Myeloid bodies associated with lipid droplets in pinealocytes of blind, blind-bulbectomized, blind-underfed or blind cold-exposed rats.

The ultrastructure of pinealocytes was studied in rats subjected to manipulations known as enhancers of pineal actions: blindness (B), blindness + olfactory bulbectomy (BObx), blindness + underfeeding (BU), blindness + cold exposure (BC). A large number of myeloid bodies (MBs) were found especially in the light pinealocytes of BObx, BU and BC rats but not in intact controls. These MBs were, in most cases, associated with lipid droplets. The presence of a large number of MBs in rats in which pineal-dependent gonadal impairment has been demonstrated, strongly supports the hypothesis that MBs play a role in pineal photoneuroendocrine activity.