Table 1.
Terms for hypothetical cellular growth of a single cell.
| Term | Definition | Unit | Description |
|---|---|---|---|
| c(t) | Measurement of the status of cell cycle of a cell with a numerical value between −1 and +1 | Cycle | The status of a cell cycle is provided with a numerical value in order to describe the quantitative progression of cell proliferation. A cell cycle exists between two endpoints: death and birth (of two daughter cells). In either case, the cell ceases to exist. A cell divides if c(t) = 1, dies if c(t) = −1, for some t > tn, where tn is the time that the cell was born |
| N(t) | Size of a tissue or a mass at time t | Cell | The total number of cells in a tissue or a mass at time t with summation of the value of all individual cells. A clone is comprised of all descendant cells from a progenitor cell borne from asymmetrical division of a tissue stem cell |
| t | Physical time, as it relates to patient age and menstrual cycle | Month | It is the physical time and can be assigned with a unit of day, month, or year. We assume that 1 year = 12 months and 1 month = 30 days for convenience |
| αp(t) | (Programed) proliferation potential (Eq. 2) | Cycles/month | Programed rate of a cell’s multiplication according to the cell’s progression in clonal development (progression of generations) and expressed as the number of cell cycles per unit time |
| kp(t) | (Programed) differentiation coefficient (Eq. 3) | 1/month | Measurement of a cell’s differentiation status, commonly with a range from 0 to Kmax (a tissue specific constant) |
| g(t) | Generation number (Eq. 4) | Cycle | Measurement of lineage progression in a clone and cellular senescence. A daughter cell assumes a new generation value of g + 1 with g as the parent generation number. It has the same unit as the cell cycle. It represents how a cell perceives senescence, and is determined by its cellular mechanism, for instance by telomere length. Although g(t) and division (d) synchronize most of time, there is a possibility that they may differ. For instance, active telomerase may maintain telomere length after many divisions |
These terms are for cells living under conditions free of any genetic insults and environmental influences, a hypothetical scenario used as a frame of reference to study the effect of genetic and environmental factors on cell growth.