首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   25篇
  免费   2篇
  国内免费   2篇
基础医学   10篇
内科学   2篇
预防医学   4篇
药学   10篇
肿瘤学   3篇
  2021年   4篇
  2020年   2篇
  2018年   1篇
  2016年   1篇
  2013年   6篇
  2012年   1篇
  2011年   2篇
  2007年   1篇
  2006年   2篇
  1999年   1篇
  1995年   1篇
  1993年   1篇
  1992年   1篇
  1991年   2篇
  1990年   2篇
  1988年   1篇
排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
目的 分析N-亚硝胺与消化道恶性肿瘤发生/死亡风险的关系。方法 通过系统检索中国生物医学文献数据库、中文期刊全文数据库、万方电子期刊、PubMed、EBSCO等文献数据库,纳入N-亚硝胺与消化道恶性肿瘤发生/死亡风险队列研究文献,采用RevMan 5.1软件进行Meta分析。结果 共检索到相关文献13篇,纳入其中7篇含有消化道恶性肿瘤的文献进行Meta分析;N-亚硝胺显著增加消化道癌症的发生风险(RR=1.12,95%CI:1.03~1.21);与食管癌发生风险无显著性关联(RR=1.18,95%CI:0.98~1.41),但显著增加食管鳞状细胞癌发生风险(RR=1.72,95%CI:1.01~2.96),而与食管腺癌无显著性相关(RR=0.88,95%CI:0.57~1.37);N-亚硝胺能显著提高胃癌的发生风险(RR=1.08,95%CI:1.00~1.18),但对贲门癌与胃腺癌发生风险的影响无显著性。结论 现有人群队列研究证据显示,N-亚硝胺会显著增加消化道恶性肿瘤的发生风险,但是对不同亚型食管癌和胃癌的影响不同,由于队列研究数量较少且在研究设计、人群选择、暴露测量等方面存在差异,仍需进一步积累相关研究证据。  相似文献   
2.
N-nitrozodimethyloamine (NDMA) is a carcinogenic compound that can be formed in vivo. NDMA is synthesized from precursors-amines and nitrosating agents. Nitrosating agents are formed through the reaction of oxide, reactive oxygen species and nitric oxide (NO). Human neutrophils (PMN) are an important source of the most reactive oxygen species as well as of the nitric oxide. The increase in oxygen metabolism of PMN can lead to the increase nitrosating agent and nitroso-forms. Inflammatory process is associated with locally decreased pH that may favor nitrosation reaction.

In the present study, we estimated the NDMA synthesis by LPS-stimulated PMN in the presence of the iNOS inhibitor – N-nitro-L-arginine methyl ester (L-NAME). In the nitrosation reaction dimethylamine (DMA) was used as substrat. The viability of the cells was measured by cytometric method. NDMA concentrations the culture media was measured by GCMS method. NO production was estimated by Griess's method. Expression of iNOS was determined by western blotting.

Results obtained showed that DMA nitrosation is most effective in pH between 3–4.5. Nonstimulated PMN produced lower concentrations of NO than LPS-stimulated cells (1.27 μg/cm3 and 1.57 μg/cm3, respectively). In the culture of nonstimulated PMN supplemented with DMA, there was NDMA (mean – 0.99 ng/cm3). In the culture of LPS-stimulated PMN in the presence of DMA, the concentration of NDMA was higher than in the culture of nonstimulated PMN (median – 1.45 ng/cm3). In the supernatants of cells incubated without DMA and with DMA, LPS and L-NAME, no NDMA was detected. These results indicate that PMN can be one of sources of nitrosating agents and can play a role in endogenous NDMA synthesis. Stimulation of PMN can lead to the increase of NDMA concentration following the increase of NO production. Different pathological conditions associated with PMN activation as well as the decreased pH may favor endogenous NDMA synthesis.  相似文献   
3.
Nitrosamine-contaminated medicinal products have raised safety concerns towards the use of various drugs, not only valsartan and all tetrazole-containing angiotensin II receptor blockers, but also ranitidine, metformin, and other medicines, many of which have been recalled and prone to shortage. At any stages, from drug substance synthesis throughout each product's lifetime, these impurities may evolve if an amine reacts with a nitrosating agent coexisting under appropriate conditions. Consequently, drug regulatory authorities worldwide have established stringent guidelines on nitrosamine contamination for all drug products in the market. This review encompasses various critical elements contributing to successful control measures against current and upcoming nitrosamine issues, ranging from accumulated knowledge of their toxicity concerns and potential root causes, precise risk evaluation, as well as suitable analytical techniques with sufficient sensitivity for impurity determination. With all these tools equipped, the impact of nitrosamine contamination in pharmaceuticals should be mitigated. An evaluation aid to tackle challenges in risk identification, as well as suitable industry-friendly analytical techniques to determine nitrosamines and other mutagenic impurities, are among unmet needs that will significantly simplify the risk assessment process.  相似文献   
4.
Cellular DNA damage that is misrepaired or not repaired, constitutes a necessary, although not sufficient prerequisite for induction of cancer. For carcinogenic oral snuffs with extremely high concentrations of tobacco specific nitrosamines (TSNA) the DNA adduct levels predicted from animal experiments exceed those found in "unexposed" individuals. On the other hand, and supported by extensive Swedish epidemiological data, no significant increase of TSNA-induced DNA damages can be anticipated in humans from the use of low-nitrosamine oral snuffs. The extrapolated adduct concentrations are orders of magnitude lower than those found in the corresponding human tissues, a discrepancy that is difficult to account for by species differences. Furthermore, in exposed subjects the observed increment in the background levels of pyridyloxobutyl(POB)-hemoglobin adducts - a relevant indicator for TSNA activation - lie in a range predicted by rodent data. When based on the same type of tissues this provides justification for extrapolating rates of TSNA induced adduct formation from animals to humans. A TSNA exposure that does not affect the background level of pro-mutagenic DNA lesions should be considered as "virtually safe". The high background concentrations of methylated and POB-DNA adducts in "unexposed" humans must be ascribed to other sources than tobacco.  相似文献   
5.
The intracellular mechanisms of NDMA-induced apoptosis of neutrophils have not yet been fully understood. The aim of this study was to explain whether the TRAIL/DR5 system is implicated in NDMA-induced apoptosis of human neutrophils. The expression of TRAIL and DR5 was examined, as well as the secretion of sTRAIL and sDR5 by human neutrophils treated with NDMA confronted with intensity apoptosis of these cells. For comparative purposes similar examinations in autologous peripheral blood mononuclear cells (PBMC) were performed. Decreased expression and secretion of TRAIL and increased expression and secretion of DR5 associated with increased intensity of apoptosis of polymorphonuclear leukocytes (PMNs) suggest that NDMA-induced apoptosis in these cells may be depend on TRAIL/DR5 system. Autologous PBMCs no exerted that changes in the expression and secretion of TRAIL as well as in the intensity of apoptosis. However, the expression and secretion of DR5 by PBMCs were similar to those by PMNs. Differences above suggest that PMNs are more sensitive to unfavorable action of NDMA than PBMCs.  相似文献   
6.
AIM: To study the association between nitrite and nitrosamine intake and gastric cancer (GC), between meat and processed meat intake, GC and oesophageal cancer (OC), and between preserved fish, vegetable and smoked food intake and GC. METHODS: In this article we reviewed all the published cohort and case-control studies from 1985-2005, and analyzed the relationship between nitrosamine and nitrite intake and the most important related food intake (meat and processed meat, preserved vegetables and fish, smoked foods and beer drinking) and GC or OC risk. Sixty-one studies, 11 cohorts and 50 case-control studies were included. RESULTS: Evidence from case-control studies supported an association between nitrite and nitrosamine intake with GC but evidence was insufficient in relation to OC. A high proportion of case-control studies found a positive association with meat intake for both tumours (11 of 16 studies on GC and 11 of 18 studies on OC). A relatively large number of case-control studies showed quite consistent results supporting a positive association between processed meat intake and GC and OC risk (10 of 14 studies on GC and 8 of 9 studies on OC). Almost all the case-control studies found a positive and significant association between preserved fish, vegetable and smoked food intake and GC. The evidence regarding OC was more limited. Overall the evidence from cohort studies was insufficient or more inconsistent than that from case-control studies. CONCLUSION: The available evidence supports a positive association between nitrite and nitrosamine intake and GC, between meat and processed meat intake and GC and OC, and between preserved fish, vegetable and smoked food intake and GC, but is not conclusive.  相似文献   
7.
目的:以聚丙烯酸树脂Ⅱ-羟丙甲基纤维素体系为模型,研究缓释制剂辅料导致盐酸二甲双胍降解生成基因毒性杂质N-亚硝基二甲胺(NDMA)的相关影响因素。方法:以高效液相色谱-三重四极杆串联质谱为NDMA监测手段,通过试剂替代确定具有降解作用的氧化剂,而后考察溶剂、氧化剂加入量、加热时间、加热温度等因素对NDMA生成量的影响。结果:缓释制剂辅料中的过硫酸钾和次氯酸钠产生协同氧化作用,可使盐酸二甲双胍降解生成NDMA。甲醇、乙醇对该降解具有抑制作用,而水则具促进作用。过硫酸钾-次氯酸钠二元体系的氧化能力大大高于过硫酸钾或次氯酸钠单一体系的氧化能力。任一氧化剂加入量的增加均可增强二元体系的氧化能力。温度对该二元氧化体系具有重要影响,NDMA的生成量随温度升高而增加,高于70℃后体系的氧化能力显著提升。该二元氧化体系下,盐酸二甲双胍氧化降解成NDMA的反应为零级反应,NDMA的生成量与反应时间成正比。结论:缓释辅料中的残留氧化剂在高温下导致盐酸二甲双胍降解生成NDMA。选择氧化剂含量低的辅料、严格控制加热温度和加热时间可有效降低甚至避免NDMA的生成。建议将残留氧化剂作为辅料的安全性指标纳入辅料质量标准,加强药用辅料的质量控制。制剂的研发应重视原辅料的相容性研究,尤其是辅料中微量氧化剂对易降解原料药的影响,确保制剂产品的安全性和质量可控性。  相似文献   
8.
1.?The objective of study was to determine the influence of ethanol and/or N-nitrosodimethyloamine (NDMA) on the inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production by human neutrophils and determination of the role of NF-κB in this process.

2.?Isolated polymorphonuclear leukocytes (PMNs) derived from 15 human volunteers were incubated in the presence of ethanol and/or NDMA. Expression of the tested proteins were evaluated using the Western blot method. Total NO metabolites was assayed in the cell cultures by Griess reaction.

3.?In neutrophils exposed to ethanol or NDMA was observed an increased NF-κB-dependent NO production mediated by iNOS with the contribution of MAP kinases: p38 and JNK. An inhibiting effect of NF-κB signaling pathway on the MAP kinases was observed, which are involved in the iNOS-dependent NO production. By the simultaneous effect, ethanol and NDMA caused stronger generation of NO by neutrophils without the contribution of iNOS. Inhibition of NF-κB in cells simultaneously exposed to the xenobiotics caused a decreased expression of MAP kinases.

4.?Individual and simultaneous effect of ethanol and NDMA may cause disorders in the response of immune system. However, the joint effect of the tested substances results in uncontrolled interactions, leading to cascading disorders of signal transduction.  相似文献   
9.
田葆萍  李珍  范春华  王中民  曹晔  夏本立  王力 《职业与健康》2012,28(10):1221-1222,1225
目的建立高效液相色谱法测定亚硝基二甲胺的方法。方法采用反相高效液相色谱法测定火箭推进剂偏二甲肼废水中亚硝基二甲胺的含量。色谱条件:色谱柱CNWSIL-C18(4.6×250 mm,5μm),流动相甲醇∶水为15∶85,流速为1.0ml/min,柱温28℃,紫外检测器检测波长为230 nm。结果亚硝基二甲胺在10~500μg/L范围内线性关系良好(r2=0.999 9);高、中、低3种浓度加标平均回收率分别为104.1%、96.93%、92.5%(RSD分别为1.6%、1.8%、1.7%),高、中、低3种浓度精密度RSD为0.13%、0.75%、0.47%,最低检测限为0.5μg/L。结论该方法准确,快速,可用于亚硝基二甲胺的测定。  相似文献   
10.
藠头和苦瓜汁抑制亚硝胺合成的体外试验   总被引:2,自引:0,他引:2  
本文报告了在模拟人胃液条件下,头(AlliumchinensisG.Don.)和苦瓜(MomordieacharantiaLinn.)对N-二甲基亚硝胺(NDMA)和N-二乙基亚硝胺(NDEA)体外合成的阻断作用。结果表明:鲜头汁能明显地阻断NDMA和NDEA的化学合成,而鲜苦瓜汁对NDMA和NDEA的化学合成仅有一定的阻断作用;头经煮沸20min和盐腌两周后,其阻断作用大大降低,而同样处理对苦瓜的影响却较小;鲜头升和鲜苦瓜汁的剂量与NDMA和NDEA的合成量呈显著的负相关关系;头阻断亚硝胺合成的主要有效成分并不是抗坏血酸,而苦瓜中抗坏血酸的阻断作用却较大;头和苦瓜阻断亚硝胺合成的机理在于头和苦瓜中的有效成分能消除反应液中的亚硝酸盐  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号