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Biomedical subjects

A Maurel

Publications and source records attributed to A Maurel.

At least 19 recordsLinked to original sources
PubMed2004

A nonuniformly stretched vortex.

A stretched vortex model is proposed which includes a nonuniform stretching in the radial direction that is clearly present in real flows, as well as a slow variation of velocity profiles along the vortex axis. Both features of this boundary layer approximation depart from the classical Burgers solution. This model is shown to be in very good agreement with experimental velocity measurements.

Journal Article↗
PubMed2001

Scattering of sound by a vorticity filament: an experimental and numerical investigation.

A vorticity filament is investigated experimentally using the transmission of an ultrasonic wave through the flow. The analysis of the wave-front distortion provides noninvasive measurements of the vortex circulation and size. The latter is estimated by analytical calculations of the scattering of a plane wave by a vorticity filament. The case of a cylindrical wave incident on a vortex leads to similar experimental results which are successfully compared to a parabolic equation simulation. Finally, a finite-difference code based on linear acoustics is presented, in order to investigate the structure of the scattered wave numerically.

Journal Article↗
PubMed2001

Irregular scattering of acoustic rays by vortices.

The scattering of high-frequency sound wave, under geometrical acoustic approximation, by three stationary vortices in two dimensions is investigated. For a sufficiently high Mach number of the vortex flow, the scattering of sound rays becomes irregular, displaying a new example of chaotic scattering for a time-reversal breaking system. The fractal dimension, as well as the unstable and stable manifolds of the scattering dynamics, is presented.

Journal Article↗
PubMed2001

Determination of Lamb mode eigenvalues.

An original method is presented to determine the complex Lamb wave spectrum by using a numerical spectral method applied to the elasticity equations. This method presents the advantage to directly determine complex wave numbers for a given frequency via a classical matricial eigenvalue problem, and allows the wave numbers to be determined at relatively high frequencies (i.e., corresponding to many propagating modes). It does not need initial guess values for the wave numbers, contrary to the usual method of root finding of the Rayleigh-Lamb frequency equations (dispersion relation) in the complex plane. Results are presented and the method is discussed.

Journal Article↗
PubMed2001

[Preoperative prognostic factors for squamous cell carcinomas of the thoracic esophagus].

AIM OF THE STUDY: To identify preoperative survival prognostic factors in patients with resectable squamous cell carcinoma of the thoracic esophagus. POPULATION: From January 1982 to September 1999, 868 patients underwent surgery for esophageal carcinoma in our department, including 493 for squamous cell carcinoma of the thoracic esophagus. The following parameters were retrospectively included in univariate and multivariate analysis: age, sex, undernutrition, dysphagia, tumor diameter and nodal involvement on the CT-scan, preoperative treatment, surgical technique, curative resection, pTNM classification, histologic type and postoperative complications. The actuarial survival was determined. RESULTS: Survival prognostic factors were dysphagia, nodal involvement on CT-scan and depth of tumor invasion at pathological examination. Three groups of patients were identified on the two preoperative variables: group 1: patients without dysphagia (n=102), group 2: patients with dysphagia but without nodal involvement on the CT- scan (n=244), group 3: patients with dysphagia and with nodal involvement on the CT- scan (n=147). The median survivals were 62.4, 19.1 and 14.4 months in groups 1, 2 and 3, respectively, and 5-year actuarial survivals were 50%, 21% and 11% (P<0.009). CONCLUSION: Our study confirms that dysphagia and nodal involvement on the CT-scan are simple preoperative prognostic factors in patients with resectable squamous cell carcinoma of the thoracic esophagus.

Aged↗
PubMed1998

A placebo-controlled study of the effects of intravenous Buflomedil on foot skin microcirculation in patients with severe intermittent claudication.

Buflomedil hydrochloride (Buflomedil), a vasoactive drug, has been proven to improve pain-free walking distance in patients with peripheral arterial occlusive disease stage II of the lower extremities. In the present double-blind, randomized study, resting skin flux motion activity and skin flux response to a local heat stress at the hallux were assessed by laser Doppler fluxmetry (LDF) in claudicants. Twenty of 39 enrolled patients with severe intermittent claudication received a daily intravenous dose of 400 mg Buflomedil, and the other 19 patients received 0.9% NaCl as placebo over a 5-day period. Before treatment mean LDF skin resting flux, flux frequency, and flux amplitude were 2 +/- 0.8 Arbitrary Units (AU), 8.4 +/- 0.5 cycles per minute (c/min), and 0.12 +/- 0.01 AU, respectively in the Buflomedil group, and 2.3 +/- 0.3 AU, 8.7 +/- 0.7 c/min, and 0.13 +/- 0.02 AU in the placebo group (NS). Also the response to heat stress was identical in both groups: a slow initial increase of skin flux, followed by a reflex reduction, with a maximal initial flux increase to 138 +/- 12% of the resting value in the Buflomedil group, and 155 +/- 16% in the placebo group (NS). After 5 days of treatment the mean LDF skin resting flux, flux frequency, and flux amplitude were unchanged in both patient groups. The response to heating on the contrary was dramatically enhanced in the Buflomedil group (226 +/- 33%), against that in the placebo group, which remained unchanged (144 +/- 13%) after 3 minutes (P < 0.05), while after reflex reduction the flux in the Buflomedil group remained stable at 200% of resting value during further heating and was only approximately 140% in the placebo group (P < 0.05). It is concluded that Buflomedil, administered in a daily intravenous dose of 400 mg, does not alter the mean LDF skin flux and flux motion at the hallux in claudicants in resting conditions. Local skin heating on the contrary provokes a significant LDF-monitored skin flux increase, suggesting an improved capacity of cutaneous microvessel perfusion in stressed conditions.

Aged↗
PubMed1997

The pathophysiological mechanism of fluid retention in advanced cancer patients treated with docetaxel, but not receiving corticosteroid comedication.

AIMS: Fluid retention is a phenomenon associated with taxoids. The principal objective of this study was to investigate the pathophysiological mechanism of docetaxel-induced fluid retention in advanced cancer patients. METHODS: Docetaxel was administered as a 1 h intravenous infusion every 3 weeks, for at least 4-6 consecutive cycles, to patients with advanced breast (n = 21) or ovarian (n = 3) carcinoma, who had received previous chemotherapy, 21 for advanced disease. Phase II clinical trials have shown that 5 day corticosteroid comedication, starting 1 day before docetaxel infusion, significantly reduces the incidence and severity of fluid retention. This prophylactic corticosteroid regimen is currently recommended for patients receiving docetaxel but was not permitted in this study because of its possible interference with the underlying pathophysiology of the fluid retention. RESULTS: Fluid retention occurred in 21 of the 24 patients but was mainly mild to moderate, with only five patients experiencing severe fluid retention. Eighteen patients received symptomatic flavonoid treatment, commonly prescribed after the last cycle. Specific investigations for fluid retention confirmed a relationship between cumulative docetaxel dose and development of fluid retention. Capillary filtration test analysis showed a two-step process for fluid retention generation, with progressive congestion of the interstitial space by proteins and water starting between the second and the fourth cycle, followed by insufficient lymphatic drainage. CONCLUSIONS: A vascular protector such as micronized diosmine hesperidine with recommended corticosteroid premedication and benzopyrones may be useful in preventing and treating docetaxel-induced fluid retention.

Adenocarcinoma↗
PubMed1997

[Obstacles to stopping smoking among patients with vascular risk].

Despite the risk, smoking has only slightly decreased and the percentage of heavy smokers increases. The reason for the paradoxical situation has now been identified in more than 95% of the cases and is due to behaviour amplified by a pharmacological dependence on nicotine. The psycho-active effects of nicotine binding to nicotine receptors in the brain, produce a quasi constant physical dependence and a psychic dependence in certain smokers.

France↗
PubMed1997

[Effect of smoking on blood rheology].

The aim of this study was to compare the effects of cigarette smoking on biologic and rheologic tests, chiefly on the red blood cells (RBC) in measuring the deformability by the Cell Transit Analyser (CTA) and their aggregation by using an ultrasonic interferometry method based on A-mode echography allowed for the measurement of the accumulation rate of particles in a solid plate which is related to their sedimentation rate (Echo-Cell). Nine male smoker subjects with a high nicotine addiction measured by Fagerström questionnaire (> 8) and level of carbon monoxide (CM) in the breathed out air (> 20 ppm), have been compared with ten healthy no-smoker volunteers (CM < 3 ppm). One smoker has been eliminated of statistic evaluations because his glucose level showed a diabetes (10.5 mmol/l). A nailfold capillaroscopy performed in all subjects has eliminated the patterns of latent vasculitis or scleroderma. RBC and platelets counts, hemoglobin, ionogram, gamma GT, ASAT, ALAT, uric acid, total cholesterol and glucose levels were not significantly different between the two groups. On the other hand, in the smoker group, white blood cells count, serum triglycerides and especially fibrinogen values were higher than in the non-smoker's group. RBC sedimentation rate was normal in the two groups but was higher in smoker's group too. Without consumption of alcohol, the mean RBC volume was more important in smokers (91.9 +/- 1.2 versus 87.5 +/- 0.4, p = 0.003). Rheologic tests were more pathologic in smokers. The transit time or RBC by CTA was longer than in control group (1.6 ms +/- 0.02 versus 1.2 +/- 0.05, p = 0.0003). Echo-Cell technic showed a number and size of RBC aggregates more important with a rate of speed of accumulation higher than in the control group. These results demonstrated the toxic effects of smoking alone on blood toward a propensity for thrombotic status.

Adult↗
PubMed1996

Effect of buflomedil on the neutrophil-endothelial cell interaction under inflammatory and hypoxia conditions.

In hypoxia/ischaemia and ischaemia/reperfusion, human neutrophils are likely to play an important role in the development of endothelial cell damage in the microcirculation. Buflomedil hypochloride improves the capillary perfusion in such related situations, evoking a possible effect upon neutrophils. Using in vitro models of cell adhesion, buflomedil decreased 100% of histamine related neutrophil adhesion (flow system) and partially inhibited adhesion after IL-1-4 hours (flow and stable systems). Hypoxia induced neutrophil adhesion (4 hours) was also reduced by buflomedil, which decreased the expression of P-selectin at the surface of endothelial cells. As adenosine (NECA) exhibited the same results in hypoxia and theophylline inhibited them, such results support an action of buflomedil presumably via the A2 receptor.

Adenosine↗
PubMed1996

Dialysis clearance of buflomedil in hemodialysed patients.

Buflomedil (CAS 55837-25-7, Fonzylane) is a peripherally vasoactive drug which improves nutritional blood flow in ischaemic tissue of patients with peripheral vascular disease by the way of an increase of perfusion in the microcirculation. Ten hemodialysed patients with chronic renal failure treated with intravenous infusion of 400 mg of buflomedil during 4 h of dialysis were included in the first study. This study was carried out to determine the dialysis plasma clearance and the amount of drug dialysed during the first intravenous administration of buflomedil. The dialysis clearance calculated from the amount recovered in dialysate was (mean +/- SD) 25.4 +/- 25.6 ml/min. The drug recovery resulting from hemodialysis represented a small fraction of the dose (< or = 5%). A second study was carried out to determine the accumulation of buflomedil in chronic hemodialysed patient. The drug concentration were measured before and at the end (4 h) of the infusion of buflomedil in six other patients maintained on intermittent hemodialysis (3 per week) for 4 weeks. The average Cmin and Cmax were stable during the 12 successive dialyses (mean +/- SD intervals were between 0.36 +/- 0.53 and 0.66 +/- 0.79 microgram/ml for Cmin and between 5.15 +/- 2.19 and 7.37 +/- 1.76 micrograms/ml for Cmax), showing no trend of accumulation of buflomedil. These results agree with the pharmacokinetics of the drug which is mainly metabolised in the liver and has a low renal clearance. Dialysis is unable to modify significantly the plasma concentration of the drug in regularly dialysed patients.

Aged↗
PubMed1995

[Action of Buflomedil on the cutaneous microcirculation studies by a cold provocation test. Multicenter, double-blind, placebo controlled trial].

The aim of this multicentre trial involving 136 cardiologists was to evaluate, in double-blind versus placebo design, the vasoactive effect of Buflomedil in out-patients with a very simple cooling-test from a practical standpoint and previously described (1). The authors have selected patients having a basal pulpar temperature below 30 degrees C by cutaneous thermometer and falling after immersion of the contralateral hand in water at 4 degrees C, with out complete recovery during 10 minutes following withdrawal. This study carried out 408 eligible patients with 398 finally included in double-blind period (200 in the Buflomedil group, 198 in the placebo group). After a run-in period of 7 days with placebo in single blind, to evaluate the stability of measures, the patients were then treated with either Buflomedil 600 mg a day or placebo at the same dosage, for 14 days. The patients in both groups had a Raynaud's phenomenon and were heavy smokers (> or = 20 packs/year), having either acrocyanosis or lower limbs arterial occlusive disease. The results have shown, after 14 days of oral treatment an increase of basal temperature of 2.01 degrees C in Buflomedil group, versus only 0.82 degrees C in placebo group. This warming-up give evidence of microcirculatory blood flux increasing. This significant difference between the both groups was the same each measurement time after immersion during the recovery phase. There also was a good parallelism between the cutaneous temperature and the global clinical improvement by visual analogic scale filled out by the investigator (p < or = 0.0001) and the patients (p < or = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

[Cutaneous pulpar temperature and cold test. Predictive specificity and sensitivity in pharmaco-clinical studies].

The aim of this study was to measure the cutaneous pulpar temperature of the fingers and assess its evolution after one minute of controlateral hand immersion in a water bath at 4 degrees C and during 10 minutes after cooling. This test was carried out in 347 subjects (120 M, 227 F) divided in 5 groups: 117 healthy volunteers (49 M, 68 F) without any vascular diseases, 46 patients (5 M, 41 F) with acrocyanosis, 87 patients (19 M, 68 F) with Raynaud's phenomenon, 31 patients (24 M, 7 F) with peripheral arterial occlusive disease and 66 patients (23 M, 43 F) with other vascular diseases (high blood pressure and coronary disease). The mean initial temperature (TO) analysis in each group, showed that 2 groups, acrocyanosis and especially Raynaud's group, had a finger temperature significantly lower than the control group (27.4 +/- 4.8 degrees C 25.3 +/- 4.9 degrees C versus 30.5 +/- 4.9, p < 0.02). The cooling test showed 3 different cutaneous temperature reactions: subjects without any modification during and after immersion, subjects with a temperature decreasing after immersion and a normal rewarming after 10 minutes and subjects with a decreasing without any total recovery after 10 minutes. In the subjects with cold hands (initial temperature < 30 degrees C), this cooling test can isolate all patients with a temperature decreasing without any rewarming after 10 minutes with a specificity at 100% (no normal subject with cold hands were abnormal to this test).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗