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At least 847 records · Page 47Linked to original sources
PubMed2000

Impact of antiandrogen treatment on the fatty acid profile of neutral lipids in human meibomian gland secretions.

The purpose of this study was to determine whether the use of antiandrogen medications is associated with significant alterations in the fatty acid (FA) profiles of neutral lipids in human meibomian gland secretions. Meibomian gland secretions were obtained from both eyes of patients receiving antiandrogen therapy and from age-related controls. Samples were processed for high-performance liquid chromatography/mass spectrometry and an evaluation of the mass/charge ratios of neutral lipid FA. Our results demonstrate that antiandrogen therapy is associated with significant and consistent alterations in the mass/charge ratios of neutral lipid fractions of meibomian gland secretions. Patients taking antiandrogen medications had significant changes in the occurrence of numerous diglyceride, triglyceride, and wax/cholesterol ester FA products, compared with age-matched controls. Statistical analyses of data within groups demonstrated very high correlation coefficients, and cross-correlation analyses revealed characteristic shifts in FA patterns between groups. Our findings show that antiandrogen use is paralleled by significant changes in the FA profiles of neutral lipid fractions in meibomian gland secretions.

Aged↗
PubMed1990

Protein kinase C and progesterone-induced maturation in Xenopus oocytes.

Though progesterone-induced maturation has been studied extensively in Xenopus oocytes, the mechanism whereby the prophase block arrest is released is not well understood. The current hypothesis suggests that a reduction in cAMP and subsequent inactivation of cAMP-dependent protein kinase is responsible for reentry into the cell cycle. However, several lines of evidence indicate that maturation can be induced without a concomitant reduction in cAMP. We show that the mass of diacylglycerol in whole oocytes and plasma membranes decreases 29% and 10% respectively, within the first 15 sec after the addition of progesterone. Diacylglycerol in plasma membranes further decreased 59% by 5 min. We also show that the protein kinase C inhibitors sphingosine and staurosporine can induce oocyte maturation. In addition, the synthetic diglyceride, DiC8, and microinjected PKC can inhibit or delay progesterone-induced maturation. These results together suggest that a transient decrease in protein kinase C activity may regulate entry into the cell cycle. The mechanism whereby DAG is decreased in response to progesterone is unclear. Initial studies show that progesterone leads to a decrease in IP3 suggesting that progesterone may act by reducing the hydrolysis of PIP2. On the other hand, progesterone caused a decrease in the amount of [3H]arachidonate labelling in DAG during the same time suggesting that progesterone may stimulate lipase activity. The relationship between postulated changes in the PKC pathway and those hypothesized for the PKA pathway are discussed.

Alkaloids↗
PubMed1977

Galactosylation of different monogalactosyldiacylglycerols by cell-free preparations from pea leaves.

The formation of digalactosyldiglycerol (DGD) from monogalactosyldiglycerol (MDG) was studied in cell-free preparations from pea leaves. Under optimized conditions UDP-[U-14C]galactose was incorporated into a single lipid which was shown to be DGD by cochromatography before and after deacylation and by cocrystallization of the acetyl derivative. Seven MGD species were prepared which had different fatty acids and from zero to eight double bonds. These substrates were dispersed at identical overall concentrations by sonication in Triton X-100 solution and galactosylation rates were measured under optimized conditions. Galactosylation rates increased with the number of double bonds up to a total of six, beyond which the rate decreased again. These galactosylation rates cannot be related to difference in the diglyceride moieties of natural MGD and DGD.

Cell-Free System↗
PubMed1975

Lipid composition of buffalo spermatozoa: a cytochemical and biochemical study.

Buffalo spermatozoa have been studied cytochemically and biochemically to investigate their phospholipids, which appear to be phosphatidyl choline, lysolecithin, phosphatidyl ethanolamine, phosphatidyl inositol, phosphatidyl glycerol and monogalactosyl diglyceride. Most of them form lipoprotein complexes in the regions of the plasma membrane, the post-nuclear cap and the mid-piece. The lipid composition of buffalo spermatozoa has been compared to and contrasted with that of bull and ram spermatozoa and species differences are indicated.

Animals↗
PubMed2001

Increased fatty acid uptake and altered fatty acid metabolism in insulin-resistant muscle of obese Zucker rats.

Altered muscle fatty acid (FA) metabolism may contribute to the presence of muscle insulin resistance in the genetically obese Zucker rat. To determine whether FA uptake and disposal are altered in insulin-resistant muscle, we measured palmitate uptake, oxidation, and incorporation into di- and triglycerides in isolated rat hindquarters, as well as muscle plasma membrane fatty acid-binding protein (FABP(PM)) content of lean (n = 16, fa/+) and obese (n = 15, fa/fa) Zucker rats (12 weeks of age). Hindquarters were perfused with 7 mmol/l glucose, 1,000 micromol/l albumin-bound palmitate, and albumin-bound [1-(14)C]palmitate at rest (no insulin). Glucose uptake was 42% lower in the obese than in the lean rats and indicated the presence of muscle insulin resistance. Fractional and total rates of palmitate uptake were 42 and 74% higher in the obese than in the lean rats and were associated with higher muscle FABP(PM) content (r(2) = 0.69, P < 0.05). The percentage of palmitate oxidized was not significantly different between groups. FA disposal to storage was altered according to fiber type. When compared with lean rats, the rate of triglyceride synthesis in red muscle was 158% higher in obese rats, and the rate of palmitate incorporation into diglycerides in white muscle was 93% higher in obese rats. Pre- and postperfusion muscle triglyceride levels were higher in both red and white muscles of the obese rats. These results show that increased FA uptake and altered FA disposal to storage may contribute to the development of muscle insulin resistance in obese Zucker rats.

Animals↗
PubMed1976

A micro-method for determination of fatty acid (FIAT) and glucose (GLIAT) incorporation and lipolysis in vitro in needle biopsies of human adipose tissue.

A method for determination of fatty acid (FIAT) and glucose (GLIAT) incorporation into adipose tissue in vitro in needle biopsy specimens of human fat has been developed. 20-150 mg of subcutaneous fat is incubated in an albumin buffer containing a physiological spectrum and concentration of fatty acids and glucose. Release of glycerol and fatty acids to the incubation medium and incorporation of labelled palmitic acid and labelled glucose into extracted adipose tissue lipids are determined simultaneously. The labelled fatty acids are found in the fatty acid part and the labelled glucose only in the glycerol part of extracted diglycerides and triglycerides. These glycerides are completely recovered and indicated FIAT and GLIAT values. Methodological errors for all vaiables are about 10%. All processes increase linearly with tissue weight and incubation time. FIAT and GLIAT increase linearly with increasing concentration of a physiological spectrum of fatty acids (=constant fractional incorporation). The method is simple, and several analyses from one subject can be performed on one day with a minimum of discomfort to the patient.

Adipose Tissue↗
PubMed1989

Angiotensin increases arachidonate metabolism in cultured anterior pituitary cells.

Angiotensin peptides produced a rapid (within 30 seconds) and concentration-dependent increase in the levels of the unesterified fatty acid and stimulated prolactin release. [3H]arachidonate appeared to be cleaved primarily from the lipid of the phosphoinositide cycle. In fact, angiotensin II produced a significant reduction of [3H]phosphatidylinositol. Conversely, [3H]diacylglycerol rapidly increased after the addition of angiotensin II to the incubation medium, returned to basal values within 2 minutes and then decreased below the control levels by 3-4 minutes, possibly due to the release of [3H]arachidonate. Finally, RHC 80267, a rather selective inhibitor of diglyceride lipase, antagonized angiotensin II-induced [3H]arachidonic acid and prolactin release. The effect of arachidonate on prolactin release has to be ascribed to further metabolism of the fatty acid to products other than prostaglandins and thromboxanes. The inhibitor of the cyclo-oxygenase pathway, indomethacin, did not significantly modify angiotensin II-induced prolactin release, whereas BW 755c and ETYA (inhibitors of cyclo-, lipo- and epoxygenase pathways) and NDGA (an inhibitor of leukotriene and epoxyeicosanoid synthesis) completely counteracted the effect of the octapeptide on hormone release.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1975

Studies on catalytic properties of purified high molecular weight pancreatic lipase.

The properties of the 500-fold purified high-molecular-weight lipase have been studied. The rate of hydrolysis of the triglycerides decreases with increasing fatty acid chain length. The lipolytic activity also increases with increase in unsaturation in the fatty acyl moiety. Diglycerides are hydrolyzed at more than twice the rate for triglycerides while monoglycerides are not hydrolyzed. Methyl esters are generally hydrolyzed at a higher rate which increases with increasing chain length of the fatty acid but the enzyme does not act on phospholipids. Emulsifying agents such as Tween 20, gum arabic, and albumin increase the rate of hydrolysis. Metal ions such as Hg2+, Zn2+, Cu2+, and Fe2+ strongly inhibit the lipolytic activity of the high-molecular-weight lipase while Ca2+ or Mg2+ by themselves show no stimulating effect. Treatment of the high-molecular-weight lipase with P-chloromercurybenzoate inhibits hydrolytic activity by 70% while iodoacetic acid has no effect.

Albumins↗
PubMed2000

[Synthesis of cationic glucosyldiglycerides].

A series of glucosyl dialkylglycerols with the pyridinium, N-morpholinium, and N-methylimidazolium polar heads were synthesized by quaternization of the corresponding bases with the acetylated glucosyl diglyceride 6-O-methane- and 6-O-toluenesulfonates. The resulting compounds were designed for the use in gene delivery systems.

Cations↗
PubMed1975

Enzymes of phospholipid metabolism in the plasma membrane of Acanthamoeba castellanii.

Phospholipase A, lyophospholipase, acyl CoA hydrolase, and palmitoyl CoA synthetase are present in the plasma membrane of Acanthamoeba castellanii. The first three of these enzymes also occur in other cell fractions but in concentrations too low for the activities in the plasma membrane fraction to be accounted for by contamination by any other cell fraction. Palmitoyl CoA synthetase is restricted almost entirely to the plasma membrane and microsomal fractions; the microsomal activity is too low for the plasma membrane activity to be due to contamination by microsomes. Acyl COA:lysolecithin acyltransferase is predominantly localized in the microsomal fraction, but the activity of the plasma membrane is probably too great to be accounted for by microsomal contamination. CDPcholine:1,2-diglyceride cholinephosphotransferase is restricted almost entirely to the microsomal fraction. Phospholipase C was not detected in any cell fraction or in the growth medium.

Acyltransferases↗
PubMed1975

Biosynthesis of bis(monoacylglyceryl)phosphate and acylphosphatidylglycerol in rat liver mitochondrial.

Bis(monoacylglyceryl)phosphate is present in trace quantities in normal liver where it represents smaller than 1 percent of total liver phospholipids. This compound is of considerable interest since its level can be greatly increased in certain lipidoses, either of a genetic nature or caused by drugs. Biosynthesis of bis(monoacylglyceryl)P in vitro has not previously been demonstrated. This paper reports the enzymatic formation of bis(monoacylglyceryl)P and acylphosphatidylglycerol as minor products from cytidine diphosphate diglyceride and radioactive sn-glycerol-3-P using a crude mitochondrial fraction from normal rat liver; phosphatidylglycerol was the principal product. Evidence is also presented which shows the enzymatic formation of acylphosphatidylglycerol and bis(monoacylglyceryl)P from [1',3'-14C]phosphatidylglycerol by a crude rat liver mitochondrial preparation in vitro. The structures of the radioactive bis(monoacylglyceryl)P and acylphosphatidylglycerol were tentatively established by thin layer chromatography, and chromatography of the products of mild alkaline hydrolysis and acetolysis. Radioactive acylphosphatidylglycerol was stoichiometrically converted to bis(monoacylglyceryl)P by treatment with bee venom phospholipase A, providing additional evidence for the structure of acylphosphatidylglycerol and bis(monoacylglyceryl)P.

Animals↗
PubMedDate not supplied

[Lipid composition of Cunninghamella elegans cultivated on n-alkanes].

The ability to oxidize n-alkanes was studied with various species of fungi belonging to the Cunninghamella genus. These fungi are able to assimilate hydrocarbons and to accumulate up to 1.5 g/litre of biomass. The most active strain was Cunninghamella elegans (-) 1204. The amount of lipids formed, and their composition, depended on the length of the carbon chain of oxidized alkane. The content of fat in the cells increased with the length of the hydrocarbon chain. The following lipid fractions have been detected: phospholipids, monoglycerides, diglycerides, triglycerides, sterols, free fatty acids, sterol esters, and hydrocarbons. The qualitative composition of the fractions depended, to a considerable extent, on the n-alkane utilized. Investigation of the fatty-acid composition of intracellular lipids has shown that fatty acids with an even number of carbon atoms are formed from hydrocarbons with an even number of these atoms, while fatty acids both with an even and odd number of carbon atoms are synthesized from hydrocarbons with an odd number of these atoms. The relative content of the acids with the same number of carbon atoms as that of the alkane being utilized increased with the length of the carbon chain.

Alkanes↗
PubMed1992

Activation of NADPH oxidase and phospholipase D in permeabilized human neutrophils. Correlation between oxidase activation and phosphatidic acid production.

A major function of human neutrophils (PMN) during inflammation is formation of oxygen radicals through activation of the respiratory burst enzyme, NADPH oxidase. Stimulus-induced production of both phosphatidic acid (PA) and diglyceride (DG) has been suggested to mediate oxidase activity; however, transductional mechanisms and cofactor requirements necessary for activation are poorly defined. We have utilized PMN permeabilized with Staphylococcus aureus alpha-toxin to elucidate the signal pathway involved in eliciting oxidase activity and to investigate whether PA or DG act as second messengers. PMN were permeabilized in cytoplasmic buffer supplemented with ATP and EGTA for 15 min before addition of NADPH and various cofactors. Oxidase activation was assessed by superoxide dismutase inhibitable reduction of ferricytochrome C; PA and DG levels were measured by radiolabeled product formation or by metabolite mass formation. Both superoxide (O2-) and PA formation were initiated by 10 microM GTP gamma S; addition of cytosolic levels of calcium ions (Ca2+, 120 nM) enhanced O2- and PA formation 1.5-2 fold. DG levels showed little change during these treatments. PA formation preceded O2- production and varying GTP gamma S levels had parallel effects on O2- and PA formation. However, while PA formation and oxidase activation occurred in tandem at Ca2+ levels of < 1 microM, higher calcium enhanced PA formation but inhibited O2- production. Removal of ATP completely blocked O2- production but had little effect on PA formation; in contrast, if ATP was replaced with ATP gamma S, parallel production of PA and O2- occurred in the absence of other cofactors. Finally, while inhibition of PA production by ethanol pretreatment led to inhibition of O2- formation in PMN treated with GTP gamma S alone, in cells stimulated with a combination of GTP gamma S and Ca2+, ethanol continued to inhibit PA formation but had no effect on O2- production. Our results do not support a role for DG in the signal transduction path leading to oxidase activation and, while we show a close correlation between oxidase activation and PA production under many physiologic conditions, we also demonstrate that PA is not sufficient to induce oxidase activation and O2- formation can occur when PA production is inhibited.

Adenine Nucleotides↗
PubMed1992

Ca2+ and partly GTP gamma S-dependent particulate phospholipase C hydrolyzing phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate is inhibited by diacyl(acyl-acetyl) glycerols.

The activity of a phosphodiesterase of the phospholipase C (PLC) type and factors influencing its activity were studied in ascites tumor cells. The enzyme confined to the 12,000 x g particulate fraction hydrolyses inositol phospholipids, with preference for phosphatidylinositol 4-phosphate (PtdIns(4)P) over phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), exhibiting maximum values of 61 and 15 nmol/min per mg protein, respectively, at a pH optimum of 5.5. The phosphodiesterase, which is strongly Ca2+ dependent with optimal free Ca2+ concentrations between 20 and 100 nM for both substrates, is almost completely inhibited (93-95%) in the presence of 2 mM EGTA. Only the PLC acting on PtdIns(4,5)P2 is significantly activated in the presence of 6-60 microM GTP gamma S. The low extent of enzymatic activity in the presence of 5 mM MgCl2 or chelating agents is suggestive of inositolphosphatase activity which is supported by the determination of small amounts of myo-inositol during HPLC analyses. Both dioleoylglycerol (DAG) and the membrane-permeable 1-oleoyl-2-acetyl-sn-glycerol (OAG) inhibit PLC activity, exhibiting IC50 values of 5 microM with PtdIns(4)P and approx. 10 microM with PtdIns(4,5)P2 as substrate and maximum inhibition up to 60% (DAG) and 80% (OAG). These data are indicative of a mechanism of direct negative feedback regulation of the enzyme by diglycerides which may explain the observed long-term effects of OAG on PLC activity in cell culture experiments.

Calcium↗
PubMed1992

Synthesis of the orally macrofilaricidal and stable glycerolipidic prodrug of melphalan, 1,3-dipalmitoyl-2-(4'(bis(2''-chloroethyl)amino)phenylalaninoyl)gl ycerol.

A new strategy is presented to develop macrofilaricidal compounds orally administered and able to concentrate in the lymphatic system. A diglyceride derivative of melphalan, 1,3-dipalmitoyl-2-(4'(bis(2''-chloroethyl)amino)phenylalaninoyl)gl y cerol, was synthesized. The esterification of melphalan by 1,3-dipalmitin allowed chemical stabilization of the alkylating agent in aqueous dispersion. No degradation of this prodrug was observed after a 3-month storage of an aqueous dispersion at 4 degrees C. The filaricidal activity of the prodrug was compared with those of melphalan in vitro against adults, infective larvae and microfilariae of Molinema dessetae, and evaluated in vivo on Molinema dessetae infected Proechimy oris. In vitro, melphalan and the glycerolipidic prodrug were inactive against microfilariae but active at 1 mmol/l against infective larvae and adults. In vivo studies were performed with rodents subcutaneously inoculated with infective larvae from Aedes aegypti. The number of macrofilariae was significantly reduced following treatment with a single oral dose of the alkylating agent prodrug (0.082 mmol/kg).

Aedes↗
PubMed2004

Nuclear production and metabolism of diacylglycerol.

The story of nuclear diacyglycerol is proving to be a complex one. Sub-pools of nuclear diglyceride that differ in their metabolism, nuclear localization and temporal regulation have been identified, suggesting potentially diverse signaling functions. One of the great remaining challenges is to assign functional roles to these diverse populations. In the last twenty years great strides have been made toward understanding the character and composition of nuclear DAG. Determining the functions of this nuclear lipid should make the next twenty years interesting indeed.

Animals↗