Deuterium magnetic resonance study of cholesteryl esters in membranes

The ternary systems EYL:H2O (50:50 wt %) containing 1 and 5 mol % cholesteryl palmitate-d31 or 1 and 5 mol % cholesteryl palmitate-16,16,16,16-d3 have been studied. Cholesteryl palmitate-d31 gave a unique deuterium magnetic resonance spectrum corresponding to a homogeneous (delta vQ = 3 and 12 kHz) and a solid phase (deltaVQ = 38 and 118 kHz). From the characteristic spectra and spin-lattice relaxation times, a procedure for calculating the amount of each phase present in the ternary mixture is given resulting in a maximum value of homogeneously dissolved cholesteryl palmitate of 0.2 +/- 0.1 mol % and a solid fraction above 0.2 mol %. The most probable order parameter for the (-CD2)n portion of the homogeneous fraction of cholesteryl palmitate-d31 was determined from the quadrupolar splittings to be S = 0.1 which is less than one-half that of the order parameter found for the lecithin chains. Possible explanations for the diminution of the order parameter for cholesteryl ester in bilayers are discussed.

The lipid composition of rat brain aggregating cell cultures during development

The lipid and fatty acid composition of rat brain was studied during its development both in vivo and in an aggregating cell culture system. Although the amount of lipid present in the cultures was very low, the increase in glycolipid content corresponded closely to the period of intense myelin formation. Very long chain fatty acids (hydroxylated and unsubstituted) were present in 41-day cultures. In comparison to the in vivo situation, myelination was delayed in vitro and, after 40 days in culture, cholesterol esters were 5-fold higher than in vivo, indicating that demyelination was occurring.

Very low density and low density lipoprotein subfractions in type III and type IV hyperlipoproteinemia. Chemical and physical properties

Subfractions of CLDL (VLDL), Sf 100-400; CLDL2, Sf 60--100; VLDL3, Sf 20--60) and LDL (LDL), Sf 12--20; LDL2, Sf 6--12; LDL3, Sf 3--6) were isolated from the plasma of three normal, three type III and four type IV hyperlipoproteinemic subjects. In the type IV group, all VLDL subspecies were of normal composition but were increased in concentration in the order VLDL1 greater than VLDL2 greater than VLDL3. In the same subjects, although LDL2 was lowered and LDL3 increased, the total plasma LDL concentration was normal. All VLDL subfractions were elevated in the type III group, but in this case VLDL3 predominated. These subfractions were enriched in cholesteryl esters and depleted in triglyceride. In the LDL density range there was a shift of mass towards the least dense fraction, LDL1, which was of normal composition. EPR studies of the VLDL and LDL subfractions in a type IV subject demonstrated a decrease in fluidity with increasing density. The major change occurred between VLDL3 and LDL1 and was attributed to a substantial alteration in the cholesteryl ester : triglyceride ratio in the particle. A similar argument was used to explain thction in normal or type IV subjects. Particle diameters, determined by laser light-scattering spectroscopy were in good agreement with the values obtained by electron microscopy. This study provides a baseline for the examination of the relationship between the physical and metabolic properties of VLDL and LDL subfractions in type III and IV hyperlipoproteinemia.

Adrenoleukodystrophy brain cholesteryl esters and other neutral lipids

Further examination of the neutral lipid fractions derived from brain tissue of two patients afflicted with adrenoleukodystrophy has demonstrated the presence not only of free cholesterol and cholesteryl ester, but also of appreciable free fatty acid and triglyceride. Using a gas--liquid chromatographic system normally employed for the analysis of long-chain fatty acids of galactolipids and spingomyelin, it was possible to establish the presence of long-chain (greater than C20) fatty acids in the cholesteryl ester, free fatty acid and triglyceride fractions. Long-chain fatty acids were most abundant in the cholesteryl esters. Fatty acids identified by gas--liquid chromatography and gas chromatography--mass spectroscopy included normal saturated and monounsaturated fatty acids as large as C34. Several unknown fatty acyl compounds, of as yet undetermined structure, were also observed. All investigations thus far would indicate that the pathogenesis of adrenoleukodystrophy is closely related to the aberrant metabolism of these long-chain fatty acids.

Lipoidal bladder concretion: an unusual autopsy finding in acute lymphoblastic leukemia

The occurrence of a large (2.3 gm.), wax-like, creamy white concretion in the bladder of a 7-year-old girl who died of acute lymphoblastic leukemia is reported. Lipids constituted 40% of the total weight and triglycerides accounted for 95% of the total lipids. The fatty acid composition of the individual lipid classes showed a predominance of saturated fatty acids (75 to 80%). Factors influencing the pathogenesis of the material are discussed. A review of the literature on childhood leukemia showed no reference to such lipid abnormalities and the occurrence of this type of concretion has not been reported previously.

Studies on the structure of low density lipoproteins isolated from Macaca fascicularis fed an atherogenic diet

Cynomolgus monkeys, Macaca fascicularis, fed cholesterol-containing saturated-fat diets develop increased levels of high molecular weight plasma low density lipoproteins (LDL), associated with accelerated atherosclerosis. To study the composition and structure of these abnormal particles, LDL from monkeys, fed atherogenic and control diets, were characterized chemically and examined by differential scanning calorimetry and low-angle X-ray scattering. LDL from animals on the experimental diet showed an increase in molecular weight (4.0 to 7.0 x 10(6), experimental diet compared with 3.0 to 3.7 x 10(6), control diet) associated with a large increase in cholesterol ester content and concomitant smaller increases in protein, phospholipid, and free cholesterol. There was a strong positive correlation between molecular weight and the number of saturated and monounsaturated cholesterol esters in the particle. In contrast, particle content of polyunsaturated cholesterol esters remained constant despite large changes in total particle cholesterol esters.When examined by calorimetry and X-ray scattering, LDL from monkeys on both diets diplayed a reversible transition of cholesterol esters from an ordered smeticlike (layered) structure to a more disordered state. For all animals on the experimental diet, the peak temperature of the cholesterol-ester transition (42-48 degrees C) was above body temperature (39 degrees C), but below body temperature on the control diet (34-38.5 degrees C). In the experimental group, the transition temperature was correlated with the LDL molecular weight. However, after thermal disruption of LDL, liquid-crystalline transitions of LDL cholesterol esters were observed in the same temperature range as in the intact lipoprotein, which shows that changes in particle size had little effect on the cholesterol-ester transition temperature. Rather, the transition temperature was determined by the degree of saturation of the LDL cholesterol ester fatty acids and the LDL cholesterol ester: triglyceride ratio, both of which correlated with increased LDL molecular weight.The existence of smectic-like cholesterol ester in LDL at body temperature was clearly a discriminating feature between monkeys on control and experimental diets. Diet-induced changes in the lipid composition of precursor lipoproteins of LDL appeared to lead to the existence of smectic-like cholesterol ester in LDL above body temperature. The altered composition and structure of the core lipids of high molecular weight LDL probably account, in part, for the previously documented correlation between increased LDL molecular weight and atherosclerosis in this species.

[Cholesterol ester storage disease in children. Comparative biochemistry of hepatocyte and fibroblast cultures]

The results of biochemical studies in three children with cholesterol ester storage disease are reported. This rare disease (13 published cases) and the related Wolman's disease are characterised by a deficiency of acid lipase. Affected children mostly present with isolated hepatomegaly. Hepatic cells (one patient) and fibroblasts (two patients) were cultured and cholesterol accumulation measured. Hepatic cells contained more cholesterol than fibroblasts but the enzyme deficiency, assessed by the abnormal degree of esterification was the same in both cell types.

[Chromatographic fractionation of cholesterol esters in Morgagni's hepatic cirrhosis. Preliminary note]

The behaviour of plasma cholesteryl esters has been investigated in patients with liver cirrhosis (so-called Laennec's cirrhosis). Both absolute and percentage values of esters containing di-, tri- and tetra-unsaturated fatty acids were decreased below the normal range; however, the various esters groups showed unequal decrement rates. These findings may be the result of a low lecithin: cholesterol-acyltransferase (LCAT) activity, due either to depression of the enzyme syntesis in the liver, or to inadequate substrate supply (possibly related with an impaired fatty acid production and lecithin synthesis). A decrease of all ester fractions, or a selective one, could also be induced by the releasing of abnormal hydrolases from damaged liver tissues.

Procedure for determination of free and total cholesterol in micro- or nanogram amounts suitable for studies with cultured cells

Procedures for the determination of free and total cholesterol in lipid extracts or sonicates of 10(4) cultured human skin fibroblasts are described. The method for free cholesterol employs cholesterol oxidase to generate H2O2 and peroxidase to catalyze the reaction of H2O2 with p-hydroxyphenylacetic acid to yield a stable fluorescent product. Cholesterol ester hydrolase is included for determination of total cholesterol. When samples of sonified cell suspensions are used directly, the extraction of lipids is avoided, permitting one person to carry out analyses of 30 or more subcultures in one day.

Regression of naturally occurring atherosclerotic lesions in pigeon aorta by intestinal bypass surgery. Early changes in arterial cholesteryl ester metabolism

Early changes in cholesteryl ester metabolism of the aorta during the regression of naturally occurring atherosclerotic lesions in pigeon aorta by ileal bypass surgery were examined. Three months after surgery, there was a decrease (50%) in the content of cholesteryl esters in the aorta. Increases in the activity of cholesteryl ester hypdrolase in the lysosomal (P less than 0.05) and the supernatant (P less than 0.01) fractions of the aorta also occurred at this time. There were no differences in the activity of cholesteryl ester synthetase and in the plasma levels of cholesterol and triglycerides between the ileal bypass group and the controls. These results suggest that ileal bypass surgery decreases the level of cholesteryl esters in the aorta, probably because of enhanced cholesteryl ester hydrolysis.

Spectrodensitometry of nanogram quantities of cholesterol

In studies of hydrolysis and synthesis of cholesterol esters by aortic enzymes, conventional methods (aside from isotope methodology) are too insensitive to measure reaction products when few aortas are used. High-performance thin-layer chromatography coupled with spectrodensitometry of plates charred after spraying with a cupric acetate-phosphoric acid reagent permitted quantitation of 10-ng amounts of cholesterol, cholesterol oleate oleate, and oleic acid. Linear calibration curves were obtained after spectrodensitometry of chromatograms containing 10-200 ng of lipid. The results were verified by radioassay.

Quantification of adipocyte free and esterified cholesterol using liquid gel chromatography

A reliable method for the separation of free and esterified cholesterol in adipocyte extracts is described. The procedure uses Sephadex LH-20, a lipophilic dextran gel, with a solvent system of chloroform-hexane 55:45 (v/v). Interference by excess triglyceride, such as that encountered in adipocyte total lipid extracts, was not observed, and overall recovery of both sterols exceeded 98%.

Changes in the adrenal cortex of the rat after chronic administration of the steroidogenic inhibitor U-8113

In concert with studies of the effects of various pharmacologic inhibitors of corticosteroidogenesis on adrenocortical morphology, U-8113, an analog of amphenone B, was administered daily to Sprague-Dawley rats for 7, 14, 21 or 30 day. The primary morphological responses involved increases in adrenal weight, width of zona fasciculata, width of zona reticularis, intracellular lipids, mitochondrial size, mitochondrial vacuolation and crystalline-like inclusions, small coated vesicles, lysosomes, autophagic vacuoles and cholesterol ester clefts. In particular, the increases in lysosomes, coated vesicles and autophagic vacuoles containing morphologically altered mitochondria were considered reflective of mechanisms designed to maintain cellular integrity amidst functional impairment. Lipid analysis revealed marked increases in cholesterol esters and phospholipids, supportive of morphological observations. When permitted a 14 day recovery period following either 14 or 30 days of inhibitor therapy, most fine structural alterations and lipid derangements were diminished, and the cells approximated normal parameters.

Lipid composition of the gastric mucous barrier in the rat

The lipid composition of the "mucous barrier" of rat stomach was investigated. Cellular mucus of the mucous cells from gastric epithelium and surface mucus from gastric mucosa were obtained by perfusion in vivo of Ghosh-Lai rat stomachs with 2 M NaCl. Lipids extracted from dialyzed and lyophilized 2 M NaCl perfusates and 0.9% NaCl (saline) controls were quantitatively separated into single components by means of two-dimensional thin layer chromatography and compared. Significant differences in the level of cholesterol esters, di- and triglycerides, and glycolipids were found. Three to 4 times greater quantities of cholesterol esters and di- and triglycerides, and 2 to 6 times greater quantities of glycolipids were found in 2 M NaCl perfusates as compared to saline controls. The glycolipid fraction consisted of neutral and acidic glyceroglucolipids and was devoid of glycosphingolipids. The phospholipids constituted the smallest portion of the lipids present in 2 M NaCl and saline perfusates and were 2 times higher in 2 M NaCl. These data indicate that mucous barrier in addition to mucins contains considerable quantities of lipids of which glyceroglucolipids are the most prominent components.

[Physical state of lipids accumulated in atherosclerotic lesions (author's transl)]

The work of Small and al. concerning the physical state of lipids accumulated in atherosclerotic plaques, is analysed. This team of biophysicists studies the composition in cholesterol, cholesterol esters and phospholipids, of each type of lesion and reports it on a phase diagram, while identifying the physical state of these lipids by polarizing microscope and by X-ray diffraction. In such a way, they show that the ordinary fatty streak has a composition which situates it in the 2 phases-zone, and actually demonstrate liquid crystals of phospholipids (+ cholesterol + cholesterol esters) and oily droplets of cholesterol esters, but never cholesterol crystals. In the other types of lesions (intermediary lesions, fibrous plaques and atheromatous plaques) they find, in addition to liquid crystals and oily droplets previously mentioned, crystals of cholesterol monohydrate, which leads to 3 phases. These findings are in accord with experimental models studied by the authors, for whom the physical state of lipids plays a very important role in the formation as well as the regression of atherosclerotic plaques.

The picomole determination of free and total cholesterol in cells in culture

An enzymatic, fluorometric method for the determination of free and total cholesterol in cells in culture is presented. The method is simple, requiring one reagent that includes all of the enzymes and a second reagent that increases the pH, which enhances the fluorescence of the product. The method is based on the enzymatic hydrolysis of cholesteryl esters to free cholesterol, the oxidation of cholesterol with the liberation of hydrogen peroxide, and the reaction of this peroxide with a fluorogen to form a fluoresencet product in the presence of a peroxidase. It is rapid, in that free cholesterol can be read in 5 minutes and total cholesterol after 20 minutes. The precision of the method is greater than that obtained from gas-liquid chromatography.

[Contribution to the study of gallstones. Morphological, radiological and cristallographic analysis (author's transl)]

The structure of gallstones has become of recent interest with the medical treatment of cholesterol stones. It seemed to us interesting to determine by morphological, radiological and above all cristallographic criteria the constituants of gallstones in order to draw up a practical classification which reflects better the biological reality. The present study confirms the existence of cholesterol and calcium carbonate in various types of stone, but reveals in addition the presence of cholesterol and bile salts associated with new mineral constituants identified for the first time (aluminium chlorite and silicate). The notion of pure stones, generally attributed to cholesterol and pigmented stones was only verified in the case of mineral stones.

The effect of digitonin-containing fixatives on the retention of free cholesterol and cholesterol esters

The influence of several fixation and dehydration procedures on the retention of free cholesterol and cholesterol esters was studied in filter paper preparations. The retention of free cholesterol by the filter paper proved to be decreased by the addition of digitonin to the aldehyde fixative (aqueous phase) and was only slightly enhanced by partial dehydration (alcoholic phase, up to 70% ethanol). Furthermore, digitonin or the presumably formed cholesterol-digitonide complex bound hardly any osmium oxides in glass-fibre paper. Up to 26% of the cholesterol esters was mobilized during the aqueous phase when digitonin was added to the aldehyde fixative. When the glass-fibre papers containing the digitonin cholesterol-ester-osmate complexes were stored in distilled water after fixation, the fluid became turbid. Particulate material isolated from this turbid solution showed ultrastructurally a close resemblance to the 'whorls' observed by several authors in tissue fixed by a digitonin-containing aldehyde fixative. Digitonin also changed the ultrastructural appearance of liposomes, containing lecithin: cholesterol: phosphatidic acid; in a molar ratio 7:2:1. Our observations lead to the conclusion that the use of digitonin-containing fixatives should be abandoned, because they give results which cannot be interpreted. By the use of K4 [Fe(CN)6] containing OSO4 in the post-fixation step were able to demonstrate an increase in the visualization of membranous structures (liposomes).

Lipid composition of Microsporum gypseum

The lipid composition of Microsporum gypseum has been studied. The lipids amounted to 10.1% and phospholipids to 1.1% of the mycelial dry weight. Phosphatidyl choline, phosphatidyl serine and phosphatidyl ethanolamine were the major components, while lysophosphatidyl choline, and phosphatidyl inositol were present in smaller quantities. Neutral lipids consisted of monoglycerides, diglycerides, triglycerides, free and esterified cholesterol.

Cerebral cortical cholesterol changes in cobalt-induced epilepsy

The present study was designed to elucidate cerebral cortical cholesterol changes observed earlier in cobalt-induced epilepsy in the rat. This model is produced by insertion of cobalt metal rods into the cerebral cortex. Seven days after implantations of cobalt (or other metals), measurements of cerebral cortical lipid concentrations were made in the direct area of metal implantation (lesion area) and in the nonnecrotic tissue immediately adjacent to the lesion site (adjacent area). The cortical concentration of free cholesterol decreased and the concentrations of cholesterol esters (CE) greatly increased in the adjacent area of rats implanted with epileptogenic metals (cobalt and nickel) but not in those implanted with nonepileptogenic metals (copper and stainless steel). Differences in the fatty acid compositions of CE from plasma and those from cobalt-lesioned cortex indicated that the accumulated CE originated in the brain rather than from the plasma CE pool. A time course study revealed that changes in the cortical concentrations of free and esterified cholesterol precedes the first appearance of epileptiform activity as measured by electrocorticography. The reduction of free cholesterol levels most likely reflects increased cholesterol metabolism in the cobalt-lesioned cortex. A major portion of this free cholesterol appears to be converted to CE, but not to bile acid or neutral sterol (potential products of cholesterol metabolism). The concentration of free fatty acids, the other substrate of CE formation, was decreased in the lesion site. The increased metabolism of cholesterol could not be explained by changes in the activities of CE synthetase and hydrolase(s). Since cholesterol in the brain is found almost exclusively in membranes, it is likely that these sterol changes reflect membrane alterations or disintegration. However, the exact relationship of these changes to the epileptogenic effect of cobalt remains unclear.

The circadian cycles of plasma corticosterone and adrenal cholesteryl esters in the normal and EFA-deficient female rat

In female rats subjected to a 12 hr light-12 hr darkness schedule and fed a semipurified diet containing 10% corn oil, plasma corticosterone concentration showed a monophasic circadian cycle with minimum and maximum concentrations at the start of the light and dark periods, respectively. Adrenal total cholesteryl ester concentration was inversely related to plasma corticosterone, as were those of several of the individual esters; changes in cholesteryl ester concentration appeared to follow rather than precede changes in plasma corticosterone. There was preferential depletion of the cholesteryl esters of 18:1, 18:2omega6, and 20:4omega6 during glucocorticoid secretion. [

ABBREVIATIONS

EFA, essential fatty acid (s);X:YomegaZ, fatty acid with X carbon atoms and Y olefinic bonds with the terminal double bond Z carbon atoms from the methyl group.] In female rats fed hydrogenated coconut oil (EFA-deficient), a monophasic cycle for plasma corticosterone was also observed, but the peak was much broader than that recorded for rats fed corn oil, although minima and maxima occurred at similar times for the two groups. No significant cycle of adrenal total cholesteryl esters was evident in the deficient rats, but the 20:3omega9 and 22:3omega9 esters did decrease significantly during the period of high plasma corticosterone concentration. Preferential net decreases in adrenal cholesteryl esters during corticosteroidogenesis were more apparent in normal than in EFA-deficient rats.

[Content of basic lipid fractions in the myocardium of different regions of the heart in healthy people]

Content of lipids was studied in five parts of myocardium of healthy people by means of thin-layer chromatography on silica gel. The higher content of triglycerides and total lipids was found in dexter parts of heart as compared with sinister parts and septum interventriculare. The same distribution was not shown for free and esterified cholesterol.

Gas-liquid chromatographic determination of cholesterol and other sterols in foods

A gas-liquid chromatographic (GLC) method, using the butyryl esters of sterols, has been developed for the measurement of cholesterol, stigmasterol, sitosterol, and campesterol in foods. An immobile phase of 1% SE-30 coated on 100-120 mesh Gas-Chrom Q packed in a 6 inch X 4 mm id glass column operated at 255 degrees C was the most satisfactory of 7 column packings evaluated. Extraction with chloroform-methanol gave 98.7% recovery with a coefficient of variation of 1.8% for cholesterol added to a variety of foods. When cholesteryl palmitate was added to vegetable oil and the butyryl derivative was prepared, followed by GLC analysis, the recovery was 99.3% with a coefficient of variation of 0.9%. Amounts as low as 1 mg/100 g food can be detected with a precision of 2.5%. The results of the analysis of a variety of foods for cholesterol, campesterol, sitosterol, and stigmasterol are given.

[Vessel wall lipids in human atherosclerosis]

Relative content of linoleic acid in the fraction of cholesterol esters was increased in "unaltered" intima of human aorta in course of aging. Due to this phenomenon the fatty acid composition of this lipid fraction became similar to the composition of cholesterol esters in lipoproteins of low density, observed in blood of persons at the age of 50 and older. Lipids were accumulated extracellularly in intima of aorta in the course of aging. The high ratio of linoleic acid was also typical for the fatty acid composition of cholesterol esters in fibrous patch with area of atheromatosis (amorphous accumulation of fat, localized out of the cells). These data demonstrate that lipoproteins of low density from blood serum may serve as a source of accumulation of lipids both in "unaltered" intima in the course of ageing and in fibrous patch. The lower ration of linoleic acid and relatively higher content of oleic acid were the characteristic properties of cholesterol esters from lipid spots ("early impairment") as compared with intima and atheroma. Cells of lipid spots, filled with fat, might apparently degrade the liproproteins from blood serum and the liberated cholesterol could be esterified by fatty acids, newly synthesized or preformed in the cells.

The extraction and partial characterization of proteins released by decalcification from calcified human aortic plaques

Tissue from severely atherosclerotic human aortas was divided into heavily calcified (plaque) and less calcified (non-plaque) areas. After defatting and thorough extraction with neutral salt solutions, further proteinaceous material was released from plaque than non-plaque areas. Although organic phosphorous was associated with the EDTA-solubilized protein from both plaque and non-plaque areas, the phosphorous to protein ratio of extracts from plaque areas was 2 to 3 times that from non-plaque areas. Analysis of the major protein component of the extract of plaque areas indicated an acidic glyco-protein which appeared to be associated with an organic phosphorous moiety as well as cholesterol and cholesterol esters.

Adrenoleukodystrophy. Accumulation of cholesterol esters with very long chain fatty acids

An accumulation of fatty acids having chain lengths of C22 to C26 was demonstrated in the cholesterol ester fraction of white matter from two boys with adrenoleukodystrophy. A similar accumulation of very long chain fatty acids was also shown in gangliosides and cerebrosides. A disorder of the one-carbon degradation system responsible for the metabolism of some of the very long chain fatty acids may be the basic enzymatic defect in this condition.

A new system for lipid analysis by liquid chromatography-mass spectrometry

A simple system for interfacing liquid chromatography with mass spectrometry for the analysis of lipids is described. The system is based on the moving chain transport principle and employs an endless stainless steel belt of perforated construction that gives it superior surface properties and capacity to entrain solvent. The entire column eluent is collected on the belt which transports it into an evaporator where the solvent is removed. The solute, which remains as a residue on the belt, is transported into a reactor where it is converted to hydrocarbons by reaction with hydrogen at 400-450 C. The hydrocarbons, which are characteristic of the structures of the parent compounds, are swept into an outlet tube where ca. 15% are drawn into the ion source of a mass spectrometer operating in the chemical ionization mode using methane as the reagent gas. The spectrum is recorded on an oscillographic recorder for identification purposes. Detection and quantitative analysis is performed by single ion monitoring of the most intense ion using a conventional analog recorder. The system is domonstrated by application to a standard mixture of tripalmitin, cholesteryl palmitate, and cholesterol separated on a 3.2 x 250 mm silica column, and exhibited a sensitivity of ca. 1 nanogram per component injected on the column.

A sensitive enzymatic method for determination of free and esterified tissue cholesterol

An enzymatic assay currently in use in clinical laboratories for quantitating total serum cholesterol has been modified for the determination of microgram quantities of tissue cholesterol. Two types of assays were developed. In the first, more generally useful method, lipids extracted with chloroform/methanol were solubilized by the addition of detergent and assayed for free and total cholesterol using laboratory prepared mixtures of reagents. Although different detergents were effective, it appears that Triton X-100 may be most universally applicable. In the second type of assay, commercially available reagent mixtures were employed for the determination of total cholesterol only. Results of both types of assays compare favorably with determination using the colorimetric assay on 3beta-hydroxysterols recovered from digitonides.

Characterization of human very low density lipoproteins containing two electrophoretic populations: double pre-beta lipoproteinemia and primary dysbetalipoproteinemia

Two discrete populations of very low density lipoproteins, with fast and slow pre-beta electrophoretic mobility, were found in 50% of normolipemic and 30% of hyperlipemic individuals selected at random. The two populations were isolated by preparative electrophoresis from five hyperlipemic subjects. The particles comprising the slow component were smaller than those of the fast component and the slow component contained a larger proportion of cholesteryl esters, free cholesterol, B-apoprotein, and arginine-rich apoprotein and a smaller proportion of triglycerides and the two most anionic apoproteins (R-glutamic acid and R-alanine). The properties of the slow component thus closely resemble those of "remnant" very low density lipoproteins that accumulate in blood plasma of functionally hepatectomized rats. The chemical composition of the slow component was also similar to that of the very low density lipoproteins with beta mobility found in primary dysbetalipoproteinemia. However, the proportion of cholesteryl esters and argininerich apoprotein was much higher in the latter. The argininerich apoprotein from very low density lipoproteins of most normolipemic and hyperlipemic subjects separates into three or four major bands upon isoelectric focusing electrophoresis in polyacrylamide gels, with pI varying from 5.57 to 6.03. In very low density lipoproteins from individuals with primary dysbetalipoproteinemia, this protein uniquely contains little or none of the two most cationic bands. The number of bands was constant in all subjects studied. The pattern was the same in very low density lipoproteins with fast and slow pre-beta mobility as well as in the beta and pre-beta components in primary dysbetalipoproteinemia. These results suggest that many individuals have "remnant" very low density lipoproteins in their plasma. However, the beta-migrating "remnant" that accumulated in large amounts in individuals with primary dysbetalipoproteinemia contains much more arginine-rich protein and this protein is structurally abnormal.

[Guinea pig brain and spinal cord phospholipids and cholesterol in tricresyl phosphate poisoning]

Chronic intoxication of guinea pigs was induced by intracutaneous inoculation of tricresylphosphate (TCP). The brain stem and spinal cord total phospholipids and total, free and esterified cholesterol were determined during the severe neuroparalytic stage of TCP intoxication. The content of phosphilipids and of total cholesterol was not altered, but cholesterol esters appeared to accumulate both in the brain stem and the spinal cord. Cholesterol esters are characteristic products of degraded myelin sheaths.

Methods for the rapid separation and estimation of the major lipids of arteries and other tissues by thin-layer chromatography on small plates followed by microchemical assays

Methods are described for the rapid separation of the major individual phospholipids and neutral lipids of tissues by thin-layer chromatography on small glass plates (75 X 75 mm), and for the specific microchemical estimation of separated lipids and for determination of fatty acid composition and radioactivity. The overall method, involving tissues extraction, thin-layer chromatographic separation and assay has been evaluated using pure standards and biological samples and gives good reproducibility and almost complete recovery of lipids.

[Lipid analysis in jaw cysts]

In patients with jaw cysts, cyst content and blood serum are examined by means of thin section chromatography with regard to their contents of cholesterol, free fatty acids, triglycerides and cholesterol esters. The increase in lipid content found in the cyst is primarily due to the increase in free cholesterol. Since the serum values are within normal ranges, it is unlikely that cysts are the result of endogenous causes. Our examinations showed that they are primarily due to local processes.

[Comparative study of lipid fraction content in different areas of the rabbit myocardium]

Comparative study of content of main lipid fractions was carried out in five parts of rabbit myocardium by means of thin-layer chromatography on silicagel with subsequent quantitative estimation. Increased concentrations of free and esterified cholesterol, free fatty acids and triglycerides were observed in atrium dextrum and triglycerides in ventriculus dexter as compared with either the corresponding left-side parts of the heart muscle or with septum interventriculare. Content of cholesterol esters, free fatty acids and triglycerides was higher in atrium dextrum as compared with ventriculus dexter. The lowest concentration of phospholipids was approximately the same in other parts of the heart muscle.

[Catabolic changes in endogenous lipids in rat adrenal glands during autolysis]

Alterations in lipid composition of rat adrenal glands were studied at various periods of autolysis by means of micro-thin layer chromatography. Phospholipids, cholesterol and its esters proved to be the most labile lipid fractions of the tissue. At early period of autolysis (4 hrs) content of total lipids was decreased mainly due to lowering in amount of phospholipids, cholesterol and its esters and only slightly - to lowering in content of free fatty acids. In subsequent necrobiotic degradation of adrenal gland tissue (10 hrs) the increase in content of total lipids was related to the distinct elevation in amount of free fatty acids and glycerides. Mechanisms of the phenomenon observed are discussed.

Lipids of transmissible gastroenteritis virus and their relation to those of two different host cells

The lipids of two cell types (primary pig kidney and secondary adult pig thyroid) and those of transmissible gastroenteritis virus (TGEV) grown in these cells were studied using 14C-palmitic acid. Differences were demonstrated between the incorporation of isotopically labelled lipid precursors in the two cell types and it was found that the phospholipid and glycolipid profiles of purified TGEV closely resembled those of the host cell in which it was grown.

An enzymatic method for the histochemical localization of free and esterified cholesterol separately

An enzymatic method for the histochemical localization of cholesterol is presented. It makes possible the localization of free cholesterol, cholesterol esters, or both and is compatible with routine histological staining procedures. The method is based on the production of H2O2 from free cholesterol by cholesterol oxidase. Sites of peroxide production are visualized by a brown reaction product formed in a peroxidase-catalysed reaction between diaminobenzidine and H2O2. Cholesterol esters can be demonstrated as cholesterol after hydrolysis by cholesterol ester hydrolase. Some examples of the application of the method are given.