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Transmission electron microscopy (TEM) was used to determine the effect of diesel engine exhaust (DEE) on the intravascular and interstitial cellular population of the lungs of exposed rats and guinea pigs. Animals with matched controls were subjected to environments of either 250, 750, 1500 or 6000 μg/m3 for either 2 weeks, 6 weeks, 10 weeks or 18 months. These animals were sacrificed immediately following the exposure periods and their lungs perfused with fixative. Following dissection, random stratified biopsies from the lungs of these animals were made. Ultrathin sections from the alveolar lung were prepared and conventionally processed for TEM and randomly photographed to compose a micrograph database. These micrographs were analyzed by point counting using a Zeiss MOP 3 Digital Image Analyzer. The results indicated no significant intravascular cellular response but a significant increase in the mononuclear population in the interstitium.

The relationship of polyploidization (DNA content) to differentiation is not well defined. We have developed centrifugal elutriation and Percoll density gradient centrifugation to obtain larye numbers of highly-purified mega-karyocytes which subsequently were stained for DNA content with Hoechst 33342 and sorted by FACS into SC, 16C and 32C ploidy classes for correlated analysis of cell surface structures by scanning electron microscopy. Each ploidy class revealed unique surface characteristics that reflect differentiation occurring in megakaryocytes independent of their DNA content.