The Biology of Senescence 



fowl pituitary described by Payne (1949, 1952) were greatly 

 hastened by gonadectomy. In other words, gonadal failure may 

 contribute to senescence, but probably does so only when it 

 occurs at a certain point in the endocrine developmental pro- 

 gramme. 



In some instances, direct estimations of the capacity of senile 

 endocrines to respond to physiological stimuli have been made. 

 Solomon and Shock (1950) tested the response of the adrenal 

 cortex in 27 young and 26 old men to a dose of adrenocortico- 

 tropic hormone (ACTH) and in 15 young and 13 old men to a 

 dose of 0-4 mg adrenaline. No difference in eosinopenia was 

 observed after ACTH, but adrenaline produced a significantly 

 greater eosinophil depression in the young group. From this it 

 was inferred that the senile cortex can still secrete 11-17 oxy- 

 steroids without gross impairment, but that the response of the 

 pituitary to acute adrenaline stimulation is lower in old than 

 young subjects. Pincus (1950) likewise found no impairment of 

 response to ACTH in old men compared with young controls. 

 But with chromatographic techniques, Rubin, Dorfman and 

 Pincus (1955) have examined the range of a- 17 ketosteroids 

 produced at different ages. There is here little difference between 

 men and women: in both, the greatest decline with age is in 

 androsterone and aetiocholan-3a-ol-17-one, and the second 

 greatest in the 5a- 11 -oxygenated steroids. Such studies offer 

 considerable promise. 



The hypophysis is clearly the site of election for 'fundamental' 

 and all-explaining endocrine changes leading to senescence — 

 the part which it has played in the provision of such emotion- 

 ally-satisfying theories follows naturally from the fact that it is 

 known or credibly suspected to be involved in the regulation of 

 almost all mammalian processes of homoeostasis. Its proximity 

 to the hypothalamus enables it to be linked with theories which 

 locate senescence in the central nervous system. Hypophysial 

 factors in senescence have also a special importance because of 

 the relation of the hypophysis to the control of growth. In its 

 simplest form, starting from cellular exhaustion, the idea of a 

 primary pituitary senescence drew plausible anatomical argu- 

 ments from the histological studies of Parsons (1936) and Sim- 

 monds (1914) on long series of glands from subjects of various 



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