References of "Hoebeke, Maryse"
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See detailDoes propofol alter membrane fluidity at clinically relevant concentrations? An ESR spin label study
Bahri, Mohamed Ali ULg; Seret, Alain ULg; Hans, Pol ULg et al

in Biophysical Chemistry (2007), 129(1), 82-91

General anesthetics have been shown to perturb the membrane properties of excitable tissues. Due to their lipid solubility, anesthetics dissolve in every membrane, penetrate into organelles and interact ... [more ▼]

General anesthetics have been shown to perturb the membrane properties of excitable tissues. Due to their lipid solubility, anesthetics dissolve in every membrane, penetrate into organelles and interact with numerous cellular structures in multiple ways. Several studies indicate that anesthetics alter membrane fluidity and decrease the phase-transition temperature. However, the required concentrations to induce such effects on the properties of membrane lipids are by far higher than clinically relevant concentrations. In the present study, the fluidizing effect of the anesthetic agent propofol (2,6-diisopropyl phenol: PPF), a general anesthetic extensively used in clinical practice, has been investigated on liposome dimyristoyi-L-alpha phosphatidylcholine (DMPC) and cell (erythrocyte, Neuro-2a) membranes using electron spin resonance spectroscopy (ESR) of nitroxide labeled fatty acid probes (5-, 16-doxyl stearic acid). A clear effect of PPF at concentrations higher than the clinically relevant ones was quantified both in liposome and cell membranes, while no evident fluidity effect was measured at the clinical PPF doses. However, absorption spectroscopy of merocyanine 540 (MC540) clearly indicates a PPF fluidizing capacity in liposome membrane even at these clinical concentrations. PPF may locally influence the structure and dynamics of membrane domains, through the formation of small-scale lipid domains, which would explain the lack of ESR information at low PPF concentrations. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detail. Study of Neuronal Preconditioning by ESR
Guelluy, Pierre-Henri ULg; Hoebeke, Maryse ULg

Poster (2007, April)

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See detailInvestigation of SDS, DTAB and CTAB micelle microviscosities by electron spin resonance
Bahri, Mohamed Ali ULg; Hoebeke, Maryse ULg; Grammenos, Angeliki ULg et al

in Colloids and Surfaces A : Physicochemical and Engineering Aspects (2006), 290(1-3), 206-212

Electron spin resonance spectroscopy (ESR) of the nitroxide labelled fatty acid probes (5-, 16-doxyl stearic acid) was used to monitor the micelle microviscosity of three surfactants at various ... [more ▼]

Electron spin resonance spectroscopy (ESR) of the nitroxide labelled fatty acid probes (5-, 16-doxyl stearic acid) was used to monitor the micelle microviscosity of three surfactants at various concentrations in aqueous solution: sodium dodecyl sulphate (SDS), dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB). At low surfactant concentration, there is no micelle, the ESR probe is dissolved in water/surfactant homogeneous phase and gives his microviscosity. At higher surfactant concentration, an abrupt increase in microviscosity indicates the apparition of micelles and, the solubilization of the probes in micelles. The microviscosity of the three surfactants, in a large surfactant range, was obtained as well as the critical micelle concentration (CMC). The microviscosity increased slightly with the increase in surfactant concentration. Phosphate buffer lowered the CMC value and generally increased the microviscosity. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailPhotochemistry of 2,6-diisopropylphenol (propofol)
Heyne, B.; Tfibel, F.; Hoebeke, Maryse ULg et al

in Photochemical & Photobiological Sciences (2006), 5(11), 1059-1067

The photochemistry of the anaesthetic agent propofol (PPF) was investigated in three different solvents of quite different polarity (cyclohexane, methanol and phosphate buffer pH 7) by means of nanosecond ... [more ▼]

The photochemistry of the anaesthetic agent propofol (PPF) was investigated in three different solvents of quite different polarity (cyclohexane, methanol and phosphate buffer pH 7) by means of nanosecond laser flash photolysis and absorption spectroscopy. GC-MS spectrometry measurements of PPF in cyclohexane have revealed the formation of two major products upon low intensity UV continuous irradiation of PPF in aerated solution: the diphenol derivative of PPF and 2,6-diisopropyl-p-benzoquinone (PPFQ). Only the diphenol compound was obtained in anaerobic solution. PPF phenoxyl radical (PPF ) generation has been assigned as the original step leading to the formation of both the diphenol compound and PPFQ in cyclohexane as revealed by laser flash photolysis at 266 nm and by electron paramagnetic resonance spectroscopy as well. Investigation of PPF by nanosecond flash photolysis at 266 nm in the other solvents revealed the occurrence of different photochemical processes depending on the nature and the polarity of the solvent. A reaction scheme is proposed in order to discuss the mechanism of reaction of PPF in all media. [less ▲]

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See detailImagerie médicale - bases physiques
Seret, Alain ULg; Hoebeke, Maryse ULg

Book published by Editions de l'Université de Liège (2006)

The book explains the physical foundations of the most common in-vivo medical imaging modalities. It is written for readers having a basic knowledge of physics. However the most essential physical ... [more ▼]

The book explains the physical foundations of the most common in-vivo medical imaging modalities. It is written for readers having a basic knowledge of physics. However the most essential physical phenomenon and their properties are described. Exploring the electromagnetic spectrum from the shortest to the longest wavelengths the book deals with nuclear imaging, RX imaging, endoscopy, thermography and MRI. Acoustic wave and ultrasonography is the next subject. The book ends with the digital image and a few radioprotection notions. [less ▲]

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See detailPhysical and chemical properties of pyropheophorbide)a-methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-a-phosphatidylcholine vesicles
Delanaye, Lisiane; Bahri, Mohamed Ali ULg; Tfibel, Francis et al

in Photochemical & Photobiological Sciences (2006), 5

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second generation hotosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the ... [more ▼]

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second generation hotosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-α-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS). [less ▲]

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See detailStudy of neuronal cells preconditionning
Guelluy, Pierre-Henri ULg; Mouithys-Mickalad, Ange ULg; Deby, Ginette et al

Poster (2005, November 25)

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See detailStudy of neuronal preconditionning by ESR
Guelluy, Pierre-Henri ULg; Mouithys-Mickalad, Ange ULg; Deby, Ginette et al

Scientific conference (2005, November 17)

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See detailSynoviocytes, not chondrocytes, release free radicals after cycles of anoxia/re-oxygenation
Schneider, Nicole ULg; Mouithys-Mickalad, Ange ULg; Lejeune, Jean-Philippe ULg et al

in Biochemical & Biophysical Research Communications (2005), 334(2), 669-673

By oxymetry and electron paramagnetic resonance (EPR), we investigated the effects of repeated anoxia/re-oxygenation (A/R) periods on the respiration and production of free radicals by synoviocytes ... [more ▼]

By oxymetry and electron paramagnetic resonance (EPR), we investigated the effects of repeated anoxia/re-oxygenation (A/R) periods on the respiration and production of free radicals by synoviocytes (rabbit HIG-82 cell line and primary equine synoviocytes) and equine articular chondrocytes. Three periods of 20 min anoxia followed by re-oxygenation were applied to 10(7)cells; O(2) consumption was measured before anoxia and after each re-oxygenation. After the last A/R, cellular free radical formation was investigated by EPR spectroscopy with spin trapping technique (n=3 for each cell line). Both types of synoviocytes showed a high O(2) consumption, which was slowered after anoxia. By EPR with the spin trap POBN, we proved a free radical formation. Results were similar for equine and rabbit synoviocytes. For chondrocytes, we observed a low O(2) consumption, unchanged by anoxia, and no free radical production. These observations suggest an oxidant activity of synoviocytes, potentially important for the onset of osteoarthritis. [less ▲]

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See detailReactivity towards singlet oxygen of propofol inside liposomes and neuronal cells
Heyne, Belinda; Brault, Daniel; Fontaine-Aupart, Marie-Pierre et al

in Biochimica et Biophysica Acta - General Subjects (2005), 1724

Singlet oxygen (1O2), a reactive oxygen species, has been found to be implicated in many cellular events and pathological disorders.Herein, we investigated the reactivity of 1O2 towards the anaesthetic ... [more ▼]

Singlet oxygen (1O2), a reactive oxygen species, has been found to be implicated in many cellular events and pathological disorders.Herein, we investigated the reactivity of 1O2 towards the anaesthetic agent propofol (PPF) encapsulated within DMPC liposomes. By time resolved luminescence, the rate constant of 1O2 quenching by PPF was evaluated, depending on the location of the sensitizer. The nature of the oxidation product, resulting from the reaction of 1O2 with PPF, was determined using absorption and HPLC techniques. Finally, the in vitro protective effect of PPF towards the1O2-induced neuronal cell toxicity was evaluated in terms of cell viability. [less ▲]

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See detailQuantification of lipid bilayer effective microviscosity and fluidity effect induced by propofol
Bahri, Mohamed Ali ULg; Heyne, Belinda; Hans, Pol ULg et al

in Biophysical Chemistry (2005), 114(1), 53-61

Electron spin resonance (ESR) spectroscopy with nitroxide spin probes was used as a method to probe the liposome microenvironments. The effective microviscosities have been determined from the calibration ... [more ▼]

Electron spin resonance (ESR) spectroscopy with nitroxide spin probes was used as a method to probe the liposome microenvironments. The effective microviscosities have been determined from the calibration of the ESR spectra of the probes in solvent mixtures of known viscosities. In the first time, by measuring ESR order parameter (S ) and correlation time (s c) of stearic spin probes, we have been able to quantify the value of effective microviscosity at different depths inside the liposome membrane. At room temperature, local microviscosities measured in dimyristoyl-l-a phosphatidylcholine (DMPC) liposome membrane at the different depths of 7.8, 16.95, and 27.7 2 were 222.53, 64.09, and 62.56 cP, respectively. In the gel state (10 °C), those microviscosity values increased to 472.56, 370.61, and 243.37 cP. In a second time, we have applied this technique to determine the modifications in membrane microviscosity induced by 2,6-diisopropyl phenol (propofol; PPF), an anaesthetic agent extensively used in clinical practice. Propofol is characterized by a unique phenolic structure, absent in the other conventional anaesthetics. Indeed, given its lipophilic property, propofol is presumed to penetrate into and interact with membrane lipids and hence to induce changes in membrane fluidity. Incorporation of propofol into dimyristoyl-L-alpha-phosphatidylcholine liposomes above the phase-transition temperature (23.9 °C) did not change microviscosity. At 10 °C, an increase of propofol concentration from 0 to 1.0 10 [less ▲]

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See detailStudy of neuronal cells preconditioning by ESR
Guelluy, Pierre-Henri ULg; Mouithys-Mickalad, Ange ULg; Deby-Dupont, G. et al

Conference (2005)

Detailed reference viewed: 4 (1 ULg)