scholarly journals Effects of anti-microtubular agents and cycloheximide on the metabolism of chylomicron cholesteryl esters by hepatocyte suspensions

1977 ◽  
Vol 162 (2) ◽  
pp. 367-377 ◽  
Author(s):  
A Nilsson
Keyword(s):  
Cholesteryl Ester ◽  
Cholesteryl Esters ◽  
Chylomicron Remnant ◽  
Trypsin Treatment ◽  
Heparin Plasma ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of

1. Post-heparin plasma that promoted rapid hydrolysis of about 90% of the triacylglycerol markedly stimulated the uptake or binding of chylomicron cholesteryl ester by suspended hepatocytes. The net hydrolysis of chyle cholesteryl ester after the uptake by the cells was, however, slower than in vivo. 2. The cholesteryl ester uptake in the presence of post-heparin plasma was larger if the cells had been preincubated for 2h. It was inhibited by the presence of colchicine, vinblastine or cycloheximide during the preincubation, and by mild trypsin treatment of the preincubated cells. 3. The results suggested that the anti-microtubular agents, but not cycloheximide, also inhibited the hydrolysis of chyle cholesteryl ester after uptake or binding to the cells. 4. The uptake of isolated chylomicron remnant particles was more efficient than that of native chyle lipoproteins. It was, however, still stimulated by heparin alone and by post-heparin plasma. The heparin-stimulated uptake was markedly decreased if cycloheximide was present during the preincubation period.

scholarly journals Dynamic nuclear polarization of biocompatible13C-enriched carbonates for in vivo pH imaging

2016 ◽  
Vol 52 (14) ◽  
pp. 3030-3033 ◽  
Author(s):  
D. E. Korenchan ◽  
R. R. Flavell ◽  
C. Baligand ◽  
R. Sriram ◽  
K. Neumann ◽  
...  
Keyword(s):  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Ph Imaging ◽  
Low Toxicity ◽  
High Concentrations ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of

High concentrations of hyperpolarized13C-bicarbonate are generatedviarapid hydrolysis of highly polarizable, low-toxicity carbonate precursors.

EFFECTS OF PROSTAGLANDINS ON THE METABOLISM OF CHOLESTERYL ESTER IN RAT TESTES: CHANGES IN THE SYNTHESIS AND HYDROLYSIS OF CHOLESTERYL ESTER AND THE ACTIVITY OF CHOLESTEROL SIDE-CHAIN CLEAVAGE ENZYME

1978 ◽  
Vol 79 (1) ◽  
pp. 41-48 ◽  
Author(s):  
T. TAKATORI ◽  
A. YAMAOKA
Keyword(s):  
Cholesteryl Ester ◽  
Subcutaneous Administration ◽  
Testicular Tissue ◽  
Male Rats ◽  
Side Chain ◽  
Cholesteryl Esters ◽  
Side Chain Cleavage ◽  
Chain Cleavage ◽  
Cleavage Enzyme ◽  
Hydrolysis Of

The effects of prostaglandins on testicular synthesis and hydrolysis of cholesteryl esters, the activity of the enzyme involved in cleavage of the cholesterol side-chain and on serum levels of testosterone and LH have been studied. Subcutaneous administration of prostaglandins to male rats caused an increase in the concentration of cholesteryl esters in the testes, a decrease in testicular synthesis and hydrolysis of cholesteryl esters but no change in the activity of the cholesterol side-chain cleavage enzyme. There was also a significant decrease in the serum level of testosterone, but the level of LH was raised. Prostaglandins also affected the fatty acid composition of lipids in rat testicular tissue; cholesteryl esters were found to contain greater amounts of arachidonic (C20:4) and docosapentaenoic (C22:5) acids. These findings suggest that prostaglandins are involved in the turnover of cholesteryl esters in rat testicular tissue and regulate the production of androgens.

scholarly journals An alternative procedure for incorporating radiolabelled cholesteryl ester into human plasma lipoproteins in vitro

1985 ◽  
Vol 226 (1) ◽  
pp. 319-322 ◽  
Author(s):  
D C K Roberts ◽  
N E Miller ◽  
S G L Price ◽  
D Crook ◽  
C Cortese ◽  
...  
Keyword(s):  
Cholesteryl Ester ◽  
Human Plasma ◽  
Specific Radioactivity ◽  
Density Lipoprotein ◽  
Plasma Lipoproteins ◽  
Cholesteryl Esters ◽  
Simple Method ◽  
High Specific Radioactivity

A simple method has been developed for labelling human plasma lipoproteins to high specific radioactivity with radioactive cholesteryl esters in vitro. After isolation by preparative ultracentrifugation, the selected lipoprotein was incubated for 30 min at 4 degrees C in human serum (d greater than 1.215) that had been prelabelled with [4-14C]cholesteryl oleate or [1,2-3H]cholesteryl linoleate, and was then re-isolated by ultracentrifugation. All major lipoprotein classes were labelled by the procedure. Specific radioactivities of up to 18 d.p.m. pmol-1 (46 d.p.m. ng-1) were achieved. When radiolabelled high-density lipoprotein was infused intravenously, the radioactive cholesteryl ester behaved in vivo indistinguishably from endogenous cholesteryl esters produced by the lecithin (phosphatidylcholine): cholesterol acyltransferase reaction.

scholarly journals Binding, interiorization and degradation of cholesterol ester-labelled chylomicron-remnant particles by rat hepatocyte monolayers

1977 ◽  
Vol 168 (3) ◽  
pp. 483-494 ◽  
Author(s):  
Claes-Henrik Florén ◽  
Åke Nilsson
Keyword(s):  
Cell Surface ◽  
Cholesteryl Ester ◽  
Time Course ◽  
Inhibitory Effect ◽  
Metabolic Inhibitors ◽  
High Density Lipoproteins ◽  
Chylomicron Remnant ◽  
Very Low Density Lipoproteins ◽  
Chylomicron Remnants ◽  
Hydrolysis Of

1. The cholesteryl ester of isolated chylomicron-remnant particles was efficiently degraded by hepatocyte monolayers. The degradation was sensitive to metabolic inhibitors. 2. With increasing amounts of remnant cholesteryl ester the rate of uptake approached saturation and conformed to a linear double-reciprocal plot. The Vmax. was determined as 80ng of cholesteryl ester/h per mg of protein and the apparent Km as 1.4μg of cholesteryl ester per mg of protein. The time course for the uptake and hydrolysis suggested that binding of particles to the cell surface preceded the degradation. 3. Cholesteryl esters of native chylomicrons were degraded to a much smaller extent and their presence had only a small inhibitory effect on the degradation of chylomicron remnants. Intestinal very-low-density lipoproteins were degraded somewhat faster than chylomicrons, and caused more inhibition of remnant degradation. Rat high-density lipoproteins inhibited the hydrolysis of remnant cholesteryl ester by up to 50%, but had less influence on the amount of cholesteryl ester that was bound to the cells. Serum decreased both the uptake and hydrolysis, whereas d=1.21 infranatant had no effect. 4. The cholesteryl ester hydrolysis after the uptake by the cells was inhibited by chloroquine and by colchicine. Only 28–36% of the unhydrolysed cholesteryl ester could be released from these cells by trypsin treatment, indicating that the major portion was truly intracellular. The particles that could be released from the cell surface by trypsin and those remaining in the medium had the same triacylglycerol/cholesteryl ester ratio as the added remnant particles. Significant amounts of denser particles were thus not formed during contact with the cell surface. 5. The presence of heparin, as well as preincubation of the cells with heparin, increased the uptake of chylomicron remnants. This effect was most marked in the presence of serum. A much smaller proportion of the other serum lipoproteins was taken up, and this proportion was not increased by heparin.

scholarly journals Lipid metabolism in Trypanosoma brucei: utilization of myristate and myristoyllysophosphatidylcholine for myristoylation of glycosyl phosphatidylinositols

1996 ◽  
Vol 318 (2) ◽  
pp. 575-581 ◽  
Author(s):  
Karl A WERBOVETZ ◽  
Paul T ENGLUND
Keyword(s):  
Fatty Acid ◽  
Trypanosoma Brucei ◽  
Surface Glycoprotein ◽  
Free System ◽  
Glycosyl Phosphatidylinositol ◽  
Physiological Importance ◽  
Fatty Acid Species ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of

Myristate is the exclusive fatty acid species in the glycosyl phosphatidylinositol (GPI) anchor of the Trypanosoma brucei variant surface glycoprotein (VSG). [3H]Myristate can be incorporated into T. brucei GPIs by two distinct processes known as fatty acid remodelling and myristate exchange. Myristoyllysophosphatidylcholine (M-LPC) can also serve as a myristate donor for VSG in trypanosomes [Bowes, Samad, Jiang, Weaver and Mellors (1993) J. Biol. Chem. 268, 13885–13892]. We have studied in detail the myristoylation of GPIs using a [3H]M-LPC substrate. Labelling of VSG and free GPIs by [3H]M-LPC in cultured trypanosomes occurred at the same rate as with [3H]myristate. Concurrent with GPI labelling, there was rapid hydrolysis of [3H]M-LPC to generate extracellular [3H]myristate. Experiments in a trypanosomal cell-free system indicated that GPI labelling by fatty acid remodelling and myristate exchange was also equally efficient with [3H]M-LPC and [3H]myristate. Furthermore, both ATP and CoA are required for the myristoylation of GPIs by [3H]M-LPC. These experiments suggest that GPI myristoylation from M-LPC involves hydrolysis of M-LPC to free myristate. To address the physiological importance of myristate and M-LPC in VSG myristoylation, we radiolabelled trypanosomes in vivo with both substrates in medium containing serum, and found that [3H]myristate labelled VSG and GPIs more efficiently. Thus, VSG myristoylation by free myristate may be favoured in bloodstream trypanosome infections.

Effect of different neutral phospholipids on apolipoprotein binding by artificial lipid particles in vivo

1986 ◽  
Vol 64 (8) ◽  
pp. 826-835 ◽  
Author(s):  
Ming-for Tong ◽  
Arnis Kuksis
Keyword(s):  
Egg Yolk ◽  
Hepatic Uptake ◽  
Plasma Lipoproteins ◽  
Variable Component ◽  
Qualitative And Quantitative ◽  
Lipid Particles ◽  
Rapid Hydrolysis ◽  
A Minor ◽  
Hydrolysis Of

Soybean triacylglycerol particles, stabilized with egg yolk sphingomyelin (SPH), phosphatidylcholine (PC), phosphatidylethanolamine (PE), or PC–PE mixtures, with diameters ranging from 170 to 550 nm were prepared by sonication and isolated by ultracentrifugation. Binding of apoproteins to the lipid particles was studied in vivo using the strategy of Connelly and Kuksis. The recoveries of the injected particles, which had decreased in size and undergone minimal changes in lipid composition, ranged from 70% and 57% for SPH- and PC-stabilized particles to 14% for particles stabilized with egg yolk PC–PE mixtures. The apoprotein (apo) composition of the recovered particles showed qualitative and quantitative differences, which were affected by the number of washes during isolation. After four washes, the SPH and PC particles contained apoE, apoC-II, and apoC-III as major components and apoA-IV as minor components. In addition, all particles, except those stabilized with egg yolk PC, contained large amounts of albumin. In contrast to egg yolk PC, the dipalmitoyl PC particles bound albumin as a major component. The recovered PC-PE and PE particles were characterized by a relative decrease of apoC and greatly increased binding of albumin. The higher rate of clearance of the PE-containing particles was attributed to a relative absence of apoC-III, which is known to delay hepatic uptake of lipid particles containing it, and to a more rapid hydrolysis of PE by lipoprotein lipases. Since PE occurs as a minor and variable component of chylomicrons and plasma lipoproteins, the present observations are of physiological interest.

scholarly journals Tissue-Specific Ablation of ACSL4 Results in Disturbed Steroidogenesis

Endocrinology ◽  
2019 ◽  
Vol 160 (11) ◽  
pp. 2517-2528 ◽  
Author(s):  
Wei Wang ◽  
Xiao Hao ◽  
Lina Han ◽  
Zhe Yan ◽  
Wen-Jun Shen ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Cholesteryl Ester ◽  
Ex Vivo ◽  
Cholesteryl Esters ◽  
Steroid Synthesis ◽  
Tissue Specific ◽  
Ester Formation ◽  
Long Chain

Abstract ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to acyl-coenzyme As, which are essential for fatty-acid incorporation and utilization in diverse metabolic pathways, including cholesteryl ester synthesis. Steroidogenic tissues such as the adrenal gland are particularly enriched in cholesteryl esters of long-chain polyunsaturated fatty acids, which constitute an important pool supplying cholesterol for steroid synthesis. The current studies addressed whether ACSL4 is required for normal steroidogenesis. CYP11A1 promoter‒mediated Cre was used to generate steroid tissue‒specific ACSL4 knockout (KO) mice. Results demonstrated that ACSL4 plays an important role in adrenal cholesteryl ester formation, as well as in determining the fatty acyl composition of adrenal cholesteryl esters, with ACSL4 deficiency leading to reductions in cholesteryl ester storage and alterations in cholesteryl ester composition. Statistically significant reductions in corticosterone and testosterone production, but not progesterone production, were observed in vivo, and these deficits were accentuated in ex vivo and in vitro studies of isolated steroid tissues and cells from ACSL4-deficient mice. However, these effects on steroid production appear to be due to reductions in cholesteryl ester stores rather than disturbances in signaling pathways. We conclude that ACSL4 is dispensable for normal steroidogenesis.

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