The formation of free radicals and the consequences of their reactions in vivo

Immunogenic and antigenic epitopes of immunoglobulin--XX. Denaturation of human IgG3 by free radicals

It has previously been demonstrated that exposure of polyclonal IgG to free radicals results in denaturation evidenced by aggregation, auto-fluorescence and destruction of cysteine, proline and aromatic amino acids. In the present study we have used a panel of monoclonal antibodies (McAb) to epitopes expressed on the IgG3 heavy chain to detect changes in antigenicity. When IgG3 was exposed to u.v. irradiation, as a source of free radicals, subclass specific epitopes were rapidly lost whilst other epitopes were unaffected. Prolonged exposure resulted in further denaturation and a progressive loss of expression of further epitopes. The IgG3 subclass specific McAb are specific to epitopes localized to the hinge region of IgG3. Thus, this exposed cysteine and proline rich region is shown to be particularly vulnerable to free radical attack; however, prolonged exposure results in structural alterations throughout the heavy chain.

Treatment of cartilage proteoglycan aggregate with hydrogen peroxide. Relationship between observed degradation products and those that occur naturally during aging

The effects of treatment of purified neonatal human articular-cartilage proteoglycan aggregate with H2O2 were studied. (1) Exposure of proteoglycan aggregate to H2O2 resulted in depolymerization of the aggregate and modification of the core protein of both the proteoglycan subunits and the link proteins. (2) Treatment of the proteoglycan aggregate with H2O2 rendered the proteoglycan subunits unable to interact with hyaluronic acid, with minimal change in their hydrodynamic size. (3) Specific cleavages of the neonatal link proteins occurred. The order in which the major products were generated and their electrophoretic mobilities resembled the pattern observed during human aging. (4) The proteolytic changes in the link proteins were inhibited in the presence of transition-metal-ion chelators, thiourea or tetramethylurea, suggesting that generation of hydroxyl radicals from H2O2 by trace transition-metal ions via a site-specific Fenton reaction may be responsible for the selective cleavages observed. (5) Cleavage of the link proteins in proteoglycan aggregates by H2O2 was shown to have a limited effect on the susceptibility of these proteins to cleavage by trypsin. (6) The relationship between these changes and those observed in cartilage during human aging suggests that some of the age-related changes in the structure of human cartilage proteoglycan aggregate may be the result of radical-mediated damage.

In vivo ethane production in vitamin E-deficient rats with DMH-induced colon cancer

The effect of both a vitamin E-deficient and a high polyunsaturated fat (PUFA) diet was tested on rats injected with the colon carcinogen 1,2-dimethylhydrazine (DMH). In vivo lipid peroxidation was monitored by measuring exhaled ethane from the animals. Higher mean weights were found in animals fed high PUFA and vitamin E-sufficient diets. There was no difference in ethane exhalation between DMH-treated and control animals regardless of diet. Mean ethane exhalation was highest in animals fed either vitamin E-deficient or high PUFA diets. There was no difference in tumor formation between the vitamin E-deficient and the vitamin E-sufficient groups. The high PUFA groups had more tumors than the low PUFA groups. Diet was shown to be the major factor affecting ethane exhalation. There was no evidence that vitamin E-deficiency promoted DMH-induced tumors or that DMH caused increased lipid peroxidation.

Induction and inactivation of catalase and superoxide dismutase of Escherichia coli by ozone

Oxyradicals have been implicated in ozone (O3) toxicity and in other oxidant stress. In this study, we investigated the effects of O3 on the biosynthesis of the antioxidant enzymes catalase and superoxide dismutase in Escherichia coli to determine their role in the defense against ozone toxicity. Inhibition of growth and loss of viability were observed in cultures exposed to ozone. Results also showed an increase in the activities of catalase and superoxide dismutase in cultures exposed to ozone, which was shown to be due to true induction rather than activation of preexisting apoproteins. Cessation of O3 exposure resulted in 30 min of continual high rate of catalase biosynthesis followed by a gradual decrease in the level of the enzyme approaching that of control cultures. This decrease was attributed to a concomitant cessation of de novo enzyme synthesis and dilution of preexisting enzyme by cellular growth. Ozonation of cell-free extracts showed that superoxide dismutase and catalase are subject to oxidative inactivation by ozone. In vivo induction of these enzymes may represent an adaptive response evolved to protect cells against ozone toxicity.

Secondary products of lipid oxidation

In the last decade, a multitude of secondary products have been identified from the radical and photosensitized oxidations of polyunsaturated lipids. These secondary products consist of oxygenated monomeric materials including epoxy-hydroperoxides, oxo-hydroperoxides, hydroperoxy epidioxides, dihydroperoxides, hydroperoxy bis-epidioxides, and hydroperoxy bicycloendoperoxides. More recently, higher molecular weight dimeric compounds have been identified from autoxidized methyl linoleate and linolenate. Decomposition of these oxidation products form a wide range of carbonyl compounds, hydrocarbons, furans, and other materials that contribute to the flavor deterioration of foods and that are implicated in biological oxidation. The interaction of some of these degradation products with DNA may be involved in cell-damaging reactions.

Enzymatic activities in the iris-ciliary body of the rabbit eye during experimentally induced acute ocular inflammation

Intravitreal injection of 5 micrograms of Shigella endotoxin, in the rabbit eye, induced an acute inflammatory response which was characterised by conjunctival hyperaemia, limbal and ciliary vascular injection, iritis, aqueous flare, miosis and reduction in intraocular pressure. Iris-ciliary body tissues, from normal and inflamed eyes, were fractionated into subcellular enriched fractions and the activities and distribution of selected enzymes were estimated. Alkaline phosphatase, a plasma membrane-bound enzyme, showed an increase in activity, whereas succinate dehydrogenase and Mn-Superoxide dismutase, both mitochondrial-bound enzymes, exhibited decreased activities. Lysosomal acid phosphatase displayed an increase in free activity and retention of latent activity inside the organelle. No alteration in free activity was shown by acid cathepsin. The cholinesterases did not exhibit any changes in activities nor did the cytosolic enzymes Cu/Zn-superoxide dismutase and lactate dehydrogenase. The decrease activity of the respiratory mitochondrial enzyme succinate dehydrogenase may contribute to the reduction in intraocular pressure, and the ability of the lysosomal organelles to retain their hydrolytic enzymes, ensures recovery of the cell from acute inflammatory attack.

Ultrastructural alteration in the rat liver produced by benzyl viologen

This report presents qualitative data of the effects of a free radical generator (benzyl viologen) on rat liver. Rats were administered benzyl viologen (0.825 mg per kg of body weight) or saline solution (controls) intraperitoneally, in single daily dosage for 15 days. For microscopic examination animals were killed after 3 or 15 days of treatment. In the control animals, liver ultrastructure remained normal throughout the experiment. But in rats with benzyl viologen it was possible to observe important morphological alterations essentially in mitochondria, frequently forming ring-like bodies. Endoplasmic reticulum was observed as concentric patterns which cover the mitochondria and, on occasion, the lipid droplets within the cell. Increased number of dense granular lysosomes were observed in the apical cytoplasm mainly close to the bile canaliculus. A large quantity of lipid inclusions and cellular degeneration of the liver of treated rats showed a marked dose-response relationship.

Bone healing following irradiation during tourniquet ischaemia

The bone harvest chamber (BHC) methodology, a titanium implant for quantitative evaluations of bone healing, was used in order to investigate the radioprotective function of anoxia, in healing bone tissue. After incorporation of one BHC in each proximal tibial metaphysis of a rabbit it was possible to collect newly formed bone specimens in 3-week-periods without animal sacrifice. The amount of bone was determined by microradiography and densitometry. Ten animals divided into 2 groups were used. One group receiving a single dose of 25 Gy during tourniquet ischaemia was compared with another receiving the same dose during normal blood perfusion. A significantly improved bone healing response was seen in the ischaemic group, with a tendency to further improvement with increasing time after irradiation.

Mutagenic and cytotoxic effects of oxygen free radicals generated by methylviologen (paraquat) on Escherichia coli with different DNA-repair capacities

Investigations were carried out to examine the mutagenic and cytotoxic effects of oxygen free radicals on E. coli. E. coli B strains with different DNA-repair capacities were exposed to methyl viologen, commonly called paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride, MV), which has been shown to act as an intracellular generator of superoxide radicals. The results obtained were as follows: The cytotoxicity of MV in E. coli was dioxygen-dependent and due to the extent of intracellular generation of superoxide radicals. Cells containing higher levels of superoxide dismutase were more resistant to the toxic effect of MV. The cytotoxicity of MV was greater in DNA repair-deficient E. coli, Bs-1(exrA uvrB), NG30(recA) and R15(polA), than in DNA-repair-proficient strains (B/r and H/r30) and Hs30 (uvrB). MV was found to be mutagenic to E. coli H/r30 and Hs30 under aerobic conditions. The mutation frequencies to streptomycin resistance and to arginine prototrophy increased with the dose of MV in both strains. However, E. coli NG30 was unmutable by MV. The mutation induction did not occur under anaerobic conditions. The expression of the umu operon in E. coli was induced by MV under aerobic conditions. From these results, it was concluded that superoxide radicals intracellularly generated by MV include DNA damage, which causes cytotoxicity and mutation induction in E. coli, and that DNA damage induced by oxygen radicals is repairable by at least recA, polA and exrA(lexA) gene-controlled mechanisms.

Lipid peroxidation in cataract of the human

Lipid peroxidation was investigated as one of the possible mechanisms of cataractogenesis in the human. Malondialdehyde (MDA), a major breakdown product of lipid peroxides, was significantly higher in cataractous lenses as compared to that in normal lenses. 2-Thiobarbituric acid-reactive material, isolated from cortical cataracts and purified by Sephadex G-10 column chromatography, was identified as MDA. In cataractous lenses the enzymic defenses against reactive species of O2 were impaired as evidenced by the significant decrease in activities of superoxide dismutase, catalase and glutathione peroxidase. Hydrogen peroxide in aqueous humor and vitreous humor of human eyes associated with cataract was increased 2-3 fold. It is possible that carbonyl groups of MDA could interact with primary amino groups of proteins and phospholipids of lenticular plasmalemmae by a cross-linking reaction forming Schiff-base conjugates and these mechanisms might be involved in the pathogenesis of cataract.

Manganese: its acquisition by and function in the lactic acid bacteria

The transition metal manganese is considered to be a minor micronutrient in both pro- and eukaryotes, usually being required from the environment at subnanomolar levels. Until recently, Mn was only known to function in cells as a cofactor for a few enzymatic reactions. A notable exception has been reported in many lactic acid bacterial species which require micromolar medium Mn levels for growth and contain up to 35 mM Mn. These high Mn concentrations are accompanied by the near or complete absence of intracellular iron and superoxide dismutase (SOD). Lacking hemes, Lactobacillus plantarum and related species contain a unique Mn-cofactored catalase as well as millimolar Mn(II) in a nonenzymic complex performing the function of the micromolar superoxide dismutase found in most other aerotolerant cells. The high Mn(II) levels are accumulated via an efficient active transport system and are stored intracellularly in a high molecular weight complex. Study of Lactobacillus plantarum has provided an interesting example of the substitution of Mn for Fe in several of the biological roles of Fe, an alternative mechanism of aerotolerance, and a better understanding of the unique biochemistry of the lactic acid bacteria.

Self-perpetuating mechanisms of immunoglobulin G aggregation in rheumatoid inflammation

When human IgG is exposed to free radical generating systems such as ultraviolet irradiation, peroxidizing lipids, or activated human neutrophils, characteristic auto-fluorescent monomeric and polymeric IgG is formed (excitation [Ex], 360 nm, emission [Em], 454 nm). 1 h ultraviolet irradiation of IgG results in the following reductions in constituent amino acids; cysteine (37.0%), tryptophan (17.0%), tyrosine (10.5%), and lysine (3.6%). The fluorescent IgG complexes, when produced in vitro, can stimulate the release of superoxide from normal human neutrophils. In the presence of excess unaltered IgG, further fluorescent damage to IgG occurs. Measurement and isolation of fluorescent monomeric and polymeric IgG by high performance liquid chromatography, from in vitro systems and from fresh rheumatoid sera and synovial fluid, indicates that identical complexes are present in vivo; all these fluorescent complexes share the property of enhancing free radical production from neutrophils. The results described in this study support the hypothesis that fluorescent monomeric and aggregated IgG may be formed in vivo by oxygen-centered free radicals derived from neutrophils, and that in rheumatoid inflammation this reaction may be self-perpetuating within the inflamed joint.

Changes in oxygen-metabolizing enzymes and lipid peroxidation in human erythrocytes as a function of age of donor

We have studied the activities of enzymes, which afford protection against superoxide radical anion and hydrogen peroxide and estimated the content of malondialdehyde. Superoxide dismutase activity decreased slightly with advanced age of donors. The activities of catalase and peroxidases were higher in the erythrocytes of the middle age group and the old age group than in the young individuals. Thiobarbituric acid-reactive product was also significantly elevated in the aged donors. These results support the hypothesis that observed differences in the activities of enzymes and the level of malondialdehyde may contribute to the changes associated with aging, produced by the free radical reactions.

Impaired phagocytic activity of neutrophils in patients receiving haemodialysis: the critical role of iron overload

The metabolic burst (as measured by the spontaneous and stimulated nitroblue tetrazolium tests), the phagocytosis of heat inactivated bakers' yeast and of Staphylococcus aureus, the killing of Staph aureus, and the myeloperoxidase activity of polymorphonuclear neutrophils were studied in 11 patients receiving maintenance haemodialysis. Of these patients, six were polytransfused and had high serum ferritin concentrations (mean 5940 (SD 2925) micrograms/l; group 1), and five had normal serum ferritin values (mean 171 (116) micrograms/l; group 2). Patients in group 1 had a history of more infectious episodes (0.167 v 0.025 per patient per month) and significantly more genitourinary infections (p = 0.015) than those in group 2. Phagocytosis and myeloperoxidase activity were severely reduced in group 1 but normal in group 2. Percentages of neutrophils ingesting one or more particles together with the index of phagocytosis in patients' serum were inversely correlated with serum ferritin concentrations. Four patients in group 1 were treated with desferrioxamine, and after six to 18 weeks of treatment phagocytosis and myeloperoxidase activity had returned to normal in three of them. These data suggest that in patients receiving haemodialysis iron overload due to multiple transfusions plays an important part in the mechanisms underlying the susceptibility to bacterial infections, mediated at least partially through impaired neutrophil function.

Alteration of alveolar surfactant function after exposure to oxidative stress and to oxygenated and native arachidonic acid in vitro

Alveolar surfactant is known to be impaired after inhalation of various oxidizing agents (NO2, ozone) as well as in inflammatory lung processes, in which leucocyte-derived active oxygen species or arachidonic acid oxygenation products may be involved. The effect of lipid peroxidation, oxygen-free radicals and oxygenated versus native arachidonic acid on the surface tension behaviour of natural surfactant was tested in vitro. The studies were performed on pooled surfactant material, obtained from bronchoalveolar lavage of rabbit lungs, in a Langmuir trough/Wilhelmy balance system. Initiation of lipid peroxidation with FeCl3/ascorbate or UV radiation and the generation of OH.(FeCl2/EDTA/H2O2), O2-. (xanthine/xanthine oxidase) and 1O2 (NaOCl/H2O2) provoked a common profile of changes: delayed reduction of surface tension during compression with an increase in minimal compressibility accelerated decrease of film pressure during expansion, reduction of hysteresis area and markedly augmented monolayer collapse rate. Addition of arachidonic acid resulted in decreased minimal compressibility, stability index and hysteresis area. Incubation with the arachidonic acid cyclooxygenase products, prostaglandin E2, I2, F2 alpha or thromboxane B2, with soybean lipoxygenase or with H2O2 and O2-exposure caused only moderate or no alteration of surfactant behaviour in vitro.

CONCLUSION

oxidative stress, but not arachidonic acid oxygenation products, provoked altered surface tension behaviour of natural surfactant in vitro.

Mutation induction in Escherichia coli incubated in the reaction mixture of NADPH-dependent lipid peroxidation of rat-liver microsomes

Experiments were carried out to examine mutation induction in E. coli cells incubated in the reaction mixture of NADPH-dependent lipid peroxidation of microsomes isolated from rat liver. The results obtained were as follows: (1) Lipid peroxidation of microsomes occurred extensively on incubation with NADPH and Fe2+. In the E. coli WP2uvrA(pKM101) system, the mutation frequency to streptomycin resistance increased markedly when the cells were incubated in the reaction mixture of microsomal lipid peroxidation. The induced mutation frequencies were dependent on the extent of the lipid peroxidation. (2) It was also found that the mutations were induced at the same rate as in the case of (1) when the cells were added to the microsomal suspensions after the reactions due to the short-lived free radicals had terminated. (3) The cytotoxicity of the lipid peroxidation products was larger in the DNA repair-defective mutant, E. coli SR18 (uvrArecA) than the wild-type strain, SR749. From these results it is concluded that some DNA-damaging and mutagenic substances are indeed produced in the degradation process of peroxidized polyunsaturated fatty acids in liver microsomal lipids.

Microspectrofluorometry of fluorescent photoproducts in photosensitized cells. Relationship to cellular quiescence and senescence in culture

Microspectrofluorometry of L and WI-38 cells reveals chemical/structural changes due to quiescence or senescence, i.e., lipid peroxidation, spontaneous or photosensitized by hematoporphyrin. Cells treated with hematoporphyrin and a lysosomal umbelliferone probe show a fast-rising umbelliferone emission, plus a fluorescent photoproduct. Studies in rapidly growing versus quiescent L, early passage/late passage WI-38 cells, suggest accumulation of fluorescence Schiff bases (i.e., their association with granular regions of cells in stationary phase, spectral properties, fast increase in photosensitized cells) and a possible lysosomal membrane permeabilization in quiescent or senescent cells.

Chemiluminescence in hypoxic brain--the first report. Correlation between energy metabolism and free radical reaction

The possibility that cerebral ischemia or cerebral hypoxia may initiate a series of free radical reactions in brain tissue lipid constituents was explored by measuring sequential changes in chemiluminescence values and energy metabolism during brain hypoxia in the rat. Brain hypoxia was induced by means of arterial hypoxemia (PaO2 17-22 mmHg), normocapnia (PaCO2 28-38 mmHg) and normotension (MABP 100-140 mmHg). To obtain lowered PaO2, 4% O2--96% N2 mixed gas was used. Analysis of the chemiluminescence spectra for the purpose of luminous mechanism investigation was again attempted. No peroxidation occurred in the pre-hypoxic state since there were no photon counts. Chemiluminescence began to rise in the hypoxic state and remained at a high value in the post-hypoxic state. Specifically in the hypoxic state, the 3 min period showed 231 +/- 35 counts/10 sec X g (n = 5) and the 5 min period showed 154 +/- 62 (n = 19) counts/10 sec X g. In the post-hypoxic state, the 5 min period showed 217 +/- 79 counts/10 sec X g (n = 9) and the 30 min period showed a decrease similar to the pre-hypoxic state. The chemiluminescence spectroanalysis showed five peaks in wavelength at 480 nm, 520-530 nm, 570 nm, 620-640 nm and 680-700 nm. Sequential changes in energy metabolism revealed that hypoxia caused marked brain lactic acidosis, an increase in both ADP and pyruvate, and a fall in glucose. However, all metabolites recovered at 30 min in the post-hypoxic state, which suggests this was reversible brain hypoxia. Sequential changes in chemiluminescence values and energy metabolism imply the occurrence of free radical reaction in the hypoxic and post-hypoxic brain. The spectroanalysis reveals the luminous mechanism as follows: 1 delta g + 1 delta g----23O2 + h mu

Effect of dietary 2-mercaptoethanol on the life span, immune system, tumor incidence and lipid peroxidation damage in spleen lymphocytes of aging BC3F1 mice

The age-related decline in immune function, which is thought to be responsible for the increased incidence with age of certain diseases, including cancer, has been attributed primarily to a loss of T-lymphocyte function. As free radical reactions may contribute to cellular deterioration and loss of cell function with age, we investigated the effect of adding an immunopotentiating antioxidant, 2-mercaptoethanol (2-ME), to the diet of BC3F1 mice in a longitudinal study. For the study, young mice were divided into two groups, one of which received the 2-ME-supplemented diet. Approximately every 3 months for 2.5 years, mice from each group were sacrificed and the spleen lymphocytes assessed for immune function (proliferative response to concanavalin A, phytohemagglutinin, and lipopolysaccharide and the humoral response to sheep red blood cells). The accumulation of fluorescent products indicative of free radical damage was measured in the spleen lymphocytes and the cytochrome P-450 content and activity assessed in the liver. The effect of the 2-ME-supplemented diet on the mean and maximum life span and tumor incidence was also determined. The results showed that the animals fed the 2-ME diet had an increased mean and maximum life span and a postponed onset and decreased incidence of tumors. In general the T-cell-dependent immune responses were higher in the 2-ME-fed mice compared to the controls when the animals were young. No difference was observed between the two groups during mid-life. The responses declined in both groups during the latter half of the life span, but the responses of the 2-ME-fed animals declined to a lesser extent. The accumulation of fluorescent products of lipid peroxidation damage was also delayed in the lymphocytes of the 2-ME-fed mice. Cytochrome P-450 content and activity in the liver was not different in the two groups. The results suggest that the antioxidant activity of 2-ME delayed the accumulation of free radical damage in spleen lymphocytes, which resulted in a delay in the decline of immune function and was associated with the decreased tumor incidence and increased life span.

Intracellular content of thiol compounds, thiobarbituric acid reactive substances and gamma-glutamyl transpeptidase in rat brain during anoxia

Intracellular thiol compounds like glutathione play an important role in scavenging free radicals. Free radical reactions occur in the respiratory chain, and free radicals are known to accumulate in hypoxia and ischaemia. The content of thiobarbituric acid (TBA) reactive substances, thiol and non-protein thiol (reduced glutathione) concentrations along with the activity of gamma-glutamyl transpeptidase (GGTP), a membrane enzyme, were estimated in three regions of the brain in rats exposed to anoxia. It was observed that no change occurred in the content of TBA-reactive substances in any one of the three brain regions, although a significant increase in the non-protein thiol concentration occurred uniformly during anoxia. A significant increase in GGTP occurred in all the three brain regions during anoxia. The increase in the activity of GGTP is suggestive of an alteration in the function of blood-brain barrier during anoxia. These results are suggestive of an absence of lipid peroxidative damage during anoxia.

On reaction of sterol hydroperoxides with superoxide

Reduction of sterol hydroperoxides 3 beta-hydroxy-5 alpha-cholest-6-ene-5-hydroperoxide and cholesterol 7 alpha-hydroperoxide by KO2 (or other strong base in air) solubilized by crown ether in dimethylsulfoxide gave only corresponding alcohols, but in the presence of cholesterol (or other sterols) gave 3 beta-hydroxycholest-5-en-7-one together with the corresponding alcohols. Both hydroperoxides likewise gave the corresponding alcohol and ketone products with KO2 in benzene and in oxidations by ceric ammonium nitrate in a biphasic system. The 7-ketone product is recognized as deriving from termination reactions of sterol peroxyl and/or oxyl radicals.

Detection of Organic Hydroperoxides in Rabbit Lung Lavage Fluid, but not in Lung Tissue Homogenate, Using GSH Peroxidase and GSH Reductase

A specific method for the detection of organic hydroperoxides in lung lavage fluid (lung surfactant system) and lung tissue homogenate is described. After the inactivation of endogenous GSH peroxidase and GSH reductase and preincubation with catalase, organic hydroperoxides are consumed by addition of GSH and GSH peroxidase. The increase of GSSG, compared to a blank without addition of GSH peroxidase, is measured in a second enzymatic step with GSH reductase. The recoveries of t-butyl hydroperoxide and of peroxidized, free fatty acids added to lavage fluid or to lung homogenate are higher than 85% in each case. The detection limits of this assay for organic hydroperoxides are 0.9 nmol/mg surfactant phospholipid (molar ratio of 0.00066) and 40 nmol/g wet lung weight. The assay detects organic hydroperoxides in the surfactant system of normal rabbit lungs, but not in lung tissue homogenate.

Molecular mechanism of cataractogenesis: III. Toxic metabolites of oxygen as initiators of lipid peroxidation and cataract

A free radical mechanism of cataractogenesis involving enzymatic and nonenzymatic reactions, is proposed. Supporting experimental evidence is briefly reviewed. H2O2, which is one of the toxic metabolites of oxygen, was significantly increased 2-3 fold in ocular humors in several experimental cataracts and in human senile cataract. Various cataractogenic agents were also found to increase H2O2 in ocular humors in vivo prior to cataract formation. Enzymatic defenses against O2-. and H2O2 provided by superoxide dismutase, catalase and glutathione peroxidase were impaired in cataracts. In some cataracts, catalase and superoxide dismutase were affected earlier. Malondialdehyde (MDA), a major breakdown product of lipid peroxides was significantly increased by 2-4-fold in human senile cataract, in cataracts induced in rabbit and rat, and in hereditary cataracts in mice. All the reactive species of O2 (O2-., H2O2, OH. and 1 delta gO2) may participate in initiating lipid peroxidation of lens in vitro. Various scavengers of these species were capable of preventing lenticular lipid peroxidation, amongst which OH. scavengers were found to be the most effective. Biological antioxidant, vitamin E afforded 44% prevention of lipid peroxidation in lens. The important observation was that vitamin E was therapeutically effective in about 50% of animals in arresting cataract induced in rabbit by 3-aminotriazole. In these rabbits, H2O2 and ascorbic acid of ocular humors and MDA of lens were close to normal. It is our working hypothesis that the carbonyl groups of MDA and amino groups of amino acids, proteins, nucleic acids and their bases, and phospholipids could interact in a cross-linking reaction producing high molecular weight aggregates by Schiff-base conjugate formation in addition to disulfide cross-linking of proteins, and finally resulting in cataract.

Superoxide dismutase in the central nervous system of Torpedo marmorata

In the central nervous system of Torpedo marmorata lipofuscin accumulates electively in the electric lobes. It has been found that the electric lobes have significantly lower superoxide dismutase activity than other areas of the central nervous system in animals of various ages and weights. These observations indicate that the lipoperoxidation action of the superoxide radicals or of their derived free radicals, due to superoxide dismutase deficit in these areas, might be related to lipofuscin accumulation.

Hemoglobin-catalyzed lipid peroxidation in the presence of mercuric chloride

In order to elucidate the possible mechanism of initiation of peroxidative processes in Hg2+-treated erythrocytes, the effect of HgCl2 on hemoglobin-catalyzed peroxidation of phospholipid liposomes was studied. It was demonstrated that HgCl2 significantly increases the rate of hemoglobin-catalyzed peroxidation. The addition of superoxide dismutase and catalase partially inhibits this effect. Furthermore, it was found that HgCl2 potentiates the hemoglobin oxidation. A suggestion was made that the acceleration of hemoglobin-catalyzed peroxidation by HgCl2 is associated at least in part with the increased production of superoxide anion radicals from hemoglobin.

Correlation between hydroperoxide-induced chemiluminescence of the heart and its function

The isolated perfused rat heart emits a spontaneous ultraweak chemiluminescence. When the perfusion is stopped, light emission decreases, indicating the dependency of this phenomenon on aerobic metabolism. Emitted chemiluminescence was markedly enhanced following perfusion with 0.05 mM H2O2 or cumene hydroperoxide or tert-butyl hydroperoxide; substitution of O2 for N2 in the gassing mixture of the perfusion media significantly lowered photon emission. Lipid peroxidation, which is known to be associated with chemiluminescence, was evaluated by HPLC analysis of peroxidized and unperoxidized heart phosphatidylcholines. During hydroperoxide perfusion, coronary flow and heart rate progressively decreased, while lactic dehydrogenase was released after complete cardiac arrest. The resultant morphology of this damage corresponds to the so-called 'stone heart', a pattern already described in both human and experimental pathology.