Biomedical subjects

Charles-Yannick Guezennec

Publications and source records attributed to Charles-Yannick Guezennec.

5 recordsLinked to original sources

PubMed2006

Influence of a high carbohydrate diet on the functional activity of 5-HT1B/1D receptors on human peripheral blood lymphocytes during intense military training.

The present study was undertaken to examine the effect of a high carbohydrate diet on the functional activity of 5-HT1B/1D receptors in human peripheral blood lymphocytes, and on serum cortisol and plasma cytokine responses during intense military training. Thirty two male soldiers (mean age: 21 +/- 2 years) were randomly assigned to two groups and received either 3200 kcal/24 h [13440 kJ; habitual diet group (HD)] or 4200 kcal/24 h [17640 kJ, high carbohydrate diet group (HCD)] by adding 1000 kcal (4200 kJ) of fruit jelly to the HD. They took part in a three-week training program followed by a five-day combat course. Blood samples were collected from each group before entry into the commando training and after the five-day combat course. The results of [35S] GTPgammaS binding assays showed that h5-HT1B/1D receptors were desensitized after the training program in the HD group, whereas no change was observed between the beginning and the end of the military training in the HCD group [(HD : IC50 = 100 +/- 14 nM to 544 +/- 178 nM; n = 16) and (HCD: IC50 = 68 +/- 14 nM to 101 +/- 22 nM; n = 16)]. Serum cortisol was only significantly increased after the commando training in the HD group (from 532.2 +/- 30 to 642 +/- 45 nmol.L(-1), p < 0.05), whereas values were not significantly changed in the HCD group (441 +/- 31 to 502 +/- 40 nmol.L(-1)). No changes were observed in IL-10, TNF-alpha and IFN-gamma levels after the training program in either group. Carbohydrate ingestion or additional dietary energy during repeated bouts of high-intensity exercise could attenuate the alterations in immune function via 5-HT1B/1D receptors and the action of 5-HT moduline, an endogenous tetrapeptide (Leu-Ser-Ala-Leu) that specifically modulates the sensitivity of 5-HT1B/1D receptors.

Adult↗

PubMed2005

EEG and ECG changes during simulator operation reflect mental workload and vigilance.

BACKGROUND: Performing mission tasks in a simulator influences many neurophysiological measures. Quantitative assessments of electroencephalography (EEG) and electrocardiography (ECG) have made it possible to develop indicators of mental workload and to estimate relative physiological responses to cognitive requirements. OBJECTIVE: To evaluate the effects of mental workload without actual physical risk, we studied the cortical and cardiovascular changes that occurred during simulated flight. METHODS: There were 12 pilots (8 novices and 4 experts) who simulated a flight composed of 10 sequences that induced several different mental workload levels. EEG was recorded at 12 electrode sites during rest and flight sequences; ECG activity was also recorded. Subjective tests were used to evaluate anxiety and vigilance levels. RESULTS: Theta band activity was lower during the two simulated flight rest sequences than during visual and instrument flight sequences at central, parietal, and occipital sites (p < 0.05). On the other hand, rest sequences resulted in higher beta (at the C4 site; p < 0.05) and gamma (at the central, parietal, and occipital sites; p < 0.05) power than active segments. The mean heart rate (HR) was not significantly different during any simulated flight sequence, but HR was lower for expert subjects than for novices. The subjective tests revealed no significant anxiety and high values for vigilance levels before and during flight. CONCLUSIONS: The different flight sequences performed on the simulator resulted in electrophysiological changes that expressed variations in mental workload. These results corroborate those found during study of real flights, particularly during sequences requiring the heaviest mental workload.

Aerospace Medicine↗

PubMed2004

EEG and ECG changes during selected flight sequences.

BACKGROUND: Mental workload has become a critical factor in the design and use of modern aircraft. Because of the complexity of the human-machine system, it is necessary to determine workload, fatigue, and level of performance using noninvasive electrophysiological measures. OBJECTIVE: Our objective was to identify the electrophysiological indicators of mental workload during piloting tasks. METHODS: Electroencephalographic (EEG) and electrocardiographic (ECG) activity was recorded during actual flight, with a profile planned to produce different levels of mental workload. RESULTS: In-flight EEG and ECG recordings enabled us to document mental workload levels. During active segments, delta and theta band activity increased (p < 0.05 or greater); results showed an increase of 22.5% for theta band activity during active flight segments compared with in-flight rest periods. Inversely, alpha band activity diminished: the decrease between ground baseline and all flight sequences was 30% (p < 0.05 or greater). These variations were reversed during the in-flight rest sequences. Instrumental flight caused an increase in the theta and alpha frequency band activity in the parietal-occipital area (p < 0.05 or greater); the alpha/beta ratio also increased. Heart rate increased during the active segments and fell during the in-flight rest periods. The mean difference between active segments and in-flight rest periods was of 8.89 bpm (i.e., an increase of 11.5%; p < 0.01). Heart rate was correlated to the EEG activity of the delta and beta bands in the central area (C3, Cz, C4, p < 0.05). CONCLUSIONS: The electrophysiological measures recorded provide useful indicators of the mental workload required by different flight sequences.

Adult↗

PubMed2004

[Overtraining syndrome].

Numerous studies have shown that enhanced physical load can result in an overtraining syndrome, with a decreased capacity for physical exercise and behavioral disturbances. Overtraining is caused by an imbalance between energy intake and output, and is facilitated by chronobiological and psychological stress. These factors are responsible for hormonal changes such as a decrease in gonadal steroids or in the hypothalamo-pituitary-adrenal axis. These metabolic and hormonal influences are lead to change in brain neuromediator activity, such as reduced monamine and increased serotonin levels. Experimental data indicate that these neuromediator changes are responsible more for behavioral changes than for decreased physical performance.

Energy Metabolism↗

PubMed2003

Regulation of proteolysis during reloading of the unweighted soleus muscle.

There is little information on the mechanisms responsible for muscle recovery following a catabolic condition. To address this point, we reloaded unweighted animals and investigated protein turnover during recovery from this highly catabolic state and the role of proteolysis in the reorganization of the soleus muscle. During early recovery (18 h of reloading) both muscle protein synthesis and breakdown were elevated (+65%, P<0.001 and +22%, P<0.05, respectively). However, only the activation of non-lysosomal and Ca(2+)-independent proteolysis was responsible for increased protein breakdown. Accordingly, mRNA levels for ubiquitin and 20S proteasome subunits C8 and C9 were markedly elevated (from +89 to +325%, P<0.03) and actively transcribed as shown by the analysis of polyribosomal profiles. In contrast, both cathepsin D and 14-kDa-ubiquitin conjugating enzyme E2 mRNA levels decreased, suggesting that the expression of such genes is an early marker of reversed muscle wasting. Following 7 days of reloading, protein synthesis was still elevated and there was no detectable change in protein breakdown rates. Accordingly, mRNA levels for all the proteolytic components tested were back to control values even though an accumulation of high molecular weight ubiquitin conjugates was still detectable. This suggests that soleus muscle remodeling was still going on. Taken together, our observations suggest that enhanced protein synthesis and breakdown are both necessary to recover from muscle atrophy and result in catch-up growth. The observed non-coordinate regulation of proteolytic systems is presumably required to target specific classes of substrates (atrophy-specific protein isoforms, damaged proteins) for replacement and/or elimination.

Animals↗