Abstract
Extract: Weanling male black-hooded rats were maintained at practically constant body weight between 24 and 52 days of age by giving them reduced amounts of their normal diet. Ten animals were then killed at 0, 3, 7, 10, and 16 days of rehabilitation on an ad libitum diet. At each age of rehabilitation, 10 control animals of the same age, and a similar number of the same body weight, were also killed. The thymuses of the animals were assayed for DNA (a measure of cell number), RNA, and protein, and the protein/DNA ratio was calculated (a measure of cell size). The thymus glands were also examined histologically.
The thymus lost 81% of its initial weight during undernutrition, but on rehabilitation returned to a normal weight relative to body weight within 10 days, and to a normal weight for age within 16 days. Thereafter it remained of normal weight. The absolute amounts of DNA and RNA responded in a way similar to weight. The absolute amount of protein also decreased during undernutrition, but on rehabilitation showed a poor response during the first 3 days, then increased rapidly to return to normal within 10 days. The protein/DNA ratio showed a sevenfold increase during undernutrition, but returned to normal within 7 days. Thus, atrophy of the thymus during undernutrition was due to a great loss of small cells, which left a population of large cells in the remnant; this was confirmed in histologic sections. However, the thymus had a remarkable capacity for recovery, and the body weight was more important than age as an influence on the rate of recovery.
Speculation: The loss of cells from the thymus during undernutrition may be one of the causes of increased susceptibility to infection in malnourished children and animals, but it is necessary to ascertain whether those cells which are lost from the thymus are immunologically active, and also to investigate whether the return to a normal cell population on rehabilitation is accompanied by a return to normal immunologic function. This work is in hand.
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McAnulty, P., Dickerson, J. The Cellular Response of the Weanling Rat Thymus Gland to Undernutrition and Rehabilitation. Pediatr Res 7, 778–785 (1973). https://doi.org/10.1203/00006450-197309000-00007
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DOI: https://doi.org/10.1203/00006450-197309000-00007
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