A Study of Aging, Thermal Killing, and Radiation Damage by Information Theory 309 



The discussion given above indicates that even though it is necessary to 

 assume p{H, 0) of different shapes for different ensembles of organisms, once 

 chosen, the same shape is required to represent survivorship data with httle 

 regard for the nature of the deleterious agent causing mortality. 



The case for loss of information content by action of chemical mutagens 

 or carcinogens is less clear than that for radiation. Radiation is no respecter 

 of local chemical detail — it sees only an electron gas held together by positive 

 charges. Side reactions complicate the experimental problems in obtaining 

 good survivorship curves for the chemical radiomimetics. In fact, we know of 

 no such curves at all, although some data of this sort are discussed by Rahn (3). 

 Nevertheless, there is good reason to believe there is considerable miming 

 (55, 56, 57) of radiation effects, in general, and of aging in particular. 



This is illustrated by a paper by Cloudman, Hamilton, Clayton and 

 Brues (58). They studied malignant tumors and survival in CF-1 female mice 

 painted with methylcholanthrene, irradiated with P^^ /? particles, and with 

 these two insults in combination. A striking decrease in life span was found 

 in those mice painted with methylcholanthrene. This was not due to any single 

 pathologic state, not even to the pulmonary tumors generated in these animals. 

 Survival was also shortened in those mice which did not have pulmonary 

 tumors. The authors had the impression that life was shortened in a general 

 way similar to the life shortening effects of total-body irradiation. 



The carcinogenic effects of the two agents used in the experiments were 

 approximately additive. This observation as well as the life shortening and 

 the carcinogenesis correlates very well with the view that these effects are 

 manifestations of the destruction of genetic information in the somatic cells. 

 Since exposure to such chemicals is probably on the increase there is a practical 

 as well as a theoretical reason for pursuing this matter further. 



IV. THE ROLE OF EQUIVOCATION IN THE GERM LINE 



It was said in my previous article in this volume that the ideas developed 

 there should be applicable both to the germ line and to the somatic line. In 

 this section we shall consider the effect of equivocation on the ability of the 

 germ line to transmit specificity. We do not have available as much experimental 

 material as that which pertains to the somatic line but there are several experi- 

 ments which are very good and are very gennane to the phase of information 

 theory in biology discussed in this section. 



It should be remembered that there are a number of error correction methods 

 peculiar to the germ line. Among these are fertilization or conjugation and the 

 selection value of the independent existence of cells in the germ line. The 

 germ line may therefore be expected to exhibit a recovery from damage to a 

 degree not found in the soma. 



An experiment in which the germ line is propagated parthenogenically 

 and so resembles very much the somatic line has been reported by Lansing 

 (59, 60). He studied the effect of parental age on the survivorship of two 

 species of the rotifer, namely, Euchlanis triquetra, which lives normally about 

 a week, and Philodina citrina, which survives normally nearly a month. 



The method of the experiment was to observe the survivorship curve for 



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