Specific pathogen-free mice were exposed to three different kinds of environmental stress during early life: (a) by infecting them with a mouse enterovirus on the second day after birth; (b) by placing the mother during pregnancy and lactation on a mildly deficient diet containing wheat gluten supplemented with

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small amounts of lysine and threonine; (c) by combining a (neonatal infection) and b (early malnutrition).

All animals survived the three types of stresses, but all exhibited marked depressions of metabolic activity, and of body weights and organ weights. These depressions lasted throughout the experimental period even though all animals were placed under optimum conditions of nutrition and husbandry after weaning, and maintained under these same conditions thereafter.

Metabolic activity was determined by measuring the turnover of 14C-acetate and 14C-glucose in respiratory CO2, and their incorporation in total lipids of liver and brain.

The utilization of 14C-acetate was profoundly depressed in all experimental groups with regard to both elimination in respiratory CO2 and their incorporation in total lipids of liver and brain.

In contrast, the utilization of 14C-glucose was much less affected; its incorporation into lipids was not decreased and its elimination in respiratory CO2 was depressed only in animals having experienced both neonatal infection and early malnutrition.

The extent of weight depression per 100 g of body weight differed according to the organ and the type of stress. Irrespective of the organ, however, depression of weight was largest in animals having experienced both neonatal infection and early malnutrition. And irrespective of the type of stress, the brain exhibited the smallest depression of weight relative to total body weight.

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