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PubMed1985

Kinetic study of deuterium-labelled polyenphosphatidylcholine after oral administration to rats.

Deuterium-labelled di-[( 15,15,16,16-2H4]-linoleoyl) -3-sn-glycero-phosphocholine was used as a tracer of the major component of soybean polyene-3-sn-phosphatidylcholine to study the pharmacokinetics of a natural product after oral administration to rats. For this purpose a method was developed to isolate the phosphatidylcholine fraction from blood in a highly purified form. Only 200 pg deuterium-labelled fatty acid generated from the phosphatidylcholine fraction and a ratio of one molecule of deuterium-labelled stearic acid to 500 molecules of stearic acid are necessary for a reproducible measurement by gas chromatography/mass spectrometry. The highest amount of di-[( 15,15,16,16-2H4]-linoleoyl) -3-sn-glycerophosphocholine (0.12% dose/ml, i.e. 2.1% of the maximum absorbed dose) was detected in blood 6 h after administration. The results are comparable with those found after administration of di-[l-14C]-linoleoyl-3-sn-glycerophosphocholine. Hence it is possible to use deuterium-labelled polyenphosphatidylcholine instead of radioactively labelled polyenphosphatidylcholine, especially if a harmless tracer is required.

Animals↗
PubMed1997

Stevastelins, a novel group of immunosuppressants, inhibit dual-specificity protein phosphatases.

BACKGROUND: Since the molecular target of the immunosuppressive reagents FK506 and cyclosporin A was revealed to be protein phosphatase PP2B (calcineurin), many researchers have been screening the protein phosphatase inhibitors from microbial metabolites to develop new immunosuppressive reagents. We isolated stevastelin B, which is composed of valine, threonine, serine and 3,5-dihydroxy-2,4-dimethyl stearic acid, and stevastelin A, which is a sulphonylated derivative of stevastelin B. To understand the action mechanism of stevastelins A and B, we synthesized a series of stevastelin derivatives and investigated their structure-activity relationships. RESULTS: A series of stevastelin derivatives have been systematically synthesized. Stevastelin B inhibited gene expression that is dependent on interleukin-2 (IL-2) or IL-6 promoters in situ, but it had no inhibitory activity against any protein phosphatases in vitro. In contrast, stevastelin A, which is a sulphonylated derivative of stevastelin B, inhibited the phosphatase activity of a dual-specificity phosphatase, VH1-related human protein (VHR), in vitro, but it had no inhibitory activity against gene expression or cell-cycle progression in situ. CONCLUSIONS: Stevastelin B is a novel immunosuppressant. It inhibited IL-2 or IL-6 dependent gene expression but did not inhibit the phosphatase activity of calcineurin. The structure-activity relationships show that the acidic functional group on the threonine residue and the stearic acid moiety in the stevastelin molecule are important for inhibitory effects on the dephosphorylation activity of VHR in vitro. Stevastelin B might be sulphonylated or phosphorylated after incorporation into the target cell, and then it interacts with protein tyrosine phosphatases and regulates cell-cycle progression.

Anti-Bacterial Agents↗
PubMedDate not supplied

Evaluation and preparation of controlled release lipid micropheres of sulphamethizole by a congealable disperse phase encapsulation method.

A congealable disperse phase encapsulation method was used to prepare controlled release lipid microspheres of sulphamethizole as a model drug. Hydrogenated cotton seed oil (HCSO) and stearic acid were employed as the lipid matrix materials. Tween 60 was the droplet stabilizer used to form microspheres. In in vitro dissolution tests, the drug release was found to be affected by the type of lipid material depending on hydrophilicity. Generally, an initial rapid release followed by a slower release of the drug from the lipid microspheres was observed. Lipid microspheres were also compressed in the tablet form to prevent the initial rapid release of the drug. But the drug release drastically decreased. To achieve a controlled release of the drug. Eudragit L as a channeling agent was added internally to HCSO-microspheres. Although the drug release increased, the controlled release pattern was not achieved. The external addition of polyethyleneglycole 4000 to HCSO-microspheres before compressing tablets, did not produce an affirmative change in the release profile. The lipid microspheres prepared by stearic acid released all of the drug within 1 h. Upon compression, the drug release was very low. Therefore, stearic acid-microspheres were compressed in the tablet form adding disintegrating agents, sodium alginate and Ac-Di-Sol (cross-linked sodium carboxymethylcellulose). A pH-dependent drug release was obtained from the tablets containing sodium alginate. With the tablets of stearic acid-microspheres containing Ac-Di-Sol, the controlled release could be achieved due to gradual disintegration from the tablet to aggregates, and to individual microspheres. Furthermore, in vivo study on 6 healthy volunteers confirmed the controlled release pattern of this dosage form.

Adult↗
PubMed2001

Single cell oil production by Yarrowia lipolytica growing on an industrial derivative of animal fat in batch cultures.

The growth of an oleaginous strain of Yarrowia lipolytica on an industrial fat composed of saturated free fatty acids (stearin) was studied. Lipid accumulation during primary anabolic growth was critically influenced by the medium pH and the incubation temperature. This process was independent of the nitrogen concentration in the culture medium, but was favored at a high carbon substrate level and at a low aeration rate. At pH 6 and a temperature of 28-33 degrees C, 9-12 g/l of dry biomass was produced, whereas significant quantities of lipids were accumulated inside the yeast cells (0.44-0.54 g of lipid per gram of biomass). The strain showed the tendency to degrade its storage lipids, although significant amounts of substrate fat, rich in stearic acid, remained unconsumed in the culture medium. Y. lipolytica presented a strong fatty acid specificity. The fatty acids C12:0, C14:0, and C16:0 were rapidly incorporated and mainly used for growth needs, while C18:0 was incorporated with reduced rates and was mainly accumulated as storage material. Reserve lipids, principally composed of triacylglycerols (55% w/w of total lipids) and free fatty acids (35% w/w), were rich in stearic acid (80% w/w), while negligible amounts of unsaturated fatty acids were detected. When industrial glycerol was used as co-substrate, together with stearin, unsaturated fatty acid concentration in the reserve lipid increased.

Air Movements↗
PubMedDate not supplied

Surface-chemical studies on chlorhexidine and related compounds: II. Interactions with monomolecular-film systems.

Interactions of chlorhexidine and structurally related biguanides with selected monomolecular-film systems (that is, stearic acid, stearyl alcohol, and N-octadecylacetamide) were explored. The data reflected the significance of ionic associations between the compounds and stearic acid films and, in the instance of the biguanide analogs, indicated that the length of the alkyl chain was an important factor in the penetration process.

Acetamides↗
PubMed1991

Proton transport at the monolayer-water interface.

It is shown that when monolayers of stearic acid, palmitic acid, DPPC, or DPPS are compressed above some critical area Ac a lateral conduction mechanism is initiated at the monolayer/water interface. The interfacial conductance increases on further increasing the molecular packing density in the monolayer. All compounds also show major changes in surface potential at Ac the potential becoming more positive in all cases. It is argued that this is a consequence of structural reorganisation at the headgroup/water interface causing a significant reduction in the local permittivity. The critical area, Ac, is approximately double the molecular areas estimated from the pressure-area isotherm, and experiments with stearic acid monolayers show that Ac decreases significantly when the chaotropic ion SCN-, which is known to disrupt the molecular structure of water, is added to the subphase. It is likely, therefore, that the structural changes occurring at Ac involve the formation of a hydrogen bonded network between monolayer headgroups and adjacent water molecules at the monolayer/water interface. It is suggested that the conduction mechanism initiated at Ac arises from proton hopping along this hydrogen-bond network.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

Effect of enzymatic interesterification on melting point of palm olein.

Immobilized PS-C 'Amano' II lipase was used to catalyze the interesterification of palm olein (POo) with 30, 50, and 70% stearic acid in n-hexane at 60 degrees C. The catalytic performance of the immobilized lipase was evaluated by determining the composition change of fatty acyl groups and triacylglycerol (TAG) by gas liquid chromatography and high-performance liquid chromatography, respectively. The interesterification process resulted in the formation of new TAGs, mainly tripalmitin and dipalmitostearin, both of which were absent in the original oil. These changes in TAG composition resulted in an increase in slip melting point, from the original 25.5 degrees C to 36.3, 37.0, and 40.0 degrees C in the modified POo with 30, 50, and 70% stearic acid, respectively. All the reactions attained steady state in about 6 h. This type of work will find great applications in food industries, such as confectionery.

Burkholderia cepacia↗
PubMed1992

Inhibition of human term placental and fetal liver glutathione-S-transferases by fatty acids and fatty acid esters.

Glutathione-S-transferase (GST) activity from human term placenta and human fetal liver towards 1-chloro-2,4-dinitrobenzene as the second substrate was significantly inhibited by the saturated fatty acids, stearic (SA) and palmitic (PA) acids and fatty acid esters, ascorbyl stearate (Asc-S) and ascorbyl palmitate (Asc-P). The nature of inhibition of human placental GST was competitive towards CDNB with Ki values of 3.1, 10.0, 13.5 and 18.5 microM for Asc-S, Asc-P, PA and SA, respectively. The inhibitory effect of Asc-S on human term placental GST was reversible. I50 values for Asc-S, Asc-P, SA and PA were 15, 45, 83 and 78 microM, respectively, for partially purified human fetal liver GSTs and 21, 6, 88 and 117 microM, respectively, for partially pure rat liver GSTs. The evidence suggests that Asc-S, Asc-P, SA and PA are potent inhibitors especially of the pi-class of GST.

Animals↗
PubMed1998

Mono (S) hydroxy fatty acids: novel ligands for cytosolic actin.

The ubiquitous hydroxylated fatty acids derived from arachidonic acid (HETEs) or linoleic acid (HODEs) exhibit diverse biological effects including chemotaxis, cell proliferation, and modulation of several enzymatic pathways, including the 5-lipoxygenase leading to the inflammatory leukotrienes. It was observed that 12(S)- and 15(S)-HETE and 13(S)-HODE (12- and 15-lipoxygenase-derived metabolites, respectively) inhibited the 5-lipoxygenase present in rat basophilic leukemia (RBL-1) cell homogenates whereas the 15(R) chiral enantiomer and the nonhydroxylated linoleic, oleic, and stearic acids were either less potent or ineffective. In examining the mechanism of this inhibition, the relative effectiveness of several fatty acids in displacing [3H]15-HETE bound to cytosol preparations were compared and the results indicated that these (S) hydroxy fatty acids and 5(S)-HETE were significantly more potent than either the 15(R) enantiomer, 15(S)-HETE methyl ester, arachidonic acid, or prostaglandin F2alpha. In order to identify the protein(s) that specifically binds HETEs, 15(S)-HETE biotin hydrazide was used as a probe to detect any HETE-protein complexes as this compound both inhibited the 5-lipoxygenase and interfered with the binding of [3H]15-HETE to cytosol preparations. SDS-PAGE analysis and chemiluminescent detection revealed that the major cytosolic proteins that bound this biotinylated probe had molecular masses of 43 and 51 kD. Fatty acid competition experiments indicated that the order of effectiveness in displacing this probe from these proteins was 13(S)-HODE > 5(S)-HETE approximately equal to 15(S)-HETE > > stearic acid approximately equal to arachidonic acid approximately equal to 15(R)-HETE. Amino acid sequence analysis showed that the 43 kD protein was actin. These findings suggest the possibility that actin may play a major role in the biological effects of monohydroxylated metabolites derived from cellular 5-, 12-, and 15-lipoxygenases.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2005

Analysis of 2-alkylcyclobutanones with accelerated solvent extraction to detect irradiated meat and fish.

A new analytical procedure has been developed to analyze 2-alkylcyclobutanones to detect gamma-ray-irradiated fat-containing foodstuffs. Samples were extracted with an accelerated solvent extraction system via hot and pressurized ethyl acetate in cells. A large amount of fat in the extract was precipitated and removed with filtration by standing at -20 degrees C after the addition of acetonitrile. The extract was further cleaned with a 1 g silica gel mini column, and the radiolytic compounds of 2-docecylcyclobutanone (2-DCB) and 2-tetradecylcyclobutanone (2-TCB) were determined with gas chromatography with mass spectrometry (GC/MS). Sample preparation time before GC/MS was 7-8 h. At first, the procedure was evaluated with a recovery test in eight samples spiked with 2-DCB and 2-TCB at 20 ng/g, resulting in 70-105% recoveries with mostly less than 10% relative standard deviations. The procedure was further evaluated with beef, pork, chicken, and salmon samples irradiated with gamma-rays from 0.7 to 7.0 kGy at -19 degrees C. Both 2-DCB and 2-TCB in most samples were detected with good dose-response relations at all doses, while salmon was detected more than 2 kGy irradiation. The amounts of 2-alkylcyclobutanones produced reflected precursor fatty acids levels in samples, especially for the combination of 2-TCB and stearic acid. The results indicated that the production rate of 2-TCB to stearic acid was more obvious than that of 2-DCB to palmitic acid in frozen samples with gamma-ray irradiation.

Animals↗
PubMed1983

The hydrogenation of gamma-linolenic acid by pure cultures of two rumen bacteria.

Two species of rumen bacteria that have been previously shown to partially hydrogenate alpha-linolenic acid have been examined for their ability to hydrogenate gamma-linolenic acid. Free gamma-linolenic acid is hydrogenated in vitro to stearic acid by a rumen Fusocillus sp. (N.C.I.B. 11026), but only to cis,trans-octadec-6,11-enoic acid by a Butyrivibrio sp. The sequential hydrogenations are preceded by a delta 12-cis-delta 11-trans isomerization identical with that observed in the hydrogenation of alpha-linolenic acid and linoleic acid.

Animals↗
PubMed1995

Molecular architecture and biophysical properties of phospholipids during thermal adaptation in fish: an experimental and model study.

Phospholipids from livers of carps (Cyprinus carpio L.) adapted to winter (5 degrees C) and summer (25 degrees C) temperatures were isolated, and the fatty acid composition of total phospholipids, as well as molecular species composition of diacyl phosphatidylcholines and ethanolamines, were determined. Order parameter of 5-doxyl stearic acid and steady-state fluorescence anisotropy of different anthroyloxy fatty acids--[2-, 12(N-9-anthroyloxy)stearic acid and 16(N-9-anthroyloxy)palmitic acid--embedded in native and synthetic (16:0/16:0, 16:0/22:6, 18:0/22:6, 18:1/22:6, 20:4/20:4, 22:6/22:6 phosphatidylcholines and 16:0/18:1, 18:1/22:6 phosphatidylethanolamines) phospholipid vesicles was also determined between -30 and 30 degrees C and 5 and 30 degrees C, respectively. There is an accumulation of 1-monoenoic, 2-polyenoic diacyl phosphatidylcholine and ethanolamine with a concomitant reduction of 1-stearoyl,2-docosahexaenoyl species in the cold-adapted state. Despite a 30% accumulation of long-chain polyunsaturated fatty acids in phospholipids in cold, there is only a 5 degrees C downshift in the solid-gel to liquid-crystalline phase transition temperature (-8 vs. -13 degrees C). Vesicles from total phospholipids of cold-adapted fish proved to be more disordered in all segments than from the warm-adapted ones when assayed using 2,12-(N-9-anthroyloxy)stearic and 16-(N-9-anthroyloxy)palmitic acid. Vesicles made from purified phosphatidylcholines showed the same pattern, but they were more disordered than the corresponding total phospholipids. This could be modelled using mixed phospholipid vesicles made of synthetic 16:0/22:6 phosphatidylcholine (75%) and either 18:1/22:6 phosphatidylethanolamine (25%) vs. 16:0/18:1 phosphatidylethanolamine (25%) and comparison of the anisotropy parameters of 100% 16:0/22:6 and 100% 18:1/22:6 phosphatidylcholine vesicles. Mixing either 16:0/18:1 (25%) or 18:1/22:6 (25%) phosphatidylethanolamines to 18:0/22:6 (75%) phosphatidylcholine shifted down or up, respectively, the transition temperature of vesicles compared to 100% 18:0/22:6 vesicles assayed by electron spin resonance spectroscopy using 5-doxylstearic acid. It is concluded that it is not the gross amount of long-chain polyunsaturated fatty acids in phospholipids, but rather their specific combination with cis delta 9 monounsaturated fatty acids in the position sn-1, especially in phosphatidylethanolamines, that is important in determining the physical properties of biomembranes in relation to adaptational temperature.

Adaptation, Physiological↗
PubMed1986

Localization of phosphatidylethanolamine in microsomal membranes and regulation of its distribution by the fatty acid composition.

Rat liver microsomes were incubated with the monofunctional aminoreagent fluorescamine. Although the probe easily penetrated the membranes, two pools of phosphatidylethanolamine (PE) could be detected. The first pool rapidly reacted with the probe and comprised 80% of the total PE. The second pool exhibited a very slow interaction. The two pools showed differences in fatty acid composition as well as in their sites of attachment. In vivo labeling with ethanolamine, glycerol, and palmitic and stearic acid resulted in a higher specific activity in the first pool after 1 hr; equilibration with the second pool took about 3 hr. No equilibration between the pools could be detected under in vitro conditions. In vivo incorporation of labeled fatty acids showed that palmitic and stearic acids were mainly incorporated into phosphatidylethanolamine by de novo synthesis, while linoleic and arachidonic acids were introduced through deacylation-reacylation processes. Injection of liposomes consisting of labeled synthetic phosphatidylethanolamines into the portal vein was followed by uptake by the hepatocytes and incorporation of the lipids into the microsomal membranes. Depending on the fatty acid composition of the injected lipid, one of either of the two pools became labeled. It is suggested that the fatty acid composition of a given phospholipid molecule exerts a signal function directing the lipid to its final intramembranous location.

Animals↗
PubMed1996

Formation and cell-medium partitioning of autoinhibitory free fatty acids and cyclodextrin's effect in the cultivation of Bordetella pertussis.

Palmitic, palmitoleic and stearic acids were found in the extracted cellular lipids of virulent Bordetella pertussis as unesterified acids in confirmation of earlier taxonomic analyses. The same free fatty acids (FFAs) were found in the spent culture supernatant in concentrations higher than in the uninoculated medium, indicating that they are released into the extracellular medium. These long-chain fatty acids are known to inhibit the growth of B. pertussis at concentrations as low as 1 ppm. Measurement of palmitate cell-medium partitioning demonstrated a strong tendency of FFAs for cellular adsorption. Inhibition kinetics indicated that the cell-bound FFA was responsible for inhibition and that the specific cellular FFA concentrations actually found during growth were similar to those determined to be inhibitory. Autoinhibition by these endogenous FFAs provides an explanation of the low maximum cell concentrations currently attainable in liquid media. Addition of soluble dimethyl-beta-cyclodextrin (MebetaCD) to FFA-inhibited cultures resulted in a rapid reversal of the inhibition. A corresponding shift in the distribution of FFAs from the cells to the extracellular medium demonstrated that MebetaCD sequesters FFAs. Although MebetaCD did not increase final cell concentrations and even had an adverse effect on growth at concentrations above 1 g l-1, it did (at 1 g l-1 extend the initial period of high growth rate leading to shorter cultivation times.

Biotechnology↗
PubMed1994

Reconstitution of 5'-nucleotidase of bull seminal plasma in spin-labeled liposomes.

Seminal plasma separated from freshly ejaculated bull semen contains vesicles with a 5'-nucleotidase activity incorporated as an ectoenzyme anchored by glycosyl phosphatidylinositol (GPI). After its extraction from bull seminal plasma vesicles, the protein was purified and reconstituted into hen egg yolk lecithin liposomes obtained through prolonged dialysis of buffered n-octylglucoside detergent solutions of lipid, protein and various effectors against detergent-free solutions. Gel filtration experiments showed that the enzyme incorporated into liposomes in a dimeric form with its two subunits linked by disulfide bridges. In the presence of reduced glutathione, the protein dissociated into monomers and failed to incorporate into liposomes. Electron spin resonance (ESR) experiments, performed with liposomes containing electron spin labels localized at the hydrophilic lipid headgroups (5-doxyl stearic acid) or in the hydrophobic lipid hydrocarbon chains (16-doxyl stearic acid), demonstrated that the incorporation of 5'-nucleotidase resulted in the immobilization of the spin probes. Furthermore, the spectral parameters obtained before and after treatment of 5'-nucleotidase-containing liposomes with phosphatidylinositol-specific phospholipase C (PI-PLC) indicated that the liposome membrane bilayer did not contain protein segments. This supports the well-known ecto-localization of 5'-nucleotidase and rules out a previously reported possibility of a proteic transmembrane anchoring of the enzyme.

5'-Nucleotidase↗
PubMed1988

Formation of fatty acid ethyl esters during chronic ethanol treatment in mice.

Ethyl esters of long-chain fatty acids are formed in the liver and brain of mice after 1-6 days of ethanol intoxication. This observation extends the reports of Lange and co-workers who detected these compounds as unusual metabolites of ethanol in human tissues [E. A. Laposata and L. G. Lange, Science 231, 497 (1986)]. Ethyl esters of oleic and linoleic acids, and, in smaller amounts, ethyl esters of palmitic and stearic acids were found in the livers of mice that had been treated with ethanol by inhalation. In the brain, only the esters of unsaturated fatty acids were found, in lower amounts than in liver. All the fatty acid ethyl esters seemed to have reached steady-state levels in the tissues after 3 or 4 days of alcohol treatment. When incorporated into synaptosomal plasma membranes in vitro, in intramembrane concentrations estimated to resemble those observed in the mice, these esters reduced the fluorescence anisotropy, i.e. they disordered the membranes.

Alcoholism↗
PubMed1975

The composition of the liver lipids of the ewe during pregnancy and lactation.

During late pregnancy and early lactation there were significant increases in the concentrations of triglycerides and cholesteryl esters in the liver lipids of the ewe. These changes were accompanied by higher concentrations of oleic acid and lower concentrations of stearic acid in both fractions, and may be related to an increased mobilisation of fatty acids from adipose tissue.

Animals↗
PubMed1984

Lipid composition of liver mitochondria and microsomes in hyperthyroid rats.

Triiodothyronine-induced alteration of the lipid pattern in rat-liver mitochondria and microsomes has been investigated. In mitochondria, a 25% total cholesterol decrease and a 14% phospholipid increase have been detected. In these hyperthyroid rat liver organelles, a strong decrease in the total cholesterol/phospholipid molar ratio occurs. On the contrary, in microsomes from the same animals, a decrease of about 23% has been measured for both total cholesterol and phospholipids; hence, in this fraction, the total cholesterol/phospholipid molar ratio is unaffected by hyperthyroidism. The liver mitochondrial phospholipid composition, unlike the microsomal composition, is altered significantly in hyperthyroid rats; a 7.4% phosphatidylcholine decrease is accompanied by a similar additive percentage increase of both phosphatidylethanolamine and cardiolipin. In regard to total phospholipid fatty acid composition in liver microsomes from hyperthyroid rats, no variation has been observed compared with the control rats, whereas in mitochondria from the same animals, a meaningful linoleic acid decrease with a similar arachidonic acid increase has been found. In addition to fatty acid alteration, the separated mitochondrial phospholipid classes also exhibit some increase in stearic acid. Among phospholipids, cardiolipin changes the most of the esterified fatty acids in hyperthyroid rat liver. In this compound, a strong increase in the percentage of both palmitic and stearic acid and a 32.4% decrease of linoleic acid have been found.

Animals↗