马兜铃酸Ⅰ-DNA加合物合成及电喷雾质谱法检测

目的建立体外合成及检测马兜铃酸Ⅰ(aristolochic acid I,AAⅠ)-DNA加合物的方法。方法分别采用酶活化法和化学活化法活化AAⅠ后与脱氧腺苷酸反应以合成AAⅠ-DNA加合物,优化各种反应条件,使用液相色谱/串联质谱(LC/MS/MS)法对合成的AAⅠ-DNA加合物进行结构鉴定。结果两种方法均可制得AAⅠ-DNA加合物,质谱负离子采集模式下测得其准分子离子峰m/z621,电喷雾串联质谱(ESI-MS/MS)谱图提供了丰富的结构信息。结论AAⅠ活化后能与腺嘌呤形成AAⅠ-DNA加合物,LC/MS/MS技术能够快速方便准确地检测AAⅠ-DNA加合物。     

Chaos and control in mass-action binding of endogenous compounds

Endogenous compounds, such as hormones and neurotransmitters, interact with cellular receptors in controlled reactions governed by the mass-action law. Autoreceptors, a subset of the receptor pool, when activated by the endogenous ligand, result in a negative feedback that reduces the further release of ligand. This paper discusses and illustrates this control system when the concentrations (free and bound) are near or slightly beyond the limits of effective feedback control. Specifically, a forced periodic input function, simulating periodic release of the ligand, is used in the simulation of this controlled binding reaction in which a parameter representing the upper limit of control is varied. The solution of the system differential equations, representing free and bound ligand, is shown to pass from periodic to chaotic as the parameter is varied.     

Biomedical applications of tunable diode laser spectrometry: Correlation between breath carbon monoxide and low level blood carboxyhemoglobin saturation

Tunable diode laser spectrometry was used to measure breath carbon monoxide (CO) concentrations in nonsmoking subjects. Corresponding blood carboxyhemoglobin (COHb) saturations between physiological levels and levels after 1 and 8 hours exposure to 9 ppm CO, the maximum permissible concentration in the air under federal regulations, were also determined. A good linear correlation between breath CO and blood COHb saturation for low levels representing ambient conditions was established, with a correlation coefficient better than 0.999 for the means and 0.945 for the individual data points. Similar studies on the other compounds of concern are also possible using tunable diode laser spectrometry, requiring only a breath sample and with no sample preparation. This technique will facilitate fast, noninvasive environmental health effect and biomedical studies.     

人鼻咽癌细胞系CNE2分泌蛋白质谱的初步建立

目的：建立鼻咽癌（nasopharyngeal carcinoma，NPC）细胞系CNE2细胞的分泌蛋白质谱。方法：采用无血清培养法培养CNE2细胞，超滤法脱盐并浓缩细胞培养上清制备分泌蛋白质，采用双向凝胶电泳技术（two-dimensional electrophoresis，2-DE)分离蛋白质，应用基质辅助激光解吸电离飞行时间质谱(matrix-assisted laser desorption/ionization time of flight mass spectrometry, MALDI-TOF-MS)鉴定蛋白质，利用生物信息学资源对所鉴定的蛋白质的功能和亚细胞定位进行分析。结果：建立了CNE2细胞分泌蛋白质的2-DE图谱，鉴定了52种非冗余的CNE2细胞分泌蛋白质，并对52种蛋白质按功能和亚细胞分布进行了初步分类。结论：初步建立CNE2细胞的分泌蛋白质谱，为研究鼻咽癌分泌蛋白质在鼻咽癌发生发展中的作用提供了有意义的资料。     

鼻咽癌转移相关的分泌蛋白质的筛选

目的：筛选鼻咽癌（nasopharyngeal carcinoma, NPC）转移相关的分泌蛋白质，为阐明NPC转移机制以及筛选NPC转移分子标志物提供实验依据。方法：应用二维凝胶电泳（two-dimensional electrophoresis，2-DE）技术分离一对来自同一亲本，具有不同转移潜能的NPC细胞系5-8F和6-10B细胞的分泌蛋白质，图像分析识别差异表达的蛋白质点，基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)和电喷雾-四极杆-串联质谱(ESI-Q-TOF MS/MS)对差异表达的蛋白质点进行鉴定。Western印迹法检测差异分泌蛋白质nm23-H1在两株细胞中的表达水平。结果：建立了5-8F和6-10B分泌蛋白质的2-DE图谱，质谱分析鉴定出14个非冗余的分泌蛋白质，其中Oncoprotein18等蛋白质在高转移潜能NPC细胞系5-8F中的表达水平高于无转移潜能的NPC细胞系，而nm23-H1等蛋白质在5-8F细胞系中的表达水平低于6-10B细胞系。Western印迹分析证实了nm23-H1在5-8F和6-10B细胞分泌蛋白质中的差异表达水平。结论：所鉴定的14个非冗余的差异分泌蛋白质为研究NPC转移机制以及筛选NPC转移分子标志物提供了实验依据。     

Tranexamic acid: Preoperative prophylactic therapy for patients with hereditary angioneurotic edema

Short-term therapy of 96-hr duration with tranexamic acid was prophylactically effective as defined by the absence of attacks of angioedema in 14 patients with hereditary angioedema undergoing 10 dental and 4 general surgical procedures. Eight of the 14 patients had previously undergone dental extractions without prophylactic therapy with antifibrinolytic agents and each had experienced one or more attacks of angioedema. Seven of these 8 patients had a cumulative experience of 13 episodes of laryngeal edema after dental extractions and the eighth had a bout of cutaneous angioedema. Although the number of dental extractions conducted without prophylactic antifibrinolytic therapy cannot be accurately defined in retrospect, the prominence of laryngeal edema in this circumstance is striking when compared with the absence of attacks in the presence of prophylaxis with tranexamic acid. Methyltestosterone and impeded androgens are now known to be effective prophylaxis for spontaneous and, presumably, postoperative attacks when employed chronically because their administration is associated with correction of the biochemical defect of hereditary angioneurotic edema, but their chronic administration to children and women of childbearing age requires further definition because of their potential pituitary suppressive action. Tranexamic acid prophylaxis makes it possible to offer to untreated patients with hereditary angioneurotic edema dental work and other operative procedures that in the past were withheld or conducted with considerable risk.     

Properties of the omega-hydroxylation system of docosahexaenoic or arachidonic acid in brain or liver homogenate of rat

The homogenate of a brain or liver obtained from a 1–55-day-old rat was incubated with NADPH and docosahexaenoic or arachidonic acid as the substrate. ω-Hydroxydocosahexaenoic or ω-hydroxyeicosatetraenoic acid from an incubation mixture of the homogenate was detected on a selected-ion monitoring chromatogram of reversed phase-HPLC-thermospray-mass spectrometry. ω-Hydroxylation activity in the brain homogenate considerably increased with growth up to 55 days. Activity in the liver homogenate decreased much with growth up to 55 days. ω-Hydroxylation activity in homogenates of rat brain gray matter, white matter, medula oblongata and cerebellum was much the same. ω-Hydroxylation activity of docosahexaenoic acid in rat brain homogenate was maximal at pH 7.5–8.0 in 50 mM Tris-HCL buffer and was inhibited by CO gas, metyrapone, ADP-Fe³⁺, heat treatment at 100°C for 5 min and without NADPH. Based on these results, it is suggested that ω-hydroxylation activity is associated with cytochrome P-450 without NADPH-ADP-Fe³⁺-dependent lipid peroxidation, and the ω-hydroxylation system may be a metabolic pathway of the fatty acids in adult rat brain or neonatal rat liver. Since ω-hydroxyeicosatetraenoic acid produces relaxation of artery, it is suggested that blood flow changes in rat brain or liver with growth are caused by ω-hydroxylation activity changes in these organs with growth.     

Rapid hydroxylation of methtryptoline (1-methyltetrahydro-β-carboline) in rat: Identification of metabolites by chiral gas chromatography-mass spectrometry

Summary Racemic methtryptoline (1-methyltetrahydro--carboline) and 5-hydroxymethtryptoline-9-carboxylic acid (6-hydroxy-1-methyltetrahydro--carboline-1-carboxylic acid) were administered intraperitoneally to rats and the components of their urine was subsequently investigated by chiral gas chromatography-mass spectrometry. Methtryptoline rapidly became hydroxylated in the 5- and 6-position and excreted in urine. There was about a ninefold predominance of the S(–) enantiomer over the other in the 5-hydroxylated species, while the 6-hydroxylation produced a small excess of the R(+) enantiomer. About 75% of the injected dose of methtryptoline was recovered in the urine as 5- and 6-hydroxylated compounds during the first 24 h period, demonstrating that hydroxylation represents the major metabolic pathway. Treatment with 6-hydroxymethtryptoline-9-carboxylic acid led to a fivefold increase in the urinary excretion of 5-hydroxymethtryptoline during the first 24 h period with a predominance of the S(–)-enantiomer, indicating a much smaller conversion rate than from methtryptoline. It was concluded that hydroxylation of methtryptoline is a likely pathway for the natural formation of 5-hydroxymethtryptoline.     

Direct quantitation of antiseptic quaternary ammonium compounds by fast atom bombardment mass spectrometry

The medicinally important quaternary ammonium salts benzyldimethyltetradecylammonium chloride (BDTA), cetylpyridinium chloride and benzethonium chloride, all afford, under fast atom bombardment (FAB) mass spectrometric conditions, abundant and persistent [M---Cl]⁺ species usefully amenable to quantitative analysis with the aid of thioglycerol as a liquid FAB matrix. The use of BDTA as an internal standard allowed a direct, precise and accurate determination of cetylpyridinium and benzethonium chlorides, either as pure samples or in dosage forms, in the concentration range 0.05–2 mg/ml.     

超高效液相色谱-串联质谱法测定鸡肉和鸡蛋中5种硝基咪唑类药物残留量

目的 采用超高效液相色谱-串联质谱法（UPLC-MS/MS）,建立鸡肉和鸡蛋中5种硝基咪唑类药物的检测方法。方法 样品经乙腈提取后,加入无水Na2SO4和NaCl,离心后上清液通过PRiME HLB固相萃取小柱净化,滤出液和乙腈洗脱液经氮吹至近干,10%甲醇水（v/v）溶液定容。以0.1 %甲酸水-甲醇为流动相,被测物经BEH C18柱(2.1 mm × 100 mm,1.7 μm)分离、正离子多反应监测模式检测,内标法定量。结果 5种硝基咪唑在0.2～20.0 ng/ml范围内相关系数均大于0.999,方法检出限为0.05～0.10 μg/kg,定量限为0.15～0.30 μg/kg。在3个加标水平下（0.25、2.0和10.0 μg/kg）,鸡肉和鸡蛋的平均回收率分别为97.9%～106.0%和97.8%～110.0%,相对标准偏差（RSD）分别为0.9%～6.4%和1.0%～4.7%。结论 该方法简便、灵敏、准确,适用于鸡肉和鸡蛋中5种硝基咪唑残留量的快速检测。