Unstable, heterogeneous physical states of nuclear bodies during the post-hepatectomy dedifferentiation-replication-redifferentiation sequence.

Nuclei are shown to undergo generalized changes of state during regeneration, as reflected by changes in equilibrium density of sucrose density gradients. The time-course of these phenomena suggests an association with changes occurring after S-phase and mitosis. Such changes are no longer observable in extensively purified nuclei (washed, polyamine-stabilized nuclei), but are apparent only in nuclei with minimal purification, rapidly isolated by centrifugation from liver homogenates. This effect implies that there exists a serious risk of selective loss of some nuclear types during standard purification procedures that use 2.1-2.4 M sucrose cushions. Although these nuclear states may largely reflect the metabolic state of the cells of origin, evidence is presented to suggest that loss and redistribution of macromolecules during handling procedures causes distortion of in vivo properties.