Immunohistochemical, conventional and immunoelectron microscopical characteristics of periodic acid-Schiff-positive granules in the mouse brain

Periodic acid-Schiff-positive granules (PGs) appear in the mouse brains in relation to advancing age. The exact location and pathophysiological signif icance of PGs, however, are not fully understood. The incidence, staining p roperties, and topographical distributions of PGs in the brains of 17 AKR m ice ranging in age from 7 to 18 months were examined histochemically and im munohistochemically using antibody KM279 raised against a polyglucosan. In addition, to define the precise site of PG formation, we investigated the b rains of 4 AKR mice of 24 months of age using conventional and immunoelectr on microscopy. PGs were seen in all mice examined and the levels were incre ased with age. The PGs were located predominantly in the hippocampus and, t o a lesser extent, in the cerebellum and olfactory bulb. Immunohistochemica lly, PGs in the hippocampus and cerebellum were labeled uniformly with KM27 9. On immunoelectron microscopy with this monoclonal antibody, the fibrilla r or membranous structures corresponding to PGs seen using light microscopy were labeled specifically with gold particles. With conventional electron microscopy, fibrillar or membranous structures were seen along with synapti c vesicles and dense-core granules. Moreover, around the cells containing P Gs, a few synaptic junctions with neighboring cells were observed, indicati ng that the cells contributing to formation of PGs were neuronal cells. The positive immunoreactivity of AKR mouse PGs for the antibody KM279 suggests that the PGs and similar structures in other species may share a common an tigenicity. Thus, it is assumed that PGs in AKR mice might result from some abnormalities in glucose metabolism.