Variations of the Ultrastructure of Neuronal Lipofuscin During Childhood and Adolescence in the Human Ammon's Horn

Abstract

The ultrastructure of lipofuscin (Lf) was studied in hippocampal and neocortical neurons of children and youngsters between 3 months and 24 years of age. As a standard, regions CA1 and CA4 of Ammon's horn and the gyrus centralis anterior of the left hemisphere were examined, and the ratio of the two components of Lf, the pigment part, and the usually droplet-like lipid part was looked at. Few and small granules with typical linear structures in the pigment part and little lipid droplets were found as early as at the age of 3 months in all brain regions. There were no morphological differences of Lf in the areas of Ammon's horn up to 3 years, but the Lf ultrastructure in Ammon's horn differed clearly from that in the neocortical region. Differences of Lf between the areas CA1 and CA4 were found to appear at the age of 6–8 years, to have a rather variable pattern between age 11 and about 20 years, and to be relatively constant thereafter. The Lf pigment part consisted of irregularly arranged three laminar linear structures. Some varieties could be seen in the size and shape of the Lf granules and in the lipid/pigment ratio. As to the question of Lf being an “age pigment,” the findings that the number of Lf granules did not further increase after the period of early adolescence was not consistent with the age pigment hypothesis. No regional or age-dependent differences were found in the Lf of astro- and oligodendroglia.