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At least 973 records · Page 54Linked to original sources
PubMed1998

Purification and characterization of recombinant human neutrophil leukotriene B4 omega-hydroxylase (cytochrome P450 4F3).

Recombinant human neutrophil leukotriene B4 (LTB4) omega-hydroxylase (cytochrome P450 4F3) has been purified to a specific content of 14. 8 nmol of P450/mg of protein from yeast cells. The purified enzyme was homogenous as judged from the SDS-PAGE, with an apparent molecular weight of 55 kDa. The enzyme catalyzed the omega-hydroxylation of LTB4 with a Km of 0.64 microM and Vmax of 34 nmol/min/nmol of P450 in the presence of rabbit hepatic NADPH-P450 reductase and cytochrome b5. Furthermore, various eicosanoids such as 20-hydroxy-LTB4, 6-trans-LTB4, lipoxin A4, lipoxin B4, 5-HETE and 12-HETE, and 12-hydroxy-stearate and 12-hydroxy-oleate were efficiently omega-hydroxylated, although their Km values were much higher than that of LTB4. In contrast, no activity was detected toward laurate, palmitate, arachidonate, 15-HETE, prostaglandin A1, and prostaglandin E1, all of which are excellent substrates for the CYP4A fatty acid omega-hydroxylases. This is the first time human neutrophil LTB4 omega-hydroxylase has been isolated in a highly purified state and characterized especially with respect to its substrate specificity.

Base Sequence↗
PubMed1998

Xanthophyll esters in human skin.

Carotenol fatty acid esters in various fruits and vegetables are sources of carotenoids for humans and are cleaved during intestinal absorption to yield the parent xanthophyll. In the present study we demonstrate that low amounts of carotenol esters are present in human skin. Eighteen different carotenol fatty acid esters were separated in extracts from human skin by means of reversed-phase high-performance liquid chromatography. After saponification of tissue samples, lutein, zeaxanthin, 2',3'-anhydrolutein, alpha-cryptoxanthin and beta-cryptoxanthin were identified as the major parent carotenoids. Based on comparison with synthetic reference compounds, several carotenol mono- and di-fatty acid esters were tentatively assigned, ranging from linoleate to stearate; the levels are low, in the range of pmol/g human skin, i.e. , several orders of magnitude lower than that of beta-carotene. Carotenol esters in human skin may be formed by reesterification of xanthophylls following absorption. Also, very small amounts of esters may circulate in the blood and subsequently accumulate in tissues such as skin.

Adult↗
PubMed1999

Binding interactions and conformational changes induced by sulfonated aluminum phthalocyanines in human serum albumin.

Phthalocyanines (Pc), which are extensively studied as tumor localizing photosensitizers for photodynamic therapy, are transported by the blood circulatory system to target tissues. Binding interactions between human serum albumin and differently sulfonated aluminum phthalocyanines (AlPcSn; n = 1-4) were studied using optical and ESR spectroscopy. AlPcSn (n = 1-3) occupy one strong binding site and eight weaker sites. The high affinity binding site interactions differ with respect to the degree of sulfonation and isomeric composition of the Pc. Phthalocyanines without SO-3 groups on adjacent iso-indole rings exhibit a high affinity binding site constant of K approximately 3-4 x 10(7) M-1, while Pc with two or three adjacent SO-3 groups show binding for this high affinity site that is no longer independent, but cooperative (alpha = 2), with K approximately 2-6 x 10(6) M-1. Binding isotherms for AlPcS4 and its close analog, tempoyl spin-labeled SL-AlPcS3, do not approach saturation at high ligand concentrations. Competition analyses between AlPcSn and spin-labeled fatty acids (5- and 16-doxyl stearate isomers) reveal that all compounds participate in cooperative (allosteric) interactions with the high affinity binding site of 16-DS, while extruding 5-DS isomer from certain sites and increasing the binding affinity for the remaining. Protein conformational dynamics was studied by ESR spectroscopy using covalent (alkylation of Cys34 residue) and noncovalent spin labeling (employing SL-AlPcS3). Phthalocyanines perturb conformational dynamics parameters (tauc and S) depending on the degree of sulfonation and isomeric composition corresponding to the type of sites, i.e., independent or cooperative, occupied on the HSA molecule.

Allosteric Regulation↗
PubMed1995

Preparation of 13C-labeled polyunsaturated fatty acids by an arachidonic acid-producing fungus Mortierella alpina 1S-4.

Three types of 13C-labeled polyunsaturated fatty acids (PUFAs) were produced in mycelia of an arachidonic acid-producing fungus, Mortierella alpina 1S-4, when grown with 13C-labeled glucose or fatty acid methyl esters. We analyzed them by negative-ion fastatom bombardment mass spectrometry. (i) PUFA in mycelia grown with [1-(13)C]glucose or [2-(13)C]glucose was a mixture of molecules containing zero to six labeled carbons. The content of 13C in the total carbon atoms of PUFA, such as arachidonic (20:4 omega 6), dihomo-gamma-linolenic (20:3 omega 6), gamma-linolenic (18:3 omega 6), and linoleic (18:2 omega 6) acids, in the mycelia grown with [1-(13)C]-glucose or [2-(13)C]glucose was about 11 or 15%, respectively. More than 80% of these PUFA had more than one 13C atom. (ii) When the fungus was grown with [U-13C]glucose, the content of PUFA molecules, all carbons of which were 13C-labeled, was about 20%. The percentage of 13C in PUFA from [U-13C]glucose was 78-83%, over 98% of which had more than one 13C atom. The 13C atoms in the labeled fatty acids formed from 13C-labeled glucose were thought to be distributed at random by a two carbon-unit. (iii) The 13C atom of PUFA in mycelia grown with 1-(13)C-labeled fatty acid methyl esters was highly localized. More than half of the 20:4 omega 6 molecules had only one 13C atom at C-3, C-5, or C-7 when the fungus was grown with methyl [1-13c]stearate, methyl [1-(13)C]palmitate, or methyl [1-(13)C]-myristate, respectively.

Arachidonic Acid↗
PubMed1994

Photophysical alterations of erythrocyte membrane by 4,5',8-trimethyl psoralen: membrane response towards psoralen phototherapy.

Despite the wide and versatile use of psoralen phototherapy in various dermal diseases including psoriasis and leukoderma, the proposed mechanism of action of psoralen is disputed. This study launches an original documentation of free-radical resulting in erythrocyte membrane damage studied by spin-labeling using the probes malnet and 5 doxyl stearate as protein and lipid domains, respectively. Both Type I and Type II photodynamics appear plausible and the therapeutic aspects of this innovation are being verified.

Animals↗
PubMed1997

A dtsR gene-disrupted mutant of Brevibacterium lactofermentum requires fatty acids for growth and efficiently produces L-glutamate in the presence of an excess of biotin.

A dtsR gene encoding a homolog of the beta subunit of some biotin-containing enzymes suppresses a detergent-sensitive mutation of Brevibacterium lactofermentum (E. Kimura et al., 1996, Biosci. Biotech. Biochem. 60, 1565-1570), which has been used for the fermentative production of L-glutamate. When the dtsR gene was disrupted, the organism exhibited strict fatty acid auxotrophy; oleate or oleate ester, but not palmitate ester or stearate ester, supported the growth of the delta dtsR mutant. Immunoblotting with an anti-DtsR antibody revealed that no intact DtsR was present in the cytosol of the delta dtsR mutant. In the presence of an excess of biotin, the wild type strain did not produce L-glutamate whereas the delta dtsR mutant efficiently produced it. The mechanism underlying the efficient production of L-glutamate by the delta dtsR mutant is discussed as to the possible role of dtsR in fatty acid metabolism.

Bacterial Proteins↗
PubMed1997

Regulation of osteoclastic bone resorption by glucose.

Osteoclasts degrade bone by pumping molar quantities of HCl to dissolve the calcium salts of bone, an energy intensive process evidently supported by abundant mitochondria. This is the first study to directly examine the ability of various metabolites to serve as potential energy sources for osteoclastic bone resorption. Glucose, and to a lesser extent lactate, supported osteoclastic bone degradation. However, fatty acids (palmitate, myristate and stearate), essential amino acids plus 20 mM alanine, or ketone bodies (acetoacetate, beta-hydroxybutyrate and alpha-ketoglutarate) did not support bone degradation. Resorption declined to 10-30% of glucose controls when fatty acids or ketoacids were substituted for glucose. Resorption was glucose concentration dependent, with maximal activity at approximately 7 mM (K(M) approximately 3 mM). Glucose transport was linear for approximately 15 minutes, specific for D-glucose, and inhibited by cytochalasin B. Osteoclasts cultured on bone transported glucose at almost twice the rate of those off bone (Vmax 23 versus 13 nmols/mg/min, respectively) and medium acid accumulation paralleled glucose uptake, while the K(M) was unchanged. We conclude that glucose is the principal energy source required for bone degradation. Further, characteristics of glucose transport are consistent with the hypothesis that fluctuations in serum glucose concentration are an important component in regulation of osteoclastic bone degradation.

Alanine↗
PubMed1999

Regulation of stearoyl-CoA desaturase genes: role in cellular metabolism and preadipocyte differentiation.

The degree of fatty acid unsaturation in cell membrane lipids determines membrane fluidity, whose alteration has been implicated in a variety of disease states including diabetes, obesity, hypertension, cancer, and neurological and heart diseases. Stearoyl-CoA desaturase (SCD) is a key rate-limiting enzyme in the synthesis of unsaturated fatty acids by insertion of a cis-double bond in the Delta9 position of fatty acid substrates. Palmitate and stearate are the preferred substrates, which are converted to palmitoleate and oleate, respectively. These monounsaturated fatty acids are the major constituents of cellular membrane phospholipids and triacylglycerol stores found in adipose tissue. Two mouse and rat SCD genes (SCD1 and SCD2) have been cloned and characterized. During the differentiation of 3T3-L1 preadipocytes into adipocytes, SCD1 and SCD2 mRNAs are induced concomitant with increased de novo synthesis of palmitoleate and oleate. The physiological significance of expressing the two isoforms in the adipocytes is currently unknown. In this review we discuss the role of the SCD isoforms in metabolism and the recent findings on the differential regulation of mouse SCD genes by the antidiabetic thiazolidinediones (TZDs), during preadipocyte differentiation.

Adipocytes↗
PubMed2000

Nitric oxide improves membrane fluidity of erythrocytes in essential hypertension: An electron paramagnetic resonance investigation.

It has been shown that rheological abnormality might be an etiological factor in hypertension. Recent studies have revealed that human erythrocytes possess a nitric oxide (NO) synthase and that this activation might be involved in the regulation of rheological properties of erythrocytes. The present study was undertaken to investigate the role of NO in the regulation of membrane functions of erythrocytes in patients with essential hypertension by means of an electron paramagnetic resonance (EPR) and spin-labeling method. The NO donor S-nitroso-N-acetylpenicillamine (SNAP) decreased the order parameter (S) for 5-nitroxide stearate (5-NS) and the peak height ratio (h(0)/h(-1)) for 16-NS obtained from EPR spectra of erythrocyte membranes in a dose-dependent manner. The finding indicated that the NO donor increased the membrane fluidity of erythrocytes. In addition, the effect of SNAP was significantly potentiated by 8-bromo-cyclic guanosine monophosphate. By contrast, the change of the fluidity induced by SNAP was reversed in the presence of L-N(G)-nitroarginine methyl ester and asymmetric dimethyl L-arginine. In patients with essential hypertension, the membrane fluidity of erythrocytes was significantly lower than in the normotensive subjects. The effect of SNAP was more pronounced in essential hypertension than in normotensive subjects. These results showed that NO increased the membrane fluidity and decreased the rigidity of cell membranes. Furthermore, the greater effect of NO on the fluidity in essential hypertension suggests that NO might actively participate in the regulation of rheological behavior of erythrocytes and have a crucial role in the improvement of microcirculation in hypertension.

Arginine↗
PubMed2001

Fatty acid modulation and sequence identity of fetal guinea pig alveolar type II cell amiloride-sensitive Na+ channel.

Removal of fetal lung fluid at birth is crucial to survival. In vivo, a reversal in the direction of vectorial, amiloride-sensitive Na+) transport can be stimulated by ETYA, a nonmetabolizable analogue of the naturally occurring unsaturated fatty acid, arachidonate. Using the patch-clamp technique, fetal guinea pig alveolar type II pneumocyte single Na+ channel activity was robustly activated by 10 microM arachidonate, ETYA, oleate and stearate; this was unaffected by cyclooxygenase and 5'lipoxygenase inhibitors. The Na+ channel expressed in fetal guinea pig alveolar epithelial type II pneumocytes has biophysical properties compatible with species-specific coexpression of a novel variant of alphaENaC with betaENaC. gammaENaC is either not expressed in this tissue or shares very little homology with the rat and human gamma subunit. Thus, dramatic stimulation of this channel by arachidonate explains the in vivo observation of gestation-dependent reversal of fetal transepithelial driving force and may, therefore, be of physiological significance during the transition to breathing air at birth.

Amiloride↗
PubMed2001

Characterisation of myogenic cell membrane: II. Dynamic changes in membrane lipids during the differentiation of mouse C2 myoblast cells.

Proliferating mouse C2 myoblast cells resist haemagglutinating virus of Japan, Sendai virus (HVJ) mediated cell fusion. However, differentiating C2 cells can be induced to fuse by HVJ, suggesting that the rigid membrane of C2 cells changes during the differentiation. To investigate this phenomenon, changes in membrane lipids which affect fluidity were examined. Membrane cholesterol gradually decreased with the differentiation of C2 cells. However, spontaneous fusion to form myotubes and artificial fusion induced by HVJ were both inhibited when the level of cholesterol was prevented from falling in the cell membrane. The membranes of differentiating C2 cells contained more unsaturated fatty acids than those of proliferating cells. Thus, when differentiating C2 cells were treated with stearate (a saturated fatty acid), they failed to form myotubes and were insensitive to HVJ-mediated fusion. Whereas, if proliferating C2 cells were given linolenate (an unsaturated fatty acid), they became capable of HVJ-induced fusion. These results indicate that differentiating C2 cells change their fusion sensitivity by decreasing cholesterol, probably at the same time as they increase the unsaturated fatty acid content of the cell membrane.

Animals↗
PubMed1993

Significance of subclinical entrapment of nerves in lead neuropathy.

We examined a left-handed 25-year-old man engaged for 2 years at a vinyl chloride resin factory where he had been exposed to lead stearate, a stabilizer of resin. Neurological examination revealed atrophy of small hand muscles, especially in the left dorsal interossei. Sensation of all modalities was intact. A nerve conduction study showed conduction block at the elbow, indicating possible cubital tunnel syndrome. Following CaEDTA therapy, continued recovery of conduction velocities, amplitude of compound muscle action potential, and diminution of conduction block at elbow were observed within a few months. In lead intoxication, nerves may incur mechanical damage. Subclinical entrapment may thus be an important factor leading to vulnerability of nerves in lead neuropathy.

Action Potentials↗
PubMed1998

Changes in T cell subpopulations in lead workers.

To investigate the effects of lead on the human immune system, we analyzed T cell subpopulations and B (CD19+) cells in peripheral blood in 71 male lead workers. They were engaged in manufacturing lead stearate in a chemical factory, aged 20 to 74 (mean 48) years. Their blood lead concentrations (PbB) were between 7 and 50 (mean 19) micrograms/dl. The control group consisted of 28 "healthy" male volunteers without a history of occupational exposure to lead or other hazardous substances, aged 33 to 67 (mean 55) years. In comparison with the controls, a significant reduction in the number of CD3+CD45RO+ (memory T) cells and a significant expansion in the percentage of CD8+ cells in the lead workers were found. There was a significant positive correlation between the percentage of CD3+CD45RA+ (naive T) cells and PbB in the lead workers. It is suggested that CD45RO+ memory T cells may be most susceptible to the effects of lead on T cell subpopulations.

Adult↗
PubMed1994

Fatty acid modulation of epidermal growth factor-induced mouse mammary epithelial cell proliferation in vitro.

Mammary epithelial cells were isolated from midpregnant BALB/c mice, grown in primary culture within collagen gels, and maintained with serum-free medium containing 10 ng/ml epidermal growth factor (EGF) as the mitogen. Supplementation of culture medium with the saturated fatty acid, Na-stearate (18:0), significantly attenuated, whereas treatment with the unsaturated fatty acid, Na-arachidonate (20:4), significantly enhanced mammary epithelial cell proliferation, as compared to untreated controls. Treatment with various doses of either 18:0 or 20:4 was also found to result in a direct dose-dependent enrichment of mammary epithelial cell membrane fatty acid composition and a concurrent decrease in the relative levels of other membrane fatty acids, as determined by gas chromatography. Administration of the prostaglandin synthesis inhibitor, indomethacin, significantly inhibited EGF-induced cell growth in all treatment groups, but did not alter the relative inhibitory (18:0) or stimulatory (20:4) effects of fatty acid treatment. EGF-induced PKC translocation into the membrane fraction of mammary epithelial cells was enhanced in 20:4 and attenuated in 18:0 treatment groups, as compared to controls. Western blot analysis of phospholipid-dependent protein kinase C isoenzymes showed that PKC alpha was the predominant isoenzyme present in mouse mammary epithelial cells grown in primary culture, and the molecular weight of this PKC isoenzyme was determined to be 85 kDa. These results suggest that supplementation of culture media with specific fatty acids is associated with significant alterations in mammary epithelial cell membrane fatty acid composition, PKC activation, and mitogenic responsiveness. Since EGF can induce both PKC activation and cell proliferation, and because PKC activation requires membrane-derived phospholipids and diacylglycerol, these data suggest that specific fatty acid modulation of mammary epithelial cell mitogenesis is mediated through alterations in PKC alpha activation.

Animals↗
PubMed1997

Retinyl palmitate in macaque retina-retinal pigment epithelium-choroid: distribution and correlation with age and vitamin E.

Retinyl palmitate (RP) and retinyl stearate (RS) are of central importance in the visual cycle because they are the major storage molecules for retinol. In some tissues (e.g. liver) the amount of vitamin A (mostly in the form of retinyl ester) is positively correlated with both the amount of alpha-tocopherol (alpha-T) and age. Furthermore, alpha-T is a noncompetitive inhibitor of the hydrolysis of RP. We measured RP, RS, alpha-T and beta+gamma-tocopherol (beta+gamma-T) as functions of distance from the foveal center (eccentricity) in the retina-RPE-choroid (NRC) of rhesus monkeys using high-pressure liquid chromatography. It was found that the central and peripheral NRC differed with respect to these parameters. The concentration (pmoles sq mm-1) of RP was higher in the central NRC than in the peripheral NRC and was at a maximum in the region of the fovea. Furthermore, although in the peripheral NRC. RP was well correlated with age and alpha-T (similar to other tissues), in the central NRC, RP per sq mm was more clearly related to photoreceptor density. These differences imply that the central NRC controls the concentration of RP within it, while the concentration of RP in the peripheral NRC is determined by its environment (e.g. nutrients available from blood) and the age of the individual.

Age Factors↗
PubMed2001

Precipitation and Solubility of Calcium Soaps in Basic Aqueous Media.

Measurements of the surface tension of aqueous media containing calcium salts of different fatty acids, whose structure only varied by the number of C=C unsaturations along their aliphatic chains, showed that their solubility increased as a function of this parameter going from near zero for calcium stearate to 4x10(-4) mol l(-1) for the linolenate homologue. The solubility product of the calcium soap corresponding to each tested fatty acid was estimated by using the anionic fatty acids adsorption isotherms in order to obtain the amount of dissolved ionic fatty acid at increasing concentration of calcium ions. These findings are discussed in terms of their serious repercussions on the operations related to flotation deinking in waste paper recycling. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

Structural Characterizations of Organo-Capped Barium Titanate Nanoparticles Prepared by the Wet Chemical Route.

In the present study, nanoscale barium titanate particles were chemically prepared with organic shells on their surfaces. Their chemical and physical structures were characterized by FT-IR, FT-Raman, XRD, and XPS. Based on the results of characterizations, it can be concluded that the presence of organic ligands greatly influences the nucleation and surface chemistry of BaTiO(3) nanoparticles. Surface Ti(4+) tends to bond to stearate ions instead of the previous Ba(2+) in the starting materials. The usual preferable orientation growths of lattice, i.e., (101), (111), and (200), were significantly restrained due to surface coordination. Although poor crystallinity was observed, a tetragonal phase of BaTiO(3) nuclei could be inferred from both XRD and Raman patterns. Finally, the formation mechanism and structural model of organo-capped nanoparticles are discussed. Copyright 2001 Academic Press.

Journal Article↗
PubMed1995

Fetal, neonatal, and long-term alterations in hepatic retinoid levels following maternal polychlorinated biphenyl exposure in rats.

This study was undertaken to investigate the effects of perinatal polychlorinated biphenyl (PCB; Aroclor 1254) exposure on hepatic and plasma retinoid levels in fetal rats, their dams, and neonatal and adult offspring. Pregnant Wistar rats were treated with 0, 5, or 25 mg Aroclor 1254/kg body wt from Days 10 to 16 of gestation. Hepatic retinoid (retinol, retinyl palmitate, and retinyl stearate) levels were determined in fetuses and dams from Day 20 of gestation, in male and female neonates 21 days postpartum, and in young adult offspring 90 days after birth. Retinol levels were determined in fetal and maternal plasma (Gestation Day 20) and plasma from the offspring 21 and 90 days after birth. Maternal and fetal plasma retinol levels were decreased by 35 and 38% on Day 20 of gestation following exposure to the highest dose of Aroclor 1254. Male, but not female, neonatal plasma retinol levels were significantly decreased (23%) in the high-dose group. No effects of PCB treatment were seen on plasma retinol levels in the offspring 90 days after birth. Only slight reductions in fetal and maternal hepatic retinol and retinyl palmitate concentrations were observed after prenatal PCB exposure. Male neonatal hepatic retinyl palmitate levels were reduced by 25 and 50% in the 5 and 25-mg Aroclor 1254/kg dose groups, respectively, while female neonatal hepatic retinyl palmitate levels were significantly reduced only in the high-dose group. Ninety days after birth, male hepatic retinyl palmitate levels were only slightly reduced in the highest dose group; however, hepatic retinol concentrations were significantly reduced by 50% in both PCB treatment groups. Female adult offspring exhibited significant reductions in hepatic retinyl palmitate levels (25%) in both PCB treatment groups, while hepatic retinol levels exhibited an unusual increase of more than 100% of controls in the low-dose group, while levels in the high-dose group were similar to controls. This study demonstrates that even a relatively low maternal dose of Aroclor 1254 results in long-term alterations in retinoid status of the offspring in the rat.

Animals↗