HYPOTHESES ON LONGEVITY HORMESIS 25Figure 1.12. Gompertz plots for control and methylene chloride-treated female Syrian
golden hamsters. Methylene chloride exposure (500-3500 ppm inhalation)
was begun at 8 weeks of age and continued for 2 additional years (6 hours
per day, 5 days per week). Time on the abscissa refers to the period
following initiation of exposure. The theoretical lines were obtained by
simultaneous fitting of Equations 3 and 11, employing weighted
least-squares regression analysis. The logarithmic-logistic equation was
used to characterize X. Note a dose-dependent increase in longevity
hormesis with increase in dose, in the absence of any apparent toxicity. The
original data came from Burek et al.94 Reprinted from Neafsey et al.,25 p.
134, by permission of Marcel Dekker, Inc.
Figure 1.13. Gompertz plots for control and methylene chloride-treated female
Sprague-Dawley rats. Methylene chloride exposure (500-3500 ppm
inhalation) was begun at 8 weeks of age and continued for 2 additional
years (6 hours per day, 5 days per week). Time on the abscissa refers to the
period following initiation of exposure. The theoretical lines were obtained
by simultaneous fitting of Equations 3 and 8, employing weighted
least-squares regression analysis. The logarithmic-logistic equation was
used to characterize 7. Note the dose-dependent increases in irreversible
toxicity, in the absence of any apparent longevity hormesis— just the
opposite of what occurred in hamsters at the same exposure levels (see
Figure 1.12). The original data came from Burek et al.94 Reprinted from
Neafsey et al.,25 p. 136, by permission of Marcel Dekker, Inc.