be difficult to maintain that irradiation simply advanced the onset of senescence, unless it could be accepted that the aging of various organs could be
advanced to different degrees.
5.
Comfort [C1] discussed similarities and differences between natural aging
and radiation-induced life-shortening.
His review is important for its effort
to define basic concepts and to differentiate between the various biological
effects observed but his analysis of data according to dose and time is less
elaborate than elsewhere.
The paper by Storer and Grahn [S3] was an objective
and accurate review of information available which is still of interest for
reference purposes.
Neary
{N1, N2]
analyzed the various therories of aging
.
and regarded them as belonging to two main groups:
-
those interpreting aging as due to random events in a population of
supposedly uniform individuals, and
-
those examining the individual and its component cells.
Neary also proposed his own theory, based on the analysis of original data on
irradiated mice.
According to his formulation aging proceeds in two succes-
Sive stages, induction and development, each characterized by appropriate
parameters.
6.
Another interesting contribution was provided by Casarett
[C2].
By a
eritical comparison of natural aging and of late radiation effects, he proposed that radiological aging could be ascribed to the damage of endothelial
cells of the fine vasculature, leading to fibrotic changes of the arterioles
and of the interstitial collagenous substance.
In due course these would be
followed by loss of parenchymal cells, replacement fibrosis of the organs,
loss of the functional reserve capacity and, eventually, an increased susceptibility to trauma, stress and disease.
T.
In recent years the contributions tended to be more experimental than
theoretical, except perhaps for the work of Sacher and Grahn [S4], Grahn and
Sacher [G1] and Sacher [S5] who further elaborated previous ideas in an attempt
to derive, from a refined analysis of the date, some basis for a comprehensive theory of a natural and radiation-induced aging.