PubMed · 7612708
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F Jorquera Plaza, J M Culebras Fernández. [Cholesterol and coronary ischemia].. https://pubmed.ncbi.nlm.nih.gov/7612708/
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In this study, we have examined a number of parameters which affect the rate of sterol desorption from a model membrane surface (a monolayer at the air/water interface) to cyclodextrins (CD) in the aqueous subphase. The desorption experiments were carried out at a constant lateral surface pressure with a zero-order trough, which allowed for a determination of desorption rates which were unaffected by monolayer substrate concentration. At a surface pressure of 20 mN/m (30 degrees C), 0.9 mM beta-CD caused a desorption of about 13 pmol of cholesterol per minute and square centimeter of monolayer area. The desorption of cholesterol proceeded linearly as a time function and was sensitive to the concentration of beta-CD in the subphase. The rate of cholesterol desorption increased as the monolayer surface pressure increased (3->35 mN/m) but decreased slightly with increasing temperature (15->30 degrees C). The rate of sterol desorption appeared to be influenced by the relative polarity of the sterols. Oxidized sterols desorbed significantly faster than cholesterol (e.g., 4-cholesten-3-one desorbed 8.4-fold faster than cholesterol), whereas less polar sterols desorbed at slower rates [e.g., 20(R)-isoheptyl-5-pregnen-3 beta-ol, a cholesterol analogue with a ten-carbon branched side chain, desorbed at 1/10 of the rate of cholesterol]. Cholesterol desorption from a monolayer membrane containing both cholesterol and a phospholipid was much slower than from a pure cholesterol monolayer. When the effect of dipalmitoylphosphatidylcholine and N-palmitoylsphingomyelin on cholesterol desorption rate was compared, it was found that cholesterol desorption was much more retarded from sphingomyelin monolayers as compared to that from phosphatidylcholine monolayers. Taken together, the results of this study show that the beta-CD-enhanced desorption of cholesterol (and other sterols) from monolayer membranes is influenced by the polarity of the desorbing molecules, as well as by lipid/lipid interactions in the membranes. Since beta-CD has no surface activity of its own, it appears to be a useful, nonintrusive catalyzer of cholesterol desorption and is expected to become a valuable probe in membrane and cell research.
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OBJECTIVES: To determine the accuracy and precision of the Accutrend GC (AGC) in measuring cholesterol totals (CT) and its use as a screening test to detect hypercholesterolaemia. DESIGN AND PARTICIPANTS: Venous blood was drawn from 104 patients to measure CT by an enzymatic method (Hitachi 717). At the same time, their capillary blood was also measured with the AGC on two consecutive occasions. Values were divided in three groupings: CT > 149 mg/dl and < or = 199 mg/dl (n = 27); CT > 199 mg/dl and < or = 249 mg/dl (n = 59); and CT > or = 250 mg/dl (n = 18). Accuracy was calculated by obtaining the mean differences (MD) and the confidence intervals of the values obtained with the AGC in the three groupings and comparing them with the values obtained by the laboratory method. Precision was assessed by correlation, the comparison of paired means and the mean coefficient of variation of the values obtained with the AGC in the two successive measurements. MAIN MEASUREMENTS AND FINDINGS: In each grouping the MD of the values obtained with the AGC were lower than those obtained by the laboratory method, respectively. CONCLUSIONS: The AGC is useful as a screening test to detect hypercholesterolaemia, because of its high accuracy and precision. As it also determines glucose it is very useful for diabetics.