Electron Spin Resonance Evidence of the Generation of Superoxide Anion, Hydroxyl Radical and Singlet Oxygen During the Photohemolysis of Human Erythrocytes with Bacteriochlorin A

in Photochemistry & Photobiology (1997), 66(4), 502-8

Photodynamic therapy with bacteriochlorin a (BCA) as sensitizer induces damage to red blood cells in vivo. To assess the extent of the contributuion of reactive oxygen species (ROS) and to determine a ... [more ▼]

Photodynamic therapy with bacteriochlorin a (BCA) as sensitizer induces damage to red blood cells in vivo. To assess the extent of the contributuion of reactive oxygen species (ROS) and to determine a possible reaction mechanism, competition experiments with assorted ROS quenching or/and enhancing agents were performed in human erythrocytes as model system and in phosphate buffer. In the erythrocyte experiments, a 2% suspension was incubated with BCA for 1 h, washed with phosphate-buffered saline, resuspended and subsequently illuminated with a diode laser using a fluence rate of 2.65 mW/cm2. Potassium leakage and hemolysis were light and BCA dose dependent. Adding tryptophan (3.3 mM), azide (1 mM) or histidine (10 mM) to the erythrocyte suspension before illumination delayed the onset of K-leakage and hemolysis suggesting a type II mechanism. The D2O did not affect K-leakage nor photohemolysis. Adding mannitol (13.3 mM) or glycerol (300 nM) also caused a delay in the onset of K-leakage and hemolysis, suggesting the involvement of radicals. In phosphate buffer experiments, it was shown using electron spin resonance (ESR) associated with spin-trapping techniques that BCA is able to generate O2-. and OH. radicals without production of aqueous electron. Visible or UV irradiation of the dye in the presence of the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) gave an ESR spectrum characteristic of the DMPO-hydroxyl radical spin adduct DMPO-OH. Addition of ethanol or sodium formate produced supplementary hyperfine splittings due to the respective CH3CHOH. and CO2-. radical adducts, indicating the presence of free OH.. Production of DMPO-OH was partly inhibited by superoxide dismutase (SOD), catalase and desferrioxamine, suggesting that the iron-catalyzed decomposition of H2O2 was partly involved in the formation of one part of the observed OH.. The complementary inhibition of DMPO-OH production by azide and 9,10-anthracenedipropionic acid (ADPA) was consistent with 1O2 production by BCA followed by reaction of 1O2 with DMPO and decay of the intermediate complex to form DMPO-OH and free OH.. All our results seem to indicate that BCA is a 50%/50% type 1/type 2 sensitizer in buffered aqueous solutions and confirmed that the dye-induced hemolysis of erythrocytes was cell caused by a mixed type 1/type 2 mechanism. [less ▲]

Investigating trickle flow in packed columns by X-ray tomography

Conference (1997, October)

Differentiation between begnin and malignant breast lesions with MR imaging and scintimammography

in Radiology (1997), 205(1), 283

No abstract for this letter.

"Le français à l'université"

Conference given outside the academic context (1997)

A High Serum Concentration of Interleukin-6 Is Predictive of Relapse in Quiescent Crohn's Disease

in European Journal of Gastroenterology & Hepatology (1997), 9(10), 939-44

BACKGROUND/AIMS: Relapses of Crohn's disease are difficult to predict. We assessed the value of serum level of interleukin-6, tumour necrosis factor alpha (TNF-alpha) and soluble TNF receptors as ... [more ▼]

BACKGROUND/AIMS: Relapses of Crohn's disease are difficult to predict. We assessed the value of serum level of interleukin-6, tumour necrosis factor alpha (TNF-alpha) and soluble TNF receptors as predictors of relapse in quiescent Crohn's disease. PATIENTS/METHODS: Thirty-six patients with inactive Crohn's disease, treated or not, were included. Various clinical and biological parameters, including interleukin-6, TNF-alpha and soluble TNF receptors serum levels were measured at inclusion in the study and the patients were followed clinically for 1 year. The relapse was defined as a Crohn's Disease Activity Index (CDAI) greater than 150 with an increase greater than 100 compared to the inclusion value. We analysed the ability of these parameters to predict relapse in parallel to clinical characteristics and other laboratory parameters. RESULTS: Among the 32 variables tested, interleukin-6 serum level had the greatest ability to predict the time-to-relapse, with 17-fold chance of relapse over a 1-year period for patients with an interleukin-6 serum level greater than 20 pg/ml than for patients with a lower level (P < 0.001). A high serum level of the soluble TNF receptors p55 and p75 also had significant predictive value, in contrast to TNF-alpha serum levels. An interleukin-6 serum level greater than 20 pg/ml and either an acid alpha-1-glycoprotein level greater than 1.1 g/l or a soluble interleukin-2 receptor serum level greater than 95 pM/l were risk factors selected by a stepwise multivariate analysis. In both models a good prognosis group was defined by the absence of the two risk factors, a bad prognostic group by the presence of the two risk factors and an intermediate in between. With both models, the good prognosis group included 17 patients who experienced no relapse over the 1-year follow-up, whereas all patients (seven with the first model and six with the second) in the bad prognosis group had a relapse during the follow-up. Looking specifically at two homogeneous subgroups including either naturally/5-aminosalicylic acid (5-ASA) quiescent or corticoid quiescent patients, a very good predictive value for interleukin-6 serum concentration was also found. CONCLUSION: Interleukin-6 serum level alone or in association with other biological parameters such as acid alpha-1-glycoprotein or the soluble interleukin-2 receptor serum level may be useful for predicting the course of the disease in patients with quiescent Crohn's disease. [less ▲]

Thrombangiitis Obliterans (Buerger's Disease): Still a Limb Threatening Disease

in Acta Chirurgica Belgica (1997), 97(5), 229-36

A series of 29 well-documented and properly analysed patients with thrombangiitis obliterans (Buerger's disease) is presented. The diagnosis of Buerger's disease was based on following criteria: smoking ... [more ▼]

A series of 29 well-documented and properly analysed patients with thrombangiitis obliterans (Buerger's disease) is presented. The diagnosis of Buerger's disease was based on following criteria: smoking history, onset before the age of 50 years, infrapopliteal arterial occlusive disease, either upper limb involvement or phlebitis migrans, absence of atherosclerotic risk factors other than smoking. In the last 10 years (1986-1996), we identified 29 patients who met these rigid criteria. There were 24 men and 5 women, aged 32.4 years at the moment of the disease first clinical symptom. The cumulative tobacco use averaged 16 pack-years for each patient. The initial symptom was limited gangrene of a toe (n = 9) or a finger (n = 2), foot claudication (n = 6), calf claudication (n = 3), rest pain (n = 3), migratory superficial phlebitis (n = 4), and Raynaud phenomenon (n = 2). Angiography and/or Doppler ultrasound revealed digital, pedal and calf artery involvement in all patients, with proximal extension in ten patients (femoropopliteal in ten, including three cases with external iliac artery involvement). Seven patients had also evidence of upper limb involvement. Histologic proof was available in only seven patients. Only nine patients completely stopped smoking. Treatment was exclusively medical in five cases. Twenty-four underwent sympathectomy (20 at lumbar, and four at thoracic level), with good immediate result in 16. In 11 patients a vascular reconstruction was done (eight femorocrural and three iliofemoral bypasses), with a patency rate of only 36% at two years. Amputation was required in 16 patients (a mean of 2.7 amputations per patient) at one or more levels: toe (n = 19), forefoot (n = 5), below knee (n = 8), above knee (n = 2), finger (n = 3). Two patients ended up with bilateral leg amputation. Overall, 23% (7/30) of the patients required major leg amputation during the course of the disease. Disease progression was moderately related to continued tobacco use. Buerger's disease still entails considerable risk of major amputation. Complete abstinence from tobacco use is crucial to expect stabilization of the process. However, in advanced stages of the disease and despite cessation of smoking recurrent episodes of ischaemia or tissue loss are not excluded. [less ▲]

Comment je traite ... une infection par le VIH. I. Bases pathogéniques des choix thérapeutiques

in Revue Médicale de Liège (1997), 52(10), 622-4

Automated Determination of Tramadol Enantiomers in Human Plasma Using Solid-Phase Extraction in Combination with Chiral Liquid Chromatography

in Journal of Chromatography. B : Biomedical Sciences and Applications (1997), 698(1-2), 161-70

A sensitive and automated method for the separation and individual determination of tramadol enantiomers in plasma has been developed using solid-phase extraction (SPE) on disposable extraction cartridges ... [more ▼]

A sensitive and automated method for the separation and individual determination of tramadol enantiomers in plasma has been developed using solid-phase extraction (SPE) on disposable extraction cartridges (DECs) in combination with chiral liquid chromatography (LC). The SPE operations were performed automatically by means of a sample processor equipped with a robotic arm (ASPEC system). The DEC filled with ethyl silica (50 mg) was first conditioned with methanol and phosphate buffer, pH 7.4. A 1.0-ml volume of plasma was then applied on the DEC. The washing step was performed with the same buffer. The analytes were eluted with 0.15 ml of methanol, and 0.35 ml of phosphate buffer, pH 6.0, containing sodium perchlorate (0.2 M) were added to the extract before injection into the LC system. The enantiomeric separation of tramadol was achieved using a Chiralcel OD-R column containing cellulose tris-(3,5-dimethylphenylcarbamate) as chiral stationary phase. The mobile phase was a mixture of phosphate buffer, pH 6.0, containing sodium perchlorate (0.2 M) and acetonitrile (75:25). The mobile-phase pH and the NaClO4 concentration were optimized with respect to enantiomeric resolution. The method developed was validated. Recoveries for both enantiomers of tramadol were about 100%. The method was found to be linear in the 2.5-150 ng/ml concentration range [r2=0.999 for (+)- and (-)-tramadol]. The repeatability and intermediate precision at a concentration of 50 ng/ml were 6.5 and 8.7% for (+)-tramadol and 6.1 and 7.6% for (-)-tramadol, respectively. [less ▲]

Un dictionnaire des verbes néo-égyptiens

Conference (1997, September 24)

Intramolecular excited-state processes of a halato-telechelic polymer, evaluated by global compartmental analysis of the fluorescence decay surface with the use of model coumpounds

in Macromolecules (1997), 30(19), 5582-5590

The excited-state processes of the halato-telechelic polymer bis[(N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)trifluoromethanesulfonate]-end-capped poly(tetrahydrofuran) at low concentrations are ... [more ▼]

The excited-state processes of the halato-telechelic polymer bis[(N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)trifluoromethanesulfonate]-end-capped poly(tetrahydrofuran) at low concentrations are investigated by time-resolved fluorescence. The photophysical processes can be described by an intramolecular three-state excited-state model. Such a system is not identifiable in the absence of a priori information. It is possible to perform a global compartmental analysis of the fluorescence decay surface using the scanning technique, based on model compound data previously obtained [Hermans et al., J. Phys. Chem. 1994, 98, 13583 and Hermans et al. Macromolecules 1995, 28, 3380]. The value boundaries on the rate constant for ring closure of the chain ends show that this process is close to diffusion-controlled. [less ▲]