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Results for “Lipid Mobilization”

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At least 1,099 records · Page 61Linked to original sources
PubMed2003

Lipid factor (bVLF) from bovine vitreous body evokes in EGFR-T17 cells a Ca2+-dependent K+ current associated with inositol 1,4,5-trisphosphate-independent Ca2+ mobilization.

Bovine vitreous lipid factor (bVLF) is a complex phospholipid isolated from bovine vitreous body with strong Ca(2+)-mobilizing activity. In this study, the effects of bVLF on membrane potential were investigated in EGFR-T17 fibroblasts with the whole-cell patch clamp technique on monolayer cells, as well as with the fluorescent dye bis-oxonol as membrane potential-sensitive probe on monolayer and suspension cells. bVLF induced a transient hyperpolarization characterized by an initial peak and subsequent return to resting membrane potential levels within 1-2 min. The increase of [Ca(2+)](i) was concomitant with an outward current responsible for the hyperpolarizing response. Results with: (a) high [K(+)](o) media; (b) the monovalent cation ionophore gramicidin; and (c) substitution of K(+) with Cs(+) in the intracellular solution were consistent with the involvement of K(+) channels. The bVLF-induced hyperpolarization was blocked by the K(+) channel blockers, quinine and tetraethylamonium chloride, and partially affected by 4-aminopyridine. The calcium ionophore ionomycin caused a similar hyperpolarization as bVLF. When intracellular calcium was buffered by adding BAPTA to the pipette solution, bVLF-activated outward current was prevented. Moreover, the hyperpolarization response was strongly reduced at low doses (3 nM) of specific Ca(2+)-activated K(+) channel blockers, charybdotoxin and iberiotoxin. Based on these observations we conclude that bVLF hyperpolarizes the cells via the activation of a Ca(2+)-dependent K(+) current. In addition, it was observed that bVLF did not have a significant effect on intercellular communication measured by a single patch-electrode technique. Thus, membrane potential changes appeared to belong to the earliest cellular responses triggered by bVLF, and are closely associated with phosphatidic acid-dependent [Ca(2+)](i) mobilization.

3T3 Cells↗
PubMed2001

Cholesterol mobilization by free and lipid-bound apoAI(Milano) and apoAI(Milano)-apoAII heterodimers.

Despite very low plasma levels of HDL, carriers of the apolipoprotein AI Arg173 --> Cys mutation apoAI(Milano) (AIM) have no apparent increase in risk for atherosclerotic vascular disease. HDL apolipoprotein species in AIM carriers include apoAI-AII heterodimers, previously found to confer the enhanced ability of tyrosyl radical-oxidized HDL to mobilize cholesterol for removal from cultured cells. To determine whether enhanced mobilization of cholesterol by apoprotein species in AIM explains a cardioprotective action of this mutation, we examined the ability of lipid-free and lipid-bound AIM and AIM-AII heterodimers to deplete cholesterol from cultured cells. Free AIM and AIM-AII heterodimers showed a decreased capacity to act as acceptors of cholesterol from cholesterol-loaded human fibroblasts compared with native apoAI but similar capacities to deplete fibroblasts of the pool of cholesterol available for esterification by acyl-CoA:cholesterol acyltransferase (ACAT). Discoidal reconstituted HDL (rHDL) containing apoAI depleted both of these cholesterol pools more readily than AIM-containing rHDL when compared at equivalent rHDL protein levels, but similar abilities of these rHDL to deplete cell cholesterol were seen when compared at equivalent phospholipid levels. Spherical rHDL generated using the whole lipid fraction of HDL and apoAI or AIM showed similar capacities to deplete total and ACAT-accessible cell cholesterol when compared at similar protein levels, but an increased capacity of AIM-containing particles was seen when compared at equivalent phospholipid levels. Unlike the apoAI-AII heterodimer in tyrosylated HDL, AIM-AII heterodimer-containing spherical rHDL showed no increased capacity to deplete either of these pools of cholesterol. These results suggest a similar or better capacity of native apoAI in lipid-free or lipid-bound form in discoidal rHDL to enhance the mobilization of cellular cholesterol when compared to AIM in its free or lipid-bound forms. Any increase in depletion of cellular cholesterol by lipid-bound AIM in spherical rHDL appears related to altered phospholipid-binding rather than intrinsic cholesterol-mobilizing characteristics of this protein compared to native apoAI. The lack of major differences in these studies in cholesterol mobilization by native apoAI and AIM, or by apoAIM-AII heterodimers, suggests that any protection against atherosclerosis conferred by this mutation is likely related to other beneficial vascular effects of AIM.

Apolipoprotein A-I↗
PubMed1996

1H-NMR visible neutral lipids in activated T lymphocytes: relationship to phosphatidylcholine cycling.

Two-dimensional 1H-NMR spectroscopy was used to compare changes in the concentration of isotropically-tumbling neutral lipid during the activation of splenic and thymic T lymphocytes. The concentration of mobile neutral lipid (MNL) was similar in splenic and thymic T cells after 72 h of activation with phorbol myristate acetate and ionomycin. However, after 120 h of activation, MNL concentrations in splenic T cells were more than 3-fold higher than in thymic T cells. An increase in choline (Cho), phosphocholine (PCho) and glycerophosphocholine (GPC) was also observed in both thymic and splenic T cells after 24 h of activation. However, after 72 h of stimulation, Cho and PCho levels had decreased and continued to decline at 96-120 h, while GPC continued to be maintained at elevated levels. The simultaneous increase in MNL and GPC and the decline in Cho and PCho leads us to propose that the synthesis of NMR-visible MNL in activated lymphocytes is linked to the phosphatidylcholine cycle.

Animals↗
PubMed1991

Effect of phenobarbitone pretreatment on isoniazid-induced lipid changes in plasma, liver and adipose tissue in the rabbit.

The subacute effect of a low dose of isoniazid (INH) (10 mg/kg/day for 11 days) in phenobarbitone sodium (PB)-pretreated rabbits (60 mg/kg/day for 4 days) on various lipid parameters in plasma, liver and adipose tissue was investigated. While treatment with PB or INH alone did not alter the lipid levels in plasma and tissues, INH treatment in PB-pretreated rabbits elevated the levels of plasma total lipid and cholesterol. In adipose tissue there was a decrease in total lipid, triglyceride and cholesterol and an elevation in free fatty acid. In contrast, all these parameters were found to be elevated in the liver. It is proposed that the enhanced release of primary amine functional groups from INH during microsomal induction by PB treatment caused increased deposition of lipids in the liver, which is presumably an outcome of enhanced breakdown and mobilization of lipids from the adipose tissue. It is suggested that the assessment of lipid profile would be a useful tool to monitor drug interactions involving INH with hepatotoxic potential.

Adipose Tissue↗
PubMed2000

Effects of normal alcohols and isoflurane on lipid headgroup dynamics in nicotinic acetylcholine receptor-rich lipid vesicles.

The trend of evidence suggests that general anesthetics act directly on proteins in the neural membrane. However, the fact that the functions of nicotinic acetylcholine receptor (sodium permeability, desensitization rate) are modulated by the composition of the membrane in which it is reconstituted has been thought to be a result of the variation of interactions between acetylcholine receptor and membrane. In this study, protein-lipid interaction at the level of the lipid headgroup was investigated using electron paramagnetic resonance (EPR) and headgroup spin label. Lipid headgroup mobility was evaluated with rotational correlation time from the EPR spectrum. Protein-lipid interaction at headgroup depth was demonstrated from the motionally restricted component of the spectrum. Rotational correlation time increased to 13 ns from 7 ns due to protein-lipid interaction. The effect of anesthetic (ethanol, 1-hexanol, and isoflurane) on protein-lipid interaction was investigated, and the correlation time was 13 ns. It is concluded that the anesthetics used in this study did not alter protein-lipid interaction at the level of the lipid headgroup, so far as observed by rotational correlation time, without excluding the possibility that anesthetics that perturb protein-lipid interactions modulate receptor functions via this mechanism.

Alcohols↗
PubMed2004

Dynamics of neutral lipid storage in yeast.

Since energy storage is a basic metabolic process, the synthesis of neutral lipids occurs in all kingdoms of life. The yeast, Saccharomyces cerevisiae, widely accepted as a model eukaryotic cell, contains two classes of neutral lipids, namely steryl esters and triacylglycerols. Triacylglycerols are synthesized through two pathways governed by the acyl-CoA diacylglycerol acyltransferase Dga1p and the phospholipid diacylglycerol acyltransferase Lro1p, respectively. Steryl esters are formed by the two steryl ester synthases Are1p and Are2p, two enzymes with overlapping function which also catalyze triacylglycerol formation, although to a minor extent. Storage of neutral lipids is tightly linked to the biogenesis of so called lipid particles. The role of this compartment in lipid homeostasis and its interplay with other organelles involved in neutral lipid dynamics, especially the endoplasmic reticulum and the plasma membrane, are subject of current investigations. In contrast to neutral lipid formation, mobilization of triacylglycerols and steryl esters in yeast are less characterized at the molecular level. Only recently, the triacylglycerol lipase Tgl3p was identified as the first yeast enzyme of this kind by function. Genes and gene products governing steryl ester mobilization still await identification. Besides biochemical properties of enzymes involved in yeast neutral lipid synthesis and degradation, regulatory aspects of these pathways and cell biological consequences of neutral lipid depletion will be discussed in this minireview.

Acyltransferases↗
PubMed1984

Lateral diffusion of lipids and glycophorin in solid phosphatidylcholine bilayers. The role of structural defects.

The lateral mobility of the lipid analog N-4-nitrobenzo-2-oxa-1,3 diazole phosphatidylethanolamine and of the integral protein glycophorin in giant dimyristoylphosphatidylcholine vesicles was studied by the photobleaching technique. Above the temperature of the chain-melting transition (Tm = 23 degrees C), the diffusion coefficient, Dp, of the protein [Dp = (4 +/- 2) X 10(-8) cm2/s at 30 degrees C] was within the experimental errors equal to the corresponding values DL of the lipid analog. In the P beta 1 phase the diffusion of lipid and glycophorin was studied as a function of the probe and the protein concentration. (a) At low lipid-probe content (cL less than 5 mmol/mol of total lipid), approximately 20% of the probe diffuses fast (D approximately equal to 10(-8) - 10(-9) cm2/s), while the mobility of the rest is strongly reduced (D less than 10(-10) cm2/s). At a higher concentration (cp approximately 20 mmol), all probe is immobilized (D less than 10(-10) cm2/s). (b) Incorporation of glycophorin up to cp = 0.4 mmol/mol of total lipid leads to a gradual increase of the fraction of mobile lipid probe due to the lateral-phase separation into a pure P beta 1 phase and a fraction of lipid that is fluidized by strong hydrophilic lipid-protein interaction. (c) The diffusion of the glycophorin molecules is characterized by a slow and a fast fraction. The latter increases with increasing protein content, which is again due to the lateral-phase separation caused by the hydrophilic lipid-protein interaction. The results are interpreted in terms of a fast transport along linear defects in the P beta 1 phase, which form quasi-fluid paths for a nearly one dimensional and thus very effective transport. Evidence for this interpretation of the diffusion measurements is provided by freeze-fracture electron microscopy.

Diffusion↗
PubMed1979

A field survey of fat mobilization and liver function of dairy cows during early lactation. Relationship to energy balance, appetite and ketosis.

NEFA, total lipids, bilirubin, GOT, acetoacetate and glucose in blood plasma of cows were measured during early lactation. Feeding and yield were also recorded. NEFA and bilirubin values showed a gradual decrease with advancing lactation, while total lipids rose gradually during the first months of lactation. GOT showed no definite trend during early lactation. Acetoacetate values were at maximum 21--30 days post partum and glucose values were high at partus and low during the first weeks of lactation. NEFA were negatively correlated to energy balance during the first month of lactation. Total lipids, bilirubin and GOT seemed not to be dependent on energy balance in cows with normal appetite. NEFA, bilirubin and GOT were significantly elevated in cows with reduced appetite. NEFA were positively correlated to bilirubin, GOT and acetoacetate and negatively correlated to glucose. The correlation coefficients were higher during the first month of lactation than during the second and third month. Cows contracting clinical ketosis showed high values of NEFA a long time before any clinical symptoms appeared. Significantly increased values of acetoacetate occurred only the last days before treatment when plasma glucose had reached low values.

Acetoacetates↗
PubMed1981

Activation of human lymphocytes by concanavalin A or purified protein derivative results in no alteration of fluorescence polarization of lipid probes although the electrophoretic mobility of the cells is changed.

Upon stimulation with either concanavalin A or the tuberculin antigen, purified protein derivative, human peripheral blood lymphocytes, purified on Ficoll-Hypaque, did not exhibit a concomitant lipid fluidity alteration as measured by fluorescence polarization (P) of the lipid probe, 1,6-diphenyl-1,3-5-hexatriene (DPH). This result was independent of the incubation period, ranging from 10 min to 72 h. However, a general reduction in polarization value, from P = 0.287 (maintained for up to 2 h of incubation) to P = 0.225 after 20 h was observed for both experimental and control samples. Moreover, fluorescence polarization studies of the nonpenetrating modified DPH cationic lipid probe, 1-[4'-trimethylaminophenyl]-6-phenyl-1,3-5-hexatriene (TMA-DPH), also failed to show any change in lipid fluidity subsequent to a 1-3 h incubation of lymphocytes with concanavalin A. Cell electrophoretic mobility, however, was altered (mean cell mobility increased by 10-15%) in a fast response to stimulation and was observed within several hours of in vitro application of concanavalin A and purified protein derivative. This initial response disappeared with further incubation at 37 degrees C (greater than 3 h) and was followed by a decline of cellular mobility of the concanavalin A-exposed cells after 48 and 72 h of incubation. The unstimulated control cells did not change in mobility as a function of incubation time. The slow decline in mean cell mobility of the experimental cells is believed to be associated with blastogenesis. It is concluded that neither blastogenic transformation nor short term membrane alterations associated with human lymphocyte activation lead to lipid fluidity changes as measured in steady state by the fluorescence polarization of both DPH and TMA-DPH.

Antigens, Bacterial↗
PubMed1980

Changes in host animal plasma lipids during hepatoma growth.

The concentrations of the major neutral lipid and phospholipid classes in the plasma of rats bearing hepatoma 7288CTC were determined at various times after transplantation. The fatty acid composition of each lipid class was also analyzed quantitatively as tumor growth progressed. Generally, most lipid classes exhibited a slight decrease between the third and sixth day after transplantation, returned to near normal levels by the 15th day, increased dramatically and peaked between the 24th and 27th days before plummeting sharply. At peak concentrations, triglycerides were increased 5 times the normal levels, whereas cholesterol, cholesterly esters and phosphatidylcholines were increased 3-fold. The percentage of hexadecenoates decreased in all lipid classes as tumor growth progressed and generally, stearate levels increased. In addition to monounsaturated fatty acids, lysophosphatidylcholines and phosphatidylcholines showed relatively large decreases in the percentage of polyunsaturated fatty acids with increased tumor growth. These results indicate that hepatoma 7288CTC can cause perturbation of host animal plasma lipids in the early stages of growth which precedes the massive hyperlipidemia. The interpretation of these results suggests that the early changes in plasma lipids may result from alterations in the normal lipid metabolism of the host, and the hyperlipidemia that develops later may result from the mobilization of lipids to compensate for the altered metabolism.

Animals↗
PubMed2006

Chemical modification of wheat protein-based natural polymers: cross-linking effect on mechanical properties and phase structures.

Chemical modification of wheat protein-based natural polymer materials was conducted using glyoxal as cross-linker, and the cross-linking effect was studied on mechanical properties under different humidity conditions, the molecular motions of each component, and the phase structures/components of the whole materials. The cross-linking significantly enhanced the mechanical strength of wheat gluten (WG) materials under RH = 50%. The elongation of materials was also increased, which was in contrast to many cross-linked protein systems. The reaction mainly occurred in proteins and starch components, resulting in the formation of a stable cross-linked network with restricted molecular motions and modified motional dynamics. Although the plasticizer glycerol could also take part in the reaction with glyoxal or other components in WG especially when the glyoxal content was higher, the amount of glycerol involved in such reactions was very little. Glycerol was predominantly hydrogen-bonded with the network. The lipid component did not seem to take part in the cross-linking reaction; its mobility was promoted while its interaction with the protein-starch network was weakened after cross-linking. The formation of the cross-linked network did not enhance the hydrophobicity of the materials; the materials still adsorbed a high level of moisture under high humidity conditions (ca. RH = 85%) with no improvement in mechanical strength. In addition, further increasing the amount of glyoxal did not generate an additional strength improvement even at RH = 50%, possibly because the enhanced mobility of lipid promoted the component to be phase-separated from the WG system. To improve the water-resistant properties, the hydrophobicity of the protein macromolecules requires enhancement by other chemical modifications.

Chemical Phenomena↗
PubMed2004

Saposins facilitate CD1d-restricted presentation of an exogenous lipid antigen to T cells.

Members of the CD1 family present antigenic lipids to T lymphocytes. CD1 molecules survey endocytic compartments for lipid antigens that are sorted into these vesicles after incorporation into the membrane bilayer, and extraction from the bilayer is likely to be a critical step for lipid association. We hypothesized that lysosomal saposins, which are cofactors required for sphingolipid degradation, might be involved in this process. Here we show that saposins, although not required for the autoreactive recognition of CD1d by natural killer T cells, are indispensable for the binding of an exogenous lipid antigen, alpha-galactosylceramide, to CD1d in the endocytic pathway. We suggest that saposins mobilize monomeric lipids from lysosomal membranes and facilitate their association with CD1d.

Animals↗
PubMed2004

In situ formation and characterization of poly(ethylene glycol)-supported lipid bilayers on gold surfaces.

Inclusion of a polymer cushion between a lipid bilayer membrane and a solid surface has been suggested as a means to provide a soft, deformable layer that will allow for transmembrane protein insertion and mobility. In this study, mobile, tethered lipid bilayers were formed on a poly(ethylene glycol) (PEG) support via a two-step adsorption process. The PEG films were prepared by coadsorbing a heterofunctional, telechelic PEG lipopolymer (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-poly(ethylene glycol)-2000-N-[3-(2-(pyridyldithio)propionate]) (DSPE-PEG-PDP) and a nonlipid functionalized PEG-PDP from an ethanol/water mixture, as described in a previous paper (Munro, J. C.; Frank, C. W. Langmuir 2004, 20, 3339-3349). Then a two-step lipid adsorption strategy was used. First, lipids were adsorbed onto the PEG support from a hexane solution. Second, vesicles were adsorbed and fused on the surface to create a bilayer in an aqueous environment. Fluorescence recovery after photobleaching experiments show that this process results in mobile bilayers with diffusion coefficients on the order of 2 microm2/s. The mobility of the bilayers is decreased slightly by increasing the density of tethered lipids. The formation of bilayers, and not multilayer structures, is also confirmed by surface plasmon resonance, which was used to determine in situ film thickness, and by fluorimetry, which was used to determine quantitatively the fluorescence intensity for each 18 by 18 mm sample. Unfortunately, fluorescence microscopy also shows that there are large defects on the samples, which limits the utility of this system.

Adsorption↗
PubMed1991

Interaction of charged and uncharged calcium channel antagonists with phospholipid membranes. Binding equilibrium, binding enthalpy, and membrane location.

The membrane location and the binding mechanism of two Ca2+ channel antagonists, amlodipine and nimodipine, in pure lipid membranes were investigated with deuterium and phosphorus-31 nuclear magnetic resonance, with thermodynamic methods such as high-sensitivity titration calorimetry, and by measuring the membrane surface charge via the zeta-potential. The two drugs exhibit quite different physical-chemical properties. The noncharged nimodipine is strongly hydrophobic, and selective deuteration of the lipid membrane reveals a homogeneous distribution of nimodipine across the whole hydrocarbon layer, but no interaction at the lipid headgroup level. The membrane behavior of the amiphiphilic amlodipine (electric charge z = +1) is distinctly more complex. Deuterium magnetic resonance demonstrates that amlodipine adopts a well-defined position in the bilayer membrane. In particular, the charged ethanolamine side group of amlodipine is located near the water-lipid interface, interacting with the dipoles of the headgroup region according to a nonspecific, electrostatic mechanism and inducing a reorientation of the phosphocholine dipoles toward the water phase. At the level of the hydrocarbon segment, the nonpolar ring system of amlodipine interacts specifically with the cis double bond of the membrane lipid, forming a weak association complex. With increasing amlodipine concentration the deuterium signal of the cis double bond gradually loses intensity, a phenomenon previously observed only in related studies on protein-lipid interactions. The binding equilibrium of amlodipine to phosphatidylcholine membranes was studied by measuring the electrophoretic mobility of lipid vesicles and with a centrifugation assay. Hydrophobic interactions of the nonpolar ring systems and electrostatic repulsions at the membrane surface contribute to the binding energy.(ABSTRACT TRUNCATED AT 250 WORDS)

Amlodipine↗
PubMedDate not supplied

[Is a change in the microviscosity and asymmetrical distribution of phospholipids in the membrane a necessary condition for signal transmission? A comparison of the mechanisms of signal transmission in the plasma membranes of the brain synaptosomes and retinal photoreceptor membranes].

The localization of amino phospholipids (phosphatidyl ethanolamine, phosphatidyl serine) and their fatty acid composition in the outer and inner monolayers of plasma membranes from rat brain synaptosomes and retinal photoreceptors in the fish Theragra chalcograma have been studied by chemical modification. The mobility of the lipid components of these membranes was investigated by fluorescent and EPR spin probing techniques after transformation of outer (chemical and physical) signals. The data obtained are discussed in terms of molecular organization of the lipids and of the changes in the mobility of the lipid components of plasma membranes from brain synaptosomes and retinal photoreceptors during transmembrane transmission of the signal.

Animals↗
PubMedDate not supplied

[The pathogenetic significance of disruption of antioxidant homeostasis status in patients with hypertension].

Antioxidative homeostasis was investigated in blood plasma and lymphocytes of patients with hypertonic disease (stage II). The intensification of lipid peroxidation was accompanied by accumulation of polyenic fatty acid derivatives and toxic dialdehydes and also by mobilization of lipid soluble vitamins. Vitamin E is probably involved into direct binding of toxic LPO products. Such changes provide high antioxidant activity and normal functioning of lymphocytes.

Antioxidants↗