Structural Organization of the Cytomatrix

Abstract

During the period when centrifugal fractionation was the popular approach to the investigation of the cellular contents and their function, some misconceptions regarding the cytomatrix became part of an established dogma. It said that mitochondria, microsomes, and secretory granules were floating around in a cytosol. Subsequently those procedures were adapted for the isolation of ribosomes, the Golgi complex, the plasma membrane, and certain components of the cytoskeleton. The results were impressive and contributed to a large literature which has perpetuated the notion that the cell is simply an assemblage of isolatable parts. Questions of how they interact or whether they are tied together for communication are seldom, if ever, asked. The dogma of fractions has dominated the thinking, in spite of long recognized facts about cells and their organization. It is well known, for example, that the cellular organelles are not randomly distributed in the cytoplasm, that cells possess anisometric forms, that they have a polarity, and that animal cells show in most instances a center (cytocentrum) around which other components (dense bodies or MTOC) are arranged, sometimes in a radial fashion (Porter et al., 1983). It has since been demonstrated that the nucleus (the nucleoplast) deprived of the bulk of this organized cytoplasm (the cytoplast) survives for only 48 hrs, even though it has ribosomes, mitochondria, as well as vesicles of the ER, some cytomatrix, and an intact plasma membrane around it all. One might imagine that, with all that, the nucleoplast might regenerate the rest. But not so; without the cell center and its associated mass of organized cytoplasm, the nucleoplast rounds up and is nonviable. The cytoplast, on the other hand, adopts the form of the parent cell; and, even though viable for only 48 hrs, it moves about independently for part of the time. An E.M. study shows it to possess centrioles and microtubules (Shay et al., 1974).