Determination of optimal conditions for synthesis of peroxynitrite by mixing acidified hydrogen peroxide with nitrite

Decreased retinal blood flow has been measured in streptozotocin (STZ)-induced diabetes of 1 week's duration, and primary insulin intervention was effective in maintaining normal retinal blood flow in diabetic rats. Retinal blood-flow abnormalities precede clinical diabetic retinopathy in both diabetic animals and patients. An important characteristic of diabetic retinopathy is the difficulty of reversibility once it has been established. Because altered retinal hemodynamics is a possible marker of early diabetic retinopathy, we investigated in this study whether retinal blood-flow changes in rats can be normalized by secondary insulin intervention following short and chronic periods of untreated STZ-induced diabetes. Subcutaneous insulin pumps were placed into diabetic rats for 1 week after 1 week of diabetes (2-week group) and after 3 weeks of diabetes (4-week group). Retinal circulatory parameters were determined using image analysis of video fluorescein angiogram recordings. For the 2-week group, retinal blood flow was significantly (P < 0.05) reduced in the untreated diabetic rats compared with nondiabetic and insulin-treated diabetic rats (80.6+/-29.2, 131.9+/-50.1, and 151.3+/-54.0 pixels2/s respectively). Retinal blood flow was also significantly (P < 0.05) reduced in the 4-week untreated diabetic rats compared with nondiabetic rats (95.7+/-22.2 vs. 125.7+/-29.5 pixels2/s). In contrast to the shorter-duration group, insulin treatment for 1 week after 3 weeks of diabetes did not totally normalize retinal blood flow (117.5+/-32.4 pixels2/s). These results suggest that vascular abnormalities could become more resistant to normalization following short-term (1 week) insulin treatment after longer periods of untreated diabetes.     

Continuous precipitation of uranium with hydrogen peroxide

Three different continuous processes were developed for the recovery of uranium from sulfate-containing simulated mill solutions. In all cases, a high-quality product, low in molybdenum and vanadium, which could be filtered and dried easily, was obtained. The presence of sulfate slows the precipitation rate and results in larger precipitated particles, which is an advantage in filtering and drying the precipitate. The morphologies of the large particles produced in the processes described in this report suggest that crystal growth predominated over nucleation in the precipitator. At 60 °C, the uranium peroxide precipitated as the dihydrate, but below 50 °C to 60 °C, the tetrahydrate was formed, and this knowledge led to important conclusions regarding the rate of the precipitation. A variety of particle morphologies was found, the most unusual being spherulitic aggregates consisting of needles radiating from a common point at the center of the particle. Formerly Senior Engineer and Professor, Ames Laboratory and Department of Chemical Engineering, respectively, Iowa State University, is deceased.     

铜催化过氧化氢氧化纳米银-原子吸收光谱法测定过氧化氢

以柠檬酸三钠作还原剂,微波高压法制备了纳米银,采用高速离心法纯化除去柠檬酸三钠获得了纯纳米银。将H2O2-Cu2+-纳米银催化反应与离心技术结合,用原子吸收光谱法做检测技术,建立了一个灵敏度高、选择性较好的测定痕量H2O2的新方法。在pH 3.8的HAc-NaAc缓冲溶液中,Cu2+催化H2O2氧化银纳米微粒生成Ag+,以原子吸收光谱法测定Ag+从而间接测定H2O2含量。随着H2O2浓度增大,氧化产生的Ag+越多,其吸光度值随之增加,H2O2浓度在5.8~63.4μmol/L范围内与离心液中Ag+的吸收值ΔA呈良好线性关系,回归方程为ΔA=0.007 7c+0.014,相关系数为0.994 1,方法检出限为2.0μmol/L。本方法用于废水中H2O2的测定,回收率在96.4%~108.3%之间,RSD为3.6%,与光度法结果相吻合。     

Formation of 8-hydroxy-2''-deoxyguanosine following treatment of 2''-deoxyguanosine or DNA by hydrogen peroxide or glutathione

Increases of oxidatively modified protein in the cell have been associated with the aging process. Such an accumulation of damaged protein may be the result of increase in the rate of protein oxidation and/or decrease in the rate of degradation of oxidized protein. The multicatalytic proteinase or proteasome is known to be the major proteolytic system involved in the removal of oxidized protein. We have reported that, after isolation of the 20S proteasome from the liver of young and old male Fischer 344 rat, out of the three peptidase activities (chymotrypsin-like, trypsin-like and peptidyl-glutamyl peptide hydrolase) we assayed with fluorogenic peptides, the peptidyl-glutamyl peptide hydrolase activity was declining with age to a value approximately 50% of that observed for protease purified from young rats. The proteasome was subjected to metal catalyzed oxidation to determine the susceptibility of the different peptidase activities to oxidative inactivation. Both trypsin-like and peptidyl-glutamyl peptide hydrolase activities were found sensitive to oxidation. Treatment of the proteasome with 4-hydroxy-2-nonenal, a major lipid peroxidation product, was also found to inactivate the trypsin-like activity. However, the trypsin-like activity was protected from inactivation by metal catalyzed oxidation in proteasome preparations contaminated with HSP 90, a protein that often copurifies with the proteasome. Upon addition of HSP 90 to pure 20S active proteasome, the trypsin-like activity was protected from inactivation by metal catalyzed oxidation and from inactivation by treatment with 4-hydroxy-2-nonenal. These results suggest a possible intervention of HSP 90 in response to oxidative stress in preventing the inactivation of the proteasome by oxidative damage.     

过氧化氢分光光度法测定湿法提钒工艺中钒

为了提高湿法提钒工艺过程控制效率,采用以过氧钒离子(VO(O₂)⁺)显色特性为基础的过氧化氢分光光度法测定钒含量,实现了样品中钒含量的现场快速测定。首先通过在试样溶液中加入适量氢氧化钠溶液,调整溶液pH值至9～10,然后加入过氧化氢将低价态钒全部氧化至钒(V),再加入硫酸调整溶液至酸性,钒(V)与过氧化氢在室温下形成稳定的红棕色过氧钒离子(VO(O₂)⁺),于450 nm处测定吸光度。钒质量浓度在2.0~400 mg/L内与吸光度值符合比尔定律。采用实验方法测定3种湿法冶金提钒液体试样(包括钒浸取溶液、钒盐沉淀后溶液以及废水等)中钒,结果的相对标准偏差(RSD,n=10)分别为0.38%、3.5%和7.6%;与高锰酸钾氧化-硫酸亚铁铵滴定法结果相一致。     

Lipoxygenase-catalyzed oxidation of chlorpromazine by hydrogen peroxide at acidic pH

The hydroperoxidase activity of soybean lipoxygenase, a non-heme protein, oxidizes chlorpromazine using H2O2 at acidic pHs ranging from 3.0 to 4.0. The enzyme is assayed at pH 3.5, at which the half-life is 2 h (lower pHs cause higher inactivation rates). This oxidation is enzymatical since boiled enzyme or even iron ions both with H2O2 failed to produce any increase in absorbance. In addition, the concentration of CPZ radical cation formed and the concomitant enzyme activity directly depends on the enzyme concentration up to 0.23 microM. The Vmax value is 125 mumol/min per mg protein and the Km for chlorpromazine and H2O2 are 2.1 mM and 0.25 mM, respectively. Similar results were obtained when linoleic acid hydroperoxide was used instead of H2O2 with a Km value of 95 microM. The radical cation obtained in the oxidation of chlorpromazine by lipoxygenase decays by a disproportionation reaction. This permits to consider the overall reaction as a sum of an enzymatic reaction coupled with a chemical second order reaction with substrate regeneration, similar to those produced by peroxidases from different sources.     

血红蛋白模拟酶催化光度法测定过氧化氢

H2O2在pH 9.8的NH3.H2O-NH4Cl介质中产生的羟自由基可以迅速氧化结晶紫使其褪色,而血红蛋白模拟酶对褪色反应具有催化作用,据此建立了一种以结晶紫为指示剂的过氧化氢-结晶紫-血红蛋白酶催化反应体系测定痕量H2O2的新方法。研究了pH值,结晶紫,血红蛋白用量等因素对体系的影响。对雨水中Zn2+,Cu2+,Mg2+,Ca2+,Fe3+,Al3+等常见离子进行了干扰试验。结果表明,除Fe3+的允许量较小外,其他离子的允许量都较大;但是Fe3+的干扰可以通过加入过量的柠檬酸消除。在最佳实验条件下,测定H2O2的线性范围为1.0×10-7~3.0×10-5mol/L,检出限为1.2×10-8mol/L。该方法可用于测定雨水及消毒水中H2O2的含量,结果与荧光法测定结果一致。     

过氧化氢分光光度法测定镍钛铌合金中钛

镍钛铌合金是一种重要的功能材料,其中的钛含量对合金性能影响显著。实验以过氧化氢为显色剂,采用分光光度法测定镍钛铌合金中高含量钛。样品用稀硫酸溶解,加入过氧化氢在室温下形成黄色络合物,于410nm处测定吸光度。试验优化了酸度、过氧化氢用量、显色时间等影响体系显色的因素。在优化的试验条件下,钛质量浓量在70.0～80.0μg/mL范围内符合朗伯比尔定律,显色体系的表观摩尔吸光系数为1.5×10² L·mol^-1·cm^-1。样品溶液无需分取而直接测定,避免了稀释带来的误差。镍的本色干扰采用基体匹配法消除。按照实验方法测定两个镍钛铌合金样品中钛,测定结果的相对标准偏差(RSD,n=6)分别0.40%和0.30%,并与滴定法测定结果相一致。方法实现了镍钛铌合金中高含量钛的准确测定。     

Toxicity of hydrogen peroxide produced by electroplated coatings to pathogenic bacteria

Four incremental protocols of knee extension exercise of different stage durations were compared to study the effect of the protocol upon power output at the last stage (Ppeak). Previous studies of knee extension have found very different power outputs with similar ergometers and these large differences have been interpreted as being the result of the fatigue due to the durations of the protocols. The knee extension device used in previous studies was modified to avoid the action of the knee and hip flexors: the subjects pushing on a lever instead of pulling a rod. In the present study five subjects performed four incremental knee extension exercises which differed with regard to stage duration (60, 90, 180 or 360 s) on this ergometer. The Ppeak, peak oxygen uptake (VO2peak) and peak heart rate (HRpeak) were measured at the end of each of these four incremental protocols. In eight subjects, the reliability of the protocols with the two shortest increments (60 and 90-s stages) was verified by measuring Ppeak at 60 s and 90 s (Ppeak60, Ppeak90) twice. The knee ergometer proposed in the present paper was easy to use without any special training and should improve the measurement of Ppeak. The Ppeak60 [49.4 (SD 5.6) W] was higher than at 180 s [Ppeak180), 43.6 (SD 5.8) W, P < 0.05] and at 360 s [Ppeak360, 43.4 (SD 5.3) W, P < 0.05]. All the other differences in Ppeak, VO2 peak and HRpeak were not significant. All correlations between Ppeak60, Ppeak90, Ppeak180 and Ppeak360 were significant, except those between Ppeak360 and Ppeak90 or Ppeak180. The effect of the stage duration on power output and oxygen uptake at the end of the knee extension exercises was not great. Consequently, the large differences in power output and oxygen uptake observed in previous studies cannot be explained by the protocol only. The significant difference between Ppeak 60 and Ppeak90 was of the order of 10% in agreement with findings in the literature using cycle ergometry. The reliability of Ppeak60 and Ppeak90 was high and the use of these protocols can be recommended if further studies show that the measurement of Ppeak, is useful in the evaluation of local endurance.     

Kinetics of galena dissolution in nitric acid solutions with hydrogen peroxide

The extraction of lead from a galena concentrate in nitric acid solutions with additional hydrogen peroxide was studied taking stirring speed, temperature, hydrogen peroxide and nitric acid concentrations, and particle size as dissolution parameters. The dissolution curves followed the surface chemical reaction controlled shrinking core model over the whole range of parameters, except at high nitric acid concentrations where the reaction was diffusion-controlled. The activation energy of 42 kJ mol^− 1 and a linear relationship between rate and inverse particle size support the reaction controlled dissolution mechanism. Hydrogen peroxide addition accelerated the reaction compared with nitric acid alone. It was concluded that the dissolution process is favourable, since the acid consumed for oxidation of galena can easily be regenerated in the same reactor by means of hydrogen peroxide.     

过氧化氢光度法测定钒钛磁铁矿中二氧化钛

钛是钢中重要的合金元素之一,可以防止钢中气泡存在,提高钢的强度和耐腐蚀性,细化晶粒,降低时效敏感性和冷脆性。钒钛磁铁矿作为炉料可提高钢中钛含量,常见的钒钛磁铁矿中Ti O2质量分数为8%～15%之间,V2O5质量分数小于0.4%,此外,Si O2,CaO,MgO,Al2O3,S含量较高,给Ti O2的测定带来一定困难。本法采用磷酸和硫酸溶解试样,在体积分数5%硫酸介质中,用过氧化氢光度法测定Ti O2。方法具备了快速、准确、测定范围宽的特点,特别适用于工厂实验室批量试样的分析。1实验部分1.1主要仪器与试剂721B型分光光度计(北京第二光学仪器厂)。磷酸(优级…     

Reactions of bovine liver catalase with superoxide radicals and hydrogen peroxide

The oxidized intermediates generated upon exposure of bovine liver catalase to hydrogen peroxide (H2O2) and superoxide radical (O2-) fluxes were examined with UV-visible spectrophotometry. H2O2 and O2- were generated by means of glucose/glucose oxidase and xanthine/xanthine oxidase systems. Serial overlay of absorption spectra in the Soret (350-450 nm) and visible (450-700 nm) regions showed that three oxidized intermediates, namely Compounds I, II and III, can be observed upon exposure of catalase to enzymatically generated H2O2 and O2-. Compound I is formed during the reaction of native enzyme with H2O2 and disappears in two ways: (i) via the catalytic reaction with H2O2 to restore native catalase and (ii) via the reaction with O2- to form Compound II. At low H2O2 concentrations (< 4.8 x 10(-9) M H2O2), Compound II reverts towards the native state mainly in a direct one-step reaction, whereas at higher H2O2 concentrations the pathway of Compound II back to the native enzyme involves Compound III. Formation of the latter from Compound II and H2O2 is irreversible and the rate constant of this reaction is 6.1 +/- 0.2 x 10(4) M-1 s-1. The formation of Compound III through the direct reaction of O2- with native enzyme has also been observed. Depending on the experimental conditions, the inactivation of catalase by O2- can be due to accumulation of Compound II ("slow" inhibition) or to the formation of Compound III ("rapid" inhibition) part of which leads to a dead end product. Formation of Compound III and of this dead end product are responsible for the irreversible inactivation in presence of an excess of H2O2.     

Characterization of sulfur-centered radical intermediates formed during the oxidation of thiols and sulfite by peroxynitrite. ESR-spin trapping and oxygen uptake studies

Using a novel phosphorylated spin trap, 5-diethoxy-phosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO), an analog of the commonly used trap 5,5'-dimethyl-1-pyrroline N-oxide (DMPO), we have investigated the reactions of sulfur-centered radicals produced from the oxidation of thiols and sulfite by peroxynitrite. The predominant species trapped in all cases are the corresponding sulfur-centered radicals, i.e. glutathionyl radical (GS) from glutathione (GSH), N-acetyl-DL-penicillamine thiyl radical (S-NAP) from N-acetyl-DL-penicillamine (NAP) and sulfate anion radical (SO3-) from sulfite. These radicals consume molecular oxygen forming either peroxyl or superoxide anion radicals. GS, S-NAP, and (SO3-)-derived radicals react with ammonium formate to form the carbon dioxide anion radical (CO2-). Further support of spin adduct assignments and radical reactions are obtained from photolysis of S-nitrosoglutathione and S-nitroso-N-acetyl-DL-penicillamine. We conclude that the direct reaction of peroxynitrite with thiols and sulfate forms thiyl and sulfate anion radicals, respectively, by a hydroxyl radical-independent mechanism. Pathological implications of thiyl radical formation and subsequent oxyradical-mediated chain reactions are discussed. Oxygen activation by thiyl radicals formed during peroxynitrite-mediated oxidation of glutathione may limit the effectiveness of GSH against peroxynitrite-mediated toxicity in cellular systems.     

Kinetic studies on the removal of extracellular hydrogen peroxide by cultured fibroblasts

To investigate the function of antioxidant enzymes in intact cells, we examined the removal of extracellular H2O2 by cultured fibroblasts (IMR-90). H2O2 concentration dependence of the reaction rate was interpreted as that the process involves two kinetically different reactions (referred to as reactions 1 and 2). Reaction 1 was characterized by a relatively low Km value (about 40 microM), and reaction 2 by linear dependence of the rate up to 500 microM H2O2. The magnitude of reaction 1 was reduced by treatment of the cells with diethyl maleate or 6-amino-nicotinamide, while reaction 2 was inhibited by 3-amino-1,2,4-triazole treatment. It was concluded that reactions 1 and 2 are principally due to GSH peroxidase and catalase, respectively. The values of kinetic parameters were estimated by curve-fitting, and it was inferred that 80 to 90% of H2O2 is decomposed by GSH peroxidase at H2O2 concentrations lower than 10 microM. The contribution of catalase increases with the increase in H2O2 concentration. The intact cells showed a low catalase activity (about 15%), as compared with the activity found in the solubilized cells. The low catalase activity was ascribed to the latency of the enzyme caused by localization in peroxisomes. Fibroblasts also removed intracellular H2O2 generated by menadione. Treatment with diethyl maleate greatly impaired the H2O2-removing capability and caused H2O2 efflux into the medium.     

The importance of sodium pyruvate in assessing damage produced by hydrogen peroxide

OBJECTIVES: The external striated urethral sphincter (rhabdosphincter) is a tubular muscle sleeve that extends from the prostato-membranous urethra and perineal membrane to the bladder neck. The male rhabdosphincter neuroanatomy remains unclear, and a better understanding of its innervation may provide insight into potential modifications of radical pelvic surgery to improve urinary continence. METHODS: Fresh cadaveric dissections of 12 male hemipelves were undertaken to investigate the neuroanatomy of the urinary rhabdosphincter. RESULTS: Neuroanatomic courses of the nerve supply to the rhabdosphincter revealed that, in the perineum, the perineal nerve (a terminal branch of the pudendal nerve) provided branches directly to the bulbospongiosus muscle and the urinary rhabdosphincter. In the pelvis, the course of the pelvic nerve was as follows: (1) arising from the inferior hypogastric plexus, it had a weblike course beneath the muscle fascia of the levator ani muscle; (2) traveling posterolateral to the rectum, it gave many branches that perforated into the lateral rectum; and (3) at the level of the prostatic apex, still beneath the levator ani muscle fascia (superior fascia), it sent multiple direct branches to the inferolateral aspect of urinary rhabdosphincter. The pudendal nerve traversed the pelvis in the pudendal canal, and, before leaving the pelvis to enter the perineum, it gave an intrapelvic branch that courses with the pelvic nerve to innervate the rhabdosphincter. CONCLUSIONS: Our understanding of the neuroanatomy of what may be the continence nerves has been improved by fresh cadaveric dissection. The rhabdosphincter receives nerve fibers from the pelvic nerve and dual innervation from an intrapelvic branch and a perineal branch of the pudendal nerve. Better understanding of these anatomic findings may have potential surgical significance with respect to improvement in postoperative urinary continence.     

过氧化氢-甲基橙动力学光度法测定亚硝酸根

研究了硫酸介质中,痕量亚硝酸根催化过氧化氢氧化甲基橙褪色反应及其动力学条件,建立了动力学光度法测定亚硝酸根的简便方法。在25mL溶液中亚硝酸根测定的线性范围为0～0.8μg,方法的检出限为6.55×10-9g/mL。测定1×10-8g/mLNO-4,Cr3+,F-,Cl-;2,以相对于NO-2量的倍数计,1000倍的Na+,K+,Mg2+,Ca2+;500倍的Pb2+,Al3+,NH+100倍的Ni2+,I-,Zn2+,Cd2+,Mo(Ⅵ),Fe3+和20倍的Cu2+不干扰。方法已用于自来水、雨水和池塘水     

Transformation in vitro of a nontumorigenic rat urothelial cell line by hydrogen peroxide

Chronic infection/inflammation of the urinary tract is a significant risk factor for the development of bladder cancer. The present study examined the hypothesis that hydrogen peroxide (H202) and cytokines released during inflammation are involved in the enhancement of bladder carcinogenesis. Using growth in soft agar and tumorigenicity in athymic nude mice as indices of transformation, we examined the effect of H202 and cytokines on the enhancement of N-methyl-N-nitrosourea (MNU)-initiated transformation of MYP3 cells, an anchorage-dependent nontumorigenic rat bladder epithelial cell line. MYP3 cells pretreated with or without MNU were exposed to H202 (0.001 to 0.1 mM) daily for 1 week in monolayer culture and were then tested for growth in soft agar. A marked increase in colony numbers was observed in the cells that were MNU-initiated and exposed to H202 (P < 0.01). Furthermore, H202 exposure alone at 0.01 mM or 0.1 mM caused colony formation in soft agar. The transformants induced by MNU plus H202 or H202 alone formed high-grade transitional cell carcinomas when injected into nude mice. The growth of these transformants was stimulated by several cytokines (interleukin 1alpha, interleukin 6, and tumor necrosis factor-alpha) better than the parental cells both on a plastic surface and in soft agar. Our results indicate that H202 causes genetic change(s) to induce tumorigenic conversion in urothelial cells and that the transformants are stimulated to grow because of their selective response to several cytokines. We suggest that these mechanisms may be involved in the in vivo carcinogenesis associated with chronic urinary tract infection.     

Catalytic decomposition of hydrogen peroxide by ferric ion in dilute sulfuric acid solutions

Hydrogen peroxide decomposition in acidic solutions is catalyzed by the free ferric ion, Fe³⁺. The following rate law for this reaction is determined by the initial rate method in solutions similar to those used for acidicin situ uranium leaching: wherek = 4.3 × 10⁻³ s^°1 at 25 °C. From 25° to 50 °C, the activation energy is 85.6 kJ/mol. The decomposition of hydrogen peroxide proceeds by a particular redox reaction sequence that depends on the ratio of the concentrations of hydrogen peroxide to free ferric ion. The rate law determined here is consistent with the form derived from the redox sequence for the case where the ratio of hydrogen peroxide to free ferric ion concentration is greater than 1.0. The magnitude of the rate constant indicates that the decomposition of hydrogen peroxide may cause rapid loss of this oxidant in leaching solutions containing ferric ion. Formerly a Graduate Student with the Department of Geochemistry and Mineralogy, Pennsylvania State University,     

过氧化氢法净化含氰废水工艺初步探讨

采用过氧化氢与稳定剂联合作用净化含氰废水,药剂耗量低,且无毒无害,不会产生任何新的污染。该工艺操作简单,无需动力,可使含氰废水一次降至渔业水域区水质标准,甚至达到国家源头水标准(0.005mg/L),社会经济效益和环境效益好。     

Modifying influence of enalaprilat on mesangial cell DNA synthesis induced by hydrogen peroxide

This study examined the effect of the angiotensin converting enzyme (ACE) inhibitor, enalaprilat, on mesangial cell (MC) DNA synthesis induced by H2O2, IL-6 and PDGF. MC were incubated with enalaprilat (2.5-100 mumol/l) alone and together with combinations of H2O2 (3 daily pulses of 10(-6) mol/l), IL-6 (5 ng/ml) and PDGF (10 ng/ml). DNA synthesis was assessed after 72 h using [3H]thymidine (3H-TdR) incorporation. Enalaprilat alone had no effect on MC DNA synthesis. Stimulation of MC by H2O2, PDGF and IL-6 alone resulted in increases in 3H-TdR of 4936.6 +/- 1147.5, 5640.5 +/- 1537.6 and 4413.5 +/- 998.4 cpm, respectively (P < 0.05 above control). Only 2.5 mumol/l enalaprilat effected a significant reduction in IL-6 and PDGF-induced DNA synthesis. Incubation of MC with H2O2 + PDGF or H2O2 + IL-6 resulted in increases of 3H-TdR of 6471.9 +/- 1785.1 and 5507.2 +/- 1270 cpm, respectively (P < 0.05 above control). Addition of enalaprilat with either H2O2 + PDGF or H2O2 + IL-6 effected significant reductions in DNA synthesis over the range 2.5-100 mumol/l. These data demonstrate that ACE inhibitors modulate MC DNA synthesis induced by reactive oxygen species.