20 BIOLOGICAL EFFECTS OF LOW LEVEL EXPOSURES
Figure 1.6.
Figure 1.7.Theoretical survival curves for a control population and one in which longevity
hormesis is operative. The survival equation for the control group
corresponds to a linear Gompertz function (Equation 3); Gompertzians for the
longevity hormesis group are characterized by Equation 11. Parameters are
identical to those in Figure 1.3. Survival percentages were calculated using
Equations A-2 and A-4 of Neafsey et al.24 Note that at approximately 50%
survival, the two curves appear somewhat parallel.Theoretical survival curves (linear Gompertz model) for a control population
and one in which caloric restriction reduces a. The survival function for the
control population is characterized by values of a and the vulnerability
parameter equal to those for the control population in Figures 1.3 and 1.6.
The calorically restricted group was assigned a value of a equal to 63.0% of
controls, since this corresponds to the reduction in a noted for caloric
restriction by Neafsey et al.28 and illustrated in Figure 1.5. Survival
percentages were calculated using Equations A-2 and A-4 of Neafsey et al.24
Note that at approximately 50% survival, the curve for the calorically
restricted group appears to have a less steep slope than that for controls.
Contrast this with Figure 1.6, where longevity hormesis is the factor
enhancing longevity.