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PubMed2003

Effect of pH on the control release of microencapsulated dye in lecithin liposomes. II.

The objective of our work has been the microencapsulation of dyes with lecithin from soybean, with the formation of liposomes, as a substitute for synthetic auxiliaries so as to improve the quality of the effluent. Current scenarios promote the disintegration and leakage of the liposomes, such as, changes in temperature, pH, and the use of surfactants. Since dyeing process is a mix of all these parameters, we pretended to study each one separately. Changes in pH at constant temperature induce a release of dye similar with changes in temperature. In acid conditions, we found a very fast initial dye release which doesn't occur in basic conditions. Using carboxyfluorescein, as a pH fluorescence probe, we concluded that the liposome membrane doesn't protect the liposome interior from changes on the external pH.

Drug Compounding↗

PubMed1973

Endoplasmic reticulum as the site of lecithin formation in castor bean endosperm.

The properties of a discrete membranous fraction isolated on sucrose gradients from castor bean endosperm have been examined. This fraction was previously shown to be the exclusive site of phosphorylcholine-glyceride transferase. The distribution of NADPH-cytochrome c reductase and antimycin insensitive NADH-cytochrome c reductase across the gradient followed closely that of the phosphorylcholine-glyceride transferase. This fraction also had NADH diaphorase activity and contained cytochromes b(5) and P 450. On sucrose gradients containing 1 mM EDTA this fraction had a mean isopycnic density of 1.12 g/cm(3) and sedimented separately from the ribosomes; electron micrographs showed that it was comprised of smooth membranes. When magnesium was included in the gradients to prevent the dissociation of membrane-bound ribosomes, the isopycnic density of the membrane fraction with its associated enzymes was increased to 1.16 g/cm(3) and under these conditions the electron micrographs showed that the membranes had the typical appearance of rough endoplasmic reticulum. Together these data show that the endoplasmic reticulum is the exclusive site of lecithin formation in the castor bean endosperm and establish a central role for this cytoplasmic component in the biogenesis of cell membranes.

Cell Fractionation↗

PubMed2001

Preventive effects of lecithinized superoxide dismutase and methylprednisolone on spinal cord injury in rats: transcriptional regulation of inflammatory and neurotrophic genes.

The effects of lecithinized superoxide dismutase (PC-SOD) and/or methylpredisolone (MP) in preventing secondary pathological changes after spinal cord injury (SCI) were investigated in rats with reference to recovery of hindlimb motor function and expression of mRNA of pro-inflammatory and neurotrophic genes. Hindlimb motor function was assessed as the BBB open field locomotor scores. The BBB scores of three groups treated with either PC-SOD (40,000 units/kg), MP (30 mg/kg), or a combination of PC-SOD and MP (PC-SOD+MP) increased with time until 3 days after SCI, and were significantly higher than that of the control group (p < 0.05). Thereafter, the score of the PC-SOD group increased, whereas that of the MP group showed a temporary decrease from day 3 to 5 and then it gradually recovered. The scores in all groups reached a plateau about 18 days after SCI. The PC-SOD+MP group did not show a synergism but a tendency similar to that of the MP group. PC-SOD and MP had down-regulatory effects on mRNA expression of pro-inflammatory substances such as interleukin-1beta (IL-1beta), intercellular adhesion molecule-1 (ICAM-1), and inducible-nitric oxide synthetase (i-NOS) after spinal cord compression at 3, 6, and 24 h, respectively, as judged by a semiquantitative reverse transcription-polymerase chain reaction and on the lipid peroxide (LPO) level 1 h after injury as determined by thiobarbituric acid-reactive substances. The suppression of pro-inflammatory genes expression, especially IL-1beta were greater in the MP group than in the PC-SOD group, while suppression of LPO level was similar in these two groups. PC-SOD+MP treatment augmented the suppression of all three pro-inflammatory genes expression and the decrease of the LPO level. The level of neurotrophin-3 (NT-3) mRNA increased from 6 h after SCI and reached a maximum after 48 h. NT-3 mRNA level was enhanced by PC-SOD treatment, but not by MP treatment. Thus, the effect of MP in suppressing these pro-inflammatory genes expression was more than that of PC-SOD. The difference in motor function in the early and later stage may be partially due to differences in expression of IL-1beta and NT-3 after either treatment, through an IL-1beta-dependent or NT-3-mediated repair response.

Animals↗

PubMed1997

Effects of lecithinized superoxide dismutase on traumatic brain injury in rats.

Only small amounts of superoxide dismutase (SOD) are present in the extracellular space to scavenge excess amounts of superoxide anions (02-) released after traumatic brain injury (TBI). Experiments were performed in rats with cerebral contusion produced by weight-drop technique. We investigated the effects of exogenous lecithinized SOD (PC-SOD) on accumulation of 02- produced in our model, by measuring the level of SOD activity (using the NBT-reducing method) and the expression of copper, zinc-SOD (Cu, Zn-SOD) mRNA (by Northern blot analysis). As determined by tissue-specific gravity, administration of PC-SOD reduced brain edema in the periphery of the lesion 6 h after contusion. SOD activity increased in the peripheral region at 30 min after contusion, but returned to normal levels at 6 h after TBI. Administration of PC-SOD increased SOD activity up to 6 h after TBI. The expression of Cu, Zn-SOD mRNA increased in the core region, peripheral portion, and contralateral hemisphere up to 6 h after TBI, then was suppressed in all three regions by PC-SOD. Our results confirm the important role of 02- in the development of brain edema after TBI and indicate that PC-SOD diminishes brain edema through a protective effect against 02-.

Animals↗

PubMed1993

An evaluation of the efficacy and safety of tetrahydroaminoacridine (THA) without lecithin in the treatment of Alzheimer's disease.

Seventy-nine patients with probable Alzheimer's disease were enrolled into a double-blind, placebo-controlled cross-over study to assess the therapeutic effect and safety of THA (tetrahydroaminoacridine; tacrine) without concomitant lecithin administration. Forty-one patients completed the trial which consisted of two 12-week treatment phases separated by a 4-week wash-out period. Twenty-six subjects were withdrawn during the active treatment phase, mostly because of elevated transaminases or cholinergic side-effects, and ten during treatment with placebo. Statistical analyses were conducted on two groups of patients; those completing the cross-over and those with at least one evaluation in the first treatment period. This latter analysis, using the last observation carried forward was used to approximate an intention-to-treat analysis. THA was favoured over placebo in all three primary outcome measures (MMSE, ADAS Non-cognitive Scale, and the Functional Life Scale), but the results did not reach statistical significance. THA was favoured over placebo in five of the seven secondary outcome measures, but for only two of these was statistical significance attained. In terms of a three-point or greater increase in MMSE score, three to four times as many subjects improved on THA as on placebo.

Activities of Daily Living↗

PubMed1985

Plasma activities of lipoprotein lipase, hepatic lipase and lecithin: cholesterol acyltransferase in patients considered for parenteral nutrition with fat emulsion.

Intralipid is a fat emulsion which is widely used for intravenous nutrition in very ill patients. In order to know more about the capacity of these patients to metabolize exogenous triglycerides, the plasma activities of lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyltransferase (LCAT), the key enzymes in the metabolism of serum lipoproteins were measured by a radioisotope technique in 23 critically ill patients and 20 patients with recent major surgery. Compared with normal volunteers, the activities were significantly decreased. On the other hand, the capacity to clear intravenously given Intralipid (0.1 g/kg), expressed as fractional removal rate (K2), was retained in patients. It is suggested that the measurement of K2 could not be useful to evaluate the capacity of Intralipid administration to satisfy the metabolic needs and also that its utilization must be reevaluated in terms of potential harmful effects.

Adult↗

PubMed1991

Plasma lecithin-cholesterol acyltransferase activity and plasma lipoprotein composition and concentrations in kwashiorkor.

Plasma lecithin-cholesterol acyltransferase (LCAT) activity, lipoprotein composition, and lipoprotein concentrations were measured in 21 children with kwashiorkor before (day 1), during (day 10), and after treatment (day 30). Day 1 LCAT activity (78.2 mumol.L-1.h-1) was decreased with respect to day 10 (139.2 mumol.L-1.h-1, P less than 0.001) and day 30 (108.0 mumol.L-1.h-1, P = 0.08). Plasma total cholesterol (TC), cholesterol ester (CE), and lipoprotein CEs (VLDL, IDL, LDL, and HDL) were reduced relative to days 10 and 30 (P less than 0.001). Before treatment HDL composition was abnormal. On days 1, 10, and 30, the respective mean HDL-apolipoprotein A-I (apo A-I) concentrations were 23.33, 39.66, and 36.08 mumol/L. LDL-apo B concentrations were 0.40, 0.68, and 0.56 mumol/L (P less than 0.01, days 10 and 30 vs day 1). LDL particles on day 1 were decreased in number, depleted of CE, and laden with triacylglycerol and surface lipids. LCAT activity on day 1 correlated with LDL-CE linoleate (P less than 0.05, r = 0.48). Reduced plasma LCAT activity is an important factor related to abnormalities in lipoprotein composition and concentrations.

Apolipoproteins B↗

PubMed1982

Correlation of amylase and lecithin sphingomyelin ratios in amniotic fluid samples.

The use of amniotic fluid amylase (AF amylase) has been proposed as a screening test to determine fetal maturity. We reviewed data from 944 amniotic fluid samples analyzed by our laboratory for amylase and lecithin sphingomyelin (L/S) ratio between 1975 and 1980. AF amylase shows poor overall correlation with L/S ratios (r = 0.256). Retrospective analysis of AF amylase as a screen to determine the need for L/S ratios showed an overall sensitivity of 57%, and an overall specificity of 86% for AF amylase. Three groups were studied: a low amylase group (amylase less than 200 U/L), a middle group (amylase 200-300 U/L), and a high amylase group (amylase greater than 300 U/L). Only 55% of the low amylase group had an immature L/S ratio. The high amylase group had the best correlation between AF amylase and L/S ratio, but 13% of these samples had an immature or borderline L/S ratio. We conclude that AF amylase cannot be used as a screening test to determine the need to perform L/S ratios.

Amniotic Fluid↗

PubMed2004

Relative bioavailability of ketoprofen 20% in a poloxamer-lecithin organogel.

PURPOSE: The bioavailability of a single, topically applied, 200-mg dose of ketoprofen (delivered in a ketoprofen 20% gel) relative to a single 50-mg oral dose in healthy volunteers was studied. METHODS: This was an open-label crossover study. The subjects were randomized to receive an oral 50-mg ketoprofen capsule or a single topical dose of ketoprofen 20% in a poloxamer-lecithin organogel (PLO). Treatment was followed by a one-week washout period. Blood samples were collected at intervals up to 10 hours after administration, and plasma ketoprofen concentrations were determined by high-performance liquid chromatography with ultraviolet or mass spectrometry detection. Noncompartmental pharmacokinetic values were obtained after each dose, and relative bioavailability was calculated. RESULTS: Eight healthy volunteers enrolled in and completed the study. Topical absorption of ketoprofen was highly variable among the subjects over the 10-hour sampling period. The median oral maximum plasma concentration (Cmax) exceeded the topical Cmax by nearly 200-fold (4.15 versus 0.021 microg/mL) (p = 0.001). The median relative bioavailability of topical ketoprofen was 0.48%, with individual subjects' values ranging from 0.18% to 2.1%. CONCLUSION: The relative bioavailability of ketoprofen was low and highly variable when the drug was administered as a single dose in a PLO-based ketoprofen 20% gel.

Adult↗

PubMed2000

Esterification of all-trans-retinol in normal human epithelial cell strains and carcinoma lines from oral cavity, skin and breast: reduced expression of lecithin:retinol acyltransferase in carcinoma lines.

When exogenous [(3)H]retinol (vitamin A) was added to culture medium, normal human epithelial cells from the oral cavity, skin, lung and breast took up and esterified essentially all of the [(3)H]retinol within a few hours. As shown by [(3)H]retinol pulse-chase experiments, normal epithelial cells then slowly hydrolyzed the [(3)H]retinyl esters to [(3)H]retinol, some of which was then oxidized to [(3)H]retinoic acid (RA) over a period of several days. In contrast, cultured normal human fibroblasts and human umbilical vein endothelial cells (HUVEC) did not esterify significant amounts of [(3)H]retinol; this lack of [(3)H]retinol esterification was correlated with a lack of expression of lecithin:retinol acyltransferase (LRAT) transcripts in normal fibroblast and HUVEC strains. These results indicate that normal, differentiated cell types differ in their ability to esterify retinol. Human carcinoma cells (neoplastically transformed epithelial cells) of the oral cavity, skin and breast did not esterify much [(3)H]retinol and showed greatly reduced LRAT expression. Transcripts of the neutral, bile salt-independent retinyl ester hydrolase and the bile salt-dependent retinyl ester hydrolase were undetectable in all of the normal cell types, including the epithelial cells. These experiments suggest that retinoid-deficiency in the tumor cells could develop because of the lack of retinyl esters, a storage form of retinol.

Acyltransferases↗

PubMed2003

Comparative pharmacokinetics and safety of a novel lyophilized amphotericin B lecithin-based oil-water microemulsion and amphotericin B deoxycholate in animal models.

Amphotericin B (AmB) has been a most effective systemic antifungal agent, but its use is circumscribed by the dose-limiting toxicity of the conventional micellar dispersion formulation Fungizone (D-AmB). To lower AmB-associated toxicity, AmB may be integrated into oil-in-water lecithin-based microemulsions. The present study compares the pharmacokinetic characteristics of D-AmB with the alternative formulation of AmB in microemulsion (M-AmB), which has proved effective in a murine candidiasis model. Both formulations were given by intravenous bolus: D-AmB 1 mg/kg, and M-AmB 0.5, 1 or 2 mg/kg. The pharmacokinetics of D-AmB and M-AmB have several differences, specifically with regard to the respective Cmax and AUC0- infinity values. Elimination of AmB from serum was biphasic for both M-AmB and D-AmB. Single-dose D-AmB (1 mg/kg) achieved a Cmax of 3.89 +/- 0.48 mg/L and an AUC0- infinity of 32.28 +/- 7.31 mg.h/L, whereas single-dose M-AmB (1 mg/kg) by comparison achieved a lower Cmax (2.92 +/- 0.54 mg/L) and a lower AUC0- infinity (21.89 +/- 5.17 mg.h/L). To evaluate the safety of M-AmB, a multiple-dose toxicity study was performed in groups of 10 mice, each receiving D-AmB 1 mg/kg, or M-AmB 1, 1.5, 2 or 3 mg/kg. The findings suggest that, in comparison with D-AmB, M-AmB produces no histologically demonstrable renal lesions, or changes in clinical chemistry.

Amphotericin B↗

PubMed1980

Effect of trans fatty acids on serum lecithin: cholesterol acyltransferase in rats.

An investigation was undertaken to study the effect of trans isomers of octadecenoic (18:1) and octadecadienoic (18:2) acids on serum lecithin:cholesterol acyltransferase (LCAT). Male rats of the Wistar strain were fed diets containing 15% fat for 9 months. The fat diets were either hydrogenated fat mixtures containing trans fatty acids, corn oil or lard. At the end of 9 months, rats were killed and serum cholesterol levels and LCAT activity were measured. It was found that free and total serum cholesterol levels were decreased when animals were fed trans fatty acids when compared with animals fed corn oil or lard. Although in vitro studies indicated that the percentage of cholesterol esterified in serum was not affected by the presence of dietary trans fatty acids, LCAT activity generally decreased when trans fatty acids were fed to rats for 9 months. In this study a negative correlation was found between serum free cholesterol and LCAT activity. Depressed total LCAT activity (mumoles of cholesterol esterified per hour per liter of serum) may have been related to a reduced amount of substrate (free cholesterol).

Animals↗

PubMed1981

Decreased plasma lecithin: cholesterol acyltransferase activity in copper-deficient rats.

The effect of dietary copper deficiency on rat plasma lecithin: cholesterol acyltransferase (LCAT) activity was examined. Three groups of rats were used: ad libitum-fed copper-deficient group (0.6 microgram Cu/g diet); pair-fed control group (5.9 microgram Cu/g diet); and an ad libitum-fed control group (5.9 microgram Cu/g diet). Copper deficiency produced a significant hypercholesterolemia (57% increase, P less than 0.001) in 63 days with a significant increase in plasma free cholesterol (44%, P less than 0.001). Despite the significant increase in plasma free cholesterol, fractional and molar LCAT activity were markedly decreased (74.2%, P less than 0.001 and 63.7%, P less than 0.005, respectively) in copper-deficient rats. The results of this study suggest that dietary copper deficiency affects LCAT activity.

Animals↗

PubMed1984

Reduction of plasma lecithin--cholesterol acyltransferase activity by acute magnesium deficiency in the rat.

Weanling Wistar rats were pair-fed for 8 days control and magnesium-deficient diets. Acute magnesium deficiency increased plasma triglycerides and free cholesterol levels and decreased esterified cholesterol levels. The plasma activity of lecithin--cholesterol acyltransferase was markedly diminished in fasting magnesium-deficient rats (54% reduction) and plasma high density lipoprotein (HDL) free cholesterol was significantly increased in the HDL fraction. The results of this study showing that dietary magnesium affects the activity of the enzyme involved in the esterification of free cholesterol to cholesterol ester provide a possible basis for the reduced plasma cholesterol esterification and hyperlipidemia associated with acute magnesium deficiency.

Animals↗

PubMed1996

N-(4-hydroxyphenyl)-retinamide increases lecithin:retinol acyltransferase activity in rat liver.

N-(4-Hydroxyphenyl)-retinamide (4-HPR; Fenretinide) is a synthetic retinoid which is undergoing investigation as a cancer chemopreventive agent. However, 4-HPR alters vitamin A kinetics and reduces the concentration of plasma retinol. We have conducted studies to examine the effects of 4-HPR on the activity of the enzyme lecithin:retinol acyltransferase (LRAT). This enzyme is implicated in the absorption and storage of vitamin A and is regulated, in liver, by vitamin A nutritional status. To determine whether 4-HPR, like retinoic acid, is able to induce liver LRAT activity, vitamin A-deficient rats having negligible liver LRAT activity were treated with single doses of 4-HPR (0.02-2.5 mg) and liver homogenates were assayed for LRAT activity using 3H-retinol bound to the cellular-retinol binding protein, CRBP, as substrate. Treatment with 4-HPR resulted in a dose- and time-dependent increase in liver LRAT activity which reached a maximum at 24 h. The activity of LRAT assayed in vitro and of hepatic 3H-retinyl ester content determined after an in vivo pulse of 3H-retinol were highly correlated (r = 0.802, P < 0.0002). When vitamin A-sufficient rats were fed a 4-HPR-supplemented diet for 30 d, LRAT activity differed significantly from control values in the liver (P < 0.0001) but not the small intestines. Changes in hepatic retinol metabolism which favor the esterification of vitamin A may be related to the mechanism by which 4-HPR alters vitamin A kinetics in vivo.

Acyltransferases↗

PubMed1997

Lecithin:retinol acyltransferase and retinyl ester hydrolase activities are differentially regulated by retinoids and have distinct distributions between hepatocyte and nonparenchymal cell fractions of rat liver.

The cellular distribution of enzymes that esterify retinol and hydrolyze retinyl esters (RE) was studied in liver of vitamin A-sufficient, -deficient, and deficient rats treated with retinoic acid or N-(4-hydroxyphenyl)-retinamide. Livers were perfused and cell fractions enriched in hepatocytes, and nonparenchymal cells were obtained for assays of RE and enzyme activity. The specific activity of lecithin:retinol acyltransferase (LRAT) was approximately 10-fold greater in the nonparenchymal cell than the hepatocyte fraction from both vitamin A-sufficient and retinoid-treated rats. Total RE mass, newly synthesized [3H]RE and LRAT activity were positively correlated in liver and isolated cells of both normal (P < 0.0001) and retinoid-treated rats (P < 0.0002). In nonparenchymal cells, these three constituents were nearly equally enriched as evaluated by their relative specific activity values (RSA, defined as the percentage of recovered activity divided by the percentage of recovered protein), which were each significantly greater than 1.0, with values of 4.3 for total RE mass (P < 0.05), 3.6 for newly synthesized [3H]RE (P < 0.01) and 3.8 for LRAT activity (P < 0.01). In contrast, the specific activities of neutral and acid bile salt-independent retinyl ester hydrolases (REH) did not vary with vitamin A status, and their RSA values were close to 1.0 in both hepatocytes and nonparenchymal cells. These data show that LRAT and REH are differentially regulated by retinoids and that these enzymes also differ in their spacial distribution between liver parenchymal and nonparenchymal cells.

Acyltransferases↗

PubMed1998

Fatty acids modulate lecithin:cholesterol acyltransferase secretion independently of effects on triglyceride secretion in primary rat hepatocytes.

The regulation of plasma lecithin:cholesterol acyltransferase (LCAT) expression is not well understood. Although oleic acid increases both the secretion of triglycerides and LCAT by primary rat hepatocytes, the effect of other fatty acids (FA) on LCAT secretion is not known. This study was designed to examine the effect of FA on the hepatic secretion of LCAT, triglyceride and apolipoprotein A-1 (apoA-1). Primary rat hepatocytes were incubated with serum-free medium, supplemented with individual FA (0-1 mmol/L) for 22-24 h. Preliminary studies indicated a linear secretion of LCAT up to 24 h in both control and FA-treated cells. When hepatocytes were incubated with 1 mmol/L FA, the LCAT secretion increased 50-100% (P < 0.01) in the presence of the 18-carbon FA (stearic, oleic, elaidic and linoleic acids), whereas the presence of butyric, lauric and palmitic acids had no significant effect. LCAT secretion decreased (P < 0.01) in the presence of docosahexaenoic acid (DHA). All FA (except DHA) significantly enhanced triglyceride secretion; however, only the 18 carbon FA significantly stimulated the synthesis and secretion of apoA-1 and secretion of LCAT. The secretion of LCAT correlated with apoA-1 secretion (r = 0.88, P = 0.004) but not with triglyceride secretion (r = 0.55, P = 0.12). Treatment with oleic acid resulted in a 1.5-fold increase in hepatocyte LCAT mRNA accumulation, whereas butyrate and palmitate had no effect. These data indicate that FA that promote the apparent synthesis and secretion of apoA-1 also stimulate the secretion of LCAT in vitro, suggesting a coordinate regulatory mechanism for apoA-1 and LCAT expression.

Animals↗

PubMed2002

Lecithin:retinol acyltransferase expression is regulated by dietary vitamin A and exogenous retinoic acid in the lung of adult rats.

Lecithin:retinol acyltransferase (LRAT), a retinol esterifying enzyme, plays a major role in the metabolism and storage of vitamin A in several animal tissues. Groups of vitamin A (VA)-adequate (control) and VA-deficient rats were treated with vehicle or 5 mg of all-trans-retinoic acid (RA); an additional group of VA-deficient rats were fed 100 microg of RA. In control rats, lung LRAT mRNA and LRAT specific activity were approximately 50% of the levels expressed in the liver. In the lung of VA-deficient rats, LRAT mRNA and specific activity levels were <10% of those in the control group. Treatment of VA-deficient rats with 100 microg RA increased lung LRAT mRNA (P < 0.005) and specific activity (P < 0.0001), and treatment with 5 mg of RA increased LRAT mRNA level and specific activity more than approximately 15- and 6-fold above those in control lung, respectively (both P < or = 0.001). The lung tissue of VA-adequate rats contained retinyl ester (approximately 3 nmol/g tissue), whereas none was detected in the lung tissue of VA-deficient rats. These results show that LRAT expression and vitamin A storage are regulated by vitamin A status and by treatment with all-trans-RA in the adult lung. These results suggest that the regulated storage of vitamin A may be important for maintaining the integrity and physiologic functions of the lung.

Acyltransferases↗