摘要:

Iron nitrosyl haemoglobin (HbFeNO) gives well defined ESR spectra, and can be detected at room temperature, in contrast with most transition metal complexes of biological importance. This is because the unpaired electron remains strongly localised on the NO ligand. It is of importance because it proves the formation of nitric oxide, which unfortunately cannot be detected directly by ESR spectroscopy. We have studied a range of tissues taken from human liver, colon and stomach tumours which have been directly frozen to 77K and studied at 77K. The results show that formation of HbFeNO is rare in tissue adjacent to tumour tissue (“peripheral tissue”), but is always found in necrotic central regions, if present. However, in several cases, HbFeNO was also detected in tumour tissue which was not necrotic. Two factors contribute to the formation of this complex. One is the presence of“free”NO molecules in the cellular regions, and the other is the presence of deoxyferrohaemoglobin, since neither ferrihaemoglobin nor oxyhaemoglobin react to give this complex. [For systems containing myoglobin these comments include the possibility of the formation of nitrosylmyoglobin, which gives very similar ESR spectra.]

ISSN:1071-5762    

DOI:10.3109/10715769409056571

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The effects of nitric oxide (NO) on xanthine oxidase (XOD) activity and the site(s) of the redox center(s) affected were investigated. XOD activity was determined by superoxide (O2−) generation and uric acid formation. NO reversibly and dose-dependently suppressed XOD activity in both determination methods. The suppression interval also disclosed a dose-dependent prolongation. The suppression occurred irrespective of the presence or absence of xanthine; indicating that the reaction product of NO and O2−, peroxynitrite, is not responsible for the suppression. Application of synthesized peroxynitrite did not affect XOD activity up to 2μM. Methylene blue, which is an electron acceptor from Fe/S center, prevented the NO-induced inactivation. The results indicate that NO suppresses XOD activity through reversible alteration of the flavin prosthetic site.

ISSN:1071-5762    

DOI:10.3109/10715769409056572

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Metabolism of ethanol to 1-hydroxyethyl radicals by rat liver microsomes was studied with three nitrone spin trapping agents (POBN, PBN, and DMPO) under essentially comparable conditions. The data indicate that POBN was the superior spin trapping agent for 1-hydroxyethyl radicals, and that DMPO was least efficient. Addition of deferoxamine completely prevented detection of 1-hydroxyethyl radicals with PBN or DMPO, but caused only 50% decrease in EPR signals when POBN was the spin trap. However, superoxide dismutase only decreased 1-hydroxyethyl radical formation when POBN was the spin trap. Other experiments demonstrated that POBN was the most effective of these nitrones for reduction of Fe(III) in aqueous solutions. Furthermore, 1-hydroxyethyl radical adducts were formed when POBN was added to mixtures of ethanol, phosphate buffer, POBN and FeCl3, but this effect did not occur with either PBN or DMPO. Thus, these data indicate that undesirable effects of POBN on iron chemistry may influence results of spin trapping experiments, and complicate interpretation of the resulting data.

ISSN:1071-5762    

DOI:10.3109/10715769409056573

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Mouse liver mitochondria were uncoupled in a time dependent by intraperitoneal injection of a radical initiator, 2,2′-azobis-(2-amidinopropane) dihydrochloride (AAPH) (100mg/kg). State 3 respiration, ADP/O ratio and respiratory control ratio (RCR) were decreased 30 min after injection but there was no effect on state 4 respiration. Lipid peroxidation was increased and oxidative phosphorylation was uncoupled at one hr after drug injection but gradually recovered to normal levels after 14 hrin vivo. State 3 respiration, RCR and ADP/O ratio but not state 4 respiration of isolated mouse mitochondria were inhibited by short term incubation with AAPHin vitro. This inhibitory action was concentration dependent (ID50 = 5 mM) but was not prevented byα-tocopherol. AAPH had no effect on electron transport or the membrane potential of these isolated mitochondria. However, mitochondria were uncoupled via lipid peroxidation and swelling by long term incubation with AAPH. These inhibitory effects of AAPH were reduced by its spontaneous degradation not onlyin vitrobut alsoin vivo. Thus AAPH induces mitochondrial dysfunction by direct action in the early period of treatment and free radicals produced from AAPH mediate mitochondrial swelling via lipid peroxidation in the late period. From these findings, it is concluded that mitochondrial phosphorylation plays an important role in the pathogenesis of liver injury induced by AAPH and that radicals generated by AAPH might be a source of liver injury and mitochondrial dysfunctionin vivo.

ISSN:1071-5762    

DOI:10.3109/10715769409056574

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Thein vitroformation of phenylhydronitroxide and 2-methylphenylhydronitroxide free radicals from nitrosobenzene (NB) and 2-nitrosotoluene (NT), respectively, in either red blood cells (RBC) or RBC hemolysates, was confirmed by electron spin resonance spectroscopy (ESR). Free radicals were generated nonenzymatically from reaction of the respective nitroso compounds with a number of biological reducing agents as corroborated by model studies of NB or NT with NAD(P)H. Under aerobic conditions, phenylhydronitroxide and 2-methylphenylhydronitroxide underwent a subsequent one-electron transfer to oxygen, which then resulted in the formation of superoxide anion (O2−). The latter product was confirmed by the superoxide dismutase (SOD)-inhibitable reduction of cytochrome c (cyt c). Apparently, oxygen is needed for continuous formation of the hydronitroxide radical derivatives. On the other hand, under anaerobic conditions, no phenylhydronitroxide radical was generated from NB in the presence of NADH, but the formation of phenylhydroxylamine from NB was detected by the absorption spectrometry. These results suggest that oxygen is a preferential electron acceptor for hydronitroxide radical derivatives.

ISSN:1071-5762    

DOI:10.3109/10715769409056575

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Carnosic acid, an antioxidant extracted from rosemary, is shown to produce radicals when in contact with oxidized methyl oleate in the absence of air above 50°C. Two radical species are formed: the first one, stable up to−110°C, is an hydroxy-phenoxy radical whose ESR spectrum was analyzed by studying its temperature dependence and its sensitivity to deuterium/proton exchange. The second species was observed above 110°C, its ESR spectrum was identical to the spectrum obtained when carnosol, another antioxidant extracted from rosemary, was heated at the same temperature in the presence of oxidized lipid. This observation is probably due to the transformation of carnosic acid into carnosol; the analysis of the corresponding ESR spectrum suggests the formation of a keto phenoxy radical exhibiting a great delocalization of the unpaired electron.

ISSN:1071-5762    

DOI:10.3109/10715769409056576

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Diet and Heart Disease: A round table of factorsEdited by M. AshwellBritish Nutrition Foundation: London, 1993, pp. 3–63. ISBN 0907667082. $13.50.Excited States and Free Radicals in Biology and MedicineContributions from flash photolysis and pulse radiolysis Edited by R.V. Bensasson, E.J. Land and T.G. Truscott. pp 431.Oxidative Stress, Cell Activation and Viral InfectionEdited by C. Pasquier, R.Y. Olivier, C. Auclair and L. PackerBirkhäuser Verlag, Basel, 1994

ISSN:1071-5762    

DOI:10.3109/10715769409056577

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

ISSN:1071-5762    

DOI:10.3109/10715769409056578

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor