The connection between the nuclei of binucleated hepatocytes: an ultrastructural study

Hepatocytes commonly have double nuclei and polyploidy. Both increase with age. The relationship of the double nuclei to each other has never been investigated at the ultrastructural level. Using a newly developed extraction and embedding technique we observed that the two nuclei were often linked by connecting DNA strands which span the gap between the two nuclei. The DNA nature of these filaments was determined by digestion with DNase. Artifactual intermolecular disulfide bonds were prevented by the employment of iodoacetamide in the extracting medium. It was further shown that partially fused and/or separated nuclei were observed by phase microscopy of living cultures as well as in fixed liver tissue. The results may indicate that one way in which binucleation occurs is through nuclear separation when the nucleus contains multiples of DNA (polyploid).