75 results on '"J. Dufaux"'
Search Results
2. Evolution of the microvascular distensibility during the embryo growth. Example of the chick chorioallantoic membrane (CAM)
- Author
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J.J. Durussel, J. Dufaux, Gérard Guiffant, and A. Laurent
- Subjects
Chorioallantoic membrane ,Average diameter ,Chemistry ,Angiogenesis ,Vasoactive ,cardiovascular system ,Biophysics ,Saline injection ,Embryo ,Anatomy ,Chick chorioallantoic membrane ,Vascular tone - Abstract
Evolution of the microvascular distensibility during embryo growth. Example of the chick chorioallantoic membrane (CAM). The purpose of this work was to determine the evolution of the microvascular distensibility during the embryo growth. The microvascular distensibility was involved in capillary flow regulation, therefore in tissular irrigation and capillaries network growth during the angiogenesis. Its value fluctuated with the arteriolar tone. We worked on the CAM of the chick embryo, because of the vessel wall structure quickly changes during its development. We performed the measurements at three stages of development: at day 6, day 12 and day 16 of incubation. We carried out the measurements on in situ vessels visualized by microscopy, without vasoactive substances in order to preserve the vascular tone. Each vessel was canulated with a micropipette, occluded by a distal compression and inflated with a saline injection under controlled pressures. The distensibility was expressed as the relative increase in diameter. We determined that: 1) The distensibility was significantly higher in the vessels smaller than 58 μm diameter than in the larger vessels at day 6 and day 12 (the 58 μm value was the average diameter of the studied vessels). 2) The distensibility of the arteries, whatever their diameter (small or large) significantly decreased between day 12 and day 16 of incubation. 3) The distensibility of the smallest veins significantly decreases between day 12 and day 16, whereas the distensibility of the largest veins did not change during the same period. 4) The arteriolar distensibility was significantly smaller than the venular distensibility at day 12 and day 16.
- Published
- 2005
3. A new experimental method for the evaluation of the release profiles of drug-loaded microbeads designed for embolisation
- Author
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Gérard Guiffant, J. L. Counord, F. Amyot, K. Jurski, J. Dufaux, V Boudy, and J.-C Chaumeil
- Subjects
Drug ,Chemistry ,media_common.quotation_subject ,Kinetics ,Biophysics ,Controlled release ,Microsphere ,DEAE-Trisacryl ,media_common ,Biomedical engineering - Abstract
The development of a galenical form must take into account the drug's physico-chemical properties as well as the external conditions that govern its performances. In the case of loaded microbeads designed for embolisation, the drug-release kinetics strongly depends on the local hydrodynamic conditions. Currently the apparatuses recommended by the European Pharmacopoeia allow the measurement in vitro of these kinetics; but the measured kinetics are very different from those met in the in vivo embolisation procedures. A new methodology is presented for evaluating the controlled release of a drug from ion exchange resins for embolisation. Experimental and numerical data are reported on the release kinetics of two closely related galenical formulations (DEAE Trisacryl LS and QAE Trisacryl LS).
- Published
- 2002
4. AN EXPERIMENTAL AND THEORETICAL STUDY OF MASS TRANSFER FROM LOADED EMBOLISATION MICROBEADS: POSSIBLE OPTIMISATION
- Author
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F. Amyot, K. Jurski, J. Dufaux, and Gérard Guiffant
- Subjects
Materials science ,Pharmaceutical technology ,General Chemical Engineering ,Mass transfer ,Mechanics ,Condensed Matter Physics ,Drug carrier ,Atomic and Molecular Physics, and Optics ,Dosage form ,Microsphere - Abstract
The development of loaded galenical formulations requires specific tests leading to a sharp discrimination of kinetics release. We have presented an experimental protocol where particular hydrodynamic conditions are implemented, permitting the drug to be transported by a controlled diffusive-convective process, after chemical liberation from the microbeads. This study shows that the procedure leads to satisfactory results regarding the characterization of closely related galenical formulations. A two dimensional phenomenological approach leads to the promising possibility of optimizing the procedure.
- Published
- 2002
5. Optical flow detection and imaging
- Author
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J. Dufaux, Kristine Jurski, Laurent Brunel, and Patrick Snabre
- Subjects
Diffusing-wave spectroscopy ,Materials science ,business.industry ,Monte Carlo method ,Optical flow ,General Physics and Astronomy ,Statistical model ,Laser Doppler velocimetry ,Physics::Fluid Dynamics ,Speckle pattern ,Optics ,Scattered light ,business ,Anisotropy - Abstract
In this paper we provide functional forms for Laser Doppler Velocimetry (LDV) and Diffusing Wave Spectroscopy (DWS) based on multiply scattered light by a random distribution of moving anisotropic centres. These results are based on statistical models and applied to single shear flows or random flows, and are compared to Monte Carlo simulations and in vitro experiments in back-scattered geometry. Finally LDV and DWS results are used to characterise red blood cell aggregation and to determine the perfusion flow rate of various human tissues.
- Published
- 2001
6. Reduced Reactive Hyperemia in HIV-Infected Patients
- Author
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Eric Vicaut, Daniel Vittecoq, Jean-Jacques Monsuez, and J. Dufaux
- Subjects
Adult ,Male ,medicine.medical_specialty ,Endothelium ,Vasodilator Agents ,Arbitrary unit ,Myocardial Infarction ,Hemodynamics ,HIV Infections ,Hyperemia ,Hyperlipidemias ,Asymptomatic ,Nitroglycerin ,Ventricular Dysfunction, Left ,Ischemia ,Internal medicine ,Laser-Doppler Flowmetry ,medicine ,Humans ,Pharmacology (medical) ,Myocardial infarction ,Reactive hyperemia ,business.industry ,Blood flow ,Middle Aged ,medicine.disease ,Acetylcholine ,Surgery ,Vasodilation ,medicine.anatomical_structure ,Infectious Diseases ,Circulatory system ,Cardiology ,Female ,medicine.symptom ,business - Abstract
Background: Given that several pathology-based studies reported some degree of coronary and arterial vasculopathy in HIV-infected patients, we investigated whether abnormal vascular reactivity may also be found in these patients. Methods: Vascular reactivity was assessed noninvasively using finger-skin blood-flow monitoring by laser-Doppler flow measurement in 10 HIV-infected-patients (mean CD4 T-cell count, 350 ± 84 cells/mm 3 ) with cardiac symptoms (previous myocardial infarction or left-ventricular dysfunction) and/or HIV-related protease inhibitor-induced hyperlipemia (group I, symptomatic), 19 HIV-infected patients free of cardiac disease, hyperlipemia, and previous opportunistic infections (mean CD4 T-cell count, 333 ± 175 cells/mm 3 ; group 2, asymptomatic), and 19 healthy control subjects (group 3). Laser-Doppler flow was measured at baseline, during postocclusive hyperemic response following transient interruption of brachial blood flow (reactive hyperemia), during transcutaneous delivery of acetylcholine (Ach) using iontophoresis (endothelium-dependent dilation) and after sublingual nitroglycerin administration (endothelium-independent dilation). Results: During reactive hyperemia, the absolute increase in flow was found to be lower in asymptomatic HIV-infected patients than in controls (median values [25th-75th percentile]: asymptomatic: 300 [200-400]; versus controls: 600 [400-750] arbitrary units [AU]; p ≤.0001). This abnormality was more pronounced in symptomatic patients (100 [100-200]; p ≤.0001). There was also a reduced peak/baseline flow ratio (symptomatic: 1.14 [1.1-1.2]; asymptomatic: 1.40 [1.25-1.5]; versus controls: 1.83 [1.6-2.2]; p
- Published
- 2000
7. Thrombosis of Angiographic Catheters in Humans: Experimental Study
- Author
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Gérard Guiffant, A. L. Bailly, J. Dufaux, Jean-Jacques Merland, A Lautier, D Labarre, A. Laurent, and E. Houdart
- Subjects
business.industry ,medicine.medical_treatment ,Biomedical Engineering ,Medicine (miscellaneous) ,Thrombogenicity ,Hemodynamics ,Bioengineering ,Blood volume ,General Medicine ,Blood flow ,Femoral artery ,030204 cardiovascular system & hematology ,030218 nuclear medicine & medical imaging ,Biomaterials ,03 medical and health sciences ,Catheter ,0302 clinical medicine ,medicine.artery ,Occlusion ,Medicine ,Embolization ,business ,Nuclear medicine - Abstract
One of the major problems in the use of catheters is their thrombogenicity since the embolization of clots near the central nervous system or the coronary arteries can cause permanent damage. Catheter thrombogenicity was evaluated in humans during angiographic procedures by their tendency to become occluded. Characterization of catheters was achieved using roughness measurements, FTIR with ATR, DSC and ESCA. The catheters were 5 commercially available catheters, made mainly of polyethylene, Pebax® or polyamide sterilized and ready for clinical use. Thirty-one patients due to have an angiographic procedure and with normal blood and hemodynamic parameters were included in the study. The 50 cm catheter test sample was inserted through an introducer into the femoral artery at the beginning of an angiographic procedure. The outcoming blood flow rate (BFR) was continuously monitored by a special computerized device for 15 min or until the total amount of blood reached 30 ml. The angiographic procedure was then normally resumed. DSC and FTIR showed results consistent with the expected composition of catheters. ESCA results showed very high Si/C ratios and could not be explained in all instances. Occlusion of the catheters occurred in 44 % of the cases and the average time to obtain occlusion was 8.5 min (3–15 min). Values of the decrease rate of BFR in ml/min2 allowed separation of the catheters into 3 groups of low, medium and high thrombogenicity. However, occlusion occurred at least one time for each type of catheter. Blood volume and BFR curves vs. time allowed the determination of 3 main types of thrombotic behavior: type I shows no significant reduction of BFR; type II shows a progressive decrease in flow rate; type III is much less frequent and shows an abrupt decrease of BFR either quickly followed by a compensatory increase and resuming of a steady flow or by abrupt occlusion. In type II curves the pattern of occlusion follows a classical diffusion model because the Peclet number is greater than 1 and then the classical Higbie solution for diffusion could be used (33). The most thrombogenic material was the smoothest. There was no correlation between surface chemical composition and thrombogenicity. However, catheters that were based on PE appeared less thrombogenic than PA catheters in this study.
- Published
- 1999
8. Production and certification of an enzyme reference material for pancreatic α-amylase (CRM 476)
- Author
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Elizabeth Colinet, D.H. Calam, J. Dufaux, Anne Vassault, Klaus Lorentz, F. Javier Gella, Francesca Canalias, Christos Profilis, Jean Marc Lessinger, Ferruccio Ceriotti, Anthony G. Hadjivassiliou, and Gemma Gubern
- Subjects
Time Factors ,Sodium ,Clinical Biochemistry ,chemistry.chemical_element ,Biochemistry ,Catalysis ,Drug Stability ,medicine ,Humans ,Amylase ,Lipase ,Pancreas ,Polyacrylamide gel electrophoresis ,Chromatography ,biology ,Biochemistry (medical) ,General Medicine ,Hydrogen-Ion Concentration ,Reference Standards ,Human serum albumin ,Enzyme assay ,Freeze Drying ,Isoelectric point ,chemistry ,Sephadex ,biology.protein ,Electrophoresis, Polyacrylamide Gel ,Indicators and Reagents ,Spectrophotometry, Ultraviolet ,alpha-Amylases ,medicine.drug - Abstract
We describe the preparation of a lyophilized material containing purified human pancreatic alpha-amylase and the certification of its catalytic concentration. The enzyme was purified from human pancreas by ammonium sulphate precipitation and chromatography successively on DEAE-Sephacel, CM-Sepharose and Sephadex G-75. The purified enzyme had a specific activity of 52.9 kU/g protein and was99% pure on polyacrylamide gel electrophoresis. Only trace amounts of lipase and lactate dehydrogenase were detected in the purified fraction. The purified pancreatic alpha-amylase had a molar mass of 57,500 g/mol and an isoelectric point at 7.1. The material was prepared by diluting the purified alpha-amylase in a matrix containing PIPES buffer 25 mmol/l, pH 7.0, sodium chloride 50 mmol/l, calcium chloride 1.5 mmol/l, EDTA 0.5 mmol/l and human serum albumin 30 g/l, dispensing in ampoules and freeze-drying. The ampoules were homogeneous and the yearly loss of activity on the basis of accelerated degradation studies was less than 0.01% at -20 degrees C. The certified value for alpha-amylase catalytic concentration in the reconstituted reference material is 555 U/l +/- 11 U/l when measured by the specified method at 37 degrees C. The material can be used to verify the comparability of results from laboratories, for intra-laboratory quality control or for calibration of alpha-amylase catalytic concentration measurements.
- Published
- 1996
9. Optic nerve head blood flow using a laser Doppler velocimeter and haemorheology in primary open angle glaucoma and normal pressure glaucoma
- Author
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J. Dufaux, P. Hamard, S Quesnot, and H. Hamard
- Subjects
Adult ,Erythrocyte Aggregation ,Male ,medicine.medical_specialty ,Intraocular pressure ,genetic structures ,Open angle glaucoma ,Blood viscosity ,Glaucoma ,Cellular and Molecular Neuroscience ,Ophthalmology ,Laser-Doppler Flowmetry ,medicine ,Humans ,Intraocular Pressure ,business.industry ,Optic Nerve ,Blood flow ,Middle Aged ,Blood Viscosity ,medicine.disease ,eye diseases ,Sensory Systems ,Surgery ,Low Tension Glaucoma ,medicine.anatomical_structure ,Regional Blood Flow ,Hemorheology ,Optic nerve ,Female ,sense organs ,business ,Blood Flow Velocity ,Glaucoma, Open-Angle ,Research Article ,Optic disc - Abstract
Optic disc blood flow velocity was measured in healthy patients, those with primary open angle glaucoma (POAG), and patients with normal pressure glaucoma (NPG). The velocity of the red blood cells (RBCs) in the capillaries of the optic nerve head (ONH) has been measured with a laser Doppler velocimeter (LDV), and blood viscosity has been evaluated notably by determining the aggregability of the RBCs with an erythroaggregameter. Our results in POAG patients and NPG patients showed that their optic nerve blood flow velocity was reduced and that the aggregability of the RBCs was increased. The hyperaggregability of the erythrocytes is responsible for the increase of the local viscosity in the papillary capillary network. These haemodynamic modifications observed in patients with glaucoma support the hypothesis of a vasogenic mechanism that could impair the optic nerve in glaucoma patients.
- Published
- 1994
10. Blood flow rate in the microvasculature of the optic nerve head in primary open angle glaucoma. A new approach
- Author
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J. Dufaux, P. Hamard, and H. Hamard
- Subjects
Adult ,Erythrocyte Aggregation ,Male ,medicine.medical_specialty ,genetic structures ,Open angle glaucoma ,Optic Disk ,Blood viscosity ,Hemodynamics ,Glaucoma ,Microcirculation ,Ophthalmology ,Laser-Doppler Flowmetry ,Humans ,Medicine ,business.industry ,Anatomy ,Blood flow ,Middle Aged ,Blood Viscosity ,medicine.disease ,eye diseases ,Capillaries ,Red blood cell ,medicine.anatomical_structure ,Optic nerve ,Female ,sense organs ,business ,Blood Flow Velocity ,Glaucoma, Open-Angle ,circulatory and respiratory physiology - Abstract
In order to evaluate the optic nerve head perfusion in patients with primary open-angle glaucoma (POAG), we measured the velocity of the red blood cells (RBCs) in the capillaries of the optic nerve head with a laser-Doppler velocimeter and evaluated the blood viscosity by determining the capacity of the RBCs to disaggregate with an erythroaggregameter. Our results showed that in POAG patients optic nerve blood velocity was reduced and that the aggregability of the RBCs was increased. The two parameters were not significantly correlated, possibly because of local papillary autoregulation and anatomical variability in the papilla vessels. These two factors could explain why the same rheological anomaly in two subjects could lead to different responses in blood velocity. The RBC hyperaggregability cannot be explained by quantitative modifications of the plasma proteins. Modifications in the membrane of the RBCs could indeed be responsible for hyperaggregability, since our data suggest that deformability of the RBCs is impaired in glaucoma.
- Published
- 1994
11. Hemorheological abnormalities in rats with experimental mild diabetes: improving effect of troxerutine and α-tocopherol
- Author
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Marie-France Berthault, J. Dufaux, Alain Ktorza, Jean-Louis Counord, Joël Guillou, and A. Othmane
- Subjects
medicine.medical_specialty ,Physiology ,business.industry ,Vitamin E ,medicine.medical_treatment ,Blood viscosity ,Hematology ,Blood flow ,medicine.disease ,Streptozotocin ,Erythrocyte aggregation ,Endocrinology ,Physiology (medical) ,Diabetes mellitus ,Internal medicine ,medicine ,Erythrocyte deformability ,Tocopherol ,Cardiology and Cardiovascular Medicine ,business ,medicine.drug - Abstract
(Received 5.7.1993~ accepted 8.10.1993) We investigated the effect of intravenous 2mM Troxerutine and lOmM (l Tocopherol (Vitamin E) and their combination on erythrocyte aggregation and deformability, blood viscosity and leukocyte adhesivity in rats made mildly diabetic (fasting glycemia: lOmM vs 6mM in controls; HbA 1c: 6.5% vs 3% in controls) by a low dose of streptozotocin (35mg/kg) injected via the saphenous vein. In diabetic rats, as compared to controls, erythrocyte aggregation and blood viscosity were dramatically increased (disaggregation shear stress: 5.2 ± 0.4 dynes/cm2 vs 3.7 ± 0.3 dynes/cm2 in controls), whereas erythrocyte deformability and mesenteric blood flow were sharply decreased. Moreover, leukocyte adhesivity was significantly increased. In diabetic rats, the combination of Troxerutine and Tocopherol improved all the above cited parameters. These data show that mild diabetes in rats results in many hemorheological disorders that can be largely corrected by Troxerutine and (l -Tocopherol.
- Published
- 1994
12. Topological analysis of microcirculatory networks and rheological blood properties from two teleost fishes - Comparison with a sea mammal and a terrestrial mammal
- Author
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Gérard Guiffant, J. Dufaux, P. Roubaud, and J.J. Durussel
- Subjects
Mammals ,Physiology ,Microcirculation ,Fishes ,Video Recording ,Biology ,Blood Viscosity ,Models, Biological ,Paleontology ,Viscosity ,Hematocrit ,Shear (geology) ,Rheology ,Erythrocyte Deformability ,Physiology (medical) ,Animals ,Mammal - Published
- 1991
13. 3. Du plasma aux globules sanguins
- Author
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J. Dufaux, P. Flaud, D. Quemada, and G. Guiffant
- Published
- 2002
14. Hemorheology in asymptomatic HIV-infected patients
- Author
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J J, Monsuez, J, Dufaux, D, Vittecoq, P, Flaud, and E, Vicaut
- Subjects
Adult ,Erythrocyte Aggregation ,Male ,Anti-HIV Agents ,HIV Infections ,Blood Sedimentation ,Middle Aged ,Kinetics ,Risk Factors ,Case-Control Studies ,Hemorheology ,Linear Models ,Humans ,Female ,Stress, Mechanical - Abstract
Although cardiac and vascular complications have been recognized among patients infected with the Human Immunodeficiency Virus-1 (HIV-1), their vascular biology and rheology have not been studied. Rheology of red blood cells (RBC) was assessed with an erythroaggregometer in 22 HIV-1 infected asymptomatic patients (pts) and 17 healthy HIV negative controls (C). All participants were normotensive, nondiabetics, had normal lipid levels and had an hematocrit ranging from 37 to 44% and hemoglobin levelsor = 12 g/100 ml. Patients had a shorter RBC aggregation characteristic time than controls (1.49 +/- 0.17 vs. 2.04 +/- 0.41 s, p = 0.001) and an increased disaggregation shear rate (166 +/- 34.9 vs. 122 +/- 25.4 s(-1), p = 0.001). This hyperaggregation tendancy was associated with increased gamma-globulin (18.3 +/- 3.3 vs. 13.7 +/- 1.9 g/l, p = 0.01) and fibrinogen (3.52 +/- 0.57 vs 3.03 +/- 0.48 g/l, p = 0.003) levels and with an increased erythrocyte sedimentation rate (ESR) (25 +/- 14.3 vs. 12.3 +/- 7.5 mm, p = 0.02). Even in patients with ESRs ranging within normal values (or = 20 mm), the aggregation characteristic time was found lower in patients than in controls (p = 0.004). There was no correlation between these rheological changes and the CD4+ T-cell count. The 17 patients receiving an antiviral therapy had lower CD4+ T-cell counts than their 5 untreated counterparts (244.7 +/- 167 vs. 410 +/- 106/mm3, p = 0.025), and a higher disaggregation shear rate (177.4 +/- 38.2 vs. 127 +/- 25.4, p = 0.01). Thus, an impairment of rheological characteristics is observed in asymptomatic HIV-I infected patients in association with changes in plasma proteins.
- Published
- 2001
15. Diffuse Laser Doppler Velocimetry from Multiple Scattering Media and Flowing Suspensions
- Author
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J. Dufaux, P. Snabre, and L. Brunel
- Subjects
Physics ,Diffusing-wave spectroscopy ,business.industry ,Velocimetry ,Laser Doppler velocimetry ,symbols.namesake ,Optics ,Particle image velocimetry ,symbols ,Heterodyne detection ,Acoustic Doppler velocimetry ,business ,Doppler effect ,Photon diffusion - Abstract
A study of the Doppler frequency spectrum (DFS) of the light multiply scattered from a random collection of moving anisotropic scatterers is presented. The analytical approach based on photon diffusion approximation and statistical models yields functional forms of DFS for random or simple shear flow consistent both with experiments in a backscatter geometry and predictions from the Diffusing Wave Spectroscopy theory (DWS). Homodyne and heterodyne detection modes are further analyzed and the potential applications of the Doppler heterodyne analysis in the field of suspension dynamics are investigated.
- Published
- 2001
16. Thrombosis of angiographic catheters in humans: experimental study
- Author
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A L, Bailly, A, Lautier, A, Laurent, G, Guiffant, J, Dufaux, E, Houdart, D, Labarre, and J J, Merland
- Subjects
Equipment Safety ,Materials Testing ,Angiography ,Humans ,Biocompatible Materials ,Thrombosis ,Risk Assessment ,Sensitivity and Specificity ,Catheterization - Abstract
One of the major problems in the use of catheters is their thrombogenicity since the embolization of clots near the central nervous system or the coronary arteries can cause permanent damage. Catheter thrombogenicity was evaluated in humans during angiographic procedures by their tendency to become occluded. Characterization of catheters was achieved using roughness measurements, FTIR with ATR, DSC and ESCA. The catheters were 5 commercially available catheters, made mainly of polyethylene, Pebax or polyamide sterilized and ready for clinical use. Thirty-one patients due to have an angiographic procedure and with normal blood and hemodynamic parameters were included in the study. The 50 cm catheter test sample was inserted through an introducer into the femoral artery at the beginning of an angiographic procedure. The outcoming blood flow rate (BFR) was continuously monitored by a special computerized device for 15 min or until the total amount of blood reached 30 ml. The angiographic procedure was then normally resumed. DSC and FTIR showed results consistent with the expected composition of catheters. ESCA results showed very high Si/C ratios and could not be explained in all instances. Occlusion of the catheters occurred in 44% of the cases and the average time to obtain occlusion was 8.5 min (3-15 min). Values of the decrease rate of BFR in ml/min2 allowed separation of the catheters into 3 groups of low, medium and high thrombogenicity. However, occlusion occurred at least one time for each type of catheter. Blood volume and BFR curves vs. time allowed the determination of 3 main types of thrombotic behavior: type I shows no significant reduction of BFR; type II shows a progressive decrease in flow rate; type III is much less frequent and shows an abrupt decrease of BFR either quickly followed by a compensatory increase and resuming of a steady flow or by abrupt occlusion. In type II curves the pattern of occlusion follows a classical diffusion model because the Peclet number is greater than 1 and then the classical Higbie solution for diffusion could be used. The most thrombogenic material was the smoothest. There was no correlation between surface chemical composition and thrombogenicity. However, catheters that were based on PE appeared less thrombogenic than PA catheters in this study.
- Published
- 1999
17. Theoretical and experimental study of intermittent blood flows in microcirculation: application to the in-vivo determination of compliance
- Author
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L. Gabet, J. Dufaux, and G. Guiffant
- Subjects
Materials science ,Deformation (mechanics) ,Non linearite ,Microcirculation ,Biomedical Engineering ,Models, Cardiovascular ,Reproducibility of Results ,Numerical Analysis, Computer-Assisted ,Mechanics ,Blood flow ,Chick Embryo ,Rats ,Compliance (physiology) ,Nonlinear system ,Nonlinear Dynamics ,Physiology (medical) ,Image Processing, Computer-Assisted ,Animals ,Rats, Inbred BB ,Rats, Wistar ,Rheology ,Simulation ,Blood Flow Velocity ,Compliance - Abstract
A new theoretical approach was used to study the nonlinear response of a microvascular segment subjected to a pressure step at one end. The method is suitable for both large and small deformations of the vessel wall in the case of an elastic response of the segment. It is shown that the use of this simulation permits an indirect determination of the compliance of the vessel. The procedure is applied in two cases of major interest: first the in-vivo study of the intermittent blood flow in the microcirculation, and second, the analysis of experiments using micropipettes. The resulting values of the compliance agree with other values found in the previous studies. The theoretical method is particularly adapted to nonlinear equations.
- Published
- 1999
18. Effects of contrast media on blood rheology: comparison in humans, pigs, and sheep
- Author
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Anne Laure Bailly, Laurence Penhouët, J. Dufaux, Michel Bonneau, Jean Jacques Merland, Alexandre Laurent, and Jean Jacques Durussel
- Subjects
Pathology ,medicine.medical_specialty ,Swine ,media_common.quotation_subject ,Iohexol ,Contrast Media ,Erythrocyte aggregation ,Animal science ,Iodinated contrast ,Rheology ,Species Specificity ,In vivo ,medicine ,Ioxaglic Acid ,Contrast (vision) ,Animals ,Humans ,Radiology, Nuclear Medicine and imaging ,Agrégation ,media_common ,Sheep ,business.industry ,Whole blood viscosity ,Blood Viscosity ,Red blood cell ,medicine.anatomical_structure ,Cardiology and Cardiovascular Medicine ,business ,Software - Abstract
To compare whole blood viscosity and erythrocyte aggregation in humans, pigs, and sheep, before and after adding water-soluble iodinated contrast medium (CM).Two CMs were studied: iopromide (nonionic) and ioxaglate (ionic). The blood-CM viscosity was measured with a Couette viscometer. Erythrocyte aggregation was measured with an erythroaggregometer.The blood-CM viscosity was increased up to +20% (relative to pure blood) with a CM concentration of 0%-10%. At CM concentrations from 10% to 50%, the viscosity decreased. The disaggregation shear stress was increased (relative to pure blood) at low CM concentration (0%-10%). When the CM concentration increased from 10% to 20%, the disaggregation shear stress was decreased, except with the pig blood-ioxaglate mixture.At low CM concentration the blood viscosity was increased in pig, sheep, and humans and the disaggregation shear stress was increased in pig and humans. The aggregation of sheep blood was too low to be detected by the erythroaggregometer. This rise can be explained by the formation of poorly deformable echinocytes. At higher CM concentration, the viscosity and the disaggregation shear stress decreased in relation to the blood dilution. We conclude that pig blood and sheep blood can both be used to study the effect of CM injection on blood viscosity. Nevertheless, the rheologic behavior of pig blood in terms of erythrocyte aggregation is closer to that of human blood than is sheep blood when mixed with CM. Pigs could thus be more suitable than sheep for in vivo studies of CM miscibility with blood during selective cannulation procedures.
- Published
- 1999
19. Effects of red blood cell hyperaggregation on the rat microcirculation blood flow
- Author
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M.F. Berthault, Gérard Guiffant, J.J. Durussel, and J. Dufaux
- Subjects
Erythrocyte Aggregation ,Male ,Physiology ,Blood viscosity ,Hemodynamics ,Hyperviscosity ,Blood Pressure ,Erythrocyte aggregation ,Microcirculation ,Injections ,Blood cell ,medicine ,Animals ,Splanchnic Circulation ,Rats, Wistar ,Muscle, Skeletal ,Chemistry ,Dextrans ,Blood flow ,Anatomy ,Blood Viscosity ,Rats ,Vasomotor System ,Red blood cell ,medicine.anatomical_structure ,Blood Circulation ,Biophysics ,Vascular Resistance ,Stress, Mechanical ,Blood Flow Velocity - Abstract
This study presents the effects of red blood cell (RBC) hyperaggregation on the blood flow and pressure in the rat mesentery and cremaster network. We exclusively studied in situ non-vasodilated organs, in order to maintain the physiological regulation mechanisms. Dextran 500 was injected at different concentrations to increase RBC aggregation. The aggregation rate was measured on very small blood samples with an erythroaggregameter (SEFAM) which evaluated the disaggregating shear stress (tau D) needed to break the RBC aggregates. Microscopic observations and laser Doppler velocimetry were used to quantify the flow rate. The plasmatic dextran concentration (C) increase had different correlated effects: for example, tau D increased from 3 dynes cm-2 (for the control sample) to 14 dynes cm-2 (for C = 75 microM L-1); the flow rate was reduced threefold and very large aggregates were observed in the venules; the arteriolar pressure increased while venular pressure decreased. In order to differentiate the effects of RBC hyperaggregation from those of plasma hyperviscosity (due to dextran 500) on microcirculatory blood flow, we injected an RBC antiaggregating drug (troxerutine) (50 or 100 mg kg-1 i.v.). The consequences were a high reduction for (tau D) (from 14 dynes cm(-2)-9 dynes cm-2), smaller aggregates and higher blood flow in the venules. No effect of troxerutine was observed on plasma viscosity (plasma control: 1.9 cP with or without troxerutine; plasma with dextran at C = 75 microM L-1: 2.45 cP with or without troxerutine). The results strongly suggest that RBC aggregation has a significant influence on blood flow rate in the microcirculatory network.
- Published
- 1998
20. Comparative viscosity and erythrocytes disaggregation shear stress of blood-radiographic contrast media mixtures in three mammalian species
- Author
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J J, Durussel, J, Dufaux, A, Laurent, L, Penhouët, A L, Bailly, M, Bonneau, and J J, Merland
- Subjects
Erythrocyte Aggregation ,Radiography ,Sheep ,Swine ,Iohexol ,Ioxaglic Acid ,Animals ,Contrast Media ,Humans ,Female ,Stress, Mechanical ,Blood Viscosity - Abstract
We compared blood viscosity and red blood cells (RBC) disaggregation shear stress in three mammalian species (humans, pigs and sheep) before and after adding water-soluble iodinated contrast media (CM): Ioxaglate (ionic CM) and Iopromide (non ionic CM). The two CMs had a diluting effect on the blood of the three species, which resulted in a viscosity decrease at all shear rates. However, viscosity rose slightly at low shear rates (in relation to increase of RBC aggregation) and low CM concentrations (10%), regardless of the ionic or non ionic nature of the CM. The two CMs had a similar proaggregant effect in human and pig's bloods. The proaggregant effect was slightly more pronounced with the ionic CM. We concluded that the pig is more suitable than the sheep for in vivo assessment of blood/CM mixture.
- Published
- 1997
21. Quantification of tumor uptake of iodized oils and emulsions of iodized oils: experimental study
- Author
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M. Ducreux, C Lagrange, Jean Lumbroso, B Aubert, X Zhang, J Ropers, J Dufaux, Ph. Rougier, Alain Roche, G Harry, and T. de Baere
- Subjects
Iodized oil ,Computed tomography ,Poppyseed oil ,Body weight ,Iodine Radioisotopes ,Animal model ,Liver Neoplasms, Experimental ,medicine ,Animals ,Radiology, Nuclear Medicine and imaging ,Lung ,Chromatography ,medicine.diagnostic_test ,business.industry ,Viscosity ,Radiation dose ,Iodized Oil ,Ethyl ester ,Radiographic Image Enhancement ,Liver ,Lipiodol ,Female ,Rabbits ,Nuclear medicine ,business ,Tomography, X-Ray Computed ,Neoplasm Transplantation ,medicine.drug - Abstract
To optimize use of iodized oil for diagnostic computed tomography (CT) enhanced with iodized oil and for interstitial radiation therapy with iodine-131-labeled iodized oil, the authors quantified the distribution of iodized oil after injection of different formulations of iodized oil into the hepatic artery.I-125-labeled iodinated ethyl ester of poppyseed oil in two viscosities (iodized oil ultrafluid [viscosity, 0.04 Pa/sec] and iodized oil fluid [viscosity, 0.17 Pa/sec]) was injected (pure forms and three different emulsions of each) into the hepatic artery of rabbits bearing VX2 tumors in the liver. All rabbits received a radiation dose of 4 MBq per kilogram of body weight in 0.1 mL/kg iodized oil. Animals were killed 4 days later, and iodized oil uptake was evaluated in the tumor, nontumorous liver, and lung.There were no statistically significant differences in uptake between pure iodized oil ultrafluid or fluid or between the same type of emulsions made with each type of iodized oil. Lung uptake was significantly higher with pure iodized oil ultrafluid and fluid (19.75 kBq/g +/- 3.25 [standard error of the mean] vs 19.48 kBq/g +/- 6.15, respectively) than with any emulsions (range, 3.72-8.14 kBq/g; mean, 5.68 kBq/g) except the small-droplet oil-in-water emulsion (10.51 kBq/g +/- 1.18). The ratio of tumor to nontumorous liver uptake of iodized oil was significantly higher with large-droplet water-in-oil emulsions made of iodized oil ultrafluid or fluid (10.26 +/- 2.88 and 9.53 +/- 0.64, respectively) than with any other product (range, 4.07-5.38; mean, 4.49).Use of large-droplet water-in-oil emulsions limited lung uptake and increased tumor uptake of iodized oil after intraarterial hepatic injection in rabbits bearing VX2 tumors in the liver.
- Published
- 1996
22. Circulatory alterations induced by intra-arterial injection of iodized oil and emulsions of iodized oil and doxorubicin: experimental study
- Author
-
M F Berthault, J Dufaux, T. de Baere, P Pappas, Alban Denys, J L Counnord, and Alain Roche
- Subjects
medicine.medical_specialty ,Iodized oil ,medicine ,Intra arterial ,Animals ,Radiology, Nuclear Medicine and imaging ,Doxorubicin ,Chemoembolization, Therapeutic ,Abdominal Muscles ,Chromatography ,business.industry ,Viscosity ,Microcirculation ,Iodized Oil ,Arteries ,Anticancer drug ,Arterial tree ,Surgery ,Rats ,Injections, Intra-Arterial ,Arterial flow ,Circulatory system ,Emulsion ,Emulsions ,Rabbits ,business ,Blood Flow Velocity ,medicine.drug - Abstract
PURPOSE: To evaluate circulatory alterations induced by intra-arterial injection of iodized oil and emulsions of iodized oil with an anticancer drug. MATERIALS AND METHODS: The viscosities and stability were evaluated in arterial flow of iodized oil and the emulsions. Doppler ultrasound was used to quantify the embolic effect in the arteries of rabbits. The behavior of doxorubicin and iodized oil in the rat cremaster muscle was studied with videomicroscopy. RESULTS: The emulsions did not break up after injection, and the size of discontinuous-phase droplets did not change. The embolic effect did not correlate with viscosity. The thinnest water-in-oil emulsion had the lowest embolic effect and induced homogeneous distribution of iodized oil droplets in the arterial tree. CONCLUSION: Changes in the formulation of emulsions obtained with the same proportions of drug and iodized oil change the distribution of iodized oil in the arterial tree, the location at which the drug is released, and the embolic effect.
- Published
- 1995
23. [In vitro evaluation of Dibie-Musset vena caval filter]
- Author
-
A, Dibie, T, Kareco, D, Musset, J, Dufaux, J L, Counord, F, Laborde, and P, Flaud
- Subjects
Vena Cava Filters ,Humans ,Thrombosis ,Blood Viscosity ,Rheology - Abstract
The Dibie-Musset (DM) vena caval filter was evaluated on a hydraulic test bench reproducing flow conditions in the inferior vena cava: pressure, flow, viscosity, diameter and elasticity of the conduit. The results were compared with those obtained with the Greenfield filter (GF). In addition to classical measurements (captation and loss of load) we measured the velocity profile with a Doppler ultrasonic probe proximal and distal to the filter to study flow conditions before and after embolisation of clots. In order to circumvent the difficulties encountered with the use of real thrombi, chemical gels with visco-elastic properties, evaluated by viscosimetry, similar to those of blood clots, were used. Clots 45 mm long and 4 mm diameter were injected in several series of measurements. The DM filter was stable and did not migrate. In the horizontal position (flexible conduit) the DM filter was significantly more effective than the GF for less than 5 clots injected successively. The filtration capacity of both filters decreased with the number of clots captured. In the vertical position (rigid conduit), when there are less than 5 clots injected the two devices were perfectly effective. There was no significant difference between the two filters when 10 clots were injected. The loss of load resulting from the presence of the filter and clots was greater with the DM filter because of the greater captation capacity. However, the velocity profile distal to the filter was less disturbed with the DM filter because there was a more uniform distribution of the clots captured over the surface of the filter.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1994
24. Red blood cell aggregation and blood viscosity in an isolated heart preparation
- Author
-
O, Charansonney, S, Mouren, J, Dufaux, M, Duvelleroy, and E, Vicaut
- Subjects
Erythrocyte Aggregation ,Male ,Dextrans ,In Vitro Techniques ,Blood Viscosity ,Coronary Vessels ,Models, Biological ,Rats ,Perfusion ,Rats, Sprague-Dawley ,Regional Blood Flow ,Animals ,Isotonic Solutions ,Rheology - Abstract
We studied the effects of moderate changes in red blood cell RBC aggregation on blood flow in the vasodilated vascular bed of an isolated rat heart. We compared a non-aggregating RBC suspension (in Krebs-albumin medium) with RBC suspensions in 1% and 2% Dextran 70 (MW 70000), exhibiting two different degrees of moderate aggregation. Degrees of aggregation were precisely estimated by in vitro laser aggregometry. Each heart was perfused by the non-aggregating RBC suspension and by one aggregating RBC suspensions. Blood flow was measured in a range of perfusion pressure from 40 to 80 mm Hg. For the three RBC suspensions, linear pressure/flow relationships were found. From the comparison between the pressure/flow relationships obtained with Krebs albumin medium and either 1% or 2% Dextran, it was possible to compare in vivo the contribution of RBC to the viscosity (i.e., the relative apparent viscosity) in the 2 aggregating RBC suspensions with that of the non-aggregating RBC suspension. The contribution of RBC to the viscosity was found to be 20% to 25% lower in the 1% RBC suspension than in the non-aggregating RBC suspension. With 2% Dextran which induced a higher degree of aggregation no differences were found between the relative apparent viscosities of the aggregating and the non-aggregating suspension. From the comparison between RBC in 1% Dextran and Krebs-albumin, we concluded that in vivo a moderate RBC aggregation reduces viscous resistance due to the presence of blood in a vascular network. Since no more effect of RBC aggregation per se was found when the degree of aggregation was higher (with RBC in 2% Dextran), this suggests that, in this case, aggregation induces opposite effects along the myocardial vascular network which cancel each other out, thus inducing a nil net balance.
- Published
- 1993
25. Thrombogenicity of angiographie catheters: Comparative and rheological study on human blood ex vivo in angiographie conditions
- Author
-
Gérard Guiffant, J. Dufaux, Jean-Jacques Merland, A. L. Bailly, and A. Laurent
- Subjects
Instantaneous flow ,Catheter ,Human blood ,Rheology ,business.industry ,Occlusion ,Thrombogenicity ,Medicine ,business ,Ex vivo ,Biomedical engineering - Abstract
We evaluated the patterns of catheter thro mbo geni ci ty by measuring the instantaneous flow of human blood in angiographie conditions on 6 different materials. We separated groups of different thrombogenicity degree. We also showed different thrombogenicity behaviours during the tubes' occlusion phenomena.
- Published
- 1992
26. [Hemo-rheology of glaucomatous neuropathy]
- Author
-
P, Hamard, H, Hamard, and J, Dufaux
- Subjects
Erythrocyte Aggregation ,Regional Blood Flow ,Animals ,Humans ,Glaucoma ,Optic Nerve ,Rabbits ,Blood Viscosity ,Blood Flow Velocity - Abstract
The vascular participation to the optic nerve pathogenesis has been contradicted. The red blood cell velocity in the optic nerve capillary with a laser Doppler velocimeter, an atraumatic and reliable method, and the aggregability was determined with an erythroaggregameter to know whether an erythrocyte hyperaggregability could slow down the optic nerve blood flow as it has been previously demonstrated in an experimental study. The experiment on the open angle glaucoma patients showed that their optic nerve blood flow was reduced, and their erythrocyte aggregability significantly increased. The two parameters were not significantly correlated, certainly because of a local papillary autoregulation and of the papilla vessels variability, those two factors could modulate the blood flow response to blood qualitative changes. The erythrocyte hyperaggregability could be explained by erythrocyte membrane modifications that could agree with the glaucoma heredity.
- Published
- 1992
27. Contrast media and microcirculation: red blood cell aggregation and deformation study
- Author
-
P. Mills, A. Othmane, Laurence Monnier, A. Laurent, J. Dufaux, and Jean-Jacques Merland
- Subjects
Red blood cell ,Contrast medium ,Iotrolan ,medicine.anatomical_structure ,Ioversol ,Chemistry ,Echinocyte ,medicine ,Biophysics ,Diatrizoate ,Iohexol ,Iopamidol ,medicine.drug - Abstract
We studied the effects of six contrast media (iohexol, ioxaglate, iopamidol, ioversol, iotrolan and diatrizoate) on red blood cell (RBC) aggregation and deformation with normal blood from a single donor. RBC aggregation was studied in an erythroaggregometer with various concentrations of contrast media or saline (0%–20%). An apparent decrease of RBC aggregation was observed with most contrast media when concentrations were increased. Similar results were observed with physiological saline, suggesting dilution interference. Thus, we observed what occurred after the dilution was corrected by adding fibrinogen: hyperaggregation was found with all agents when fibrinogen was added to the solution. RBC deformation was quantified after short contact with contrast media (20% vol/vol) by light microscopy. It depends on the nature of the contrast medium. Deformation was always reversible.
- Published
- 1991
28. [Laser-Doppler velocimetry on the optic nerve head and hemorheology. Animal experiments. First results in humans]
- Author
-
P, Hamard, J, Dufaux, H, Hamard, and A, Parent de Curzon
- Subjects
Adult ,Male ,Microcirculation ,Optic Disk ,Animals ,Humans ,Female ,Glaucoma ,Rabbits ,Middle Aged ,Rheology ,Ultrasonography - Abstract
We study capillary microcirculation on the optic nerve head and its interrelation with blood rheological modifications. The mean maximal velocity has been evaluated in the capillaries of the rabbit optic nerve with a laser doppler velocimeter, in physiological conditions and after intravenous Dextrane 250 injections. Dextrane 250 increases red blood cells aggregation and induces blood hyperviscosity at low flow rates. This hyperaggregation is determined with a reflectometric method. Experimental results show a significant reduction of blood velocity when blood viscosity increases. In our present study, we compare blood capillaries flow rate in the optic nerve, between two groups: healthy humans and subjects suffering from glaucoma. The aggregation level is simultaneously measured for the two groups. First results seem to prove that blood flow rate decrease is associated with red blood cells aggregation increase for the second group.
- Published
- 1990
29. Holographic visualization of the thermal perturbation around a hot wire in a thermally stratified medium heated from above
- Author
-
Daniel Quemada, G. Guiffant, and J. Dufaux
- Subjects
Convection ,Thermal perturbation ,Materials science ,business.industry ,General Chemical Engineering ,Holography ,Perturbation (astronomy) ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Plume ,law.invention ,Visualization ,Optics ,law ,Thermal ,Panache ,business - Abstract
We show and discuss some examples of thermal plumes generated by hot wires in a thermally stratified medium heated from above. The use of a holographic bench allows the visualization of either the thermal distribution around the wire or only the thermal perturbation brought by the wire in the thermally stratified medium.
- Published
- 1986
30. Determination of rheological properties of red blood cells by Couette viscometry
- Author
-
Daniel Quemada, J. Dufaux, and P. Mills
- Subjects
Materials science ,coaxial cylinders ,viscometers ,0206 medical engineering ,Thermodynamics ,02 engineering and technology ,cellular transport and dynamics ,Couette viscometer ,01 natural sciences ,Viscosity measurement ,red blood cell aggregation ,Viscosity ,Rheology ,blood ,0103 physical sciences ,suspensions ,Couette viscometry ,red blood cell suspensions ,Biorheology ,010304 chemical physics ,viscosity measurement ,Viscometer ,pathological cases ,020601 biomedical engineering ,biorheology ,Red blood cell aggregation ,rheological properties ,[PHYS.HIST]Physics [physics]/Physics archives ,viscosity ,red blood cell deformation state ,Coaxial cylinder - Abstract
The use of a Couette viscometer with coaxial cylinders enables us to measure the viscosity of red blood cell suspensions, the shear rate varying from 0.017 5 s-1 to 128 s-1. Red blood cells aggregation and deformation states are obtained by fitting a rheological relation on experimental results. Different types of suspensions are studied. An application to pathological cases is proposed.
- Published
- 1980
31. Etude de la cinétique d'agrégation érythrocytaire dans un écoulement de Couette
- Author
-
P. Mills, J. Dufaux, and Daniel Quemada
- Subjects
0303 health sciences ,haemodynamics ,Chemistry ,laser light backscattering ,030204 cardiovascular system & hematology ,light scattering ,rouleaux size ,blood suspension aggregation ,orientation ,03 medical and health sciences ,0302 clinical medicine ,[PHYS.HIST]Physics [physics]/Physics archives ,transmitted light ,suspensions ,backscattered light ,Couette flow ,mean shear rate ,030304 developmental biology - Abstract
Etude de la cinétique d'agrégation érythrocytaire dans un écoulement de Couette. Une théorie de la lumière transmise et rétrodiffusée par une suspension sanguine a été étudiée en tenant compte de l'agrégation et de l'orientation des particules dans un écoulement de Couette. Les résultats théoriques permettent d'interpréter quantitativement les mesures expérimentales de la lumière laser rétrodiffusée par une suspension sanguine dans un écoulement de Couette. On propose une relation entre la taille des rouleaux et le taux de cisaillement moyen.
- Published
- 1980
32. The use of the Walsh functions for the study of periodic diffusive phenomena in a multilayer medium
- Author
-
J. Dufaux, A. Arhaliass, and Gérard Guiffant
- Subjects
Fluid Flow and Transfer Processes ,Materials science ,Mechanical Engineering ,Walsh function ,Mathematical analysis ,Thermodynamics ,Condensed Matter Physics ,Thermal diffusivity ,Thermal conduction - Published
- 1988
33. [Characteristic rheograms of pathological bloods. Application to dynamic pharmacology (author's transl)]
- Author
-
J, Dufaux, D, Quemada, P, Mills, and M, Lambert
- Subjects
Aspirin ,Lysine ,Humans ,Female ,Raynaud Disease ,Plethysmography, Impedance ,Blood Viscosity ,Aged - Abstract
The viscosity of normal and pathological blood samples is determined using a Couette viscometer (5.10-2s-1 less than or equal to shear rate less than to equal to 125 s-1). In different pathological cases, the rheograms show an abnormal behaviour. The viscosity curves exhibits a break between 0.1 and 1 s-1. This work shows the results obtained in the case of a patient suffering from Raynaud's disease. During therapy with lysine acetylsalycilate one observed the gradual shift of the breack to low shaer values, then, the return to a normal rheogram. In the same time, acroyanosis has completely disappeared, recovering normal nail growth.
- Published
- 1980
34. [Flow rate and concentration profiles in a suspension flowing in a narrow channel]
- Author
-
D, Quemada, J, Dufaux, and J J, Delgove
- Subjects
Hematocrit ,Animals ,Cattle ,Doppler Effect ,In Vitro Techniques ,Rheology ,Blood Flow Velocity - Published
- 1976
35. The Influence of the Internal Viscosity of Washed Red Blood Cells on Their Rheological Behaviour
- Author
-
P. Mills, R. Glaser, D. Lerche, J. Dufaux, and Daniel Quemada
- Subjects
Shear (sheet metal) ,Shear rate ,Chemical engineering ,Rheology ,Chemistry ,Ionic strength ,Relative viscosity ,Osmotic pressure ,Viscometer ,Hemoglobin - Abstract
The rheological characterization of washed RBC suspensions has been performed both using a low shear viscosimeter and a optical light back scattering system. Changing the volume of the cells and in such a way the hemoglobin concentration in the cells and/or the structure of the cell membrane by treatments with the antibiotic Amphotericin B and different pH, osmotic pressure or ionic strengths of the medium it was found that the rheological behaviour (relative viscosity in dependence on the shear rate,.02 s−1 – 128 s−1; intrinsic viscosities and the relaxation time corresponding to the orientation and desorientation) seems to be mainly connected with the change of the internal hemoglobin concentration.
- Published
- 1980
36. [Velocity profile measurements by Laser-Doppler velocimetry (LDV) in plane capillaries in high concentrated medium. Application to human blood (author's transl)]
- Author
-
J, Dufaux, P, Mills, and D, Quemada
- Subjects
Hematocrit ,Lasers ,Humans ,Blood Pressure ,Doppler Effect ,Models, Biological ,Blood Flow Velocity ,Capillaries - Abstract
A Laser Doppler velocimeter (LDV) was modified in order to reduce the dimensions of the crossing section of the two light beams. This LDV has been used on plane capillary tubes (100 mu m less than or equal to inside thickness less than or equal to 400 mu m) in which different sorts of suspensions were flowing. The flow rate Q, and pressure, delta p, measurements were recorded simultaneously. The velocity profile measurements were done. We have verified that the velocity profile blunting depended on hematocrit, flow rate. Such profiles were in good agreement with theoretical ones obtained with a model where aggregation and deformation levels were described by characteristic coefficients involved in a viscosity equation.
- Published
- 1981
37. [Maximum rate of sedimentation of a suspension placed in a viscosimeter with coaxial cylinders. Application to a number of pathological blood samples (author's transl)]
- Author
-
P, Mills, D, Quemada, J, Dufaux, and M, Lambert
- Subjects
Humans ,Blood Sedimentation ,Blood Viscosity ,Liver Diseases, Alcoholic - Abstract
Erythrocyte sedimentation of normal and pathological human bloods at varying controlled shear rates has been measured. Erythrocyte sedimentation rate (ESR) was found to reach a maximum at a characteristic shear rate gamma c [gamma c less than .1 s-1 for normal bloods; gamma c greater than .1 s-1 for pathological bloods]. Records of viscosity versus shear rate exhibit a break near gamma c. Examples show that ESR is well correlated with viscometric data.
- Published
- 1980
38. [Characteristic transient times measured by backscattered laser light in blood suspension flow (author's transl)]
- Author
-
P, Mills, D, Quemada, and J, Dufaux
- Subjects
Erythrocyte Aggregation ,Kinetics ,Time Factors ,Suspensions ,Lasers ,Humans ,Scattering, Radiation ,Blood Viscosity ,Rheology ,Blood Flow Velocity - Abstract
An optical method is proposed for studying rouleaux formation and red blood cells (RBC) orientation. Both relations, first between m, the mean number of RBCs per rouleau and reflectivity, and second between the oriented RBCs fraction and the variation of the isotropic reflectivity are proposed. Our experimental data about aggregation relaxation time and orientation relaxation time are discussed and compared to viscometric results.
- Published
- 1981
39. An Optical Method for Studying Red Blood Cells Orientation and Aggregation in a Couette Flow of Blood Suspension
- Author
-
J. Dufaux, P. Mills, and Daniel Quemada
- Subjects
Stress (mechanics) ,Shear rate ,Rouleaux ,Materials science ,Steady state ,Flow (psychology) ,Biophysics ,Couette flow ,Non-Newtonian fluid ,Suspension (chemistry) - Abstract
Red blood cell aggregation is certainly the most important factor in the non newtonian behaviour of normal human blood. Aggregated red blood cells build up rouleaux; this aggregation is reversible: at rest, the rouleaux form a three dimensional network structure; when a finite stress is applied to the suspension the structure breaks. Increasing the stress, the rouleaux are gradually disrupted and are finally reduced up to individual cells. With decrease in stress individual cells build up again rouleaux. In a steady state a dynamical equilibrium exists between the size of rouleaux and the stress applied. When the applied stress is high enough to break the rouleaux, cells can be oriented and deformed in the flow. There was studied an experimental method which allows us to rely the luminous flux backscattered by rouleaux and individual cells to their mean size and to their orientation.
- Published
- 1980
40. Measurement of erythrocyte orientation in flow by spin labeling III--erythrocyte orientation and rheological conditions
- Author
-
F. Leterrier, J. Dufaux, M. Bitbol, and Daniel Quemada
- Subjects
Erythrocyte Aggregation ,Erythrocytes ,Physiology ,Chemistry ,Blood viscosity ,Thermodynamics ,Site-directed spin labeling ,Erythrocyte Aging ,Blood Viscosity ,Erythrocyte aggregation ,Biomechanical Phenomena ,Shear rate ,Viscosity ,Nuclear magnetic resonance ,Rheology ,Hematocrit ,Physiology (medical) ,Phenomenological model ,Erythrocyte deformability ,Humans ,Spin Labels - Abstract
The measurements of erythrocyte orientation, obtained through a spin labeling technique, are compared with a phenomenological model. Several rheological conditions are varied: hematocrit, suspending medium viscosity, blood age, artificial reversible aggregation. We found that the onset of orientation is very sensitive to any variation of these conditions, and that its measurement would be a good method to assess erythrocyte deformability. A critical shear rate for the orientation process is then determined and compared to the corresponding parameter obtained from viscosity measurements of identical suspensions. A close qualitative relationship is found between the two sets of values of the critical shear rate.
- Published
- 1985
41. [Toxicologic control of cosmetics]
- Author
-
B, Beys, J, Dufaux, F, Prohoroff, and M, Millet
- Subjects
Time Factors ,Carcinogens ,Methods ,Animals ,Humans ,Cosmetics ,Photosensitivity Disorders ,Eye ,Hair ,Mutagens ,Skin - Published
- 1975
42. [Chronic fluorine poisoning. Presentation of a case with renal insufficiency]
- Author
-
J, MAES, J, DUFAUX, and J, VANDENBRO UCKE
- Subjects
Fluorides ,Drug-Related Side Effects and Adverse Reactions ,Chronic Disease ,Humans ,Fluorine ,Renal Insufficiency ,Acute Kidney Injury ,Aged - Published
- 1960
43. [Problems encountered in sonometry in the SNGB]
- Author
-
J, Dufaux and N, Nordvik
- Subjects
Occupational Diseases ,Audiometry ,Belgium ,Hearing Loss, Noise-Induced ,Humans ,Hearing Disorders ,Railroads - Published
- 1971
44. Description and validation of a new, simple, easy-to handle, point-of-care technique for measuring erythrocyte aggregation kinetics.
- Author
-
Charansonney OL, Morel P, Dufaux J, and Vicaut E
- Subjects
- Blood Viscosity, Erythrocytes, Humans, Kinetics, Erythrocyte Aggregation, Point-of-Care Systems
- Abstract
Erythrocyte aggregation (EA) is a physiological process by which erythrocytes reversibly stick together within the blood vessels. EA plays a major role in blood viscosity in vivo, thereby impacting blood flow to organs. EA is no doubt greatly important in both physiological and pathophysiological conditions, but the studies its importance calls for are complicated by the lack of a reliable and easy way to measure it. We have developed a new point-of-care technique which can very specifically measure EA initial kinetics (EAK) in 20 s directly on blood samples routinely collected in tubes commonly used in clinical settings. We present the results of the validation studies of this EAK test: A mono-exponential curve explains 99% of EAK variance. EAK is normally distributed in healthy individuals, with an interindividual 15% coefficient of variation and is stable for least one hour after blood collection. Intraindividual coefficient of variation is 2.6%. EA can now be easily measured in any clinical setting., (© 2022. The Author(s).)
- Published
- 2022
- Full Text
- View/download PDF
45. Determination of lipase catalytic activity in two reference materials: BCR 693 and BCR 694 by titrimetry at constant pH.
- Author
-
Lessinger JM, Parashou S, Arzoglou P, Ramos P, Chapus C, Dufaux J, Junge W, Profilis C, and Férard G
- Subjects
- Animals, Catalysis, Humans, Hydrogen-Ion Concentration, Lipase isolation & purification, Pancreas enzymology, Swine, Titrimetry, Triolein, Lipase metabolism
- Abstract
Because routine assays for pancreatic lipase catalytic activity are not yet standardized, between-method comparability is very poor. This is mainly due to the lack of reference materials (RMs). The aim of this study was to assign values of catalytic concentration to two human pancreatic lipase RMs, one prepared from human pancreatic juice (BCR 693), the other obtained by recombinant technology (BCR 694). Lipase catalytic activity was assayed in five experienced laboratories, using aliquots from the same lot of triolein emulsion and a standardized titrimetric procedure, optimized with regard to substrate, cofactors and pH. The accepted sets of data (n = 4) gave a mean +/- the corresponding uncertainty expressed as the 0.95 confidence interval of 1732 +/- 72 U/l and 1043 +/- 60 U/l for BCR 693 and 694, respectively. Transferability of the whole operating procedure proved to be quite satisfactory. The authors conclude that both RMs can be used to verify the correct implementation of the standardized measurement procedure and to assign values to secondary lipase materials (commercial calibrators, control products) which, in turn, ensures traceability to the standardized procedure in this study, and contributes to the harmonization of laboratory results according to the Directive for in vitro Diagnostic Medical Devices.
- Published
- 2004
- Full Text
- View/download PDF
46. Reduced reactive hyperemia in HIV-infected patients.
- Author
-
Monsuez JJ, Dufaux J, Vittecoq D, and Vicaut E
- Subjects
- Acetylcholine pharmacology, Adult, Female, HIV Infections physiopathology, Humans, Hyperemia etiology, Hyperlipidemias complications, Ischemia physiopathology, Laser-Doppler Flowmetry methods, Male, Middle Aged, Myocardial Infarction complications, Nitroglycerin pharmacology, Vasodilation drug effects, Vasodilator Agents pharmacology, Ventricular Dysfunction, Left complications, HIV Infections complications, Hyperemia physiopathology
- Abstract
Background: Given that several pathology-based studies reported some degree of coronary and arterial vasculopathy in HIV-infected patients, we investigated whether abnormal vascular reactivity may also be found in these patients., Methods: Vascular reactivity was assessed noninvasively using finger-skin blood-flow monitoring by laser-Doppler flow measurement in 10 HIV-infected-patients (mean CD4 T-cell count, 350+/-84 cells/mm3) with cardiac symptoms (previous myocardial infarction or left-ventricular dysfunction) and/or HIV-related protease inhibitor-induced hyperlipemia (group 1, symptomatic), 19 HIV-infected patients free of cardiac disease, hyperlipemia, and previous opportunistic infections (mean CD4 T-cell count, 333+/-175 cells/mm3; group 2, asymptomatic), and 19 healthy control subjects (group 3). Laser-Doppler flow was measured at baseline, during postocclusive hyperemic response following transient interruption of brachial blood flow (reactive hyperemia), during transcutaneous delivery of acetylcholine (Ach) using iontophoresis (endothelium-dependent dilation) and after sublingual nitroglycerin administration (endothelium-independent dilation)., Results: During reactive hyperemia, the absolute increase in flow was found to be lower in asymptomatic HIV-infected patients than in controls (median values [25th-75th percentile]: asymptomatic: 300 [200-400]; versus controls: 600 [400-750] arbitrary units [AU]; p< or =.0001). This abnormality was more pronounced in symptomatic patients (100 [100-200]; p< or =.0001). There was also a reduced peak/baseline flow ratio (symptomatic: 1.14 [1.1-1.2]; asymptomatic: 1.40 [1.25-1.5]; versus controls: 1.83 [1.6-2.2]; p<.0001 for both comparisons) and a reduced hyperemic response, as assessed by the curve of area under the flow versus time from deflation to the end of the hyperemic response (symptomatic: 1850 [1100-2225]; asymptomatic: 6000 [2850-7950]; versus controls: 23,735 [16,000-31, 800] AU x sec; p<.0001 for both comparisons). Although there was no statistically significant difference in acetylcholine (Ach)-induced increases in flow between asymptomatic HIV patients and controls (peak/baseline flow ratio: 6 [4.4-10] versus 5.3 [4-8]; p =.47), a trend to lower values was seen in symptomatic patients (4.4 [1.2-5]; p =.06). Administration of 0.4 mg sublingual nitroglycerin resulted in increases in flow without statistically significant difference between patients and controls: peak/baseline flow ratio for symptomatic: 2.4 [1.9-2.7]; asymptomatic: 2.1 [1.75-2.34] versus controls: 1.97 [1.8-2.4]; p =.2 and.83, respectively)., Conclusions: Postischemic reactive hyperemia is reduced in HIV-infected patients. In addition, there was is trend for a reduced response to Ach only in those with cardiac disease and/or hyperlipemia.
- Published
- 2000
- Full Text
- View/download PDF
47. Hemorheology in asymptomatic HIV-infected patients.
- Author
-
Monsuez JJ, Dufaux J, Vittecoq D, Flaud P, and Vicaut E
- Subjects
- Adult, Anti-HIV Agents pharmacology, Anti-HIV Agents therapeutic use, Blood Sedimentation drug effects, Case-Control Studies, Erythrocyte Aggregation drug effects, Female, HIV Infections drug therapy, Humans, Kinetics, Linear Models, Male, Middle Aged, Risk Factors, Stress, Mechanical, HIV Infections blood, Hemorheology drug effects
- Abstract
Although cardiac and vascular complications have been recognized among patients infected with the Human Immunodeficiency Virus-1 (HIV-1), their vascular biology and rheology have not been studied. Rheology of red blood cells (RBC) was assessed with an erythroaggregometer in 22 HIV-1 infected asymptomatic patients (pts) and 17 healthy HIV negative controls (C). All participants were normotensive, nondiabetics, had normal lipid levels and had an hematocrit ranging from 37 to 44% and hemoglobin levels > or = 12 g/100 ml. Patients had a shorter RBC aggregation characteristic time than controls (1.49 +/- 0.17 vs. 2.04 +/- 0.41 s, p = 0.001) and an increased disaggregation shear rate (166 +/- 34.9 vs. 122 +/- 25.4 s(-1), p = 0.001). This hyperaggregation tendancy was associated with increased gamma-globulin (18.3 +/- 3.3 vs. 13.7 +/- 1.9 g/l, p = 0.01) and fibrinogen (3.52 +/- 0.57 vs 3.03 +/- 0.48 g/l, p = 0.003) levels and with an increased erythrocyte sedimentation rate (ESR) (25 +/- 14.3 vs. 12.3 +/- 7.5 mm, p = 0.02). Even in patients with ESRs ranging within normal values (< or = 20 mm), the aggregation characteristic time was found lower in patients than in controls (p = 0.004). There was no correlation between these rheological changes and the CD4+ T-cell count. The 17 patients receiving an antiviral therapy had lower CD4+ T-cell counts than their 5 untreated counterparts (244.7 +/- 167 vs. 410 +/- 106/mm3, p = 0.025), and a higher disaggregation shear rate (177.4 +/- 38.2 vs. 127 +/- 25.4, p = 0.01). Thus, an impairment of rheological characteristics is observed in asymptomatic HIV-I infected patients in association with changes in plasma proteins.
- Published
- 2000
48. Thrombosis of angiographic catheters in humans: experimental study.
- Author
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Bailly AL, Lautier A, Laurent A, Guiffant G, Dufaux J, Houdart E, Labarre D, and Merland JJ
- Subjects
- Biocompatible Materials standards, Catheterization instrumentation, Equipment Safety, Humans, Materials Testing, Risk Assessment, Sensitivity and Specificity, Angiography instrumentation, Biocompatible Materials adverse effects, Catheterization adverse effects, Thrombosis etiology
- Abstract
One of the major problems in the use of catheters is their thrombogenicity since the embolization of clots near the central nervous system or the coronary arteries can cause permanent damage. Catheter thrombogenicity was evaluated in humans during angiographic procedures by their tendency to become occluded. Characterization of catheters was achieved using roughness measurements, FTIR with ATR, DSC and ESCA. The catheters were 5 commercially available catheters, made mainly of polyethylene, Pebax or polyamide sterilized and ready for clinical use. Thirty-one patients due to have an angiographic procedure and with normal blood and hemodynamic parameters were included in the study. The 50 cm catheter test sample was inserted through an introducer into the femoral artery at the beginning of an angiographic procedure. The outcoming blood flow rate (BFR) was continuously monitored by a special computerized device for 15 min or until the total amount of blood reached 30 ml. The angiographic procedure was then normally resumed. DSC and FTIR showed results consistent with the expected composition of catheters. ESCA results showed very high Si/C ratios and could not be explained in all instances. Occlusion of the catheters occurred in 44% of the cases and the average time to obtain occlusion was 8.5 min (3-15 min). Values of the decrease rate of BFR in ml/min2 allowed separation of the catheters into 3 groups of low, medium and high thrombogenicity. However, occlusion occurred at least one time for each type of catheter. Blood volume and BFR curves vs. time allowed the determination of 3 main types of thrombotic behavior: type I shows no significant reduction of BFR; type II shows a progressive decrease in flow rate; type III is much less frequent and shows an abrupt decrease of BFR either quickly followed by a compensatory increase and resuming of a steady flow or by abrupt occlusion. In type II curves the pattern of occlusion follows a classical diffusion model because the Peclet number is greater than 1 and then the classical Higbie solution for diffusion could be used. The most thrombogenic material was the smoothest. There was no correlation between surface chemical composition and thrombogenicity. However, catheters that were based on PE appeared less thrombogenic than PA catheters in this study.
- Published
- 1999
49. Effects of contrast media on blood rheology: comparison in humans, pigs, and sheep.
- Author
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Laurent A, Durussel JJ, Dufaux J, Penhouët L, Bailly AL, Bonneau M, and Merland JJ
- Subjects
- Animals, Humans, Iohexol pharmacology, Rheology, Sheep, Software, Species Specificity, Swine, Blood Viscosity drug effects, Contrast Media pharmacology, Iohexol analogs & derivatives, Ioxaglic Acid pharmacology
- Abstract
Purpose: To compare whole blood viscosity and erythrocyte aggregation in humans, pigs, and sheep, before and after adding water-soluble iodinated contrast medium (CM)., Methods: Two CMs were studied: iopromide (nonionic) and ioxaglate (ionic). The blood-CM viscosity was measured with a Couette viscometer. Erythrocyte aggregation was measured with an erythroaggregometer., Results: The blood-CM viscosity was increased up to +20% (relative to pure blood) with a CM concentration of 0%-10%. At CM concentrations from 10% to 50%, the viscosity decreased. The disaggregation shear stress was increased (relative to pure blood) at low CM concentration (0%-10%). When the CM concentration increased from 10% to 20%, the disaggregation shear stress was decreased, except with the pig blood-ioxaglate mixture., Conclusion: At low CM concentration the blood viscosity was increased in pig, sheep, and humans and the disaggregation shear stress was increased in pig and humans. The aggregation of sheep blood was too low to be detected by the erythroaggregometer. This rise can be explained by the formation of poorly deformable echinocytes. At higher CM concentration, the viscosity and the disaggregation shear stress decreased in relation to the blood dilution. We conclude that pig blood and sheep blood can both be used to study the effect of CM injection on blood viscosity. Nevertheless, the rheologic behavior of pig blood in terms of erythrocyte aggregation is closer to that of human blood than is sheep blood when mixed with CM. Pigs could thus be more suitable than sheep for in vivo studies of CM miscibility with blood during selective cannulation procedures.
- Published
- 1999
- Full Text
- View/download PDF
50. Theoretical and experimental study of intermittent blood flows in microcirculation: application to the in-vivo determination of compliance.
- Author
-
Guiffant G, Gabet L, and Dufaux J
- Subjects
- Animals, Chick Embryo, Compliance, Image Processing, Computer-Assisted, Numerical Analysis, Computer-Assisted, Rats, Rats, Inbred BB, Rats, Wistar, Reproducibility of Results, Blood Flow Velocity physiology, Microcirculation physiology, Models, Cardiovascular, Nonlinear Dynamics, Rheology
- Abstract
A new theoretical approach was used to study the nonlinear response of a microvascular segment subjected to a pressure step at one end. The method is suitable for both large and small deformations of the vessel wall in the case of an elastic response of the segment. It is shown that the use of this simulation permits an indirect determination of the compliance of the vessel. The procedure is applied in two cases of major interest: first the in-vivo study of the intermittent blood flow in the microcirculation, and second, the analysis of experiments using micropipettes. The resulting values of the compliance agree with other values found in the previous studies. The theoretical method is particularly adapted to nonlinear equations.
- Published
- 1998
- Full Text
- View/download PDF
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