554 NIACIN 



In all other species, except possibly the cat (p. 570), a deficiency of 

 nicotinic acid is manifested by the same signs and symptoms as can be 

 produced by many other deficiencies. Actually, there are only six deficiency 

 phenomena which can be found in all species susceptible to the deficiency. 

 These are: (1) reduced growth in young animals, (2) weight loss in either 

 young or adult animals if the deficiency is severe, (3) loss of appetite, (4) 

 reduced concentration of nicotinic acid and coenzymes I and II in some 

 but not all tissues, (5) reduced excretion of nicotinic acid and its derivatives 

 in the urine, and (6) death, if the deficiency is severe or long continued. 

 Difficulties in reproduction and lactation could probably be added to this 

 list, but these subjects have received little attention. All these phenomena, 

 except possibly the reduced tissue and urine levels, can be produced by 

 other deficiencies. 



The general signs and symptoms and the pathology observed in various 

 species is described in Section XL The discussion in this section will deal 

 with some of the physiological and biochemical defects which have been 

 reported in various species as well as some of the interesting and fairly 

 characteristic defects which are seen in human pellagra. 



3. Nicotinic Acid and Coenzyme Tissue Levels 



Nicotinic acid-deficient chicks,^''. 21 dogs,^^"-^ pigs,"^' "^ rats,^^-^^ rabbits,^" 

 and men^i exhibit a lowered concentration of nicotinic acid (and nicotinic 

 acid-containing coenzymes) in tissues such as liver, muscle, and, in some 

 species, brain. Other tissues such as red blood cells, heart, lung, spleen, and 

 kidney may maintain normal concentrations.-'^^- ^^"** The level of nicotinic 



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