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T Lefevre

Publications and source records attributed to T Lefevre.

At least 19 recordsLinked to original sources
PubMed2006

Do distantly related parasites rely on the same proximate factors to alter the behaviour of their hosts?

Phylogenetically unrelated parasites often increase the chances of their transmission by inducing similar phenotypic changes in their hosts. However, it is not known whether these convergent strategies rely on the same biochemical precursors. In this paper, we explored such aspects by studying two gammarid species (Gammarus insensibilis and Gammarus pulex; Crustacea: Amphipoda: Gammaridae) serving as intermediate hosts in the life cycle of two distantly related parasites: the trematode, Microphallus papillorobustus and the acanthocephalan, Polymorphus minutus. Both these parasite species are known to manipulate the behaviour of their amphipod hosts, bringing them towards the water surface, where they are preferentially eaten by aquatic birds (definitive hosts). By studying and comparing the brains of infected G. insensibilis and G. pulex with proteomics tools, we have elucidated some of the proximate causes involved in the parasite-induced alterations of host behaviour for each system. Protein identifications suggest that altered physiological compartments in hosts can be similar (e.g. immunoneural connexions) or different (e.g. vision process), and hence specific to the host-parasite association considered. Moreover, proteins required to alter the same physiological compartment can be specific or conversely common in both systems, illustrating in the latter case a molecular convergence in the proximate mechanisms of manipulation.

Acanthocephala↗
PubMed2005

Critical swimming speed does not represent the speed at maximal lactate steady state.

Critical power and critical swimming speed (CSS) are mathematically defined as intensities that could theoretically be maintained indefinitely without exhaustion. Several investigations have been conducted to attribute a physiological meaning to these variables, but results in swimming remain equivocal. Thus, the purpose of this study was to compare CSS with direct determination of the speed at maximal lactate steady state (S (MLSS)). Eight well-trained swimmers (aged 18.6 +/- 1.9 years) performed four tests to exhaustion (95, 100, 105, and 110 % of maximal aerobic speed [MAS]) in order to determine CSS from the distance-time relationship. S (MLSS) was determined from four sub-maximal 30-min constant intensity tests (ranging from 75 % to 90 % MAS). CSS (92.7 +/- 2.6 % MAS) was significantly higher than S (MLSS) (88.3 +/- 2.9 % of MAS) and the bias +/- 95 % limits of agreement for comparisons between CSS and S (MLSS) (0.07 +/- 0.13 m x s(-1)) indicated that the extent of disagreement was too great to use these two variables interchangeably. However, CSS and S (MLSS) were strongly correlated (r = 0.87; SEE = 0.033 m x s(-1); p < 0.01). Results from the present study demonstrate that in swimming, CSS does not represent the maximal speed that can be maintained without a continuous rise of blood lactate concentration and direct determination of S (MLSS) is necessary if precision is required in experimental studies.

Adult↗
PubMed2005

Self selected speed and maximal lactate steady state speed in swimming.

AIM: The purposes of this study were to ascertain whether physiological and stroking parameters remain stable during a 2-hour exercise performed at self-selected swimming speed (S4) and whether this speed corresponds to those associated with the maximal lactate steady state (SMLSS). METHODS: Ten well-trained competitive swimmers performed a maximal 400-m front crawl test, 4 30-min swimming tests in order to determine S(MLSS) and a 2-hour test swum at their preferred paces to determine self-selected swimming speed (S4), stroke rate (SR4), and stroke length (SL4) defined as the mean values observed between the 5th and the 15th min of this test. The stroking, metabolic and respiratory parameters, and ratings of perceived exertion (CR10) were reported throughout the 2-hour test. RESULTS: S4 and SMLSS were not significantly different and were highly correlated (r=0.891). S4 and SL4 decreased significantly after a steady state of 68 min and 100 min, respectively, whereas SR4 remained constant. Mean VO2, dioxide output, and heart rate values did not evolve significantly between the 10th and 120th minute of the test whereas capillary blood lactate concentration (La) decreased significantly (p<0.05). Moreover, respiratory CR10 did not evolve significantly between the 10th and the 120th minute of the test whereas general CR10 and muscular CR10 increased significantly. CONCLUSIONS: Considering the (La), SL4 and CR10 values variations, muscular parameters and a probably glycogenic depletion seem to be the main limiting factors that prevent maintaining the self selected swimming speed.

Adult↗
PubMed2001

Assessing health benefits of controlling air pollution from power generation: the case of a lignite-fired power plant in Thailand.

The impact pathway approach (IPA) is used to estimate quantitatively the level of health effects caused by particulate matter (PM10) and sulfur dioxide (SO2) emission from a lignite-fired power plant located in the Mae Moh area in northern region of Thailand. Health benefits are then assessed by comparing the levels of estimated health impacts without and with the installation of the flue gas desulfurization (FGD) equipment. The US EPA industrial source complex model is used to model air pollution dispersion at the local scale, and the sector average limited mixing meso-scale model is used to model air pollution transport at the regional scale. The quantification of the health end points in physical terms is carried out using the dose-response functions established recently for the population in Bangkok, Thailand. Monetarization of these effects is based on the benefit transfer method with appropriate adjustment. Finally, it has been found that the installation of the FGD to control SO2 emission at Mae Moh significantly reduces adverse health effects not only on the population living near the power plant but also all over the country. A FGD unit installed at the 300-MW power unit can result, on average, in 16 fewer cases of acute mortality, 12 fewer cases of respiratory and cardiac hospital admissions, and almost 354,000 fewer days with acute respiratory symptoms annually. In monetary terms this benefit is equivalent to US $18.2 million (1995 prices) per annum. This benefit is much higher than the annualized investment and operation costs of FGD (US $7.4 million/yr).

Air Pollutants↗
PubMed2001

Coronary angiography using 4 or 6 French diagnostic catheters: a prospective, randomized study.

Diagnostic catheter size has been progressively decreased in order to reduce complications (particularly access-site complications) and permit early ambulation after coronary angiography. However, excessive down-sizing can result in poor catheter conformation and poor imaging quality of coronary angiograms (CA). This study randomly compared the accuracy and angiographic quality (QUAL) of CA performed with 4 French (Fr) vs. 6 Fr diagnostic catheters. Injections were done manually using a low-viscosity, non-heated, low-osmolality contrast media (Iomeprol). CAs were performed via the femoral approach using Judkins catheters. Handling, torque, selectively and stability were graded from 1 (excellent) to 4 (unacceptable) by the operator. QUAL was also graded from 1 (unacceptable) to 10 (excellent) by the operator in all patients and by an independent Core laboratory in 50 patients matched for gender and weight. Between January and April 1997, a total of 405 consecutive patients were randomized. Mean age was 63.4 +/- 11.1 years and 79% were male. Clinical characteristics of patients, quality of left coronary catheter and cross-over rates (1.5% with 6 Fr vs. 3.9% with 4 Fr catheters) were similar in both groups. Using the right coronary catheters, the only difference was handling, which was found to be easier with 6 Fr catheters (1.16 +/- 0.55 vs. 1.34 +/- 0.77, respectively; p = 0.007). Similarly, handling difficulty using the pigtail catheter was the only significant difference between the two groups (1.16 +/- 0.50 vs. 1.33 +/- 0.77, respectively; p = 0.009), but no cross-over was necessary in either group. The QUAL of CA was slightly but significantly better with 6 Fr than with 4 Fr catheters but considered non-diagnostic (< 7/10) in 1.4% vs. 6.8% of left CAs (p = NS). Procedural time (21.0 +/- 7.2 minutes vs. 19.0 +/- 8.1 minutes; p = 0.007) was shorter with 4 Fr catheters, but x-ray exposure, compression times and amount of contrast media used were similar. Ambulation was obtained at 2 hours in 15.1% vs. 34.0% of patients (p < 0.001) and at 4 hours in 43.8% vs. 52.4% (p < 0.05), respectively. The incidence of the worst access-site complication (moderate hematoma) was similar (1%) in both groups. CA can be performed using 4 Fr catheters and manual injections of low-viscosity contrast media with acceptable angiographic results in the majority of cases. This is associated with a shorter procedural time and earlier ambulation, and a decreased but acceptable angiographic quality.

Age Factors↗
PubMed2000

Free-electron laser as a driver for a resonant cavity at 35 GHz

An intense beam of relativistic electrons (800 A, 6.7 MeV) has been bunched at 35 GHz by a free-electron laser, in which output power levels exceeding 100 MW were obtained. The beam was then extracted and transported through a resonant cavity, which was excited by its passage. Microwave power levels of 10 MW were extracted from the cavity, in reasonable agreement with the simple formula which relates power to known properties of both the beam and the cavity.

Journal Article↗
PubMed2000

[Optimal myocardial revascularization by coronary bypass and complementary angioplasty. Study of 100 patients].

One hundred patients underwent early coronary angiography (average 20.5 days) after coronary bypass surgery between 1994 and 1996. The indications in clinically asymptomatic patients were: study of double mammary grafts, non respect of the preoperative plan (grafts not available, technical difficulties), and/or postoperative ECG changes. 12.1% of internal mammary grafts and 18.2% of the saphenous vein grafts were considered to be non-fractional: due to occlusion in 3 and 11.9%, due to poor implantation site (persistence of a distal stenosis): 3 and 0.8% respectively. After investigations to detect ischaemia in the region concerned or persistence of a critical lesion on a non-revascularised main artery, 26 complementary angioplasties were performed: 3 on internal mammary grafts, 4 on saphenous vein grafts and 19 on the native vessels. Surgery alone resulted in complete revascularisation in 70% and its association with cardiological interventional techniques increased the value to 85%. The association of coronary bypass surgery and transluminal angioplasty may therefore result in optimal revascularisation. This should reduce the morbidity rate, the number of hospital admissions (recurrent ischaemia and reoperation) and improve survival. However, the exact modalities of this combined revascularisation remain to be defined.

Adult↗
PubMed1998

Role of sodium in contrast medium-induced polymorphic ventricular tachycardia: results in a rabbit model of lengthened QT interval.

RATIONALE AND OBJECTIVES: The authors (a) compared the proarrhythmic effects of ioxaglate (152 mmol/L sodium) and iohexol (no sodium) in a rabbit model and (b) assessed the effect of adding 150 mmol/L sodium to isotonic iohexol. MATERIALS AND METHODS: Either ioxaglate (320 mg of iodine per milliliter) or iohexol (350 mg of iodine per milliliter) was selectively injected into the right coronary artery (1.5 mL over 30 seconds) of 10 rabbits, some of which also received the alpha 1-adrenergic receptor agonist methoxamine. To validate the model, the class III antiarrhythmic agent clofilium was injected intravenously during methoxamine infusion. Frontal electrocardiography was performed continuously to detect polymorphic ventricular tachycardia (PVT). In a second study, the authors assessed the frequency of arrhythmias after injection of isotonic iohexol solution (145 mg of iodine per milliliter), either alone or with 150 mmol/L sodium. RESULTS: Methoxamine significantly lengthened the QT, QTc, and RR intervals (P < .05). The use of clofilium alone induced no PVT, whereas five of eight methoxamine-infused rabbits developed PVT after clofilium injection (P = .03). Both contrast media prolonged the repolarization period. Iohexol alone induced a higher frequency of PVT than did ioxaglate alone (P = .0006). Methoxamine infusion did not potentiate the frequency of PVT in the ioxaglate-injected rabbits. The addition of sodium to isotonic iohexol prevented the occurrence of PVT (P = .0006). CONCLUSION: Although ioxaglate prolonged the repolarization period, it did not cause a higher frequency of arrhythmia when injected in association with methoxamine. Iohexol, which contains no sodium, induced a high frequency of arrhythmia. The addition of a physiologic concentration of sodium to isotonic iohexol can prevent ventricular arrhythmias.

Adrenergic alpha-Agonists↗
PubMed1998

Influence of Contrast Media on the Results of Percutaneous Transluminal Coronary Angioplasty with Provisional Stenting: A Comparative Study.

Contradictory data concerning the use of non-ionic contrast media during percutaneous coronary angioplasty (PTCA) have been published. Many clinical studies have suggested that a higher rate of PTCA complications (using balloon angioplasty) was observed using non-ionic versus ionic contrast media. In order to verify these results in the era of coronary stenting, we compared the in-hospital outcome of 384 patients (pts) dilated using ionic contrast media (ioxaglate) and 387 pts dilated with non ionic contrast media (iopamidol). From October 15th 1993 to July 15th 1994, 773 consecutive pts were included in this study. At the beginning of the procedure, the pts received a first bolus of heparin (7500 IU for pts who had not been pretreated with heparin and 5000 IU for pts already treated with heparin). After the first bolus the activated clotting time (ACT) was measured and the pts received an additional bolus of 2500 IU when the ACT was below 300 sec. When the procedure exceeded one hour an additional bolus of 5000 IU was injected. The main characteristics of the 2 groups (Ioxaglate vs Iopamidol) were comparable (demographic data, indication of PTCA, procedural data, first dose of heparin, total dose of heparin). The final ACT was higher in the ioxaglate group (634 +/- 111 vs. 474 +/- 310, p < 0.001). During the hospital course, blood transfusion or vascular surgery was necessary in 1.6 vs. 1.0% (NS), acute closure occurred in 2.1 vs. 4.9% (p = 0.03), acute Q-wave myocardial infarction in 0.5 vs. 0.75% (p = NS), emergency bypass surgery in 0 vs. 0.5% (NS), death in 0.8 vs. 0.3% (NS) and major cardiac event (death, myocardial infarction, coronary artery bypass surgery) in 0.8 vs. 1.6% (NS). Stents were less frequently used in the Ioxaglate group (21.5 vs. 28.5%, p = 0.03) especially in the subset of bailout stenting (2.0 vs. 4.9%, p = 0.04). CONCLUSION: This study suggests that PTCA with provisional stenting can be performed safely using ionic or non-ionic contrast media. However, the ACT obtained with the same dosage of heparin is significantly higher with the ionic contrast media whereas the risk of acute closure and the rate of bail-out coronary stenting is lower.

Journal Article↗
PubMed1998

[Recurrent bronchogenic cyst with rupture into the pericardium. A case report].

A case of tamponnade due to intrapericardial rupture of a recurrent bronchogenic cyst, presenting as pericarditis, is described. This case is unique because it demonstrates the possibility of rupture of a bronchogenic cyst into the pericardium and by the unusual mode of presentation. It also shows that bronchogenic cysts may recur many years after incomplete ablation. Bronchogenic cysts are benign dysembrioplasic formations characterised by their respiratory epithelial lining. The usual presentation in the adult is by haemorrhage or infection, but our case shows that recurrent pericarditis without an obvious cause may be due to bronchogenic cyst, which should be systematically excluded. The diagnosis suspected after medical imaging (chest X-ray, scanner, magnetic resonance imaging) is confirmed by histology. Total surgical ablation is the treatment of choice and may be curative.

Adult↗
PubMed1998

[Single coronary artery arising from the right coronary sinus. Report of two cases].

The authors report two cases of single coronary artery arising from the right coronary sinus. Both patients had angina with reversible myocardial ischaemia on exercise Thallium scintigraphy. Coronary angiography showed single coronary artery arising from the right coronary sinus in both cases with severe stenosis of the right coronary artery in the first and occlusion of the right coronary artery in the second patient. Both underwent surgical revascularisation with a good result. Single coronary artery is a rare congenital abnormality (approximately 0.36 per 1,000) diagnosed at autopsy until 1963, and thereafter at coronary angiography. A review of the literature shows that an equal number of single coronary arteries arise from the right as from the left coronary sinus: there does not seem to be an increased risk of complication when a branch runs between the aorta and pulmonary artery. On the other hand, single coronary arteries arising from the right coronary sinus seem to be more commonly associated with atherosclerosis than a network with two coronary arteries, but when the lesions are proximal, the risk is high. Revascularisation is indicated only when myocardial ischaemia has been documented.

Aged↗
PubMed1997

Early versus late coronary stenting following acute myocardial infarction: results of the STENTIM I Study (French Registry of Stenting in Acute Myocardial Infarction).

This study was undertaken to determine the feasibility and safety of coronary stenting in acute myocardial infarction (AMI). In AMI, primary percutaneous transluminal coronary angioplasty (PTCA) is accepted as the preferred method of reperfusion for patients presenting at highly experienced centres. Until recently, however, stenting has been avoided during AMI because of a potential high risk of thrombosis. This prospective observational study carried out in 20 centres and included 648 consecutive patients who underwent PTCA with stent implantation for AMI. Of these 648 patients, 269 (41.5%, Group 1) were dilated early (< 24 hr) after the onset of the symptoms (75% treated by direct PTCA) and 379 (58.5%, Group 2) were dilated between 24 hr and 14 days after AMI. Combined therapy with ticlopidin and aspirin was used after the procedure. Bailout stenting occurred more often in Group 1 than in Group 2 (17% vs. 9.5%)(P < 0.05). Angiographic successful stenting was similar in both groups of patients (96% vs. 97%). During the hospital follow-up period, stent thrombosis occurred in eight patients (3%) in Group 1 and in six patients (1.6%) in Group 2 (NS). There was 14 deaths (5.2%) in Group 1 and 11 deaths (3.9%) in Group 2 (NS). After multivariate analysis bailout stenting was identified as the sole predictor of stent thrombosis (P < 0.0001). Vascular access-site complications occurred in six patients (1%) with no difference between the two groups. This study indicates that patients who receive a coronary stent in AMI can be managed safely with antiplatelet therapy. Randomized studies are needed to determine the precise indication for coronary stenting as an adjunct to primary PTCA.

Adult↗
PubMed1997

Comparison of 6F with 7F and 8F guiding catheters for elective coronary angioplasty: results of a prospective, multicenter, randomized trial.

A group of 460 patients was considered in our prospective study of assessment of the efficiency and safety of 6F (internal diameter 0.062 inches) guiding catheters to perform elective percutaneous coronary angioplasty by the femoral approach by using conventional balloon systems. The patients were randomly assigned either a 6F guiding catheter (first group, n = 231; 247 coronary lesions), or a 7F or 8F guiding catheter (second group, n = 229; 252 coronary lesions). The exclusion criteria were the ongoing myocardial infarction, the marked reduction of left ventricular function, and the decision to treat the lesion with a device not fitting the 6F guiding catheter. The angioplasty success rates (87% in the 6F group vs 88% in the 7F or 8F group) and the stent implantation rates (21% vs 25%) were similar in both groups. The ischemic complication rates (death, 2 vs 1 ) were also similar. The incidence of the femoral complications was significantly less important in the 6F group than in the 7/8F group (13.8% vs 23.5%; p < 0.01). Significant differences also were noted for the procedural time (36 +/- 22 vs 41 +/- 28 min; p < 0.01), the fluoroscopy time (11 +/- 10 vs 14 +/- 4 min; p < 0.05), the volume of contrast injected (136 +/- 68 ml vs 168 +/- 95 ml; p < 0.0001), and the time of femoral compression after the introducer sheath removal (11.7 +/- 9 vs 14.1 +/- 12 min; p < 0.01). Our data suggest that 6F guiding catheters for elective coronary angioplasty are more effective than are the larger diameter catheters. Besides a significant decrease of vascular complications, angioplasty with a 6F guiding catheter reduces the procedural time and the amount of contrast.

Angioplasty, Balloon, Coronary↗
PubMed1997

[Isolated left ventricular muscular diverticulum in an adult. Value of non-invasive examinations].

The authors report a case of ventriculum in a 45 year old women investigated for chest pain. This was a congenital muscular left ventricular diverticulum confirmed by a complete imaging series including echocardiography, magnetic resonance imaging, angio-scintigraphy and conventional angiography. This diverticulum was unusual due to the fact that there was no associated congenital disease and that it was discovered in an adult. The authors review the literature and discuss the value of non-invasive imaging procedures.

Angiocardiography↗
PubMed1996

Intracoronary stent implantation without ultrasound guidance and with replacement of conventional anticoagulation by antiplatelet therapy. 30-day clinical outcome of the French Multicenter Registry.

BACKGROUND: Stenting reduces both acute complications of coronary angioplasty and restenosis rates but increases subacute thrombosis rates and hemorrhagic complications when used with coumadin anticoagulation. METHODS AND RESULTS: To simplify postcoronary stenting treatment and to reduce these drawbacks, we evaluated the 1-month outcome of a prospective registry of 2900 patients in whom successful coronary artery stenting was performed without coumadin anticoagulation. Patients received 100 mg/d aspirin and 250 mg/d ticlopidine for 1 month. Low-molecular-weight heparin (LMWH) treatment was progressively reduced in four consecutive stages, from 1-month treatment to none. Event-free outcome at 1 month was achieved in 2816 patients (97.1%). Major stent-related cardiac events were subacute closure in 51 patients (1.8%), including death in 12 (0.5%), acute myocardial infarction in 17 (0.6%), and coronary artery bypass graft surgery in 9 (0.3%). Stent thrombosis was more frequent with balloon size of < 3.0 mm (< or = 2.5 mm, 10%; 3.0 mm, 2.3%; > or = 3.5 mm, 1.0%; P < .001), bail-out situations (6.67% versus 1.38%, P < .001), and patients with unstable angina or acute myocardial infarction (2.2% versus 1.12%, P = .02). Bleeding complications that required transfusion, surgical repair, or both occurred in 55 patients (1.9%). Bleeding complications were related to female gender (4.0% versus 1.51%, P < .001), duration of LMWH treatment (3.83% in phase II/III versus 0.69% in phase IV/V, P < .001), sheath size (6F, 0.52%; 7F, 1.04%; > or = 8F, 4.23%; P < .001), bail-out situations (4.76% versus 1.67%, P < .01), and saphenous graft stenting (4.38% versus 1.75%, P = .04). CONCLUSIONS: These results suggest that poststenting treatment by ticlopidine/aspirin is an effective alternative to coumadin anticoagulation, achieving low rates of subacute closure and bleeding complications. LMWH treatment does not improve subacute reocclusion rates but increases bleeding complications. Furthermore, as bleeding complications were independently related to sheath size, we suggest that stenting with 6F guiding catheters may prevent local complications. Furthermore, the ticlopidine/aspirin combination allows a low-cost stenting strategy without ultrasound assessment of stent deployment and permits short inhospital stay.

Aged↗
PubMed1996

Effects of chloride ion substitutes and chloride channel blockers on the transient outward current in rat ventricular myocytes.

The Cai(2+)-insensitive transient outward current, ilo was studied at 20-24 degrees C in rat ventricular myocytes with the whole cell recording patch-clamp technique. The current was recorded before and after replacement of chloride by methanesulfonate or aspartate or in the absence and the presence of chloride channel blockers, SITS or 9-anthracene carboxylic acid. In control conditions (in the presence of external divalent cations, Ca2+ and Cd2+, Cd2+ being used to suppress Ca2+ current), ilo inactivation was composed of a fast and a slow component. When methanesulfonate was substituted for external Cl-, the peak current decreased to a variable extent, but the inactivation of the remaining current was still composed of a fast and a slow component. In contrast, the inactivation of the difference current was well fitted by a single exponential. The time to peak of the difference current was shorter than that of the current recorded either in the absence or the presence of methanesulfonate. Both activation- and steady-state inactivation-voltage curves were either unchanged (n = 4) or shifted by a few mV (5.5 mV, n = 14) towards positive potentials when methanesulfonate was substituted for Cl-. The current remaining in methanesulfonate reversed at potentials closed to EK. The difference current was composed of a peak and a steady-state component. The peak was suppressed by 4-aminopyridine whereas the steady-state component was not. The peak was also suppressed when pipette solution contained Cs+ instead of K+ but was still present when the Hepes concentration in both external and pipette media was increased 5-fold (50 mM vs. 10 mM). When aspartate was substituted for Cl- or when 2 mM SITS was added to the external solution (in the absence of Ca2+ and Cd2+ because aspartate is known to chelate Ca2+ ions and possibly other divalent cations), ilo was reduced to a similar extent in the two cases and the difference current was composed of a peak (inactivation fitted by a single exponential) and a steady-state component. The SITS-sensitive transient current reversed at a potential close to ECl. When 5 mM 9-anthracene carboxylic acid was added to external solution (in the presence of Ca2+ and Cd2+), the peak of the difference current was similar to that observed when Cl- was substituted by methanesulfonate. The difference current resulting from the substitution of methanesulfonate for chloride was not changed when the pipette solution contained either 50 mM EGTA (instead of 5 mM) or 10 mM EGTA and 10 mM BAPTA. The nature of Cs(+)- and 4-aminopyridine-sensitive transient outward current suppressed by chloride ion substitutes or chloride channel blockers is discussed.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗