Membranous structures in pinealocytes of the infertile diabetic mutant mouse (C 57 BL/Ks-db/db).

The fine structure of the pineal gland of the infertile, diabetic mutant mouse (C 57 BL/Ks-db/db) has been studied. Light and dark parenchymal cells were observed. The major population of pinealocytes in these animals is characterized by an abundance of highly organized membranes located in both the cell body and cell processes. Pinealocytes containing these membranous structures have low electron density (light pinealocytes) and large amounts of perinuclear cytoplasm containing granular vesicles and extensive Golgi. Dilated cisternae of the membranous structures may indicate secretory activity or selective aggregations or raw material. Changes in granule and vesicle content of the central core of cytoplasm of the concentric-shaped membranes and their apparent migration from the cell body to terminal process suggest a synthetic or secretory role. It is not known whether the membranous structures are related to the infertile condition or to the hyperglycemic syndrome; however, the presence of comparable membranes in subterranaen mammals lends support to the theory that the structures may be involved in the synthesis of pineal compounds.