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Biomedical subjects

A Kuksis

Publications and source records attributed to A Kuksis.

31 records · Page 2Linked to original sources
PubMed1977

Acylglycerol structure of peanut oils of different atherogenic potential.

Detailed investigation was made of the triacylglycerol structure of native, simulated, and interesterified peanut oils, which had previously been shown to differ markedly in their atherogenic potential. By means of chromatographic and stereospecific analyses, it was shown that the more atherogenic native oil contains a significantly greater proportion of triacylglycerols with linoleic in sn-2-position and arachidic, behenic, and lignoceric acids in sn-3-position that the synthetic oils. It is suggested that the atherogenicity may arise from a relative metabolic unavailability of the linoleic acid from the native oil, which may be due in part to the presence of long chain saturated acids in the outer position. This might render the oil metabolically more saturated that the interesterified oils of the same total fatty acid composition, which contain a much greater proportion of the linoleic acid in the primary postions of the triacylglycerol molecule. The identification of specific triacylglycerols may allow the experimental testing of this hypothesis by feeding synthetic triacylglycerols incorporating the potentially atherogenic features.

Arachis↗
PubMed1977

Resolution of molecular species of intact serine and ethanolamine phosphatides by argentation chromatography of their trifluoroacetamides.

An effective resolution of intact phosphatidylserines on the basis of unsaturation has been achieved by conventional argentation thin layer chromatography (TLC) following trifluoracetylaction. The trifluoroacetamides are prepared by treatment with trifluoroacetic anhydride or N-methyl-bis-trifluoroacetamide. The acetamides are resolved with chloroform-methanol-water (65:25:4, v/v/v) on Silica Gel G containing 20% silver nitrate. Subfractions with 0-6 double bonds per molecule were obtained for the phosphatidylserines of pig and ox brain, pig erythrocytes, rat liver, and rabbit skeletal muscle. The preparation of trifluoroacetamides is also advantageous for the silver ion fractionation of phosphatidylethanolamines. The method is applicable to metabolic studies of molecular species using radioactive precursors of neutral lipids, phosphorus, and nitrogenous bases.

Acetamides↗
PubMed1977

Preferential in vivo accumulation of sn-2,3-diacylglycerols in postheparin plasma of rats.

The stereochemical course of in vivo hydrolysis of triacylglycerols by lipoprotein lipase was investigated by determining the structure of diacylglycerol intermediates in postheparin plasma of rats which had been fed [3H]glycerol-labeled Intralipid 2 h before an injection of heparin or had been given an injection of a mixture of [3H]glycerol-Intralipid and heparin. During the clearance of both the natural chylomicrons and the artificial emulsion, sn-2,3-diacylglycerols (60-80%) were found to be the dominant enantiomers. Similar results were obtained when the contribution of the hepatic lipase was altered, either by tying off the mesentery artery and portal vein before injection of heparin, or by injection of heparin directly into the portal vein. These findings are consistent with a preferential release of the acyl group from the sn-1 position of the triacylglycerol molecule as demonstrated previously in vitro. A preferential orientation of the substrate in the enzyme-substrate complex or at the oil-water interface is discussed as a possible basis for these effects.

Animals↗
PubMed1976

Identification of plant sterols in plasma and red blood cells of man and experimental animals.

Direct gas liquid chromatography (GLC) of total plasma lipids showed small peaks (0.5-1.5% of total free sterol area) corresponding to free C28 and C29 sterols in ca. 50% of some 3,000 normal subjects and patients with hyperlipemia. Comparable proportions of similar peaks were present in the sterol fraction isolated from the red blood cells of many of these subjects. The maximum levels of these components in the plasma and red blood cells of domestic and laboratory animals were up to 10 times higher than those seen in man. Detailed gas chromatography/mass spectrometry analyses of the plasma lipids from a much more limited number of subjects and animals showed that the GLC peaks corresponding to the free C28 and C29 sterols were largely due to the plant sterols campesterol, stigmasterol, and beta-sitosterol. In all instances, variable amounts (0.05-0.2% of the total free sterol area) of 7-dehydrocholesterol, desmosterol, lanosterol, and cholesterol alpha-oxide were also detected. While the total content and composition of the plasma plant sterols appeared to vary greatly among the subjects, it never exceeded 2% of total sterol in the normal subjects and patients examined. There was no evidence for a significant increase in the plant sterol content of the plasma of patients with hypercholesterolemia or hypertriglyceridemia.

Animals↗
PubMed1976

Utilization of L-serine in the in vivo biosynthesis of glycerophospholipids by rat liver.

The incorporation of L-serine-U-14C, L-serine-3-14C, and D,L-serine-1-14-C into the glycerophospholipids of rat liver in vivo was determined over a period of 3 min to 13 hr following intravenous injection. The radioactivity from these serines was transferred to variable extent into the glycerol, fatty acid, and nitrogenous base parts of all the glycerophospholipids and neutral lipids. The half-lives and turnover rates of phosphatidylserine calculated from the precursor-product specific activity curves obtained with L-serine-U-14C were 14 min and 0.28 mumol/min/liver, respectively. The half-lives and turnover rates of phosphatidylserine as measured from the decay data of lipid serine from all markers averaged, respectively, 8.2 hr and 0.0008 mumol/min/liver. The discrepancy between these turnover rates was attributed to an understimation of degradation of phosphatidylserine due to its continued biosynthesis and/or an extensive reutilization of L-serine. By monitoring the formation of radioactive lipid ethanolamine, it was found that phosphatidylserine was decarboxylated at one-half the rate of lipid serine biosynthesis. It is suggested that as much as one-half of total phosphatidylserine may be degraded by other mechanisms, such as base exchange with choline, ethanolamine, and serine, as already demonstrated in vitro by other workers. The time course and nature of labeling of phosphatidylcholine was consistent with an extensive conversion of radioactive L-serine to 1-carbon fragments and a rapid methylation of phosphatidylethanolamine to phosphatidylcholine.

Animals↗
PubMed1976

Identification of isomeric doxyl stearic acids by gas-liquid chromatography and mass spectrometry.

Direct probe and GC/MS spectra were determined for the isomeric 4- to 16-doxyl stearic acids and their methyl and silyl esters in pure form and in mixture with natural fatty acids and their esters. The base peak for all free and esterified doxyl stearic acids was at m/e 281. The methyl esters of all isomers gave nearly identical fragments in the high mass regions having M+ at m/e 398 with intensities of 2-3%. The isomers were identified on the basis of the fragments retaining the doxyl group, which had positive charge and were different for each compound. It was shown that the fragment m/e 281 may be used to identify and quantitate the stearate derivatives in presence of natural fatty acids. The silyl esters of the doxyl stearates gave complex mass spectra. The isomeric doxyl stearates were resolved by GLC on 3 ft. glass columns containing 1% SE-30 packing as methyl esters.

Electron Spin Resonance Spectroscopy↗
PubMed1976

Total parenteral nutrition at home: studies in patients surviving 4 months to 5 years.

Total parenteral nutrition at home has been delivered to 12 patients surviving for periods ranging from 4 months to 5 years. The route used is a silicone rubber catheter introduced into the superior vena cava. The mean survival of uncomplicated catheters is 15.8 months, but in 4 patients it is in excess of 28 months. The delivery system is a simple pneumatic infusor set, portable and safe to use, and not requiring complicated electronics. All patients have maintained ideal body weight and have been socially rehabilitated, with two exceptions. Detailed metabolic studies are presented and the data include routine biochemical analyses, liver function tests, liver biopsy results, blood aminograms, the plasma phospholipid fatty acid pattern, the plasma lipoprotein pattern, and blood vitamin and trace element profiles. Based on these findings a nutrient program is recommended and discussed.

Adolescent↗
PubMed1975

Lipd profiles of plasma lipoproteins of fasted and fed normal and choline-deficient rats.

Three major density classes of lipoproteins and a residual protein (d greater than 1.21) were isolated by ultracentrifugation from plasma of fasted, fed normal, and choline-deficient rats. Lipid extracts were obtained from total plasma and the various density classes of lipoproteins, and each extract was examined in detail by thin layer and gas chromatographies. The results indicated essentially identical compositions of molecular species of phosphatidyl choline, which suggested their rapid equilibration among the different plasma lipoprotein classes. In contrast, the molecular species of the triacylglycerols and cholesteryl esters showed significant differences among the chylomicrons, very low and low, and high density lipoproteins, which excluded the possibility of their ready equilibration in vivo. Omission of choline from diet resulted in a sharp and statistically significant decrease in all lipid components of the very low and low density lipoproteins with 2 days. After 10 days of choline deficiency, the lipid levels of chylomicrons and very low and low density lipoproteins were ca. one-half the levels found in the choline supplemented animals, and there were discernible distortions in their lipid composition. Reintroduction of choline led to a prompt return to normal levels and lipid composition of both chylomicron and very low and low density lipoprotein fractions. The lack of equilibration of the triacylglycerols among the lipoprotein classes under normal conditions and in choline deficiency demonstrates an as yet unrecgnized source of compartmentation of plasma lipids.

Body Weight↗