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At least 163 records · Page 9Linked to original sources
PubMed1997

New carotenoids from the thermophilic green sulfur bacterium Chlorobium tepidum: 1',2'-dihydro-gamma-carotene, 1',2'-dihydrochlorobactene, and OH-chlorobactene glucoside ester, and the carotenoid composition of different strains.

The complete carotenoid composition of the thermophilic green sulfur bacterium Chlorobium tepidum strain TNO was determined by spectroscopic methods. Major carotenoids were four kinds of carotenes: gamma-carotene, chlorobactene, and their 1',2'-dihydro derivatives (1',2'-dihydro-gamma-carotene and 1',2'-dihydrochlorobactene). In lesser amounts, hydroxyl gamma-carotene, hydroxyl chlorobactene, and their glucoside fatty acid esters were found. The only esterified fatty acid present was laurate, and OH-chlorobactene glucoside laurate is a novel carotenoid. In other strains of C. tepidum, the same carotenoids were found, but the composition varied from strain to strain. The overall pigment composition in cells of strain TNO was 4 mol carotenoids and 40 mol bacteriochlorophyll c per mol bacteriochlorophyll a. The effects of nicotine on carotenoid biosynthesis in C. tepidum differed from those in the thermophilic green nonsulfur bacterium Chloroflexus aurantiacus.

Carotenoids↗
PubMed1991

Examination of factors that may influence disposition of benzo[a]pyrene in vivo: vehicles and asbestos.

Effects of vehicles and of asbestos on disposition of benzo[a]pyrene (B[a]P) were examined in vivo. [3H]B[a]P dissolved in triethylene glycol, ethyl laurate, or tricaprylin was intratracheally administered to male Sprague-Dawley rats. Excretion was most rapid when triethylene glycol was the vehicle, with 70.5% of the recovered dose appearing in bile in 6 h. Lower amounts were excreted into bile when ethyl laurate (58.4%) or tricaprylin (56.2%) were the vehicles, with comparably higher amounts remaining in lungs. When chrysotile asbestos was intratracheally instilled 24 h prior to instillation of [3H]B[a]P dissolved in triethylene glycol, the rate of excretion of radioactivity was slower than without asbestos pretreatment, with only 61.8% of the dose appearing in bile in 6 h.

Animals↗
PubMed2001

Cold-induced changes in the energy coupling and the UCP3 level in rodent skeletal muscles.

The mechanism of thermoregulatory uncoupling of respiration and phosphorylation in skeletal muscles has been studied. It is found that 24 h cold exposure results in (i) a 3-fold increase in the amount of UCP3 protein in rat skeletal muscle mitochondria, and (ii) pronounced lowering of the membrane potential in isolated rat or mouse skeletal muscle mitochondria. The decrease in membrane potential is reversed by adding bovine serum albumin. Cold exposure is also found to sensitize the membrane potential to the uncoupling action of added fatty acid (laurate). After laurate addition, the recoupling effects of GDP and carboxyatractylate decrease whereas that of albumin increases in mitochondria from cold-treated rats or mice. Changes similar to those induced by cold can be initiated by the in vivo addition of thyroxine. Cold exposure does not affect energy coupling in liver mitochondria. The possible involvement of UCP3 isoforms in nucleotide-sensitive and -insensitive uncoupling is discussed.

Animals↗
PubMed1977

Some enzymatic properties of peptidyl dipeptide hydrolase (angiotensin I-converting enzyme).

Peptidyldipeptide hydrolase [angiotensin I-converting enzyme, EC 3.4.15.1] was inhibited by inorganic and organic phosphorus compounds tested, except for beta-glycerophosphate, 5'-AMP, and 5'-ADP, at the reagent concentrations used. Orthophosphate and pyrophosphate nonspecifically inhibited the enzyme activity. The enzyme was also inhibited specifically by carboxylates. The degree of inhibition by aliphatic monocarboxylates increased in proportion to their chain length up to C14. Aromatic and omega-phenylalkylcarboxylates also inhibited the enzyme activity. The enzyme was noncompetitively inhibited by acetate, 3-phenylpropionate and laurate. The Ki's for acetate, 3-phenylpropionate, and laurate were 60, 3.3, and 2.5 mM, respectively.

Acetates↗
PubMed2006

Expression of a Porphyromonas gingivalis lipid A palmitylacyltransferase in Escherichia coli yields a chimeric lipid A with altered ability to stimulate interleukin-8 secretion.

In Escherichia coli the gene htrB codes for an acyltransferase that catalyses the incorporation of laurate into lipopolysaccharide (LPS) as a lipid A substituent. We describe the cloning, expression and characterization of a Porphyromonas gingivalis htrB homologue. When the htrB homologue was expressed in wild-type E. coli or a mutant strain deficient in htrB, a chimeric LPS with altered lipid A structure was produced. Compared with wild-type E. coli lipid A, the new lipid A species contained a palmitate (C16) in the position normally occupied by laurate (C12) suggesting that the cloned gene performs the same function as E. coli htrB but preferentially transfers the longer-chain palmitic acid that is known to be present in P. gingivalis LPS. LPS was purified from wild-type E. coli, the E. coli htrB mutant strain and the htrB mutant strain expressing the P. gingivalis acyltransferase. LPS from the palmitate bearing chimeric LPS as well as the htrB mutant exhibited a reduced ability to activate human embryonic kidney 293 (HEK293) cells transfected with TLR4/MD2. LPS from the htrB mutant also had a greatly reduced ability to stimulate interleukin-8 (IL-8) secretion in both endothelial cells and monocytes. In contrast, the activity of LPS from the htrB mutant bacteria expressing the P. gingivalis gene displayed wild-type activity to stimulate IL-8 production from endothelial cells but a reduced ability to stimulate IL-8 secretion from monocytes. The intermediate activation observed in monocytes for the chimeric LPS was similar to the pattern seen in HEK293 cells expressing TLR4/MD2 and CD14. Thus, the presence of a longer-chain fatty acid on E. coli lipid A altered the activity of the LPS in monocytes but not endothelial cell assays and the difference in recognition does not appear to be related to differences in Toll-like receptor utilization.

Acyltransferases↗
PubMed1987

Oxidation of fatty acids by Leishmania braziliensis panamensis.

Heating cultures of Leishmania braziliensis panamensis (grown at 26 degrees C) to 34 degrees C for 1.5-12 h transformed the cells to an ellipsoidally shaped form. The heat treatment caused an increase in the rate of oxidation of both medium and long chain fatty acids but decreased the rate of oxidation of [1-14C]glucose. The rate of fatty acid oxidation continued to increase for times as long as 20 h after returning the cultures to 26 degrees C. In both the promastigote and heat-induced ellipsoidal forms, the ratio of 14CO2 release from [1-14C]laurate to that from [12-14C]laurate was generally larger than four, whereas this ratio from [1-14C]oleate relative to [10-14C]oleate was approximately two. These data show that metabolic and morphological differentiation begin after a short heat treatment and that some metabolic changes may continue even after the reverse transformation is initiated. The data also suggest that either the omega-terminal portion of the fatty acids is not completely oxidized to acetyl CoA and/or that there are two functional fatty acid oxidation pathways in Leishmania.

Acetyl Coenzyme A↗
PubMed2000

Effect of several factors on the mechanical properties of pressure-sensitive adhesives used in transdermal therapeutic systems.

The effects of coating thickness, type of adhesive, and type and concentration of enhancer on the mechanical properties of two acrylic pressure-sensitive adhesives (PSAs) were investigated using a 2(4) factorial design and an optimization technique. Sixteen formulations containing 0% or 10% of either caprylic acid or methyl laurate in two different PSAs, namely Duro-Tak 87-2196 and Duro-Tak 87-2097, were prepared. The adhesive properties of these laminates were evaluated by applying the 90 degrees Dynamic Adhesive Strength Peel Test (90 degrees DASPT) and 1800 Release Liner Peel Test (180 degrees RLPT). Coating thickness, concentration of enhancer, and type of adhesive did affect the 90 degrees DASPT. For the 180 degrees RLPT, the most significant factors were coating thickness and concentration of enhancer, with a strong interaction observed between the two. Coating thickness and concentration of enhancer were also used to create mathematical models that correlated these factors with the mechanical properties of the PSAs. For this purpose, the optimization technique 3(2) was applied. It was found that the correlation of the above factors can be adequately described with polynomial equations, which can be used for predicting the mechanical properties of the laminates containing the above PSAs and methyl laurate (0%-10%).

Acrylates↗
PubMed1988

[The effects of eicosapentaenoic acid ethyl ester (EPA-E) on arterial thrombosis in rabbits and vascular lesions in rats].

The effects of highly purified ethyl ester of eicosapentaenoic acid (EPA-E) on ellagic acid-induced thrombus formation in the stenosed femoral artery in rabbits and on the progression of laurate-induced vascular lesions in rats were examined. (1) EPA-E in single administration significantly prevented the thrombus formation induced by ellagic acid in the stenosed femoral artery of rabbits. (2) EPA-E restored the hypercoagulation activity at 5 min and 3 hr after the ellagic acid injection. Platelet aggregability induced by arachidonic acid decreased at 5 min and 3 hr after the ellagic acid injection; EPA-E had little effect on this change. EPA-E showed almost no effect on fibrinolytic activity, blood viscosity and filterability of washed red blood cells after the ellagic acid injection. (3) Moreover, EPA-E in daily administrations showed a significant preventative effect against the laurate-induced vascular lesions in rats. The efficacy of EPA-E on arterial thrombosis and vascular lesions observed in this study suggests that EPA-E is a candidate for the treatment of peripheral circulatory disturbance.

Animals↗
PubMed1986

Interfacial reaction dynamics and acyl-enzyme mechanism for lipoprotein lipase-catalyzed hydrolysis of lipid p-nitrophenyl esters.

The fatty acyl (lipid) p-nitrophenyl esters p-nitrophenyl caprylate, p-nitrophenyl laurate and p-nitrophenyl palmitate that are incorporated at a few mol % into mixed micelles with Triton X-100 are substrates for bovine milk lipoprotein lipase. When the concentration of components of the mixed micelles is approximately equal to or greater than the critical micelle concentration, time courses for lipoprotein lipase-catalyzed hydrolysis of the esters are described by the integrated form of the Michaelis-Menten equation. Least square fitting to the integrated equation therefore allows calculation of the interfacial kinetic parameters Km and Vmax from single runs. The computational methodology used to determine the interfacial kinetic parameters is described in this paper and is used to determine the intrinsic substrate fatty acyl specificity of lipoprotein lipase catalysis, which is reflected in the magnitude of kcat/Km and kcat. The results for interfacial lipoprotein lipase catalysis, along with previously determined kinetic parameters for the water-soluble esters p-nitrophenyl acetate and p-nitrophenyl butyrate, indicate that lipoprotein lipase has highest specificity for the substrates that have fatty acyl chains of intermediate length (i.e. p-nitrophenyl butyrate and p-nitrophenyl caprylate). The fatty acid products do not cause product inhibition during lipoprotein lipase-catalyzed hydrolysis of lipid p-nitrophenyl esters that are contained in Triton X-100 micelles. The effects of the nucleophiles hydroxylamine, hydrazine, and ethylenediamine on Km and Vmax for lipoprotein lipase catalyzed hydrolysis of p-nitrophenyl laurate are consistent with trapping of a lauryl-lipoprotein lipase intermediate. This mechanism is confirmed by analysis of the product lauryl hydroxamate when hydroxylamine is the nucleophile. Hence, lipoprotein lipase-catalyzed hydrolysis of lipid p-nitrophenyl esters that are contained in Triton X-100 micelles occurs via an interfacial acyl-lipoprotein lipase mechanism that is rate-limited by hydrolysis of the acyl-enzyme intermediate.

Animals↗
PubMed1987

Effects of in vivo administration of detergents on the hepatic microsomal cytochrome P-450 system in rat.

The influence of in vivo administration of detergents on the hepatic microsomal cytochrome P-450 system was studied in rat. Male Wistar rats were administered detergents, Emulgen 913 (50 mg or 100 mg kg-1 of body weight (B.W.], or sodium dodecylsulfate (SDS, 25 mg or 50 mg kg-1 of B.W.) intraperitoneally once a day for 3 days. Cytochrome P-450 content in liver microsomes was significantly decreased to 85% and 73% of control by the administration of 50 mg or 100 mg Emulgen, respectively, but the microsomal protein concentration was not changed by these administrations. The content of cytochrome P-450 was also reduced to 76% and 70% of control by the administration of 25 mg or 50 mg SDS/kg of B.W., respectively. The total hydroxylation activity (the sum of omega- and (omega-1)-hydroxylase activity) of laurate almost paralleled the decrease in cytochrome P-450 in detergent-treated rats. However, the omega/omega-1-hydroxylation ratio was not changed. These results suggest that the administration of these detergents lowered the level of cytochrome P-450 species catalyzing omega- and (omega-1)-hydroxylation of laurate to a similar extent. On the other hand, aminopyrine N- and p-nitroanisole O-demethylation activities in Emulgen 913-treated rats was decreased while those in SDS-treated rats did not change, though the content of cytochrome P-450 was decreased by both administrations. Thus, it was demonstrated that the livers of rats responded to exogenous detergents in different manners.

Aminopyrine N-Demethylase↗
PubMed1982

Synthesis and bioevaluation of a series of fatty acid esters of p-[N,N-bis(2-chloroethyl)amino]phenol.

A series of even numbered fatty acid esters (C2-C18) of p-[N,N-bis(2-chloroethyl)amino]phenol were synthesized and evaluated as to acute toxicity as well as effectiveness against L-1210 mouse leukemia. The acetate through the decanoate derivatives demonstrated toxicity between 2 and 3 times that of phenol mustard in HA/ICR mice. The less soluble laurate, myristate, palmitate, and stearate derivatives were less toxic. Significant survival times in the leukemia studies (T/C% greater than or equal to 125) were observed for all compounds except the acetate and hexanoate derivatives. The myristate derivative produced the greatest significant increase in survival time, 162%. The palmitate and stearate derivatives produced significant survival at five and four dosage levels, respectively. The butyrate and laurate derivatives produced significant survival at three dosage levels and the octanoate, decanoate, and myristate at two dosage levels.

Aniline Mustard↗
PubMed1992

Studies of in vitro skin permeation and retention of a leukotriene antagonist from topical vehicles with a hairless guinea pig model.

A leukotriene antagonist [Ro 23-3544; 6-acetyl-7-[5-(4-acetyl-3-hydroxy-2-propylphenoxy)pentyloxy] -3,4-dihydro-2H-1-benzopyran-2-carboxylic acid; 1] was studied in vitro for its permeation through and retention in hairless guinea pig skin from various topical vehicles. Both the free acid and the sodium salt forms of the drug were used. The vehicles evaluated were polyethylene glycol 400, propylene glycol, dimethyl sulfoxide (DMSO), C12-C15 alcohol lactates, dimethyl isosorbide, butyrolactone, methylpyrrolidone, hexyl laurate, isopropyl myristate, and caprylic/capric triglyceride (Neobee M5). For the salt form of the drug, the highest permeability coefficient and retention were obtained from DMSO and methylpyrrolidone, respectively. For the acid form, however, the highest permeability coefficient and retention were obtained from hexyl laurate and DMSO, respectively. The highest permeation and retention values were not obtained from the same vehicle for either the salt or the acid form of the drug. This observation questions the validity of using permeation (flux) measurements to screen topical drugs and formulations. Although the precise reasons for this lack of correlation between permeation and retention are not known at this time, this study has shown that the solubility parameters of the drug and the vehicles used may play an important role. It seems logical to conduct skin retention studies rather than flux measurements in evaluating drug delivery from dermatological products.

Administration, Cutaneous↗
PubMed2005

Water-soluble nanoparticles from random copolymer and oppositely charged surfactant, 3a. Nanoparticles of poly(ethylene glycol)-based cationic random copolymer and fatty acid salts.

In this report, we investigate the nanoparticle formation between random copolymers (RCPs) of methoxy-poly(ethylene glycol) monomethacrylate (MePEGMA) and (3-(methacryloylamino)propyl)trimethylammonium chloride (MAPTAC) and oppositely charged natural surfactants, sodium oleate and sodium laurate, using turbidimetric titration, steady-state fluorescence, dynamic light scattering, and electron microscopy. Though sodium oleate and sodium laurate are sparingly soluble in water, the nanoparticle complexes formed between the RCPs and these surfactants are soluble in the entire range of compositions studied here, including the stoichiometric electronetural complexes. The spherical nature of these nanoparticle complexes is revealed by electron microscopic (EM) analysis. Dynamic light scattering (DLS) showed that the average diameters of the nanoparticles are in the range 50 to 150 nm, which is supported by EM analysis. Pyrene fluorescence experiments suggested that these soluble nanoparticles have hydrophobic cores, which may solubilize hydrophobic drug molecules. The polarity index (I(1)/I(3)) obtained from the pyrene fluorescence spectra and the conductometric measurements showed that the critical concentration of fatty acid salts needed to obtain nanoparticles are in the order of 10(-4) M. Further, the complexation of such poorly water-soluble amphiphilic surfactants with polymers offers a useful method for the immobilization of hydrophobic compounds towards water-soluble drug carrier formulations. The formation of water-soluble nanoparticles by the self-assembly of fatty acid salts upon interacting with oppositely charged poly(ethylene glycol)-based polyions.

Bile Acids and Salts↗
PubMed1998

A conserved proline-rich sequence between the N-terminal signal-anchor and catalytic domains is required for assembly of functional cytochrome P450 2C2.

In cytochrome P450 2C2, the region which links the N-terminal signal anchor with the catalytic domain contains a highly conserved proline-rich region with the sequence, 30-PPGPTPFP-37. Mutation of proline-30 or proline-33 diminished activities of the mutants expressed in COS-1 cells (Chen, C., and Kemper, B. (1996) J. Biol. Chem. 271, 28697-28611). Substitution of alanine, proline, or arginine for glycine-32 abolished laurate hydroxylase activity of the proteins expressed in COS-1 cells, which suggests that this residue is also functionally important. To determine the basis for the decreased activity in COS-1 cells, the activities and spectral properties of mutant proteins expressed in insect cells and bacteria were determined. Substitution of alanine for either proline-30 or -33 resulted in reduced expression in insect cells of functional cytochrome P450 hemoprotein and an increase in the expression of inactive cytochrome P420. In contrast, substitution of alanine for proline-31, -35, or -37 resulted in hemoproteins with spectra similar to cytochrome P450 2C2 so that the amount of cytochrome P450 expressed in insect cells correlated with the activities of the mutants in COS-1 cells. The laurate hydroxylase activities per nanomole of cytochrome P450 in insect microsomes were similar for wild type and all mutants, indicating that, once folded, the catalytic activity of membrane-bound cytochrome P450 was not affected by the mutations. Expression in bacteria resulted in diminished expression of cytochrome P450 for all mutants, with the greatest decrease for the proline-30 and -33 mutants, and increased cytochrome P420. In contrast to the insect cell studies, the proline-30 and -33 mutants were inactive, while the other mutants had specific activities 30-70% of cytochrome P450 2C2. These data are consistent with a role for the proline-rich region in efficient assembly of cytochrome P450 2C2 in eukaryotic cells. Mutations of this region also may affect the conformational integrity of the proteins, which was revealed by assays of solubilized bacterially expressed proteins.

Animals↗
PubMed2002

Sensing specific adhesion of liposomal and micellar systems with attached carbohydrate recognition structures at lectin surfaces.

A quartz crystal microbalance was used to investigate the adsorption behavior of liposomes and mixed micelles with attached carbohydrate recognition structures at lectin-coated quartz plates. With a self-assembly technique, the quartz was coated with the lectin Concanavalin A. In a first attempt, liposomes of natural soybean PC as well as synthetic POPC, containing 10% reactive N-Glut-PE each, were decorated with a mannopyranoside recognition structure to investigate the specific adsorption at the lectin-coated quartz surface in dependence on the concentration. In a second model, the bile salt sodium cholate was introduced to solubilize the mannopyranoside-modified liposomes and to transform them into mannopyranoside-modified binary mixed micelles. The adsorption of these micelles was further investigated. In a third approach, the adsorption behavior of mannopyranoside-modified ternary mixed bile salt-phosphatidylcholine-fatty acid micelles was characterized with sodium laurate, palmitate, and oleate as fatty acids. The micelles with oleate showed only a small frequency decrease, whereas the micelles with laurate and palmitate induced higher frequency changes. A dependence on the alkyl chain length could be detected. While the adsorption of liposomes containing recognition structures at QCM surfaces is nowadays well-established, the QCM detection of the adsorption of mixed bile salt micelles, transformed from these liposomes by solubilization, is a novel and very promising field for the development of innovative colloidal drug delivery systems.

Bile Acids and Salts↗
PubMed1996

Effects of saturated fatty acids on amylase release from exocrine pancreatic segments of sheep, rats, hamsters, field voles and mice.

Stimulatory effects of saturated fatty acids consisting of 4 (butyrate), 8 (octanoate), 12 (laurate) and 16 (palmitate) carbon atoms, as well as acetylcholine on pancreatic amylase release were assessed in tissue segments isolated from sheep, rats, hamsters, field voles and mice. The amount of amylase release induced by the fatty acids (1 mumol.l-1 to 10 mml.l-1) and by acetylcholine (10 nmol.l-1 to 100 mumol.l-1) increased in a concentration-dependent manner, and the maximum response in response to the fatty acids was obtained at the maximal dose used. The maximum increase in amylase release in response to butyrate or octanoate was highly and significantly (r = 0.974, P < 0.001) dependent on the log value of the mean body mass in the following order: sheep > rats > hamsters > field voles > mice. On the other hand, the response to laurate and palmitate was variable among animal species. Addition of atropine (1.4 mumol.l-1) to the medium did not reduce the responses to octanoate stimulation, but significantly reduced acetylcholine-induced responses, implying that the effects of the fatty acids were not mediated through activation of muscarinic acetylcholine receptors. Reduction of calcium ion concentration in the medium significantly inhibited the responses induced by the fatty acids and acetylcholine, suggesting that amylase release depends on extracellular calcium ions.

Acetylcholine↗
PubMed1987

Rapid isolation of microsomes for studies of lipid peroxidation.

Conventional isolation of microsomes by high-speed centrifugation from isotonic sucrose requires exposure to air for several hours, leading to the formation of low levels of lipid peroxidation products. Sucrose interferes in protein and malondialdehyde assays and provides no protection against lipid peroxidation during workup. A new procedure for the purification of microsomes from rat liver substitutes mannitol (a hydroxyl radical scavenger) for sucrose and takes advantage of the properties of morpholinopropane sulfonic acid (MOPS) buffer and triethylenetetramine to provide protection against lipid peroxidation during the rapid (less than one hour) workup and subsequent low-temperature storage. The microsomal fractions prepared by the proposed method are free of detectable mitochondrial contamination and at least as pure overall as those prepared by the conventional method, but they have higher glucose-6-phosphatase and laurate hydroxylase activities and significantly less malondialdehyde than conventional microsomes at the time isolation is complete. Laurate hydroxylase activity is more stable during frozen storage in mannitol medium. The kinetics of lipid peroxidation in vitro are quite different for microsomes prepared by the two methods.

Animals↗
PubMed1992

Subterminal hydroxylation of lauric acid by microsomes from a marine fish.

Microsomes from the liver of sea bass (Dicentrarchus labrax) were shown to hydroxylate lauric acid at subterminal positions. The cytochrome P-450 system converted lauric acid to several mono-hydroxylated metabolites including omega-1 hydroxylaurate, which was the major metabolite (44% of total products). In addition, omega-2, omega-3, omega-4 and a small amount (2.3%) of omega hydroxylaurates were found. Reaction products were identified using thin-layer chromatography (TLC) and gas chromatography/mass spectrometry (GC/MS). Oxidation reactions were dependent upon O2 and NADPH, and did not occur with boiled microsomes or in the presence of a mixture of CO/O2. Hydroxylation proceeded linearly up to 20 min at 28 degrees C for protein concentrations below 380 micrograms. Treatment of fish with benzo(a)pyrene (BP) (20 mg/kg) drastically increased xenobiotic metabolism (ECOD, EROD and BPMO activities), but no difference in laurate hydroxylase activity was observed between untreated and treated fish. Starvation strongly enhanced laurate hydroxylase activity, and resumption of feeding reduced by half this increase of activity. In all of the experiments we did not observe any modification of the regioselectivity of lauric acid hydroxylation by this microsomal in-chain hydroxylating system. We suggest that cytochrome P-450 enzymes involved in lauric acid and xenobiotics metabolism are regulated independently.

Animals↗