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11.
Hugo P. Montiero Glenn F. Vile Christine C. Winterbourn 《Free radical biology & medicine》1989,6(6):587-591
The cytotoxicity of many xenobiotics is related to their ability to undergo redox reactions and iron dependent free radical reactions. We have measured the ability of a number of redox active compounds to release iron from the cellular iron storage protein, ferritin. Compounds were reduced to their corresponding radicals with xanthine oxidase/hypoxanthine under N2 and the release of Fe2+ was monitored by complexation with ferrozine. Ferritin iron was released by a number of bipyridyl radicals including those derived from diquat and paraquat, the anthracycline radicals of adriamycin, daunorubicin and epirubicin, the semiquinones of anthraquinone-2-sulphonate, 1,5 and 2,6-dihydroxyanthraquinone, 1-hydroxyanthraquinone, purpurin, and plumbagin, and the nitroaromatic radicals of nitrofurantoin and metronidazole. In each case, iron release was more efficient than with an equivalent flux of superoxide. Introduction of air decreased the rate of iron release, presumably because the organic radicals reacted with O2 to form superoxide. In air, iron release was inhibited by superoxide dismutase. Semiquinones of menadione, benzoquinone, duroquinone, anthraquinone 1,5 and 2,6-disulphonate, 1,4 naphthoquinone-2-sulphonate and naphthoquinone, when formed under N2, were unable to release ferrin iron. In air, these systems gave low rates of superoxide dismutase-inhibitible iron release. Of the compounds investigated, those with a single electron reduction potential less than that of ferritin were able to release ferritin iron. 相似文献
12.
Electron spin resonance evidence for the formation of free radicals in plants exposed to ozone 总被引:9,自引:0,他引:9
Electron spin resonance (ESR) spectroscopy was used to demonstrate that free radicals are formed in O3 -fumigated plant leaves prior to the formation of visible leaf injury. ESR signals with a g-value of 2.0037 to 2.0043, were observed in pea ( Pisum sativum L. cv. Feltham first) and bean ( Phaseolus vulgaris L. cv. Pinto) plants that had been fumigated for 4 h with 70–300 nl l−1 of ozone after they had been treated with the spin-trap N- t -butyl-α-phenylnitrone (PBN). The size of the ESR signals increased with the concentration of ozone used but the nature of the trapped radicals could not be identified. However, further experiments using an inhibitor of ethylene biosynthesis, arninoethoxyvinyl glycine (AVG), showed that the reaction between ozone and ethylene is the cause for ozone toxicity. 相似文献
13.
Summary We present a simple model of habitat selection in which individuals differ in their ability to discriminate between resource sites' profitabilities. The model investigates the effects of violating the ideal assumption of the well-known ideal free distribution (IFD). We show that (1) variability in perceptual limits within a population can significantly change the distribution of foraging animals even though the mean perceptual limit is the same, (2) the direction of this change depends on the proportion of the population that choose randomly between resource sites and (3) better perceivers are more likely to be found at individually more profitable sites, which, because of undermatching with respect to the IFD, are also the absolutely more profitable sites. We note that variability in perceptual limits almost always led to an undermatching of organisms to resources, thereby extending previous workers' results implying that the incorporation of any form of perceptual limits leads to undermatching with respect to the IFD. 相似文献
14.
Anthony T.W. Cheung Richard B. Moss Geoffrey Kurland Albin B. Leong William J. Novick 《Journal of medical primatology》1993,22(4):257-262
We have recently established a rhesus monkey model of chronic Pseudomonas aeruginosa (PA) endobronchitis by bronchoscopic instillation of PA-embedded agar beads. All experimental animals developed chronic neutrophilic endobronchitis similar to chronic PA endobronchitis in cystic fibrosis (CF). Histopathologic studies further confirmed similarities to chronic PA endobronchitis in CF, including marked peribronchial inflammation, epithelial damage, presence of degraded cilia and ciliary abnormalities, appearance of PA bacterial clusters, mucosal hyperplasia, goblet cell hypertrophy/hypersecretion, airway obstruction, alveolar abnormalities, bronchiectasis, and fibrosis. 相似文献
15.
The aim of the present study was to separate and characterise products formed by oxidation of uric acid by hydroxyl radicals with a view to probing for these products in vivo in clinical contexts. Aerated solutions of 200 μM uric acid, or its oxidation products, allantoin or parabanic acid, were exposed to gamma radiolysis, (52.0 Gy/min), as a source of HO- radicals, at pH 3.4 and 7.4. Aliquots were taken every 5 minutes for 20 minutes and oxidation products were separated by HPLC and analysed with a diode array detector. Identities of oxidation products were confirmed on the basis of similarity of retention times and absorbance spectra and peak purity parameters of known standards. Hydroperoxides were measured by tri-iodide formation in the 20 minute sample. Exposure of uric acid to such HO fluxes produced a net loss of the parent compound with formation of a complex mixture of products with allantoin and parabanic acid being the predominant products at pH 3.4. The rate of uric acid degradation at physiological pH was slower and the distribution of oxidation products was different. A small but significant amount of uric acid hydroperoxide was detected at both pHs. A mechanism for uric acid oxidation under these conditions is presented. 相似文献
16.
The centennial of the Fenton reaction 总被引:4,自引:0,他引:4
A short account is given of Fenton's life and research, with special emphasis on the Fenton reactions. 相似文献
17.
Substance use disorders (SUDs) are highly prevalent and exact a large toll on individuals’ health, well-being, and social functioning. Long-lasting changes in brain networks involved in reward, executive function, stress reactivity, mood, and self-awareness underlie the intense drive to consume substances and the inability to control this urge in a person who suffers from addiction (moderate or severe SUD). Biological (including genetics and developmental life stages) and social (including adverse childhood experiences) determinants of health are recognized factors that contribute to vulnerability for or resilience against developing a SUD. Consequently, prevention strategies that target social risk factors can improve outcomes and, when deployed in childhood and adolescence, can decrease the risk for these disorders. SUDs are treatable, and evidence of clinically significant benefit exists for medications (in opioid, nicotine and alcohol use disorders), behavioral therapies (in all SUDs), and neuromodulation (in nicotine use disorder). Treatment of SUDs should be considered within the context of a Chronic Care Model, with the intensity of intervention adjusted to the severity of the disorder and with the concomitant treatment of comorbid psychiatric and physical conditions. Involvement of health care providers in detection and management of SUDs, including referral of severe cases to specialized care, offers sustainable models of care that can be further expanded with the use of telehealth. Despite advances in our understanding and management of SUDs, individuals with these conditions continue to be stigmatized and, in some countries, incarcerated, highlighting the need to dismantle policies that perpetuate their criminalization and instead develop policies to ensure support and access to prevention and treatment. 相似文献
18.
Sonodynamic therapy, a promising new approach to cancer treatment, is based on synergistic cell killing by combination of certain drugs (sonosensitizers) and ultrasound. Although the mechanism of sonodynamic action is not understood, the role of free radicals produced from sonosensitizers by ultrasound is implicated. In this work, we studied formation of free radicals during the decomposition of several water-soluble azo compounds by 50 kHz ultrasound in aqueous solutions. Using the spin trap 3, 5-dibromo-4-nitrosobenzene sulfonate (DBNBS) tertiary carbon-centered radicals from 2, 2'-azobis (N,N'-dimethyl-eneisobutyramidine) dihydrochloride (VA-044), 2-(carbamoylazo)-isobutyronitrile (V-30), and 2, 2'-azobis (2-amidinopropane) dihydrochloride (AAPH) and CH3 radicals from 1, 1'-azobis (N,N'-dimethylformamide) (ADMF) were detected in argonsaturated solutions and the corresponding oxygen-centered radicals (alkoxyl and peroxyl) from VA-044, V-30, and AAPH were identified using the spin trap 5, 5'-dimethyl-l-pyrroline-N-oxide (DMPO) in aerated sonicated solutions. No free radicals from 4, 4'-dihydroxyazobenzene-3, 3'-dicarboxylic acid, disodium salt (DHAB) could be found in either system. While VA-044 and AAPH could also be readily decomposed by heat (42.5°C and 80°C), V-30 decomposition only occurred in the ultrasound-exposed solutions. The most likely mechanism of decomposition of azo compounds by ultrasound is their thermolysis in the heated shell of the liquid surrounding ca vita ting bubbles driven by ultrasound and/or by pyrolysis inside these bubbles. Experiments using scavengers of ·OH and ·H, which are produced by sonolysis in aqueous solutions, demonstrated that these radicals are not involved in the ultrasound-mediated radical production from the azo compounds. Due to the known cytotoxic potential of free radicals produced from azo compounds, the use of these compounds as ultrasound sensitizers appears to be a promising approach for sonodynamic cell killing. 相似文献
19.
20.
Richard L. Atkinson Roy C. Blank Donald Schumacher Nikhil V. Dhurandhar Douglas L. Ritch Eric Chan Thomas S. Rieg 《Obesity (Silver Spring, Md.)》1997,5(6):578-586
ATKINSON, RICHARD L, ROY C BLANK, DONALD SCHUMACHER, NIKHIL V DHURANDHAR, DOUGLAS L RITCH. Long-term drug treatment of obesity in a private practice setting. This study evaluated the long-term efficacy and safety of the combination of phentermine and fenfluramine for the treatment of obesity in a private practice setting. A total of 1388 consecutive, qualified patients presenting to a private general internal medicine practice in Charlotte, NC, were enrolled with eligibility criteria including: age 18 years to 60 years, 20% over “desirable” bodyweight or body mass index <27, no serious medical or psychiatric disease, and no contraindications to drug therapy. Patients were instructed in diet, exercise, and behavior modification techniques and received phentermine (15 mg/day to 30 mg/day) and fenfluramine (20 mg/day to 60 mg/day) continuously for over 3 years. Average duration of treatment was 15. 9 months, and average weight loss at the last visit was 11. 6 kg, or 11. 7% of initial bodyweight. For patients completing 1 year of drug treatment, mean weight loss was 16. 5 kg, or 16% of initial weight. Weight loss persisted for 2 years, but partial regain was seen at 3 years. The dropout rates were 18% at 6 months, 39% at 1 year, 68% at 2 years, and 78% at 3 years. At 1 year, blood pressure of hypertensive patients fell from 151/95 mm Hg to 127/78 mm Hg, and serum cholesterol and triglycerides of hyperlipidemic patients fell by 0. 750 mmol/L (29 mg/dL) and 0. 937 mmol/L (83 mg/dL), respectively. Adverse events were modest. We conclude that, in a private practice setting, long-term treatment of obesity with the combination of phentermine, fenfluramine, and a weight maintenance program is generally safe and effective. More research is needed to determine efficacy and safety for longer than 3 years. 相似文献