Biomedical Engineering Reference
In-Depth Information
4C
2C
G1
S
G2M
0.0
0.2
0.4
0.6
0.8
1.0
Cell age
FIGURE 14.3
DNA and number of events versus cell age. This figure shows two parametric
relations: DNA versus cell age and number of cells or events versus cell age. An ideal DNA
histogram is the solution of these two relations where the G1 and G2M peaks are located at 2C
and 4C, respectively. The areas of G1, S, and G2M are equal to the areas under the number-cell
age curve partitioned by the cell age
ΒΌ
0.4 and 0.8 boundaries.
assumptions about the relation between cell age and number of cells. It could be a
complicated or simple relationship. It really does not matter.
14.3.4 Eliminating Cell Age
I remember giving lectures back in the late 1970s in which I would show that DNA
versus cell age and number of cells versus cell age were two parametric equations,
where you could eliminate the common parameter of cell age and end up with a DNA
histogram with DNA content on the x-axis and number of cells on the y-axis. It never
occurred to me or any one else that we should not have been so hasty to eliminate this
important common parameter.
14.3.5 Cell Age As a Parametric Parameter
Let us not make that mistake this time. Let us keep cell age around and see where it
leads us. You can easily imagine that if we couldmeasure cell age, the best way to look
at coordinated expressions of cell cycle proteins would be to use cell age as a common
axis much like our parametric equation variable, t. If we produced a graphical overlay
with parameter intensities on the y-axis and cell age on the x-axis, wewould be able to
visualize how cyclins and other cell cycle proteins modulate as cells progress through
the cycle. We could examine all the correlations of a very large number of parameters.
We really would not be limited by number of parameters. The more the better
If we
had cell age as a parameter, we would have never gone down the road of displaying
one measured parameter versus another.
...
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