Morphometric studies of chromatin structure and nuclear organization: hepatic polyploidy and mammalian erythropoiesis

Abstract

Morphometric techniques have seen only limited application in the establishment of quantitative parameters relating to chromatin structure and nuclear organization at the EM level. The usefulness of this approach, however, was recently demonstrated by studies on avian erythropoiesis, showing that contrary to subjective impression there is no progressive increase in the amount of condensed chromatin in developing erythrocyte nuclei. This report extends similar analysis to liver nuclei of different ploidy classes and to mammalian erythroid cells.Materials and MethodsRat liver and bone marrow from anemic rabbits were prepared for microscopy as described. Data for 2c and 4c liver nuclei were obtained using rats of appropriate ages: 28 days, >90% 2c; 400 days, >70% 4c; 8c nuclei are larger than 380 μm3. Mean nuclear volumes were calculated from the major and minor axes of at least 50 nuclei of each type measured with a micrometer using 2-3 μm thick sections. Nuclei were treated as prolate spheroids. Morphometric analysis was carried out as described, using the point counting stereological method.