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At least 721 records · Page 40Linked to original sources
PubMed2001

Influence of rice bran oil on serum lipid peroxides and lipids in human subjects.

To study the effect of rice bran oil (RBO) on serum lipids and lipid peroxides in human volunteers. Nine healthy volunteers, aged between 42 to 57 years were given 75 ml of RBO thrice daily as the cooking medium with break fast, lunch and dinner for a period of 50 days. At the beginning and at the end of 50 days, 5 ml of blood were drawn from an ante cubital vein. Serum lipids and lipid peroxides levels were estimated from the blood sample. There was a significant decrease in the levels of lipid peroxides, triglycerides, LDL, VLDL, and total cholesterol in human volunteers who switched over to RBO. RBO has evidently antioxidant and antilipidemic activities in human subjects.

Adult↗
PubMed1992

Study of lipid changes in freeze-dried fish during storage. I. The interaction of relative humidity and tissue lipids.

Several studies on lipid stability of freeze-dried fish pointed out the relationship between relative humidity (RH) and autoxidation of highly unsaturated fatty acids. The present study shows the changes of tissue lipids in two different fish, freeze-dried and stored under various RH conditions. Fillets of Scomber scomber L and Sardina pilchardus sardina were freeze-dried and stored for 1, 3, 6 and 9 months. periodically, the sample of both fish were analyzed to evaluate the autoxidation of lipids. The results show that the autoxidation of lipids is quicker during 1st-3rd month of storage, while in a high humidity environment the tissue lipids change slower. According to these results both time of storage and relative humidity must be controlled to maintain the nutritive value of freeze-dried fish.

Animals↗
PubMed1992

Role of lipid modification on a starch-debranching enzyme, Klebsiella pullulanase: comparison of properties of lipid-modified and unmodified pullulanases.

Klebsiella pullulanase is a lipoprotein synthesized as a precursor with a signal peptide, which is processed by lipoprotein signal peptidase. To clarify the role of lipid modification of pullulanase, we purified lipid-modified wild-type and the unmodified (mutant) pullulanases and compared their properties. The Km and Vmax values of both pullulanases for pullulan were the same. The optimal pH and temperature, the stabilities over pH and temperature ranges, the specificity of substrates, and the patterns of inhibition of the lipid-modified and unmodified pullulanases were also the same. However, we found that the wild-type pullulanase formed trimers whereas the unmodified enzyme did not, and that the migrations of the two enzymes on sodium dodecyl sulphate/electrophoresis were different when the samples were applied on the gel without heating. The results presented in this paper and in previous work show that the correct processing and translocation of pullulanase in K. aerogenes require modification of lipid. However, the enzymatic properties and physical stabilities of pullulanase were not affected by the lipid modification.

Electrophoresis, Polyacrylamide Gel↗
PubMed1992

Red blood cell susceptibility to lipid peroxidation, membrane lipid composition, and antioxidant enzymes in continuous ambulatory peritoneal dialysis patients.

OBJECTIVE: To investigate the overall susceptibility of red blood cells (RBC) to lipid peroxidation from patients on continuous ambulatory peritoneal dialysis (CAPD). METHODS: The following parameters were measured: RBC malondialdehyde (MDA) production after oxidative stress with H2O2, RBC antioxidant enzymes glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), and RBC membrane lipid composition. The levels of plasma vitamin E and serum selenium were also assayed. PATIENTS: Eleven patients on continuous ambulatory peritoneal dialysis. Twenty-one healthy blood donors of similar age were used as normal controls. RESULTS: The MDA formation after H2O2 stimulation was normal in CAPD patients (0.79 +/- 0.1 mumol/gHb versus 0.78 +/- 0.1 in the control group). RBC from CAPD patients also showed a normal SOD activity, a more than adequate vitamin E status, and a peculiar pattern of membrane lipids, with reduced polyunsaturated fatty acids (p less than 0.001) and increased monounsaturated fatty acids (p less than 0.001). Both RBC GSH-Px activity, a selenium-dependent enzyme, and serum selenium levels were significantly lower in CAPD patients, and a significant positive correlation (r = 0.68; p less than 0.02) between the two parameters was found. CONCLUSIONS: This study found a normal sensitivity to oxidant stress in RBC from a group of CAPD patients, despite an impaired GSH-Px activity. The peculiar lipid pattern of RBC membrane, characterized by reduced PUFA and increased MUFA content, may contribute, in addition to adequate SOD activity and vitamin E status, to normal RBC lipid peroxidation.

Aged↗
PubMedDate not supplied

Cholesterol and lipid levels in the hair: indicators of the lipid metabolism balance.

A new method of long term, retrospective evaluation of the lipid metabolism balance, by cholesterol and lipid assays in the human hair, is described. The correlation index between the blood and the hair cholesterol and lipid concentrations was + 0.980 and + 0.9925, respectively. The effects of hypolipemic diet and drug therapy on the cholesterol and lipid values were studied comparatively in the blood and in successive hair segments. The results demonstrate that the new method permits an evaluation of the therapy effectiveness and of the lipid metabolism variations during several weeks or months.

Cholesterol↗
PubMed1982

Reconstitution of bacteriorhodopsin vesicles with Halobacterium halobium lipids. Effects of variations in lipid composition.

Reconstitution of bacteriorhodopsin into vesicles has been studied using individual and defined mixtures of fractionated Halobacterium halobium polar lipids. The lipids varied greatly in their ability to form vesicles that translocated protons and showed stimulation by valinomycin. Thus, phosphatidylglycerol phosphate gave mainly lipid-protein aggregates, while glycolipid sulfate gave mainly functional vesicles. Addition of glycolipid sulfate to phosphatidylglycerol phosphate promoted vesicle formation. Reconstitutions performed with different combinations of the purified lipids showed: 1) that vesicles with maximal proton pumping are obtained with a mixture of phosphatidylglycerol phosphate and glycolipid sulfate at a ratio close to that found in the purple membrane; 2) increasing the concentration of glycolipid sulfate in vesicles increases the stimulation of proton translocation by valinomycin; 3) phosphatidylglycerol sulfate cannot replace glycolipid sulfate or phosphatidylglycerol phosphate, and 4) vesicles containing sulfated polar lipids only are inferior to those in which liquid combinations containing phosphatidylglycerol phosphate are used.

Bacteriorhodopsins↗
PubMedDate not supplied

[Phase transitions, lipid-lipid interactions and their role in some biostructures].

The phase states and phase transitions of some lipids, lipid mixtures of blood and tissues of some animals and human were examined by the method of scanning calorimetry (DSC-2, "Perkin--Elmer"). It was determined that in monohydrated and in hydrated systems, cholesterol produces a liquefying effect on the total phospholipids of the brain and blood. In complex multicomponent lipid systems changes of the phase states and of temperatures of the phase transitions of some lipids were discovered. The role of these phase transitions and miscibility of lipids for functioning of the cellular membranes and of the key-enzymes in the process of changes of lipoproteins of the blood (LCAT) is being discussed, as well as the connection of the phase transitions of cholesterol esters of the blood with atherosclerosis.

Animals↗
PubMedDate not supplied

[Participation of lipid radicals and active oxygen forms in the peroxidation of microsomal membrane lipids induced by organic hydroperoxides].

The peroxidative radicals arizing after destruction of exogenous hydroperoxides catalyzed by cytochrome P-450, carried out important functions in induction of lipid peroxidation, dependent on organic hydroperoxides. Only a slight inhibitory effect of singlet oxygen and anion radicals of superoxide on organic hydroperoxide dependent process of lipid peroxidation suggested that these active forms of oxygen participated apparently in lipid peroxidation. The traps of hydroxyl radicals (.OH) did not affect the lipid peroxidation induced by organic hydroperoxides. A mechanism is discussed for generation and function of peroxidative radicals as well as of active oxygen forms in lipid peroxidation, induced by organic hydroperoxides in liver microsomal membranes.

Animals↗
PubMed1994

Smokeless tobacco induced increases in hepatic lipid peroxidation, DNA damage and excretion of urinary lipid metabolites.

The possible role of reactive oxygen species in the toxicity of smokeless tobacco (ST) was explored. The effects of an aqueous smokeless tobacco extract (STE) at doses of 125, 250 and 500 mg STE/kg in rats on the induction of hepatic mitochondrial and microsomal lipid peroxidation and the incidence of hepatic nuclear DNA damage 24 hours post treatment were examined. Dose-dependent increases of 1.8, 2.3 and 4.4-fold in mitochondrial and 1.5, 2.1 and 3.6-fold in microsomal lipid peroxidation occurred at 125, 250 and 500 mg STE/kg, respectively, relative to control values. At these same three doses of STE, 1.3, 1.4 and 2.7-fold increases in hepatic DNA single-strand breaks occurred relative to control values. STE administration also resulted in significant increases in excretion of urinary metabolites. Urinary excretion of the four lipid metabolites malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT) and acetone (ACON) was monitored by HPLC for 72 hours after treatment of rats with 125 and 250 mg STE/kg. Increases occurred in the excretion of the four lipid metabolites at every dose and time point with maximum increases in the excretion of all lipid metabolites being observed between 12 and 24 hours post treatment. The results suggest the involvement of an oxidative stress in the toxicity of STE.

Acetone↗
PubMed1998

Study on the lipid organization of stratum corneum lipid models by (cryo-) electron diffraction.

The barrier function of the skin resides in the stratum corneum (SC). This outermost layer consists of protein-rich corneocytes and lipid-rich intercellular domains. These domains form the rate-limiting step for transepidermal water loss and the penetration of substances from the environment. To study the nature of the barrier function, stratum corneum lipid models have been examined with wide-angle X-ray diffraction. A disadvantage of this technique is that it requires bulk quantities of lipid and thus information on variations in the lateral packing cannot be obtained in the microm-range. To the best of our knowledge, this is the first study in which electron diffraction is applied on SC lipid model systems. Using this technique, local structural information was obtained about mixtures prepared from isolated pig ceramides, cholesterol, and long-chain free fatty acids. It appeared that addition of free fatty acids caused a transition from a hexagonal to an orthorhombic packing and that electron diffraction can be applied to distinguish between these two lattices. The results are in good agreement with wide-angle X-ray diffraction data and suggest that application of electron diffraction in skin studies can provide new information on the lipid organization in well-defined areas of the stratum corneum.

Animals↗
PubMedDate not supplied

Lipid peroxidation intensity and lipid status parameters in the estimation of the severity of ischemic heart disease.

Atherosclerotic changes on the coronary arteries are the basis of the ischemic heart disease. It is assumed that the initial changes in this process occur as a consequence of the lipid peroxidation in the vessel wall. We estimated this process through the level of malondialdehyde (MDA) in the serum of 86 patients in whom selective coronary angiography was done for the suspected ischemic heart disease. According to the number of the stenotic coronary arteries (stenosis greater than 50%), we divided the patients into four groups: the control group with normal coronary angiography finding, simple, double or triple vessel coronary disease. In all the patients we also estimated the other parameters of the lipid status (cholesterol, triglycerides, LDL, HDL, Apo-AI, Apo B) and atherogenic indices Apo-AI/Apo B, LDL/HDL and HDL/total cholesterol. No significant changes were observed in the lipid parameters between the control and experimental group. However, mean MDA level in the whole experimental group was 3.89 mumol/L, 3.93 mumol/L in triple vessel coronary disease, 3.83 mumol/L in double vessel and 3.92 mumol/L in single vessel disease group. The difference between all the experimental and the control group was highly significant (p < 0.001). We concluded that the level of MDA--lipid peroxidation index had the better correlation with the disease status than the other parameters of lipid status and the sensitive atherogenic indices.

Adult↗
PubMed2004

Polymyxin B-lipid interactions in Langmuir-Blodgett monolayers of Escherichia coli lipids: a thermodynamic and atomic force microscopy study.

The dramatically increased frequency of antibiotic resistance has led to intensive efforts towards developing new families of antibiotics. Membrane-active antibiotic peptides such as polymyxin B (PxB) hold promise as the next generation of antibiotics, since they rarely spur the evolution of resistance. At low concentrations in the membrane, PxB forms vesicle-vesicle contacts and induces lipid exchange without leakage or fusion, a phenomenon that can explain its specificity towards gram-negative bacteria by contact formation between the two phospholipids interfaces in the periplasmatic space. In this work, the interaction of PxB and the nonantibiotic derivative polymyxin B nonapeptide (PxB-NP) with monolayers of Escherichia coli membrane lipids (ECL) has been studied by thermodynamic and structural methods. PxB inserts itself into ECL monolayers as a conformation that forms intermembrane contacts with vesicles injected underneath, and induces lipid exchange when the monolayer surface pressure is set at 32 mN/m (membrane equivalence pressure) or net transfer vesicle-to-monolayer at lower surface pressures. Thermodynamic analysis of the compression isotherms of mixed monolayers indicates that PxB inserts into the monolayer with an expansion of the mean molecular area, implying that peptide and lipids form nonideal mixtures. At low concentrations, corresponding to the membrane-membrane contact form of PxB, the mixed monolayers present positive excess energy values (deltaGm(Ex)), and atomic force microscopy (AFM) imaging reveals structures of approximately 120-nm diameter that protrude from the lipid surface approximately 0.7 nm. At concentrations of PxB above 4 mol %, thermodynamic analysis gives a very high deltaGm(Ex), corresponding to nonfavorable interactions, and AFM images show round structures of 20-30 nm diameter. PxB-NP behaves in a totally different way, in agreement with its inability to form vesicle-vesicle contacts and its lack of antibiotic effect. These results are discussed in the light of the mechanism of action of PxB on the membrane of gram-negative bacteria.

Anti-Bacterial Agents↗
PubMed1995

Lipid apheresis: an in vivo application of plasma delipidation with organic solvents resulting in acute transient reduction of circulating plasma lipids in animals.

Despite primary and secondary prevention of coronary disease with lowering plasma cholesterol by diet and drug therapy, coronary heart disease remains the major cause of death in Western countries. Low density lipoprotein apheresis had the potential to make a significant impact as it acutely leads to a marked reduction in plasma cholesterol. However, recent preliminary results suggest that low density lipoprotein apheresis may not be more effective in preventing progression of coronary disease than current drug therapy. We have devised a new technique, termed lipid apheresis, which removes cholesterol and triglycerides from plasma but retains the apolipoproteins. This procedure shows great promise in stimulating regression beyond current therapy. Lipid apheresis, a new extracorporeal procedure based on plasma delipidation with the organic solvent mixture butanol-diisopropyl ether, was applied to hypercholesterolemic and normocholesterolemic roosters. Approximately 25% of the calculated blood volume was removed from the animals. The plasma was separated from the blood cells. The plasma was delipidated for 20 min with the organic solvent mixture. The delipidated plasma containing all proteins, including the apolipoproteins and other ionic constituents, was remixed with the blood cells and infused back into the identical donor animals. Analyses of serial blood samples collected from lipid apheresed and sham treated animals up to 16 h after infusion revealed that lipid apheresis caused acute, marked reductions in plasma lipids. The pattern and extent of the plasma levels of cholesterol were different in the hypercholesterolemic animals when compared with normocholesterolemic animals, indicating that a readily extraplasma cholesterol pool in the hypercholesterolemic animals was rapidly mobilized into the plasma pool.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Neutral lipid accumulation in macrophages during lipid-induced macrophage growth.

We previously reported that lipids such as cholesterol esters, triglycerides, and some phospholipids that are components of cell membranes or serum lipoproteins induced the growth of mouse peritoneal macrophages in vitro. Here, we report that macrophage growth was directly induced by lipids without any soluble factors and that the continuous presence of lipids was required for their growth during culture. When macrophages were cultured with several phospholipids that stimulated macrophage growth, their triglyceride content was dramatically increased during culture, whereas their contents of phospholipids, cholesterol, and esterified cholesterols were scarcely changed. On the other hand, phosphatidylcholine and sphingomyelin, which did not stimulate macrophage growth, caused less accumulation of triglycerides in the cells. Macrophages in which triglycerides accumulated resembled foam cells, since they contained many particles that stained with oil red O. Macrophages that cultured with cholesteryl linoleate also contained many oil red O-stainable particles. These data suggest that accumulation of lipid droplets is correlated with macrophage growth induced by lipids and that foam cells in pathological states such as those in atherosclerotic or xanthoma lesions might proliferate in situ.

Animals↗
PubMed1992

Selective suppression of lipid resonances by lipid-soluble nitroxides in NMR spectroscopy.

The ability of lipid-soluble nitroxides to suppress selectively the peaks of lipid resonances in 31P, 1H, and 13C NMR spectra was investigated in serum as part of studies aimed at using these contrast agents for magnetic resonance imaging and magnetic resonance spectroscopy in vivo. Nitroxides are especially interesting potential contrast agents because they can reversibly be converted in cells to diamagnetic hydroxylamines, with conversion rates that are dependent on the redox potential and the intracellular concentration of oxygen; the characterization of nitroxide-dependent changes in NMR spectra may therefore be a useful means to measure oxygen-dependent redox metabolism in vivo. The fatty acid analogs, doxyl stearates, suppressed the methyl resonance of choline and the methyl and methylene peaks of lipids in the 1H NMR spectra of serum samples. As a consequence, lactate peaks, which were not readily detected became clearly resolved and could be evaluated quantitatively. The 31P resonance of phosphatidylcholine in the 31P NMR spectrum was suppressed by 5-doxyl stearate and 4-(N,N-dimethyl-N-hexadecyl)ammonium-2,2,6,6-tetramethylpiperidine-1-oxy l,iodid e (Cat16). In the 13C NMR spectrum, the resonances of the methyl groups of choline and the lipids also were broadened significantly by addition of 5-doxyl stearate. Differential suppression of lipid resonances can be employed to facilitate quantitation of lactate.

Contrast Media↗
PubMed1995

Lipid hydroperoxide-induced endogenous DNA adducts in hamsters: possible mechanism of lipid hydroperoxide-mediated carcinogenesis.

DNA of livers or kidneys of rodents contain endogenously modified nucleotides of as yet unknown structure or function. As part of our examination of the origin of endogenous DNA modifications, we examined polar adducts of hamster liver and kidney DNA by 32P-postlabeling analysis (central and upper cuts) and compared them to adducts generated by incubation of DNA with [9Z,11E,(13S)]-13-hydroperoxyoctadecadienoic acid or with malondialdehyde. The central and upper cuts of DNA adduct maps of intact female retired breeder hamsters contained one and three adducts called C1, U1, U2, and U3, respectively, which cochromatographed with similar adducts in DNA incubated with the hydroperoxide or with malondialdehyde. Concentrations of adducts C1, U1, and U2 in organs of 1-month-old hamsters were lower than those in the 5-month-old female retired breeder hamsters. Adduct concentrations increased in tandem with lipid peroxide concentrations in livers and kidneys of hamsters treated with carbon tetrachloride compared to controls. A linear dependence of the concentrations of adducts on those of lipid peroxides was demonstrated independent of the treatment conditions or the organ examined. The polar endogenous adducts U1, U2, and U3 were identified by cochromatography in five different chromatographic systems with adducts induced by linoleic hydroperoxide or malondialdehyde. Adducts U1, U2, or U3 were also formed by incubating malondialdehyde with dAMP or with dGMP, respectively. The dependence of adduct concentrations in vivo on lipid peroxide levels are taken as evidence that decomposition products of lipid peroxides such as malondialdehyde induced endogenous DNA adducts in intact animals. Moreover, these adducts may mediate carcinogenic processes induced by chemicals which raise lipid peroxide levels.

Age Factors↗
PubMed2000

Interaction of the peptide antibiotic alamethicin with bilayer- and non-bilayer-forming lipids: influence of increasing alamethicin concentration on the lipids supramolecular structures.

Incorporation of the helical antimicrobial peptide alamethicin from aqueous phase into hydrated phases of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC) was investigated within a range of peptide concentrations and temperatures by time-resolved synchrotron X-ray diffraction. It was found that alamethicin influences the organizations of the non-bilayer-forming (DOPE) and the bilayer-forming (DOPC) lipids in different ways. In DOPC, only the bilayer thickness was affected, while in DOPE new phases were induced. At low peptide concentrations (<1.10(-4) M), an inverted hexagonal (H(II)) phase was observed as with DOPE dispersions in pure buffer solution. A coexistence of two cubic structures was found at the critical peptide concentration for induction of new lipid/peptide phases. The first one Q224 (space group Pn3m) was identified within the entire temperature region studied (from 1 to 45 degrees C) and was found in coexistence with H(II)-phase domains. The second lipid/peptide cubic structure was present only at temperatures below 16 degrees C and its X-ray reflections were better fitted by a Q212 (P4(3)32) space group, rather than by the expected Q229 (Im3m) space group. At alamethicin concentrations of 1 mM and higher, a nonlamellar phase transition from a Q224 cubic phase into an H(II) phase was observed. Within the investigated range of peptide concentrations, lamellar structures of two different bilayer periods were established with the bilayer-forming lipid DOPC. They correspond to lipid domains of associated and nonassociated helical peptide. The obtained X-ray results suggest that the amphiphilic alamethicin molecules adsorb from the aqueous phase at the lipid head group/water interface of the DOPE and DOPC membranes. At sufficiently high (>1.10(-4) M) solution concentrations, the peptide is probably accommodated in the head group region of the lipids thus inducing structural features of mixed lipid/peptide phases.

Alamethicin↗
PubMed1997

TLC blotting: application to microscale analysis of lipids and as a new approach to lipid-protein interaction.

A simple method for the transfer of phospholipids and glycosphingolipids from a high-performance thin-layer chromatography (HPTLC) plate to a polyvinylidene difluoride (PVDF) membrane, called thin-layer chromatography (TLC) blotting, and its application in lipid research are described. Most of the lipids developed on the HPTLC plate are blotted quantitatively. Detection of the lipids on the membrane is done by chemical and immunological staining. This method makes it possible to purify individual lipid components separated on an HPTLC plate and to determine the structures of lipids in limited biological samples when combined with direct mass spectrometric analysis (TLC blotting/MS). A binding assay and the identification of ligands for microorganisms can be made using TLC blotting/MS. In addition, simple methods for the detection of enzymes on a substrate-immobilized PVDF membrane are described.

Animals↗