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At least 811 records · Page 45Linked to original sources
PubMed2004

Enzymatic synthesis of monolaurin.

The aim of this study was to produce monolaurin utilizing a commercial immobilized lipase (Lipozyme IM-20; Novo Nordisk, Bagsvaerd, Denmark) through the direct esterification of lauric acid and glycerol in a solvent-free system. The influence of fatty acid/glycerol molar ratio, temperature, and Lipozyme (IM-20) concentration on the molar fraction of monolaurin were determined using an experimental design. The best conditions employed were 55 degrees C, lauric acid/glycerol molar ratio of 1.0, and 3.0% (w/w) enzyme concentration. The final product, obtained after 6 h of reaction, was 45.5% monolaurin, 26.8% dilaurin, 3.1% trilaurin, and 24.6% lauric acid. The reusability of the enzyme was also studied.

Biotechnology↗
PubMed2005

Nanosecond dynamics of a mimicked membrane-water interface observed by time-resolved stokes shift of LAURDAN.

We studied the dipolar relaxation of the surfactant-water interface in reverse micelles of AOT-water in isooctane in the nanosecond and subnanosecond time ranges by incorporating the amphipathic solvatochromic fluorescent probes LAURDAN and TOE. A negative component was observed in the fluorescence decays in the red edge of the emission spectrum-the signature of an excited state reaction-with LAURDAN but not for TOE. The deconvolution of the transient reconstructed spectra of LAURDAN based on a model constructed by adding together three log-normal Gaussian equations made it possible to separate the specific dynamic solvent response from the intramolecular excited state reactions of the probe. The deconvoluted spectrum of lowest energy displayed the largest Stokes shift. This spectral shift was described by unimodal kinetics on the nanosecond timescale, whereas the relaxation kinetics of water-soluble probes have been reported to be biphasic (on the subnanosecond and nanosecond timescales) due to the heterogeneous distribution of these probes in the water pool. Most of this spectral shift probably resulted from water relaxation as it was highly sensitive to the water to surfactant molar ratio (w(0)) (60-65 nm at w(0) = 20-30). A small part of this spectral shift (9 nm at w(0) = 0) probably resulted from dipolar interaction with the AOT polar headgroup. The measured relaxation time values were in the range of the rotational motion of the AOT polar headgroup region as assessed by LAURDAN and TOE fluorescence anisotropy decays.

2-Naphthylamine↗
PubMed2002

Coexistence of domains with distinct order and polarity in fluid bacterial membranes.

In this study we sought the detection and characterization of bacterial membrane domains. Fluorescence generalized polarization (GP) spectra of laurdan-labeled Escherichia coli and temperature dependencies of both laurdan's GP and fluorescence anisotropy of 1,3-diphenyl-1,3,5-hexatriene (DPH) (rDPH) affirmed that at physiological temperatures, the E. coli membrane is in a liquid-crystalline phase. However, the strong excitation wavelength dependence of rlaurdan at 37 degrees C reflects membrane heterogeneity. Time-resolved fluorescence emission spectra, which display distinct biphasic redshift kinetics, verified the coexistence of two subpopulations of laurdan. In the initial phase, <50 ps, the redshift in the spectral mass center is much faster for laurdan excited at the blue edge (350 nm), whereas at longer time intervals, similar kinetics is observed upon excitation at either blue or red edge (400 nm). Excitation in the blue region selects laurdan molecules presumably located in a lipid domain in which fast intramolecular relaxation and low anisotropy characterize laurdan's emission. In the proteo-lipid domain, laurdan motion and conformation are restricted as exhibited by a slower relaxation rate, higher anisotropy and a lower GP value. Triple-Gaussian decomposition of laurdan emission spectra showed a sharp phase transition in the temperature dependence of individual components when excited in the blue but not in the red region. At least two kinds of domains of distinct polarity and order are suggested to coexist in the liquid-crystalline bacterial membrane: a lipid-enriched and a proteolipid domain. In bacteria with chloramphenicol (Cam)-inhibited protein synthesis, laurdan showed reduced polarity and restoration of an isoemissive point in the temperature-dependent spectra. These results suggest a decrease in membrane heterogeneity caused by Cam-induced domain dissipation.

2-Naphthylamine↗
PubMed1981

Toxicological studies of a leachable stabilizer di-n-butyltin dilaurate(DBTL): effects on hepatic drug metabolizing enzyme activities.

Toxicological studies of a leachable stabilizer Di-n-butyltin dilaurate (DBTL) were undertaken. Effects of DBTL after 15 days oral exposure to rats were studied on brain and liver enzyme activities. A significant decrease in body weight gain of DBTL exposed rats were observed. No effect was observed in the activities of brain enzymes, succinic dehydrogenase, adenosine triphosphatase, acetylcholine esterase and monoamine oxidase. In liver, DBTL treatment resulted in a significant decrease in the activities of microsomal enzymes glucose-6-phosphatase, aminopyrine-N-demethylase, benzphetamine-N-demethylase, aniline hydroxylase, benzo(a)pyrene hydroxylase and also on cytochrome P-450 content, whereas no difference in the activities of mitochondrial enzymes, succinic dehydrogenase, Mg2+-adenosine triphosphatase as well as in the activity of lysosomal enzyme acid phosphatase was observed. Duration of exposure dependent increase in pentabarbital induced sleeping time was also observed. DBTL treatment produced an induction in heme oxygenase activity whereas the activity of -aminolevulinic acid synthetase remained unaltered. The results demonstrate that DBTL significantly affects the biotransformation mechanism and heme metabolism of hepatocytes.

Animals↗
PubMedDate not supplied

Use of the fluorescent probe Laurdan to investigate structural organization of the vesicular stomatitis virus (VSV) membrane.

We have used 6-dodecanoil-2-dimethylaminonaphtalene (Laurdan) to study the membrane fluidity of Vesicular Stomatitis Virus (VSV) during virus activation at acidic pH 5.8). The fluorescence properties of Laurdan provide a unique possibility to study lipid organization because of the different excitation and emission spectra of this probe in the gel and liquid crystalline phase. Acidification to pH 5.8 (the pH which triggers VSV fusion with target membranes) generates a decrease in VSV membrane fluidity that could be reversed perfectly after neutralization. We conclude that lipid reorganization of the VSV membrane in the endocytic vesicles is needed for virus activation.

2-Naphthylamine↗
PubMed1997

Effect of aluminium ions on liposomal membranes as detected by Laurdan fluorescence.

We report here an investigation of the influence of aluminium on iron-induced peroxidation in brain model membranes. Laurdan fluorescence emission spectra and generalised polarisation measurements have been used to investigate how ferrous and aluminium ions can affect the phase components of phospholipid membranes. An increase in the generalised polarisation of oxidised liposomes with respect to controls has been observed, which reveals the presence of a less polar environment surrounding the probe that changes the properties of the bilayer. Aluminium has been shown to facilitate iron-mediated oxidation as detected from emission fluorescence spectra. However, no quantitative influence has been calculated relative to general polarisation and derived phase state determinations. The structural influence of aluminium on membranes may therefore be less significantly marked than initially expected.

2-Naphthylamine↗
PubMed2003

Localized epidural and bone amyloidosis, rare cause of paraplegia in multiple myeloma.

We report two cases of spinal cord compression by AL amyloid deposits in the setting of multiple myeloma. The first patient, a 57 year old man, had a surgical procedure late in his course, when his neurological status worsened despite medical treatment. The second patient, a 61 year old man, had surgical treatment as soon as vertebral body collapse and epiduritis were diagnosed and spinal amyloidosis revealed a non secretory myeloma. Neurological recovery was significant in both cases and neither developed manifestations of systemic amyloidosis 4 years later.

Amyloidosis↗
PubMed1987

Effect of exogenous long-chain fatty acids on individual fatty acid synthesis by dispersed ruminant mammary gland cells.

We investigated the effect of exogenously added fatty acids on de novo synthesis of individual fatty acids and their incorporation into triacylglycerols by dispersed lactating ruminant mammary gland epithelial cells. Palmitate addition strongly stimulated synthesis and incorporation of butyrate and, to a smaller extent, palmitate synthesis and incorporation. Oleic acid strongly inhibited synthesis of all fatty acids except butyrate, whereas the effect of lauric acid was nearly neutral. Free fatty acid depletion of the mammary gland cells potentiated the effect of palmitate and made oleate less inhibitory.

Animals↗
PubMed1992

Evaluation of postmilking teat germicides containing Lauricidin, saturated fatty acids, and lactic acid.

The efficacies of postmilking teat germicides containing Lauricidin (glyceryl monolaurate), saturated fatty acids, lactic acid, and lauric acid were determined against new IMI caused by Staphylococcus aureus and Streptococcus agalactiae in three controlled infection trials. In trial 1, a germicide was evaluated containing 1% Lauricidin, 5% caprylic and capric acids, 6% lactic acid, and .85% lauric acid. New IMI with Staph. aureus and Strep. agalactiae were reduced 81.3 and 49.6%, respectively. Trial 2 germicide involved an artificially aged sample of the formulation evaluated in trial 1. The germicide was aged at 40 degrees C for 5 mo, which was approximately equal to 2 yr at room temperature (24 degrees C). Reductions in new IMI were 81.2 and 27.5% for Staph. aureus and Strep. agalactiae, respectively. In trial 3, a teat germicide aged at ambient temperature for 33 mo, which was originally formulated to contain 1% Lauricidin, 5% caprylic and capric acids, and 6% lactic acid, was evaluated. Reductions in new IMI were 75.5 and 40.4% for Staph. aureus and Strep. agalactiae, respectively. The formulation evaluated in trial 1 was superior to other formulations in reducing new IMI by the two test organisms.

Animals↗
PubMed1991

Enhancement of antibody production by lysophosphatidylcholine and alkylglycerol.

Inflammation products of normal and cancerous tissues, lysophosphatidylcholine and dodecylglycerol, were tested for their adjuvant effect on the antibody response. Mice treated with these agents and immunized with sheep erythrocytes simultaneously or at 3 days posttreatment developed a greatly enhanced antibody production as demonstrated by the Jerne plaque assay. Mice immunized at 3 days postadministration of agents did not significantly produce enhanced antibody-secreting cells as compared with those of mice simultaneously immunized. Since the mechanism of macrophage activation by lysophospholipids requires contribution of B and T cells, BALB/c-nu/nu mice treated with these agents and subsequently immunized with sheep erythrocytes did not produce antibodies. However, conditioned medium of in vitro-treated BALB/c-nu/nu B cells efficiently transmitted a signal to untreated BALB/c +/+ T cells for enhanced macrophage ingestion activity. This observation suggests that lysophospholipid-activated macrophages and T cells efficiently transmitted antigenic signal to the antibody-producing B cell population. Therefore, we conclude that these lipid metabolites have dual beneficial effects for the host by enhancing phagocytosis and antibody production. Thus, lysophosphatidylcholine and dodecylglycerol have potential practical application as adjuvants that could be administered separately or in combination with antigens.

Animals↗
PubMed1991

Activation of peritoneal macrophages by orally administered ether analogues of lysophospholipids.

Oral administration of dodecylglycerol, inflammatory product of cancerous tissues, and the alkyl lysophospholipid derivative, 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3-choline), greatly activated mouse peritoneal macrophages. The activation was dose related and was assessed as increased Fc-mediated ingestion of red blood cells, superoxide production, chemiluminescence activity, and incorporation of radioactive thymidine and leucine. Furthermore, the data show that dodecylglycerol or ET-18-OCH3-choline was capable of inducing equally high levels of macrophage activation and cytotoxic action on tumor cells, just as occurs with intraperitoneal administration. Dodecylglycerol appeared to activate the macrophages at a relatively lower dose (5 micrograms/mouse) than ET-18-OCH3-choline (15 micrograms/mouse). The optimal oral doses required to activate macrophages for ingestion and cytotoxic activities were relatively higher than previously observed when these agents were administered intraperitoneally. Thus, the dose difference provided crucial information for correlating oral dosages with in vivo concentration of these agents as bioassayed by macrophage activation. These observations have extended and further support our earlier findings that these agents are effective immunopotentiators and thus could therapeutically be used to activate macrophages for cytotoxic effects on tumor cells via the oral route.

Administration, Oral↗
PubMed1996

Monolaurin and acetic acid inactivation of Listeria monocytogenes attached to stainless steel.

Individual and combined antimicrobial effects of monolaurin and acetic acid on Listeria monocytogenes planktonic cells or stainless-steel-adherent cells were determined in order to evaluate cell viability during a 25-min exposure period at 25 degrees C. A 10(7)-colony-forming units (CFU)/ml population of planktonic cells was completely inactivated by the synergistic combination of 1% acetic acid with 50 or 100 microg/ml of monolaurin within 25 or 20 min, respectively. Either compound alone caused partial but incomplete inactivation within the same time periods. A population of 10(5) CFU/cm2 of 1-day adherent cells on stainless steel was completely inactivated within 25 min, but with the highest concentrations of the combined chemicals, i.e., 1% acetic acid and 100 microg/ml of monolaurin. The combined chemical treatment again synergistically produced greater inhibition. A 10(6)-CFU/cm2 population of 7-day adherent cells was not completely inactivated within 25 min of exposure, although counts did decline. The results demonstrate increased resistance of attached L. monocytogenes to acetic acid and monolaurin and show that resistance increased with culture age. Combinations of organic acids and monolaurin might be considered as sanitizers of food contact surfaces, but activities of such combinations are likely to be less than other commonly used sanitizers.

Acetic Acid↗
PubMed2004

Development of a laboratory scale clean-in-place system to test the effectiveness of "natural" antimicrobials against dairy biofilms.

A laboratory scale system, partially reproducing dairy plant conditions, was developed to quantify the effectiveness of chlorine and alternative sanitizers in reducing the number of viable bacteria attached to stainless steel surfaces. Stainless steel tubes fouled in a continuous flow reactor were exposed to a standard clean-in-place regime (water rinse, 1% sodium hydroxide at 70 degrees C for 10 min, water rinse, 0.8% nitric acid at 70 degrees C for 10 min, water rinse) followed by exposure to either chlorine (200 ppm) or combinations of nisin (500 ppm), lauricidin (100 ppm), and the lactoperoxidase system (LPS) (200 ppm) for 10 min or 2, 4, 8, 18, or 24 h. There was significant variation in the effectiveness of the alkaline-acid wash steps in reducing cell numbers (log reduction between 0 and 2). Following a 10-min treatment, none of the sanitizers significantly reduced the number of attached cells. Two hours of exposure to chlorine, nisin + the LPS, or lauricidin + the LPS achieved 2.8, 2.2, and 1.6 log reductions, respectively. Exposure times > 2 h did not further decrease the number of viable bacteria attached to the stainless steel. The effectiveness of combinations of nisin, lauricidin, and the LPS was similar to that of chlorine (P > 0.05), and these sanitizers could be used to decontaminate the surfaces of small-volume or critical hard-to-clean milk processing equipment.

Animals↗
PubMed1990

A54145, a new lipopeptide antibiotic complex: factor control through precursor directed biosynthesis.

A54145 is a complex of new lipopeptide antibiotics produced by Streptomyces fradiae. Eight factors, containing four similar peptide nuclei in combination with three different fatty acid acyl side chains, have been isolated from the natural fermentation and characterized. The nuclei differ only in valine/isoleucine and glutamate/3-CH3-glutamate substitutions at one or both of two locations on the peptide ring. Prior deacylation of all four nuclei with Actinoplanes utahensis had permitted chemical reacylation of each nucleus with new fatty acid acyl chains for structure-activity relationship studies. In an effort to induce the native biosynthesis of preferred factors or analogs by S. fradiae, the effect of fatty acid precursors on the fermentation was examined. Many fatty acids were extremely toxic to S. fradiae, which limited experiments to slow, continuous feeding of the lipids in stirred bioreactors that were equipped for on-line respiration analysis by mass spectrometry. These studies determined that precursing with aliphatic fatty acids of various chain lengths did enhance the biosynthesis of factors containing specific fatty acid acyl side chains. Caprate, for example, increased the n-decanoyl-containing factors from the natural level of approximately 14% to approximately 80%. The percentage of factors containing branched-chain fatty acid acyl substituents was also increased, in shaken-flask studies, by enriching the medium with valine or isoleucine. These amino acids additionally enhanced the percentage of nuclei containing either valine or isoleucine.

Amino Acid Sequence↗
PubMed1999

A model for the interaction of 6-lauroyl-2-(N,N-dimethylamino)naphthalene with lipid environments: implications for spectral properties.

Although 6-lauroyl-2-(N,N-dimethylamino)naphthalene (LAURDAN) is now widely used as a probe for lipid systems, most studies focus on the effect of the lipid environment on its emission properties but not on the excitation properties. The present study is intended to investigate the excitation properties of LAURDAN in diverse lipid environments. To this end, the fluorescence properties of LAURDAN were studied in synthetic ester and ether phosphatidylcholines and sphingomyelin vesicles below, at and above the corresponding lipid main phase-transition temperature. The excitation spectra of LAURDAN in these environments always show at least two well-resolved bands. In the different lipid vesicles the behavior of the red band in the LAURDAN excitation spectra is sensitive to the lipid chemical environment near the probe fluorescent moiety and to the packing of the different lipid phases (gel and liquid crystalline). We propose that the interaction between the LAURDAN dimethylamino group and the ester linkage of ester phospholipids is responsible for the strong stabilization of LAURDAN's red excitation band in the gel phase of ester phospholipid vesicles. We discuss the consequence of these proposed ground-state interactions on LAURDAN's emission generalized polarization function. In the context of variable excitation wavelengths, information concerning solvent dipolar relaxation through excitation generalized polarization function is also discussed.

2-Naphthylamine↗