THE NATURE OF BLOOD LIPIDS 377 



blue produces changes in the lipoprotein pattern similar to those after irra- 

 diation. Whereas exposure to extreme cold ( — 12°C. for thirty minutes) re- 

 sulted in increased cholesterol levels and an augmentation of ultracen- 

 trifugally determined lipoproteins in rabbits, a milder exposure (0°C.) was 

 found to produce less severe histopathologic changes, although some in- 

 crease in lipoproteins in the plasma was observed. 181 



The functioning of the liver has been shown to be closely connected with 

 the maintenance of blood lipoproteins. Thus, Lewis, Page, and Thomas 182 

 reported that although no change in the lipoprotein pattern obtained in the 

 plasma of dogs for the first six hours after hepatectomy, later all lipopro- 

 teins and cholesterol began to decrease in the blood, in spite of a general 

 hemoconcentration. However, the lipoprotein pattern was unchanged 

 under the latter condition, which indicated the importance of the liver in 

 the metabolism of all types of lipoproteins. On the other hand, Kunkel 

 and Ahrens 183 stated that the electrophoretic patterns of the sera of pa- 

 tients suffering from an unexplained biliary cirrhosis do show alteration, 

 with marked increase in the /3-globulins ; the latter were directly propor- 

 tional to the total lipid concentration. An abnormal lipoprotein composi- 

 tion was demonstrated. Whereas the normal lipoprotein had a protein con- 

 tent of 28%, that prepared from the serum of patients with primary biliary 

 cirrhosis had only 14% protein and 86% lipid. 



The concentration of lipoproteins is regulated by the thyroid gland. 

 Thus, Lewis et al. m reported that the administration of cholesterol to dogs 

 and rats whose thyroid glands had been inactivated by treatment with I 131 

 resulted in a great increase in the concentration of lipoproteins with S f 

 greater than 23. On the other hand, this condition was corrected by 

 feeding desiccated thyroid powder. Species having large concentrations 

 of lipoproteins with S f 35 or faster are most susceptible to atheroma. For a 

 discussion of the relationship of lipoproteins to atherosclerosis, the reader is 

 referred to pages 466-481. 



The administration of estrogens resulted in no marked or sustained 

 change in any of the serum lipid fractions or in the cholesterol: phospholipid 

 ratio. Analysis of the S f 12-20 lipoproteins showed no consistent trend. 184 

 In a later report by Lewis and co-workers, 185 it was demonstrated that the 



181 W. W. Calhoun, L. J. Milch, and R. F. Redmond, Federation Proc, 12, 22 (1953). 



182 L. A. Lewis, I. H Page, and C. Thomas. Am. J. Physiol, 172, 83-85 (1953). 



183 H. K. Kunkel and E. H. Ahrens, Jr., J. Clin. Invest., 28, 1575-1579 (1949). 



184 S. J. Glass, H. Engelberg, R. Marcus, and J. W. Gofman, Proc. Soc. Exptl. Biol. 

 Med., 80, 264-265 (1952). 



185 L. A. Lewis, G. M. C. Masson, and I. H. Page, Proc. Soc. Expil. Biol. Med., 82, 

 684-686 (1953). 



