Ultrastructure and function of the amoeboid microglial cells in the periventricular white matter in postnatal rat brain following a hypoxic exposure

The ameboid microglial cells (AMC), located in the periventricular white ma tter, were examined ultrastucturally in neonatal rats following a hypoxic e xposure. From 10 min to 1 day, following the hypoxic exposure, a large numb er of glial cells with nuclear chromatin condensation, undergoing degenerat ion, were observed in the white matter. Such cells were often being phagocy tosed by the AMC. At 3-7 days after the hypoxic exposure, the cytoplasm of many AMC contained a number of phagosomes whereas at 14-28 days a large amo unt of lipid accumulation was observed in them. AMC were labeled intensely with horseradish peroxidase (HRP) administered intraperitoneally following the hypoxic exposure. The phagocytosis of degenerating cells by the AMC and uptake of HRP by them indicates that these cells efficiently remove the de generating cells/debris from the neonatal white matter following hypoxia in an attempt to protect it from a ny harmful substances that may be secreted by the degenerating eel Is or from serum derived substances that may enter the brain through blood circulation. (C) 2000 Elsevier Science Ireland Ltd . All rights reserved.