B VITAMIN DEFICIENCY STATES 429 



Trypanosoma lewisi infection and pneumonia having been particularly 

 studied. 193 A deep brown pigmentation has also been reported on the back 

 of deficient rats, particularly males (and deficient human infants) . Male 

 rats are said to be more sensitive than females. 



Biotin-deficient chicks also develop a characteristic dermatitis: the feet 

 become calloused and cracked, the corners of the mouth and the area 

 about the beak develop severe lesions, and the eyelids become swollen 

 and stick together. Similar symptoms of no distinctive interest occur as 

 the result of egg-white feeding to a wide variety of other animals — 

 rabbits, monkeys, 194, 195 mice, guinea pigs, and swine. Little is known of 

 the biochemical changes that occur in abiotinosis. Studies with liver slices 

 from biotin-deficient rats have shown that added biotin increases the 

 efficacy of this material in utilizing lactate, and it may be that the con- 

 version of pyruvate to oxalacetate will be shown to be seriously impaired 

 in this deficiency (p. 171 ). 196 Impaired ovalacetate formation might cause 

 a collateral impairment of pyruvate oxidation, which may explain the 

 observed depression in oxygen consumption of biotin-deficient duck 

 heart. 197 



p-Aminobenzoic Acid Deficiency. Relatively little is known about 

 p-aminobenzoic acid (PABA) deficiency and its incidence in man, or 

 about the relationship of this vitamin to another in which it is contained, 

 folic acid. There is good evidence to indicate, however, that it is effective 

 in the treatment of certain types of hair graying in man. Folic and 

 pantothenic acids have been reported to have similar effects, and it has 

 been suggested that p-aminobenzoic acid may act through folic acid 

 synthesis. There is some reason to believe that pantothenic acid functions 

 with PABA in hair pigmentation. The effect of PABA ultimately is in- 

 volved in melanin formation however, and the oxidation of tyrosine to 

 melanin may in some manner be related to the apparent relationship 

 between tyrosine and folic acid (p. 415). 



PABA stimulates the growth of rats and chicks on a deficiency diet, 

 and is a growth requirement for certain microorganisms. In the black or 

 piebald rat, deficiency results in graying of the hair (nutritional achromo- 

 trichia) — a condition which, like hydroquinone-induced achromotrichia, 

 can be cured by PABA administration. Female albino rats have been 

 reported to have lactation disturbances when fed a PABA-deficient diet. 

 The high efficacy of the sulfonamides in inhibiting bacterial growth indi- 

 cates that PABA plays an unusually critical role in cellular metabolism, 

 particularly since analogues of many other metabolites have not proved 

 effective therapeutic agents. It would seem, therefore, that PABA occu- 

 pies some key metabolic position, which when blocked causes the break- 

 down of a number of metabolic sequences. The reversal of sulfanilamide 



