Biomedical subjects

D Chollet

Publications and source records attributed to D Chollet.

At least 37 records · Page 2Linked to original sources

PubMed2001

The homeostatic regulation of sleep need is under genetic control.

Delta power, a measure of EEG activity in the 1-4 Hz range, in slow-wave sleep (SWS) is in a quantitative and predictive relationship with prior wakefulness. Thus, sleep loss evokes a proportional increase in delta power, and excess sleep a decrease. Therefore, delta power is thought to reflect SWS need and its underlying homeostatically regulated recovery process. The neurophysiological substrate of this process is unknown and forward genetics might help elucidate the nature of what is depleted during wakefulness and recovered during SWS. We applied a mathematical method that quantifies the relationship between the sleep-wake distribution and delta power to sleep data of six inbred mouse strains. The results demonstrated that the rate at which SWS need accumulated varied greatly with genotype. This conclusion was confirmed in a "dose-response" study of sleep loss and changes in delta power; delta power strongly depended on both the duration of prior wakefulness and genotype. We followed the segregation of the rebound of delta power after sleep deprivation in 25 BXD recombinant inbred strains by quantitative trait loci (QTL) analysis. One "significant" QTL was identified on chromosome 13 that accounted for 49% of the genetic variance in this trait. Interestingly, the rate at which SWS need decreases did not vary with genotype in any of the 31 inbred strains studied. These results demonstrate, for the first time, that the increase of SWS need is under a strong genetic control, and they provide a basis for identifying genes underlying SWS homeostasis.

Animals↗

PubMed2001

Magnesium involvement in sleep: genetic and nutritional models.

Alterations of peripheral magnesium (Mg) concentration have been reported in association with several behavioral disorders and sleep organization. Blood Mg regulation is under a strong genetic control, whereas brain Mg regulation does not seem to be affected. We have studied peripheral and central levels of Mg and analyzed sleep in two lines of mice selected for low (MGL) and high (MGH) red blood cell (RBC) Mg levels. The same variables were also studied in C57BL/6J mice before and after 3 weeks of Mg deficiency. Whereas blood Mg was highly affected by the selection, brain Mg exhibited only small differences between the two lines. In contrast, Mg deficiency strongly decreased both central and peripheral Mg levels. Sleep analysis indicated that in both models the amount of paradoxical sleep was lower in mice with higher Mg levels. The amplitude of daily variation in sleep and slow-wave sleep delta power was markedly decreased in MGH line. Quantitative electroencephalogram (EEG) analysis also revealed a faster theta peak frequency in MGH mice, irrespective of behavioral states. Central Mg showed significant correlations with the amount of paradoxical sleep and sleep consolidation. However, because the direction of these correlations was not consistent, it is concluded that optimal, (physiological) rather than high or low, Mg levels are needed for normal sleep regulation.

Animals↗

PubMed2000

Effects of drafting behind a two- or a six-beat kick swimmer in elite female triathletes.

The metabolic and drag responses, together with the distance between the draftee and the leader, were studied in six female triathletes swimming behind a lead swimmer who used either a two- or a six-beat kick, at an average velocity of 1.24 m x s(-1) (range 1.20-1.31). Drag was measured by passive towing. Oxygen consumption [49.1 (3.8) versus 50.4 (5.0) ml x min(-1) x kg(-1)], blood lactate [6.7 (2.3) versus 6.8 (1.9) mM], heart rate [172 (13.6) versus 173.5 (12.5) beats x min(-1)), rating of perceived exertion [13.7 (1.2) versus 13.5 (1.0)], stroke rate [38.3 (1.5) versus 39.5 (1.4) cycle x min(-1)], stroke length [1.95 (0.09) versus 1.89 (0.15) m x cycle(-1)] were not statistically different between the two-beat and the six-beat kick situations. The energy cost of swimming per unit of distance [0.65 (0.06) versus 0.67 (0.08) ml O2 x m(-1)] and the passive drag were similar for both kicks. The distance separating the draftee from the lead swimmer was between 14 cm and 85 cm and was inversely correlated with passive drag: r=-0.82, P < 0.05, for the two-beat kick and r=-0.82, P < 0.05, for the six-beat kick. The higher the passive drag, the closer the hand of the draftee to the feet of the lead swimmer. It was of no more benefit to triathletes to draft behind a two-beat kick swimmer than behind a six-beat kick swimmer.

Adult↗

PubMed2000

The effects of drafting on stroking variations during swimming in elite male triathletes.

The aim of this study was to determine the effects of drafting behind another swimmer on the metabolic response and stroke characteristics. Six highly trained male triathletes performed two maximal 400-m swims, one in a drafting (D) and one in a non-drafting condition (ND). Their metabolic response was assessed by measuring the oxygen uptake (VO2) and the blood lactate concentration at the end of each 400 m. Swimming velocity, stroke frequency, stroke length, and stroke index (velocity multiplied by stroke length) were recorded every 50 m. In the D and ND conditions, there was no difference in VO2 [66.7 (1.7) ml x kg(-1) x min(-1) vs 65.6 (1.2) ml x kg(-1) min(-1) respectively], however, the lactate concentrations were lower in D than in ND [9.6 (0.9) mM vs 10.8 (0.9) mM, respectively, P < 0.01]. In D, the performance [1.39 (0.02) m x s(-1) vs 1.34 (0.02) m x s(-1), respectively, P < 0.01] and the stroking parameters (i.e., stroke length and stroke index) increased significantly, while the stroke frequency remain unchanged. In D, a stable pace was maintained, while in ND, velocity decreased significantly throughout the 400 m. In D, the performance gains were related to the 400-m D velocity (r = 0.78, P < 0.05), and to the body fat mass (BFM, r = 0.99, P < 0.01). The stroke index in D was also related to BFM (r = 0.78, P < 0.05). Faster and leaner swimmers achieved greater performance gains and stroke index when drafting. Thus, drafting during swimming increases the performance and contributes to the maintenance of stable stroking parameters such as stroke frequency and stroke length during a 400-m swim.

Adult↗

PubMed2000

A new index of coordination for the crawl: description and usefulness.

This study analyzes stroke phases and arm and leg coordination during front crawl swimming as a function of swim velocity and performance level. Forty-three swimmers constituted three groups based on performance level. All swam at three different swim velocities, corresponding to the paces appropriate for the 800 m, 100 m, and 50 m. The different stroke phases and the arm and leg coordination were identified by video analysis. Arm coordination was quantified using a new index of coordination (IdC), which expresses the three major modalities opposition, catch-up and superposition. Opposition, where one arm begins the pull phase when the other is finishing the push phase; catch up, which has a lag time (LT) between propulsive phases of the two arms; and superposition, which describes an overlap in the propulsive phases. The IdC is an index which characterizes coordination patterns by measure of LT between propulsive phases of each arm. The most important results showed that duration of the propulsive phases (B + C) increased significantly with increasing velocity: 43.1 +/- 3.3% for V800; 46.5 +/- 3% for V100 and 49 +/- 3% for V50. The arm and leg synchronization was modified in the sense of an increase in six-beat kick. The IdC increased significantly with velocity: IdCV800 = -7.6 +/- 6.4%; IdCV100 = -3.2 +/- 5.1% and IdCV50 = -0.9 +/- 5.6%. IdC increased also significantly with performance level: IdCG3 = -6.07 +/- 5.3%; IdCG2 = -3.9 +/- 4.2% and IdCG1 = -1.76 +/- 5.6% for the mean of the 3 velocity. The two extreme IdC were IdCG3V800 = -9.4 +/- 5.4% and IdCG1V50 = +2.53 +/- 4.4%.

Adolescent↗

PubMed2000

Performance level and cardiopulmonary responses during a cycle-run trial.

To determine the effect of triathlete performance level on the cardiorespiratory responses elicited by the cycle-run succession, eight regionally and nationally-ranked (Competitive) and five internationally-ranked (Elite) male triathletes underwent four successive laboratory trials: 1) an incremental treadmill test, 2) an incremental cycle test, 3) 30 min of cycling followed by 20 min of running (C-R), and 4) a 20-min control run (R) at the same speed as the run in C-R. Before and 10 min after the third and fourth trials the triathletes underwent lung function testing: spirometry and diffusing capacity testing for carbon monoxide (DL(CO)). During the C-R trial blood samples were drawn to measure venous lactate concentration. During all trials ventilatory data were collected every minute using an automated breath-by-breath system. The results showed that 1) the oxygen uptake (VO2) of post-cycling running versus running alone was similar for both groups; 2) the ventilatory responses (VE, VE/VO2, VE/VC02 and f) of C-R running versus R were significantly higher (P < 0.005) for the Competitive group; and 3) a significant decrease (P< 0.05) in DL(CO) was also noted after the C-R trial in the Competitive group but not in the Elite group. We concluded that 1) the ventilatory responses during a run subsequent to cycling may be related to the triathlete performance level, and 2) the C-R trial induced specific alterations in pulmonary function that may be associated with respiratory muscle alteration and exercise-induced hypoxemia in the Competitive triathletes.

Adult↗

PubMed2000

Ventilatory threshold and maximal oxygen uptake in present triathletes.

The aim of this study was to determine the physiological profile of young triathletes who began triathlon competition as their first sport. Twenty-nine male competitive triathletes (23 regionally and nationally ranked triathletes and 6 elite, internationally ranked triathletes) performed two tests, one on a cycle ergometer (CE VO2max) and one on a treadmill (TM VO2max). Results showed (a) no difference between CE VO2max and TM VO2max in the triathletes (69.1 +/- 7.2 vs. 70.2 +/- 6.2 mL x kg(-1) x min(-1), respectively), (b) values of CE VO2max and TM VO2max in elite triathletes (75.9 +/- 5.2 and 78.5 +/- 3.6 mL x kg(-1) x min(-1), respectively) that were comparable to those reported in elite single-sport athletes in these specialities, and (c) although the ventilatory threshold (Th(vent)) was similar in CE and TM, TM Th(vent) was consistently lower for triathletes than TM Th(vent) usually reported for runners.

Adaptation, Physiological↗

PubMed2000

Blood and brain magnesium in inbred mice and their correlation with sleep quality.

A strong genetic component in the regulation of blood magnesium (Mg) levels has been demonstrated. The regulation and distribution of brain Mg levels, however, have never been assessed. Herein we report on the genetic variation of peripheral and central Mg levels in six inbred strains of mice. In addition, the possible involvement of Mg in sleep regulation was assessed by establishing correlations between Mg and sleep parameters obtained before and after a 6-h sleep deprivation. Although genotype strongly determined blood Mg levels, it did not affect brain Mg, suggesting that central and peripheral Mg are regulated differently. Central Mg displayed a highly structure-specific distribution with frontal cortex having the highest and brain stem the lowest values. Whereas for the amount and distribution of baseline sleep only marginal correlations with Mg were found, Mg contents in four of nine brain structures were highly positively correlated with the length of slow-wave sleep episodes during recovery. This relationship suggests that higher levels of Mg in specific brain sites promote sleep quality as part of a recovery process.

Animals↗

PubMed2000

Analysis of breathing in the crawl as a function of skill and stroke characteristics.

The purpose of this study was to measure and compare the durations of exhalation (DE), inhalation (DI), and inhalatory apnea (DAI) expressed as percentage of stroke-cycle duration using two groups (more expert and less expert) of 6 front crawl swimmers each at near 100-m speed (high speed) and 800-m speed (low speed). Two breathing conditions were considered, breathing to the preferred side with and without a nose-clip. The relationships between stroking characteristics (swimming speed, stroke rate, and stroke length) and the three durations of breathing were examined as a function of skill and swimming speed. The data show that use of a nose-clip does not significantly change those measures. At high speed, the more expert group had a lower inhalation and a higher exhalation than the less expert group. The stroke rate correlated with speed .92 (p<.01) and was mainly associated with inhalation (r=-.78, p<.01). Inclusion of exhalation as a second variable improved significantly (p<.01) the accuracy of the regression up to .97. At low speed, the less expert had lower inhalatory apnea than the more expert. Stroke length correlated with speed .86 (p<.01) and was mainly associated with inhalatory apnea (r=.70, p<.05). At high speed, the more expert had a lower inhalation than at low speed, while durations of exhalation and inhalatory apnea did not vary significantly. On the contrary, the less expert had a lower exhalation and a higher inhalatory apnea, while duration of inhalation remained relatively unchanged. The present study shows that these durations and their relations to stroking characteristics could be considered significant indicators of skill in swimming.

Aerobiosis↗

PubMed1999

Quantitative trait loci approach to the genetics of sleep in recombinant inbred mice.

Sleep is a complex trait controlled by many genes, the environment, and probably by gene-environment interactions. Among different approaches to the genetics of sleep, analysis of quantitative traits (QTL) has the advantage of being able to detect, along with major genes, minor and/or modifier genes influencing different quantitative aspects of sleep. We have used QTL analysis in two different sets of recombinant inbred (RI) strains and sought for confirmation of several localizations in eight histocompatibility congenic strains. Several QTLs were identified which influenced the amount of vigilance states. In a first RI series (seven strains) the only QTLs identified were those affecting paradoxical sleep (PS), whereas analysis in a second RI series (25 strains) revealed QTLs influencing PS, slow-wave sleep, and total sleep. Among these, a single QTL on chromosome 5 was associated with all vigilance states, suggesting the presence of a major gene influencing a basic aspect of sleep amount. Search for candidate genes around the identified QTLs indicated several immune related genes that have been implicated in sleep regulation. Transgenic animals carrying loss-of-function and/or gain-of-function mutations affecting these candidate genes should confirm these findings.

Alleles↗

PubMed1999

Ventilatory responses during experimental cycle-run transition in triathletes.

PURPOSE AND METHODS: To determine the effects of cycling on a subsequent triathlon run, nine male triathletes underwent four successive laboratory trials: 1) an incremental treadmill test, 2) an incremental cycle test, 3) 30 min of cycling followed by 5 km of running (C-R), and 4) 30 min of running followed by 5 km of running (R-R). Before and 10 min after the third and fourth trials, the triathletes underwent pulmonary function testing including spirometry and diffusing capacity testing for carbon monoxide (DL(CO)). During the C-R and R-R trials, arterialized blood samples were obtained to measure arterial oxygen pressure (PaO2). During all trials, ventilatory data were collected every minute using an automated breath-by-breath system. RESULTS: The results showed that 1) the oxygen uptake (VO2) observed during subsequent running was similar for the C-R and R-R trials; 2) the ventilatory response (VE) during the first 8 min of subsequent running was significantly greater in the C-R than in R-R trial (P < 0.05); 3) only the C-R trial induced a significant increase (P < 0.05) in residual volume (RV), functional residual capacity (FRC), and the ratio of residual volume to total lung capacity (RV/TLC); and 4) although a significant decrease (P < 0.05) in DL(CO) was noted after C-R, no difference between the two exercise trials was found for the maximal drop in PaO2. CONCLUSIONS: We concluded that 1) the C-R trial induced specific alterations in pulmonary function that may be associated with respiratory muscle fatigue and/or exercise-induced hypoxemia, and 2) the greater VE observed during the first minute of running after cycling was due to the specificity of cycling. This reinforces the necessity for triathletes to practice multi-trial training to stimulate the physiological responses experienced during the swim-cycle and the cycle-run transitions.

Adolescent↗

PubMed1999

Stroking parameters in top level swimmers with a disability.

PURPOSE: The purposes of this study were to analyze velocity (V), stroke length (SL), and stroke rate (SR) values during the 100-m freestyle competitive events in top level male and female swimmers with a disability (DS) according to the international Functional Classification System (FCS) and to compare the results obtained with those of able-bodied swimmers (ABS). METHODS: DS (N = 119) and ABS (N = 32) were tested in real competitive conditions during European and French swimming championships in the A finals of the 100-m freestyle. RESULTS: V and SL increased significantly (P < 0.01) according to the level of ability from class S3 up to S10. SL values were significantly different (P < 0.01) between males and females in each class group. On the contrary, SR was not significantly different between genders, between each class group of FCS, and also with ABS. The major result of this study was that stroke length was related to velocity whereas stroke rate was not. The differences in weekly training time between each class of DS were not significantly different and showed that performances seemed to be more related to the various locomotor disabilities than to the training status. CONCLUSIONS: These findings, which are discussed, showed that stroke index (SI = V.SL) could be used as a sensitive criterion to assess the swimmer with a disability in relationship to his classification level.

Persons with Disabilities↗

PubMed1998

The influence of prior cycling on biomechanical and cardiorespiratory response profiles during running in triathletes.

The aim of the present study was to determine the effects of 40 km of cycling on the biomechanical and cardiorespiratory responses measured during the running segment of a classic triathlon, with particular emphasis on the time course of these responses. Seven male triathletes underwent four successive laboratory trials: (1) 40 km of cycling followed by a 10-km triathlon run (TR), (2) a 10-km control run (CR) at the same speed as TR, (3) an incremental treadmill test, and (4) an incremental cycle test. The following ventilatory data were collected every minute using an automated breath-by-breath system: pulmonary ventilation VE, l x min[-1]), oxygen uptake (VO2, ml x min(-1) x kg[-1]), carbon dioxide output (ml x min[-1]), respiratory equivalents for oxygen (VE/VO2) and carbon dioxide (VE/VCO2), respiratory exchange ratio (R) respiratory frequency (f, breaths x min[-1]), and tidal volume (ml). Heart rate (HR, beats x min[-1]) was monitored using a telemetric system. Biomechanical variables included stride length (SL) and stride frequency (SF) recorded on a video tape. The results showed that the following variables were significantly higher (analysis of variance, P < 0.05) for TR than for CR: VO2 [51.7 (3.4) vs 48.3 (3.9) ml x kg(-1) x min(-1), respectively], VE [100.4 (1.4) l x min(-1) vs 84.4 (7.0) l x min(-1)], VE/VO2 [24.2 (2.6) vs 21.5 (2.7)] VE/VCO2 [25.2 (2.6) vs 22.4 (2.6)], f[55.8 (11.6) vs 49.0 (12.4) breaths x min(-1)] and HR [175 (7) vs 168 (9) beats x min(-1)]. Moreover, the time needed to reach steady-state was shorter for HR and VO2 (1 min and 2 min, respectively) and longer for VE (7 min). In contrast, the biomechanical parameters, i.e. SL and SF, remained unchanged throughout TR versus CR. We conclude that the first minutes of the run segment after cycling in an experimental triathlon were specific in terms of VO2 and cardiorespiratory variables, and nonspecific in terms of biomechanical variables.

Adult↗

PubMed1998

Performance and drag during drafting swimming in highly trained triathletes.

PURPOSE: The influence of drafting was studied on the swimming performance, metabolic response, and passive drag of eight triathletes. METHODS: The performance in drafting position was measured directly behind another swimmer during a 400-m swim and compared with the nondrafting position. Metabolic response concerned VO(2), blood lactate, stroke rate, stroke length, and rating of perceived exertion. Drag was measured by passive towing. RESULTS: In drafting position, the triathletes swam on average faster (3.2%) over the 400-m swim than in nondrafting position (4 min, 47.69 +/- 10.35 s vs 4 min, 57.25 +/- 7.24 s; P < 0.01). Blood lactate and stroke rate were significantly lower (9.6 mM vs 10.8 mM; 39.9 cyclexmin(-1) vs 41.3 cyclexmin(-1) P < 0.02) and stroke length higher (2.10 mx cycle(-1) vs 1.97 mxcycle(-1), P < 0.01) than in nondrafting position. VO(2) and rating of perceived exertion were not statistically different. Passive drag was lower in drafting than in nondrafting position (P < 0.01). However, the gain in drag decreased with the towed velocity (from 26% at 1.1 mxs(-1) to 13% at 1.7mxs(-1)). In drafting position, the performance gain was related to the 400-m time (r = 0.80, P < 0.01) and to the skinfold thickness (r = 0.94, P < 0.01), with faster and leaner swimmers having greater gains of performance. CONCLUSIONS: Swimming behind another swimmer in a race is advantageous for triathletes.

Adult↗

PubMed1997

Weak association between blood sodium, potassium, and calcium and intensity of symptoms in major depressed patients.

In previous reports, we showed that plasma and erythrocyte magnesium were increased in many drug-free hospitalized depressed patients. Furthermore, we observed that erythrocyte magnesium content was related to the intensity of the symptoms. Highly depressed patients had the highest magnesium values. Today, we report the results of plasma and erythrocyte sodium and potassium, and of total and ultrafilterable plasma calcium in 66 hospitalized patients with major depression compared to 58 healthy controls. No consistent differences in these biochemical parameters are observed between patients when separated according to intensity of anxiety, psychomotor retardation, and moral distress. Plasma sodium is higher and plasma potassium lower in female patients of all subgroups as compared to controls. Both male patients and controls have erythrocyte sodium and potassium levels that are significantly different from those of females. This clearly suggests a separation into genders in such studies. In conclusion--in contrast to blood magnesium--sodium, potassium, and calcium levels do not seem to be related to the intensity of the main clinical symptoms in hospitalized patients with major depression.

Adult↗

PubMed1997

Stroking characteristic variations in the 100-M freestyle for male swimmers of differing skill.

The purpose of the study was to identify the stroking characteristics such as rate and length used by male swimmers of differing skill and to analyze the variations of velocity, stroke rate, and stroke length during the course of the race. The performance of 442 male subjects including 40 swimmers competing at an international 100-m freestyle event was videotaped and later analyzed to measure velocity, stroke rate, and stroke length on each lap of the race. Stroke length seemed to be the best predictor of swimming velocity. Different levels of performance could be discriminated by the variations of velocity, stroke rate, and especially stroke length, throughout the race. Besides higher values for velocity, stroke rate, and stroke length, the best swimmers were characterized by the capacity to maintain these parameters constant throughout the course of the race. Such results could be used by coaches to assess technique and training for certain racing strategies.

Achievement↗

PubMed1997

[Complete atrioventricular block disclosing Fabry's disease].

Fabry's disease is a hereditary sex-linked sphinglopidosis characterised by abnormal cellular lipid overload in most organs due to deficiencies in enzymes implicated in the catabolism of certain neutral glycolipids. There are two main clinical forms; cardiovascular manifestations usually congestive cardiac failure, and renal manifestations progressing to renal failure and death due to uraemic coma. The authors report a case presenting with juvenile, symptomatic complete infrahisian atrioventricular block. They describe the different cardiovascular complications of Fabry's disease from a review of the medical literature.

Cardiovascular Diseases↗

PubMed1996

High-speed liquid chromatographic method for the monitoring of carbamazepine and its active metabolite, carbamazepine-10,11-epoxide, in human plasma.

The assays of antiepileptic drugs, which are performed by central laboratories in Phase II and III clinical trials, require both a very fast turn-around time and a suitable specificity. In order to decrease the run time and to keep the powerful specificity of the liquid chromatography (HPLC), the use of a reversed-phase 1.5 microns monosized non-porous silicon dioxide microspheres column instead of regular columns containing spherical porous C18 material was studied. The determination of carbamazepine (CBZ) and its active metabolite, carbamazepine-10,11-epoxide (CBZ-E), in human plasma or serum was chosen to demonstrate the utility of these columns. As a prerequisite of this work, no modification of a regular HPLC system was allowed. The samples were prepared in autosampler vials by protein precipitation with acetonitrile, followed by a quick centrifugation. Without any change to a conventional HPLC system, CBZ and CBZ-E are well separated in less than 2.5 min using a Kovasil MS C14 column. No interference was observed with endogenous compounds and with nine antiepileptic drugs commonly prescribed as co-medication, and their metabolites. Due to the very low specific surface area of the packing, the required organic modifier volume per chromatographic run was decreased by a factor of 25. The method was validated. The developed method is well suited for the determination of CBZ and CBZ-E in clinical trials. It can be easily adapted to the monitoring of other antiepileptic drugs. No modification of a regular HPLC system was required.

Anticonvulsants↗