Interaction of ethidium bromide with DNA as studied by kinetic spectrophotometry.

The interaction of ethidium bromide (EB) with DNA has been investigated using the pulse radiolysis technique. In particular, the absolute rate constant for the reaction of hydrated electrons, generated by single pulses of high-energy electrons, with EB is shown to drop dramatically in the presence of DNA. This drop in diffusion-limited reactivity results from the interaction of EB with DNA, effectively immobilising it, thus lowering the reaction cross-section or probability. Analysis of the resulting kinetic spectrophotometric data shows that they are consistent with a reversible interaction of EB with DNA as described by the law of mass action. The Scatchard-type plots obtained are linear, and give quantitative information on the extent and degree of association, comparable with that obtained by more conventional methods. The potential of the pulse radiolysis technique for studying different types of interactions between small molecules and various biopolymers has been demonstrated.     

Effects of electromagnetic radiation from a cellular telephone on the oxidant and antioxidant levels in rabbits

The number of reports on the effects induced by electromagnetic radiation (EMR) in various cellular systems is still increasing. Until now no satisfactory mechanism has been proposed to explain the biological effects of this radiation. Oxygen free radicals may play a role in mechanisms of adverse effects of EMR. This study was undertaken to investigate the influence of electromagnetic radiation of a digital GSM mobile telephone (900 MHz) on oxidant and antioxidant levels in rabbits. Adenosine deaminase, xanthine oxidase, catalase, myeloperoxidase, superoxide dismutase (SOD) and glutathione peroxidase activities as well as nitric oxide (NO) and malondialdehyde levels were measured in sera and brains of EMR-exposed and sham-exposed rabbits. Serum SOD activity increased, and serum NO levels decreased in EMR-exposed animals compared to the sham group. Other parameters were not changed in either group. This finding may indicate the possible role of increased oxidative stress in the pathophysiology of adverse effect of EMR. Decreased NO levels may also suggest a probable role of NO in the adverse effect.     

Protective agent, erdosteine, against cisplatin-induced hepatic oxidant injury in rats

Cisplatin, one of the most active cytotoxic agents against cancer, has several toxicities. Hepatotoxicity is one of them occurred during high doses treatment. The aim of this study was to determine the effects of erdosteine against cisplatin-induced liver injury through tissue oxidant/antioxidant parameters and light microscopic evaluation. The rats were randomly divided into three groups: control (n=5), cisplatin (10 mg/kg, n=6) and cisplatin+erdosteine (50 mg/kg/day oral erdosteine, n=8) groups. The rats were sacrificed at the 5th day of cisplatin treatment. The liver tissues were examined with light microscopy and oxidant/antioxidant biochemical parameters. The malondialdehyde (MDA) and nitric oxide (NO) levels were increased in the cisplatin group in comparison with the control and cisplatin+erdosteine groups (p<0.05). There was no significant difference in MDA and NO levels between control and cisplatin+erdosteine groups. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were higher in cisplatin+erdosteine group than cisplatin group (p<0.05). However, the CAT and GSH-Px activities were significantly lower in cisplatin group than in control group (p<0.05). The light microscopic examination revealed that cytoplasmic changes especially around cells of central vein were observed in cisplatin group. Hepatocellular vacuolization was seen in these cells. In the cisplatin plus erdosteine group, a decrease in cytoplasmic changes with the hepatocytes and sinusoidal dilatations around cells of central vein were noticed in as compared to cisplatin group. In the light of microscopic and biochemical results, it was concluded that cisplatin-induced liver damage in high dose and erdosteine prevented this toxic side effect by the way of its antioxidant and radical scavenging effects. (Mol Cell Biochem 278: 79–84, 2005)     

A simplified in vitro model of oxidant injury using vascular endothelial cells

Summary Oxidant injury of the vascular endothelium is considered an early event in the pathogenesis of atherosclerosis. The model of oxidant injury is crucial to the investigation of antioxidants. In the present study, a convenient in vitro model of oxidant injury induced by hydrogen peroxide (H₂O₂) was developed using bovine pulmonary artery endothelial cells (PAEC). Viability of PAEC grown in 96-well culture plates was determined with methylthiazol tetrazolium (MTT) colorimetric assay. Cell membrane integrity was measured by lactate dehydrogenase (LDH) release from PAEC grown in 24-well plates. Malondialdehyde (MDA, a product of lipid peroxidation) in PAEC grown in 6-well plates was detected by a thiobarbituric acid fluorometric assay. Incubation of H₂O₂ with PAEC caused a dose-dependent decrease of cell viability, an increase of LDH release, and an elevation of MDA production. MTT assay was convenient, quantitative, non-radioactive, and suitable for testing a large number of samples. The fluorometric assay for measuring MDA production in endothelial cells used 6-well plates instead of 80-cm² flasks employed by previous investigators. The use of multiwell culture plates in these assays made it possible for more samples to be tested in any single experiment. The three assays are reproducible with low intraplate and interplate coefficients of variation. This in vitro model is suitable for screening antioxidants and for studying pharmacodynamics at the cellular level.     

Melanin as a Target for Melanoma Chemotherapy: Pro‐oxidant Effect of Oxygen and Metals on Melanoma Viability

Melanoma cells have a poor ability to mediate oxidative stress, which may be attributed to constitutive abnormalities in their melanosomes. We hypothesize that disorganization of the melanosomes will allow chemical targeting of the melanin within. Chemical studies show that under oxidative conditions, synthetic melanins demonstrate increased metal affinity and a susceptibility to redox cycling with oxygen to form reactive oxygen species. The electron paramagnetic resonance (EPR)‐active 5,5′‐dimethyl‐pyrollidine N‐oxide spin adduct was used to show that binding of divalent Zn or Cu to melanin induces a pro‐oxidant response under oxygen, generating superoxide and hydroxyl radicals. A similar pro‐oxidant behaviour is seen in melanoma cell lines under external peroxide stress. Melanoma cultures grown under 95% O₂/5% CO₂ atmospheres show markedly reduced viability as compared with normal melanocytes. Cu‐ and Zn‐dithiocarbamate complexes, which induce passive uptake of the metal ions into cells, show significant antimelanoma activity. The antimelanoma effect of metal‐ and oxygen‐induced stress appears additive rather than synergistic; both treatments are shown to be significantly less toxic to melanocytes.     

Sensitive and selective turn‐on fluorescence method for cetyltrimethylammonium bromide determination based on acridine orange–polystyrene sulfonate complex

This work proposed a rapid and novel fluorescence‐sensing system using a complex of acridine orange (AO) and polystyrene sulfonate (PSS) to sensitively recognize and monitor cetyltrimethylammonium bromide (CTAB) in an aqueous medium. AO can interact with PSS and a complex is formed via electrostatic attraction and hydrophobic interaction. The fluorescence of AO is greatly quenched after the introduction of PSS. Upon its subsequent addition, CTAB can interact and form a complex with PSS because the electrostatic attraction between CTAB and PSS is much stronger than that between AO and PSS, which results in significant fluorescence recovery. Interestingly, the proposed method can be applied for the discrimination and detection of surfactants with different hydrocarbon chain lengths due to their different binding affinity toward PSS. The detection limit for CTAB is as low as 0.2 µg/mL and the linear range is from 0.5 to 3.5 µg/mL. Moreover, we applied the sensor to the successful detection of CTAB in water samples. Copyright © 2015 John Wiley & Sons, Ltd.     

Population dynamics of Daphnia magna as modified by chronic bromide stress

Two chronic toxicity experiments were conducted with Daphnia magna. In a semi-static experiment with cohorts, the no effect level for bromide in respect of the intrinsic rate of natural increase (derived from age-specific survival and fecundity) was 10 mg l^–1. A second test was started with small populations in an intermittent-flow system. These populations had a stable age distribution, were composed of cohorts of different ages, and showed an almost perfect logistic growth. Model calculations showed that bromide reduced the upper numerical limit (carrying capacity). It also increased the time-lag required to attain the maximum reproduction rate. For the first parameter, a no effect level of 14 mg l^–1 was calculated. For the latter a threshold could not be detected. The EC₅₀ and EC₁₀ were 27 and 18 mg l^–1, respectively. Additional experiments showed that individual growth of D. magna in time could also be described by a logistic equation. The age structure of the populations changed when food became limiting. This was parallelled by a reduction of the mean brood size. In conclusion it is stated that the results of the toxicity studies with populations support Halbach's view (1984), that population dynamics can be used like a magnifying glass to detect small sublethal ecotoxicological effects of environmental pollutants.     

Ascorbic acid decreases oxidant stress in endothelial cells caused by the nitroxide tempol

Stable nitroxide radicals have been considered as therapeutic antioxidants because they can scavenge more toxic radicals in biologic systems. However, as radicals they also have the potential to increase oxidant stress in cells and tissues. We studied the extent to which this occurs in cultured EA.hy926 endothelial cells exposed to the nitroxide Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl). Tempol was rapidly reduced by the cells, as manifest by an increase in the ability of the cells to reduce extracellular ferricyanide and by disappearance of the Tempol EPR signal. Cells loaded with ascorbic acid, which directly reacts with Tempol, showed increased rates of Tempol-dependent ferricyanide reduction, and a more rapid loss of the Tempol EPR signal than cells not containing ascorbate. In this process, intracellular ascorbate was oxidized, and was depleted at lower Tempol concentrations than was GSH, another important intracellular low molecular weight antioxidant. Further evidence that Tempol concentrations of 100-1000 μM induced an oxidant stress was that it caused an increase in the oxidation of dihydrofluorescein in cells and inhibited ascorbate transport at concentrations as low as 50-100 μM. The presence of intracellular ascorbate both prevented dihydrofluorescein oxidation and spared GSH from oxidation by Tempol. Such sparing was not observed when GSH was depleted by other mechanisms, indicating that it was likely due to protection against oxidant stress. These results show that whereas Tempol may scavenge other more toxic radicals, care must be taken to ensure that it does not itself induce an oxidant stress, especially with regard to depletion of ascorbic acid.     

海水中苯扎溴铵除藻剂的紫外可见分光光度法测定

Benzalkonium bromide is a high-efficiency algaecide. Its concentration in seawater was measured by the method of spectrophotometer. The results indicated that the deposition appeared if the concentration of benzalkonium bromide in seawater was more than 50mg- L- 1 and affected the detection of benzalkonium bromide. But, there was a good linear relationship between concentration and absorbanee when the concentration was lower than 50mg-L-1 (R2= 0. 9996). Therefore, spectrophotometer could be used to detect benzalkonium bromide in seawater.     

Virucidal activity of cetyltrimethylammonium bromide below the critical micelle concentration

Abstract The virucidal activity of cetyltrimethylammonium bromide (CTAB) was investigated against a variety of different lipid-containing and non-lipid-containing bacterial viruses and 2 mammalian viruses. In all cases, the maximum virucidal effectiveness was obtained under conditions of low ionic strength and moderately basic pH. The virucidal effect is present well below the critical micelle concentration of CTAB, indicating that the initial interaction with viral surfaces is by monomers of CTAB and sodium dodecyl sulfate (SDS) exhibited no virucidal activity.     

Ethidium bromide inhibits rat brain acetylcholinesterase activity in vitro

Ethidium bromide (EtBr), a fluorescent dark red compound and stain for double-stranded DNA and RNA was used to study acetylcholinesterase (AChE) activity in vitro together with kinetic parameters of this enzyme in the striatum (ST), hippocampus (HP), cerebral cortex (CC) and cerebellum (CB) of adult rats. AChE activity in vitro in the ST, HP, CC and CB was significantly reduced (p<0.05) in the presence of EtBr at concentrations of 0.00625, 0.0125, 0.025, 0.05 and 0.1 mM. For the analysis of the kinetic three concentrations of EtBr were tested (0.00625, 0.025 and 0.1 mM). An uncompetitive inhibition type was observed in the ST, HP and CC, whereas in the CB the inhibition type was mixed. These data indicate that EtBr should be considered a strong inhibitor of AChE activity demonstrating that there is an interaction between this compound and the cholinergic system.     

Assay method for the perfluorooctyl bromide (perflubron) in rat blood by gas chromatography–mass spectrometry

This paper describes a GC–MS method (SIM mode) for the analysis of perfluorooctyl bromide (perflubron, I) in rat blood. The chromatographic separation was performed by injection in the split mode using a CP-select 624 CB capillary column. Following destruction of the emulsion by addition of ethanol, the analytical procedure involves a liquid–liquid extraction with 1,1,2-trichlorotrifluoroethane. The bis(F-butyl)ethene (II) was used as internal standard. Observed retention times were 3.22 min for I and 2.32 min for II. Two calibration curves were used; linear detection responses were obtained for concentrations ranging from 0.009 to 0.9 mg/ml and from 0.9 to 13.5 mg/ml. The extraction efficiency averaged 50% for I and 93% for II. Precision ranged from 0.7 to 14%, and accuracy was between 91 and 109%. The limit of quantification was 9 μg/ml. The method validation results indicate that the performance characteristics of the method fulfilled the requirements for assay method for use in pharmacokinetic studies.     

Pro‐oxidant effects of phenothiazine and phenoxazine on erythrocytes in the presence of peroxyl radical

Phenothiazine (PtzNH) and phenoxazine (PozNH) can protect human erythrocytes against hemolysis induced by 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH), a peroxyl radical supplier. However, an antioxidant may be a pro‐oxidant to accelerate the oxidation in the presence of radicals. The aim of this work is to assess whether PtzNH and PozNH have the potential to be pro‐oxidants in AAPH‐induced hemolysis of human erythrocytes. It has been found that high concentrations of PtzNH and PozNH employed were able to initiate hemolysis even in the absence of AAPH. In the presence of AAPH, the period of PtzNH and PozNH to lag hemolysis (t_lag) decreased with the increase in the concentrations of PtzNH and PozNH, implicating that high concentration of PtzNH and PozNH accelerated hemolysis. So, PtzNH and PozNH played pro‐oxidants' role in this case. Furthermore, high concentrations of AAPH employed made the pro‐oxidant effect of PtzNH more remarkable. On the contrary, PozNH played a pro‐oxidant role if only low concentration of AAPH was employed. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:280–286, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20290     

十六烷基三甲基溴化铵对枯草杆菌( B. subtilis )黄嘌呤缺陷型菌株产生腺苷的影响

在枯草杆菌中,嘌呤核柑酸合成途径中丰在AMP和GMP转变成IMP的环行途径,而在该菌的黄嘌呤缺陷型菌株中IMP至XMP的分枝途径被阻塞,同时在该菌株内又有强的5’一核苷酸酶活性,这使其可以生成腺苷（AR）,但反馈抑制是腺苷产率的一个重要影响因素,使用季铵盐阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）可改善细胞的渗透性,减少细胞内产物的反馈抑制,促进产物的分泌,结果表明,在发酵60h添加4％的CTAB能使产率从3．0g/l提高到3．6g/l,提高幅度达20％。     

Effects of ethidium bromide and berenil on protein synthesis

The effects of ethidium bromide, an intercalating dye and berenil, a nonintercalating dye on the biological activities ofEscherichia coli ribosomes have been studied. Ethidium bromide treatment drastically reduced both enzymatic and nonenzymatic initiation complex formation, enzymatic as well as nonenzymatic binding of phenylalanyl tRNA, peptidyl transferase, GTPase as well as the overall protein synthesising activity as measured by the poly U-dependent polymerization of phenylalanine. On berenil treatment, however, only enzymatic formation of the initiation complex is marginally reduced. Other reactions are not markedly affected except the enzymatic phenylalanyl tRNA binding which is slightly decreased only at high Mg²⁺ concentration; the treated ribosome has lowered polymerizing activity at sub-optimal Mg²⁺ concentration (10 mM). Although it has already been shown in this laboratory that treatment with either dye leads to the unfolding of the structure of the ribosome, the present studies indicate that berenil treatment does not alter the structure of the ribosome drastically in contrast to ethidium bromide treatment.     

海洋中溴甲烷的研究进展

溴甲烷是大气中重要的痕量温室气体,对全球变暖和大气化学具有重要作用.海洋在溴甲烷的生物地球化学循环中作用复杂,海洋既是大气溴甲烷的源也是其汇,开展海洋环境中溶存溴甲烷的化学研究,对大气臭氧层的保护工作具有一定的指导意义,也可为在全球尺度上估算海洋环境中溴甲烷对全球环境变化的贡献提供理论依据.本文从溴甲烷的生物地球化学循环、分析测定方法、浓度分布、海-气通量、源汇平衡等方面综述了国内外海洋环境中溴甲烷的研究进展,探讨了目前该领域研究中存在的不足,并对未来的研究进行了展望.