Discussion 97 



can convince that castration is a good thing! We have supplemented 

 our studies with specimens of testes obtained from volunteer prisoners. 

 Ageing in the human testis is a very gradual process. There is no 

 period at which ageing processes are really precipitous. The testes from 

 a man, 72 years old — the oldest individual we have — still look pretty 

 good, and still have a certain amount of spermatogenesis going on. 

 Beginning from about 45 years or so, and this is variable with indi- 

 viduals, spermatogenesis gradually slows down and together with this 

 there is an increase in the number of cells which look like Sertoli cells. 

 I call them Sertoli cells because their nuclear morphology and cyto- 

 plasmic inclusions, such as glycogen and lipid granules, are identical with 

 those of Sertoli cells. 



The oldest testes usually contain numerous Sertoli cells and sper- 

 matogonia and no other cells. The seminiferous tubules do not become 

 aged all at once. That is, whereas one seminiferous tubule might appear 

 entirely normal, one next to it might show strong ageing changes. Some 

 tubules show a banding of ageing changes, a phenomenon which I shall 

 discuss again when I speak about the sweat glands later on. Within the 

 same tubules a segment might show ageing changes, but other segments 

 might still have spermatogenesis. The basement membrane of the 

 seminiferous tubule, which is composed of three layers, undergoes some 

 interesting changes. The middle hyaline or glassy layer of the mem- 

 brane becomes disproportionately large with advancing age. 



I want to come back to the general misconception of calling the Sertoli 

 cells the Sertoli syncytium. In very young or in very old testes, where 

 Sertoli cells are numerous and not mixed with all the spermatogenic 

 cells, one can see, even with the obsolete methods of the light or 

 phase contrast microscope, a fairly distinct membrane between the 

 individual cells. 



I am glad to hear Prof. Fawcett refer to certain cells in the inter- 

 stitium as fibroblast-like. In human testes there are, indeed, cells which 

 one cannot tell from fibroblasts. These cells, however, always predict- 

 ably contain some perinuclear sudanophil bodies. Although even the 

 fibroblasts in connective tissue elsewhere may have visible lipid inclu- 

 sions, these are more striking in the fibroblasts of the testes. I fancied 

 some years ago seeing a transition from ordinary fibroblasts to com- 

 pletely differentiated Ley dig cells. I say ' I fancied ' because I have not 

 the vaguest idea if we have a bimodality of action in the fibroblasts : 

 one going towards the fibroblasts and one going towards the Leydig 

 cells. I would like to hear Prof. Fawcett express his opinion on this 

 matter. 



Fawcett: Up to a year ago I was doubtful of the reported transition 

 from fibroblasts to Leydig cells but it is certainly true that in electron 

 micrographs there are two distinct categories of cells in the interstitium 

 of the testis ; those that have a filamentous cytoplasm and few in- 

 clusions, and those whose cytoplasm is filled with minute vesicles and 

 contains a variety of lipid, pigment and crystal inclusions. One also 

 finds cells with intermediate characteristics having both the little 

 vesicles and the delicate filaments in varying proportions. It is easy to 



AGEING VOL. 2 5 



