Nuclear Ploidy in Mammalian Parenchymal Liver Cells

Abstract

ALTHOUGH it has generally been assumed that the nuclei of the parenchymal cells of mammalian liver have ploidies in the ratio of 2N : 4N : 8N : 16N … (ref. 1), contradictory reports have recently appeared. One described the existence in C3H mice of nuclei with ploidies of 3N, 6N and 12N, the first amounting to as much as 25–50 per cent of the nuclei during the first 2 weeks of life². The other claimed that there is, in human liver, a continuum of nuclear DNA contents and volumes, and that individual classes of nuclei are not present³. The reasons for the discrepancies between these results and the generally accepted theory are not known, but one possibility is that the methods of preparation and measurement of the material may produce systematic errors. Both the studies were carried out on sections of fixed tissues with micro-spectrophotometric methods that were less than optimal. During the course of the investigation of the relationship of cell size to cell ploidy⁴, measurements of nuclear size and ploidy have been carried out with intact, single parenchymal cells. The results obtained again confirm the existence of clearly defined classes of parenchymal cell nuclei.