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Biomedical subjects

F Lemaître

Publications and source records attributed to F Lemaître.

14 recordsLinked to original sources
PubMed2006

Pulmonary function in children after a single scuba dive.

This study evaluated the respiratory effects of a single dive in children. Eighteen young divers and 18 controls participated in our study (age range: 9 - 13 years). Volumes and expiratory flow rates were measured 20 minutes before and 10 minutes after one air dive (3 meters, 25 minutes). Before the dive, no differences were noted regarding pulmonary parameters. Ten minutes after the dive, decreases were noted in forced expiratory volume in 1 s (FEV1) and maximal voluntary ventilation (- 8 %, - 5.3 %, respectively; p < 0.01), peak expiratory flow, maximal expiratory flow rates at 50 % of FVC (MEF(50 %)) and MEF(25 %), forced mid-expiratory flow rate (FEF(25 - 75 %)), and FEV1/FVC(- 5.9 %, - 14.3 %, - 21.4 %, - 4.2 %, - 3.5 %, respectively; p < 0.05). The respiratory pattern observed 10 minutes after a single dive to three meters indicated airway narrowing. However, no association between diving experience and lung function was obtained.

Age Factors↗
PubMed2006

Ventilatory function in experienced recreational scuba divers: Evidence of small airways disease?

Diving has shown long-term effects on respiratory function in trained professional divers, indicating the development of small airways disease. The results are more controversial in trained recreational divers because of the different degrees of exposure and training. The aim of this study was to investigate the effects of recreational diving on respiratory function in highly experienced divers. Volumes and expiratory flow rates were measured in 32 older recreational divers (51.6 +/- 7.4 years). The forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were higher (+ 4.9 % and + 6 %, respectively; p < 0.01) than the theoretical standards (ERS 93). These values tended to decrease more rapidly as the age advanced (age range: 43 - 73 years) (p < 0.05). Moreover, the mid-expiratory flows at 50 %, 25 % and 25 - 75 % of vital capacity (MEF(50 %), MEF(25 %) and MEF(25 - 75 %)) were significantly decreased. These early signs of decrease suggest slight small airways disease in older experienced recreational divers.

Adult↗
PubMed2006

Effect of high-intensity intermittent cycling sprints on neuromuscular activity.

High-intensity intermittent sprints induce changes in metabolic and mechanical parameters. However, very few data are available about electrical manifestations of muscle fatigue following such sprints. In this study, quadriceps electromyographic (EMG) responses to repeated all-out exercise bouts of short duration were assessed from maximal voluntary isometric contractions (MVC) performed before and after sprints. Twelve men performed ten 6-s maximal cycling sprints, separated by 30-s rest. The MVC were performed pre-sprints ( pre), post-sprints ( post), and 5 min post-sprints ( post5). Values of root-mean-square (RMS) and median frequency (MF) of vastus lateralis (VL) and vastus medialis (VM) were recorded during each MVC. During sprints, PPO decreased significantly in sprints 8, 9, and 10, compared to sprint 1 (- 8 %, - 10 %, and - 11 %, respectively, p < 0.05). Significant decrements were found in MVC post (- 13 %, p < 0.05) and MVC post5 (- 10.5 %, p < 0.05) compared to MVC pre. The RMS value of VL muscle increased significantly after sprints (RMS pre vs. RMS post: + 15 %, p < 0.05). Values of MF decreased significantly in both VL and VM after sprints. In conclusion, our results indicate that the increase in quadriceps EMG amplitude following high-intensity intermittent short sprints was not sufficient to maintain the required force output. The concomitant decrease in frequency components would suggest a modification in the pattern of muscle fiber recruitment, and a decrease in conduction velocity of active fibers.

Adult↗
PubMed2005

Arterial oxygen saturation and heart rate variation during breath-holding: comparison between breath-hold divers and controls.

Breath-holding induces cardiovascular responses, notably bradycardia and peripheral vasoconstriction, which are known collectively as the diving response. This response is oxygen-conserving, i.e. an augmented response attenuates arterial oxygen desaturation, and is enhanced by apnoea training. To test this hypothesis, we compared heart rate (HR) and arterial oxygen saturation (SaO (2)) in breath-hold divers (BHD) and non-divers (ND). Nine BHD and nine healthy ND performed two static apnoeas (for 30 s and 45 s) and two dynamic apnoeas (for 30 s and 45 s) while swimming underwater at 0.7 m . s (-1). The pool temperature was 26 degrees C. The apnoeas were performed at 60 % of forced vital capacity. Heart rate (HR) and SaO (2) were recorded before breath-holding and at its end and are expressed in % change from rest values (DeltaHR and DeltaSaO (2)). Comparisons between BHD and ND showed that DeltaSaO (2) were lower in divers after both static apnoeas for 30 s and 45 s (- 2.8 % vs. - 5.5 %; - 3.2 % vs. 6.3 %; p < 0.05, respectively) and dynamic apnoeas (- 6 % vs. - 10.1 %; - 7.2 % vs. - 12.3 %; p < 0.05, respectively). The change in HR did not differ between the two groups and negative linear relations were found between DeltaHR and DeltaSaO (2) in both divers and ND (r = 0.66 and 0.61, respectively; p < 0.001). Moreover, the slope was lower for the divers (- 0.785 vs. - 0.1429; p < 0.001). Our results suggest that apnoea training explained the greater oxygen conservation seen in the divers in both static and dynamic conditions.

Adult↗
PubMed2002

Pulmonary function of recreational divers: a cross sectional study.

Long term effects on respiratory function have been found in adult professional divers and have indicated the development of small-airway disease. The aim of this report was to investigate pulmonary lung function and breathing pattern of recreational divers, especially in young subjects. Pulmonary function was measured in 84 air divers (aged 8 - 38 years) and in a matched control group of 89 subjects (aged 8 - 34 years). Static lung volumes, dynamic lung volumes and flows, transfer factor for carbon monoxide (T(Lco) ), maximal static pressures and CO(2) rebreathing test were measured. We observed no significant differences for all lung function parameters between divers and non divers in children and adolescents. Adult air divers showed a significant decrease in T(Lco) in absolute values (5.74 vs 6.26 ml x min(-1) x mmHg(-1) x l(-1), p = 0.03) and normal values and no significant difference in % predicted (112 vs 119 %), a higher maximal inspiratory pressure at functional residual capacity (-92 vs -74 cm H(2)O, p < 0.05) and at residual volume (-108 vs -88 cm H(2)O, p < 0.05) than adult controls. Adult divers also had a decreased resting respiratory frequency (13 c x min (-1) vs 17 c x min (-1) respectively, p < 0.01) and a higher carbon dioxide threshold (52 mm Hg vs 49 mm Hg respectively, p < 0.05) than adult controls. No significant differences occurred between adults divers and non divers for obstruction parameters. In this study, no airway obstruction or transfer factor reduction was observed in young recreational divers. Lower CO(2) threshold and higher inspiratory pressure were obtained in adult recreational divers compared to controls.

Adolescent↗
PubMed2002

Effect of air diving exposure generally encountered by recreational divers: oxidative stress?

Long term effects on respiratory function have been found in air divers and have indicated the development of small-airway disease. These effects have been attributed to oxygen toxicity or to venous gas micro emboli (VGM). The airway obstructions observed in air divers raise fundamental questions about whether these alterations exist after one simulated dive. The aim of this report was to study the oxidative stress induced by brief normobaric hyperoxia (FiO2 = 0.6 for 30 min) by measuring breath-exhaled compounds. Oxidative stress was measured by pentane in the expirate of 7 subjects ventilated with hydrocarbon-free air (HFA) before and after the hyperoxic exposure. NO concentration allowed us to determine the inflammatory response in the airway. Venous blood was drawn before and after the O2 breathing period for measurements of malondialdehyde (MDA). In all seven subjects, pentane elimination rates on 60%O2 do not increase after hyperoxia. NO rates during the HFA and hyperoxic exposures are significantly increased (p < 0.05). MDA concentrations are not changed after the hyperoxic exposure. Pulmonary function parameters obtained 225 minutes after hyperoxia are not changed. These results provide evidence that a dry gas and oxygen breathing (FiO2 = 0.6) for 30 min can raise exhaled NO. Oxidative stress assessed by pentane and MDA does not exist. We conclude that dry gas and the mild, 30 minute hyperoxic exposure, frequently encountered by recreational divers may be responsible for an airway inflammation. The consequences of such chronic exposure remains to be established.

Adult↗
PubMed2001

Improving Escherichia coli alkaline phosphatase efficacy by additional mutations inside and outside the catalytic pocket.

We describe a strategy that allowed us to confer on a bacterial (E. coli) alkaline phosphatase (AP) the high catalytic activity of the mammalian enzyme while maintaining its high thermostability. First, we identified mutations, at positions other than those occupied by essential catalytic residues, which inactivate the bacterial enzyme without destroying its overall conformation. We transferred concomitantly into the bacterial enzyme four residues of the mammalian enzyme, two being in the catalytic pocket and two being outside. Second, the gene encoding the inactive mutant was submitted to random mutagenesis. Enzyme activity was restored upon the single mutation D330N, at a position that is 12 A away from the center of the catalytic pocket. Third, this mutation was combined with other mutations previously reported to increase AP activity slightly in the presence of magnesium. As a result, at pH 10.0 the phosphatase activity of both mutants D330N/D153H and D330N/D153G was 17-fold higher than that of the wild-type AP. Strikingly, although the two individual mutations D153H and D153G destabilize the enzyme, the double mutant D330N/D153G remained highly stable (T(m)=87 degrees C). Moreover, when combining the phosphatase and transferase activities, the catalytic activity of the mutant D330N/D153G increased 40-fold (k(cat)=3200 s-1) relative to that of the wild-type enzyme (k(cat)=80 s-1). Due to the simultaneous increase in K(m), the resulting k(cat)/K(m) value was only increased by a factor of two. Therefore, a single mutation occurring outside a catalytic pocket can dramatically control not only the activity of an enzyme, but also its thermostability. Preliminary crystallographic data of a covalent D330N/D153G enzyme-phosphate complex show that the phosphate group has significantly moved away from the catalytic pocket, relative to its position in the structure of another mutant previously reported.

Alkaline Phosphatase↗
PubMed2000

Delayed and separate costimulation in vitro supports the evidence of a transient "excited" state of CD8+ T cells during activation.

Although the two-signal model for T cell activation states that a signal-1 through the TCR and a costimulatory signal-2 are required for optimal stimulation, it is now clear that the requirement for costimulation can be bypassed under certain conditions. We previously reported that this is the case for naive CD8+ T cells in vitro. In the present study we tested the effect of signal-2 when delivered after signal-1 has been disrupted. Naive CD8+ T cells from TCR transgenic mice were stimulated in vitro by using immobilized recombinant single-chain MHC molecules alone as signal-1. This signal was then stopped after different lengths of time, and anti-CD28 mAb as signal-2 was given either immediately or after a time lag. We found that signal-2 can potentiate a short signal-1 when added sequentially. Moreover, a time lag between the two signals does not abolish this potentiation. If the strength of signal-1, but not its duration, is increased, then the time lag between the delivery of signals 1 and 2 can be lengthen without loss of potentiation. Together, our results indicate that the two signals do not need to be delivered concomitantly to get optimal T cell activation. We suggest that the CD8+ T cells can reach a transient "excited" state after being stimulated with signal-1 alone, characterized by the cell's ability to respond to separate and delayed signal-2.

Animals↗
PubMed2000

The peripheral CD8 T cell repertoire is largely independent of the presence of intestinal flora.

While numerous studies have analyzed the shaping of T cell repertoires by self or foreign peptides, little is known on the influence of commensal self peptides derived from the intestinal flora (IF). Here, we have analyzed naive and immune repertoires in mice devoid of IF [germ-free (GF) mice]. First, by means of an extensive CDR3beta sequencing strategy, we show that the naive peripheral CD8 T cell repertoire does not exhibit a major imprint of IF antigens. Second, using MHC-peptide tetramers, CDR3beta length distribution analyses and TCR sequencing, we show that cytotoxic T lymphocyte (CTL) responses specific for two distinct epitopes are quasi-identical in normal and GF mice. Our findings indicate that, in general, peptides derived from the intestinal microflora have little if any influence on CTL responses in the mouse.

Animals↗
PubMed1998

CD8 expression allows T cell signaling by monomeric peptide-MHC complexes.

Physiologically, TCR signaling is unlikely to result from the cross-linking of TCR-CD3 complexes, given the low density of specific peptide-MHC complexes on antigen-presenting cells. We therefore have tested directly an alternative model for antigen recognition. We show that monomers of soluble peptide-MHC trigger Ca2+ responses in CD8alphabeta+ T cells. This response is not observed in CD8- T cells and when either the CD8:MHC or CD8:Lck interactions are prevented. This demonstrates that an intact CD8 coreceptor is necessary for effective TCR signaling in response to monomeric peptide-MHC molecules. We propose that this heterodimerization of TCR and CD8 by peptide-MHC corresponds to the physiological event normally involved during antigen-specific signal transduction.

Amino Acid Sequence↗
PubMed1995

[Osteoarticular tuberculosis. Diagnostic contribution of local sampling].

Bone and joint tuberculosis have recently gained a renewal of interest, especially with the spread of HIV infection which may increase its frequency. Bone and joint locations of tuberculosis are pauci-bacillary often requiring local sampling in order to confirm the diagnosis and to initiate early therapy. From 1983 to 1992 we have studied 19 patients with bone and joint tuberculosis. Seventeen local sampling were performed: 12 biopsies and five abscess punctures. Pathological examination of samples disclosed diagnosis of tuberculosis in eight cases out of 12. Among the remaining four patients, direct smear was positive once, and cultures grew Mycobacterium tuberculosis in two, yielding the diagnosis in 11 out of the 12 patients. Bacteriological and pathological examinations were non contributive in only one patient. Microbiological examination of pus disclosed two positive direct smear and three positive cultures. Treatment lasted 9 to 18 months. The outcome was favourable in all patients.

Abscess↗
PubMedDate not supplied

Heart rate responses during a breath-holding competition in well-trained divers.

The diving response elicited by breath-holding (BH) and immersion mainly consists of bradycardia, decreased cardiac output, and peripheral vasoconstriction. These responses reduce oxygen consumption and thereby prolong the duration of the dive. They may also lead to cardiac arrhythmias or hypoxia, however, which in turn may play a role in the occurrence of syncope during BH. The aim of the present study was to analyze the cardiac responses to prolonged breath-holding in elite divers during a competition. Heart rate behaviour and the incidence of arrhythmia were recorded in 16 well-trained breath-hold divers (BHD) using a cardio-frequency meter (for 15 divers) and a Holter (for one diver) during maximal static breath-holding. Anthropometric, spirometric, and training characteristics such as percentage of body fat, pulmonary volumes and years of BH training were also determined. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV (1)) were higher than the predicted values (+7.7%, p<0.05 and+6.6%, p<0.05, respectively). During the static BH, divers presented apneic bradycardia (-44%) correlated with static BH times (p<0.05); this was associated with cardiac arrhythmias (supraventricular extrasystoles and ventricular extrasystoles) in the Holter-equipped subject. These results are in agreement with those obtained in laboratory conditions and confirm the existence of cardiac arrhythmias in well-trained BHD.

Adaptation, Physiological↗
PubMedDate not supplied

Phase II and III studies with new drugs for non-small cell lung cancer: a systematic review of the literature with a methodology quality assessment.

We carried out a systematic review of new drugs active in non-small cell lung carcinoma (NSCLC). Fifty five phase II and III trials were reviewed (vinorelbine (19 trials), paclitaxel (15), gemcitabine (11), docetaxel (6), topotecan (2) or irinotecan (2)). The first four ones could be considered as active drugs when given as single agent. More information is required for the camptothecin derivatives. Four phase III randomised studies were available, all concerning vinorelbine. They showed that in combination with cisplatin, vinorelbine improved the response rate and perhaps survival, in comparison to vinorelbine alone and that vinorelbine was better than 5 fluorouracil and vindesine. A quantitative overview was impracticable, because of too few randomised trials. A qualitative overview was carried out using the European Lung Cancer Working Party score. The overall median quality score was 65.3%. There was no statistically significant difference between the drugs, but there was a positive correlation between the score and the number of patients. There was also an improvement of the quality score in favour of the randomised trials. Some important methodological aspects were often missing in the articles. In conclusion, gemcitabine, vinorelbine, paclitaxel and docetaxel are active against NSCLC but more good-quality data are required to define their exact role in the routine.

Antineoplastic Agents↗