426 THE BIOCHEMISTRY OF B VITAMINS 



It is believed that the hypoglycemia (and presumed low liver glycogen) 

 seen in dogs in advanced stages of depletion is responsible for the coma 

 that occurs in these animals. The fact that thyroid administration in- 

 creases the pantothenate requirement is apparently associated with the 

 overall metabolic stimulation, since the pyridoxine and thiamine require- 

 ments are similarly increased. 



Pantothenic acid is apparently associated with the mobilization of 

 liver riboflavin, but the mechanism is obscure. 174 Vitamin B 6 deficient 

 animals are said to be more resistant to hair graying in pantothenate 

 deficiency, and cystine is believed to speed the remission of this symptom 

 on pantothenate treatment; but the reasons for these relationships are 

 unknown. 175 Finally, and perhaps most peculiar, is the evidence that 

 chronic zinc chloride poisoning causes a syndrome extremely similar to 

 pantothenate deficiency, that is said to respond to administration of the 

 vitamin. 176 



Vitamin B Deficiency. As in the case of pantothenic acid, no well 

 recognized syndrome in man is known to be due to vitamin B 6 deficiency, 

 although a variety of conditions have been reported to respond to vitamin 

 B 6 administration. There seems little doubt that vitamin B 6 deficiency 

 is a factor in some compound deficiencies, such as beriberi, pellagra, and 

 sprue, but attempts to deplete humans of this vitamin specifically have 

 been generally quite unsuccessful (p. 249). 



It has been reported that many of the nervous symptoms that remain 

 in pellagrins after thiamine, riboflavin, and niacin therapy respond rapidly 

 to pyridoxine administration. 177 There is also some evidence that the 

 characteristic cheilosis of ariboflavinosis may also frequently be due to 

 vitamin B 6 deficiency, this vitamin having been effective in the cure of 

 this symptom in a number of cases. 178 Other reports suggesting the 

 efficacy of pyridoxine in epilepsy, Parkinson's disease, pseudohyper- 

 trophic muscular dystrophy, and macrocytic anemia are scattered and 

 lack general confirmation, although it is entirely certain that some 

 benefit would result in any one of these conditions should the nature 

 of the affliction in some manner interfere with the normal degree of 

 efficiency in vitamin B 6 metabolism. Generally, therefore, it seems that 

 vitamin B G plays an important role in human nutrition, but the circum- 

 stances attending vitamin B c deficiency in man are as yet obscure. 179 



Vitamin B 6 deficiency has been induced in a number of animals by the 

 use of depletion diets, and the rat has been much studied in this regard. 

 Most characteristic of the vitamin B 6 -depleted rat is the dermatitis or 

 acrodynia, which is manifest on the peripheral portions of the animal 

 such as the tail, ears, nose, mouth and paws. There is an accompanying 

 scaliness and edema, an ulcerated tongue, and cessation of growth with 



