Hemicastration in the rat is followed by hypertrophy of the remaining gonad (Heller, Heller & Sevringhaus, 1942), presumably as a result of increased pituitary secretion of gonadotrophins (Benson, Sorrentino & Evens, 1969). Howland (1972) food restriction of 50% was imposed and continued for 14 days; the animals were housed individually, the food intake of the intact and hemicastrated controls was measured daily and the experimental animals were fed 50% of these amounts. On the 15th day after the operation, the animals were killed and the left gonads from both the intact and hemicastrate rats were removed and weighed. Although different methods of observation from those of Howland (1972) were used, a 50% caloric restriction in the adult female prevented the ovarian compensatory hypertrophy; in the immature female, the hypertrophy was curtailed considerably. In the immature male rat, however, the gonadal hypertrophy was not affected (Table 1).Since the hemicastrated male showed gonadal hypertrophy when fed a restricted diet for 2 weeks, a preoperative period of dieting was also studied.Immature male rats were allocated to two groups. Those in one group were restricted in caloric intake 10 days before hemicastration and, in the other group, at the time of operation. In both groups, the restriction was continued for another 14 days. The experimental animals were compared to intact rats having similar dietary regimens (Table 2).At the time of the operation, the rats were 10 days older than those in the first experiment, which would account for the fact that the fully fed rats showed little or no gonadal hypertrophy. In those on a restricted intake for 14 and 24 159

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