When foods are exposed to ionizing radiation under conditions envisioned for commercial application, no significant impairment in the nutritional quality of protein, lipid and carbohydrate constituents was observed. Irradiation was no more destructive to vitamins than other food preservation methods. Protection of nutrients is improved by holding the food at low temperature during irradiation and by reducing or excluding free oxygen from the radiation milieu. 'Deceased. Kennedy (1965) observed little change in nutritive value of animal feeds (protein concentrates) when 0.5 and 1.0 Mrad doses were appliedand no nutritional changes with frozen eggs irradiated at 0.5 and 5.0 Mrad. Ley (1972Ley ( , 1975 noted excellent results with radappertized feed for germ-free rat and mouse colonies which were maintained for 5 years. Radappertization and radicidation have been used in preference to thermal sterilization to sustain germ-free and specific-pathogen-free rats, mice, pigs and chickens (Sato 1970;Schoen and Hiller 1971;Udes et al. 1971;Ley et al. 1969;Coates et al. 1963). Others have reported that both the biological value of proteins, and the metabolizable energy value, of composite rodent diets are unaltered by radappertization a t 5.6 Mrad (Raica and Howie 1966;Read et al. 1961;Kraybill 1960).
Adult rats were fed a low fat (4%) or a high fat (40%) diet, and groups of other rats selected for good running were fed these two diets and were treadmill exercised 5 days a week for 6 weeks. The serum triglycerides were significantly lower in exercised rats fed the low fat diet, but not in those fed the high fat diet, as compared with corresponding controls. The liver lipids were vastly elevated in sedentary rats fed the high fat diet as compared with those fed the low fat diet. An interesting effect of exercise was reflected by the near normal liver lipid levels in rats fed the high fat diet and exercised. However, in these animals, the muscle concentration of cholesterol was significantly higher than that in all other groups. The very low density lipoproteins tended to be lower while the low density lipoproteins tended to be greater in exercised as compared with sedentary rats. It was suggested that the decline in very low density lipoproteins was due to decreased synthesis resulting from adaptive changes in the exercised animal. It was further postulated that the increase in low density lipoproteins was possibly due to increased synthesis necessitated by the need to enhance the catabolism and excretion of cholesterol in exercised animals.
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