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At least 1,243 records · Page 69Linked to original sources
PubMed2001

A method for forensic identification of vegetable oil stains--rapid analysis of carboxylic acids with methyl esterification using purge-and-trap gas chromatography/mass spectrometry.

A simple method using purge-and-trap gas chromatography/mass spectrometry (P&T-GC/MS) for forensic examination of oil stains was studied. Carboxylic acids, chosen as target components for discrimination of oil samples, were extracted from stains with ether, methyl esterified by tetramethylammonium hydroxide, and analyzed by P&T-GC/MS. Vegetable oils were discriminated according to their carboxylic acid compositions. Carboxylic acid composition was independent of the substrate material of the stain. Although the carboxylic acid composition of the oil changed on exposure to sunlight, identification of oil was possible for oil stains that had been in the shade, if analysis was made within 20 days.

Journal Article↗
PubMed2003

[Esterification of fatty acids by alcohols and functional role of polar and non-polar lipids in blood flow. Double bonds of lipid fatty acids in lipoproteins].

An original method of automatic titration of dual bindings by ozone was made use of to show the functional role of alcohols, i.e. glycerin and cholesterol, in the transfer, within the lipoproteins' composition, and in the receptor absorption of saturated and essential polyene acids by cells. The values of correlations dual bindings/glycerin and dual bindings/cholesterol are indicative of that the saturated fat acids are etherified by glycerin in blood serum, and the essential polyene fat acids are etherified by cholesterol. The presence of dual bindings in lipids of some lipoproteins shows that lipoproteins of a very low density are carriers of saturated fat acids (in the form of non-polar triacilglycerides), and lipoproteins of low density are the key carrier of essential polyene fat acids (in the form of non-polar ethers of cholesterol). The cells absorb passively the fat acids (in the form of polar lipids); and they absorb actively the fat acids (in the form of non-polar lipids and by means of receptor endocytosis). A stable correlation dual binding/cholesterol at alterations of the alcohol content in the blood serum by 20 times, and similar correlation values in man, rats and mice demonstrate that the cells absorb, be means of receptor endocytosis, the essential polyene fat acids (in the form of ethers of cholesterol). The level of cholesterol depends on a content of fat acids, mainly of the omega-3 and omega-6 essential polyene fat acids, in the blood serum.

Adolescent↗
PubMed1989

Distribution and functions of lecithin:cholesterol acyltransferase and cholesteryl ester transfer protein in plasma lipoproteins. Evidence for a functional unit containing these activities together with apolipoproteins A-I and D that catalyzes the esterification and transfer of cell-derived cholesterol.

The distribution of apolipoprotein A-I, apolipoprotein D, lecithin:cholesterol acyltransferase, and cholesteryl ester transfer protein in fasting normal human plasma was determined by two-dimensional electrophoresis followed by immunoblotting. The synthesis and transfer of labeled cholesteryl esters generated in plasma briefly incubated with [3H]cholesterol-labeled fibroblasts was followed in terms of the lipoprotein species containing these antigens. Following the early appearance of labeled free cholesterol in two pre beta-migrating apolipoprotein A-I species (Castro, G. R., and Fielding, C. J. (1988) Biochemistry 27, 25-29), labeled esters were first detected, after a 2-min delay, in a third pre beta-migrating species which also contained apolipoprotein D, lecithin:cholesterol acyltransferase, and cholesteryl ester transfer protein. Pulse-chase experiments determined that label generated in this fraction was the precursor of at least a major part of labeled cholesteryl esters in the bulk of alpha-migrating high density lipoprotein. Over the maximum time course of these experiments (15 min, 37 degrees C), less than 10% of labeled cholesteryl esters were recovered in low or very low density lipoproteins separated by electrophoresis, immunoaffinity, or heparin-agarose chromatography. These data suggest channeling of cell-derived cholesterol and cholesteryl esters derived from it through a preferred pathway involving several minor pre beta-migrating lipoproteins to alpha-migrating high density lipoprotein.

Antibodies, Monoclonal↗
PubMed1978

Studies on cholesterol esterification in human tissues.

In vitro cholesteryl synthesis from oleic acid [1-14C] was studied with enzyme preparations from human thoracic aorta and liver. Results from studies on the properties of the esterifying system provide good evidence that the mechanism involves fatty acyl-CoA-cholesterol acyl transferase. In studies on human thoracic aorta with varying degrees of atherosclerotic disease, and pairs of normal and diseased aorta from the same subject, there was no obvious relationship between aortic cholesteryl esterifying activity and severity of atheroma. Normal aorta from two young males, presumably free of atherosclerosis, had relatively very low esterifying activity. In the six liver samples tested, there was negligible esterifying activity, in contrast to the high activity seen in the case of rat liver. For the thin layer chromatographic isolation of the labeled cholesteryl oleate a solvent system of isooctane:diethyl ether (100:6) was found to give a better separation of the ester than the petroleum ether: diethylether:acetic acid system generally used.

Adolescent↗
PubMed1986

Cold labelled substrate and estimation of cholesterol esterification rate in lecithin cholesterol acyltransferase radioassay.

A simple and reproducible radioassay of lecithin cholesterol acyltransferase (LCAT E.C. 2.3.1.43) activity is described. The method is based on cold labelling of the serum, plasma or other LCAT and lipoproteins containing fluids with a trace of 14C-cholesterol spread in ready made sorbent discs. Since the procedure minimizes the chemical, heating and time consuming steps, it may be particularly suitable for routine investigation of the defects of cholesterol kinetics and also for experimental studies.

Animals↗
PubMedDate not supplied

[Effect of proliferation-stimulating factors on cholesterol esterification in the serum of rats with acute tetrachloromethane poisoning].

Three phases of cholesterolemia were detected in rats after single administration of CCl4 at a dose of 0.3 ml of oil solution per 100 g of body mass. Factors, stimulating proliferation of hepatocytes and isolated from regenerating liver tissue, did not affect the type of cholesterolemia whereas they stimulated cholesterol esters formation in circulation.

Acute Disease↗
PubMed1986

Cholesterol esterification rate and its relation to lipoprotein levels in plasma in normal human pregnancy.

The lecithin:cholesterol acyl transfer (LCAT) reaction produces cholesteryl esters and lysolecithin in plasma. The rate of LCAT is related to the plasma lipoprotein concentrations. During pregnancy there are pronounced elevations of the lipid and lipoprotein concentrations. Therefore, we studied the LCAT rate and its relation to the lipid levels in plasma lipoproteins in 19 healthy women before conception, every sixth to eighth week during pregnancy, and 8 weeks after delivery. In the first part of gestation the mean molar LCAT rate (the amount of cholesteryl esters produced during a certain time, in micromoles per liter per hour) remained unchanged, whereas pronounced elevations were seen in the very low-density lipoprotein (VLDL), high-density lipoprotein (HDL), and HDL2 levels. The molar LCAT rate did not increase until the last trimester of pregnancy, when it reached a maximal 20% mean increase simultaneous with the maximal increase of the mean triglyceride and VLDL levels and a slight decline of the HDL2 elevation. The mean fractional LCAT rate (the part of unesterified cholesterol that is esterified during a certain time, in percent per hour) showed a continuous decrease from the fourteenth until the twenty-eighth week, simultaneous with a progressive rise of the mean cholesterol and low-density lipoprotein (LDL) concentrations. During pregnancy the molar LCAT rate was positively correlated to the VLDL concentration and negatively to the HDL2 level, and the fractional LCAT rate was negatively correlated to the LDL concentration.

Adult↗