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At least 847 records · Page 47Linked to original sources
PubMed1997

Cell swelling activates phospholipase A2 in Ehrlich ascites tumor cells.

Ehrlich ascites tumor cells, loaded with 3H-labeled arachidonic acid and 14C-labeled stearic acid for two hours, were washed and transferred to either isotonic or hypotonic media containing BSA to scavenge the labeled fatty acids released from the cells. During the first two minutes of hypo-osmotic exposure the rate of 3H-labeled arachidonic acid release is 3.3 times higher than that observed at normal osmolality. Cell swelling also causes an increase in the production of 14C-stearic acid-labeled lysophosphatidylcholine. This indicates that a phospholipase A2 is activated by cell swelling in the Ehrlich cells. Within the same time frame there is no swelling-induced increase in 14C-labeled stearic acid release nor in the synthesis of phosphatidyl 14C-butanol in the presence of 14C-butanol. Furthermore, U7312, an inhibitor of phospholipase C, does not affect the swelling induced release of 14C-labeled arachidonic acid. Taken together these results exclude involvement of phospholipase A1, C and D in the swelling-induced liberation of arachidonic acid. The swelling-induced release of 3H-labeled arachidonic acid from Ehrlich cells as well as the volume regulatory response are inhibited after preincubation with GDP beta S or with AACOCF3, an inhibitor of the 85 kDa, cytosolic phospholipase A2. Based on these results we propose that cell swelling activates a phospholipase A2--perhaps the cytosolic 85 kDa type--by a partly G-protein coupled process, and that this activation is essential for the subsequent volume regulatory response.

Arachidonic Acid↗
PubMed2002

Amphiphilic effects of local anesthetics on rotational mobility in neuronal and model membranes.

To provide a basis for studying the molecular mechanism of pharmacological action of local anesthetics, we carried out a study of the membrane actions of tetracaine, bupivacaine, lidocaine, prilocaine and procaine. Fluorescence polarization of 12-(9-anthroyloxy)stearic acid (12-AS) and 2-(9-anthroyloxy)stearic acid (2-AS) were used to examine the effects of local anesthetics on differential rotational mobility between polar region and hydrocarbon interior of synaptosomal plasma membrane vesicles (SPMV) isolated from bovine cerebral cortex, and liposomes of total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from the SPMV. The two membrane components differed with respect to 2 and 12 anthroyloxy stearate (2-AS, 12-AS) probes, indicating that a difference in the membrane fluidity may be present. In a dose-dependent manner, tetracaine, bupivacaine, lidocaine, prilocaine and procaine decreased anisotropy of 12-AS in the hydrocarbon interior of the SPMV, SPMVTL and SPMVPL, but tetracaine, bupivacaine, lidocaine and prilocaine increased anisotropy of 2-AS in the membrane interface. These results indicate that local anesthetics have significant disordering effects on hydrocarbon interior of the SPMV, SPMVTL and SPMVPL, but have significant ordering effects on the membrane interface, and thus they could affect the transport of Na(+) and K(+) in nerve membranes, leading to anesthetic action.

Anesthetics, Local↗
PubMed2001

Enzymatic modification of high-laurate canola to produce margarine fat.

Stearic acid was enzymatically transesterified with high-laurate canola using a nonspecific lipase from Candida antarctica to produce structured lipids (SL) suitable for margarine application. Stearic acid levels ranged from 10 to 40 wt % of high-laurate canola oil. Differential scanning calorimetry was used to evaluate melting characteristics of the transesterified products. A stearic acid level of 30% was found to best match the melting characteristics of fat extracted from commercially available stick margarine. This SL was used to prepare nonrefrigerated and refrigerated margarine samples. Refrigerated margarine was prepared using 60% SL and 40% canola oil, whereas 100% SL was used for the nonrefrigerated margarine. Slip melting point, solid fat content, and hardness index were determined for all samples. Application of a dynamic temperature step using a dynamic stress rheometer showed complete breakdown of the commercial stick margarine and the experimental refrigerated margarine at approximately 30 degrees C and complete breakdown of the nonrefrigerated margarine at approximately 35 degrees C. Addition of canola oil to the SL improved spreadability at refrigeration temperatures and reduced the hardening effect of lauric acid in the SL. The nonrefrigerated margarine was spreadable at room temperature and exhibited no oil exudation or phase separation.

Calorimetry, Differential Scanning↗
PubMed1992

Punch geometry and formulation considerations in reducing tablet friability and their effect on in vitro dissolution.

The tablet friability resulting from formulation variations was studied under controlled granulation moisture content and tablet crushing strength. Tablets made with lactose were more friable than tablets made with microcrystalline cellulose. Replacement of 0.5% magnesium stearate with 0.5% stearic acid in the formula reduced tablet friability, whereas the combination of 0.5% stearic acid and up to 0.25% magnesium stearate did not increase tablet friability, decrease drug dissolution rate, or increase tablet-to-tablet variability in dissolution. Tablets compressed with extra deep concave punches resulted in lower friability compared with tablets compressed with standard concave or deep concave punches. The friabilities of the standard convex and deep convex tablets were similar, indicating that a critical level of punch tip curvature was important in reducing tablet friability. The dissolution rate was not affected by the punch tip geometry, but the tablet-to-tablet dissolution variability at the 0.5% stearic acid level for the extra deep convex tablets was higher compared with the standard convex tablets.

Chemical Phenomena↗
PubMed1999

Synthetic peptide sequence from the C-terminus of the insulin-like growth factor-I receptor that induces apoptosis and inhibition of tumor growth.

Although the type 1 insulin-like growth factor receptor (IGF-IR) is a potent inhibitor of apoptosis, its C-terminus sequence sends contradictory signals, including a clearly proapoptotic signal. We have synthesized a peptide, peptide 2, having the sequence of the IGF-IR from residue 1282 to residue 1298 (C-terminus of the beta subunit). To favor its uptake into cells, we linked it to a stearic acid moiety at its NH-terminus. Peptide 2 is taken up by the cells, where it inhibits DNA synthesis and causes apoptosis, while a scrambled peptide (with stearic acid) and peptide 2 without stearic acid are completely ineffective. Peptide 2 is more effective when cells are in anchorage-independent conditions than when they grow in monolayer cultures. Accordingly, we find that peptide 2 can inhibit the growth of a human prostatic cell line in nude mice. The proapoptotic effect of peptide 2 is inhibited by the expression of Bcl-2 or by a dominant negative mutant of caspase 9. These and other data indicate that peptide 2 does not seem to be competing directly with the IGF-IR for common substrates, but that its proapoptotic effect is related to its ability to activate the caspase cascade.

Amino Acid Sequence↗
PubMed1968

Composition and synthesis of fatty acids in atherosclerotic aortas of the pigeon.

The composition, synthesis, and esterification of fatty acids were studied in aortas of White Carneau and Show Racer pigeons after perfusion of the aortas with a medium containing acetate-1-(14)C. For both breeds of pigeons the principal change in aortic fatty acids, in response to an atherogenic diet, was a marked increase in the percentage of oleic acid in the cholesteryl ester fraction. In atherosclerotic aortas incorporation of acetate-1-(14)C into the phospholipid and glyceride fractions increased 2-fold, while a much greater increase (up to 10-fold) was seen in incorporation into cholesteryl esters. In those birds receiving the atherogenic diet, palmitic acid accounted for approximately 50% of the fatty acid radioactivity, compared with approximately 25% from control aortas. Calculation of fatty acid synthesis showed the major newly synthesized fatty acids to be stearic acid in the phospholipid fraction; stearic, palmitic, and oleic acids in the glycerides; and oleic acid in the cholesteryl esters. The pattern of fatty acid synthesis was closely similar to the actual fatty acid composition of the aorta. In atherosclerotic aortas an increased synthesis of all fatty acids was seen, but the greatest increase was seen in the synthesis of oleic acid and its esterification to cholesterol.

Acetates↗
PubMed1987

Early feeding of a high-cholesterol diet enhances intestinal permeability to lipids in rabbits.

This study was undertaken in young and growing rabbits to establish the of feeding a high- (2%) cholesterol diet (HC) on the intestinal in vitro uptake of a homologous series of saturated fatty acids, dodecanol, cholesterol, and bile acids. In the jejunum there was an increase in the uptake of myristic acid and dodecanol in HC as compared with animals fed Purina Chow, whereas in the ileum the uptake of stearic acid, cholesterol, and taurocholic acid was reduced. There was increased jejunal uptake of medium-chain length fatty acids, increased incremental change in free energy (integral of delta Fw----l), increased uptake of palmitic, taurocholic acid, and glycocholic acid and reduced uptake of myristic acid and dodecanol in animals fed the high-cholesterol diet for 10 days followed by Purina Chow for 18 days (HC-chow), as compared with HC. There was also increased ileal uptake of palmitic acid in HC-chow as compared with HC but reduced ileal uptake of stearic acid, cholesterol, taurocholic acid, and glycocholic acid. In the colon, there was increased uptake of stearic acid and dodecanol in HC-C as compared with HC, but reduced uptake of cholesterol, taurocholic acid and glycocholic acid. These changes in lipid uptake were not explained by alterations in the mucosal surface area or in the animals' body weight gain. It is proposed that early feeding experiences with a high-cholesterol diet may alter the normal development of intestinal transport of lipids with increased jejunal permeability to medium-chain fatty acids and increased effective resistance of the intestinal unstirred water layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Physical state abnormality of erythrocyte membrane in myotonic dystrophy: a spin label study.

Biophysical abnormalities of the erythrocyte membrane in muscular dystrophies have been described by numerous authors. This work presents the results we have obtained on 23 subjects suffering from myotonic muscular dystrophy (MyD, Steinert disease) by the spin label method. Two types of fatty acid spin labels were used: 5-nitroxide stearic acid (5NS) and 16-nitroxide stearic acid (16NS) which probe the membranes respectively near their polar heads and in their hydrophobic core. We measured the classical order parameter, the saturation behaviour of the electron paramagnetic resonance signal, and the label apparent rotation correlation time as a function of the temperature, on fresh and in vitro stored red blood cells. With the 5NS label, no differences were found between controls and patients. With the 16NS label, a highly significant variation in the thermic behaviour of the membrane is observed in its hydrophobic and fluid core. This last result may suggest some similarities between the red blood cell membranes of adult MyD's and healthy children.

Adolescent↗
PubMed1975

Bovine serum albumin. Study of the fatty acid and steroid binding sites using spin-labeled lipids.

Three spin-labeled derivatives of stearic acid and two derivatives of palmitic acid have been used to study the structure of the strong fatty acid binding site of bovine serum albumin. The steroid and indole binding sites have been studied using spin-labeled derivatives of androstol and indole, respectively. Paramagnetic resonance and fluorescence quenching data suggest that the fatty acid, steroid, and indole binding sites may be identical. The mobility of the nitroxyl group at C-8 of palmitic acid bound to albumin at a 1:1 molar ratio is unaffected when the carboxyl group is esterified. When the nitroxyl group is located at C-5 on this acid its motion is detectably increased by esterification of the carboxyl group but the magnitude of this change is small. This result suggests that the carboxyl group may play a minor role in the binding of fatty acids to the strongest fatty acid binding site of albumin. When stearic acid derivatives bearing the nitroxide at C-5, C-12, and C-16 are bound to albumin at a ligand to albumin ratio of 1, the order of mobility at 0-30 degrees is C-16 greater than C-12 congruent to C-5. Although motion at the methyl terminus is always greater than at the COOH terminus in the range 0-60 degrees, a simple monotonic increase in chain motion between the two termini is not observed. Arrhenius plots of the motion parameters for these bound fatty acids show two abrupt changes in slope. The temperature ranges for these changes are 15-23 degrees and 38-45 degrees. These results suggest that when one mole of spin-labeled fatty acid is bound to albumin, the protein undergoes a conformational change in each of these temperature ranges.

Animals↗
PubMed1991

Arachidonic acid and docosahexaenoic acid are increased in human colorectal cancer.

Increased arachidonic acid concentrations in experimental rodent colonic cancer have been described recently. In humans, a reduced erythrocyte stearic acid to oleic acid ratio has been reported in patients with colorectal cancer and it has been proposed that similar changes exist in the cancer tissue. The long chain fatty acids in the cancers of 15 patients with colorectal cancer were measured and compared with values in the unaffected mucosa. The values were expressed as mean (SD) mg fatty acid/g tissue and compared by analysis of variance. In the cancer tissue arachidonic acid was increased (0.703 (0.109) mg/g v 0.603 (0.127) mg/g, p less than 0.05) as was docosahexaenoic acid (0.211 (0.066) mg/g v 0.148 (0.039) mg/g, p less than 0.001). In contrast, the stearic acid to oleic acid ratio in the cancer tissue was increased rather than decreased, as previously suggested (0.36 (0.05) v 0.29 (0.7), p less than 0.01). Increased arachidonic acid and docosahexaenoic acid concentrations may be related to reduced lipid peroxidation, which is a feature of rapidly growing cells. Alternatively, the increased arachidonic acid values could be due to enhanced desaturase activity upon linoleic and linolenic acid, leading perhaps to increased formation of prostaglandins and other lipoxygenase products.

Aged↗
PubMed2005

Dilution rate and pH effects on the conversion of oleic acid to trans C18:1 positional isomers in continuous culture.

In a previous in vitro study, mixed ruminal microorganisms converted oleic acid to a variety of trans monenes when grown in batch cultures under constant environmental conditions. To determine whether a similar conversion occurs under environmental conditions more typical of the rumen, conversion of 13C-labeled oleic acid to biohydrogenation intermediates was determined in ruminal microorganisms grown in continuous culture at two pH (5.5 and 6.5) and liquid dilution rates (0.05 and 0.10/h) arranged factorially. After each morning feeding of the dual-flow continuous cultures, 250 mg of oleic acid in 5 mL of ethanol were injected into each culture. On d 10, 250 mg of oleic-1-(13C) replaced the unlabelled oleic acid in ethanol. Trans fatty acids were isolated from culture samples by solid phase extraction, and 13C enrichment and identity of double bond position was determined by gas chromatography-mass spectroscopy. At pH 6.5 and 0.10/h dilution rate, 13C enrichment was detected in all trans-C18:1 isomers having double bond positions from C6 through C16 in the acyl chain. However, when pH or dilution rate in fermentors was lowered, no 13C enrichment was detected in any trans isomer with a double bond position beyond C10. Enrichment in stearic acid increased by reducing culture pH from 6.5 to 5.5, but decreased when dilution rate dropped from 0.10 to 0.05/h. The stearic acid carbons that originated from oleic acid biohydrogenation increased from 30 to 72% when pH dropped from 6.5 to 5.5. The 13C enrichment of trans-10 was reduced under low pH and dilution rate conditions. The results of this study confirm that ruminal microorganisms are capable of converting oleic acid to a wide variety of trans-C18:1 positional isomers when ruminal conditions are favorable (such as the pH 6.5 and 0.10/h dilution rate treatment). However, at low pH and dilution rate, the conversion of oleic acid to trans-C18:1 still occurs, but positional isomers produced are restricted to double bond positions from C6 to C10. Low pH conditions also increased the conversion of oleic acid to stearic acid.

Animals↗
PubMed1999

Fatty acid composition of six varieties of dehulled African yam bean (Sphenostylis stenocarpa) flour.

The proximate and fatty acids compositions of dehulled African yam bean (Sphenostylis stenocarpa, Hochst ex A. Rich. Harms) flour were reported. The crude protein values ranged from 20.18 +/- 0.02 to 25.78 +/- 0.05 g/100 g; the ether extract values ranged from 1.93 +/- 0.05 to 10.18 +/- 0.04 g/100 g; crude fibre values ranged from 1.61 +/- 0.02 to 2.38 +/- 0.00 g/100 g; total ash ranged from 2.06 +/- 0.03 to 2.36 +/- 0.05 g/100 g and carbohydrate values ranged from 58.46 +/- 0.04 to 63.34 +/- 0.05 g/100 g. The values of the moisture content ranged from 3.20 +/- 0.03 to 7.10 +/- 0.02 g/100 g. Significant differences were found (P < 0.05) among the samples in the proximate compositions. The most concentrated fatty acids were palmitic acid (18.18 to 19.78%) < linoleic acid (28.33 to 35.16%) < stearic acid (29.01 to 36.71%). Caprylic, capric, lauric, myristic, palmitoleic, oleic, eicosenoic and erucic acids were present in small quantities with none of them recording up to 2.00% in any of the samples. However, the values of alpha-linolenic acid ranged from 2.01 to 2.96%. Significant differences were observed in the fatty acid compositions among the African yam bean dehulled seed cultivars.

Flour↗
PubMed2006

Control of CaCO3 crystallization by demixing of monolayers.

In this paper we describe how to template a demixed monolayer into a spatially patterned inorganic replica. For this purpose a new amphiphilic monomer was synthesized which can be polymerized both in solution and in the monolayer of a Langmuir-Blodgett (LB) trough. Since it inhibits the crystallization of CaCO3, it can be used--in combination with stearic acid (nucleation-promotor)--to control CaCO3 crystals formed under the monolayer. Investigations of the two-component monolayer (Langmuir isotherms and AFM measurements of transferred films) show--in the biphasic region--demixing in solid analogue stearic acid domains and the liquid analogue phase of the monomer. Crystallization of CaCO3 starts under the stearic acid domains whose size varies from less than 100 nm to several tens of micrometers. The addition of poly(acrylic acid) into the subphase hinders the three-dimensional growth of CaCO3 crystals from the monolayer into the solution. Thus, it becomes possible to transfer the pattern of the demixed domains into an inorganic replica of CaCO3.

Acrylic Resins↗
PubMed1968

Metabolism of hydroxy fatty acids in dogs with steatorrhea secondary to experimentally produced intestinal blind loops.

Several aspects of the metabolism of hydroxy fatty acids were studied in dogs with steatorrhea resulting from an experimentally produced jejunal blind loop. In these animals hydroxy acids were present in the stool in amounts far above normal. These acids disappeared from the feces during tetracycline administration and after exclusion of the blind loop-both procedures that corrected the steatorrhea apparently by reducing bacterial overgrowth. Hydroxy acids persisted in higher than normal amounts, however, after administration of taurocholic acid, which also corrected the steatorrhea, but by a different mechanism. Both in normal dogs and in those with blind loops, hydroxy acid constituted a higher percentage of total fatty acids in the jejunum. A possible conclusion is that hydroxy fatty acids have an enterohepatic circulation via the portal system. When hydroxy acids were fed to normal dogs, steatorrhea was not produced and absorption in amounts similar to that of unsubstituted stearic acid was observed. Isotopic oleic and linoleic acids were converted to hydroxy acids both in vivo and during in vitro incubation with feces; stearic acid was not. These findings support the idea that hydroxy acids arise by the addition of water across double bonds, this addition being catalyzed by enzymes of intestinal bacteria.

Animals↗
PubMed2000

Arachidonic acid-containing phosphatidylcholine inhibits lymphocyte proliferation and decreases interleukin-2 and interferon-gamma production from concanavalin A-stimulated rat lymphocytes.

The proliferation of concanavalin A (Con A)-stimulated rat lymphocytes was markedly inhibited by phosphatidylcholine containing arachidonic and stearic acids (PC(A-S)), but not by phosphatidylcholine containing oleic and stearic acids or phosphatidylinositol containing arachidonic and stearic acids. The concentration of PC(A-S) which inhibited Con A-stimulated proliferation by 50% was 31 microM and near total inhibition was observed at 154 microM . Phosphatidylserine containing only oleic acid enhanced proliferation by 37% at a concentration of 31 microM , but phosphatidylethanolamine and phosphatidylcholine containing only oleic acid did not affect proliferation at this concentration. It is concluded that both the head group and the fatty acid composition contribute to the influence of phospholipids on lymphocyte proliferation. The effects of PC(A-S) on T-lymphocyte responses were investigated further. In parallel with the inhibition of proliferation PC(A-S) caused a concentration-dependent decrease in the production of the Th1-type cytokines interleukin (IL)-2 and interferon (IFN)-gamma; inhibition of cytokine production was >85% at the highest concentration of PC(A-S) used (154 microM ). Production of the Th2-type cytokines IL-4 and IL-10 was not affected. The possible role of prostaglandins in mediating the effects of PC(A-S) was examined by adding indomethacin into the medium and the participation of lipid peroxidation was examined by adding vitamin E and vitamin C. Indomethacin and vitamin E did not affect the inhibition caused by PC(A-S) but vitamin C caused a partial reversal. It is concluded that inhibition of T-lymphocyte proliferation by phospholipids involves both the head group and the fatty acyl chains, that this inhibition is not mediated by prostaglandins but may involve some form of oxidant stress and that some phospholipids (e.g., PC(A-S)) can markedly influence cytokine profiles.

Animals↗
PubMed1976

Control of long chain fatty acid oxidation in heart mitochondria as studied by spin labeling.

Spin-labeled stearic acid is shown to exhibit the same beta-oxidation kinetics as normal stearic acid. ESR spectra recorded in conditions allowing beta-oxidation indicate that membrane-bound fatty acids can be directly beta-oxidized and that the rate of this reaction depends on the concentration of albumin in the medium. The regulating function of albumin and pool role of the lipidic phase of the mitochondrial membranes are discussed.

Albumins↗
PubMed1987

Comparative effects of ethanol and other depressant drugs on membrane order in rat synaptosomes using ESR spectroscopy.

The effects of ethanol, t-butanol and pentobarbitone on the membrane order of rat synaptosomal membranes have been compared using 3 spin-label probes, 5-doxyl-stearic acid which reports from a lipid site near the membrane surface, 16-doxyl-stearic acid which reports from a deeper lipid site, and maleimide-TEMPO which covalently binds to membrane protein. The sensitivity of the membrane proteins to a fluidizing effect of ethanol was increased by lowering the concentration of protein-binding probe. Significant decreases in membrane order were observed at anaesthetic concentrations of ethanol and t-butanol with all three probes; pentobarbitone produced a similar effect but only at very high concentrations. Pentobarbitone caused a marked change in high-field peak shape of the 16-doxyl-stearic acid spectra at anaesthetic concentrations; this effect was seen slightly with t-butanol and trichlorethanol but not with ethanol. These studies indicate that the membrane sites of action of ethanol and pentobarbitone as shown by ESR probes are different.

Animals↗
PubMed2006

Sulfatide with short fatty acid dominates in astrocytes and neurons.

Glycosphingolipids are located in cell membranes and the brain is especially enriched. We speculated that the subcellular location of glycosphingolipids depends on their fatty acid chain length because their sugar residues are constant, whereas fatty acid chain length can vary within the same molecule. To test this hypothesis we analysed the glycosphingolipid sulfatide, which is highly abundant in myelin and has mostly long fatty acids. We used a negative ion electrospray tandem mass spectrometry precursor ion scan to analyse the molecular species of sulfatide in cultured astrocytes and a mouse model of the human disease metachromatic leukodystrophy. In these arylsulfatase A (ASA)-deficient mice sulfatide accumulates intracellularly in neurons and astrocytes. Immunocytochemistry was also performed on cultured astrocytes and analysed using confocal laser scanning microscopy. Analyses of the molecular species showed that cultured astrocytes contained sulfatide with a predominance of stearic acid (C18), which was located in large intracellular vesicles throughout the cell body and along the processes. The same was seen in ASA-deficient mice, which accumulated a higher proportion (15 mol% compared with 8 mol% in control mice) of sulfatide with stearic acid. We conclude that the major fatty acid composition of sulfatide differs between white and grey matter, with neurons and astrocytes containing mostly short-chain fatty acids with an emphasis on stearic acid. Based on our results, we speculate that the fatty acid chain length of sulfatide might determine its intracellular (short chain) or extracellular (long chain) location and thereby its functions.

Animals↗