Effects of advancing age on the ultrastructure of pinealocytes in the male white‐footed mouse (Peromyscus leucopus)

Quantitative comparison of pinealocyte ultrastructure in 3‐month‐old and 28‐month‐old male white‐footed mice (Peromyscus leucopus) revealed decreases both in the area of the Golgi apparatus and in the number of dense‐core vesicles. In contrast, no differences between these two age groups were noted in the areas of granular endoplasmic reticulum, vacuoles with flocculent content, lysosome‐like bodies, or motochondra. Nor were any changes between groups of mice apparent in pinealocyte nuclear or cytoplasmic areas, nuclear: cytoplasmic ratios, or the number of pinealocyte nuclei per unit area. areas of unusual, annulate lamellae‐like structures were increased in the pinealocytes of a group of 28‐month‐old mice. These observations suggest a possible age‐associated decrease in the neurosecretory‐like (but not ependymal‐like) secretory process in the pinealocyte of white‐footed mice.