428 THE BIOCHEMISTRY OF B VITAMINS 



blood vitamin B 6 levels — a fact further involving vitamin B 6 with vitamin 

 B12 185 in the overall picture of normal hematopoiesis. The relationship 

 of the pdracins to folic acid has already been discussed (p. 421). 



Previous mention has been made of many of the biochemical aspects 

 of vitamin B 6 deficiency. There is a lowering of blood, tissue and body 

 levels of this vitamin in most cases, and loading tests have been employed 

 in the diagnosis of apyridoxosis. Studies of the anemia produced in swine 

 have resulted in the conclusion that hemoglobin synthesis is decreased 

 in this deficiency. Thus during vitamin B 6 deficiency in swine, erythrocyte 

 protoporphyrin is reduced by over 50 per cent, plasma iron is more than 

 doubled and plasma copper is decreased by 20 per cent, while urinary 

 coproporphyrin remains constant. It is thus felt that the fundamental 

 disturbance involves impaired protoporphyrin synthesis. 186 



One of the most striking changes that occurs in apyridoxosis is the 

 interference in tryptophan metabolism which results in increased urinary 

 excretion of xanthurenic acid and decreased excretion of kynurenic acid 

 by deficient animals. Various aspects of this derangement have been dis- 

 cussed in relation to the earlier study of vitamin metabolism (p. 354) . 

 Transaminase activity is distinctly decreased in vitamin B 6 -deficient 

 rat tissue, 187-190 and can be increased by the addition of pyridoxal and 

 adenosine triphosphate. Pyridoxine is said to alleviate the toxic symptoms 

 of DL-serine in rats. 191 



Biotin Deficiency. So far as is now known, biotin deficiencies are not 

 naturally occurring, probably largely because of the considerable intes- 

 tinal synthesis of this vitamin. Deficiencies induced in a number of species 

 by the feeding of avidin-containing raw egg white are well known, how- 

 ever. Sydenstricker et al. fed a group of human volunteers a diet con- 

 taining 30 per cent of the total calories in the form of desiccated egg 

 white and observed a fine scaly dermatitis ; a variety of mental symptoms, 

 including depression, lassitude, hallucinations and panic; pallor; and a 

 drop in urinary excretion of biotin from 29-62 fig per day to 3.5-7.5 /xg 

 per day after ten weeks on the diet. All these symptoms disappeared after 

 administration of biotin. 192 There have been a number of reports of suc- 

 cessful biotin therapy of various skin disturbances (acne vulgaris, rosacea, 

 furunculosis, baldness due to seborrhea), but there is at present insuffi- 

 cient evidence to support such claims. 



Egg-white injury has been extensively studied in the rat, the symptoms 

 being highly typical. There is a cessation of growth, a spectacle-eyed 

 appearance, a desquamous dermatitis of the neck and groin which becomes 

 generalized, and stiffened joints, which result in an awkward movement 

 of the animal. Progressive emaciation terminates in death. Such rats are 

 said to be unusually susceptible to infection with various organisms, 



