TRIGLYCERIDES AND FATTY ACIDS 181 



that of galactose; however, a higher level of glycogen was maintained in 

 the liver for a longer period (twelve to seventy-two hours) after galactose 

 feeding than when glucose was the sugar administered. This variation in 

 retention of liver glycogen offers an excellent explanation for the prolonged 

 inhibition of ketonuria following the ingestion of galactose. 



It is not known whether or not the more prolonged retention of glycogen 

 after galactose feeding, as compared with that after glucose, is related to a 

 difference in composition or structure of the glycogen laid down. Galacto- 

 gen, or "animal sinistrin," which is a polysaccharide composed of galactose 

 molecules obtained from the protein gland and eggs of Helix pomatia 

 (Roman land-snail) and also found in mussels, fish, and mammals, includ- 

 ing man, has been described by several workers^^'^"^^^ since its original 

 discovery by Hammersten.*''"' However, it is not believed that this is the 

 explanation, since Jew^eP"^ found that the glycogen arising after galactose 

 feeding in dogs yielded sugars on hydrolysis which are completely ferment- 

 able with yeast. On the other hand, BelP^ reported that the glycogen 

 formed following galactose feeding is composed of 18 glucose units, as 

 contrasted with the glycogen containing 12 glucose units which is normally 

 formed. 



In addition to galactose, there is some evidence that fructose and sucrose 

 exhibit a more pronounced effect on ketonuria than does glucose. ^^^ In 

 rat experiments, lactose was shown to have an action intermediate between 

 the high ketolytic effect exerted by galactose and the lower one which 

 results from glucose. ^^'^ 



g. The Metabolism of Acetone. Whenever ketosis occurs, definite 

 amounts of acetone (CH3 • CO • CH3) appear in the blood, and usually in the 

 liver. It has generally been assumed that, under such conditions, iS-hy- 

 droxy butyric acid, acetoacetic acid, and acetone are all present. Whereas 

 the reaction between /3-hydroxybutyrate and acetoacetate has been 

 recognized to be reversible, until recently the general opinion has been that 

 the change of acetoacetate to acetone represented an irreversible reaction. 

 However, in view of the experiments of Plaut and Lardy^^'' with labeled 

 acetone one must accept the fact that the reaction, acetoacetate ;=^ acetone 



"' E. Baldwin and D. J. Bell, J. Chem. Soc, 1938, 1481-1465; 1941, 125-132. 



"8 F. May, Z. Biol., 92, 319-324, 325-330 (1932). 



"^ F. May, Z. Biol, 95, 277-297, 401-430, 606-613, 614-634 (1934). 



««o O. Hammersten, Arch. ges. Physiol. (Pfliiger's), 36, 373-456 (1885). 



^1 P. W. Jewel, A Chemical Study of the Glycogens Formed After the Administration of 

 Glucose, Fructose, and Galactose, Thesis, Dept. Biochem. Nutrition, Univ. Southern 

 California, 1932. 



6«2 D. J. Bell, Biochem. J., 30, 1612-1616 (1936). 



