ULTRASTRUCTURAL CYTOCHEMISTRY OF CIS-DICHLORODIAMMINE PLATINUM-II INDUCED APOPTOSIS IN IMMATURE RAT CEREBELLUM

We have used cis-dichlorodiammine platinum II (cis-DDP) to induce apoptosis in germinative compartment of the external granular layer of rat cerebellum which is most sensitive to acute treatment with this drug. Ten-day-old animals were injected with 5-mu-g/g b.w. and killed after 2, 4, 8, 16 or 24 hr and the molecular architectonics of apoptotic cell nuclei was studied at the electron microscopy level. A Feulgen type reaction with osmium ammine complex (OAC) and a proteolytic treatment with pronase were used for EM cytochemistry. The data show that at the onset of apoptosis most of the OAC-stained DNA was located at the periphery of the nucleus, where heterochromatin masses accumulate. In the center of the nucleus, only thin fibers and small aggregates of DNA were detected. At later stages of apoptosis, the OAC-stained DNA was randomly distributed in dense roundish masses or clumps near the nuclear membrane surrounding a central OAC-negative area. Treatment of serial sections with pronase and EDTA regressive staining for RNPs revealed that the OAC-negative areas were mainly composed of nuclear proteins and RNPs.