Hepatocyte fine structure during maturation and senescence

Abstract

Aging is accompanied by a myriad of changes in cell structure, function, and composition. The fact that much of the information concerning age-related alterations in cellular morphology is qualitative precludes meaningful correlations with biochemical changes in order to enhance data interpretation. The mammalian liver has been subjected to both qualitative and quantitative evaluations of hepatocyte structure as a function of aging, i.e., development, maturation, and senescence. Although these data are characterized by considerable variability and, in some instances, blatant contradictions, there exists sufficient agreement in several parameters to permit a consensus in the inbred rat model. Certainly the volume of individual hepatocytes increases with age, and many of the organelle compartments reflect this change. While old rats exhibit a high incidence of polyploidy, there is no definitive evidence to demonstrate a concomitant increase in the binuclear hepatocyte index. Several specific hepatocellular organelles undergo changes in their relative volume or surface area that appear to correlate with functional alterations. The volume density of the lysosomal compartment enlarges significantly during senescence and is accompanied by increased activities of several constituent hydrolases. The hepatic concentration of smooth-surfaced endoplasmic reticulum declines markedly with aging, as does the yield of liver microsomes and the activities of several microsomal enzymes, e.g., mono-oxygenases and glucose-6-phosphatase. However, the responses of the majority of hepatocyte organelles to aging is varied and inconsistent based on the limited data currently available.

Ultrastructural Morphometrical and Immunocytochemical Analyses of Hepatocyte Nuclei from Mice Fed on Genetically Modified Soybean.

“…It is known that cell nuclei become progressively larger as age increases (Schmucker, 1990), but, in our animals, they are also generally larger in control than in GM soybean fed mice. However, the differences in nuclear size between control and GM-fed mice do not imply differences in N/C ratio; conversely, N/C ratio changes are related to the age.…”

Position-specific Gene Expression in the Liver Lobule Is Directed by the Microenvironment and Not by the Previous Cell Differentiation State

“…This peculiar zonal selection of gene expression has been correlated with structural features of cells, e.g. the occurrence of greater hepatocellular ploidy in perivenous areas of the liver lobule (32). Similarly, post-translationally regulated distributions of gene products in cellular compartments and plasma membrane domains have been interpreted as unique positionspecific features of some hepatocytes (2).…”

Effects of aluminium sulphate in the mouse liver: Similarities to the aging process

“…Total iron accumulation and anaemia are increased in the elderly and in experimentally aged animals (Levenson and Tassabehji, 2004). During ageing of the liver, besides parenchymal cells (reviewed by Schmucker, 1990), morphological changes involved the endothelium, bile duct cells and non parenchymal cells (Kmiec, 2001;Schmucker, 2005). In particular, alterations in microvascular hemodynamic in rats (Vollmar et al, 2002) and age related sinusoidal thickening ("pseudocapillarization" ) has been reported in humans (Mc Lean et al, 2003), rats , and mice (Warren et al, 2005;Ito et al, 2007).…”