Studies on the Behavior of Lipoproteins

FIGURE 6.24 Cloudiness of serum samples taken at various times. Comparison of four normal subjects (shaded area) and four hyperlipoproteinemic subjects (symbols). (Redrawn with permission from Berger, 1986.) 

A woman suffered a gunshot woimd just below the left side of the neck. A ceaseless leakage of fluid issued from the unclosed wound. After eating, the leaking fluid became miUcy. The patient lost 5 poimds per week over the coiuse of 1 month. What structure had been ruptured (Consult Crandall et ah, 1943.) 

FIGURE 6.25 Concentration of TGs in blood plasma after a meal of com oil. Normal ( ) and h3rpertriglyceridemic (O) subjects consumed a meal of com oil. The TG concentrations in blood samples withdrawn before and at the indicated times after the meal are plotted. (Redrawn with permission from Barr et al, 1985.) 

Transfer of Apo E from One Particle to Another after Eating 

In this study, blood samples taken before and after human subjects consumed a breakfast of com oil (100 g) were analyzed for the total TG and apo E content. A more subtle parameter was measured also, namely the proportion of apo E associated with HDLs and with chylomicrons. This parameter can be measured by molecular sieve chromatography. (Details of this method are presented in the next section.) Results from three normal subjects appear in Table 6.7. The data in Table 6.7 demonstrate that the plasma TG levels increased postprandially (after eating), as expected. The data a show that the overall concentration of apo E in the bloodstream was fairly constant before and after eating. This constancy should not be interpreted to mean that apo E is not changing in any way. The proportion of 

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Conversion of VLDLs to VLDL Remnants in the Bloodstream HDLs and the Cycling of Cholesterol Lipids in Lipoproteins Studies on the Behavior of Lipoproteins Appearance of Chylomicrons in the Bloodstream Following a Meal of Fat or Oil... 

Because of its occurence in diseased tissue, the mode of association of cholesterol esters with biomembranes is of interest. Possible modes of association could be droplets within the hydrophobic core of the membrane bilayer, binding to membrane protein or as part of membrane attached serum lipoproteins. A potentially useful model system for investigating this association is the membrane of the microorganism Mycoplasma capricolum. The Mycoplasma due to their simplicity have served as model membrane systems in many studies. As mentioned previously, cholesterol esters show complex behavior that is a function of thermal history, impurities and physical packing constraints. Using DSC on native membranes and extracted membrane material, it was possible to demonstrate that the majority of cholesterol esters associated with the membranes of M. capricolum exist as relatively large and pure liquid droplets (17). 

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