%0 Thesis %9 Doctoral %A Conlon, Ian John %B Biology %D 2001 %F discovery:10098413 %I UCL (University College London) %K Biological sciences %P 107 %T Cell growth control %U https://discovery.ucl.ac.uk/id/eprint/10098413/ %X This thesis investigates the fundamental relationship between cell growth and cell-cycle progression. Understanding this relationship is crucial to understanding how cells proliferate, yet very little attention has been paid to it, especially in vertebrate cells. In yeast cells it has been demonstrated that cell growth regulates cell-cycle progression through the action of a cell-size checkpoint. Using normal rat Schwann cells, I demonstrate that it is not necessary to invoke a cell-size checkpoint to explain why these cells maintain their size while proliferating in vitro. I show that an extracellular signalling molecule can promote Schwann cell-cycle progression without promoting cell growth, and thus cell growth rate is not the sole determinant of the rate of cell-cycle progression or cell size. Also, I investigate the intracellular signalling pathways stimulated by extracellular signals that exert different effects on Schwann cell growth and cell-cycle progression. It has previously been assumed that animal cells co-ordinate cell growth and cell-cycle progression in a similar way to yeasts. Taken together with other studies, my findings suggest that this assumption is incorrect. %Z Thesis digitised by ProQuest.