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At least 145 records · Page 8Linked to original sources
PubMed2005

Relationship of MR-derived lactate, mobile lipids, and relative blood volume for gliomas in vivo.

BACKGROUND AND PURPOSE: Gliomas are heterogeneous tumors with increased microvasculature, hypoxia, and necrosis. The purpose of this study was to examine the distribution and relationship of the MR-derived relative cerebral blood volume (rCBV), lactate (Lac), and mobile lipids (Lip), which have been proposed as markers for these phenomena of gliomas in vivo. METHODS: Twenty-three patients with newly diagnosed gliomas were examined before surgical biopsy and/or resection (seven grade II, five grade III, and 11 grade IV), and 27 patients were studied after surgery but before radiation treatment and/or chemotherapy (11 grade II, two grade III, and 14 grade IV gliomas). Lac and Lip were estimated from Lac-edited three-dimensional MR spectroscopic images. Dynamic susceptibility-contrast MR imaging was applied to obtain perfusion-weighted images and rCBV maps. RESULTS: Before surgical biopsy/resection, one low-grade and 12 of 16 high-grade gliomas had significantly elevated Lac. No low-grade and 10 of 16 high-grade gliomas had significantly elevated Lip. In presurgical high-grade gliomas, volumes of elevated Lip and macronecrosis were significantly correlated. rCBV was significantly increased in regions with elevated Lac. After we excluded macronecrosis, the rCBV for regions with elevated Lip but no Lac was significantly higher than rCBV in regions with elevated Lac but no Lip. After surgical biopsy/resection, more low-grade patients showed significantly elevated Lac and Lip than before. CONCLUSION: The in vivo distribution of rCBV, Lac, and Lip, as evaluated with three-dimensional MR spectroscopic imaging, may help in the diagnosis and selection of the most appropriate therapy for patients with gliomas.

Blood Volume↗
PubMed1991

Studies of chemotactic factor-induced polarity in human neutrophils. Lipid mobility, receptor distribution and the time-sequence of polarization.

Differences in membrane composition between the anterior and posterior poles of human blood neutrophils on exposure to chemoattractant were studied using a laser microscope, and the effects of attractant concentration and time on the ability of neutrophils to polarize were determined. The findings were as follows. (1) The fluorescein-labelled chemotactic hexapeptide fLeu-Norleu-Phe-Norleu-Tyr-Lys was asymmetrically distributed on polarized cells with the highest concentration at the anterior pole of the cell. (2) Differences in membrane lipid behaviour were studied by fluorescence recovery after photobleaching (FRAP) using the probe 5-N-(octadecanoyl)-aminofluorescein. Recovery curves suggested that the proportion of mobile lipid probe at the anterior pole of the cell was higher than at the posterior. However, no difference was found in the rate of recovery between the two poles. (3) Studies of the time-course of polarization were undertaken using neutrophils in suspension exposed to different isotropic concentrations of fMet-Leu-Phe (fMLP). At low concentrations (less than or equal to 10(-9) M), the cells polarized immediately on exposure to the attractant. At a high concentration (10(-7) M) they assumed multipolar morphologies and polarized very poorly, suggesting that ligand binding was too rapid for the cells to form a dominant pole. At the optimal concentration, 10(-8) M fMLP, the cells assumed irregular, ruffled, morphologies after 30s, but showed an increasing proportion of polarized forms over the next 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2001

The relationship between 1H-NMR mobile lipid intensity and cholesterol in two human tumor multidrug resistant cell lines (MCF-7 and LoVo).

The high resolution proton nuclear magnetic resonance (1H-NMR) spectra of two different cell lines exhibiting multidrug resistance (MDR) as demonstrated by the expression of the well-known energy-driven, membrane-bound 170 kDa P-glycoprotein pump known as Pgp were investigated. In particular, the mobile lipid (ML) profile, and the growth and biochemical characteristics of MCF-7 (human mammary carcinoma) and LoVo (human colon adenocarcinoma) sensitive and resistant tumor cells were compared. The results indicate that both MCF-7 and LoVo resistant cells have a higher ML intensity than their respective sensitive counterparts. However, since sensitive and resistant cells of each pair grow in the same manner, variations in growth characteristics do not appear to be the cause of the ML changes as has been suggested by other authors in non-resistant tumor cells. In order to investigate further the origin of the ML changes, lipid analyses were conducted in sensitive and resistant cell types. The results of these experiments show that resistant cells of both cell types have a greater amount of esterified cholesterol and saturated cholesteryl ester and triglyceride fatty acid than their sensitive counterparts. From a thorough analysis of the data obtained in this paper utilizing numerous techniques including biological, biophysical and biochemical ones, it is hypothesized that cholesterol and triglyceride play a pivotal role in inducing changes in NMR ML signals. The importance of these lipid variations in MDR is discussed in view of the controversy regarding the origin of ML signals and the paramount role played by the Pgp pump in resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1975

The relation between lipid mobility and the specific hormone binding of thyroid membranes.

1. The specific binding of thyroid-stimulating hormone to isolated human thyroid membranes was examined under a variety of conditions. 2. In phosphate-saline buffer (in the presence of 0.14 M-NaCl) on increasing the temperature the binding of the hormone is increased, the plots of bound/free hormone against temperature showing a distinct break around 30 degrees C. 3. Detailed analysis showed that the increased binding is associated with an increase in the number of binding sites. 4. The motional characteristics of three membrane-bound fluorescent probes, 2-(9-anthroyl)palmitic acid, 12-(9-anthryl)stearic acid and N-1-naphthyl-N-phenylamine, were also examined as a function of temperature by measuring both fluorescence polarizations and lifetimes. 5. The results indicated that the 'fluidity' of membrane lipids also increased with temperature. The temperature-dependence of this property also shows a change at about 30 degrees C. 6. Bivalent cations decreased both membrane fluidity and hormone binding. 7. Similar correlations were found between the binding of adrenocorticotrophic hormone and the fluidity of the plasma membranes obtained from adrenal-cortical cells, with the discontinuity occurring in this case at 23 degrees C. 8. The possibility of lipid mobility being important in controlling hormone-receptor function is discussed.

Anthracenes↗
PubMed1996

Modulation of MR-visible mobile lipid levels by cell culture conditions and correlations with chemotactic response.

A transformed murine fibroblast cell line has been used to assess which criteria govern the appearance of a lipid pool that is mobile on the MR time scale. A high-resolution proton MR signal arising from neutral lipids, including triglyceride and cholesteryl esters, has previously been associated with membrane events in stimulated, transformed and malignant cells. We report that the attenuation of cellular proliferation by confluence or low pH caused significant increases in MR-visible lipid and that the lipid signal could be amplified at high density by the removal of serum. A significant decrease in chemotactic response accompanied the culture of cells at high density, but chemotactic response was not generally linked to alteration of the lipid signal. The appearance of the signal was also not correlated with the proportion of cells in any phase of the cell cycle. Significant changes in the MR-visible pools of the lipid metabolites choline, phosphocholine and glycerophosphocholine were measured under the culture conditions employed with 2D MRS and suggest that MR-visible lipid may arise from the catabolism of phospholipids.

Animals↗
PubMed1987

Dynamic fluorescence quenching studies on lipid mobilities in phosphatidylcholine-cholesterol membranes.

Bimolecular collision rate of 8-anilinonaphthalene-1-sulfonic acid (ANS) and the nitroxide doxyl group attached to various carbons on stearic acid spin labels (n-SASL) in phosphatidylcholine-cholesterol membranes in the fluid phase was studied by observing dynamic quenching of ANS fluorescence by n-SASL's. The excited-state lifetime of ANS and its reduction by the n-SASL doxyl group were directly measured by the time-correlated single photon counting technique to observe only dynamic quenching separately from static quenching and were analyzed by using Stern-Volmer relations. The collision rate of ANS with the n-SASL doxyl group ranges between 1 X 10(7) and 6 X 10(7), and the extent of dynamic quenching by n-SASL is in the order of 5-much much greater than 6- greater than 7- less than 9- less than 10- less than 12- less than 16-SASL (less than 5-SASL) in dimyristoylphosphatidylcholine (DMPC) membranes. Collision rate of 16-SASL is only 10% less than that of 5-SASL. Since the naphthalene ring of ANS is located in the near-surface region of the membrane, these results indicate that the methyl terminal of SASL appears in the near surface area frequently, probably due to extensive gauche-trans isomerism of the methylene chain. The presence of 30 mol% cholesterol decreases the collision rate of ANS with 12- and 16-SASL doxyl groups but not with the 5-SASL doxyl group in DMPC membranes. On the other hand, in egg-yolk phosphatidylcholine membranes, inclusion of 30 mol% cholesterol does not affect the collision of ANS with either 5-SASL or 16-SASL doxyl groups, in agreement with our previous observation that alkyl chain unsaturation moderates cholesterol effects on lipid motion in the membrane (Kusumi et al., Biochim. Biophys. Acta 854, 307-317). It is suggested that dynamic quenching of ANS fluorescence by lipid-type spin labels is a useful new monitor of membrane fluidity that reports on various lipid mobilities in the membrane; a class of motion can be preferentially observed over others by selecting a proper spin label, i.e., rotational diffusion of lipid about its long axis and translational diffusion by using 5-SASL, wobbling motion of the lipid long axis by using 7-SASL or androstane spin label, and gauche-trans isomerism by using 16-SASL.

Anilino Naphthalenesulfonates↗
PubMed2005

Analysis of 1H NMR-detectable mobile lipid domains for assessment of apoptosis induced by inhibitors of DNA synthesis and replication.

Cell membrane rearrangements coincident with apoptosis may contribute to the increase in the ratio of methylene (CH(2) at 1.3 ppm) to methyl (CH(3) at 0.9 ppm) resonance signal intensity as observed by proton nuclear magnetic resonance ((1)H NMR). We studied CH(2) and CH(3) resonances in cultured cell lines treated with etoposide and fludarabine or bioflavonoid quercetin. Etoposide treatment (10 microM, 18 h) resulted in 3.3 fold increase of the CH(2)/CH(3) signal intensity ratio and 6.4 fold decrease in choline signal of MT4 cells. Incubation of Namalwa cells with fludarabine (3 microM, 72 h) increased the CH(2)/CH(3) signal intensity ratio by 2.4 fold and choline resonance intensity was unchanged. Quercetin treatment (30 microM, 1.5 month) increased CH(2)/CH(3) ratio by 2.1 fold. Necrotic cell death upon ethanol (20%) or DMSO (30%) treatment did not change the CH(2)/CH(3) signal intensity ratio. (1)H NMR-based study of mobile lipid domains is sensitive for detection of early engagement into apoptosis.

Apoptosis↗
PubMed1986

Insulin antagonizes epinephrine activation of the membrane transport of fatty acids. Potential site for hormonal suppression of lipid mobilization.

Membrane transport of long chain fatty acids in the isolated rat adipocyte can be strongly stimulated by epinephrine (Abumrad, N. A., Perry, P. R., and Whitesell, R. R. (1985) J. Biol. Chem. 260, 9969-9971). We now report that insulin at physiological concentrations can completely block or reverse the epinephrine effect. Insulin was optimally effective at a concentration of about 0.1 nM in inhibiting transport activation by 0.3 and 3 microM epinephrine (0.1 and 1.0 microgram/ml). High concentrations of insulin (above 1 nM) were generally less effective and this was particularly true at the highest dose of epinephrine (1.0 microgram/ml). The insulin effect was shown to be on the transport process since insulin inhibited epinephrine activation of transport in both directions (influx and efflux). No effect of insulin on basal transport was observed over a wide range of concentrations (0.01-10 nM). Insulin's antagonism of transport activation by epinephrine appeared dependent on ATP metabolism since it was abolished by preincubating the cells with dinitrophenol (1 mM). Dinitrophenol, however, could not reverse the insulin effect when exposure to the hormone preceded that to dinitrophenol, consistent with an action of insulin at the transport step. The data indicate that regulation of the membrane transport of fatty acids is a potential site for insulin's action to suppress lipid mobilization.

Adipose Tissue↗
PubMed1987

Lipid mobility and order in bovine rod outer segment disk membranes. A spin-label study of lipid-protein interactions.

Lipid-protein interactions in bovine rod outer segment disk membranes have been studied by using a series of eight stearic acid spin-label probes which were labeled at different carbon atom positions in the chain. In randomly oriented membrane dispersions, the electron spin resonance (ESR) spectra of the C-8, C-9, C-10, C-11, C-12, C-13, and C-14 atom positional isomers all apparently consist of two components. One of the components corresponds closely to the spectra obtained from dispersions of the extracted membrane lipids, and the other, which is characterized by a considerably greater degree of motional restriction of the lipid chains, is induced by the presence of the protein. Digital subtraction has been used to separate the two components. The proportion of the motionally restricted lipid component is approximately constant, independent of the position of the spin-label group, and corresponds to 30-40% of the total spin-label spectral intensity. The hyperfine splitting of the outer maxima in the difference spectra of the motionally restricted component decreases, and concomitantly, the line widths increase with increasing temperature but change relatively little with increasing distance of the spin-label group from the polar head-group region. This indicates that the corresponding chain motions of the protein-interacting lipids lie in the slow-motion regime of spin-label ESR spectroscopy (tau R approximately 10(-8) S) and that the mobility of these lipids increases with increasing temperature but does not vary greatly along the length of the chain. The data from the hyperfine splittings also suggest the existence of a polarity gradient immediately adjacent to the protein surface, as observed in the fluid lipid regions of the membrane. The more fluid lipid component is only slightly perturbed relative to the lipids alone (for label positions 5-14, inclusive), indicating the presence of chain motions on the nanosecond time scale, and the spectra also reveal a similar polarity profile in both lipid and membrane environments. ESR spectra have also been obtained as a function of magnetic field orientation with oriented membrane samples. For the C-14 atom positional isomer, the motionally restricted component is observed to have a large hyperfine splitting, with the magnetic field oriented both parallel and perpendicular to the membrane normal. This indicates that the motionally restricted lipid chains have a broad distribution of orientations at this label position.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Effect of reproductive states on lipid mobilization and linoleic acid metabolism in mammary glands.

Effects of pregnancy and lactation on lipid metabolism in mouse mammary fat pads and nonmammary adipose tissues have been studied. In order to address the question whether the influence of hormonal milieu on lipid metabolism in mammary epithelial cells during pregnancy and lactation is the same as in fat cells, we have studied the mobilization of lipids and metabolism of fatty acids in the intact mammary glands, parenchyma-free mammary fat pads and in the perimetrial fat tissues of virgin, pregnant and lactating mice. Compared to parenchyma-free mammary fat pads, the perimetrial adipose tissues accumulated 5-fold higher levels of triglycerides during pregnancy. Mammary fat cells maintained overall lipid levels during pregnancy and lactation (16-20 micrograms/fat pad). In contrast, lactation depleted total lipid stores from 108 +/- 5 to 24 +/- 4.5 micrograms/fat pad in perimetrial fat pads. Results of comparative analysis of fatty acid composition of mammary fat pads, with and without epithelial tissue, from virgin and lactating mice showed stimulation of 18:2 omega 6 metabolism leading to 130% increase in the ratio 20:4 omega 6 to 18:2 omega 6 in the epithelial compartment. Pregnancy and lactation resulted in the elevation of 20:4 omega 6 levels probably due to a 4-fold increase in delta 5 desaturase activity and a decrease in oxidative degradation of 18:2 omega 6. These results suggest that, unlike other adipose tissues, the metabolic pathways in mammary fat cells are not dedicated to sequestration and accumulation of dietary lipids during pregnancy. Lactation favors mammary epithelial cell-stimulated production of precursors of eicosanoids which are known to have agonist-like effect on mammary epithelial cells.

Adipose Tissue↗
PubMed1997

Structural elucidation of oxygenated storage lipids in cucumber cotyledons. Implication of lipid body lipoxygenase in lipid mobilization during germination.

At early stages of germination, a special lipoxygenase is expressed in cotyledons of cucumber and several other plants. This enzyme is localized at the lipid storage organelles and oxygenates their storage triacylglycerols. We have isolated this lipid body lipoxygenase from cucumber seedlings and found that it is capable of oxygenating in vitro di- and trilinolein to the corresponding mono-, di-, and trihydroperoxy derivatives. To investigate the in vivo activity of this enzyme during germination, lipid bodies were isolated from cucumber seedlings at different stages of germination, and the triacylglycerols were analyzed for oxygenated derivatives by a combination of high pressure liquid chromatography, gas chromatography/mass spectrometry, and nuclear magnetic resonance spectroscopy. We identified as major oxygenation products triacylglycerols that contained one, two, or three 13S-hydroperoxy-9(Z),11(E)-octadecadienoic acid residues. During germination, the amount of oxygenated lipids increased strongly, reaching a maximum after 72 h and declining afterward. The highly specific pattern of hydroperoxy lipids formed suggested the involvement of the lipid body lipoxygenase in their biosynthesis. These data suggest that this lipoxygenase may play an important role during the germination process of cucumber and other plants and support our previous hypothesis that the specific oxygenation of the storage lipids may initiate their mobilization as a carbon and energy source for the growing seedling.

Chromatography, High Pressure Liquid↗
PubMed1994

[Lipid mobilizing activity in blood serum during the follicular and luteal phases of the menstrual cycle].

The lipid mobilising activity of woman's blood serum in the follicular and luteal phases has been investigated. This activity was determined according to the Buckle method concerning parametrial adipose tissue of female rats. It was found to enhance the lipid mobilising activity in the follicular phase of the menstrual cycle. The increment of the lipid mobilising activity in the luteal phase was lower than in the follicular phase.

Adult↗