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.

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The purpose of the present study was to analyse the arousing effects of noise on sleep inertia as a function of circadian placement of a one-hour nap. In a first experiment, we measured the effects of sleep inertia in a neutral acoustic environment after a one-hour nap placed either at 0100 or 0400 on response time during a spatial memory test. In a second experiment were analysed the effects of an intense continuous noise on sleep inertia. The results showed that noise produced a total abolition of sleep inertia after an early nap (0000 to 0100). This may be due to the arousing effect of noise; however, results are less clear after a late nap 0300 to 0400 as noise seems to be ineffective. This result is discussed in terms of either a function of time-of-day effect or of prior sleep intensity. Moreover, our data suggest a possible interaction of noise with partial sleep deprivation leading to a slight deleterious effect those subjects who did not sleep at all.

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.

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