EFFECT OF DEFICIENCY IN ANIMALS 



Biotin and Infected Animals 



A deficiency of biotin increased the severity of Plasmodium lophurae 

 infection in chicks ,^^ but had no effect on the susceptibility of Swiss 

 mice to experimental poliomyelitis.^^ Biotin-deficiency in rats led to 

 a delayed or lowered production of the antibody that inhibited the 

 reproduction of Trypanosoma lewisi,^^ so that the parasites multiplied 

 unchecked. 



Biotin and Cancer 



Nakahara et al.^^ reported that rats were protected against 

 cancer induced by butter yellow (NN-dimethyl-amino-azo-benzene) 

 by administering liver and yeast supplements. This observation 

 was followed up by du Vigneaud et al^^ to determine whether the 

 effect was due to biotin. They gave concentrates of biotin pre- 

 pared from liver and yeast to susceptible rats, together with butter 

 yellow, and obtained indications of a protective effect. Marked 

 protection was also obtained with casein supplemented by ribofiavine. 

 When pure biotin was given, however, either with or without the pro- 

 tective casein-ribofiavine supplement, the incidence of liver tumours 

 among the mice was markedly increased. It would appear that not 

 only has biotin no protective effect in cancer, but that it actually 

 destroys the effect of the protective factor present in yeast and liver 

 and is therefore a pro-carcinogenic substance. It was suggested that 

 avidin, the egg white injury factor, might have a beneficial effect 

 on cancer. 



This was tested by Kensler et aL,^"^ who fed a diet rich in egg 

 white and avidin to mice with spontaneous mammary carcinoma, but 

 could observe no favourable effect on the disease. Nor was the effect 

 of high levels of egg white any more marked on mice with Flexner- 

 Jobling carcinoma or mouse sarcoma i8o. Avidin equivalent to i6 

 to 40 times the amount necessary to combine with the dietary biotin 

 was fed over a period of thirty weeks to a patient with mammary 

 carcinoma and to another with lymphatic leukemia, without any 

 apparent improvement being observed in the patient's condition ; *^ 

 oddly enough, no clinical signs of biotin deficiency appeared, nor was 

 the urinary excretion of biotin reduced. The inability of avidin to 

 affect the course of cancer was confirmed by I. I. Kaplan,^^ who gave 

 the whites of 36 to 42 eggs daily to cancer patients maintained on a 

 diet low in biotin without effecting a cure, although there was some 

 improvement in certain of the cases. 



Animal experiments were also carried out by Kline et al.^"^ They 

 fed rats o-o6 % of butter yellow in highly purified diets containing a 

 sub-protective level of ribofiavine, together with heated or unheated 



429 



