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At least 793 records · Page 44Linked to original sources
PubMed2000

Equivalence of lauric acid and glycerol monolaurate as inhibitors of signal transduction in Staphylococcus aureus.

Glycerol monolaurate (GML) inhibits the expression of virulence factors in Staphylococus aureus and the induction of vancomycin resistance in Enterococcus faecalis, presumably by blocking signal transduction. Although GML is rapidly hydrolyzed by bacteria, one of the products, lauric acid, has identical inhibitory activity and is metabolized much more slowly. At least four distinct GML-hydrolyzing activities are identified in S. aureus: the secreted Geh lipase, residual supernatant activity in a geh-null mutant strain, a novel membrane-bound esterase, and a cytoplasmic activity.

Chromatography, Thin Layer↗
PubMed1998

Thermal acclimation of phase behavior in plasma membrane lipids of rainbow trout hepatocytes.

The fluorescent probes laurdan (6-dodecanoyl-2-dimethylaminonapthalene) and N-[7-nitrobenz-2-oxa-1, 3-diazol-4-yl] dipalmitoyl-L-alpha-phosphatidylethanolamine (NBD-PE) in addition to Fourier transform infrared spectroscopy (FTIR) were employed to measure the phase behavior and physical properties of hepatocyte plasma membranes isolated from the livers of thermally acclimated (5 and 20 degreesC) rainbow trout (Oncorhynchus mykiss). The primary objective was to determine the extent to which the phase behavior of membrane lipids is conserved at different growth temperatures. Arrhenius plots of laurdan-generalized polarization revealed a single discontinuity believed to reflect either the onset of the gel-fluid phase transition or the formation of gel phase microdomains, and this discontinuity occurred at significantly higher temperatures in membranes of 20 degrees C (13.2 +/- 0.7 degrees C)- than 5 degrees C (7.2 +/- 0.1 degrees C)-acclimated trout. Similarly, acclimation from 5 to 20 degrees C increased both the onset temperature (from 2.0 +/- 0.3 to 7.2 +/- 0.6 degrees C) and the thermal range (from 10.9 +/- 0.5 to 16.0 +/- 1.0) of the gel-fluid transition as assessed by FTIR. The gel-fluid transition midpoint (approximately -2 degrees C) and completion temperatures (-9 degrees C) were unchanged by thermal acclimation. The anisotropy of NBD-PE fluorescence displayed a distinct minimum in membranes of both warm- and cold-acclimated trout (reflecting alterations in lipid packing that in pure lipid membranes ultimately lead to the formation of nonlamellar phases) in the range of 56-58 degrees C; only membranes of 5 degrees C-acclimated trout displayed an additional minimum at significantly lower temperatures (24.5 +/- 1.7 degrees C). Collectively, these data suggest that the regulation of both the temperature at which gel phase lipids begin to form in response to cooling as well as the propensity of membrane lipids to form nonlamellar phases at higher temperatures may be key features of membrane organization subject to adaptive regulation.

2-Naphthylamine↗
PubMed2002

Effects of fatty acids on mitochondrial beta-oxidation enzyme gene expression in renal cell lines.

Regulatory effects of fatty acids on gene expression of medium-chain acyl-CoA dehydrogenase (MCAD), a mitochondrial beta-oxidation enzyme, were investigated in rabbit kidney cell lines derived from proximal tubule (RC.SV1), thick ascending limb of Henle's loop (RC.SV2), or collecting duct (RC.SV3). Exposure to long-chain fatty acids led to significant increases (2-fold) in MCAD mRNA abundance in RC.SV1 and RC.SV2 cells; kinetics and dose-response studies established that maximal MCAD gene stimulation was reached 4 h after addition of 50 microM oleate (C18:1) in the culture medium. These effects of fatty acids were totally abolished in the presence of 1 microg/ml actinomycin D, a transcription inhibitor. Staining of cellular lipids revealed that fatty acid-induced gene stimulation could occur in the absence of cellular fatty acid accumulation. Altogether, these data indicate that small changes in cellular fatty acid flux can have direct short-term effects on fatty acid oxidation enzyme gene expression in renal cells, and this might take part in the regulation of cellular fatty acid homeostasis in response to changes in tubular fluid composition.

Acyl-CoA Dehydrogenase↗
PubMed2005

Erythrocyte plasma membrane perturbations in rats fed a cholesterol-rich diet: effect of drinking sulphurous mineral water.

AIMS: The purpose of the present study was to evaluate the ability of calcic and magnesic-sulphate-sulphurous spring mineral water (SMW) to reduce total and erythrocyte plasma membrane cholesterol in rats fed a cholesterol-rich diet. METHODS: By using different fluorescent probes, 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-[4-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH) and Laurdan, a possible correlation was evaluated between cholesterol content changes of the membranes and membrane fluidity. RESULTS: The results clearly show that hydropinic treatment reduced cholesterol level. No significant change was observed in DPH and TMA-DPH anisotropy values. By using Laurdan, an increase was observed in generalized polarization (GP(340)) in both groups of rats (the one that drank tap water and the one that drank SMW) compared with the controls. The rate of haemolysis was reduced in those erythrocyte suspensions in which cholesterol was increased, even if the enzymatic activity of glutathione peroxidase and catalase decreased. CONCLUSION: Hydropinic treatment with SMW is of interest from the biomedical point of view, because it could represent an alternative approach in interventions aimed at ameliorating biological injury deriving from hypercholesterolaemia.

2-Naphthylamine↗
PubMed1989

Pyrene-methyl lauryl ester, a new fluorescent substrate for lipases: use for diagnosis of acid lipase deficiency in Wolman's and cholesteryl ester storage diseases.

Fluorescent pyrene-methyl lauryl ester (PMLes) was synthesized and used for the determination of cellular lipase activities in lymphoblasts and fibroblasts from normal subjects and from patients affected with Wolman's or cholesteryl ester storage diseases (both exhibiting a deficiency of the lysosomal acid lipase). The hydrolysis of PMLes by acid lipase could be followed directly in a spectrofluorometer; this was possible because of the very high fluorescence emission of pyrene-methanol at 378 nm (monomeric form) in aqueous medium, whereas the substrate has practically no monomeric emission at 378 nm but emits only at 475 nm (excimeric form) in the experimental conditions used: this property permitted us to use PMLes as a fluorogenic substrate. In an alternative procedure, the enzymatic reaction could be determined after partition of the reaction mixture in a biphasic system of heptane and aqueous ethanol; the residual undegraded substrate partitioned into the upper heptane phase and the fluorescence of the product (i.e. pyrene-methanol) was read in the lower aqueous-ethanolic phase, at 378 nm. PMLes was hydrolyzed in extracts of normal lymphoblasts and fibroblasts by at least two lipases, one acidic lipase (pH 4.0) and a second more neutral enzyme (pH 6.5). The acidic lipase activity was practically absent in lymphoblasts and fibroblasts from Wolman's or cholesteryl ester storage diseases. This demonstrates that the fluorescent PMLes is hydrolyzed by the lysosomal acid lipase and can be used as a very sensitive fluorogenic substrate which permits direct recording of product formation and is suitable for the enzymatic diagnosis of either of these diseases.

Cell Line↗
PubMed2001

In vivo downregulation of T helper cell 1 immune responses reduces atherogenesis in apolipoprotein E-knockout mice.

BACKGROUND: A chronic immune response involving proinflammatory T helper cell 1 (Th1) lymphocyte activation occurs in the atherosclerotic lesion, but whether this activation is protective or deleterious remains unclear. Methods and Results-- We modulated the immune response of the atherosclerosis-prone apolipoprotein E-deficient (apoE(-/-)) mouse. Eight-week-old apoE(-/-) mice were treated daily with pentoxifylline (PTX), a known inhibitor of the Th1 differentiation pathway, or PBS (control) for 4 weeks or 12 weeks. Twelve-week PTX treatment reduced atherosclerotic lesion size by 60% (P<0.01). PTX-treated mice developed lesions that were limited to the degree of fatty streaks. In contrast, control mice developed mature fibrofatty atherosclerotic lesions. In parallel, the proportion of interferon (IFN)-gamma-producing Th1 splenic lymphocytes was significantly reduced by PTX, and lesion size was correlated to the proportion of IFN-gamma(+) T cells. In vitro addition of PTX to cultured spleen cells did not modify the production of IFN-gamma but increased the production of IL-10 by T cells, indicating that PTX does not suppress IFN-gamma production but rather blocks Th1 polarization while promoting Th2 polarization. CONCLUSIONS: Thus, PTX protected mice from atherosclerosis by reducing the Th1 polarization of T helper lymphocytes. This study demonstrates that the Th1 immune response associated with atherosclerosis is deleterious and that a modulation of the Th1 differentiation pathway may provide a new pharmacological tool to treat this disease.

Animals↗
PubMed1984

The effects of fatty acids and their monoesters on the metabolic activity of dental plaque.

We examined the effects of the saturated series of fatty acids and their esters on plaque bacterial metabolism. Fatty acids with a chain length of 8-15 carbons inhibited Streptococcus mutans and dental plaque in vitro. The glycerol monoesters with a fatty acid chain of 10-14 carbons were inhibitory to a similar extent. The glycolipid (sucrose monolaurate) reduced plaque bacterial glycolysis and sucrose oxidation in a non-competitive manner but stimulated sucrose incorporation at low sucrose concentrations. The relationship between surface activity and inhibition is discussed, since this may help to explain the anti-caries effects of these compounds.

Adult↗
PubMed2002

Glycated low density lipoproteins modify platelet properties: a compositional and functional study.

The interaction between low density lipoproteins (LDL) and platelets might play a central role in the development of atherosclerosis in diabetes. The aim of the present study was to investigate whether the glycation of LDL is associated with modifications of their physico-chemical and functional properties and to study the action of glycated LDL (glycLDL) on platelets. LDL and platelets were isolated from 15 healthy subjects. The content of thiobarbituric acid-reactive substances and the generalized polarization of the fluorescent probe Laurdan were determined in LDL glycated in vitro. Platelets were incubated with native LDL, GlycLDL, and minimally oxidized LDL, and the following parameters were evaluated: platelet aggregation, nitric oxide production, intracellular Ca(2+) concentrations, Na(+)/K(+)-adenosine triphosphatase (Na(+)/K(+)-ATPase), and Ca(2+)-ATPase activities. GlycLDL showed increased thiobarbituric acid-reactive substance levels, a red shift of the Laurdan emission maximum, and a decrease in generalized polarization, indicating a higher polarity and a reduced molecular order compared with native LDL. GlycLDL caused a significant increase in platelet nitric oxide production, intracellular Ca(2+) concentration, and aggregating response to ADP; an inhibition of the platelet membrane Na(+)/K(+)-ATPase activity; and a stimulation of Ca(2+)-ATPase activity. Minimally oxidized LDL did not cause statistically significant changes in the parameters studied. The present work demonstrates that glycation induces compositional and structural changes in LDL and suggests that an altered interaction between glycLDL and platelets might play a role in the vascular complications of diabetes.

2-Naphthylamine↗
PubMed1994

Effect of fatty acid on the accumulation of thiamine disulfide in rat skin.

The effect of long chain fatty acid (FA) and its analogs on the accumulation of thiamine disulfide (TDS) in rat skin using propylene glycol as a vehicle was studied in vitro. Lauric acid (12:0) increased the accumulation of TDS in skin, while myristic acid and stearic acid caused a slight decrease in accumulation. Lauryl alcohol and lauric acid methyl ester did not change the accumulation of TDS in the skin. The ratio of the amount of TDS accumulated in skin to the solubility of TDS in the vehicle increased dependent on the concentration of 12:0 added in the vehicle. It was suggested that the increase in the permeability coefficient of TDS by 12:0 results from the enhanced transport of TDS from the vehicle to skin.

Animals↗
PubMed1996

l-Menthol, oleic acid and lauricidin in absorption enhancement of free and sodium salt of diclofenac using ethanol treated silicone membrane as model for skin.

The mechanism of l-menthol, oleic acid and lauricidin as enhancers on percutaneous absorption was examined using diclofenac (DH) as a hydrophobic drug and sodium diclofenac (DNa) as a hydrophilic drug in in vitro diffusion experiments with two kinds of membranes: ethanol-treated and untreated silicone membranes; these were models for the lipid and pore pathways of skin. A 20% w/w ethanol-aqueous solution decreased the flux of DH but increased the flux of DNa significantly across the treated membrane compared with those fluxes across the untreated membrane, suggesting that DH penetrated by the lipid pathway and DNa by the pore pathway. The permeability of DNa through the pore pathway decreased significantly across the treated membrane with the addition of oleic acid and lauricidin. l-Menthol increased the permeability coefficients of DH and DNa more in a treated membrane than in an untreated one, showing the same tendency as in rat skin. Thus, while oleic acid and lauricidin did not increase the permeation of DNa by the pore pathway, l-menthol appeared to enhance the permeation of the drug by both the lipid and pore pathways.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

Effect of polyvinylpyrrolidone and sodium lauroyl isethionate on kaolinite suspension in an aqueous phase.

Suspension of concentrated kaolinite (20 g/30 ml-medium) in the presence of polyvinylpyrrolidone (PVP) and sodium lauroyl isethionate (SLI) was allowed to evaluate its degree of dispersion based on their rheological studies. Flow curves at low shear rate, measured by means of cone-plate method, showed a non-Newtonian flow. Plastic viscosity and Bingham yield value were derived from the flow curves. Relative viscosity, effective volume fraction and void fraction of secondary particle were also obtained. Results of dispersity and fluidity of the suspension were explained. PVP acted as a flocculant at a concentration lower than 0.1% but as a dispersant at a higher concentration. The presence of SLI could decrease both the Bingham yield value and suspension viscosity. Cooperative and competitive effects of PVP and SLI were found. Results indicated that SLI enhanced the degree of dispersion of kaolinite when PVP was less than 0.1%. The suspension, however, showed a maximum flocculation (i.e., aggregation) at 4 mM SLI when the concentration of PVP was higher than 0.1%.

Isethionic Acid↗
PubMed2002

Application of an all-solid-state, frequency-doubled Nd:YAP laser to the generation of twin beams at 1080 nm.

A laser-diode-pumped intracavity frequency-doubled Nd:YAP/KTP laser is presented. Over 110 mw of TEM00 single-frequency output power at 540-nm wavelength was obtained. The output green laser was employed to pump a semimonolithic nondegenerate optical parametric oscillator to produce intensity quantum correlated twin beams at 1080 nm, and the maximum quantum noise squeezing of 74% (5.9dB) on the intensity difference fluctuation between the twin beams is observed. The threshold was reduced and the stability was increased significantly when compared with similar lamp-pumped systems.

Journal Article↗
PubMed2005

Experimental evidence of spontaneous symmetry breaking in intracavity type II second-harmonic generation with triple resonance.

We describe a spontaneous symmetry-breaking phenomenon between the intensities of the ordinary and extraordinary components of the fundamental field in intracavity type II harmonic generation. It is based on a triply resonant cavity containing a type II chi(2) crystal pumped at fundamental frequency omega0. The pump beam generates a second-harmonic mode at frequency 2omega0 that acts as a pump for frequency-degenerate type II parametric downconversion. Under operating conditions symmetric with respect to the ordinary and extraordinary components of the fundamental wave, we show a breaking of the symmetry of the intensities of these two waves.

Journal Article↗
PubMed2005

Experimental investigation of amplitude and phase quantum correlations in a type II optical parametric oscillator above threshold: from nondegenerate to degenerate operation.

We describe a stable type II optical parametric oscillator operated above threshold that provides 9.7 +/- 0.5 dB (89%) of quantum noise reduction on the intensity difference of the signal and idler modes. We also report the first experimental study, to our knowledge, by homodyne detection of the generated bright two-mode state in the case of frequency-degenerate operation obtained by the introduction of a birefringent plate inside an optical cavity.

Journal Article↗
PubMed2006

Structure-guided recombination creates an artificial family of cytochromes P450.

Creating artificial protein families affords new opportunities to explore the determinants of structure and biological function free from many of the constraints of natural selection. We have created an artificial family comprising 3,000 P450 heme proteins that correctly fold and incorporate a heme cofactor by recombining three cytochromes P450 at seven crossover locations chosen to minimize structural disruption. Members of this protein family differ from any known sequence at an average of 72 and by as many as 109 amino acids. Most (>73%) of the properly folded chimeric P450 heme proteins are catalytically active peroxygenases; some are more thermostable than the parent proteins. A multiple sequence alignment of 955 chimeras, including both folded and not, is a valuable resource for sequence-structure-function studies. Logistic regression analysis of the multiple sequence alignment identifies key structural contributions to cytochrome P450 heme incorporation and peroxygenase activity and suggests possible structural differences between parents CYP102A1 and CYP102A2.

Amino Acid Sequence↗