Biochemistry of the Dividing Cell

Abstract

The normal form of cell reproduction involves the duplication of the nu clear genetic material, the partitioning of the genetic material into two equiv alent, or "sister," nuclei, and the partitioning of the cytoplasm into two separate cells, each with one of the nuclei, Nuclear division is not necessarily followed by cytoplasmic division ; the production of multinucleated cells is a common occurrence in nature and in experiments. On the other hand, cell division without nuclear division, which would produce anucleate cytoplasmic masses, is a rare occurrence, obtainable only under special experimental con ditions (36,70,159).In all plant and animal celIs, in protozoa, and in a great many algae and fungi, ceIl division involves the method of mitosis. The defining features of the mitotic method are: the "packaging" of the genetic units in chromo somes, the condensation of the chromosomes at the time of division, and the transportation of sister chromosomes to opposite poles. Thus, the major problems of mitosis are problems of structure and of very specific movement; therefore, a discussion of the biochemistry of the dividing cell takes place in a different context from discussions of metabolic biochemistry and biosyn thesis. It involves the polarization of the whole ceIl, specific "connections" or "attractions" between large bodies, large-scale movements, and, normally, an exact partitioning of the entire cell.Unfortunately, we do not have an adequate account of the method of nuclear division in bacteria and blue-green algae in the sense that mitosis is the method employed by plant and animal cells.

The Centriole Cycle in Synchronized Hela Cells

“…The absence of the centrosome, a structure whose character most likely reflects centriole activity, suggests that, aside from the separatory movement, G 1 is a phase of centriolar quiescence. This discrepancy between our findings and those of Mazia et al (4) are, in all probability, due to the short generation time of their marine eggs compared to the 17 hr life cycle of the HeLa cell.…”

“…Centriole replication by orthogonal budding from a parent centriole has been described in both the light and electron microscopes (1)(2)(3). Its temporal relationship to the telophase stage of the cell cycle has been inferred, in sea urchin, from the morphological modification of cell division induced by mercaptoethanol (4), and Cleveland's extensive work on centriole replication in flagellates is well known (5). In mammalian cells, replication is assumed to occur sometime during interphase; however, the lack of more precise data is due in large part to the dearth of morphological criteria which might distinguish individual segments of interphase.…”

Evidence for cell cycle suppression and microRNA regulation of cyclin D1 during anoxia exposure in turtles

“…Previous reports have suggested that a withdrawal of ATP supply induces proliferation arrest in the G 1 phase of the cell cycle. 20 Indeed, a recent study of freezetolerant and anoxia-tolerant wood frogs, Rana sylvatica, showed that anoxia exposure induced a significant decrease in critical cell cycle components (type D1 and E1 cyclins, type 2, 4 and 6 cyclindependent kinases) as well as an increase in cell cycle inhibitors (p16 INK4A and p27…”

Regulation of cell cycle components during exposure to anoxia or dehydration stress in the wood frog, Rana sylvatica

“…but, on the molecular scale, many intracellular energy‐expensive enzymes, pathways and functions are specifically targeted and strongly suppressed (Storey and Storey, 2004b, 2007). One of the most energy‐expensive activities that organisms undertake is the proliferation of cells to support growth or development and to replace damaged cells (Mazia, '62). Therefore, we hypothesized that cell cycle arrest would be a very important component of global metabolic rate depression as a survival strategy for dealing with anoxia or dehydration stresses.…”