Chromatin supraorganization and extensibility in mouse hepatocytes following starvation and refeeding

Abstract

Background:The effect of 48 h of starvation and of 48 h of refeeding subsequent to starvation on chromatin supraorganization and extensibility was studied in hepatocytes from adult mice. Methods: Methods used involved topochemical assays, image analysis, gravity action, and polarization microscopy. Results: Starvation increased the chromatin packing states, especially in areas of noncondensed chromatin, and induced drastic decreases in concanavalin A reactivity due to nuclear matrix glycoproteins and the frequency of nuclei with chromatin extensibility under gravity. Changes in chromatin packing state were accompanied by shifts of nuclear areas of part of the nuclear population to smaller values but did not affect the respective Feulgen-DNA amounts except for a few nuclei. The extent of chromatin unpackaging, but not of frequency of nuclei with formation of extended chromatin fibers, in starved mice that were refed was greater than in well-fed controls.

Nucleus image properties assessed by video image analysis in mouse hepatocytes under a short lysis for extended chromatin fiber formation

“…Even so, Feulgen-and toluidine blue-stained materials still remain inside the nuclear remnants, indicating that part of the DNA does not flow from the nuclei, possibly because of some structural constraint. Con-A binding sites assumed to pertain to nuclear glycoproteins are detected at least partly in the cell nucleus remnants under this lysis protocol (5).…”

“…Extended chromatin fibers (ECF) flow from cell nuclei subjected to treatment with concentrated saline and detergent solutions, under the action of gravity (1)(2)(3)(4)(5). ECF formation and DNA flow are affected not only by rheologic properties of the DNA (6,7) but also by the presence of nuclear protein molecules.…”

“…ECF formation and DNA flow are affected not only by rheologic properties of the DNA (6,7) but also by the presence of nuclear protein molecules. Consequently, they are affected by nuclear physiology and by the extrinsic assay factors involved, such as cell fixation and the lysis treatment protocol (2,3,5).…”

“…In mouse hepatocytes, a short (5-10 min) lysis protocol as applied vertically to unfixed preparations results in formation of extremely long ECFs in all of the nuclei (5). Even so, Feulgen-and toluidine blue-stained materials still remain inside the nuclear remnants, indicating that part of the DNA does not flow from the nuclei, possibly because of some structural constraint.…”

“…Should a variation occurs, it could even mean that the putative structural constraint to DNA flow might be caused by differences in nuclear architecture possibly in association to differences in nuclear matrix interactions and transcriptional activities (5,8,9) in the hepatocyte nuclei. In addition, the presence of especial richness in DNA AT bases in the nuclear remnants of mouse hepatocytes could be associated with chromocenters generated by condensed centromere regions originally rich in repetitive AT-containing DNA (10)(11)(12).…”