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Biomedical subjects

A Kuksis

Publications and source records attributed to A Kuksis.

At least 19 recordsLinked to original sources
PubMed1979

Identification of lipoprotein X-like particles in rat plasma following Intralipid infusion.

Fasting rats were infused with 10% Intralipid for 24 h (0.33 mL/h per 100 g body weight) and the plasma lipoproteins isolated and compared with those of fed animals and animals with bile duct ligatures as controls. There was a 6- to 10-fold increase in the free cholesterol and phospholipid content of total plasma in animals infused with Intralipid or with ligated bile ducts. The changes were largely restricted to the low density lipoproteins (d=1.019--1.063 g/mL) where free cholesterol and phospholipid increased 30- to 60-fold compared with fed control animals. Hydroxylapatite chromatography of the low density lipoprotein fractions of both Intralipid-infused and bile duct ligated animals yielded a subfraction which was rich in free cholesterol (27%), phosphatidylcholine (66%), and protein (6%); the latter was composed primarily of albumin and apo C proteins. The electrophoretic mobility and polyanionic precipitation properties of the abnormal lipoprotein were indistinguishable from those of lipoprotein X isolated from the animals with bile duct ligatures. The albumin in the abnormal lipoprotein from both groups of experimental animals was detected immunochemically only after delipidation of the lipoprotein. Twice as much of the lipoprotein X accumulated in Intralipid-infused than in the bile duct ligated animals. On rechromatography of the residual low density lipoprotein other subfractions could be isolated which possessed lipid and protein proportions intermediate between those of the lipoprotein X and of normal rat plasma low density lipoprotein. The activity of lecithin cholesterol acyl transferase was increased twofold in the Intralipid-infused animals when compared with control animals, but it decreased by 50% in the animals with bile duct ligatures. It is concluded that the unusual lipoprotein X accumulates in the plasma of Intralipid-infused animals owing to incomplete clearance of the exogenous phospholipid, which mobilized tissue cholesterol and in the form of vesicular particles serves as a lipid phase for apo C proteins. A comparable mechanism is suggested for the formation of lipoprotein X in the animals with bile duct ligature.

Animals↗
PubMed1979

Stereospecific analysis of triacylglycerols via racemic phosphatidylcholines and phospholipase C.

A method of simultaneous determination of stereospecific distribution and molecular association of acyl groups in triacylglycerols has been developed. The analysis is based on a random generation of rac-1,2-diacylglycerols by Grignard degradation, synthesis of rac-phosphatidylcholines, and a stereospecific stepwise release of 1,2-sn- and 2,3-sn-diacylglycerols by phospholipase C. The exact structure of the original triacylglycerols is reconstituted on the basis of complete analysis of the molecular species of the 1,2-sn- and 2,3-sn-diacylglycerols as the tertiary-butyldimethylsilyl ethers by gas chromatography with mass spectrometry. The validity of the method is demonstrated by analyses of synthetic triacylglycerols of known structure. A practical application is illustrated by determination of the fatty acid distribution in lard.

Diglycerides↗
PubMed1979

Preparation and mass spectral behaviour of some 5 beta-cholenoic acids.

Monounsaturated 5 beta-cholanoic acids with double bonds in rings A, B, and C were prepared by POCl3 and ZnCl2 dehydration from natural bile acids with selectively blocked hydroxyl functions. The yields ranged from 15 to 100%. The products were purified by thin-layer and AgNO3 thin-layer chromatography and the structures were confirmed by nuclear magnetic resonance spectroscopy and mass spectrometry. The methyl ester acetates of the unsaturated 5 beta-cholanoic acids possessed chromatographic properties closely similar to those of the corresponding saturated bile acids. Several characteristic fragments were seen in the mass spectra which, in conjunction with the chromatographic properties, permitted an unambiguous distinction between different monounsaturated acids, and between saturated and unsaturated bile acids of the same number and configuration of functional groups. The 20 5 beta-cholenoic acids examined represent all of the simple chemical and enzymatic dehydration products of natural bile acids and can be completely identified by their combined chromatographic and mass spectral properties.

Bile Acids and Salts↗
PubMed1979

Resolution of saturated and unsaturated 5 beta-cholanoic acids by gas-liquid and thin-layer chromatography.

The thin-layer and gas-liquid chromatographic properties of the methyl ester acetates were determined for a series of 20 monounsaturated 5 beta-cholanoic acids representing the simple chemical and enzymic dehydration products of the common bile acids. The unsaturated acids were generally indistinguishable from their saturated analogues by thin-layer chromatography on plain silica gel, but resolution was achieved on silica gel impregnated with silver nitrate for compounds having sterically exposed double bonds. The gas-liquid chromatographic behaviour of the unsaturated bile acids on the OV-225, SE-30, and Poly-S-179 liquid phases was closely similar to that observed for the saturated bile acids. The 5 beta-cholenoic acids obeyed the general rules of chromatographic mobility based on the overall shape of the molecule and the number and configuration of functional groups, with a constant retention factor attributable to the olefinic bond. The structural information provided by the chromatographic behaviour of the standard unsaturated bile acids allows a distinction to be made among most of the isomeric 5 beta-cholenoates. A complete identification of all isomeric olefins is possible when chromatographic and mass spectrometric data are combined.

Bile Acids and Salts↗
PubMed1979

Acylglycerol structure of mustard seed oil and of cardiac lipids of rats during dietary lipidosis.

Stereospecific degradation and combined gas chromatographic--mass spectrometric (gc/ms) analysis were employed in a detailed investigation of the triacylglycerol structure of mustard seed oil and of the triacylglycerols transiently accumulating in the hearts of young rats receiving the oil in their diet. It was shown that feeding of mustard seed oil at 40% of the daily caloric requirement resulted in a deposition of cardiac triacylglycerols containing a high proportion of enantiomers of a positional distribution and molecular association of fatty acids which were closely similar to those found in the dietary oil. Complete structures were derived for a total of 88 species representing 75 to 85% of the triacylglycerols. About 90% of the accumulated triacylglycerol contained at least one long-chain (C20--C22) monounsaturated fatty acid per molecule. The long-chain acids were confined mainly to the primary positions and preferentially to the sn-3-position of the glycerol molecule. The dietary lipidosis, is, therefore, accompanied by little or no accumulation of the normal rat tissue triacylglycerols containing C16 and C18 fatty acids. It is suggested that the deposition and eventual clearance of the enantiomeric long-chain triacylglycerols in the rat heart during mustard seed oil feeding may be largely a result of a gradual change in specificity of the cardiac lipases.

Animals↗
PubMed1979

Improved isolation of villus and crypt cells from rat small intestinal mucosa.

An enzymic method is described which allows the isolation under comparable conditions of crypt and villus cells from rat jejunum with normal morphologic appearance and high metabolic activity when compared with previous preparations. The method is based on a differential scraping of short lengths of everted small intestine to yield two villus cell fractions and a gut wall residue. The scrapings and the gut tube are incubated for the same length of time in a HEPES-buffered modified Hanks' balanced salt solution containing hyaluronidase, DNase, and soybean trypsin inhibitor. The cells of the crypt region are recovered by a further scraping of the digested gut wall. Cells from all fractions are dispersed by gentle agitation, washed, and harvested by centrifugation. The final crypt and villus cells are 95--99% viable by dye exclusion and exhibit 5--20% cross-contamination on the basis of differential marker enzymes. The isolated crypt and villus cells prepared by the new procedure are suitable for comparative studies of metabolic activity in the absence of chelation-induced structural and metabolic abnormalities.

Animals↗
PubMed1979

Appearance and characterization of lipoprotein X during continuous intralipid infusions in the neonate.

The development of hyperphospholipidemia and hypercholesterolemia was studied in infants that required total parenteral nutrition and given a continuous infusion of Intralipid, (1-4 g/kg body wt per 24 h. Detailed studies were carried out on infusion periods lasting 1-10 d. After 24 h there was a marked increase in plasma free cholesterol (68%) and phospholipid (77%) concentrations. Based on the amount of cholesterol in Intralipid, and the rate of infusion, it was estimated that at least 50% of the plasma cholesterol increment during 64-h infusions was derived from endogenous sources. By contrast, the hyperphospholipidemia could be attributed to the Intralipid as the rise in plasma was calculated to be equivalent to only 16% of the exogenous phospholipid infused. Approximately 10% of the phospholipid in Intralipid was in a triglyceride-free mesophase form with a free cholesterol:phospholipid molar ratio of 0.063. There were no systematic changes in plasma concentrations of cholesterol ester or triglyceride during Intralipid infusions. The increase in free cholesterol and phospholipid was localized in the low density lipoproteins (d = 1.006-1.063 g/ml). The presence of lipoprotein X (Lp-X) in the low density lipoprotein fraction was demonstrated by electrophoresis in agar and by isolation and chemical characterization with hydroxylapatite chromatography. Isoelectric focusing of urea-soluble protein of Lp-X revealed that albumin and apolipoproteins CII and CIII were major components, whereas apolipoprotein E and AI were minor constituents. The abnormal lipoprotein was apparent by 16 h during 64 h of infusion. After 6 d of continuous infusions the free cholesterol in Lp-X was 30+/-10 mg/dl (mean+/-SD), which represents a total Lp-X mass of 90 mg/dl. After cessation of the infusion, Lp-X, as monitored by electrophoresis in agar, disappeared within 72-96 h. Thus, during infusion of Intralipid in infants at rates commonly employed, the capacity of the clearance mechanisms for phospholipid are exceeded, which causes the accumulation of phospholipid and free cholesterol in the form of Lp-X particles. It is suggested that mesophase phospholipids in Intralipid may play a significant role in this process.

Apolipoproteins↗
PubMed1979

Lipid absorption and metabolism.

Metabolic processes occurring within the mucosal cell are critical in determining results of interactions between environmental agents and the alimentary tract. The absorption, metabolism, and transport of lipids affects most those agents which are lipid soluble. The understanding of the process involved in lipid absorption and transport is therefore important for both appreciation of the mechanism of uptake of these toxins and for an effective interference with it. Most of the detailed mechanisms of lipid absorption and transport have been proposed from in vitro studies with soluble cell-free systems. The present review integrates these results with recent in vivo and in vitro findings with intact animal tissues and isolated mucosal cells. While there is much general agreement occasional startling differences are also observed, which may have a bearing on the mechanism of normal fat absorption and on the understanding of the transport of the fat-soluble toxins across the mucosal villus cell.

Animals↗
PubMed1978

Choline.

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Animals↗
PubMed1978

Inositol.

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Cell Survival↗
PubMed1978

Bile acids of a 3200-year-old Egyptian mummy.

The bile acids of the gall bladder and hepatic tissue of a 3200-year-old Egyptian mummy were isolated by thin-layer chromatography and identified by combined gas-liquid chromatrography and mass spectrometry. Except for complete deconjugation and extensive dehydration, the bile acids were found to correspond in their qualitative and quantitative composition to the gall bladder bile acids of modern man. The secondary bile acids constituted about 50% of the total and were identified as the normal bacterial oxidoreduction products of the primary bile acids and their dehydration products. In addition a series of unsaturated bile acids were identified, which corresponded to the dehydration products of cholic and chenodeoxycholic acids. It is suggested that both bile acid deconjugation and the limited oxidoreduction were probably brought about by the Clostridium organisms identified in the tissue. On the basis of the bile acid composition it is concluded that the ancient man metabolized cholesterol along the same pathways as modern man.

Bile Acids and Salts↗
PubMed1977

Lack of fatty acid specificity in the lipolysis of oligo and polyunsaturated triacylglycerols by milk lipoprotein lipase.

Native soybean and rapeseed oils and native and rearranged cod liver and peanut oils were subjected to partial hydrolysis with milk lipoprotein lipase and the fatty acid composition and molecular association in the substrates and lipolysis products were determined. In both native and rearranged oils the lack of significant differences in the fatty acid composition and molecular association between the residual and total triacylglycerols suggested that all triacylglycerols were attacked by the lipoprotein lipase at about the same rate. Any enrichment of a specific fatty acid in the diacyl- or monoacylglycerol products of a native oil generally reflected the preferential association of the fatty acid with the 2-position, and to a lesser extent the sn-3-position of the glycerol molecule and was accompanied by a decreased level of the corresponding free fatty acid product. In general, the products of the rearranged oils closely resembled the original triacylglycerols in the fatty acid composition. It is concluded that lipoprotein lipase does not show any detectable specificity for the unsaturated and polyunsaturated fatty acids with double bonds located at carbons 3 to 19 from the carboxyl end of the fatty acid molecules. These findings are compatible with the possible binding of the substrate to lipoprotein lipase through atoms involved in the acyl ester groups of the triacylglycerol molecules.

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↗