Stereology of Cellular Reaction Patterns

Morphometric (strictly stereologic) methods, based on simple mathematical formulae and elementary statistical principles, permit the synthesis of quantitative models having the coordinates of three-dimensional space, of organelle, cell, and tissue structures. This provides a sounder basis than has previously been available for the detailed comparison of the results of structural investigations with those obtained by other techniques, e.g., physiology or biochemistry. After a brief outline of the methods of determining volume and area, the estimation of numbers of objects is considered in more detail. The influence of fixatives upon results and the use of correction factors for various systematic errors are discussed. A summary of the available data on various differentiated organs in steadystate is provided, with emphasis on the liver. A description of the changes of cellularity in liver during the life cycle and in response to various stimuli (e.g., hormones, nutrition pharmaceuticals, etc.) is followed by sections on cellular and organelle organization. Other organs are given a comparable treatment as far as available results permit. A comparison of models of selected phenomena (e.g., mitochondrial changes and ER biosynthesis) derived from morphometric investigations are made with equivalent models derived from other techniques, illustrating some of the advantages and difficulties of this comparative approach and emphasizing the importance of an integrated viewpoint for the understanding of cellular reaction patterns.