K.J. Farmer

Effect of age on oxygen consumption, superoxide dismutase, catalase, glutathione, inorganic peroxides and chloroform-soluble antioxidants in the adult male housefly, Musca domestica.

The objective of this study was to determine whether aging in the housefly is associated with a general decline in the efficiency of the mechanisms protective against the intermediates of oxygen metabolism. The rate of oxygen consumption, activities of superoxide dismutase (total and cyanide-insensitive) and catalase, and levels of inorganic peroxides, glutathione (GSH and GSSG) and chloroform-soluble antioxidants were measured in adult male houseflies at different ages. Rate of oxygen consumption declined in flies approaching the average life span of the population. Activity of total and cyanide-insensitive superoxide dismutase decreased during the last trimester of life. Catalase activity steadily declined with age while the concentration of inorganic peroxides gradually increased during the later two-thirds of the average life span. Levels of total glutathione and GSH decreased during later half of life whereas the relative concentration of GSSG increased during this period. The concentration of chloroform-soluble antioxidants sharply declined during the first half of life. These results are interpreted to suggest that the enzymatic and non-enzymatic defenses against oxygen free radicals and hydroperoxides tend to deteriorate with age in the adult housefly.

Effects of diethyldithiocarbamate on life span, metabolic rate, superoxide dismutase, catalase, inorganic peroxides and glutathione in the adult male housefly, Musca domestica

The effect of inactivation of superoxide dismutase, by diethyldithiocarbamate, on life span, metabolic rate, superoxide dismutase activity, catalase activity, inorganic peroxide concentration and glutathione levels in adult male houseflies was determined. The general objective was to examine the role of free radical defenses in the aging process. Houseflies were administered 0. 1 and 10 mM diethyldithiocarbamate in their drinking water. Administration of diethyldithiocarbamate caused an extension in the average life spans of the populations while the metabolic rates were depressed. Superoxide dismutase activity was significantly reduced. Inorganic peroxide concentration and catalase activity declined in rough correspondence to the decrease in the metabolic rate. The levels of reduced glutathione were significantly elevated whereas oxidized glutathione concentrations remained relatively unaffected. The results are interpreted to indicate that a decrease in superoxide dismutase activity in the housefly, by diethyldithiocarbamate administration, is compensated by an elevation in reduced glutathione levels and reduction of oxygen consumption, suggesting the existence of alternative free radical defenses in vivo.

Effects of paraquat administration on longevity, oxygen consumption, lipid peroxidation, superoxide dismutase, catalase, glutathione reductase, inorganic peroxides and glutathione in the adult housefly

The effects of oxidative stress in the adult male housefly were examined by the administration of 1 mM paraquat. Houseflies exhibit NADH and NADPH-diaphorase activity. Paraquat caused a significant decrease in life span, metabolic rate and the concentration of thiobarbituric acid-reactants. Concentrations of reduced glutathione and inorganic peroxides were increased by paraquat. Paraquat stimulated the activity of catalase but did not affect activities of superoxide dismutase and glutathione reductase. The levels of oxidized glutathione and the rate of fluorescent age pigment accumulation were unaffected by paraquat. Results indicate that paraquat toxicity does not result from lipid peroxidation.

Effects of exogenous antioxidants on the levels of endogenous antioxidants, lipid-soluble fluorescent material and life span in the housefly, Musca domestica

Effects of exogenous antioxidant administration (0.5% and 2% ascorbate, beta-carotene and alpha-tocopherol in sucrose) on life-span, metabolic rate, activities of superoxide dismutase and catalase, levels of glutathione, inorganic peroxides and chloroform-soluble fluorescent material (lipofuscin) were examined in adult male houseflies. Administration of antioxidants at a level of 0.5% did not affect life-span, whereas, 2% ascorbate and alpha-tocopherol decreased average life-span. Metabolic rate of flies was unaffected, except by 2% ascorbate, which caused a decrease. Superoxide dismutase activity was depressed by 2% ascorbate at all ages, and by beta-carotene and alpha-tocopherol in older flies. Catalase activity was unaffected except by alpha-tocopherol at younger ages. Glutathione concentration was decreased by ascorbate and beta-carotene at both concentrations administered. Inorganic peroxides (H2O2) were increased by 2% beta-carotene and alpha-tocopherol. Only high concentrations of ascorbate and beta-carotene decreased the level of soluble fluorescent material. Results suggest that administration of exogenous antioxidants causes a compensatory depression of endogenous defenses.

Effect of physical activity on superoxide dismutase, catalase, inorganic peroxides and glutathione in the adult male housefly, Musca domestica

Average and maximum life spans of the adult male housefly are considerably prolonged by the elimination of flying activity. The objective of this study was to elucidate further the biochemical basis of this phenomenon. Activities of the enzymes superoxide dismutase and catalase, and the concentrations of inorganic peroxides and glutathione were compared between houseflies kept under conditions of relatively high and low levels of physical activity at different ages. The activities of superoxide dismutase and catalase were not appreciably affected by the level of physical activity whereas the concentrations of inorganic peroxides and glutathione were higher in flies undergoing relatively high level of physical activity. These results are interpreted to support the concept that by-products of oxygen metabolism may play a causal role in the aging process.

Effects of the free radical generator paraquat on differentiation, superoxide dismutase, glutathione and inorganic peroxides in microplasmodia of Physarum polycephalum.

Abstract. The herbicide paraquat was used to investigate the effects of oxidative stress on the spherulation of Physarum polycephalum microplasmodia. the responses of a white non‐differentiating strain of Physarum were compared with those of a common yellow strain that readily spherulates in salts‐only starvation medium. the addition of paraquat to the salts medium increased the specific activity of superoxide dismutase in both strains; it also induced an increase in the intracellular inorganic peroxide concentration in both strains. Glutathione concentration was higher in the paraquat‐treated yellow strain than in the controls. Paraquat had no effect on glutathione concentration in white microplasmodia. Paraquat accelerated spherulation in yellow microplasmodia. the white microplasmodia responded to the herbicide by cleaving into structures similar to immature spherules; however, these structures were not viable. the results of this study support the hypothesis that free radicals are involved in cell state transitions.

Age-related changes in the redox status of the housefly, Musca domestica

The objective of this study was to further test the hypothesis that aging in the housefly is associated with increased oxidative stress. Age-related changes in the concentration of glutathione, NAD and NADP, which undergo oxidation-reduction reactions, and of H2O2, a potent cellular oxidant, were examined in the homogenates of adult male houseflies at 4, 8, 12 and 16 days of age. Sixteen days of age represents the beginning of the dying phase of the population when about 20% mortality usually occurs. Results indicate that the ratios of reduced/oxidized forms decline with age; H2O2 concentration steadily increases with age. Results suggest that the intracellular redox potential of the housefly becomes progressively more pro-oxidizing or less reducing during the aging process.

Involvement of glutathione in the differentiation of the slime mold Physarum polycephalum

The effects of experimentally‐altered glutathione concentration on differentiation of the slime mold, Physarum polycephalum were examined. Spherulation was induced by transfer of Physarum from growth medium to a salts‐only starvation medium. As differentiation proceeded, superoxide dismutase (SOD) activity in control cultures increased by as much as 21‐fold. This increase in SOD activity paralleled the rate of differentiation. Glutathione (GSH) concentration decreased during differentiation by more than 80% in all cultures, regardless of the initial concentration. The rate of differentiation was inversely related to the initial GSH concentration and directly proportional to the SOD activity. These observations suggest that a free radical mechanism may be involved in the differentiation of Physarum microplasmodia into spherules.

IRON INDUCES OXIDATIVE STRESS AND MAY ALTER THE RATE OF AGING IN THE HOUSEFLY, MUSCA DOMESTICA

Iron is known to play a catalytic role in the generation of oxygen free radicals in vitro. The present study was conducted in order to determine the in vivo effects of iron intake. Administration of 2 mM ferrous chloride to adult male houseflies in their drinking water significantly shortened their life span, increased the concentration of inorganic peroxides and chloroform-soluble fluorescent material, and stimulated the activity of catalase. Levels of superoxide dismutase activity, glutathione and oxygen utilization were unaffected. Overall, these results indicate that iron causes oxidative stress in vivo and may influence the rate of aging.

Superoxide dismutase activity during the plasmodial life cycle ofPhysarum polycephalum

Superoxide dismutase activity was slow throughout the cell cycle of surface cultures ofPhysarum polycephalum. This activity increased markedly when the organism was induced to spherulate. Glutathione (GSH) and hydrogen peroxide (H2O2) concentrations changed very little during the cell cycle. During spherulation GSH decreased; H2O2 and the cyanide-resistant respiration of plasmodial homogenates increased.