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2 results on '"H L Hak-Lemmers"'

1. Single spin density gradient ultracentrifugation method for the detection and isolation of light and heavy low density lipoprotein subfractions

Author

D W Swinkels, H L Hak-Lemmers, and P N Demacker

Subjects
Biochemistry, QD415-436
Abstract

A single spin density gradient ultracentrifugation method in a swinging bucket rotor has been applied for the detection and isolation of low density lipoprotein (LDL) subfractions. The visualization of the LDL heterogeneity was facilitated by prestaining the serum with Coomassie Brilliant Blue R prior to density gradient ultracentrifugation for 19.5 hr. A total of 13 human serum pools was analyzed. In each pool, two LDL subfractions, a lighter LDL1 subfraction, occasionally showing a subdivision into two bands, LDL1A and LDL1B, and a heavier LDL2 could be clearly distinguished by the banding pattern in the density gradient. Physicochemical characteristics of the isolated LDL subfractions were determined. The simple method for detection and isolation of these subfractions presented here may facilitate future studies on LDL heterogeneity.

Published
1987
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2. Improved measurement of low-density-lipoprotein susceptibility to copper-induced oxidation: application of a short procedure for isolating low-density lipoprotein

Author

H A, Kleinveld, H L, Hak-Lemmers, A F, Stalenhoef, and P N, Demacker

Subjects
Lipoproteins, LDL, Kinetics, Temperature, Humans, Vitamin E, Butylated Hydroxytoluene, Oxidation-Reduction, Ultracentrifugation, Antioxidants, Copper, Edetic Acid
Abstract

Low-density-lipoprotein (LDL) oxidation may provide the crucial link between plasma LDL and atherosclerotic-lesion formation. Oxidation can be induced in vitro by incubating LDL with cells or metal ions and can be measured by continuously monitoring conjugated-diene absorbance at 234 nm. Measurement of LDL oxidizability was improved by performing the assay with 0.05 g of LDL-protein per liter of phosphate buffer containing 1 mumol of EDTA, by initiating oxidation by adding CuCl2 (5 mumol/L) at 30 degrees C, and by using a short-run ultracentrifugation method for isolating LDL, which reduced the time needed for obtaining purified LDL and thus reduced in vitro oxidation. LDL apolipoprotein analysis and oxidizability determination showed that this method is better than the longer sequential-isolation procedure. Adding butylated hydroxytoluene (BHT) to plasma as an antioxidant unpredictably increased the LDL oxidation lag time, making BHT unsuitable as an antioxidant. Adding EDTA appeared to be sufficient to prevent in vitro oxidation. Additionally, the diene production correlated highly with the concentration of thiobarbituric acid-reactive substances (r = 0.97). No relation between the vitamin E content of LDL and the oxidation lag time was found.

Published
1992

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