DOUGLAS M. SURGENOR 



and Lever and associates in Boston (21), using an analytical 

 fractionation of small amounts of plasma, have shown that in 

 diseases associated with lipemia, the increased lipid is found 

 almost exclusively in the /3-lipoprotein compartment. These 

 increases may represent an acceleration of processes which occur 

 more slowly in normals with increased chronological age. 

 Differences in /3-lipoprotein concentration are observed between 

 young men and young women, suggesting that the lipid com- 

 position is under partial hormonal control. Working on this 

 hypothesis, Barr, Russ, and Eder found that administration of 

 estrogen in adult males with high /3-lipoprotein levels resulted 

 in a decrease in both plasma and j8-lipoprotein cholesterol. 

 The levels of a-lipoprotein, the other major lipoprotein group, 

 remain strikingly constant with respect to age and sex and during 

 disturbances in lipid metabolism; no physiological function has 

 been suggested for this lipoprotein species. Further proof of a 

 relationship between the /3-lipoproteins and lipid metabolism 

 and transport comes from the findings of Gofman and his collab- 

 orators at Berkeley (14,15). In addition to the major /S-lipo- 

 protein isolated by Oncley, they have discovered a related series 

 of trace lipoproteins within the /3 group with increasing amounts 

 of triglycerides, decreasing density, and increasing molecular 

 weight; these are characterized by their rate of flotation (Sf 

 constant) during ultracentrifugation in media of high density. 

 Originally it was thought that a high degree of correladon 

 existed between the amounts of discrete 6) classes of lipoproteins 

 and predisposition to or actual occurrence of atherosclerosis. 

 An "atherosclerogenic index" was derived to express this 

 correlation. However, as the studies have continued, the 

 correlating spectrum has been broadened until it now includes 

 essentially the whole /3-lipoprotein compartment as isolated by 

 chemical fractionation. 



Despite these and many other studies which strongly associ- 

 ate the occurrence of atherosclerosis with abnormalities in the 

 plasma lipoproteins and more specifically with the lipoprotein 

 cholesterol, and the diagnostic aid off'ered by analytical studies 



658 



