NUTRITIONAL EFFECTS 



679 



stitution of wheat gluten and peanut flour 

 for casein, limited the increase in the weight 

 of the seminal vesicles to less than 100 per 

 cent. In fact, seminal vesicle weight as re- 

 lated to body weight did not increase in 

 animals fed 20 per cent wheat gluten. 



The withholding of dietary protein from 

 an immature rat for 30 days, during which 

 time maturation occurs in the fully fed ani- 

 mal, did not impose a permanent damage. 

 Refeeding of protein permitted the rapid re- 

 covery of testis weight and the appearance 

 of spermatoza, 70 per cent of all animals 

 having recovered in 30 days when fully fed, 

 whereas only 25 per cent recovered when 

 6 per cent casein was fed. Recovery of 

 androgen secretion was somewhat slower 

 than that of the tubules as estimated by 

 seminal vesicle weight. 



Variations in protein quality are a re- 

 flection of amino acid patterns, and amino 

 acid deficiencies interfere with testis matu- 

 ration (Scott, 1956; Pomeranze, Piliero, 

 Medeci and Plachta, 1959). Alterations in 

 food intake which follow amino acid de- 

 ficiencies have required forced feeding or 

 pair-fed controls, but it is clear from what 

 w^as found in the controls that the gonadal 

 changes were not entirely due to inanition 

 (Ershoff, 1952). 



If the diet is varied so that caloric intake 

 per gram is reduced to half while retaining 

 the dietary casein level at 20 per cent, im- 

 mature rat testis growth is prevented. The 

 effect is unlike that obtained with this level 

 of protein in the presence of adequate calo- 

 ries. Furthermore, the caloric restriction 

 may increase testis glycogen (Leathem, 

 1959c). 



Protein anabolic levels are higher in the 

 tissues of young growing animals and the 

 body is more dependent on dietary protein 

 level and quality for maintenance of the 

 metabolic nitrogen pool than in adult ani- 

 mals. On the other hand, body protein re- 

 serves in adult animals permit internal 

 shifts of nitrogen to the metabolic pool and 

 to tissues when dietary sources are reduced 

 or endocrine imbalances are imposed. Thus, 

 Cole, Guilbert and Goss (1932) fed a low 

 protein diet to adult male rats for 60 to 90 

 days before the sperm disappeared, but the 

 animals would not mate. Amount of semen 

 and sperm produced by sheep have been re- 



TABLE 12.7 



Arlult rat testes and seminal vesicles 



after protein depletion 



(From J. H. Leatliem, Recent Progr. Hormone 



Res., 14, 141, 1958.) 



* PFD = Protein-free diet. 



lated to the dietary protein level (Popoff 

 and Okultilschew, 1936). Removal of pro- 

 tein from the diet for 30 days had little 

 effect on the adult rat testis weight, sper- 

 matogenesis, or nitrogen content (Leathem, 

 1954). However, seminal vesicle w^eight was 

 reduced 50 per cent (Aschkenasy, 1954). 

 Prolonged protein depletion was required 

 before the testis exhibited a loss in protein 

 and a reduction in size. A loss of sperma- 

 tozoa was not observed consistently, al- 

 though some testes were completely atrophic 

 (Table 12.7). Accessory organ weight de- 

 crease reflected the disappearance of andro- 

 gen (Leathem, 1958a). Interstitial cell at- 

 rophy has also been noted in rats fed a low 

 vegetable protein (cassava) diet (Adams, 

 Fernand and Schnieden, 1958). 



Sterility may or may not be induced with 

 diets containing 65 per cent protein (Reid. 

 1949; Leathem, 1959c) but a 15 to 18 per 

 cent dietary level of a poor protein such 

 as maize or gelatin will decrease sperm mo- 

 tility and increase the number of abnormal 

 sperm. The influence of proteins having dif- 

 ferent nutritional values in support of the 

 growth of testes from the level to which 

 they were depressed by stilbestrol indicated 

 that casein, lactalbumin, and wheat gluten 

 are equally competent to support testis 

 growth whereas gelatin is deficient. Whole 

 proteins may have several amino acid de- 

 ficiencies, but the administration of amino 

 acid antagonists may help to identify im- 

 portant individual amino acids. As an ex- 

 ample, ethionine causes severe seminiferous 

 tubule atrophy and Leydig cell hypoplasia 

 (Kaufman, Klavins and Kinney, 1956; 

 Goldberg, Pfau and Ungar, 1959). Studies 

 in man have indicated a sharp reduction in 



