Localisation of thiamine pyrophosphatase in the amoeboid microglial cells in the brain of postnatal rats.

The activity of TPPase in amoeboid microglial cells has been studied in postnatal rats. When examined with the light microscope such cells in 1-10 days old rats perfused with 4% paraformaldehyde were round and showed a dark brown reaction in their cytoplasm. In older rats (10-30 days), the reactive amoeboid microglial cells were oval, flattened or branched. Electron microscopic examination revealed that the reaction product was seen on the plasma membrane, in the subplasmalemmal vacuoles, in tubular invaginations of plasma membrane and in the transface of the Golgi saccules. In rats perfused with the mixed aldehyde solution, the amoeboid microglial cells did not show a positive TPPase reaction with the light microscope but at the ultrastructural level a weak reaction was seen in some cytoplasmic vacuoles and in the Golgi saccules.