)水平的变化。方法 :采用示波极谱法测定了 6 0例OLP患者 (糜烂型 30例、光滑型 30例 )唾液中NO2 -浓度 ,按性别及年龄 2∶1配对 ,同期收集 30例健康志愿者唾液为对照组。并以浓度Χ唾液流量计算唾液NO2 -产出。结果 :所得数据表明 :糜烂型OLP组唾液NO2 -浓度 2 2 .6 9± 15 .0 3μmol/L ,显著高于健康对照组 (10 .74± 7.98μmol/L) (P <0 .0 5 )与光滑型OLP组 (11.5 5± 6 .5 2 μmol/L) ,P <0 .0 0 2。结论 :本研究中发现OLP患者唾液NO2 -水平上调 ,这种差异主要在于糜烂型OLP患者。推论NO可能在OLP发病及发展中起一定作用。本研究为进一步研究NO在OLP发病及发展中的作用奠定了初步基础     

The Nitrite/Elastin Reaction

Nitrite ion is a by-product of nitrogen oxides (nitric oxide and nitrogen dioxide) from cigarette smoke and is used as a preservative for curing meats. Therefore, study of the reaction of nitrite with elastin in vitro was undertaken. By colorimetric assay, reactivity of nitrite with insoluble elastin at neutral pH, 37±C, and physiologic concentration was confirmed. In histochemical studies on in situ human aortic elastin, nitrite-treated sections displayed marked structural disruptions. Determinations of fluorescence and absorbance on nitrite-treated soluble bovine elastin revealed marked alterations of fluorescence, and increased UV and visible absorbance. Amino acid analysis confirmed that it reacted with tyrosine. The findings indicate that non-enzymatic nitration by nitrite may have deleterious effects on elastin in vivo and may provide insights into the pathogenesis of chronic elastin degenerative processes, including aortic aneurysms, pulmonary emphysema, and premature skin wrinkling, all of which have been well known to have associations with cigarette smoking.