Postmortem changes in stereological parameters of cerebral capillaries

The present study investigated the influence of different postmortem times on stereological parameters of capillaries in the cerebral cortex. For the human investigation different brain regions of two 77 and 79 year-old subjects were examined. The animal experiment, carried out on 10 male cats, allowed a comparison between intravitam deep-frozen cerebral cortex and tissue obtained after decapitation. The parameters were diameter Di, volume fraction VVi, surface-to-volume ratio Si/Vi, mean minimal distance between capillary centers of gravity deltaAB, length per unit cortex volume LVi, and number of fragments per measuring field Ni, AT. Neither the cat experiment nor the human investigation yielded a noteworthy change of the capillary diameter in the postmortem cortical tissue. Nevertheless, a significantly enlarged mean minimal distance between capillaries in the cat cerebral cortex shortly after decapitation (30 sec) suggests the formation of edema which then regresses. Furthermore the experiment revealed that 22 hours after death there is a significantly (p less than 0.01) diminished volume fraction and length per unit cortex volume with an augmented surface-to-volume ratio. These changes are thought to be a consequence of water loss. In contrast to the animal experiment the human cerebral capillaries showed no changes in stereological parameters at two different postmortem times. These results encourage continuation of further stereological investigations on human brains obtained at autopsy and may contribute to the understanding of the aging process in the human cerebral cortex.