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G Dewasmes

Publications and source records attributed to G Dewasmes.

30 records · Page 2Linked to original sources
PubMed1991

Temperature and sweating responses in one-legged and two-legged exercise.

In looking at the thermoregulatory responses resulting from symmetrical or asymmetrical exercise, this paper has focused on the effect of local skin temperature (Tsk,local) on local sweat rates (msw,local) during one-legged (W1) and two-legged (W2) exercise on an ergocycle. Five subjects underwent four 3-h tests at 36 degrees C, each consisting of six 25-min exercise periods alternating with 5-min rest periods. The subjects performed W1 and W2 at 45 and 90 W, respectively, either dehydrated or rehydrated. Body temperatures and total sweat rate were measured as well as four msw,local (on chest and thighs), assessed from sweat capsules under which Tsk,local was maintained at predetermined levels (37.0 degrees C and 35.5 degrees C). The combinations of Tsk,local levels, capsule locations, exercise intensity and hydration level chosen in our protocol led to the following results. The hydration level affected rectal temperature but not total or msw,local. No specific effect of muscle activity was found; msw,local on thighs of resting and working legs were similar. The msw,local were only influenced by exercise intensity, msw,local being more elevated during the higher intensity. No significant effect of Tsk,local on msw,local was found, whatever the experimental condition and/or the location. It was concluded that local thermal effects on msw,local could have been masked by the strong central drive for sweating which has been found to exist in subjects exercising in a warm environment.

Adult↗
PubMed1991

Leg skin temperature and thigh sweat output: possible central influence of local thermal inputs.

To demonstrate whether or not the skin temperature of one lower limb can have an influence on the sweat rate of the contralateral leg, the two legs of five subjects were exposed inside leg-chambers to specific local thermal conditions while sweat rates were measured on both limbs. Three experiments (C I, II, III) of 3 h were carried out: each included two phases A and B. During A, the right leg was not ventilated, while the left leg was (C I) or was not (C II-III) ventilated. During B, the legs were either removed from the leg-chambers (C I) or ventilated inside the chambers at differently controlled levels of leg skin temperature (C II-III). At all times, sweat capsules on both legs measured the sweat rates of local areas of the thigh which were also temperature-controlled. Results showed that, at constant or slightly increased mean skin and core temperatures, the sweat output of one leg could be decreased at constant (C II) or higher local skin temperature (C III) probably due to a decrease in the temperature of the opposite leg. This finding is interpreted as a consequence of a central negative effect, originating from contralateral thermal inputs.

Adult↗
PubMed1991

Fasting-induced rise in locomotor activity in rats coincides with increased protein utilization.

The aim of this study was to investigate the possible relation between the modifications in locomotor activity (on running wheel) which occur during prolonged fasting and changes in the utilization of energy reserves. In 18-week-old rats, we found that the rate of body mass loss reflects the changes in nitrogen excretion that occur over three phases of fasting: (I) initially decreasing, (II) maintained at a low level and (III) increasing. Locomotor activity started to increase during phase II without a change in its nycthemeral pattern. By contrast, the 10-fold higher daily locomotor activity that occurred in phase III was marked by a higher proportion of diurnal activity. Using 9-, 18-, and 33-week-old rats, in order to obtain a different timing in the metabolic changes during fasting, we could confirm the coincidence between the later rise in locomotor activity and the occurrence of phase III. Refeeding of rats of either age in phase III rapidly suppressed fasting-induced changes in locomotor activity. These data accord with the idea that behavioral changes reflecting the search for food are triggered by a later and reversible change in the utilization of body protein vs. lipid stores during prolonged fasting.

Animals↗
PubMed1991

Sleep changes in fasting rats after chronic glycerol feeding.

Species which do not enter torpor during fasting and which were efficiently able to spare their body proteins during the first two phases of fasting (which are commonly comprised of 3 successive phases) also increase their daily amount of slow-wave sleep (SWS) during the first two phases. Since in fasting animals the ability to spare proteins was reported to be improved when they were previously fed with a diet enriched with glycerol, it was supposed that, after such a diet, food-deprived rats would increase their daily quota of SWS. In addition, the tolerance to food deprivation, defined as the time elapsed to reach the end of phase II, should also be improved since this tolerance is known to be critically modulated by protein utilization. The daily proportions of wakefulness (W), SWS and paradoxical sleep (PS) were thus studied in Wistar rats after 16 weeks of feeding (i.e., when they were 27 weeks old) with an enriched glycerol diet. These daily W and sleep state proportions were then evaluated until the middle of fasting phase II (MII), i.e., when protein catabolism in the rat appears to be at its lowest level. The rats were able to tolerate more than 5 weeks of food deprivation, which represented an increase of 123% of the fasting tolerance previously reported in rats of the same age but which were fed normally before fasting onset. At MII the daily proportion of SWS was significantly (vs. fed state, p less than 0.01) increased (due to an increase in the daily mean episode duration), at the expense of W (due to a lowering in the daily occurrence of W episodes).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Sleep changes in fasting rats.

The proportion and the distribution of wakefulness (W) slow-wave sleep (SWS) and paradoxical sleep (PS) were studied in 27-week-old rats over 24 hr periods, both in the fed state and after having been deprived of food for 2 to 3 weeks. In these rodents, prolonged fasting has been characterized by 3 successive metabolic phases which have been found to correspond to changes in protein metabolism. Sleep-waking changes were not studied during the first phase which was often of short duration (24 hr). During the second phase, i.e., when proteins were spared, the 24 hr proportions of W and sleep states remained unchanged. There were, however, profound changes in the daily mean episodic characteristics of each vigilance state (duration and frequency) except in the case of PS. During the phase II, the differences in the day/night proportions observed in each vigilance state were less than in the fed state. This reflected a lowering in the amplitude of their daily rhythms. In contrast, when protein use rose (phase III), W was increased sharply at the expense of SWS and PS, the latter being almost completely suppressed. During this last phase, which was also of short duration (by mean 3 days) alertness was greatly enhanced and the rats, which were typically nocturnal when fed, became diurnal. The changes in sleep and wakefulness were examined in relation to their effects on the homeostatic and cyclic components of sleep mechanisms and adaptive strategy to food deprivation in rat.

Animals↗
PubMed1989

Sleep changes in emperor penguins during fasting.

The proportion and the distribution over 24 h of the different arousal stages characterized in emperor penguins [wakefulness (W), drowsiness (D), slow-wave sleep (SWS), and paradoxical sleep (PS)] were studied under natural ambient conditions in four subjects that were first fed and then deprived of food for 7-18 days. In both fed and fasting states, each arousal stage was distributed through numerous episodes of short duration. The fasting state provoked only a slight increase in D. There was, however, a large increase in SWS, which increased from 37.5 to 55.4%/day, mainly at the expense of W, which fell from 42.7 to 21.9%/day, in close relation to the first two fasting phases when proteins were saved and when most of the energy was derived from lipids. PS proportions were lower during fasting (from 5.7 to 2.4%/day). These changes in the arousal stages in emperor penguins are examined for their implications in sleep mechanisms and energy saving. Their possible consequences, due to the reduced alertness, are also discussed.

Animals↗
PubMed1986

An electrophysiological and behavioral study of sleep in emperor penguins under natural ambient conditions.

In two pairs of emperor penguins surgically implanted for chronic recordings of EEG, EOG and EMG, four arousal stages were characterized on the basis of behavioral and electrophysiological criteria: wakefulness (W), drowsiness (D), slow-wave sleep (SWS) and paradoxical sleep (PS). The general patterns of electrographic correlates observed for each arousal stage resemble those reported in other birds. Sleep patterns were examined with these two pairs placed under natural ambient conditions of light and air temperature, the first pair being exposed to moderate cold under alternate conditions of day and night, and the second studied when daylight was total at thermoneutrality. The time spent in sleep (TST) by each group was 41.3% and 45.1% of the 24 hr period respectively, the difference not being significant. As in other birds, PS occurred in very brief episodes lasting, on average, 8 to 10 seconds and occupying only 5 to 6% of the 24 hr period. Whatever the external conditions, the PS to TST ratio appeared to remain unchanged (12 to 14%). Its relatively high value is discussed in relation to predation susceptibility.

Animals↗
PubMed1985

Polygraphic and behavioral study of sleep in geese: existence of nuchal atonia during paradoxical sleep.

In adult geese, chronic polygraphic recordings of EEG, EOG, EMG, ECG and respiratory rate completed with behavioral observations allowed the characterization of four states of vigilance: wakefulness (W), drowsiness (D), slow wave sleep (SWS) and paradoxical sleep (PS). The EEG, EOG, EMG general patterns observed during W, D, SWS and PS episodes with nuchal isotonia or hypotonia were similar to those reported in other birds. The characteristic brevity of avian PS was confirmed since this sleep state occupied only 2.8% of the nycthemere in geese. For the first time in an adult bird it was shown that numerous PS episodes were accompanied, as in mammals, by a total disappearance of nuchal EMG activity. These observations made in a bird species with a stable head support when sleeping, suggest that, as in mammals, inhibitory mechanisms leading to a PS related nuchal atonia do exist and that head falling is not the cause of PS episodes brevity in birds.

Animals↗
PubMed1984

Sleep changes in long-term fasting geese in relation to lipid and protein metabolism.

The proportion and the distribution over 24 h of the different arousal stages characterized in geese--wakefulness (W), drowsiness (D), and slow-wave (SWS) and paradoxical sleep (PS)--were studied in caged birds when fed and then fasted during about 40 days. In both the fed and fasted state, each arousal stage was distributed through numerous episodes of a short duration. The geese slept a little more during the night than during the day, a difference that was moderately emphasized during the fast. Fasting induced only a slight decrease in W. There were important changes in SWS and D in relation to the periods of fasting that were previously found to correspond to changes in lipid and protein utilization. When proteins were spared and lipids accounted for most of the energy expenditure, the fasted geese went more and more rapidly from W to SWS (proportion of D decreased from 33 to 13%/day) and slept for progressively longer periods (SWS increased from 23 to 49%/day). By contrast, when protein utilization rose, the general trend in sleep was a decrease in SWS and an increase in D. During the fast, changes in PS were in the same proportion as those in SWS. These reactions are examined for their implications in energy-saving and sleep mechanisms.

Animals↗
PubMed1981

Body composition, energy expenditure, and plasma metabolites in long-term fasting geese.

Starvation in 15 geese (mean initial body mass, m = 6.3 kg) fasting for about 40 days (mean decrease in m = 2.5 kg) was characterized by three periods. Period I (3-8 days), an adaptation period, was marked by a considerable decrease in the daily rate of change in m (dm) as well as in resting metabolic rate (RMR), and by high fat mobilization. In period II (a period of economy) the decreases in dm, RMR, and daily rate of nitrogen excretion (dne) were reduced: when expressed per unit of body mass these rates were either constant or decreased slightly. Period III, a critical period, was characterized by a rapid increase in both dm and dne that appeared when body mass had dropped to 4.7-3.2 kg. In parallel there was a greater decrease in intracellular fluid volume below 5 kg. Throughout the fast, in contrast to fasting mammals, plasma glucose and alanine concentrations were maintained at high levels (8-10 and 0.4 mM, respectively), and there was no increase in acetoacetate. However, after 20 days of fasting, plasma beta-hydroxybutyrate concentration (beta-OHB) increased to about 20 mM, while blood pH remained constant and blood PCO2 decreased. Thus, compensation for metabolic acidosis was partly attributed to respiratory alkalosis. Throughout the fast, the variations in beta-OHB were a mirror image of those for daily changes in body mass and in nitrogen excretion. This presumably reflects a hormonal change, but might also suggest a key role of beta-OHB in the control of energy expenditure and/or in regulation of body mass as well as in protein sparing.

Adipose Tissue↗
PubMed1980

Resting metabolic rate and cost of locomotion in long-term fasting emperor penguins.

During the Antarctic winter emperor penguins fast for up to 120 days when breeding at rookeries, which may be as much as 120 km from open water. Emperors have lost almost half of their body mass by the time they walk back to the sea to feed. Resting metabolic rate and metabolic rate during treadmill walking at 1.4 km times h-1 were measured regularly along the course of 63-118 days of fasting in four emperors that lost between 33 and 55% of their body mass. Resting metabolic rate decreased linearly with body mass throughout the fast; it was 76 and 50 W at 39 and 18 kg body mass, respectively, which therefore corresponds to a limited increase in the resting metabolic rate per unit of body mass. There was a considerable decrease in the metabolic rate for walking at 1.4 km times h-1, from 340 to 140 W at body masses of 39 and 18 kg, respectively; this decrease was linear with body mass but at a steeper rate below 23 kg. From 39 to 23 kg, the cost of walking per unit of body mass remained constant. Below 23 kg (a point where about 2.5 kg of fat remain), the increased efficiency for walking may be due to a change in the mechanics of locomotion.

Adipose Tissue↗