摘要:

In BHK-21 cells (baby hamster kidney fibroblasts) cellularly generated active oxygen species such as hydrogen peroxide and superoxide appear to be important growth regulatory signals as judged from the growth inhibitory effects of catalase, superoxide dismutase and superoxide dismutase mimics. These active oxygen species may contribute a novel redox system of regulatory control superimposed upon established growth signal pathways. This may be achieved by direct oxidative modification of cell regulatory proteins such as transcription factors or protein kinases or indirectly through, for example alterations in levels of glutathione (GSH). This latter possibility is suggested from observations that catalase, or superoxide dismutase treatment of BHK-21 cells brings about increased cellular levels of GSH. However during the normal growth phase cellular levels of GSH actually decline although this effect can be partly reversed by N-acetylcysteine and by mercaptosuccinate which also impair proliferation of these cells.

ISSN:1071-5762    

DOI:10.3109/10715769409056564

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Human erythrocytes suspended in plasma, or in phosphate buffered saline (PBS), were exposed to ionizing radiation. Potassium leakage from irradiated erythrocytes is significantly higher in PBS than in plasma. The potassium leakage decreases when PBS is gradually replaced by plasma. These findings suggest that some of the plasma constituents have radioprotective properties. The potassium leakage per cell is independent of the hematocrit, Hct. The potassium leakage is attributed to the formation of radiation defects in the membrane. Analysis of the effect of radiation dose, plasma and cell concentrations on the product of the number and surface area of the radiation defects indicates that the radiation damage is mainly due to the direct formation of free radicals in the cell membrane. The radioprotective effect of plasma is attributed to surface reactions of these free radicals with plasma constituents adsorbed on the membrane.

ISSN:1071-5762    

DOI:10.3109/10715769409056565

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

E.P.R. spin trapping has been employed to study radical production during the bactericidal action of three peroxide compounds (peracetic acid, 4-percarboxy-N-isobutyltrimellitimide and magnesium monoperoxyphthalate) upon both Gram negative (Escherichia Coll) and Gram positive (Staphylococcus Aureus) bacteria. Use of the spin trap 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) has allowed direct detection of both carbon-centred and hydroxyl radicals, which are produced at varying rates for the different bacteria/peracid systems studied. The inhibition of bactericidal action, by DMPO and two antioxidants, Vitamin C and Trolox C, indicates that radicals are the lethal species and evidence is presented which suggests that radical production is internal to the bacterial cell. Hydroxyl radicals are believed to be the lethal species. The effect of added iron chelators and haem protein inhibitors indicates that iron species and haem proteins in particular are involved. A marked variation is found in observed hydroxyl-radical adduct signals with both the nature and concentration of peracid. A strong inverse correlation is found between the concentration of the observed radical adduct signal and the relative strength of the peroxide as a bactericide; use of a stable nitroxide as a radical scavenger confirms that strong bactericides produce radicals at a much faster rate than weak bactericides. Plots of radical generation versus time are correlated with % bacterial kill, offering further evidence that hydroxyl radicals are the lethal species.

ISSN:1071-5762    

DOI:10.3109/10715769409056566

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The reduction of nitroxide free radicals was investigated in detail by Electron Paramagnetic Resonance (EPR) spectroscopy in perfused liver. The nitroxide free radical was rapidly reduced to the corresponding hydroxylamine more efficiently at the lower flow rate of 8 [ml/min], while at higher flow rates, the amount of reduced nitroxide showed a significant decrease. Oxidation of hydroxylamine using hydrogen peroxide provided dynamic information concerning the reduction of the free radical within the liver. In addition, liver homogenates were also investigated to determine the level of nitroxide uptake. The results suggested that a portion of the infused nitroxide was taken up by the liver and cleared from the circulation.

ISSN:1071-5762    

DOI:10.3109/10715769409056567

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Superoxide scavenging activities (SSA) of newly synthesized spin-labeled nitrosourea and triazene derivatives, and their precursor nitroxides were investigated by the ESR/spin-trapping method using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and hypoxanthine/xanthine oxidase as the superoxide-generating system. The spin-labeled nitrosoureas, triazenes and their precursor nitroxides exhibited excellent SSA, whereas clinically used nitrosourea and triazene, which do not contain the nitroxide moiety, did not show any SSA. Furthermore, it was deduced that these nitroxides scavenge superoxide by redox cycling between nitroxide and corresponding hydroxylamine.

ISSN:1071-5762    

DOI:10.3109/10715769409056568

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The synthetic oestrogens diethylstilboestrol, hexoestrol and 17α-ethynyloestradiol are known to be good antioxidants, and we now report that they decrease membrane fluidity, in ox-brain phospholipid liposomes. The order of effectiveness was diethylstilboestrol>hexoestrol>17α-ethynyloestradiol and a good positive correlation was demonstrated between decreased membrane fluidity and antioxidant ability (measured as inhibition of liposomal lipid peroxidation: correlation coefficient,r= 0.99). This ability of diethylstilboestrol, hexoestrol and 17α-ethynyloestradiol to decrease membrane fluidity is suggested, therefore, to be the mechanism of their antioxidant action. The membrane-modulating antioxidant action of these synthetic oestrogens is compared to that of tamoxifen and their potential use as anticancer and cardioprotective agents is discussed.

ISSN:1071-5762    

DOI:10.3109/10715769409056569

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

ISSN:1071-5762    

DOI:10.3109/10715769409056570

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor