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PubMed1997

Interaction of bee venom melittin with zwitterionic and negatively charged phospholipid bilayers: a spin-label electron spin resonance study.

Electron spin resonance (ESR) spectroscopy was used to study the penetration and interaction of bee venom melittin with dimyristoylphosphatidylcholine (DMPC) and ditetradecylphosphatidylglycerol (DTPG) bilayer membranes. Melittin is a surface-active, amphipathic peptide and serves as a useful model for a variety of membrane interactions, including those of presequences and signal peptides, as well as the charged subdomain of the cardiac regulatory protein phospholamban. Derivatives of phosphatidylcholine and phosphatidylglycerol spin-labeled at various positions along the sn-2 acyl chain were used to establish the chain flexibility gradient for the two membranes in the presence and absence of melittin. Negatively charged DTPG bilayer membranes showed a higher capacity for binding melittin without bilayer disruption than did membranes formed by the zwitterionic DMPC, demonstrating the electrostatic neutralization of bound melittin by DTPG. The temperature dependence of the ESR spectra showed that the gel-to-liquid crystalline phase transition is eliminated by binding melittin to DTPG bilayers, whereas a very broad transition remains in the case of DMPC bilayers. None of the spin labels used showed a two-component spectrum characteristic of a specific restriction of their chain motion by melittin, but the outer hyperfine splittings and effective chain order parameters were increased for all labels upon binding melittin. This indicates a reduced flexibility of the lipid chains induced by a surface orientation of the bound melittin. Whereas the characteristic shape of the chain flexibility gradient was maintained upon melittin addition to DMPC bilayers, the chain flexibility profile in DTPG bilayers was much more strongly perturbed. It was found that the steepest change in segmental flexibility was shifted toward the bilayer interior when melittin was bound to DTPG membranes, indicating a greater depth of penetration than in DMPC membranes. pH titration of stearic acid labeled at the C-5 position, used as a probe of interfacial interactions, showed net downward shifts in interfacial pK of 0.8 and 1.2 pH units contributed from the positive charge of melittin, outweighing upward shifts from interfacial dehydration, when melittin was bound to DTPG and DMPC, respectively. The perturbation of the outer hyperfine splitting was used to determine the interactions of melittin with spin-labeled lipids of different polar headgroups in DTPG and DMPC. Anionic lipids (phosphatidylserine, phosphatidylglycerol, and stearic acid) and zwitterionic lipids (phosphatidylethanolamine and phosphatidylcholine) had the largest outer splittings in the presence of melittin. Neutral lipids (protonated stearic acid and diacylglycerol) displayed the largest increase in outer splitting on binding melittin, which was attributed to a change in the vertical location of these lipids in the bilayer. Both effects were more pronounced in DTPG than in DMPC.

Amino Acid Sequence↗
PubMed1999

Lipid binding to sterol carrier protein-2 is inhibited by ethanol.

Sterol carrier protein-2 (SCP-2) is an intracellular lipid carrier protein that binds cholesterol, phospholipids, fatty acids and other ligands. It has been reported that expression of SCP-2 was increased in brain nerve endings or synaptosomes of chronic ethanol-treated mice and it was shown that cholesterol homeostasis was altered in brain membranes of chronic ethanol-treated animals. Ethanol may interfere with the capacity of SCP-2 to bind cholesterol as well as other lipids. This hypothesis was tested using recombinant SCP-2 and fluorescent-labeled cholesterol, phosphatidylcholine (PC), and stearic acid. The association constants (Ka) of the ligand-SCP-2 complex were in the following order: NBD-cholesterol>NBD-PC>NBD-stearic acid. Ethanol, beginning at a concentration of 25 mM, significantly reduced the affinity of NBD-cholesterol and NBD-PC for SCP-2. Effects of ethanol on the Ka of NBD-stearic acid was significant only at the highest concentration that was examined (200 mM). Ethanol significantly increased the Bmax of NBD-cholesterol for SCP-2 but did not have a significant effect on the Bmax of NBD-PC. Similar results were found for effects of ethanol on the Kas and Bmaxs using pyrene-labeled cholesterol and PC. In conclusion, ethanol beginning at a physiological concentration of 25 mM inhibited binding of cholesterol and PC to SCP-2. However, effects of ethanol on lipid binding to SCP-2 were dependent on the type of lipid. Ethanol in vivo may interfere with lipid binding to SCP-2 and disrupt lipid trafficking within cells.

4-Chloro-7-nitrobenzofurazan↗
PubMed2001

Manganese absorption and retention in rats is affected by the type of dietary fat.

There is evidence that manganese (Mn) metabolism may be altered by the form and amount of dietary fat. Also, iron (Fe) absorption is greater with saturated fats, as compared to polyunsaturated fatty acids (PUFAs). The absorption of Fe and Mn are interrelated in many aspects; therefore, the form of dietary fat may indirectly alter Mn absorption. The reported studies were conducted to determine whether saturated fat, as compared to unsaturated fat, affected Mn absorption, retention, and metabolism. In experiment I, adult rats were fed diets containing either 0.7 or 100.4 microg/g Mn with the fat source as high-linoleic safflower oil or stearic acid. After 2 wk of equilibration, the animals were fed a test meal of 54Mn followed by whole-body counting for 10 d. Manganese absorption was significantly (p < 0.05) lower in the stearic acid group (0.9-4.8%) than in the safflower oil group (20-33.8%); however, the biological half-life was shorter in the safflower oil group. Retention of 54Mn and total Mn was always significantly (p < 0.05) greater in the safflower oil group when dietary Mn was low, but it was the same when dietary Mn was high. In experiment II, weanling rats were fed 1.3, 39.3, or 174.6 microg Mn/g and either stearate, high-oleic safflower oil or high-linoleic safflower oil for 8 wk. Long-term feeding of the stearate and low Mn-containing diet resulted in a significant (p < 0.0001) reduction in heart superoxide dismutase activity and kidney and liver Mn concentrations compared to the other diets. These data show that stearic acid inhibitits Mn absorption, but it may not inhibit Mn retention when dietary Mn is high.

Animals↗
PubMed2002

Short-term diets enriched in stearic or palmitic acids do not alter plasma lipids, platelet aggregation or platelet activation status.

OBJECTIVE: To determine whether healthy males who consumed increased amounts of dietary stearic acid compared with increased dietary palmitic acid through the consumption of commercially available foods, exhibited any changes in plasma lipids, platelet aggregation or platelet activation status. DESIGN: A randomised cross-over dietary intervention. SUBJECTS AND INTERVENTIONS: Nine free-living healthy males consumed two experimental diets (stearic acid enriched, diet S, and palmitic acid enriched, diet P) for 3 weeks in a randomised cross-over design separated by a 3 week washout phase. The diets consisted of approximately 30% of energy as fat (30% of which was derived from the treatment diets) providing approximately 13 g/day as stearic acid and 17 g/day as palmitic acid on diet S and approximately 7 g/day as stearic acid and 22 g/day as palmitic acid on diet P. The dietary ratio of stearic to palmitic acids was 0.76 on diet S compared with 0.31 on diet P. Blood samples were collected on days 0 and 21 of each dietary period. RESULTS: LDL cholesterol levels and platelet aggregation response to the agonist ADP were significantly decreased (P<0.025) in subjects on diet S compared with day 0. Apart from that, there were no significant changes in plasma lipids, platelet aggregation, mean platelet volume and platelet reactivity between diets. There were no significant changes in stearic or palmitic acid levels in plasma phospholipid or triacylglycerol. There was a significant difference in palmitic acid levels in platelet phospholipids between the two diets. CONCLUSIONS: Use of commonly available foods led to a 27% increase in stearic acid (diet S) and a 19% increase in palmitic acid (diet P), on diets S and P respectively, and no significant differences between the two diets in plasma lipoprotein concentrations, platelet aggregation or platelet activation status.

Adult↗
PubMed1985

Regional differences in the lipid composition and fluidity of rat colonic brush-border membranes.

The lipid composition and fluidity of brush-border membranes prepared from rat proximal and distal colonocytes were determined. Fluidity, as assessed by steady-state fluorescence polarization techniques using the fluorophores 1,6-diphenyl-1,3,5-hexatriene, DL-2(9-anthroyl)stearic acid and DL-12(9-anthroyl)stearic acid, was decreased in distal compared to proximal plasma membranes. This pattern was similar to that previously described for both antipodal plasma membranes in rat enterocytes of the small intestine. The decrease in fluidity of the distal as compared to the proximal membranes resulted from an increase in cholesterol content, cholesterol/phospholipid molar ratio and degree of saturation of the fatty acid residues in the distal membranes. The specific activities of total alkaline phosphatase and cysteine-sensitive alkaline phosphatase, enzymes previously shown to be functionally dependent on the physical state of the colonic brush-border membrane's lipid, were also significantly lower in distal as compared to proximal clonic plasma membranes. These studies, therefore, demonstrate that differences in the lipid fluidity, lipid composition and certain enzymatic activities exist in brush-border membranes prepared from rat proximal and distal colonocytes. The regional variation in rat colonic luminal membrane lipid fluidity and composition may, at least partially, be responsible for differences in these enzymatic activities as well as in sodium and water absorption along the length of this organ.

Alkaline Phosphatase↗
PubMed2006

EPR spin label study of walnut oil effects on phosphatidylcholine membranes.

Effects of walnut oil (WO) on dynamic and thermodynamic properties of 0-50 wt% cholesterol (CH) containing dimyristoylphosphatidylcholine (DMPC) and 10 wt% CH containing dipalmitoylphosphatidylcholine (DPPC) membrane dispersions were studied by electron paramagnetic resonance (EPR), using 5-doxyl stearic acid (5-DSA) and 16-doxyl stearic acid (16-DSA). Incorporation of 10 wt% WO alone decreased the phase transition temperature and created depth-dependent effects at the gel phase. The order increased close to the head region and decreased in the hydrocarbon core of the DMPC bilayer. For DPPC, the order decreased both close to head region and in the hydrocarbon core. Ten weight percent WO did not have considerable effect at the fluid phase for both DMPC and DPPC. Incorporation of 40 wt% WO into DMPC created an abrupt decrease in the maximum hyperfine splitting values after 305 K. The effect of 10 wt% WO in CH containing DMPC dispersions was dependent on the CH concentration. An increase and a decrease in the order were observed at low and high CH concentrations, respectively. Incorporation of WO created different effects on fluidity of 10 wt% CH containing DMPC and DPPC dispersions. Close to the head group region, the order in DMPC increased both in the gel and fluid phases; but for DPPC, an opposite effect was observed in both of the phases. In the hydrocarbon core of the bilayer, addition of 10 wt% WO into 10 wt% CH containing DMPC decreased the order in the gel phase and WO did not affect the order in the fluid phase. For DPPC, WO effects were observed to alter with temperature. In the studied temperature range, order parameters, diffusion constants and effective tilt angles were obtained from simulations of the spectra using Microscopic Order Macroscopic Disorder (MOMD) and Vary Anisotropic Reorientation (VAR) models. For 16-DSA, spectra were also simulated using two domains with EPRSIM.

Chemical Phenomena↗
PubMed1992

Physiochemical interactions of praziquantel, oxamniquine and tablet excipients.

A differential scanning calorimetry and infrared spectrophotometry study of potential interactions between oxamniquine and praziquantel, two synergistic anti-parasitic drugs, indicated that they did not interact on fusion. Mixtures of the two drugs with each of nine common pharmaceutical excipients (Ac-Di-Sol, Avicel, Crospovidone, calcium phosphate, magnesium stearate, starch, lactose, PEG 6000, stearic acid) appeared to interact only with stearic acid. These results suggested that a combination solid dosage form was feasible.

Calorimetry, Differential Scanning↗
PubMed1972

Uptake of individual free fatty acids by skeletal muscle and liver in man.

Arterial-venous concentration differences for individual free fatty acids (FFA) were measured across the deep tissues of the forearm, the splanchnic vascular bed, and the kidney in healthy, postabsorptive subjects. In addition, arterial-portal venous FFA differences were determined in five patients undergoing elective cholecystectomy. The differences in fractional uptake among the individual FFA across the forearm were small and not statistically significant. Splanchnic fractional uptake was high for FFA with short chain lengths and rose with increasing degree of unsaturation. Small, negative arterial-portal venous differences for individual FFA were observed, indicating that arterial-hepatic venous FFA differences mainly reflect hepatic uptake. When the arterial FFA concentration was reduced to approximately 25% of the control values by the administration of nicotinic acid, net uptake of total FFA ceased but there was release of stearic acid and uptake of lauric, myristic, and palmitoleic acid to the splanchnic region. Muscle and liver uptakes of individual FFA were both dependent on their arterial concentrations with the exception of the splanchnic uptake of stearic acid. There was no uptake of free arachidonic acid by either muscle or liver, nor was there significant uptake of any of the free fatty acids by the kidney. It is concluded (a) that there are important quantitative differences between the net exchanges of individual FFA across the splanchnic vascular bed, (b) that tracer studies of FFA metabolism require the determination of individual FFA specific activities, (c) that palmitic and oleic acid appear to be suitable tracers for the entire FFA fraction in most instances.

Adult↗
PubMed1986

Premalignant alterations in the lipid composition and fluidity of colonic brush border membranes of rats administered 1,2 dimethylhydrazine.

Dimethylhydrazine (DMH) is a potent procarcinogen with selectivity for the colon. To determine whether alterations in the lipid composition and fluidity of rat colonic brush border membranes existed before the development of DMH-induced colon cancer, rats were injected s.c. with this agent (20 mg/kg body weight per wk) or diluent for 5, 10, and 15 wk. Animals were killed at these time periods and brush border membranes were prepared from proximal and distal colonocytes of each group. The "static" and "dynamic" components of fluidity of each membrane were then assessed, by steady-state fluorescence polarization techniques using limiting hindered fluorescence anisotropy and order parameter values of the fluorophore 1,6 diphenyl-1,3,5-hexatriene (DPH) and fluorescence anisotropy values of DL-2-(9-anthroyl) stearic acid and DL-12-(9-anthroyl) stearic acid, respectively. Membrane lipids were extracted and analyzed by thin-layer chromatography and gas-liquid chromatography. Phospholipid methylation activity in these membranes was also measured using S-adenosyl-L-methionine as the methyl donor. The results of these studies demonstrate that: the lipid composition and both components of fluidity of proximal DMH-treated and control membranes and their liposomes were similar at all time periods examined; at 5, 10, and 15 wk the "dynamic component of fluidity" of distal DMH-treated membranes and their liposomes was found to be higher, similar, and lower, respectively, than their control counterparts; the "static component of fluidity" of distal DMH-treated membranes and their liposomes, however, was similar to control preparations at all three time periods; and alterations in the lipid composition and phospholipid methylation activities appeared to be responsible for these differences in the "dynamic component of fluidity" at these various time periods.

1,2-Dimethylhydrazine↗
PubMed2000

Feeding oleamide to lactating Jersey cows 1. Effects on lactation performance and milk fatty acid composition.

Oleamide was previously reported to resist ruminal biohydrogenation and elevate milk oleic acid concentration when fed to lactating Holstein cows. To determine if Jersey cows responded similarly to oleamide, four lactating Jersey cows (mean 417 kg of body weight and 64 days in milk) were fed four diets in a 4x4 Latin square with 2-wk periods. Diets were total mixed ration containing 47% corn silage and 53% concentrate (dry matter basis) and were supplemented with no added fat (control), or with 3.5% added fat from either higholeic canola oil, a commercial source of oleamide, or oleamide synthesized from oleic acid and urea. The canola oil supplement had no effect on milk yield or composition. Compared to canola oil, the oleamide supplements reduced milk yield, dry matter intake, and milk fat and protein contents. Milk oleic acid concentration increased from 17.4% of total fatty acids for the control diet to 22.1% for the canola oil diet. Both oleamides further increased milk oleic acid to 30.0 and 27.1% of total fatty acids for the commercial and synthesized oleamides, respectively. Milk palmitic acid was reduced and stearic acid was increased by all fat supplements but more so by the oleamides than by the canola oil. Consistent with previous reports that fatty acyl amides resist ruminal biohydrogenation, feeding oleamide to Jersey cows in this study increased milk oleic acid concentration but had negative effects on feed intake and milk yield.

Animal Feed↗
PubMed1985

Correction of abnormal lipid fluidity and composition of rat ileal microvillus membranes in chronic streptozotocin-induced diabetes by insulin therapy.

Diabetes was induced in rats by administration of streptozotocin. After 90-120 days, one group of chronic diabetic animals was treated with insulin for chronic diabetic animals was treated with insulin for 10 days. The lipid fluidity and composition of microvillus membranes prepared from ileal enterocytes of control, diabetic, and insulin-treated diabetic animals were determined. Lipid fluidity, as assessed by steady-state fluorescence polarization techniques using the probes 1,6-diphenyl-1,3,5-hexatriene, DL-2-(9-anthroyl)stearic acid and DL-12-(9-anthroyl)stearic acid, was decreased in membranes of diabetic animals compared to membranes of control and insulin-treated diabetic membranes. The differences in fluidity resulted from an increased cholesterol content and cholesterol/phospholipid molar ratio in membranes of diabetic animals. The activities of sucrase and alkaline phosphatase were also found to be higher in membranes of diabetic animals. Insulin treatment, however, failed to significantly influence the enzymatic activities of these membranes. These studies, therefore, demonstrate that alterations in the lipid fluidity, lipid composition, and certain enzymatic activities exist in microvillus membranes of enterocytes prepared from chronic streptozotocin-induced diabetic rats. Administration of insulin for 10 days to these animals restored membrane fluidity and lipid composition but not enzymatic activities to control membrane levels.

Alkaline Phosphatase↗
PubMed1968

Lipid components of sialosylgalactosylceramide of human brain.

A ganglioside, previously designated HG-B in our laboratory, was isolated from mixed human brain ganglioside preparations and shown to contain equimolar quantities of sialic acid, galactose, and sphingosine. Treatment of this material with neuraminidase yielded a galactosylceramide. The ganglioside, now referred to as sialosylgalactosylceramide, thus appears to be identical with G(gal) reported by Kuhn and Wiegandt. The fatty acids and long-chain bases of this material were analyzed by gas-liquid chromatography. Approximately equal amounts of normal and hydroxy acids were found. Oleic, palmitic, and stearic acids were the only normal fatty acids present. In the hydroxy series, the C(24) and C(23) saturated acids were the major components. The ratio of C(20) to C(18) long-chain base was approximately 5:3. These data suggest that sialosylgalactosylceramide has no direct metabolic relationship with either the major brain gangliosides or adult brain cerebroside.

Brain Chemistry↗
PubMed2001

Effects of lipids on n-alkane attenuation in media supporting oil-utilizing microorganisms from the oily Arabian Gulf coasts.

The Arabian Gulf is one of the most extensively oil-polluted areas of the world. The major objectives of this work were to study whether hydrocarbon-utilizing microorganisms indigenous to that area would readily accumulate added lipids, and whether this might affect their hydrocarbon consumption potential. Two prokaryotes, Arthrobacter nicotianae KCC B35 and the unidentified organisms KCC B6, as well as one eukaryote, Candida parapsilosis KCC Y1, were selected for this study. Biomass samples of the test organisms were incubated in an inorganic medium containing various concentrations of cholesterol, stearic acid, triolein or egg-phospholipids. The results revealed that all lipid classes were readily accumulated by the three test organisms. In addition, biomass samples were incubated for 6 h in an inorganic medium containing mixtures of individual lipid classes and either n-octadecane or n-docosane. The cells were removed and the residual alkanes in the medium were quantitatively recovered and analyzed by GLC. The results showed that out of the tested lipid classes only stearic acid exhibited a common stimulatory effect on the consumption of both n-alkanes by all test organisms. Other lipid classes were either inhibitory or had less pronounced effects than stearic acid.

Alkanes↗
PubMed2006

Langmuir-Blodgett monolayers of long-chain NBD derivatives on silver island films: Well-organized probe layer for the metal-enhanced fluorescence studies.

The metal-enhanced fluorescence (MEF) from the well-organized monolayers of two newly prepared long-chain alkylamine derivatives of nitrobenzoxadiazole (NBD-C16 and NBD-C18) deposited on silver island films (SIFs) has been investigated. The NBD derivatives were conveniently prepared by using a single step procedure in quantitative yields. The monolayers of the probes on SIFs as well as on bare-glass slides were obtained by using the Langmuir-Blodgett (LB) technique. Orientation of the NBD probe molecule in LB monolayer film was measured with polarized absorption spectroscopy. The observed tilt angle of the probe transition dipole moment with respect to the surface normal of approximately 67-68 degrees was evaluated. We observed that the NBD monolayers deposited in close proximity to silver islands show about a 16-fold increase in fluorescence intensity and shortened fluorescence lifetime compared to those on bare-glass, which are due to metal enhanced fluorescence. On the other hand, the corresponding MEF from randomly oriented film obtained by using spin coating of the probes on SIFs was only 2.5-fold. Further, we deposited mixed monolayers of NBD-C16 or NBD-C18 with various molar ratios of stearic acid to understand the polarity effect on MEF. Interestingly, we found a consistent increase in MEF efficiency with increasing molar ratio of stearic acid. Along with MEF, we also found a continuous blue-shift in emission band maxima of the probes with an increasing molar ratio of stearic acid. The observed increase in MEF efficiency is justified based on cooperative effects of (1) the modulations in electronic density of the surface plasmon absorption band of SIFs and (2) defined probe orientation that might lead to preferential excitation.

Fluorescence↗
PubMed1983

Unique profile for erythrocyte membrane acetylcholinesterase in hereditary spherocytosis.

Acetylcholinesterase of human erythrocytes from healthy donors and from patients with hematological disorders was analysed in a search for differential membrane parameters. Two substrates were used to estimate the exposure of acetylcholinesterase active site in the membrane: phenylacetate, a hydrophobic substrate, to determine total enzyme activity, and acetylcholine, an ionic substrate, to measure the externally reactive enzyme. The sensitivity of acetylcholinesterase to added stearic acid was also analysed. Three categories of the disorders studied were discerned: (a) The erythrocyte acetylcholinesterase profile was indistinguishable from normal control in beta-thalassemia minor and groups of patients with autoimmune hemolytic anemia or congenital dyserythropoietic anemia type II. (b) A marked decline in acetylcholinesterase with both substrates and reduced sensitivity to stearic acid were exhibited by the erythrocytes of paroxysmal nocturnal hemoglobinuria, beta-thalassemia major and other autoimmune hemolytic anemia and congenital dyserythropoietic anemia type II patients. Normal erythrocytes, either aged or pretreated to 50 degrees C, also showed similar characteristics. (c) Hereditary spherocytosis was singly differentiated by an elevated acetylcholinesterase activity with acetylthiocholine and by a vastly diminished sensitivity to stearic acid, while activity with phenylacetate was equal to control. This distinct profile may reflect the unique organization of the erythrocyte membrane in hereditary spherocytosis.

Acetylcholinesterase↗
PubMed1990

Dissociation of calcium soaps of long-chain fatty acids in rumen fluid.

Dissociation of 5% solutions of calcium soaps of soya, tallow, stearic acid, and palm fatty acid distillate was studied by titration with 1 N HCl. Release of calcium ions was directly correlated with decrease in pH value. Estimated pKa values were 5.6, 4.6, 4.5, and 4.5 for calcium soaps of soya, palm fatty acid distillate, tallow, and stearic acid, respectively. Dissociation of 5% solutions in acetate buffer at pH values of 5.0, 5.5, 6.0, and 6.5 was measured in terms of release of soluble calcium. Dissociation was maximum at pH 5.0, minimum at pH 6.5, and dependent on unsaturation of fatty acids in the soaps. Soluble calcium in the acetate-buffered rumen fluid was higher than predicted from pKa of calcium soaps, due to formation of soluble calcium acetate; however, the relative patterns were similar to their pKa values. Unsaturated soaps are less satisfactory for maintaining normal rumen function, because dissociation is relatively higher. Calcium soaps of palm fatty acid distillate were satisfactorily stable to pH 5.5.

Animals↗
PubMed2003

Lipid-protein interactions and effect of local anesthetics in acetylcholine receptor-rich membranes from Torpedo marmorata electric organ.

The selectivity of lipid-protein interaction for spin-labeled phospholipids and gangliosides in nicotinic acetylcholine receptor-rich membranes from Torpedo marmorata has been studied by ESR spectroscopy. The association constants of the spin-labeled lipids (relative to phosphatidylcholine) at pH 8.0 are in the order cardiolipin (5.1) approximately equal to stearic acid (4.9) approximately equal to phosphatidylinositol (4.7) > phosphatidylserine (2.7) > phosphatidylglycerol (1.7) > G(D1b) approximately equal to G(M1) approximately equal to G(M2) approximately equal to G(M3) approximately equal to phosphatidylcholine (1.0) > phosphatidylethanolamine (0.5). No selectivity for mono- or disialogangliosides is found over that for phosphatidylcholine. Aminated local anesthetics were found to compete with spin-labeled phosphatidylinositol, but to a much lesser extent with spin-labeled stearic acid, for sites on the intramembranous surface of the protein. The relative association constant of phosphatidylinositol was reduced in the presence of the different local anesthetics to the following extents: tetracaine (55%) > procaine (35%) approximately benzocaine (30%). For stearic acid, only tetracaine gave an appreciable reduction (30%) in association constant. These displacements represent an intrinsic difference in affinity of the local anesthetics for the lipid-protein interface because the membrane partition coefficients are in the order benzocaine >> tetracaine approximately procaine.

Anesthetics, Local↗
PubMed1997

Delayed phospholipid degradation in rat brain after traumatic brain injury.

Lipid second messengers such as arachidonic acid and its metabolites and diacylglycerols (DAGs) are affected in brain injury. Therefore, changes in the pool size and the fatty acid composition of free fatty acids (FFAs) and DAGs were analyzed in different rat brain areas 4 and 35 days after traumatic injury. Cortical impact injury of low-grade severity was applied in the right frontal somatosensory cortex. Four days after injury, FFAs and DAGs were increased by three- and twofold, respectively, in the injured cortex and to a lesser extent in the contralateral cortex compared with sham-operated animals. Docosahexaenoic acid followed by stearic acid, and arachidonic acid, displayed the greatest changes in both FFAs and DAGs. By day 35, free stearic, oleic, and arachidonic acids remained elevated in the damaged cortex (1.5-fold each). DAGs showed the greatest change, reaching values 2.7-fold higher than sham in all frontal and occipital cortical areas, including brainstem. Oleoyl- and arachidonoyl-DAGs (four- and threefold increase, respectively) followed by docosahexaenoyl-DAGs (twofold) contributed to the DAG accumulation. These results reveal that traumatic brain injury triggers a sustained and time-dependent activation of phospholipase-mediated signaling pathways leading to membrane phospholipid degradation and targeting, early on, docosahexaenoyl phospholipid-enriched excitable membranes.

Animals↗