[Histological study of early postmortem changes in various organs: comparison of the paraffin embedding method and the epoxy resin embedding method].

For the purpose of morphological assessment of the early postmortem interval, Wistar rats were killed by cervical dislocation and left at 23 degrees C for 1, 3, 5, 10, 15 and 24 hours. After a given postmortem interval, tissue samples taken from kidney, pancreas, liver, heart and skeletal muscle were embedded in paraffin or epoxy resin and examined by light microscopy. Specimens obtained from the paraffin block did not show a good correlation between histological changes and postmortem interval, because the postmortem changes continued during the fixation period. On the other hand, the time course of histological changes in specimens obtained from the epoxy block, particularly the development of clumping of nuclear chromatin and cytoplasmic vacuolation in each organ, reflected the postmortem interval because of the rapid fixation by glutaraldehyde. These histological changes were characteristic of each organ up to 24 hours after death. In addition, the semithin epoxy resin section made high-resolution light microscopy possible. Therefore, the epoxy resin embedding method is superior to the paraffin embedding method for the purpose of estimation of the time of death. The morphological changes characterising time after death are as follows: at 1 hour after death, cytoplasmic vacuolization and slight clumping of nuclear chromatin in pancreatic acinar cells; at 3 hours after death, slight clumping of nuclear chromatin in distal tubules, cytoplasmic vacuolization in skeletal muscle, and edema in cardiac muscle; at 5 hours after death, clumping of nuclear chromatin in proximal tubules as well as distal tubules, and cytoplasmic vacuolization in hepatocytes; at 10 hours after death, edema in proximal tubules, condensation of nuclear chromatin (apoptosis) and edema in distal tubules, and atrophy of acinar cells in the pancreas; at 15 hours after death, cytolysis of distal tubules; at 24 hours after death, cytolysis of hepatocytes and clumping of chromatin in skeletal muscle. Thus we can conclude that the time course of histological changes is useful for the estimation of postmortem interval.